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>

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,

include/net/flow_dissector.h

@@ -200,6 +200,14 @@ struct flow_dissector_key_ip {
 	__u8	ttl;
 };
 
+/**
+ * struct flow_dissector_key_meta:
+ * @ingress_ifindex: ingress ifindex
+ */
+struct flow_dissector_key_meta {
+	int ingress_ifindex;
+};
+
 enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_CONTROL, /* struct flow_dissector_key_control */
 	FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */
@@ -225,6 +233,7 @@ enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_CVLAN, /* struct flow_dissector_key_vlan */
 	FLOW_DISSECTOR_KEY_ENC_IP, /* struct flow_dissector_key_ip */
 	FLOW_DISSECTOR_KEY_ENC_OPTS, /* struct flow_dissector_key_enc_opts */
+	FLOW_DISSECTOR_KEY_META, /* struct flow_dissector_key_meta */
 
 	FLOW_DISSECTOR_KEY_MAX,
 };

net/core/flow_dissector.c

@@ -199,6 +199,22 @@ __be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
 }
 EXPORT_SYMBOL(__skb_flow_get_ports);
 
+void skb_flow_dissect_meta(const struct sk_buff *skb,
+			   struct flow_dissector *flow_dissector,
+			   void *target_container)
+{
+	struct flow_dissector_key_meta *meta;
+
+	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_META))
+		return;
+
+	meta = skb_flow_dissector_target(flow_dissector,
+					 FLOW_DISSECTOR_KEY_META,
+					 target_container);
+	meta->ingress_ifindex = skb->skb_iif;
+}
+EXPORT_SYMBOL(skb_flow_dissect_meta);
+
 static void
 skb_flow_dissect_set_enc_addr_type(enum flow_dissector_key_id type,
 				   struct flow_dissector *flow_dissector,