diff mbox series

[bpf-next,v2,7/7] libbpf: add selftest for bpf_link based TC-BPF management API

Message ID 20210604063116.234316-8-memxor@gmail.com
State New
Headers show
Series Add bpf_link based TC-BPF API | expand

Commit Message

Kumar Kartikeya Dwivedi June 4, 2021, 6:31 a.m. UTC
This covers basic attach/detach/update, and tests interaction with the
netlink API. It also exercises the bpf_link_info and fdinfo codepaths.

Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../selftests/bpf/prog_tests/tc_bpf_link.c    | 285 ++++++++++++++++++
 1 file changed, 285 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c

Comments

Yonghong Song June 5, 2021, 5:26 p.m. UTC | #1
On 6/3/21 11:31 PM, Kumar Kartikeya Dwivedi wrote:
> This covers basic attach/detach/update, and tests interaction with the

> netlink API. It also exercises the bpf_link_info and fdinfo codepaths.

> 

> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>.

> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

> ---

>   .../selftests/bpf/prog_tests/tc_bpf_link.c    | 285 ++++++++++++++++++

>   1 file changed, 285 insertions(+)

>   create mode 100644 tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c

> 

> diff --git a/tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c b/tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c

> new file mode 100644

> index 000000000000..beaf06e0557c

> --- /dev/null

> +++ b/tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c

> @@ -0,0 +1,285 @@

> +// SPDX-License-Identifier: GPL-2.0

> +

> +#include <test_progs.h>

> +#include <linux/pkt_cls.h>

> +

> +#include "test_tc_bpf.skel.h"

> +

> +#define LO_IFINDEX 1

> +

> +static int test_tc_bpf_link_basic(struct bpf_tc_hook *hook,

> +				  struct bpf_program *prog)

> +{

> +	DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);

> +	DECLARE_LIBBPF_OPTS(bpf_tc_opts, qopts, .handle = 1, .priority = 1);

> +	struct bpf_prog_info info = {};

> +	__u32 info_len = sizeof(info);

> +	struct bpf_link *link, *invl;

> +	int ret;

> +

> +	link = bpf_program__attach_tc(prog, hook, &opts);

> +	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))

> +		return PTR_ERR(link);


If we changed the bpf_program__attach_tc return semantics such that
the return "link" value can only be NULL or a valid pointer, you can do
	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))
		return -EINVAL;

The true error code should have been printed inside ASSERT_OK_PTR.

The same for a few other cases below.

> +

> +	ret = bpf_obj_get_info_by_fd(bpf_program__fd(prog), &info, &info_len);

> +	if (!ASSERT_OK(ret, "bpf_obj_get_info_by_fd"))

> +		goto end;

> +

> +	ret = bpf_tc_query(hook, &qopts);

> +	if (!ASSERT_OK(ret, "bpf_tc_query"))

> +		goto end;

> +

> +	if (!ASSERT_EQ(qopts.prog_id, info.id, "prog_id match"))

> +		goto end;

> +

> +	opts.gen_flags = ~0u;

> +	invl = bpf_program__attach_tc(prog, hook, &opts);

> +	if (!ASSERT_ERR_PTR(invl, "bpf_program__attach_tc with invalid flags")) {

> +		bpf_link__destroy(invl);

> +		ret = -EINVAL;

> +	}

> +

> +end:

> +	bpf_link__destroy(link);

> +	return ret;

> +}

> +

[...]
> +

> +static int test_tc_bpf_link_info_api(struct bpf_tc_hook *hook,

> +				     struct bpf_program *prog)

> +{

> +	DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);

> +	__u32 ifindex, parent, handle, gen_flags, priority;

> +	char buf[4096], path[256], *begin;

> +	struct bpf_link_info info = {};

> +	__u32 info_len = sizeof(info);

> +	struct bpf_link *link;

> +	int ret, fdinfo;

> +

> +	link = bpf_program__attach_tc(prog, hook, &opts);

> +	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))

> +		return PTR_ERR(link);

> +

> +	ret = bpf_obj_get_info_by_fd(bpf_link__fd(link), &info, &info_len);

> +	if (!ASSERT_OK(ret, "bpf_obj_get_info_by_fd"))

> +		goto end;

