selftests/bpf: Add link detach tests for cgroup, netns, and xdp bpf_links

Add bpf_link__detach() testing to selftests for cgroup, netns, and xdp
bpf_links.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200731182830.286260-4-andriin@fb.com

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

@@ -2,6 +2,7 @@
 
 #include <test_progs.h>
 #include "cgroup_helpers.h"
+#include "testing_helpers.h"
 #include "test_cgroup_link.skel.h"
 
 static __u32 duration = 0;
@@ -37,7 +38,8 @@ void test_cgroup_link(void)
 	int last_cg = ARRAY_SIZE(cgs) - 1, cg_nr = ARRAY_SIZE(cgs);
 	DECLARE_LIBBPF_OPTS(bpf_link_update_opts, link_upd_opts);
 	struct bpf_link *links[ARRAY_SIZE(cgs)] = {}, *tmp_link;
-	__u32 prog_ids[ARRAY_SIZE(cgs)], prog_cnt = 0, attach_flags;
+	__u32 prog_ids[ARRAY_SIZE(cgs)], prog_cnt = 0, attach_flags, prog_id;
+	struct bpf_link_info info;
 	int i = 0, err, prog_fd;
 	bool detach_legacy = false;
 
@@ -219,6 +221,22 @@ void test_cgroup_link(void)
 	/* BPF programs should still get called */
 	ping_and_check(0, cg_nr);
 
+	prog_id = link_info_prog_id(links[0], &info);
+	CHECK(prog_id == 0, "link_info", "failed\n");
+	CHECK(info.cgroup.cgroup_id == 0, "cgroup_id", "unexpected %llu\n", info.cgroup.cgroup_id);
+
+	err = bpf_link__detach(links[0]);
+	if (CHECK(err, "link_detach", "failed %d\n", err))
+		goto cleanup;
+
+	/* cgroup_id should be zero in link_info */
+	prog_id = link_info_prog_id(links[0], &info);
+	CHECK(prog_id == 0, "link_info", "failed\n");
+	CHECK(info.cgroup.cgroup_id != 0, "cgroup_id", "unexpected %llu\n", info.cgroup.cgroup_id);
+
+	/* First BPF program shouldn't be called anymore */
+	ping_and_check(0, cg_nr - 1);
+
 	/* leave cgroup and remove them, don't detach programs */
 	cleanup_cgroup_environment();
 

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

@@ -34,6 +34,7 @@
 #include "bpf_util.h"
 #include "cgroup_helpers.h"
 #include "network_helpers.h"
+#include "testing_helpers.h"
 #include "test_sk_lookup.skel.h"
 
 /* External (address, port) pairs the client sends packets to. */
@@ -469,34 +470,10 @@ static int update_lookup_map(struct bpf_map *map, int index, int sock_fd)
 	return 0;
 }
 
