Removing Windows Server support

README.md

@@ -32,8 +32,7 @@ All DNS protocols are supported, including:
 
 
 ## OS Support
-- Windows (386, amd64, arm)
-- Windows Server (386, amd64)
+- Windows Desktop (386, amd64, arm)
 - MacOS (amd64, arm64)
 - Linux (386, amd64, arm, mips)
 - FreeBSD (386, amd64, arm)

cmd/cli/ad_others.go

@@ -8,8 +8,3 @@ import (
 
 // addExtraSplitDnsRule adds split DNS rule if present.
 func addExtraSplitDnsRule(_ *ctrld.Config) bool { return false }
-
-// getActiveDirectoryDomain returns AD domain name of this computer.
-func getActiveDirectoryDomain() (string, error) {
-	return "", nil
-}

cmd/cli/cli.go

@@ -1147,20 +1147,15 @@ func tryUpdateListenerConfig(cfg *ctrld.Config, notifyFunc func(), fatal bool) (
 	lcc := make(map[string]*listenerConfigCheck)
 	cdMode := cdUID != ""
 	nextdnsMode := nextdns != ""
-	// For Windows server with local Dns server running, we can only try on random local IP.
-	hasLocalDnsServer := hasLocalDnsServerRunning()
 	isDesktop := ctrld.IsDesktopPlatform()
 	for n, listener := range cfg.Listener {
 		lcc[n] = &listenerConfigCheck{}
 		if listener.IP == "" {
 			listener.IP = "0.0.0.0"
-			// Windows Server lies to us that we could listen on 0.0.0.0:53
-			// even there's a process already done that, stick to local IP only.
-			//
 			// For desktop clients, also stick the listener to the local IP only.
 			// Listening on 0.0.0.0 would expose it to the entire local network, potentially
 			// creating security vulnerabilities (such as DNS amplification or abusing).
-			if hasLocalDnsServer || isDesktop {
+			if isDesktop {
 				listener.IP = "127.0.0.1"
 			}
 			lcc[n].IP = true
@@ -1171,15 +1166,9 @@ func tryUpdateListenerConfig(cfg *ctrld.Config, notifyFunc func(), fatal bool) (
 		}
 		// In cd mode, we always try to pick an ip:port pair to work.
 		// Same if nextdns resolver is used.
-		//
-		// Except on Windows Server with local Dns running,
-		// we could only listen on random local IP port 53.
 		if cdMode || nextdnsMode {
 			lcc[n].IP = true
 			lcc[n].Port = true
-			if hasLocalDnsServer {
-				lcc[n].Port = false
-			}
 		}
 		updated = updated || lcc[n].IP || lcc[n].Port
 	}
@@ -1258,16 +1247,6 @@ func tryUpdateListenerConfig(cfg *ctrld.Config, notifyFunc func(), fatal bool) (
 		// config, so we can always listen on localhost port 53, but no traffic could be routed there.
 		tryLocalhost := !isLoopback(listener.IP)
 		tryAllPort53 := true
-		// We should not try to listen on any port other than 53,
-		// if we do, this will break the dns resolution for the system.
-		// TODO: cleanup these codes when refactoring this function.
-		tryOldIPPort5354 := false
-		tryPort5354 := false
-		if hasLocalDnsServer {
-			tryAllPort53 = false
-			tryOldIPPort5354 = false
-			tryPort5354 = false
-		}
 
 		attempts := 0
 		maxAttempts := 10
@@ -1318,28 +1297,6 @@ func tryUpdateListenerConfig(cfg *ctrld.Config, notifyFunc func(), fatal bool) (
 				}
 				continue
 			}
-			if tryOldIPPort5354 {
-				tryOldIPPort5354 = false
-				if check.IP {
-					listener.IP = oldIP
-				}
-				if check.Port {
-					listener.Port = 5354
-				}
-				logMsg(il.Info(), n, "could not listen on address: %s, trying current ip with port 5354", addr)
-				continue
-			}
-			if tryPort5354 {
-				tryPort5354 = false
-				if check.IP {
-					listener.IP = "0.0.0.0"
-				}
-				if check.Port {
-					listener.Port = 5354
-				}
-				logMsg(il.Info(), n, "could not listen on address: %s, trying 0.0.0.0:5354", addr)
-				continue
-			}
 			if check.IP && !isZeroIP { // for "0.0.0.0" or "::", we only need to try new port.
 				listener.IP = randomLocalIP()
 			} else {

