On Fri, Jul 24, 2026 at 12:41 PM Lucas Vargas Dias <[email protected]>
wrote:

> Until now, creating or deleting a logical switch forced a full recompute
> of the en_lflow engine node.  Handle it incrementally instead, mirroring
> the existing logical router datapath handling.
>
> Add lflow_handle_northd_ls_changes(), invoked from lflow_northd_handler()
> for the tracked switch changes: deleted switches have their datapath
> flows resynced away via od->datapath_lflows, while created/updated
> switches are (re)built with build_lswitch_and_lrouter_iterate_by_ls() and
> synced.  To make this possible the datapath-wide switch flows built there
> are now anchored to od->datapath_lflows instead of being untracked (NULL
> lflow_ref), so they can be generated and torn down incrementally.
>
> Two of those flows have a different owner and are handled accordingly:
>
>   - The network function flows are moved into build_ls_stateful_flows()
>     so they are owned by the per-switch ls_stateful lflow_ref (which is
>     already processed incrementally for switch add/delete).  The now
>     redundant build_network_function() calls in the ls_stateful and port
>     change handlers are removed.
>
>   - The multicast flood flow is owned by the multicast_igmp node's
>     lflow_ref (built in build_igmp_lflows()).
> multicast_igmp_northd_handler()
>     now recomputes that (cheap) node when switches are created/deleted so
>     the flood flows are added/removed for them.
>
> Update the "Logical switch incremental processing" test: adding and
> deleting a logical switch no longer recomputes the lflow node.
>
> Assisted-bt: Claude Opus 4.8, Claude Code
>

nit: Assisted-by


> Signed-off-by: Lucas Vargas Dias <[email protected]>
> ---
>  northd/en-lflow.c     |  23 ++++-
>  northd/en-multicast.c |   9 ++
>  northd/northd.c       | 191 ++++++++++++++++++++++++++++++++++++------
>  northd/northd.h       |   5 ++
>  tests/ovn-northd.at   |   4 +-
>  5 files changed, 201 insertions(+), 31 deletions(-)
>
> diff --git a/northd/en-lflow.c b/northd/en-lflow.c
> index 99df5f08f..9a517ae48 100644
> --- a/northd/en-lflow.c
> +++ b/northd/en-lflow.c
> @@ -145,16 +145,31 @@ lflow_northd_handler(struct engine_node *node,
>          return EN_UNHANDLED;
>      }
>
> -    if (northd_has_lswitches_in_tracked_data(&northd_data->trk_data)) {
> -        return EN_UNHANDLED;
> -    }
> -
>      const struct engine_context *eng_ctx = engine_get_context();
>      struct lflow_data *lflow_data = data;
>
>      struct lflow_input lflow_input;
>      lflow_get_input_data(node, &lflow_input);
>
> +    /* The switch datapath handler also (re)builds the per-switch
> ls_stateful
> +     * flows of created/deleted switches, coordinated with their
> +     * datapath_lflows so that shared datapath groups are updated in place
> +     * rather than churned.
> +     * It therefore needs the ls_stateful tracked data. */
> +    struct ed_type_ls_stateful *ls_stateful_data =
> +        engine_get_input_data("ls_stateful", node);
> +    struct ls_stateful_tracked_data *ls_sful_trk =
> +        ls_stateful_has_tracked_data(&ls_stateful_data->trk_data)
> +        ? &ls_stateful_data->trk_data : NULL;
> +
> +    if (!lflow_handle_northd_ls_changes(eng_ctx->ovnsb_idl_txn,
> +
> &northd_data->trk_data.trk_switches,
> +                                        ls_sful_trk,
> +                                        &lflow_input,
> +                                        lflow_data->lflow_table)) {
> +        return EN_UNHANDLED;
> +    }
> +
>      if (!lflow_handle_northd_lr_changes(eng_ctx->ovnsb_idl_txn,
>
>  &northd_data->trk_data.trk_routers,
>                                          &lflow_input,
> diff --git a/northd/en-multicast.c b/northd/en-multicast.c
> index bfe3c4d92..c8167b479 100644
> --- a/northd/en-multicast.c
> +++ b/northd/en-multicast.c
> @@ -153,6 +153,15 @@ multicast_igmp_northd_handler(struct engine_node
> *node, void *data OVS_UNUSED)
>          return EN_UNHANDLED;
>      }
>
> +    /* A created/deleted logical switch owns per-datapath multicast flood
