tests: Make scan and scan_only more robust

These can fail during heavy CPU load due to active scan dwell time not
being long enough to catch the delayed Probe Response frame from the AP.
Work around this by allowing multiple scan attempts to see the response.

Signed-off-by: Jouni Malinen <j@w1.fi>

tests/hwsim/test_scan.py

@@ -45,6 +45,13 @@ def check_scan(dev, params, other_started=False):
     if "id=" + str(id) not in ev:
         raise Exception("Scan id not included in completed event")
 
+def check_scan_retry(dev, params, bssid):
+    for i in range(0, 5):
+        check_scan(dev, "freq=2412-2462,5180 use_id=1")
+        if int(dev.get_bss(bssid)['age']) <= 1:
+            return
+    raise Exception("Unexpectedly old BSS entry")
+
 def test_scan(dev, apdev):
     """Control interface behavior on scan parameters"""
     hostapd.add_ap(apdev[0]['ifname'], { "ssid": "test-scan" })
@@ -54,9 +61,7 @@ def test_scan(dev, apdev):
     check_scan(dev[0], "use_id=1")
 
     logger.info("Limited channel scan")
-    check_scan(dev[0], "freq=2412-2462,5180 use_id=1")
-    if int(dev[0].get_bss(bssid)['age']) > 1:
-        raise Exception("Unexpectedly old BSS entry")
+    check_scan_retry(dev[0], "freq=2412-2462,5180 use_id=1", bssid)
 
     # wait long enough to allow next scans to be verified not to find the AP
     time.sleep(2)
@@ -69,9 +74,7 @@ def test_scan(dev, apdev):
         raise Exception("Unexpectedly updated BSS entry")
 
     logger.info("Active single-channel scan on AP's operating channel")
-    check_scan(dev[0], "freq=2412 passive=0 use_id=1")
-    if int(dev[0].get_bss(bssid)['age']) > 1:
-        raise Exception("Unexpectedly old BSS entry")
+    check_scan_retry(dev[0], "freq=2412 passive=0 use_id=1", bssid)
 
 def test_scan_only(dev, apdev):
     """Control interface behavior on scan parameters with type=only"""
@@ -82,9 +85,7 @@ def test_scan_only(dev, apdev):
     check_scan(dev[0], "type=only use_id=1")
 
     logger.info("Limited channel scan")
-    check_scan(dev[0], "type=only freq=2412-2462,5180 use_id=1")
-    if int(dev[0].get_bss(bssid)['age']) > 1:
-        raise Exception("Unexpectedly old BSS entry")
+    check_scan_retry(dev[0], "type=only freq=2412-2462,5180 use_id=1", bssid)
 
     # wait long enough to allow next scans to be verified not to find the AP
     time.sleep(2)
@@ -97,9 +98,7 @@ def test_scan_only(dev, apdev):
         raise Exception("Unexpectedly updated BSS entry")
 
     logger.info("Active single-channel scan on AP's operating channel")
-    check_scan(dev[0], "type=only freq=2412 passive=0 use_id=1")
-    if int(dev[0].get_bss(bssid)['age']) > 1:
-        raise Exception("Unexpectedly old BSS entry")
+    check_scan_retry(dev[0], "type=only freq=2412 passive=0 use_id=1", bssid)
 
 def test_scan_external_trigger(dev, apdev):
     """Avoid operations during externally triggered scan"""