Date: Tue, 29 Aug 2006 14:02:22 +0200 (CEST) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-net@FreeBSD.ORG, julian@elischer.org Subject: Re: possible patch for implementing split DNS Message-ID: <200608291202.k7TC2MnX012960@lurza.secnetix.de> In-Reply-To: <44EF6E18.6090905@elischer.org>
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Julian Elischer wrote:
> I need some processes to look elsewhere for DNS information from where
> the rest
> of the system looks.. This patch seems to me a simple solution.
> We over-ride where the resolver looks for resolv.conf using an
> environment variable.
> This would allow me to reset this to an application specific config file
> that
> specifies a different server.
I think that could be useful indeed. In fact it could have
been very helpful to me recently when I had to debug a very
strange resolver problem (it turned out that the DSL modem
dropped SOA and ANY requests).
In theory, there would be a different (and maybe better)
solution to the problem. On the "FreeBSD Ideas" web page
there is an entry to port variant symlinks from DragonFly
(but as far as I know, nobody is actually working on it).
Using variant symlinks, the problem could easily be solved:
$ ls -l /etc/resolv*
-r--r--r-- 1 root wheel ... /etc/resolv.conf -> resolv-${RES}.conf
-r--r--r-- 1 root wheel ... /etc/resolv-default.conf
-r--r--r-- 1 root wheel ... /etc/resolv-special.conf
$ varsym RES
RES=default
$ cat /etc/resolv.conf
nameserver 11.22.33.44
$ varsym RES=special
$ cat /etc/resolv.conf
nameserver 55.66.77.88
It also has the advantage that the admin still has some
control over it, because the symlink can only point to
existing files under /etc in this case. By the way, the
varsym variables can be set globally, per-user and per-
process.
However, I'm aware that variant symlinks are probably not
going to be available in FreeBSD anytime soon. Therefore
I think your patch to libc/net/res_init.c would be useful.
Best regards
Oliver
--
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.
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-- Bruce Eckel, ANSI C++ Comitee member, author
of "Thinking in C++" and "Thinking in Java"
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