Improve local DNS server

dns/transport/local/local.go

@@ -35,6 +35,7 @@ func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, opt
 	}
 	return &Transport{
 		TransportAdapter: dns.NewTransportAdapterWithLocalOptions(C.DNSTypeLocal, tag, options),
+		ctx:              ctx,
 		hosts:            hosts.NewFile(hosts.DefaultPath),
 		dialer:           transportDialer,
 	}, nil
@@ -57,7 +58,7 @@ func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg,
 			return dns.FixedResponse(message.Id, question, addresses, C.DefaultDNSTTL), nil
 		}
 	}
-	systemConfig := getSystemDNSConfig()
+	systemConfig := getSystemDNSConfig(t.ctx)
 	if systemConfig.singleRequest || !(message.Question[0].Qtype == mDNS.TypeA || message.Question[0].Qtype == mDNS.TypeAAAA) {
 		return t.exchangeSingleRequest(ctx, systemConfig, message, domain)
 	} else {

dns/transport/local/resolv.go

@@ -1,6 +1,7 @@
 package local
 
 import (
+	"context"
 	"os"
 	"runtime"
 	"strings"
@@ -23,19 +24,21 @@ type resolverConfig struct {
 
 var resolvConf resolverConfig
 
-func getSystemDNSConfig() *dnsConfig {
-	resolvConf.tryUpdate("/etc/resolv.conf")
+func getSystemDNSConfig(ctx context.Context) *dnsConfig {
+	resolvConf.tryUpdate(ctx, "/etc/resolv.conf")
 	return resolvConf.dnsConfig.Load()
 }
 
-func (conf *resolverConfig) init() {
-	conf.dnsConfig.Store(dnsReadConfig("/etc/resolv.conf"))
+func (conf *resolverConfig) init(ctx context.Context) {
+	conf.dnsConfig.Store(dnsReadConfig(ctx, "/etc/resolv.conf"))
 	conf.lastChecked = time.Now()
 	conf.ch = make(chan struct{}, 1)
 }
 
-func (conf *resolverConfig) tryUpdate(name string) {
-	conf.initOnce.Do(conf.init)
+func (conf *resolverConfig) tryUpdate(ctx context.Context, name string) {
+	conf.initOnce.Do(func() {
+		conf.init(ctx)
+	})
 
 	if conf.dnsConfig.Load().noReload {
 		return
@@ -59,7 +62,7 @@ func (conf *resolverConfig) tryUpdate(name string) {
 			return
 		}
 	}
-	dnsConf := dnsReadConfig(name)
+	dnsConf := dnsReadConfig(ctx, name)
 	conf.dnsConfig.Store(dnsConf)
 }
 

dns/transport/local/resolv_darwin_cgo.go

@@ -11,6 +11,7 @@ package local
 import "C"
 
 import (
+	"context"
 	"time"
 
 	E "github.com/sagernet/sing/common/exceptions"
@@ -18,7 +19,7 @@ import (
 	"github.com/miekg/dns"
 )
 
-func dnsReadConfig(_ string) *dnsConfig {
+func dnsReadConfig(_ context.Context, _ string) *dnsConfig {
 	if C.res_init() != 0 {
 		return &dnsConfig{
 			servers:  defaultNS,

dns/transport/local/resolv_unix.go

@@ -4,6 +4,7 @@ package local
 
 import (
 	"bufio"
+	"context"
 	"net"
 	"net/netip"
 	"os"
@@ -13,7 +14,7 @@ import (
 	"github.com/miekg/dns"
 )
 
-func dnsReadConfig(name string) *dnsConfig {
+func dnsReadConfig(_ context.Context, name string) *dnsConfig {
 	conf := &dnsConfig{
 		ndots:    1,
 		timeout:  5 * time.Second,

dns/transport/local/resolv_windows.go

@@ -1,6 +1,7 @@
 package local
 
 import (
+	"context"
 	"net"
 	"net/netip"
 	"os"
@@ -8,10 +9,13 @@ import (
 	"time"
 	"unsafe"
 
