selftests/net: Be consistent in kconfig checks

Most of the functions in tcp-ao lib/ return negative errno or -1 in case
of a failure. That creates inconsistencies in lib/kconfig, which saves
what was the error code. As well as the uninitialized kconfig value is
-1, which also may be the result of a check.

Define KCONFIG_UNKNOWN and save negative return code, rather than
libc-style errno.
Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com>
Link: https://patch.msgid.link/20240823-tcp-ao-selftests-upd-6-12-v4-3-05623636fe8c@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/tcp_ao/lib/kconfig.c

@@ -6,7 +6,7 @@
 #include "aolib.h"
 
 struct kconfig_t {
-	int _errno;		/* the returned error if not supported */
+	int _error;		/* negative errno if not supported */
 	int (*check_kconfig)(int *error);
 };
 
@@ -62,7 +62,7 @@ static int has_tcp_ao(int *err)
 	memcpy(&tmp.addr, &addr, sizeof(addr));
 	*err = 0;
 	if (setsockopt(sk, IPPROTO_TCP, TCP_AO_ADD_KEY, &tmp, sizeof(tmp)) < 0) {
-		*err = errno;
+		*err = -errno;
 		if (errno != ENOPROTOOPT)
 			ret = -errno;
 	}
@@ -87,7 +87,7 @@ static int has_tcp_md5(int *err)
 	 */
 	*err = 0;
 	if (test_set_md5(sk, addr_any, 0, -1, DEFAULT_TEST_PASSWORD)) {
-		*err = errno;
+		*err = -errno;
 		if (errno != ENOPROTOOPT && errno == ENOMEM) {
 			test_print("setsockopt(TCP_MD5SIG_EXT): %m");
 			ret = -errno;
@@ -116,13 +116,14 @@ static int has_vrfs(int *err)
 	return ret;
 }
 
+#define KCONFIG_UNKNOWN			1
 static pthread_mutex_t kconfig_lock = PTHREAD_MUTEX_INITIALIZER;
 static struct kconfig_t kconfig[__KCONFIG_LAST__] = {
-	{ -1, has_net_ns },
-	{ -1, has_veth },
-	{ -1, has_tcp_ao },
-	{ -1, has_tcp_md5 },
-	{ -1, has_vrfs },
+	{ KCONFIG_UNKNOWN, has_net_ns },
+	{ KCONFIG_UNKNOWN, has_veth },
+	{ KCONFIG_UNKNOWN, has_tcp_ao },
+	{ KCONFIG_UNKNOWN, has_tcp_md5 },
+	{ KCONFIG_UNKNOWN, has_vrfs },
 };
 
 const char *tests_skip_reason[__KCONFIG_LAST__] = {
@@ -138,11 +139,11 @@ bool kernel_config_has(enum test_needs_kconfig k)
 	bool ret;
 
 	pthread_mutex_lock(&kconfig_lock);
-	if (kconfig[k]._errno == -1) {
-		if (kconfig[k].check_kconfig(&kconfig[k]._errno))
+	if (kconfig[k]._error == KCONFIG_UNKNOWN) {
+		if (kconfig[k].check_kconfig(&kconfig[k]._error))
 			test_error("Failed to initialize kconfig %u", k);
 	}
-	ret = kconfig[k]._errno == 0;
+	ret = kconfig[k]._error == 0;
 	pthread_mutex_unlock(&kconfig_lock);
 	return ret;
 }