-static __u32 link_info_prog_id(struct bpf_link *link)
-{
-	struct bpf_link_info info = {};
-	__u32 info_len = sizeof(info);
-	int link_fd, err;
-
-	link_fd = bpf_link__fd(link);
-	if (CHECK(link_fd < 0, "bpf_link__fd", "failed\n")) {
-		errno = -link_fd;
-		log_err("bpf_link__fd failed");
-		return 0;
-	}
-
-	err = bpf_obj_get_info_by_fd(link_fd, &info, &info_len);
-	if (CHECK(err, "bpf_obj_get_info_by_fd", "failed\n")) {
-		log_err("bpf_obj_get_info_by_fd");
-		return 0;
-	}
-	if (CHECK(info_len != sizeof(info), "bpf_obj_get_info_by_fd",
-		  "unexpected info len %u\n", info_len))
-		return 0;
-
-	return info.prog_id;
-}
-
 static void query_lookup_prog(struct test_sk_lookup *skel)
 {
 	struct bpf_link *link[3] = {};
+	struct bpf_link_info info;
 	__u32 attach_flags = 0;
 	__u32 prog_ids[3] = {};
 	__u32 prog_cnt = 3;
@@ -534,18 +511,36 @@ static void query_lookup_prog(struct test_sk_lookup *skel)
 	if (CHECK(prog_cnt != 3, "bpf_prog_query",
 		  "wrong program count on query: %u", prog_cnt))
 		goto detach;
-	prog_id = link_info_prog_id(link[0]);
+	prog_id = link_info_prog_id(link[0], &info);
 	CHECK(prog_ids[0] != prog_id, "bpf_prog_query",
 	      "invalid program #0 id on query: %u != %u\n",
 	      prog_ids[0], prog_id);
-	prog_id = link_info_prog_id(link[1]);
+	CHECK(info.netns.netns_ino == 0, "netns_ino",
+	      "unexpected netns_ino: %u\n", info.netns.netns_ino);
+	prog_id = link_info_prog_id(link[1], &info);
 	CHECK(prog_ids[1] != prog_id, "bpf_prog_query",
 	      "invalid program #1 id on query: %u != %u\n",
 	      prog_ids[1], prog_id);
-	prog_id = link_info_prog_id(link[2]);
+	CHECK(info.netns.netns_ino == 0, "netns_ino",
+	      "unexpected netns_ino: %u\n", info.netns.netns_ino);
+	prog_id = link_info_prog_id(link[2], &info);
 	CHECK(prog_ids[2] != prog_id, "bpf_prog_query",
 	      "invalid program #2 id on query: %u != %u\n",
 	      prog_ids[2], prog_id);
+	CHECK(info.netns.netns_ino == 0, "netns_ino",
+	      "unexpected netns_ino: %u\n", info.netns.netns_ino);
+
+	err = bpf_link__detach(link[0]);
+	if (CHECK(err, "link_detach", "failed %d\n", err))
+		goto detach;
+
+	/* prog id is still there, but netns_ino is zeroed out */
+	prog_id = link_info_prog_id(link[0], &info);
+	CHECK(prog_ids[0] != prog_id, "bpf_prog_query",
+	      "invalid program #0 id on query: %u != %u\n",
+	      prog_ids[0], prog_id);
+	CHECK(info.netns.netns_ino != 0, "netns_ino",
+	      "unexpected netns_ino: %u\n", info.netns.netns_ino);
 
 detach:
 	if (link[2])

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

@@ -131,6 +131,20 @@ void test_xdp_link(void)
 	CHECK(link_info.xdp.ifindex != IFINDEX_LO, "link_ifindex",
 	      "got %u != exp %u\n", link_info.xdp.ifindex, IFINDEX_LO);
 
+	err = bpf_link__detach(link);
+	if (CHECK(err, "link_detach", "failed %d\n", err))
+		goto cleanup;
+
+	memset(&link_info, 0, sizeof(link_info));
+	err = bpf_obj_get_info_by_fd(bpf_link__fd(link), &link_info, &link_info_len);
+	if (CHECK(err, "link_info", "failed: %d\n", err))
+		goto cleanup;
+	CHECK(link_info.prog_id != id1, "link_prog_id",
+	      "got %u != exp %u\n", link_info.prog_id, id1);
+	/* ifindex should be zeroed out */
+	CHECK(link_info.xdp.ifindex != 0, "link_ifindex",
+	      "got %u != exp %u\n", link_info.xdp.ifindex, 0);
+
 cleanup:
 	test_xdp_link__destroy(skel1);
 	test_xdp_link__destroy(skel2);

tools/testing/selftests/bpf/testing_helpers.c

@@ -64,3 +64,17 @@ int parse_num_list(const char *s, bool **num_set, int *num_set_len)
 
 	return 0;
 }
+
+__u32 link_info_prog_id(const struct bpf_link *link, struct bpf_link_info *info)
+{
+	__u32 info_len = sizeof(*info);
+	int err;
+
+	memset(info, 0, sizeof(*info));
+	err = bpf_obj_get_info_by_fd(bpf_link__fd(link), info, &info_len);
+	if (err) {
+		printf("failed to get link info: %d\n", -errno);
+		return 0;
+	}
+	return info->prog_id;
+}

tools/testing/selftests/bpf/testing_helpers.h

@@ -1,5 +1,8 @@
 /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
 /* Copyright (C) 2020 Facebook, Inc. */
 #include <stdbool.h>
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
 
 int parse_num_list(const char *s, bool **set, int *set_len);
+__u32 link_info_prog_id(const struct bpf_link *link, struct bpf_link_info *info);