selftests/bpf: Test bpf_sk_storage_get in tcp iterators

This extends the existing bpf_sk_storage_get test where a socket is created and tagged with its creator's pid by a task_file iterator. A TCP iterator is now also used at the end of the test to negate the values already stored in the local storage. The test therefore expects -getpid() to be stored in the local storage. 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/20201204113609.1850150-6-revest@google.com

Author: FlorentRevest

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

@@ -978,6 +978,8 @@ static void test_bpf_sk_storage_delete(void)
 /* 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.
+ * It then runs a tcp socket iterator that negates the value in the existing
+ * socket local storage, the test verifies that the resulting value is -pid.
  */
 static void test_bpf_sk_storage_get(void)
 {
@@ -994,6 +996,10 @@ static void test_bpf_sk_storage_get(void)
 if (CHECK(sock_fd < 0, "socket", "errno: %d\n", errno))
 goto out;
 
+err = listen(sock_fd, 1);
+if (CHECK(err != 0, "listen", "errno: %d\n", errno))
+goto close_socket;
+
 map_fd = bpf_map__fd(skel->maps.sk_stg_map);
 
 err = bpf_map_update_elem(map_fd, &sock_fd, &val, BPF_NOEXIST);
@@ -1003,9 +1009,17 @@ static void test_bpf_sk_storage_get(void)
 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",
+if (CHECK(err || val != getpid(), "bpf_map_lookup_elem",
+ "map value wasn't set correctly (expected %d, got %d, err=%d)\n",
+ getpid(), val, err))
+goto close_socket;
+
+do_dummy_read(skel->progs.negate_socket_local_storage);
+
+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);
+ -getpid(), val, err);
 
 close_socket:
 close(sock_fd);

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

@@ -45,3 +45,21 @@ int fill_socket_owner(struct bpf_iter__task_file *ctx)
 
 return 0;
 }
+
+SEC("iter/tcp")
+int negate_socket_local_storage(struct bpf_iter__tcp *ctx)
+{
+struct sock_common *sk_common = ctx->sk_common;
+int *sock_tgid;
+
+if (!sk_common)
+return 0;
+
+sock_tgid = bpf_sk_storage_get(&sk_stg_map, sk_common, 0, 0);
+if (!sock_tgid)
+return 0;
+
+*sock_tgid = -*sock_tgid;
+
+return 0;
+}