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Re: [libvirt] libvirt plans: dns support for IPv6?



On 09/13/2012 02:00 PM, Gene Czarcinski wrote:
> I would like to know what the plans are for supporting dns for virtual
> guests with only IPv6.
>
> My objective is to be able to reference a virtual guest for the host
> ... doing ssh, scp, etc.  such functions work just fine if you specify
> the ip-address but, after a while, those ip-addresses are difficult to
> remember ... afterall, that is why dns exists.
>
> For IPv4, with a some patches to libvert implementing "--local=/virt/
> --domain-needed" if "--domain virt" is specified, I am now able to ssh
> to guests by name.
>
> The additions needed are to run the NetworkManager supporting
> "--conf-dir=/etc/NetworkManager/dnsmasq.d/" (or patch it like I did),
> and add a file specifying the dnsmasq on the virtual NIC.  For
> example, server=/virt/,192.168.122.1 will forward queries.
>
> Alternatively, you can run yet another dnsmasq on the host which just
> passes queries to the dnsmasq and modify your upstream dns server to
> forward any queries for the virtual domains to the dnsmasq on the host.
>
> IPv6 is another situation entirely.  And it may be even more important
> to have dns support because if IPv4 address are difficult to remember,
> IPv6 are practically impossible.
>
> So, are there any plans for providing dns on the IPv6 virtual networks?
>
> I can see a couple of solutions and each has pluses and minuses.
>
> 1. Do it the same way the it is done for IPv4.  The current version of
> dnsmasq (2.63) supports dhcp for IPv6 and, IIRC, has since 2.61. I
> realize that you need to continue support of libvirt on RHEL 6 and
> possibly others that are running an old version of dnsmasq, but isn't
> it time to move along?  While you can manually configure IPv6
> interfaces so that you can add the definitions to a /etc/host file,
> this is not a good approach from my perspective.  The use of dnsmasq
> also allows specification of different domains for each virtual IPv6
> network.
>
> 2. There is another approach and it would be useful for both dnsmasq
> and this approach be available.  That is, continue to use radvd and
> have the virtual guests autoconf the ip addresses.  Then use mDNS
> (avahi and nss-mdns) to support access by name.  This does not require
> doing anything about dnsmasq.  In fact, it is possible thatyou do not
> need it at all.  In addition, the plans for Fedora 18 are to make mDNS
> the default for Desktop installs [I am not sure what that means].  A
> big problem is that there is only a single domain which is ".local" by
> default.  An even bigger problem is that ssh (openssh) has an error if
> a mDNS name is specified.
>
> I noticed that Daniel Berrange has put in a bugzilla request that
> dnsmasq be updated.
>
> If someone is already coding up patches to add dhcp for IPv6 or will
> "real soon now", I will be happy to test it.  Otherwise, I could take
> a shot at coming up with the patches.

AFAIK nobody else is working on that right now, so I'd say go for it :-)


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