Installing and enabling rdnssd by default

St├ęphane Graber stgraber at
Fri Sep 9 00:51:28 UTC 2011

On 09/08/2011 10:30 AM, Leon Weber wrote:
> Hi all,
> in the process of implementing IPv6 in my home network, I noticed that
> one of the major points preventing the IPv6 implementation from
> reaching IPv4-quality is the lack of support for DNS autoconfiguration.
> I also help building networks for hacker events from time to time,
> where the idea of offering IPv6-only connectivity regularly comes up
> and usually has to be discarded for mostly this reason. It is also one
> of the main conclusions that Arkko&  Keranen of Ericsson draw from their
> extensive testing in an IPv6-only network (see [0]).
> While there are two methods available to implement DNS autoconfiguration,
> namely DHCPv6 and including the RDNSS information in Router Advertisements
> as specified in RFC 6106[1], I prefer the latter solution, as it is simpler
> and more elegant while providing all the functionality most environments
> need. (However, I am convinced that this particular question is a matter
> of personal taste and will be subject of neverending debates in the
> future, so eventually, both methods will need to be implemented.)
> The RFC 6106 method is implemented by radvd on the server side and
> a userland daemon named rdnssd on the client side. This daemon reads the
> recursive DNS server information from Router Advertisements and updates
> /etc/resolv.conf accordingly. rdnssd[2] is included in Ubuntu, however
> it is not installed and enabled in the default installation. I suggest
> to change this.
> Possible downsides include:
> * One more process that is running all the time on everyone's
>    installation.
> * Possible security issues (since more code running generally means more
>    places for bugs to hide).
> Since rdnssd's resource usage are negligable and it really is not a lot
> of code, I believe those are no serious problems. Instead, I think the
> fact that Neighbour Discovery is enabled by default actually demands to
> also enable rdnssd in order to provide a complete autoconfiguration
> process that does not rely on IPv4 connectivity.
> In conclusion, I think this is a relatively minor change that would
> complete the Stateless Address Autoconfiguration process and remove a
> majorblocker for IPv6-only networks. Such networks might be rare today,
> but there is no doubt they will be common in the future.
> Regards,
>      -- Leon.
> [0]
> [1]
> [2]


Oneiric will probably be the first Ubuntu release with proper IPv6 
support. Our current implementation doesn't include rdnssd by default 
and won't as it's a bit late in the cycle.

I think it'd be interesting to have it for server installs where you 
don't have Network Manager.

Desktop installs have Network Manager which supports all the IPv6 setups 
I could think of including setting DNS and search path through router 
For this, rather than relying on rndssd Network Manager has its own code 
as part of it's router advertisement handling code, if I remember well, 
this code is pretty much copy/paste from rdnssd and adapted to integrate 
with Network Manager.

I also seem to remember debian-installer either supporting rdnssd by 
default or having an equivalent implemented in netcfg.

I'd think the next steps to get rdnssd by default for Ubuntu Server 
would be to make sure ifupdown can use it properly, check that it won't 
conflict with dhclient v4 and dhclient v6 and then have it included on 
the server builds (all the others should come with Network Manager).

St├ęphane Graber
Ubuntu developer

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