Ubuntu 10.10: “fixed channel mon0: -1” Aircrack Problem With iwl3945

Update for Ubuntu 12.04 users: see this post.

After upgrading to Ubuntu Maverick recently, the Aircrack suite stopped working for me.

After setting airodump to a channel (like usual):

airodump --channel **X**

It still displayed its status as:

fixed channel mon0: -1

Some forum users advised to use:

airodump --channel X,X

But this didn’t work. For the record, I’m using a Thinkpad X60, with the iwl3945 driver. lshw output:

       description: Wireless interface
       product: PRO/Wireless 3945ABG [Golan] Network Connection
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: eth1
       version: 02
       width: 32 bits
       clock: 33MHz
       capabilities: bus_master cap_list ethernet physical wireless

Luckily, there is an easy to follow thread on the forums which fixes the problem for a similar card. This solution also worked with my 3945ABG.

Here are the commands:

wget http://wireless.kernel.org/download/compat-wireless-2.6/compat-wireless-2010-10-16.tar.bz2
tar -jxf compat-wireless-2010-10-16.tar.bz2
cd compat-wireless-2010-10-16
wget http://patches.aircrack-ng.org/mac80211.compat08082009.wl_frag+ack_v1.patch
patch -p1 < mac80211.compat08082009.wl_frag+ack_v1.patch
wget http://patches.aircrack-ng.org/channel-negative-one-maxim.patch
patch ./net/wireless/chan.c channel-negative-one-maxim.patch
gedit scripts/update-initramfs

#*** FIND LINE 13: KLIB=/lib/modules/2.6.31-wl/build
#*** REPLACE WITH: KLIB=/lib/modules/$(uname -r)/build

sudo make install
sudo make unload
sudo modprobe iwl3945

Alternatively you can also use sudo reboot instead of sudo modprobe if you’re unsure which driver module you need to load.

Aircrack should work fine again now. Note that kernel updates might overwrite the module again (and, hopefully, fix the bug at the same time).