WLAN: current status and new bits of weirdness

[Werner Almesberger]

Three of the current WLAN problems appear to be caused by flaws in the
firmware. I've reported them to Atheros and they're looking into the
issues. Specifically, these are:

- Target assertion at line 0x393
- Target assertion at line 0x87A
- AR6k sometimes associates at the wrong channel when roaming

The target associations are serious because all we can do to recover
from them is to reset the module. The channel problem causes obscure
performance degradation when it happens, but it seems to need a fairly
exotic environment to occur and may not matter all that much in real
life.

There are two more issues that I'm currently investigating:

- sometimes, the key exchange of wpa_supplicant fails, causing
  indefinite attempts to associate.

  So far, this appears to happen only when I do one successful
  association, get a DHCP lease, and then restart wpa_supplicant.
  I've also only seen it with a WRT54G running the orignal Linksys
  firmware, but not with a PC acting as AP.

  The key exchange fails because the answers wpa_supplicant thinks
  it's sending apparently never get put in the air, but I don't
  know yet where exactly they get lost.

- FSO MS5 is reported to have troubles with WPA as well. I haven't
  reproduced this one yet.

- Werner