[libvirt PATCH v2 2/3] conf: add an attribute to turn on NAT for IPv6 virtual networks

Daniel P. Berrangé berrange at redhat.com
Wed Jun 10 09:27:03 UTC 2020


On Wed, Jun 10, 2020 at 12:14:51AM -0400, Laine Stump wrote:
> On 6/9/20 12:17 PM, Daniel P. Berrangé wrote:
> > Historically IPv6 did not support NAT, so when IPv6 was added to
> > libvirt's virtual networks, when requesting <forward mode="nat"/>
> > libvirt will NOT apply NAT to IPv6 traffic, only IPv4 traffic.
> > 
> > This is an annoying historical design decision as it means we
> > cannot enable IPv6 automatically. We thus need to introduce a
> > new attribute
> > 
> >     <forward mode="nat">
> >       <nat ipv6="yes"/>
> >     </forward>
> > 
> > The new attribute is a tri-state, so it leaves open the possibility of
> > us intentionally changing the default behaviour in future to honour
> > NAT for IPv6.
> 
> 
> Any network defined with an older libvirt, and even newly defined networks
> that don't have ipv6 set explicitly in the input XML, won't have an explicit
> value saved in the config. So if we change the default, those existing
> networks will have different behavior. I don't see how we could change the
> default without those existing networks getting automatically changed to
> ipv6='yes'.

Yeah, with my comment about auto-addressing, we wouldn't need to change
this default anyway.


Regards,
Daniel
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