From b2630955339a7d25437a59b6f5ce37b99f65d2ab Mon Sep 17 00:00:00 2001
From: duama <30264485+duament@users.noreply.github.com>
Date: Tue, 10 Mar 2020 20:36:24 +0800
Subject: [PATCH] Fix: TPROXY fakeip (#572)

---
 proxy/redir/udp.go   | 15 ++++++---------
 proxy/redir/utils.go | 11 +++++------
 tunnel/connection.go |  6 +++++-
 tunnel/tunnel.go     |  8 +++++++-
 4 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/proxy/redir/udp.go b/proxy/redir/udp.go
index 83506d86..89209aa9 100644
--- a/proxy/redir/udp.go
+++ b/proxy/redir/udp.go
@@ -35,8 +35,7 @@ func NewRedirUDPProxy(addr string) (*RedirUDPListener, error) {
 		oob := make([]byte, 1024)
 		for {
 			buf := pool.BufPool.Get().([]byte)
-
-			n, oobn, _, remoteAddr, err := c.ReadMsgUDP(buf, oob)
+			n, oobn, _, lAddr, err := c.ReadMsgUDP(buf, oob)
 			if err != nil {
 				pool.BufPool.Put(buf[:cap(buf)])
 				if rl.closed {
@@ -45,11 +44,11 @@ func NewRedirUDPProxy(addr string) (*RedirUDPListener, error) {
 				continue
 			}
 
-			origDst, err := getOrigDst(oob, oobn)
+			rAddr, err := getOrigDst(oob, oobn)
 			if err != nil {
 				continue
 			}
-			handleRedirUDP(l, buf[:n], remoteAddr, origDst)
+			handleRedirUDP(l, buf[:n], lAddr, rAddr)
 		}
 	}()
 
@@ -65,13 +64,11 @@ 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)
-
+func handleRedirUDP(pc net.PacketConn, buf []byte, lAddr *net.UDPAddr, rAddr *net.UDPAddr) {
+	target := socks5.ParseAddrToSocksAddr(rAddr)
 	packet := &fakeConn{
 		PacketConn: pc,
-		origDst:    origDst,
-		rAddr:      addr,
+		lAddr:      lAddr,
 		buf:        buf,
 	}
 	tunnel.AddPacket(adapters.NewPacket(target, packet, C.REDIR))
diff --git a/proxy/redir/utils.go b/proxy/redir/utils.go
index 71756d4d..f6a60d46 100644
--- a/proxy/redir/utils.go
+++ b/proxy/redir/utils.go
@@ -8,18 +8,17 @@ import (
 
 type fakeConn struct {
 	net.PacketConn
-	origDst net.Addr
-	rAddr   net.Addr
-	buf     []byte
+	lAddr *net.UDPAddr
+	buf   []byte
 }
 
 func (c *fakeConn) Data() []byte {
 	return c.buf
 }
 
-// WriteBack opens a new socket binding `origDst` to wirte UDP packet back
+// WriteBack opens a new socket binding `addr` 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))
+	tc, err := dialUDP("udp", addr.(*net.UDPAddr), c.lAddr)
 	if err != nil {
 		n = 0
 		return
@@ -31,7 +30,7 @@ func (c *fakeConn) WriteBack(b []byte, addr net.Addr) (n int, err error) {
 
 // LocalAddr returns the source IP/Port of UDP Packet
 func (c *fakeConn) LocalAddr() net.Addr {
-	return c.rAddr
+	return c.lAddr
 }
 
 func (c *fakeConn) Close() error {
diff --git a/tunnel/connection.go b/tunnel/connection.go
index b1d9978c..9553ed73 100644
--- a/tunnel/connection.go
+++ b/tunnel/connection.go
@@ -88,7 +88,7 @@ func handleUDPToRemote(packet C.UDPPacket, pc C.PacketConn, metadata *C.Metadata
 	DefaultManager.Upload() <- int64(len(packet.Data()))
 }
 
-func handleUDPToLocal(packet C.UDPPacket, pc net.PacketConn, key string) {
+func handleUDPToLocal(packet C.UDPPacket, pc net.PacketConn, key string, fAddr net.Addr) {
 	buf := pool.BufPool.Get().([]byte)
 	defer pool.BufPool.Put(buf[:cap(buf)])
 	defer natTable.Delete(key)
@@ -101,6 +101,10 @@ func handleUDPToLocal(packet C.UDPPacket, pc net.PacketConn, key string) {
 			return
 		}
 
+		if fAddr != nil {
+			from = fAddr
+		}
+
 		n, err = packet.WriteBack(buf[:n], from)
 		if err != nil {
 			return
diff --git a/tunnel/tunnel.go b/tunnel/tunnel.go
index b35688aa..7dbb61e0 100644
--- a/tunnel/tunnel.go
+++ b/tunnel/tunnel.go
@@ -182,6 +182,12 @@ func handleUDPConn(packet *inbound.PacketAdapter) {
 		return
 	}
 
+	// make a fAddr if requset ip is fakeip
+	var fAddr net.Addr
+	if enhancedMode != nil && enhancedMode.IsFakeIP(metadata.DstIP) {
+		fAddr = metadata.UDPAddr()
+	}
+
 	if err := preHandleMetadata(metadata); err != nil {
 		log.Debugln("[Metadata PreHandle] error: %s", err)
 		return
@@ -231,7 +237,7 @@ func handleUDPConn(packet *inbound.PacketAdapter) {
 			natTable.Set(key, pc)
 			natTable.Delete(lockKey)
 			wg.Done()
-			go handleUDPToLocal(packet.UDPPacket, pc, key)
+			go handleUDPToLocal(packet.UDPPacket, pc, key, fAddr)
 		}
 
 		wg.Wait()