cmd/cli/commands.go

@@ -899,10 +899,7 @@ NOTE: Uninstalling will set DNS to values provided by DHCP.`,
 					}
 					return nil
 				})
-				// Windows forwarders file.
-				if hasLocalDnsServerRunning() {
-					files = append(files, ctrld.AbsHomeDir(windowsForwardersFilename))
-				}
+
 				// Binary itself.
 				bin, _ := os.Executable()
 				if bin != "" && supportedSelfDelete {

cmd/cli/dns_proxy.go

@@ -51,12 +51,6 @@ var privateUpstreamConfig = &ctrld.UpstreamConfig{
 	Timeout: 2000,
 }
 
-var localUpstreamConfig = &ctrld.UpstreamConfig{
-	Name:    "Local resolver",
-	Type:    ctrld.ResolverTypeLocal,
-	Timeout: 2000,
-}
-
 // proxyRequest contains data for proxying a DNS query to upstream.
 type proxyRequest struct {
 	msg            *dns.Msg
@@ -500,17 +494,6 @@ func (p *prog) proxy(ctx context.Context, req *proxyRequest) *proxyResponse {
 	if len(upstreamConfigs) == 0 {
 		upstreamConfigs = []*ctrld.UpstreamConfig{osUpstreamConfig}
 		upstreams = []string{upstreamOS}
-		// For OS resolver, local addresses are ignored to prevent possible looping.
-		// However, on Active Directory Domain Controller, where it has local DNS server
-		// running and listening on local addresses, these local addresses must be used
-		// as nameservers, so queries for ADDC could be resolved as expected.
-		if p.isAdDomainQuery(req.msg) {
-			ctrld.Log(ctx, p.Debug(),
-				"AD domain query detected for %s in domain %s",
-				req.msg.Question[0].Name, p.adDomain)
-			upstreamConfigs = []*ctrld.UpstreamConfig{localUpstreamConfig}
-			upstreams = []string{upstreamOSLocal}
-		}
 	}
 
 	res := &proxyResponse{}
@@ -631,7 +614,6 @@ func (p *prog) proxy(ctx context.Context, req *proxyRequest) *proxyResponse {
 		logger := p.Debug().
 			Str("upstream", upstreamConfig.String()).
 			Str("query", req.msg.Question[0].Name).
-			Bool("is_ad_query", p.isAdDomainQuery(req.msg)).
 			Bool("is_lan_query", isLanOrPtrQuery)
 
 		if p.isLoop(upstreamConfig) {
@@ -747,14 +729,6 @@ func (p *prog) upstreamConfigsFromUpstreamNumbers(upstreams []string) []*ctrld.U
 	return upstreamConfigs
 }
 
-func (p *prog) isAdDomainQuery(msg *dns.Msg) bool {
-	if p.adDomain == "" {
-		return false
-	}
-	cDomainName := canonicalName(msg.Question[0].Name)
-	return dns.IsSubDomain(p.adDomain, cDomainName)
-}
-
 // canonicalName returns canonical name from FQDN with "." trimmed.
 func canonicalName(fqdn string) string {
 	q := strings.TrimSpace(fqdn)

cmd/cli/os_windows.go

@@ -1,16 +1,12 @@
 package cli
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"net"
 	"net/netip"
-	"os"
-	"os/exec"
 	"slices"
 	"strings"
-	"sync"
 
 	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/registry"
@@ -25,11 +21,6 @@ const (
 	v6InterfaceKeyPathFormat = `SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\Interfaces\`
 )
 
