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Subject: Re: No connection with TP-Link TL-WN823N (rtl8192cu)
From: Dan Williams <dcbw@redhat.com>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: linux-wireless@vger.kernel.org
Date: Wed, 25 Sep 2013 14:06:37 -0500
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On Wed, 2013-09-25 at 11:46 -0500, Larry Finger wrote:
> On 09/25/2013 07:47 AM, Dan Williams wrote:
> > On Tue, 2013-09-24 at 17:43 -0500, Larry Finger wrote:
> >> On 09/09/2013 05:15 PM, Dan Williams wrote:
> >>> On Mon, 2013-09-09 at 16:52 -0500, Larry Finger wrote:
> >>
> >>>> I have been running rtl8192cu for the past 24 hours without a permanent
> >>>> disconnect. Under NetworkManager, I see some reason 7 deauthentications, but
> >>>
> >>> Running wpa_supplicant with debugging on might shed some light on these;
> >>> basically:
> >>>
> >>> mv /usr/sbin/wpa_supplicant /
> >>> killall -TERM wpa_supplicant
> >>> /wpa_supplicant -dddtu <piped to your favorite log file>
> >>>
> >>> and NM should automatically reconnect, and then we can figure out what's
> >>> going on in the supplicant.
> >>
> >> Dan,
> >>
> >> The log of wpa_supplicant associated with the reason 7 disconnects are as follows:
> >
> > So reason 7 is "Incorrect frame type or subtype received from
> > unassociated station" which seems like the AP thinks we got
> > disconnected, and would seem to be a driver/mac80211 issue still, right?
> 
> Yes. These only happen with rtl8192ce and rtl8192cu. They are a bit more common 
> when running NetworkManager than with ifup. In my current run, they have been at 
> intervals of 1000 to 30,000 seconds apart. Capturing them with wireshark may not 
> be practical.
> 
> --snip--
> 
> > And got reconnected after a bit more than one second.  So at least it
> > recovers quickly, but the question is more about why the reason 7
> > happened, and what frames caused it, I think.
> 
> I agree. The sequence seems to start with an MLME Event 39:
> 
> .908249: nl80211: MLME event 39
> .908252: nl80211: MLME event frame - hexdump(len=26): c0 00 3a 01 1c 65 9d 5a c3 
> 9d 20 e5 2a 01 f7 ea 20 e5 2a 01 f7 ea a0 f6 07 00
> .908269: wlan3: Event DEAUTH (12) received
> .908273: wlan3: Deauthentication notification
> 
> All that happens within 25 usec, but I have no clue what triggers that. In 
> addition, I have been unable to find any documentation on MLME events. Any 
> suggestions regarding a source would be appreciated.

Periodic scanning maybe and some mis-management of nullfunc frames in
the driver when switching channels for a scan?  That used to be the most
common cause of issues like this, where the device would go scan a
channel but forget the nullfunc, so while it was off-channel the AP
wouldn't hear anything from it and disassociate it.

Dan