Commit bd9b327e authored by Florent Revest's avatar Florent Revest Committed by Daniel Borkmann
Browse files

selftests/bpf: Add an iterator selftest for bpf_sk_storage_get 



The eBPF program iterates over all files and tasks. For all socket
files, it stores the tgid of the last task it encountered with a handle
to that socket. This is a heuristic for finding the "owner" of a socket
similar to what's done by lsof, ss, netstat or fuser. Potentially, this
information could be used from a cgroup_skb/*gress hook to try to
associate network traffic with processes.

The test makes sure that a socket it created is tagged with prog_tests's
pid.

Signed-off-by: default avatarFlorent Revest <revest@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201204113609.1850150-5-revest@google.com
parent 593f6d41

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

+40 −0
Original line number Diff line number Diff line
@@ -975,6 +975,44 @@ out: 
	bpf_iter_bpf_sk_storage_helpers__destroy(skel);

}



/* This creates a socket and its local storage. It then runs a task_iter BPF

 * program that replaces the existing socket local storage with the tgid of the

 * only task owning a file descriptor to this socket, this process, prog_tests.

 */

static void test_bpf_sk_storage_get(void)

{

	struct bpf_iter_bpf_sk_storage_helpers *skel;

	int err, map_fd, val = -1;

	int sock_fd = -1;



	skel = bpf_iter_bpf_sk_storage_helpers__open_and_load();

	if (CHECK(!skel, "bpf_iter_bpf_sk_storage_helpers__open_and_load",

		  "skeleton open_and_load failed\n"))

		return;



	sock_fd = socket(AF_INET6, SOCK_STREAM, 0);

	if (CHECK(sock_fd < 0, "socket", "errno: %d\n", errno))

		goto out;



	map_fd = bpf_map__fd(skel->maps.sk_stg_map);



	err = bpf_map_update_elem(map_fd, &sock_fd, &val, BPF_NOEXIST);

	if (CHECK(err, "bpf_map_update_elem", "map_update_failed\n"))

		goto close_socket;



	do_dummy_read(skel->progs.fill_socket_owner);



	err = bpf_map_lookup_elem(map_fd, &sock_fd, &val);

	CHECK(err || val != getpid(), "bpf_map_lookup_elem",

	      "map value wasn't set correctly (expected %d, got %d, err=%d)\n",

	      getpid(), val, err);



close_socket:

	close(sock_fd);

out:

	bpf_iter_bpf_sk_storage_helpers__destroy(skel);

}



static void test_bpf_sk_storage_map(void)

{

	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
@@ -1131,6 +1169,8 @@ void test_bpf_iter(void) 
		test_bpf_sk_storage_map();

	if (test__start_subtest("bpf_sk_storage_delete"))

		test_bpf_sk_storage_delete();

	if (test__start_subtest("bpf_sk_storage_get"))

		test_bpf_sk_storage_get();

	if (test__start_subtest("rdonly-buf-out-of-bound"))

		test_rdonly_buf_out_of_bound();

	if (test__start_subtest("buf-neg-offset"))

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

+24 −0
Original line number Diff line number Diff line
@@ -21,3 +21,27 @@ int delete_bpf_sk_storage_map(struct bpf_iter__bpf_sk_storage_map *ctx) 


	return 0;

}



SEC("iter/task_file")

int fill_socket_owner(struct bpf_iter__task_file *ctx)

{

	struct task_struct *task = ctx->task;

	struct file *file = ctx->file;

	struct socket *sock;

	int *sock_tgid;



	if (!task || !file)

		return 0;



	sock = bpf_sock_from_file(file);

	if (!sock)

		return 0;



	sock_tgid = bpf_sk_storage_get(&sk_stg_map, sock->sk, 0, 0);

	if (!sock_tgid)

		return 0;



	*sock_tgid = task->tgid;



	return 0;

}

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