docs: fix reference links in config.md

bump go min version

.dockerignore

@@ -0,0 +1,2 @@
+Dockerfile
+.git/

.gitignore

@@ -1,3 +1,5 @@
-
 dist/
 gon.hcl
+
+/Build
+.DS_Store

.goreleaser-darwin.yaml

@@ -9,6 +9,8 @@ builds:
       - -trimpath
     ldflags:
       - -s -w
+      - -X main.version={{.Version}}
+      - -X main.commit={{.Commit}}
     goos:
       - darwin
     goarch:

.goreleaser-qf.yaml

@@ -9,11 +9,15 @@ builds:
       - -trimpath
     ldflags:
       - -s -w
+      - -X main.version={{.Version}}
+      - -X main.commit={{.Commit}}
     goos:
       - darwin
       - linux
       - windows
     goarch:
+      - 386
+      - arm
       - amd64
       - arm64
     tags:

.goreleaser.yaml

@@ -9,6 +9,8 @@ builds:
       - -trimpath
     ldflags:
       - -s -w
+      - -X main.version={{.Version}}
+      - -X main.commit={{.Commit}}
     goos:
       - linux
       - freebsd
@@ -17,6 +19,7 @@ builds:
       - 386
       - arm
       - mips
+      - mipsle
       - amd64
       - arm64
     goarm:

README.md

@@ -9,6 +9,11 @@ A highly configurable DNS forwarding proxy with support for:
 - Multiple upstreams with fallbacks
 - Multiple network policy driven DNS query steering
 - Policy driven domain based "split horizon" DNS with wildcard support
+- Integrations with common router vendors and firmware
+- LAN client discovery via DHCP, mDNS, and ARP
+
+## TLDR
+Proxy legacy DNS traffic to secure DNS upstreams in highly configurable ways. 
 
 All DNS protocols are supported, including:
 - `UDP 53`
@@ -17,23 +22,46 @@ All DNS protocols are supported, including:
 - `DNS-over-HTTP/3` (DOH3)
 - `DNS-over-QUIC`
 
-## Use Cases
+# Use Cases
 1. Use secure DNS protocols on networks and devices that don't natively support them (legacy routers, legacy OSes, TVs, smart toasters).
 2. Create source IP based DNS routing policies with variable secure DNS upstreams. Subnet 1 (admin) uses upstream resolver A, while Subnet 2 (employee) uses upstream resolver B.
 3. Create destination IP based DNS routing policies with variable secure DNS upstreams. Listener 1 uses upstream resolver C, while Listener 2 uses upstream resolver D.
 4. Create domain level "split horizon" DNS routing policies to send internal domains (*.company.int) to a local DNS server, while everything else goes to another upstream.
+5. Deploy on a router and create LAN client specific DNS routing policies from a web GUI (When using ControlD.com).
 
 
 ## OS Support
 - Windows (386, amd64, arm)
 - Mac (amd64, arm64)
 - Linux (386, amd64, arm, mips)
+- FreeBSD
+- Common routers (See Router Mode below)
 
-## Download
+# Install
-Download pre-compiled binaries from the [Releases](https://github.com/Control-D-Inc/ctrld/releases) section.
+There are several ways to download and install `ctrld.
+
+## Quick Install
+The simplest way to download and install `ctrld` is to use the following installer command on any UNIX-like platform:
+
+```shell
+sh -c 'sh -c "$(curl -sL https://api.controld.com/dl)"'
+```
+
+Windows user and prefer Powershell (who doesn't)? No problem, execute this command instead in administrative cmd:
+```shell
+powershell -Command "(Invoke-WebRequest -Uri 'https://api.controld.com/dl' -UseBasicParsing).Content | Set-Content 'ctrld_install.bat'" && ctrld_install.bat
+```
+
+Or you can pull and run a Docker container from [Docker Hub](https://hub.docker.com/r/controldns/ctrld)
+```
+$ docker pull controldns/ctrld
+```
+
+## Download Manually
+Alternatively, if you know what you're doing you can download pre-compiled binaries from the [Releases](https://github.com/Control-D-Inc/ctrld/releases) section for the appropriate platform. 
 
 ## Build
-`ctrld` requires `go1.19+`:
+Lastly, you can build `ctrld` from source which requires `go1.20+`:
 
 ```shell
 $ go build ./cmd/ctrld
@@ -45,6 +73,17 @@ or
 $ go install github.com/Control-D-Inc/ctrld/cmd/ctrld@latest
 ```
 
+or 
+
+```
+$ docker build -t controldns/ctrld . -f docker/Dockerfile
+$ docker run -d --name=ctrld -p 53:53/tcp -p 53:53/udp controldns/ctrld --cd=RESOLVER_ID_GOES_HERE -vv
+```
+
+
+# Usage
+The cli is self documenting, so free free to run `--help` on any sub-command to get specific usages. 
+
 ## Arguments
 ```
         __         .__       .___
@@ -60,18 +99,23 @@ Usage:
 Available Commands:
   run         Run the DNS proxy server
   service     Manage ctrld service
-  start       Quick start service and configure DNS on default interface
+  start       Quick start service and configure DNS on interface
-  stop        Quick stop service and remove DNS from default interface
+  stop        Quick stop service and remove DNS from interface
+  restart     Restart the ctrld service
+  status      Show status of the ctrld service
+  uninstall   Stop and uninstall the ctrld service
+  clients     Manage clients
 
 Flags:
   -h, --help            help for ctrld
+  -s, --silent          do not write any log output
   -v, --verbose count   verbose log output, "-v" basic logging, "-vv" debug level logging
       --version         version for ctrld
 
 Use "ctrld [command] --help" for more information about a command.
 ```
 
-## Usage
+## Basic Run Mode
 To start the server with default configuration, simply run: `./ctrld run`. This will create a generic `ctrld.toml` file in the **working directory** and start the application in foreground. 
 1. Start the server
   ```
@@ -85,40 +129,33 @@ To start the server with default configuration, simply run: `./ctrld run`. This
   147.185.34.1
   ```
 
-If `verify.controld.com` resolves, you're successfully using the default Control D upstream.
+If `verify.controld.com` resolves, you're successfully using the default Control D upstream. From here, you can start editing the config file and go nuts with it. To enforce a new config, restart the server. 
 
-### Service Mode
+## Service Mode
-To run the application in service mode, simply run: `./ctrld start` as system/root user. This will create a generic `ctrld.toml` file in the **user home** directory, start the system service, and configure the listener on the default interface. Service will start on OS boot.
+To run the application in service mode on any Windows, MacOS, Linux distibution or supported router, simply run: `./ctrld start` as system/root user. This will create a generic `ctrld.toml` file in the **user home** directory (on Windows) or `/etc/controld/` (almost everywhere else), start the system service, and configure the listener on the default network interface. Service will start on OS boot.
 
-In order to stop the service, and restore your DNS to original state, simply run `./ctrld stop`.
+When Control D upstreams are used, `ctrld` willl [relay your network topology](https://docs.controld.com/docs/device-clients) to Control D (LAN IPs, MAC addresses, and hostnames), and you will be able to see your LAN devices in the web panel, view analytics and apply unique profiles to them. 
 
-For granular control of the service, run the `service` command. Each sub-command has its own help section so you can see what arguments you can supply.
+In order to stop the service, and restore your DNS to original state, simply run `./ctrld stop`. If you wish to stop and uninstall the service permanently, run `./ctrld uninstall`. 
 
-```
-  Manage ctrld service
 
-  Usage:
+### Supported Routers
-    ctrld service [command]
+You can run `ctrld` on any supported router, which will function similarly to the Service Mode mentioned above. The list of supported routers and firmware includes:
+- Asus Merlin
+- DD-WRT
+- Firewalla
+- FreshTomato
+- GL.iNet
+- OpenWRT
+- pfSense / OPNsense
+- Synology 
+- Ubiquiti (UniFi, EdgeOS)
 
-  Available Commands:
+`ctrld` will attempt to interface with dnsmasq whenever possible and set itself as the upstream, while running on port 5354. On FreeBSD based OSes, `ctrld` will terminate dnsmasq and unbound in order to be able to listen on port 53 directly.  
-    interfaces  Manage network interfaces
-    restart     Restart the ctrld service
-    start       Start the ctrld service
-    status      Show status of the ctrld service
-    stop        Stop the ctrld service
-    uninstall   Uninstall the ctrld service
 
-  Flags:
-    -h, --help   help for service
-
-  Global Flags:
-    -v, --verbose count   verbose log output, "-v" basic logging, "-vv" debug level logging
-
-  Use "ctrld service [command] --help" for more information about a command.
-```
 
 ### Control D Auto Configuration
-Application can be started with a specific resolver config, instead of the default one. Simply supply your resolver ID with a `--cd` flag, when using the `run` (foreground) or `start` (service) modes. 
+Application can be started with a specific resolver config, instead of the default one. Simply supply your Resolver ID with a `--cd` flag, when using the `run` (foreground) or `start` (service) modes. 
 
 The following command will start the application in foreground mode, using the free "p2" resolver, which blocks Ads & Trackers. 
 
@@ -126,22 +163,22 @@ The following command will start the application in foreground mode, using the f
 ./ctrld run --cd p2
 ```
 
-Alternatively, you can use your own personal Control D Device resolver, and start the application in service mode. Your resolver ID is the part after the slash of your DNS-over-HTTPS resolver. ie. https://dns.controld.com/abcd1234
+Alternatively, you can use your own personal Control D Device resolver, and start the application in service mode. Your resolver ID is displayed on the "Show Resolvers" screen for the relevant Control D Device. 
 
 ```shell
 ./ctrld start --cd abcd1234
 ```
 
-Once you run the above command, the following things will happen:
+Once you run the above commands (in service mode only), the following things will happen:
 - You resolver configuration will be fetched from the API, and config file templated with the resolver data
-- Application will start as a service, and keep running (even after reboot) until you run the `stop` or `service uninstall` sub-commands
+- Application will start as a service, and keep running (even after reboot) until you run the `stop` or `uninstall` sub-commands
 - Your default network interface will be updated to use the listener started by the service
 - All OS DNS queries will be sent to the listener
 
-## Configuration
+# Configuration
 See [Configuration Docs](docs/config.md).
 
-### Example 
+## Example 
 - Start `listener.0` on 127.0.0.1:53
 - Accept queries from any source address
 - Send all queries to `upstream.0` via DoH protocol
@@ -151,8 +188,8 @@ See [Configuration Docs](docs/config.md).
 [listener]
 
   [listener.0]
-    ip = "127.0.0.1"
+    ip = ""
-    port = 53
+    port = 0
     restricted = false
 
 [network]
@@ -183,17 +220,19 @@ See [Configuration Docs](docs/config.md).
 
 ```
 
-### Advanced
+`ctrld` will pick a working config for `listener.0` then writing the default config to disk for the first run.
+
+## Advanced Configuration
 The above is the most basic example, which will work out of the box. If you're looking to do advanced configurations using policies, see [Configuration Docs](docs/config.md) for complete documentation of the config file.
 
 You can also supply configuration via launch argeuments, in [Ephemeral Mode](docs/ephemeral_mode.md).
 
 ## Contributing
-
 See [Contribution Guideline](./docs/contributing.md)
 
 ## Roadmap
 The following functionality is on the roadmap and will be available in future releases. 
-- Router self-installation
-- Client hostname/MAC passthrough
 - Prometheus metrics exporter 
+- DNS intercept mode
+- Direct listener mode
+- Support for more routers (let us know which ones)

client_info.go

@@ -0,0 +1,22 @@
+package ctrld
+
+// ClientInfoCtxKey is the context key to store client info.
+type ClientInfoCtxKey struct{}
+
+// ClientInfo represents ctrld's clients information.
+type ClientInfo struct {
+	Mac          string
+	IP           string
+	Hostname     string
+	Self         bool
+	ClientIDPref string
+}
+
+// LeaseFileFormat specifies the format of DHCP lease file.
+type LeaseFileFormat string
+
+const (
+	Dnsmasq  LeaseFileFormat = "dnsmasq"
+	IscDhcpd LeaseFileFormat = "isc-dhcpd"
+	KeaDHCP4 LeaseFileFormat = "kea-dhcp4"
+)

cmd/cli/cli_test.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import (
 	"os"

cmd/cli/conn.go

@@ -0,0 +1,51 @@
+package cli
+
+import (
+	"net"
+	"time"
+)
+
+// logConn wraps a net.Conn, override the Write behavior.
+// runCmd uses this wrapper, so as long as startCmd finished,
+// ctrld log won't be flushed with un-necessary write errors.
+type logConn struct {
+	conn net.Conn
+}
+
+func (lc *logConn) Read(b []byte) (n int, err error) {
+	return lc.conn.Read(b)
+}
+
+func (lc *logConn) Close() error {
+	return lc.conn.Close()
+}
+
+func (lc *logConn) LocalAddr() net.Addr {
+	return lc.conn.LocalAddr()
+}
+
+func (lc *logConn) RemoteAddr() net.Addr {
+	return lc.conn.RemoteAddr()
+}
+
+func (lc *logConn) SetDeadline(t time.Time) error {
+	return lc.conn.SetDeadline(t)
+}
+
+func (lc *logConn) SetReadDeadline(t time.Time) error {
+	return lc.conn.SetReadDeadline(t)
+}
+
+func (lc *logConn) SetWriteDeadline(t time.Time) error {
+	return lc.conn.SetWriteDeadline(t)
+}
+
+func (lc *logConn) Write(b []byte) (int, error) {
+	// Write performs writes with underlying net.Conn, ignore any errors happen.
+	// "ctrld run" command use this wrapper to report errors to "ctrld start".
+	// If no error occurred, "ctrld start" may finish before "ctrld run" attempt
+	// to close the connection, so ignore errors conservatively here, prevent
+	// un-necessary error "write to closed connection" flushed to ctrld log.
+	_, _ = lc.conn.Write(b)
+	return len(b), nil
+}

cmd/cli/control_client.go

@@ -0,0 +1,29 @@
+package cli
+
+import (
+	"context"
+	"io"
+	"net"
+	"net/http"
+	"time"
+)
+
+type controlClient struct {
+	c *http.Client
+}
+
+func newControlClient(addr string) *controlClient {
+	return &controlClient{c: &http.Client{
+		Transport: &http.Transport{
+			DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
+				d := net.Dialer{}
+				return d.DialContext(ctx, "unix", addr)
+			},
+		},
+		Timeout: time.Second * 30,
+	}}
+}
+
+func (c *controlClient) post(path string, data io.Reader) (*http.Response, error) {
+	return c.c.Post("http://unix"+path, contentTypeJson, data)
+}

cmd/cli/control_server.go

@@ -0,0 +1,156 @@
+package cli
+
+import (
+	"context"
+	"encoding/json"
+	"net"
+	"net/http"
+	"os"
+	"reflect"
+	"sort"
+	"time"
+
+	dto "github.com/prometheus/client_model/go"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+const (
+	contentTypeJson = "application/json"
+	listClientsPath = "/clients"
+	startedPath     = "/started"
+	reloadPath      = "/reload"
+)
+
+type controlServer struct {
+	server *http.Server
+	mux    *http.ServeMux
+	addr   string
+}
+
+func newControlServer(addr string) (*controlServer, error) {
+	mux := http.NewServeMux()
+	s := &controlServer{
+		server: &http.Server{Handler: mux},
+		mux:    mux,
+	}
+	s.addr = addr
+	return s, nil
+}
+
+func (s *controlServer) start() error {
+	_ = os.Remove(s.addr)
+	unixListener, err := net.Listen("unix", s.addr)
+	if l, ok := unixListener.(*net.UnixListener); ok {
+		l.SetUnlinkOnClose(true)
+	}
+	if err != nil {
+		return err
+	}
+	go s.server.Serve(unixListener)
+	return nil
+}
+
+func (s *controlServer) stop() error {
+	_ = os.Remove(s.addr)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*2)
+	defer cancel()
+	return s.server.Shutdown(ctx)
+}
+
+func (s *controlServer) register(pattern string, handler http.Handler) {
+	s.mux.Handle(pattern, jsonResponse(handler))
+}
+
+func (p *prog) registerControlServerHandler() {
+	p.cs.register(listClientsPath, http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
+		clients := p.ciTable.ListClients()
+		sort.Slice(clients, func(i, j int) bool {
+			return clients[i].IP.Less(clients[j].IP)
+		})
+		if p.cfg.Service.MetricsQueryStats {
+			for _, client := range clients {
+				client.IncludeQueryCount = true
+				dm := &dto.Metric{}
+				m, err := statsClientQueriesCount.MetricVec.GetMetricWithLabelValues(
+					client.IP.String(),
+					client.Mac,
+					client.Hostname,
+				)
+				if err != nil {
+					mainLog.Load().Debug().Err(err).Msgf("could not get metrics for client: %v", client)
+					continue
+				}
+				if err := m.Write(dm); err == nil {
+					client.QueryCount = int64(dm.Counter.GetValue())
+				}
+			}
+		}
+
+		if err := json.NewEncoder(w).Encode(&clients); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	}))
+	p.cs.register(startedPath, http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
+		select {
+		case <-p.onStartedDone:
+			w.WriteHeader(http.StatusOK)
+		case <-time.After(10 * time.Second):
+			w.WriteHeader(http.StatusRequestTimeout)
+		}
+	}))
+	p.cs.register(reloadPath, http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
+		listeners := make(map[string]*ctrld.ListenerConfig)
+		p.mu.Lock()
+		for k, v := range p.cfg.Listener {
+			listeners[k] = &ctrld.ListenerConfig{
+				IP:   v.IP,
+				Port: v.Port,
+			}
+		}
+		oldSvc := p.cfg.Service
+		p.mu.Unlock()
+		if err := p.sendReloadSignal(); err != nil {
+			mainLog.Load().Err(err).Msg("could not send reload signal")
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		select {
+		case <-p.reloadDoneCh:
+		case <-time.After(5 * time.Second):
+			http.Error(w, "timeout waiting for ctrld reload", http.StatusInternalServerError)
+			return
+		}
+
+		p.mu.Lock()
+		defer p.mu.Unlock()
+
+		// Checking for cases that we could not do a reload.
+
+		// 1. Listener config ip or port changes.
+		for k, v := range p.cfg.Listener {
+			l := listeners[k]
+			if l == nil || l.IP != v.IP || l.Port != v.Port {
+				w.WriteHeader(http.StatusCreated)
+				return
+			}
+		}
+
+		// 2. Service config changes.
+		if !reflect.DeepEqual(oldSvc, p.cfg.Service) {
+			w.WriteHeader(http.StatusCreated)
+			return
+		}
+
+		// Otherwise, reload is done.
+		w.WriteHeader(http.StatusOK)
+	}))
+}
+
+func jsonResponse(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		next.ServeHTTP(w, r)
+	})
+}

cmd/cli/control_server_test.go

@@ -0,0 +1,54 @@
+package cli
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"os"
+	"testing"
+)
+
+func TestControlServer(t *testing.T) {
+	f, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(f.Name())
+	f.Close()
+
+	s, err := newControlServer(f.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	pattern := "/ping"
+	respBody := []byte("pong")
+	s.register(pattern, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write(respBody)
+	}))
+	if err := s.start(); err != nil {
+		t.Fatal(err)
+	}
+
+	c := newControlClient(f.Name())
+	resp, err := c.post(pattern, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		t.Fatalf("unepxected response code: %d", resp.StatusCode)
+	}
+	if ct := resp.Header.Get("content-type"); ct != contentTypeJson {
+		t.Fatalf("unexpected content type: %s", ct)
+	}
+	buf, err := io.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(buf, respBody) {
+		t.Errorf("unexpected response body, want: %q, got: %q", string(respBody), string(buf))
+	}
+	if err := s.stop(); err != nil {
+		t.Fatal(err)
+	}
+}

cmd/cli/dns.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 //lint:ignore U1000 use in os_linux.go
 type getDNS func(iface string) []string

cmd/cli/dns_proxy.go

@@ -0,0 +1,938 @@
+package cli
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"net"
+	"net/netip"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/miekg/dns"
+	"golang.org/x/sync/errgroup"
+	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netaddr"
+	"tailscale.com/net/tsaddr"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/Control-D-Inc/ctrld/internal/dnscache"
+	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
+)
+
+const (
+	staleTTL = 60 * time.Second
+	localTTL = 3600 * time.Second
+	// EDNS0_OPTION_MAC is dnsmasq EDNS0 code for adding mac option.
+	// https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=blob;f=src/dns-protocol.h;h=76ac66a8c28317e9c121a74ab5fd0e20f6237dc8;hb=HEAD#l81
+	// This is also dns.EDNS0LOCALSTART, but define our own constant here for clarification.
+	EDNS0_OPTION_MAC = 0xFDE9
+)
+
+var osUpstreamConfig = &ctrld.UpstreamConfig{
+	Name:    "OS resolver",
+	Type:    ctrld.ResolverTypeOS,
+	Timeout: 2000,
+}
+
+var privateUpstreamConfig = &ctrld.UpstreamConfig{
+	Name:    "Private resolver",
+	Type:    ctrld.ResolverTypePrivate,
+	Timeout: 2000,
+}
+
+// proxyRequest contains data for proxying a DNS query to upstream.
+type proxyRequest struct {
+	msg            *dns.Msg
+	ci             *ctrld.ClientInfo
+	failoverRcodes []int
+	ufr            *upstreamForResult
+}
+
+// proxyResponse contains data for proxying a DNS response from upstream.
+type proxyResponse struct {
+	answer     *dns.Msg
+	cached     bool
+	clientInfo bool
+	upstream   string
+}
+
+// upstreamForResult represents the result of processing rules for a request.
+type upstreamForResult struct {
+	upstreams      []string
+	matchedPolicy  string
+	matchedNetwork string
+	matchedRule    string
+	matched        bool
+	srcAddr        string
+}
+
+func (p *prog) serveDNS(listenerNum string) error {
+	listenerConfig := p.cfg.Listener[listenerNum]
+	// make sure ip is allocated
+	if allocErr := p.allocateIP(listenerConfig.IP); allocErr != nil {
+		mainLog.Load().Error().Err(allocErr).Str("ip", listenerConfig.IP).Msg("serveUDP: failed to allocate listen ip")
+		return allocErr
+	}
+
+	handler := dns.HandlerFunc(func(w dns.ResponseWriter, m *dns.Msg) {
+		p.sema.acquire()
+		defer p.sema.release()
+		if len(m.Question) == 0 {
+			answer := new(dns.Msg)
+			answer.SetRcode(m, dns.RcodeFormatError)
+			_ = w.WriteMsg(answer)
+			return
+		}
+		reqId := requestID()
+		ctx := context.WithValue(context.Background(), ctrld.ReqIdCtxKey{}, reqId)
+		if !listenerConfig.AllowWanClients && isWanClient(w.RemoteAddr()) {
+			ctrld.Log(ctx, mainLog.Load().Debug(), "query refused, listener does not allow WAN clients: %s", w.RemoteAddr().String())
+			answer := new(dns.Msg)
+			answer.SetRcode(m, dns.RcodeRefused)
+			_ = w.WriteMsg(answer)
+			return
+		}
+		go p.detectLoop(m)
+		q := m.Question[0]
+		domain := canonicalName(q.Name)
+		remoteIP, _, _ := net.SplitHostPort(w.RemoteAddr().String())
+		ci := p.getClientInfo(remoteIP, m)
+		ci.ClientIDPref = p.cfg.Service.ClientIDPref
+		stripClientSubnet(m)
+		remoteAddr := spoofRemoteAddr(w.RemoteAddr(), ci)
+		fmtSrcToDest := fmtRemoteToLocal(listenerNum, ci.Hostname, remoteAddr.String())
+		t := time.Now()
+		ctrld.Log(ctx, mainLog.Load().Info(), "QUERY: %s: %s %s", fmtSrcToDest, dns.TypeToString[q.Qtype], domain)
+		ur := p.upstreamFor(ctx, listenerNum, listenerConfig, remoteAddr, ci.Mac, domain)
+
+		labelValues := make([]string, 0, len(statsQueriesCountLabels))
+		labelValues = append(labelValues, net.JoinHostPort(listenerConfig.IP, strconv.Itoa(listenerConfig.Port)))
+		labelValues = append(labelValues, ci.IP)
+		labelValues = append(labelValues, ci.Mac)
+		labelValues = append(labelValues, ci.Hostname)
+
+		var answer *dns.Msg
+		if !ur.matched && listenerConfig.Restricted {
+			ctrld.Log(ctx, mainLog.Load().Info(), "query refused, %s does not match any network policy", remoteAddr.String())
+			answer = new(dns.Msg)
+			answer.SetRcode(m, dns.RcodeRefused)
+			labelValues = append(labelValues, "") // no upstream
+		} else {
+			var failoverRcode []int
+			if listenerConfig.Policy != nil {
+				failoverRcode = listenerConfig.Policy.FailoverRcodeNumbers
+			}
+			pr := p.proxy(ctx, &proxyRequest{
+				msg:            m,
+				ci:             ci,
+				failoverRcodes: failoverRcode,
+				ufr:            ur,
+			})
+			answer = pr.answer
+			rtt := time.Since(t)
+			ctrld.Log(ctx, mainLog.Load().Debug(), "received response of %d bytes in %s", answer.Len(), rtt)
+			upstream := pr.upstream
+			switch {
+			case pr.cached:
+				upstream = "cache"
+			case pr.clientInfo:
+				upstream = "client_info_table"
+			}
+			labelValues = append(labelValues, upstream)
+		}
+		labelValues = append(labelValues, dns.TypeToString[q.Qtype])
+		labelValues = append(labelValues, dns.RcodeToString[answer.Rcode])
+		go func() {
+			p.WithLabelValuesInc(statsQueriesCount, labelValues...)
+			p.WithLabelValuesInc(statsClientQueriesCount, []string{ci.IP, ci.Mac, ci.Hostname}...)
+		}()
+		if err := w.WriteMsg(answer); err != nil {
+			ctrld.Log(ctx, mainLog.Load().Error().Err(err), "serveDNS: failed to send DNS response to client")
+		}
+	})
+
+	g, ctx := errgroup.WithContext(context.Background())
+	for _, proto := range []string{"udp", "tcp"} {
+		proto := proto
+		if needLocalIPv6Listener() {
+			g.Go(func() error {
+				s, errCh := runDNSServer(net.JoinHostPort("::1", strconv.Itoa(listenerConfig.Port)), proto, handler)
+				defer s.Shutdown()
+				select {
+				case <-p.stopCh:
+				case <-ctx.Done():
+				case err := <-errCh:
+					// Local ipv6 listener should not terminate ctrld.
+					// It's a workaround for a quirk on Windows.
+					mainLog.Load().Warn().Err(err).Msg("local ipv6 listener failed")
+				}
+				return nil
+			})
+		}
+		// When we spawn a listener on 127.0.0.1, also spawn listeners on the RFC1918
+		// addresses of the machine. So ctrld could receive queries from LAN clients.
+		if needRFC1918Listeners(listenerConfig) {
+			g.Go(func() error {
+				for _, addr := range ctrld.Rfc1918Addresses() {
+					func() {
+						listenAddr := net.JoinHostPort(addr, strconv.Itoa(listenerConfig.Port))
+						s, errCh := runDNSServer(listenAddr, proto, handler)
+						defer s.Shutdown()
+						select {
+						case <-p.stopCh:
+						case <-ctx.Done():
+						case err := <-errCh:
+							// RFC1918 listener should not terminate ctrld.
+							// It's a workaround for a quirk on system with systemd-resolved.
+							mainLog.Load().Warn().Err(err).Msgf("could not listen on %s: %s", proto, listenAddr)
+						}
+					}()
+				}
+				return nil
+			})
+		}
+		g.Go(func() error {
+			addr := net.JoinHostPort(listenerConfig.IP, strconv.Itoa(listenerConfig.Port))
+			s, errCh := runDNSServer(addr, proto, handler)
+			defer s.Shutdown()
+			select {
+			case err := <-errCh:
+				return err
+			case <-time.After(5 * time.Second):
+				p.started <- struct{}{}
+			}
+			select {
+			case <-p.stopCh:
+			case <-ctx.Done():
+			case err := <-errCh:
+				return err
+			}
+			return nil
+		})
+	}
+	return g.Wait()
+}
+
+// upstreamFor returns the list of upstreams for resolving the given domain,
+// matching by policies defined in the listener config. The second return value
+// reports whether the domain matches the policy.
+//
+// Though domain policy has higher priority than network policy, it is still
+// processed later, because policy logging want to know whether a network rule
+// is disregarded in favor of the domain level rule.
+func (p *prog) upstreamFor(ctx context.Context, defaultUpstreamNum string, lc *ctrld.ListenerConfig, addr net.Addr, srcMac, domain string) (res *upstreamForResult) {
+	upstreams := []string{upstreamPrefix + defaultUpstreamNum}
+	matchedPolicy := "no policy"
+	matchedNetwork := "no network"
+	matchedRule := "no rule"
+	matched := false
+	res = &upstreamForResult{srcAddr: addr.String()}
+
+	defer func() {
+		res.upstreams = upstreams
+		res.matched = matched
+		res.matchedPolicy = matchedPolicy
+		res.matchedNetwork = matchedNetwork
+		res.matchedRule = matchedRule
+	}()
+
+	if lc.Policy == nil {
+		return
+	}
+
+	do := func(policyUpstreams []string) {
+		upstreams = append([]string(nil), policyUpstreams...)
+	}
+
+	var networkTargets []string
+	var sourceIP net.IP
+	switch addr := addr.(type) {
+	case *net.UDPAddr:
+		sourceIP = addr.IP
+	case *net.TCPAddr:
+		sourceIP = addr.IP
+	}
+
+networkRules:
+	for _, rule := range lc.Policy.Networks {
+		for source, targets := range rule {
+			networkNum := strings.TrimPrefix(source, "network.")
+			nc := p.cfg.Network[networkNum]
+			if nc == nil {
+				continue
+			}
+			for _, ipNet := range nc.IPNets {
+				if ipNet.Contains(sourceIP) {
+					matchedPolicy = lc.Policy.Name
+					matchedNetwork = source
+					networkTargets = targets
+					matched = true
+					break networkRules
+				}
+			}
+		}
+	}
+
+macRules:
+	for _, rule := range lc.Policy.Macs {
+		for source, targets := range rule {
+			if source != "" && strings.EqualFold(source, srcMac) {
+				matchedPolicy = lc.Policy.Name
+				matchedNetwork = source
+				networkTargets = targets
+				matched = true
+				break macRules
+			}
+		}
+	}
+
+	for _, rule := range lc.Policy.Rules {
+		// There's only one entry per rule, config validation ensures this.
+		for source, targets := range rule {
+			if source == domain || wildcardMatches(source, domain) {
+				matchedPolicy = lc.Policy.Name
+				if len(networkTargets) > 0 {
+					matchedNetwork += " (unenforced)"
+				}
+				matchedRule = source
+				do(targets)
+				matched = true
+				return
+			}
+		}
+	}
+
+	if matched {
+		do(networkTargets)
+	}
+
+	return
+}
+
+func (p *prog) proxyPrivatePtrLookup(ctx context.Context, msg *dns.Msg) *dns.Msg {
+	cDomainName := msg.Question[0].Name
+	locked := p.ptrLoopGuard.TryLock(cDomainName)
+	defer p.ptrLoopGuard.Unlock(cDomainName)
+	if !locked {
+		return nil
+	}
+	ip := ipFromARPA(cDomainName)
+	if name := p.ciTable.LookupHostname(ip.String(), ""); name != "" {
+		answer := new(dns.Msg)
+		answer.SetReply(msg)
+		answer.Compress = true
+		answer.Answer = []dns.RR{&dns.PTR{
+			Hdr: dns.RR_Header{
+				Name:   msg.Question[0].Name,
+				Rrtype: dns.TypePTR,
+				Class:  dns.ClassINET,
+			},
+			Ptr: dns.Fqdn(name),
+		}}
+		ctrld.Log(ctx, mainLog.Load().Info(), "private PTR lookup, using client info table")
+		ctrld.Log(ctx, mainLog.Load().Debug(), "client info: %v", ctrld.ClientInfo{
+			Mac:      p.ciTable.LookupMac(ip.String()),
+			IP:       ip.String(),
+			Hostname: name,
+		})
+		return answer
+	}
+	return nil
+}
+
+func (p *prog) proxyLanHostnameQuery(ctx context.Context, msg *dns.Msg) *dns.Msg {
+	q := msg.Question[0]
+	hostname := strings.TrimSuffix(q.Name, ".")
+	locked := p.lanLoopGuard.TryLock(hostname)
+	defer p.lanLoopGuard.Unlock(hostname)
+	if !locked {
+		return nil
+	}
+	if ip := p.ciTable.LookupIPByHostname(hostname, q.Qtype == dns.TypeAAAA); ip != nil {
+		answer := new(dns.Msg)
+		answer.SetReply(msg)
+		answer.Compress = true
+		switch {
+		case ip.Is4():
+			answer.Answer = []dns.RR{&dns.A{
+				Hdr: dns.RR_Header{
+					Name:   msg.Question[0].Name,
+					Rrtype: dns.TypeA,
+					Class:  dns.ClassINET,
+					Ttl:    uint32(localTTL.Seconds()),
+				},
+				A: ip.AsSlice(),
+			}}
+		case ip.Is6():
+			answer.Answer = []dns.RR{&dns.AAAA{
+				Hdr: dns.RR_Header{
+					Name:   msg.Question[0].Name,
+					Rrtype: dns.TypeAAAA,
+					Class:  dns.ClassINET,
+					Ttl:    uint32(localTTL.Seconds()),
+				},
+				AAAA: ip.AsSlice(),
+			}}
+		}
+		ctrld.Log(ctx, mainLog.Load().Info(), "lan hostname lookup, using client info table")
+		ctrld.Log(ctx, mainLog.Load().Debug(), "client info: %v", ctrld.ClientInfo{
+			Mac:      p.ciTable.LookupMac(ip.String()),
+			IP:       ip.String(),
+			Hostname: hostname,
+		})
+		return answer
+	}
+	return nil
+}
+
+func (p *prog) proxy(ctx context.Context, req *proxyRequest) *proxyResponse {
+	var staleAnswer *dns.Msg
+	upstreams := req.ufr.upstreams
+	serveStaleCache := p.cache != nil && p.cfg.Service.CacheServeStale
+	upstreamConfigs := p.upstreamConfigsFromUpstreamNumbers(upstreams)
+	if len(upstreamConfigs) == 0 {
+		upstreamConfigs = []*ctrld.UpstreamConfig{osUpstreamConfig}
+		upstreams = []string{upstreamOS}
+	}
+
+	res := &proxyResponse{}
+
+	// LAN/PTR lookup flow:
+	//
+	// 1. If there's matching rule, follow it.
+	// 2. Try from client info table.
+	// 3. Try private resolver.
+	// 4. Try remote upstream.
+	isLanOrPtrQuery := false
+	if req.ufr.matched {
+		ctrld.Log(ctx, mainLog.Load().Debug(), "%s, %s, %s -> %v", req.ufr.matchedPolicy, req.ufr.matchedNetwork, req.ufr.matchedRule, upstreams)
+	} else {
+		switch {
+		case isPrivatePtrLookup(req.msg):
+			isLanOrPtrQuery = true
+			if answer := p.proxyPrivatePtrLookup(ctx, req.msg); answer != nil {
+				res.answer = answer
+				res.clientInfo = true
+				return res
+			}
+			upstreams, upstreamConfigs = p.upstreamsAndUpstreamConfigForLanAndPtr(upstreams, upstreamConfigs)
+			ctrld.Log(ctx, mainLog.Load().Debug(), "private PTR lookup, using upstreams: %v", upstreams)
+		case isLanHostnameQuery(req.msg):
+			isLanOrPtrQuery = true
+			if answer := p.proxyLanHostnameQuery(ctx, req.msg); answer != nil {
+				res.answer = answer
+				res.clientInfo = true
+				return res
+			}
+			upstreams, upstreamConfigs = p.upstreamsAndUpstreamConfigForLanAndPtr(upstreams, upstreamConfigs)
+			ctrld.Log(ctx, mainLog.Load().Debug(), "lan hostname lookup, using upstreams: %v", upstreams)
+		default:
+			ctrld.Log(ctx, mainLog.Load().Debug(), "no explicit policy matched, using default routing -> %v", upstreams)
+		}
+	}
+
+	// Inverse query should not be cached: https://www.rfc-editor.org/rfc/rfc1035#section-7.4
+	if p.cache != nil && req.msg.Question[0].Qtype != dns.TypePTR {
+		for _, upstream := range upstreams {
+			cachedValue := p.cache.Get(dnscache.NewKey(req.msg, upstream))
+			if cachedValue == nil {
+				continue
+			}
+			answer := cachedValue.Msg.Copy()
+			answer.SetRcode(req.msg, answer.Rcode)
+			now := time.Now()
+			if cachedValue.Expire.After(now) {
+				ctrld.Log(ctx, mainLog.Load().Debug(), "hit cached response")
+				setCachedAnswerTTL(answer, now, cachedValue.Expire)
+				res.answer = answer
+				res.cached = true
+				return res
+			}
+			staleAnswer = answer
+		}
+	}
+	resolve1 := func(n int, upstreamConfig *ctrld.UpstreamConfig, msg *dns.Msg) (*dns.Msg, error) {
+		ctrld.Log(ctx, mainLog.Load().Debug(), "sending query to %s: %s", upstreams[n], upstreamConfig.Name)
+		dnsResolver, err := ctrld.NewResolver(upstreamConfig)
+		if err != nil {
+			ctrld.Log(ctx, mainLog.Load().Error().Err(err), "failed to create resolver")
+			return nil, err
+		}
+		resolveCtx, cancel := context.WithCancel(ctx)
+		defer cancel()
+		if upstreamConfig.Timeout > 0 {
+			timeoutCtx, cancel := context.WithTimeout(resolveCtx, time.Millisecond*time.Duration(upstreamConfig.Timeout))
+			defer cancel()
+			resolveCtx = timeoutCtx
+		}
+		return dnsResolver.Resolve(resolveCtx, msg)
+	}
+	resolve := func(n int, upstreamConfig *ctrld.UpstreamConfig, msg *dns.Msg) *dns.Msg {
+		if upstreamConfig.UpstreamSendClientInfo() && req.ci != nil {
+			ctrld.Log(ctx, mainLog.Load().Debug(), "including client info with the request")
+			ctx = context.WithValue(ctx, ctrld.ClientInfoCtxKey{}, req.ci)
+		}
+		answer, err := resolve1(n, upstreamConfig, msg)
+		if err != nil {
+			ctrld.Log(ctx, mainLog.Load().Error().Err(err), "failed to resolve query")
+			if errNetworkError(err) {
+				p.um.increaseFailureCount(upstreams[n])
+				if p.um.isDown(upstreams[n]) {
+					go p.um.checkUpstream(upstreams[n], upstreamConfig)
+				}
+			}
+			// For timeout error (i.e: context deadline exceed), force re-bootstrapping.
+			var e net.Error
+			if errors.As(err, &e) && e.Timeout() {
+				upstreamConfig.ReBootstrap()
+			}
+			return nil
+		}
+		return answer
+	}
+	for n, upstreamConfig := range upstreamConfigs {
+		if upstreamConfig == nil {
+			continue
+		}
+		if p.isLoop(upstreamConfig) {
+			mainLog.Load().Warn().Msgf("dns loop detected, upstream: %q, endpoint: %q", upstreamConfig.Name, upstreamConfig.Endpoint)
+			continue
+		}
+		if p.um.isDown(upstreams[n]) {
+			ctrld.Log(ctx, mainLog.Load().Warn(), "%s is down", upstreams[n])
+			continue
+		}
+		answer := resolve(n, upstreamConfig, req.msg)
+		if answer == nil {
+			if serveStaleCache && staleAnswer != nil {
+				ctrld.Log(ctx, mainLog.Load().Debug(), "serving stale cached response")
+				now := time.Now()
+				setCachedAnswerTTL(staleAnswer, now, now.Add(staleTTL))
+				res.answer = staleAnswer
+				res.cached = true
+				return res
+			}
+			continue
+		}
+		// We are doing LAN/PTR lookup using private resolver, so always process next one.
+		// Except for the last, we want to send response instead of saying all upstream failed.
+		if answer.Rcode != dns.RcodeSuccess && isLanOrPtrQuery && n != len(upstreamConfigs)-1 {
+			ctrld.Log(ctx, mainLog.Load().Debug(), "no response from %s, process to next upstream", upstreams[n])
+			continue
+		}
+		if answer.Rcode != dns.RcodeSuccess && len(upstreamConfigs) > 1 && containRcode(req.failoverRcodes, answer.Rcode) {
+			ctrld.Log(ctx, mainLog.Load().Debug(), "failover rcode matched, process to next upstream")
+			continue
+		}
+
+		// set compression, as it is not set by default when unpacking
+		answer.Compress = true
+
+		if p.cache != nil && req.msg.Question[0].Qtype != dns.TypePTR {
+			ttl := ttlFromMsg(answer)
+			now := time.Now()
+			expired := now.Add(time.Duration(ttl) * time.Second)
+			if cachedTTL := p.cfg.Service.CacheTTLOverride; cachedTTL > 0 {
+				expired = now.Add(time.Duration(cachedTTL) * time.Second)
+			}
+			setCachedAnswerTTL(answer, now, expired)
+			p.cache.Add(dnscache.NewKey(req.msg, upstreams[n]), dnscache.NewValue(answer, expired))
+			ctrld.Log(ctx, mainLog.Load().Debug(), "add cached response")
+		}
+		hostname := ""
+		if req.ci != nil {
+			hostname = req.ci.Hostname
+		}
+		ctrld.Log(ctx, mainLog.Load().Info(), "REPLY: %s -> %s (%s): %s", upstreams[n], req.ufr.srcAddr, hostname, dns.RcodeToString[answer.Rcode])
+		res.answer = answer
+		res.upstream = upstreamConfig.Endpoint
+		return res
+	}
+	ctrld.Log(ctx, mainLog.Load().Error(), "all %v endpoints failed", upstreams)
+	answer := new(dns.Msg)
+	answer.SetRcode(req.msg, dns.RcodeServerFailure)
+	res.answer = answer
+	return res
+}
+
+func (p *prog) upstreamsAndUpstreamConfigForLanAndPtr(upstreams []string, upstreamConfigs []*ctrld.UpstreamConfig) ([]string, []*ctrld.UpstreamConfig) {
+	if len(p.localUpstreams) > 0 {
+		tmp := make([]string, 0, len(p.localUpstreams)+len(upstreams))
+		tmp = append(tmp, p.localUpstreams...)
+		tmp = append(tmp, upstreams...)
+		return tmp, p.upstreamConfigsFromUpstreamNumbers(tmp)
+	}
+	return append([]string{upstreamOS}, upstreams...), append([]*ctrld.UpstreamConfig{privateUpstreamConfig}, upstreamConfigs...)
+}
+
+func (p *prog) upstreamConfigsFromUpstreamNumbers(upstreams []string) []*ctrld.UpstreamConfig {
+	upstreamConfigs := make([]*ctrld.UpstreamConfig, 0, len(upstreams))
+	for _, upstream := range upstreams {
+		upstreamNum := strings.TrimPrefix(upstream, upstreamPrefix)
+		upstreamConfigs = append(upstreamConfigs, p.cfg.Upstream[upstreamNum])
+	}
+	return upstreamConfigs
+}
+
+// canonicalName returns canonical name from FQDN with "." trimmed.
+func canonicalName(fqdn string) string {
+	q := strings.TrimSpace(fqdn)
+	q = strings.TrimSuffix(q, ".")
+	// https://datatracker.ietf.org/doc/html/rfc4343
+	q = strings.ToLower(q)
+
+	return q
+}
+
+func wildcardMatches(wildcard, domain string) bool {
+	// Wildcard match.
+	wildCardParts := strings.Split(wildcard, "*")
+	if len(wildCardParts) != 2 {
+		return false
+	}
+
+	switch {
+	case len(wildCardParts[0]) > 0 && len(wildCardParts[1]) > 0:
+		// Domain must match both prefix and suffix.
+		return strings.HasPrefix(domain, wildCardParts[0]) && strings.HasSuffix(domain, wildCardParts[1])
+
+	case len(wildCardParts[1]) > 0:
+		// Only suffix must match.
+		return strings.HasSuffix(domain, wildCardParts[1])
+
+	case len(wildCardParts[0]) > 0:
+		// Only prefix must match.
+		return strings.HasPrefix(domain, wildCardParts[0])
+	}
+
+	return false
+}
+
+func fmtRemoteToLocal(listenerNum, hostname, remote string) string {
+	return fmt.Sprintf("%s (%s) -> listener.%s", remote, hostname, listenerNum)
+}
+
+func requestID() string {
+	b := make([]byte, 3) // 6 chars
+	if _, err := rand.Read(b); err != nil {
+		panic(err)
+	}
+	return hex.EncodeToString(b)
+}
+
+func containRcode(rcodes []int, rcode int) bool {
+	for i := range rcodes {
+		if rcodes[i] == rcode {
+			return true
+		}
+	}
+	return false
+}
+
+func setCachedAnswerTTL(answer *dns.Msg, now, expiredTime time.Time) {
+	ttlSecs := expiredTime.Sub(now).Seconds()
+	if ttlSecs < 0 {
+		return
+	}
+
+	ttl := uint32(ttlSecs)
+	for _, rr := range answer.Answer {
+		rr.Header().Ttl = ttl
+	}
+	for _, rr := range answer.Ns {
+		rr.Header().Ttl = ttl
+	}
+	for _, rr := range answer.Extra {
+		if rr.Header().Rrtype != dns.TypeOPT {
+			rr.Header().Ttl = ttl
+		}
+	}
+}
+
+func ttlFromMsg(msg *dns.Msg) uint32 {
+	for _, rr := range msg.Answer {
+		return rr.Header().Ttl
+	}
+	for _, rr := range msg.Ns {
+		return rr.Header().Ttl
+	}
+	return 0
+}
+
+func needLocalIPv6Listener() bool {
+	// On Windows, there's no easy way for disabling/removing IPv6 DNS resolver, so we check whether we can
+	// listen on ::1, then spawn a listener for receiving DNS requests.
+	return ctrldnet.SupportsIPv6ListenLocal() && runtime.GOOS == "windows"
+}
+
+// ipAndMacFromMsg extracts IP and MAC information included in a DNS message, if any.
+func ipAndMacFromMsg(msg *dns.Msg) (string, string) {
+	ip, mac := "", ""
+	if opt := msg.IsEdns0(); opt != nil {
+		for _, s := range opt.Option {
+			switch e := s.(type) {
+			case *dns.EDNS0_LOCAL:
+				if e.Code == EDNS0_OPTION_MAC {
+					mac = net.HardwareAddr(e.Data).String()
+				}
+			case *dns.EDNS0_SUBNET:
+				if len(e.Address) > 0 && !e.Address.IsLoopback() {
+					ip = e.Address.String()
+				}
+			}
+		}
+	}
+	return ip, mac
+}
+
+// stripClientSubnet removes EDNS0_SUBNET from DNS message if the IP is RFC1918 or loopback address,
+// passing them to upstream is pointless, these cannot be used by anything on the WAN.
+func stripClientSubnet(msg *dns.Msg) {
+	if opt := msg.IsEdns0(); opt != nil {
+		opts := make([]dns.EDNS0, 0, len(opt.Option))
+		for _, s := range opt.Option {
+			if e, ok := s.(*dns.EDNS0_SUBNET); ok && (e.Address.IsPrivate() || e.Address.IsLoopback()) {
+				continue
+			}
+			opts = append(opts, s)
+		}
+		if len(opts) != len(opt.Option) {
+			opt.Option = opts
+		}
+	}
+}
+
+func spoofRemoteAddr(addr net.Addr, ci *ctrld.ClientInfo) net.Addr {
+	if ci != nil && ci.IP != "" {
+		switch addr := addr.(type) {
+		case *net.UDPAddr:
+			udpAddr := &net.UDPAddr{
+				IP:   net.ParseIP(ci.IP),
+				Port: addr.Port,
+				Zone: addr.Zone,
+			}
+			return udpAddr
+		case *net.TCPAddr:
+			udpAddr := &net.TCPAddr{
+				IP:   net.ParseIP(ci.IP),
+				Port: addr.Port,
+				Zone: addr.Zone,
+			}
+			return udpAddr
+		}
+	}
+	return addr
+}
+
+// runDNSServer starts a DNS server for given address and network,
+// with the given handler. It ensures the server has started listening.
+// Any error will be reported to the caller via returned channel.
+//
+// It's the caller responsibility to call Shutdown to close the server.
+func runDNSServer(addr, network string, handler dns.Handler) (*dns.Server, <-chan error) {
+	s := &dns.Server{
+		Addr:    addr,
+		Net:     network,
+		Handler: handler,
+	}
+
+	waitLock := sync.Mutex{}
+	waitLock.Lock()
+	s.NotifyStartedFunc = waitLock.Unlock
+
+	errCh := make(chan error)
+	go func() {
+		defer close(errCh)
+		if err := s.ListenAndServe(); err != nil {
+			waitLock.Unlock()
+			mainLog.Load().Error().Err(err).Msgf("could not listen and serve on: %s", s.Addr)
+			errCh <- err
+		}
+	}()
+	waitLock.Lock()
+	return s, errCh
+}
+
+func (p *prog) getClientInfo(remoteIP string, msg *dns.Msg) *ctrld.ClientInfo {
+	ci := &ctrld.ClientInfo{}
+	if p.appCallback != nil {
+		ci.IP = p.appCallback.LanIp()
+		ci.Mac = p.appCallback.MacAddress()
+		ci.Hostname = p.appCallback.HostName()
+		ci.Self = true
+		return ci
+	}
+	ci.IP, ci.Mac = ipAndMacFromMsg(msg)
+	switch {
+	case ci.IP != "" && ci.Mac != "":
+		// Nothing to do.
+	case ci.IP == "" && ci.Mac != "":
+		// Have MAC, no IP.
+		ci.IP = p.ciTable.LookupIP(ci.Mac)
+	case ci.IP == "" && ci.Mac == "":
+		// Have nothing, use remote IP then lookup MAC.
+		ci.IP = remoteIP
+		fallthrough
+	case ci.IP != "" && ci.Mac == "":
+		// Have IP, no MAC.
+		ci.Mac = p.ciTable.LookupMac(ci.IP)
+	}
+
+	// If MAC is still empty here, that mean the requests are made from virtual interface,
+	// like VPN/Wireguard clients, so we use ci.IP as hostname to distinguish those clients.
+	if ci.Mac == "" {
+		if hostname := p.ciTable.LookupHostname(ci.IP, ""); hostname != "" {
+			ci.Hostname = hostname
+		} else {
+			// Only use IP as hostname for IPv4 clients.
+			// For Android devices, when it joins the network, it uses ctrld to resolve
+			// its private DNS once and never reaches ctrld again. For each time, it uses
+			// a different IPv6 address, which causes hundreds/thousands different client
+			// IDs created for the same device, which is pointless.
+			//
+			// TODO(cuonglm): investigate whether this can be a false positive for other clients?
+			if !ctrldnet.IsIPv6(ci.IP) {
+				ci.Hostname = ci.IP
+				p.ciTable.StoreVPNClient(ci)
+			}
+		}
+	} else {
+		ci.Hostname = p.ciTable.LookupHostname(ci.IP, ci.Mac)
+	}
+	ci.Self = queryFromSelf(ci.IP)
+	p.spoofLoopbackIpInClientInfo(ci)
+	return ci
+}
+
+// spoofLoopbackIpInClientInfo replaces loopback IPs in client info.
+//
+// - Preference IPv4.
+// - Preference RFC1918.
+func (p *prog) spoofLoopbackIpInClientInfo(ci *ctrld.ClientInfo) {
+	if ip := net.ParseIP(ci.IP); ip == nil || !ip.IsLoopback() {
+		return
+	}
+	if ip := p.ciTable.LookupRFC1918IPv4(ci.Mac); ip != "" {
+		ci.IP = ip
+	}
+}
+
+// queryFromSelf reports whether the input IP is from device running ctrld.
+func queryFromSelf(ip string) bool {
+	netIP := netip.MustParseAddr(ip)
+	ifaces, err := interfaces.GetList()
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not get interfaces list")
+		return false
+	}
+	for _, iface := range ifaces {
+		addrs, err := iface.Addrs()
+		if err != nil {
+			mainLog.Load().Warn().Err(err).Msgf("could not get interfaces addresses: %s", iface.Name)
+			continue
+		}
+		for _, a := range addrs {
+			switch v := a.(type) {
+			case *net.IPNet:
+				if pfx, ok := netaddr.FromStdIPNet(v); ok && pfx.Addr().Compare(netIP) == 0 {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}
+
+func needRFC1918Listeners(lc *ctrld.ListenerConfig) bool {
+	return lc.IP == "127.0.0.1" && lc.Port == 53
+}
+
+// ipFromARPA parses a FQDN arpa domain and return the IP address if valid.
+func ipFromARPA(arpa string) net.IP {
+	if arpa, ok := strings.CutSuffix(arpa, ".in-addr.arpa."); ok {
+		if ptrIP := net.ParseIP(arpa); ptrIP != nil {
+			return net.IP{ptrIP[15], ptrIP[14], ptrIP[13], ptrIP[12]}
+		}
+	}
+	if arpa, ok := strings.CutSuffix(arpa, ".ip6.arpa."); ok {
+		l := net.IPv6len * 2
+		base := 16
+		ip := make(net.IP, net.IPv6len)
+		for i := 0; i < l && arpa != ""; i++ {
+			idx := strings.LastIndexByte(arpa, '.')
+			off := idx + 1
+			if idx == -1 {
+				idx = 0
+				off = 0
+			} else if idx == len(arpa)-1 {
+				return nil
+			}
+			n, err := strconv.ParseUint(arpa[off:], base, 8)
+			if err != nil {
+				return nil
+			}
+			b := byte(n)
+			ii := i / 2
+			if i&1 == 1 {
+				b |= ip[ii] << 4
+			}
+			ip[ii] = b
+			arpa = arpa[:idx]
+		}
+		return ip
+	}
+	return nil
+}
+
+// isPrivatePtrLookup reports whether DNS message is an PTR query for LAN/CGNAT network.
+func isPrivatePtrLookup(m *dns.Msg) bool {
+	if m == nil || len(m.Question) == 0 {
+		return false
+	}
+	q := m.Question[0]
+	if ip := ipFromARPA(q.Name); ip != nil {
+		if addr, ok := netip.AddrFromSlice(ip); ok {
+			return addr.IsPrivate() ||
+				addr.IsLoopback() ||
+				addr.IsLinkLocalUnicast() ||
+				tsaddr.CGNATRange().Contains(addr)
+		}
+	}
+	return false
+}
+
+// isLanHostnameQuery reports whether DNS message is an A/AAAA query with LAN hostname.
+func isLanHostnameQuery(m *dns.Msg) bool {
+	if m == nil || len(m.Question) == 0 {
+		return false
+	}
+	q := m.Question[0]
+	switch q.Qtype {
+	case dns.TypeA, dns.TypeAAAA:
+	default:
+		return false
+	}
+	name := strings.TrimSuffix(q.Name, ".")
+	return !strings.Contains(name, ".") ||
+		strings.HasSuffix(name, ".domain") ||
+		strings.HasSuffix(name, ".lan")
+}
+
+// isWanClient reports whether the input is a WAN address.
+func isWanClient(na net.Addr) bool {
+	var ip netip.Addr
+	if ap, err := netip.ParseAddrPort(na.String()); err == nil {
+		ip = ap.Addr()
+	}
+	return !ip.IsLoopback() &&
+		!ip.IsPrivate() &&
+		!ip.IsLinkLocalUnicast() &&
+		!ip.IsLinkLocalMulticast() &&
+		!tsaddr.CGNATRange().Contains(ip)
+}

