Date: Tue, 06 Sep 2005 02:29:53 +0900 From: Hajimu UMEMOTO <ume@FreeBSD.org> To: Randy Bush <randy@psg.com> Cc: arch@FreeBSD.org, Robert Watson <rwatson@FreeBSD.org> Subject: Re: [CFR] reflect resolv.conf update to running application Message-ID: <ygeslwjbey6.wl%ume@mahoroba.org> In-Reply-To: <17160.29026.1724.73259@roam.psg.com> References: <ygefyt4yiaz.wl%ume@mahoroba.org> <20050821003536.P14178@fledge.watson.org> <17160.29026.1724.73259@roam.psg.com>
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Hi,
>>>>> On Sun, 21 Aug 2005 12:19:46 +0000
>>>>> Randy Bush <randy@psg.com> said:
> (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.
randy> hmmmmm
randy> dunno about others' use patterns, but in my world, resolv.conf only
randy> changes when my mobile platform moves layer three binding (i.e. not
randy> an an 802.11 access point move). so the frequency is low, and it
randy> is usually not issuing dns queries as i move. but when i get to
randy> the new binding, i am annoyed if i have to whack the resolver.
Yes, I believe resolv.conf is not updated so often. Once, it is
updated, we cannot do DNS lookup correctly without restarting an
application. My patch solves this situation.
Even when re-reading resolv.conf fails unfortunately, you will be
able to recover easily by touching resolv.conf instead of restarting
your application.
Sincerely,
--
Hajimu UMEMOTO @ Internet Mutual Aid Society Yokohama, Japan
ume@mahoroba.org ume@{,jp.}FreeBSD.org
http://www.imasy.org/~ume/
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