question regarding tap/tun devices

[Robert Watson]

On Mon, 29 May 2006, Brooks Davis wrote:

> On Sun, May 28, 2006 at 08:33:32PM +0200, Goran Gajic wrote:
>> I'm running 7.0-CURRENT build Thu May 25 23:17:10 CEST 2006 GENERIC config.
>> While playing with dynamips emulator which uses tap I've noticed that
>> ifconifg tun0 create or ifconfig tap0 create doesn't work (this doesn't
>> have anything to do with emulator which works great).
>
> These interfaces don't use the network interface cloning interface and thus 
> can not be created with ifconfig.  This should be fixed, but the /dev based 
> cloning hackes they use make this difficult.

I've never quite understood if this is a problem or a benefit.  Devfs-cloning 
of tap and tun are very convenient from an application writer perspective -- 
you just open /dev/tap or /dev/tun, and magic happens.  With our current ifnet 
cloning interface, is it possible to say "atomically create and return the 
next available interface number"?

Robert N M Watson