netdev - Re: [PATCH bpf-next v4 3/7] selftests/bpf: add MPTCP test base

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Date:   Mon, 16 May 2022 15:43:36 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Mat Martineau <mathew.j.martineau@...ux.intel.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Nicolas Rybowski <nicolas.rybowski@...sares.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, mptcp@...ts.linux.dev,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        Geliang Tang <geliang.tang@...e.com>
Subject: Re: [PATCH bpf-next v4 3/7] selftests/bpf: add MPTCP test base

On Fri, May 13, 2022 at 3:48 PM Mat Martineau
<mathew.j.martineau@...ux.intel.com> wrote:
>
> From: Nicolas Rybowski <nicolas.rybowski@...sares.net>
>
> This patch adds a base for MPTCP specific tests.
>
> It is currently limited to the is_mptcp field in case of plain TCP
> connection because there is no easy way to get the subflow sk from a msk
> in userspace. This implies that we cannot lookup the sk_storage attached
> to the subflow sk in the sockops program.
>
> v4:
>  - add copyright 2022 (Andrii)
>  - use ASSERT_* instead of CHECK_FAIL (Andrii)
>  - drop SEC("version") (Andrii)
>  - use is_mptcp in tcp_sock, instead of bpf_tcp_sock (Martin & Andrii)
>
> Acked-by: Matthieu Baerts <matthieu.baerts@...sares.net>
> Co-developed-by: Geliang Tang <geliang.tang@...e.com>
> Signed-off-by: Geliang Tang <geliang.tang@...e.com>
> Signed-off-by: Nicolas Rybowski <nicolas.rybowski@...sares.net>
> Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
> ---
>  MAINTAINERS                                   |   1 +
>  tools/testing/selftests/bpf/bpf_tcp_helpers.h |   1 +
>  tools/testing/selftests/bpf/config            |   1 +
>  tools/testing/selftests/bpf/network_helpers.c |  43 ++++--
>  tools/testing/selftests/bpf/network_helpers.h |   4 +
>  .../testing/selftests/bpf/prog_tests/mptcp.c  | 136 ++++++++++++++++++
>  .../testing/selftests/bpf/progs/mptcp_sock.c  |  53 +++++++
>  7 files changed, 231 insertions(+), 8 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/mptcp.c
>  create mode 100644 tools/testing/selftests/bpf/progs/mptcp_sock.c
>

Seems like bpf_core_field_exists() works fine for your use case and CI
is green. See some selftest-specific issues below, though.

[...]

> +static int run_test(int cgroup_fd, int server_fd, bool is_mptcp)
> +{
> +       int client_fd, prog_fd, map_fd, err;
> +       struct bpf_program *prog;
> +       struct bpf_object *obj;
> +       struct bpf_map *map;
> +
> +       obj = bpf_object__open("./mptcp_sock.o");
> +       if (libbpf_get_error(obj))
> +               return -EIO;
> +
> +       err = bpf_object__load(obj);
> +       if (!ASSERT_OK(err, "bpf_object__load"))
> +               goto out;
> +
> +       prog = bpf_object__find_program_by_name(obj, "_sockops");

can you please use BPF skeleton instead of doing these lookups by
name? See other tests that are including .skel.h headers for example

> +       if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name")) {
> +               err = -EIO;
> +               goto out;
> +       }
> +

[...]

> +void test_base(void)
> +{
> +       int server_fd, cgroup_fd;
> +
> +       cgroup_fd = test__join_cgroup("/mptcp");
> +       if (CHECK_FAIL(cgroup_fd < 0))
> +               return;
> +
> +       /* without MPTCP */
> +       server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0);
> +       if (CHECK_FAIL(server_fd < 0))
> +               goto with_mptcp;
> +
> +       CHECK_FAIL(run_test(cgroup_fd, server_fd, false));

please don't add new uses of CHECK_FAIL()

> +
> +       close(server_fd);
> +

[...]