fix tproxy udp "unable to get destination" in IPv6 environment

transport/internet/sockopt_linux.go

@@ -3,6 +3,7 @@ package internet
 import (
 	"net"
 	"syscall"
+
 	"golang.org/x/sys/unix"
 )
 
@@ -99,10 +100,12 @@ func applyInboundSocketOptions(network string, fd uintptr, config *SocketConfig)
 	}
 
 	if config.ReceiveOriginalDestAddress && isUDPSocket(network) {
+		if err := syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, unix.IPV6_RECVORIGDSTADDR, 1); err != nil {
 			if err := syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_RECVORIGDSTADDR, 1); err != nil {
 				return err
 			}
 		}
+	}
 
 	if err := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, unix.SO_REUSEPORT, 1); err != nil {
 		return newError("failed to set SO_REUSEPORT").Base(err).AtWarning()

transport/internet/udp/hub_linux.go

@@ -5,6 +5,7 @@ package udp
 import (
 	"syscall"
 
+	"golang.org/x/sys/unix"
 	"v2ray.com/core/common/net"
 )
 
@@ -18,7 +19,7 @@ func RetrieveOriginalDest(oob []byte) net.Destination {
 			ip := net.IPAddress(msg.Data[4:8])
 			port := net.PortFromBytes(msg.Data[2:4])
 			return net.UDPDestination(ip, port)
-		} else if msg.Header.Level == syscall.SOL_IPV6 && msg.Header.Type == syscall.IP_RECVORIGDSTADDR {
+		} else if msg.Header.Level == syscall.SOL_IPV6 && msg.Header.Type == unix.IPV6_RECVORIGDSTADDR {
 			ip := net.IPAddress(msg.Data[8:24])
 			port := net.PortFromBytes(msg.Data[2:4])
 			return net.UDPDestination(ip, port)