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@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/bpf_iter.c | 40 +++++++++++++++++++
.../progs/bpf_iter_bpf_sk_storage_helpers.c | 25 ++++++++++++
2 files changed, 65 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index bb4a638f2e6f..9336d0f18331 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -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"))
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c
index 01ff3235e413..d7a7a802d172 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c
@@ -21,3 +21,28 @@ 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 || task->tgid != task->pid)
+ 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;
+}
+
--
2.29.2.454.gaff20da3a2-goog
