linux-kernel - [PATCH net-next v02 0/2] net: af_packet: allow joining a fanout when link is down

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Message-ID: <cover.1728382839.git.gur.stavi@huawei.com>
Date: Tue, 8 Oct 2024 13:27:57 +0300
From: Gur Stavi <gur.stavi@...wei.com>
To: Gur Stavi <gur.stavi@...wei.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Shuah Khan
	<shuah@...nel.org>, Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	<linux-kselftest@...r.kernel.org>
Subject: [PATCH net-next v02 0/2] net: af_packet: allow joining a fanout when link is down

PACKET socket can retain its fanout membership through link down and up
and leave a fanout while closed regardless of link state.
However, socket was forbidden from joining a fanout while it was not
RUNNING.

This patch allows PACKET socket to join a fanout while not RUNNING.
Selftest psock_fanout is extended to test this scenario.
This is the only test that was performed.

This scenario was identified while studying DPDK pmd_af_packet_drv.
Since sockets are only created during initialization, there is no reason
to fail the initialization if a single link is temporarily down.

I hope it is not considered as breaking user space and that applications
are not designed to expect this failure.

Changes:

V02:
* psock_fanout: use explicit loopback up/down instead of toggle.
* psock_fanout: don't try to restore loopback state on failure.
* Rephrase commit message about "leaving a fanout".

V01: https://lore.kernel.org/netdev/cover.1728303615.git.gur.stavi@huawei.com/

Gur Stavi (2):
  af_packet: allow fanout_add when socket is not RUNNING
  selftests: net/psock_fanout: socket joins fanout when link is down

 net/packet/af_packet.c                     | 10 +++---
 tools/testing/selftests/net/psock_fanout.c | 42 ++++++++++++++++++++--
 2 files changed, 44 insertions(+), 8 deletions(-)

base-commit: f95b4725e796b12e5f347a0d161e1d3843142aa8
-- 
2.45.2