Re: Pruning the active AP

[Markus Becker <mab comnets uni-bremen de>]

On Thu, 3 Jul 2008, Dan Williams wrote:

> On Thu, 2008-07-03 at 17:28 +0200, Markus Becker wrote:
> > Hello,
> >
> > I was checking how NM reacts, when an AP, that we are connected to,
> > dies or is getting out of range. I was expecting NM to notice that and
> > remove the current AP from the list of available APs. However, NM keeps
> > the AP in its list. I think this is because of this in nm-device-wifi.c:
>
> Have you tried it with the patch from Adel Gallah for the scan timeout
> stuff from last week?  That patch specifically fixed the issue of never
> noticing that the AP was out of range even after the supplicant had sent
> the disconnection status.

No, I was trying without it (with Michael Biebl's packages). With r3811 
NM seems to notice that an AP is gone, after about 30 sec. And it takes 
about 50s to figure out that an AP has come back (Including the booting 
time of the AP.)

But what I was looking for, but didn't see, is link_timeout_cb().

> > /* Don't ever prune the AP we're currently associated with */
> > if (cur_ap_path && !strcmp (cur_ap_path, nm_ap_get_dbus_path (ap)))
> >    keep = TRUE;
> >
> > What was the reasoning behind keeping the AP we're connected to, when it
> > is not in the scanning list anymore? Are some cards not reporting the AP
> > we are connected to in the scanning list or why?
>
> Yes, even though they technically should, drivers and cards don't
> necessarily do this.  Since wireless is a fairly unreliable medium, it's
> not always the case that the connected AP's beacons will show up in a
> given scan.  We simply cannot rely on that unless drivers are mandated
> to include that upstream in the kernel.

Well, it works with the ndiswrapper for the Marvell card (sorry, 
currently no time for the mrv8k driver).

> Dan
>
> > Markus
> >
> > ------------------------------------------------
> > | Dipl.-Ing. Markus Becker
> > | Communication Networks
> > | Mobile Research Center
> > | TZI - Center for Computing Technologies
> > | University Bremen
> > | Germany
> > ------------------------------------------------
> > | web: http://www.comnets.uni-bremen.de/~mab/
> > | mailto: mab comnets uni-bremen de
> > | telephone: +49 421 218 2287
> > | building: NW1 room: N2260
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