Ubuntu 7.10 and “Random” Disconnects with Your WPA2 Wireless Connection

I began noticing that my wireless connection was having issues a few weeks back. I have a Broadcom BCM94311MCG (43xx series) mini-PCI card in my laptop and I’m running Kubuntu 7.10. The symptom was pretty benign, I would lose network connectivity for short periods but it would restore itself in a few seconds.

I began watching my wireless card statistics using knetworkmanager and noticed that the signal strength wasn’t dropping out, though it would fluctuate, indicating that it was in fact working correctly. I began looking through the logs for any indication of the problem when I discovered these messages in my dmesg output:

SoftMAC: Open Authentication completed with xx:xx:xx:xx:xx:xx
CCMP: decrypt failed: STA=xx:xx:xx:xx:xx:xx

You will see similar messages in your /var/log/kern.log and /var/log/debug log files. Some people report these errors in great frequency, one gentlemen claiming that his log files grew to 1.5G in one day.

This seems to be caused by a bug in the Linux kernel. This problem is addressed in kernel 2.6.24, which is included in Ubuntu 8.04 Hardy Heron. This bug is discussed in Launchpad bug #190475. In my limited testing using the LiveCD version of Heron I haven’t experienced the problem, so I’m keeping my fingers crossed.

The necessary drivers are not on the LiveCD, so if you plan on doing your own testing you’ll be in for a bit of a chore. The simplest path to getting your wireless up and running is to boot from the LiveCD, bring up your wired network, then enable the following two repositories in your /etc/apt/sources.list file:

deb http://archive.ubuntu.com/ubuntu hardy universe
deb-src http://archive.ubuntu.com/ubuntu hardy universe

Then run the following commands to make your machine aware of the packages in the repository you just added and install the firmware installer. During the installation it will prompt you to download the firmware files, you’ll need to choose “Yes”.

sudo apt-get update
sudo apt-get install b43-fwcutter

My recommendation to you for solving this problem would be to wait the few weeks until 8.04 is out in it’s full release and simply upgrade. 8.04 is a LTS (Long Term Support) release, so it should be very stable right out of the gates. If you simply can’t wait that long then your answer is going to be downloading and compiling your own kernel, finding packages for an updated kernel, or applying the patches to your current kernel sources and compiling from there.