-var (
-	setDNSOnce   sync.Once
-	resetDNSOnce sync.Once
-)
-
 // setDnsIgnoreUnusableInterface likes setDNS, but return a nil error if the interface is not usable.
 func setDnsIgnoreUnusableInterface(iface *net.Interface, nameservers []string) error {
 	return setDNS(iface, nameservers)
@@ -40,49 +31,7 @@ func setDNS(iface *net.Interface, nameservers []string) error {
 	if len(nameservers) == 0 {
 		return errors.New("empty DNS nameservers")
 	}
-	setDNSOnce.Do(func() {
-		// If there's a Dns server running, that means we are on AD with Dns feature enabled.
-		// Configuring the Dns server to forward queries to ctrld instead.
-		if hasLocalDnsServerRunning() {
-			mainLog.Load().Debug().Msg("Local DNS server detected, configuring forwarders")
 
-			file := ctrld.AbsHomeDir(windowsForwardersFilename)
-			mainLog.Load().Debug().Msgf("Using forwarders file: %s", file)
-
-			oldForwardersContent, err := os.ReadFile(file)
-			if err != nil {
-				mainLog.Load().Debug().Err(err).Msg("Could not read existing forwarders file")
-			} else {
-				mainLog.Load().Debug().Msgf("Existing forwarders content: %s", string(oldForwardersContent))
-			}
-
-			hasLocalIPv6Listener := needLocalIPv6Listener()
-			mainLog.Load().Debug().Bool("has_ipv6_listener", hasLocalIPv6Listener).Msg("IPv6 listener status")
-
-			forwarders := slices.DeleteFunc(slices.Clone(nameservers), func(s string) bool {
-				if !hasLocalIPv6Listener {
-					return false
-				}
-				return s == "::1"
-			})
-			mainLog.Load().Debug().Strs("forwarders", forwarders).Msg("Filtered forwarders list")
-
-			if err := os.WriteFile(file, []byte(strings.Join(forwarders, ",")), 0600); err != nil {
-				mainLog.Load().Warn().Err(err).Msg("could not save forwarders settings")
-			} else {
-				mainLog.Load().Debug().Msg("Successfully wrote new forwarders file")
-			}
-
-			oldForwarders := strings.Split(string(oldForwardersContent), ",")
-			mainLog.Load().Debug().Strs("old_forwarders", oldForwarders).Msg("Previous forwarders")
-
-			if err := addDnsServerForwarders(forwarders, oldForwarders); err != nil {
-				mainLog.Load().Warn().Err(err).Msg("could not set forwarders settings")
-			} else {
-				mainLog.Load().Debug().Msg("Successfully configured DNS server forwarders")
-			}
-		}
-	})
 	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
 	if err != nil {
 		return fmt.Errorf("setDNS: %w", err)
@@ -126,25 +75,7 @@ func resetDnsIgnoreUnusableInterface(iface *net.Interface) error {
 	return resetDNS(iface)
 }
 
-// TODO(cuonglm): should we use system API?
 func resetDNS(iface *net.Interface) error {
-	resetDNSOnce.Do(func() {
-		// See corresponding comment in setDNS.
-		if hasLocalDnsServerRunning() {
-			file := ctrld.AbsHomeDir(windowsForwardersFilename)
-			content, err := os.ReadFile(file)
-			if err != nil {
-				mainLog.Load().Error().Err(err).Msg("could not read forwarders settings")
-				return
-			}
-			nameservers := strings.Split(string(content), ",")
-			if err := removeDnsServerForwarders(nameservers); err != nil {
-				mainLog.Load().Error().Err(err).Msg("could not remove forwarders settings")
-				return
-			}
-		}
-	})
-
 	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
 	if err != nil {
 		return fmt.Errorf("resetDNS: %w", err)
@@ -285,49 +216,3 @@ func parseDNSServers(val string) []string {
 	}
 	return servers
 }
-
-// addDnsServerForwarders adds given nameservers to DNS server forwarders list,
-// and also removing old forwarders if provided.
-func addDnsServerForwarders(nameservers, old []string) error {
-	newForwardersMap := make(map[string]struct{})
-	newForwarders := make([]string, len(nameservers))
-	for i := range nameservers {
-		newForwardersMap[nameservers[i]] = struct{}{}
-		newForwarders[i] = fmt.Sprintf("%q", nameservers[i])
-	}
-	oldForwarders := old[:0]
-	for _, fwd := range old {
-		if _, ok := newForwardersMap[fwd]; !ok {
-			oldForwarders = append(oldForwarders, fwd)
-		}
-	}
-	// NOTE: It is important to add new forwarder before removing old one.
-	//       Testing on Windows Server 2022 shows that removing forwarder1
-	//       then adding forwarder2 sometimes ends up adding both of them
-	//       to the forwarders list.
-	cmd := fmt.Sprintf("Add-DnsServerForwarder -IPAddress %s", strings.Join(newForwarders, ","))
-	if len(oldForwarders) > 0 {
-		cmd = fmt.Sprintf("%s ; Remove-DnsServerForwarder -IPAddress %s -Force", cmd, strings.Join(oldForwarders, ","))
-	}
-	if out, err := powershell(cmd); err != nil {
-		return fmt.Errorf("%w: %s", err, string(out))
-	}
-	return nil
-}
-
-// removeDnsServerForwarders removes given nameservers from DNS server forwarders list.
-func removeDnsServerForwarders(nameservers []string) error {
-	for _, ns := range nameservers {
-		cmd := fmt.Sprintf("Remove-DnsServerForwarder -IPAddress %s -Force", ns)
-		if out, err := powershell(cmd); err != nil {
-			return fmt.Errorf("%w: %s", err, string(out))
-		}
-	}
-	return nil
-}
-
-// powershell runs the given powershell command.
-func powershell(cmd string) ([]byte, error) {
-	out, err := exec.Command("powershell", "-Command", cmd).CombinedOutput()
-	return bytes.TrimSpace(out), err
-}