cmd/cli/dns_proxy_test.go

@@ -0,0 +1,433 @@
+package cli
+
+import (
+	"context"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/miekg/dns"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/Control-D-Inc/ctrld/internal/dnscache"
+	"github.com/Control-D-Inc/ctrld/testhelper"
+)
+
+func Test_wildcardMatches(t *testing.T) {
+	tests := []struct {
+		name     string
+		wildcard string
+		domain   string
+		match    bool
+	}{
+		{"prefix parent should not match", "*.windscribe.com", "windscribe.com", false},
+		{"prefix", "*.windscribe.com", "anything.windscribe.com", true},
+		{"prefix not match other domain", "*.windscribe.com", "example.com", false},
+		{"prefix not match domain in name", "*.windscribe.com", "wwindscribe.com", false},
+		{"suffix", "suffix.*", "suffix.windscribe.com", true},
+		{"suffix not match other", "suffix.*", "suffix1.windscribe.com", false},
+		{"both", "suffix.*.windscribe.com", "suffix.anything.windscribe.com", true},
+		{"both not match", "suffix.*.windscribe.com", "suffix1.suffix.windscribe.com", false},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := wildcardMatches(tc.wildcard, tc.domain); got != tc.match {
+				t.Errorf("unexpected result, wildcard: %s, domain: %s, want: %v, got: %v", tc.wildcard, tc.domain, tc.match, got)
+			}
+		})
+	}
+}
+
+func Test_canonicalName(t *testing.T) {
+	tests := []struct {
+		name      string
+		domain    string
+		canonical string
+	}{
+		{"fqdn to canonical", "windscribe.com.", "windscribe.com"},
+		{"already canonical", "windscribe.com", "windscribe.com"},
+		{"case insensitive", "Windscribe.Com.", "windscribe.com"},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := canonicalName(tc.domain); got != tc.canonical {
+				t.Errorf("unexpected result, want: %s, got: %s", tc.canonical, got)
+			}
+		})
+	}
+}
+
+func Test_prog_upstreamFor(t *testing.T) {
+	cfg := testhelper.SampleConfig(t)
+	p := &prog{cfg: cfg}
+	p.um = newUpstreamMonitor(p.cfg)
+	p.lanLoopGuard = newLoopGuard()
+	p.ptrLoopGuard = newLoopGuard()
+	for _, nc := range p.cfg.Network {
+		for _, cidr := range nc.Cidrs {
+			_, ipNet, err := net.ParseCIDR(cidr)
+			if err != nil {
+				t.Fatal(err)
+			}
+			nc.IPNets = append(nc.IPNets, ipNet)
+		}
+	}
+
+	tests := []struct {
+		name               string
+		ip                 string
+		mac                string
+		defaultUpstreamNum string
+		lc                 *ctrld.ListenerConfig
+		domain             string
+		upstreams          []string
+		matched            bool
+		testLogMsg         string
+	}{
+		{"Policy map matches", "192.168.0.1:0", "", "0", p.cfg.Listener["0"], "abc.xyz", []string{"upstream.1", "upstream.0"}, true, ""},
+		{"Policy split matches", "192.168.0.1:0", "", "0", p.cfg.Listener["0"], "abc.ru", []string{"upstream.1"}, true, ""},
+		{"Policy map for other network matches", "192.168.1.2:0", "", "0", p.cfg.Listener["0"], "abc.xyz", []string{"upstream.0"}, true, ""},
+		{"No policy map for listener", "192.168.1.2:0", "", "1", p.cfg.Listener["1"], "abc.ru", []string{"upstream.1"}, false, ""},
+		{"unenforced loging", "192.168.1.2:0", "", "0", p.cfg.Listener["0"], "abc.ru", []string{"upstream.1"}, true, "My Policy, network.1 (unenforced), *.ru -> [upstream.1]"},
+		{"Policy Macs matches upper", "192.168.0.1:0", "14:45:A0:67:83:0A", "0", p.cfg.Listener["0"], "abc.xyz", []string{"upstream.2"}, true, "14:45:a0:67:83:0a"},
+		{"Policy Macs matches lower", "192.168.0.1:0", "14:54:4a:8e:08:2d", "0", p.cfg.Listener["0"], "abc.xyz", []string{"upstream.2"}, true, "14:54:4a:8e:08:2d"},
+		{"Policy Macs matches case-insensitive", "192.168.0.1:0", "14:54:4A:8E:08:2D", "0", p.cfg.Listener["0"], "abc.xyz", []string{"upstream.2"}, true, "14:54:4a:8e:08:2d"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			for _, network := range []string{"udp", "tcp"} {
+				var (
+					addr net.Addr
+					err  error
+				)
+				switch network {
+				case "udp":
+					addr, err = net.ResolveUDPAddr(network, tc.ip)
+				case "tcp":
+					addr, err = net.ResolveTCPAddr(network, tc.ip)
+				}
+				require.NoError(t, err)
+				require.NotNil(t, addr)
+				ctx := context.WithValue(context.Background(), ctrld.ReqIdCtxKey{}, requestID())
+				ufr := p.upstreamFor(ctx, tc.defaultUpstreamNum, tc.lc, addr, tc.mac, tc.domain)
+				p.proxy(ctx, &proxyRequest{
+					msg: newDnsMsgWithHostname("foo", dns.TypeA),
+					ufr: ufr,
+				})
+				assert.Equal(t, tc.matched, ufr.matched)
+				assert.Equal(t, tc.upstreams, ufr.upstreams)
+				if tc.testLogMsg != "" {
+					assert.Contains(t, logOutput.String(), tc.testLogMsg)
+				}
+			}
+		})
+	}
+}
+
+func TestCache(t *testing.T) {
+	cfg := testhelper.SampleConfig(t)
+	prog := &prog{cfg: cfg}
+	for _, nc := range prog.cfg.Network {
+		for _, cidr := range nc.Cidrs {
+			_, ipNet, err := net.ParseCIDR(cidr)
+			if err != nil {
+				t.Fatal(err)
+			}
+			nc.IPNets = append(nc.IPNets, ipNet)
+		}
+	}
+	cacher, err := dnscache.NewLRUCache(4096)
+	require.NoError(t, err)
+	prog.cache = cacher
+
+	msg := new(dns.Msg)
+	msg.SetQuestion("example.com", dns.TypeA)
+	msg.MsgHdr.RecursionDesired = true
+	answer1 := new(dns.Msg)
+	answer1.SetRcode(msg, dns.RcodeSuccess)
+
+	prog.cache.Add(dnscache.NewKey(msg, "upstream.1"), dnscache.NewValue(answer1, time.Now().Add(time.Minute)))
+	answer2 := new(dns.Msg)
+	answer2.SetRcode(msg, dns.RcodeRefused)
+	prog.cache.Add(dnscache.NewKey(msg, "upstream.0"), dnscache.NewValue(answer2, time.Now().Add(time.Minute)))
+
+	req1 := &proxyRequest{
+		msg:            msg,
+		ci:             nil,
+		failoverRcodes: nil,
+		ufr: &upstreamForResult{
+			upstreams:      []string{"upstream.1"},
+			matchedPolicy:  "",
+			matchedNetwork: "",
+			matchedRule:    "",
+			matched:        false,
+		},
+	}
+	req2 := &proxyRequest{
+		msg:            msg,
+		ci:             nil,
+		failoverRcodes: nil,
+		ufr: &upstreamForResult{
+			upstreams:      []string{"upstream.0"},
+			matchedPolicy:  "",
+			matchedNetwork: "",
+			matchedRule:    "",
+			matched:        false,
+		},
+	}
+	got1 := prog.proxy(context.Background(), req1)
+	got2 := prog.proxy(context.Background(), req2)
+	assert.NotSame(t, got1, got2)
+	assert.Equal(t, answer1.Rcode, got1.answer.Rcode)
+	assert.Equal(t, answer2.Rcode, got2.answer.Rcode)
+}
+
+func Test_ipAndMacFromMsg(t *testing.T) {
+	tests := []struct {
+		name    string
+		ip      string
+		wantIp  bool
+		mac     string
+		wantMac bool
+	}{
+		{"has ip v4 and mac", "1.2.3.4", true, "4c:20:b8:ab:87:1b", true},
+		{"has ip v6 and mac", "2606:1a40:3::1", true, "4c:20:b8:ab:87:1b", true},
+		{"no ip", "1.2.3.4", false, "4c:20:b8:ab:87:1b", false},
+		{"no mac", "1.2.3.4", false, "4c:20:b8:ab:87:1b", false},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			ip := net.ParseIP(tc.ip)
+			if ip == nil {
+				t.Fatal("missing IP")
+			}
+			hw, err := net.ParseMAC(tc.mac)
+			if err != nil {
+				t.Fatal(err)
+			}
+			m := new(dns.Msg)
+			m.SetQuestion("example.com.", dns.TypeA)
+			o := &dns.OPT{Hdr: dns.RR_Header{Name: ".", Rrtype: dns.TypeOPT}}
+			if tc.wantMac {
+				ec1 := &dns.EDNS0_LOCAL{Code: EDNS0_OPTION_MAC, Data: hw}
+				o.Option = append(o.Option, ec1)
+			}
+			if tc.wantIp {
+				ec2 := &dns.EDNS0_SUBNET{Address: ip}
+				o.Option = append(o.Option, ec2)
+			}
+			m.Extra = append(m.Extra, o)
+			gotIP, gotMac := ipAndMacFromMsg(m)
+			if tc.wantMac && gotMac != tc.mac {
+				t.Errorf("mismatch, want: %q, got: %q", tc.mac, gotMac)
+			}
+			if !tc.wantMac && gotMac != "" {
+				t.Errorf("unexpected mac: %q", gotMac)
+			}
+			if tc.wantIp && gotIP != tc.ip {
+				t.Errorf("mismatch, want: %q, got: %q", tc.ip, gotIP)
+			}
+			if !tc.wantIp && gotIP != "" {
+				t.Errorf("unexpected ip: %q", gotIP)
+			}
+		})
+	}
+}
+
+func Test_remoteAddrFromMsg(t *testing.T) {
+	loopbackIP := net.ParseIP("127.0.0.1")
+	tests := []struct {
+		name string
+		addr net.Addr
+		ci   *ctrld.ClientInfo
+		want string
+	}{
+		{"tcp", &net.TCPAddr{IP: loopbackIP, Port: 12345}, &ctrld.ClientInfo{IP: "192.168.1.10"}, "192.168.1.10:12345"},
+		{"udp", &net.UDPAddr{IP: loopbackIP, Port: 12345}, &ctrld.ClientInfo{IP: "192.168.1.11"}, "192.168.1.11:12345"},
+		{"nil client info", &net.UDPAddr{IP: loopbackIP, Port: 12345}, nil, "127.0.0.1:12345"},
+		{"empty ip", &net.UDPAddr{IP: loopbackIP, Port: 12345}, &ctrld.ClientInfo{}, "127.0.0.1:12345"},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			addr := spoofRemoteAddr(tc.addr, tc.ci)
+			if addr.String() != tc.want {
+				t.Errorf("unexpected result, want: %q, got: %q", tc.want, addr.String())
+			}
+		})
+	}
+}
+
+func Test_ipFromARPA(t *testing.T) {
+	tests := []struct {
+		IP   string
+		ARPA string
+	}{
+		{"1.2.3.4", "4.3.2.1.in-addr.arpa."},
+		{"245.110.36.114", "114.36.110.245.in-addr.arpa."},
+		{"::ffff:12.34.56.78", "78.56.34.12.in-addr.arpa."},
+		{"::1", "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa."},
+		{"1::", "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.ip6.arpa."},
+		{"1234:567::89a:bcde", "e.d.c.b.a.9.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.7.6.5.0.4.3.2.1.ip6.arpa."},
+		{"1234:567:fefe:bcbc:adad:9e4a:89a:bcde", "e.d.c.b.a.9.8.0.a.4.e.9.d.a.d.a.c.b.c.b.e.f.e.f.7.6.5.0.4.3.2.1.ip6.arpa."},
+		{"", "asd.in-addr.arpa."},
+		{"", "asd.ip6.arpa."},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.IP, func(t *testing.T) {
+			t.Parallel()
+			if got := ipFromARPA(tc.ARPA); !got.Equal(net.ParseIP(tc.IP)) {
+				t.Errorf("unexpected ip, want: %s, got: %s", tc.IP, got)
+			}
+		})
+	}
+}
+
+func newDnsMsgWithClientIP(ip string) *dns.Msg {
+	m := new(dns.Msg)
+	m.SetQuestion("example.com.", dns.TypeA)
+	o := &dns.OPT{Hdr: dns.RR_Header{Name: ".", Rrtype: dns.TypeOPT}}
+	o.Option = append(o.Option, &dns.EDNS0_SUBNET{Address: net.ParseIP(ip)})
+	m.Extra = append(m.Extra, o)
+	return m
+}
+
+func Test_stripClientSubnet(t *testing.T) {
+	tests := []struct {
+		name       string
+		msg        *dns.Msg
+		wantSubnet bool
+	}{
+		{"no edns0", new(dns.Msg), false},
+		{"loopback IP v4", newDnsMsgWithClientIP("127.0.0.1"), false},
+		{"loopback IP v6", newDnsMsgWithClientIP("::1"), false},
+		{"private IP v4", newDnsMsgWithClientIP("192.168.1.123"), false},
+		{"private IP v6", newDnsMsgWithClientIP("fd12:3456:789a:1::1"), false},
+		{"public IP", newDnsMsgWithClientIP("1.1.1.1"), true},
+		{"invalid IP", newDnsMsgWithClientIP(""), true},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			stripClientSubnet(tc.msg)
+			hasSubnet := false
+			if opt := tc.msg.IsEdns0(); opt != nil {
+				for _, s := range opt.Option {
+					if _, ok := s.(*dns.EDNS0_SUBNET); ok {
+						hasSubnet = true
+					}
+				}
+			}
+			if tc.wantSubnet != hasSubnet {
+				t.Errorf("unexpected result, want: %v, got: %v", tc.wantSubnet, hasSubnet)
+			}
+		})
+	}
+}
+
+func newDnsMsgWithHostname(hostname string, typ uint16) *dns.Msg {
+	m := new(dns.Msg)
+	m.SetQuestion(hostname, typ)
+	return m
+}
+
+func Test_isLanHostnameQuery(t *testing.T) {
+	tests := []struct {
+		name               string
+		msg                *dns.Msg
+		isLanHostnameQuery bool
+	}{
+		{"A", newDnsMsgWithHostname("foo", dns.TypeA), true},
+		{"AAAA", newDnsMsgWithHostname("foo", dns.TypeAAAA), true},
+		{"A not LAN", newDnsMsgWithHostname("example.com", dns.TypeA), false},
+		{"AAAA not LAN", newDnsMsgWithHostname("example.com", dns.TypeAAAA), false},
+		{"Not A or AAAA", newDnsMsgWithHostname("foo", dns.TypeTXT), false},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := isLanHostnameQuery(tc.msg); tc.isLanHostnameQuery != got {
+				t.Errorf("unexpected result, want: %v, got: %v", tc.isLanHostnameQuery, got)
+			}
+		})
+	}
+}
+
+func newDnsMsgPtr(ip string, t *testing.T) *dns.Msg {
+	t.Helper()
+	m := new(dns.Msg)
+	ptr, err := dns.ReverseAddr(ip)
+	if err != nil {
+		t.Fatal(err)
+	}
+	m.SetQuestion(ptr, dns.TypePTR)
+	return m
+}
+
+func Test_isPrivatePtrLookup(t *testing.T) {
+	tests := []struct {
+		name               string
+		msg                *dns.Msg
+		isPrivatePtrLookup bool
+	}{
+		// RFC 1918 allocates 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as
+		{"10.0.0.0/8", newDnsMsgPtr("10.0.0.123", t), true},
+		{"172.16.0.0/12", newDnsMsgPtr("172.16.0.123", t), true},
+		{"192.168.0.0/16", newDnsMsgPtr("192.168.1.123", t), true},
+		{"CGNAT", newDnsMsgPtr("100.66.27.28", t), true},
+		{"Loopback", newDnsMsgPtr("127.0.0.1", t), true},
+		{"Link Local Unicast", newDnsMsgPtr("fe80::69f6:e16e:8bdb:433f", t), true},
+		{"Public IP", newDnsMsgPtr("8.8.8.8", t), false},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := isPrivatePtrLookup(tc.msg); tc.isPrivatePtrLookup != got {
+				t.Errorf("unexpected result, want: %v, got: %v", tc.isPrivatePtrLookup, got)
+			}
+		})
+	}
+}
+
+func Test_isWanClient(t *testing.T) {
+	tests := []struct {
+		name        string
+		addr        net.Addr
+		isWanClient bool
+	}{
+		// RFC 1918 allocates 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as
+		{"10.0.0.0/8", &net.UDPAddr{IP: net.ParseIP("10.0.0.123")}, false},
+		{"172.16.0.0/12", &net.UDPAddr{IP: net.ParseIP("172.16.0.123")}, false},
+		{"192.168.0.0/16", &net.UDPAddr{IP: net.ParseIP("192.168.1.123")}, false},
+		{"CGNAT", &net.UDPAddr{IP: net.ParseIP("100.66.27.28")}, false},
+		{"Loopback", &net.UDPAddr{IP: net.ParseIP("127.0.0.1")}, false},
+		{"Link Local Unicast", &net.UDPAddr{IP: net.ParseIP("fe80::69f6:e16e:8bdb:433f")}, false},
+		{"Public", &net.UDPAddr{IP: net.ParseIP("8.8.8.8")}, true},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := isWanClient(tc.addr); tc.isWanClient != got {
+				t.Errorf("unexpected result, want: %v, got: %v", tc.isWanClient, got)
+			}
+		})
+	}
+}

cmd/cli/library.go

@@ -0,0 +1,19 @@
+package cli
+
+// AppCallback provides hooks for injecting certain functionalities
+// from mobile platforms to main ctrld cli.
+type AppCallback struct {
+	HostName   func() string
+	LanIp      func() string
+	MacAddress func() string
+	Exit       func(error string)
+}
+
+// AppConfig allows overwriting ctrld cli flags from mobile platforms.
+type AppConfig struct {
+	CdUID         string
+	HomeDir       string
+	UpstreamProto string
+	Verbose       int
+	LogPath       string
+}

cmd/cli/loop.go

@@ -0,0 +1,141 @@
+package cli
+
+import (
+	"context"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/miekg/dns"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+const (
+	loopTestDomain = ".test"
+	loopTestQtype  = dns.TypeTXT
+)
+
+// newLoopGuard returns new loopGuard.
+func newLoopGuard() *loopGuard {
+	return &loopGuard{inflight: make(map[string]struct{})}
+}
+
+// loopGuard guards against DNS loop, ensuring only one query
+// for a given domain is processed at a time.
+type loopGuard struct {
+	mu       sync.Mutex
+	inflight map[string]struct{}
+}
+
+// TryLock marks the domain as being processed.
+func (lg *loopGuard) TryLock(domain string) bool {
+	lg.mu.Lock()
+	defer lg.mu.Unlock()
+	if _, inflight := lg.inflight[domain]; !inflight {
+		lg.inflight[domain] = struct{}{}
+		return true
+	}
+	return false
+}
+
+// Unlock marks the domain as being done.
+func (lg *loopGuard) Unlock(domain string) {
+	lg.mu.Lock()
+	defer lg.mu.Unlock()
+	delete(lg.inflight, domain)
+}
+
+// isLoop reports whether the given upstream config is detected as having DNS loop.
+func (p *prog) isLoop(uc *ctrld.UpstreamConfig) bool {
+	p.loopMu.Lock()
+	defer p.loopMu.Unlock()
+	return p.loop[uc.UID()]
+}
+
+// detectLoop checks if the given DNS message is initialized sent by ctrld.
+// If yes, marking the corresponding upstream as loop, prevent infinite DNS
+// forwarding loop.
+//
+// See p.checkDnsLoop for more details how it works.
+func (p *prog) detectLoop(msg *dns.Msg) {
+	if len(msg.Question) != 1 {
+		return
+	}
+	q := msg.Question[0]
+	if q.Qtype != loopTestQtype {
+		return
+	}
+	unFQDNname := strings.TrimSuffix(q.Name, ".")
+	uid := strings.TrimSuffix(unFQDNname, loopTestDomain)
+	p.loopMu.Lock()
+	if _, loop := p.loop[uid]; loop {
+		p.loop[uid] = loop
+	}
+	p.loopMu.Unlock()
+}
+
+// checkDnsLoop sends a message to check if there's any DNS forwarding loop
+// with all the upstreams. The way it works based on dnsmasq --dns-loop-detect.
+//
+// - Generating a TXT test query and sending it to all upstream.
+// - The test query is formed by upstream UID and test domain: <uid>.test
+// - If the test query returns to ctrld, mark the corresponding upstream as loop (see p.detectLoop).
+//
+// See: https://thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html
+func (p *prog) checkDnsLoop() {
+	mainLog.Load().Debug().Msg("start checking DNS loop")
+	upstream := make(map[string]*ctrld.UpstreamConfig)
+	p.loopMu.Lock()
+	for n, uc := range p.cfg.Upstream {
+		if p.um.isDown("upstream." + n) {
+			continue
+		}
+		// Do not send test query to external upstream.
+		if !canBeLocalUpstream(uc.Domain) {
+			mainLog.Load().Debug().Msgf("skipping external: upstream.%s", n)
+			continue
+		}
+		uid := uc.UID()
+		p.loop[uid] = false
+		upstream[uid] = uc
+	}
+	p.loopMu.Unlock()
+
+	for uid := range p.loop {
+		msg := loopTestMsg(uid)
+		uc := upstream[uid]
+		resolver, err := ctrld.NewResolver(uc)
+		if err != nil {
+			mainLog.Load().Warn().Err(err).Msgf("could not perform loop check for upstream: %q, endpoint: %q", uc.Name, uc.Endpoint)
+			continue
+		}
+		if _, err := resolver.Resolve(context.Background(), msg); err != nil {
+			mainLog.Load().Warn().Err(err).Msgf("could not send DNS loop check query for upstream: %q, endpoint: %q", uc.Name, uc.Endpoint)
+		}
+	}
+	mainLog.Load().Debug().Msg("end checking DNS loop")
+}
+
+// checkDnsLoopTicker performs p.checkDnsLoop every minute.
+func (p *prog) checkDnsLoopTicker(ctx context.Context) {
+	timer := time.NewTicker(time.Minute)
+	defer timer.Stop()
+	for {
+		select {
+		case <-p.stopCh:
+			return
+		case <-ctx.Done():
+			return
+		case <-timer.C:
+			p.checkDnsLoop()
+		}
+	}
+}
+
+// loopTestMsg generates DNS message for checking loop.
+func loopTestMsg(uid string) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(uid+loopTestDomain), loopTestQtype)
+	return msg
+}

cmd/cli/loop_test.go

@@ -0,0 +1,42 @@
+package cli
+
+import (
+	"sync"
+	"sync/atomic"
+	"testing"
+)
+
+func Test_loopGuard(t *testing.T) {
+	lg := newLoopGuard()
+	key := "foo"
+
+	var i atomic.Int64
+	var started atomic.Int64
+	n := 1000
+	do := func() {
+		locked := lg.TryLock(key)
+		defer lg.Unlock(key)
+		started.Add(1)
+		for started.Load() < 2 {
+			// Wait until at least 2 goroutines started, otherwise, on system with heavy load,
+			// or having only 1 CPU, all goroutines can be scheduled to run consequently.
+		}
+		if locked {
+			i.Add(1)
+		}
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(n)
+	for i := 0; i < n; i++ {
+		go func() {
+			defer wg.Done()
+			do()
+		}()
+	}
+	wg.Wait()
+
+	if i.Load() == int64(n) {
+		t.Fatalf("i must not be increased %d times", n)
+	}
+}

cmd/cli/main.go

@@ -0,0 +1,172 @@
+package cli
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"sync/atomic"
+	"time"
+
+	"github.com/kardianos/service"
+	"github.com/rs/zerolog"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+var (
+	configPath        string
+	configBase64      string
+	daemon            bool
+	listenAddress     string
+	primaryUpstream   string
+	secondaryUpstream string
+	domains           []string
+	logPath           string
+	homedir           string
+	cacheSize         int
+	cfg               ctrld.Config
+	verbose           int
+	silent            bool
+	cdUID             string
+	cdOrg             string
+	cdDev             bool
+	iface             string
+	ifaceStartStop    string
+	nextdns           string
+	cdUpstreamProto   string
+
+	mainLog       atomic.Pointer[zerolog.Logger]
+	consoleWriter zerolog.ConsoleWriter
+	noConfigStart bool
+)
+
+const (
+	cdUidFlagName   = "cd"
+	cdOrgFlagName   = "cd-org"
+	nextdnsFlagName = "nextdns"
+)
+
+func init() {
+	l := zerolog.New(io.Discard)
+	mainLog.Store(&l)
+}
+
+func Main() {
+	ctrld.InitConfig(v, "ctrld")
+	initCLI()
+	if err := rootCmd.Execute(); err != nil {
+		mainLog.Load().Error().Msg(err.Error())
+		os.Exit(1)
+	}
+}
+
+func normalizeLogFilePath(logFilePath string) string {
+	if logFilePath == "" || filepath.IsAbs(logFilePath) || service.Interactive() {
+		return logFilePath
+	}
+	if homedir != "" {
+		return filepath.Join(homedir, logFilePath)
+	}
+	dir, _ := userHomeDir()
+	if dir == "" {
+		return logFilePath
+	}
+	return filepath.Join(dir, logFilePath)
+}
+
+// initConsoleLogging initializes console logging, then storing to mainLog.
+func initConsoleLogging() {
+	consoleWriter = zerolog.NewConsoleWriter(func(w *zerolog.ConsoleWriter) {
+		w.TimeFormat = time.StampMilli
+	})
+	multi := zerolog.MultiLevelWriter(consoleWriter)
+	l := mainLog.Load().Output(multi).With().Timestamp().Logger()
+	mainLog.Store(&l)
+	switch {
+	case silent:
+		zerolog.SetGlobalLevel(zerolog.NoLevel)
+	case verbose == 1:
+		zerolog.SetGlobalLevel(zerolog.InfoLevel)
+	case verbose > 1:
+		zerolog.SetGlobalLevel(zerolog.DebugLevel)
+	default:
+		zerolog.SetGlobalLevel(zerolog.NoticeLevel)
+	}
+}
+
+// initLogging initializes global logging setup.
+func initLogging() {
+	zerolog.TimeFieldFormat = time.RFC3339 + ".000"
+	initLoggingWithBackup(true)
+}
+
+// initLoggingWithBackup initializes log setup base on current config.
+// If doBackup is true, backup old log file with ".1" suffix.
+//
+// This is only used in runCmd for special handling in case of logging config
+// change in cd mode. Without special reason, the caller should use initLogging
+// wrapper instead of calling this function directly.
+func initLoggingWithBackup(doBackup bool) {
+	writers := []io.Writer{io.Discard}
+	if logFilePath := normalizeLogFilePath(cfg.Service.LogPath); logFilePath != "" {
+		// Create parent directory if necessary.
+		if err := os.MkdirAll(filepath.Dir(logFilePath), 0750); err != nil {
+			mainLog.Load().Error().Msgf("failed to create log path: %v", err)
+			os.Exit(1)
+		}
+
+		// Default open log file in append mode.
+		flags := os.O_CREATE | os.O_RDWR | os.O_APPEND
+		if doBackup {
+			// Backup old log file with .1 suffix.
+			if err := os.Rename(logFilePath, logFilePath+".1"); err != nil && !os.IsNotExist(err) {
+				mainLog.Load().Error().Msgf("could not backup old log file: %v", err)
+			} else {
+				// Backup was created, set flags for truncating old log file.
+				flags = os.O_CREATE | os.O_RDWR
+			}
+		}
+		logFile, err := os.OpenFile(logFilePath, flags, os.FileMode(0o600))
+		if err != nil {
+			mainLog.Load().Error().Msgf("failed to create log file: %v", err)
+			os.Exit(1)
+		}
+		writers = append(writers, logFile)
+	}
+	writers = append(writers, consoleWriter)
+	multi := zerolog.MultiLevelWriter(writers...)
+	l := mainLog.Load().Output(multi).With().Logger()
+	mainLog.Store(&l)
+	// TODO: find a better way.
+	ctrld.ProxyLogger.Store(&l)
+
+	zerolog.SetGlobalLevel(zerolog.NoticeLevel)
+	logLevel := cfg.Service.LogLevel
+	switch {
+	case silent:
+		zerolog.SetGlobalLevel(zerolog.NoLevel)
+		return
+	case verbose == 1:
+		logLevel = "info"
+	case verbose > 1:
+		logLevel = "debug"
+	}
+	if logLevel == "" {
+		return
+	}
+	level, err := zerolog.ParseLevel(logLevel)
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not set log level")
+		return
+	}
+	zerolog.SetGlobalLevel(level)
+}
+
+func initCache() {
+	if !cfg.Service.CacheEnable {
+		return
+	}
+	if cfg.Service.CacheSize == 0 {
+		cfg.Service.CacheSize = 4096
+	}
+}

cmd/cli/main_test.go

@@ -0,0 +1,17 @@
+package cli
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/rs/zerolog"
+)
+
+var logOutput strings.Builder
+
+func TestMain(m *testing.M) {
+	l := zerolog.New(&logOutput)
+	mainLog.Store(&l)
+	os.Exit(m.Run())
+}

cmd/cli/metrics.go

@@ -0,0 +1,150 @@
+package cli
+
+import (
+	"context"
+	"encoding/json"
+	"net"
+	"net/http"
+	"runtime"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/prometheus/prom2json"
+)
+
+// metricsServer represents a server to expose Prometheus metrics via HTTP.
+type metricsServer struct {
+	server  *http.Server
+	mux     *http.ServeMux
+	reg     *prometheus.Registry
+	addr    string
+	started bool
+}
+
+// newMetricsServer returns new metrics server.
+func newMetricsServer(addr string, reg *prometheus.Registry) (*metricsServer, error) {
+	mux := http.NewServeMux()
+	ms := &metricsServer{
+		server: &http.Server{Handler: mux},
+		mux:    mux,
+		reg:    reg,
+	}
+	ms.addr = addr
+	ms.registerMetricsServerHandler()
+	return ms, nil
+}
+
+// register adds handlers for given pattern.
+func (ms *metricsServer) register(pattern string, handler http.Handler) {
+	ms.mux.Handle(pattern, handler)
+}
+
+// registerMetricsServerHandler adds handlers for metrics server.
+func (ms *metricsServer) registerMetricsServerHandler() {
+	ms.register("/metrics", promhttp.HandlerFor(
+		ms.reg,
+		promhttp.HandlerOpts{
+			EnableOpenMetrics: true,
+			Timeout:           10 * time.Second,
+		},
+	))
+	ms.register("/metrics/json", jsonResponse(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		g := prometheus.ToTransactionalGatherer(ms.reg)
+		mfs, done, err := g.Gather()
+		defer done()
+		if err != nil {
+			msg := "could not gather metrics"
+			mainLog.Load().Warn().Err(err).Msg(msg)
+			http.Error(w, msg, http.StatusInternalServerError)
+			return
+		}
+		result := make([]*prom2json.Family, 0, len(mfs))
+		for _, mf := range mfs {
+			result = append(result, prom2json.NewFamily(mf))
+		}
+		if err := json.NewEncoder(w).Encode(result); err != nil {
+			msg := "could not marshal metrics result"
+			mainLog.Load().Warn().Err(err).Msg(msg)
+			http.Error(w, msg, http.StatusInternalServerError)
+			return
+		}
+	})))
+}
+
+// start runs the metricsServer.
+func (ms *metricsServer) start() error {
+	listener, err := net.Listen("tcp", ms.addr)
+	if err != nil {
+		return err
+	}
+	go ms.server.Serve(listener)
+	ms.started = true
+	return nil
+}
+
+// stop shutdowns the metricsServer within 2 seconds timeout.
+func (ms *metricsServer) stop() error {
+	if !ms.started {
+		return nil
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*1)
+	defer cancel()
+	return ms.server.Shutdown(ctx)
+}
+
+// runMetricsServer initializes metrics stats and runs the metrics server if enabled.
+func (p *prog) runMetricsServer(ctx context.Context, reloadCh chan struct{}) {
+	if !p.metricsEnabled() {
+		return
+	}
+
+	// Reset all stats.
+	statsVersion.Reset()
+	statsQueriesCount.Reset()
+	statsClientQueriesCount.Reset()
+
+	reg := prometheus.NewRegistry()
+	// Register queries count stats if enabled.
+	if cfg.Service.MetricsQueryStats {
+		reg.MustRegister(statsQueriesCount)
+		reg.MustRegister(statsClientQueriesCount)
+	}
+
+	addr := p.cfg.Service.MetricsListener
+	ms, err := newMetricsServer(addr, reg)
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not create new metrics server")
+		return
+	}
+	// Only start listener address if defined.
+	if addr != "" {
+		// Go runtime stats.
+		reg.MustRegister(collectors.NewBuildInfoCollector())
+		reg.MustRegister(collectors.NewGoCollector(
+			collectors.WithGoCollectorRuntimeMetrics(collectors.MetricsAll),
+		))
+		// ctrld stats.
+		reg.MustRegister(statsVersion)
+		statsVersion.WithLabelValues(commit, runtime.Version(), curVersion()).Inc()
+		reg.MustRegister(statsTimeStart)
+		statsTimeStart.Set(float64(time.Now().Unix()))
+		mainLog.Load().Debug().Msgf("starting metrics server on: %s", addr)
+		if err := ms.start(); err != nil {
+			mainLog.Load().Warn().Err(err).Msg("could not start metrics server")
+			return
+		}
+	}
+
+	select {
+	case <-p.stopCh:
+	case <-ctx.Done():
+	case <-reloadCh:
+	}
+
+	if err := ms.stop(); err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not stop metrics server")
+		return
+	}
+}

cmd/cli/net_darwin.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import (
 	"bufio"
@@ -17,7 +17,7 @@ func patchNetIfaceName(iface *net.Interface) error {
 
 	if name := networkServiceName(iface.Name, bytes.NewReader(b)); name != "" {
 		iface.Name = name
-		mainLog.Debug().Str("network_service", name).Msg("found network service name for interface")
+		mainLog.Load().Debug().Str("network_service", name).Msg("found network service name for interface")
 	}
 	return nil
 }

cmd/cli/net_darwin_test.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import (
 	"strings"

cmd/cli/net_others.go

@@ -1,6 +1,6 @@
 //go:build !darwin
 
-package main
+package cli
 
 import "net"
 

cmd/cli/netlink_linux.go

@@ -0,0 +1,34 @@
+package cli
+
+import (
+	"context"
+
+	"github.com/vishvananda/netlink"
+	"golang.org/x/sys/unix"
+)
+
+func (p *prog) watchLinkState(ctx context.Context) {
+	ch := make(chan netlink.LinkUpdate)
+	done := make(chan struct{})
+	defer close(done)
+	if err := netlink.LinkSubscribe(ch, done); err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not subscribe link")
+		return
+	}
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case lu := <-ch:
+			if lu.Change == 0xFFFFFFFF {
+				continue
+			}
+			if lu.Change&unix.IFF_UP != 0 {
+				mainLog.Load().Debug().Msgf("link state changed, re-bootstrapping")
+				for _, uc := range p.cfg.Upstream {
+					uc.ReBootstrap()
+				}
+			}
+		}
+	}
+}

cmd/cli/netlink_others.go

@@ -0,0 +1,7 @@
+//go:build !linux
+
+package cli
+
+import "context"
+
+func (p *prog) watchLinkState(ctx context.Context) {}

cmd/cli/network_manager_linux.go

@@ -1,8 +1,9 @@
-package main
+package cli
 
 import (
 	"context"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"time"
 
@@ -16,45 +17,56 @@ const (
 dns=none
 systemd-resolved=false
 `
-	nmSystemdUnitName   = "NetworkManager.service"
+	nmSystemdUnitName = "NetworkManager.service"
-	systemdEnabledState = "enabled"
 )
 
 var networkManagerCtrldConfFile = filepath.Join(nmConfDir, nmCtrldConfFilename)
 
+// hasNetworkManager reports whether NetworkManager executable found.
+func hasNetworkManager() bool {
+	exe, _ := exec.LookPath("NetworkManager")
+	return exe != ""
+}
+
 func setupNetworkManager() error {
+	if !hasNetworkManager() {
+		return nil
+	}
 	if content, _ := os.ReadFile(nmCtrldConfContent); string(content) == nmCtrldConfContent {
-		mainLog.Debug().Msg("NetworkManager already setup, nothing to do")
+		mainLog.Load().Debug().Msg("NetworkManager already setup, nothing to do")
 		return nil
 	}
 	err := os.WriteFile(networkManagerCtrldConfFile, []byte(nmCtrldConfContent), os.FileMode(0644))
 	if os.IsNotExist(err) {
-		mainLog.Debug().Msg("NetworkManager is not available")
+		mainLog.Load().Debug().Msg("NetworkManager is not available")
 		return nil
 	}
 	if err != nil {
-		mainLog.Debug().Err(err).Msg("could not write NetworkManager ctrld config file")
+		mainLog.Load().Debug().Err(err).Msg("could not write NetworkManager ctrld config file")
 		return err
 	}
 
 	reloadNetworkManager()
-	mainLog.Debug().Msg("setup NetworkManager done")
+	mainLog.Load().Debug().Msg("setup NetworkManager done")
 	return nil
 }
 
 func restoreNetworkManager() error {
+	if !hasNetworkManager() {
+		return nil
+	}
 	err := os.Remove(networkManagerCtrldConfFile)
 	if os.IsNotExist(err) {
-		mainLog.Debug().Msg("NetworkManager is not available")
+		mainLog.Load().Debug().Msg("NetworkManager is not available")
 		return nil
 	}
 	if err != nil {
-		mainLog.Debug().Err(err).Msg("could not remove NetworkManager ctrld config file")
+		mainLog.Load().Debug().Err(err).Msg("could not remove NetworkManager ctrld config file")
 		return err
 	}
 
 	reloadNetworkManager()
-	mainLog.Debug().Msg("restore NetworkManager done")
+	mainLog.Load().Debug().Msg("restore NetworkManager done")
 	return nil
 }
 
@@ -63,14 +75,15 @@ func reloadNetworkManager() {
 	defer cancel()
 	conn, err := dbus.NewSystemConnectionContext(ctx)
 	if err != nil {
-		mainLog.Error().Err(err).Msg("could not create new system connection")
+		mainLog.Load().Error().Err(err).Msg("could not create new system connection")
 		return
 	}
 	defer conn.Close()
 
 	waitCh := make(chan string)
 	if _, err := conn.ReloadUnitContext(ctx, nmSystemdUnitName, "ignore-dependencies", waitCh); err != nil {
-		mainLog.Debug().Err(err).Msg("could not reload NetworkManager")
+		mainLog.Load().Debug().Err(err).Msg("could not reload NetworkManager")
+		return
 	}
 	<-waitCh
 }

cmd/cli/network_manager_others.go

@@ -1,6 +1,6 @@
 //go:build !linux
 
-package main
+package cli
 
 func setupNetworkManager() error {
 	reloadNetworkManager()

cmd/cli/nextdns.go

@@ -0,0 +1,31 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+const nextdnsURL = "https://dns.nextdns.io"
+
+func generateNextDNSConfig(uid string) {
+	if uid == "" {
+		return
+	}
+	mainLog.Load().Info().Msg("generating ctrld config for NextDNS resolver")
+	cfg = ctrld.Config{
+		Listener: map[string]*ctrld.ListenerConfig{
+			"0": {
+				IP:   "0.0.0.0",
+				Port: 53,
+			},
+		},
+		Upstream: map[string]*ctrld.UpstreamConfig{
+			"0": {
+				Type:     ctrld.ResolverTypeDOH3,
+				Endpoint: fmt.Sprintf("%s/%s", nextdnsURL, uid),
+				Timeout:  5000,
+			},
+		},
+	}
+}

cmd/cli/os_darwin.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import (
 	"net"
@@ -12,7 +12,7 @@ import (
 func allocateIP(ip string) error {
 	cmd := exec.Command("ifconfig", "lo0", "alias", ip, "up")
 	if err := cmd.Run(); err != nil {
-		mainLog.Error().Err(err).Msg("allocateIP failed")
+		mainLog.Load().Error().Err(err).Msg("allocateIP failed")
 		return err
 	}
 	return nil
@@ -21,7 +21,7 @@ func allocateIP(ip string) error {
 func deAllocateIP(ip string) error {
 	cmd := exec.Command("ifconfig", "lo0", "-alias", ip)
 	if err := cmd.Run(); err != nil {
-		mainLog.Error().Err(err).Msg("deAllocateIP failed")
+		mainLog.Load().Error().Err(err).Msg("deAllocateIP failed")
 		return err
 	}
 	return nil
@@ -36,7 +36,7 @@ func setDNS(iface *net.Interface, nameservers []string) error {
 	args = append(args, nameservers...)
 
 	if err := exec.Command(cmd, args...).Run(); err != nil {
-		mainLog.Error().Err(err).Msgf("setDNS failed, ips = %q", nameservers)
+		mainLog.Load().Error().Err(err).Msgf("setDNS failed, ips = %q", nameservers)
 		return err
 	}
 	return nil
@@ -48,7 +48,7 @@ func resetDNS(iface *net.Interface) error {
 	args := []string{"-setdnsservers", iface.Name, "empty"}
 
 	if err := exec.Command(cmd, args...).Run(); err != nil {
-		mainLog.Error().Err(err).Msgf("resetDNS failed")
+		mainLog.Load().Error().Err(err).Msgf("resetDNS failed")
 		return err
 	}
 	return nil

cmd/cli/os_freebsd.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import (
 	"net"
@@ -14,7 +14,7 @@ import (
 func allocateIP(ip string) error {
 	cmd := exec.Command("ifconfig", "lo0", ip, "alias")
 	if err := cmd.Run(); err != nil {
-		mainLog.Error().Err(err).Msg("allocateIP failed")
+		mainLog.Load().Error().Err(err).Msg("allocateIP failed")
 		return err
 	}
 	return nil
@@ -23,7 +23,7 @@ func allocateIP(ip string) error {
 func deAllocateIP(ip string) error {
 	cmd := exec.Command("ifconfig", "lo0", ip, "-alias")
 	if err := cmd.Run(); err != nil {
-		mainLog.Error().Err(err).Msg("deAllocateIP failed")
+		mainLog.Load().Error().Err(err).Msg("deAllocateIP failed")
 		return err
 	}
 	return nil
@@ -33,7 +33,7 @@ func deAllocateIP(ip string) error {
 func setDNS(iface *net.Interface, nameservers []string) error {
 	r, err := dns.NewOSConfigurator(logf, iface.Name)
 	if err != nil {
-		mainLog.Error().Err(err).Msg("failed to create DNS OS configurator")
+		mainLog.Load().Error().Err(err).Msg("failed to create DNS OS configurator")
 		return err
 	}
 
