selftests/bpf: Add selftests allowing cgroup prog pre-ordering

Add a few selftests with cgroup prog pre-ordering.

Signed-off-by: Yonghong Song <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/prog_tests/cgroup_preorder.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 cg_child, int sock_fd, bool all_preorder)
+{
+	LIBBPF_OPTS(bpf_prog_attach_opts, opts);
+	enum bpf_attach_type prog_c_atype, prog_c2_atype, prog_p_atype, prog_p2_atype;
+	int prog_c_fd, prog_c2_fd, 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;
+
+	buf = 0x00;
+	err = setsockopt(sock_fd, SOL_IP, IP_TOS, &buf, 1);
+	if (!ASSERT_OK(err, "setsockopt"))
+		goto close_skel;
+
+	opts.flags = BPF_F_ALLOW_MULTI;
+	if (all_preorder)
+		opts.flags |= BPF_F_PREORDER;
+	prog = skel->progs.child;
+	prog_c_fd = bpf_program__fd(prog);
+	prog_c_atype = bpf_program__expected_attach_type(prog);
+	err = bpf_prog_attach_opts(prog_c_fd, cg_child, prog_c_atype, &opts);
+	if (!ASSERT_OK(err, "bpf_prog_attach_opts-child"))
+		goto close_skel;
+
+	opts.flags = BPF_F_ALLOW_MULTI | BPF_F_PREORDER;
+	prog = skel->progs.child_2;
+	prog_c2_fd = bpf_program__fd(prog);
+	prog_c2_atype = bpf_program__expected_attach_type(prog);
+	err = bpf_prog_attach_opts(prog_c2_fd, cg_child, prog_c2_atype, &opts);
+	if (!ASSERT_OK(err, "bpf_prog_attach_opts-child_2"))
+		goto detach_child;
+
+	optlen = 1;
+	err = getsockopt(sock_fd, SOL_IP, IP_TOS, &buf, &optlen);
+	if (!ASSERT_OK(err, "getsockopt"))
+		goto detach_child_2;
+
+	result = skel->bss->result;
+	if (all_preorder)
+		ASSERT_TRUE(result[0] == 1 && result[1] == 2, "child only");
+	else
+		ASSERT_TRUE(result[0] == 2 && result[1] == 1, "child only");
+
+	skel->bss->idx = 0;
+	memset(result, 0, 4);
+
+	opts.flags = BPF_F_ALLOW_MULTI;
+	if (all_preorder)
+		opts.flags |= BPF_F_PREORDER;
+	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 detach_child_2;
+
+	opts.flags = BPF_F_ALLOW_MULTI | BPF_F_PREORDER;
+	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;
+
+	if (all_preorder)
+		ASSERT_TRUE(result[0] == 3 && result[1] == 4 && result[2] == 1 && result[3] == 2,
+			    "parent and child");
+	else
+		ASSERT_TRUE(result[0] == 4 && result[1] == 2 && result[2] == 1 && result[3] == 3,
+			    "parent and child");
+
+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");
+detach_child_2:
+	ASSERT_OK(bpf_prog_detach2(prog_c2_fd, cg_child, prog_c2_atype),
+		  "bpf_prog_detach2-child_2");
+detach_child:
+	ASSERT_OK(bpf_prog_detach2(prog_c_fd, cg_child, prog_c_atype),
+		  "bpf_prog_detach2-child");
+close_skel:
+	cgroup_preorder__destroy(skel);
+	return err;
+}
+
+void test_cgroup_preorder(void)
+{
+	int cg_parent = -1, cg_child = -1, sock_fd = -1;
+
+	cg_parent = test__join_cgroup("/parent");
+	if (!ASSERT_GE(cg_parent, 0, "join_cgroup /parent"))
+		goto out;
+
+	cg_child = test__join_cgroup("/parent/child");
+	if (!ASSERT_GE(cg_child, 0, "join_cgroup /parent/child"))
+		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, cg_child, sock_fd, false), "getsockopt_test_1");
+	ASSERT_OK(run_getsockopt_test(cg_parent, cg_child, sock_fd, true), "getsockopt_test_2");
+
+out:
+	close(sock_fd);
+	close(cg_child);
+	close(cg_parent);
+}

tools/testing/selftests/bpf/progs/cgroup_preorder.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";
+
+unsigned int idx;
+__u8 result[4];
+
+SEC("cgroup/getsockopt")
+int child(struct bpf_sockopt *ctx)
+{
+	if (idx < 4)
+		result[idx++] = 1;
+	return 1;
+}
+
+SEC("cgroup/getsockopt")
+int child_2(struct bpf_sockopt *ctx)
+{
+	if (idx < 4)
+		result[idx++] = 2;
+	return 1;
+}
+
+SEC("cgroup/getsockopt")
+int parent(struct bpf_sockopt *ctx)
+{
+	if (idx < 4)
+		result[idx++] = 3;
+	return 1;
+}
+
+SEC("cgroup/getsockopt")
+int parent_2(struct bpf_sockopt *ctx)
+{
+	if (idx < 4)
+		result[idx++] = 4;
+	return 1;
+}