selftests/bpf: Add two selftests for mprog API based cgroup progs

Two tests are added:
- cgroup_mprog_opts, which mimics tc_opts.c ([1]). Both prog and link
attach are tested. Some negative tests are also included.
- cgroup_mprog_ordering, which actually runs the program with some mprog
API flags.

[1] https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/prog_tests/tc_opts.c

Signed-off-by: Yonghong Song <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/testing/selftests/bpf/prog_tests/cgroup_mprog_opts.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include "cgroup_helpers.h"
+#include "cgroup_mprog.skel.h"
+
+static void assert_mprog_count(int cg, int atype, int expected)
+{
+	__u32 count = 0, attach_flags = 0;
+	int err;
+
+	err = bpf_prog_query(cg, atype, 0, &attach_flags,
+			     NULL, &count);
+	ASSERT_EQ(count, expected, "count");
+	ASSERT_EQ(err, 0, "prog_query");
+}
+
+static void test_prog_attach_detach(int atype)
+{
+	LIBBPF_OPTS(bpf_prog_attach_opts, opta);
+	LIBBPF_OPTS(bpf_prog_detach_opts, optd);
+	LIBBPF_OPTS(bpf_prog_query_opts, optq);
+	__u32 fd1, fd2, fd3, fd4, id1, id2, id3, id4;
+	struct cgroup_mprog *skel;
+	__u32 prog_ids[10];
+	int cg, err;
+
+	cg = test__join_cgroup("/prog_attach_detach");
+	if (!ASSERT_GE(cg, 0, "join_cgroup /prog_attach_detach"))
+		return;
+
+	skel = cgroup_mprog__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	fd1 = bpf_program__fd(skel->progs.getsockopt_1);
+	fd2 = bpf_program__fd(skel->progs.getsockopt_2);
+	fd3 = bpf_program__fd(skel->progs.getsockopt_3);
+	fd4 = bpf_program__fd(skel->progs.getsockopt_4);
+
+	id1 = id_from_prog_fd(fd1);
+	id2 = id_from_prog_fd(fd2);
+	id3 = id_from_prog_fd(fd3);
+	id4 = id_from_prog_fd(fd4);
+
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_BEFORE | BPF_F_AFTER,
+		.expected_revision = 1,
+	);
+
+	/* ordering: [fd1] */
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup;
+
+	assert_mprog_count(cg, atype, 1);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_BEFORE,
+		.expected_revision = 2,
+	);
+
+	/* ordering: [fd2, fd1] */
+	err = bpf_prog_attach_opts(fd2, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup1;
+
+	assert_mprog_count(cg, atype, 2);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_AFTER,
+		.relative_fd = fd2,
+		.expected_revision = 3,
+	);
+
+	/* ordering: [fd2, fd3, fd1] */
+	err = bpf_prog_attach_opts(fd3, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup2;
+
+	assert_mprog_count(cg, atype, 3);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI,
+		.expected_revision = 4,
+	);
+
+	/* ordering: [fd2, fd3, fd1, fd4] */
+	err = bpf_prog_attach_opts(fd4, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup3;
+
+	assert_mprog_count(cg, atype, 4);
+
+	/* retrieve optq.prog_cnt */
+	err = bpf_prog_query_opts(cg, atype, &optq);
+	if (!ASSERT_OK(err, "prog_query"))
+		goto cleanup4;
+
+	/* optq.prog_cnt will be used in below query */
+	memset(prog_ids, 0, sizeof(prog_ids));
+	optq.prog_ids = prog_ids;
+	err = bpf_prog_query_opts(cg, atype, &optq);
+	if (!ASSERT_OK(err, "prog_query"))
+		goto cleanup4;
+
+	ASSERT_EQ(optq.count, 4, "count");
+	ASSERT_EQ(optq.revision, 5, "revision");
+	ASSERT_EQ(optq.prog_ids[0], id2, "prog_ids[0]");
+	ASSERT_EQ(optq.prog_ids[1], id3, "prog_ids[1]");
+	ASSERT_EQ(optq.prog_ids[2], id1, "prog_ids[2]");
+	ASSERT_EQ(optq.prog_ids[3], id4, "prog_ids[3]");
+	ASSERT_EQ(optq.prog_ids[4], 0, "prog_ids[4]");
+	ASSERT_EQ(optq.link_ids, NULL, "link_ids");
+
+cleanup4:
+	optd.expected_revision = 5;
+	err = bpf_prog_detach_opts(fd4, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 3);
+
+cleanup3:
