Encrypted wireless networks inaccessible with backported modules: lbm_cw-ieee80211_crypt_* modules are not detected correctly

[Conn O Griofa]

System information: Ubuntu Intrepid x86 (all updates as of November 12th 2008)
Kernel revision: Linux inspiron 2.6.27-8-generic #1 SMP Thu Nov 6 17:33:54 UTC 2008 i686 GNU/Linux
Wireless card: 01:03.0 Network controller: Intel Corporation PRO/Wireless LAN 2100 3B Mini PCI Adapter (rev 04)

Summary: if a user with an Intel ipw2100 wireless connection (and possibly other cards which use the ieee80211 drivers) attempts to install the linux-backports-modules-intrepid package, their wireless card will no longer be able to connect to any encrypted networks upon rebooting their machine. This problem is due to the crypto modules not being recognised correctly.

Steps to reproduce: install the "linux-backports-modules-intrepid" package & reboot.

Expected result: Wireless networking with encrypted networks will continue to function normally, as before.

Actual result: Network Manager will begin connecting to the network (one green dot), and after about 15 seconds, you will be prompted to re-enter your wireless network password.

Cause: the incorrect version of the ieee80211 crypto modules are loaded, possibly due to the backported modules having a different naming convention than usual. Look at the following lsmod output:

Default kernel (no backported modules):
conn@inspiron:~$ lsmod | grep ieee80211
ieee80211_crypt_tkip 17024 1
ieee80211_crypt_ccmp 13568 1
ieee80211 38088 1 ipw2100
ieee80211_crypt 13572 3 ieee80211_crypt_tkip,ieee80211_crypt_ccmp,ieee80211

Default kernel with backported modules installed:
conn@inspiron:~$ lsmod | grep ieee80211
ieee80211_crypt_tkip 17024 0
ieee80211_crypt_ccmp 13568 0
ieee80211_crypt 13572 2 ieee80211_crypt_tkip,ieee80211_crypt_ccmp
lbm_cw_ieee80211 37636 1 ipw2100
lbm_cw_ieee80211_crypt 13828 1 lbm_cw_ieee80211

Here is what it *should* look like:
conn@inspiron:~$ lsmod | grep ieee80211
lbm_cw_ieee80211_crypt_tkip 17024 1
lbm_cw_ieee80211_crypt_ccmp 13568 1
lbm_cw_ieee80211 37636 1 ipw2100
lbm_cw_ieee80211_crypt 13828 3 lbm_cw_ieee80211_crypt_tkip,lbm_cw_ieee80211_crypt_ccmp,lbm_cw_ieee80211

Resolution (manual):
conn@inspiron:~$ sudo rmmod ipw2100 ieee80211_crypt ieee80211_crypt_tkip ieee80211_crypt_ccmp
conn@inspiron:~$ sudo modprobe lbm_cw_ieee80211_crypt_tkip lbm_cw_ieee80211_crypt_ccmp ipw2100

Resolution (development): ensure that the ieee80211_crypt_* modules are either blacklisted or given a lower priority to the lbm_cw_ieee80211_crypt_* modules.

The problem (and resolution) seems pretty straightforward, but if you need any other logs to confirm, please let me know.

[al_mckin (amckinley03)]

I also experienced this bug and it was fixed for me by removing the linux-backports-modules package.

[Danilo Piazzalunga (danilopiazza)]

This also happens on Hardy when using LBM. See bug #322434.