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From:   James Prestwood <prestwoj@gmail.com>
Date:   Wed, 6 May 2020 08:44:41 -0700
Message-ID: <CAPv5Ue5DY07E3=JDwjJkuad6Z3cuYtJg=dypUjy0KyBhn=JL9A@mail.gmail.com>
Subject: Potential IBSS race
To:     linux-wireless@vger.kernel.org
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Hi,

It appears that when two IBSS networks are started at the same time
they sometimes don't pick each other up and two separate IBSS networks
are created. I have turned on IBSS logging and see beacons coming in
from both networks AFTER each interface creates its own IBSS, but they
dont come soon enough for either interface to realize there is already
an IBSS. Is there any mitigation in the kernel or anything outlined in
802.11 that handles this case of two IBSS networks being created
simultaneously (or close to it)? Even delaying the second network by a
full second sometimes results in this behavior.

[    3.915143] wlan1: sta_find_ibss (active_ibss=0)
[    3.916022] wlan1: sta_find_ibss: did not try to join ibss
[    3.960484] wlan0: sta_find_ibss (active_ibss=0)
[    3.961643] wlan0: sta_find_ibss: did not try to join ibss
[    5.798696] wlan1: sta_find_ibss (active_ibss=0)
[    5.800526] wlan1: sta_find_ibss: did not try to join ibss
[    5.802579] wlan0: sta_find_ibss (active_ibss=0)
[    5.804300] wlan0: sta_find_ibss: did not try to join ibss
[    7.782708] wlan0: sta_find_ibss (active_ibss=0)
[    7.784529] wlan0: sta_find_ibss: did not try to join ibss
[    7.786557] wlan0: Trigger new scan to find an IBSS to join
[    7.788525] wlan1: sta_find_ibss (active_ibss=0)
[    7.789132] wlan1: sta_find_ibss: did not try to join ibss
[    7.789779] wlan1: Trigger new scan to find an IBSS to join
[    8.471675] wlan1: sta_find_ibss (active_ibss=0)
[    8.473610] wlan1: sta_find_ibss: did not try to join ibss
[    8.475957] wlan0: sta_find_ibss (active_ibss=0)
[    8.477434] wlan0: sta_find_ibss: did not try to join ibss
[   10.790703] wlan0: sta_find_ibss (active_ibss=0)
[   10.792698] wlan0: sta_find_ibss: did not try to join ibss
[   10.795035] wlan0: Trigger new scan to find an IBSS to join
[   10.796543] wlan1: sta_find_ibss (active_ibss=0)
[   10.797125] wlan1: sta_find_ibss: did not try to join ibss
[   10.797988] wlan1: Trigger new scan to find an IBSS to join
[   11.480676] wlan1: sta_find_ibss (active_ibss=0)
[   11.482586] wlan1: sta_find_ibss: did not try to join ibss
[   11.484822] wlan1: Creating new IBSS network, BSSID 62:f3:4f:db:22:e8
[   11.486643] wlan0: sta_find_ibss (active_ibss=0)
[   11.487302] wlan0: sta_find_ibss: did not try to join ibss
[   11.487995] wlan0: Creating new IBSS network, BSSID da:4d:66:a0:ca:52
[   11.590664] wlan1: RX beacon SA=02:00:00:00:00:00
BSSID=da:4d:66:a0:ca:52 TSF=0x5a4fc850a65c2
[   11.592753] wlan1: BCN=0x5a4fc850a6133 diff=1167 @4294678818
[   11.594002] wlan0: RX beacon SA=02:00:00:00:01:00
BSSID=62:f3:4f:db:22:e8 TSF=0x5a4fc850a72cd
[   11.595688] wlan0: BCN=0x5a4fc850a614a diff=4483 @4294678821

(beacons continue for a while until the test fails)

Thanks,
James