> +

> +	ret = snprintf(path, sizeof(path), "/proc/self/fdinfo/%d",

> +		       bpf_link__fd(link));

> +	if (!ASSERT_TRUE(!ret || ret < sizeof(path), "snprintf pathname"))

> +		goto end;

> +

> +	fdinfo = open(path, O_RDONLY);

> +	if (!ASSERT_GT(fdinfo, -1, "open fdinfo"))

> +		goto end;

> +

> +	ret = read(fdinfo, buf, sizeof(buf));

> +	if (!ASSERT_GT(ret, 0, "read fdinfo")) {

> +		ret = -EINVAL;

> +		goto end_file;

> +	}

> +

> +	begin = strstr(buf, "ifindex");

> +	if (!ASSERT_OK_PTR(begin, "find beginning of fdinfo info")) {

> +		ret = -EINVAL;

> +		goto end_file;

> +	}

> +

> +	ret = sscanf(begin, "ifindex:\t%u\n"

> +			    "parent:\t%u\n"

> +			    "handle:\t%u\n"

> +			    "priority:\t%u\n"

> +			    "gen_flags:\t%u\n",

> +			    &ifindex, &parent, &handle, &priority, &gen_flags);

> +	if (!ASSERT_EQ(ret, 5, "sscanf fdinfo")) {

> +		ret = -EINVAL;

> +		goto end_file;

> +	}

> +

> +	ret = -EINVAL;

> +

> +#define X(a, b, c) (!ASSERT_EQ(a, b, #a " == " #b) || !ASSERT_EQ(b, c, #b " == " #c))

> +	if (X(info.tc.ifindex, ifindex, 1) ||

> +	    X(info.tc.parent, parent,

> +	      TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS)) ||

> +	    X(info.tc.handle, handle, 1) ||

> +	    X(info.tc.gen_flags, gen_flags, TCA_CLS_FLAGS_NOT_IN_HW) ||

> +	    X(info.tc.priority, priority, 1))

> +#undef X

> +		goto end_file;


Maybe put "#undef X" after "goto end_file" is a little bit better?

> +

> +	ret = 0;

> +

> +end_file:

> +	close(fdinfo);

> +end:

> +	bpf_link__destroy(link);

> +	return ret;

> +}

> +

[...]
Andrii Nakryiko June 7, 2021, 11:57 p.m. UTC | #2
On Thu, Jun 3, 2021 at 11:32 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>

> This covers basic attach/detach/update, and tests interaction with the

> netlink API. It also exercises the bpf_link_info and fdinfo codepaths.

>

> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>.

> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

> ---

>  .../selftests/bpf/prog_tests/tc_bpf_link.c    | 285 ++++++++++++++++++

>  1 file changed, 285 insertions(+)

>  create mode 100644 tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c

>


[...]

> +static int test_tc_bpf_link_netlink_interaction(struct bpf_tc_hook *hook,

> +                                               struct bpf_program *prog)

> +{

> +       DECLARE_LIBBPF_OPTS(bpf_link_update_opts, lopts,

> +                           .old_prog_fd = bpf_program__fd(prog));

> +       DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);

> +       DECLARE_LIBBPF_OPTS(bpf_tc_opts, nopts, .handle = 1, .priority = 1);

> +       DECLARE_LIBBPF_OPTS(bpf_tc_opts, dopts, .handle = 1, .priority = 1);

> +       struct bpf_link *link;

> +       int ret;

> +

> +       /* We need to test the following cases:

> +        *      1. BPF link owned filter cannot be replaced by netlink

> +        *      2. Netlink owned filter cannot be replaced by BPF link

> +        *      3. Netlink cannot do targeted delete of BPF link owned filter

> +        *      4. Filter is actually deleted (with chain cleanup)

> +        *         We actually (ab)use the kernel behavior of returning EINVAL when

> +        *         target chain doesn't exist on tc_get_tfilter (which maps to

> +        *         bpf_tc_query) here, to know if the chain was really cleaned

> +        *         up on tcf_proto destruction. Our setup is so that there is

> +        *         only one reference to the chain.

