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

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))
+}