cmd/cli/os_windows_test.go

@@ -1,8 +1,10 @@
 package cli
 
 import (
+	"bytes"
 	"fmt"
 	"net"
+	"os/exec"
 	"slices"
 	"strings"
 	"testing"
@@ -66,3 +68,9 @@ func currentStaticDnsPowershell(iface *net.Interface) ([]string, error) {
 	}
 	return ns, nil
 }
+
+// powershell runs the given powershell command.
+func powershell(cmd string) ([]byte, error) {
+	out, err := exec.Command("powershell", "-Command", cmd).CombinedOutput()
+	return bytes.TrimSpace(out), err
+}

cmd/cli/prog.go

@@ -128,8 +128,6 @@ type prog struct {
 	internalLogSent           time.Time
 	runningIface              string
 	requiredMultiNICsConfig   bool
-	adDomain                  string
-	runningOnDomainController bool
 
 	selfUninstallMu       sync.Mutex
 	refusedQueryCount     int
@@ -279,11 +277,6 @@ func (p *prog) preRun() {
 
 func (p *prog) postRun() {
 	if !service.Interactive() {
-		if runtime.GOOS == "windows" {
-			isDC, roleInt := isRunningOnDomainController()
-			p.runningOnDomainController = isDC
-			p.Debug().Msgf("running on domain controller: %t, role: %d", p.runningOnDomainController, roleInt)
-		}
 		p.resetDNS(false, false)
 		ns := ctrld.InitializeOsResolver(ctrld.LoggerCtx(context.Background(), p.logger.Load()), false)
 		p.Debug().Msgf("initialized OS resolver with nameservers: %v", ns)
@@ -481,10 +474,6 @@ func (p *prog) run(reload bool, reloadCh chan struct{}) {
 			}
 		}
 	}
-	if domain, err := getActiveDirectoryDomain(); err == nil && domain != "" && hasLocalDnsServerRunning() {
-		p.Debug().Msgf("active directory domain: %s", domain)
-		p.adDomain = domain
-	}
 
 	var wg sync.WaitGroup
 	wg.Add(len(p.cfg.Listener))
@@ -1481,26 +1470,5 @@ func (p *prog) leakOnUpstreamFailure() bool {
 	if ptr := p.cfg.Service.LeakOnUpstreamFailure; ptr != nil {
 		return *ptr
 	}
-
-	// if we are running on ADDC, we should not leak on upstream failure
-	if p.runningOnDomainController {
-		return false
-	}
 	return true
 }
-
-// Domain controller role values from Win32_ComputerSystem
-// https://learn.microsoft.com/en-us/windows/win32/cimwin32prov/win32-computersystem
-const (
-	BackupDomainController  = 4
-	PrimaryDomainController = 5
-)
-
-// isRunningOnDomainController checks if the current machine is a domain controller
-// by querying the DomainRole property from Win32_ComputerSystem via WMI.
-func isRunningOnDomainController() (bool, int) {
-	if runtime.GOOS != "windows" {
-		return false, 0
-	}
-	return isRunningOnDomainControllerWindows()
-}

cmd/cli/prog_windows.go

@@ -2,11 +2,7 @@ package cli
 
 import "github.com/kardianos/service"
 