> +        *

> +        *         So on query, chain ? (filter ?: ENOENT) : EINVAL

> +        */

> +

> +       link = bpf_program__attach_tc(prog, hook, &opts);

> +       if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))

> +               return PTR_ERR(link);

> +

> +       nopts.prog_fd = bpf_program__fd(prog);

> +       ret = bpf_tc_attach(hook, &nopts);

> +       if (!ASSERT_EQ(ret, -EEXIST, "bpf_tc_attach without replace"))

> +               goto end;

> +

> +       nopts.flags = BPF_TC_F_REPLACE;

> +       ret = bpf_tc_attach(hook, &nopts);

> +       if (!ASSERT_EQ(ret, -EPERM, "bpf_tc_attach with replace"))

> +               goto end;

> +

> +       ret = bpf_tc_detach(hook, &dopts);

> +       if (!ASSERT_EQ(ret, -EPERM, "bpf_tc_detach"))

> +               goto end;

> +

> +       lopts.flags = BPF_F_REPLACE;

> +       ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),

> +                             &lopts);

> +       ASSERT_OK(ret, "bpf_link_update");

> +       ret = ret < 0 ? -errno : ret;


all selftests run in libbpf 1.0 mode, so you get actual error
directly, so no need to deal with -errno here.

> +

> +end:

> +       bpf_link__destroy(link);

> +       if (!ret && !ASSERT_EQ(bpf_tc_query(hook, &dopts), -EINVAL,

> +                              "chain empty delete"))

> +               ret = -EINVAL;

> +       return ret;

> +}

> +

> +static int test_tc_bpf_link_update_ways(struct bpf_tc_hook *hook,

> +                                       struct bpf_program *prog)

> +{

> +       DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);

> +       DECLARE_LIBBPF_OPTS(bpf_link_update_opts, uopts, 0);

> +       struct test_tc_bpf *skel;

> +       struct bpf_link *link;

> +       int ret;

> +

> +       skel = test_tc_bpf__open_and_load();

> +       if (!ASSERT_OK_PTR(skel, "test_tc_bpf__open_and_load"))

> +               return PTR_ERR(skel);

> +

> +       link = bpf_program__attach_tc(prog, hook, &opts);

> +       if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc")) {

> +               ret = PTR_ERR(link);

> +               goto end;

> +       }

> +

> +       ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),

> +                             &uopts);

> +       if (!ASSERT_OK(ret, "bpf_link_update no old prog"))

> +               goto end;

> +

> +       uopts.old_prog_fd = bpf_program__fd(prog);

> +       ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),

> +                             &uopts);


please keep all such calls single-line, they aren't excessively long at all

> +       if (!ASSERT_TRUE(ret < 0 && errno == EINVAL,

> +                        "bpf_link_update with old prog without BPF_F_REPLACE")) {


same as above, ret should already be -EINVAL, so just check directly

> +               ret = -EINVAL;

> +               goto end;

> +       }

> +

> +       uopts.flags = BPF_F_REPLACE;

> +       ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),

> +                             &uopts);

> +       if (!ASSERT_OK(ret, "bpf_link_update with old prog with BPF_F_REPLACE"))

> +               goto end;

> +

> +       uopts.old_prog_fd = bpf_program__fd(skel->progs.cls);

> +       ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),

> +                             &uopts);

> +       if (!ASSERT_TRUE(ret < 0 && errno == EINVAL,

> +                        "bpf_link_update with wrong old prog")) {


and here

> +               ret = -EINVAL;

> +               goto end;

> +       }

> +       ret = 0;

> +

> +end:

> +       test_tc_bpf__destroy(skel);

> +       return ret;

> +}

> +

> +static int test_tc_bpf_link_info_api(struct bpf_tc_hook *hook,

> +                                    struct bpf_program *prog)

> +{

> +       DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);

> +       __u32 ifindex, parent, handle, gen_flags, priority;

> +       char buf[4096], path[256], *begin;

> +       struct bpf_link_info info = {};

> +       __u32 info_len = sizeof(info);

> +       struct bpf_link *link;

> +       int ret, fdinfo;

> +

> +       link = bpf_program__attach_tc(prog, hook, &opts);

> +       if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))

> +               return PTR_ERR(link);

> +

> +       ret = bpf_obj_get_info_by_fd(bpf_link__fd(link), &info, &info_len);

> +       if (!ASSERT_OK(ret, "bpf_obj_get_info_by_fd"))

> +               goto end;

> +

> +       ret = snprintf(path, sizeof(path), "/proc/self/fdinfo/%d",

> +                      bpf_link__fd(link));

> +       if (!ASSERT_TRUE(!ret || ret < sizeof(path), "snprintf pathname"))

> +               goto end;


ASSERT_TRUE is very generic, it's better to do ASSERT_LT(ret,
sizeof(path), "snprintf") here

not sure why `!ret` is allowed?..

