arping/tests: better handle wait timeout for test IPv4 DAD

The test tries to do IPv4 DAD. That necessarily involves waiting
for a timeout. Since the NMArpingManager spawns arping processes,
the precise timings depend on the load of the machine and may be
large in some cases.

Usually, our test would run fast to successful completion.
However, sometimes, it can take several hundered milliseconds.

Instead of increasing the timeout to a large value (which would
needlessly extend the run time of our tests in the common cases),
try first with a reasonably short timeout. A timeout which commonly
results in success. If the test with the short timeout fails, just
try again with an excessively large timeout.

This saves about 400 msec for the common case, but extends the
races that we saw where not even 250 msec of wait time were
sufficient.

1 files changed, 32 insertions, 8 deletions

diff --git a/src/devices/tests/test-arping.c b/src/devices/tests/test-arping.c
index bcbc1140d6..f053754523 100644
--- a/src/devices/tests/test-arping.c
+++ b/src/devices/tests/test-arping.c
@@ -65,12 +65,22 @@ test_arping_common (test_fixture *fixture, TestInfo *info)
 	gs_unref_object NMArpingManager *manager = NULL;
 	GMainLoop *loop;
 	int i;
+	const guint WAIT_TIME_OPTIMISTIC = 50;
+	guint wait_time;
+	gulong signal_id;
 
 	if (!nm_utils_find_helper ("arping", NULL, NULL)) {
 		g_test_skip ("arping binary is missing");
 		return;
 	}
 
+	/* first, try with a short waittime. We hope that this is long enough
+	 * to successfully complete the test. Only if that's not the case, we
+	 * assume the computer is currently busy (high load) and we retry with
+	 * a longer timeout. */
+	wait_time = WAIT_TIME_OPTIMISTIC;
+again:
+
 	manager = nm_arping_manager_new (fixture->ifindex0);
 	g_assert (manager != NULL);
 
@@ -83,18 +93,32 @@ test_arping_common (test_fixture *fixture, TestInfo *info)
 	}
 
 	loop = g_main_loop_new (NULL, FALSE);
-	g_signal_connect (manager, NM_ARPING_MANAGER_PROBE_TERMINATED,
-	                  G_CALLBACK (arping_manager_probe_terminated), loop);
-	g_assert (nm_arping_manager_start_probe (manager, 250, NULL));
+	signal_id = g_signal_connect (manager, NM_ARPING_MANAGER_PROBE_TERMINATED,
+	                              G_CALLBACK (arping_manager_probe_terminated), loop);
+	g_assert (nm_arping_manager_start_probe (manager, wait_time, NULL));
 	g_assert (nmtst_main_loop_run (loop, 2000));
+	g_signal_handler_disconnect (manager, signal_id);
+	g_main_loop_unref (loop);
 
 	for (i = 0; info->addresses[i]; i++) {
-		g_assert_cmpint (nm_arping_manager_check_address (manager, info->addresses[i]),
-		                 ==,
-		                 info->expected_result[i]);
+		gboolean val;
+
+		val = nm_arping_manager_check_address (manager, info->addresses[i]);
+		if (val == info->expected_result[i])
+			continue;
+
+		if (wait_time == WAIT_TIME_OPTIMISTIC) {
+			/* probably we just had a glitch and the system took longer than
+			 * expected. Re-verify with a large timeout this time. */
+			wait_time = 1000;
+			g_clear_object (&manager);
+			goto again;
+		}
+
+		g_error ("expected check for address #%d (%s) to %s, but it didn't",
+		         i, nm_utils_inet4_ntop (info->addresses[i], NULL),
+		         info->expected_result[i] ? "detect no duplicated" : "detect a duplicate");
 	}
-
-	g_main_loop_unref (loop);
 }
 
 static void