all: add router client info detection

This commit add the ability for ctrld to gather client information,
including mac/ip/hostname, and send to Control-D server through a
config per upstream.

 - Add send_client_info upstream config.
 - Read/Watch dnsmasq leases files on supported platforms.
 - Add corresponding client info to DoH query header

All of these only apply for Control-D upstream, though.

client_info.go

@@ -0,0 +1,11 @@
+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
+}

cmd/ctrld/dns_proxy.go

@@ -20,7 +20,13 @@ import (
 	"github.com/Control-D-Inc/ctrld/internal/router"
 )
 
-const staleTTL = 60 * time.Second
+const (
+	staleTTL = 60 * 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",
@@ -230,6 +236,12 @@ func (p *prog) proxy(ctx context.Context, upstreams []string, failoverRcodes []i
 		return dnsResolver.Resolve(resolveCtx, msg)
 	}
 	resolve := func(n int, upstreamConfig *ctrld.UpstreamConfig, msg *dns.Msg) *dns.Msg {
+		if upstreamConfig.UpstreamSendClientInfo() {
+			ci := router.GetClientInfoByMac(macFromMsg(msg))
+			if ci != nil {
+				ctx = context.WithValue(ctx, ctrld.ClientInfoCtxKey{}, ci)
+			}
+		}
 		answer, err := resolve1(n, upstreamConfig, msg)
 		if err != nil {
 			ctrld.Log(ctx, mainLog.Debug().Err(err), "could not resolve query on first attempt, retrying...")
@@ -386,3 +398,17 @@ func dnsListenAddress(lc *ctrld.ListenerConfig) string {
 	}
 	return net.JoinHostPort(lc.IP, strconv.Itoa(lc.Port))
 }
+
+func macFromMsg(msg *dns.Msg) string {
+	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 {
+					return net.HardwareAddr(e.Data).String()
+				}
+			}
+		}
+	}
+	return ""
+}

cmd/ctrld/dns_proxy_test.go

@@ -155,3 +155,39 @@ func TestCache(t *testing.T) {
 	assert.Equal(t, answer1.Rcode, got1.Rcode)
 	assert.Equal(t, answer2.Rcode, got2.Rcode)
 }
+
+func Test_macFromMsg(t *testing.T) {
+	tests := []struct {
+		name    string
+		mac     string
+		wantMac bool
+	}{
+		{"has mac", "4c:20:b8:ab:87:1b", true},
+		{"no mac", "4c:20:b8:ab:87:1b", false},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			hw, err := net.ParseMAC(tc.mac)
+			if err != nil {
+				t.Fatal(err)
+			}
+			m := new(dns.Msg)
+			m.SetQuestion(selfCheckFQDN+".", 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)
+			}
+			m.Extra = append(m.Extra, o)
+			got := macFromMsg(m)
+			if tc.wantMac && got != tc.mac {
+				t.Errorf("mismatch, want: %q, got: %q", tc.mac, got)
+			}
+			if !tc.wantMac && got != "" {
+				t.Errorf("unexpected mac: %q", got)
+			}
+		})
+	}
+}

cmd/ctrld/prog.go

@@ -139,6 +139,9 @@ func (p *prog) Stop(s service.Service) error {
 		return err
 	}
 	p.preStop()
+	if err := router.Stop(); err != nil {
+		mainLog.Warn().Err(err).Msg("problem occurred while stopping router")
+	}
 	mainLog.Info().Msg("Service stopped")
 	close(p.stopCh)
 	return nil

config.go

@@ -80,6 +80,17 @@ 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
+}
+
 // ServiceConfig specifies the general ctrld config.
 type ServiceConfig struct {
 	LogLevel         string `mapstructure:"log_level" toml:"log_level,omitempty"`
@@ -101,12 +112,15 @@ type NetworkConfig struct {
 
