Re: gobbledegook in iwconfig after NM disconnect

[Dan Williams <dcbw redhat com>]

On Sun, 2010-04-11 at 05:20 +0100, Richard Neill wrote:
> Dear All,
> 
> Not sure if this is a bug, but if I disconnect a wireless interface from 
> network manager, the result of iwconfig's ESSID becomes gibberish.
> I have no idea where the value of
>  
> \x90\xEF\xFD\xA5+ dUB5\xAB3q8\xE2\xCF\xDC\x8Db+\xA3\x9F\x1D\xAA1\x82\xA4\xFA\xDCZsl
> comes from, or what it means!

The Linux Wireless Extensions API (the older API that programs use to
control wifi) doesn't have a clean way to say "Disconnect and stop doing
anything until I tell you."  This random SSID is done by wpa_supplicant
when disconnecting from the network to ensure that the driver/firmware
does not attempt to automatically connect to anything else until it's
told to do so.  It's not anything that NM is doing, and it's normal.

The new kernel wireless API (cfg80211) has fixed this problem by
properly including a "disassociate" command that idles the device.

If you've told NM (or the card) to disconnect, you probably did mean for
it to disconnect.  Without this random SSID the card (depending on the
driver or firmware) may well attempt to connect to some SSID that you
didn't want it to.

Dan

> Here is an example:
> 
> 1. While NM is connected to the network
> 
> $ iwconfig wlan0
> wlan0     IEEE 802.11abg  ESSID:"26PPWG602"
>            Mode:Managed  Frequency:2.427 GHz  Access Point:
> 		00:0C:F6:7E:FA:18
>            Bit Rate=54 Mb/s   Tx-Power=15 dBm
>            Retry  long limit:7   RTS thr:off   Fragment thr:off
>            Power Management:off
>            Link Quality=65/70  Signal level=-45 dBm
>            Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
>            Tx excessive retries:0  Invalid misc:0   Missed beacon:0
> 
> 
> 2. Immediately after disconnecting the Wifi, via the NM gui
> 
> $ iwconfig wlan0
> wlan0     IEEE 802.11abg  ESSID:"\x90\xEF\xFD\xA5+ dUB5\xAB3q8\xE2\xCF
> 		\xDC\x8Db+\xA3\x9F\x1D\xAA1\x82\xA4\xFA\xDCZsl"
>            Mode:Managed  Frequency:2.427 GHz  Access Point:
> 		Not-Associated
>            Tx-Power=15 dBm
>            Retry  long limit:7   RTS thr:off   Fragment thr:off
>            Power Management:off
> 
> 
> 3. After running ifconfig wlan0 down
> 
> $ iwconfig wlan0
> 
> wlan0     IEEE 802.11abg  ESSID:off/any
>            Mode:Managed  Frequency:2.427 GHz  Access Point: 		
> 		Not-Associated
>            Tx-Power=15 dBm
>            Retry  long limit:7   RTS thr:off   Fragment thr:off
>            Power Management:off
> 
> 
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