From 350a65a36b479457622cc3608a76481191102bae Mon Sep 17 00:00:00 2001
From: gVisor bot <gvisor-bot@google.com>
Date: Thu, 31 Dec 2020 18:58:03 +0800
Subject: [PATCH] Fix: support unspecified UDP bind address (#1159)

---
 adapters/outbound/socks5.go | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/adapters/outbound/socks5.go b/adapters/outbound/socks5.go
index 78a59468..eb65d513 100644
--- a/adapters/outbound/socks5.go
+++ b/adapters/outbound/socks5.go
@@ -122,7 +122,21 @@ func (ss *Socks5) DialUDP(metadata *C.Metadata) (_ C.PacketConn, err error) {
 		pc.Close()
 	}()
 
-	return newPacketConn(&socksPacketConn{PacketConn: pc, rAddr: bindAddr.UDPAddr(), tcpConn: c}, ss), nil
+	// Support unspecified UDP bind address.
+	bindUDPAddr := bindAddr.UDPAddr()
+	if bindUDPAddr == nil {
+		err = errors.New("invalid UDP bind address")
+		return
+	} else if bindUDPAddr.IP.IsUnspecified() {
+		serverAddr, err := resolveUDPAddr("udp", ss.Addr())
+		if err != nil {
+			return nil, err
+		}
+
+		bindUDPAddr.IP = serverAddr.IP
+	}
+
+	return newPacketConn(&socksPacketConn{PacketConn: pc, rAddr: bindUDPAddr, tcpConn: c}, ss), nil
 }
 
 func NewSocks5(option Socks5Option) *Socks5 {