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selftests/bpf: Add an iterator selftest for bpf_sk_storage_get

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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: Florent Revest <revest@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201204113609.1850150-5-revest@google.com
This commit is contained in:
Florent Revest 2020-12-04 12:36:08 +01:00 committed by Daniel Borkmann
parent 593f6d41ab
commit bd9b327e58
2 changed files with 64 additions and 0 deletions
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40
tools/testing/selftests/bpf/prog_tests/bpf_iter.c
View file

@ -975,6 +975,44 @@ static void test_bpf_sk_storage_delete(void)
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"))

24
tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c
View file

@ -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;
}