Re: [PATCH bpf-next v3 3/3] libbpf: add selftests for TC-BPF API

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Tue, Apr 20, 2021 at 12:37 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> This adds some basic tests for the low level bpf_tc_* API.
>
> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  .../selftests/bpf/prog_tests/test_tc_bpf.c    | 169 ++++++++++++++++++
>  .../selftests/bpf/progs/test_tc_bpf_kern.c    |  12 ++
>  2 files changed, 181 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/test_tc_bpf.c

we normally don't call prog_test's files with "test_" prefix, it can
be just tc_bpf.c (or just tc.c)

>  create mode 100644 tools/testing/selftests/bpf/progs/test_tc_bpf_kern.c

we also don't typically call BPF source code files with _kern suffix,
just test_tc_bpf.c would be more in line with most common case

>
> diff --git a/tools/testing/selftests/bpf/prog_tests/test_tc_bpf.c b/tools/testing/selftests/bpf/prog_tests/test_tc_bpf.c
> new file mode 100644
> index 000000000000..563a3944553c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/test_tc_bpf.c
> @@ -0,0 +1,169 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <linux/err.h>
> +#include <linux/limits.h>
> +#include <bpf/libbpf.h>
> +#include <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <test_progs.h>
> +#include <linux/if_ether.h>
> +
> +#define LO_IFINDEX 1
> +
> +static int test_tc_internal(int fd, __u32 parent_id)
> +{
> +       DECLARE_LIBBPF_OPTS(bpf_tc_opts, opts, .handle = 1, .priority = 10,
> +                           .class_id = TC_H_MAKE(1UL << 16, 1));
> +       struct bpf_tc_attach_id id = {};
> +       struct bpf_tc_info info = {};
> +       int ret;
> +
> +       ret = bpf_tc_attach(fd, LO_IFINDEX, parent_id, &opts, &id);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_attach"))
> +               return ret;
> +
> +       ret = bpf_tc_get_info(LO_IFINDEX, parent_id, &id, &info);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_get_info"))
> +               goto end;
> +
> +       if (!ASSERT_EQ(info.id.handle, id.handle, "handle mismatch") ||
> +           !ASSERT_EQ(info.id.priority, id.priority, "priority mismatch") ||
> +           !ASSERT_EQ(info.id.handle, 1, "handle incorrect") ||
> +           !ASSERT_EQ(info.chain_index, 0, "chain_index incorrect") ||
> +           !ASSERT_EQ(info.id.priority, 10, "priority incorrect") ||
> +           !ASSERT_EQ(info.class_id, TC_H_MAKE(1UL << 16, 1),
> +                      "class_id incorrect") ||
> +           !ASSERT_EQ(info.protocol, ETH_P_ALL, "protocol incorrect"))
> +               goto end;
> +
> +       opts.replace = true;
> +       ret = bpf_tc_attach(fd, LO_IFINDEX, parent_id, &opts, &id);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_attach in replace mode"))
> +               return ret;
> +
> +       /* Demonstrate changing attributes */
> +       opts.class_id = TC_H_MAKE(1UL << 16, 2);
> +
> +       ret = bpf_tc_attach(fd, LO_IFINDEX, parent_id, &opts, &id);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc attach in replace mode"))
> +               goto end;
> +
> +       ret = bpf_tc_get_info(LO_IFINDEX, parent_id, &id, &info);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_get_info"))
> +               goto end;
> +
> +       if (!ASSERT_EQ(info.class_id, TC_H_MAKE(1UL << 16, 2),
> +                      "class_id incorrect after replace"))
> +               goto end;
> +       if (!ASSERT_EQ(info.bpf_flags & TCA_BPF_FLAG_ACT_DIRECT, 1,
> +                      "direct action mode not set"))
> +               goto end;
> +
> +end:
> +       ret = bpf_tc_detach(LO_IFINDEX, parent_id, &id);
> +       ASSERT_EQ(ret, 0, "detach failed");
> +       return ret;
> +}
> +
> +int test_tc_info(int fd)
> +{
> +       DECLARE_LIBBPF_OPTS(bpf_tc_opts, opts, .handle = 1, .priority = 10,
> +                           .class_id = TC_H_MAKE(1UL << 16, 1));
> +       struct bpf_tc_attach_id id = {}, old;
> +       struct bpf_tc_info info = {};
> +       int ret;
> +
> +       ret = bpf_tc_attach(fd, LO_IFINDEX, BPF_TC_CLSACT_INGRESS, &opts, &id);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_attach"))
> +               return ret;
> +       old = id;
> +
> +       ret = bpf_tc_get_info(LO_IFINDEX, BPF_TC_CLSACT_INGRESS, &id, &info);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_get_info"))
> +               goto end_old;
> +
> +       if (!ASSERT_EQ(info.id.handle, id.handle, "handle mismatch") ||
> +           !ASSERT_EQ(info.id.priority, id.priority, "priority mismatch") ||
> +           !ASSERT_EQ(info.id.handle, 1, "handle incorrect") ||
> +           !ASSERT_EQ(info.chain_index, 0, "chain_index incorrect") ||
> +           !ASSERT_EQ(info.id.priority, 10, "priority incorrect") ||
> +           !ASSERT_EQ(info.class_id, TC_H_MAKE(1UL << 16, 1),
> +                      "class_id incorrect") ||
> +           !ASSERT_EQ(info.protocol, ETH_P_ALL, "protocol incorrect"))
> +               goto end_old;
> +
> +       /* choose a priority */
> +       opts.priority = 0;
> +       ret = bpf_tc_attach(fd, LO_IFINDEX, BPF_TC_CLSACT_INGRESS, &opts, &id);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_attach"))
> +               goto end_old;
> +
> +       ret = bpf_tc_get_info(LO_IFINDEX, BPF_TC_CLSACT_INGRESS, &id, &info);
> +       if (!ASSERT_EQ(ret, 0, "bpf_tc_get_info"))
> +               goto end;
> +
> +       if (!ASSERT_NEQ(id.priority, old.priority, "filter priority mismatch"))
> +               goto end;
> +       if (!ASSERT_EQ(info.id.priority, id.priority, "priority mismatch"))
> +               goto end;
> +
> +end:
> +       ret = bpf_tc_detach(LO_IFINDEX, BPF_TC_CLSACT_INGRESS, &id);
> +       ASSERT_EQ(ret, 0, "detach failed");
> +end_old:
> +       ret = bpf_tc_detach(LO_IFINDEX, BPF_TC_CLSACT_INGRESS, &old);
> +       ASSERT_EQ(ret, 0, "detach failed");
> +       return ret;
> +}
> +
> +void test_test_tc_bpf(void)

