Steve Bellovin wrote:

> I'm currently configuring a laptop for someone; given the likely usage 
> environment, setting up dhclient is going to be painful.  I tend to 
> think that the model we're using is wrong.  Windows XP, at least as 
> configured by IBM, seems to do it properly.

sure there are still things to do in the mobility area.

> 
> The machine will be used in both wireless (built-in am0 interface) and 
> wired mode.  For fairly obvious reasons, it's generally better to use 
> the wired interface if it's available.
> 
> Right now, dhclient cycles through various media options for devices 
> listed in dhclient.conf.  This is especially important for 802.11 
> devices, where there might be several combinations of keys.  In a 
> fairly strong sense, dhclient shouldn't bother trying the DHCP protocol 
> unless it sees RF carrier on a wireless interface; similarly, it 
> shouldn't try DHCP on a wired interface if the cable is disconnected.
 > [snip]

This is also true for modems vs ethernet cards. or even if you have 2 
nics with different capabilities/configs/...

I like the idea of "interface instance priority" and of conditional 
configuration.

Another idea is that if a program tries to connect to a remote system 
(or if another host that is using us as a gateway tries to route through 
us) and the "right" interfaces are not configured, then signal dhclient 
to acquire an address (probably only once during a boot session, to 
avoid useless failure repetition). This is better than waiting for the 
next dhclient try.
Up so far, the only option I got was to connect to the gateway and 
manually do it. Unfortunately, this would require hooks in the IP stack 
(unless I'm mistaken).


mouss