From owner-freebsd-net@FreeBSD.ORG  Wed Jan 14 19:14:01 2004
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: freebsd-net@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 2C15016A4CE
	for <freebsd-net@freebsd.org>; Wed, 14 Jan 2004 19:14:01 -0800 (PST)
Received: from fledge.watson.org (fledge.watson.org [204.156.12.50])
	by mx1.FreeBSD.org (Postfix) with ESMTP id C2A1A43D53
	for <freebsd-net@freebsd.org>; Wed, 14 Jan 2004 19:13:59 -0800 (PST)
	(envelope-from robert@fledge.watson.org)
Received: from fledge.watson.org (localhost [127.0.0.1])
	by fledge.watson.org (8.12.10/8.12.10) with ESMTP id i0F3CHUd060984;
	Wed, 14 Jan 2004 22:12:17 -0500 (EST)
	(envelope-from robert@fledge.watson.org)
Received: from localhost (robert@localhost)i0F3CH8c060981;
	Wed, 14 Jan 2004 22:12:17 -0500 (EST)
	(envelope-from robert@fledge.watson.org)
Date: Wed, 14 Jan 2004 22:12:16 -0500 (EST)
From: Robert Watson <rwatson@freebsd.org>
X-Sender: robert@fledge.watson.org
To: ms419@freezone.co.uk
In-Reply-To: <173CC3C8-45A5-11D8-B102-000A95C71776@freezone.co.uk>
Message-ID: <Pine.NEB.3.96L.1040114220930.55901A-100000@fledge.watson.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: freebsd-net@freebsd.org
Subject: Re: Dummy Network Interface
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 15 Jan 2004 03:14:01 -0000


On Tue, 13 Jan 2004 ms419@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.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Senior Research Scientist, McAfee Research