Feature: add UDP TPROXY support on Linux (#562)

proxy/listener.go

@@ -5,6 +5,7 @@ import (
 	"net"
 	"strconv"
 
+	"github.com/Dreamacro/clash/log"
 	"github.com/Dreamacro/clash/proxy/http"
 	"github.com/Dreamacro/clash/proxy/redir"
 	"github.com/Dreamacro/clash/proxy/socks"
@@ -18,6 +19,7 @@ var (
 	socksUDPListener *socks.SockUDPListener
 	httpListener     *http.HttpListener
 	redirListener    *redir.RedirListener
+	redirUDPListener *redir.RedirUDPListener
 )
 
 type listener interface {
@@ -131,6 +133,14 @@ func ReCreateRedir(port int) error {
 		redirListener = nil
 	}
 
+	if redirUDPListener != nil {
+		if redirUDPListener.Address() == addr {
+			return nil
+		}
+		redirUDPListener.Close()
+		redirUDPListener = nil
+	}
+
 	if portIsZero(addr) {
 		return nil
 	}
@@ -141,6 +151,11 @@ func ReCreateRedir(port int) error {
 		return err
 	}
 
+	redirUDPListener, err = redir.NewRedirUDPProxy(addr)
+	if err != nil {
+		log.Warnln("Failed to start Redir UDP Listener: %s", err)
+	}
+
 	return nil
 }
 

proxy/redir/udp.go

@@ -0,0 +1,78 @@
+package redir
+
+import (
+	"net"
+
+	adapters "github.com/Dreamacro/clash/adapters/inbound"
+	"github.com/Dreamacro/clash/common/pool"
+	"github.com/Dreamacro/clash/component/socks5"
+	C "github.com/Dreamacro/clash/constant"
+	"github.com/Dreamacro/clash/tunnel"
+)
+
+type RedirUDPListener struct {
+	net.PacketConn
+	address string
+	closed  bool
+}
+
+func NewRedirUDPProxy(addr string) (*RedirUDPListener, error) {
+	l, err := net.ListenPacket("udp", addr)
+	if err != nil {
+		return nil, err
+	}
+
+	rl := &RedirUDPListener{l, addr, false}
+
+	c := l.(*net.UDPConn)
+
+	err = setsockopt(c, addr)
+	if err != nil {
+		return nil, err
+	}
+
+	go func() {
+		oob := make([]byte, 1024)
+		for {
+			buf := pool.BufPool.Get().([]byte)
+
+			n, oobn, _, remoteAddr, err := c.ReadMsgUDP(buf, oob)
+			if err != nil {
+				pool.BufPool.Put(buf[:cap(buf)])
+				if rl.closed {
+					break
+				}
+				continue
+			}
+
+			origDst, err := getOrigDst(oob, oobn)
+			if err != nil {
+				continue
+			}
+			handleRedirUDP(l, buf[:n], remoteAddr, origDst)
+		}
+	}()
+
+	return rl, nil
+}
+
+func (l *RedirUDPListener) Close() error {
+	l.closed = true
+	return l.PacketConn.Close()
+}
+
+func (l *RedirUDPListener) Address() string {
+	return l.address
+}
+
+func handleRedirUDP(pc net.PacketConn, buf []byte, addr *net.UDPAddr, origDst *net.UDPAddr) {
+	target := socks5.ParseAddrToSocksAddr(origDst)
+
+	packet := &fakeConn{
+		PacketConn: pc,
+		origDst:    origDst,
+		rAddr:      addr,
+		buf:        buf,
+	}
+	tunnel.AddPacket(adapters.NewPacket(target, packet, C.REDIR))
+}

proxy/redir/udp_linux.go

@@ -0,0 +1,69 @@
+// +build linux
+
+package redir
+
+import (
+	"encoding/binary"
+	"errors"
+	"net"
+	"syscall"
+)
+
+const (
+	IPV6_TRANSPARENT     = 0x4b
+	IPV6_RECVORIGDSTADDR = 0x4a
+)
+
+func setsockopt(c *net.UDPConn, addr string) error {
+	isIPv6 := true
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return err
+	}
+	ip := net.ParseIP(host)
+	if ip != nil && ip.To4() != nil {
+		isIPv6 = false
+	}
+
+	rc, err := c.SyscallConn()
+	if err != nil {
+		return err
+	}
+
+	rc.Control(func(fd uintptr) {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_TRANSPARENT, 1)
+		if err == nil && isIPv6 {
+			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, IPV6_TRANSPARENT, 1)
+		}
+
+		if err == nil {
+			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_RECVORIGDSTADDR, 1)
+		}
+		if err == nil && isIPv6 {
+			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, IPV6_RECVORIGDSTADDR, 1)
+		}
+	})
+
+	return err
+}
+
+func getOrigDst(oob []byte, oobn int) (*net.UDPAddr, error) {
+	msgs, err := syscall.ParseSocketControlMessage(oob[:oobn])
+	if err != nil {
+		return nil, err
+	}
+
+	for _, msg := range msgs {
+		if msg.Header.Level == syscall.SOL_IP && msg.Header.Type == syscall.IP_RECVORIGDSTADDR {
+			ip := net.IP(msg.Data[4:8])
+			port := binary.BigEndian.Uint16(msg.Data[2:4])
+			return &net.UDPAddr{IP: ip, Port: int(port)}, nil
+		} else if msg.Header.Level == syscall.SOL_IPV6 && msg.Header.Type == IPV6_RECVORIGDSTADDR {
+			ip := net.IP(msg.Data[8:24])
+			port := binary.BigEndian.Uint16(msg.Data[2:4])
+			return &net.UDPAddr{IP: ip, Port: int(port)}, nil
+		}
+	}
+
+	return nil, errors.New("cannot find origDst")
+}

