fix: tproxy start error

listener/tproxy/setsockopt_linux.go

@@ -36,13 +36,21 @@ func setsockopt(rc syscall.RawConn, addr string) error {
 		}
 
 		if err == nil {
-			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_RECVTOS, 1)
-		}
-
-		if err == nil {
-			err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, syscall.IPV6_RECVTCLASS, 1)
+			_ = setDSCPsockopt(fd, isIPv6)
 		}
 	})
 
 	return err
 }
+
+func setDSCPsockopt(fd uintptr, isIPv6 bool) (err error) {
+	if err == nil {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_RECVTOS, 1)
+	}
+
+	if err == nil && isIPv6 {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, syscall.IPV6_RECVTCLASS, 1)
+	}
+
+	return
+}

listener/tproxy/udp_linux.go

@@ -104,7 +104,14 @@ func getOrigDst(oob []byte) (netip.AddrPort, error) {
 	}
 
 	// retrieve the destination address from the SCM.
-	sa, err := unix.ParseOrigDstAddr(&scms[1])
+	var sa unix.Sockaddr
+	for i := range scms {
+		sa, err = unix.ParseOrigDstAddr(&scms[i])
+		if err == nil {
+			break
+		}
+	}
+
 	if err != nil {
 		return netip.AddrPort{}, fmt.Errorf("retrieve destination: %w", err)
 	}
@@ -123,12 +130,19 @@ func getOrigDst(oob []byte) (netip.AddrPort, error) {
 	return rAddr, nil
 }
 
-func getDSCP (oob []byte) (uint8, error) {
+func getDSCP(oob []byte) (uint8, error) {
 	scms, err := unix.ParseSocketControlMessage(oob)
 	if err != nil {
 		return 0, fmt.Errorf("parse control message: %w", err)
 	}
-	dscp, err := parseDSCP(&scms[0])
+	var dscp uint8
+	for i := range scms {
+		dscp, err = parseDSCP(&scms[i])
+		if err == nil {
+			break
+		}
+	}
+
 	if err != nil {
 		return 0, fmt.Errorf("retrieve DSCP: %w", err)
 	}