Subject: Re: [RFC 3/3] mac80211: Store basic rates for bss when joining
 ibss network
From: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
To: ext Johannes Berg <johannes@sipsolutions.net>
Cc: "linville@tuxdriver.com" <linville@tuxdriver.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
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Date: Thu, 10 Jun 2010 14:37:30 +0300
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On Wed, 2010-06-09 at 09:36 +0200, ext Johannes Berg wrote:
> On Wed, 2010-06-09 at 07:45 +0300, Teemu Paasikivi wrote:
> 
> > > However this kinda confuses me.
> > > 
> > > We had a long-standing TODO item on our list at
> > > http://wireless.kernel.org/en/developers/todo-list
> > > 
> > > "when leaving an IBSS and we were the only member, remove it from
> > > cfg80211's BSS list"
> > > 
> > > Maybe that would help here too?
> > > 
> > 
> > Yes, I think that would propably solve that issue where IBSS was
> > recreated and requested basic rates are changed.
> 
> Want to take a look at it? It shouldn't be too hard -- just call
> cfg80211_unlink_bss() somewhere where we still have the BSS pointer.
> Actually we don't keep it as you saw with the update, so need to find it
> first and then unlink it.
> 

I'll take a look at this. I think BSS can be got by the same method as
in the ieee80211_sta_find_ibss function.

> > > However I don't understand the scenario anyway. If you create an IBSS,
> > > you start beaconing and tell cfg80211 about it with a frame that
> > > includes the supported and basic rates. Then you leave, but the BSS
> > > stays around in cfg80211 for 15 seconds. If you re-join within those 15
> > > seconds, the scan results will pick up the old IBSS that no longer
> > > exists, and we "join" it rather than creating it.
> > > 
> > > However -- joining it will take the basic rates from it. So wouldn't you
> > > get the old basic rates which is fine? What do you mean by "left unset"?
> > > 
> > 
> > By "left unset" I mean that in the sniffer logs there's no rates marked
> > as basic rates in the beacons. No old ones or new ones.
> 
> Ok that's what I thought. But ... are they marked in our TX beacons when
> we _first_ created the IBSS?

Yes those were marked. In any case, lets see if this is an issue after
implementing that removal of the BSS from the cfg80211's list.

> 
> > > What happens if you join an IBSS that already exists?
> > > 
> > 
> > It works, but I haven't captured what's in the air. That's one reason
> > why I sent these patches as RFC.
> 
> I don't really see how the two scenarios differ, so that's odd...
> 
> johannes
> 

Teemu