refactor: DNS

dns/transport/tcp.go

@@ -0,0 +1,99 @@
+package transport
+
+import (
+	"context"
+	"encoding/binary"
+	"io"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*TCPTransport)(nil)
+
+func RegisterTCP(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.RemoteDNSServerOptions](registry, C.DNSTypeTCP, NewTCP)
+}
+
+type TCPTransport struct {
+	dns.TransportAdapter
+	dialer     N.Dialer
+	serverAddr M.Socksaddr
+}
+
+func NewTCP(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewRemoteDialer(ctx, options)
+	if err != nil {
+		return nil, err
+	}
+	serverAddr := options.ServerOptions.Build()
+	if serverAddr.Port == 0 {
+		serverAddr.Port = 53
+	}
+	return &TCPTransport{
+		TransportAdapter: dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeTCP, tag, options),
+		dialer:           transportDialer,
+		serverAddr:       serverAddr,
+	}, nil
+}
+
+func (t *TCPTransport) Reset() {
+}
+
+func (t *TCPTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	conn, err := t.dialer.DialContext(ctx, N.NetworkTCP, t.serverAddr)
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Close()
+	err = WriteMessage(conn, 0, message)
+	if err != nil {
+		return nil, err
+	}
+	return ReadMessage(conn)
+}
+
+func ReadMessage(reader io.Reader) (*mDNS.Msg, error) {
+	var responseLen uint16
+	err := binary.Read(reader, binary.BigEndian, &responseLen)
+	if err != nil {
+		return nil, err
+	}
+	if responseLen < 10 {
+		return nil, mDNS.ErrShortRead
+	}
+	buffer := buf.NewSize(int(responseLen))
+	defer buffer.Release()
+	_, err = buffer.ReadFullFrom(reader, int(responseLen))
+	if err != nil {
+		return nil, err
+	}
+	var message mDNS.Msg
+	err = message.Unpack(buffer.Bytes())
+	return &message, err
+}
+
+func WriteMessage(writer io.Writer, messageId uint16, message *mDNS.Msg) error {
+	requestLen := message.Len()
+	buffer := buf.NewSize(3 + requestLen)
+	defer buffer.Release()
+	common.Must(binary.Write(buffer, binary.BigEndian, uint16(requestLen)))
+	exMessage := *message
+	exMessage.Id = messageId
+	exMessage.Compress = true
+	rawMessage, err := exMessage.PackBuffer(buffer.FreeBytes())
+	if err != nil {
+		return err
+	}
+	buffer.Truncate(2 + len(rawMessage))
+	return common.Error(writer.Write(buffer.Bytes()))
+}