RE: Problems with OpenBSD dhclient

From: Eric Anderson
> 
> Here's what I think would work well in most situations:
> 
>   If another interface (B) is currently down, that has 
> dhclient running 
> on it, then when interface (A) comes up with a valid ip, it should 
> remove the ip info from interface (B).

This is a very bad idea.  Unless the interfaces have been bonded or
configured as redundant for each other, they're independent by design.
If I'm using the wired port to do any of the many useful things one can
do with multiple interfaces (diagnostics, configuring new devices
without loss of internet access, etc.), I don't want the unavoidable
link-state changes on that interface to result in my wireless connection
going down.

> If an interface (A) changes from down->up has conflicting IP 
> information 
> with an interface (B) that is down, that dhclient manages, it should 
> remove the IP setup from interface (B), and set routes 
> according to the 
> newly upped interface.
>
> If an interface (A) changes from down->up, and there is another 
> interface (B) that is up that dhclient manages, then 
> configure interface 
> (A) only if it will not conflict with the other interface's 
> (B) network. 
>   This could be an rc.conf option - to force newly brought up 
> interfaces 
> to override currently up interfaces.

No.  Multiple interfaces with addresses in the same subnet (or even the
same address) is a routing issue.  Dhclient is not the correct tool to
solve routing issues.

A dhclient program needs to do only one thing: negotiate a lease for the
interface specified.