@@ -43,7 +43,7 @@ func setDNS(iface *net.Interface, nameservers []string) error {
 	}
 
 	if err := r.SetDNS(dns.OSConfig{Nameservers: ns}); err != nil {
-		mainLog.Error().Err(err).Msg("failed to set DNS")
+		mainLog.Load().Error().Err(err).Msg("failed to set DNS")
 		return err
 	}
 	return nil
@@ -52,12 +52,12 @@ func setDNS(iface *net.Interface, nameservers []string) error {
 func resetDNS(iface *net.Interface) error {
 	r, err := dns.NewOSConfigurator(logf, iface.Name)
 	if err != nil {
-		mainLog.Error().Err(err).Msg("failed to create DNS OS configurator")
+		mainLog.Load().Error().Err(err).Msg("failed to create DNS OS configurator")
 		return err
 	}
 
 	if err := r.Close(); err != nil {
-		mainLog.Error().Err(err).Msg("failed to rollback DNS setting")
+		mainLog.Load().Error().Err(err).Msg("failed to rollback DNS setting")
 		return err
 	}
 	return nil

cmd/cli/os_linux.go

@@ -0,0 +1,367 @@
+package cli
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net"
+	"net/netip"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+	"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
+	"github.com/insomniacslk/dhcp/dhcpv6"
+	"github.com/insomniacslk/dhcp/dhcpv6/client6"
+	"tailscale.com/util/dnsname"
+
+	"github.com/Control-D-Inc/ctrld/internal/dns"
+	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
+	"github.com/Control-D-Inc/ctrld/internal/resolvconffile"
+)
+
+const (
+	resolvConfPath            = "/etc/resolv.conf"
+	resolvConfBackupFailedMsg = "open /etc/resolv.pre-ctrld-backup.conf: read-only file system"
+)
+
+// allocate loopback ip
+// sudo ip a add 127.0.0.2/24 dev lo
+func allocateIP(ip string) error {
+	cmd := exec.Command("ip", "a", "add", ip+"/24", "dev", "lo")
+	if out, err := cmd.CombinedOutput(); err != nil {
+		mainLog.Load().Error().Err(err).Msgf("allocateIP failed: %s", string(out))
+		return err
+	}
+	return nil
+}
+
+func deAllocateIP(ip string) error {
+	cmd := exec.Command("ip", "a", "del", ip+"/24", "dev", "lo")
+	if err := cmd.Run(); err != nil {
+		mainLog.Load().Error().Err(err).Msg("deAllocateIP failed")
+		return err
+	}
+	return nil
+}
+
+const maxSetDNSAttempts = 5
+
+// set the dns server for the provided network interface
+func setDNS(iface *net.Interface, nameservers []string) error {
+	r, err := dns.NewOSConfigurator(logf, iface.Name)
+	if err != nil {
+		mainLog.Load().Error().Err(err).Msg("failed to create DNS OS configurator")
+		return err
+	}
+
+	ns := make([]netip.Addr, 0, len(nameservers))
+	for _, nameserver := range nameservers {
+		ns = append(ns, netip.MustParseAddr(nameserver))
+	}
+
+	osConfig := dns.OSConfig{
+		Nameservers:   ns,
+		SearchDomains: []dnsname.FQDN{},
+	}
+	defer func() {
+		if r.Mode() == "direct" {
+			go watchResolveConf(osConfig)
+		}
+	}()
+
+	trySystemdResolve := false
+	for i := 0; i < maxSetDNSAttempts; i++ {
+		if err := r.SetDNS(osConfig); err != nil {
+			if strings.Contains(err.Error(), "Rejected send message") &&
+				strings.Contains(err.Error(), "org.freedesktop.network1.Manager") {
+				mainLog.Load().Warn().Msg("Interfaces are managed by systemd-networkd, switch to systemd-resolve for setting DNS")
+				trySystemdResolve = true
+				break
+			}
+			// This error happens on read-only file system, which causes ctrld failed to create backup
+			// for /etc/resolv.conf file. It is ok, because the DNS is still set anyway, and restore
+			// DNS will fallback to use DHCP if there's no backup /etc/resolv.conf file.
+			// The error format is controlled by us, so checking for error string is fine.
+			// See: ../../internal/dns/direct.go:L278
+			if r.Mode() == "direct" && strings.Contains(err.Error(), resolvConfBackupFailedMsg) {
+				return nil
+			}
+			return err
+		}
+		if useSystemdResolved {
+			if out, err := exec.Command("systemctl", "restart", "systemd-resolved").CombinedOutput(); err != nil {
+				mainLog.Load().Warn().Err(err).Msgf("could not restart systemd-resolved: %s", string(out))
+			}
+		}
+		currentNS := currentDNS(iface)
+		if isSubSet(nameservers, currentNS) {
+			return nil
+		}
+	}
+	if trySystemdResolve {
+		// Stop systemd-networkd and retry setting DNS.
+		if out, err := exec.Command("systemctl", "stop", "systemd-networkd").CombinedOutput(); err != nil {
+			return fmt.Errorf("%s: %w", string(out), err)
+		}
+		args := []string{"--interface=" + iface.Name, "--set-domain=~"}
+		for _, nameserver := range nameservers {
+			args = append(args, "--set-dns="+nameserver)
+		}
+		for i := 0; i < maxSetDNSAttempts; i++ {
+			if out, err := exec.Command("systemd-resolve", args...).CombinedOutput(); err != nil {
+				return fmt.Errorf("%s: %w", string(out), err)
+			}
+			currentNS := currentDNS(iface)
+			if isSubSet(nameservers, currentNS) {
+				return nil
+			}
+			time.Sleep(time.Second)
+		}
+	}
+	mainLog.Load().Debug().Msg("DNS was not set for some reason")
+	return nil
+}
+
+func resetDNS(iface *net.Interface) (err error) {
+	defer func() {
+		if err == nil {
+			return
+		}
+		// Start systemd-networkd if present.
+		if exe, _ := exec.LookPath("/lib/systemd/systemd-networkd"); exe != "" {
+			_ = exec.Command("systemctl", "start", "systemd-networkd").Run()
+		}
+		if r, oerr := dns.NewOSConfigurator(logf, iface.Name); oerr == nil {
+			_ = r.SetDNS(dns.OSConfig{})
+			if err := r.Close(); err != nil {
+				mainLog.Load().Error().Err(err).Msg("failed to rollback DNS setting")
+				return
+			}
+			err = nil
+		}
+	}()
+
+	var ns []string
+	c, err := nclient4.New(iface.Name)
+	if err != nil {
+		return fmt.Errorf("nclient4.New: %w", err)
+	}
+	defer c.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+	defer cancel()
+	lease, err := c.Request(ctx)
+	if err != nil {
+		return fmt.Errorf("nclient4.Request: %w", err)
+	}
+	for _, nameserver := range lease.ACK.DNS() {
+		if nameserver.Equal(net.IPv4zero) {
+			continue
+		}
+		ns = append(ns, nameserver.String())
+	}
+
+	// TODO(cuonglm): handle DHCPv6 properly.
+	if ctrldnet.IPv6Available(ctx) {
+		c := client6.NewClient()
+		conversation, err := c.Exchange(iface.Name)
+		if err != nil && !errAddrInUse(err) {
+			mainLog.Load().Debug().Err(err).Msg("could not exchange DHCPv6")
+		}
+		for _, packet := range conversation {
+			if packet.Type() == dhcpv6.MessageTypeReply {
+				msg, err := packet.GetInnerMessage()
+				if err != nil {
+					mainLog.Load().Debug().Err(err).Msg("could not get inner DHCPv6 message")
+					return nil
+				}
+				nameservers := msg.Options.DNS()
+				for _, nameserver := range nameservers {
+					ns = append(ns, nameserver.String())
+				}
+			}
+		}
+	}
+
+	return ignoringEINTR(func() error {
+		return setDNS(iface, ns)
+	})
+}
+
+func currentDNS(iface *net.Interface) []string {
+	for _, fn := range []getDNS{getDNSByResolvectl, getDNSBySystemdResolved, getDNSByNmcli, resolvconffile.NameServers} {
+		if ns := fn(iface.Name); len(ns) > 0 {
+			return ns
+		}
+	}
+	return nil
+}
+
+func getDNSByResolvectl(iface string) []string {
+	b, err := exec.Command("resolvectl", "dns", "-i", iface).Output()
+	if err != nil {
+		return nil
+	}
+
+	parts := strings.Fields(strings.SplitN(string(b), "%", 2)[0])
+	if len(parts) > 2 {
+		return parts[3:]
+	}
+	return nil
+}
+
+func getDNSBySystemdResolved(iface string) []string {
+	b, err := exec.Command("systemd-resolve", "--status", iface).Output()
+	if err != nil {
+		return nil
+	}
+	return getDNSBySystemdResolvedFromReader(bytes.NewReader(b))
+}
+
+func getDNSBySystemdResolvedFromReader(r io.Reader) []string {
+	scanner := bufio.NewScanner(r)
+	var ret []string
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if len(ret) > 0 {
+			if net.ParseIP(line) != nil {
+				ret = append(ret, line)
+			}
+			continue
+		}
+		after, found := strings.CutPrefix(line, "DNS Servers: ")
+		if !found {
+			continue
+		}
+		if net.ParseIP(after) != nil {
+			ret = append(ret, after)
+		}
+	}
+	return ret
+}
+
+func getDNSByNmcli(iface string) []string {
+	b, err := exec.Command("nmcli", "dev", "show", iface).Output()
+	if err != nil {
+		return nil
+	}
+	s := bufio.NewScanner(bytes.NewReader(b))
+	var dns []string
+	do := func(line string) {
+		parts := strings.SplitN(line, ":", 2)
+		if len(parts) > 1 {
+			dns = append(dns, strings.TrimSpace(parts[1]))
+		}
+	}
+	for s.Scan() {
+		line := s.Text()
+		switch {
+		case strings.HasPrefix(line, "IP4.DNS"):
+			fallthrough
+		case strings.HasPrefix(line, "IP6.DNS"):
+			do(line)
+		}
+	}
+	return dns
+}
+
+func ignoringEINTR(fn func() error) error {
+	for {
+		err := fn()
+		if err != syscall.EINTR {
+			return err
+		}
+	}
+}
+
+// isSubSet reports whether s2 contains all elements of s1.
+func isSubSet(s1, s2 []string) bool {
+	ok := true
+	for _, ns := range s1 {
+		// TODO(cuonglm): use slices.Contains once upgrading to go1.21
+		if sliceContains(s2, ns) {
+			continue
+		}
+		ok = false
+		break
+	}
+	return ok
+}
+
+// sliceContains reports whether v is present in s.
+func sliceContains[S ~[]E, E comparable](s S, v E) bool {
+	return sliceIndex(s, v) >= 0
+}
+
+// sliceIndex returns the index of the first occurrence of v in s,
+// or -1 if not present.
+func sliceIndex[S ~[]E, E comparable](s S, v E) int {
+	for i := range s {
+		if v == s[i] {
+			return i
+		}
+	}
+	return -1
+}
+
+// watchResolveConf watches any changes to /etc/resolv.conf file,
+// and reverting to the original config set by ctrld.
+func watchResolveConf(oc dns.OSConfig) {
+	mainLog.Load().Debug().Msg("start watching /etc/resolv.conf file")
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not create watcher for /etc/resolv.conf")
+		return
+	}
+
+	// We watch /etc instead of /etc/resolv.conf directly,
+	// see: https://github.com/fsnotify/fsnotify#watching-a-file-doesnt-work-well
+	watchDir := filepath.Dir(resolvConfPath)
+	if err := watcher.Add(watchDir); err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not add /etc/resolv.conf to watcher list")
+		return
+	}
+
+	r, err := dns.NewOSConfigurator(func(format string, args ...any) {}, "lo") // interface name does not matter.
+	if err != nil {
+		mainLog.Load().Error().Err(err).Msg("failed to create DNS OS configurator")
+		return
+	}
+
+	for {
+		select {
+		case event, ok := <-watcher.Events:
+			if !ok {
+				return
+			}
+			if event.Name != resolvConfPath { // skip if not /etc/resolv.conf changes.
+				continue
+			}
+			if event.Has(fsnotify.Write) || event.Has(fsnotify.Create) {
+				mainLog.Load().Debug().Msg("/etc/resolv.conf changes detected, reverting to ctrld setting")
+				if err := watcher.Remove(watchDir); err != nil {
+					mainLog.Load().Error().Err(err).Msg("failed to pause watcher")
+					continue
+				}
+				if err := r.SetDNS(oc); err != nil {
+					mainLog.Load().Error().Err(err).Msg("failed to revert /etc/resolv.conf changes")
+				}
+				if err := watcher.Add(watchDir); err != nil {
+					mainLog.Load().Error().Err(err).Msg("failed to continue running watcher")
+					return
+				}
+			}
+		case err, ok := <-watcher.Errors:
+			if !ok {
+				return
+			}
+			mainLog.Load().Err(err).Msg("could not get event for /etc/resolv.conf")
+		}
+	}
+}

cmd/cli/os_linux_test.go

@@ -0,0 +1,23 @@
+package cli
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func Test_getDNSBySystemdResolvedFromReader(t *testing.T) {
+	r := strings.NewReader(`Link 2 (eth0)
+      Current Scopes: DNS
+       LLMNR setting: yes
+MulticastDNS setting: no
+      DNSSEC setting: no
+    DNSSEC supported: no
+         DNS Servers: 8.8.8.8
+                      8.8.4.4`)
+	want := []string{"8.8.8.8", "8.8.4.4"}
+	ns := getDNSBySystemdResolvedFromReader(r)
+	if !reflect.DeepEqual(ns, want) {
+		t.Logf("unexpected result, want: %v, got: %v", want, ns)
+	}
+}

cmd/cli/os_others.go

@@ -1,6 +1,6 @@
 //go:build !linux && !darwin && !freebsd
 
-package main
+package cli
 
 // TODO(cuonglm): implement.
 func allocateIP(ip string) error {

cmd/cli/os_windows.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import (
 	"errors"
@@ -30,12 +30,12 @@ func setDNS(iface *net.Interface, nameservers []string) error {
 func resetDNS(iface *net.Interface) error {
 	if ctrldnet.SupportsIPv6ListenLocal() {
 		if output, err := netsh("interface", "ipv6", "set", "dnsserver", strconv.Itoa(iface.Index), "dhcp"); err != nil {
-			mainLog.Warn().Err(err).Msgf("failed to reset ipv6 DNS: %s", string(output))
+			mainLog.Load().Warn().Err(err).Msgf("failed to reset ipv6 DNS: %s", string(output))
 		}
 	}
 	output, err := netsh("interface", "ipv4", "set", "dnsserver", strconv.Itoa(iface.Index), "dhcp")
 	if err != nil {
-		mainLog.Error().Err(err).Msgf("failed to reset ipv4 DNS: %s", string(output))
+		mainLog.Load().Error().Err(err).Msgf("failed to reset ipv4 DNS: %s", string(output))
 		return err
 	}
 	return nil
@@ -49,7 +49,7 @@ func setPrimaryDNS(iface *net.Interface, dns string) error {
 	idx := strconv.Itoa(iface.Index)
 	output, err := netsh("interface", ipVer, "set", "dnsserver", idx, "static", dns)
 	if err != nil {
-		mainLog.Error().Err(err).Msgf("failed to set primary DNS: %s", string(output))
+		mainLog.Load().Error().Err(err).Msgf("failed to set primary DNS: %s", string(output))
 		return err
 	}
 	if ipVer == "ipv4" && ctrldnet.SupportsIPv6ListenLocal() {
@@ -67,7 +67,7 @@ func addSecondaryDNS(iface *net.Interface, dns string) error {
 	}
 	output, err := netsh("interface", ipVer, "add", "dns", strconv.Itoa(iface.Index), dns, "index=2")
 	if err != nil {
-		mainLog.Warn().Err(err).Msgf("failed to add secondary DNS: %s", string(output))
+		mainLog.Load().Warn().Err(err).Msgf("failed to add secondary DNS: %s", string(output))
 	}
 	return nil
 }
@@ -79,12 +79,12 @@ func netsh(args ...string) ([]byte, error) {
 func currentDNS(iface *net.Interface) []string {
 	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
 	if err != nil {
-		mainLog.Error().Err(err).Msg("failed to get interface LUID")
+		mainLog.Load().Error().Err(err).Msg("failed to get interface LUID")
 		return nil
 	}
 	nameservers, err := luid.DNS()
 	if err != nil {
-		mainLog.Error().Err(err).Msg("failed to get interface DNS")
+		mainLog.Load().Error().Err(err).Msg("failed to get interface DNS")
 		return nil
 	}
 	ns := make([]string, 0, len(nameservers))

cmd/cli/prog.go

@@ -0,0 +1,651 @@
+package cli
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"math/rand"
+	"net"
+	"net/netip"
+	"net/url"
+	"os"
+	"runtime"
+	"sort"
+	"strconv"
+	"sync"
+	"syscall"
+
+	"github.com/kardianos/service"
+	"github.com/spf13/viper"
+	"tailscale.com/net/interfaces"
+	"tailscale.com/net/tsaddr"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/Control-D-Inc/ctrld/internal/clientinfo"
+	"github.com/Control-D-Inc/ctrld/internal/dnscache"
+	"github.com/Control-D-Inc/ctrld/internal/router"
+)
+
+const (
+	defaultSemaphoreCap  = 256
+	ctrldLogUnixSock     = "ctrld_start.sock"
+	ctrldControlUnixSock = "ctrld_control.sock"
+	upstreamPrefix       = "upstream."
+	upstreamOS           = upstreamPrefix + "os"
+	upstreamPrivate      = upstreamPrefix + "private"
+)
+
+var logf = func(format string, args ...any) {
+	mainLog.Load().Debug().Msgf(format, args...)
+}
+
+var svcConfig = &service.Config{
+	Name:        "ctrld",
+	DisplayName: "Control-D Helper Service",
+	Option:      service.KeyValue{},
+}
+
+var useSystemdResolved = false
+
+type prog struct {
+	mu           sync.Mutex
+	waitCh       chan struct{}
+	stopCh       chan struct{}
+	reloadCh     chan struct{} // For Windows.
+	reloadDoneCh chan struct{}
+	logConn      net.Conn
+	cs           *controlServer
+
+	cfg            *ctrld.Config
+	localUpstreams []string
+	ptrNameservers []string
+	appCallback    *AppCallback
+	cache          dnscache.Cacher
+	sema           semaphore
+	ciTable        *clientinfo.Table
+	um             *upstreamMonitor
+	router         router.Router
+	ptrLoopGuard   *loopGuard
+	lanLoopGuard   *loopGuard
+
+	loopMu sync.Mutex
+	loop   map[string]bool
+
+	started       chan struct{}
+	onStartedDone chan struct{}
+	onStarted     []func()
+	onStopped     []func()
+}
+
+func (p *prog) Start(s service.Service) error {
+	go p.runWait()
+	return nil
+}
+
+// runWait runs ctrld components, waiting for signal to reload.
+func (p *prog) runWait() {
+	p.mu.Lock()
+	p.cfg = &cfg
+	p.mu.Unlock()
+	reloadSigCh := make(chan os.Signal, 1)
+	notifyReloadSigCh(reloadSigCh)
+
+	reload := false
+	logger := mainLog.Load()
+	for {
+		reloadCh := make(chan struct{})
+		done := make(chan struct{})
+		go func() {
+			defer close(done)
+			p.run(reload, reloadCh)
+			reload = true
+		}()
+		select {
+		case sig := <-reloadSigCh:
+			logger.Notice().Msgf("got signal: %s, reloading...", sig.String())
+		case <-p.reloadCh:
+			logger.Notice().Msg("reloading...")
+		case <-p.stopCh:
+			close(reloadCh)
+			return
+		}
+
+		waitOldRunDone := func() {
+			close(reloadCh)
+			<-done
+		}
+		newCfg := &ctrld.Config{}
+		v := viper.NewWithOptions(viper.KeyDelimiter("::"))
+		ctrld.InitConfig(v, "ctrld")
+		if configPath != "" {
+			v.SetConfigFile(configPath)
+		}
+		if err := v.ReadInConfig(); err != nil {
+			logger.Err(err).Msg("could not read new config")
+			waitOldRunDone()
+			continue
+		}
+		if err := v.Unmarshal(&newCfg); err != nil {
+			logger.Err(err).Msg("could not unmarshal new config")
+			waitOldRunDone()
+			continue
+		}
+		if cdUID != "" {
+			if err := processCDFlags(newCfg); err != nil {
+				logger.Err(err).Msg("could not fetch ControlD config")
+				waitOldRunDone()
+				continue
+			}
+		}
+
+		waitOldRunDone()
+
+		p.mu.Lock()
+		curListener := p.cfg.Listener
+		p.mu.Unlock()
+
+		for n, lc := range newCfg.Listener {
+			curLc := curListener[n]
+			if curLc == nil {
+				continue
+			}
+			if lc.IP == "" {
+				lc.IP = curLc.IP
+			}
+			if lc.Port == 0 {
+				lc.Port = curLc.Port
+			}
+		}
+		if err := validateConfig(newCfg); err != nil {
+			logger.Err(err).Msg("invalid config")
+			continue
+		}
+
+		// This needs to be done here, otherwise, the DNS handler may observe an invalid
+		// upstream config because its initialization function have not been called yet.
+		mainLog.Load().Debug().Msg("setup upstream with new config")
+		p.setupUpstream(newCfg)
+
+		p.mu.Lock()
+		*p.cfg = *newCfg
+		p.mu.Unlock()
+
+		logger.Notice().Msg("reloading config successfully")
+		select {
+		case p.reloadDoneCh <- struct{}{}:
+		default:
+		}
+	}
+}
+
+func (p *prog) preRun() {
+	if !service.Interactive() {
+		p.setDNS()
+	}
+	if runtime.GOOS == "darwin" {
+		p.onStopped = append(p.onStopped, func() {
+			if !service.Interactive() {
+				p.resetDNS()
+			}
+		})
+	}
+}
+
+func (p *prog) setupUpstream(cfg *ctrld.Config) {
+	localUpstreams := make([]string, 0, len(cfg.Upstream))
+	ptrNameservers := make([]string, 0, len(cfg.Upstream))
+	for n := range cfg.Upstream {
+		uc := cfg.Upstream[n]
+		uc.Init()
+		if uc.BootstrapIP == "" {
+			uc.SetupBootstrapIP()
+			mainLog.Load().Info().Msgf("bootstrap IPs for upstream.%s: %q", n, uc.BootstrapIPs())
+		} else {
+			mainLog.Load().Info().Str("bootstrap_ip", uc.BootstrapIP).Msgf("using bootstrap IP for upstream.%s", n)
+		}
+		uc.SetCertPool(rootCertPool)
+		go uc.Ping()
+
+		if canBeLocalUpstream(uc.Domain) {
+			localUpstreams = append(localUpstreams, upstreamPrefix+n)
+		}
+		if uc.IsDiscoverable() {
+			ptrNameservers = append(ptrNameservers, uc.Endpoint)
+		}
+	}
+	p.localUpstreams = localUpstreams
+	p.ptrNameservers = ptrNameservers
+}
+
+// run runs the ctrld main components.
+//
+// The reload boolean indicates that the function is run when ctrld first start
+// or when ctrld receive reloading signal. Platform specifics setup is only done
+// on started, mean reload is "false".
+//
+// The reloadCh is used to signal ctrld listeners that ctrld is going to be reloaded,
+// so all listeners could be terminated and re-spawned again.
+func (p *prog) run(reload bool, reloadCh chan struct{}) {
+	// Wait the caller to signal that we can do our logic.
+	<-p.waitCh
+	if !reload {
+		p.preRun()
+	}
+	numListeners := len(p.cfg.Listener)
+	if !reload {
+		p.started = make(chan struct{}, numListeners)
+	}
+	p.onStartedDone = make(chan struct{})
+	p.loop = make(map[string]bool)
+	p.lanLoopGuard = newLoopGuard()
+	p.ptrLoopGuard = newLoopGuard()
+	if p.cfg.Service.CacheEnable {
+		cacher, err := dnscache.NewLRUCache(p.cfg.Service.CacheSize)
+		if err != nil {
+			mainLog.Load().Error().Err(err).Msg("failed to create cacher, caching is disabled")
+		} else {
+			p.cache = cacher
+		}
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(len(p.cfg.Listener))
+
+	for _, nc := range p.cfg.Network {
+		for _, cidr := range nc.Cidrs {
+			_, ipNet, err := net.ParseCIDR(cidr)
+			if err != nil {
+				mainLog.Load().Error().Err(err).Str("network", nc.Name).Str("cidr", cidr).Msg("invalid cidr")
+				continue
+			}
+			nc.IPNets = append(nc.IPNets, ipNet)
+		}
+	}
+
+	p.um = newUpstreamMonitor(p.cfg)
+
+	if !reload {
+		p.sema = &chanSemaphore{ready: make(chan struct{}, defaultSemaphoreCap)}
+		if mcr := p.cfg.Service.MaxConcurrentRequests; mcr != nil {
+			n := *mcr
+			if n == 0 {
+				p.sema = &noopSemaphore{}
+			} else {
+				p.sema = &chanSemaphore{ready: make(chan struct{}, n)}
+			}
+		}
+		p.setupUpstream(p.cfg)
+		p.ciTable = clientinfo.NewTable(&cfg, defaultRouteIP(), cdUID, p.ptrNameservers)
+		if leaseFile := p.cfg.Service.DHCPLeaseFile; leaseFile != "" {
+			mainLog.Load().Debug().Msgf("watching custom lease file: %s", leaseFile)
+			format := ctrld.LeaseFileFormat(p.cfg.Service.DHCPLeaseFileFormat)
+			p.ciTable.AddLeaseFile(leaseFile, format)
+		}
+	}
+
+	// context for managing spawn goroutines.
+	ctx, cancelFunc := context.WithCancel(context.Background())
+	defer cancelFunc()
+
+	// Newer versions of android and iOS denies permission which breaks connectivity.
+	if !isMobile() && !reload {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			p.ciTable.Init()
+			p.ciTable.RefreshLoop(ctx)
+		}()
+		go p.watchLinkState(ctx)
+	}
+
+	for listenerNum := range p.cfg.Listener {
+		p.cfg.Listener[listenerNum].Init()
+		if !reload {
+			go func(listenerNum string) {
+				listenerConfig := p.cfg.Listener[listenerNum]
+				upstreamConfig := p.cfg.Upstream[listenerNum]
+				if upstreamConfig == nil {
+					mainLog.Load().Warn().Msgf("no default upstream for: [listener.%s]", listenerNum)
+				}
+				addr := net.JoinHostPort(listenerConfig.IP, strconv.Itoa(listenerConfig.Port))
+				mainLog.Load().Info().Msgf("starting DNS server on listener.%s: %s", listenerNum, addr)
+				if err := p.serveDNS(listenerNum); err != nil {
+					mainLog.Load().Fatal().Err(err).Msgf("unable to start dns proxy on listener.%s", listenerNum)
+				}
+			}(listenerNum)
+		}
+		go func() {
+			defer func() {
+				cancelFunc()
+				wg.Done()
+			}()
+			select {
+			case <-p.stopCh:
+			case <-ctx.Done():
+			case <-reloadCh:
+			}
+		}()
+	}
+
+	if !reload {
+		for i := 0; i < numListeners; i++ {
+			<-p.started
+		}
+		for _, f := range p.onStarted {
+			f()
+		}
+	}
+
+	close(p.onStartedDone)
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		// Check for possible DNS loop.
+		p.checkDnsLoop()
+		// Start check DNS loop ticker.
+		p.checkDnsLoopTicker(ctx)
+	}()
+
+	wg.Add(1)
+	// Prometheus exporter goroutine.
+	go func() {
+		defer wg.Done()
+		p.runMetricsServer(ctx, reloadCh)
+	}()
+
+	if !reload {
+		// Stop writing log to unix socket.
+		consoleWriter.Out = os.Stdout
+		initLoggingWithBackup(false)
+		if p.logConn != nil {
+			_ = p.logConn.Close()
+		}
+		if p.cs != nil {
+			p.registerControlServerHandler()
+			if err := p.cs.start(); err != nil {
+				mainLog.Load().Warn().Err(err).Msg("could not start control server")
+			}
+		}
+	}
+	wg.Wait()
+}
+
+// metricsEnabled reports whether prometheus exporter is enabled/disabled.
+func (p *prog) metricsEnabled() bool {
+	return p.cfg.Service.MetricsQueryStats || p.cfg.Service.MetricsListener != ""
+}
+
+func (p *prog) Stop(s service.Service) error {
+	mainLog.Load().Info().Msg("Service stopped")
+	close(p.stopCh)
+	if err := p.deAllocateIP(); err != nil {
+		mainLog.Load().Error().Err(err).Msg("de-allocate ip failed")
+		return err
+	}
+	return nil
+}
+
+func (p *prog) allocateIP(ip string) error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if !p.cfg.Service.AllocateIP {
+		return nil
+	}
+	return allocateIP(ip)
+}
+
+func (p *prog) deAllocateIP() error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if !p.cfg.Service.AllocateIP {
+		return nil
+	}
+	for _, lc := range p.cfg.Listener {
+		if err := deAllocateIP(lc.IP); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (p *prog) setDNS() {
+	if cfg.Listener == nil {
+		return
+	}
+	if iface == "" {
+		return
+	}
+	if iface == "auto" {
+		iface = defaultIfaceName()
+	}
+	lc := cfg.FirstListener()
+	if lc == nil {
+		return
+	}
+	logger := mainLog.Load().With().Str("iface", iface).Logger()
+	netIface, err := netInterface(iface)
+	if err != nil {
+		logger.Error().Err(err).Msg("could not get interface")
+		return
+	}
+	if err := setupNetworkManager(); err != nil {
+		logger.Error().Err(err).Msg("could not patch NetworkManager")
+		return
+	}
+
+	logger.Debug().Msg("setting DNS for interface")
+	ns := lc.IP
+	switch {
+	case lc.IsDirectDnsListener():
+		// If ctrld is direct listener, use 127.0.0.1 as nameserver.
+		ns = "127.0.0.1"
+	case lc.Port != 53:
+		ns = "127.0.0.1"
+		if resolver := router.LocalResolverIP(); resolver != "" {
+			ns = resolver
+		}
+	default:
+		// If we ever reach here, it means ctrld is running on lc.IP port 53,
+		// so we could just use lc.IP as nameserver.
+	}
+
+	nameservers := []string{ns}
+	if needRFC1918Listeners(lc) {
+		nameservers = append(nameservers, ctrld.Rfc1918Addresses()...)
+	}
+	if err := setDNS(netIface, nameservers); err != nil {
+		logger.Error().Err(err).Msgf("could not set DNS for interface")
+		return
+	}
+	logger.Debug().Msg("setting DNS successfully")
+}
+
+func (p *prog) resetDNS() {
+	if iface == "" {
+		return
+	}
+	if iface == "auto" {
+		iface = defaultIfaceName()
+	}
+	logger := mainLog.Load().With().Str("iface", iface).Logger()
+	netIface, err := netInterface(iface)
+	if err != nil {
+		logger.Error().Err(err).Msg("could not get interface")
+		return
+	}
+	if err := restoreNetworkManager(); err != nil {
+		logger.Error().Err(err).Msg("could not restore NetworkManager")
+		return
+	}
+	logger.Debug().Msg("Restoring DNS for interface")
+	if err := resetDNS(netIface); err != nil {
+		logger.Error().Err(err).Msgf("could not reset DNS")
+		return
+	}
+	logger.Debug().Msg("Restoring DNS successfully")
+}
+
+func randomLocalIP() string {
+	n := rand.Intn(254-2) + 2
+	return fmt.Sprintf("127.0.0.%d", n)
+}
+
+func randomPort() int {
+	max := 1<<16 - 1
+	min := 1025
+	n := rand.Intn(max-min) + min
+	return n
+}
+
+// runLogServer starts a unix listener, use by startCmd to gather log from runCmd.
+func runLogServer(sockPath string) net.Conn {
+	addr, err := net.ResolveUnixAddr("unix", sockPath)
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("invalid log sock path")
+		return nil
+	}
+	ln, err := net.ListenUnix("unix", addr)
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not listen log socket")
+		return nil
+	}
+	defer ln.Close()
+
+	server, err := ln.Accept()
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not accept connection")
+		return nil
+	}
+	return server
+}
+
+func errAddrInUse(err error) bool {
+	var opErr *net.OpError
+	if errors.As(err, &opErr) {
+		return errors.Is(opErr.Err, syscall.EADDRINUSE) || errors.Is(opErr.Err, windowsEADDRINUSE)
+	}
+	return false
+}
+
+var _ = errAddrInUse
+
+// https://learn.microsoft.com/en-us/windows/win32/winsock/windows-sockets-error-codes-2
+var (
+	windowsECONNREFUSED = syscall.Errno(10061)
+	windowsENETUNREACH  = syscall.Errno(10051)
+	windowsEINVAL       = syscall.Errno(10022)
+	windowsEADDRINUSE   = syscall.Errno(10048)
+	windowsEHOSTUNREACH = syscall.Errno(10065)
+)
+
+func errUrlNetworkError(err error) bool {
+	var urlErr *url.Error
+	if errors.As(err, &urlErr) {
+		return errNetworkError(urlErr.Err)
+	}
+	return false
+}
+
+func errNetworkError(err error) bool {
+	var opErr *net.OpError
+	if errors.As(err, &opErr) {
+		if opErr.Temporary() {
+			return true
+		}
+		switch {
+		case errors.Is(opErr.Err, syscall.ECONNREFUSED),
+			errors.Is(opErr.Err, syscall.EINVAL),
+			errors.Is(opErr.Err, syscall.ENETUNREACH),
+			errors.Is(opErr.Err, windowsENETUNREACH),
+			errors.Is(opErr.Err, windowsEINVAL),
+			errors.Is(opErr.Err, windowsECONNREFUSED),
+			errors.Is(opErr.Err, windowsEHOSTUNREACH):
+			return true
+		}
+	}
+	return false
+}
+
+func ifaceFirstPrivateIP(iface *net.Interface) string {
+	if iface == nil {
+		return ""
+	}
+	do := func(addrs []net.Addr, v4 bool) net.IP {
+		for _, addr := range addrs {
+			if netIP, ok := addr.(*net.IPNet); ok && netIP.IP.IsPrivate() {
+				if v4 {
+					return netIP.IP.To4()
+				}
+				return netIP.IP
+			}
+		}
+		return nil
+	}
+	addrs, _ := iface.Addrs()
+	if ip := do(addrs, true); ip != nil {
+		return ip.String()
+	}
+	if ip := do(addrs, false); ip != nil {
+		return ip.String()
+	}
+	return ""
+}
+
+// defaultRouteIP returns private IP string of the default route if present, prefer IPv4 over IPv6.
+func defaultRouteIP() string {
+	dr, err := interfaces.DefaultRoute()
+	if err != nil {
+		return ""
+	}
+	drNetIface, err := netInterface(dr.InterfaceName)
+	if err != nil {
+		return ""
+	}
+	mainLog.Load().Debug().Str("iface", drNetIface.Name).Msg("checking default route interface")
+	if ip := ifaceFirstPrivateIP(drNetIface); ip != "" {
+		mainLog.Load().Debug().Str("ip", ip).Msg("found ip with default route interface")
+		return ip
+	}
+
+	// If we reach here, it means the default route interface is connected directly to ISP.
+	// We need to find the LAN interface with the same Mac address with drNetIface.
+	//
+	// There could be multiple LAN interfaces with the same Mac address, so we find all private
+	// IPs then using the smallest one.
+	var addrs []netip.Addr
+	interfaces.ForeachInterface(func(i interfaces.Interface, prefixes []netip.Prefix) {
+		if i.Name == drNetIface.Name {
+			return
+		}
+		if bytes.Equal(i.HardwareAddr, drNetIface.HardwareAddr) {
+			for _, pfx := range prefixes {
+				addr := pfx.Addr()
+				if addr.IsPrivate() {
+					addrs = append(addrs, addr)
+				}
+			}
+		}
+	})
+
+	if len(addrs) == 0 {
+		mainLog.Load().Warn().Msg("no default route IP found")
+		return ""
+	}
+	sort.Slice(addrs, func(i, j int) bool {
+		return addrs[i].Less(addrs[j])
+	})
+
+	ip := addrs[0].String()
+	mainLog.Load().Debug().Str("ip", ip).Msg("found LAN interface IP")
+	return ip
+}
+
+// canBeLocalUpstream reports whether the IP address can be used as a local upstream.
+func canBeLocalUpstream(addr string) bool {
+	if ip, err := netip.ParseAddr(addr); err == nil {
+		return ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() || tsaddr.CGNATRange().Contains(ip)
+	}
+	return false
+}

cmd/cli/prog_darwin.go

@@ -0,0 +1,11 @@
+package cli
+
+import (
+	"github.com/kardianos/service"
+)
+
+func setDependencies(svc *service.Config) {}
+
+func setWorkingDirectory(svc *service.Config, dir string) {
+	svc.WorkingDirectory = dir
+}

cmd/cli/prog_freebsd.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import (
 	"os"
@@ -6,12 +6,6 @@ import (
 	"github.com/kardianos/service"
 )
 
-func (p *prog) preRun() {
-	if !service.Interactive() {
-		p.setDNS()
-	}
-}
-
 func setDependencies(svc *service.Config) {
 	// TODO(cuonglm): remove once https://github.com/kardianos/service/issues/359 fixed.
 	_ = os.MkdirAll("/usr/local/etc/rc.d", 0755)

cmd/cli/prog_linux.go

@@ -1,12 +1,14 @@
-package main
+package cli
 
 import (
 	"github.com/kardianos/service"
+
+	"github.com/Control-D-Inc/ctrld/internal/dns"
 )
 
-func (p *prog) preRun() {
+func init() {
-	if !service.Interactive() {
+	if r, err := dns.NewOSConfigurator(func(format string, args ...any) {}, "lo"); err == nil {
-		p.setDNS()
+		useSystemdResolved = r.Mode() == "systemd-resolved"
 	}
 }
 
@@ -16,6 +18,9 @@ func setDependencies(svc *service.Config) {
 		"After=network-online.target",
 		"Wants=NetworkManager-wait-online.service",
 		"After=NetworkManager-wait-online.service",
+		"Wants=systemd-networkd-wait-online.service",
+		"Wants=nss-lookup.target",
+		"After=nss-lookup.target",
 	}
 }
 

cmd/cli/prog_others.go

@@ -1,11 +1,9 @@
-//go:build !linux && !freebsd
+//go:build !linux && !freebsd && !darwin
 
-package main
+package cli
 
 import "github.com/kardianos/service"
 
-func (p *prog) preRun() {}
-
 func setDependencies(svc *service.Config) {}
 
 func setWorkingDirectory(svc *service.Config, dir string) {

cmd/cli/prometheus.go

@@ -0,0 +1,57 @@
+package cli
+
+import "github.com/prometheus/client_golang/prometheus"
+
+const (
+	metricsLabelListener       = "listener"
+	metricsLabelClientSourceIP = "client_source_ip"
+	metricsLabelClientMac      = "client_mac"
+	metricsLabelClientHostname = "client_hostname"
+	metricsLabelUpstream       = "upstream"
+	metricsLabelRRType         = "rr_type"
+	metricsLabelRCode          = "rcode"
+)
+
+// statsVersion represent ctrld version.
+var statsVersion = prometheus.NewCounterVec(prometheus.CounterOpts{
+	Name: "ctrld_build_info",
+	Help: "Version of ctrld process.",
+}, []string{"gitref", "goversion", "version"})
+
+// statsTimeStart represents start time of ctrld service.
+var statsTimeStart = prometheus.NewGauge(prometheus.GaugeOpts{
+	Name: "ctrld_time_seconds",
+	Help: "Start time of the ctrld process since unix epoch in seconds.",
+})
+
+var statsQueriesCountLabels = []string{
+	metricsLabelListener,
+	metricsLabelClientSourceIP,
+	metricsLabelClientMac,
+	metricsLabelClientHostname,
+	metricsLabelUpstream,
+	metricsLabelRRType,
+	metricsLabelRCode,
+}
+
+// statsQueriesCount counts total number of queries.
+var statsQueriesCount = prometheus.NewCounterVec(prometheus.CounterOpts{
+	Name: "ctrld_queries_count",
+	Help: "Total number of queries.",
+}, statsQueriesCountLabels)
+
+// statsClientQueriesCount counts total number of queries of a client.
+//
+// The labels "client_source_ip", "client_mac", "client_hostname" are unbounded,
+// thus this stat is highly inefficient if there are many devices.
+var statsClientQueriesCount = prometheus.NewCounterVec(prometheus.CounterOpts{
+	Name: "ctrld_client_queries_count",
+	Help: "Total number queries of a client.",
+}, []string{metricsLabelClientSourceIP, metricsLabelClientMac, metricsLabelClientHostname})
+
+// WithLabelValuesInc increases prometheus counter by 1 if query stats is enabled.
+func (p *prog) WithLabelValuesInc(c *prometheus.CounterVec, lvs ...string) {
+	if p.cfg.Service.MetricsQueryStats {
+		c.WithLabelValues(lvs...).Inc()
+	}
+}

cmd/cli/reload_others.go

@@ -0,0 +1,17 @@
+//go:build !windows
+
+package cli
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+func notifyReloadSigCh(ch chan os.Signal) {
+	signal.Notify(ch, syscall.SIGUSR1)
+}
+
+func (p *prog) sendReloadSignal() error {
+	return syscall.Kill(syscall.Getpid(), syscall.SIGUSR1)
+}

cmd/cli/reload_windows.go

@@ -0,0 +1,18 @@
+package cli
+
+import (
+	"errors"
+	"os"
+	"time"
+)
+
+func notifyReloadSigCh(ch chan os.Signal) {}
+
+func (p *prog) sendReloadSignal() error {
+	select {
+	case p.reloadCh <- struct{}{}:
+		return nil
+	case <-time.After(5 * time.Second):
+	}
+	return errors.New("timeout while sending reload signal")
+}

cmd/cli/sema.go

@@ -0,0 +1,24 @@
+package cli
+
+type semaphore interface {
+	acquire()
+	release()
+}
+
+type noopSemaphore struct{}
+
+func (n noopSemaphore) acquire() {}
+
+func (n noopSemaphore) release() {}
+
+type chanSemaphore struct {
+	ready chan struct{}
+}
+
+func (c *chanSemaphore) acquire() {
+	c.ready <- struct{}{}
+}
+
+func (c *chanSemaphore) release() {
+	<-c.ready
+}

cmd/cli/service.go

@@ -0,0 +1,167 @@
+package cli
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+
+	"github.com/kardianos/service"
+
+	"github.com/Control-D-Inc/ctrld/internal/router"
+)
+
+// newService wraps service.New call to return service.Service
+// wrapper which is suitable for the current platform.
+func newService(i service.Interface, c *service.Config) (service.Service, error) {
+	s, err := service.New(i, c)
+	if err != nil {
+		return nil, err
+	}
+	switch {
+	case router.IsOldOpenwrt():
+		return &procd{&sysV{s}}, nil
+	case router.IsGLiNet():
+		return &sysV{s}, nil
+	case s.Platform() == "unix-systemv":
+		return &sysV{s}, nil
+	case s.Platform() == "linux-systemd":
+		return &systemd{s}, nil
+	}
+	return s, nil
+}
+
+// sysV wraps a service.Service, and provide start/stop/status command
+// base on "/etc/init.d/<service_name>".
+//
+// Use this on system where "service" command is not available, like GL.iNET router.
+type sysV struct {
+	service.Service
+}
+
+func (s *sysV) installed() bool {
+	fi, err := os.Stat("/etc/init.d/ctrld")
+	if err != nil {
+		return false
+	}
+	mode := fi.Mode()
+	return mode.IsRegular() && (mode&0111) != 0
+}
+
+func (s *sysV) Start() error {
+	if !s.installed() {
+		return service.ErrNotInstalled
+	}
+	_, err := exec.Command("/etc/init.d/ctrld", "start").CombinedOutput()
+	return err
+}
+
+func (s *sysV) Stop() error {
+	if !s.installed() {
+		return service.ErrNotInstalled
+	}
+	_, err := exec.Command("/etc/init.d/ctrld", "stop").CombinedOutput()
+	return err
+}
+
+func (s *sysV) Restart() error {
+	if !s.installed() {
+		return service.ErrNotInstalled
+	}
+	// We don't care about error returned by s.Stop,
+	// because the service may already be stopped.
+	_ = s.Stop()
+	return s.Start()
+}
+
+func (s *sysV) Status() (service.Status, error) {
+	if !s.installed() {
+		return service.StatusUnknown, service.ErrNotInstalled
+	}
+	return unixSystemVServiceStatus()
+}
+
+// procd wraps a service.Service, and provide start/stop command
+// base on "/etc/init.d/<service_name>", status command base on parsing "ps" command output.
+//
+// Use this on system where "/etc/init.d/<service_name> status" command is not available,
+// like old GL.iNET Opal router.
+type procd struct {
+	*sysV
+}
+
+func (s *procd) Status() (service.Status, error) {
+	if !s.installed() {
+		return service.StatusUnknown, service.ErrNotInstalled
+	}
+	exe, err := os.Executable()
+	if err != nil {
+		return service.StatusUnknown, nil
+	}
+	// Looking for something like "/sbin/ctrld run ".
+	shellCmd := fmt.Sprintf("ps | grep -q %q", exe+" [r]un ")
+	if err := exec.Command("sh", "-c", shellCmd).Run(); err != nil {
+		return service.StatusStopped, nil
+	}
+	return service.StatusRunning, nil
+}
+
+// procd wraps a service.Service, and provide status command to
+// report the status correctly.
+type systemd struct {
+	service.Service
+}
+
+func (s *systemd) Status() (service.Status, error) {
+	out, _ := exec.Command("systemctl", "status", "ctrld").CombinedOutput()
+	if bytes.Contains(out, []byte("/FAILURE)")) {
+		return service.StatusStopped, nil
+	}
+	return s.Service.Status()
+}
+
+type task struct {
+	f            func() error
+	abortOnError bool
+}
+
+func doTasks(tasks []task) bool {
+	var prevErr error
+	for _, task := range tasks {
+		if err := task.f(); err != nil {
+			if task.abortOnError {
+				mainLog.Load().Error().Msg(errors.Join(prevErr, err).Error())
+				return false
+			}
+			prevErr = err
+		}
+	}
+	return true
+}
+
+func checkHasElevatedPrivilege() {
+	ok, err := hasElevatedPrivilege()
+	if err != nil {
+		mainLog.Load().Error().Msgf("could not detect user privilege: %v", err)
+		return
+	}
+	if !ok {
+		mainLog.Load().Error().Msg("Please relaunch process with admin/root privilege.")
+		os.Exit(1)
+	}
+}
+
+func unixSystemVServiceStatus() (service.Status, error) {
+	out, err := exec.Command("/etc/init.d/ctrld", "status").CombinedOutput()
+	if err != nil {
+		return service.StatusUnknown, nil
+	}
+
+	switch string(bytes.ToLower(bytes.TrimSpace(out))) {
+	case "running":
+		return service.StatusRunning, nil
+	default:
+		return service.StatusStopped, nil
+	}
+}

cmd/cli/service_others.go

@@ -1,6 +1,6 @@
 //go:build !windows
 
-package main
+package cli
 
 import (
 	"os"

cmd/cli/service_windows.go

@@ -1,4 +1,4 @@
-package main
+package cli
 
 import "golang.org/x/sys/windows"
 

cmd/cli/upstream_monitor.go

@@ -0,0 +1,112 @@
+package cli
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/miekg/dns"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+const (
+	// maxFailureRequest is the maximum failed queries allowed before an upstream is marked as down.
+	maxFailureRequest = 100
+	// checkUpstreamBackoffSleep is the time interval between each upstream checks.
+	checkUpstreamBackoffSleep = 2 * time.Second
+)
+
+// upstreamMonitor performs monitoring upstreams health.
+type upstreamMonitor struct {
+	cfg *ctrld.Config
+
+	mu         sync.Mutex
+	checking   map[string]bool
+	down       map[string]bool
+	failureReq map[string]uint64
+}
+
+func newUpstreamMonitor(cfg *ctrld.Config) *upstreamMonitor {
+	um := &upstreamMonitor{
+		cfg:        cfg,
+		checking:   make(map[string]bool),
+		down:       make(map[string]bool),
+		failureReq: make(map[string]uint64),
+	}
+	for n := range cfg.Upstream {
+		upstream := upstreamPrefix + n
+		um.reset(upstream)
+	}
+	um.reset(upstreamOS)
+	return um
+}
+
+// increaseFailureCount increase failed queries count for an upstream by 1.
+func (um *upstreamMonitor) increaseFailureCount(upstream string) {
+	um.mu.Lock()
+	defer um.mu.Unlock()
+
+	um.failureReq[upstream] += 1
+	failedCount := um.failureReq[upstream]
+	um.down[upstream] = failedCount >= maxFailureRequest
+}
+
+// isDown reports whether the given upstream is being marked as down.
+func (um *upstreamMonitor) isDown(upstream string) bool {
+	um.mu.Lock()
+	defer um.mu.Unlock()
+
+	return um.down[upstream]
+}
+
+// reset marks an upstream as up and set failed queries counter to zero.
+func (um *upstreamMonitor) reset(upstream string) {
+	um.mu.Lock()
+	defer um.mu.Unlock()
+
+	um.failureReq[upstream] = 0
+	um.down[upstream] = false
+}
+
+// checkUpstream checks the given upstream status, periodically sending query to upstream
+// until successfully. An upstream status/counter will be reset once it becomes reachable.
+func (um *upstreamMonitor) checkUpstream(upstream string, uc *ctrld.UpstreamConfig) {
+	um.mu.Lock()
+	isChecking := um.checking[upstream]
+	if isChecking {
+		um.mu.Unlock()
+		return
+	}
+	um.checking[upstream] = true
+	um.mu.Unlock()
+	defer func() {
+		um.mu.Lock()
+		um.checking[upstream] = false
+		um.mu.Unlock()
+	}()
+
+	resolver, err := ctrld.NewResolver(uc)
+	if err != nil {
+		mainLog.Load().Warn().Err(err).Msg("could not check upstream")
+		return
+	}
+	msg := new(dns.Msg)
+	msg.SetQuestion(".", dns.TypeNS)
+
+	check := func() error {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		defer cancel()
+		uc.ReBootstrap()
+		_, err := resolver.Resolve(ctx, msg)
+		return err
+	}
+	for {
+		if err := check(); err == nil {
+			mainLog.Load().Debug().Msgf("upstream %q is online", uc.Endpoint)
+			um.reset(upstream)
+			return
+		}
+		time.Sleep(checkUpstreamBackoffSleep)
+	}
+}

