Re: [RFC net-next 08/15] ipxlat: add translation engine and dispatch core

[Beniamino Galvani <bgalvani@redhat.com>]

On Thu, Jun 04, 2026 at 08:23:51PM +0200, Toke Høiland-Jørgensen wrote:
> Ralf Lici <ralf@mandelbit.com> writes:
> 
> > This commit introduces the core start_xmit processing flow: validate,
> > select action, translate, and forward. It centralizes action resolution
> > in the dispatch layer and keeps per-direction translation logic separate
> > from device glue. The result is a single data-path entry point with
> > explicit control over drop/forward/emit behavior.
> >
> > Signed-off-by: Ralf Lici <ralf@mandelbit.com>
> 
> This is very cool! Going quickly through the series, this seems like
> thorough work that will be cool to have available in the kernel, so
> thanks for doing this! I'll be quite happy to retire my barebones
> BPF-based implementation once this lands :)


Hi,

speaking as a maintainer of NetworkManager, I would also like to see
this feature in the kernel!

In NetworkManager currently we are using a BPF program [1] to
implement the CLAT, but that approach comes with limitations: for
example, we can't fragment v4->v6 packets if needed, and it's not
possible to recompute checksums in certain cases (e.g. for v4->v6 UDP
packets with zero checksum, and for fragmented ICMP). systemd-networkd
is also adding CLAT support via BPF [2], with a fallback to userspace
for the cases that can't be handled in kernel.

It would be very useful to have a native in-kernel CLAT that solves
the limitations of BPF-based solutions, and can be used by different
tools without having to re-implement everything from scratch.

Beniamino

[1] https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/1.57.2-dev/src/core/bpf/clat.bpf.c
[2] https://github.com/systemd/systemd/pull/41412