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

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.


> 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???

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