cmd/ctrld/cli.go

@@ -1,738 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"context"
-	"encoding/base64"
-	"errors"
-	"fmt"
-	"log"
-	"net"
-	"net/netip"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"runtime"
-	"strconv"
-	"strings"
-	"time"
-
-	"github.com/fsnotify/fsnotify"
-
-	"github.com/go-playground/validator/v10"
-	"github.com/kardianos/service"
-	"github.com/miekg/dns"
-	"github.com/pelletier/go-toml/v2"
-	"github.com/spf13/cobra"
-	"github.com/spf13/viper"
-	"tailscale.com/logtail/backoff"
-	"tailscale.com/net/interfaces"
-
-	"github.com/Control-D-Inc/ctrld"
-	"github.com/Control-D-Inc/ctrld/internal/controld"
-	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
-)
-
-const selfCheckFQDN = "verify.controld.com"
-
-var (
-	v                    = viper.NewWithOptions(viper.KeyDelimiter("::"))
-	defaultConfigWritten = false
-	defaultConfigFile    = "ctrld.toml"
-)
-
-var basicModeFlags = []string{"listen", "primary_upstream", "secondary_upstream", "domains"}
-
-func isNoConfigStart(cmd *cobra.Command) bool {
-	for _, flagName := range basicModeFlags {
-		if cmd.Flags().Lookup(flagName).Changed {
-			return true
-		}
-	}
-	return false
-}
-
-const rootShortDesc = `
-        __         .__       .___
-  _____/  |________|  |    __| _/
-_/ ___\   __\_  __ \  |   / __ |
-\  \___|  |  |  | \/  |__/ /_/ |
- \___  >__|  |__|  |____/\____ |
-     \/ dns forwarding proxy  \/
-`
-
-func initCLI() {
-	// Enable opening via explorer.exe on Windows.
-	// See: https://github.com/spf13/cobra/issues/844.
-	cobra.MousetrapHelpText = ""
-	cobra.EnableCommandSorting = false
-
-	rootCmd := &cobra.Command{
-		Use:     "ctrld",
-		Short:   strings.TrimLeft(rootShortDesc, "\n"),
-		Version: "1.1.2",
-	}
-	rootCmd.PersistentFlags().CountVarP(
-		&verbose,
-		"verbose",
-		"v",
-		`verbose log output, "-v" basic logging, "-vv" debug level logging`,
-	)
-	rootCmd.SetHelpCommand(&cobra.Command{Hidden: true})
-	rootCmd.CompletionOptions.HiddenDefaultCmd = true
-
-	runCmd := &cobra.Command{
-		Use:   "run",
-		Short: "Run the DNS proxy server",
-		Args:  cobra.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			if daemon && runtime.GOOS == "windows" {
-				log.Fatal("Cannot run in daemon mode. Please install a Windows service.")
-			}
-			noConfigStart := isNoConfigStart(cmd)
-			writeDefaultConfig := !noConfigStart && configBase64 == ""
-			configs := []struct {
-				name    string
-				written bool
-			}{
-				// For compatibility, we check for config.toml first, but only read it if exists.
-				{"config", false},
-				{"ctrld", writeDefaultConfig},
-			}
-			for _, config := range configs {
-				ctrld.SetConfigName(v, config.name)
-				v.SetConfigFile(configPath)
-				if readConfigFile(config.written) {
-					break
-				}
-			}
-
-			readBase64Config()
-			processNoConfigFlags(noConfigStart)
-			if err := v.Unmarshal(&cfg); err != nil {
-				log.Fatalf("failed to unmarshal config: %v", err)
-			}
-			fmt.Println("starting ctrld...")
-			// Wait for network up.
-			if !ctrldnet.Up() {
-				log.Fatal("network is not up yet")
-			}
-			processLogAndCacheFlags()
-			// Log config do not have thing to validate, so it's safe to init log here,
-			// so it's able to log information in processCDFlags.
-			initLogging()
-			processCDFlags()
-			if err := ctrld.ValidateConfig(validator.New(), &cfg); err != nil {
-				log.Fatalf("invalid config: %v", err)
-			}
-			initCache()
-
-			if daemon {
-				exe, err := os.Executable()
-				if err != nil {
-					mainLog.Error().Err(err).Msg("failed to find the binary")
-					os.Exit(1)
-				}
-				curDir, err := os.Getwd()
-				if err != nil {
-					mainLog.Error().Err(err).Msg("failed to get current working directory")
-					os.Exit(1)
-				}
-				// If running as daemon, re-run the command in background, with daemon off.
-				cmd := exec.Command(exe, append(os.Args[1:], "-d=false")...)
-				cmd.Dir = curDir
-				if err := cmd.Start(); err != nil {
-					mainLog.Error().Err(err).Msg("failed to start process as daemon")
-					os.Exit(1)
-				}
-				mainLog.Info().Int("pid", cmd.Process.Pid).Msg("DNS proxy started")
-				os.Exit(0)
-			}
-
-			s, err := service.New(&prog{}, svcConfig)
-			if err != nil {
-				mainLog.Fatal().Err(err).Msg("failed create new service")
-			}
-			serviceLogger, err := s.Logger(nil)
-			if err != nil {
-				mainLog.Error().Err(err).Msg("failed to get service logger")
-				return
-			}
-
-			if err := s.Run(); err != nil {
-				if sErr := serviceLogger.Error(err); sErr != nil {
-					mainLog.Error().Err(sErr).Msg("failed to write service log")
-				}
-				mainLog.Error().Err(err).Msg("failed to start service")
-			}
-		},
-	}
-	runCmd.Flags().BoolVarP(&daemon, "daemon", "d", false, "Run as daemon")
-	runCmd.Flags().StringVarP(&configPath, "config", "c", "", "Path to config file")
-	runCmd.Flags().StringVarP(&configBase64, "base64_config", "", "", "Base64 encoded config")
-	runCmd.Flags().StringVarP(&listenAddress, "listen", "", "", "Listener address and port, in format: address:port")
-	runCmd.Flags().StringVarP(&primaryUpstream, "primary_upstream", "", "", "Primary upstream endpoint")
-	runCmd.Flags().StringVarP(&secondaryUpstream, "secondary_upstream", "", "", "Secondary upstream endpoint")
-	runCmd.Flags().StringSliceVarP(&domains, "domains", "", nil, "List of domain to apply in a split DNS policy")
-	runCmd.Flags().StringVarP(&logPath, "log", "", "", "Path to log file")
-	runCmd.Flags().IntVarP(&cacheSize, "cache_size", "", 0, "Enable cache with size items")
-	runCmd.Flags().StringVarP(&cdUID, "cd", "", "", "Control D resolver uid")
-	runCmd.Flags().StringVarP(&homedir, "homedir", "", "", "")
-	_ = runCmd.Flags().MarkHidden("homedir")
-	runCmd.Flags().StringVarP(&iface, "iface", "", "", `Update DNS setting for iface, "auto" means the default interface gateway`)
-	_ = runCmd.Flags().MarkHidden("iface")
-
-	rootCmd.AddCommand(runCmd)
-
-	startCmd := &cobra.Command{
-		PreRun: checkHasElevatedPrivilege,
-		Use:    "start",
-		Short:  "Install and start the ctrld service",
-		Args:   cobra.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			sc := &service.Config{}
-			*sc = *svcConfig
-			osArgs := os.Args[2:]
-			if os.Args[1] == "service" {
-				osArgs = os.Args[3:]
-			}
-			setDependencies(sc)
-			sc.Arguments = append([]string{"run"}, osArgs...)
-
-			// No config path, generating config in HOME directory.
-			noConfigStart := isNoConfigStart(cmd)
-			writeDefaultConfig := !noConfigStart && configBase64 == ""
-			if configPath != "" {
-				v.SetConfigFile(configPath)
-			}
-			if dir, err := os.UserHomeDir(); err == nil {
-				setWorkingDirectory(sc, dir)
-				if configPath == "" && writeDefaultConfig {
-					defaultConfigFile = filepath.Join(dir, defaultConfigFile)
-					v.SetConfigFile(defaultConfigFile)
-				}
-				sc.Arguments = append(sc.Arguments, "--homedir="+dir)
-			}
-
-			readConfigFile(writeDefaultConfig && cdUID == "")
-			if err := v.Unmarshal(&cfg); err != nil {
-				log.Fatalf("failed to unmarshal config: %v", err)
-			}
-
-			logPath := cfg.Service.LogPath
-			cfg.Service.LogPath = ""
-			initLogging()
-			cfg.Service.LogPath = logPath
-
-			processCDFlags()
-			// On Windows, the service will be run as SYSTEM, so if ctrld start as Admin,
-			// the user home dir is different, so pass specific arguments that relevant here.
-			if runtime.GOOS == "windows" {
-				if configPath == "" {
-					sc.Arguments = append(sc.Arguments, "--config="+defaultConfigFile)
-				}
-			}
-
-			prog := &prog{}
-			s, err := service.New(prog, sc)
-			if err != nil {
-				stderrMsg(err.Error())
-				return
-			}
-			tasks := []task{
-				{s.Stop, false},
-				{s.Uninstall, false},
-				{s.Install, false},
-				{s.Start, true},
-			}
-			if doTasks(tasks) {
-				status, err := s.Status()
-				if err != nil {
-					mainLog.Warn().Err(err).Msg("could not get service status")
-					return
-				}
-
-				status = selfCheckStatus(status)
-				switch status {
-				case service.StatusRunning:
-					mainLog.Info().Msg("Service started")
-				default:
-					mainLog.Error().Msg("Service did not start, please check system/service log for details error")
-					if runtime.GOOS == "linux" {
-						prog.resetDNS()
-					}
-					os.Exit(1)
-				}
-				prog.setDNS()
-			}
-		},
-	}
-	// Keep these flags in sync with runCmd above, except for "-d".
-	startCmd.Flags().StringVarP(&configPath, "config", "c", "", "Path to config file")
-	startCmd.Flags().StringVarP(&configBase64, "base64_config", "", "", "Base64 encoded config")
-	startCmd.Flags().StringVarP(&listenAddress, "listen", "", "", "Listener address and port, in format: address:port")
-	startCmd.Flags().StringVarP(&primaryUpstream, "primary_upstream", "", "", "Primary upstream endpoint")
-	startCmd.Flags().StringVarP(&secondaryUpstream, "secondary_upstream", "", "", "Secondary upstream endpoint")
-	startCmd.Flags().StringSliceVarP(&domains, "domains", "", nil, "List of domain to apply in a split DNS policy")
-	startCmd.Flags().StringVarP(&logPath, "log", "", "", "Path to log file")
-	startCmd.Flags().IntVarP(&cacheSize, "cache_size", "", 0, "Enable cache with size items")
-	startCmd.Flags().StringVarP(&cdUID, "cd", "", "", "Control D resolver uid")
-	startCmd.Flags().StringVarP(&iface, "iface", "", "", `Update DNS setting for iface, "auto" means the default interface gateway`)
-
-	stopCmd := &cobra.Command{
-		PreRun: checkHasElevatedPrivilege,
-		Use:    "stop",
-		Short:  "Stop the ctrld service",
-		Args:   cobra.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			prog := &prog{}
-			s, err := service.New(prog, svcConfig)
-			if err != nil {
-				stderrMsg(err.Error())
-				return
-			}
-			initLogging()
-			if doTasks([]task{{s.Stop, true}}) {
-				prog.resetDNS()
-				mainLog.Info().Msg("Service stopped")
-			}
-		},
-	}
-	stopCmd.Flags().StringVarP(&iface, "iface", "", "", `Reset DNS setting for iface, "auto" means the default interface gateway`)
-
-	restartCmd := &cobra.Command{
-		PreRun: checkHasElevatedPrivilege,
-		Use:    "restart",
-		Short:  "Restart the ctrld service",
-		Args:   cobra.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			s, err := service.New(&prog{}, svcConfig)
-			if err != nil {
-				stderrMsg(err.Error())
-				return
-			}
-			initLogging()
-			if doTasks([]task{{s.Restart, true}}) {
-				stdoutMsg("Service restarted")
-			}
-		},
-	}
-
-	statusCmd := &cobra.Command{
-		Use:   "status",
-		Short: "Show status of the ctrld service",
-		Args:  cobra.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			s, err := service.New(&prog{}, svcConfig)
-			if err != nil {
-				stderrMsg(err.Error())
-				return
-			}
-			status, err := s.Status()
-			if err != nil {
-				stderrMsg(err.Error())
-				os.Exit(1)
-			}
-			switch status {
-			case service.StatusUnknown:
-				stdoutMsg("Unknown status")
-				os.Exit(2)
-			case service.StatusRunning:
-				stdoutMsg("Service is running")
-				os.Exit(0)
-			case service.StatusStopped:
-				stdoutMsg("Service is stopped")
-				os.Exit(1)
-			}
-		},
-	}
-
-	uninstallCmd := &cobra.Command{
-		PreRun: checkHasElevatedPrivilege,
-		Use:    "uninstall",
-		Short:  "Stop and uninstall the ctrld service",
-		Args:   cobra.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			prog := &prog{}
-			s, err := service.New(prog, svcConfig)
-			if err != nil {
-				stderrMsg(err.Error())
-				return
-			}
-			tasks := []task{
-				{s.Stop, false},
-				{s.Uninstall, true},
-			}
-			initLogging()
-			if doTasks(tasks) {
-				prog.resetDNS()
-				mainLog.Info().Msg("Service uninstalled")
-				return
-			}
-		},
-	}
-	uninstallCmd.Flags().StringVarP(&iface, "iface", "", "auto", `Reset DNS setting for iface, "auto" means the default interface gateway`)
-
-	listIfacesCmd := &cobra.Command{
-		Use:   "list",
-		Short: "List network interfaces of the host",
-		Args:  cobra.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			err := interfaces.ForeachInterface(func(i interfaces.Interface, prefixes []netip.Prefix) {
-				fmt.Printf("Index : %d\n", i.Index)
-				fmt.Printf("Name  : %s\n", i.Name)
-				addrs, _ := i.Addrs()
-				for i, ipaddr := range addrs {
-					if i == 0 {
-						fmt.Printf("Addrs : %v\n", ipaddr)
-						continue
-					}
-					fmt.Printf("        %v\n", ipaddr)
-				}
-				for i, dns := range currentDNS(i.Interface) {
-					if i == 0 {
-						fmt.Printf("DNS   : %s\n", dns)
-						continue
-					}
-					fmt.Printf("      : %s\n", dns)
-				}
-				println()
-			})
-			if err != nil {
-				stderrMsg(err.Error())
-			}
-		},
-	}
-	interfacesCmd := &cobra.Command{
-		Use:   "interfaces",
-		Short: "Manage network interfaces",
-		Args:  cobra.OnlyValidArgs,
-		ValidArgs: []string{
-			listIfacesCmd.Use,
-		},
-	}
-	interfacesCmd.AddCommand(listIfacesCmd)
-
-	serviceCmd := &cobra.Command{
-		Use:   "service",
-		Short: "Manage ctrld service",
-		Args:  cobra.OnlyValidArgs,
-		ValidArgs: []string{
-			statusCmd.Use,
-			stopCmd.Use,
-			restartCmd.Use,
-			statusCmd.Use,
-			uninstallCmd.Use,
-			interfacesCmd.Use,
-		},
-	}
-	serviceCmd.AddCommand(startCmd)
-	serviceCmd.AddCommand(stopCmd)
-	serviceCmd.AddCommand(restartCmd)
-	serviceCmd.AddCommand(statusCmd)
-	serviceCmd.AddCommand(uninstallCmd)
-	serviceCmd.AddCommand(interfacesCmd)
-	rootCmd.AddCommand(serviceCmd)
-	startCmdAlias := &cobra.Command{
-		PreRun: checkHasElevatedPrivilege,
-		Use:    "start",
-		Short:  "Quick start service and configure DNS on interface",
-		Run: func(cmd *cobra.Command, args []string) {
-			if !cmd.Flags().Changed("iface") {
-				os.Args = append(os.Args, "--iface="+ifaceStartStop)
-			}
-			iface = ifaceStartStop
-			startCmd.Run(cmd, args)
-		},
-	}
-	startCmdAlias.Flags().StringVarP(&ifaceStartStop, "iface", "", "auto", `Update DNS setting for iface, "auto" means the default interface gateway`)
-	startCmdAlias.Flags().AddFlagSet(startCmd.Flags())
-	rootCmd.AddCommand(startCmdAlias)
-	stopCmdAlias := &cobra.Command{
-		PreRun: checkHasElevatedPrivilege,
-		Use:    "stop",
-		Short:  "Quick stop service and remove DNS from interface",
-		Run: func(cmd *cobra.Command, args []string) {
-			if !cmd.Flags().Changed("iface") {
-				os.Args = append(os.Args, "--iface="+ifaceStartStop)
-			}
-			iface = ifaceStartStop
-			stopCmd.Run(cmd, args)
-		},
-	}
-	stopCmdAlias.Flags().StringVarP(&ifaceStartStop, "iface", "", "auto", `Reset DNS setting for iface, "auto" means the default interface gateway`)
-	stopCmdAlias.Flags().AddFlagSet(stopCmd.Flags())
-	rootCmd.AddCommand(stopCmdAlias)
-
-	if err := rootCmd.Execute(); err != nil {
-		stderrMsg(err.Error())
-		os.Exit(1)
-	}
-}
-
-func writeConfigFile() error {
-	if cfu := v.ConfigFileUsed(); cfu != "" {
-		defaultConfigFile = cfu
-	} else if configPath != "" {
-		defaultConfigFile = configPath
-	}
-	f, err := os.OpenFile(defaultConfigFile, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, os.FileMode(0o644))
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-	if cdUID != "" {
-		if _, err := f.WriteString("# AUTO-GENERATED VIA CD FLAG - DO NOT MODIFY\n\n"); err != nil {
-			return err
-		}
-	}
-	enc := toml.NewEncoder(f).SetIndentTables(true)
-	if err := enc.Encode(&cfg); err != nil {
-		return err
-	}
-	if err := f.Close(); err != nil {
-		return err
-	}
-	return nil
-}
-
-func readConfigFile(writeDefaultConfig bool) bool {
-	// If err == nil, there's a config supplied via `--config`, no default config written.
-	err := v.ReadInConfig()
-	if err == nil {
-		fmt.Println("loading config file from:", v.ConfigFileUsed())
-		defaultConfigFile = v.ConfigFileUsed()
-		v.OnConfigChange(func(in fsnotify.Event) {
-			if err := v.UnmarshalKey("listener", &cfg.Listener); err != nil {
-				log.Printf("failed to unmarshal listener config: %v", err)
-				return
-			}
-		})
-		v.WatchConfig()
-		return true
-	}
-
-	if !writeDefaultConfig {
-		return false
-	}
-
-	// If error is viper.ConfigFileNotFoundError, write default config.
-	if _, ok := err.(viper.ConfigFileNotFoundError); ok {
-		if err := writeConfigFile(); err != nil {
-			log.Fatalf("failed to write default config file: %v", err)
-		} else {
-			fmt.Println("writing default config file to: " + defaultConfigFile)
-		}
-		defaultConfigWritten = true
-		return false
-	}
-	// Otherwise, report fatal error and exit.
-	log.Fatalf("failed to decode config file: %v", err)
-	return false
-}
-
-func readBase64Config() {
-	if configBase64 == "" {
-		return
-	}
-	configStr, err := base64.StdEncoding.DecodeString(configBase64)
-	if err != nil {
-		log.Fatalf("invalid base64 config: %v", err)
-	}
-	if err := v.ReadConfig(bytes.NewReader(configStr)); err != nil {
-		log.Fatalf("failed to read base64 config: %v", err)
-	}
-}
-
-func processNoConfigFlags(noConfigStart bool) {
-	if !noConfigStart {
-		return
-	}
-	if listenAddress == "" || primaryUpstream == "" {
-		log.Fatal(`"listen" and "primary_upstream" flags must be set in no config mode`)
-	}
-	processListenFlag()
-
-	upstream := map[string]*ctrld.UpstreamConfig{
-		"0": {
-			Name:     primaryUpstream,
-			Endpoint: primaryUpstream,
-			Type:     ctrld.ResolverTypeDOH,
-		},
-	}
-	if secondaryUpstream != "" {
-		upstream["1"] = &ctrld.UpstreamConfig{
-			Name:     secondaryUpstream,
-			Endpoint: secondaryUpstream,
-			Type:     ctrld.ResolverTypeLegacy,
-		}
-		rules := make([]ctrld.Rule, 0, len(domains))
-		for _, domain := range domains {
-			rules = append(rules, ctrld.Rule{domain: []string{"upstream.1"}})
-		}
-		lc := v.Get("listener").(map[string]*ctrld.ListenerConfig)["0"]
-		lc.Policy = &ctrld.ListenerPolicyConfig{Name: "My Policy", Rules: rules}
-	}
-	v.Set("upstream", upstream)
-}
-
-func processCDFlags() {
-	if cdUID == "" {
-		return
-	}
-	if iface == "" {
-		iface = "auto"
-	}
-	logger := mainLog.With().Str("mode", "cd").Logger()
-	logger.Info().Msgf("fetching Controld D configuration from API: %s", cdUID)
-	resolverConfig, err := controld.FetchResolverConfig(cdUID)
-	if uer, ok := err.(*controld.UtilityErrorResponse); ok && uer.ErrorField.Code == controld.InvalidConfigCode {
-		s, err := service.New(&prog{}, svcConfig)
-		if err != nil {
-			logger.Warn().Err(err).Msg("failed to create new service")
-			return
-		}
-
-		if netIface, _ := netInterface(iface); netIface != nil {
-			if err := restoreNetworkManager(); err != nil {
-				logger.Error().Err(err).Msg("could not restore NetworkManager")
-				return
-			}
-			logger.Debug().Str("iface", netIface.Name).Msg("Restoring DNS for interface")
-			if err := resetDNS(netIface); err != nil {
-				logger.Warn().Err(err).Msg("something went wrong while restoring DNS")
-			} else {
-				logger.Debug().Str("iface", netIface.Name).Msg("Restoring DNS successfully")
-			}
-		}
-
-		tasks := []task{{s.Uninstall, true}}
-		if doTasks(tasks) {
-			logger.Info().Msg("uninstalled service")
-		}
-		logger.Fatal().Err(uer).Msg("failed to fetch resolver config")
-	}
-	if err != nil {
-		logger.Warn().Err(err).Msg("could not fetch resolver config")
-		return
-	}
-
-	logger.Info().Msg("generating ctrld config from Controld-D configuration")
-	cfg = ctrld.Config{}
-	cfg.Network = make(map[string]*ctrld.NetworkConfig)
-	cfg.Network["0"] = &ctrld.NetworkConfig{
-		Name:  "Network 0",
-		Cidrs: []string{"0.0.0.0/0"},
-	}
-	cfg.Upstream = make(map[string]*ctrld.UpstreamConfig)
-	cfg.Upstream["0"] = &ctrld.UpstreamConfig{
-		Endpoint: resolverConfig.DOH,
-		Type:     ctrld.ResolverTypeDOH,
-		Timeout:  5000,
-	}
-	rules := make([]ctrld.Rule, 0, len(resolverConfig.Exclude))
-	for _, domain := range resolverConfig.Exclude {
-		rules = append(rules, ctrld.Rule{domain: []string{}})
-	}
-	cfg.Listener = make(map[string]*ctrld.ListenerConfig)
-	cfg.Listener["0"] = &ctrld.ListenerConfig{
-		IP:   "127.0.0.1",
-		Port: 53,
-		Policy: &ctrld.ListenerPolicyConfig{
-			Name:  "My Policy",
-			Rules: rules,
-		},
-	}
-
-	processLogAndCacheFlags()
-	if err := writeConfigFile(); err != nil {
-		logger.Fatal().Err(err).Msg("failed to write config file")
-	} else {
-		logger.Info().Msg("writing config file to: " + defaultConfigFile)
-	}
-}
-
-func processListenFlag() {
-	if listenAddress == "" {
-		return
-	}
-	host, portStr, err := net.SplitHostPort(listenAddress)
-	if err != nil {
-		log.Fatalf("invalid listener address: %v", err)
-	}
-	port, err := strconv.Atoi(portStr)
-	if err != nil {
-		log.Fatalf("invalid port number: %v", err)
-	}
-	lc := &ctrld.ListenerConfig{
-		IP:   host,
-		Port: port,
-	}
-	v.Set("listener", map[string]*ctrld.ListenerConfig{
-		"0": lc,
-	})
-}
-
-func processLogAndCacheFlags() {
-	if logPath != "" {
-		cfg.Service.LogLevel = "debug"
-		cfg.Service.LogPath = logPath
-	}
-
-	if cacheSize != 0 {
-		cfg.Service.CacheEnable = true
-		cfg.Service.CacheSize = cacheSize
-	}
-	v.Set("service", cfg.Service)
-}
-
-func netInterface(ifaceName string) (*net.Interface, error) {
-	if ifaceName == "auto" {
-		ifaceName = defaultIfaceName()
-	}
-	var iface *net.Interface
-	err := interfaces.ForeachInterface(func(i interfaces.Interface, prefixes []netip.Prefix) {
-		if i.Name == ifaceName {
-			iface = i.Interface
-		}
-	})
-	if iface == nil {
-		return nil, errors.New("interface not found")
-	}
-	if err := patchNetIfaceName(iface); err != nil {
-		return nil, err
-	}
-	return iface, err
-}
-
-func defaultIfaceName() string {
-	dri, err := interfaces.DefaultRouteInterface()
-	if err != nil {
-		mainLog.Fatal().Err(err).Msg("failed to get default route interface")
-	}
-	return dri
-}
-
-func selfCheckStatus(status service.Status) service.Status {
-	c := new(dns.Client)
-	bo := backoff.NewBackoff("self-check", logf, 10*time.Second)
-	bo.LogLongerThan = 500 * time.Millisecond
-	ctx := context.Background()
-	err := errors.New("query failed")
-	maxAttempts := 20
-	mainLog.Debug().Msg("Performing self-check")
-	for i := 0; i < maxAttempts; i++ {
-		lc := cfg.Listener["0"]
-		m := new(dns.Msg)
-		m.SetQuestion(selfCheckFQDN+".", dns.TypeA)
-		m.RecursionDesired = true
-		r, _, _ := c.ExchangeContext(ctx, m, net.JoinHostPort(lc.IP, strconv.Itoa(lc.Port)))
-		if r != nil && r.Rcode == dns.RcodeSuccess && len(r.Answer) > 0 {
-			mainLog.Debug().Msgf("self-check against %q succeeded", selfCheckFQDN)
-			return status
-		}
-		bo.BackOff(ctx, err)
-	}
-	mainLog.Debug().Msgf("self-check against %q failed", selfCheckFQDN)
-	return service.StatusUnknown
-}

cmd/ctrld/dns_proxy.go

@@ -1,348 +0,0 @@
-package main
-
-import (
-	"context"
-	"crypto/rand"
-	"encoding/hex"
-	"fmt"
-	"net"
-	"runtime"
-	"strconv"
-	"strings"
-	"time"
-
-	"github.com/miekg/dns"
-	"golang.org/x/sync/errgroup"
-
-	"github.com/Control-D-Inc/ctrld"
-	"github.com/Control-D-Inc/ctrld/internal/dnscache"
-	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
-)
-
-const staleTTL = 60 * time.Second
-
-func (p *prog) serveDNS(listenerNum string) error {
-	listenerConfig := p.cfg.Listener[listenerNum]
-	// make sure ip is allocated
-	if allocErr := p.allocateIP(listenerConfig.IP); allocErr != nil {
-		mainLog.Error().Err(allocErr).Str("ip", listenerConfig.IP).Msg("serveUDP: failed to allocate listen ip")
-		return allocErr
-	}
-	var failoverRcodes []int
-	if listenerConfig.Policy != nil {
-		failoverRcodes = listenerConfig.Policy.FailoverRcodeNumbers
-	}
-	handler := dns.HandlerFunc(func(w dns.ResponseWriter, m *dns.Msg) {
-		q := m.Question[0]
-		domain := canonicalName(q.Name)
-		reqId := requestID()
-		fmtSrcToDest := fmtRemoteToLocal(listenerNum, w.RemoteAddr().String(), w.LocalAddr().String())
-		t := time.Now()
-		ctx := context.WithValue(context.Background(), ctrld.ReqIdCtxKey{}, reqId)
-		ctrld.Log(ctx, mainLog.Debug(), "%s received query: %s %s", fmtSrcToDest, dns.TypeToString[q.Qtype], domain)
-		upstreams, matched := p.upstreamFor(ctx, listenerNum, listenerConfig, w.RemoteAddr(), domain)
-		var answer *dns.Msg
-		if !matched && listenerConfig.Restricted {
-			answer = new(dns.Msg)
-			answer.SetRcode(m, dns.RcodeRefused)
-
-		} else {
-			answer = p.proxy(ctx, upstreams, failoverRcodes, m)
-			rtt := time.Since(t)
-			ctrld.Log(ctx, mainLog.Debug(), "received response of %d bytes in %s", answer.Len(), rtt)
-		}
-		if err := w.WriteMsg(answer); err != nil {
-			ctrld.Log(ctx, mainLog.Error().Err(err), "serveUDP: failed to send DNS response to client")
-		}
-	})
-
-	g := new(errgroup.Group)
-	for _, proto := range []string{"udp", "tcp"} {
-		proto := proto
-		// On Windows, there's no easy way for disabling/removing IPv6 DNS resolver, so we check whether we can
-		// listen on ::1, then spawn a listener for receiving DNS requests.
-		if runtime.GOOS == "windows" && ctrldnet.SupportsIPv6ListenLocal() {
-			g.Go(func() error {
-				s := &dns.Server{
-					Addr:    net.JoinHostPort("::1", strconv.Itoa(listenerConfig.Port)),
-					Net:     proto,
-					Handler: handler,
-				}
-				if err := s.ListenAndServe(); err != nil {
-					mainLog.Error().Err(err).Msg("could not serving on ::1")
-				}
-				return nil
-			})
-		}
-		g.Go(func() error {
-			s := &dns.Server{
-				Addr:    net.JoinHostPort(listenerConfig.IP, strconv.Itoa(listenerConfig.Port)),
-				Net:     proto,
-				Handler: handler,
-			}
-			if err := s.ListenAndServe(); err != nil {
-				mainLog.Error().Err(err).Msgf("could not listen and serve on: %s", s.Addr)
-				return err
-			}
-			return nil
-		})
-	}
-	return g.Wait()
-}
-
-func (p *prog) upstreamFor(ctx context.Context, defaultUpstreamNum string, lc *ctrld.ListenerConfig, addr net.Addr, domain string) ([]string, bool) {
-	upstreams := []string{"upstream." + defaultUpstreamNum}
-	matchedPolicy := "no policy"
-	matchedNetwork := "no network"
-	matchedRule := "no rule"
-	matched := false
-
-	defer func() {
-		if !matched && lc.Restricted {
-			ctrld.Log(ctx, mainLog.Info(), "query refused, %s does not match any network policy", addr.String())
-			return
-		}
-		ctrld.Log(ctx, mainLog.Info(), "%s, %s, %s -> %v", matchedPolicy, matchedNetwork, matchedRule, upstreams)
-	}()
-
-	if lc.Policy == nil {
-		return upstreams, false
-	}
-
-	do := func(policyUpstreams []string) {
-		upstreams = append([]string(nil), policyUpstreams...)
-	}
-
-	for _, rule := range lc.Policy.Rules {
-		// There's only one entry per rule, config validation ensures this.
-		for source, targets := range rule {
-			if source == domain || wildcardMatches(source, domain) {
-				matchedPolicy = lc.Policy.Name
-				matchedRule = source
-				do(targets)
-				matched = true
-				return upstreams, matched
-			}
-		}
-	}
-
-	var sourceIP net.IP
-	switch addr := addr.(type) {
-	case *net.UDPAddr:
-		sourceIP = addr.IP
-	case *net.TCPAddr:
-		sourceIP = addr.IP
-	}
-	for _, rule := range lc.Policy.Networks {
-		for source, targets := range rule {
-			networkNum := strings.TrimPrefix(source, "network.")
-			nc := p.cfg.Network[networkNum]
-			if nc == nil {
-				continue
-			}
-
-			for _, ipNet := range nc.IPNets {
-				if ipNet.Contains(sourceIP) {
-					matchedPolicy = lc.Policy.Name
-					matchedNetwork = source
-					do(targets)
-					matched = true
-					return upstreams, matched
-				}
-			}
-		}
-	}
-
-	return upstreams, matched
-}
-
-func (p *prog) proxy(ctx context.Context, upstreams []string, failoverRcodes []int, msg *dns.Msg) *dns.Msg {
-	var staleAnswer *dns.Msg
-	serveStaleCache := p.cache != nil && p.cfg.Service.CacheServeStale
-	upstreamConfigs := p.upstreamConfigsFromUpstreamNumbers(upstreams)
-	if len(upstreamConfigs) == 0 {
-		upstreamConfigs = []*ctrld.UpstreamConfig{osUpstreamConfig}
-		upstreams = []string{"upstream.os"}
-	}
-	// Inverse query should not be cached: https://www.rfc-editor.org/rfc/rfc1035#section-7.4
-	if p.cache != nil && msg.Question[0].Qtype != dns.TypePTR {
-		for _, upstream := range upstreams {
-			cachedValue := p.cache.Get(dnscache.NewKey(msg, upstream))
-			if cachedValue == nil {
-				continue
-			}
-			answer := cachedValue.Msg.Copy()
-			answer.SetRcode(msg, answer.Rcode)
-			now := time.Now()
-			if cachedValue.Expire.After(now) {
-				ctrld.Log(ctx, mainLog.Debug(), "hit cached response")
-				setCachedAnswerTTL(answer, now, cachedValue.Expire)
-				return answer
-			}
-			staleAnswer = answer
-		}
-	}
-	resolve1 := func(n int, upstreamConfig *ctrld.UpstreamConfig, msg *dns.Msg) (*dns.Msg, error) {
-		ctrld.Log(ctx, mainLog.Debug(), "sending query to %s: %s", upstreams[n], upstreamConfig.Name)
-		dnsResolver, err := ctrld.NewResolver(upstreamConfig)
-		if err != nil {
-			ctrld.Log(ctx, mainLog.Error().Err(err), "failed to create resolver")
-			return nil, err
-		}
-		resolveCtx, cancel := context.WithCancel(ctx)
-		defer cancel()
-		if upstreamConfig.Timeout > 0 {
-			timeoutCtx, cancel := context.WithTimeout(resolveCtx, time.Millisecond*time.Duration(upstreamConfig.Timeout))
-			defer cancel()
-			resolveCtx = timeoutCtx
-		}
-		return dnsResolver.Resolve(resolveCtx, msg)
-	}
-	resolve := func(n int, upstreamConfig *ctrld.UpstreamConfig, msg *dns.Msg) *dns.Msg {
-		answer, err := resolve1(n, upstreamConfig, msg)
-		if err != nil {
-			ctrld.Log(ctx, mainLog.Debug().Err(err), "could not resolve query on first attempt, retrying...")
-			// If any error occurred, re-bootstrap transport/ip, retry the request.
-			upstreamConfig.ReBootstrap()
-			answer, err = resolve1(n, upstreamConfig, msg)
-			if err == nil {
-				return answer
-			}
-			ctrld.Log(ctx, mainLog.Error().Err(err), "failed to resolve query")
-			return nil
-		}
-		return answer
-	}
-	for n, upstreamConfig := range upstreamConfigs {
-		answer := resolve(n, upstreamConfig, msg)
-		if answer == nil {
-			if serveStaleCache && staleAnswer != nil {
-				ctrld.Log(ctx, mainLog.Debug(), "serving stale cached response")
-				now := time.Now()
-				setCachedAnswerTTL(staleAnswer, now, now.Add(staleTTL))
-				return staleAnswer
-			}
-			continue
-		}
-		if answer.Rcode != dns.RcodeSuccess && len(upstreamConfigs) > 1 && containRcode(failoverRcodes, answer.Rcode) {
-			ctrld.Log(ctx, mainLog.Debug(), "failover rcode matched, process to next upstream")
-			continue
-		}
-		if p.cache != nil {
-			ttl := ttlFromMsg(answer)
-			now := time.Now()
-			expired := now.Add(time.Duration(ttl) * time.Second)
-			if cachedTTL := p.cfg.Service.CacheTTLOverride; cachedTTL > 0 {
-				expired = now.Add(time.Duration(cachedTTL) * time.Second)
-			}
-			setCachedAnswerTTL(answer, now, expired)
-			p.cache.Add(dnscache.NewKey(msg, upstreams[n]), dnscache.NewValue(answer, expired))
-			ctrld.Log(ctx, mainLog.Debug(), "add cached response")
-		}
-		return answer
-	}
-	ctrld.Log(ctx, mainLog.Error(), "all upstreams failed")
-	answer := new(dns.Msg)
-	answer.SetRcode(msg, dns.RcodeServerFailure)
-	return answer
-}
-
-func (p *prog) upstreamConfigsFromUpstreamNumbers(upstreams []string) []*ctrld.UpstreamConfig {
-	upstreamConfigs := make([]*ctrld.UpstreamConfig, 0, len(upstreams))
-	for _, upstream := range upstreams {
-		upstreamNum := strings.TrimPrefix(upstream, "upstream.")
-		upstreamConfigs = append(upstreamConfigs, p.cfg.Upstream[upstreamNum])
-	}
-	return upstreamConfigs
-}
-
-// canonicalName returns canonical name from FQDN with "." trimmed.
-func canonicalName(fqdn string) string {
-	q := strings.TrimSpace(fqdn)
-	q = strings.TrimSuffix(q, ".")
-	// https://datatracker.ietf.org/doc/html/rfc4343
-	q = strings.ToLower(q)
-
-	return q
-}
-
-func wildcardMatches(wildcard, domain string) bool {
-	// Wildcard match.
-	wildCardParts := strings.Split(wildcard, "*")
-	if len(wildCardParts) != 2 {
-		return false
-	}
-
-	switch {
-	case len(wildCardParts[0]) > 0 && len(wildCardParts[1]) > 0:
-		// Domain must match both prefix and suffix.
-		return strings.HasPrefix(domain, wildCardParts[0]) && strings.HasSuffix(domain, wildCardParts[1])
-
-	case len(wildCardParts[1]) > 0:
-		// Only suffix must match.
-		return strings.HasSuffix(domain, wildCardParts[1])
-
-	case len(wildCardParts[0]) > 0:
-		// Only prefix must match.
-		return strings.HasPrefix(domain, wildCardParts[0])
-	}
-
-	return false
-}
-
-func fmtRemoteToLocal(listenerNum, remote, local string) string {
-	return fmt.Sprintf("%s -> listener.%s: %s:", remote, listenerNum, local)
-}
-
-func requestID() string {
-	b := make([]byte, 3) // 6 chars
-	if _, err := rand.Read(b); err != nil {
-		panic(err)
-	}
-	return hex.EncodeToString(b)
-}
-
-func containRcode(rcodes []int, rcode int) bool {
-	for i := range rcodes {
-		if rcodes[i] == rcode {
-			return true
-		}
-	}
-	return false
-}
-
-func setCachedAnswerTTL(answer *dns.Msg, now, expiredTime time.Time) {
-	ttlSecs := expiredTime.Sub(now).Seconds()
-	if ttlSecs < 0 {
-		return
-	}
-
-	ttl := uint32(ttlSecs)
-	for _, rr := range answer.Answer {
-		rr.Header().Ttl = ttl
-	}
-	for _, rr := range answer.Ns {
-		rr.Header().Ttl = ttl
-	}
-	for _, rr := range answer.Extra {
-		if rr.Header().Rrtype != dns.TypeOPT {
-			rr.Header().Ttl = ttl
-		}
-	}
-}
-
-func ttlFromMsg(msg *dns.Msg) uint32 {
-	for _, rr := range msg.Answer {
-		return rr.Header().Ttl
-	}
-	for _, rr := range msg.Ns {
-		return rr.Header().Ttl
-	}
-	return 0
-}
-
-var osUpstreamConfig = &ctrld.UpstreamConfig{
-	Name:    "OS resolver",
-	Type:    ctrld.ResolverTypeOS,
-	Timeout: 2000,
-}

cmd/ctrld/dns_proxy_test.go

@@ -1,154 +0,0 @@
-package main
-
-import (
-	"context"
-	"net"
-	"testing"
-	"time"
-
-	"github.com/miekg/dns"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"github.com/Control-D-Inc/ctrld"
-	"github.com/Control-D-Inc/ctrld/internal/dnscache"
-	"github.com/Control-D-Inc/ctrld/testhelper"
-)
-
-func Test_wildcardMatches(t *testing.T) {
-	tests := []struct {
-		name     string
-		wildcard string
-		domain   string
-		match    bool
-	}{
-		{"prefix parent should not match", "*.windscribe.com", "windscribe.com", false},
-		{"prefix", "*.windscribe.com", "anything.windscribe.com", true},
-		{"prefix not match other domain", "*.windscribe.com", "example.com", false},
-		{"prefix not match domain in name", "*.windscribe.com", "wwindscribe.com", false},
-		{"suffix", "suffix.*", "suffix.windscribe.com", true},
-		{"suffix not match other", "suffix.*", "suffix1.windscribe.com", false},
-		{"both", "suffix.*.windscribe.com", "suffix.anything.windscribe.com", true},
-		{"both not match", "suffix.*.windscribe.com", "suffix1.suffix.windscribe.com", false},
-	}
-
-	for _, tc := range tests {
-		tc := tc
-		t.Run(tc.name, func(t *testing.T) {
-			t.Parallel()
-			if got := wildcardMatches(tc.wildcard, tc.domain); got != tc.match {
-				t.Errorf("unexpected result, wildcard: %s, domain: %s, want: %v, got: %v", tc.wildcard, tc.domain, tc.match, got)
-			}
-		})
-	}
-}
-
-func Test_canonicalName(t *testing.T) {
-	tests := []struct {
-		name      string
-		domain    string
-		canonical string
-	}{
-		{"fqdn to canonical", "windscribe.com.", "windscribe.com"},
-		{"already canonical", "windscribe.com", "windscribe.com"},
-		{"case insensitive", "Windscribe.Com.", "windscribe.com"},
-	}
-
-	for _, tc := range tests {
-		tc := tc
-		t.Run(tc.name, func(t *testing.T) {
-			t.Parallel()
-			if got := canonicalName(tc.domain); got != tc.canonical {
-				t.Errorf("unexpected result, want: %s, got: %s", tc.canonical, got)
-			}
-		})
-	}
-}
-
-func Test_prog_upstreamFor(t *testing.T) {
-	cfg := testhelper.SampleConfig(t)
-	prog := &prog{cfg: cfg}
-	for _, nc := range prog.cfg.Network {
-		for _, cidr := range nc.Cidrs {
-			_, ipNet, err := net.ParseCIDR(cidr)
-			if err != nil {
-				t.Fatal(err)
-			}
-			nc.IPNets = append(nc.IPNets, ipNet)
-		}
-	}
-
-	tests := []struct {
-		name               string
-		ip                 string
-		defaultUpstreamNum string
-		lc                 *ctrld.ListenerConfig
-		domain             string
-		upstreams          []string
-		matched            bool
-	}{
-		{"Policy map matches", "192.168.0.1:0", "0", prog.cfg.Listener["0"], "abc.xyz", []string{"upstream.1", "upstream.0"}, true},
-		{"Policy split matches", "192.168.0.1:0", "0", prog.cfg.Listener["0"], "abc.ru", []string{"upstream.1"}, true},
-		{"Policy map for other network matches", "192.168.1.2:0", "0", prog.cfg.Listener["0"], "abc.xyz", []string{"upstream.0"}, true},
-		{"No policy map for listener", "192.168.1.2:0", "1", prog.cfg.Listener["1"], "abc.ru", []string{"upstream.1"}, false},
-	}
-
-	for _, tc := range tests {
-		tc := tc
-		t.Run(tc.name, func(t *testing.T) {
-			t.Parallel()
-			for _, network := range []string{"udp", "tcp"} {
-				var (
-					addr net.Addr
-					err  error
-				)
-				switch network {
-				case "udp":
-					addr, err = net.ResolveUDPAddr(network, tc.ip)
-				case "tcp":
-					addr, err = net.ResolveTCPAddr(network, tc.ip)
-				}
-				require.NoError(t, err)
-				require.NotNil(t, addr)
-				ctx := context.WithValue(context.Background(), ctrld.ReqIdCtxKey{}, requestID())
-				upstreams, matched := prog.upstreamFor(ctx, tc.defaultUpstreamNum, tc.lc, addr, tc.domain)
-				assert.Equal(t, tc.matched, matched)
-				assert.Equal(t, tc.upstreams, upstreams)
-			}
-		})
-	}
-}
-
-func TestCache(t *testing.T) {
-	cfg := testhelper.SampleConfig(t)
-	prog := &prog{cfg: cfg}
-	for _, nc := range prog.cfg.Network {
-		for _, cidr := range nc.Cidrs {
-			_, ipNet, err := net.ParseCIDR(cidr)
-			if err != nil {
-				t.Fatal(err)
-			}
-			nc.IPNets = append(nc.IPNets, ipNet)
-		}
-	}
-	cacher, err := dnscache.NewLRUCache(4096)
-	require.NoError(t, err)
-	prog.cache = cacher
-
-	msg := new(dns.Msg)
-	msg.SetQuestion("example.com", dns.TypeA)
-	msg.MsgHdr.RecursionDesired = true
-	answer1 := new(dns.Msg)
-	answer1.SetRcode(msg, dns.RcodeSuccess)
-
-	prog.cache.Add(dnscache.NewKey(msg, "upstream.1"), dnscache.NewValue(answer1, time.Now().Add(time.Minute)))
-	answer2 := new(dns.Msg)
-	answer2.SetRcode(msg, dns.RcodeRefused)
-	prog.cache.Add(dnscache.NewKey(msg, "upstream.0"), dnscache.NewValue(answer2, time.Now().Add(time.Minute)))
-
-	got1 := prog.proxy(context.Background(), []string{"upstream.1"}, nil, msg)
-	got2 := prog.proxy(context.Background(), []string{"upstream.0"}, nil, msg)
-	assert.NotSame(t, got1, got2)
-	assert.Equal(t, answer1.Rcode, got1.Rcode)
-	assert.Equal(t, answer2.Rcode, got2.Rcode)
-}

cmd/ctrld/main.go

@@ -1,109 +1,7 @@
 package main
 
-import (
+import "github.com/Control-D-Inc/ctrld/cmd/cli"
-	"io"
-	"log"
-	"os"
-	"path/filepath"
-	"time"
-
-	"github.com/kardianos/service"
-	"github.com/rs/zerolog"
-
-	"github.com/Control-D-Inc/ctrld"
-)
-
-var (
-	configPath        string
-	configBase64      string
-	daemon            bool
-	listenAddress     string
-	primaryUpstream   string
-	secondaryUpstream string
-	domains           []string
-	logPath           string
-	homedir           string
-	cacheSize         int
-	cfg               ctrld.Config
-	verbose           int
-
-	rootLogger = zerolog.New(io.Discard)
-	mainLog    = rootLogger
-
-	cdUID          string
-	iface          string
-	ifaceStartStop string
-)
 
 func main() {
-	ctrld.InitConfig(v, "ctrld")
+	cli.Main()
-	initCLI()
-}
-
-func normalizeLogFilePath(logFilePath string) string {
-	if logFilePath == "" || filepath.IsAbs(logFilePath) || service.Interactive() {
-		return logFilePath
-	}
-	if homedir != "" {
-		return filepath.Join(homedir, logFilePath)
-	}
-	dir, _ := os.UserHomeDir()
-	if dir == "" {
-		return logFilePath
-	}
-	return filepath.Join(dir, logFilePath)
-}
-
-func initLogging() {
-	writers := []io.Writer{io.Discard}
-	if logFilePath := normalizeLogFilePath(cfg.Service.LogPath); logFilePath != "" {
-		// Create parent directory if necessary.
-		if err := os.MkdirAll(filepath.Dir(logFilePath), 0750); err != nil {
-			log.Printf("failed to create log path: %v", err)
-			os.Exit(1)
-		}
-		// Backup old log file with .1 suffix.
-		if err := os.Rename(logFilePath, logFilePath+".1"); err != nil && !os.IsNotExist(err) {
-			log.Printf("could not backup old log file: %v", err)
-		}
-		logFile, err := os.OpenFile(logFilePath, os.O_CREATE|os.O_RDWR, os.FileMode(0o600))
-		if err != nil {
-			log.Printf("failed to create log file: %v", err)
-			os.Exit(1)
-		}
-		writers = append(writers, logFile)
-	}
-	zerolog.TimeFieldFormat = zerolog.TimeFormatUnixMs
-	consoleWriter := zerolog.NewConsoleWriter(func(w *zerolog.ConsoleWriter) {
-		w.TimeFormat = time.StampMilli
-	})
-	writers = append(writers, consoleWriter)
-	multi := zerolog.MultiLevelWriter(writers...)
-	mainLog = mainLog.Output(multi).With().Timestamp().Logger()
-	// TODO: find a better way.
-	ctrld.ProxyLog = mainLog
-
-	zerolog.SetGlobalLevel(zerolog.InfoLevel)
-	logLevel := cfg.Service.LogLevel
-	if verbose > 1 {
-		logLevel = "debug"
-	}
-	if logLevel == "" {
-		return
-	}
-	level, err := zerolog.ParseLevel(logLevel)
-	if err != nil {
-		mainLog.Warn().Err(err).Msg("could not set log level")
-		return
-	}
-	zerolog.SetGlobalLevel(level)
-}
-
-func initCache() {
-	if !cfg.Service.CacheEnable {
-		return
-	}
-	if cfg.Service.CacheSize == 0 {
-		cfg.Service.CacheSize = 4096
-	}
 }

cmd/ctrld/os_linux.go

@@ -1,195 +0,0 @@
-package main
-
-import (
-	"bufio"
-	"bytes"
-	"context"
-	"fmt"
-	"net"
-	"net/netip"
-	"os/exec"
-	"reflect"
-	"strings"
-	"syscall"
-	"time"
-
-	"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
-	"github.com/insomniacslk/dhcp/dhcpv6"
-	"github.com/insomniacslk/dhcp/dhcpv6/client6"
-	"tailscale.com/util/dnsname"
-
-	"github.com/Control-D-Inc/ctrld/internal/dns"
-	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
-	"github.com/Control-D-Inc/ctrld/internal/resolvconffile"
-)
-
-// allocate loopback ip
-// sudo ip a add 127.0.0.2/24 dev lo
-func allocateIP(ip string) error {
-	cmd := exec.Command("ip", "a", "add", ip+"/24", "dev", "lo")
-	if out, err := cmd.CombinedOutput(); err != nil {
-		mainLog.Error().Err(err).Msgf("allocateIP failed: %s", string(out))
-		return err
-	}
-	return nil
-}
-
-func deAllocateIP(ip string) error {
-	cmd := exec.Command("ip", "a", "del", ip+"/24", "dev", "lo")
-	if err := cmd.Run(); err != nil {
-		mainLog.Error().Err(err).Msg("deAllocateIP failed")
-		return err
-	}
-	return nil
-}
-
-const maxSetDNSAttempts = 5
-
-// set the dns server for the provided network interface
-func setDNS(iface *net.Interface, nameservers []string) error {
-	r, err := dns.NewOSConfigurator(logf, iface.Name)
-	if err != nil {
-		mainLog.Error().Err(err).Msg("failed to create DNS OS configurator")
-		return err
-	}
-
-	ns := make([]netip.Addr, 0, len(nameservers))
-	for _, nameserver := range nameservers {
-		ns = append(ns, netip.MustParseAddr(nameserver))
-	}
-
-	osConfig := dns.OSConfig{
-		Nameservers:   ns,
-		SearchDomains: []dnsname.FQDN{},
-	}
-
-	for i := 0; i < maxSetDNSAttempts; i++ {
-		if err := r.SetDNS(osConfig); err != nil {
-			return err
-		}
-		currentNS := currentDNS(iface)
-		if reflect.DeepEqual(currentNS, nameservers) {
-			return nil
-		}
-	}
-	mainLog.Debug().Msg("DNS was not set for some reason")
-	return nil
-}
-
-func resetDNS(iface *net.Interface) (err error) {
-	defer func() {
-		if err == nil {
-			return
-		}
-		if r, oerr := dns.NewOSConfigurator(logf, iface.Name); oerr == nil {
-			_ = r.SetDNS(dns.OSConfig{})
-			if err := r.Close(); err != nil {
-				mainLog.Error().Err(err).Msg("failed to rollback DNS setting")
-				return
-			}
-			err = nil
-		}
-	}()
-
-	var ns []string
-	c, err := nclient4.New(iface.Name)
-	if err != nil {
-		return fmt.Errorf("nclient4.New: %w", err)
-	}
-	defer c.Close()
-
-	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
-	defer cancel()
-	lease, err := c.Request(ctx)
-	if err != nil {
-		return fmt.Errorf("nclient4.Request: %w", err)
-	}
-	for _, nameserver := range lease.ACK.DNS() {
-		if nameserver.Equal(net.IPv4zero) {
-			continue
-		}
-		ns = append(ns, nameserver.String())
-	}
-
-	// TODO(cuonglm): handle DHCPv6 properly.
-	if ctrldnet.SupportsIPv6() {
-		c := client6.NewClient()
-		conversation, err := c.Exchange(iface.Name)
-		if err != nil {
-			mainLog.Debug().Err(err).Msg("could not exchange DHCPv6")
-		}
-		for _, packet := range conversation {
-			if packet.Type() == dhcpv6.MessageTypeReply {
-				msg, err := packet.GetInnerMessage()
-				if err != nil {
-					mainLog.Debug().Err(err).Msg("could not get inner DHCPv6 message")
-					return nil
-				}
-				nameservers := msg.Options.DNS()
-				for _, nameserver := range nameservers {
-					ns = append(ns, nameserver.String())
-				}
-			}
-		}
-	}
-
-	return ignoringEINTR(func() error {
-		return setDNS(iface, ns)
-	})
-}
-
-func currentDNS(iface *net.Interface) []string {
-	for _, fn := range []getDNS{getDNSByResolvectl, getDNSByNmcli, resolvconffile.NameServers} {
-		if ns := fn(iface.Name); len(ns) > 0 {
-			return ns
-		}
-	}
-	return nil
-}
-
-func getDNSByResolvectl(iface string) []string {
-	b, err := exec.Command("resolvectl", "dns", "-i", iface).Output()
-	if err != nil {
-		return nil
-	}
-
-	parts := strings.Fields(strings.SplitN(string(b), "%", 2)[0])
-	if len(parts) > 2 {
-		return parts[3:]
-	}
-	return nil
-}
-
-func getDNSByNmcli(iface string) []string {
-	b, err := exec.Command("nmcli", "dev", "show", iface).Output()
-	if err != nil {
-		return nil
-	}
-	s := bufio.NewScanner(bytes.NewReader(b))
-	var dns []string
-	do := func(line string) {
-		parts := strings.SplitN(line, ":", 2)
-		if len(parts) > 1 {
-			dns = append(dns, strings.TrimSpace(parts[1]))
-		}
-	}
-	for s.Scan() {
-		line := s.Text()
-		switch {
-		case strings.HasPrefix(line, "IP4.DNS"):
-			fallthrough
-		case strings.HasPrefix(line, "IP6.DNS"):
-			do(line)
-		}
-	}
-	return dns
-}
-
-func ignoringEINTR(fn func() error) error {
-	for {
-		err := fn()
-		if err != syscall.EINTR {
-			return err
-		}
-	}
-}

