route: Per route IP tunnel metadata via lightweight tunnel

This introduces a new IP tunnel lightweight tunnel type which allows
to specify IP tunnel instructions per route. Only IPv4 is supported
at this point.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 91da18b..519ec23 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1693,7 +1693,7 @@
 	   by fib_lookup.
 	 */
 
-	tun_info = skb_tunnel_info(skb);
+	tun_info = skb_tunnel_info(skb, AF_INET);
 	if (tun_info && tun_info->mode == IP_TUNNEL_INFO_RX)
 		fl4.flowi4_tun_key.tun_id = tun_info->key.tun_id;
 	else