Re: [PATCH v3 net] net: bridge: switchdev: Skip MDB replays of pending events

[Tobias Waldekranz <tobias@waldekranz.com>]

On tor, feb 01, 2024 at 17:24, Jiri Pirko <jiri@resnulli.us> wrote:
> Thu, Feb 01, 2024 at 05:10:45PM CET, tobias@waldekranz.com wrote:
>>Before this change, generation of the list of events MDB to replay
>>would race against the IGMP/MLD snooping logic, which could concurrently
>>enqueue events to the switchdev deferred queue, leading to duplicate
>>events being sent to drivers. As a consequence of this, drivers which
>>reference count memberships (at least DSA), would be left with orphan
>>groups in their hardware database when the bridge was destroyed.
>>
>>Avoid this by grabbing the write-side lock of the MDB while generating
>>the replay list, making sure that no deferred version of a replay
>>event is already enqueued to the switchdev deferred queue, before
>>adding it to the replay list.
>>
>>An easy way to reproduce this issue, on an mv88e6xxx system, was to
>>create a snooping bridge, and immediately add a port to it:
>>
>>    root@infix-06-0b-00:~$ ip link add dev br0 up type bridge mcast_snooping 1 && \
>>    > ip link set dev x3 up master br0
>>    root@infix-06-0b-00:~$ ip link del dev br0
>>    root@infix-06-0b-00:~$ mvls atu
>>    ADDRESS             FID  STATE      Q  F  0  1  2  3  4  5  6  7  8  9  a
>>    DEV:0 Marvell 88E6393X
>>    33:33:00:00:00:6a     1  static     -  -  0  .  .  .  .  .  .  .  .  .  .
>>    33:33:ff:87:e4:3f     1  static     -  -  0  .  .  .  .  .  .  .  .  .  .
>>    ff:ff:ff:ff:ff:ff     1  static     -  -  0  1  2  3  4  5  6  7  8  9  a
>>    root@infix-06-0b-00:~$
>>
>>The two IPv6 groups remain in the hardware database because the
>>port (x3) is notified of the host's membership twice: once via the
>>original event and once via a replay. Since only a single delete
>>notification is sent, the count remains at 1 when the bridge is
>>destroyed.
>>
>>Fixes: 4f2673b3a2b6 ("net: bridge: add helper to replay port and host-joined mdb entries")
>>Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
>
> Could you please maintain 24 hours period between sending another patch
> version?
>
> https://www.kernel.org/doc/html/v6.7/process/maintainer-netdev.html#tl-dr

Sorry, I will avoid that going forward.