[PATCH net-next] selftests: net: Add a missing config option

[PATCH net-next] selftests: net: Add a missing config option

[Alice Mikityanska]

From: Alice Mikityanska <alice@isovalent.com>

Commit 5cb53743e1ff ("selftests: net: Add a test for BIG TCP in UDP
tunnels") used iptables match comment, which was missed from the CI
kernel config. Add the missing config option.

Signed-off-by: Alice Mikityanska <alice@isovalent.com>
---
 tools/testing/selftests/net/config | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/net/config b/tools/testing/selftests/net/config
index 96fffca6547c..a2d14ec9df1a 100644
--- a/tools/testing/selftests/net/config
+++ b/tools/testing/selftests/net/config
@@ -82,6 +82,7 @@ CONFIG_NETFILTER=y
 CONFIG_NETFILTER_ADVANCED=y
 CONFIG_NETFILTER_XTABLES_LEGACY=y
 CONFIG_NETFILTER_XT_MATCH_BPF=m
+CONFIG_NETFILTER_XT_MATCH_COMMENT=y
 CONFIG_NETFILTER_XT_MATCH_LENGTH=m
 CONFIG_NETFILTER_XT_MATCH_POLICY=m
 CONFIG_NETFILTER_XT_NAT=m
-- 
2.55.0

Re: [PATCH net-next] selftests: net: Add a missing config option

[Matthieu Baerts]

Hi Alice,

On 23/07/2026 16:02, Alice Mikityanska wrote:
> From: Alice Mikityanska <alice@isovalent.com>
> 
> Commit 5cb53743e1ff ("selftests: net: Add a test for BIG TCP in UDP
> tunnels") used iptables match comment, which was missed from the CI
> kernel config. Add the missing config option.

It helps, the CI can now run this test!

Reviewed-by: Matthieu Baerts <matttbe@kernel.org>


But I think another follow-up patch is required, because this test is
flaky when using a debug kernel config:


https://netdev.bots.linux.dev/flakes.html?min-flip=0&tn-needle=big-tcp-tunnels-sh

Maybe because wait_local_port_listen() is required after having called
netserver?

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Re: [PATCH net-next] selftests: net: Add a missing config option

[Alice Mikityanska]

On Mon, 27 Jul 2026 at 12:09, Matthieu Baerts <matttbe@kernel.org> wrote:
>
> Hi Alice,
>
> On 23/07/2026 16:02, Alice Mikityanska wrote:
> > From: Alice Mikityanska <alice@isovalent.com>
> >
> > Commit 5cb53743e1ff ("selftests: net: Add a test for BIG TCP in UDP
> > tunnels") used iptables match comment, which was missed from the CI
> > kernel config. Add the missing config option.
>
> It helps, the CI can now run this test!
>
> Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
>
>
> But I think another follow-up patch is required, because this test is
> flaky when using a debug kernel config:
>
>
> https://netdev.bots.linux.dev/flakes.html?min-flip=0&tn-needle=big-tcp-tunnels-sh
>
> Maybe because wait_local_port_listen() is required after having called
> netserver?

The issue is hard to reproduce on my machine, but I could reproduce it
in ~12 hours of non-stop testing in a loop. It reproduces even with
wait_local_port_listen, so it must be something else. The log above
(and my repro attempts) shows that it fails in a non-first test, but
netserver starts only once, before the first test. If the failure was
due to netserver not being ready, it would fail in the first test.
I'll keep investigating.

> Cheers,
> Matt
> --
> Sponsored by the NGI0 Core fund.
>

Re: [PATCH net-next] selftests: net: Add a missing config option

[Paolo Abeni]

On 7/29/26 10:44 PM, Alice Mikityanska wrote:
> On Mon, 27 Jul 2026 at 12:09, Matthieu Baerts <matttbe@kernel.org> wrote:
>> On 23/07/2026 16:02, Alice Mikityanska wrote:
>>> From: Alice Mikityanska <alice@isovalent.com>
>>>
>>> Commit 5cb53743e1ff ("selftests: net: Add a test for BIG TCP in UDP
>>> tunnels") used iptables match comment, which was missed from the CI
>>> kernel config. Add the missing config option.
>>
>> It helps, the CI can now run this test!
>>
>> Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
>>
>>
>> But I think another follow-up patch is required, because this test is
>> flaky when using a debug kernel config:
>>
>>
>> https://netdev.bots.linux.dev/flakes.html?min-flip=0&tn-needle=big-tcp-tunnels-sh
>>
>> Maybe because wait_local_port_listen() is required after having called
>> netserver?
> 
> The issue is hard to reproduce on my machine, but I could reproduce it
> in ~12 hours of non-stop testing in a loop. It reproduces even with
> wait_local_port_listen, so it must be something else. The log above
> (and my repro attempts) shows that it fails in a non-first test, but
> netserver starts only once, before the first test. If the failure was
> due to netserver not being ready, it would fail in the first test.
> I'll keep investigating.
I *think* this kind of flakes are sort of expected for 'performance'
related tests when running on debug kernel: the environment can be
painful slow, and few failed iterations I saw has csum offload disabled
- even lower expected tput.