> +     * flows (build_mcast_flood_lswitch() via build_igmp_lflows()).  The
> lflow
> +     * node now processes switch datapaths incrementally, so it no longer
> +     * forces a full recompute; recompute this (cheap) node so its
> lflow_ref
> +     * picks up (or drops) the switch's flood flows. */
> +    if (northd_has_lswitches_in_tracked_data(&northd_data->trk_data)) {
> +        return EN_UNHANDLED;
> +    }
> +
>      struct tracked_ovn_ports *trk_lsps = &northd_data->trk_data.trk_lsps;
>      if (hmapx_count(&trk_lsps->created) ||
>          hmapx_count(&trk_lsps->updated) ||
> diff --git a/northd/northd.c b/northd/northd.c
> index eca5d6f0e..9ecc072f3 100644
> --- a/northd/northd.c
> +++ b/northd/northd.c
> @@ -6962,10 +6962,11 @@ enum mirror_filter {
>
>  static void
>  build_mirror_default_lflow(struct ovn_datapath *od,
> -                           struct lflow_table *lflows)
> +                           struct lflow_table *lflows,
> +                           struct lflow_ref *lflow_ref)
>  {
> -    ovn_lflow_add(lflows, od, S_SWITCH_IN_MIRROR, 0, "1", "next;", NULL);
> -    ovn_lflow_add(lflows, od, S_SWITCH_OUT_MIRROR, 0, "1", "next;", NULL);
> +    ovn_lflow_add(lflows, od, S_SWITCH_IN_MIRROR, 0, "1", "next;",
> lflow_ref);
> +    ovn_lflow_add(lflows, od, S_SWITCH_OUT_MIRROR, 0, "1", "next;",
> lflow_ref);
>  }
>
>  static void
> @@ -19912,6 +19913,11 @@ build_lr_stateful_flows(const struct
> lr_stateful_record *lr_stateful_rec,
>                                        lr_stateful_rec->lflow_ref);
>  }
>
> +static void build_network_function(const struct ovn_datapath *od,
> +                                   struct lflow_table *lflows,
> +                                   const struct ls_port_group_table
> *ls_pgs,
> +                                   struct lflow_ref *lflow_ref);
> +
>

I think moving the build_network_function() and its helpers above
build_ls_stateful_flows() would make it cleaner and avoid the forward
decleration


>  static void
>  build_ls_stateful_flows(const struct ls_stateful_record *ls_stateful_rec,
>                          const struct ovn_datapath *od,
> @@ -19943,6 +19949,12 @@ build_ls_stateful_flows(const struct
> ls_stateful_record *ls_stateful_rec,
>      }
>
>      build_lb_hairpin(ls_stateful_rec, od, lflows,
> ls_stateful_rec->lflow_ref);
> +
> +    /* Network function flows are datapath-wide but owned by the
> per-switch
> +     * ls_stateful lflow_ref, so that they are (re)generated and torn down
> +     * together with the rest of the switch's stateful flows during
> +     * incremental processing. */
> +    build_network_function(od, lflows, ls_pgs,
> ls_stateful_rec->lflow_ref);
>  }
>
>  /* For packets received on tunnel and egressing towards a
> network-function port
> @@ -20764,33 +20776,41 @@ build_lswitch_and_lrouter_iterate_by_ls(struct
> ovn_datapath *od,
>                                          struct lswitch_flow_build_info
> *lsi)
>  {
>      ovs_assert(od->nbs);
> -    build_mirror_default_lflow(od, lsi->lflows);
> +    build_mirror_default_lflow(od, lsi->lflows, od->datapath_lflows);
>      build_lswitch_lflows_pre_acl_and_acl(od, lsi->lflows,
> -                                         lsi->meter_groups, NULL);
> -    build_network_function(od, lsi->lflows, lsi->ls_port_groups, NULL);
> -    build_fwd_group_lflows(od, lsi->lflows, NULL);
> -    build_lswitch_lflows_admission_control(od, lsi->lflows, NULL);
> -    build_lswitch_learn_fdb_od(od, lsi->lflows, NULL);
> +                                         lsi->meter_groups,
> +                                         od->datapath_lflows);
> +    build_fwd_group_lflows(od, lsi->lflows, od->datapath_lflows);
> +    build_lswitch_lflows_admission_control(od, lsi->lflows,
> +                                           od->datapath_lflows);
> +    build_lswitch_learn_fdb_od(od, lsi->lflows, od->datapath_lflows);
>      build_lswitch_arp_nd_evpn_responder(od, lsi->lflows,
> lsi->meter_groups,
> -                                        NULL);
