Dummy Network Interface

[Michael W. Oliver]

On Thu, Jan 15, 2004 at 03:07:20PM -0500, Robert Watson wrote:
> 
> On Thu, 15 Jan 2004, Vlad Galu wrote:
> 
> > |On Tue, 13 Jan 2004 ms419 at freezone.co.uk wrote:
> > |
> > |> How does one create a dummy network interface in FreeBSD? 
> > |
> > |Dummy in what sense?  An interface where the packets are simply
> > |dropped? if_tap and if_tun both provide pseudo-device in /dev that a
> > |userspace process can attach to in order to emulate a network interface
> > |(used by VMWare, ppp, various tunneling bits, ...)  In the absense of a
> > |process sitting on the device, they simply drop the packets.  Although
> > |they may get garbage-collected if unused on -CURRENT...  You can also
> > |use netgraph to bring pseudo-interfaces, perhaps without anywhere for
> > |packets to go. 
> > |
> > |And, I suppose, create in what sense?  Are you looking at this from a
> > |developer perspective, or you just need one from a user perspective. 
> > |If writing a device driver (and hence needing a starting point), if_tap
> > |and if_tun are fairly decent models for a pseudo-interface.
> > 
> > 	I think he could use the discard interface smoothly. On Linux
> > (from which the dummy interface notion is taken from) it is simply used
> > for testing purposes, as in routing, or perhaps socket programming. I
> > personally have used it for a while, but then I used interface aliasing,
> > which became a habit. 
> 
> Does the discard interface in Linux "act like" another type of interface,
> such as point-to-point, ethernet, etc? 

I believe that he was referring to the discard interface in FreeBSD.  I
don't know about Linux at all, but I have used the discard interface in
a FreeBSD router much like a Null interface in a cisco router.

pseudo-device       disc

man 4 disc

-- 
Mike
perl -e 'print unpack("u","88V]N=&%C=\"!I;F9O(&EN(&AE861E<G,*");'

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