Hi {Frode, Dumitru},
Thanks a lot!
I sent v5-v6 as well which addresses some of Alexandra's feedback from
https://mail.openvswitch.org/pipermail/ovs-dev/2026-June/433584.html.
If you have any early feedback too - it would help a lot.
On Tuesday, June 23rd, 2026 at 8:22 PM, Frode Nordahl <[email protected]>
wrote:
> Hello, Dmitrii,
>
> On 6/18/26 12:23, Dumitru Ceara wrote:
> > On 6/12/26 2:20 PM, Dmitrii Shcherbakov wrote:
> >> OVN 26.03 introduced distributed load balancers [1]: when a
> >> Load_Balancer has options:distributed=true and ip_port_mappings is
> >> configured, each chassis delivers traffic only to the local backend.
> >> Deployments that use BGP to advertise tenant routes into the fabric
> >> [2] could previously advertise LB VIPs only as a single prefix per
> >> VIP, with no per-chassis health awareness. The fabric could ECMP
> >> across chassis but could not prefer those hosting healthy backends
> >> or withdraw routes from chassis with unhealthy ones.
> >>
> >> This series splits the Advertised_Route emission for LB VIPs from
> >> one-per-VIP to one-per-(VIP, backend LSP) and adds a controller-side
> >> gate that skips route installation when the Service_Monitor for the
> >> corresponding backend is offline. This allows the local dynamic
> >> routing speaker to advertise the VIP prefix only from chassis that
> >> host a healthy backend, so fabric ECMP converges onto
> >> healthy chassis.
> >>
> >> The series also installs local forwarding routes on the advertising
> >> logical router for peer-LR LB VIPs and NAT external IPs enumerated for
> >> redistribution, so that the advertising LR can forward traffic to
> >> those addresses through the peer.
> >>
> >
> > Hi Dmitrii,
> >
> > Thanks a lot for the series, judging by the cover it looks like it
> > includes a lot of good stuff!
> >
> > I do plan to review it closely in the near future but I was wondering if
> > others (e.g., Martin, Frode, Felix) maybe have some time to review it too.
>
> I second Dumitru's statement of there appearing to be lots of goodness here,
> I endeavor to give the series a review within a reasonable time frame.
>
> --
> Frode Nordahl
>
> > Regards,
> > Dumitru
> >
> >> Patch 1 fixes an existing bug where attaching a distributed LB to a
> >> router with a chassis-redirect port can leave stale lr_in_admission
> >> guards, dropping ingress LB traffic on non-gateway chassis.
> >>
> >> Patch 2 fixes a pre-existing bug in parsed_route_lookup() where the
> >> IPv6 nexthop comparison skipped matching routes instead of
> >> non-matching ones, causing false lookups for IPv6 routes with
> >> non-zero nexthops. The forwarding-route tests in patch 3 exercise
> >> this code path: the nexthop mutation test checks that a route whose
> >> nexthop changes is not treated as unchanged.
> >>
> >> Patch 3 installs local forwarding routes for peer-LR LB VIPs and NAT
> >> external IPs that an advertising LRP has enumerated for redistribution.
> >>
> >> Patch 4 splits Advertised_Route emission from one-per-VIP to
> >> one-per-(VIP, backend LSP), populating service selector columns
> >> that let ovn-controller match the Service_Monitor row for each
> >> backend.
> >>
> >> Patch 5 adds the controller-side gate: kernel-route installation is
> >> skipped when the Service_Monitor for a backend is offline.
> >>
> >> Changes since v3 (patch 1):
> >> - Fix -Wshadow violation in build_lb_datapaths: rename inner
> >> loop variable od to grp_od to avoid shadowing the outer-scope
> >> od declared earlier in the same function.
> >>
> >> Changes since v2 (all in patch 1):
> >> - Track has_distributed_lb on LB-group expansion and deletion paths
> >> so that the northd handler's distributed-LB guard covers all
> >> incremental code paths that involve distributed LBs.
> >> - Instead of unconditionally forcing a full northd recompute when
> >> any distributed LB change is tracked, collect a snapshot of each
> >> affected LR's is_distributed state before incremental processing,
> >> then after processing recompute the flag per LR using the per-LR
> >> LB list (lr_lb_map). If any LR's flag changed, fall back to full
> >> recompute. Otherwise the incremental path is safe to use.
> >> - Expose find_od_lb_data() so the post-check can walk only the LBs
> >> attached to each affected LR, not every LB in the system.
> >> - Add regression tests covering direct LB attach/detach, LB-group
> >> attach/detach, options:distributed toggle, LB-group membership
> >> changes, multiple distributed LBs on the same LR, the incremental
> >> path when a second distributed LB is attached (no is_distributed
> >> transition) and full LB deletion while still attached to an LR.
