RDNSS daemon and dhclient concurrent to /etc/resolv.conf

[Pierre Ynard]

Hello,

The recently published RFC5006 defines a new mechanism in IPv6
stateless autoconfiguration, to acquire DNS configuration information,
namely the Recursive DNS Servers (RDNSS) option. Kernel-side support
will be included in Linux 2.6.24, and we are currently working on a
complementary user-space daemon.

The role of the daemon is to receive nameserver information, and
subsequently update /etc/resolv.conf. Obviously, it would modify
/etc/resolv.conf in a way directly concurrent with other daemons,
especially IPv4 DHCP clients.

Our approach is to generate our own resolver file, typically
/var/run/rdnssd/resolv.conf, and call an external hook to merge RDNSS
nameservers with existing configuration from other sources. We have been
thinking about best ways to coexist system-wide with other daemons; one
of them could be that such daemons, instead of directly overwriting
/etc/resolv.conf, allow the use of an external, "central" script
responsible for this.

In the case of dhclient, it would be technically possible to add a
hook script in the configuration, to overwrite dhclient-script's
make_resolv_conf() function and preempt whatever dhclient-script is
supposed to do. Actually, this is what Debian's resolvconf package does.
But I do not think that this is a very elegant way.

What are your thoughts about this? How about adding an explicit
configuration option to replace the default, direct behavior of
make_resolv_conf() by an external script? We believe that this would
facilitate the upcoming necessary coexistence between IPv4 and IPv6
stacks.

For reference:
http://rdnssd.linkfanel.net/
http://anonsvn.remlab.net/svn/ndisc6/trunk/rdnssd/

Regards,

-- 
Pierre Ynard
For hire in Quebec City, Canada, during Fall 2007
"Une âme dans un corps, c'est comme un dessin sur une feuille de papier."