feat: introduce a new robust approach to handle tproxy udp. (#389)

listener/shadowsocks/utils.go

@@ -7,6 +7,7 @@ import (
 	"net/url"
 
 	"github.com/Dreamacro/clash/common/pool"
+	C "github.com/Dreamacro/clash/constant"
 	"github.com/Dreamacro/clash/transport/socks5"
 )
 
@@ -44,6 +45,13 @@ func (c *packet) InAddr() net.Addr {
 	return c.pc.LocalAddr()
 }
 
+func (c *packet) SetNatTable(natTable C.NatTable) {
+	// no need
+}
+
+func (c *packet) SetUdpInChan(in chan<- C.PacketAdapter) {
+	// no need
+}
 func ParseSSURL(s string) (addr, cipher, password string, err error) {
 	u, err := url.Parse(s)
 	if err != nil {

listener/sing/sing.go

@@ -166,3 +166,11 @@ func (c *packet) Drop() {
 func (c *packet) InAddr() net.Addr {
 	return c.lAddr
 }
+
+func (c *packet) SetNatTable(natTable C.NatTable) {
+	// no need
+}
+
+func (c *packet) SetUdpInChan(in chan<- C.PacketAdapter) {
+	// no need
+}

listener/socks/utils.go

@@ -4,6 +4,7 @@ import (
 	"net"
 
 	"github.com/Dreamacro/clash/common/pool"
+	C "github.com/Dreamacro/clash/constant"
 	"github.com/Dreamacro/clash/transport/socks5"
 )
 
@@ -39,3 +40,11 @@ func (c *packet) Drop() {
 func (c *packet) InAddr() net.Addr {
 	return c.pc.LocalAddr()
 }
+
+func (c *packet) SetNatTable(natTable C.NatTable) {
+	// no need
+}
+
+func (c *packet) SetUdpInChan(in chan<- C.PacketAdapter) {
+	// no need
+}

listener/tproxy/packet.go

@@ -1,16 +1,22 @@
 package tproxy
 
 import (
+	"errors"
+	"fmt"
+	"github.com/Dreamacro/clash/adapter/inbound"
+	"github.com/Dreamacro/clash/common/pool"
+	C "github.com/Dreamacro/clash/constant"
+	"github.com/Dreamacro/clash/log"
 	"net"
 	"net/netip"
-
-	"github.com/Dreamacro/clash/common/pool"
 )
 
 type packet struct {
-	pc    net.PacketConn
-	lAddr netip.AddrPort
-	buf   []byte
+	pc       net.PacketConn
+	lAddr    netip.AddrPort
+	buf      []byte
+	natTable C.NatTable
+	in       chan<- C.PacketAdapter
 }
 
 func (c *packet) Data() []byte {
@@ -19,13 +25,12 @@ func (c *packet) Data() []byte {
 
 // WriteBack opens a new socket binding `addr` to write UDP packet back
 func (c *packet) WriteBack(b []byte, addr net.Addr) (n int, err error) {
-	tc, err := dialUDP("udp", addr.(*net.UDPAddr).AddrPort(), c.lAddr)
+	tc, err := createOrGetLocalConn(addr, c.LocalAddr(), c.natTable, c.in)
 	if err != nil {
 		n = 0
 		return
 	}
 	n, err = tc.Write(b)
-	tc.Close()
 	return
 }
 
@@ -41,3 +46,82 @@ func (c *packet) Drop() {
 func (c *packet) InAddr() net.Addr {
 	return c.pc.LocalAddr()
 }
+
+func (c *packet) SetNatTable(natTable C.NatTable) {
+	c.natTable = natTable
+}
+
+func (c *packet) SetUdpInChan(in chan<- C.PacketAdapter) {
+	c.in = in
+}
+
+// this function listen at rAddr and write to lAddr
+// for here, rAddr is the ip/port client want to access
+// lAddr is the ip/port client opened
+func createOrGetLocalConn(rAddr, lAddr net.Addr, natTable C.NatTable, in chan<- C.PacketAdapter) (*net.UDPConn, error) {
+	remote := rAddr.String()
+	local := lAddr.String()
+	localConn := natTable.GetLocalConn(local, remote)
+	// localConn not exist
+	if localConn == nil {
+		lockKey := remote + "-lock"
+		cond, loaded := natTable.GetOrCreateLockForLocalConn(local, lockKey)
+		if loaded {
+			cond.L.Lock()
+			cond.Wait()
+			// we should get localConn here
+			localConn = natTable.GetLocalConn(local, remote)
+			if localConn == nil {
+				return nil, fmt.Errorf("localConn is nil, nat entry not exist")
+			}
+			cond.L.Unlock()
+		} else {
+			if cond == nil {
+				return nil, fmt.Errorf("cond is nil, nat entry not exist")
+			}
+			defer func() {
+				natTable.DeleteLocalConnMap(local, lockKey)
+				cond.Broadcast()
+			}()
+			conn, err := listenLocalConn(rAddr, lAddr, in)
+			if err != nil {
+				log.Errorln("listenLocalConn failed with error: %s, packet loss", err.Error())
+				return nil, err
+			}
+			natTable.AddLocalConn(local, remote, conn)
+			localConn = conn
+		}
+	}
+	return localConn, nil
+}
+
+// this function listen at rAddr
+// and send what received to program itself, then send to real remote
+func listenLocalConn(rAddr, lAddr net.Addr, in chan<- C.PacketAdapter) (*net.UDPConn, error) {
+	additions := []inbound.Addition{
+		inbound.WithInName("DEFAULT-TPROXY"),
+		inbound.WithSpecialRules(""),
+	}
+	lc, err := dialUDP("udp", rAddr.(*net.UDPAddr).AddrPort(), lAddr.(*net.UDPAddr).AddrPort())
+	if err != nil {
+		return nil, err
+	}
+	go func() {
+		log.Debugln("TProxy listenLocalConn rAddr=%s lAddr=%s", rAddr.String(), lAddr.String())
+		for {
+			buf := pool.Get(pool.UDPBufferSize)
+			br, err := lc.Read(buf)
+			if err != nil {
+				pool.Put(buf)
+				if errors.Is(err, net.ErrClosed) {
+					log.Debugln("TProxy local conn listener exit.. rAddr=%s lAddr=%s", rAddr.String(), lAddr.String())
+					return
+				}
+			}
+			// since following localPackets are pass through this socket which listen rAddr
+			// I choose current listener as packet's packet conn
+			handlePacketConn(lc, in, buf[:br], lAddr.(*net.UDPAddr).AddrPort(), rAddr.(*net.UDPAddr).AddrPort(), additions...)
+		}
+	}()
+	return lc, nil
+}

listener/tunnel/packet.go

@@ -4,6 +4,7 @@ import (
 	"net"
 
 	"github.com/Dreamacro/clash/common/pool"
+	C "github.com/Dreamacro/clash/constant"
 )
 
 type packet struct {
@@ -33,3 +34,11 @@ func (c *packet) Drop() {
 func (c *packet) InAddr() net.Addr {
 	return c.pc.LocalAddr()
 }
+
+func (c *packet) SetNatTable(natTable C.NatTable) {
+	// no need
+}
+
+func (c *packet) SetUdpInChan(in chan<- C.PacketAdapter) {
+	// no need
+}