+	LIBBPF_OPTS_RESET(optd);
+	err = bpf_prog_detach_opts(fd3, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 2);
+
+	/* Check revision after two detach operations */
+	err = bpf_prog_query_opts(cg, atype, &optq);
+	ASSERT_OK(err, "prog_query");
+	ASSERT_EQ(optq.revision, 7, "revision");
+
+cleanup2:
+	err = bpf_prog_detach_opts(fd2, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 1);
+
+cleanup1:
+	err = bpf_prog_detach_opts(fd1, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 0);
+
+cleanup:
+	cgroup_mprog__destroy(skel);
+	close(cg);
+}
+
+static void test_link_attach_detach(int atype)
+{
+	LIBBPF_OPTS(bpf_cgroup_opts, opta);
+	LIBBPF_OPTS(bpf_cgroup_opts, optd);
+	LIBBPF_OPTS(bpf_prog_query_opts, optq);
+	struct bpf_link *link1, *link2, *link3, *link4;
+	__u32 fd1, fd2, fd3, fd4, id1, id2, id3, id4;
+	struct cgroup_mprog *skel;
+	__u32 prog_ids[10];
+	int cg, err;
+
+	cg = test__join_cgroup("/link_attach_detach");
+	if (!ASSERT_GE(cg, 0, "join_cgroup /link_attach_detach"))
+		return;
+
+	skel = cgroup_mprog__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	fd1 = bpf_program__fd(skel->progs.getsockopt_1);
+	fd2 = bpf_program__fd(skel->progs.getsockopt_2);
+	fd3 = bpf_program__fd(skel->progs.getsockopt_3);
+	fd4 = bpf_program__fd(skel->progs.getsockopt_4);
+
+	id1 = id_from_prog_fd(fd1);
+	id2 = id_from_prog_fd(fd2);
+	id3 = id_from_prog_fd(fd3);
+	id4 = id_from_prog_fd(fd4);
+
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.expected_revision = 1,
+	);
+
+	/* ordering: [fd1] */
+	link1 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_1, cg, &opta);
+	if (!ASSERT_OK_PTR(link1, "link_attach"))
+		goto cleanup;
+
+	assert_mprog_count(cg, atype, 1);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_BEFORE | BPF_F_LINK,
+		.relative_id = id_from_link_fd(bpf_link__fd(link1)),
+		.expected_revision = 2,
+	);
+
+	/* ordering: [fd2, fd1] */
+	link2 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_2, cg, &opta);
+	if (!ASSERT_OK_PTR(link2, "link_attach"))
+		goto cleanup1;
+
+	assert_mprog_count(cg, atype, 2);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_AFTER | BPF_F_LINK,
+		.relative_fd = bpf_link__fd(link2),
+		.expected_revision = 3,
+	);
+
+	/* ordering: [fd2, fd3, fd1] */
+	link3 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_3, cg, &opta);
+	if (!ASSERT_OK_PTR(link3, "link_attach"))
+		goto cleanup2;
+
+	assert_mprog_count(cg, atype, 3);
+
+	LIBBPF_OPTS_RESET(opta,
+		.expected_revision = 4,
+	);
+
+	/* ordering: [fd2, fd3, fd1, fd4] */
+	link4 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_4, cg, &opta);
+	if (!ASSERT_OK_PTR(link4, "link_attach"))
+		goto cleanup3;
+
+	assert_mprog_count(cg, atype, 4);
+
+	/* retrieve optq.prog_cnt */
+	err = bpf_prog_query_opts(cg, atype, &optq);
+	if (!ASSERT_OK(err, "prog_query"))
+		goto cleanup4;
+
+	/* optq.prog_cnt will be used in below query */
+	memset(prog_ids, 0, sizeof(prog_ids));
+	optq.prog_ids = prog_ids;
+	err = bpf_prog_query_opts(cg, atype, &optq);
+	if (!ASSERT_OK(err, "prog_query"))
+		goto cleanup4;
+
+	ASSERT_EQ(optq.count, 4, "count");
+	ASSERT_EQ(optq.revision, 5, "revision");
+	ASSERT_EQ(optq.prog_ids[0], id2, "prog_ids[0]");
+	ASSERT_EQ(optq.prog_ids[1], id3, "prog_ids[1]");
+	ASSERT_EQ(optq.prog_ids[2], id1, "prog_ids[2]");
+	ASSERT_EQ(optq.prog_ids[3], id4, "prog_ids[3]");
+	ASSERT_EQ(optq.prog_ids[4], 0, "prog_ids[4]");
+	ASSERT_EQ(optq.link_ids, NULL, "link_ids");
+
+cleanup4:
+	bpf_link__destroy(link4);
+	assert_mprog_count(cg, atype, 3);
+
+cleanup3:
+	bpf_link__destroy(link3);
+	assert_mprog_count(cg, atype, 2);
+
+	/* Check revision after two detach operations */
