flow_dissector: add support for ingress ifindex dissection

Add new key meta that contains ingress ifindex value and add a function
to dissect this from skb. The key and function is prepared to cover
other potential skb metadata values dissection.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 28bdaf9..b5d427b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1320,6 +1320,10 @@ skb_flow_dissect_flow_keys_basic(const struct net *net,
 				  data, proto, nhoff, hlen, flags);
 }
 
+void skb_flow_dissect_meta(const struct sk_buff *skb,
+			   struct flow_dissector *flow_dissector,
+			   void *target_container);
+
 void
 skb_flow_dissect_tunnel_info(const struct sk_buff *skb,
 			     struct flow_dissector *flow_dissector,