From owner-freebsd-arch@FreeBSD.ORG  Sun Aug 21 17:17:10 2005
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
X-Original-To: arch@freebsd.org
Delivered-To: freebsd-arch@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 4CCA116A41F;
	Sun, 21 Aug 2005 17:17:10 +0000 (GMT)
	(envelope-from phk@phk.freebsd.dk)
Received: from haven.freebsd.dk (haven.freebsd.dk [130.225.244.222])
	by mx1.FreeBSD.org (Postfix) with ESMTP id E521043D45;
	Sun, 21 Aug 2005 17:17:09 +0000 (GMT)
	(envelope-from phk@phk.freebsd.dk)
Received: from phk.freebsd.dk (unknown [192.168.48.2])
	by haven.freebsd.dk (Postfix) with ESMTP id 93F1DBC66;
	Sun, 21 Aug 2005 17:17:06 +0000 (UTC)
To: Alexander Leidinger <Alexander@Leidinger.net>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Sun, 21 Aug 2005 11:54:54 +0200."
	<20050821115454.55441a64@Magellan.Leidinger.net> 
Date: Sun, 21 Aug 2005 19:17:06 +0200
Message-ID: <58449.1124644626@phk.freebsd.dk>
Sender: phk@phk.freebsd.dk
Cc: arch@freebsd.org, Robert Watson <rwatson@freebsd.org>
Subject: Re: [CFR] reflect resolv.conf update to running application 
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 21 Aug 2005 17:17:10 -0000

In message <20050821115454.55441a64@Magellan.Leidinger.net>, Alexander Leidinger writes:
>On Sun, 21 Aug 2005 00:37:56 +0100 (BST)
>Robert Watson <rwatson@freebsd.org> wrote:
>
>> (2) By reading the configuration file more frequently and more quickly
>>      after a change, we increase the chances of a race condition in which
>>      the resolve reads a partially written resolv.conf file during an
>>      update.  Does this happen in practice?  I've always been very leery of
>>      re-reading configuration files automatically based on a time-stamp, as
>>      updates to files are not atomic at all.
>
>Can kqueue be used instead of polling?

Programs writing resolv.conf should just this the right way:

	1. Write new contents to temorary file.
	2. Rename temporary file to resolv.conf.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.