tests: Make ap_track_sta_no_probe_resp more robust

Check whether the unexpected BSS entry is based on having received a
Beacon frame instead of Probe Response frame. While this test case is
using a huge beacon_int value, it is still possible for mac80211_hwsim
timing to work in a way that a Beacon frame is sent. That made this test
case fail in some rare cases. Fix this by ignoring the BSS entry if it
is based on Beacon frame instead of Probe Response frame.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

tests/hwsim/test_ap_track.py

@@ -11,6 +11,7 @@ import time
 
 import hostapd
 from wpasupplicant import WpaSupplicant
+from utils import parse_ie
 
 def test_ap_track_sta(dev, apdev):
     """Dualband AP tracking unconnected stations"""
@@ -110,8 +111,15 @@ def _test_ap_track_sta_no_probe_resp(dev, apdev):
     dev[0].scan(freq=2437, type="ONLY")
     dev[0].scan(freq=2437, type="ONLY")
 
-    if dev[0].get_bss(bssid):
-        raise Exception("2.4 GHz AP found unexpectedly")
+    bss = dev[0].get_bss(bssid)
+    if bss:
+        ie = parse_ie(bss['ie'])
+        # Check whether this is from a Beacon frame (TIM element included) since
+        # it is possible that a Beacon frame was received during the active
+        # scan. This test should fail only if a Probe Response frame was
+        # received.
+        if 5 not in ie:
+            raise Exception("2.4 GHz AP found unexpectedly")
 
 def test_ap_track_sta_no_auth(dev, apdev):
     """Dualband AP rejecting authentication from dualband STA on 2.4 GHz"""

tests/hwsim/utils.py

@@ -4,7 +4,9 @@
 # This software may be distributed under the terms of the BSD license.
 # See README for more details.
 
+import binascii
 import os
+import struct
 import time
 import remotehost
 
@@ -102,3 +104,15 @@ def get_phy(ap, ifname=None):
             phy = "phy" + words[1]
             break
     return phy
+
+def parse_ie(buf):
+    ret = {}
+    data = binascii.unhexlify(buf)
+    while len(data) >= 2:
+        ie,elen = struct.unpack('BB', data[0:2])
+        data = data[2:]
+        if elen > len(data):
+            break
+        ret[ie] = data[0:elen]
+        data = data[elen:]
+    return ret