selftests/bpf: Set expect_errno for cgroup_skb_sk_lookup

EINPROGRESS is skipped in run_lookup_test() in cgroup_skb_sk_lookup
tests, but it is still showed in the log:

 ./test_progs -t cgroup_skb_sk_lookup -v

 run_cgroup_bpf_test:PASS:skel_open_load 0 nsec
 run_cgroup_bpf_test:PASS:cgroup_join 0 nsec
 run_cgroup_bpf_test:PASS:cgroup_attach 0 nsec
 run_lookup_test:PASS:start_server 0 nsec
 run_lookup_test:PASS:getsockname 0 nsec
 (network_helpers.c:300: errno: Operation now in progress) Failed to \
                                                connect to server
 run_lookup_test:PASS:connect_fd_to_fd 0 nsec
 run_lookup_test:PASS:connect_to_fd 0 nsec
 run_lookup_test:PASS:accept 0 nsec
 #51      cgroup_skb_sk_lookup:OK

To fix this, set EINPROGRESS as "expect_errno" of network_helper_opts and
pass it to connect_fd_to_fd(). Skip this expect_errno when must_fail is
false too in connect_fd_to_addr().

connect_fd_to_fd() returns "0" when connect() fails but "expect_errno"
matched. So "err" is "0" after invoking connect_fd_to_fd() in
run_lookup_test(). "err = -errno" is needed to get the real error number
before checking value of "err".

Signed-off-by: Geliang Tang <[email protected]>

Author: Geliang Tang

tools/testing/selftests/bpf/network_helpers.c

@@ -296,7 +296,7 @@ static int connect_fd_to_addr(int fd,
 			return -1;
 		}
 	} else {
-		if (ret) {
+		if (ret && errno != expect_errno) {
 			log_err("Failed to connect to server");
 			return -1;
 		}

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

@@ -10,6 +10,7 @@ static void run_lookup_test(__u16 *g_serv_port, int out_sk)
 {
 	struct network_helper_opts opts = {
 		.timeout_ms	= 1000,
+		.expect_errno	= EINPROGRESS,
 	};
 	int serv_sk = -1, in_sk = -1, serv_in_sk = -1, err;
 	struct sockaddr_in6 addr = {};
@@ -28,6 +29,8 @@ static void run_lookup_test(__u16 *g_serv_port, int out_sk)
 
 	/* Client outside of test cgroup should fail to connect by timeout. */
 	err = connect_fd_to_fd(out_sk, serv_sk, &opts);
+	if (!err)
+		err = -errno;
 	if (CHECK(!err || errno != EINPROGRESS, "connect_fd_to_fd",
 		  "unexpected result err %d errno %d\n", err, errno))
 		goto cleanup;