test_test_ tautology, drop one test?

> +{
> +       const char *file = "./test_tc_bpf_kern.o";

please use BPF skeleton instead, see lots of other selftests doing
that already. You won't even need find_program_by_{name,title}, among
other things.

> +       struct bpf_program *clsp;
> +       struct bpf_object *obj;
> +       int cls_fd, ret;
> +
> +       obj = bpf_object__open(file);
> +       if (!ASSERT_OK_PTR(obj, "bpf_object__open"))
> +               return;
> +
> +       clsp = bpf_object__find_program_by_title(obj, "classifier");
> +       if (!ASSERT_OK_PTR(clsp, "bpf_object__find_program_by_title"))
> +               goto end;
> +
> +       ret = bpf_object__load(obj);
> +       if (!ASSERT_EQ(ret, 0, "bpf_object__load"))
> +               goto end;
> +
> +       cls_fd = bpf_program__fd(clsp);
> +
> +       system("tc qdisc del dev lo clsact");

can this fail? also why is this necessary? it's still not possible to
do anything with only libbpf APIs?

> +
> +       ret = test_tc_internal(cls_fd, BPF_TC_CLSACT_INGRESS);
> +       if (!ASSERT_EQ(ret, 0, "test_tc_internal INGRESS"))
> +               goto end;
> +
> +       if (!ASSERT_EQ(system("tc qdisc del dev lo clsact"), 0,
> +                      "clsact qdisc delete failed"))
> +               goto end;
> +
> +       ret = test_tc_info(cls_fd);
> +       if (!ASSERT_EQ(ret, 0, "test_tc_info"))
> +               goto end;
> +
> +       if (!ASSERT_EQ(system("tc qdisc del dev lo clsact"), 0,
> +                      "clsact qdisc delete failed"))
> +               goto end;
> +
> +       ret = test_tc_internal(cls_fd, BPF_TC_CLSACT_EGRESS);
> +       if (!ASSERT_EQ(ret, 0, "test_tc_internal EGRESS"))
> +               goto end;
> +
> +       ASSERT_EQ(system("tc qdisc del dev lo clsact"), 0,
> +                 "clsact qdisc delete failed");
> +
> +end:
> +       bpf_object__close(obj);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_tc_bpf_kern.c b/tools/testing/selftests/bpf/progs/test_tc_bpf_kern.c
> new file mode 100644
> index 000000000000..18a3a7ed924a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_tc_bpf_kern.c
> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +/* Dummy prog to test TC-BPF API */
> +
> +SEC("classifier")
> +int cls(struct __sk_buff *skb)
> +{
> +       return 0;
> +}
> --
> 2.30.2
>