selftests: net: udpgso_bench_tx: Cater for pending datagrams zerocopy benchmarking

stable inclusion
from stable-v5.10.168
commit 812236bb6a89f1a00ac29e6a78033e8ad9f6e73c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7URR4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=812236bb6a89f1a00ac29e6a78033e8ad9f6e73c



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[ Upstream commit 329c9cd7 ]

The test tool can check that the zerocopy number of completions value is
valid taking into consideration the number of datagram send calls. This can
catch the system into a state where the datagrams are still in the system
(for example in a qdisk, waiting for the network interface to return a
completion notification, etc).

This change adds a retry logic of computing the number of completions up to
a configurable (via CLI) timeout (default: 2 seconds).

Fixes: 79ebc3c2 ("net/udpgso_bench_tx: options to exercise TX CMSG")
Signed-off-by: Andrei Gherzan <andrei.gherzan@canonical.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20230201001612.515730-4-andrei.gherzan@canonical.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>