Add TLS record fragment support

common/tlsfragment/conn.go

@@ -1,7 +1,9 @@
 package tf
 
 import (
+	"bytes"
 	"context"
+	"encoding/binary"
 	"math/rand"
 	"net"
 	"strings"
@@ -17,17 +19,19 @@ type Conn struct {
 	tcpConn            *net.TCPConn
 	ctx                context.Context
 	firstPacketWritten bool
+	splitRecord        bool
 	fallbackDelay      time.Duration
 }
 
-func NewConn(conn net.Conn, ctx context.Context, fallbackDelay time.Duration) (*Conn, error) {
+func NewConn(conn net.Conn, ctx context.Context, splitRecord bool, fallbackDelay time.Duration) *Conn {
 	tcpConn, _ := N.UnwrapReader(conn).(*net.TCPConn)
 	return &Conn{
 		Conn:          conn,
 		tcpConn:       tcpConn,
 		ctx:           ctx,
+		splitRecord:   splitRecord,
 		fallbackDelay: fallbackDelay,
-	}, nil
+	}
 }
 
 func (c *Conn) Write(b []byte) (n int, err error) {
@@ -37,10 +41,12 @@ func (c *Conn) Write(b []byte) (n int, err error) {
 		}()
 		serverName := indexTLSServerName(b)
 		if serverName != nil {
-			if c.tcpConn != nil {
-				err = c.tcpConn.SetNoDelay(true)
-				if err != nil {
-					return
+			if !c.splitRecord {
+				if c.tcpConn != nil {
+					err = c.tcpConn.SetNoDelay(true)
+					if err != nil {
+						return
+					}
 				}
 			}
 			splits := strings.Split(serverName.ServerName, ".")
@@ -61,16 +67,25 @@ func (c *Conn) Write(b []byte) (n int, err error) {
 					currentIndex++
 				}
 			}
+			var buffer bytes.Buffer
 			for i := 0; i <= len(splitIndexes); i++ {
 				var payload []byte
 				if i == 0 {
 					payload = b[:splitIndexes[i]]
+					if c.splitRecord {
+						payload = payload[recordLayerHeaderLen:]
+					}
 				} else if i == len(splitIndexes) {
 					payload = b[splitIndexes[i-1]:]
 				} else {
 					payload = b[splitIndexes[i-1]:splitIndexes[i]]
 				}
-				if c.tcpConn != nil && i != len(splitIndexes) {
+				if c.splitRecord {
+					payloadLen := uint16(len(payload))
+					buffer.Write(b[:3])
+					binary.Write(&buffer, binary.BigEndian, payloadLen)
+					buffer.Write(payload)
+				} else if c.tcpConn != nil && i != len(splitIndexes) {
 					err = writeAndWaitAck(c.ctx, c.tcpConn, payload, c.fallbackDelay)
 					if err != nil {
 						return
@@ -82,11 +97,18 @@ func (c *Conn) Write(b []byte) (n int, err error) {
 					}
 				}
 			}
-			if c.tcpConn != nil {
-				err = c.tcpConn.SetNoDelay(false)
+			if c.splitRecord {
+				_, err = c.tcpConn.Write(buffer.Bytes())
 				if err != nil {
 					return
 				}
+			} else {
+				if c.tcpConn != nil {
+					err = c.tcpConn.SetNoDelay(false)
+					if err != nil {
+						return
+					}
+				}
 			}
 			return len(b), nil
 		}

common/tlsfragment/conn_test.go

@@ -0,0 +1,32 @@
+package tf_test
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+	"testing"
+
+	tf "github.com/sagernet/sing-box/common/tlsfragment"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestTLSFragment(t *testing.T) {
+	t.Parallel()
+	tcpConn, err := net.Dial("tcp", "1.1.1.1:443")
+	require.NoError(t, err)
+	tlsConn := tls.Client(tf.NewConn(tcpConn, context.Background(), false, 0), &tls.Config{
+		ServerName: "www.cloudflare.com",
+	})
+	require.NoError(t, tlsConn.Handshake())
+}
+
+func TestTLSRecordFragment(t *testing.T) {
+	t.Parallel()
+	tcpConn, err := net.Dial("tcp", "1.1.1.1:443")
+	require.NoError(t, err)
+	tlsConn := tls.Client(tf.NewConn(tcpConn, context.Background(), true, 0), &tls.Config{
+		ServerName: "www.cloudflare.com",
+	})
+	require.NoError(t, tlsConn.Handshake())
+}