linux-kernel - Re: [PATCH v2 0/3] selftests/net: A couple of typos fixes in key-management/rst tests

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Message-ID: <44d893b4-10b0-4876-bbf7-f6a81940b300@arista.com>
Date: Thu, 1 Feb 2024 22:25:45 +0000
From: Dmitry Safonov <dima@...sta.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 Shuah Khan <shuah@...nel.org>, Dmitry Safonov <0x7f454c46@...il.com>,
 Mohammad Nassiri <mnassiri@...na.com>, Simon Horman <horms@...nel.org>,
 netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] selftests/net: A couple of typos fixes in
 key-management/rst tests

Hi Jakub,

On 2/1/24 21:21, Jakub Kicinski wrote:
> On Thu, 1 Feb 2024 00:50:46 +0000 Dmitry Safonov wrote:
>> Please, let me know if there will be other issues with tcp-ao tests :)
>>
>> Going to work on tracepoints and some other TCP-AO stuff for net-next.
> 
> Since you're being nice and helpful I figured I'll try testing TCP-AO
> with debug options enabled :) (kernel/configs/debug.config and
> kernel/configs/x86_debug.config included),

Haha :)

> that slows things down 
> and causes a bit of flakiness in unsigned-md5-* tests:
> 
> https://netdev.bots.linux.dev/flakes.html?br-cnt=75&tn-needle=tcp-ao
> 
> This has links to outputs:
> https://netdev.bots.linux.dev/contest.html?executor=vmksft-tcp-ao-dbg&pass=0
> 
> If it's a timing thing - FWIW we started exporting
> KSFT_MACHINE_SLOW=yes on the slow runners.

I think, I know what happens here:

# ok 8 AO server (AO_REQUIRED): AO client: counter TCPAOGood increased 4
=> 6
# ok 9 AO server (AO_REQUIRED): unsigned client
# ok 10 AO server (AO_REQUIRED): unsigned client: counter TCPAORequired
increased 1 => 2
# not ok 11 AO server (AO_REQUIRED): unsigned client: Counter
netns_ao_good was not expected to increase 7 => 8

for each of tests the server listens at a new port, but re-uses the same
namespaces+veth. If the node/machine is quite slow, I guess a segment
might have been retransmitted and the test that initiated it had already
finished.
And as result, the per-namespace counters are incremented, which makes
the test fail (IOW, the test expects all segments in ns being dropped).

So, I should do one of the options:

1. relax per-namespace checks (the per-socket and per-key counters are
   checked)
2. unshare(net) + veth setup for each test
3. split the selftest on smaller ones (as they create new net-ns in
   initialization)

I'd probably prefer (2), albeit it slows down that slow machine even
more, but I don't think creating 2 net-ns + veth pair per each test
would add a lot more overhead even on some rpi board. But let's see,
maybe I'll just go with (1) as that's really easy.

I'll cook a patch this week.

Thanks,
             Dmitry