cmd/ctrld/prog.go

@@ -1,209 +0,0 @@
-package main
-
-import (
-	"errors"
-	"fmt"
-	"math/rand"
-	"net"
-	"os"
-	"strconv"
-	"sync"
-	"syscall"
-
-	"github.com/kardianos/service"
-
-	"github.com/Control-D-Inc/ctrld"
-	"github.com/Control-D-Inc/ctrld/internal/dnscache"
-)
-
-var logf = func(format string, args ...any) {
-	mainLog.Debug().Msgf(format, args...)
-}
-
-var errWindowsAddrInUse = syscall.Errno(0x2740)
-
-var svcConfig = &service.Config{
-	Name:        "ctrld",
-	DisplayName: "Control-D Helper Service",
-}
-
-type prog struct {
-	cfg   *ctrld.Config
-	cache dnscache.Cacher
-}
-
-func (p *prog) Start(s service.Service) error {
-	p.cfg = &cfg
-	go p.run()
-	return nil
-}
-
-func (p *prog) run() {
-	p.preRun()
-	if p.cfg.Service.CacheEnable {
-		cacher, err := dnscache.NewLRUCache(p.cfg.Service.CacheSize)
-		if err != nil {
-			mainLog.Error().Err(err).Msg("failed to create cacher, caching is disabled")
-		} else {
-			p.cache = cacher
-		}
-	}
-	var wg sync.WaitGroup
-	wg.Add(len(p.cfg.Listener))
-
-	for _, nc := range p.cfg.Network {
-		for _, cidr := range nc.Cidrs {
-			_, ipNet, err := net.ParseCIDR(cidr)
-			if err != nil {
-				mainLog.Error().Err(err).Str("network", nc.Name).Str("cidr", cidr).Msg("invalid cidr")
-				continue
-			}
-			nc.IPNets = append(nc.IPNets, ipNet)
-		}
-	}
-	for n := range p.cfg.Upstream {
-		uc := p.cfg.Upstream[n]
-		uc.Init()
-		if uc.BootstrapIP == "" {
-			uc.SetupBootstrapIP()
-			mainLog.Info().Str("bootstrap_ip", uc.BootstrapIP).Msgf("Setting bootstrap IP for upstream.%s", n)
-		} else {
-			mainLog.Info().Str("bootstrap_ip", uc.BootstrapIP).Msgf("Using bootstrap IP for upstream.%s", n)
-		}
-		uc.SetupTransport()
-	}
-
-	for listenerNum := range p.cfg.Listener {
-		p.cfg.Listener[listenerNum].Init()
-		go func(listenerNum string) {
-			defer wg.Done()
-			listenerConfig := p.cfg.Listener[listenerNum]
-			upstreamConfig := p.cfg.Upstream[listenerNum]
-			if upstreamConfig == nil {
-				mainLog.Error().Msgf("missing upstream config for: [listener.%s]", listenerNum)
-				return
-			}
-			addr := net.JoinHostPort(listenerConfig.IP, strconv.Itoa(listenerConfig.Port))
-			mainLog.Info().Msgf("Starting DNS server on listener.%s: %s", listenerNum, addr)
-			err := p.serveDNS(listenerNum)
-			if err != nil && !defaultConfigWritten && cdUID == "" {
-				mainLog.Fatal().Err(err).Msgf("Unable to start dns proxy on listener.%s", listenerNum)
-				return
-			}
-			if err == nil {
-				return
-			}
-
-			if opErr, ok := err.(*net.OpError); ok && listenerNum == "0" {
-				if sErr, ok := opErr.Err.(*os.SyscallError); ok && errors.Is(opErr.Err, syscall.EADDRINUSE) || errors.Is(sErr.Err, errWindowsAddrInUse) {
-					mainLog.Warn().Msgf("Address %s already in used, pick a random one", addr)
-					ip := randomLocalIP()
-					listenerConfig.IP = ip
-					port := listenerConfig.Port
-					cfg.Upstream = map[string]*ctrld.UpstreamConfig{"0": cfg.Upstream["0"]}
-					if err := writeConfigFile(); err != nil {
-						mainLog.Fatal().Err(err).Msg("failed to write config file")
-					} else {
-						mainLog.Info().Msg("writing config file to: " + defaultConfigFile)
-					}
-					p.cfg.Service.AllocateIP = true
-					p.preRun()
-					mainLog.Info().Msgf("Starting DNS server on listener.%s: %s", listenerNum, net.JoinHostPort(ip, strconv.Itoa(port)))
-					if err := p.serveDNS(listenerNum); err != nil {
-						mainLog.Fatal().Err(err).Msgf("Unable to start dns proxy on listener.%s", listenerNum)
-						return
-					}
-				}
-			}
-			mainLog.Fatal().Err(err).Msgf("Unable to start dns proxy on listener.%s", listenerNum)
-		}(listenerNum)
-	}
-
-	wg.Wait()
-}
-
-func (p *prog) Stop(s service.Service) error {
-	if err := p.deAllocateIP(); err != nil {
-		mainLog.Error().Err(err).Msg("de-allocate ip failed")
-		return err
-	}
-	mainLog.Info().Msg("Service stopped")
-	return nil
-}
-
-func (p *prog) allocateIP(ip string) error {
-	if !p.cfg.Service.AllocateIP {
-		return nil
-	}
-	return allocateIP(ip)
-}
-
-func (p *prog) deAllocateIP() error {
-	if !p.cfg.Service.AllocateIP {
-		return nil
-	}
-	for _, lc := range p.cfg.Listener {
-		if err := deAllocateIP(lc.IP); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-func (p *prog) setDNS() {
-	if cfg.Listener == nil || cfg.Listener["0"] == nil {
-		return
-	}
-	if iface == "" {
-		return
-	}
-	if iface == "auto" {
-		iface = defaultIfaceName()
-	}
-	logger := mainLog.With().Str("iface", iface).Logger()
-	netIface, err := netInterface(iface)
-	if err != nil {
-		logger.Error().Err(err).Msg("could not get interface")
-		return
-	}
-	if err := setupNetworkManager(); err != nil {
-		logger.Error().Err(err).Msg("could not patch NetworkManager")
-		return
-	}
-	logger.Debug().Msg("setting DNS for interface")
-	if err := setDNS(netIface, []string{cfg.Listener["0"].IP}); err != nil {
-		logger.Error().Err(err).Msgf("could not set DNS for interface")
-		return
-	}
-	logger.Debug().Msg("setting DNS successfully")
-}
-
-func (p *prog) resetDNS() {
-	if iface == "" {
-		return
-	}
-	if iface == "auto" {
-		iface = defaultIfaceName()
-	}
-	logger := mainLog.With().Str("iface", iface).Logger()
-	netIface, err := netInterface(iface)
-	if err != nil {
-		logger.Error().Err(err).Msg("could not get interface")
-		return
-	}
-	if err := restoreNetworkManager(); err != nil {
-		logger.Error().Err(err).Msg("could not restore NetworkManager")
-		return
-	}
-	logger.Debug().Msg("Restoring DNS for interface")
-	if err := resetDNS(netIface); err != nil {
-		logger.Error().Err(err).Msgf("could not reset DNS")
-		return
-	}
-	logger.Debug().Msg("Restoring DNS successfully")
-}
-
-func randomLocalIP() string {
-	n := rand.Intn(254-2) + 2
-	return fmt.Sprintf("127.0.0.%d", n)
-}

cmd/ctrld/service.go

@@ -1,45 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"os"
-
-	"github.com/spf13/cobra"
-)
-
-func stderrMsg(msg string) {
-	_, _ = fmt.Fprintln(os.Stderr, msg)
-}
-
-func stdoutMsg(msg string) {
-	_, _ = fmt.Fprintln(os.Stdout, msg)
-}
-
-type task struct {
-	f            func() error
-	abortOnError bool
-}
-
-func doTasks(tasks []task) bool {
-	for _, task := range tasks {
-		if err := task.f(); err != nil {
-			if task.abortOnError {
-				stderrMsg(err.Error())
-				return false
-			}
-		}
-	}
-	return true
-}
-
-func checkHasElevatedPrivilege(cmd *cobra.Command, args []string) {
-	ok, err := hasElevatedPrivilege()
-	if err != nil {
-		fmt.Printf("could not detect user privilege: %v", err)
-		return
-	}
-	if !ok {
-		fmt.Println("Please relaunch process with admin/root privilege.")
-		os.Exit(1)
-	}
-}

cmd/ctrld_library/main.go

@@ -0,0 +1,75 @@
+package ctrld_library
+
+import (
+	"github.com/Control-D-Inc/ctrld/cmd/cli"
+)
+
+// Controller holds global state
+type Controller struct {
+	stopCh      chan struct{}
+	AppCallback AppCallback
+	Config      cli.AppConfig
+}
+
+// NewController provides reference to global state to be managed by android vpn service and iOS network extension.
+// reference is not safe for concurrent use.
+func NewController(appCallback AppCallback) *Controller {
+	return &Controller{AppCallback: appCallback}
+}
+
+// AppCallback provides access to app instance.
+type AppCallback interface {
+	Hostname() string
+	LanIp() string
+	MacAddress() string
+	Exit(error string)
+}
+
+// Start configures utility with config.toml from provided directory.
+// This function will block until Stop is called
+// Check port availability prior to calling it.
+func (c *Controller) Start(CdUID string, HomeDir string, UpstreamProto string, logLevel int, logPath string) {
+	if c.stopCh == nil {
+		c.stopCh = make(chan struct{})
+		c.Config = cli.AppConfig{
+			CdUID:         CdUID,
+			HomeDir:       HomeDir,
+			UpstreamProto: UpstreamProto,
+			Verbose:       logLevel,
+			LogPath:       logPath,
+		}
+		appCallback := mapCallback(c.AppCallback)
+		cli.RunMobile(&c.Config, &appCallback, c.stopCh)
+	}
+}
+
+// As workaround to avoid circular dependency between cli and ctrld_library module
+func mapCallback(callback AppCallback) cli.AppCallback {
+	return cli.AppCallback{
+		HostName: func() string {
+			return callback.Hostname()
+		},
+		LanIp: func() string {
+			return callback.LanIp()
+		},
+		MacAddress: func() string {
+			return callback.MacAddress()
+		},
+		Exit: func(err string) {
+			callback.Exit(err)
+		},
+	}
+}
+
+func (c *Controller) Stop() bool {
+	if c.stopCh != nil {
+		close(c.stopCh)
+		c.stopCh = nil
+		return true
+	}
+	return false
+}
+
+func (c *Controller) IsRunning() bool {
+	return c.stopCh != nil
+}

config.go

@@ -2,11 +2,23 @@ package ctrld
 
 import (
 	"context"
+	crand "crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/hex"
+	"errors"
+	"io"
+	"math/rand"
 	"net"
 	"net/http"
+	"net/netip"
 	"net/url"
 	"os"
+	"runtime"
+	"sort"
+	"strconv"
 	"strings"
+	"sync"
 	"sync/atomic"
 	"time"
 
@@ -14,33 +26,74 @@ import (
 	"github.com/miekg/dns"
 	"github.com/spf13/viper"
 	"golang.org/x/sync/singleflight"
+	"tailscale.com/logtail/backoff"
+	"tailscale.com/net/tsaddr"
 
 	"github.com/Control-D-Inc/ctrld/internal/dnsrcode"
 	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
 )
 
-// SetConfigName set the config name that ctrld will look for.
+// IpStackBoth ...
-func SetConfigName(v *viper.Viper, name string) {
+const (
-	v.SetConfigName(name)
+	// IpStackBoth indicates that ctrld will use either ipv4 or ipv6 for connecting to upstream,
+	// depending on which stack is available when receiving the DNS query.
+	IpStackBoth = "both"
+	// IpStackV4 indicates that ctrld will use only ipv4 for connecting to upstream.
+	IpStackV4 = "v4"
+	// IpStackV6 indicates that ctrld will use only ipv6 for connecting to upstream.
+	IpStackV6 = "v6"
+	// IpStackSplit indicates that ctrld will use either ipv4 or ipv6 for connecting to upstream,
+	// depending on the record type of the DNS query.
+	IpStackSplit = "split"
 
+	controlDComDomain = "controld.com"
+	controlDNetDomain = "controld.net"
+	controlDDevDomain = "controld.dev"
+)
+
+var (
+	controldParentDomains  = []string{controlDComDomain, controlDNetDomain, controlDDevDomain}
+	controldVerifiedDomain = map[string]string{
+		controlDComDomain: "verify.controld.com",
+		controlDDevDomain: "verify.controld.dev",
+	}
+)
+
+// SetConfigName set the config name that ctrld will look for.
+// DEPRECATED: use SetConfigNameWithPath instead.
+func SetConfigName(v *viper.Viper, name string) {
 	configPath := "$HOME"
 	// viper has its own way to get user home directory:  https://github.com/spf13/viper/blob/v1.14.0/util.go#L134
 	// To be consistent, we prefer os.UserHomeDir instead.
 	if homeDir, err := os.UserHomeDir(); err == nil {
 		configPath = homeDir
 	}
+	SetConfigNameWithPath(v, name, configPath)
+}
+
+// SetConfigNameWithPath set the config path and name that ctrld will look for.
+func SetConfigNameWithPath(v *viper.Viper, name, configPath string) {
+	v.SetConfigName(name)
 	v.AddConfigPath(configPath)
 	v.AddConfigPath(".")
 }
 
 // InitConfig initializes default config values for given *viper.Viper instance.
 func InitConfig(v *viper.Viper, name string) {
-	SetConfigName(v, name)
-
 	v.SetDefault("listener", map[string]*ListenerConfig{
 		"0": {
-			IP:   "127.0.0.1",
+			IP:   "",
-			Port: 53,
+			Port: 0,
+			Policy: &ListenerPolicyConfig{
+				Name: "Main Policy",
+				Networks: []Rule{
+					{"network.0": []string{"upstream.0"}},
+				},
+				Rules: []Rule{
+					{"example.com": []string{"upstream.0"}},
+					{"*.ads.com": []string{"upstream.1"}},
+				},
+			},
 		},
 	})
 	v.SetDefault("network", map[string]*NetworkConfig{
@@ -75,16 +128,77 @@ type Config struct {
 	Upstream map[string]*UpstreamConfig `mapstructure:"upstream" toml:"upstream" validate:"min=1,dive"`
 }
 
+// HasUpstreamSendClientInfo reports whether the config has any upstream
+// is configured to send client info to Control D DNS server.
+func (c *Config) HasUpstreamSendClientInfo() bool {
+	for _, uc := range c.Upstream {
+		if uc.UpstreamSendClientInfo() {
+			return true
+		}
+	}
+	return false
+}
+
+// FirstListener returns the first listener config of current config. Listeners are sorted numerically.
+//
+// It panics if Config has no listeners configured.
+func (c *Config) FirstListener() *ListenerConfig {
+	listeners := make([]int, 0, len(c.Listener))
+	for k := range c.Listener {
+		n, err := strconv.Atoi(k)
+		if err != nil {
+			continue
+		}
+		listeners = append(listeners, n)
+	}
+	if len(listeners) == 0 {
+		panic("missing listener config")
+	}
+	sort.Ints(listeners)
+	return c.Listener[strconv.Itoa(listeners[0])]
+}
+
+// FirstUpstream returns the first upstream of current config. Upstreams are sorted numerically.
+//
+// It panics if Config has no upstreams configured.
+func (c *Config) FirstUpstream() *UpstreamConfig {
+	upstreams := make([]int, 0, len(c.Upstream))
+	for k := range c.Upstream {
+		n, err := strconv.Atoi(k)
+		if err != nil {
+			continue
+		}
+		upstreams = append(upstreams, n)
+	}
+	if len(upstreams) == 0 {
+		panic("missing listener config")
+	}
+	sort.Ints(upstreams)
+	return c.Upstream[strconv.Itoa(upstreams[0])]
+}
+
 // ServiceConfig specifies the general ctrld config.
 type ServiceConfig struct {
-	LogLevel         string `mapstructure:"log_level" toml:"log_level,omitempty"`
+	LogLevel                string `mapstructure:"log_level" toml:"log_level,omitempty"`
-	LogPath          string `mapstructure:"log_path" toml:"log_path,omitempty"`
+	LogPath                 string `mapstructure:"log_path" toml:"log_path,omitempty"`
-	CacheEnable      bool   `mapstructure:"cache_enable" toml:"cache_enable,omitempty"`
+	CacheEnable             bool   `mapstructure:"cache_enable" toml:"cache_enable,omitempty"`
-	CacheSize        int    `mapstructure:"cache_size" toml:"cache_size,omitempty"`
+	CacheSize               int    `mapstructure:"cache_size" toml:"cache_size,omitempty"`
-	CacheTTLOverride int    `mapstructure:"cache_ttl_override" toml:"cache_ttl_override,omitempty"`
+	CacheTTLOverride        int    `mapstructure:"cache_ttl_override" toml:"cache_ttl_override,omitempty"`
-	CacheServeStale  bool   `mapstructure:"cache_serve_stale" toml:"cache_serve_stale,omitempty"`
+	CacheServeStale         bool   `mapstructure:"cache_serve_stale" toml:"cache_serve_stale,omitempty"`
-	Daemon           bool   `mapstructure:"-" toml:"-"`
+	MaxConcurrentRequests   *int   `mapstructure:"max_concurrent_requests" toml:"max_concurrent_requests,omitempty" validate:"omitempty,gte=0"`
-	AllocateIP       bool   `mapstructure:"-" toml:"-"`
+	DHCPLeaseFile           string `mapstructure:"dhcp_lease_file_path" toml:"dhcp_lease_file_path" validate:"omitempty,file"`
+	DHCPLeaseFileFormat     string `mapstructure:"dhcp_lease_file_format" toml:"dhcp_lease_file_format" validate:"required_unless=DHCPLeaseFile '',omitempty,oneof=dnsmasq isc-dhcp"`
+	DiscoverMDNS            *bool  `mapstructure:"discover_mdns" toml:"discover_mdns,omitempty"`
+	DiscoverARP             *bool  `mapstructure:"discover_arp" toml:"discover_arp,omitempty"`
+	DiscoverDHCP            *bool  `mapstructure:"discover_dhcp" toml:"discover_dhcp,omitempty"`
+	DiscoverPtr             *bool  `mapstructure:"discover_ptr" toml:"discover_ptr,omitempty"`
+	DiscoverHosts           *bool  `mapstructure:"discover_hosts" toml:"discover_hosts,omitempty"`
+	DiscoverRefreshInterval int    `mapstructure:"discover_refresh_interval" toml:"discover_refresh_interval,omitempty"`
+	ClientIDPref            string `mapstructure:"client_id_preference" toml:"client_id_preference,omitempty" validate:"omitempty,oneof=host mac"`
+	MetricsQueryStats       bool   `mapstructure:"metrics_query_stats" toml:"metrics_query_stats,omitempty"`
+	MetricsListener         string `mapstructure:"metrics_listener" toml:"metrics_listener,omitempty"`
+	Daemon                  bool   `mapstructure:"-" toml:"-"`
+	AllocateIP              bool   `mapstructure:"-" toml:"-"`
 }
 
 // NetworkConfig specifies configuration for networks where ctrld will handle requests.
@@ -96,26 +210,62 @@ type NetworkConfig struct {
 
 // UpstreamConfig specifies configuration for upstreams that ctrld will forward requests to.
 type UpstreamConfig struct {
-	Name              string            `mapstructure:"name" toml:"name,omitempty"`
+	Name        string `mapstructure:"name" toml:"name,omitempty"`
-	Type              string            `mapstructure:"type" toml:"type,omitempty" validate:"oneof=doh doh3 dot doq os legacy"`
+	Type        string `mapstructure:"type" toml:"type,omitempty" validate:"oneof=doh doh3 dot doq os legacy"`
-	Endpoint          string            `mapstructure:"endpoint" toml:"endpoint,omitempty" validate:"required_unless=Type os"`
+	Endpoint    string `mapstructure:"endpoint" toml:"endpoint,omitempty"`
-	BootstrapIP       string            `mapstructure:"bootstrap_ip" toml:"bootstrap_ip,omitempty"`
+	BootstrapIP string `mapstructure:"bootstrap_ip" toml:"bootstrap_ip,omitempty"`
-	Domain            string            `mapstructure:"-" toml:"-"`
+	Domain      string `mapstructure:"-" toml:"-"`
-	Timeout           int               `mapstructure:"timeout" toml:"timeout,omitempty" validate:"gte=0"`
+	IPStack     string `mapstructure:"ip_stack" toml:"ip_stack,omitempty" validate:"ipstack"`
-	transport         *http.Transport   `mapstructure:"-" toml:"-"`
+	Timeout     int    `mapstructure:"timeout" toml:"timeout,omitempty" validate:"gte=0"`
-	http3RoundTripper http.RoundTripper `mapstructure:"-" toml:"-"`
+	// The caller should not access this field directly.
+	// Use UpstreamSendClientInfo instead.
+	SendClientInfo *bool `mapstructure:"send_client_info" toml:"send_client_info,omitempty"`
+	// The caller should not access this field directly.
+	// Use IsDiscoverable instead.
+	Discoverable *bool `mapstructure:"discoverable" toml:"discoverable"`
 
-	g               singleflight.Group
+	g                  singleflight.Group
-	bootstrapIPs    []string
+	rebootstrap        atomic.Bool
-	nextBootstrapIP atomic.Uint32
+	bootstrapIPs       []string
+	bootstrapIPs4      []string
+	bootstrapIPs6      []string
+	transport          *http.Transport
+	transportOnce      sync.Once
+	transport4         *http.Transport
+	transport6         *http.Transport
+	http3RoundTripper  http.RoundTripper
+	http3RoundTripper4 http.RoundTripper
+	http3RoundTripper6 http.RoundTripper
+	certPool           *x509.CertPool
+	u                  *url.URL
+	uid                string
 }
 
 // ListenerConfig specifies the networks configuration that ctrld will run on.
 type ListenerConfig struct {
-	IP         string                `mapstructure:"ip" toml:"ip,omitempty" validate:"ip"`
+	IP              string                `mapstructure:"ip" toml:"ip,omitempty" validate:"iporempty"`
-	Port       int                   `mapstructure:"port" toml:"port,omitempty" validate:"gt=0"`
+	Port            int                   `mapstructure:"port" toml:"port,omitempty" validate:"gte=0"`
-	Restricted bool                  `mapstructure:"restricted" toml:"restricted,omitempty"`
+	Restricted      bool                  `mapstructure:"restricted" toml:"restricted,omitempty"`
-	Policy     *ListenerPolicyConfig `mapstructure:"policy" toml:"policy,omitempty"`
+	AllowWanClients bool                  `mapstructure:"allow_wan_clients" toml:"allow_wan_clients,omitempty"`
+	Policy          *ListenerPolicyConfig `mapstructure:"policy" toml:"policy,omitempty"`
+}
+
+// IsDirectDnsListener reports whether ctrld can be a direct listener on port 53.
+// It returns true only if ctrld can listen on port 53 for all interfaces. That means
+// there's no other software listening on port 53.
+//
+// If someone listening on port 53, or ctrld could only listen on port 53 for a specific
+// interface, ctrld could only be configured as a DNS forwarder.
+func (lc *ListenerConfig) IsDirectDnsListener() bool {
+	if lc == nil || lc.Port != 53 {
+		return false
+	}
+	switch lc.IP {
+	case "", "::", "0.0.0.0":
+		return true
+	default:
+		return false
+	}
 }
 
 // ListenerPolicyConfig specifies the policy rules for ctrld to filter incoming requests.
@@ -123,6 +273,7 @@ type ListenerPolicyConfig struct {
 	Name                 string   `mapstructure:"name" toml:"name,omitempty"`
 	Networks             []Rule   `mapstructure:"networks" toml:"networks,omitempty,inline,multiline" validate:"dive,len=1"`
 	Rules                []Rule   `mapstructure:"rules" toml:"rules,omitempty,inline,multiline" validate:"dive,len=1"`
+	Macs                 []Rule   `mapstructure:"macs" toml:"macs,omitempty,inline,multiline" validate:"dive,len=1"`
 	FailoverRcodes       []string `mapstructure:"failover_rcodes" toml:"failover_rcodes,omitempty" validate:"dive,dnsrcode"`
 	FailoverRcodeNumbers []int    `mapstructure:"-" toml:"-"`
 }
@@ -134,91 +285,141 @@ type Rule map[string][]string
 
 // Init initialized necessary values for an UpstreamConfig.
 func (uc *UpstreamConfig) Init() {
+	uc.uid = upstreamUID()
 	if u, err := url.Parse(uc.Endpoint); err == nil {
 		uc.Domain = u.Host
+		switch uc.Type {
+		case ResolverTypeDOH, ResolverTypeDOH3:
+			uc.u = u
+		}
 	}
-	if uc.Domain != "" {
+	if uc.Domain == "" {
-		return
+		if !strings.Contains(uc.Endpoint, ":") {
+			uc.Domain = uc.Endpoint
+			uc.Endpoint = net.JoinHostPort(uc.Endpoint, defaultPortFor(uc.Type))
+		}
+		host, _, _ := net.SplitHostPort(uc.Endpoint)
+		uc.Domain = host
+		if net.ParseIP(uc.Domain) != nil {
+			uc.BootstrapIP = uc.Domain
+		}
 	}
+	if uc.IPStack == "" {
+		if uc.isControlD() {
+			uc.IPStack = IpStackSplit
+		} else {
+			uc.IPStack = IpStackBoth
+		}
+	}
+}
 
-	if !strings.Contains(uc.Endpoint, ":") {
+// VerifyDomain returns the domain name that could be resolved by the upstream endpoint.
-		uc.Domain = uc.Endpoint
+// It returns empty for non-ControlD upstream endpoint.
-		uc.Endpoint = net.JoinHostPort(uc.Endpoint, defaultPortFor(uc.Type))
+func (uc *UpstreamConfig) VerifyDomain() string {
+	domain := uc.Domain
+	if domain == "" {
+		if u, err := url.Parse(uc.Endpoint); err == nil {
+			domain = u.Hostname()
+		}
 	}
-	host, _, _ := net.SplitHostPort(uc.Endpoint)
+	for _, parent := range controldParentDomains {
-	uc.Domain = host
+		if dns.IsSubDomain(parent, domain) {
-	if net.ParseIP(uc.Domain) != nil {
+			return controldVerifiedDomain[parent]
-		uc.BootstrapIP = uc.Domain
+		}
 	}
+	return ""
+}
+
+// UpstreamSendClientInfo reports whether the upstream is
+// configured to send client info to Control D DNS server.
+//
+// Client info includes:
+//   - MAC
+//   - Lan IP
+//   - Hostname
+func (uc *UpstreamConfig) UpstreamSendClientInfo() bool {
+	if uc.SendClientInfo != nil {
+		return *uc.SendClientInfo
+	}
+	switch uc.Type {
+	case ResolverTypeDOH, ResolverTypeDOH3:
+		if uc.isControlD() || uc.isNextDNS() {
+			return true
+		}
+	}
+	return false
+}
+
+// IsDiscoverable reports whether the upstream can be used for PTR discovery.
+// The caller must ensure uc.Init() was called before calling this.
+func (uc *UpstreamConfig) IsDiscoverable() bool {
+	if uc.Discoverable != nil {
+		return *uc.Discoverable
+	}
+	switch uc.Type {
+	case ResolverTypeOS, ResolverTypeLegacy, ResolverTypePrivate:
+		if ip, err := netip.ParseAddr(uc.Domain); err == nil {
+			return ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() || tsaddr.CGNATRange().Contains(ip)
+		}
+	}
+	return false
+}
+
+// BootstrapIPs returns the bootstrap IPs list of upstreams.
+func (uc *UpstreamConfig) BootstrapIPs() []string {
+	return uc.bootstrapIPs
+}
+
+// SetCertPool sets the system cert pool used for TLS connections.
+func (uc *UpstreamConfig) SetCertPool(cp *x509.CertPool) {
+	uc.certPool = cp
 }
 
 // SetupBootstrapIP manually find all available IPs of the upstream.
 // The first usable IP will be used as bootstrap IP of the upstream.
 func (uc *UpstreamConfig) SetupBootstrapIP() {
-	bootstrapIP := func(record dns.RR) string {
+	uc.setupBootstrapIP(true)
-		switch ar := record.(type) {
+}
-		case *dns.A:
-			return ar.A.String()
-		case *dns.AAAA:
-			return ar.AAAA.String()
-		}
-		return ""
-	}
 
-	resolver := &osResolver{nameservers: availableNameservers()}
+// UID returns the unique identifier of the upstream.
-	resolver.nameservers = append([]string{net.JoinHostPort(bootstrapDNS, "53")}, resolver.nameservers...)
+func (uc *UpstreamConfig) UID() string {
-	ProxyLog.Debug().Msgf("Resolving %q using bootstrap DNS %q", uc.Domain, resolver.nameservers)
+	return uc.uid
-	timeoutMs := 2000
+}
-	if uc.Timeout > 0 && uc.Timeout < timeoutMs {
-		timeoutMs = uc.Timeout
-	}
-	do := func(dnsType uint16) {
-		ctx, cancel := context.WithTimeout(context.Background(), time.Duration(timeoutMs)*time.Millisecond)
-		defer cancel()
-		m := new(dns.Msg)
-		m.SetQuestion(uc.Domain+".", dnsType)
-		m.RecursionDesired = true
 
-		r, err := resolver.Resolve(ctx, m)
+// SetupBootstrapIP manually find all available IPs of the upstream.
-		if err != nil {
+// The first usable IP will be used as bootstrap IP of the upstream.
-			ProxyLog.Error().Err(err).Str("type", dns.TypeToString[dnsType]).Msgf("could not resolve domain %s for upstream", uc.Domain)
+func (uc *UpstreamConfig) setupBootstrapIP(withBootstrapDNS bool) {
-			return
+	b := backoff.NewBackoff("setupBootstrapIP", func(format string, args ...any) {}, 10*time.Second)
-		}
+	isControlD := uc.isControlD()
-		if r.Rcode != dns.RcodeSuccess {
+	for {
-			ProxyLog.Error().Msgf("could not resolve domain return code: %d, upstream", r.Rcode)
+		uc.bootstrapIPs = lookupIP(uc.Domain, uc.Timeout, withBootstrapDNS)
-			return
+		// For ControlD upstream, the bootstrap IPs could not be RFC 1918 addresses,
-		}
+		// filtering them out here to prevent weird behavior.
-		if len(r.Answer) == 0 {
+		if isControlD {
-			ProxyLog.Error().Msg("no answer from bootstrap DNS server")
+			n := 0
-			return
+			for _, ip := range uc.bootstrapIPs {
-		}
+				netIP := net.ParseIP(ip)
-		for _, a := range r.Answer {
+				if netIP != nil && !netIP.IsPrivate() {
-			ip := bootstrapIP(a)
+					uc.bootstrapIPs[n] = ip
-			if ip == "" {
+					n++
-				continue
-			}
-
-			// Storing the ip to uc.bootstrapIPs list, so it can be selected later
-			// when retrying failed request due to network stack changed.
-			uc.bootstrapIPs = append(uc.bootstrapIPs, ip)
-			if uc.BootstrapIP == "" {
-				// Remember what's the current IP in bootstrap IPs list,
-				// so we can select next one upon re-bootstrapping.
-				uc.nextBootstrapIP.Add(1)
-
-				// If this is an ipv6, and ipv6 is not available, don't use it as bootstrap ip.
-				if !ctrldnet.SupportsIPv6() && ctrldnet.IsIPv6(ip) {
-					continue
 				}
-				uc.BootstrapIP = ip
 			}
+			uc.bootstrapIPs = uc.bootstrapIPs[:n]
+		}
+		if len(uc.bootstrapIPs) > 0 {
+			break
+		}
+		ProxyLogger.Load().Warn().Msg("could not resolve bootstrap IPs, retrying...")
+		b.BackOff(context.Background(), errors.New("no bootstrap IPs"))
+	}
+	for _, ip := range uc.bootstrapIPs {
+		if ctrldnet.IsIPv6(ip) {
+			uc.bootstrapIPs6 = append(uc.bootstrapIPs6, ip)
+		} else {
+			uc.bootstrapIPs4 = append(uc.bootstrapIPs4, ip)
 		}
 	}
-	// Find all A, AAAA records of the upstream.
+	ProxyLogger.Load().Debug().Msgf("bootstrap IPs: %v", uc.bootstrapIPs)
-	for _, dnsType := range []uint16{dns.TypeAAAA, dns.TypeA} {
-		do(dnsType)
-	}
-	ProxyLog.Debug().Msgf("Bootstrap IPs: %v", uc.bootstrapIPs)
 }
 
 // ReBootstrap re-setup the bootstrap IP and the transport.
@@ -228,44 +429,14 @@ func (uc *UpstreamConfig) ReBootstrap() {
 	default:
 		return
 	}
-	_, _, _ = uc.g.Do("rebootstrap", func() (any, error) {
+	_, _, _ = uc.g.Do("ReBootstrap", func() (any, error) {
-		ProxyLog.Debug().Msg("re-bootstrapping upstream ip")
+		if uc.rebootstrap.CompareAndSwap(false, true) {
-		n := uint32(len(uc.bootstrapIPs))
+			ProxyLogger.Load().Debug().Msg("re-bootstrapping upstream ip")
-
-		timeoutMs := 1000
-		if uc.Timeout > 0 && uc.Timeout < timeoutMs {
-			timeoutMs = uc.Timeout
 		}
-		ctx, cancel := context.WithTimeout(context.Background(), time.Duration(timeoutMs)*time.Millisecond)
-		defer cancel()
-
-		hasIPv6 := ctrldnet.IPv6Available(ctx)
-		// Only attempt n times, because if there's no usable ip,
-		// the bootstrap ip will be kept as-is.
-		for i := uint32(0); i < n; i++ {
-			// Select the next ip in bootstrap ip list.
-			next := uc.nextBootstrapIP.Add(1)
-			ip := uc.bootstrapIPs[(next-1)%n]
-			if !hasIPv6 && ctrldnet.IsIPv6(ip) {
-				continue
-			}
-			uc.BootstrapIP = ip
-			break
-		}
-		uc.setupTransportWithoutPingUpstream()
 		return true, nil
 	})
 }
 
-func (uc *UpstreamConfig) setupTransportWithoutPingUpstream() {
-	switch uc.Type {
-	case ResolverTypeDOH:
-		uc.setupDOHTransportWithoutPingUpstream()
-	case ResolverTypeDOH3:
-		uc.setupDOH3TransportWithoutPingUpstream()
-	}
-}
-
 // SetupTransport initializes the network transport used to connect to upstream server.
 // For now, only DoH upstream is supported.
 func (uc *UpstreamConfig) SetupTransport() {
@@ -278,48 +449,186 @@ func (uc *UpstreamConfig) SetupTransport() {
 }
 
 func (uc *UpstreamConfig) setupDOHTransport() {
-	uc.setupDOHTransportWithoutPingUpstream()
+	switch uc.IPStack {
-	uc.pingUpstream()
+	case IpStackBoth, "":
+		uc.transport = uc.newDOHTransport(uc.bootstrapIPs)
+	case IpStackV4:
+		uc.transport = uc.newDOHTransport(uc.bootstrapIPs4)
+	case IpStackV6:
+		uc.transport = uc.newDOHTransport(uc.bootstrapIPs6)
+	case IpStackSplit:
+		uc.transport4 = uc.newDOHTransport(uc.bootstrapIPs4)
+		if hasIPv6() {
+			uc.transport6 = uc.newDOHTransport(uc.bootstrapIPs6)
+		} else {
+			uc.transport6 = uc.transport4
+		}
+		uc.transport = uc.newDOHTransport(uc.bootstrapIPs)
+	}
 }
 
-func (uc *UpstreamConfig) setupDOHTransportWithoutPingUpstream() {
+func (uc *UpstreamConfig) newDOHTransport(addrs []string) *http.Transport {
-	uc.transport = http.DefaultTransport.(*http.Transport).Clone()
+	transport := http.DefaultTransport.(*http.Transport).Clone()
-	uc.transport.IdleConnTimeout = 5 * time.Second
+	transport.MaxIdleConnsPerHost = 100
+	transport.TLSClientConfig = &tls.Config{
+		RootCAs:            uc.certPool,
+		ClientSessionCache: tls.NewLRUClientSessionCache(0),
+	}
 
 	dialerTimeoutMs := 2000
 	if uc.Timeout > 0 && uc.Timeout < dialerTimeoutMs {
 		dialerTimeoutMs = uc.Timeout
 	}
 	dialerTimeout := time.Duration(dialerTimeoutMs) * time.Millisecond
-	uc.transport.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
+	transport.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
-		dialer := &net.Dialer{
+		_, port, _ := net.SplitHostPort(addr)
-			Timeout:   dialerTimeout,
-			KeepAlive: dialerTimeout,
-		}
-		// if we have a bootstrap ip set, use it to avoid DNS lookup
 		if uc.BootstrapIP != "" {
-			if _, port, _ := net.SplitHostPort(addr); port != "" {
+			dialer := net.Dialer{Timeout: dialerTimeout, KeepAlive: dialerTimeout}
-				addr = net.JoinHostPort(uc.BootstrapIP, port)
+			addr := net.JoinHostPort(uc.BootstrapIP, port)
-			}
+			Log(ctx, ProxyLogger.Load().Debug(), "sending doh request to: %s", addr)
+			return dialer.DialContext(ctx, network, addr)
+		}
+		pd := &ctrldnet.ParallelDialer{}
+		pd.Timeout = dialerTimeout
+		pd.KeepAlive = dialerTimeout
+		dialAddrs := make([]string, len(addrs))
+		for i := range addrs {
+			dialAddrs[i] = net.JoinHostPort(addrs[i], port)
+		}
+		conn, err := pd.DialContext(ctx, network, dialAddrs)
+		if err != nil {
+			return nil, err
+		}
+		Log(ctx, ProxyLogger.Load().Debug(), "sending doh request to: %s", conn.RemoteAddr())
+		return conn, nil
+	}
+	runtime.SetFinalizer(transport, func(transport *http.Transport) {
+		transport.CloseIdleConnections()
+	})
+	return transport
+}
+
+// Ping warms up the connection to DoH/DoH3 upstream.
+func (uc *UpstreamConfig) Ping() {
+	switch uc.Type {
+	case ResolverTypeDOH, ResolverTypeDOH3:
+	default:
+		return
+	}
+
+	ping := func(t http.RoundTripper) {
+		if t == nil {
+			return
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+		defer cancel()
+		req, _ := http.NewRequestWithContext(ctx, "HEAD", uc.Endpoint, nil)
+		resp, _ := t.RoundTrip(req)
+		if resp == nil {
+			return
+		}
+		defer resp.Body.Close()
+		_, _ = io.Copy(io.Discard, resp.Body)
+	}
+
+	for _, typ := range []uint16{dns.TypeA, dns.TypeAAAA} {
+		switch uc.Type {
+		case ResolverTypeDOH:
+			ping(uc.dohTransport(typ))
+		case ResolverTypeDOH3:
+			ping(uc.doh3Transport(typ))
 		}
-		Log(ctx, ProxyLog.Debug(), "sending doh request to: %s", addr)
-		return dialer.DialContext(ctx, network, addr)
 	}
 }
 
-func (uc *UpstreamConfig) pingUpstream() {
+func (uc *UpstreamConfig) isControlD() bool {
-	// Warming up the transport by querying a test packet.
+	domain := uc.Domain
-	dnsResolver, err := NewResolver(uc)
+	if domain == "" {
-	if err != nil {
+		if u, err := url.Parse(uc.Endpoint); err == nil {
-		ProxyLog.Error().Err(err).Msgf("failed to create resolver for upstream: %s", uc.Name)
+			domain = u.Hostname()
-		return
+		}
 	}
-	msg := new(dns.Msg)
+	for _, parent := range controldParentDomains {
-	msg.SetQuestion(".", dns.TypeNS)
+		if dns.IsSubDomain(parent, domain) {
-	msg.MsgHdr.RecursionDesired = true
+			return true
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		}
-	defer cancel()
+	}
-	_, _ = dnsResolver.Resolve(ctx, msg)
+	return false
+}
+
+func (uc *UpstreamConfig) isNextDNS() bool {
+	domain := uc.Domain
+	if domain == "" {
+		if u, err := url.Parse(uc.Endpoint); err == nil {
+			domain = u.Hostname()
+		}
+	}
+	return domain == "dns.nextdns.io"
+}
+
+func (uc *UpstreamConfig) dohTransport(dnsType uint16) http.RoundTripper {
+	uc.transportOnce.Do(func() {
+		uc.SetupTransport()
+	})
+	if uc.rebootstrap.CompareAndSwap(true, false) {
+		uc.SetupTransport()
+	}
+	switch uc.IPStack {
+	case IpStackBoth, IpStackV4, IpStackV6:
+		return uc.transport
+	case IpStackSplit:
+		switch dnsType {
+		case dns.TypeA:
+			return uc.transport4
+		default:
+			return uc.transport6
+		}
+	}
+	return uc.transport
+}
+
+func (uc *UpstreamConfig) bootstrapIPForDNSType(dnsType uint16) string {
+	switch uc.IPStack {
+	case IpStackBoth:
+		return pick(uc.bootstrapIPs)
+	case IpStackV4:
+		return pick(uc.bootstrapIPs4)
+	case IpStackV6:
+		return pick(uc.bootstrapIPs6)
+	case IpStackSplit:
+		switch dnsType {
+		case dns.TypeA:
+			return pick(uc.bootstrapIPs4)
+		default:
+			if hasIPv6() {
+				return pick(uc.bootstrapIPs6)
+			}
+			return pick(uc.bootstrapIPs4)
+		}
+	}
+	return pick(uc.bootstrapIPs)
+}
+
+func (uc *UpstreamConfig) netForDNSType(dnsType uint16) (string, string) {
+	switch uc.IPStack {
+	case IpStackBoth:
+		return "tcp-tls", "udp"
+	case IpStackV4:
+		return "tcp4-tls", "udp4"
+	case IpStackV6:
+		return "tcp6-tls", "udp6"
+	case IpStackSplit:
+		switch dnsType {
+		case dns.TypeA:
+			return "tcp4-tls", "udp4"
+		default:
+			if hasIPv6() {
+				return "tcp6-tls", "udp6"
+			}
+			return "tcp4-tls", "udp4"
+		}
+	}
+	return "tcp-tls", "udp"
 }
 
 // Init initialized necessary values for an ListenerConfig.
@@ -335,6 +644,9 @@ func (lc *ListenerConfig) Init() {
 // ValidateConfig validates the given config.
 func ValidateConfig(validate *validator.Validate, cfg *Config) error {
 	_ = validate.RegisterValidation("dnsrcode", validateDnsRcode)
+	_ = validate.RegisterValidation("ipstack", validateIpStack)
+	_ = validate.RegisterValidation("iporempty", validateIpOrEmpty)
+	validate.RegisterStructValidation(upstreamConfigStructLevelValidation, UpstreamConfig{})
 	return validate.Struct(cfg)
 }
 
@@ -342,6 +654,49 @@ func validateDnsRcode(fl validator.FieldLevel) bool {
 	return dnsrcode.FromString(fl.Field().String()) != -1
 }
 
+func validateIpStack(fl validator.FieldLevel) bool {
+	switch fl.Field().String() {
+	case IpStackBoth, IpStackV4, IpStackV6, IpStackSplit, "":
+		return true
+	default:
+		return false
+	}
+}
+
+func validateIpOrEmpty(fl validator.FieldLevel) bool {
+	val := fl.Field().String()
+	if val == "" {
+		return true
+	}
+	return net.ParseIP(val) != nil
+}
+
+func upstreamConfigStructLevelValidation(sl validator.StructLevel) {
+	uc := sl.Current().Addr().Interface().(*UpstreamConfig)
+	if uc.Type == ResolverTypeOS {
+		return
+	}
+
+	// Endpoint is required for non os resolver.
+	if uc.Endpoint == "" {
+		sl.ReportError(uc.Endpoint, "endpoint", "Endpoint", "required_unless", "")
+		return
+	}
+
+	// DoH/DoH3 requires endpoint is an HTTP url.
+	if uc.Type == ResolverTypeDOH || uc.Type == ResolverTypeDOH3 {
+		u, err := url.Parse(uc.Endpoint)
+		if err != nil || u.Host == "" {
+			sl.ReportError(uc.Endpoint, "endpoint", "Endpoint", "http_url", "")
+			return
+		}
+		if u.Scheme != "http" && u.Scheme != "https" {
+			sl.ReportError(uc.Endpoint, "endpoint", "Endpoint", "http_url", "")
+			return
+		}
+	}
+}
+
 func defaultPortFor(typ string) string {
 	switch typ {
 	case ResolverTypeDOH, ResolverTypeDOH3:
@@ -354,17 +709,42 @@ func defaultPortFor(typ string) string {
 	return "53"
 }
 
-func availableNameservers() []string {
+// ResolverTypeFromEndpoint tries guessing the resolver type with a given endpoint
-	nss := nameservers()
+// using following rules:
-	n := 0
+//
-	for _, ns := range nss {
+// - If endpoint is an IP address ->  ResolverTypeLegacy
-		ip, _, _ := net.SplitHostPort(ns)
+// - If endpoint starts with "https://" -> ResolverTypeDOH
-		// skipping invalid entry or ipv6 nameserver if ipv6 not available.
+// - If endpoint starts with "quic://" -> ResolverTypeDOQ
-		if ip == "" || (ctrldnet.IsIPv6(ip) && !ctrldnet.SupportsIPv6()) {
+// - For anything else -> ResolverTypeDOT
+func ResolverTypeFromEndpoint(endpoint string) string {
+	switch {
+	case strings.HasPrefix(endpoint, "https://"):
+		return ResolverTypeDOH
+	case strings.HasPrefix(endpoint, "quic://"):
+		return ResolverTypeDOQ
+	}
+	host := endpoint
+	if strings.Contains(endpoint, ":") {
+		host, _, _ = net.SplitHostPort(host)
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		return ResolverTypeLegacy
+	}
+	return ResolverTypeDOT
+}
+
+func pick(s []string) string {
+	return s[rand.Intn(len(s))]
+}
+
+// upstreamUID generates an unique identifier for an upstream.
+func upstreamUID() string {
+	b := make([]byte, 4)
+	for {
+		if _, err := crand.Read(b); err != nil {
+			ProxyLogger.Load().Warn().Err(err).Msg("could not generate uid for upstream, retrying...")
 			continue
 		}
-		nss[n] = ns
+		return hex.EncodeToString(b)
-		n++
 	}
-	return nss[:n]
 }

config_internal_test.go

@@ -0,0 +1,339 @@
+package ctrld
+
+import (
+	"net/url"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUpstreamConfig_SetupBootstrapIP(t *testing.T) {
+	uc := &UpstreamConfig{
+		Name:     "test",
+		Type:     ResolverTypeDOH,
+		Endpoint: "https://freedns.controld.com/p2",
+		Timeout:  5000,
+	}
+	uc.Init()
+	uc.setupBootstrapIP(false)
+	if len(uc.bootstrapIPs) == 0 {
+		t.Log(nameservers())
+		t.Fatal("could not bootstrap ip without bootstrap DNS")
+	}
+	t.Log(uc)
+}
+
+func TestUpstreamConfig_Init(t *testing.T) {
+	u1, _ := url.Parse("https://example.com")
+	u2, _ := url.Parse("https://example.com?k=v")
+	tests := []struct {
+		name     string
+		uc       *UpstreamConfig
+		expected *UpstreamConfig
+	}{
+		{
+			"doh+doh3",
+			&UpstreamConfig{
+				Name:        "doh",
+				Type:        "doh",
+				Endpoint:    "https://example.com",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+			},
+			&UpstreamConfig{
+				Name:        "doh",
+				Type:        "doh",
+				Endpoint:    "https://example.com",
+				BootstrapIP: "",
+				Domain:      "example.com",
+				Timeout:     0,
+				IPStack:     IpStackBoth,
+				u:           u1,
+			},
+		},
+		{
+			"doh+doh3 with query param",
+			&UpstreamConfig{
+				Name:        "doh",
+				Type:        "doh",
+				Endpoint:    "https://example.com?k=v",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+			},
+			&UpstreamConfig{
+				Name:        "doh",
+				Type:        "doh",
+				Endpoint:    "https://example.com?k=v",
+				BootstrapIP: "",
+				Domain:      "example.com",
+				Timeout:     0,
+				IPStack:     IpStackBoth,
+				u:           u2,
+			},
+		},
+		{
+			"dot+doq",
+			&UpstreamConfig{
+				Name:        "dot",
+				Type:        "dot",
+				Endpoint:    "freedns.controld.com:8853",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+			},
+			&UpstreamConfig{
+				Name:        "dot",
+				Type:        "dot",
+				Endpoint:    "freedns.controld.com:8853",
+				BootstrapIP: "",
+				Domain:      "freedns.controld.com",
+				Timeout:     0,
+				IPStack:     IpStackSplit,
+			},
+		},
+		{
+			"dot+doq without port",
+			&UpstreamConfig{
+				Name:        "dot",
+				Type:        "dot",
+				Endpoint:    "freedns.controld.com",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+				IPStack:     IpStackSplit,
+			},
+			&UpstreamConfig{
+				Name:        "dot",
+				Type:        "dot",
+				Endpoint:    "freedns.controld.com:853",
+				BootstrapIP: "",
+				Domain:      "freedns.controld.com",
+				Timeout:     0,
+				IPStack:     IpStackSplit,
+			},
+		},
+		{
+			"legacy",
+			&UpstreamConfig{
+				Name:        "legacy",
+				Type:        "legacy",
+				Endpoint:    "1.2.3.4:53",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+			},
+			&UpstreamConfig{
+				Name:        "legacy",
+				Type:        "legacy",
+				Endpoint:    "1.2.3.4:53",
+				BootstrapIP: "1.2.3.4",
+				Domain:      "1.2.3.4",
+				Timeout:     0,
+				IPStack:     IpStackBoth,
+			},
+		},
+		{
+			"legacy without port",
+			&UpstreamConfig{
+				Name:        "legacy",
+				Type:        "legacy",
+				Endpoint:    "1.2.3.4",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+			},
+			&UpstreamConfig{
+				Name:        "legacy",
+				Type:        "legacy",
+				Endpoint:    "1.2.3.4:53",
+				BootstrapIP: "1.2.3.4",
+				Domain:      "1.2.3.4",
+				Timeout:     0,
+				IPStack:     IpStackBoth,
+			},
+		},
+		{
+			"doh+doh3 with send client info set",
+			&UpstreamConfig{
+				Name:           "doh",
+				Type:           "doh",
+				Endpoint:       "https://example.com?k=v",
+				BootstrapIP:    "",
+				Domain:         "",
+				Timeout:        0,
+				SendClientInfo: ptrBool(false),
+				IPStack:        IpStackBoth,
+			},
+			&UpstreamConfig{
+				Name:           "doh",
+				Type:           "doh",
+				Endpoint:       "https://example.com?k=v",
+				BootstrapIP:    "",
+				Domain:         "example.com",
+				Timeout:        0,
+				SendClientInfo: ptrBool(false),
+				IPStack:        IpStackBoth,
+				u:              u2,
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			tc.uc.Init()
+			tc.uc.uid = "" // we don't care about the uid.
+			assert.Equal(t, tc.expected, tc.uc)
+		})
+	}
+}
+
+func TestUpstreamConfig_VerifyDomain(t *testing.T) {
+	tests := []struct {
+		name         string
+		uc           *UpstreamConfig
+		verifyDomain string
+	}{
+		{
+			controlDComDomain,
+			&UpstreamConfig{Endpoint: "https://freedns.controld.com/p2"},
+			controldVerifiedDomain[controlDComDomain],
+		},
+		{
+			controlDDevDomain,
+			&UpstreamConfig{Endpoint: "https://freedns.controld.dev/p2"},
+			controldVerifiedDomain[controlDDevDomain],
+		},
+		{
+			"non-ControlD upstream",
+			&UpstreamConfig{Endpoint: "https://dns.google/dns-query"},
+			"",
+		},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := tc.uc.VerifyDomain(); got != tc.verifyDomain {
+				t.Errorf("unexpected verify domain, want: %q, got: %q", tc.verifyDomain, got)
+			}
+		})
+	}
+}
+
+func TestUpstreamConfig_UpstreamSendClientInfo(t *testing.T) {
+	tests := []struct {
+		name           string
+		uc             *UpstreamConfig
+		sendClientInfo bool
+	}{
+		{
+			"default with controld upstream DoH",
+			&UpstreamConfig{Endpoint: "https://freedns.controld.com/p2", Type: ResolverTypeDOH},
+			true,
+		},
+		{
+			"default with controld upstream DoH3",
+			&UpstreamConfig{Endpoint: "https://freedns.controld.com/p2", Type: ResolverTypeDOH3},
+			true,
+		},
+		{
+			"default with non-ControlD upstream",
+			&UpstreamConfig{Endpoint: "https://dns.google/dns-query", Type: ResolverTypeDOH},
+			false,
+		},
+		{
+			"set false with controld upstream",
+			&UpstreamConfig{Endpoint: "https://freedns.controld.com/p2", Type: ResolverTypeDOH, SendClientInfo: ptrBool(false)},
+			false,
+		},
+		{
+			"set true with controld upstream",
+			&UpstreamConfig{Endpoint: "https://freedns.controld.com/p2", SendClientInfo: ptrBool(true)},
+			true,
+		},
+		{
+			"set false with non-ControlD upstream",
+			&UpstreamConfig{Endpoint: "https://dns.google/dns-query", SendClientInfo: ptrBool(false)},
+			false,
+		},
+		{
+			"set true with non-ControlD upstream",
+			&UpstreamConfig{Endpoint: "https://dns.google/dns-query", Type: ResolverTypeDOH, SendClientInfo: ptrBool(true)},
+			true,
+		},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := tc.uc.UpstreamSendClientInfo(); got != tc.sendClientInfo {
+				t.Errorf("unexpected result, want: %v, got: %v", tc.sendClientInfo, got)
+			}
+		})
+	}
+}
+
+func TestUpstreamConfig_IsDiscoverable(t *testing.T) {
+	tests := []struct {
+		name         string
+		uc           *UpstreamConfig
+		discoverable bool
+	}{
+		{
+			"loopback",
+			&UpstreamConfig{Endpoint: "127.0.0.1", Type: ResolverTypeLegacy},
+			true,
+		},
+		{
+			"rfc1918",
+			&UpstreamConfig{Endpoint: "192.168.1.1", Type: ResolverTypeLegacy},
+			true,
+		},
+		{
+			"CGNAT",
+			&UpstreamConfig{Endpoint: "100.66.67.68", Type: ResolverTypeLegacy},
+			true,
+		},
+		{
+			"Public IP",
+			&UpstreamConfig{Endpoint: "8.8.8.8", Type: ResolverTypeLegacy},
+			false,
+		},
+		{
+			"override discoverable",
+			&UpstreamConfig{Endpoint: "127.0.0.1", Type: ResolverTypeLegacy, Discoverable: ptrBool(false)},
+			false,
+		},
+		{
+			"override non-public",
+			&UpstreamConfig{Endpoint: "1.1.1.1", Type: ResolverTypeLegacy, Discoverable: ptrBool(true)},
+			true,
+		},
+		{
+			"non-legacy upstream",
+			&UpstreamConfig{Endpoint: "https://192.168.1.1/custom-doh", Type: ResolverTypeDOH},
+			false,
+		},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			tc.uc.Init()
+			if got := tc.uc.IsDiscoverable(); got != tc.discoverable {
+				t.Errorf("unexpected result, want: %v, got: %v", tc.discoverable, got)
+			}
+		})
+	}
+}
+
+func ptrBool(b bool) *bool {
+	return &b
+}

config_quic.go

@@ -5,40 +5,158 @@ package ctrld
 import (
 	"context"
 	"crypto/tls"
+	"errors"
 	"net"
+	"net/http"
+	"runtime"
+	"sync"
 
