netdev - Re: [PATCH bpf-next v5 11/11] selftests/bpf: add test cases for redirection between udp and unix

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Date:   Thu, 5 Aug 2021 19:34:04 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Cong Wang <cong.wang@...edance.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [PATCH bpf-next v5 11/11] selftests/bpf: add test cases for
 redirection between udp and unix

On Thu, Aug 5, 2021 at 3:43 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Sun, Jul 4, 2021 at 12:05 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
> >
> > From: Cong Wang <cong.wang@...edance.com>
> >
> > Add two test cases to ensure redirection between udp and unix
> > work bidirectionally.
> >
> > Cc: John Fastabend <john.fastabend@...il.com>
> > Cc: Daniel Borkmann <daniel@...earbox.net>
> > Cc: Jakub Sitnicki <jakub@...udflare.com>
> > Cc: Lorenz Bauer <lmb@...udflare.com>
> > Signed-off-by: Cong Wang <cong.wang@...edance.com>
> > ---
> >  .../selftests/bpf/prog_tests/sockmap_listen.c | 170 ++++++++++++++++++
> >  1 file changed, 170 insertions(+)
> >
>
> [...]
>
> > +       n = write(c1, "a", 1);
> > +       if (n < 0)
> > +               FAIL_ERRNO("%s: write", log_prefix);
> > +       if (n == 0)
> > +               FAIL("%s: incomplete write", log_prefix);
> > +       if (n < 1)
> > +               goto close;
> > +
> > +       key = SK_PASS;
> > +       err = xbpf_map_lookup_elem(verd_mapfd, &key, &pass);
> > +       if (err)
> > +               goto close;
> > +       if (pass != 1)
> > +               FAIL("%s: want pass count 1, have %d", log_prefix, pass);
> > +
> > +       n = read(mode == REDIR_INGRESS ? p0 : c0, &b, 1);
> > +       if (n < 0)
> > +               FAIL_ERRNO("%s: read", log_prefix);
>
> Hey Cong,
>
> This test is pretty flaky and quite frequently fails in our CIs (e.g., [0]):
>
> ./test_progs-no_alu32:unix_udp_redir_to_connected:1949: egress: read:
> Resource temporarily unavailable
>   unix_udp_redir_to_connected:FAIL:1949
>
> Please send a fix to make it more reliable. Thanks!

Using an unbound number of retries makes this reliable, but you
dislike it. ;) But, there must be some reason for the delay of
packet delivery, I guess it might be related to workqueue scheduling,
let me check it tomorrow.

Thanks.