[libvirt] libvirt plans: dns support for IPv6?

[Daniel P. Berrange]

On Thu, Sep 13, 2012 at 02:00:48PM -0400, 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.

FYI, already libvirt aims to work with old dnsmasq, in general there is
no problem with using features from new dnsmasq. If the host has an old
dnsmasq, they simply won't be able to take advantage of new features
libvirt might support. The key is simply that if the host has the old
dnsmasq, we should be careful not to invoke it in the wrong way for
existing features.

Daniel
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