make wireless work

Environment: thinkpad x61 laptop, CENTOS 5 OS

Problem: When access "System > Administration > Network" and try to active wireless wlan, following error occurs:
Determining IP information for wlan0...SIOCSIFFLAGS: No such file or directory

Solution:
1. check wireless hardware model
>lspci | grep Wireless
#output is: Network controller: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection
#The wireless hardware is Intel Corporation PRO/Wireless 3945ABG

2. add "RPMforge" yum repository
> wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm
> rpm -i rpmforge-release-0.5.2-2.el5.rf.*.rpm

3. install firmware
> yum list *firmware*
> yum install iwl3945-firmware
> (optional) rmmod iwl3945; modprobe iwl3945

After step 3, try to active wireless lan again, another error
Error for wireless request "Set Mode" (8B06) :
    SET failed on device wlan0 ; Invalid argument.

4. close SElinux
Access "System > Administration > Security level and Firewall > SElinux tab", select "disabled" option.

5.  set network manager on
  1) open a shell, run following command
  > system-config-services
  2) in the popup window, tick "NetworkManager" node in the list, Click "save" button, and then click "Start" button.

这时，在desktop的右上角的tray icon里就会多了一个icon: wireless lan manager。通过它，你就可以上网了！

Note: if you restart linux, [Error for wireless request "Set Mode" (8B06)] still happens before login interface is shown. Hence it is recommended that Untick "activate device when computer starts" option in "System > Administration > Network > double click wlan item"


* ref link: http://www.33dots.com/index.php/linux/setting-up-intel-pro-3945-abg-wireless-in-centos-5.html

* ref link: http://acyk.icesoft.cc/post/442.html

* how to add "RPMforge" yum repository or install RPMforge
http://wiki.centos.org/AdditionalResources/Repositories/RPMForge#head-54c2bfab2ebfdb90aa800698abb69102098d04a8