 // UpstreamConfig specifies configuration for upstreams that ctrld will forward requests to.
 type UpstreamConfig struct {
-	Name              string            `mapstructure:"name" toml:"name,omitempty"`
-	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"`
-	BootstrapIP       string            `mapstructure:"bootstrap_ip" toml:"bootstrap_ip,omitempty"`
-	Domain            string            `mapstructure:"-" toml:"-"`
-	Timeout           int               `mapstructure:"timeout" toml:"timeout,omitempty" validate:"gte=0"`
+	Name        string `mapstructure:"name" toml:"name,omitempty"`
+	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"`
+	BootstrapIP string `mapstructure:"bootstrap_ip" toml:"bootstrap_ip,omitempty"`
+	Domain      string `mapstructure:"-" toml:"-"`
+	Timeout     int    `mapstructure:"timeout" toml:"timeout,omitempty" validate:"gte=0"`
+	// The caller should not access this field directly.
+	// Use UpstreamSendClientInfo instead.
+	SendClientInfo    *bool             `mapstructure:"send_client_info" toml:"send_client_info,omitempty"`
 	transport         *http.Transport   `mapstructure:"-" toml:"-"`
 	http3RoundTripper http.RoundTripper `mapstructure:"-" toml:"-"`
 	certPool          *x509.CertPool    `mapstructure:"-" toml:"-"`
@@ -163,6 +177,34 @@ func (uc *UpstreamConfig) Init() {
 	}
 }
 
+// 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 && !(*uc.SendClientInfo) {
+		return false
+	}
+	if uc.SendClientInfo == nil {
+		return true
+	}
+	switch uc.Type {
+	case ResolverTypeDOH, ResolverTypeDOH3:
+		if u, err := url.Parse(uc.Endpoint); err == nil {
+			domain := u.Hostname()
+			for _, parent := range []string{"controld.com", "controld.net"} {
+				if dns.IsSubDomain(parent, domain) {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}
+
 // SetCertPool sets the system cert pool used for TLS connections.
 func (uc *UpstreamConfig) SetCertPool(cp *x509.CertPool) {
 	uc.certPool = cp

config_internal_test.go

@@ -147,6 +147,28 @@ func TestUpstreamConfig_Init(t *testing.T) {
 				Timeout:     0,
 			},
 		},
+		{
+			"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),
+			},
+			&UpstreamConfig{
+				Name:           "doh",
+				Type:           "doh",
+				Endpoint:       "https://example.com?k=v",
+				BootstrapIP:    "",
+				Domain:         "example.com",
+				Timeout:        0,
+				SendClientInfo: ptrBool(false),
+				u:              u2,
+			},
+		},
 	}
 
 	for _, tc := range tests {
@@ -158,3 +180,7 @@ func TestUpstreamConfig_Init(t *testing.T) {
 		})
 	}
 }
+
+func ptrBool(b bool) *bool {
+	return &b
+}

config_test.go

@@ -24,10 +24,12 @@ 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")
@@ -42,6 +44,8 @@ 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) {

doh.go

@@ -12,12 +12,22 @@ import (
 	"github.com/miekg/dns"
 )
 
+const (
+	DoHMacHeader  = "Dns-Mac"
+	DoHIPHeader   = "Dns-IP"
+	DoHHostHeader = "Dns-Host"
+
+	headerContentTypeValue = "application/dns-message"
+	headerAcceptValue      = "application/dns-message"
+)
+
 func newDohResolver(uc *UpstreamConfig) *dohResolver {
 	r := &dohResolver{
 		endpoint:          uc.u,
 		isDoH3:            uc.Type == ResolverTypeDOH3,
 		transport:         uc.transport,
 		http3RoundTripper: uc.http3RoundTripper,
+		sendClientInfo:    uc.UpstreamSendClientInfo(),
 	}
 	return r
 }
@@ -27,6 +37,7 @@ type dohResolver struct {
 	isDoH3            bool
 	transport         *http.Transport
 	http3RoundTripper http.RoundTripper
+	sendClientInfo    bool
 }
 
