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

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Message-ID: <ZbvFwVSQI1M_2WZo@nanopsycho>
Date: Thu, 1 Feb 2024 17:24:33 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Tobias Waldekranz <tobias@...dekranz.com>
Cc: davem@...emloft.net, kuba@...nel.org, olteanv@...il.com,
	atenart@...nel.org, roopa@...dia.com, razor@...ckwall.org,
	bridge@...ts.linux.dev, netdev@...r.kernel.org, ivecera@...hat.com
Subject: Re: [PATCH v3 net] net: bridge: switchdev: Skip MDB replays of
 pending events

Thu, Feb 01, 2024 at 05:10:45PM CET, tobias@...dekranz.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@...ix-06-0b-00:~$ ip link add dev br0 up type bridge mcast_snooping 1 && \
>    > ip link set dev x3 up master br0
>    root@...ix-06-0b-00:~$ ip link del dev br0
>    root@...ix-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@...ix-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@...dekranz.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