AFAICS the target packet number is independent from KSFT_MACHINE_SLOW
and the actual offload setting. Possibly you can tune the target value a
bit WRT the mentioned variables or skip entirely pkts number validation
in the slowest permutation (note that the self-test will still have some
value due to code coverage with sanitizers enabled).

/p

Re: [PATCH net-next] selftests: net: Add a missing config option

[Alice Mikityanska]

On Thu, Jul 30, 2026, at 10:46, Paolo Abeni wrote:
> On 7/29/26 10:44 PM, Alice Mikityanska wrote:
>> On Mon, 27 Jul 2026 at 12:09, Matthieu Baerts <matttbe@kernel.org> wrote:
>>> On 23/07/2026 16:02, Alice Mikityanska wrote:
>>>> From: Alice Mikityanska <alice@isovalent.com>
>>>>
>>>> Commit 5cb53743e1ff ("selftests: net: Add a test for BIG TCP in UDP
>>>> tunnels") used iptables match comment, which was missed from the CI
>>>> kernel config. Add the missing config option.
>>>
>>> It helps, the CI can now run this test!
>>>
>>> Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
>>>
>>>
>>> But I think another follow-up patch is required, because this test is
>>> flaky when using a debug kernel config:
>>>
>>>
>>> https://netdev.bots.linux.dev/flakes.html?min-flip=0&tn-needle=big-tcp-tunnels-sh
>>>
>>> Maybe because wait_local_port_listen() is required after having called
>>> netserver?
>> 
>> The issue is hard to reproduce on my machine, but I could reproduce it
>> in ~12 hours of non-stop testing in a loop. It reproduces even with
>> wait_local_port_listen, so it must be something else. The log above
>> (and my repro attempts) shows that it fails in a non-first test, but
>> netserver starts only once, before the first test. If the failure was
>> due to netserver not being ready, it would fail in the first test.
>> I'll keep investigating.
> I *think* this kind of flakes are sort of expected for 'performance'
> related tests when running on debug kernel: the environment can be
> painful slow, and few failed iterations I saw has csum offload disabled
> - even lower expected tput.
>
> AFAICS the target packet number is independent from KSFT_MACHINE_SLOW
> and the actual offload setting. Possibly you can tune the target value a
> bit WRT the mentioned variables or skip entirely pkts number validation
> in the slowest permutation (note that the self-test will still have some
> value due to code coverage with sanitizers enabled).

Hmm, the above makes sense for the failures like this:

https://netdev-ctrl.bots.linux.dev/logview.html?f=/logs/vmksft/net-dbg/results/754376/28-big-tcp-tunnels-sh/stdout

971 is slightly below than 1000 (even though it's typically 1600-1700 on
the CI runners, in this configuration). Tuning the thresholds can help.

But I also see failures like this:

https://netdev-ctrl.bots.linux.dev/logview.html?f=/logs/vmksft/net-dbg/results/751124/21-big-tcp-tunnels-sh/stdout

It's a complete zero, so lowering the threshold won't help here. I could
reproduce it on my machine, although it requires hours of retries. I'd
like to capture the tcpdump and see what actually happens in this case.

> /p

Re: [PATCH net-next] selftests: net: Add a missing config option

[Paolo Abeni]

On 7/30/26 5:46 PM, Alice Mikityanska wrote:
> On Thu, Jul 30, 2026, at 10:46, Paolo Abeni wrote:
>> AFAICS the target packet number is independent from KSFT_MACHINE_SLOW
>> and the actual offload setting. Possibly you can tune the target value a
>> bit WRT the mentioned variables or skip entirely pkts number validation
>> in the slowest permutation (note that the self-test will still have some
>> value due to code coverage with sanitizers enabled).
> 
> Hmm, the above makes sense for the failures like this:
> 
> https://netdev-ctrl.bots.linux.dev/logview.html?f=/logs/vmksft/net-dbg/results/754376/28-big-tcp-tunnels-sh/stdout
> 
> 971 is slightly below than 1000 (even though it's typically 1600-1700 on
> the CI runners, in this configuration). Tuning the thresholds can help.
> 
> But I also see failures like this:
> 
> https://netdev-ctrl.bots.linux.dev/logview.html?f=/logs/vmksft/net-dbg/results/751124/21-big-tcp-tunnels-sh/stdout
> 
> It's a complete zero, so lowering the threshold won't help here. I could
> reproduce it on my machine, although it requires hours of retries. I'd
> like to capture the tcpdump and see what actually happens in this case.
Ah, sorry, I haven't seen such failure yet. I *think* that one deserves
a better investigation. Are you able to reproduce locally that kind of
failure? If the such event frequency is low, perhaps it makes sense to
improve the stability incrementally?

/P

Re: [PATCH net-next] selftests: net: Add a missing config option

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 23 Jul 2026 17:02:41 +0300 you wrote:
> From: Alice Mikityanska <alice@isovalent.com>
> 
> Commit 5cb53743e1ff ("selftests: net: Add a test for BIG TCP in UDP
> tunnels") used iptables match comment, which was missed from the CI
> kernel config. Add the missing config option.
> 
> Signed-off-by: Alice Mikityanska <alice@isovalent.com>
> 
> [...]

Here is the summary with links:
  - [net-next] selftests: net: Add a missing config option
    https://git.kernel.org/netdev/net-next/c/8fe79aa2f1d6

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html