1 files changed, 12 insertions, 6 deletions
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 53cb6694f..13b42d34b 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -71,22 +71,24 @@ type Route struct {
 // ownership of the provided local address.
 //
 // Returns an empty route if validation fails.
-func constructAndValidateRoute(netProto tcpip.NetworkProtocolNumber, addressEndpoint AssignableAddressEndpoint, localAddressNIC, outgoingNIC *NIC, gateway, remoteAddr tcpip.Address, handleLocal, multicastLoop bool) Route {
-	addrWithPrefix := addressEndpoint.AddressWithPrefix()
+func constructAndValidateRoute(netProto tcpip.NetworkProtocolNumber, addressEndpoint AssignableAddressEndpoint, localAddressNIC, outgoingNIC *NIC, gateway, localAddr, remoteAddr tcpip.Address, handleLocal, multicastLoop bool) Route {
+	if len(localAddr) == 0 {
+		localAddr = addressEndpoint.AddressWithPrefix().Address
+	}
 
-	if localAddressNIC != outgoingNIC && header.IsV6LinkLocalAddress(addrWithPrefix.Address) {
+	if localAddressNIC != outgoingNIC && header.IsV6LinkLocalAddress(localAddr) {
 		addressEndpoint.DecRef()
 		return Route{}
 	}
 
 	// If no remote address is provided, use the local address.
 	if len(remoteAddr) == 0 {
-		remoteAddr = addrWithPrefix.Address
+		remoteAddr = localAddr
 	}
 
 	r := makeRoute(
 		netProto,
-		addrWithPrefix.Address,
+		localAddr,
 		remoteAddr,
 		outgoingNIC,
 		localAddressNIC,
@@ -99,7 +101,7 @@ func constructAndValidateRoute(netProto tcpip.NetworkProtocolNumber, addressEndp
 	// broadcast it.
 	if len(gateway) > 0 {
 		r.NextHop = gateway
-	} else if subnet := addrWithPrefix.Subnet(); subnet.IsBroadcast(remoteAddr) {
+	} else if subnet := addressEndpoint.Subnet(); subnet.IsBroadcast(remoteAddr) {
 		r.RemoteLinkAddress = header.EthernetBroadcastAddress
 	}
 
@@ -113,6 +115,10 @@ func makeRoute(netProto tcpip.NetworkProtocolNumber, localAddr, remoteAddr tcpip
 		panic(fmt.Sprintf("cannot create a route with NICs from different stacks"))
 	}
 
+	if len(localAddr) == 0 {
+		localAddr = localAddressEndpoint.AddressWithPrefix().Address
+	}
+
 	loop := PacketOut
 
 	// TODO(gvisor.dev/issue/4689): Loopback interface loops back packets at the