> +

> +       fdinfo = open(path, O_RDONLY);

> +       if (!ASSERT_GT(fdinfo, -1, "open fdinfo"))

> +               goto end;

> +

> +       ret = read(fdinfo, buf, sizeof(buf));

> +       if (!ASSERT_GT(ret, 0, "read fdinfo")) {

> +               ret = -EINVAL;

> +               goto end_file;

> +       }

> +

> +       begin = strstr(buf, "ifindex");

> +       if (!ASSERT_OK_PTR(begin, "find beginning of fdinfo info")) {

> +               ret = -EINVAL;

> +               goto end_file;

> +       }

> +

> +       ret = sscanf(begin, "ifindex:\t%u\n"

> +                           "parent:\t%u\n"

> +                           "handle:\t%u\n"

> +                           "priority:\t%u\n"

> +                           "gen_flags:\t%u\n",

> +                           &ifindex, &parent, &handle, &priority, &gen_flags);

> +       if (!ASSERT_EQ(ret, 5, "sscanf fdinfo")) {

> +               ret = -EINVAL;

> +               goto end_file;

> +       }

> +

> +       ret = -EINVAL;

> +

> +#define X(a, b, c) (!ASSERT_EQ(a, b, #a " == " #b) || !ASSERT_EQ(b, c, #b " == " #c))

> +       if (X(info.tc.ifindex, ifindex, 1) ||

> +           X(info.tc.parent, parent,

> +             TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS)) ||

> +           X(info.tc.handle, handle, 1) ||

> +           X(info.tc.gen_flags, gen_flags, TCA_CLS_FLAGS_NOT_IN_HW) ||

> +           X(info.tc.priority, priority, 1))

> +#undef X


This seems to be a bit too convoluted and over-engineered. Just
validate all the equalities unconditionally.

ASSERT_EQ(info.tc.ifindex, 1, "info.tc.ifindex");
ASSERT_EQ(ifindex, 1, "fdinfo.ifindex");
ASSERT_EQ(info.tc.parent, TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS),
"info.tc.parent");

and so on.

Then, you don't really need to propagate errors from
test_tc_bpf_link_info_api, because each ASSERT_EQ() marks the test (or
subtest) as failed, so you don't have to do that below in
test_tc_bpf_link.

> +               goto end_file;

> +

> +       ret = 0;

> +

> +end_file:

> +       close(fdinfo);

> +end:

> +       bpf_link__destroy(link);

> +       return ret;

> +}

> +

> +void test_tc_bpf_link(void)

> +{

> +       DECLARE_LIBBPF_OPTS(bpf_tc_hook, hook, .ifindex = LO_IFINDEX,

> +                           .attach_point = BPF_TC_INGRESS);

> +       struct test_tc_bpf *skel = NULL;

> +       bool hook_created = false;

> +       int ret;

> +

> +       skel = test_tc_bpf__open_and_load();

> +       if (!ASSERT_OK_PTR(skel, "test_tc_bpf__open_and_load"))

> +               return;

> +

> +       ret = bpf_tc_hook_create(&hook);

> +       if (ret == 0)

> +               hook_created = true;

> +

> +       ret = ret == -EEXIST ? 0 : ret;

> +       if (!ASSERT_OK(ret, "bpf_tc_hook_create(BPF_TC_INGRESS)"))

> +               goto end;

> +

> +       ret = test_tc_bpf_link_basic(&hook, skel->progs.cls);

> +       if (!ASSERT_OK(ret, "test_tc_bpf_link_basic"))

> +               goto end;

> +

> +       bpf_tc_hook_destroy(&hook);

> +

> +       hook.attach_point = BPF_TC_EGRESS;