+	"github.com/miekg/dns"
 	"github.com/quic-go/quic-go"
 	"github.com/quic-go/quic-go/http3"
 )
 
 func (uc *UpstreamConfig) setupDOH3Transport() {
-	uc.setupDOH3TransportWithoutPingUpstream()
+	switch uc.IPStack {
-	uc.pingUpstream()
+	case IpStackBoth, "":
+		uc.http3RoundTripper = uc.newDOH3Transport(uc.bootstrapIPs)
+	case IpStackV4:
+		uc.http3RoundTripper = uc.newDOH3Transport(uc.bootstrapIPs4)
+	case IpStackV6:
+		uc.http3RoundTripper = uc.newDOH3Transport(uc.bootstrapIPs6)
+	case IpStackSplit:
+		uc.http3RoundTripper4 = uc.newDOH3Transport(uc.bootstrapIPs4)
+		if hasIPv6() {
+			uc.http3RoundTripper6 = uc.newDOH3Transport(uc.bootstrapIPs6)
+		} else {
+			uc.http3RoundTripper6 = uc.http3RoundTripper4
+		}
+		uc.http3RoundTripper = uc.newDOH3Transport(uc.bootstrapIPs)
+	}
 }
 
-func (uc *UpstreamConfig) setupDOH3TransportWithoutPingUpstream() {
+func (uc *UpstreamConfig) newDOH3Transport(addrs []string) http.RoundTripper {
 	rt := &http3.RoundTripper{}
+	rt.TLSClientConfig = &tls.Config{RootCAs: uc.certPool}
 	rt.Dial = func(ctx context.Context, addr string, tlsCfg *tls.Config, cfg *quic.Config) (quic.EarlyConnection, error) {
-		host := addr
+		_, port, _ := net.SplitHostPort(addr)
-		ProxyLog.Debug().Msgf("debug dial context D0H3 %s - %s", addr, bootstrapDNS)
 		// if we have a bootstrap ip set, use it to avoid DNS lookup
 		if uc.BootstrapIP != "" {
-			if _, port, _ := net.SplitHostPort(addr); port != "" {
+			addr = net.JoinHostPort(uc.BootstrapIP, port)
-				addr = net.JoinHostPort(uc.BootstrapIP, port)
+			ProxyLogger.Load().Debug().Msgf("sending doh3 request to: %s", addr)
+			udpConn, err := net.ListenUDP("udp", nil)
+			if err != nil {
+				return nil, err
 			}
-			ProxyLog.Debug().Msgf("sending doh3 request to: %s", addr)
+			remoteAddr, err := net.ResolveUDPAddr("udp", addr)
+			if err != nil {
+				return nil, err
+			}
+			return quic.DialEarly(ctx, udpConn, remoteAddr, tlsCfg, cfg)
 		}
-		remoteAddr, err := net.ResolveUDPAddr("udp", addr)
+		dialAddrs := make([]string, len(addrs))
+		for i := range addrs {
+			dialAddrs[i] = net.JoinHostPort(addrs[i], port)
+		}
+		pd := &quicParallelDialer{}
+		conn, err := pd.Dial(ctx, dialAddrs, tlsCfg, cfg)
 		if err != nil {
 			return nil, err
 		}
+		ProxyLogger.Load().Debug().Msgf("sending doh3 request to: %s", conn.RemoteAddr())
+		return conn, err
+	}
+	runtime.SetFinalizer(rt, func(rt *http3.RoundTripper) {
+		rt.CloseIdleConnections()
+	})
+	return rt
+}
 
-		udpConn, err := net.ListenUDP("udp", nil)
+func (uc *UpstreamConfig) doh3Transport(dnsType uint16) http.RoundTripper {
-		if err != nil {
+	uc.transportOnce.Do(func() {
-			return nil, err
+		uc.SetupTransport()
+	})
+	if uc.rebootstrap.CompareAndSwap(true, false) {
+		uc.SetupTransport()
+	}
+	switch uc.IPStack {
+	case IpStackBoth, IpStackV4, IpStackV6:
+		return uc.http3RoundTripper
+	case IpStackSplit:
+		switch dnsType {
+		case dns.TypeA:
+			return uc.http3RoundTripper4
+		default:
+			return uc.http3RoundTripper6
 		}
-		return quic.DialEarlyContext(ctx, udpConn, remoteAddr, host, tlsCfg, cfg)
+	}
+	return uc.http3RoundTripper
+}
+
+// Putting the code for quic parallel dialer here:
+//
+//   - quic dialer is different with net.Dialer
+//   - simplification for quic free version
+type parallelDialerResult struct {
+	conn quic.EarlyConnection
+	err  error
+}
+
+type quicParallelDialer struct{}
+
+// Dial performs parallel dialing to the given address list.
+func (d *quicParallelDialer) Dial(ctx context.Context, addrs []string, tlsCfg *tls.Config, cfg *quic.Config) (quic.EarlyConnection, error) {
+	if len(addrs) == 0 {
+		return nil, errors.New("empty addresses")
+	}
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	done := make(chan struct{})
+	defer close(done)
+	ch := make(chan *parallelDialerResult, len(addrs))
+	var wg sync.WaitGroup
+	wg.Add(len(addrs))
+	go func() {
+		wg.Wait()
+		close(ch)
+	}()
+
+	for _, addr := range addrs {
+		go func(addr string) {
+			defer wg.Done()
+			remoteAddr, err := net.ResolveUDPAddr("udp", addr)
+			if err != nil {
+				ch <- &parallelDialerResult{conn: nil, err: err}
+				return
+			}
+			udpConn, err := net.ListenUDP("udp", nil)
+			if err != nil {
+				ch <- &parallelDialerResult{conn: nil, err: err}
+				return
+			}
+			conn, err := quic.DialEarly(ctx, udpConn, remoteAddr, tlsCfg, cfg)
+			select {
+			case ch <- &parallelDialerResult{conn: conn, err: err}:
+			case <-done:
+				if conn != nil {
+					conn.CloseWithError(quic.ApplicationErrorCode(http3.ErrCodeNoError), "")
+				}
+				if udpConn != nil {
+					udpConn.Close()
+				}
+			}
+		}(addr)
 	}
 
-	uc.http3RoundTripper = rt
+	errs := make([]error, 0, len(addrs))
+	for res := range ch {
+		if res.err == nil {
+			cancel()
+			return res.conn, res.err
+		}
+		errs = append(errs, res.err)
+	}
+
+	return nil, errors.Join(errs...)
 }

config_quic_free.go

@@ -2,6 +2,8 @@
 
 package ctrld
 
+import "net/http"
+
 func (uc *UpstreamConfig) setupDOH3Transport() {}
 
-func (uc *UpstreamConfig) setupDOH3TransportWithoutPingUpstream() {}
+func (uc *UpstreamConfig) doh3Transport(dnsType uint16) http.RoundTripper { return nil }

config_test.go

@@ -1,6 +1,8 @@
 package ctrld_test
 
 import (
+	"os"
+	"strings"
 	"testing"
 
 	"github.com/go-playground/validator/v10"
@@ -24,10 +26,12 @@ func TestLoadConfig(t *testing.T) {
 	assert.Contains(t, cfg.Network, "0")
 	assert.Contains(t, cfg.Network, "1")
 
-	assert.Len(t, cfg.Upstream, 3)
+	assert.Len(t, cfg.Upstream, 4)
 	assert.Contains(t, cfg.Upstream, "0")
 	assert.Contains(t, cfg.Upstream, "1")
 	assert.Contains(t, cfg.Upstream, "2")
+	assert.Contains(t, cfg.Upstream, "3")
+	assert.NotNil(t, cfg.Upstream["3"].SendClientInfo)
 
 	assert.Len(t, cfg.Listener, 2)
 	assert.Contains(t, cfg.Listener, "0")
@@ -42,16 +46,37 @@ func TestLoadConfig(t *testing.T) {
 	assert.Len(t, cfg.Listener["0"].Policy.Rules, 2)
 	assert.Contains(t, cfg.Listener["0"].Policy.Rules[0], "*.ru")
 	assert.Contains(t, cfg.Listener["0"].Policy.Rules[1], "*.local.host")
+
+	assert.True(t, cfg.HasUpstreamSendClientInfo())
 }
 
 func TestLoadDefaultConfig(t *testing.T) {
 	cfg := defaultConfig(t)
 	validate := validator.New()
 	require.NoError(t, ctrld.ValidateConfig(validate, cfg))
-	assert.Len(t, cfg.Listener, 1)
+	if assert.Len(t, cfg.Listener, 1) {
+		l0 := cfg.Listener["0"]
+		require.NotNil(t, l0.Policy)
+		assert.Len(t, l0.Policy.Networks, 1)
+		assert.Len(t, l0.Policy.Rules, 2)
+	}
 	assert.Len(t, cfg.Upstream, 2)
 }
 
+func TestConfigOverride(t *testing.T) {
+	v := viper.NewWithOptions(viper.KeyDelimiter("::"))
+	ctrld.InitConfig(v, "test_load_config")
+	v.SetConfigType("toml")
+	require.NoError(t, v.ReadConfig(strings.NewReader(testhelper.SampleConfigStr(t))))
+	cfg := ctrld.Config{Listener: map[string]*ctrld.ListenerConfig{
+		"0": {IP: "127.0.0.1", Port: 53},
+	}}
+	require.NoError(t, v.Unmarshal(&cfg))
+
+	assert.Equal(t, "10.10.42.69", cfg.Listener["1"].IP)
+	assert.Equal(t, 1337, cfg.Listener["1"].Port)
+}
+
 func TestConfigValidation(t *testing.T) {
 	tests := []struct {
 		name    string
@@ -61,6 +86,7 @@ func TestConfigValidation(t *testing.T) {
 		{"invalid Config", &ctrld.Config{}, true},
 		{"default Config", defaultConfig(t), false},
 		{"sample Config", testhelper.SampleConfig(t), false},
+		{"empty listener IP", emptyListenerIP(t), false},
 		{"invalid cidr", invalidNetworkConfig(t), true},
 		{"invalid upstream type", invalidUpstreamType(t), true},
 		{"invalid upstream timeout", invalidUpstreamTimeout(t), true},
@@ -70,6 +96,12 @@ func TestConfigValidation(t *testing.T) {
 		{"os upstream", configWithOsUpstream(t), false},
 		{"invalid rules", configWithInvalidRules(t), true},
 		{"invalid dns rcodes", configWithInvalidRcodes(t), true},
+		{"invalid max concurrent requests", configWithInvalidMaxConcurrentRequests(t), true},
+		{"non-existed lease file", configWithNonExistedLeaseFile(t), true},
+		{"lease file format required if lease file exist", configWithExistedLeaseFile(t), true},
+		{"invalid lease file format", configWithInvalidLeaseFileFormat(t), true},
+		{"invalid doh/doh3 endpoint", configWithInvalidDoHEndpoint(t), true},
+		{"invalid client id pref", configWithInvalidClientIDPref(t), true},
 	}
 
 	for _, tc := range tests {
@@ -89,6 +121,29 @@ func TestConfigValidation(t *testing.T) {
 	}
 }
 
+func TestConfigDiscoverOverride(t *testing.T) {
+	v := viper.NewWithOptions(viper.KeyDelimiter("::"))
+	ctrld.InitConfig(v, "test_config_discover_override")
+	v.SetConfigType("toml")
+	configStr := `
+[service]
+discover_arp = false
+discover_dhcp = false
+discover_hosts = false
+discover_mdns = false
+discover_ptr = false
+`
+	require.NoError(t, v.ReadConfig(strings.NewReader(configStr)))
+	cfg := ctrld.Config{}
+	require.NoError(t, v.Unmarshal(&cfg))
+
+	require.False(t, *cfg.Service.DiscoverARP)
+	require.False(t, *cfg.Service.DiscoverDHCP)
+	require.False(t, *cfg.Service.DiscoverHosts)
+	require.False(t, *cfg.Service.DiscoverMDNS)
+	require.False(t, *cfg.Service.DiscoverPtr)
+}
+
 func defaultConfig(t *testing.T) *ctrld.Config {
 	v := viper.New()
 	ctrld.InitConfig(v, "test_load_default_config")
@@ -130,9 +185,15 @@ func invalidListenerIP(t *testing.T) *ctrld.Config {
 	return cfg
 }
 
+func emptyListenerIP(t *testing.T) *ctrld.Config {
+	cfg := defaultConfig(t)
+	cfg.Listener["0"].IP = ""
+	return cfg
+}
+
 func invalidListenerPort(t *testing.T) *ctrld.Config {
 	cfg := defaultConfig(t)
-	cfg.Listener["0"].Port = 0
+	cfg.Listener["0"].Port = -1
 	return cfg
 }
 
@@ -166,115 +227,44 @@ func configWithInvalidRcodes(t *testing.T) *ctrld.Config {
 	return cfg
 }
 
-func TestUpstreamConfig_Init(t *testing.T) {
+func configWithInvalidMaxConcurrentRequests(t *testing.T) *ctrld.Config {
-	tests := []struct {
+	cfg := defaultConfig(t)
-		name     string
+	n := -1
-		uc       *ctrld.UpstreamConfig
+	cfg.Service.MaxConcurrentRequests = &n
-		expected *ctrld.UpstreamConfig
+	return cfg
-	}{
+}
-		{
+
-			"doh+doh3",
+func configWithNonExistedLeaseFile(t *testing.T) *ctrld.Config {
-			&ctrld.UpstreamConfig{
+	cfg := defaultConfig(t)
-				Name:        "doh",
+	cfg.Service.DHCPLeaseFile = "non-existed"
-				Type:        "doh",
+	return cfg
-				Endpoint:    "https://example.com",
+}
-				BootstrapIP: "",
+
-				Domain:      "",
+func configWithExistedLeaseFile(t *testing.T) *ctrld.Config {
-				Timeout:     0,
+	cfg := defaultConfig(t)
-			},
+	exe, err := os.Executable()
-			&ctrld.UpstreamConfig{
+	if err != nil {
-				Name:        "doh",
+		t.Fatal(err)
-				Type:        "doh",
+	}
-				Endpoint:    "https://example.com",
+	cfg.Service.DHCPLeaseFile = exe
-				BootstrapIP: "",
+	return cfg
-				Domain:      "example.com",
+}
-				Timeout:     0,
+
-			},
+func configWithInvalidLeaseFileFormat(t *testing.T) *ctrld.Config {
-		},
+	cfg := defaultConfig(t)
-		{
+	cfg.Service.DHCPLeaseFileFormat = "invalid"
-			"dot+doq",
+	return cfg
-			&ctrld.UpstreamConfig{
+}
-				Name:        "dot",
+
-				Type:        "dot",
+func configWithInvalidDoHEndpoint(t *testing.T) *ctrld.Config {
-				Endpoint:    "freedns.controld.com:8853",
+	cfg := defaultConfig(t)
-				BootstrapIP: "",
+	cfg.Upstream["0"].Endpoint = "1.1.1.1"
-				Domain:      "",
+	cfg.Upstream["0"].Type = ctrld.ResolverTypeDOH
-				Timeout:     0,
+	return cfg
-			},
+}
-			&ctrld.UpstreamConfig{
+
-				Name:        "dot",
+func configWithInvalidClientIDPref(t *testing.T) *ctrld.Config {
-				Type:        "dot",
+	cfg := defaultConfig(t)
-				Endpoint:    "freedns.controld.com:8853",
+	cfg.Service.ClientIDPref = "foo"
-				BootstrapIP: "",
+	return cfg
-				Domain:      "freedns.controld.com",
-				Timeout:     0,
-			},
-		},
-		{
-			"dot+doq without port",
-			&ctrld.UpstreamConfig{
-				Name:        "dot",
-				Type:        "dot",
-				Endpoint:    "freedns.controld.com",
-				BootstrapIP: "",
-				Domain:      "",
-				Timeout:     0,
-			},
-			&ctrld.UpstreamConfig{
-				Name:        "dot",
-				Type:        "dot",
-				Endpoint:    "freedns.controld.com:853",
-				BootstrapIP: "",
-				Domain:      "freedns.controld.com",
-				Timeout:     0,
-			},
-		},
-		{
-			"legacy",
-			&ctrld.UpstreamConfig{
-				Name:        "legacy",
-				Type:        "legacy",
-				Endpoint:    "1.2.3.4:53",
-				BootstrapIP: "",
-				Domain:      "",
-				Timeout:     0,
-			},
-			&ctrld.UpstreamConfig{
-				Name:        "legacy",
-				Type:        "legacy",
-				Endpoint:    "1.2.3.4:53",
-				BootstrapIP: "1.2.3.4",
-				Domain:      "1.2.3.4",
-				Timeout:     0,
-			},
-		},
-		{
-			"legacy without port",
-			&ctrld.UpstreamConfig{
-				Name:        "legacy",
-				Type:        "legacy",
-				Endpoint:    "1.2.3.4",
-				BootstrapIP: "",
-				Domain:      "",
-				Timeout:     0,
-			},
-			&ctrld.UpstreamConfig{
-				Name:        "legacy",
-				Type:        "legacy",
-				Endpoint:    "1.2.3.4:53",
-				BootstrapIP: "1.2.3.4",
-				Domain:      "1.2.3.4",
-				Timeout:     0,
-			},
-		},
-	}
-
-	for _, tc := range tests {
-		tc := tc
-		t.Run(tc.name, func(t *testing.T) {
-			t.Parallel()
-			tc.uc.Init()
-			assert.Equal(t, tc.expected, tc.uc)
-		})
-	}
 }

docker/Dockerfile

@@ -0,0 +1,32 @@
+# Using Debian bullseye for building regular image.
+# Using scratch image for minimal image size.
+# The final image has:
+#
+# - Timezone info file.
+# - CA certs file.
+# - /etc/{passwd,group} file.
+# - Non-cgo ctrld binary.
+#
+# CI_COMMIT_TAG is used to set the version of ctrld binary.
+FROM golang:1.20-bullseye as base
+
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y upx-ucl
+
+COPY . .
+
+ARG tag=master
+ENV CI_COMMIT_TAG=$tag
+RUN CTRLD_NO_QF=yes CGO_ENABLED=0 ./scripts/build.sh
+
+FROM scratch
+
+COPY --from=base /usr/share/zoneinfo /usr/share/zoneinfo
+COPY --from=base /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=base /etc/passwd /etc/passwd
+COPY --from=base /etc/group /etc/group
+
+COPY --from=base /app/ctrld-linux-*-nocgo ctrld
+
+ENTRYPOINT ["./ctrld", "run"]

docker/Dockerfile.debug

@@ -0,0 +1,32 @@
+# Using Debian bullseye for building regular image.
+# Using scratch image for minimal image size.
+# The final image has:
+#
+# - Timezone info file.
+# - CA certs file.
+# - /etc/{passwd,group} file.
+# - Non-cgo ctrld binary.
+#
+# CI_COMMIT_TAG is used to set the version of ctrld binary.
+FROM golang:1.20-bullseye as base
+
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y upx-ucl
+
+COPY . .
+
+ARG tag=master
+ENV CI_COMMIT_TAG=$tag
+RUN CTRLD_NO_QF=yes CGO_ENABLED=0 ./scripts/build.sh
+
+FROM alpine
+
+COPY --from=base /usr/share/zoneinfo /usr/share/zoneinfo
+COPY --from=base /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=base /etc/passwd /etc/passwd
+COPY --from=base /etc/group /etc/group
+
+COPY --from=base /app/ctrld-linux-*-nocgo ctrld
+
+ENTRYPOINT ["./ctrld", "run"]

docs/config.md

@@ -14,10 +14,15 @@ The config file allows for advanced configuration of the `ctrld` utility to cove
 
 
 ## Config Location
-`ctrld` uses [TOML](toml_link) format for its configuration file. Default configuration file is `config.toml` found in following order:
+`ctrld` uses [TOML][toml_link] format for its configuration file. Default configuration file is `ctrld.toml` found in following order:
 
- - `$HOME/.ctrld`
+ - `/etc/controld` on *nix.
- - Current directory
+ - User's home directory on Windows.
+ - Same directory with `ctrld` binary on these routers:
+   - `ddwrt`
+   - `merlin`
+   - `freshtomato`
+ - Current directory.
 
 The user can choose to override default value using command line `--config` or `-c`:
 
@@ -38,6 +43,8 @@ if it's existed.
     log_path = ""
     cache_enable = true
     cache_size = 4096
+    cache_ttl_override = 60
+    cache_serve_stale = true
 
 [network.0]
     cidrs = ["0.0.0.0/0"]
@@ -53,6 +60,7 @@ if it's existed.
     name = "Control D - Anti-Malware"
     timeout = 5000
     type = "doh"
+    ip_stack = "both"
 
 [upstream.1]
     bootstrap_ip = "76.76.2.11"
@@ -60,6 +68,7 @@ if it's existed.
     name = "Control D - No Ads"
     timeout = 5000
     type = "doq"
+    ip_stack = "split"
 
 [upstream.2]
     bootstrap_ip = "76.76.2.22"
@@ -67,6 +76,7 @@ if it's existed.
     name = "Control D - Private"
     timeout = 5000
     type = "dot"
+    ip_stack = "v4"
 
 [listener.0]
     ip = "127.0.0.1"
@@ -104,8 +114,8 @@ Logging level you wish to enable.
 
  - Type: string
  - Required: no
- - Valid values: `debug`, `info`, `warn`, `error`, `fatal`, `panic`
+ - Valid values: `debug`, `info`, `warn`, `notice`, `error`, `fatal`, `panic`
- - Default: `info`
+ - Default: `notice`
 
 
 ### log_path
@@ -113,12 +123,14 @@ Relative or absolute path of the log file.
 
 - Type: string
 - Required: no
+- Default: ""
 
 ### cache_enable
 When `cache_enable = true`, all resolved DNS query responses will be cached for duration of the upstream record TTLs.
 
 - Type: boolean
 - Required: no
+- Default: false
 
 ### cache_size
 The number of cached records, must be a positive integer. Tweaking this value with care depends on your available RAM. 
@@ -128,29 +140,113 @@ An invalid `cache_size` value will disable the cache, regardless of `cache_enabl
 
 - Type: int
 - Required: no
+- Default: 4096
 
 ### cache_ttl_override
 When `cache_ttl_override` is set to a positive value (in seconds), TTLs are overridden to this value and cached for this long.
 
 - Type: int
 - Required: no
+- Default: 0
 
 ### cache_serve_stale
 When `cache_serve_stale = true`, in cases of upstream failures (upstreams not reachable), `ctrld` will keep serving
 stale cached records (regardless of their TTLs) until upstream comes online.
 
-The above config will look like this at query time.
+- Type: boolean
+- Required: no
+- Default: false
 
-```
+### max_concurrent_requests
-2022-11-14T22:18:53.808 INF Setting bootstrap IP for upstream.0 bootstrap_ip=76.76.2.11
+The number of concurrent requests that will be handled, must be a non-negative integer. 
-2022-11-14T22:18:53.808 INF Starting DNS server on listener.0: 127.0.0.1:53
+Tweaking this value depends on the capacity of your system.
-2022-11-14T22:18:56.381 DBG [9fd5d3] 127.0.0.1:53978 -> listener.0: 127.0.0.1:53: received query: verify.controld.com
+
-2022-11-14T22:18:56.381 INF [9fd5d3] no policy, no network, no rule -> [upstream.0]
+- Type: number
-2022-11-14T22:18:56.381 DBG [9fd5d3] sending query to upstream.0: Control D - DOH Free
+- Required: no
-2022-11-14T22:18:56.381 DBG [9fd5d3] debug dial context freedns.controld.com:443 - tcp - 76.76.2.0
+- Default: 256
-2022-11-14T22:18:56.381 DBG [9fd5d3] sending doh request to: 76.76.2.11:443
+
-2022-11-14T22:18:56.420 DBG [9fd5d3] received response of 118 bytes in 39.662597ms
+### discover_mdns
-```
+Perform LAN client discovery using mDNS. This will spawn a listener on port 5353. 
+
+- Type: boolean
+- Required: no
+- Default: true
+
+### discover_arp
+Perform LAN client discovery using ARP.  
+
+- Type: boolean
+- Required: no
+- Default: true
+
+### discover_dhcp
+Perform LAN client discovery using DHCP leases files. Common file locations are auto-discovered.  
+
+- Type: boolean
+- Required: no
+- Default: true
+
+### discover_ptr
+Perform LAN client discovery using PTR queries.  
+
+- Type: boolean
+- Required: no
+- Default: true
+
+### discover_hosts
+Perform LAN client discovery using hosts file.
+
+- Type: boolean
+- Required: no
+- Default: true
+
+### discover_refresh_interval
+Time in seconds between each discovery refresh loop to update new client information data. 
+The default value is 120 seconds, lower this value to make the discovery process run more aggressively.
+
+- Type: integer
+- Required: no
+- Default: 120
+
+### dhcp_lease_file_path
+Relative or absolute path to a custom DHCP leases file location. 
+
+- Type: string
+- Required: no
+- Default: ""
+
+### dhcp_lease_file_format
+DHCP leases file format. 
+
+- Type: string
+- Required: no
+- Valid values: `dnsmasq`, `isc-dhcp`
+- Default: ""
+
+### client_id_preference
+Decide how the client ID is generated
+
+If `host` -> client id will only use the hostname i.e.`hash(hostname)`.
+If `mac` -> client id will only use the MAC address `hash(mac)`.
+Else -> client ID will use both Mac and Hostname i.e. `hash(mac + host)
+- Type: string
+- Required: no
+- Valid values: `mac`, `host`
+- Default: ""
+
+### metrics_query_stats
+If set to `true`, collect and export the query counters, and show them in `clients list` command.
+
+- Type: boolean
+- Required: no
+- Default: false
+
+### metrics_listener
+Specifying the `ip` and `port` of the metrics server.
+
+- Type: string
+- Required: no
+- Default: ""
 
 ## Upstream
 The `[upstream]` section specifies the DNS upstream servers that `ctrld` will forward DNS requests to.
@@ -162,6 +258,7 @@ The `[upstream]` section specifies the DNS upstream servers that `ctrld` will fo
   name = "Control D - DOH"
   timeout = 5000
   type = "doh"
+  ip_stack = "split"
   
 [upstream.1]
   bootstrap_ip = ""
@@ -169,6 +266,7 @@ The `[upstream]` section specifies the DNS upstream servers that `ctrld` will fo
   name = "Control D - DOH3"
   timeout = 5000
   type = "doh3"
+  ip_stack = "both"
   
 [upstream.2]
   bootstrap_ip = ""
@@ -176,6 +274,7 @@ The `[upstream]` section specifies the DNS upstream servers that `ctrld` will fo
   name = "Controld D - DOT"
   timeout = 5000
   type = "dot"
+  ip_stack = "v4"
   
 [upstream.3]
   bootstrap_ip = ""
@@ -183,6 +282,7 @@ The `[upstream]` section specifies the DNS upstream servers that `ctrld` will fo
   name = "Controld D - DOT"
   timeout = 5000
   type = "doq"
+  ip_stack = "v6"
   
 [upstream.4]
   bootstrap_ip = ""
@@ -190,6 +290,7 @@ The `[upstream]` section specifies the DNS upstream servers that `ctrld` will fo
   name = "Control D - Ad Blocking"
   timeout = 5000
   type = "legacy"
+  ip_stack = "both"
 ```
 
 ### bootstrap_ip
@@ -200,6 +301,7 @@ If `bootstrap_ip` is empty, `ctrld` will resolve this itself using its own boots
 
  - type: ip address string
  - required: no
+ - Default: ""
 
 ### endpoint
 IP address, hostname or URL of upstream DNS. Used together with `Type` of the endpoint.
@@ -214,6 +316,7 @@ Human-readable name of the upstream.
 
 - Type: string
 - Required: no
+- Default: ""
 
 ### timeout
 Timeout in milliseconds before request failsover to the next upstream (if defined). 
@@ -221,15 +324,52 @@ Timeout in milliseconds before request failsover to the next upstream (if define
 Value `0` means no timeout.
 
  - Type: number
- - required: no
+ - Required: no
+ - Default: 0
 
 ### type
 The protocol that `ctrld` will use to send DNS requests to upstream.
 
  - Type: string
- - required: yes
+ - Required: yes
  - Valid values: `doh`, `doh3`, `dot`, `doq`, `legacy`, `os`
 
+### ip_stack
+Specifying what kind of ip stack that `ctrld` will use to connect to upstream.
+
+ - Type: string
+ - Required: no
+ - Valid values:
+   - `both`: using either ipv4 or ipv6.
+   - `v4`:   only dial upstream via IPv4, never dial IPv6.
+   - `v6`:   only dial upstream via IPv6, never dial IPv4.
+   - `split`:
+     - If `A` record is requested -> dial via ipv4.
+     - If `AAAA` or any other record is requested -> dial ipv6 (if available, otherwise ipv4)
+
+If `ip_stack` is empty, or undefined:
+
+ - Default value is `both` for non-Control D resolvers.
+ - Default value is `split` for Control D resolvers.
+
+### send_client_info
+Specifying whether to include client info when sending query to upstream. **This will only work with `doh` or `doh3` type upstreams.** 
+
+- Type: boolean
+- Required: no
+- Default:
+  - `true` for ControlD upstreams.
+  - `false` for other upstreams.
+
+### discoverable
+Specifying whether the upstream can be used for PTR discovery.
+
+- Type: boolean
+- Required: no
+- Default:
+    - `true` for loopback/RFC1918/CGNAT IP address.
+    - `false` for public IP address.
+
 ## Network
 The `[network]` section defines networks from which DNS queries can originate from. These are used in policies. You can define multiple networks, and each one can have multiple cidrs.
 
@@ -248,12 +388,14 @@ Name of the network.
 
  - Type: string
  - Required: no
+ - Default: ""
 
 ### cidrs
 Specifies the network addresses that the `listener` will accept requests from. You will see more details in the listener policy section.
 
  - Type: array of network CIDR string
  - Required: no
+ - Default: []
 
 
 ## listener
@@ -271,28 +413,46 @@ The `[listener]` section specifies the ip and port of the local DNS server. You
 ```
 
 ### ip
-IP address that serves the incoming requests.
+IP address that serves the incoming requests. If `ip` is empty, ctrld will listen on all available addresses.
 
-- Type: string
+- Type: ip address string
-- Required: yes
+- Required: no
+- Default: "0.0.0.0" or RFC1918 addess or "127.0.0.1" (depending on platform)
 
 ### port
-Port number that the listener will listen on for incoming requests.
+Port number that the listener will listen on for incoming requests. If `port` is `0`, a random available port will be chosen.
 
 - Type: number
-- Required: yes
+- Required: no
+- Default: 0 or 53 or 5354 (depending on platform)
 
 ### restricted
-If set to `true` makes the listener `REFUSE` DNS queries from all source IP addresses that are not explicitly defined in the policy using a `network`. 
+If set to `true`, makes the listener `REFUSED` DNS queries from all source IP addresses that are not explicitly defined in the policy using a `network`. 
 
 - Type: bool
 - Required: no
+- Default: false
+
+### allow_wan_clients
+The listener will refuse DNS queries from WAN IPs using `REFUSED` RCODE by default. Set to `true` to disable this behavior, but this is not recommended. 
+
+- Type: bool
+- Required: no
+- Default: false
 
 ### policy
 Allows `ctrld` to set policy rules to determine which upstreams the requests will be forwarded to.
 If no `policy` is defined or the requests do not match any policy rules, it will be forwarded to corresponding upstream of the listener. For example, the request to `listener.0` will be forwarded to `upstream.0`.
 
-The policy `rule` syntax is a simple `toml` inline table with exactly one key/value pair per rule. `key` is either the `network` or a domain. Value is the list of the upstreams. For example:
+The policy `rule` syntax is a simple `toml` inline table with exactly one key/value pair per rule. `key` is either:
+
+ - Network.
+ - Domain.
+ - Mac Address.
+
+Value is the list of the upstreams.
+
+For example:
 
 ```toml
 [listener.0.policy]
@@ -306,12 +466,18 @@ rules = [
     {"*.local" = ["upstream.1"]},
     {"test.com" = ["upstream.2", "upstream.1"]},
 ]
+
+macs = [
+    {"14:54:4a:8e:08:2d" = ["upstream.3"]},
+]
 ```
 
 Above policy will:
-- Forward requests on `listener.0` from `network.0` to `upstream.1`.
+
 - Forward requests on `listener.0` for `.local` suffixed domains to `upstream.1`.
 - Forward requests on `listener.0` for `test.com` to `upstream.2`. If timeout is reached, retry on `upstream.1`.
+- Forward requests on `listener.0` from client with Mac `14:54:4a:8e:08:2d` to `upstream.3`.
+- Forward requests on `listener.0` from `network.0` to `upstream.1`.
 - All other requests on `listener.0` that do not match above conditions will be forwarded to `upstream.0`.
 
 An empty upstream would not route the request to any defined upstreams, and use the OS default resolver.
@@ -325,24 +491,54 @@ rules = [
 ]
 ```
 
+---
+
+Note that the order of matching preference:
+
+```
+rules => macs => networks
+```
+
+And within each policy, the rules are processed from top to bottom.
+
+---
+
 #### name
 `name` is the name for the policy.
 
 - Type: string
 - Required: no
+- Default: ""
 
 ### networks:
 `networks` is the list of network rules of the policy.
 
-- type: array of networks
+- Type: array of networks
+- Required: no
+- Default: []
 
 ### rules:
 `rules` is the list of domain rules within the policy. Domain can be either FQDN or wildcard domain.
 
-- type: array of rule
+- Type: array of rule
+- Required: no
+- Default: []
+
+### macs:
+`macs` is the list of mac rules within the policy. Mac address value is case-insensitive.
+
+- Type: array of macs
+- Required: no
+- Default: []
 
 ### failover_rcodes
-For non success response, `failover_rcodes` allows the request to be forwarded to next upstream, if the response `RCODE` matches any value defined in `failover_rcodes`. For example:
+For non success response, `failover_rcodes` allows the request to be forwarded to next upstream, if the response `RCODE` matches any value defined in `failover_rcodes`.
+
+- Type: array of string
+- Required: no
+- Default: []
+- 
+For example:
 
 ```toml
 [listener.0.policy]
@@ -355,7 +551,7 @@ networks = [
 
 If `upstream.0` returns a NXDOMAIN response, the request will be forwarded to `upstream.1` instead of returning immediately to the client.
 
-See all available DNS Rcodes value [here](rcode_link).
+See all available DNS Rcodes value [here][rcode_link].
 
 [toml_link]: https://toml.io/en
 [rcode_link]: https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6

doh.go

@@ -7,52 +7,122 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
+	"runtime"
+	"strings"
+	"sync"
+
+	"github.com/cuonglm/osinfo"
 
 	"github.com/miekg/dns"
 )
 
+const (
+	dohMacHeader          = "x-cd-mac"
+	dohIPHeader           = "x-cd-ip"
+	dohHostHeader         = "x-cd-host"
+	dohOsHeader           = "x-cd-os"
+	dohClientIDPrefHeader = "x-cd-cpref"
+	headerApplicationDNS  = "application/dns-message"
+)
+
+// EncodeOsNameMap provides mapping from OS name to a shorter string, used for encoding x-cd-os value.
+var EncodeOsNameMap = map[string]string{
+	"windows": "1",
+	"darwin":  "2",
+	"linux":   "3",
+	"freebsd": "4",
+}
+
+// DecodeOsNameMap provides mapping from encoded OS name to real value, used for decoding x-cd-os value.
+var DecodeOsNameMap = map[string]string{}
+
+// EncodeArchNameMap provides mapping from OS arch to a shorter string, used for encoding x-cd-os value.
+var EncodeArchNameMap = map[string]string{
+	"amd64":  "1",
+	"arm64":  "2",
+	"arm":    "3",
+	"386":    "4",
+	"mips":   "5",
+	"mipsle": "6",
+	"mips64": "7",
+}
+
+// DecodeArchNameMap provides mapping from encoded OS arch to real value, used for decoding x-cd-os value.
+var DecodeArchNameMap = map[string]string{}
+
+func init() {
+	for k, v := range EncodeOsNameMap {
+		DecodeOsNameMap[v] = k
+	}
+	for k, v := range EncodeArchNameMap {
+		DecodeArchNameMap[v] = k
+	}
+}
+
+// TODO: use sync.OnceValue when upgrading to go1.21
+var xCdOsValueOnce sync.Once
+var xCdOsValue string
+
+func dohOsHeaderValue() string {
+	xCdOsValueOnce.Do(func() {
+		oi := osinfo.New()
+		xCdOsValue = strings.Join([]string{EncodeOsNameMap[runtime.GOOS], EncodeArchNameMap[runtime.GOARCH], oi.Dist}, "-")
+	})
+	return xCdOsValue
+}
+
 func newDohResolver(uc *UpstreamConfig) *dohResolver {
 	r := &dohResolver{
-		endpoint:          uc.Endpoint,
+		endpoint:          uc.u,
 		isDoH3:            uc.Type == ResolverTypeDOH3,
-		transport:         uc.transport,
 		http3RoundTripper: uc.http3RoundTripper,
+		uc:                uc,
 	}
 	return r
 }
 
 type dohResolver struct {
-	endpoint          string
+	uc                *UpstreamConfig
+	endpoint          *url.URL
 	isDoH3            bool
-	transport         *http.Transport
 	http3RoundTripper http.RoundTripper
 }
 
+// Resolve performs DNS query with given DNS message using DOH protocol.
 func (r *dohResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, error) {
 	data, err := msg.Pack()
 	if err != nil {
 		return nil, err
 	}
+
 	enc := base64.RawURLEncoding.EncodeToString(data)
-	url := fmt.Sprintf("%s?dns=%s", r.endpoint, enc)
+	query := r.endpoint.Query()
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	query.Add("dns", enc)
+
+	endpoint := *r.endpoint
+	endpoint.RawQuery = query.Encode()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint.String(), nil)
 	if err != nil {
 		return nil, fmt.Errorf("could not create request: %w", err)
 	}
-	req.Header.Set("Content-Type", "application/dns-message")
+	addHeader(ctx, req, r.uc)
-	req.Header.Set("Accept", "application/dns-message")
+	dnsTyp := uint16(0)
-
+	if len(msg.Question) > 0 {
-	c := http.Client{Transport: r.transport}
+		dnsTyp = msg.Question[0].Qtype
+	}
+	c := http.Client{Transport: r.uc.dohTransport(dnsTyp)}
 	if r.isDoH3 {
-		if r.http3RoundTripper == nil {
+		transport := r.uc.doh3Transport(dnsTyp)
+		if transport == nil {
 			return nil, errors.New("DoH3 is not supported")
 		}
-		c.Transport = r.http3RoundTripper
+		c.Transport = transport
 	}
 	resp, err := c.Do(req)
 	if err != nil {
 		if r.isDoH3 {
-			if closer, ok := r.http3RoundTripper.(io.Closer); ok {
+			if closer, ok := c.Transport.(io.Closer); ok {
 				closer.Close()
 			}
 		}
@@ -70,5 +140,73 @@ func (r *dohResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, erro
 	}
 
 	answer := new(dns.Msg)
-	return answer, answer.Unpack(buf)
+	if err := answer.Unpack(buf); err != nil {
+		return nil, fmt.Errorf("answer.Unpack: %w", err)
+	}
+	return answer, nil
+}
+
+// addHeader adds necessary HTTP header to request based on upstream config.
+func addHeader(ctx context.Context, req *http.Request, uc *UpstreamConfig) {
+	printed := false
+	dohHeader := make(http.Header)
+	if uc.UpstreamSendClientInfo() {
+		if ci, ok := ctx.Value(ClientInfoCtxKey{}).(*ClientInfo); ok && ci != nil {
+			printed = ci.Mac != "" || ci.IP != "" || ci.Hostname != ""
+			switch {
+			case uc.isControlD():
+				dohHeader = newControlDHeaders(ci)
+			case uc.isNextDNS():
+				dohHeader = newNextDNSHeaders(ci)
+			}
+		}
+	}
+	if printed {
+		Log(ctx, ProxyLogger.Load().Debug(), "sending request header: %v", dohHeader)
+	}
+	dohHeader.Set("Content-Type", headerApplicationDNS)
+	dohHeader.Set("Accept", headerApplicationDNS)
+	req.Header = dohHeader
+}
+
+// newControlDHeaders returns DoH/Doh3 HTTP request headers for ControlD upstream.
+func newControlDHeaders(ci *ClientInfo) http.Header {
+	header := make(http.Header)
+	header.Set(dohOsHeader, dohOsHeaderValue())
+	if ci.Mac != "" {
+		header.Set(dohMacHeader, ci.Mac)
+	}
+	if ci.IP != "" {
+		header.Set(dohIPHeader, ci.IP)
+	}
+	if ci.Hostname != "" {
+		header.Set(dohHostHeader, ci.Hostname)
+	}
+	if ci.Self {
+		header.Set(dohOsHeader, dohOsHeaderValue())
+	}
+	switch ci.ClientIDPref {
+	case "mac":
+		header.Set(dohClientIDPrefHeader, "1")
+	case "host":
+		header.Set(dohClientIDPrefHeader, "2")
+	}
+	return header
+}
+
+// newNextDNSHeaders returns DoH/Doh3 HTTP request headers for nextdns upstream.
+// https://github.com/nextdns/nextdns/blob/v1.41.0/resolver/doh.go#L100
+func newNextDNSHeaders(ci *ClientInfo) http.Header {
+	header := make(http.Header)
+	if ci.Mac != "" {
+		// https: //github.com/nextdns/nextdns/blob/v1.41.0/run.go#L543
+		header.Set("X-Device-Model", "mac:"+ci.Mac[:8])
+	}
+	if ci.IP != "" {
+		header.Set("X-Device-Ip", ci.IP)
+	}
+	if ci.Hostname != "" {
+		header.Set("X-Device-Name", ci.Hostname)
+	}
+	return header
 }

doh_test.go

@@ -0,0 +1,23 @@
+package ctrld
+
+import (
+	"runtime"
+	"testing"
+)
+
+func Test_dohOsHeaderValue(t *testing.T) {
+	val := dohOsHeaderValue()
+	if val == "" {
+		t.Fatalf("empty %s", dohOsHeader)
+	}
+	t.Log(val)
+
+	encodedOs := EncodeOsNameMap[runtime.GOOS]
+	if encodedOs == "" {
+		t.Fatalf("missing encoding value for: %q", runtime.GOOS)
+	}
+	decodedOs := DecodeOsNameMap[encodedOs]
+	if decodedOs == "" {
+		t.Fatalf("missing decoding value for: %q", runtime.GOOS)
+	}
+}

doq.go

@@ -20,11 +20,17 @@ type doqResolver struct {
 func (r *doqResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, error) {
 	endpoint := r.uc.Endpoint
 	tlsConfig := &tls.Config{NextProtos: []string{"doq"}}
-	if r.uc.BootstrapIP != "" {
+	ip := r.uc.BootstrapIP
-		tlsConfig.ServerName = r.uc.Domain
+	if ip == "" {
-		_, port, _ := net.SplitHostPort(endpoint)
+		dnsTyp := uint16(0)
-		endpoint = net.JoinHostPort(r.uc.BootstrapIP, port)
+		if msg != nil && len(msg.Question) > 0 {
+			dnsTyp = msg.Question[0].Qtype
+		}
+		ip = r.uc.bootstrapIPForDNSType(dnsTyp)
 	}
+	tlsConfig.ServerName = r.uc.Domain
+	_, port, _ := net.SplitHostPort(endpoint)
+	endpoint = net.JoinHostPort(ip, port)
 	return resolve(ctx, msg, endpoint, tlsConfig)
 }
 
