net: bridge: add option to allow activity notifications for any fdb entries

This patch adds the ability to notify about activity of any entries
(static, permanent or ext_learn). EVPN multihoming peers need it to
properly and efficiently handle mac sync (peer active/locally active).
We add a new NFEA_ACTIVITY_NOTIFY attribute which is used to dump the
current activity state and to control if static entries should be monitored
at all. We use 2 bits - one to activate fdb entry tracking (disabled by
default) and the second to denote that an entry is inactive. We need
the second bit in order to avoid multiple notifications of inactivity.
Obviously this makes no difference for dynamic entries since at the time
of inactivity they get deleted, while the tracked non-dynamic entries get
the inactive bit set and get a notification.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_private.h

@@ -48,6 +48,8 @@ enum {
 /* Path to usermode spanning tree program */
 #define BR_STP_PROG	"/sbin/bridge-stp"
 
+#define BR_FDB_NOTIFY_SETTABLE_BITS (FDB_NOTIFY_BIT | FDB_NOTIFY_INACTIVE_BIT)
+
 typedef struct bridge_id bridge_id;
 typedef struct mac_addr mac_addr;
 typedef __u16 port_id;
@@ -184,6 +186,8 @@ enum {
 	BR_FDB_ADDED_BY_USER,
 	BR_FDB_ADDED_BY_EXT_LEARN,
 	BR_FDB_OFFLOADED,
+	BR_FDB_NOTIFY,
+	BR_FDB_NOTIFY_INACTIVE
 };
 
 struct net_bridge_fdb_key {