> +       ret = test_tc_bpf_link_basic(&hook, skel->progs.cls);

> +       if (!ASSERT_OK(ret, "test_tc_bpf_link_basic"))

> +               goto end;

> +

> +       bpf_tc_hook_destroy(&hook);

> +

> +       ret = test_tc_bpf_link_netlink_interaction(&hook, skel->progs.cls);

> +       if (!ASSERT_OK(ret, "test_tc_bpf_link_netlink_interaction"))

> +               goto end;

> +

> +       bpf_tc_hook_destroy(&hook);

> +

> +       ret = test_tc_bpf_link_update_ways(&hook, skel->progs.cls);

> +       if (!ASSERT_OK(ret, "test_tc_bpf_link_update_ways"))

> +               goto end;

> +

> +       bpf_tc_hook_destroy(&hook);

> +

> +       ret = test_tc_bpf_link_info_api(&hook, skel->progs.cls);

> +       if (!ASSERT_OK(ret, "test_tc_bpf_link_info_api"))


I was talking about this above, it's completely unnecessary and
redundant. Just complicates everything.

> +               goto end;

> +

> +end:

> +       if (hook_created) {

> +               hook.attach_point = BPF_TC_INGRESS | BPF_TC_EGRESS;

> +               bpf_tc_hook_destroy(&hook);

> +       }

> +       test_tc_bpf__destroy(skel);

