ap scanning?

Dan Williams dcbw at redhat.com
Wed May 4 15:28:30 EDT 2011


On Tue, 2011-05-03 at 16:57 -0700, Daniel Halperin wrote:
> On Tue, May 3, 2011 at 2:18 PM, Johannes Berg <johannes at sipsolutions.net> wrote:
> >
> > I don't think hostapd scans, but how are you connecting the client? It
> > could be scanning.
> 
> The problem is hard to reproduce, but appears to happen ~30s after
> something I do, such as associating or connecting the card or starting
> a TCP session, (usually between seconds 25-27 of the iperf transfer).
> Both endpoints are running Ubuntu 10.04.2 LTS, and I've uninstalled
> from both Network-Manager, which is the typical source of these woes.

NM has (for quite some time) disabled it's periodic scanning behavior if
you lock the connection to a single BSSID.  If you don't, then you're
assumed to want to roam between APs in a multi-AP network and thus you
probably actually do want periodic scanning, if only to make sure that
AP roaming works smoothly.

Dan

> The AP is set up as follows:
> 
> rmmod iwlagn cfg80211 mac80211
> modprobe iwlagn debug=0x40000
> sudo ifconfig wlan0 192.168.1.2 up
> sudo ~/hostap/hostapd/hostapd ~/hostap/hostapd/hostapd.conf -dd &!
> iperf -s -i1
> 
> the client is set up:
> 
> sudo rmmod ath9k ath9k_common ath9k_hw ath mac80211 cfg80211
> sudo modprobe ath9k
> sudo ifconfig wlan1 up 192.168.1.11
> sudo iwconfig wlan1 essid <essid>
> iperf -c 192.168.1.2 -i1 -t 30
> 
> Dan
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