wpa_supplicant auto reconnect

Jouni Malinen j at w1.fi
Mon Mar 27 07:02:30 PDT 2017

On Thu, Mar 16, 2017 at 09:48:12PM -0500, Dan Williams wrote:
> On Thu, 2017-03-16 at 15:39 -0500, Jake Magee wrote:
> > So I think the log is too big to send (400K)... here is a link to it.
> > 
> > https://drive.google.com/file/d/0B3BKPLtbQtZrZnNlaHRvb3BJZDQ/view?usp
> > =sharing

> Yeah, so changing the password gets you into trouble.  The supplicant
> keeps trying to connect and keeps failing, so it starts backing off:

Well.. Changing the password (or any similar difference that looks like
the network does not accept the station anymore) does indeed result in
backing off from connection attempts and I would not call this part the
one that is getting into trouble; this is very much by design..

> 1489691439.907335: wlan0: CTRL-EVENT-SSID-TEMP-DISABLED id=0
> ssid="AndroidAP" auth_failures=4 duration=77 reason=CONN_FAILED

> Where the supplicant has decided to ignore your AP for 77 seconds
> because the connection failed 4 times.  It then does a scheduled scan
> (asks the driver to notify it when the AP shows up again) and basically
> goes to sleep.
> The bug here is probably that the supplicant doesn't set a wakeup timer
> for when the temporary disablement expires, and then clear the
> disablement and retry the connection.

That's indeed the real issue here. This works fine with the internal
scan iterations in wpa_supplicant, but apparently not with sched_scan
offload.. In other words, the expected behavior here is that there would
indeed be another scan iteration at some point after that 77 second
back-off period and that would then result in yet another connection

It is not exactly clear how sched_scan should work here, though.
wpa_supplicant does request the driver to report scan results for the
specific SSID here and one does get reported 30 seconds after the
sched_scan has started, but that's still within the temporary disabled
period.. After that, the driver did not report the scan results again.

I guess it might be reasonable to add a new timeout within
wpa_supplicant to stop and restart ongoing sched_scan at the point the
temporary disablement of a network (that is part of that sched_scan
operation) times out.. Or alternatively, set a timeout for the
sched_scan to handle this as part of the existing mechanism to run
continuous sched_scan operations when needing to search for more SSIDs
than the driver supports in the offload case.

Jouni Malinen                                            PGP id EFC895FA

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