Strange behavior with wpa_supplicant -u

[Dan Williams]

On Thu, 2009-11-12 at 13:27 -0500, Mike Edenfield wrote:
> On 11/12/2009 1:07 PM, Dan Williams wrote:
> > On Wed, 2009-11-11 at 18:14 -0500, Mike Edenfield wrote:
> >> Hi,
> >>
> >> I am having a connectivity issue with my wireless adapter that only
> >> occurs when using wpa_supplicant's DBus interface, and only on one
> >> specific AP.  My laptop has an internal Intel 3945ABG wireless adapter,
> >> which I'm using via the Linux in-kernel iwlwifi driver.  When I try to
> >> connect DLink AirPlus G 6000, using uses WPA-PSK with TKIP, that's in my
> >> office, weird things happen.
> >
> > What kernel version?  This could be due to periodic scanning which is
> > triggered by NM to keep an up-to-date list of APs available for various
> > reasons (fast roaming, UI display, etc).  Drivers *should* be able to
> > handle this, if they don't, then the driver needs to be fixed.
> >
> > Apparently you're running drivers that aren't :(
> 
> This looks like exactly the problem.  Once I realized I could run 
> wpa_supplicant -u *before* running NM (thanks to Hogler), and saw the 
> debug logs, it's pretty obvious.
> 
> > Kernel versions lower than 2.6.29 had various problems that caused them
> > to fail in this case for software scans, and I've seen the iwlwifi
> > hardware scans also fail here for some reason.  Recent kernels (2.6.30
> > and later) work well here, and 2.6.32 has a "background scan"
> > infrastructure that improves scan performance as well.
> 
> I'm using 2.6.31, so I guess I'll head back to the iwlwifi people and 
> see whats up.  But if it's a driver problem, I still don't understand 
> why just *this* AP is broken.  There are 3 different APs in this 
> building, and two of them work fine.
> 
> On the network test lab's AP, which works, I get this:
> 
> CTRL-EVENT-SCAN-RESULTS
> Selecting BSS from priority group 0
> Try to find WPA-enabled AP
> 0: 00:18:f8:2f:7f:13 ssid='Informa-Guests' wpa_ie_len=22 rsn_ie_len=0 
> caps=0x11
>     skip - disabled
>     selected based on WPA IE
>     selected WPA AP 00:18:f8:2f:7f:13 ssid='Informa-Guests'
> Already associated with the selected AP.
> 
> On the one that I need to use, the scan request results in this:
> 
> CTRL-EVENT-SCAN-RESULTS
> Selecting BSS from priority group 0
> Try to find WPA-enabled AP
> 0: 00:1e:58:04:1e:ec ssid='Informagration' wpa_ie_len=22 rsn_ie_len=0 
> caps=0x11
>     selected based on WPA IE
>     selected WPA AP 00:1e:58:04:1e:ec ssid='Informagration'
> Already associated with the selected AP.
> RTM_NEWLINK: operstate=1 ifi_flags=0x1043 ([UP][RUNNING])
> RTM_NEWLINK, IFLA_IFNAME: Interface 'wlan0' added
> Wireless event: cmd=0x8b15 len=24
> Wireless event: new AP: 00:00:00:00:00:00
> Setting scan request: 0 sec 100000 usec
> Added BSSID 00:1e:58:04:1e:ec into blacklist
> CTRL-EVENT-DISCONNECTED - Disconnect event - remove keys
> 
> Is that 00:00:00:00:00:00 causing the problem?  Any way I can find out 
> where its coming from?

Yes.  That means the driver has lost association to the AP, which can be
from any one of:

1) too many beacons
2) the AP disassociated you
3) somebody turned on a microwave

I think your problem is #2 given your previous logs.

Can you try loading iwl3945.ko with "disable_hw_scan=1" and report
whether that works better than hardware scanning?  That turns on
mac80211 software scanning which (for 2.6.31) definitely has the correct
nullfunc-before-scan handling.  That can help isolate the problem with
hardware scanning and then we can further debug with the Intel folks to
figure out what's going on in the firmware.

Also, what specific vendor & model are the APs, and which one of those
is the one that doesn't work?  Are they all the same model?

Dan