linux-kernel - Re: [PATCH bpf-next v2 6/6] selftests/bpf: fix file descriptor assertion in open

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Message-ID: <f037f7f8-a171-428f-a5a3-77eda5d1bc8b@hetzner-cloud.de>
Date: Wed, 19 Feb 2025 15:58:43 +0100
From: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Cc: jasowang@...hat.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, ast@...nel.org,
 daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev,
 eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev,
 john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, jolsa@...nel.org, mykolal@...com, shuah@...nel.org,
 hawk@...nel.org
Subject: Re: [PATCH bpf-next v2 6/6] selftests/bpf: fix file descriptor
 assertion in open_tuntap helper

Am 18.02.25 um 02:56 schrieb Willem de Bruijn:
> Marcus Wichelmann wrote:
>> [...]
>> When running the BPF selftests locally, this incorrect assertion was not
>> an issue, but the BPF kernel-patches CI failed because of this:
>>
>>    open_tuntap:FAIL:open(/dev/net/tun) unexpected open(/dev/net/tun):
>>    actual 0 <= expected 0
> 
> Wow. What kind of environment is this that 0 is not assigned stdin.
>   
>> Signed-off-by: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>
> 
> The code makes sense.
> 
> I suppose that if this condition can hit, then it can also affect
> existing lwt_* tests and thus should be a fix to commit 43a7c3ef8a15
> ("selftests/bpf: Add lwt_xmit tests for BPF_REDIRECT"), sent
> separately to bpf (not bpf-next)?
> 
> Since it's a test and no failure was reported so far, maybe fine
> to just merge as part of this bpf-next series, not my call.
I'm not sure why this only became an issue after I added the
xdp_context_tuntap test and never before. This may have to do with
the order of test execution.

If nobody speaks up, I'll leave it in this patch series for now.

Marcus