> >>
> >> Changes since v1:
> >> - Patch 3: the nexthop mutation test provides regression coverage
> >> for the parsed_route_lookup() fix in patch 2 (verifies that a route
> >> whose nexthop changes is not treated as unchanged).
> >> - Patch 3: compare tracked_port in parsed_route_lookup() so that
> >> forwarding routes with different tracked_port values are not
> >> treated as identical.
> >> - Patch 3: fix pre-existing typos in en-advertised-route-sync.c
> >> comments.
> >> - Patch 3: add regression test for nexthop mutation (change peer LRP
> >> address and verify forwarding flow updates).
> >> - Patch 3: add negative test for LB-level dynamic-routing-advertise=
> >> false (verify both Advertised_Route and forwarding flow are
> >> not installed).
> >>
> >> Changes since v0:
> >> - New patch 2: fix nexthop comparison in parsed_route_lookup().
> >> - Patch 3 (was 2): swap in pre-existing parsed_route objects on
> >> match so that pointers held by group_ecmp_route remain valid.
> >> Detach from old_parsed_routes first to avoid corrupting the
> >> source hmap.
> >> - Share-advertise system tests moved to the deferred
> >> share-advertise-routes follow-up, since they depend on
> >> the dynamic-routing-share-advertise-routes option.
> >> - Inline diagrams switched to ASCII-only characters.
> >> - Line lengths rewrapped per checkpatch feedback.
> >>
> >> A separate LRP option for VRF route sharing (share-advertise-routes)
> >> is deferred to a follow-up series. Deployments that need cross-VRF
> >> route sharing before the option lands can achieve the same effect
> >> by configuring the dynamic routing speaker to import routes between
> >> the OVN-managed VRFs on each chassis.
> >>
> >> Prior work: RFC for LB BGP advertisement [3] in which a review [4]
> >> suggested a separate incremental processing node for dynamic routes,
> >> which this series adopts. For tracked_port, patch 3 uses the peer LRP
> >> for forwarding routes and patch 4 uses the backend LSP (from
> >> ip_port_mappings) for per-backend locality rows. Patch 5 adds
> >> Service_Monitor gating on the per-backend rows.
> >>
> >> The SB schema (version 21.9.0) gains tracked_service_{ip,port,protocol}
> >> columns on Advertised_Route for the service selector. All new columns
> >> are optional with safe defaults, so rolling upgrades are supported.
> >> Builds on the distributed LB feature (OVN 26.03+).
> >>
> >> Tests cover LB and NAT route redistribution (IPv4/IPv6), forwarding
> >> route installation, per-backend selector emission, SCTP exclusion,
> >> ip_port_mappings fallback (per-backend rows when mappings exist,
> >> one peer-LRP row when none do), and Service_Monitor gating.
> >>
> >> [1] commit 7b0eb4d9ed ("northd: Add distributed load balancer support.")
> >> [2]
> >> https://opendev.org/openstack/neutron-specs/src/branch/master/specs/2025.2/ovn-bgp-integration.rst
> >> [3]
> >> https://mail.openvswitch.org/pipermail/ovs-dev/2025-February/420552.html
> >> [4]
> >> https://mail.openvswitch.org/pipermail/ovs-dev/2025-February/420789.html
> >>
> >> Dmitrii Shcherbakov (5):
> >> northd: Recompute only when LR is_distributed flips on LB.
> >> northd: Fix nexthop comparison in parsed_route_lookup().
> >> northd: Install forwarding routes for redistribute={lb,nat}.
> >> northd: Emit per-backend Advertised_Route for LB redistribution.
> >> controller: Skip LB route install when Service_Monitor is offline.
> >>
> >> controller/ovn-controller.c | 25 +-
> >> controller/route.c | 101 +++
> >> controller/route.h | 1 +
> >> northd/en-advertised-route-sync.c | 540 ++++++++++++++--
> >> northd/en-advertised-route-sync.h | 25 +-
> >> northd/en-group-ecmp-route.c | 76 +-
> >> northd/en-group-ecmp-route.h | 4 +
> >> northd/en-lb-data.c | 22 +-
> >> northd/en-lb-data.h | 3 +
> >> northd/en-lr-stateful.c | 2 +
> >> northd/en-northd.c | 1 +
> >> northd/inc-proc-northd.c | 5 +
> >> northd/lb.c | 2 +
> >> northd/lb.h | 15 +
> >> northd/northd.c | 217 +++++-
> >> northd/northd.h | 3 +
> >> ovn-sb.ovsschema | 18 +-
> >> ovn-sb.xml | 56 +-
> >> tests/ovn-inc-proc-graph-dump.at | 9 +-
> >> tests/ovn-northd.at | 1413 ++++++++++++++++++++++++++++++-
> >> tests/system-ovn.at | 521 ++++++++++++
> >> 21 files changed, 2946 insertions(+), 113 deletions(-)
> >>
> >
>
>
>
>
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