-func setDependencies(svc *service.Config) {
-	if hasLocalDnsServerRunning() {
-		svc.Dependencies = []string{"DNS"}
-	}
-}
+func setDependencies(svc *service.Config) {}
 
 func setWorkingDirectory(svc *service.Config, dir string) {
 	// WorkingDirectory is not supported on Windows.

cmd/cli/service_others.go

@@ -14,9 +14,4 @@ func openLogFile(path string, flags int) (*os.File, error) {
 	return os.OpenFile(path, flags, os.FileMode(0o600))
 }
 
-// hasLocalDnsServerRunning reports whether we are on Windows and having Dns server running.
-func hasLocalDnsServerRunning() bool { return false }
-
 func ConfigureWindowsServiceFailureActions(serviceName string) error { return nil }
-
-func isRunningOnDomainControllerWindows() (bool, int) { return false, 0 }

cmd/cli/service_windows.go

@@ -2,18 +2,11 @@ package cli
 
 import (
 	"os"
-	"reflect"
 	"runtime"
-	"strconv"
-	"strings"
 	"syscall"
 	"time"
 	"unsafe"
 
-	"github.com/microsoft/wmi/pkg/base/host"
-	"github.com/microsoft/wmi/pkg/base/instance"
-	"github.com/microsoft/wmi/pkg/base/query"
-	"github.com/microsoft/wmi/pkg/constant"
 	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/svc/mgr"
 )
@@ -151,77 +144,3 @@ func openLogFile(path string, mode int) (*os.File, error) {
 
 	return os.NewFile(uintptr(handle), path), nil
 }
-
-const processEntrySize = uint32(unsafe.Sizeof(windows.ProcessEntry32{}))
-
-// hasLocalDnsServerRunning reports whether we are on Windows and having Dns server running.
-func hasLocalDnsServerRunning() bool {
-	h, e := windows.CreateToolhelp32Snapshot(windows.TH32CS_SNAPPROCESS, 0)
-	if e != nil {
-		return false
-	}
-	p := windows.ProcessEntry32{Size: processEntrySize}
-	for {
-		e := windows.Process32Next(h, &p)
-		if e != nil {
-			return false
-		}
-		if strings.ToLower(windows.UTF16ToString(p.ExeFile[:])) == "dns.exe" {
-			return true
-		}
-	}
-}
-
-func isRunningOnDomainControllerWindows() (bool, int) {
-	whost := host.NewWmiLocalHost()
-	q := query.NewWmiQuery("Win32_ComputerSystem")
-	instances, err := instance.GetWmiInstancesFromHost(whost, string(constant.CimV2), q)
-	if err != nil {
-		mainLog.Load().Debug().Err(err).Msg("WMI query failed")
-		return false, 0
-	}
-	if instances == nil {
-		mainLog.Load().Debug().Msg("WMI query returned nil instances")
-		return false, 0
-	}
-	defer instances.Close()
-
-	if len(instances) == 0 {
-		mainLog.Load().Debug().Msg("no rows returned from Win32_ComputerSystem")
-		return false, 0
-	}
-
-	val, err := instances[0].GetProperty("DomainRole")
-	if err != nil {
-		mainLog.Load().Debug().Err(err).Msg("failed to get DomainRole property")
-		return false, 0
-	}
-	if val == nil {
-		mainLog.Load().Debug().Msg("DomainRole property is nil")
-		return false, 0
-	}
-
-	// Safely handle varied types: string or integer
-	var roleInt int
-	switch v := val.(type) {
-	case string:
-		// "4", "5", etc.
-		parsed, parseErr := strconv.Atoi(v)
-		if parseErr != nil {
-			mainLog.Load().Debug().Err(parseErr).Msgf("failed to parse DomainRole value %q", v)
-			return false, 0
-		}
-		roleInt = parsed
-	case int8, int16, int32, int64:
-		roleInt = int(reflect.ValueOf(v).Int())
-	case uint8, uint16, uint32, uint64:
-		roleInt = int(reflect.ValueOf(v).Uint())
-	default:
-		mainLog.Load().Debug().Msgf("unexpected DomainRole type: %T value=%v", v, v)
-		return false, 0
-	}
-
-	// Check if role indicates a domain controller
-	isDC := roleInt == BackupDomainController || roleInt == PrimaryDomainController
-	return isDC, roleInt
-}

