Re: No inter-AP Roaming?

On Tue, 2007-12-04 at 16:08 -0500, Derek Atkins wrote:
> Quoting Dan Williams <dcbw redhat com>:
> > On Tue, 2007-12-04 at 15:31 -0500, Derek Atkins wrote:
> >> I'm sitting at the IETF, connected to the 802.11 network..
> >> But as I wander from room to room, NM doesn't roam.  It wont
> >> jump from one AP to another as I move around the conference
> >> facility.  I'll get to my new room and find that I no longer
> >> have any network and then have to wait for a full connection
> >> sequence.
> >>
> >> What gives?  I certainly don't have this problem if I just
> >> let the driver/hardware roam on its own.
> >
> > Well, NM doesn't control roaming at all, wpa_supplicant and the driver
> > do.  Sometimes wpa_supplicant will push the BSSID down to the driver
> > when connecting (not entirely sure when that is) and if the driver
> > actually follows WEXT (which lots don't) that would cause the driver to
> > lock to that single BSSID and not switch.  That bit is highly driver
> > dependent.  It looks like wpa_supplicant will only do this when it has
> > previously timed out authentication with the station but tries again
> > (like it should).  It then passes the BSSID down to the association code
> > which tries to lock the card to that BSSID specifically.
> Interesting.
> I'm using the iwl3945 driver.  I DO see some authentication timeouts,
> which is really weird.. Sometimes to the point where it wont even
> successfully authenticate to the card at all and I have to reset.
> Very frustrating.
> How do I tell whether wpa_supplicant is locking me to a particular
> BSSID, and how do I undo that once it's done?

You'd have to patch the source to say when it's going to do that.  You
could test this out by using iwconfig yourself.  Without NM and
wpa_supplicant running, connect to an access point using something like:

iwconfig wlan0 essid foobar bssid xx:xx:xx:xx:xx:xx

then walk out of coverage of that BSS but _still_ in the same ESS while
pinging or something, and then see if the driver/firmware roamed to a
different BSS in the same ESS.  You can clear the BSS lock by setting
iwconfig wlan0 bssid 00:00:00:00:00:00.


> > Dan
> -derek
> Strangely, it DID just roam as I went from my lunch meeting to
> my first after lunch session.  But it's still annoying that it
> can drop the session so easily/quickly whereas non-NM will gladly
> re-acquire the association as I move between areas, even if I hit
> an area of no coverage.

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