Add hijack_dns for tun

inbound/dns.go

@@ -0,0 +1,107 @@
+package inbound
+
+import (
+	"context"
+	"encoding/binary"
+	"io"
+	"net"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	N "github.com/sagernet/sing/common/network"
+
+	"golang.org/x/net/dns/dnsmessage"
+)
+
+func NewDNSConnection(ctx context.Context, router adapter.Router, logger log.Logger, conn net.Conn, metadata adapter.InboundContext) error {
+	_buffer := buf.StackNewSize(1024)
+	defer common.KeepAlive(_buffer)
+	buffer := common.Dup(_buffer)
+	defer buffer.Release()
+	for {
+		var queryLength uint16
+		err := binary.Read(conn, binary.BigEndian, &queryLength)
+		if err != nil {
+			return err
+		}
+		if queryLength > 1024 {
+			return io.ErrShortBuffer
+		}
+		buffer.FullReset()
+		_, err = buffer.ReadFullFrom(conn, int(queryLength))
+		if err != nil {
+			return err
+		}
+		var message dnsmessage.Message
+		err = message.Unpack(buffer.Bytes())
+		if err != nil {
+			return err
+		}
+		if len(message.Questions) > 0 {
+			question := message.Questions[0]
+			metadata.Domain = string(question.Name.Data[:question.Name.Length-1])
+			logger.WithContext(ctx).Debug("inbound dns query ", formatDNSQuestion(question), " from ", metadata.Source)
+		}
+		response, err := router.Exchange(adapter.WithContext(ctx, &metadata), &message)
+		if err != nil {
+			return err
+		}
+		buffer.FullReset()
+		responseBuffer, err := response.AppendPack(buffer.Index(0))
+		if err != nil {
+			return err
+		}
+		err = binary.Write(conn, binary.BigEndian, uint16(len(responseBuffer)))
+		if err != nil {
+			return err
+		}
+		_, err = conn.Write(responseBuffer)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func NewDNSPacketConnection(ctx context.Context, router adapter.Router, logger log.Logger, conn N.PacketConn, metadata adapter.InboundContext) error {
+	for {
+		buffer := buf.StackNewSize(1024)
+		destination, err := conn.ReadPacket(buffer)
+		if err != nil {
+			buffer.Release()
+			return err
+		}
+		var message dnsmessage.Message
+		err = message.Unpack(buffer.Bytes())
+		if err != nil {
+			return err
+		}
+		if len(message.Questions) > 0 {
+			question := message.Questions[0]
+			metadata.Domain = string(question.Name.Data[:question.Name.Length-1])
+			logger.WithContext(ctx).Debug("inbound dns query ", formatDNSQuestion(question), " from ", metadata.Source)
+		}
+		go func() error {
+			defer buffer.Release()
+			response, err := router.Exchange(adapter.WithContext(ctx, &metadata), &message)
+			if err != nil {
+				return err
+			}
+			buffer.FullReset()
+			responseBuffer, err := response.AppendPack(buffer.Index(0))
+			if err != nil {
+				return err
+			}
+			buffer.Truncate(len(responseBuffer))
+			err = conn.WritePacket(buffer, destination)
+			return err
+		}()
+	}
+}
+
+func formatDNSQuestion(question dnsmessage.Question) string {
+	domain := question.Name.String()
+	domain = domain[:len(domain)-1]
+	return string(question.Name.Data[:question.Name.Length-1]) + " " + question.Type.String()[4:] + " " + question.Class.String()[5:]
+}