Re: Turn off passive scanning?

[Dan Williams <dcbw redhat com>]

On Mon, 2009-03-23 at 18:32 -0400, Derek Atkins wrote:
> Dan et al,
> 
> I seem to have found a bug in the iwl3945/mac80211 driver in the
> 2.6.27.19-170.2.35.fc10.i686 kernel where it dies in a page
> fault in skb_free().  Unfortunately I couldn't grab the full
> stack trace, but I saw about 5 hard crashes within an hour
> earlier today.
> 
> I'm sitting in an extremely saturated network at the IETF, and
> I was attempting to perform a 'yum update'.
> 
> I'm guessing it's a passive scan issue because the backtrace had
> a copy scan result entry.
> 
> Moreover, I turned off network manager, brought wlan0 up by hand,
> and I haven't seen another crash.
> 
> Unfortunately the crash is very low level.  Even when siting on
> the console the system locks up hard.  I couldn't even page-up/page-down
> to see the full stack trace (and I didn't spend the time to leave
> my meeting, find a piece of paper, and copy it all down by hand).
> 
> So...  Is there some way I can turn off passive scanning in NM?

Not really; you should be able to achieve the same result by
periodically running 'iwlist wlan0 scan' without NM running; there
clearly needs to be some fixes to the driver here...

It may well not have anything to do with "passive" scanning itself, but
just scanning in general.  There's passive (card just jumps to a channel
and listens for a split second, then to the next channel and listen,
etc) or active (jump to a channel, send a probe request, wait short time
for response).

Dan