linux-kernel - Re: [PATCH bpf-next v5 4/4] selftests/bpf: Add a selftest for the tracing bpf_get_socket

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Date:   Wed, 20 Jan 2021 18:07:52 +0100
From:   KP Singh <kpsingh@...nel.org>
To:     Florent Revest <revest@...omium.org>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Florent Revest <revest@...gle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v5 4/4] selftests/bpf: Add a selftest for the
 tracing bpf_get_socket_cookie

On Tue, Jan 19, 2021 at 5:00 PM Florent Revest <revest@...omium.org> wrote:
>
> This builds up on the existing socket cookie test which checks whether
> the bpf_get_socket_cookie helpers provide the same value in
> cgroup/connect6 and sockops programs for a socket created by the
> userspace part of the test.
>
> Adding a tracing program to the existing objects requires a different
> attachment strategy and different headers.
>
> Signed-off-by: Florent Revest <revest@...omium.org>

Acked-by: KP Singh <kpsingh@...nel.org>

(one minor note, doesn't really need fixing as a part of this though)

> ---
>  .../selftests/bpf/prog_tests/socket_cookie.c  | 24 +++++++----
>  .../selftests/bpf/progs/socket_cookie_prog.c  | 41 ++++++++++++++++---
>  2 files changed, 52 insertions(+), 13 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/socket_cookie.c b/tools/testing/selftests/bpf/prog_tests/socket_cookie.c
> index 53d0c44e7907..e5c5e2ea1deb 100644
> --- a/tools/testing/selftests/bpf/prog_tests/socket_cookie.c
> +++ b/tools/testing/selftests/bpf/prog_tests/socket_cookie.c
> @@ -15,8 +15,8 @@ struct socket_cookie {
>
>  void test_socket_cookie(void)
>  {
> +       struct bpf_link *set_link, *update_sockops_link, *update_tracing_link;
>         socklen_t addr_len = sizeof(struct sockaddr_in6);
> -       struct bpf_link *set_link, *update_link;
>         int server_fd, client_fd, cgroup_fd;
>         struct socket_cookie_prog *skel;
>         __u32 cookie_expected_value;
> @@ -39,15 +39,21 @@ void test_socket_cookie(void)
>                   PTR_ERR(set_link)))
>                 goto close_cgroup_fd;
>
> -       update_link = bpf_program__attach_cgroup(skel->progs.update_cookie,
> -                                                cgroup_fd);
> -       if (CHECK(IS_ERR(update_link), "update-link-cg-attach", "err %ld\n",
> -                 PTR_ERR(update_link)))
> +       update_sockops_link = bpf_program__attach_cgroup(
> +               skel->progs.update_cookie_sockops, cgroup_fd);
> +       if (CHECK(IS_ERR(update_sockops_link), "update-sockops-link-cg-attach",
> +                 "err %ld\n", PTR_ERR(update_sockops_link)))
>                 goto free_set_link;
>
> +       update_tracing_link = bpf_program__attach(
> +               skel->progs.update_cookie_tracing);
> +       if (CHECK(IS_ERR(update_tracing_link), "update-tracing-link-attach",
> +                 "err %ld\n", PTR_ERR(update_tracing_link)))
> +               goto free_update_sockops_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;
> +               goto free_update_tracing_link;
>
>         client_fd = connect_to_fd(server_fd, 0);
>         if (CHECK(client_fd < 0, "connect_to_fd", "errno %d\n", errno))
> @@ -71,8 +77,10 @@ void test_socket_cookie(void)
>         close(client_fd);
>  close_server_fd:
>         close(server_fd);
> -free_update_link:
> -       bpf_link__destroy(update_link);
> +free_update_tracing_link:
> +       bpf_link__destroy(update_tracing_link);

I don't think this need to block submission unless there are other
issues but the
bpf_link__destroy can just be called in a single cleanup label because
it handles null or
erroneous inputs:

int bpf_link__destroy(struct bpf_link *link)
{
    int err = 0;

    if (IS_ERR_OR_NULL(link))
         return 0;
[...]