linux-kernel - Re: [PATCH bpf-next v5 3/4] selftests/bpf: Integrate the socket_cookie test to test

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Message-ID: <CABRcYm+gWJcsFxqriUMHeu3sFFLWWRGy=_wQ5R6hNoYu92c0PQ@mail.gmail.com>
Date:   Fri, 22 Jan 2021 15:35:38 +0100
From:   Florent Revest <revest@...omium.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        KP Singh <kpsingh@...omium.org>,
        Florent Revest <revest@...gle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v5 3/4] selftests/bpf: Integrate the
 socket_cookie test to test_progs

On Thu, Jan 21, 2021 at 8:55 AM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Tue, Jan 19, 2021 at 8:00 AM Florent Revest <revest@...omium.org> wrote:
> >
> > Currently, the selftest for the BPF socket_cookie helpers is built and
> > run independently from test_progs. It's easy to forget and hard to
> > maintain.
> >
> > This patch moves the socket cookies test into prog_tests/ and vastly
> > simplifies its logic by:
> > - rewriting the loading code with BPF skeletons
> > - rewriting the server/client code with network helpers
> > - rewriting the cgroup code with test__join_cgroup
> > - rewriting the error handling code with CHECKs
> >
> > Signed-off-by: Florent Revest <revest@...omium.org>
> > ---
>
> Few nits below regarding skeleton and ASSERT_xxx usage.
>
> >  tools/testing/selftests/bpf/Makefile          |   3 +-
> >  .../selftests/bpf/prog_tests/socket_cookie.c  |  82 +++++++
> >  .../selftests/bpf/progs/socket_cookie_prog.c  |   2 -
> >  .../selftests/bpf/test_socket_cookie.c        | 208 ------------------
>
> please also update .gitignore

Good catch!

> >  4 files changed, 83 insertions(+), 212 deletions(-)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/socket_cookie.c
> >  delete mode 100644 tools/testing/selftests/bpf/test_socket_cookie.c
> >
>
> [...]
>
> > +
> > +       skel = socket_cookie_prog__open_and_load();
> > +       if (CHECK(!skel, "socket_cookie_prog__open_and_load",
> > +                 "skeleton open_and_load failed\n"))
>
> nit: ASSERT_PTR_OK

Ah great, I find the ASSERT semantic much easier to follow than CHECKs.

> > +               return;
> > +
> > +       cgroup_fd = test__join_cgroup("/socket_cookie");
> > +       if (CHECK(cgroup_fd < 0, "join_cgroup", "cgroup creation failed\n"))
> > +               goto destroy_skel;
> > +
> > +       set_link = bpf_program__attach_cgroup(skel->progs.set_cookie,
> > +                                             cgroup_fd);
>
> you can use skel->links->set_cookie here and it will be auto-destroyed
> when the whole skeleton is destroyed. More simplification.

Sick. :)

> > +       if (CHECK(IS_ERR(set_link), "set-link-cg-attach", "err %ld\n",
> > +                 PTR_ERR(set_link)))
> > +               goto close_cgroup_fd;
> > +
> > +       update_link = bpf_program__attach_cgroup(skel->progs.update_cookie,
> > +                                                cgroup_fd);
>
> same as above, no need to maintain your link outside of skeleton
>
>
> > +       if (CHECK(IS_ERR(update_link), "update-link-cg-attach", "err %ld\n",
> > +                 PTR_ERR(update_link)))
> > +               goto free_set_link;
> > +
> > +       server_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0, 0);
> > +       if (CHECK(server_fd < 0, "start_server", "errno %d\n", errno))
> > +               goto free_update_link;
> > +
> > +       client_fd = connect_to_fd(server_fd, 0);
> > +       if (CHECK(client_fd < 0, "connect_to_fd", "errno %d\n", errno))
> > +               goto close_server_fd;
>
> nit: ASSERT_OK is nicer (here and in few other places)

Did you mean ASSERT_OK for the two following err checks ?

ASSERT_OK does not seem right for a fd check where we want fd to be
positive. ASSERT_OK does: "bool ___ok = ___res == 0;"

I will keep my "CHECK(fd < 0" but maybe there could be an
ASSERT_POSITIVE that does "bool ___ok = ___res >= 0;"

> > +
> > +       err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.socket_cookies),
> > +                                 &client_fd, &val);
> > +       if (CHECK(err, "map_lookup", "err %d errno %d\n", err, errno))
> > +               goto close_client_fd;
> > +
> > +       err = getsockname(client_fd, (struct sockaddr *)&addr, &addr_len);
> > +       if (CHECK(err, "getsockname", "Can't get client local addr\n"))
> > +               goto close_client_fd;
> > +
> > +       cookie_expected_value = (ntohs(addr.sin6_port) << 8) | 0xFF;
> > +       CHECK(val.cookie_value != cookie_expected_value, "",
> > +             "Unexpected value in map: %x != %x\n", val.cookie_value,
> > +             cookie_expected_value);
>
> nit: ASSERT_NEQ is nicer

Indeed.

> > +
> > +close_client_fd:
> > +       close(client_fd);
> > +close_server_fd:
> > +       close(server_fd);
> > +free_update_link:
> > +       bpf_link__destroy(update_link);
> > +free_set_link:
> > +       bpf_link__destroy(set_link);
> > +close_cgroup_fd:
> > +       close(cgroup_fd);
> > +destroy_skel:
> > +       socket_cookie_prog__destroy(skel);
> > +}
>
> [...]