NM Success and Failure

["Joshua L. Phillips" <mandingueiro users sourceforge net>]

I have been experimenting with NetworkManager and wpa_supplicant for the 
last month. I am writing this little note to share some of my 
experiences with this software and also to see if others have 
encountered the same issues that I have (from the looks of other Linux 
mailing-lists I have had many of the same problems as others.)

First, this is an excellent piece of software. I say that because we 
have been needing something like this for mobile linux. It's the simple 
wireless network switching and browsing that I like the most. And I also 
like the fact that it tries to connect to a wired connection as soon as 
it is plugged in. It seems to make sense. Most of the time, it works 
just fine.

It works well with the orinoco_cs drivers (I am working on a i686-FC5 
(fully updated) box and have used Network Manager with two PCMCIA 
wireless cards. These are a Netgear MA401RA and a Microsoft MN-520. Both 
can be used with the orinoco_cs driver.) I had to blacklist the hostap 
drivers like many others who use these cards, but that was just a couple 
of lines in /etc/modprobe.d/blacklist This setup worked well.

However, the wireless network at the University that I attend uses WPA2 
Enterprise authentication and encryption. I also wanted to use the 
WPA-PSK option on my home router instead of WEP. Thus, the orinoco_cs 
drivers were no longer able to fulfill my needs since they only support 
WEP. I promptly unblacklisted hostap_cs, upgraded the firmware on both 
cards and blacklisted the orinoco modules so that my stock kernel would 
no longer load them. I am able to successfully authenticate with my home 
router using WPA-PSK and the University's wireless network using 
PEAP/MSCHAPV2. Excellent, but there are still a few issues...

With this setup, once I have authenticated with a particular network, it 
is perilous to switch either to the wire or to another wireless network. 
My system will sometimes (usually) lock-up when I try either of these 
two options after connecting to a wireless network. (Sometimes it will 
happen without any noticable change whatsoever which is very 
frustrating.) There were no problems with orinoco_cs and actually I 
don't think the problem is with hostap_cs. It seems to be with 
wpa_supplicant... sort of. I can duplicate the same lock-up by running 
wpa_supplicant independently and then killing the process using killall. 
If I do this, sometimes the machine locks. I don't know the exact 
circumstances yet, but I will continue to search. However, I can 
alleviate this issue by doing something a little nicer to wpa_supplicant:

wpa_cli -iwlan0 disconnect
wpa_cli -iwlan0 terminate

The machine has NEVER locked when I use this method. I think that this 
may be the better way to shutdown the process unless it simply will not 
respond at all. This might never be an issue on some setups, but it has 
been a headache for me. Since it happens with both cards, I suspect that 
wpa_supplicant leaves the hostap driver in an unfortunate state which 
then locks my machine. For now, I have switched to using wpa_supplicant 
and connecting it to my ifup-wireless script and then to ifdown 
performing the suggested commands.

Does anyone know how and when NM stops wpa_supplicant? Maybe this will 
solve this problem that I and others are having?

ref: http://www.ubuntuforums.org/showthread.php?t=180160

If NM keeps the same wpa_supplicant process running when switching 
networks, does it issue a disconnect command before loading the new 
configuration? Or does it simply kill and start a new process (which 
could explain my freeze-up problems?)

Even if I do not switch wireless networks, when I shut-down the system, 
it cannot complete the shutdown process. It locks up when trying to stop 
named. I know that named is connected to NM vi DBUS, but what if these 
connections aren't being closed properly and this is the another reason 
that my system might occasionally be hanging. I don't know how to test 
this independently and my logs are completely silent no matter which 
situation I am trying to analyze.

JLP