@@ -45,7 +51,7 @@ func resolve(ctx context.Context, msg *dns.Msg, endpoint string, tlsConfig *tls.
 }
 
 func doResolve(ctx context.Context, msg *dns.Msg, endpoint string, tlsConfig *tls.Config) (*dns.Msg, error) {
-	session, err := quic.DialAddr(endpoint, tlsConfig, nil)
+	session, err := quic.DialAddr(ctx, endpoint, tlsConfig, nil)
 	if err != nil {
 		return nil, err
 	}

dot.go

@@ -14,18 +14,26 @@ type dotResolver struct {
 
 func (r *dotResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, error) {
 	// The dialer is used to prevent bootstrapping cycle.
-	// If r.endpoing is set to dns.controld.dev, we need to resolve
+	// If r.endpoint is set to dns.controld.dev, we need to resolve
 	// dns.controld.dev first. By using a dialer with custom resolver,
 	// we ensure that we can always resolve the bootstrap domain
 	// regardless of the machine DNS status.
 	dialer := newDialer(net.JoinHostPort(bootstrapDNS, "53"))
+	dnsTyp := uint16(0)
+	if msg != nil && len(msg.Question) > 0 {
+		dnsTyp = msg.Question[0].Qtype
+	}
+
+	tcpNet, _ := r.uc.netForDNSType(dnsTyp)
 	dnsClient := &dns.Client{
-		Net:    "tcp-tls",
+		Net:       tcpNet,
-		Dialer: dialer,
+		Dialer:    dialer,
+		TLSConfig: &tls.Config{RootCAs: r.uc.certPool},
 	}
 	endpoint := r.uc.Endpoint
 	if r.uc.BootstrapIP != "" {
-		dnsClient.TLSConfig = &tls.Config{ServerName: r.uc.Domain}
+		dnsClient.TLSConfig.ServerName = r.uc.Domain
+		dnsClient.Net = "tcp-tls"
 		_, port, _ := net.SplitHostPort(endpoint)
 		endpoint = net.JoinHostPort(r.uc.BootstrapIP, port)
 	}

errors.go

@@ -1,43 +0,0 @@
-package ctrld
-
-// TODO(cuonglm): use stdlib once we bump minimum version to 1.20
-
-func joinErrors(errs ...error) error {
-	n := 0
-	for _, err := range errs {
-		if err != nil {
-			n++
-		}
-	}
-	if n == 0 {
-		return nil
-	}
-	e := &joinError{
-		errs: make([]error, 0, n),
-	}
-	for _, err := range errs {
-		if err != nil {
-			e.errs = append(e.errs, err)
-		}
-	}
-	return e
-}
-
-type joinError struct {
-	errs []error
-}
-
-func (e *joinError) Error() string {
-	var b []byte
-	for i, err := range e.errs {
-		if i > 0 {
-			b = append(b, '\n')
-		}
-		b = append(b, err.Error()...)
-	}
-	return string(b)
-}
-
-func (e *joinError) Unwrap() []error {
-	return e.errs
-}

go.mod

@@ -1,76 +1,95 @@
 module github.com/Control-D-Inc/ctrld
 
-go 1.19
+go 1.20
 
 require (
-	github.com/coreos/go-systemd/v22 v22.3.3-0.20220203105225-a9a7ef127534
+	github.com/coreos/go-systemd/v22 v22.5.0
-	github.com/frankban/quicktest v1.14.3
+	github.com/cuonglm/osinfo v0.0.0-20230921071424-e0e1b1e0bbbf
+	github.com/frankban/quicktest v1.14.5
 	github.com/fsnotify/fsnotify v1.6.0
 	github.com/go-playground/validator/v10 v10.11.1
-	github.com/godbus/dbus/v5 v5.0.6
+	github.com/godbus/dbus/v5 v5.1.0
 	github.com/hashicorp/golang-lru/v2 v2.0.1
 	github.com/illarion/gonotify v1.0.1
-	github.com/insomniacslk/dhcp v0.0.0-20211209223715-7d93572ebe8e
+	github.com/insomniacslk/dhcp v0.0.0-20230407062729-974c6f05fe16
+	github.com/jaytaylor/go-hostsfile v0.0.0-20220426042432-61485ac1fa6c
+	github.com/josharian/native v1.1.1-0.20230202152459-5c7d0dd6ab86
 	github.com/kardianos/service v1.2.1
-	github.com/miekg/dns v1.1.50
+	github.com/mdlayher/ndp v1.0.1
-	github.com/pelletier/go-toml/v2 v2.0.6
+	github.com/miekg/dns v1.1.55
-	github.com/quic-go/quic-go v0.32.0
+	github.com/olekukonko/tablewriter v0.0.5
+	github.com/pelletier/go-toml/v2 v2.0.8
+	github.com/prometheus/client_golang v1.15.1
+	github.com/prometheus/prom2json v1.3.3
+	github.com/quic-go/quic-go v0.38.0
 	github.com/rs/zerolog v1.28.0
-	github.com/spf13/cobra v1.4.0
+	github.com/spf13/cobra v1.7.0
-	github.com/spf13/viper v1.14.0
+	github.com/spf13/pflag v1.0.5
-	github.com/stretchr/testify v1.8.1
+	github.com/spf13/viper v1.16.0
-	golang.org/x/sync v0.1.0
+	github.com/stretchr/testify v1.8.3
-	golang.org/x/sys v0.5.0
+	github.com/vishvananda/netlink v1.2.1-beta.2
+	golang.org/x/net v0.17.0
+	golang.org/x/sync v0.2.0
+	golang.org/x/sys v0.13.0
 	golang.zx2c4.com/wireguard/windows v0.5.3
-	tailscale.com v1.34.1
+	tailscale.com v1.44.0
 )
 
 require (
 	github.com/alexbrainman/sspi v0.0.0-20210105120005-909beea2cc74 // indirect
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-playground/locales v0.14.0 // indirect
 	github.com/go-playground/universal-translator v0.18.0 // indirect
-	github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0 // indirect
+	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
 	github.com/golang/mock v1.6.0 // indirect
+	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/google/pprof v0.0.0-20210407192527-94a9f03dee38 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
-	github.com/inconshreveable/mousetrap v1.0.0 // indirect
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
-	github.com/josharian/native v1.0.0 // indirect
+	github.com/jsimonetti/rtnetlink v1.3.2 // indirect
-	github.com/jsimonetti/rtnetlink v1.1.2-0.20220408201609-d380b505068b // indirect
+	github.com/kr/pretty v0.3.1 // indirect
-	github.com/kr/pretty v0.3.0 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/leodido/go-urn v1.2.1 // indirect
 	github.com/magiconair/properties v1.8.7 // indirect
-	github.com/mattn/go-colorable v0.1.12 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
-	github.com/mattn/go-isatty v0.0.14 // indirect
+	github.com/mattn/go-isatty v0.0.18 // indirect
+	github.com/mattn/go-runewidth v0.0.14 // indirect
+	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
 	github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7 // indirect
-	github.com/mdlayher/netlink v1.6.0 // indirect
+	github.com/mdlayher/netlink v1.7.2 // indirect
 	github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065 // indirect
-	github.com/mdlayher/socket v0.2.3 // indirect
+	github.com/mdlayher/socket v0.4.1 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
-	github.com/onsi/ginkgo/v2 v2.2.0 // indirect
+	github.com/onsi/ginkgo/v2 v2.9.5 // indirect
-	github.com/pelletier/go-toml v1.9.5 // indirect
+	github.com/pierrec/lz4/v4 v4.1.17 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/prometheus/client_model v0.4.0 // indirect
+	github.com/prometheus/common v0.44.0 // indirect
+	github.com/prometheus/procfs v0.9.0 // indirect
 	github.com/quic-go/qpack v0.4.0 // indirect
-	github.com/quic-go/qtls-go1-18 v0.2.0 // indirect
+	github.com/quic-go/qtls-go1-20 v0.3.2 // indirect
-	github.com/quic-go/qtls-go1-19 v0.2.0 // indirect
+	github.com/rivo/uniseg v0.4.4 // indirect
-	github.com/quic-go/qtls-go1-20 v0.1.0 // indirect
+	github.com/rogpeppe/go-internal v1.10.0 // indirect
-	github.com/rogpeppe/go-internal v1.8.1-0.20211023094830-115ce09fd6b4 // indirect
+	github.com/spf13/afero v1.9.5 // indirect
-	github.com/spf13/afero v1.9.3 // indirect
+	github.com/spf13/cast v1.5.1 // indirect
-	github.com/spf13/cast v1.5.0 // indirect
 	github.com/spf13/jwalterweatherman v1.1.0 // indirect
-	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/subosito/gotenv v1.4.2 // indirect
-	github.com/subosito/gotenv v1.4.1 // indirect
+	github.com/u-root/uio v0.0.0-20230305220412-3e8cd9d6bf63 // indirect
-	github.com/u-root/uio v0.0.0-20220204230159-dac05f7d2cb4 // indirect
+	github.com/vishvananda/netns v0.0.4 // indirect
-	go4.org/mem v0.0.0-20210711025021-927187094b94 // indirect
+	go4.org/mem v0.0.0-20220726221520-4f986261bf13 // indirect
-	golang.org/x/crypto v0.4.0 // indirect
+	golang.org/x/crypto v0.14.0 // indirect
-	golang.org/x/exp v0.0.0-20221205204356-47842c84f3db // indirect
+	golang.org/x/exp v0.0.0-20230425010034-47ecfdc1ba53 // indirect
-	golang.org/x/mod v0.6.0 // indirect
+	golang.org/x/mod v0.10.0 // indirect
-	golang.org/x/net v0.7.0 // indirect
+	golang.org/x/text v0.13.0 // indirect
-	golang.org/x/text v0.7.0 // indirect
+	golang.org/x/tools v0.9.1 // indirect
-	golang.org/x/tools v0.2.0 // indirect
+	google.golang.org/protobuf v1.30.0 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect
-	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
+
+replace github.com/mr-karan/doggo => github.com/Windscribe/doggo v0.0.0-20220919152748-2c118fc391f8
+
+replace github.com/rs/zerolog => github.com/Windscribe/zerolog v0.0.0-20230503170159-e6aa153233be

go.sum

@@ -38,22 +38,29 @@ cloud.google.com/go/storage v1.14.0/go.mod h1:GrKmX003DSIwi9o29oFT7YDnHYwZoctc3f
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
+github.com/Windscribe/zerolog v0.0.0-20230503170159-e6aa153233be h1:qBKVRi7Mom5heOkyZ+NCIu9HZBiNCsRqrRe5t9pooik=
+github.com/Windscribe/zerolog v0.0.0-20230503170159-e6aa153233be/go.mod h1:/tk+P47gFdPXq4QYjvCmT5/Gsug2nagsFWBWhAiSi1w=
 github.com/alexbrainman/sspi v0.0.0-20210105120005-909beea2cc74 h1:Kk6a4nehpJ3UuJRqlA3JxYxBZEqCeOmATOvrbT4p9RA=
 github.com/alexbrainman/sspi v0.0.0-20210105120005-909beea2cc74/go.mod h1:cEWa1LVoE5KvSD9ONXsZrj0z6KqySlCCNKHlLzbqAt4=
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
+github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
+github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
 github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
 github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
-github.com/cilium/ebpf v0.8.1 h1:bLSSEbBLqGPXxls55pGr5qWZaTqcmfDJHhou7t254ao=
+github.com/cilium/ebpf v0.10.0 h1:nk5HPMeoBXtOzbkZBWym+ZWq1GIiHUsBFXxwewXAHLQ=
-github.com/cilium/ebpf v0.8.1/go.mod h1:f5zLIM0FSNuAkSyLAN7X+Hy6yznlF1mNiWUMfxMtrgk=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
 github.com/cncf/udpa/go v0.0.0-20200629203442-efcf912fb354/go.mod h1:WmhPx2Nbnhtbo57+VJT5O0JRkEi1Wbu0z5j0R8u5Hbk=
 github.com/cncf/udpa/go v0.0.0-20201120205902-5459f2c99403/go.mod h1:WmhPx2Nbnhtbo57+VJT5O0JRkEi1Wbu0z5j0R8u5Hbk=
-github.com/coreos/go-systemd/v22 v22.3.3-0.20220203105225-a9a7ef127534 h1:rtAn27wIbmOGUs7RIbVgPEjb31ehTVniDwPGXyMxm5U=
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@@ -63,15 +70,14 @@ github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1m
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@@ -80,11 +86,11 @@ github.com/go-playground/universal-translator v0.18.0 h1:82dyy6p4OuJq4/CByFNOn/j
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@@ -112,7 +118,9 @@ github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvq
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@@ -124,8 +132,7 @@ github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
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@@ -148,7 +155,6 @@ github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+
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@@ -156,34 +162,32 @@ github.com/hashicorp/golang-lru/v2 v2.0.1/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyf
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@@ -192,74 +196,88 @@ github.com/leodido/go-urn v1.2.1 h1:BqpAaACuzVSgi/VLzGZIobT2z4v53pjosyNd9Yv6n/w=
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 github.com/yuin/goldmark v1.1.25/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.32/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
@@ -289,18 +311,18 @@ go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.3/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.4/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.5/go.mod h1:5pWMHQbX5EPX2/62yrJeAkowc+lfs/XD7Uxpq3pI6kk=
-go4.org/mem v0.0.0-20210711025021-927187094b94 h1:OAAkygi2Js191AJP1Ds42MhJRgeofeKGjuoUqNp1QC4=
+go4.org/mem v0.0.0-20220726221520-4f986261bf13 h1:CbZeCBZ0aZj8EfVgnqQcYZgf0lpZ3H9rmp5nkDTAst8=
-go4.org/mem v0.0.0-20210711025021-927187094b94/go.mod h1:reUoABIJ9ikfM5sgtSF3Wushcza7+WeD01VB9Lirh3g=
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 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
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-golang.org/x/crypto v0.4.0/go.mod h1:3quD/ATkf6oY+rnes5c3ExXTbLc8mueNue5/DoinL80=
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@@ -311,8 +333,8 @@ golang.org/x/exp v0.0.0-20191227195350-da58074b4299/go.mod h1:2RIsYlXP63K8oxa1u0
 golang.org/x/exp v0.0.0-20200119233911-0405dc783f0a/go.mod h1:2RIsYlXP63K8oxa1u096TMicItID8zy7Y6sNkU49FU4=
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-golang.org/x/exp v0.0.0-20221205204356-47842c84f3db h1:D/cFflL63o2KSLJIwjlcIt8PR064j/xsmdEJL/YvY/o=
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 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
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 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
@@ -337,8 +359,8 @@ golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.4.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
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-golang.org/x/mod v0.6.0 h1:b9gGHsz9/HhJ3HF5DHQytPpuwocVTChQJK3AvoLRD5I=
+golang.org/x/mod v0.10.0 h1:lFO9qtOdlre5W1jxS3r/4szv2/6iXxScdzjoBMXNhYk=
-golang.org/x/mod v0.6.0/go.mod h1:4mET923SAdbXp2ki8ey+zGs1SLqsuM2Y0uvdZR/fUNI=
+golang.org/x/mod v0.10.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
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@@ -352,8 +374,6 @@ golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
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@@ -368,20 +388,15 @@ golang.org/x/net v0.0.0-20200520182314-0ba52f642ac2/go.mod h1:qpuaurCH72eLCgpAm/
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@@ -402,12 +417,11 @@ golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
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-golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
+golang.org/x/sync v0.2.0 h1:PUR+T4wwASmuSTYdKjYHI5TD22Wy5ogLU5qZCOLxBrI=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.2.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
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 golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20190411185658-b44545bcd369/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
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@@ -416,15 +430,14 @@ golang.org/x/sys v0.0.0-20190606122018-79a91cf218c4/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20190606165138-5da285871e9c/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
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-golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191228213918-04cbcbbfeed8/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200113162924-86b910548bc1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200122134326-e047566fdf82/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200212091648-12a6c2dcc1e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200217220822-9197077df867/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200302150141-5c8b2ff67527/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -433,12 +446,11 @@ golang.org/x/sys v0.0.0-20200501052902-10377860bb8e/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200511232937-7e40ca221e25/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200515095857-1151b9dac4a9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200523222454-059865788121/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200728102440-3e129f6d46b1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200803210538-64077c9b5642/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200905004654-be1d3432aa8f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201009025420-dfb3f7c4e634/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201101102859-da207088b7d1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201201145000-ef89a241ccb3/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210104204734-6f8348627aad/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -448,19 +460,18 @@ golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210423185535-09eb48e85fd7/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20210525143221-35b2ab0089ea/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210806184541-e5e7981a1069/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20210906170528-6f6e22806c34/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210927094055-39ccf1dd6fa6/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20211216021012-1d35b9e2eb4e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220622161953-175b2fd9d664/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220128215802-99c3d69c2c27/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220908164124-27713097b956/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
+golang.org/x/sys v0.4.1-0.20230131160137-e7d7f63158de/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
+golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -469,8 +480,8 @@ golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.4/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/text v0.7.0 h1:4BRB4x83lYWy72KwLD/qYDuTu7q9PjSagHvijDw7cLo=
+golang.org/x/text v0.13.0 h1:ablQoSUd0tRdKxZewP80B+BaqeKJuVhuRxj/dkrun3k=
-golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
+golang.org/x/text v0.13.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20191024005414-555d28b269f0/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
@@ -480,7 +491,6 @@ golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20190312151545-0bb0c0a6e846/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20190312170243-e65039ee4138/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
-golang.org/x/tools v0.0.0-20190328211700-ab21143f2384/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20190425150028-36563e24a262/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
 golang.org/x/tools v0.0.0-20190506145303-2d16b83fe98c/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
 golang.org/x/tools v0.0.0-20190524140312-2c0ae7006135/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
@@ -523,9 +533,8 @@ golang.org/x/tools v0.0.0-20210105154028-b0ab187a4818/go.mod h1:emZCQorbCU4vsT4f
 golang.org/x/tools v0.0.0-20210108195828-e2f9c7f1fc8e/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/tools v0.1.0/go.mod h1:xkSsbof2nBLbhDlRMhhhyNLN/zl3eTqcnHD5viDpcZ0=
 golang.org/x/tools v0.1.1/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
-golang.org/x/tools v0.1.6-0.20210726203631-07bc1bf47fb2/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
+golang.org/x/tools v0.9.1 h1:8WMNJAz3zrtPmnYC7ISf5dEn3MT0gY7jBJfw27yrrLo=
-golang.org/x/tools v0.2.0 h1:G6AHpWxTMGY1KyEYoAQ5WTtIekUUvDNjan3ugu60JvE=
+golang.org/x/tools v0.9.1/go.mod h1:owI94Op576fPu3cIGQeHs3joujW/2Oc6MtlxbF5dfNc=
-golang.org/x/tools v0.2.0/go.mod h1:y4OqIKeOV/fWJetJ8bXPU1sEVniLMIyDAZWeHdV+NTA=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
@@ -620,7 +629,10 @@ google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2
 google.golang.org/protobuf v1.23.1-0.20200526195155-81db48ad09cc/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
 google.golang.org/protobuf v1.24.0/go.mod h1:r/3tXBNzIEhYS9I1OUVjXDlt8tc493IdKGjtUeSXeh4=
 google.golang.org/protobuf v1.25.0/go.mod h1:9JNX74DMeImyA3h4bdi1ymwjUzf21/xIlbajtzgsN7c=
-google.golang.org/protobuf v1.28.1 h1:d0NfwRgPtno5B1Wa6L2DAG+KivqkdutMf1UhdNx175w=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
+google.golang.org/protobuf v1.30.0 h1:kPPoIgf3TsEvrm0PFe15JQ+570QVxYzEvvHqChK+cng=
+google.golang.org/protobuf v1.30.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
@@ -629,8 +641,6 @@ gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
 gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
-gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
@@ -645,5 +655,5 @@ honnef.co/go/tools v0.0.1-2020.1.4/go.mod h1:X/FiERA/W4tHapMX5mGpAtMSVEeEUOyHaw9
 rsc.io/binaryregexp v0.2.0/go.mod h1:qTv7/COck+e2FymRvadv62gMdZztPaShugOCi3I+8D8=
 rsc.io/quote/v3 v3.1.0/go.mod h1:yEA65RcK8LyAZtP9Kv3t0HmxON59tX3rD+tICJqUlj0=
 rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
-tailscale.com v1.34.1 h1:tqm9Ww4ltyYp3IPe7vCGch6tT6j5G/WXPQ6BrVZ6pdI=
+tailscale.com v1.44.0 h1:MPos9n30kJvdyfL52045gVFyNg93K+bwgDsr8gqKq2o=
-tailscale.com v1.34.1/go.mod h1:ZsBP7rjzzB2rp+UCOumr9DAe0EQ6OPivwSXcz/BrekQ=
+tailscale.com v1.44.0/go.mod h1:+iYwTdeHyVJuNDu42Zafwihq1Uqfh+pW7pRaY1GD328=

internal/certs/root_ca.go

@@ -0,0 +1,22 @@
+package certs
+
+import (
+	"crypto/x509"
+	_ "embed"
+	"sync"
+)
+
+var (
+	//go:embed cacert.pem
+	caRoots        []byte
+	caCertPoolOnce sync.Once
+	caCertPool     *x509.CertPool
+)
+
+func CACertPool() *x509.CertPool {
+	caCertPoolOnce.Do(func() {
+		caCertPool = x509.NewCertPool()
+		caCertPool.AppendCertsFromPEM(caRoots)
+	})
+	return caCertPool
+}

internal/certs/root_ca_test.go

@@ -0,0 +1,27 @@
+package certs
+
+import (
+	"crypto/tls"
+	"net/http"
+	"testing"
+	"time"
+)
+
+func TestCACertPool(t *testing.T) {
+	c := &http.Client{
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{
+				RootCAs: CACertPool(),
+			},
+		},
+		Timeout: 2 * time.Second,
+	}
+	resp, err := c.Get("https://freedns.controld.com/p1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if !resp.TLS.HandshakeComplete {
+		t.Error("TLS handshake is not complete")
+	}
+}

internal/clientinfo/arp.go

@@ -0,0 +1,49 @@
+package clientinfo
+
+import "sync"
+
+type arpDiscover struct {
+	mac sync.Map // ip  => mac
+	ip  sync.Map // mac => ip
+}
+
+func (a *arpDiscover) refresh() error {
+	a.scan()
+	return nil
+}
+
+func (a *arpDiscover) LookupIP(mac string) string {
+	val, ok := a.ip.Load(mac)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+func (a *arpDiscover) LookupMac(ip string) string {
+	val, ok := a.mac.Load(ip)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+func (a *arpDiscover) String() string {
+	return "arp"
+}
+
+func (a *arpDiscover) List() []string {
+	if a == nil {
+		return nil
+	}
+	var ips []string
+	a.ip.Range(func(key, value any) bool {
+		ips = append(ips, value.(string))
+		return true
+	})
+	a.mac.Range(func(key, value any) bool {
+		ips = append(ips, key.(string))
+		return true
+	})
+	return ips
+}

internal/clientinfo/arp_linux.go

@@ -0,0 +1,28 @@
+package clientinfo
+
+import (
+	"bufio"
+	"os"
+	"strings"
+)
+
+const procNetArpFile = "/proc/net/arp"
+
+func (a *arpDiscover) scan() {
+	f, err := os.Open(procNetArpFile)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	s := bufio.NewScanner(f)
+	s.Scan() // skip header
+	for s.Scan() {
+		line := s.Text()
+		fields := strings.Fields(line)
+		ip := fields[0]
+		mac := fields[3]
+		a.mac.Store(ip, mac)
+		a.ip.Store(mac, ip)
+	}
+}

internal/clientinfo/arp_test.go

@@ -0,0 +1,23 @@
+package clientinfo
+
+import (
+	"sync"
+	"testing"
+)
+
+func TestArpScan(t *testing.T) {
+	a := &arpDiscover{}
+	a.scan()
+
+	for _, table := range []*sync.Map{&a.mac, &a.ip} {
+		count := 0
+		table.Range(func(key, value any) bool {
+			count++
+			t.Logf("%s => %s", key, value)
+			return true
+		})
+		if count == 0 {
+			t.Error("empty result from arp scan")
+		}
+	}
+}

internal/clientinfo/arp_unix.go

@@ -0,0 +1,30 @@
+//go:build !linux && !windows
+
+package clientinfo
+
+import (
+	"os/exec"
+	"strings"
+)
+
+func (a *arpDiscover) scan() {
+	data, err := exec.Command("arp", "-an").Output()
+	if err != nil {
+		return
+	}
+
+	for _, line := range strings.Split(string(data), "\n") {
+		fields := strings.Fields(line)
+		if len(fields) <= 3 {
+			continue
+		}
+
+		// trim brackets
+		ip := strings.ReplaceAll(fields[1], "(", "")
+		ip = strings.ReplaceAll(ip, ")", "")
+
+		mac := fields[3]
+		a.mac.Store(ip, mac)
+		a.ip.Store(mac, ip)
+	}
+}

internal/clientinfo/arp_windows.go

@@ -0,0 +1,38 @@
+package clientinfo
+
+import (
+	"os/exec"
+	"strings"
+)
+
+func (a *arpDiscover) scan() {
+	data, err := exec.Command("arp", "-a").Output()
+	if err != nil {
+		return
+	}
+
+	header := false
+	for _, line := range strings.Split(string(data), "\n") {
+		if len(line) == 0 {
+			continue // empty lines
+		}
+		if line[0] != ' ' {
+			header = true // "Interface:" lines, next is header line.
+			continue
+		}
+		if header {
+			header = false // header lines
+			continue
+		}
+
+		fields := strings.Fields(line)
+		if len(fields) < 2 {
+			continue
+		}
+
+		ip := fields[0]
+		mac := strings.ReplaceAll(fields[1], "-", ":")
+		a.mac.Store(ip, mac)
+		a.ip.Store(mac, ip)
+	}
+}

internal/clientinfo/client_info.go

@@ -0,0 +1,493 @@
+package clientinfo
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/netip"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/Control-D-Inc/ctrld/internal/controld"
+)
+
+// IpResolver is the interface for retrieving IP from Mac.
+type IpResolver interface {
+	fmt.Stringer
+	// LookupIP returns ip of the device with given mac.
+	LookupIP(mac string) string
+}
+
+// MacResolver is the interface for retrieving Mac from IP.
+type MacResolver interface {
+	fmt.Stringer
+	// LookupMac returns mac of the device with given ip.
+	LookupMac(ip string) string
+}
+
+// HostnameByIpResolver is the interface for retrieving hostname from IP.
+type HostnameByIpResolver interface {
+	// LookupHostnameByIP returns hostname of the given ip.
+	LookupHostnameByIP(ip string) string
+}
+
+// HostnameByMacResolver is the interface for retrieving hostname from Mac.
+type HostnameByMacResolver interface {
+	// LookupHostnameByMac returns hostname of the device with given mac.
+	LookupHostnameByMac(mac string) string
+}
+
+// HostnameResolver is the interface for retrieving hostname from either IP or Mac.
+type HostnameResolver interface {
+	fmt.Stringer
+	HostnameByIpResolver
+	HostnameByMacResolver
+}
+
+type refresher interface {
+	refresh() error
+}
+
+type ipLister interface {
+	fmt.Stringer
+	// List returns list of ip known by the resolver.
+	List() []string
+}
+
+type Client struct {
+	IP                netip.Addr
+	Mac               string
+	Hostname          string
+	Source            map[string]struct{}
+	QueryCount        int64
+	IncludeQueryCount bool
+}
+
+type Table struct {
+	ipResolvers       []IpResolver
+	macResolvers      []MacResolver
+	hostnameResolvers []HostnameResolver
+	refreshers        []refresher
+	initOnce          sync.Once
+	refreshInterval   int
+
+	dhcp           *dhcp
+	merlin         *merlinDiscover
+	ubios          *ubiosDiscover
+	arp            *arpDiscover
+	ndp            *ndpDiscover
+	ptr            *ptrDiscover
+	mdns           *mdns
+	hf             *hostsFile
+	vni            *virtualNetworkIface
+	svcCfg         ctrld.ServiceConfig
+	quitCh         chan struct{}
+	selfIP         string
+	cdUID          string
+	ptrNameservers []string
+}
+
+func NewTable(cfg *ctrld.Config, selfIP, cdUID string, ns []string) *Table {
+	refreshInterval := cfg.Service.DiscoverRefreshInterval
+	if refreshInterval <= 0 {
+		refreshInterval = 2 * 60 // 2 minutes
+	}
+	return &Table{
+		svcCfg:          cfg.Service,
+		quitCh:          make(chan struct{}),
+		selfIP:          selfIP,
+		cdUID:           cdUID,
+		ptrNameservers:  ns,
+		refreshInterval: refreshInterval,
+	}
+}
+
+func (t *Table) AddLeaseFile(name string, format ctrld.LeaseFileFormat) {
+	if !t.discoverDHCP() {
+		return
+	}
+	clientInfoFiles[name] = format
+}
+
+// RefreshLoop runs all the refresher to update new client info data.
+func (t *Table) RefreshLoop(ctx context.Context) {
+	timer := time.NewTicker(time.Second * time.Duration(t.refreshInterval))
+	defer timer.Stop()
+	for {
+		select {
+		case <-timer.C:
+			for _, r := range t.refreshers {
+				_ = r.refresh()
+			}
+		case <-ctx.Done():
+			close(t.quitCh)
+			return
+		}
+	}
+}
+
+func (t *Table) Init() {
+	t.initOnce.Do(t.init)
+}
+
+func (t *Table) init() {
+	// Custom client ID presents, use it as the only source.
+	if _, clientID := controld.ParseRawUID(t.cdUID); clientID != "" {
+		ctrld.ProxyLogger.Load().Debug().Msg("start self discovery")
+		t.dhcp = &dhcp{selfIP: t.selfIP}
+		t.dhcp.addSelf()
+		t.ipResolvers = append(t.ipResolvers, t.dhcp)
+		t.macResolvers = append(t.macResolvers, t.dhcp)
+		t.hostnameResolvers = append(t.hostnameResolvers, t.dhcp)
+		return
+	}
+
+	// Otherwise, process all possible sources in order, that means
+	// the first result of IP/MAC/Hostname lookup will be used.
+	//
+	// Routers custom clients:
+	//  - Merlin
+	//  - Ubios
+	if t.discoverDHCP() || t.discoverARP() {
+		t.merlin = &merlinDiscover{}
+		t.ubios = &ubiosDiscover{}
+		discovers := map[string]interface {
+			refresher
+			HostnameResolver
+		}{
+			"Merlin": t.merlin,
+			"Ubios":  t.ubios,
+		}
+		for platform, discover := range discovers {
+			if err := discover.refresh(); err != nil {
+				ctrld.ProxyLogger.Load().Error().Err(err).Msgf("could not init %s discover", platform)
+			} else {
+				t.hostnameResolvers = append(t.hostnameResolvers, discover)
+				t.refreshers = append(t.refreshers, discover)
+			}
+		}
+	}
+	// Hosts file mapping.
+	if t.discoverHosts() {
+		t.hf = &hostsFile{}
+		ctrld.ProxyLogger.Load().Debug().Msg("start hosts file discovery")
+		if err := t.hf.init(); err != nil {
+			ctrld.ProxyLogger.Load().Error().Err(err).Msg("could not init hosts file discover")
+		} else {
+			t.hostnameResolvers = append(t.hostnameResolvers, t.hf)
+			t.refreshers = append(t.refreshers, t.hf)
+		}
+		go t.hf.watchChanges()
+	}
+	// DHCP lease files.
+	if t.discoverDHCP() {
+		t.dhcp = &dhcp{selfIP: t.selfIP}
+		ctrld.ProxyLogger.Load().Debug().Msg("start dhcp discovery")
+		if err := t.dhcp.init(); err != nil {
+			ctrld.ProxyLogger.Load().Error().Err(err).Msg("could not init DHCP discover")
+		} else {
+			t.ipResolvers = append(t.ipResolvers, t.dhcp)
+			t.macResolvers = append(t.macResolvers, t.dhcp)
+			t.hostnameResolvers = append(t.hostnameResolvers, t.dhcp)
+		}
+		go t.dhcp.watchChanges()
+	}
+	// ARP/NDP table.
+	if t.discoverARP() {
+		t.arp = &arpDiscover{}
+		t.ndp = &ndpDiscover{}
+		ctrld.ProxyLogger.Load().Debug().Msg("start arp discovery")
+		discovers := map[string]interface {
+			refresher
+			IpResolver
+			MacResolver
+		}{
+			"ARP": t.arp,
+			"NDP": t.ndp,
+		}
+
+		for protocol, discover := range discovers {
+			if err := discover.refresh(); err != nil {
+				ctrld.ProxyLogger.Load().Error().Err(err).Msgf("could not init %s discover", protocol)
+			} else {
+				t.ipResolvers = append(t.ipResolvers, discover)
+				t.macResolvers = append(t.macResolvers, discover)
+				t.refreshers = append(t.refreshers, discover)
+			}
+		}
+		ctx, cancel := context.WithCancel(context.Background())
+		go func() {
+			<-t.quitCh
+			cancel()
+		}()
+		go t.ndp.listen(ctx)
+	}
+	// PTR lookup.
+	if t.discoverPTR() {
+		t.ptr = &ptrDiscover{resolver: ctrld.NewPrivateResolver()}
+		if len(t.ptrNameservers) > 0 {
+			nss := make([]string, 0, len(t.ptrNameservers))
+			for _, ns := range t.ptrNameservers {
+				host, port := ns, "53"
+				if h, p, err := net.SplitHostPort(ns); err == nil {
+					host, port = h, p
+				}
+				// Only use valid ip:port pair.
+				if _, portErr := strconv.Atoi(port); portErr == nil && port != "0" && net.ParseIP(host) != nil {
+					nss = append(nss, net.JoinHostPort(host, port))
+				} else {
+					ctrld.ProxyLogger.Load().Warn().Msgf("ignoring invalid nameserver for ptr discover: %q", ns)
+				}
+			}
+			if len(nss) > 0 {
+				t.ptr.resolver = ctrld.NewResolverWithNameserver(nss)
+				ctrld.ProxyLogger.Load().Debug().Msgf("using nameservers %v for ptr discovery", nss)
+			}
+
+		}
+		ctrld.ProxyLogger.Load().Debug().Msg("start ptr discovery")
+		if err := t.ptr.refresh(); err != nil {
+			ctrld.ProxyLogger.Load().Error().Err(err).Msg("could not init PTR discover")
+		} else {
+			t.hostnameResolvers = append(t.hostnameResolvers, t.ptr)
+			t.refreshers = append(t.refreshers, t.ptr)
+		}
+	}
+	// mdns.
+	if t.discoverMDNS() {
+		t.mdns = &mdns{}
+		ctrld.ProxyLogger.Load().Debug().Msg("start mdns discovery")
+		if err := t.mdns.init(t.quitCh); err != nil {
+			ctrld.ProxyLogger.Load().Error().Err(err).Msg("could not init mDNS discover")
+		} else {
+			t.hostnameResolvers = append(t.hostnameResolvers, t.mdns)
+		}
+	}
+	// VPN clients.
+	if t.discoverDHCP() || t.discoverARP() {
+		t.vni = &virtualNetworkIface{}
+		t.hostnameResolvers = append(t.hostnameResolvers, t.vni)
+	}
+}
+
+func (t *Table) LookupIP(mac string) string {
+	t.initOnce.Do(t.init)
+	for _, r := range t.ipResolvers {
+		if ip := r.LookupIP(mac); ip != "" {
+			return ip
+		}
+	}
+	return ""
+}
+
+func (t *Table) LookupMac(ip string) string {
+	t.initOnce.Do(t.init)
+	for _, r := range t.macResolvers {
+		if mac := r.LookupMac(ip); mac != "" {
+			return mac
+		}
+	}
+	return ""
+}
+
+func (t *Table) LookupHostname(ip, mac string) string {
+	t.initOnce.Do(t.init)
+	for _, r := range t.hostnameResolvers {
+		if name := r.LookupHostnameByIP(ip); name != "" {
+			return name
+		}
+		if name := r.LookupHostnameByMac(mac); name != "" {
+			return name
+		}
+	}
+	return ""
+}
+
+// LookupRFC1918IPv4 returns the RFC1918 IPv4 address for the given MAC address, if any.
+func (t *Table) LookupRFC1918IPv4(mac string) string {
+	t.initOnce.Do(t.init)
+	for _, r := range t.ipResolvers {
+		ip, err := netip.ParseAddr(r.LookupIP(mac))
+		if err != nil || ip.Is6() {
+			continue
+		}
+		if ip.IsPrivate() {
+			return ip.String()
+		}
+	}
+	return ""
+}
+
+type macEntry struct {
+	mac string
+	src string
+}
+
+type hostnameEntry struct {
+	name string
+	src  string
+}
+
+func (t *Table) lookupMacAll(ip string) []*macEntry {
+	var res []*macEntry
+	for _, r := range t.macResolvers {
+		res = append(res, &macEntry{mac: r.LookupMac(ip), src: r.String()})
+	}
+	return res
+}
+
+func (t *Table) lookupHostnameAll(ip, mac string) []*hostnameEntry {
+	var res []*hostnameEntry
+	for _, r := range t.hostnameResolvers {
+		src := r.String()
+		// For ptrDiscover, lookup hostname may block due to server unavailable,
+		// so only lookup from cache to prevent timeout reached.
+		if ptrResolver, ok := r.(*ptrDiscover); ok {
+			if name := ptrResolver.lookupHostnameFromCache(ip); name != "" {
+				res = append(res, &hostnameEntry{name: name, src: src})
+			}
+			continue
+		}
+		if name := r.LookupHostnameByIP(ip); name != "" {
+			res = append(res, &hostnameEntry{name: name, src: src})
+			continue
+		}
+		if name := r.LookupHostnameByMac(mac); name != "" {
+			res = append(res, &hostnameEntry{name: name, src: src})
+			continue
+		}
+	}
+	return res
+}
+
+// ListClients returns list of clients discovered by ctrld.
+func (t *Table) ListClients() []*Client {
+	for _, r := range t.refreshers {
+		_ = r.refresh()
+	}
+	ipMap := make(map[string]*Client)
+	il := []ipLister{t.dhcp, t.arp, t.ndp, t.ptr, t.mdns, t.vni}
+	for _, ir := range il {
+		for _, ip := range ir.List() {
+			c, ok := ipMap[ip]
+			if !ok {
+				c = &Client{
+					IP:     netip.MustParseAddr(ip),
+					Source: map[string]struct{}{ir.String(): {}},
+				}
+				ipMap[ip] = c
+			} else {
+				c.Source[ir.String()] = struct{}{}
+			}
+		}
+	}
+	for ip := range ipMap {
+		c := ipMap[ip]
+		for _, e := range t.lookupMacAll(ip) {
+			if c.Mac == "" && e.mac != "" {
+				c.Mac = e.mac
+			}
+			if e.mac != "" {
+				c.Source[e.src] = struct{}{}
+			}
+		}
+		for _, e := range t.lookupHostnameAll(ip, c.Mac) {
+			if c.Hostname == "" && e.name != "" {
+				c.Hostname = e.name
+			}
+			if e.name != "" {
+				c.Source[e.src] = struct{}{}
+			}
+		}
+	}
+	clients := make([]*Client, 0, len(ipMap))
+	for _, c := range ipMap {
+		clients = append(clients, c)
+	}
+	return clients
+}
+
+// StoreVPNClient stores client info for VPN clients.
+func (t *Table) StoreVPNClient(ci *ctrld.ClientInfo) {
+	if ci == nil || t.vni == nil {
+		return
+	}
+	t.vni.mac.Store(ci.IP, ci.Mac)
+	t.vni.ip2name.Store(ci.IP, ci.Hostname)
+}
+
+// ipFinder is the interface for retrieving IP address from hostname.
+type ipFinder interface {
+	lookupIPByHostname(name string, v6 bool) string
+}
+
+// LookupIPByHostname returns the ip address of given hostname.
+// If v6 is true, return IPv6 instead of default IPv4.
+func (t *Table) LookupIPByHostname(hostname string, v6 bool) *netip.Addr {
+	if t == nil {
+		return nil
+	}
+	for _, finder := range []ipFinder{t.hf, t.ptr, t.mdns, t.dhcp} {
+		if addr := finder.lookupIPByHostname(hostname, v6); addr != "" {
+			if ip, err := netip.ParseAddr(addr); err == nil {
+				return &ip
+			}
+		}
+	}
+	return nil
+}
+
+func (t *Table) discoverDHCP() bool {
+	if t.svcCfg.DiscoverDHCP == nil {
+		return true
+	}
+	return *t.svcCfg.DiscoverDHCP
+}
+
+func (t *Table) discoverARP() bool {
+	if t.svcCfg.DiscoverARP == nil {
+		return true
+	}
+	return *t.svcCfg.DiscoverARP
+}
+
+func (t *Table) discoverMDNS() bool {
+	if t.svcCfg.DiscoverMDNS == nil {
+		return true
+	}
+	return *t.svcCfg.DiscoverMDNS
+}
+
+func (t *Table) discoverPTR() bool {
+	if t.svcCfg.DiscoverPtr == nil {
+		return true
+	}
+	return *t.svcCfg.DiscoverPtr
+}
+
+func (t *Table) discoverHosts() bool {
+	if t.svcCfg.DiscoverHosts == nil {
+		return true
+	}
+	return *t.svcCfg.DiscoverHosts
+}
+
+// normalizeIP normalizes the ip parsed from dnsmasq/dhcpd lease file.
+func normalizeIP(in string) string {
+	// dnsmasq may put ip with interface index in lease file, strip it here.
+	ip, _, found := strings.Cut(in, "%")
+	if found {
+		return ip
+	}
+	return in
+}
+
+func normalizeHostname(name string) string {
+	if before, _, found := strings.Cut(name, "."); found {
+		return before // remove ".local.", ".lan.", ... suffix
+	}
+	return name
+}

internal/clientinfo/client_info_test.go

@@ -0,0 +1,46 @@
+package clientinfo
+
+import (
+	"testing"
+)
+
+func Test_normalizeIP(t *testing.T) {
+	tests := []struct {
+		name string
+		in   string
+		want string
+	}{
+		{"v4", "127.0.0.1", "127.0.0.1"},
+		{"v4 with index", "127.0.0.1%lo", "127.0.0.1"},
+		{"v6", "fe80::1", "fe80::1"},
+		{"v6 with index", "fe80::1%22002", "fe80::1"},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := normalizeIP(tc.in); got != tc.want {
+				t.Errorf("normalizeIP() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestTable_LookupRFC1918IPv4(t *testing.T) {
+	table := &Table{
+		dhcp: &dhcp{},
+		arp:  &arpDiscover{},
+	}
+
+	table.ipResolvers = append(table.ipResolvers, table.dhcp)
+	table.ipResolvers = append(table.ipResolvers, table.arp)
+
+	macAddress := "cc:19:f9:8a:49:e6"
+	rfc1918IPv4 := "10.0.10.245"
+	table.dhcp.ip.Store(macAddress, "127.0.0.1")
+	table.arp.ip.Store(macAddress, rfc1918IPv4)
+
+	if got := table.LookupRFC1918IPv4(macAddress); got != rfc1918IPv4 {
+		t.Fatalf("unexpected result, want: %s, got: %s", rfc1918IPv4, got)
+	}
+}

internal/clientinfo/dhcp.go

@@ -0,0 +1,408 @@
+package clientinfo
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/csv"
+	"fmt"
+	"io"
+	"net"
+	"net/netip"
+	"os"
+	"sort"
+	"strings"
+	"sync"
+
+	"github.com/fsnotify/fsnotify"
+	"tailscale.com/net/interfaces"
+	"tailscale.com/util/lineread"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/Control-D-Inc/ctrld/internal/router"
+)
+
+type dhcp struct {
+	mac2name sync.Map // mac => name
+	ip2name  sync.Map // ip  => name
+	ip       sync.Map // mac => ip
+	mac      sync.Map // ip  => mac
+
+	watcher *fsnotify.Watcher
+	selfIP  string
+}
+
+func (d *dhcp) init() error {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return err
+	}
+	d.addSelf()
+	d.watcher = watcher
+	for file, format := range clientInfoFiles {
+		// Ignore errors for default lease files.
+		_ = d.addLeaseFile(file, format)
+	}
+	return nil
+}
+
+func (d *dhcp) watchChanges() {
+	if d.watcher == nil {
+		return
+	}
+	if dir := router.LeaseFilesDir(); dir != "" {
+		if err := d.watcher.Add(dir); err != nil {
+			ctrld.ProxyLogger.Load().Err(err).Str("dir", dir).Msg("could not watch lease dir")
+		}
+	}
+	for {
+		select {
+		case event, ok := <-d.watcher.Events:
+			if !ok {
+				return
+			}
+			if event.Has(fsnotify.Create) {
+				if format, ok := clientInfoFiles[event.Name]; ok {
+					if err := d.addLeaseFile(event.Name, format); err != nil {
+						ctrld.ProxyLogger.Load().Err(err).Str("file", event.Name).Msg("could not add lease file")
+					}
+				}
+				continue
+			}
+			if event.Has(fsnotify.Write) || event.Has(fsnotify.Rename) || event.Has(fsnotify.Chmod) || event.Has(fsnotify.Remove) {
+				format := clientInfoFiles[event.Name]
+				if err := d.readLeaseFile(event.Name, format); err != nil && !os.IsNotExist(err) {
+					ctrld.ProxyLogger.Load().Err(err).Str("file", event.Name).Msg("leases file changed but failed to update client info")
+				}
+			}
+		case err, ok := <-d.watcher.Errors:
+			if !ok {
+				return
+			}
+			ctrld.ProxyLogger.Load().Err(err).Msg("could not watch client info file")
+		}
+	}
+
+}
+
+func (d *dhcp) LookupIP(mac string) string {
+	val, ok := d.ip.Load(mac)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+func (d *dhcp) LookupMac(ip string) string {
+	val, ok := d.mac.Load(ip)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+func (d *dhcp) LookupHostnameByIP(ip string) string {
+	val, ok := d.ip2name.Load(ip)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+func (d *dhcp) LookupHostnameByMac(mac string) string {
+	val, ok := d.mac2name.Load(mac)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+func (d *dhcp) String() string {
+	return "dhcp"
+}
+
+func (d *dhcp) List() []string {
+	if d == nil {
+		return nil
+	}
+	var ips []string
+	d.ip.Range(func(key, value any) bool {
+		ips = append(ips, value.(string))
+		return true
+	})
+	d.mac.Range(func(key, value any) bool {
+		ips = append(ips, key.(string))
+		return true
+	})
+	return ips
+}
+
+func (d *dhcp) lookupIPByHostname(name string, v6 bool) string {
+	if d == nil {
+		return ""
+	}
+	var (
+		rfc1918Addrs []netip.Addr
+		others       []netip.Addr
+	)
+	d.ip2name.Range(func(key, value any) bool {
+		if value != name {
+			return true
+		}
+		if addr, err := netip.ParseAddr(key.(string)); err == nil && addr.Is6() == v6 {
+			if addr.IsPrivate() {
+				rfc1918Addrs = append(rfc1918Addrs, addr)
+			} else {
+				others = append(others, addr)
+			}
+		}
+		return true
+	})
+	result := [][]netip.Addr{rfc1918Addrs, others}
+	for _, addrs := range result {
+		if len(addrs) > 0 {
+			sort.Slice(addrs, func(i, j int) bool {
+				return addrs[i].Less(addrs[j])
+			})
+			return addrs[0].String()
+		}
+	}
+	return ""
+}
+
+// AddLeaseFile adds given lease file for reading/watching clients info.
+func (d *dhcp) addLeaseFile(name string, format ctrld.LeaseFileFormat) error {
+	if d.watcher == nil {
+		return nil
+	}
+	if err := d.readLeaseFile(name, format); err != nil {
+		return fmt.Errorf("could not read lease file: %w", err)
+	}
+	clientInfoFiles[name] = format
+	return d.watcher.Add(name)
+}
+
+// readLeaseFile reads the lease file with given format, saving client information to dhcp table.
+func (d *dhcp) readLeaseFile(name string, format ctrld.LeaseFileFormat) error {
+	switch format {
+	case ctrld.Dnsmasq:
+		return d.dnsmasqReadClientInfoFile(name)
+	case ctrld.IscDhcpd:
+		return d.iscDHCPReadClientInfoFile(name)
+	case ctrld.KeaDHCP4:
+		return d.keaDhcp4ReadClientInfoFile(name)
+	}
+	return fmt.Errorf("unsupported format: %s, file: %s", format, name)
+}
+
+// dnsmasqReadClientInfoFile populates dhcp table with client info reading from dnsmasq lease file.
+func (d *dhcp) dnsmasqReadClientInfoFile(name string) error {
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return d.dnsmasqReadClientInfoReader(f)
+
+}
+
+// dnsmasqReadClientInfoReader performs the same task as dnsmasqReadClientInfoFile,
+// but by reading from an io.Reader instead of file.
+func (d *dhcp) dnsmasqReadClientInfoReader(reader io.Reader) error {
+	return lineread.Reader(reader, func(line []byte) error {
+		fields := bytes.Fields(line)
+		if len(fields) < 4 {
+			return nil
+		}
+
+		mac := string(fields[1])
+		if _, err := net.ParseMAC(mac); err != nil {
+			// The second field is not a dhcp, skip.
+			return nil
+		}
+		ip := normalizeIP(string(fields[2]))
+		if net.ParseIP(ip) == nil {
+			ctrld.ProxyLogger.Load().Warn().Msgf("invalid ip address entry: %q", ip)
+			ip = ""
+		}
+
+		d.mac.Store(ip, mac)
+		d.ip.Store(mac, ip)
+		hostname := string(fields[3])
+		if hostname == "*" {
+			return nil
+		}
+		name := normalizeHostname(hostname)
+		d.mac2name.Store(mac, name)
+		d.ip2name.Store(ip, name)
+		return nil
+	})
+}
+
+// iscDHCPReadClientInfoFile populates dhcp table with client info reading from isc-dhcpd lease file.
+func (d *dhcp) iscDHCPReadClientInfoFile(name string) error {
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return d.iscDHCPReadClientInfoReader(f)
+}
+
+// iscDHCPReadClientInfoReader performs the same task as iscDHCPReadClientInfoFile,
+// but by reading from an io.Reader instead of file.
+func (d *dhcp) iscDHCPReadClientInfoReader(reader io.Reader) error {
+	s := bufio.NewScanner(reader)
+	var ip, mac, hostname string
+	for s.Scan() {
+		line := s.Text()
+		if strings.HasPrefix(line, "}") {
+			d.mac.Store(ip, mac)
+			d.ip.Store(mac, ip)
+			if hostname != "" && hostname != "*" {
+				name := normalizeHostname(hostname)
+				d.mac2name.Store(mac, name)
+				d.ip2name.Store(ip, hostname)
+				ip, mac, hostname = "", "", ""
+			}
+			continue
+		}
+		fields := strings.Fields(line)
+		if len(fields) < 2 {
+			continue
+		}
+		switch fields[0] {
+		case "lease":
+			ip = normalizeIP(strings.ToLower(fields[1]))
+			if net.ParseIP(ip) == nil {
+				ctrld.ProxyLogger.Load().Warn().Msgf("invalid ip address entry: %q", ip)
+				ip = ""
+			}
+		case "hardware":
+			if len(fields) >= 3 {
+				mac = strings.ToLower(strings.TrimRight(fields[2], ";"))
+				if _, err := net.ParseMAC(mac); err != nil {
+					// Invalid dhcp, skip.
+					mac = ""
+				}
+			}
+		case "client-hostname":
+			hostname = strings.Trim(fields[1], `";`)
+		}
+	}
+	return nil
+}
+
+// keaDhcp4ReadClientInfoFile populates dhcp table with client info reading from kea dhcp4 lease file.
+func (d *dhcp) keaDhcp4ReadClientInfoFile(name string) error {
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return d.keaDhcp4ReadClientInfoReader(bufio.NewReader(f))
+
+}
+
+// keaDhcp4ReadClientInfoReader performs the same task as keaDhcp4ReadClientInfoFile,
+// but by reading from an io.Reader instead of file.
+func (d *dhcp) keaDhcp4ReadClientInfoReader(r io.Reader) error {
+	cr := csv.NewReader(r)
+	for {
+		record, err := cr.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return err
+		}
+		if len(record) < 9 {
+			continue // hostname is at 9th field, so skipping record with not enough fields.
+		}
+		if record[0] == "address" {
+			continue // skip header.
+		}
+		mac := record[1]
+		if _, err := net.ParseMAC(mac); err != nil { // skip invalid MAC
+			continue
+		}
+		ip := normalizeIP(record[0])
+		if net.ParseIP(ip) == nil {
+			ctrld.ProxyLogger.Load().Warn().Msgf("invalid ip address entry: %q", ip)
+			ip = ""
+		}
+
+		d.mac.Store(ip, mac)
+		d.ip.Store(mac, ip)
+		hostname := record[8]
+		if hostname == "*" {
+			continue
+		}
+		name := normalizeHostname(hostname)
+		d.mac2name.Store(mac, name)
+		d.ip2name.Store(ip, name)
+	}
+	return nil
+}
+
+// addSelf populates current host info to dhcp, so queries from
+// the host itself can be attached with proper client info.
+func (d *dhcp) addSelf() {
+	hostname, err := os.Hostname()
+	if err != nil {
+		ctrld.ProxyLogger.Load().Err(err).Msg("could not get hostname")
+		return
+	}
+	hostname = normalizeHostname(hostname)
+	d.ip2name.Store("127.0.0.1", hostname)
+	d.ip2name.Store("::1", hostname)
+	found := false
+	interfaces.ForeachInterface(func(i interfaces.Interface, prefixes []netip.Prefix) {
+		mac := i.HardwareAddr.String()
+		// Skip loopback interfaces, info was stored above.
+		if mac == "" {
+			return
+		}
+		addrs, _ := i.Addrs()
+		for _, addr := range addrs {
+			if found {
+				return
+			}
+			ipNet, ok := addr.(*net.IPNet)
+			if !ok {
+				continue
+			}
+			ip := ipNet.IP
+			d.mac.Store(ip.String(), mac)
+			d.ip.Store(mac, ip.String())
+			if ip.To4() != nil {
+				d.mac.Store("127.0.0.1", mac)
+			} else {
+				d.mac.Store("::1", mac)
+			}
+			d.mac2name.Store(mac, hostname)
+			d.ip2name.Store(ip.String(), hostname)
+			// If we have self IP set, and this IP is it, use this IP only.
+			if ip.String() == d.selfIP {
+				found = true
+			}
+		}
+	})
+	for _, netIface := range router.SelfInterfaces() {
+		mac := netIface.HardwareAddr.String()
+		if mac == "" {
+			return
+		}
+		d.mac2name.Store(mac, hostname)
+		addrs, _ := netIface.Addrs()
+		for _, addr := range addrs {
+			ipNet, ok := addr.(*net.IPNet)
+			if !ok {
+				continue
+			}
+			ip := ipNet.IP
+			d.mac.LoadOrStore(ip.String(), mac)
+			d.ip.LoadOrStore(mac, ip.String())
+			d.ip2name.Store(ip.String(), hostname)
+		}
+	}
+}

