bridge: fdb: Add support for FDB activity notification control

bridge: fdb: Add support for FDB activity notification control

Add support for FDB activity notification control [1].

Users can use this to enable activity notifications on a new FDB entry
that was learned on an ES (Ethernet Segment) peer and mark it as locally
inactive:

 # bridge fdb add 00:11:22:33:44:55 dev bond1 master static activity_notify inactive
 $ bridge -d fdb get 00:11:22:33:44:55 br br1
 00:11:22:33:44:55 dev bond1 activity_notify inactive master br1 static
 $ bridge -d -j -p fdb get 00:11:22:33:44:55 br br1
 [ {
         "mac": "00:11:22:33:44:55",
         "ifname": "bond1",
         "activity_notify": true,
         "inactive": true,
         "flags": [ ],
         "master": "br1",
         "state": "static"
     } ]

User space will receive a notification when the entry becomes active and
the control plane will be able to mark the entry as locally active.

It is also possible to enable activity notifications on an existing
dynamic entry:

 $ bridge -d -s -j -p fdb get 00:aa:bb:cc:dd:ee br br1
 [ {
         "mac": "00:aa:bb:cc:dd:ee",
         "ifname": "bond1",
         "used": 8,
         "updated": 8,
         "flags": [ ],
         "master": "br1",
         "state": ""
     } ]
 # bridge fdb replace 00:aa:bb:cc:dd:ee dev bond1 master static activity_notify norefresh
 $ bridge -d -s -j -p fdb get 00:aa:bb:cc:dd:ee br br1
 [ {
         "mac": "00:aa:bb:cc:dd:ee",
         "ifname": "bond1",
         "activity_notify": true,
         "used": 3,
         "updated": 23,
         "flags": [ ],
         "master": "br1",
         "state": "static"
     } ]

The "norefresh" keyword is used to avoid resetting the entry's last
active time (i.e., "updated" time).

User space will receive a notification when the entry becomes inactive
and the control plane will be able to mark the entry as locally
inactive. Note that the entry was converted from a dynamic entry to a
static entry to prevent the kernel from automatically deleting it upon
inactivity.

An existing inactive entry can only be marked as active by the kernel or
by disabling and enabling activity notifications:

 $ bridge -d fdb get 00:11:22:33:44:55 br br1
 00:11:22:33:44:55 dev bond1 activity_notify inactive master br1 static
 # bridge fdb replace 00:11:22:33:44:55 dev bond1 master static activity_notify
 $ bridge -d fdb get 00:11:22:33:44:55 br br1
 00:11:22:33:44:55 dev bond1 activity_notify inactive master br1 static
 # bridge fdb replace 00:11:22:33:44:55 dev bond1 master static
 # bridge fdb replace 00:11:22:33:44:55 dev bond1 master static activity_notify
 $ bridge -d fdb get 00:11:22:33:44:55 br br1
 00:11:22:33:44:55 dev bond1 activity_notify master br1 static

Marking an entry as inactive while activity notifications are disabled
does not make sense and will be rejected by the kernel:

 # bridge fdb replace 00:11:22:33:44:55 dev bond1 master static inactive
 RTNETLINK answers: Invalid argument

[1] https://lore.kernel.org/netdev/20200623204718.1057508-1-nikolay@cumulusnetworks.com/

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David Ahern <dsahern@kernel.org>