> -    build_lswitch_arp_nd_responder_default(od, lsi->lflows, NULL);
> +                                        od->datapath_lflows);
> +    build_lswitch_arp_nd_responder_default(od, lsi->lflows,
> +                                           od->datapath_lflows);
>      build_lswitch_dns_lookup_and_response(od, lsi->lflows,
> lsi->meter_groups,
> -                                          NULL);
> -    build_lswitch_dhcp_and_dns_defaults(od, lsi->lflows, NULL);
> +                                          od->datapath_lflows);
> +    build_lswitch_dhcp_and_dns_defaults(od, lsi->lflows,
> od->datapath_lflows);
>      build_lswitch_destination_lookup_bmcast(od, lsi->lflows,
> &lsi->actions,
> -                                            lsi->meter_groups, NULL);
> -    build_lswitch_output_port_sec_od(od, lsi->lflows, NULL);
> +                                            lsi->meter_groups,
> +                                            od->datapath_lflows);
> +    build_lswitch_output_port_sec_od(od, lsi->lflows,
> od->datapath_lflows);
>      /* CT extraction flows are built with stateful flows, but default
> rule is
>       * always needed */
>      ovn_lflow_add(lsi->lflows, od, S_SWITCH_IN_CT_EXTRACT, 0, "1",
> "next;",
> -                  NULL);
> -    build_lswitch_lb_affinity_default_flows(od, lsi->lflows, NULL);
> +                  od->datapath_lflows);
> +    build_lswitch_lb_affinity_default_flows(od, lsi->lflows,
> +                                            od->datapath_lflows);
>      if (od->has_evpn_vni) {
> -        build_lswitch_lflows_evpn_l2_unknown(od, lsi->lflows, NULL);
> +        build_lswitch_lflows_evpn_l2_unknown(od, lsi->lflows,
> +                                             od->datapath_lflows);
>      } else {
> -        build_lswitch_lflows_l2_unknown(od, lsi->lflows, NULL);
> +        build_lswitch_lflows_l2_unknown(od, lsi->lflows,
> od->datapath_lflows);
>      }
> -    build_mcast_flood_lswitch(od, lsi->lflows, &lsi->actions, NULL);
> +    /* build_network_function() flows are owned by the per-switch
> ls_stateful
> +     * lflow_ref (built in build_ls_stateful_flows()).  The multicast
> flood
> +     * flow (build_mcast_flood_lswitch()) is owned by the multicast_igmp
> +     * node's lflow_ref (built in build_igmp_lflows()). */
>  }
>
>  /* Helper function to combine all lflow generation which is iterated by
> @@ -21480,6 +21500,132 @@ lflow_reset_northd_refs(struct lflow_input
> *lflow_input)
>      }
>  }
>
> +bool
> +lflow_handle_northd_ls_changes(struct ovsdb_idl_txn *ovnsb_txn,
> +                               struct tracked_dps *tracked_lses,
> +                               struct ls_stateful_tracked_data
> *ls_sful_trk,
> +                               struct lflow_input *lflow_input,
> +                               struct lflow_table *lflows)
> +{
> +    bool handled = true;
> +    struct hmapx_node *hmapx_node;
> +
> +    struct lswitch_flow_build_info lsi = {
> +        .ls_datapaths = lflow_input->ls_datapaths,
> +        .ls_ports = lflow_input->ls_ports,
> +        .ls_port_groups = lflow_input->ls_port_groups,
> +        .meter_groups = lflow_input->meter_groups,
> +        .features = lflow_input->features,
> +        .lflows = lflows,
> +        .match = DS_EMPTY_INITIALIZER,
> +        .actions = DS_EMPTY_INITIALIZER,
> +    };
> +
> +    /* A switch datapath's logical flows are split across two lflow_refs:
> the
> +     * per-switch 'od->datapath_lflows' (built here, by_ls) and the
> per-switch
> +     * ls_stateful lflow_ref (built by build_ls_stateful_flows()).  When a
> +     * switch datapath is added or removed, any datapath group shared by
> these
> +     * flows gains or loses that datapath.  To let ovn_dp_group_create()
> update
> +     * the group's SB row in place (instead of deleting and re-creating
> it,
> +     * which would churn the SB) the old group must be fully released
> before it
> +     * is re-synced.  That only happens if _all_ of the switch's flows --
> from
> +     * both refs -- are unlinked/rebuilt before _any_ of them is synced.