internal/clientinfo/dhcp_lease_files.go

@@ -0,0 +1,19 @@
+package clientinfo
+
+import "github.com/Control-D-Inc/ctrld"
+
+// clientInfoFiles specifies client info files and how to read them on supported platforms.
+var clientInfoFiles = map[string]ctrld.LeaseFileFormat{
+	"/tmp/dnsmasq.leases":                      ctrld.Dnsmasq,  // ddwrt
+	"/tmp/dhcp.leases":                         ctrld.Dnsmasq,  // openwrt
+	"/var/lib/misc/dnsmasq.leases":             ctrld.Dnsmasq,  // merlin
+	"/mnt/data/udapi-config/dnsmasq.lease":     ctrld.Dnsmasq,  // UDM Pro
+	"/data/udapi-config/dnsmasq.lease":         ctrld.Dnsmasq,  // UDR
+	"/etc/dhcpd/dhcpd-leases.log":              ctrld.Dnsmasq,  // Synology
+	"/tmp/var/lib/misc/dnsmasq.leases":         ctrld.Dnsmasq,  // Tomato
+	"/run/dnsmasq-dhcp.leases":                 ctrld.Dnsmasq,  // EdgeOS
+	"/run/dhcpd.leases":                        ctrld.IscDhcpd, // EdgeOS
+	"/var/dhcpd/var/db/dhcpd.leases":           ctrld.IscDhcpd, // Pfsense
+	"/home/pi/.router/run/dhcp/dnsmasq.leases": ctrld.Dnsmasq,  // Firewalla
+	"/var/lib/kea/dhcp4.leases":                ctrld.KeaDHCP4, // Pfsense
+}

internal/clientinfo/dhcp_test.go

@@ -0,0 +1,141 @@
+package clientinfo
+
+import (
+	"io"
+	"strings"
+	"testing"
+)
+
+func Test_readClientInfoReader(t *testing.T) {
+	d := &dhcp{}
+	tests := []struct {
+		name     string
+		in       string
+		readFunc func(r io.Reader) error
+		mac      string
+		hostname string
+	}{
+		{
+			"good dnsmasq",
+			`1683329857 e6:20:59:b8:c1:6d 192.168.1.186 host1 01:e6:20:59:b8:c1:6d
+`,
+			d.dnsmasqReadClientInfoReader,
+			"e6:20:59:b8:c1:6d",
+			"host1",
+		},
+		{
+			"bad dnsmasq seen on UDMdream machine",
+			`1683329857 e6:20:59:b8:c1:6e 192.168.1.111 host1 01:e6:20:59:b8:c1:6e
+duid 00:01:00:01:2b:e4:2e:2c:52:52:14:26:dc:1c
+1683322985 117442354 2600:4040:b0e6:b700::111 ASDASD 00:01:00:01:2a:d0:b9:81:00:07:32:4c:1c:07
+`,
+			d.dnsmasqReadClientInfoReader,
+			"e6:20:59:b8:c1:6e",
+			"host1",
+		},
+		{
+			"isc-dhcpd good",
+			`lease 192.168.1.1 {
+    hardware ethernet 00:00:00:00:00:01;
+    client-hostname "host-1";
+}
+`,
+			d.iscDHCPReadClientInfoReader,
+			"00:00:00:00:00:01",
+			"host-1",
+		},
+		{
+			"isc-dhcpd bad dhcp",
+			`lease 192.168.1.1 {
+    hardware ethernet invalid-dhcp;
+    client-hostname "host-1";
+}
+
+lease 192.168.1.2 {
+    hardware ethernet 00:00:00:00:00:02;
+    client-hostname "host-2";
+}
+`,
+			d.iscDHCPReadClientInfoReader,
+			"00:00:00:00:00:02",
+			"host-2",
+		},
+		{
+			"",
+			`1685794060 00:00:00:00:00:04 192.168.0.209 example 00:00:00:00:00:04 9`,
+			d.dnsmasqReadClientInfoReader,
+			"00:00:00:00:00:04",
+			"example",
+		},
+		{
+			"kea-dhcp4 good",
+			`address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state,user_context,pool_id
+192.168.0.123,00:00:00:00:00:05,00:00:00:00:00:05,7200,1703290639,1,0,0,foo,0,,0
+`,
+			d.keaDhcp4ReadClientInfoReader,
+			"00:00:00:00:00:05",
+			"foo",
+		},
+		{
+			"kea-dhcp4 no-header",
+			`192.168.0.123,00:00:00:00:00:05,00:00:00:00:00:05,7200,1703290639,1,0,0,foo,0,,0`,
+			d.keaDhcp4ReadClientInfoReader,
+			"00:00:00:00:00:05",
+			"foo",
+		},
+		{
+			"kea-dhcp4 hostname *",
+			`address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state,user_context,pool_id
+192.168.0.123,00:00:00:00:00:05,00:00:00:00:00:05,7200,1703290639,1,0,0,*,0,,0
+`,
+			d.keaDhcp4ReadClientInfoReader,
+			"00:00:00:00:00:05",
+			"*",
+		},
+		{
+			"kea-dhcp4 bad",
+			`address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state,user_context,pool_id
+192.168.0.123,00:00:00:00:00:05,00:00:00:00:00:05,7200,1703290639,1,0,0,foo,0,,0
+192.168.0.124,invalid_MAC,00:00:00:00:00:05,7200,1703290639,1,0,0,foo,0,,0
+`,
+			d.keaDhcp4ReadClientInfoReader,
+			"00:00:00:00:00:05",
+			"foo",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			d.mac2name.Delete(tc.mac)
+			if err := tc.readFunc(strings.NewReader(tc.in)); err != nil {
+				t.Errorf("readClientInfoReader() error = %v", err)
+			}
+			val, existed := d.mac2name.Load(tc.mac)
+			if tc.hostname == "*" {
+				if existed {
+					t.Errorf("* hostname must be skipped")
+				}
+				return
+			}
+			if !existed {
+				t.Error("client info missing")
+			}
+			hostname := val.(string)
+			if existed && hostname != tc.hostname {
+				t.Errorf("hostname mismatched, want: %q, got: %q", tc.hostname, hostname)
+			}
+		})
+	}
+}
+
+func Test_dhcp_lookupIPByHostname(t *testing.T) {
+	d := &dhcp{}
+	want := "192.168.1.123"
+	d.ip2name.Store(want, "foo")
+	d.ip2name.Store("127.0.0.1", "foo")
+	d.ip2name.Store("169.254.123.123", "foo")
+
+	if got := d.lookupIPByHostname("foo", false); got != want {
+		t.Fatalf("unexpected result, want: %s, got: %s", want, got)
+	}
+}

internal/clientinfo/hostsfile.go

@@ -0,0 +1,190 @@
+package clientinfo
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"net/netip"
+	"os"
+	"strings"
+	"sync"
+
+	"github.com/fsnotify/fsnotify"
+	"github.com/jaytaylor/go-hostsfile"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+const (
+	ipv4LocalhostName   = "localhost"
+	ipv6LocalhostName   = "ip6-localhost"
+	ipv6LoopbackName    = "ip6-loopback"
+	hostEntriesConfPath = "/var/unbound/host_entries.conf"
+)
+
+// hostsFile provides client discovery functionality using system hosts file.
+type hostsFile struct {
+	watcher *fsnotify.Watcher
+	mu      sync.Mutex
+	m       map[string][]string
+}
+
+// init performs initialization works, which is necessary before hostsFile can be fully operated.
+func (hf *hostsFile) init() error {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return err
+	}
+	hf.watcher = watcher
+	if err := hf.watcher.Add(hostsfile.HostsPath); err != nil {
+		return err
+	}
+	// Conservatively adding hostEntriesConfPath, since it is not available everywhere.
+	_ = hf.watcher.Add(hostEntriesConfPath)
+	return hf.refresh()
+}
+
+// refresh reloads hosts file entries.
+func (hf *hostsFile) refresh() error {
+	m, err := hostsfile.ParseHosts(hostsfile.ReadHostsFile())
+	if err != nil {
+		return err
+	}
+	hf.mu.Lock()
+	hf.m = m
+	// override hosts file with host_entries.conf content if present.
+	hem, err := parseHostEntriesConf(hostEntriesConfPath)
+	if err != nil && !os.IsNotExist(err) {
+		ctrld.ProxyLogger.Load().Debug().Err(err).Msg("could not read host_entries.conf file")
+	}
+	for k, v := range hem {
+		hf.m[k] = v
+	}
+	hf.mu.Unlock()
+	return nil
+}
+
+// watchChanges watches and updates hosts file data if any changes happens.
+func (hf *hostsFile) watchChanges() {
+	if hf.watcher == nil {
+		return
+	}
+	for {
+		select {
+		case event, ok := <-hf.watcher.Events:
+			if !ok {
+				return
+			}
+			if event.Has(fsnotify.Write) || event.Has(fsnotify.Rename) || event.Has(fsnotify.Chmod) || event.Has(fsnotify.Remove) {
+				if err := hf.refresh(); err != nil && !os.IsNotExist(err) {
+					ctrld.ProxyLogger.Load().Err(err).Msg("hosts file changed but failed to update client info")
+				}
+			}
+		case err, ok := <-hf.watcher.Errors:
+			if !ok {
+				return
+			}
+			ctrld.ProxyLogger.Load().Err(err).Msg("could not watch client info file")
+		}
+	}
+
+}
+
+// LookupHostnameByIP returns hostname for given IP from current hosts file entries.
+func (hf *hostsFile) LookupHostnameByIP(ip string) string {
+	hf.mu.Lock()
+	defer hf.mu.Unlock()
+	if names := hf.m[ip]; len(names) > 0 {
+		isLoopback := ip == "127.0.0.1" || ip == "::1"
+		for _, hostname := range names {
+			name := normalizeHostname(hostname)
+			// Ignoring ipv4/ipv6 loopback entry.
+			if isLoopback && isLocalhostName(name) {
+				continue
+			}
+			return name
+		}
+	}
+	return ""
+}
+
+// LookupHostnameByMac returns hostname for given Mac from current hosts file entries.
+func (hf *hostsFile) LookupHostnameByMac(mac string) string {
+	return ""
+}
+
+// String returns human-readable format of hostsFile.
+func (hf *hostsFile) String() string {
+	return "hosts"
+}
+
+func (hf *hostsFile) lookupIPByHostname(name string, v6 bool) string {
+	if hf == nil {
+		return ""
+	}
+	hf.mu.Lock()
+	defer hf.mu.Unlock()
+	for addr, names := range hf.m {
+		if ip, err := netip.ParseAddr(addr); err == nil && !ip.IsLoopback() {
+			for _, n := range names {
+				if n == name && ip.Is6() == v6 {
+					return ip.String()
+				}
+			}
+		}
+	}
+	return ""
+}
+
+// isLocalhostName reports whether the given hostname represents localhost.
+func isLocalhostName(hostname string) bool {
+	switch hostname {
+	case ipv4LocalhostName, ipv6LocalhostName, ipv6LoopbackName:
+		return true
+	default:
+		return false
+	}
+}
+
+// parseHostEntriesConf parses host_entries.conf file and returns parsed result.
+func parseHostEntriesConf(path string) (map[string][]string, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	return parseHostEntriesConfFromReader(bytes.NewReader(b)), nil
+}
+
+// parseHostEntriesConfFromReader is like parseHostEntriesConf, but read from an io.Reader instead of file.
+func parseHostEntriesConfFromReader(r io.Reader) map[string][]string {
+	hostsMap := map[string][]string{}
+	scanner := bufio.NewScanner(r)
+
+	localZone := ""
+	for scanner.Scan() {
+		line := scanner.Text()
+		if after, found := strings.CutPrefix(line, "local-zone:"); found {
+			after = strings.TrimSpace(after)
+			fields := strings.Fields(after)
+			if len(fields) > 1 {
+				localZone = strings.Trim(fields[0], `"`)
+			}
+			continue
+		}
+		// Only read "local-data-ptr: ..." line, it has all necessary information.
+		after, found := strings.CutPrefix(line, "local-data-ptr:")
+		if !found {
+			continue
+		}
+		after = strings.TrimSpace(after)
+		after = strings.Trim(after, `"`)
+		fields := strings.Fields(after)
+		if len(fields) != 2 {
+			continue
+		}
+		ip := fields[0]
+		name := strings.TrimSuffix(fields[1], "."+localZone)
+		hostsMap[ip] = append(hostsMap[ip], name)
+	}
+	return hostsMap
+}

internal/clientinfo/hostsfile_test.go

@@ -0,0 +1,77 @@
+package clientinfo
+
+import (
+	"strings"
+	"testing"
+)
+
+func Test_hostsFile_LookupHostnameByIP(t *testing.T) {
+	tests := []struct {
+		name             string
+		ip               string
+		hostnames        []string
+		expectedHostname string
+	}{
+		{"ipv4 loopback", "127.0.0.1", []string{ipv4LocalhostName}, ""},
+		{"ipv6 loopback", "::1", []string{ipv6LocalhostName, ipv6LoopbackName}, ""},
+		{"non-localhost", "::1", []string{"foo"}, "foo"},
+		{"multiple hostnames", "::1", []string{ipv4LocalhostName, "foo"}, "foo"},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			hf := &hostsFile{m: make(map[string][]string)}
+			hf.mu.Lock()
+			hf.m[tc.ip] = tc.hostnames
+			hf.mu.Unlock()
+			if got := hf.LookupHostnameByIP(tc.ip); got != tc.expectedHostname {
+				t.Errorf("unpexpected result, want: %q, got: %q", tc.expectedHostname, got)
+			}
+		})
+	}
+}
+
+func Test_parseHostEntriesConfFromReader(t *testing.T) {
+	const content = `local-zone: "localdomain" transparent
+local-data-ptr: "127.0.0.1 localhost"
+local-data: "localhost A 127.0.0.1"
+local-data: "localhost.localdomain A 127.0.0.1"
+local-data-ptr: "::1 localhost"
+local-data: "localhost AAAA ::1"
+local-data: "localhost.localdomain AAAA ::1"
+local-data-ptr: "10.0.10.227 OPNsense.localdomain"
+local-data: "OPNsense.localdomain A 10.0.10.227"
+local-data: "OPNsense A 10.0.10.227"
+local-data-ptr: "fe80::5a78:4e29:caa3:f9f7 OPNsense.localdomain"
+local-data: "OPNsense.localdomain AAAA fe80::5a78:4e29:caa3:f9f7"
+local-data: "OPNsense AAAA fe80::5a78:4e29:caa3:f9f7"
+local-data-ptr: "1.1.1.1 banana-party.local.com"
+local-data: "banana-party.local.com IN A 1.1.1.1"
+local-data-ptr: "1.1.1.1 cheese-land.lan"
+local-data: "cheese-land.lan IN A 1.1.1.1"
+`
+	r := strings.NewReader(content)
+	hostsMap := parseHostEntriesConfFromReader(r)
+	if len(hostsMap) != 5 {
+		t.Fatalf("unexpected number of entries, want 5, got: %d", len(hostsMap))
+	}
+	for ip, names := range hostsMap {
+		switch ip {
+		case "1.1.1.1":
+			for _, name := range names {
+				if name != "banana-party.local.com" && name != "cheese-land.lan" {
+					t.Fatalf("unexpected names for 1.1.1.1: %v", names)
+				}
+			}
+		case "10.0.10.227":
+			if len(names) != 1 {
+				t.Fatalf("unexpected names for 10.0.10.227: %v", names)
+			}
+			if names[0] != "OPNsense" {
+				t.Fatalf("unexpected name: %s", names[0])
+			}
+		}
+	}
+}

internal/clientinfo/mdns.go

@@ -0,0 +1,282 @@
+package clientinfo
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"net"
+	"net/netip"
+	"os"
+	"os/exec"
+	"strings"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/miekg/dns"
+	"tailscale.com/logtail/backoff"
+
+	"github.com/Control-D-Inc/ctrld"
+	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
+)
+
+var (
+	mdnsV4Addr = &net.UDPAddr{
+		IP:   net.ParseIP("224.0.0.251"),
+		Port: 5353,
+	}
+	mdnsV6Addr = &net.UDPAddr{
+		IP:   net.ParseIP("ff02::fb"),
+		Port: 5353,
+	}
+)
+
+type mdns struct {
+	name sync.Map // ip => hostname
+}
+
+func (m *mdns) LookupHostnameByIP(ip string) string {
+	val, ok := m.name.Load(ip)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+func (m *mdns) LookupHostnameByMac(mac string) string {
+	return ""
+}
+
+func (m *mdns) String() string {
+	return "mdns"
+}
+
+func (m *mdns) List() []string {
+	if m == nil {
+		return nil
+	}
+	var ips []string
+	m.name.Range(func(key, value any) bool {
+		ips = append(ips, key.(string))
+		return true
+	})
+	return ips
+}
+
+func (m *mdns) lookupIPByHostname(name string, v6 bool) string {
+	if m == nil {
+		return ""
+	}
+	var ip string
+	m.name.Range(func(key, value any) bool {
+		if value == name {
+			if addr, err := netip.ParseAddr(key.(string)); err == nil && addr.Is6() == v6 {
+				ip = addr.String()
+				//lint:ignore S1008 This is used for readable.
+				if addr.IsLoopback() { // Continue searching if this is loopback address.
+					return true
+				}
+				return false
+			}
+		}
+		return true
+	})
+	return ip
+}
+
+func (m *mdns) init(quitCh chan struct{}) error {
+	ifaces, err := multicastInterfaces()
+	if err != nil {
+		return err
+	}
+
+	v4ConnList := make([]*net.UDPConn, 0, len(ifaces))
+	v6ConnList := make([]*net.UDPConn, 0, len(ifaces))
+	for _, iface := range ifaces {
+		if iface.Flags&net.FlagLoopback != 0 {
+			continue
+		}
+		if conn, err := net.ListenMulticastUDP("udp4", &iface, mdnsV4Addr); err == nil {
+			v4ConnList = append(v4ConnList, conn)
+			go m.readLoop(conn)
+		}
+		if ctrldnet.IPv6Available(context.Background()) {
+			if conn, err := net.ListenMulticastUDP("udp6", &iface, mdnsV6Addr); err == nil {
+				v6ConnList = append(v6ConnList, conn)
+				go m.readLoop(conn)
+			}
+		}
+	}
+
+	go m.probeLoop(v4ConnList, mdnsV4Addr, quitCh)
+	go m.probeLoop(v6ConnList, mdnsV6Addr, quitCh)
+	go m.getDataFromAvahiDaemonCache()
+
+	return nil
+}
+
+// probeLoop performs mdns probe actively to get hostname updates.
+func (m *mdns) probeLoop(conns []*net.UDPConn, remoteAddr net.Addr, quitCh chan struct{}) {
+	bo := backoff.NewBackoff("mdns probe", func(format string, args ...any) {}, time.Second*30)
+	for {
+		err := m.probe(conns, remoteAddr)
+		if isErrNetUnreachableOrInvalid(err) {
+			ctrld.ProxyLogger.Load().Warn().Msgf("stop probing %q: network unreachable or invalid", remoteAddr)
+			break
+		}
+		if err != nil {
+			ctrld.ProxyLogger.Load().Warn().Err(err).Msg("error while probing mdns")
+			bo.BackOff(context.Background(), errors.New("mdns probe backoff"))
+			continue
+		}
+		break
+	}
+	<-quitCh
+	for _, conn := range conns {
+		_ = conn.Close()
+	}
+}
+
+// readLoop reads from mdns connection, save/update any hostnames found.
+func (m *mdns) readLoop(conn *net.UDPConn) {
+	defer conn.Close()
+	buf := make([]byte, dns.MaxMsgSize)
+
+	for {
+		_ = conn.SetReadDeadline(time.Now().Add(time.Second * 30))
+		n, _, err := conn.ReadFromUDP(buf)
+		if err != nil {
+			if err, ok := err.(*net.OpError); ok && (err.Timeout() || err.Temporary()) {
+				continue
+			}
+			// Do not complain about use of closed network connection.
+			if errors.Is(err, net.ErrClosed) {
+				return
+			}
+			ctrld.ProxyLogger.Load().Debug().Err(err).Msg("mdns readLoop error")
+			return
+		}
+
+		var msg dns.Msg
+		if err := msg.Unpack(buf[:n]); err != nil {
+			continue
+		}
+
+		var ip, name string
+		rrs := make([]dns.RR, 0, len(msg.Answer)+len(msg.Extra))
+		rrs = append(rrs, msg.Answer...)
+		rrs = append(rrs, msg.Extra...)
+		for _, rr := range rrs {
+			switch ar := rr.(type) {
+			case *dns.A:
+				ip, name = ar.A.String(), ar.Hdr.Name
+			case *dns.AAAA:
+				ip, name = ar.AAAA.String(), ar.Hdr.Name
+			}
+			if ip != "" && name != "" {
+				name = normalizeHostname(name)
+				if val, loaded := m.name.LoadOrStore(ip, name); !loaded {
+					ctrld.ProxyLogger.Load().Debug().Msgf("found hostname: %q, ip: %q via mdns", name, ip)
+				} else {
+					old := val.(string)
+					if old != name {
+						ctrld.ProxyLogger.Load().Debug().Msgf("update hostname: %q, ip: %q, old: %q via mdns", name, ip, old)
+						m.name.Store(ip, name)
+					}
+				}
+				ip, name = "", ""
+			}
+		}
+	}
+}
+
+// probe performs mdns queries with known services.
+func (m *mdns) probe(conns []*net.UDPConn, remoteAddr net.Addr) error {
+	msg := new(dns.Msg)
+	msg.Question = make([]dns.Question, len(services))
+	msg.Compress = true
+	for i, service := range services {
+		msg.Question[i] = dns.Question{
+			Name:   dns.CanonicalName(service),
+			Qtype:  dns.TypePTR,
+			Qclass: dns.ClassINET,
+		}
+	}
+
+	buf, err := msg.Pack()
+	if err != nil {
+		return err
+	}
+	for _, conn := range conns {
+		_ = conn.SetWriteDeadline(time.Now().Add(time.Second * 30))
+		if _, werr := conn.WriteTo(buf, remoteAddr); werr != nil {
+			err = werr
+		}
+	}
+	return err
+}
+
+// getDataFromAvahiDaemonCache reads entries from avahi-daemon cache to update mdns data.
+func (m *mdns) getDataFromAvahiDaemonCache() {
+	if _, err := exec.LookPath("avahi-browse"); err != nil {
+		ctrld.ProxyLogger.Load().Debug().Err(err).Msg("could not find avahi-browse binary, skipping.")
+		return
+	}
+	// Run avahi-browse to discover services from cache:
+	//  - "-a" -> all services.
+	//  - "-r" -> resolve found services.
+	//  - "-p" -> parseable format.
+	//  - "-c" -> read from cache.
+	out, err := exec.Command("avahi-browse", "-a", "-r", "-p", "-c").Output()
+	if err != nil {
+		ctrld.ProxyLogger.Load().Debug().Err(err).Msg("could not browse services from avahi cache")
+		return
+	}
+	m.storeDataFromAvahiBrowseOutput(bytes.NewReader(out))
+}
+
+// storeDataFromAvahiBrowseOutput parses avahi-browse output from reader, then updating found data to mdns table.
+func (m *mdns) storeDataFromAvahiBrowseOutput(r io.Reader) {
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		fields := strings.FieldsFunc(scanner.Text(), func(r rune) bool {
+			return r == ';'
+		})
+		if len(fields) < 8 || fields[0] != "=" {
+			continue
+		}
+		ip := fields[7]
+		name := normalizeHostname(fields[6])
+		// Only using cache value if we don't have existed one.
+		if _, loaded := m.name.LoadOrStore(ip, name); !loaded {
+			ctrld.ProxyLogger.Load().Debug().Msgf("found hostname: %q, ip: %q via avahi cache", name, ip)
+		}
+	}
+}
+
+func multicastInterfaces() ([]net.Interface, error) {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return nil, err
+	}
+	interfaces := make([]net.Interface, 0, len(ifaces))
+	for _, ifi := range ifaces {
+		if (ifi.Flags & net.FlagUp) == 0 {
+			continue
+		}
+		if (ifi.Flags & net.FlagMulticast) > 0 {
+			interfaces = append(interfaces, ifi)
+		}
+	}
+	return interfaces, nil
+}
+
+func isErrNetUnreachableOrInvalid(err error) bool {
+	var se *os.SyscallError
+	if errors.As(err, &se) {
+		return se.Err == syscall.ENETUNREACH || se.Err == syscall.EINVAL
+	}
+	return false
+}

internal/clientinfo/mdns_services.go

@@ -0,0 +1,70 @@
+package clientinfo
+
+var services = [...]string{
+	// From: https://jonathanmumm.com/tech-it/mdns-bonjour-bible-common-service-strings-for-various-vendors/
+	"_afpovertcp._tcp.local.",
+	"_airdroid._tcp.local.",
+	"_airdrop._tcp.local.",
+	"_airplay._tcp.local.",
+	"_airport._tcp.local.",
+	"_amzn-wplay._tcp.local.",
+	"_sub._apple-mobdev2._tcp.local.",
+	"_apple-mobdev2._tcp.local.",
+	"_apple-sasl._tcp.local.",
+	"_atc._tcp.local.",
+	"_sketchmirror._tcp.local.",
+	"_bp2p._tcp.local.",
+	"_Friendly._sub._bp2p._tcp.local.",
+	"_invoke._sub._bp2p._tcp.local.",
+	"_webdav._sub._bp2p._tcp.local.",
+	"_device-info._tcp.local.",
+	"_distcc._tcp.local.",
+	"_dpap._tcp.local.",
+	"_eppc._tcp.local.",
+	"_esdevice._tcp.local.",
+	"_esfileshare._tcp.local.",
+	"_ftp._tcp.local.",
+	"_googlecast._tcp.local.",
+	"_googlezone._tcp.local.",
+	"_hap._tcp.local.",
+	"_homekit._tcp.local.",
+	"_home-sharing._tcp.local.",
+	"_http._tcp.local.",
+	"_hudson._tcp.local.",
+	"_ica-networking._tcp.local.",
+	"_print._sub._ipp._tcp.local.",
+	"_cups._sub._ipps._tcp.local.",
+	"_print._sub._ipps._tcp.local.",
+	"_jenkins._tcp.local.",
+	"_KeynoteControl._tcp.local.",
+	"_keynotepair._tcp.local.",
+	"_mediaremotetv._tcp.local.",
+	"_nfs._tcp.local.",
+	"_nvstream._tcp.local.",
+	"_androidtvremote._tcp.local.",
+	"_omnistate._tcp.local.",
+	"_photoshopserver._tcp.local.",
+	"_printer._tcp.local.",
+	"_raop._tcp.local.",
+	"_readynas._tcp.local.",
+	"_rfb._tcp.local.",
+	"_physicalweb._tcp.local.",
+	"_rsp._tcp.local.",
+	"_scanner._tcp.local.",
+	"_sftp-ssh._tcp.local.",
+	"_sleep-proxy._udp.local.",
+	"_smb._tcp.local.",
+	"_spotify-connect._tcp.local.",
+	"_ssh._tcp.local.",
+	"_teamviewer._tcp.local.",
+	"_telnet._tcp.local.",
+	"_touch-able._tcp.local.",
+	"_tunnel._tcp.local.",
+	"_webdav._tcp.local.",
+	"_webdav._tcp.local.",
+	"_workstation._tcp.local.",
+	"_xserveraid._tcp.local.",
+
+	// Merlin
+	"_alexa._tcp",
+}

internal/clientinfo/mdns_test.go

@@ -0,0 +1,27 @@
+package clientinfo
+
+import (
+	"strings"
+	"testing"
+)
+
+func Test_mdns_storeDataFromAvahiBrowseOutput(t *testing.T) {
+	const content = `+;wlp0s20f3;IPv6;Foo\032\0402\041;_companion-link._tcp;local
++;wlp0s20f3;IPv4;Foo\032\0402\041;_companion-link._tcp;local
+=;wlp0s20f3;IPv6;Foo\032\0402\041;_companion-link._tcp;local;Foo-2.local;192.168.1.123;64842;"rpBA=00:00:00:00:00:01" "rpHI=e6ae2cbbca0e" "rpAD=36566f4d850f" "rpVr=510.71.1" "rpHA=0ddc20fdddc8" "rpFl=0x30000" "rpHN=1d4a03afdefa" "rpMac=0"
+=;wlp0s20f3;IPv4;Foo\032\0402\041;_companion-link._tcp;local;Foo-2.local;192.168.1.123;64842;"rpBA=00:00:00:00:00:01" "rpHI=e6ae2cbbca0e" "rpAD=36566f4d850f" "rpVr=510.71.1" "rpHA=0ddc20fdddc8" "rpFl=0x30000" "rpHN=1d4a03afdefa" "rpMac=0"
+`
+	m := &mdns{}
+	m.storeDataFromAvahiBrowseOutput(strings.NewReader(content))
+	ip := "192.168.1.123"
+	val, loaded := m.name.LoadOrStore(ip, "")
+	if !loaded {
+		t.Fatal("missing Foo-2 data from mdns table")
+	}
+
+	wantHostname := "Foo-2"
+	hostname := val.(string)
+	if hostname != wantHostname {
+		t.Fatalf("unexpected hostname, want: %q, got: %q", wantHostname, hostname)
+	}
+}

internal/clientinfo/merlin.go

@@ -0,0 +1,71 @@
+package clientinfo
+
+import (
+	"strings"
+	"sync"
+
+	"github.com/Control-D-Inc/ctrld/internal/router"
+	"github.com/Control-D-Inc/ctrld/internal/router/merlin"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/Control-D-Inc/ctrld/internal/router/nvram"
+)
+
+const merlinNvramCustomClientListKey = "custom_clientlist"
+
+type merlinDiscover struct {
+	hostname sync.Map // mac => hostname
+}
+
+func (m *merlinDiscover) refresh() error {
+	if router.Name() != merlin.Name {
+		return nil
+	}
+	out, err := nvram.Run("get", merlinNvramCustomClientListKey)
+	if err != nil {
+		return err
+	}
+	ctrld.ProxyLogger.Load().Debug().Msg("reading Merlin custom client list")
+	m.parseMerlinCustomClientList(out)
+	return nil
+}
+
+func (m *merlinDiscover) LookupHostnameByIP(ip string) string {
+	return ""
+}
+
+func (m *merlinDiscover) LookupHostnameByMac(mac string) string {
+	val, ok := m.hostname.Load(mac)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+// "nvram get custom_clientlist" output:
+//
+// <client 1>00:00:00:00:00:01>0>4>><client 2>00:00:00:00:00:02>0>24>>...
+//
+// So to parse it, do the following steps:
+//
+//   - Split by "<"                 => entries
+//   - For each entry, split by ">" => parts
+//   - Empty parts                  => skip
+//   - Empty parts[0]               => skip empty hostname
+//   - Empty parts[1]               => skip empty MAC
+func (m *merlinDiscover) parseMerlinCustomClientList(data string) {
+	entries := strings.Split(data, "<")
+	for _, entry := range entries {
+		parts := strings.SplitN(string(entry), ">", 3)
+		if len(parts) < 2 || len(parts[0]) == 0 || len(parts[1]) == 0 {
+			continue
+		}
+		hostname := normalizeHostname(parts[0])
+		mac := strings.ToLower(parts[1])
+		m.hostname.Store(mac, hostname)
+	}
+}
+
+func (m *merlinDiscover) String() string {
+	return "merlin"
+}

internal/clientinfo/merlin_test.go

@@ -0,0 +1,82 @@
+package clientinfo
+
+import (
+	"testing"
+)
+
+func TestParseMerlinCustomClientList(t *testing.T) {
+	tests := []struct {
+		name              string
+		clientList        string
+		macList           []string
+		hostnameList      []string
+		macNotPresentList []string
+	}{
+		{
+			"normal",
+			"<client1>00:00:00:00:00:01>0>4>>",
+			[]string{"00:00:00:00:00:01"},
+			[]string{"client1"},
+			nil,
+		},
+		{
+			"multiple clients",
+			"<client1>00:00:00:00:00:01>0>4>><client2>00:00:00:00:00:02>0>24>>",
+			[]string{"00:00:00:00:00:01", "00:00:00:00:00:02"},
+			[]string{"client1", "client2"},
+			nil,
+		},
+		{
+			"empty hostname",
+			"<client1>00:00:00:00:00:01>0>4>><>00:00:00:00:00:02>0>24>>",
+			[]string{"00:00:00:00:00:01"},
+			[]string{"client1"},
+			[]string{"00:00:00:00:00:02"},
+		},
+		{
+			"empty dhcp",
+			"<client1>00:00:00:00:00:01>0>4>><client 1>>>",
+			[]string{"00:00:00:00:00:01"},
+			[]string{"client1"},
+			[]string{""},
+		},
+		{
+			"invalid",
+			"qwerty",
+			nil,
+			nil,
+			nil,
+		},
+		{
+			"empty",
+			"",
+
+			nil,
+			nil,
+			nil,
+		},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			m := &merlinDiscover{}
+			m.parseMerlinCustomClientList(tc.clientList)
+			for i, mac := range tc.macList {
+				val, ok := m.hostname.Load(mac)
+				if !ok {
+					t.Errorf("missing hostname: %s", mac)
+				}
+				hostname := val.(string)
+				if hostname != tc.hostnameList[i] {
+					t.Errorf("hostname mismatch, want: %q, got: %q", tc.hostnameList[i], hostname)
+				}
+			}
+			for _, mac := range tc.macNotPresentList {
+				if _, ok := m.hostname.Load(mac); ok {
+					t.Errorf("mac2name address %q should not be present", mac)
+				}
+			}
+		})
+	}
+}

internal/clientinfo/ndp.go

@@ -0,0 +1,219 @@
+package clientinfo
+
+import (
+	"bufio"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/netip"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/mdlayher/ndp"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+// ndpDiscover provides client discovery functionality using NDP protocol.
+type ndpDiscover struct {
+	mac sync.Map // ip  => mac
+	ip  sync.Map // mac => ip
+}
+
+// refresh re-scans the NDP table.
+func (nd *ndpDiscover) refresh() error {
+	nd.scan()
+	return nil
+}
+
+// LookupIP returns the ipv6 associated with the input MAC address.
+func (nd *ndpDiscover) LookupIP(mac string) string {
+	val, ok := nd.ip.Load(mac)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+// LookupMac returns the MAC address of the given IP address.
+func (nd *ndpDiscover) LookupMac(ip string) string {
+	val, ok := nd.mac.Load(ip)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+// String returns human-readable format of ndpDiscover.
+func (nd *ndpDiscover) String() string {
+	return "ndp"
+}
+
+// List returns all known IP addresses.
+func (nd *ndpDiscover) List() []string {
+	if nd == nil {
+		return nil
+	}
+	var ips []string
+	nd.ip.Range(func(key, value any) bool {
+		ips = append(ips, value.(string))
+		return true
+	})
+	nd.mac.Range(func(key, value any) bool {
+		ips = append(ips, key.(string))
+		return true
+	})
+	return ips
+}
+
+// listen listens on ipv6 link local for Neighbor Solicitation message
+// to update new neighbors information to ndp table.
+func (nd *ndpDiscover) listen(ctx context.Context) {
+	ifi, err := firstInterfaceWithV6LinkLocal()
+	if err != nil {
+		ctrld.ProxyLogger.Load().Debug().Err(err).Msg("failed to find valid ipv6")
+		return
+	}
+	c, ip, err := ndp.Listen(ifi, ndp.LinkLocal)
+	if err != nil {
+		ctrld.ProxyLogger.Load().Debug().Err(err).Msg("ndp listen failed")
+		return
+	}
+	defer c.Close()
+	ctrld.ProxyLogger.Load().Debug().Msgf("listening ndp on: %s", ip.String())
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+		_ = c.SetReadDeadline(time.Now().Add(30 * time.Second))
+		msg, _, from, readErr := c.ReadFrom()
+		if readErr != nil {
+			var opErr *net.OpError
+			if errors.As(readErr, &opErr) && (opErr.Timeout() || opErr.Temporary()) {
+				continue
+			}
+			ctrld.ProxyLogger.Load().Debug().Err(readErr).Msg("ndp read loop error")
+			return
+		}
+
+		// Only looks for neighbor solicitation message, since new clients
+		// which join network will broadcast this message to us.
+		am, ok := msg.(*ndp.NeighborSolicitation)
+		if !ok {
+			continue
+		}
+		fromIP := from.String()
+		for _, opt := range am.Options {
+			if lla, ok := opt.(*ndp.LinkLayerAddress); ok {
+				mac := lla.Addr.String()
+				nd.mac.Store(fromIP, mac)
+				nd.ip.Store(mac, fromIP)
+			}
+		}
+	}
+}
+
+// scanWindows populates NDP table using information from "netsh" command.
+func (nd *ndpDiscover) scanWindows(r io.Reader) {
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) < 3 {
+			continue
+		}
+		if mac := parseMAC(fields[1]); mac != "" {
+			nd.mac.Store(fields[0], mac)
+			nd.ip.Store(mac, fields[0])
+		}
+	}
+}
+
+// scanUnix populates NDP table using information from "ndp" command.
+func (nd *ndpDiscover) scanUnix(r io.Reader) {
+	scanner := bufio.NewScanner(r)
+	scanner.Scan() // skip header
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) < 2 {
+			continue
+		}
+		if mac := parseMAC(fields[1]); mac != "" {
+			ip := fields[0]
+			if idx := strings.IndexByte(ip, '%'); idx != -1 {
+				ip = ip[:idx]
+			}
+			nd.mac.Store(ip, mac)
+			nd.ip.Store(mac, ip)
+		}
+	}
+}
+
+// normalizeMac ensure the given MAC address have the proper format
+// before being parsed.
+//
+// Example, changing "00:0:00:0:00:01" to "00:00:00:00:00:01", which
+// can be seen on Darwin.
+func normalizeMac(mac string) string {
+	if len(mac) == 17 {
+		return mac
+	}
+	// Windows use "-" instead of ":" as separator.
+	mac = strings.ReplaceAll(mac, "-", ":")
+	parts := strings.Split(mac, ":")
+	if len(parts) != 6 {
+		return ""
+	}
+	for i, c := range parts {
+		if len(c) == 1 {
+			parts[i] = "0" + c
+		}
+	}
+	return strings.Join(parts, ":")
+}
+
+// parseMAC parses the input MAC, doing normalization,
+// and return the result after calling net.ParseMac function.
+func parseMAC(mac string) string {
+	hw, _ := net.ParseMAC(normalizeMac(mac))
+	return hw.String()
+}
+
+// firstInterfaceWithV6LinkLocal returns the first interface which is capable of using NDP.
+func firstInterfaceWithV6LinkLocal() (*net.Interface, error) {
+	ifis, err := net.Interfaces()
+	if err != nil {
+		return nil, err
+	}
+
+	for _, ifi := range ifis {
+		// Skip if iface is down/loopback/non-multicast.
+		if ifi.Flags&net.FlagUp == 0 || ifi.Flags&net.FlagLoopback != 0 || ifi.Flags&net.FlagMulticast == 0 {
+			continue
+		}
+
+		addrs, err := ifi.Addrs()
+		if err != nil {
+			return nil, err
+		}
+
+		for _, addr := range addrs {
+			ipNet, ok := addr.(*net.IPNet)
+			if !ok {
+				continue
+			}
+			ip, ok := netip.AddrFromSlice(ipNet.IP)
+			if !ok {
+				return nil, fmt.Errorf("invalid ip address: %s", ipNet.String())
+			}
+			if ip.Is6() && !ip.Is4In6() {
+				return &ifi, nil
+			}
+		}
+	}
+	return nil, errors.New("no interface can be used")
+}

internal/clientinfo/ndp_linux.go

@@ -0,0 +1,24 @@
+package clientinfo
+
+import (
+	"github.com/vishvananda/netlink"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+// scan populates NDP table using information from system mappings.
+func (nd *ndpDiscover) scan() {
+	neighs, err := netlink.NeighList(0, netlink.FAMILY_V6)
+	if err != nil {
+		ctrld.ProxyLogger.Load().Warn().Err(err).Msg("could not get neigh list")
+		return
+	}
+
+	for _, n := range neighs {
+		ip := n.IP.String()
+		mac := n.HardwareAddr.String()
+		nd.mac.Store(ip, mac)
+		nd.ip.Store(mac, ip)
+	}
+
+}

internal/clientinfo/ndp_others.go

@@ -0,0 +1,31 @@
+//go:build !linux
+
+package clientinfo
+
+import (
+	"bytes"
+	"os/exec"
+	"runtime"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+// scan populates NDP table using information from system mappings.
+func (nd *ndpDiscover) scan() {
+	switch runtime.GOOS {
+	case "windows":
+		data, err := exec.Command("netsh", "interface", "ipv6", "show", "neighbors").Output()
+		if err != nil {
+			ctrld.ProxyLogger.Load().Warn().Err(err).Msg("could not query ndp table")
+			return
+		}
+		nd.scanWindows(bytes.NewReader(data))
+	default:
+		data, err := exec.Command("ndp", "-an").Output()
+		if err != nil {
+			ctrld.ProxyLogger.Load().Warn().Err(err).Msg("could not query ndp table")
+			return
+		}
+		nd.scanUnix(bytes.NewReader(data))
+	}
+}

internal/clientinfo/ndp_test.go

@@ -0,0 +1,64 @@
+package clientinfo
+
+import (
+	"strings"
+	"sync"
+	"testing"
+)
+
+func Test_ndpDiscover_scanUnix(t *testing.T) {
+	r := strings.NewReader(`Neighbor                                Linklayer Address  Netif Expire    St Flgs Prbs
+2405:4802:1f90:fda0:1459:ec89:523d:3583 00:0:00:0:00:01      en0 permanent R
+2405:4802:1f90:fda0:186b:c54a:1370:c196 (incomplete)         en0 expired   N
+2405:4802:1f90:fda0:88de:14ef:6a8c:579a 00:0:00:0:00:02      en0 permanent R
+fe80::1%lo0                             (incomplete)         lo0 permanent R
+`)
+	nd := &ndpDiscover{}
+	nd.scanUnix(r)
+
+	for _, m := range []*sync.Map{&nd.mac, &nd.ip} {
+		count := 0
+		m.Range(func(key, value any) bool {
+			count++
+			return true
+		})
+		if count != 2 {
+			t.Errorf("unexpected count, want 2, got: %d", count)
+		}
+	}
+}
+
+func Test_ndpDiscover_scanWindows(t *testing.T) {
+	r := strings.NewReader(`Interface 14: Wi-Fi
+
+
+Internet Address                              Physical Address   Type
+--------------------------------------------  -----------------  -----------
+2405:4802:1f90:fda0:ffff:ffff:ffff:ff88       00-00-00-00-00-00  Unreachable
+fe80::1                                       60-57-47-21-dd-00  Reachable (Router)
+fe80::6257:47ff:fe21:dd00                     60-57-47-21-dd-00  Reachable (Router)
+ff02::1                                       33-33-00-00-00-01  Permanent
+ff02::2                                       33-33-00-00-00-02  Permanent
+ff02::c                                       33-33-00-00-00-0c  Permanent
+`)
+	nd := &ndpDiscover{}
+	nd.scanWindows(r)
+
+	count := 0
+	nd.mac.Range(func(key, value any) bool {
+		count++
+		return true
+	})
+	if count != 6 {
+		t.Errorf("unexpected count, want 6, got: %d", count)
+	}
+
+	count = 0
+	nd.ip.Range(func(key, value any) bool {
+		count++
+		return true
+	})
+	if count != 5 {
+		t.Errorf("unexpected count, want 5, got: %d", count)
+	}
+}

internal/clientinfo/ptr_lookup.go

@@ -0,0 +1,139 @@
+package clientinfo
+
+import (
+	"context"
+	"net/netip"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/miekg/dns"
+	"tailscale.com/logtail/backoff"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+type ptrDiscover struct {
+	hostname   sync.Map // ip => hostname
+	resolver   ctrld.Resolver
+	serverDown atomic.Bool
+}
+
+func (p *ptrDiscover) refresh() error {
+	p.hostname.Range(func(key, value any) bool {
+		ip := key.(string)
+		if name := p.lookupHostname(ip); name != "" {
+			p.hostname.Store(ip, name)
+		}
+		return true
+	})
+	return nil
+}
+
+func (p *ptrDiscover) LookupHostnameByIP(ip string) string {
+	if val, ok := p.hostname.Load(ip); ok {
+		return val.(string)
+	}
+	return p.lookupHostname(ip)
+}
+func (p *ptrDiscover) LookupHostnameByMac(mac string) string {
+	return ""
+}
+
+func (p *ptrDiscover) String() string {
+	return "ptr"
+}
+
+func (p *ptrDiscover) List() []string {
+	if p == nil {
+		return nil
+	}
+	var ips []string
+	p.hostname.Range(func(key, value any) bool {
+		ips = append(ips, key.(string))
+		return true
+	})
+	return ips
+}
+
+func (p *ptrDiscover) lookupHostnameFromCache(ip string) string {
+	if val, ok := p.hostname.Load(ip); ok {
+		return val.(string)
+	}
+	return ""
+}
+
+func (p *ptrDiscover) lookupHostname(ip string) string {
+	// If nameserver is down, do nothing.
+	if p.serverDown.Load() {
+		return ""
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	msg := new(dns.Msg)
+	addr, err := dns.ReverseAddr(ip)
+	if err != nil {
+		ctrld.ProxyLogger.Load().Info().Str("discovery", "ptr").Err(err).Msg("invalid ip address")
+		return ""
+	}
+	msg.SetQuestion(addr, dns.TypePTR)
+	ans, err := p.resolver.Resolve(ctx, msg)
+	if err != nil {
+		if p.serverDown.CompareAndSwap(false, true) {
+			ctrld.ProxyLogger.Load().Info().Str("discovery", "ptr").Err(err).Msg("could not perform PTR lookup")
+			go p.checkServer()
+		}
+		return ""
+	}
+	for _, rr := range ans.Answer {
+		if ptr, ok := rr.(*dns.PTR); ok {
+			hostname := normalizeHostname(ptr.Ptr)
+			p.hostname.Store(ip, hostname)
+			return hostname
+		}
+	}
+	return ""
+}
+
+func (p *ptrDiscover) lookupIPByHostname(name string, v6 bool) string {
+	if p == nil {
+		return ""
+	}
+	var ip string
+	p.hostname.Range(func(key, value any) bool {
+		if value == name {
+			if addr, err := netip.ParseAddr(key.(string)); err == nil && addr.Is6() == v6 {
+				ip = addr.String()
+				//lint:ignore S1008 This is used for readable.
+				if addr.IsLoopback() { // Continue searching if this is loopback address.
+					return true
+				}
+				return false
+			}
+		}
+		return true
+	})
+	return ip
+}
+
+// checkServer monitors if the resolver can reach its nameserver. When the nameserver
+// is reachable, set p.serverDown to false, so p.lookupHostname can continue working.
+func (p *ptrDiscover) checkServer() {
+	bo := backoff.NewBackoff("ptrDiscover", func(format string, args ...any) {}, time.Minute*5)
+	m := new(dns.Msg)
+	m.SetQuestion(".", dns.TypeNS)
+	ping := func() error {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		defer cancel()
+		_, err := p.resolver.Resolve(ctx, m)
+		return err
+	}
+	for {
+		if err := ping(); err != nil {
+			bo.BackOff(context.Background(), err)
+			continue
+		}
+		break
+	}
+	p.serverDown.Store(false)
+}

internal/clientinfo/ubios.go

@@ -0,0 +1,78 @@
+package clientinfo
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"os/exec"
+	"strings"
+	"sync"
+
+	"github.com/Control-D-Inc/ctrld/internal/router"
+	"github.com/Control-D-Inc/ctrld/internal/router/ubios"
+)
+
+// ubiosDiscover provides client discovery functionality on Ubios routers.
+type ubiosDiscover struct {
+	hostname sync.Map // mac => hostname
+}
+
+// refresh reloads unifi devices from database.
+func (u *ubiosDiscover) refresh() error {
+	if router.Name() != ubios.Name {
+		return nil
+	}
+	return u.refreshDevices()
+}
+
+// LookupHostnameByIP returns hostname for given IP.
+func (u *ubiosDiscover) LookupHostnameByIP(ip string) string {
+	return ""
+}
+
+// LookupHostnameByMac returns unifi device custom hostname for the given MAC address.
+func (u *ubiosDiscover) LookupHostnameByMac(mac string) string {
+	val, ok := u.hostname.Load(mac)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+// refreshDevices updates unifi devices name from local mongodb.
+func (u *ubiosDiscover) refreshDevices() error {
+	cmd := exec.Command("/usr/bin/mongo", "localhost:27117/ace", "--quiet", "--eval", `
+		DBQuery.shellBatchSize = 256;
+		db.user.find({name: {$exists: true, $ne: ""}}, {_id:0, mac:1, name:1});`)
+	b, err := cmd.Output()
+	if err != nil {
+		return err
+	}
+	return u.storeDevices(bytes.NewReader(b))
+}
+
+// storeDevices saves unifi devices name for caching.
+func (u *ubiosDiscover) storeDevices(r io.Reader) error {
+	decoder := json.NewDecoder(r)
+	device := struct {
+		MAC  string
+		Name string
+	}{}
+	for {
+		err := decoder.Decode(&device)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return err
+		}
+		mac := strings.ToLower(device.MAC)
+		u.hostname.Store(mac, normalizeHostname(device.Name))
+	}
+	return nil
+}
+
+// String returns human-readable format of ubiosDiscover.
+func (u *ubiosDiscover) String() string {
+	return "ubios"
+}

internal/clientinfo/ubios_test.go

@@ -0,0 +1,43 @@
+package clientinfo
+
+import (
+	"strings"
+	"testing"
+)
+
+func Test_ubiosDiscover_storeDevices(t *testing.T) {
+	ud := &ubiosDiscover{}
+	r := strings.NewReader(`{ "mac": "00:00:00:00:00:01", "name": "device 1" }
+{ "mac": "00:00:00:00:00:02", "name": "device 2" }
+`)
+	if err := ud.storeDevices(r); err != nil {
+		t.Fatal(err)
+	}
+
+	tests := []struct {
+		name     string
+		mac      string
+		hostname string
+	}{
+		{"device 1", "00:00:00:00:00:01", "device 1"},
+		{"device 2", "00:00:00:00:00:02", "device 2"},
+		{"non-existed", "00:00:00:00:00:03", ""},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := ud.LookupHostnameByMac(tc.mac); got != tc.hostname {
+				t.Errorf("hostname mismatched, want: %q, got: %q", tc.hostname, got)
+			}
+		})
+	}
+
+	// Test for invalid input.
+	r = strings.NewReader(`{ "mac": "00:00:00:00:00:01", "name": "device 1"`)
+	if err := ud.storeDevices(r); err == nil {
+		t.Fatal("expected error, got nil")
+	} else {
+		t.Log(err)
+	}
+}

internal/clientinfo/virtual_iface.go

@@ -0,0 +1,43 @@
+package clientinfo
+
+import (
+	"sync"
+)
+
+// virtualNetworkIface is the manager for clients from virtual network interface.
+type virtualNetworkIface struct {
+	ip2name sync.Map // ip  => name
+	mac     sync.Map // ip  => mac
+}
+
+// LookupHostnameByIP returns hostname of the given VPN client ip.
+func (v *virtualNetworkIface) LookupHostnameByIP(ip string) string {
+	val, ok := v.ip2name.Load(ip)
+	if !ok {
+		return ""
+	}
+	return val.(string)
+}
+
+// LookupHostnameByMac always returns empty string.
+func (v *virtualNetworkIface) LookupHostnameByMac(mac string) string {
+	return ""
+}
+
+// String returns the string representation of virtualNetworkIface struct.
+func (v *virtualNetworkIface) String() string {
+	return ""
+}
+
+// List lists all known VPN clients IP.
+func (v *virtualNetworkIface) List() []string {
+	if v == nil {
+		return nil
+	}
+	var ips []string
+	v.mac.Range(func(key, value any) bool {
+		ips = append(ips, key.(string))
+		return true
+	})
+	return ips
+}