Re: Problem with IEEE80211_MONITORING_INTERVAL

[Kalle Valo <kalle.valo@iki.fi>]

Johannes Berg <johannes@sipsolutions.net> writes:

> On Thu, 2009-04-16 at 09:14 +0300, Kalle Valo wrote:
>
>> Basically the problem is that if you scan in an area where there are no
>> or very few APs and scan takes more than two seconds (like abg band
>> scans usually take), sta->last_rx won't get updated because mac80211 is
>> not receiving any frames. This is why the beacon loss check will trigger
>> in ieee80211_associated().
>> 
>> The problem won't happen if there are lot of APs in the neighbourhood
>> distributed throughout the channels because then sta->last_rx is updated
>> often enough and the beacon loss check won't trigger.
>
> That doesn't make sense, why would our AP sta->last_rx be updated for
> other APs? I think you mean sdata->u.mgd.last_beacon, which is, probably
> wrongly, updated for all beacons.

Yes, I meant sta->last_beacon. But the principle is the same anyway.

>> I have been thinking two ways to fix this, either disabling the timer
>> for the duration of the scan or add a check for scan scan in
>> ieee80211_associated(). I started implementing the former but haven't
>> finished it yet. It would be great if someone else can fix it.
>
> But that doesn't make sense to me now. ieee80211_associated() is only
> run from the station work (ieee80211_sta_work) which doesn't do anything
> when we're scanning (and gets restarted on scan end). So even if last_rx
> or last_beacon isn't updated we should only run the evaluation of that
> after the scan finishes.

ifmgd->timer is run every two seconds, even then scanning and it calls
like this:

ieee80211_sta_timer() -> ieee80211_sta_work() -> ieee80211_associated()

And to my knowledge the timer is run even when scanning. Or am I missing
something?

Like you have sometime ago said, this MLME code we would need a rewrite.
It's getting messier all the time.

-- 
Kalle Valo