flow_dissector: Dissect layer 2 miss from tc skb extension

Extend the 'FLOW_DISSECTOR_KEY_META' key with a new 'l2_miss' field and
populate it from a field with the same name in the tc skb extension.
This field is set by the bridge driver for packets that incur an FDB or
MDB miss.

The next patch will extend the flower classifier to be able to match on
layer 2 misses.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/flow_dissector.h

@@ -243,10 +243,12 @@ struct flow_dissector_key_ip {
  * struct flow_dissector_key_meta:
  * @ingress_ifindex: ingress ifindex
  * @ingress_iftype: ingress interface type
+ * @l2_miss: packet did not match an L2 entry during forwarding
  */
 struct flow_dissector_key_meta {
 	int ingress_ifindex;
 	u16 ingress_iftype;
+	u8 l2_miss;
 };
 
 /**

net/core/flow_dissector.c

@@ -27,6 +27,7 @@
 #include <linux/tcp.h>
 #include <linux/ptp_classify.h>
 #include <net/flow_dissector.h>
+#include <net/pkt_cls.h>
 #include <scsi/fc/fc_fcoe.h>
 #include <uapi/linux/batadv_packet.h>
 #include <linux/bpf.h>
@@ -241,6 +242,15 @@ void skb_flow_dissect_meta(const struct sk_buff *skb,
 					 FLOW_DISSECTOR_KEY_META,
 					 target_container);
 	meta->ingress_ifindex = skb->skb_iif;
+#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
+	if (tc_skb_ext_tc_enabled()) {
+		struct tc_skb_ext *ext;
+
+		ext = skb_ext_find(skb, TC_SKB_EXT);
+		if (ext)
+			meta->l2_miss = ext->l2_miss;
+	}
+#endif
 }
 EXPORT_SYMBOL(skb_flow_dissect_meta);