 func (r *dohResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, error) {
@@ -45,8 +56,7 @@ func (r *dohResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, erro
 	if err != nil {
 		return nil, fmt.Errorf("could not create request: %w", err)
 	}
-	req.Header.Set("Content-Type", "application/dns-message")
-	req.Header.Set("Accept", "application/dns-message")
+	addHeader(ctx, req, r.sendClientInfo)
 
 	c := http.Client{Transport: r.transport}
 	if r.isDoH3 {
@@ -78,3 +88,21 @@ func (r *dohResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, erro
 	answer := new(dns.Msg)
 	return answer, answer.Unpack(buf)
 }
+
+func addHeader(ctx context.Context, req *http.Request, sendClientInfo bool) {
+	req.Header.Set("Content-Type", headerContentTypeValue)
+	req.Header.Set("Accept", headerAcceptValue)
+	if sendClientInfo {
+		if ci, ok := ctx.Value(ClientInfoCtxKey{}).(*ClientInfo); ok && ci != nil {
+			if ci.Mac != "" {
+				req.Header.Set(DoHMacHeader, ci.Mac)
+			}
+			if ci.IP != "" {
+				req.Header.Set(DoHIPHeader, ci.IP)
+			}
+			if ci.Hostname != "" {
+				req.Header.Set(DoHHostHeader, ci.Hostname)
+			}
+		}
+	}
+}

internal/router/client_info.go

@@ -0,0 +1,88 @@
+package router
+
+import (
+	"bytes"
+	"log"
+	"os"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+	"tailscale.com/util/lineread"
+
+	"github.com/Control-D-Inc/ctrld"
+)
+
+var clientInfoFiles = []string{
+	"/tmp/dnsmasq.leases",                  // ddwrt
+	"/tmp/dhcp.leases",                     // openwrt
+	"/var/lib/misc/dnsmasq.leases",         // merlin
+	"/mnt/data/udapi-config/dnsmasq.lease", // UDM Pro
+	"/data/udapi-config/dnsmasq.lease",     // UDR
+}
+
+func (r *router) watchClientInfoTable() {
+	if r.watcher == nil {
+		return
+	}
+	timer := time.NewTicker(time.Minute * 5)
+	for {
+		select {
+		case <-timer.C:
+			for _, name := range r.watcher.WatchList() {
+				_ = readClientInfoFile(name)
+			}
+		case event, ok := <-r.watcher.Events:
+			if !ok {
+				return
+			}
+			if event.Has(fsnotify.Write) {
+				if err := readClientInfoFile(event.Name); err != nil && !os.IsNotExist(err) {
+					log.Println("could not read client info file:", err)
+				}
+			}
+		case err, ok := <-r.watcher.Errors:
+			if !ok {
+				return
+			}
+			log.Println("error:", err)
+		}
+	}
+}
+
+func Stop() error {
+	if Name() == "" {
+		return nil
+	}
+	r := routerPlatform.Load()
+	if r.watcher != nil {
+		if err := r.watcher.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func GetClientInfoByMac(mac string) *ctrld.ClientInfo {
+	if mac == "" {
+		return nil
+	}
+	_ = Name()
+	r := routerPlatform.Load()
+	val, ok := r.mac.Load(mac)
+	if !ok {
+		return nil
+	}
+	return val.(*ctrld.ClientInfo)
+}
+
+func readClientInfoFile(name string) error {
+	r := routerPlatform.Load()
+	return lineread.File(name, func(line []byte) error {
+		fields := bytes.Fields(line)
+		mac := string(fields[1])
+		ip := string(fields[2])
+		hostname := string(fields[3])
+		r.mac.Store(mac, &ctrld.ClientInfo{Mac: mac, IP: ip, Hostname: hostname})
+		return nil
+	})
+}

internal/router/ddwrt.go

@@ -20,9 +20,9 @@ https://wiki.dd-wrt.com/wiki/index.php/Journalling_Flash_File_System
 `)
 
