Re: [PATCHv7 2/3] mac80211: add radar detection command/event

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2013-01-31 at 18:47 +0100, Simon Wunderlich wrote:

> > > What I've tried:
> > >  * configure 2 SSIDs in hostapd, start it
> > >  * both wlan0 and wlan0-1 got created
> > >  * only wlan0 comes up, wlan0-1 was rejected because of missing channel combinations
> > >  * now I've injected a radar - which should be sent to wlan0 and wlan0-1
> > >  * wlan0 could send the event, but wlan0-1 had no bss configured and therefore no chandef
> > > 
> > > I can change this comment to "may happen to devices which have currently no BSS configured",
> > > maybe that it is not so confusing ...
> > 
> > Not sure I understand, how would the radar detected event come to an
> > interface that doesn't really exist for the driver?
> 
> wlan0-1 exists and was created, but no AP was ever started - because hostapd tried
> to start the AP on a DFS channel when wlan0 was already active, and thanks to our
> interface combinations this is not allowed. Therefore, the vif.bss_conf.chandef is empty.
> 
> The interface does exist for the driver (interface add succeeded), but start_ap failed,
> so it is a virgin AP interface.
> 
> I think this behaviour is correct like that ...

So ... starting the AP failed because it was a different channel, it was
added to the driver because multiple AP interfaces were allowed but the
specific channel wasn't allowed (in addition) when it was started? But I
still don't see why that interface should get an event since it doesn't
even have a channel yet, except maybe preset_chan which is really only
for backward compatibility reasons?

What am I missing? Where does the event on wlan0-1 come from anyway?

johannes