proxy/redir/udp_other.go

@@ -0,0 +1,16 @@
+// +build !linux
+
+package redir
+
+import (
+	"errors"
+	"net"
+)
+
+func setsockopt(c *net.UDPConn, addr string) error {
+	return errors.New("UDP redir not supported on current platform")
+}
+
+func getOrigDst(oob []byte, oobn int) (*net.UDPAddr, error) {
+	return nil, errors.New("UDP redir not supported on current platform")
+}

proxy/redir/utils.go

@@ -0,0 +1,41 @@
+package redir
+
+import (
+	"net"
+
+	"github.com/Dreamacro/clash/common/pool"
+)
+
+type fakeConn struct {
+	net.PacketConn
+	origDst net.Addr
+	rAddr   net.Addr
+	buf     []byte
+}
+
+func (c *fakeConn) Data() []byte {
+	return c.buf
+}
+
+// WriteBack opens a new socket binding `origDst` to wirte UDP packet back
+func (c *fakeConn) WriteBack(b []byte, addr net.Addr) (n int, err error) {
+	tc, err := dialUDP("udp", c.origDst.(*net.UDPAddr), c.rAddr.(*net.UDPAddr))
+	if err != nil {
+		n = 0
+		return
+	}
+	n, err = tc.Write(b)
+	tc.Close()
+	return
+}
+
+// LocalAddr returns the source IP/Port of UDP Packet
+func (c *fakeConn) LocalAddr() net.Addr {
+	return c.rAddr
+}
+
+func (c *fakeConn) Close() error {
+	err := c.PacketConn.Close()
+	pool.BufPool.Put(c.buf[:cap(c.buf)])
+	return err
+}

proxy/redir/utils_linux.go

@@ -0,0 +1,96 @@
+// +build linux
+
+package redir
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+	"syscall"
+)
+
+// dialUDP acts like net.DialUDP for transparent proxy.
+// It binds to a non-local address(`lAddr`).
+func dialUDP(network string, lAddr *net.UDPAddr, rAddr *net.UDPAddr) (*net.UDPConn, error) {
+	rSockAddr, err := udpAddrToSockAddr(rAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	lSockAddr, err := udpAddrToSockAddr(lAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	fd, err := syscall.Socket(udpAddrFamily(network, lAddr, rAddr), syscall.SOCK_DGRAM, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	if err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	if err = syscall.SetsockoptInt(fd, syscall.SOL_IP, syscall.IP_TRANSPARENT, 1); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	if err = syscall.Bind(fd, lSockAddr); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	if err = syscall.Connect(fd, rSockAddr); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	fdFile := os.NewFile(uintptr(fd), fmt.Sprintf("net-udp-dial-%s", rAddr.String()))
+	defer fdFile.Close()
+
+	c, err := net.FileConn(fdFile)
+	if err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	return c.(*net.UDPConn), nil
+}
+
+func udpAddrToSockAddr(addr *net.UDPAddr) (syscall.Sockaddr, error) {
+	switch {
+	case addr.IP.To4() != nil:
+		ip := [4]byte{}
+		copy(ip[:], addr.IP.To4())
+
+		return &syscall.SockaddrInet4{Addr: ip, Port: addr.Port}, nil
+
+	default:
+		ip := [16]byte{}
+		copy(ip[:], addr.IP.To16())
+
+		zoneID, err := strconv.ParseUint(addr.Zone, 10, 32)
+		if err != nil {
+			zoneID = 0
+		}
+
+		return &syscall.SockaddrInet6{Addr: ip, Port: addr.Port, ZoneId: uint32(zoneID)}, nil
+	}
+}
+
+func udpAddrFamily(net string, lAddr, rAddr *net.UDPAddr) int {
+	switch net[len(net)-1] {
+	case '4':
+		return syscall.AF_INET
+	case '6':
+		return syscall.AF_INET6
+	}
+
+	if (lAddr == nil || lAddr.IP.To4() != nil) && (rAddr == nil || lAddr.IP.To4() != nil) {
+		return syscall.AF_INET
+	}
+	return syscall.AF_INET6
+}

proxy/redir/utils_other.go

@@ -0,0 +1,12 @@
+// +build !linux
+
+package redir
+
+import (
+	"errors"
+	"net"
+)
+
+func dialUDP(network string, lAddr *net.UDPAddr, rAddr *net.UDPAddr) (*net.UDPConn, error) {
+	return nil, errors.New("UDP redir not supported on current platform")
+}