Comment 82 for bug 291760

Got tired of the limitations of wicd and decided to dig deeper... here is what I found:

So this is happening because NM tells wpa_supplicant to do periodic background scanning (which apparently, wicd does not do). With ath5k and AR5212 (at least), the scan is very intrusive, changes frequencies from 2.4Ghz and 5Ghz etc... this causes all traffic to stop until it's done.

Running wpa_supplicant in debug mode, and also watching iwconfig output, gives some insight...

<pings normal>

Jul 12 20:57:58 bluetote wpa_supplicant[11018]: Setting scan request: 0 sec 0 usec
Jul 12 20:57:59 bluetote wpa_supplicant[11018]: Starting AP scan (broadcast SSID)
Jul 12 20:57:59 bluetote wpa_supplicant[11018]: Scan requested (ret=0) - scan timeout 30 seconds

<no pings here while scan is in progress, iwconfig shows interface hopping frequencies>

Jul 12 20:58:05 bluetote NetworkManager: <debug> [1247457485.033371] periodic_update(): Roamed from BSSID 00:1E:E5:2D:5A:99 (leslielady) to (none) ((none))

<oops, nm is confused now... still scanning and no pings>

Jul 12 20:58:08 bluetote wpa_supplicant[11018]: RTM_NEWLINK: operstate=1 ifi_flags=0x11043 ([UP][RUNNING][LOWER_UP])
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: RTM_NEWLINK, IFLA_IFNAME: Interface 'ath0' added
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: Wireless event: cmd=0x8b19 len=8
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: Received 1554 bytes of scan results (5 BSSes)
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: CTRL-EVENT-SCAN-RESULTS
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: Selecting BSS from priority group 0
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: Try to find WPA-enabled AP
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: 0: 00:1e:e5:2d:5a:99 ssid='leslielady' wpa_ie_len=0 rsn_ie_len=20 caps=0x11
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: selected based on RSN IE
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: selected WPA AP 00:1e:e5:2d:5a:99 ssid='leslielady'
Jul 12 20:58:08 bluetote wpa_supplicant[11018]: Already associated with the selected AP.
Jul 12 20:58:11 bluetote NetworkManager: <debug> [1247457491.002278] periodic_update(): Roamed from BSSID (none) ((none)) to 00:1E:E5:2D:5A:99 (leslielady)

<done, pings resume>

To solidify the point, I can duplicate this traffic pause behavior by doing a "sudo iwlist ath0 scan".

So... it seems this may be a bug within the atk5k driver and/or wpa_supplicant with this hardware. The roams to (none) etc is just a side effect...

I don't readily see a way to fix the ath5k driver into the 2.4GHz range (ex like iwpriv ath0 mode 11b with madwifi), which I suspect may help. Anyone here have insight into ath5k's background scanning limitations?