> So we
> +     * do all the unlinking and building first, then sync.
> +     *
> +     * The ls_stateful records are also (re)processed by
> +     * lflow_ls_stateful_handler(); doing it here as well is redundant but
> +     * harmless (the group is already stable, so the second pass reuses
> it). */
>

I don't think this last sentance matches the code. Could it be changed to
something like:
"The ls_stateful records are fully processed by
lflow_ls_stateful_handler(); unlinking the flows for ls_stateful records
for deleted switches insures that we can correctly remove flows that are no
longer referenced. The ls_stateful records are fully processed by
lflow_ls_stateful_handler()"

Something like that. Mention that only the  deletion occurs here and why.

> +
> +    /* Phase 1: unlink (and, for created/updated switches, rebuild). */
> +    HMAPX_FOR_EACH (hmapx_node, &tracked_lses->deleted) {
> +        struct ovn_datapath *od = hmapx_node->data;
> +        lflow_ref_unlink_lflows(od->datapath_lflows);
> +    }
> +    if (ls_sful_trk) {
> +        HMAPX_FOR_EACH (hmapx_node, &ls_sful_trk->deleted) {
> +            struct ls_stateful_record *ls_stateful_rec = hmapx_node->data;
> +            lflow_ref_unlink_lflows(ls_stateful_rec->lflow_ref);
>
+        }
> +    }
> +    HMAPX_FOR_EACH (hmapx_node, &tracked_lses->crupdated) {
> +        struct ovn_datapath *od = hmapx_node->data;
> +
> +        lflow_ref_unlink_lflows(od->datapath_lflows);
> +        build_lswitch_and_lrouter_iterate_by_ls(od, &lsi);
> +
> +        const struct ls_stateful_record *ls_stateful_rec =
> +            ls_stateful_table_find(lflow_input->ls_stateful_table,
> od->nbs);
> +        if (ls_stateful_rec) {
> +            lflow_ref_unlink_lflows(ls_stateful_rec->lflow_ref);
> +            build_ls_stateful_flows(ls_stateful_rec, od,
> +                                    lflow_input->ls_port_groups,
> +                                    lflow_input->meter_groups,
> +                                    lflow_input->sampling_apps,
> +                                    lflow_input->features, lflows,
> +                                    lflow_input->sbrec_acl_id_table);
> +        }
> +    }
> +
> +    /* Phase 2: sync.  All datapath groups are now allocated, so this
> won't
> +     * recompute the same groups over and over again. */
> +    HMAPX_FOR_EACH (hmapx_node, &tracked_lses->deleted) {
> +        struct ovn_datapath *od = hmapx_node->data;
> +        handled = lflow_ref_sync_lflows(
> +            od->datapath_lflows, lflows, ovnsb_txn, lflow_input->dps,
> +            lflow_input->ovn_internal_version_changed,
> +            lflow_input->sbrec_logical_flow_table,
> +            lflow_input->sbrec_logical_dp_group_table);
> +        if (!handled) {
> +            goto out;
> +        }
> +    }
> +    if (ls_sful_trk) {
> +        HMAPX_FOR_EACH (hmapx_node, &ls_sful_trk->deleted) {
> +            struct ls_stateful_record *ls_stateful_rec = hmapx_node->data;
> +            handled = lflow_ref_sync_lflows(
> +                ls_stateful_rec->lflow_ref, lflows, ovnsb_txn,
> +                lflow_input->dps,
> +                lflow_input->ovn_internal_version_changed,
> +                lflow_input->sbrec_logical_flow_table,
> +                lflow_input->sbrec_logical_dp_group_table);
> +            if (!handled) {
> +                goto out;
> +            }
> +        }
> +    }
> +    HMAPX_FOR_EACH (hmapx_node, &tracked_lses->crupdated) {
> +        struct ovn_datapath *od = hmapx_node->data;
> +
> +        handled = lflow_ref_sync_lflows(
> +            od->datapath_lflows, lflows, ovnsb_txn, lflow_input->dps,
> +            lflow_input->ovn_internal_version_changed,
> +            lflow_input->sbrec_logical_flow_table,
> +            lflow_input->sbrec_logical_dp_group_table);
> +        if (!handled) {
