netdev - Re: [PATCH bpf-next 2/2] selftests/bpf: Add bpf_program__attach_netfilter

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Date: Thu, 25 May 2023 14:05:55 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Florian Westphal <fw@...len.de>
Cc: bpf@...r.kernel.org, ast@...nel.org, netdev@...r.kernel.org, dxu@...uu.xyz, 
	qde@...cy.de
Subject: Re: [PATCH bpf-next 2/2] selftests/bpf: Add bpf_program__attach_netfilter_opts
 helper test

On Thu, May 25, 2023 at 4:01 AM Florian Westphal <fw@...len.de> wrote:
>
> Call bpf_program__attach_netfilter_opts() with different
> protocol/hook/priority combinations.
>
> Test fails if supposedly-illegal attachments work
> (e.g., bogus protocol family, illegal priority and so on)
> or if a should-work attachment fails.
>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  .../bpf/prog_tests/netfilter_basic.c          | 87 +++++++++++++++++++
>  .../bpf/progs/test_netfilter_link_attach.c    | 14 +++
>  2 files changed, 101 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/netfilter_basic.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_netfilter_link_attach.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/netfilter_basic.c b/tools/testing/selftests/bpf/prog_tests/netfilter_basic.c
> new file mode 100644
> index 000000000000..a64b5feaaca4
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/netfilter_basic.c
> @@ -0,0 +1,87 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +#include <netinet/in.h>
> +#include <linux/netfilter.h>
> +
> +#include "test_progs.h"
> +#include "test_netfilter_link_attach.skel.h"
> +
> +struct nf_hook_options {
> +       __u32 pf;
> +       __u32 hooknum;
> +       __s32 priority;
> +       __u32 flags;
> +
> +       bool expect_success;
> +};
> +
> +struct nf_hook_options nf_hook_attach_tests[] = {
> +       {  },
> +       { .pf = NFPROTO_NUMPROTO, },
> +       { .pf = NFPROTO_IPV4, .hooknum = 42, },
> +       { .pf = NFPROTO_IPV4, .priority = INT_MIN },
> +       { .pf = NFPROTO_IPV4, .priority = INT_MAX },
> +       { .pf = NFPROTO_IPV4, .flags = UINT_MAX },
> +
> +       { .pf = NFPROTO_INET, .priority = 1, },
> +
> +       { .pf = NFPROTO_IPV4, .priority = -10000, .expect_success = true },
> +       { .pf = NFPROTO_IPV6, .priority = 10001, .expect_success = true },
> +};
> +
> +static void __test_netfilter_link_attach(struct bpf_program *prog)
> +{
> +       LIBBPF_OPTS(bpf_netfilter_opts, opts);
> +       int i;
> +
> +       for (i = 0; i < ARRAY_SIZE(nf_hook_attach_tests); i++) {
> +               struct bpf_link *link;
> +
> +#define X(opts, m, i)  opts.m = nf_hook_attach_tests[(i)].m
> +               X(opts, pf, i);
> +               X(opts, hooknum, i);
> +               X(opts, priority, i);
> +               X(opts, flags, i);
> +#undef X
> +               link = bpf_program__attach_netfilter_opts(prog, &opts);
> +               if (nf_hook_attach_tests[i].expect_success) {
> +                       struct bpf_link *link2;
> +
> +                       if (!ASSERT_OK_PTR(link, "program attach successful"))
> +                               continue;
> +
> +                       link2 = bpf_program__attach_netfilter_opts(prog, &opts);
> +                       ASSERT_NULL(link2, "attach program with same pf/hook/priority");

we have ASSERT_ERR_PTR(), which semantically is a bit more explicit,
let's use it here and below for !expect_success case

> +
> +                       if (!ASSERT_EQ(bpf_link__destroy(link), 0, "link destroy"))

ASSERT_OK()

> +                               break;
> +
> +                       link2 = bpf_program__attach_netfilter_opts(prog, &opts);
> +                       if (!ASSERT_OK_PTR(link2, "program reattach successful"))
> +                               continue;
> +                       if (!ASSERT_EQ(bpf_link__destroy(link2), 0, "link destroy"))

same, ASSERT_OK()

> +                               break;
> +               } else {
> +                       ASSERT_NULL(link, "program load failure");
> +               }
> +       }
> +}
> +
> +static void test_netfilter_link_attach(void)
> +{
> +       struct test_netfilter_link_attach *skel;
> +
> +       skel = test_netfilter_link_attach__open_and_load();
> +       if (!ASSERT_OK_PTR(skel, "test_netfilter_link_attach__open_and_load"))
> +               goto out;
> +
> +       __test_netfilter_link_attach(skel->progs.nf_link_attach_test);

nit: I'd just inline that function here instead of having
double-underscored helper function

> +out:
> +       test_netfilter_link_attach__destroy(skel);
> +}
> +
> +void test_netfilter_basic(void)
> +{
> +       if (test__start_subtest("netfilter link attach"))
> +               test_netfilter_link_attach();

Do you plan to add more subtests? If not, then this should be just a
test. Single subtest per test doesn't make much sense. Alternatively
(and perhaps better) is to treat each combination in
nf_hook_attach_tests as its own subtest.

> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_netfilter_link_attach.c b/tools/testing/selftests/bpf/progs/test_netfilter_link_attach.c
> new file mode 100644
> index 000000000000..03a475160abe
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_netfilter_link_attach.c
> @@ -0,0 +1,14 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +
> +#define NF_ACCEPT 1
> +
> +SEC("netfilter")
> +int nf_link_attach_test(struct bpf_nf_ctx *ctx)
> +{
> +       return NF_ACCEPT;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.39.3
>