netdev - Re: [bpf-next PATCH 4/4] selftests/bpf: Migrate tcpbpf

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Date:   Thu, 29 Oct 2020 16:20:28 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin Lau <kafai@...com>,
        john fastabend <john.fastabend@...il.com>,
        Kernel Team <kernel-team@...com>,
        Networking <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Lawrence Brakmo <brakmo@...com>, alexanderduyck@...com
Subject: Re: [bpf-next PATCH 4/4] selftests/bpf: Migrate tcpbpf_user.c to use
 BPF skeleton

On Thu, Oct 29, 2020 at 12:57 AM Alexander Duyck
<alexander.duyck@...il.com> wrote:
>
> From: Alexander Duyck <alexanderduyck@...com>
>
> Update tcpbpf_user.c to make use of the BPF skeleton. Doing this we can
> simplify test_tcpbpf_user and reduce the overhead involved in setting up
> the test.
>
> Signed-off-by: Alexander Duyck <alexanderduyck@...com>
> ---

Few suggestions below, but overall looks good:

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>  .../testing/selftests/bpf/prog_tests/tcpbpf_user.c |   48 +++++++++-----------
>  1 file changed, 21 insertions(+), 27 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c b/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c
> index 4e1190894e1e..7e92c37976ac 100644
> --- a/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c
> +++ b/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c
> @@ -5,6 +5,7 @@
>
>  #include "test_tcpbpf.h"
>  #include "cgroup_helpers.h"
> +#include "test_tcpbpf_kern.skel.h"
>
>  #define LO_ADDR6 "::1"
>  #define CG_NAME "/tcpbpf-user-test"
> @@ -162,39 +163,32 @@ static void run_test(int map_fd, int sock_map_fd)
>
>  void test_tcpbpf_user(void)
>  {
> -       const char *file = "test_tcpbpf_kern.o";
> -       int prog_fd, map_fd, sock_map_fd;
> -       struct bpf_object *obj;
> +       struct test_tcpbpf_kern *skel;
> +       int map_fd, sock_map_fd;
> +       struct bpf_link *link;
>         int cg_fd = -1;
> -       int rv;
> -
> -       cg_fd = cgroup_setup_and_join(CG_NAME);
> -       if (CHECK_FAIL(cg_fd < 0))
> -               goto err;
>
> -       if (CHECK_FAIL(bpf_prog_load(file, BPF_PROG_TYPE_SOCK_OPS, &obj, &prog_fd))) {
> -               fprintf(stderr, "FAILED: load_bpf_file failed for: %s\n", file);
> -               goto err;
> -       }
> +       skel = test_tcpbpf_kern__open_and_load();
> +       if (CHECK(!skel, "open and load skel", "failed"))
> +               return;
>
> -       rv = bpf_prog_attach(prog_fd, cg_fd, BPF_CGROUP_SOCK_OPS, 0);
> -       if (CHECK_FAIL(rv)) {
> -               fprintf(stderr, "FAILED: bpf_prog_attach: %d (%s)\n",
> -                      errno, strerror(errno));
> -               goto err;
> -       }
> +       cg_fd = test__join_cgroup(CG_NAME);
> +       if (CHECK_FAIL(cg_fd < 0))

please use either CHECK() or one of the newer ASSERT_xxx() macro (also
defined in test_progs.h), CHECK_FAIL should be avoided in general.

> +               goto cleanup_skel;
>
> -       map_fd = bpf_find_map(__func__, obj, "global_map");
> -       if (CHECK_FAIL(map_fd < 0))
> -               goto err;
> +       map_fd = bpf_map__fd(skel->maps.global_map);
> +       sock_map_fd = bpf_map__fd(skel->maps.sockopt_results);
>
> -       sock_map_fd = bpf_find_map(__func__, obj, "sockopt_results");
> -       if (CHECK_FAIL(sock_map_fd < 0))
> -               goto err;
> +       link = bpf_program__attach_cgroup(skel->progs.bpf_testcb, cg_fd);

you can do skel->links.bpf_testcb = bpf_program__attach_cgroup() and
skeleton's __destroy() call will take care of destroying the link

> +       if (CHECK(IS_ERR(link), "attach_cgroup(estab)", "err: %ld\n",
> +                 PTR_ERR(link)))

there is a convenient ASSERT_OK_PTR() specifically for pointers like
this (and NULL ones as well, of course); saves a lot of typing and
encapsulates error extraction internally.

> +               goto cleanup_namespace;
>
>         run_test(map_fd, sock_map_fd);
> -err:
> -       bpf_prog_detach(cg_fd, BPF_CGROUP_SOCK_OPS);
> +
> +       bpf_link__destroy(link);
> +cleanup_namespace:
>         close(cg_fd);
> -       cleanup_cgroup_environment();
> +cleanup_skel:
> +       test_tcpbpf_kern__destroy(skel);
>  }
>
>