> +            goto out;
> +        }
> +
> +        const struct ls_stateful_record *ls_stateful_rec =
> +            ls_stateful_table_find(lflow_input->ls_stateful_table,
> od->nbs);
> +        if (ls_stateful_rec) {
> +            handled = lflow_ref_sync_lflows(
> +                ls_stateful_rec->lflow_ref, lflows, ovnsb_txn,
> +                lflow_input->dps,
> +                lflow_input->ovn_internal_version_changed,
> +                lflow_input->sbrec_logical_flow_table,
> +                lflow_input->sbrec_logical_dp_group_table);
> +            if (!handled) {
> +                goto out;
> +            }
> +        }
> +    }
> +
> +out:
> +    ds_destroy(&lsi.actions);
> +    ds_destroy(&lsi.match);
> +    return handled;
> +}
> +
>  bool
>  lflow_handle_northd_lr_changes(struct ovsdb_idl_txn *ovnsb_txn,
>                                  struct tracked_dps *tracked_lrs,
> @@ -21699,8 +21845,6 @@ lflow_handle_northd_port_changes(struct
> ovsdb_idl_txn *ovnsb_txn,
>                                  lflow_input->features,
>                                  lflows,
>                                  lflow_input->sbrec_acl_id_table);
> -        build_network_function(od, lflows, lflow_input->ls_port_groups,
> -                               ls_stateful_rec->lflow_ref);
>          handled = lflow_ref_sync_lflows(
>              ls_stateful_rec->lflow_ref, lflows, ovnsb_txn,
>              lflow_input->dps,
> @@ -22005,9 +22149,6 @@ lflow_handle_ls_stateful_changes(struct
> ovsdb_idl_txn *ovnsb_txn,
>                                  lflow_input->features,
>                                  lflows,
>                                  lflow_input->sbrec_acl_id_table);
> -        build_network_function(od, lflows,
> -                               lflow_input->ls_port_groups,
> -                               ls_stateful_rec->lflow_ref);
>      }
>
>      /* We need to make sure that all datapath groups are allocated before
> diff --git a/northd/northd.h b/northd/northd.h
> index 61546bdd2..217f3c6fb 100644
> --- a/northd/northd.h
> +++ b/northd/northd.h
> @@ -997,6 +997,11 @@ void build_route_data_flows_for_lrouter(
>      const struct group_ecmp_datapath *route_node,
>      const struct sset *bfd_ports);
>
> +bool lflow_handle_northd_ls_changes(struct ovsdb_idl_txn *ovnsb_txn,
> +                                    struct tracked_dps *,
> +                                    struct ls_stateful_tracked_data *,
> +                                    struct lflow_input *,
> +                                    struct lflow_table *lflows);
>  bool lflow_handle_northd_lr_changes(struct ovsdb_idl_txn *ovnsh_txn,
>                                       struct tracked_dps *,
>                                       struct lflow_input *,
> diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
> index 9a0ed2f01..eaaec17a2 100644
> --- a/tests/ovn-northd.at
> +++ b/tests/ovn-northd.at
> @@ -16186,7 +16186,7 @@ check as northd ovn-appctl -t ovn-northd
> inc-engine/clear-stats
>  check ovn-nbctl --wait=sb ls-add sw0
>  check_engine_stats northd norecompute compute
>  check_engine_stats ls_stateful norecompute compute
> -check_engine_stats lflow recompute nocompute
> +check_engine_stats lflow norecompute compute
>
>  # For the below engine nodes, en_northd is input.  So check
>  # their engine status.
> @@ -16224,7 +16224,7 @@ check as northd ovn-appctl -t ovn-northd
> inc-engine/clear-stats
>  check ovn-nbctl --wait=sb ls-del sw0
>  check_engine_stats northd norecompute compute
>  check_engine_stats ls_stateful norecompute compute
> -check_engine_stats lflow recompute nocompute
> +check_engine_stats lflow norecompute compute
>
>  # For the below engine nodes, en_northd is input.  So check
>  # their engine status.
> --
> 2.43.0
>
>
> --
>
>
>
>
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