 var nvramKeys = map[string]string{
-	"dns_dnsmasq":     "1",                  // Make dnsmasq running but disable DNS ability, ctrld will replace it.
-	"dnsmasq_options": dnsMasqConfigContent, // Configuration of dnsmasq set by ctrld.
-	"dns_crypt":       "0",                  // Disable DNSCrypt.
+	"dns_dnsmasq":     "1", // Make dnsmasq running but disable DNS ability, ctrld will replace it.
+	"dnsmasq_options": "",  // Configuration of dnsmasq set by ctrld, filled by setupDDWrt.
+	"dns_crypt":       "0", // Disable DNSCrypt.
 }
 
 func setupDDWrt() error {
@@ -31,6 +31,11 @@ func setupDDWrt() error {
 		return nil
 	}
 
+	data, err := dnsMasqConf()
+	if err != nil {
+		return err
+	}
+	nvramKeys["dnsmasq_options"] = data
 	// Backup current value, store ctrld's configs.
 	for key, value := range nvramKeys {
 		old, err := nvram("get", key)

internal/router/dnsmasq.go

@@ -1,14 +1,22 @@
 package router
 
-const dnsMasqConfigContent = `# GENERATED BY ctrld - DO NOT MODIFY
+import (
+	"strings"
+	"text/template"
+)
+
+const dnsMasqConfigContentTmpl = `# GENERATED BY ctrld - DO NOT MODIFY
 no-resolv
 server=127.0.0.1#5354
+{{- if .SendClientInfo}}
+add-mac
+{{- end}}
 `
 
 const merlinDNSMasqPostConfPath = "/jffs/scripts/dnsmasq.postconf"
 const merlinDNSMasqPostConfMarker = `# GENERATED BY ctrld - EOF`
 
-const merlinDNSMasqPostConf = `# GENERATED BY ctrld - DO NOT MODIFY
+const merlinDNSMasqPostConfTmpl = `# GENERATED BY ctrld - DO NOT MODIFY
 
 #!/bin/sh
 
@@ -20,7 +28,9 @@ if [ -n "$pid" ] && [ -f "/proc/${pid}/cmdline" ]; then
   pc_delete "servers-file" "$config_file"           # no WAN DNS settings
   pc_append "no-resolv" "$config_file"              # do not read /etc/resolv.conf
   pc_append "server=127.0.0.1#5354" "$config_file"  # use ctrld as upstream
-
+  {{- if .SendClientInfo}}
+  pc_append "add-mac" "$config_file"                 # add client mac
+  {{- end}}
 	
   # For John fork
   pc_delete "resolv-file" "$config_file"            # no WAN DNS settings
@@ -32,3 +42,24 @@ if [ -n "$pid" ] && [ -f "/proc/${pid}/cmdline" ]; then
   exit 0
 fi
 `
+
+func dnsMasqConf() (string, error) {
+	var sb strings.Builder
+	var tmplText string
+	switch Name() {
+	case DDWrt, OpenWrt, Ubios:
+		tmplText = dnsMasqConfigContentTmpl
+	case Merlin:
+		tmplText = merlinDNSMasqPostConfTmpl
+	}
+	tmpl := template.Must(template.New("").Parse(tmplText))
+	var to = &struct {
+		SendClientInfo bool
+	}{
+		routerPlatform.Load().sendClientInfo,
+	}
+	if err := tmpl.Execute(&sb, to); err != nil {
+		return "", err
+	}
+	return sb.String(), nil
+}

internal/router/merlin.go

@@ -19,6 +19,10 @@ func setupMerlin() error {
 		return err
 	}
 
+	merlinDNSMasqPostConf, err := dnsMasqConf()
+	if err != nil {
+		return err
+	}
 	data := strings.Join([]string{
 		merlinDNSMasqPostConf,
 		"\n",
@@ -38,7 +42,7 @@ func setupMerlin() error {
 }
 
 func cleanupMerlin() error {
-	buf, err := os.ReadFile(merlinDNSMasqPostConf)
+	buf, err := os.ReadFile(merlinDNSMasqPostConfPath)
 	if err != nil && !os.IsNotExist(err) {
 		return err
 	}

