Re: Support for equivalent to slirp guestfwd

[Peter Foley <pefoley@google.com>]

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On Thu, Feb 26, 2026 at 7:47 AM Stefano Brivio <sbrivio@redhat.com> wrote:

>
> ...there's ongoing effort to make this more flexible, by adding support
> for generic NAT rules (https://bugs.passt.top/show_bug.cgi?id=140) so
> that you can specifically map different ports and addresses to
> specific ports and addresses. And do so dynamically, at runtime, too.
>
> We now have a rather generic "forwarding rules" table implementation,
> even if not entirely complete:
>
>
> https://archives.passt.top/passt-dev/20260116005926.616085-1-david@gibson.dropbear.id.au/
>
> and a very rudimentary draft of pesto(1), the client that would enable
> configuring all that at runtime (I'm working on it these days):
>
>
> https://archives.passt.top/passt-dev/20260204234209.455262-1-sbrivio@redhat.com/
>
> ...there's quite a bit left to do, and patches are warmly welcome.
>

Alright, that's about what I expected.

We currently heavily rely on stuff
like guestfwd=udp:[::]:1000-udp:[::1]:14418,
where we want to redirect all outbound traffic from the guest to port 1000
to a different dynamically allocated port where a server binary is
listening on the host.

We don't need runtime configuration, just the ability to specify everything
statically when starting qemu.

I can't promise anything, but I'll see if this is something other people on
my team would have cycles to help out with.

Thanks,

Peter Foley

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