> +}

> --

> 2.31.1

>
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c b/tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c
new file mode 100644
index 000000000000..beaf06e0557c
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tc_bpf_link.c
@@ -0,0 +1,285 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include <linux/pkt_cls.h>
+
+#include "test_tc_bpf.skel.h"
+
+#define LO_IFINDEX 1
+
+static int test_tc_bpf_link_basic(struct bpf_tc_hook *hook,
+				  struct bpf_program *prog)
+{
+	DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);
+	DECLARE_LIBBPF_OPTS(bpf_tc_opts, qopts, .handle = 1, .priority = 1);
+	struct bpf_prog_info info = {};
+	__u32 info_len = sizeof(info);
+	struct bpf_link *link, *invl;
+	int ret;
+
+	link = bpf_program__attach_tc(prog, hook, &opts);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))
+		return PTR_ERR(link);
+
+	ret = bpf_obj_get_info_by_fd(bpf_program__fd(prog), &info, &info_len);
+	if (!ASSERT_OK(ret, "bpf_obj_get_info_by_fd"))
+		goto end;
+
+	ret = bpf_tc_query(hook, &qopts);
+	if (!ASSERT_OK(ret, "bpf_tc_query"))
+		goto end;
+
+	if (!ASSERT_EQ(qopts.prog_id, info.id, "prog_id match"))
+		goto end;
+
+	opts.gen_flags = ~0u;
+	invl = bpf_program__attach_tc(prog, hook, &opts);
+	if (!ASSERT_ERR_PTR(invl, "bpf_program__attach_tc with invalid flags")) {
+		bpf_link__destroy(invl);
+		ret = -EINVAL;
+	}
+
+end:
+	bpf_link__destroy(link);
+	return ret;
+}
+
+static int test_tc_bpf_link_netlink_interaction(struct bpf_tc_hook *hook,
+						struct bpf_program *prog)
+{
+	DECLARE_LIBBPF_OPTS(bpf_link_update_opts, lopts,
+			    .old_prog_fd = bpf_program__fd(prog));
+	DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);
+	DECLARE_LIBBPF_OPTS(bpf_tc_opts, nopts, .handle = 1, .priority = 1);
+	DECLARE_LIBBPF_OPTS(bpf_tc_opts, dopts, .handle = 1, .priority = 1);
+	struct bpf_link *link;
+	int ret;
+
+	/* We need to test the following cases:
+	 *	1. BPF link owned filter cannot be replaced by netlink
+	 *	2. Netlink owned filter cannot be replaced by BPF link
+	 *	3. Netlink cannot do targeted delete of BPF link owned filter
+	 *	4. Filter is actually deleted (with chain cleanup)
+	 *	   We actually (ab)use the kernel behavior of returning EINVAL when
+	 *	   target chain doesn't exist on tc_get_tfilter (which maps to
+	 *	   bpf_tc_query) here, to know if the chain was really cleaned
+	 *	   up on tcf_proto destruction. Our setup is so that there is
+	 *	   only one reference to the chain.
+	 *
+	 *	   So on query, chain ? (filter ?: ENOENT) : EINVAL
+	 */
+
+	link = bpf_program__attach_tc(prog, hook, &opts);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))
+		return PTR_ERR(link);
+
+	nopts.prog_fd = bpf_program__fd(prog);
+	ret = bpf_tc_attach(hook, &nopts);
+	if (!ASSERT_EQ(ret, -EEXIST, "bpf_tc_attach without replace"))
+		goto end;
+
+	nopts.flags = BPF_TC_F_REPLACE;
+	ret = bpf_tc_attach(hook, &nopts);
+	if (!ASSERT_EQ(ret, -EPERM, "bpf_tc_attach with replace"))
+		goto end;
+
+	ret = bpf_tc_detach(hook, &dopts);
+	if (!ASSERT_EQ(ret, -EPERM, "bpf_tc_detach"))
+		goto end;
+
+	lopts.flags = BPF_F_REPLACE;
+	ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),
+			      &lopts);
+	ASSERT_OK(ret, "bpf_link_update");
+	ret = ret < 0 ? -errno : ret;
+
+end:
+	bpf_link__destroy(link);
+	if (!ret && !ASSERT_EQ(bpf_tc_query(hook, &dopts), -EINVAL,
+			       "chain empty delete"))
+		ret = -EINVAL;
+	return ret;
+}
+
+static int test_tc_bpf_link_update_ways(struct bpf_tc_hook *hook,
+					struct bpf_program *prog)
+{
+	DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);
+	DECLARE_LIBBPF_OPTS(bpf_link_update_opts, uopts, 0);
+	struct test_tc_bpf *skel;
+	struct bpf_link *link;
+	int ret;
+
+	skel = test_tc_bpf__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_tc_bpf__open_and_load"))
+		return PTR_ERR(skel);
+
+	link = bpf_program__attach_tc(prog, hook, &opts);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc")) {
+		ret = PTR_ERR(link);
+		goto end;
+	}
+
+	ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),
+			      &uopts);
+	if (!ASSERT_OK(ret, "bpf_link_update no old prog"))
+		goto end;
+
+	uopts.old_prog_fd = bpf_program__fd(prog);