cmd/cli/service_windows_test.go

@@ -1,25 +0,0 @@
-package cli
-
-import (
-	"testing"
-	"time"
-)
-
-func Test_hasLocalDnsServerRunning(t *testing.T) {
-	start := time.Now()
-	hasDns := hasLocalDnsServerRunning()
-	t.Logf("Using Windows API takes: %d", time.Since(start).Milliseconds())
-
-	start = time.Now()
-	hasDnsPowershell := hasLocalDnsServerRunningPowershell()
-	t.Logf("Using Powershell takes: %d", time.Since(start).Milliseconds())
-
-	if hasDns != hasDnsPowershell {
-		t.Fatalf("result mismatch, want: %v, got: %v", hasDnsPowershell, hasDns)
-	}
-}
-
-func hasLocalDnsServerRunningPowershell() bool {
-	_, err := powershell("Get-Process -Name DNS")
-	return err == nil
-}

config.go

@@ -403,7 +403,7 @@ func (uc *UpstreamConfig) IsDiscoverable() bool {
 		return *uc.Discoverable
 	}
 	switch uc.Type {
-	case ResolverTypeOS, ResolverTypeLegacy, ResolverTypePrivate, ResolverTypeLocal:
+	case ResolverTypeOS, ResolverTypeLegacy, ResolverTypePrivate:
 		if ip, err := netip.ParseAddr(uc.Domain); err == nil {
 			return ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() || tsaddr.CGNATRange().Contains(ip)
 		}

resolver.go

@@ -34,8 +34,6 @@ const (
 	ResolverTypeLegacy = "legacy"
 	// ResolverTypePrivate is like ResolverTypeOS, but use for private resolver only.
 	ResolverTypePrivate = "private"
-	// ResolverTypeLocal is like ResolverTypeOS, but use for local resolver only.
-	ResolverTypeLocal = "local"
 	// ResolverTypeSDNS specifies resolver with information encoded using DNS Stamps.
 	// See: https://dnscrypt.info/stamps-specifications/
 	ResolverTypeSDNS = "sdns"
@@ -45,12 +43,6 @@ const controldPublicDns = "76.76.2.0"
 
 var controldPublicDnsWithPort = net.JoinHostPort(controldPublicDns, "53")
 
-var localResolver Resolver
-
-func init() {
-	localResolver = newLocalResolver()
-}
-
 var (
 	resolverMutex    sync.Mutex
 	or               *osResolver
@@ -58,14 +50,6 @@ var (
 	defaultLocalIPv6 atomic.Value // holds net.IP (IPv6)
 )
 
-func newLocalResolver() Resolver {
-	var nss []string
-	for _, addr := range Rfc1918Addresses() {
-		nss = append(nss, net.JoinHostPort(addr, "53"))
-	}
-	return NewResolverWithNameserver(nss)
-}
-
 // LanQueryCtxKey is the context.Context key to indicate that the request is for LAN network.
 type LanQueryCtxKey struct{}
 
@@ -198,8 +182,6 @@ func NewResolver(ctx context.Context, uc *UpstreamConfig) (Resolver, error) {
 		return &legacyResolver{uc: uc}, nil
 	case ResolverTypePrivate:
 		return NewPrivateResolver(ctx), nil
-	case ResolverTypeLocal:
-		return localResolver, nil
 	}
 	return nil, fmt.Errorf("%w: %s", errUnknownResolver, typ)
 }