internal/router/merlin_test.go

@@ -9,7 +9,7 @@ import (
 func Test_merlinParsePostConf(t *testing.T) {
 	origContent := "# foo"
 	data := strings.Join([]string{
-		merlinDNSMasqPostConf,
+		merlinDNSMasqPostConfTmpl,
 		"\n",
 		merlinDNSMasqPostConfMarker,
 		"\n",

internal/router/openwrt.go

@@ -19,6 +19,10 @@ func setupOpenWrt() error {
 		return err
 	}
 	// Disable dnsmasq as DNS server.
+	dnsMasqConfigContent, err := dnsMasqConf()
+	if err != nil {
+		return err
+	}
 	if err := os.WriteFile(openwrtDNSMasqConfigPath, []byte(dnsMasqConfigContent), 0600); err != nil {
 		return err
 	}

internal/router/router.go

@@ -5,8 +5,10 @@ import (
 	"errors"
 	"os"
 	"os/exec"
+	"sync"
 	"sync/atomic"
 
+	"github.com/fsnotify/fsnotify"
 	"github.com/kardianos/service"
 
 	"github.com/Control-D-Inc/ctrld"
@@ -25,7 +27,10 @@ var ErrNotSupported = errors.New("unsupported platform")
 var routerPlatform atomic.Pointer[router]
 
 type router struct {
-	name string
+	name           string
+	sendClientInfo bool
+	mac            sync.Map
+	watcher        *fsnotify.Watcher
 }
 
 // SupportedPlatforms return all platforms that can be configured to run with ctrld.
@@ -33,18 +38,37 @@ func SupportedPlatforms() []string {
 	return []string{DDWrt, Merlin, OpenWrt, Ubios}
 }
 
+var configureFunc = map[string]func() error{
+	DDWrt:   setupDDWrt,
+	Merlin:  setupMerlin,
+	OpenWrt: setupOpenWrt,
+	Ubios:   setupUbiOS,
+}
+
 // Configure configures things for running ctrld on the router.
 func Configure(c *ctrld.Config) error {
 	name := Name()
 	switch name {
-	case DDWrt:
-		return setupDDWrt()
-	case Merlin:
-		return setupMerlin()
-	case OpenWrt:
-		return setupOpenWrt()
-	case Ubios:
-		return setupUbiOS()
+	case DDWrt, Merlin, OpenWrt, Ubios:
+		if c.HasUpstreamSendClientInfo() {
+			r := routerPlatform.Load()
+			r.sendClientInfo = true
+			watcher, err := fsnotify.NewWatcher()
+			if err != nil {
+				return err
+			}
+			r.watcher = watcher
+			go r.watchClientInfoTable()
+			for _, file := range clientInfoFiles {
+				_ = readClientInfoFile(file)
+				_ = r.watcher.Add(file)
+			}
+		}
+		configure := configureFunc[name]
+		if err := configure(); err != nil {
+			return err
+		}
+		return nil
 	default:
 		return ErrNotSupported
 	}

internal/router/ubios.go

@@ -12,6 +12,10 @@ const (
 
 func setupUbiOS() error {
 	// Disable dnsmasq as DNS server.
+	dnsMasqConfigContent, err := dnsMasqConf()
+	if err != nil {
+		return err
+	}
 	if err := os.WriteFile(ubiosDNSMasqConfigPath, []byte(dnsMasqConfigContent), 0600); err != nil {
 		return err
 	}

testhelper/config.go

@@ -50,6 +50,13 @@ type = "legacy"
 endpoint = "8.8.8.8"
 timeout = 5
 
+[upstream.3]
+name = "DOH with client info"
+type = "doh"
+endpoint = "https://dns.controld.com/client_info_upstream/main-device"
+timeout = 5
+send_client_info = false
+
 [listener.0]
 ip = "127.0.0.1"
 port = 53