Re: nl80211 and wext interoperability

[Pavel Roskin <proski@gnu.org>]

On Thu, 2009-07-09 at 13:43 +0200, Johannes Berg wrote:

> Currently, if you use wpa_supplicant -Dwext and -Dnl80211 mixed,
> -Dnl80211 gets confused because -Dwext will set a 32-byte random SSID to
> "disconnect". When then the interface is brought UP again, the cfg80211
> code assumes that you set configuration while it was DOWN, and tries to
> recover that configuration. This means it will start scanning for the
> network, which means -Dnl80211 gets -EBUSY for the scan and it all gets
> very delayed. This also happens if you set an SSID with iwconfig before
> using -Dnl80211.

I'm seeing delay is I start wpa_supplicant with -Dwext on the current
wireless-testing.  I don't use -Dnl80211 on that system at all, as it
has stock Fedora 11 wpa_supplicant without nl80211 support.

I think using random data is a problem by itself.  Are we exposing
random pieces of kernel memory in probe requests?  That's bad.

> Do we just ignore that issue? It's only added timeout and people using
> purely nl80211 will never have a problem.
> 
> I'm all for ignoring wext issues, but I can also see people complain
> about things like this. Not sure what mac80211 did, did it just ignore
> settings while interfaces were down? I never really made sense of that
> code.

If your description is correct, I think the fix should be easy.

-- 
Regards,
Pavel Roskin