chore: dns outbound support tcp

adapter/outbound/dns.go

@@ -2,10 +2,10 @@ package outbound
 
 import (
 	"context"
-	"fmt"
 	"net"
 	"time"
 
+	N "github.com/metacubex/mihomo/common/net"
 	"github.com/metacubex/mihomo/common/pool"
 	"github.com/metacubex/mihomo/component/dialer"
 	"github.com/metacubex/mihomo/component/resolver"
@@ -24,7 +24,9 @@ type DnsOption struct {
 
 // DialContext implements C.ProxyAdapter
 func (d *Dns) DialContext(ctx context.Context, metadata *C.Metadata, opts ...dialer.Option) (C.Conn, error) {
-	return nil, fmt.Errorf("dns outbound does not support tcp")
+	left, right := N.Pipe()
+	go resolver.RelayDnsConn(context.Background(), right, 0)
+	return NewConn(left, d), nil
 }
 
 // ListenPacketContext implements C.ProxyAdapter
@@ -76,15 +78,29 @@ func (d *dnsPacketConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
 }
 
 func (d *dnsPacketConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
+	select {
+	case <-d.ctx.Done():
+		return 0, net.ErrClosed
+	default:
+	}
+
+	if len(p) > resolver.SafeDnsPacketSize {
+		// wtf???
+		return len(p), nil
+	}
+
 	ctx, cancel := context.WithTimeout(d.ctx, resolver.DefaultDnsRelayTimeout)
 	defer cancel()
 
 	buf := pool.Get(resolver.SafeDnsPacketSize)
 	put := func() { _ = pool.Put(buf) }
-	buf, err = resolver.RelayDnsPacket(ctx, p, buf)
+	copy(buf, p) // avoid p be changed after WriteTo returned
+
+	go func() { // don't block the WriteTo function
+		buf, err = resolver.RelayDnsPacket(ctx, buf[:len(p)], buf)
 		if err != nil {
 			put()
-		return 0, err
+			return
 		}
 
 		packet := dnsPacket{
@@ -94,11 +110,12 @@ func (d *dnsPacketConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
 		}
 		select {
 		case d.response <- packet:
-		return len(p), nil
+			break
 		case <-d.ctx.Done():
 			put()
-		return 0, net.ErrClosed
 		}
+	}()
+	return len(p), nil
 }
 
 func (d *dnsPacketConn) Close() error {

common/net/deadline/conn.go

@@ -26,6 +26,11 @@ type Conn struct {
 	resultCh     chan *connReadResult
 }
 
+func IsConn(conn any) bool {
+	_, ok := conn.(*Conn)
+	return ok
+}
+
 func NewConn(conn net.Conn) *Conn {
 	c := &Conn{
 		ExtendedConn: bufio.NewExtendedConn(conn),

common/net/deadline/pipe_sing.go

@@ -215,3 +215,8 @@ func (p *pipe) waitReadBuffer() (buffer *buf.Buffer, err error) {
 		return nil, os.ErrDeadlineExceeded
 	}
 }
+
+func IsPipe(conn any) bool {
+	_, ok := conn.(*pipe)
+	return ok
+}

common/net/sing.go

@@ -23,6 +23,12 @@ type ExtendedReader = network.ExtendedReader
 var WriteBuffer = bufio.WriteBuffer
 
 func NewDeadlineConn(conn net.Conn) ExtendedConn {
+	if deadline.IsPipe(conn) || deadline.IsPipe(network.UnwrapReader(conn)) {
+		return NewExtendedConn(conn) // pipe always have correctly deadline implement
+	}
+	if deadline.IsConn(conn) || deadline.IsConn(network.UnwrapReader(conn)) {
+		return NewExtendedConn(conn) // was a *deadline.Conn
+	}
 	return deadline.NewConn(conn)
 }
 

component/resolver/relay.go

@@ -17,15 +17,15 @@ const DefaultDnsRelayTimeout = time.Second * 5
 
 const SafeDnsPacketSize = 2 * 1024 // safe size which is 1232 from https://dnsflagday.net/2020/, so 2048 is enough
 
-func RelayDnsConn(ctx context.Context, conn net.Conn) error {
+func RelayDnsConn(ctx context.Context, conn net.Conn, readTimeout time.Duration) error {
 	buff := pool.Get(pool.UDPBufferSize)
 	defer func() {
 		_ = pool.Put(buff)
 		_ = conn.Close()
 	}()
 	for {
-		if conn.SetReadDeadline(time.Now().Add(DefaultDnsReadTimeout)) != nil {
+		if readTimeout > 0 {
-			break
+			_ = conn.SetReadDeadline(time.Now().Add(readTimeout))
 		}
 
 		length := uint16(0)

listener/sing_tun/dns.go

@@ -37,7 +37,7 @@ func (h *ListenerHandler) ShouldHijackDns(targetAddr netip.AddrPort) bool {
 func (h *ListenerHandler) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
 	if h.ShouldHijackDns(metadata.Destination.AddrPort()) {
 		log.Debugln("[DNS] hijack tcp:%s", metadata.Destination.String())
-		return resolver.RelayDnsConn(ctx, conn)
+		return resolver.RelayDnsConn(ctx, conn, resolver.DefaultDnsReadTimeout)
 	}
 	return h.ListenerHandler.NewConnection(ctx, conn, metadata)
 }