Re: Thoughts on interface modes / multiple guest addresses

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 18 Dec 2025 14:47:06 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> For multi-address support there are at least four things to consider:

For the bits related https://bugs.passt.top/show_bug.cgi?id=141, I
thought Jon was working on a proposal.

> (a) What goes in our internal list of addresses to give the guest?
> 
>     a.1. Everything listed with -a?

If anything is passed, yes, those, and just those (separately for IP
version), because the user is clearly overriding addresses (as
currently implemented and documented).

>     a.2. Everything on the host?

No, because you can't assume you can configure all those addresses on
a single interface. Adding multiple interfaces is something we could
consider later.

>     a.3. Everything on the host template interface?

Everything on the host template interface if available (as currently
documented).

>     a.4. A link local address we pick?

A link-local address if nothing else is available (as currently
documented). This will need to be permanent for the requirement we
already discussed months ago with Podman developers.

>     a.5. Some combination of the above.
> 
> Unlike routes (that I can see), I'm pretty sure there are use cases
> where we want both host-copied addresses (for transparency) and
> explicit addresses (for a stable way of communicating with the host).

Podman needs some anyway if we start with link-local addresses, to
keep DNS resolution working.

The rest just looks beyond the scope of
https://bugs.passt.top/show_bug.cgi?id=141 to me. I won't stand in the
way of this discussion, of course, but I won't participate either,
because I really don't see it as a priority at the moment.

-- 
Stefano