+	err = bpf_prog_query_opts(cg, atype, &optq);
+	ASSERT_OK(err, "prog_query");
+	ASSERT_EQ(optq.revision, 7, "revision");
+
+cleanup2:
+	bpf_link__destroy(link2);
+	assert_mprog_count(cg, atype, 1);
+
+cleanup1:
+	bpf_link__destroy(link1);
+	assert_mprog_count(cg, atype, 0);
+
+cleanup:
+	cgroup_mprog__destroy(skel);
+	close(cg);
+}
+
+static void test_preorder_prog_attach_detach(int atype)
+{
+	LIBBPF_OPTS(bpf_prog_attach_opts, opta);
+	LIBBPF_OPTS(bpf_prog_detach_opts, optd);
+	__u32 fd1, fd2, fd3, fd4;
+	struct cgroup_mprog *skel;
+	int cg, err;
+
+	cg = test__join_cgroup("/preorder_prog_attach_detach");
+	if (!ASSERT_GE(cg, 0, "join_cgroup /preorder_prog_attach_detach"))
+		return;
+
+	skel = cgroup_mprog__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	fd1 = bpf_program__fd(skel->progs.getsockopt_1);
+	fd2 = bpf_program__fd(skel->progs.getsockopt_2);
+	fd3 = bpf_program__fd(skel->progs.getsockopt_3);
+	fd4 = bpf_program__fd(skel->progs.getsockopt_4);
+
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI,
+		.expected_revision = 1,
+	);
+
+	/* ordering: [fd1] */
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup;
+
+	assert_mprog_count(cg, atype, 1);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_PREORDER,
+		.expected_revision = 2,
+	);
+
+	/* ordering: [fd1, fd2] */
+	err = bpf_prog_attach_opts(fd2, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup1;
+
+	assert_mprog_count(cg, atype, 2);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_AFTER,
+		.relative_fd = fd2,
+		.expected_revision = 3,
+	);
+
+	err = bpf_prog_attach_opts(fd3, cg, atype, &opta);
+	if (!ASSERT_EQ(err, -EINVAL, "prog_attach"))
+		goto cleanup2;
+
+	assert_mprog_count(cg, atype, 2);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_AFTER | BPF_F_PREORDER,
+		.relative_fd = fd2,
+		.expected_revision = 3,
+	);
+
+	/* ordering: [fd1, fd2, fd3] */
+	err = bpf_prog_attach_opts(fd3, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup2;
+
+	assert_mprog_count(cg, atype, 3);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI,
+		.expected_revision = 4,
+	);
+
+	/* ordering: [fd2, fd3, fd1, fd4] */
+	err = bpf_prog_attach_opts(fd4, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup3;
+
+	assert_mprog_count(cg, atype, 4);
+
+	err = bpf_prog_detach_opts(fd4, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 3);
+
+cleanup3:
+	err = bpf_prog_detach_opts(fd3, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 2);
+
+cleanup2:
+	err = bpf_prog_detach_opts(fd2, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 1);
+
+cleanup1:
+	err = bpf_prog_detach_opts(fd1, cg, atype, &optd);
+	ASSERT_OK(err, "prog_detach");
+	assert_mprog_count(cg, atype, 0);
+
+cleanup:
+	cgroup_mprog__destroy(skel);
+	close(cg);
+}
+
+static void test_preorder_link_attach_detach(int atype)
+{
+	LIBBPF_OPTS(bpf_cgroup_opts, opta);
+	struct bpf_link *link1, *link2, *link3, *link4;
+	struct cgroup_mprog *skel;
+	__u32 fd2;
+	int cg;
+
+	cg = test__join_cgroup("/preorder_link_attach_detach");
+	if (!ASSERT_GE(cg, 0, "join_cgroup /preorder_link_attach_detach"))
+		return;
+
+	skel = cgroup_mprog__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	fd2 = bpf_program__fd(skel->progs.getsockopt_2);
+
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.expected_revision = 1,
+	);
+
+	/* ordering: [fd1] */
+	link1 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_1, cg, &opta);
+	if (!ASSERT_OK_PTR(link1, "link_attach"))
+		goto cleanup;
+
+	assert_mprog_count(cg, atype, 1);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_PREORDER,
+		.expected_revision = 2,
+	);
+
