Re: connection lost on roaming wifi networks

[Jirka Klimes <jklimes redhat com>]

On Monday 20 of September 2010 09:36:27 Frederik Himpe wrote:
> On Fri, 17 Sep 2010 10:55:23 +0200, Jirka Klimes wrote:
> > On Wednesday 15 of September 2010 14:52:02 Frederik Himpe wrote:
> >> I'm using Debian Squeeze kernel 2.6.32-21 (iwlagn 1.3.27ks) with an
> >> Intel Corporation Ultimate N WiFi Link 5300 [8086:4235].
> >> 
> >> Whenever I use my laptop in a place where different APs provide roaming
> >> for a wifi network, my system seems to suddenly (without moving) roam
> >> to another AP, after which the connection stops working completely
> >> (cannot ping anymore, etc) while NetworkManager shows I'm still
> >> connected.
> >> 
> >> I can easily reproduce this, on two different roaming networks.
> >> 
> >> I also tried kernel 2.6.35-1~experimental.3, but it has the same
> >> problematic behaviour.
> > 
> > There's a problem with getting IP from DHCP server. See DHCPREQUEST
> > requests, but no reply. Is the DHCP server properly running, replying?
> > Try to capture packets in wireshark to see if there is any DHCP server
> > response.
> > Or just configure the connection with static IP to verify that the
> > issues are indeed due to DHCP.
> 
> No, the issue is not DHCP: the fact that there is no reply to the
> DHCPREQUEST is just a symptom of my problem, but it is not the cause. The
> problem already starts from Sep 14 09:14:43, when it decides to roam.
> From that moment on, the connection is broken. A few minutes later, when
> my old DHCP lease expires, and then it fails to get a new one because the
> wifi connection is broken.

The issue can be caused by a number of things. DHCP was just a guess from the 
logs you've provided.
Try to collect and analyze more logs to find the real issue.
One cause of the problem could be the iwlagn driver. Is anything interesting 
in dmesg? Try removing and inserting the driver: rmmod iwlagn; modprobe iwlagn
You can also disable "n" band using driver options: see 
https://bugzilla.redhat.com/show_bug.cgi?id=587825#c8

What about wpa_supplicant logs?

Jirka