From da63981d96adcdfbe1602ca2282a317fd3a99a1f Mon Sep 17 00:00:00 2001
From: tobyxdd <tobyxdd@gmail.com>
Date: Sun, 11 Jun 2023 16:22:42 -0700
Subject: [PATCH] fix: socks5 udp listen addr when omitting address & udp
 domain

---
 app/socks5/server.go | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/app/socks5/server.go b/app/socks5/server.go
index a308f79..11cc7bc 100644
--- a/app/socks5/server.go
+++ b/app/socks5/server.go
@@ -254,9 +254,11 @@ func (s *Server) handleUDP(c *net.TCPConn, r *socks5.Request) error {
 		s.UDPErrorFunc(c.RemoteAddr(), closeErr)
 	}()
 	// Start local UDP server
+	// Bind to the same address that the incoming TCP connection is sending to
 	udpConn, err := net.ListenUDP("udp", &net.UDPAddr{
-		IP:   s.TCPAddr.IP,
-		Zone: s.TCPAddr.Zone,
+		IP:   c.LocalAddr().(*net.TCPAddr).IP,
+		Zone: c.LocalAddr().(*net.TCPAddr).Zone,
+		Port: 0, // Random port
 	})
 	if err != nil {
 		_ = sendReply(c, socks5.RepServerFailure)
@@ -348,6 +350,9 @@ func (s *Server) udpServer(clientConn, localRelayConn *net.UDPConn, hyUDP cs.HyU
 					if err != nil {
 						continue
 					}
+					if atyp == socks5.ATYPDomain {
+						addr = addr[1:] // Remove the leading length byte
+					}
 					d := socks5.NewDatagram(atyp, addr, port, bs)
 					_, _ = clientConn.WriteToUDP(d.Bytes(), clientAddr)
 				}
@@ -362,6 +367,9 @@ func (s *Server) udpServer(clientConn, localRelayConn *net.UDPConn, hyUDP cs.HyU
 							if err != nil {
 								continue
 							}
+							if atyp == socks5.ATYPDomain {
+								addr = addr[1:] // Remove the leading length byte
+							}
 							d := socks5.NewDatagram(atyp, addr, port, buf[:n])
 							_, _ = clientConn.WriteToUDP(d.Bytes(), clientAddr)
 						}