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From: Peter Foley <pefoley@google.com>
Date: Wed, 25 Feb 2026 17:35:06 -0500
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Message-ID: <CAAAKUPPEG3EpR5Kow8kb3Gmvjx=TcL+Jwh7vP+OXa5sMpRCdNA@mail.gmail.com>
Subject: Support for equivalent to slirp guestfwd
To: passt-dev@passt.top
CC: Felix Wu <flwu@google.com>
List-Id: <passt-dev.passt.top>

Hi,

I'm investigating migrating Google-internal uses of qemu's slirp-based
networking to passt.
One major gap I've discovered is the apparent lack of support in passt for
something like the "guestfwd" flag the slirp network backend handles:
https://www.qemu.org/docs/master/system/invocation.html
This allows us to open outbound connections from the VM to an external
service listening on a known port.

As far as I can tell, passt's tcp-ports and udp-ports flags appear to map
to slirp's hostfwd flags, only allowing traffic to flow into the VM.

Am I missing something? If this functionality indeed isn't supported, are
there plans to add it?

Thanks,

Peter Foley