[libvirt] IPv6 migration

[Daniel P. Berrange]

On Thu, Mar 21, 2013 at 01:16:35PM +0100, Ján Tomko wrote:
> On 03/21/2013 11:52 AM, Daniel P. Berrange wrote:
> > On Tue, Mar 19, 2013 at 03:21:31PM +0100, Jiri Denemark wrote:
> >> On Mon, Mar 11, 2013 at 19:40:52 +0100, Ján Tomko wrote:
> ...
> >>
> >> Yeah, I think using an explicit flag would be the best approach. As we
> >> learnt several times, implementing automagic behavior is too fragile and
> >> leads to ugly code and confusion. IIUC, we would tell QEMU to listen on
> >> :: iff either migrateuri uses IPv6 address explicitly or
> >> VIR_DOMAIN_MIGRATE_IPV6 flag is set. In all other cases, 0.0.0.0 address
> >> will be passed to QEMU. In other words, unless a user takes an explicit
> >> action, migration will use IPv4 regardless on libvirt version.
> > 
> > That would mean that migration is broken by default in an IPv6 only
> > environment, so I don't think that is an satisfactory approach. We
> > should be checking whether.
> 
> Checking whether...?

IPv6 is present.

> 
> > 
> > Listening on '[::]' means that QEMU will accept connections on *both*
> > IPv4 and IPv6, if configured with dual-stack. So if IPv6 is present
> > on the target host, it is entirely reasonable to default to '[::]' if
> > given a hostname.
> 
> I thought this might break IPv4 migration on FreeBSD, but QEMU turns
> IPV6_V6ONLY off since the support of IPv6 migration in 1.1.
> 
> So this would only break migration with QEMU older than 1.1 and could be
> worked around by specifying the IPv4 address in the migration URI?

We know the QEMU version from the capabilities, so it should not need
to break QEMU < 1.1


Daniel
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