netdev - Re: [PATCH bpf-next 07/10] bpf: selftests: Restore netns after each test

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Date:   Fri, 26 Jun 2020 15:45:04 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Kernel Team <kernel-team@...com>,
        Lawrence Brakmo <brakmo@...com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Networking <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH bpf-next 07/10] bpf: selftests: Restore netns after each test

On Fri, Jun 26, 2020 at 10:56 AM Martin KaFai Lau <kafai@...com> wrote:
>
> It is common for networking tests creating its netns and making its own
> setting under this new netns (e.g. changing tcp sysctl).  If the test
> forgot to restore to the original netns, it would affect the
> result of other tests.
>
> This patch saves the original netns at the beginning and then restores it
> after every test.  Since the restore "setns()" is not expensive, it does it
> on all tests without tracking if a test has created a new netns or not.
>
> Signed-off-by: Martin KaFai Lau <kafai@...com>
> ---
>  tools/testing/selftests/bpf/test_progs.c | 21 +++++++++++++++++++++
>  tools/testing/selftests/bpf/test_progs.h |  2 ++
>  2 files changed, 23 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
> index 54fa5fa688ce..b521ce366381 100644
> --- a/tools/testing/selftests/bpf/test_progs.c
> +++ b/tools/testing/selftests/bpf/test_progs.c
> @@ -121,6 +121,24 @@ static void reset_affinity() {
>         }
>  }
>
> +static void save_netns(void)
> +{
> +       env.saved_netns_fd = open("/proc/self/ns/net", O_RDONLY);
> +       if (env.saved_netns_fd == -1) {
> +               perror("open(/proc/self/ns/net)");
> +               exit(-1);
> +       }
> +}
> +
> +static void restore_netns(void)
> +{
> +       if (setns(env.saved_netns_fd, CLONE_NEWNET) == -1) {
> +               stdio_restore();
> +               perror("setns(CLONE_NEWNS)");
> +               exit(-1);
> +       }
> +}
> +
>  void test__end_subtest()
>  {
>         struct prog_test_def *test = env.test;
> @@ -643,6 +661,7 @@ int main(int argc, char **argv)
>                 return -1;
>         }
>
> +       save_netns();

you should probably do this also after each sub-test in test__end_subtest()?

Otherwise everything looks good.

>         stdio_hijack();
>         for (i = 0; i < prog_test_cnt; i++) {
>                 struct prog_test_def *test = &prog_test_defs[i];
> @@ -673,6 +692,7 @@ int main(int argc, char **argv)
>                         test->error_cnt ? "FAIL" : "OK");
>
>                 reset_affinity();
> +               restore_netns();
>                 if (test->need_cgroup_cleanup)
>                         cleanup_cgroup_environment();
>         }
> @@ -686,6 +706,7 @@ int main(int argc, char **argv)
>         free_str_set(&env.subtest_selector.blacklist);
>         free_str_set(&env.subtest_selector.whitelist);
>         free(env.subtest_selector.num_set);
> +       close(env.saved_netns_fd);
>
>         return env.fail_cnt ? EXIT_FAILURE : EXIT_SUCCESS;
>  }
> diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
> index f4503c926aca..b80924603918 100644
> --- a/tools/testing/selftests/bpf/test_progs.h
> +++ b/tools/testing/selftests/bpf/test_progs.h
> @@ -78,6 +78,8 @@ struct test_env {
>         int sub_succ_cnt; /* successful sub-tests */
>         int fail_cnt; /* total failed tests + sub-tests */
>         int skip_cnt; /* skipped tests */
> +
> +       int saved_netns_fd;
>  };
>
>  extern struct test_env env;
> --
> 2.24.1
>