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing/service"
+
 	"golang.org/x/sys/windows"
 )
 
-func dnsReadConfig(_ string) *dnsConfig {
+func dnsReadConfig(ctx context.Context, _ string) *dnsConfig {
 	conf := &dnsConfig{
 		ndots:    1,
 		timeout:  5 * time.Second,
@@ -22,35 +26,35 @@ func dnsReadConfig(_ string) *dnsConfig {
 			conf.servers = defaultNS
 		}
 	}()
-	aas, err := adapterAddresses()
+	addresses, err := adapterAddresses()
 	if err != nil {
 		return nil
 	}
-
-	for _, aa := range aas {
-		// Only take interfaces whose OperStatus is IfOperStatusUp(0x01) into DNS configs.
-		if aa.OperStatus != windows.IfOperStatusUp {
+	var dnsAddresses []struct {
+		ifName string
+		netip.Addr
+	}
+	for _, address := range addresses {
+		if address.OperStatus != windows.IfOperStatusUp {
 			continue
 		}
-
-		// Only take interfaces which have at least one gateway
-		if aa.FirstGatewayAddress == nil {
+		if address.IfType == windows.IF_TYPE_TUNNEL {
 			continue
 		}
-
-		for dns := aa.FirstDnsServerAddress; dns != nil; dns = dns.Next {
-			sa, err := dns.Address.Sockaddr.Sockaddr()
+		if address.FirstGatewayAddress == nil {
+			continue
+		}
+		for dnsServerAddress := address.FirstDnsServerAddress; dnsServerAddress != nil; dnsServerAddress = dnsServerAddress.Next {
+			rawSockaddr, err := dnsServerAddress.Address.Sockaddr.Sockaddr()
 			if err != nil {
 				continue
 			}
-			var ip netip.Addr
-			switch sa := sa.(type) {
+			var dnsServerAddr netip.Addr
+			switch sockaddr := rawSockaddr.(type) {
 			case *syscall.SockaddrInet4:
-				ip = netip.AddrFrom4([4]byte{sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3]})
+				dnsServerAddr = netip.AddrFrom4(sockaddr.Addr)
 			case *syscall.SockaddrInet6:
-				var addr16 [16]byte
-				copy(addr16[:], sa.Addr[:])
-				if addr16[0] == 0xfe && addr16[1] == 0xc0 {
+				if sockaddr.Addr[0] == 0xfe && sockaddr.Addr[1] == 0xc0 {
 					// fec0/10 IPv6 addresses are site local anycast DNS
 					// addresses Microsoft sets by default if no other
 					// IPv6 DNS address is set. Site local anycast is
@@ -58,14 +62,27 @@ func dnsReadConfig(_ string) *dnsConfig {
 					// https://datatracker.ietf.org/doc/html/rfc3879
 					continue
 				}
-				ip = netip.AddrFrom16(addr16)
+				dnsServerAddr = netip.AddrFrom16(sockaddr.Addr)
 			default:
 				// Unexpected type.
 				continue
 			}
-			conf.servers = append(conf.servers, net.JoinHostPort(ip.String(), "53"))
+			dnsAddresses = append(dnsAddresses, struct {
+				ifName string
+				netip.Addr
+			}{ifName: windows.UTF16PtrToString(address.FriendlyName), Addr: dnsServerAddr})
 		}
 	}
+	var myInterface string
+	if networkManager := service.FromContext[adapter.NetworkManager](ctx); networkManager != nil {
+		myInterface = networkManager.InterfaceMonitor().MyInterface()
+	}
+	for _, address := range dnsAddresses {
+		if address.ifName == myInterface {
+			continue
+		}
+		conf.servers = append(conf.servers, net.JoinHostPort(address.String(), "53"))
+	}
 	return conf
 }