+	ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),
+			      &uopts);
+	if (!ASSERT_TRUE(ret < 0 && errno == EINVAL,
+			 "bpf_link_update with old prog without BPF_F_REPLACE")) {
+		ret = -EINVAL;
+		goto end;
+	}
+
+	uopts.flags = BPF_F_REPLACE;
+	ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),
+			      &uopts);
+	if (!ASSERT_OK(ret, "bpf_link_update with old prog with BPF_F_REPLACE"))
+		goto end;
+
+	uopts.old_prog_fd = bpf_program__fd(skel->progs.cls);
+	ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog),
+			      &uopts);
+	if (!ASSERT_TRUE(ret < 0 && errno == EINVAL,
+			 "bpf_link_update with wrong old prog")) {
+		ret = -EINVAL;
+		goto end;
+	}
+	ret = 0;
+
+end:
+	test_tc_bpf__destroy(skel);
+	return ret;
+}
+
+static int test_tc_bpf_link_info_api(struct bpf_tc_hook *hook,
+				     struct bpf_program *prog)
+{
+	DECLARE_LIBBPF_OPTS(bpf_tc_link_opts, opts, .handle = 1, .priority = 1);
+	__u32 ifindex, parent, handle, gen_flags, priority;
+	char buf[4096], path[256], *begin;
+	struct bpf_link_info info = {};
+	__u32 info_len = sizeof(info);
+	struct bpf_link *link;
+	int ret, fdinfo;
+
+	link = bpf_program__attach_tc(prog, hook, &opts);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tc"))
+		return PTR_ERR(link);
+
+	ret = bpf_obj_get_info_by_fd(bpf_link__fd(link), &info, &info_len);
+	if (!ASSERT_OK(ret, "bpf_obj_get_info_by_fd"))
+		goto end;
+
+	ret = snprintf(path, sizeof(path), "/proc/self/fdinfo/%d",
+		       bpf_link__fd(link));
+	if (!ASSERT_TRUE(!ret || ret < sizeof(path), "snprintf pathname"))
+		goto end;
+
+	fdinfo = open(path, O_RDONLY);
+	if (!ASSERT_GT(fdinfo, -1, "open fdinfo"))
+		goto end;
+
+	ret = read(fdinfo, buf, sizeof(buf));
+	if (!ASSERT_GT(ret, 0, "read fdinfo")) {
+		ret = -EINVAL;
+		goto end_file;
+	}
+
+	begin = strstr(buf, "ifindex");
+	if (!ASSERT_OK_PTR(begin, "find beginning of fdinfo info")) {
+		ret = -EINVAL;
+		goto end_file;
+	}
+
+	ret = sscanf(begin, "ifindex:\t%u\n"
+			    "parent:\t%u\n"
+			    "handle:\t%u\n"
+			    "priority:\t%u\n"
+			    "gen_flags:\t%u\n",
+			    &ifindex, &parent, &handle, &priority, &gen_flags);
+	if (!ASSERT_EQ(ret, 5, "sscanf fdinfo")) {
+		ret = -EINVAL;
+		goto end_file;
+	}
+
+	ret = -EINVAL;
+
+#define X(a, b, c) (!ASSERT_EQ(a, b, #a " == " #b) || !ASSERT_EQ(b, c, #b " == " #c))
+	if (X(info.tc.ifindex, ifindex, 1) ||
+	    X(info.tc.parent, parent,
+	      TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS)) ||
+	    X(info.tc.handle, handle, 1) ||
+	    X(info.tc.gen_flags, gen_flags, TCA_CLS_FLAGS_NOT_IN_HW) ||
+	    X(info.tc.priority, priority, 1))
+#undef X
+		goto end_file;
+
+	ret = 0;
+
+end_file:
+	close(fdinfo);
+end:
+	bpf_link__destroy(link);
+	return ret;
+}
+
+void test_tc_bpf_link(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_tc_hook, hook, .ifindex = LO_IFINDEX,
+			    .attach_point = BPF_TC_INGRESS);
+	struct test_tc_bpf *skel = NULL;
+	bool hook_created = false;
+	int ret;
+
+	skel = test_tc_bpf__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_tc_bpf__open_and_load"))
+		return;
+
+	ret = bpf_tc_hook_create(&hook);
+	if (ret == 0)
+		hook_created = true;
+
+	ret = ret == -EEXIST ? 0 : ret;
+	if (!ASSERT_OK(ret, "bpf_tc_hook_create(BPF_TC_INGRESS)"))
+		goto end;
+
+	ret = test_tc_bpf_link_basic(&hook, skel->progs.cls);
+	if (!ASSERT_OK(ret, "test_tc_bpf_link_basic"))
+		goto end;
+
+	bpf_tc_hook_destroy(&hook);
+
+	hook.attach_point = BPF_TC_EGRESS;
+	ret = test_tc_bpf_link_basic(&hook, skel->progs.cls);
+	if (!ASSERT_OK(ret, "test_tc_bpf_link_basic"))
+		goto end;
+
+	bpf_tc_hook_destroy(&hook);
+
+	ret = test_tc_bpf_link_netlink_interaction(&hook, skel->progs.cls);
+	if (!ASSERT_OK(ret, "test_tc_bpf_link_netlink_interaction"))
+		goto end;
+
+	bpf_tc_hook_destroy(&hook);
+
+	ret = test_tc_bpf_link_update_ways(&hook, skel->progs.cls);
+	if (!ASSERT_OK(ret, "test_tc_bpf_link_update_ways"))
+		goto end;
+
+	bpf_tc_hook_destroy(&hook);
+
+	ret = test_tc_bpf_link_info_api(&hook, skel->progs.cls);
+	if (!ASSERT_OK(ret, "test_tc_bpf_link_info_api"))
+		goto end;
+
+end:
+	if (hook_created) {
+		hook.attach_point = BPF_TC_INGRESS | BPF_TC_EGRESS;
+		bpf_tc_hook_destroy(&hook);
+	}
+	test_tc_bpf__destroy(skel);
+}