+	/* ordering: [fd1, fd2] */
+	link2 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_2, cg, &opta);
+	if (!ASSERT_OK_PTR(link2, "link_attach"))
+		goto cleanup1;
+
+	assert_mprog_count(cg, atype, 2);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_AFTER,
+		.relative_fd = fd2,
+		.expected_revision = 3,
+	);
+
+	link3 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_3, cg, &opta);
+	if (!ASSERT_ERR_PTR(link3, "link_attach"))
+		goto cleanup2;
+
+	assert_mprog_count(cg, atype, 2);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_AFTER | BPF_F_PREORDER | BPF_F_LINK,
+		.relative_fd = bpf_link__fd(link2),
+		.expected_revision = 3,
+	);
+
+	/* ordering: [fd1, fd2, fd3] */
+	link3 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_3, cg, &opta);
+	if (!ASSERT_OK_PTR(link3, "link_attach"))
+		goto cleanup2;
+
+	assert_mprog_count(cg, atype, 3);
+
+	LIBBPF_OPTS_RESET(opta,
+		.expected_revision = 4,
+	);
+
+	/* ordering: [fd2, fd3, fd1, fd4] */
+	link4 = bpf_program__attach_cgroup_opts(skel->progs.getsockopt_4, cg, &opta);
+	if (!ASSERT_OK_PTR(link4, "prog_attach"))
+		goto cleanup3;
+
+	assert_mprog_count(cg, atype, 4);
+
+	bpf_link__destroy(link4);
+	assert_mprog_count(cg, atype, 3);
+
+cleanup3:
+	bpf_link__destroy(link3);
+	assert_mprog_count(cg, atype, 2);
+
+cleanup2:
+	bpf_link__destroy(link2);
+	assert_mprog_count(cg, atype, 1);
+
+cleanup1:
+	bpf_link__destroy(link1);
+	assert_mprog_count(cg, atype, 0);
+
+cleanup:
+	cgroup_mprog__destroy(skel);
+	close(cg);
+}
+
+static void test_invalid_attach_detach(int atype)
+{
+	LIBBPF_OPTS(bpf_prog_attach_opts, opta);
+	__u32 fd1, fd2, id2;
+	struct cgroup_mprog *skel;
+	int cg, err;
+
+	cg = test__join_cgroup("/invalid_attach_detach");
+	if (!ASSERT_GE(cg, 0, "join_cgroup /invalid_attach_detach"))
+		return;
+
+	skel = cgroup_mprog__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	fd1 = bpf_program__fd(skel->progs.getsockopt_1);
+	fd2 = bpf_program__fd(skel->progs.getsockopt_2);
+
+	id2 = id_from_prog_fd(fd2);
+
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_BEFORE | BPF_F_AFTER,
+		.relative_id = id2,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -EINVAL, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_BEFORE | BPF_F_ID,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -ENOENT, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_AFTER | BPF_F_ID,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -ENOENT, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_BEFORE | BPF_F_AFTER,
+		.relative_id = id2,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -EINVAL, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_LINK,
+		.relative_id = id2,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -EINVAL, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI,
+		.relative_id = id2,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -EINVAL, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_BEFORE,
+		.relative_fd = fd1,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -ENOENT, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_AFTER,
+		.relative_fd = fd1,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -ENOENT, "prog_attach");
+	assert_mprog_count(cg, atype, 0);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	if (!ASSERT_EQ(err, 0, "prog_attach"))
+		goto cleanup;
+	assert_mprog_count(cg, atype, 1);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_AFTER,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -EINVAL, "prog_attach");
+	assert_mprog_count(cg, atype, 1);
+
+	LIBBPF_OPTS_RESET(opta,
+		.flags = BPF_F_ALLOW_MULTI | BPF_F_REPLACE | BPF_F_AFTER,
+		.replace_prog_fd = fd1,
