I think backporting 1872d61e34aa is fine by me as well.

On Tue, Jun 30, 2026 at 7:42 AM Dumitru Ceara <[email protected]> wrote:
>
> Hi Ales,
>
> On 6/26/26 3:02 PM, Ales Musil wrote:
> > On Fri, Jun 26, 2026 at 2:09 PM Dumitru Ceara via dev <
> > [email protected]> wrote:
> >
> >> The flows in ls_in_l2_lkup, generated by
> >> build_lswitch_rport_arp_req_flow(), matched ARP requests and
> >> ND_NS for router-owned IPs without restricting eth.dst to
> >> broadcast/multicast.  This caused unicast ARP requests
> >> (eth.dst == router_MAC) to be intercepted and flooded into the
> >> L2 domain.
> >>
> >> On switches with 200+ ports this flooding can exceed the OVS
> >> 4096 resubmit limit, dropping the packet.
> >>
> >> Fix arp_nd_ns_match() to add "eth.dst == ff:ff:ff:ff:ff:ff"
> >> for IPv4 ARP and "eth.mcast" for IPv6 ND_NS.  This follows
> >> the precedent set by commit c05c565548 which added the same
> >> eth.dst restriction to the priority 75 self-originated ARP
> >> flood flow in the same pipeline stage.
> >>
> >> After this fix, unicast ARP and ND requests for router-owned
> >> IPs fall through to the L2_LKUP stage flows for direct L2
> >> delivery.
> >>
> >> Reported-at: https://issues.redhat.com/browse/FDP-3885
> >> Assisted-by: Claude Opus 4.6, Claude Code
> >> Signed-off-by: Dumitru Ceara <[email protected]>
> >> ---
> >> NOTE: this depends on 1872d61e34aa ("northd: Use MC_UNKNOWN for
> >> broadcast ARP requests.") which is only present on the main branch.
> >> For backporting this fix to 26.03 we'd have to backport its dependency
> >> too.
> >> ---
> >>  northd/northd.c     |   7 +-
> >>  tests/ovn-northd.at | 265 ++++++++++++++++++++++++--------------------
> >>  tests/ovn.at        | 206 ++++++++++++++++++++++++++++++++++
> >>  3 files changed, 358 insertions(+), 120 deletions(-)
> >>
>
> ...
>
> >>
> >>
> > Looks good to me, thanks.
> >
> > Acked-by: Ales Musil <[email protected]>
> >
>
> Thanks for the review!  Applied to main.
>
> As this is a bug fix, I'd like to backport it to 26.03 but in order for
> it to function properly we'd also need to backport its dependency,
> 1872d61e34aa ("northd: Use MC_UNKNOWN for broadcast ARP requests.").
>
> Are there any objections for me doing that (maintainers in CC)?
>
> Regards,
> Dumitru
>

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