netdev - Re: [PATCH bpf-next] selftests/bpf: Fix spurious failures in accept due to EAGAIN

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Date:   Thu, 12 Mar 2020 20:19:06 +0100
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        kernel-team@...udflare.com
Subject: Re: [PATCH bpf-next] selftests/bpf: Fix spurious failures in accept due to EAGAIN

On Thu, Mar 12, 2020 at 06:57 PM CET, Andrii Nakryiko wrote:
> On Thu, Mar 12, 2020 at 10:11 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
>>
>> Andrii Nakryiko reports that sockmap_listen test suite is frequently
>> failing due to accept() calls erroring out with EAGAIN:
>>
>>   ./test_progs:connect_accept_thread:733: accept: Resource temporarily unavailable
>>   connect_accept_thread:FAIL:733
>>
>> This is because we are needlessly putting the listening TCP sockets in
>> non-blocking mode.
>>
>> Fix it by using the default blocking mode in all tests in this suite.
>>
>> Fixes: 44d28be2b8d4 ("selftests/bpf: Tests for sockmap/sockhash holding listening sockets")
>> Reported-by: Andrii Nakryiko <andrii.nakryiko@...il.com>
>> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
>> ---
>
> Thanks for looking into this. Can you please verify that test
> successfully fails (not hangs) when, say, network is down (do `ip link
> set lo down` before running test?). The reason I'm asking is that I
> just fixed a problem in tcp_rtt selftest, in which accept() would
> block forever, even if listening socket was closed.

Right, good point. We don't want tests hanging. Let me rework it.

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