Re: iwi loses ssid

Sergey Matveychuk wrote:
> Andrew Thompson wrote:
>> On Sun, Jul 08, 2007 at 12:42:11PM +0400, Sergey Matveychuk wrote:
>>> Hi.
>>>
>>> After I upgraded to Jul 1 CURRENT my notebook's iwi adapter started
>>> work  unstable. It loses carrier. When I take a look at ifconfig
>>> output I see a strange ssid. After I make ifconfig iwi0 ssid myssid,
>>> everything is recovered. Time between ssid losses is accidental.
>>> Sometimes minutes, sometimes hours.
>>  
>> Could you enable logging with 'wlandebug -i iwi0 +roam' and paste the
>> output when it switches access points.
> 
> When everything OK:
> ul  8 19:49:22 solem kernel: iwi0: sta_roam_check: currssi 80 currate 2
> roamrssi 14 roamrate 10
> Jul  8 19:49:22 solem kernel: iwi0:  macaddr          bssid         chan
>  rssi  rate flag  wep  essid
> Jul  8 19:49:22 solem kernel: - 00:19:5b:54:26:39 00:19:5b:54:26:39    6
>    44  54M   ess   no! "default"
> Jul  8 19:49:22 solem kernel: + 00:16:e3:f3:c6:32 00:16:e3:f3:c6:32   11
>    39  54M   ess  wep  "ZXDSL531BII-1A0EE6"
> Jul  8 19:49:22 solem kernel: + 00:18:f8:a3:7a:58 00:18:f8:a3:7a:58   11
>    80  54M   ess  wep  "sem-home"*
> Jul  8 19:49:37 solem kernel: iwi0: sta_roam_check: currssi 80 currate 2
> roamrssi 14 roamrate 10
> 
> SSID is reseted to ZXDSL531BII-1A0EE6:
> Jul  8 19:50:07 solem kernel: iwi0:  macaddr          bssid         chan
>  rssi  rate flag  wep  essid
> Jul  8 19:50:07 solem kernel: - 00:19:5b:54:26:39 00:19:5b:54:26:39    6
>    43  54M   ess   no! "default"
> Jul  8 19:50:07 solem kernel: + 00:16:e3:f3:c6:32 00:16:e3:f3:c6:32   11
>    38  54M   ess  wep  "ZXDSL531BII-1A0EE6"
> Jul  8 19:50:07 solem kernel: ^ 00:18:f8:a3:7a:58 00:18:f8:a3:7a:58   11
>    80  54M   ess  wep  "sem-home"*
> Jul  8 19:50:07 solem kernel: iwi0: sta_roam_check: ROAM: curRate 2,
> roamRate 10, curRssi 80, roamRssi 14
> Jul  8 19:50:07 solem kernel: iwi0: link state changed to DOWN
> 
> How can I protect self from an alien AP?
> 

First thing to notice is that iwi is reporting rssi that is not
calibrated to .5 dBm units. Initially this is unimportant since the
threshold is 7 dBm (14) and hence it doesn't trigger roaming--but later
on it does suppress roaming back to your desired ap.  However the
current tx rate in the first case is set to 1 Mb/s (currssi 2) and that
is below the roaming threshold (5 Mb/s) so net80211 looks to roam to a
better ap.  You can avoid this several ways:

ifconfig iwi -bgscan

will disable bg scanning and implicitly roaming but then you'll
potentially do a full scan when you need to roam or respond to your ap
dropping you (e.g. due to inactivity).  Otherwise I think you can do:

ifconfig iwi roam:rate11g 1

to set the threshold on the tx rate to 1 Mb/s.  But the better fix is to
correct the driver so it reports calibrated rssi and figure out why the
tx rate is dropping so low given the apparent strong signal.

Another way to disable roaming is:

ifconfig iwi roaming device

though that won't work if you're using wpa_supplicant as it will set
roaming mode to manual so it can control operation of the net80211 state
machine.

	Sam