[patch] tun(4) and tap(4) if_clone support.

[Bruce M. Simpson]

Landon Fuller wrote:
> Nick Barkas (snb at threerings.net) and I have added interface cloning 
> support to the tun(4) and tap(4) drivers.
>
> We maintained backwards-compatible support for devfs cloning, which is 
> now disabled by default -- it can be re-enabled via a sysctl. 
> Interfaces that are created via devfs cloning may still be removed via 
> ifconfig destroy.
>
> The latest patch is available here
>     http://www.opendarwin.org/~landonf/code/patch-tuntap_ifclone
>
> I've submitted kern/105228 with the patch, and I'd be most 
> appreciative of comments/suggestions.

Interesting stuff. If it eliminates a race on creation, that has to be a 
good thing; I may have run into this race in the past month or two. It 
would however change tap/tun behaviour in that currently I have a few 
scripts which use dd(1) to force the device node to be created. This is 
undocumented behaviour specific to its devfs implementation which 
perhaps I shouldn't be relying upon, before I go on to create a bridge 
from several tap instances (which are then hooked up to QEMU virtual 
machines).

Good work!

BMS