Re: Limit on number of APs? Some way to force-rescan?

[Dan Williams <dcbw redhat com>]

On Wed, 2006-07-12 at 13:35 -0400, Derek Atkins wrote:
> I'm sitting here in the IETF, and from where I sit I can hear at least
> 15 Access Points, some A, some B/G.  I get this number by manually
> running "iwlist ath0 scan" and looking at the results.  I see
> "three" ESSIDS:
> 
> [warlord cliodev ~]$ iwlist ath0 scan | grep ESSID | sort -u
>                     ESSID:""
>                     ESSID:"IETF66A"
>                     ESSID:"IETF66B"
> 
> However, nm-applet is only showing IETF66B, and wont let me connect to
> IETF66A, even when I tell it to by "Connect to other wireless
> network".

Hmm.  I blame madwifi :)  Ok, just kidding.

However, I was just at a Hyatt in San Diego last weekend, and there were
a _ton_ of access points there.  > 30.  And ipw2200 displayed them all,
and I could even connect to some.  The differences between your setup
and mine are, of course, (a) ipw2200 vs. madwifi-ng and (b) you have
802.11a and I don't.

It could be that madwifi doesn't do a good job of caching the scan
results, since both NM and wpa_supplicant will request the results when
they get notification that a scan event has completed.  Some drivers,
most notably old ones, won't survive two processes requesting scan
results around the same time.  But I wouldn't expect madwifi to have
that issue, though it might.

An interesting thing to do would be to write a small application that
listens to netlink events, and when the scan result event comes in, try
to grab scan results and compare those results with the ones that
NetworkManager retrieves.

Dan

> Now, going back to my scan-list, the IETF66A network doesn't show
> up until "Cell 10" in my scan list.   Is there some limit to the
> number of returns from a scan?  Does NM stop looking after some
> point?
> 
> Right now I can't figure out how to tell it to connect to the A
> network.  I can see it's there, but NM doesn't see it.  I've tried
> restarting NM to no avail.  I haven't tried rebooting, but honestly I
> shouldn't have to.  Is there some way to tell NM: "Hey, I know there's
> more networks out there -- can you go look again right now?"
> 
> Any suggestions of things to try?  I suspect that my situation will
> change in an hour when I move to another room.
> 
> -derek
> 
> PS: Why do I feel like I really stress test both Madwifi and NM all
> the time with my personal usage patterns???
>