From owner-freebsd-current@FreeBSD.ORG  Sat Sep 18 12:55:35 2004
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 8F50C16A4CE; Sat, 18 Sep 2004 12:55:35 +0000 (GMT)
Received: from fledge.watson.org (fledge.watson.org [204.156.12.50])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 3C41E43D1F; Sat, 18 Sep 2004 12:55:35 +0000 (GMT)
	(envelope-from robert@fledge.watson.org)
Received: from fledge.watson.org (localhost [127.0.0.1])
	by fledge.watson.org (8.13.1/8.13.1) with ESMTP id i8ICt2jT088257;
	Sat, 18 Sep 2004 08:55:02 -0400 (EDT)
	(envelope-from robert@fledge.watson.org)
Received: from localhost (robert@localhost)i8ICt2dJ088254;
	Sat, 18 Sep 2004 08:55:02 -0400 (EDT)
	(envelope-from robert@fledge.watson.org)
Date: Sat, 18 Sep 2004 08:55:01 -0400 (EDT)
From: Robert Watson <rwatson@FreeBSD.org>
X-Sender: robert@fledge.watson.org
To: Brooks Davis <brooks@one-eyed-alien.net>
In-Reply-To: <20040918051758.GA18656@odin.ac.hmc.edu>
Message-ID: <Pine.NEB.3.96L.1040918085237.88212A-100000@fledge.watson.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=ISO-8859-1
Content-Transfer-Encoding: QUOTED-PRINTABLE
cc: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= <des@des.no>
cc: re@FreeBSD.org
cc: current@FreeBSD.org
Subject: Re: 5.3-RELEASE TODO
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 18 Sep 2004 12:55:35 -0000


On Fri, 17 Sep 2004, Brooks Davis wrote:

> On Fri, Sep 17, 2004 at 09:30:19PM +0200, Dag-Erling Sm=F8rgrav wrote:
> > Brooks Davis <brooks@one-eyed-alien.net> writes:
> > >                      Thus, so you have to know how much space you wil=
l
> > > need before doing any kind of allocation, hence the double loop and t=
he
> > > potential race.
> >=20
> > Using sbufs removes the need for loop and greatly simplifies how you
> > deal with overflows.
>=20
> Indeed it does.  I'm not fully happy with the hardcoding of a maximum
> size, but I doubt anyone will hit it in practice.  Here's a new and
> improved patch that makes a single pass and uses sbufs.=20

Have you tried seeing just how many addresses you can add before
getifaddrs() fails to return the complete list?  128k seems like a lot,
but I instrumente ifconf() locally a couple of weeks ago when I first
became aware of this problem, and discovered that even on my notebook
(which has a wireless card with one IP, and an unused ethernet card) that
I see moderately large buffers being read from user space:

ifconf: 16384 space
ifconf: 2048 space
ifconf: 2048 space
ifconf: 4095 space

This is from a printf of ifc->ifc_len before the loop begins.

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