[Chilli] Thoughts on making Chilli's DHCP network interface aware

IT-Systemmanagement Pieter Hollants pieter at hollants.com
Sun May 23 21:21:50 UTC 2010

Hi David,

Am 23.05.2010 06:40, schrieb David Bird:
> You have all your EAP subscribers on one VLAN with UAM on the other? If
> so, then that is how you should reliably know which network (EAP/UAM)
> the user is on. If you are not getting any indication from the EAP NAS
> about the subscriber disconnect, then I don't see how chilli would
> otherwise know if that same client came back to UAM. It should work, but
> as you noted, chilli doesn't really know (because EAP and UAM *can* work
> together, of course). 

Exactly there was the mistake in my thinking. First of all, I've read
through IEEE 802.11i and IEEE 802.1x and there simply is no such thing
as a disconnect indication from the access point to the RADIUS server.
The AP simply doesn't share its state, so all CoovaChilli can see at any
time is a request to "open the gate". Which is logical, since both
standards don't want the RADIUS server (or a proxy such as CoovaChilli)
to track state.

Second, I was under the misconception that the two WLANs end up in
different VLANs, which they actually do not currently -- I explicitly
routed the EAP VLAN through CoovaChilli as well since I wanted to reuse
the same IP network independent of the WLAN chosen and it doesn't hurt
if CoovaChilli implements a "second switch" behind the AP, considering
it acts as Radiusproxy.

Now you got me thinking, however. Either use a seperate VLAN for EAP,
then I'd have to assign a second IP net, or extend CoovaChilli so it can
do "dhcpif" on two interfaces at once. Running two Chilli instances
doesn't make much sense in this scenario, I guess.

> Perhaps what you want is a VLAN based option to not allow logout? 
> I mentioned it before, but I personally think removing the logout
> ability is one thing, but probably more important is just to remove the
> LINK to the logout feature for these users. Another idea might be to add
> a query string parameter indicating a "auth=eap" so your portal can know
> not to show a logout link...

In the patch I developed so far I did something similar: I added a
"allow_logoff" parameter so the portal knows whether it should show a
link or not. Independently, I also had to consider the case where users
enter the word "logout" because it's advertised all over the portal. So
it makes sense to do both: indicate to the portal not to show the link
but also disable the two ways the user has (http://IP/logout and "logout").

Dipl.-Wirtsch.-Inform. Pieter Hollants
IT-Systemmanagement Pieter Hollants          Tel. : (+49) (0)6192-910717
Rossertstraße 80                             Fax  : (+49) (0)6192-910713
65830 Kriftel                                eMail: pieter at hollants.com

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