+	);
+
+	err = bpf_prog_attach_opts(fd1, cg, atype, &opta);
+	ASSERT_EQ(err, -EINVAL, "prog_attach");
+	assert_mprog_count(cg, atype, 1);
+cleanup:
+	cgroup_mprog__destroy(skel);
+	close(cg);
+}
+
+void test_cgroup_mprog_opts(void)
+{
+	if (test__start_subtest("prog_attach_detach"))
+		test_prog_attach_detach(BPF_CGROUP_GETSOCKOPT);
+	if (test__start_subtest("link_attach_detach"))
+		test_link_attach_detach(BPF_CGROUP_GETSOCKOPT);
+	if (test__start_subtest("preorder_prog_attach_detach"))
+		test_preorder_prog_attach_detach(BPF_CGROUP_GETSOCKOPT);
+	if (test__start_subtest("preorder_link_attach_detach"))
+		test_preorder_link_attach_detach(BPF_CGROUP_GETSOCKOPT);
+	if (test__start_subtest("invalid_attach_detach"))
+		test_invalid_attach_detach(BPF_CGROUP_GETSOCKOPT);
+}

tools/testing/selftests/bpf/prog_tests/cgroup_mprog_ordering.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include "cgroup_helpers.h"
+#include "cgroup_preorder.skel.h"
+
+static int run_getsockopt_test(int cg_parent, int sock_fd, bool has_relative_fd)
+{
+	LIBBPF_OPTS(bpf_prog_attach_opts, opts);
+	enum bpf_attach_type prog_p_atype, prog_p2_atype;
+	int prog_p_fd, prog_p2_fd;
+	struct cgroup_preorder *skel = NULL;
+	struct bpf_program *prog;
+	__u8 *result, buf;
+	socklen_t optlen;
+	int err = 0;
+
+	skel = cgroup_preorder__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "cgroup_preorder__open_and_load"))
+		return 0;
+
+	LIBBPF_OPTS_RESET(opts);
+	opts.flags = BPF_F_ALLOW_MULTI;
+	prog = skel->progs.parent;
+	prog_p_fd = bpf_program__fd(prog);
+	prog_p_atype = bpf_program__expected_attach_type(prog);
+	err = bpf_prog_attach_opts(prog_p_fd, cg_parent, prog_p_atype, &opts);
+	if (!ASSERT_OK(err, "bpf_prog_attach_opts-parent"))
+		goto close_skel;
+
+	opts.flags = BPF_F_ALLOW_MULTI | BPF_F_BEFORE;
+	if (has_relative_fd)
+		opts.relative_fd = prog_p_fd;
+	prog = skel->progs.parent_2;
+	prog_p2_fd = bpf_program__fd(prog);
+	prog_p2_atype = bpf_program__expected_attach_type(prog);
+	err = bpf_prog_attach_opts(prog_p2_fd, cg_parent, prog_p2_atype, &opts);
+	if (!ASSERT_OK(err, "bpf_prog_attach_opts-parent_2"))
+		goto detach_parent;
+
+	err = getsockopt(sock_fd, SOL_IP, IP_TOS, &buf, &optlen);
+	if (!ASSERT_OK(err, "getsockopt"))
+		goto detach_parent_2;
+
+	result = skel->bss->result;
+	ASSERT_TRUE(result[0] == 4 && result[1] == 3, "result values");
+
+detach_parent_2:
+	ASSERT_OK(bpf_prog_detach2(prog_p2_fd, cg_parent, prog_p2_atype),
+		  "bpf_prog_detach2-parent_2");
+detach_parent:
+	ASSERT_OK(bpf_prog_detach2(prog_p_fd, cg_parent, prog_p_atype),
+		  "bpf_prog_detach2-parent");
+close_skel:
+	cgroup_preorder__destroy(skel);
+	return err;
+}
+
+void test_cgroup_mprog_ordering(void)
+{
+	int cg_parent = -1, sock_fd = -1;
+
+	cg_parent = test__join_cgroup("/parent");
+	if (!ASSERT_GE(cg_parent, 0, "join_cgroup /parent"))
+		goto out;
+
+	sock_fd = socket(AF_INET, SOCK_STREAM, 0);
+	if (!ASSERT_GE(sock_fd, 0, "socket"))
+		goto out;
+
+	ASSERT_OK(run_getsockopt_test(cg_parent, sock_fd, false), "getsockopt_test_1");
+	ASSERT_OK(run_getsockopt_test(cg_parent, sock_fd, true), "getsockopt_test_2");
+
+out:
+	close(sock_fd);
+	close(cg_parent);
+}

tools/testing/selftests/bpf/progs/cgroup_mprog.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("cgroup/getsockopt")
+int getsockopt_1(struct bpf_sockopt *ctx)
+{
+	return 1;
+}
+
+SEC("cgroup/getsockopt")
+int getsockopt_2(struct bpf_sockopt *ctx)
+{
+	return 1;
+}
+
+SEC("cgroup/getsockopt")
+int getsockopt_3(struct bpf_sockopt *ctx)
+{
+	return 1;
+}
+
+SEC("cgroup/getsockopt")
+int getsockopt_4(struct bpf_sockopt *ctx)
+{
+	return 1;
+}