Re: kde (again)?

[Michael Blakeley <mike+gnome blakeley com>]

Dan Williams wrote:
> On Thu, 2005-12-15 at 12:07 -0800, Michael Blakeley wrote:
>
> > My AP never shows up from a 'sudo iwlist wlan0 scan' at all - that's
> > kind of the point, as I understand it. If you don't know that it's
> > there, you can't access it. But I'm sure you know more about wifi than I do.
> >
> > My card is a broadcom, via ndiswrapper. Perhaps that's the problem? I 
> > believe ndis (and thus ndiswrapper) doesn't support some scanning modes.
>
>
> Right, there are 3 possible cases here:
>
> 1) completely invisible access point; I've heard at least one other case
> where the access point doesn't broadcast its ESSID or its BSSID, but I
> consider these to be broken.  AFAIK, by the spec, access points are
> required to broadcast beacon packets.  And if you're not broadcasting at
> least your BSSID (the 'Address' in iwconfig) in the beacon packet, then
> the beacon packet is pretty much useless because you can't tell what the
> heck its for.
>
> 2) The broadcom/ndiswrapper combination isn't reporting access points
> correctly.  Ideally, you could pop in another type of card and see what
> it says, to determine whether the driver is at issue.
>
> 3) The card has "privacy" mode set.  Privacy mode (or sometimes "drop
> unencrypted") is part of the 802.11 spec that causes the card to drop
> all unencrypted packets when the card is in encrypted mode (ie, when you
> have a key set on it).  However, I don't believe that the card can drop
> management frames like the beacon broadcasts.  Sometimes this is
> filtered in the driver.  I'd call drivers that drop management frames
> from non-encrypted access points broken as well.  If the driver is in
> the Linux kernel, then it can be fixed.  ndiswrapper drivers likely
> cannot be fixed in this way.
>
> In any case, if the access point is set only to not broadcast its ESSID
> (but still broadcasts beacon frames) then NM should be able to handle
> it; otherwise it's a bug.  I've got my home AP doing this, so I know it
> should work (except for certain Cisco cards as mentioned earlier).

Thanks, and those sounds like good suggestions, but I can't really 
narrow it down. Does the cisco problem have something to do with 
"monitor" mode (aka "master" mode, I think)? I believe the ndis drivers 
can't put the card into monitor mode: as I understand it, there simply 
isn't any API call to do so. There's some discussion of this problem at 
http://wiki.ethereal.com/CaptureSetup/WLAN and 
http://ndiswrapper.sourceforge.net/mediawiki/index.php/FAQ#Is_master_mode_supported.3F 
- the subject is a little google-bombed, sadly, so I couldn't find much 
detail.

Barring that, I'm afraid all I can really do is repeat my symptoms: on 
an unencrypted network, everything "just works". On the corporate WEP 
that I most often visit, though:

0. boot+login or resume-from-suspend on-site, with NetworkManager and 
nm-applet running

1. sudo iwlist wlan0 scan => nothing at all, no matter how many times I 
rescan. The nm-applet list is also empty.

2. sudo iwconfig wlan0 essid my-essid key resticted 00DEADBEEF
   (not my real essid or key)

3. after a few seconds, iwlist scan shows my-essid, and nm-applet 
reports 'Waiting for network key from  wireless network "my-essid"'

4. nm-applet keeps waiting for that key

5. click on nm-applet icon, select my-essid

6. at this point, gnome-keyring pops up, if the keyring is locked

7. nm-applet establishes connection and gets an address

The Windows 2k/XP wifi systray thingy deals with the situation 
reasonably well (at least, about as well as it deals with anything). It 
can't autodiscover the AP, but once you've manually entered the key, it 
remembers and tries to connect automatically. I suspect that it simply 
looks for the first ssid that it knows about, and if it can't find one, 
start to blindly try known ssids until it hits one.

If nm-applet or NetworkManager has any debug info that could be useful, 
I'd be happy to collect it and forward it.

thanks,
-- Mike