Hi Lucas, thanks for the patch!

I like the concept, but I'm curious about something. northd calls
lsp_can_be_inc_processed() on all ovn_ports and caches the result. I
wonder if you could invert the logic of virtual_lsp_needs_recompute()
into a virtual_lsp_can_be_inc_processed() function instead. Then, you
could incorporate this function into lsp_can_be_inc_processed(). This
way, you would not need to make any alterations to
handle_lsp_changes().

Would that work, or is there something I'm missing?

On Thu, Jul 16, 2026 at 3:23 PM Lucas Vargas Dias
<[email protected]> wrote:
>
> Until now any change to a logical switch port of type "virtual" fell back
> to a full northd recompute, because lsp_can_be_inc_processed() only allowed
> plain VIF and remote ports.  Enable incremental processing for creation and
> deletion of virtual ports as well.
>
> The per-port lflows of a virtual port (the "bind_vport" ARP/ND responder
> flows) are anchored on the port's own lflow_ref and are already handled by
> the generic created/deleted tracked-port paths in the lflow engine.  The
> dependency on the virtual parents is likewise already handled (existing
> virtual ports are re-tracked when a parent VIF is created or deleted).
>
> Some virtual ports, however, have dependencies that live outside of their
> own lflow_ref and that the incremental LSP path does not keep in sync.  For
> those we detect the situation and fall back to a full recompute:
>
>   - A distributed NAT rule whose logical_port is the virtual port adds a
>     S_ROUTER_IN_GW_REDIRECT drop flow owned by the router datapath's
>     lflow_ref (see build_lrouter_nat_defrag_and_lb()).
>
>   - Dynamic routing on a connected router advertises host routes for a
>     virtual port based on its SB "virtual_parent", i.e. once the port is
>     claimed.  The claim reaches northd as an "up"-only change on the NB
>     port, which the incremental path otherwise ignores, so the advertised
>     route engine would not be re-run.  The fallback is therefore also
>     applied on the update path, before the "ignore_lsp_down" shortcut.
>
> Add tests covering incremental create/delete of a virtual port as well as
> the recompute fallbacks for the distributed-NAT and dynamic-routing cases.
>
> Assisted-by: Claude Opus 4.8, ClaudeCode
> Signed-off-by: Lucas Vargas Dias <[email protected]>
> ---
>  northd/northd.c     |  75 +++++++++++++++++++++++++-
>  tests/ovn-northd.at | 129 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 202 insertions(+), 2 deletions(-)
>
> diff --git a/northd/northd.c b/northd/northd.c
> index 3a4afa063..4f4c0733a 100644
> --- a/northd/northd.c
> +++ b/northd/northd.c
> @@ -1278,6 +1278,12 @@ lsp_is_remote(const struct nbrec_logical_switch_port 
> *nbsp)
>      return !strcmp(nbsp->type, "remote");
>  }
>
> +static bool
> +lsp_is_virtual(const struct nbrec_logical_switch_port *nbsp)
> +{
> +    return !strcmp(nbsp->type, "virtual");
> +}
> +
>  static bool
>  lsp_is_localnet(const struct nbrec_logical_switch_port *nbsp)
>  {
> @@ -4620,8 +4626,8 @@ destroy_northd_tracked_data(struct northd_data *nd)
>  static bool
>  lsp_can_be_inc_processed(const struct nbrec_logical_switch_port *nbsp)
>  {
> -    /* Support only normal VIF and remote ports for now. */
> -    if (nbsp->type[0] && !lsp_is_remote(nbsp)) {
> +    /* Support only normal VIF, remote and virtual ports for now. */
> +    if (nbsp->type[0] && !lsp_is_remote(nbsp) && !lsp_is_virtual(nbsp)) {
>          return false;
>      }
>
> @@ -4666,6 +4672,48 @@ lsp_can_be_inc_processed(const struct 
> nbrec_logical_switch_port *nbsp)
>      return true;
>  }
>
> +/* A logical switch port of type "virtual" can have dependencies that live
> + * outside of its own 'lflow_ref' and that the incremental LSP path does not
> + * keep in sync.  When any such dependency is present on a logical router
> + * connected to the port's logical switch, the caller must fall back to a 
> full
> + * recompute.  The known dependencies are:
> + *
> + *  - A distributed NAT rule whose 'logical_port' is this virtual port.  It
> + *    adds a S_ROUTER_IN_GW_REDIRECT drop flow (see
> + *    build_lrouter_nat_defrag_and_lb()) owned by the router datapath's
> + *    'lflow_ref', not by the virtual port.
> + *
> + *  - Dynamic routing on the connected router.  Host routes for a virtual 
> port
> + *    are advertised based on its SB 'virtual_parent' (i.e. once the port is
> + *    claimed, see publish_host_routes_for_virtual_ports()).  The claim 
> reaches
> + *    northd as an "up"-only change on the NB port, which the incremental 
> path
> + *    ignores, so the advertised-route engine would not be re-run. */
> +static bool
> +virtual_lsp_needs_recompute(struct ovn_datapath *od, const char *lport)
> +{
> +    struct ovn_port *rp;
> +    VECTOR_FOR_EACH (&od->router_ports, rp) {
> +        struct ovn_port *lrp = rp->peer;
> +        if (!lrp || !lrp->od || !lrp->od->nbr) {
> +            continue;
> +        }
> +
> +        if (lrp->od->dynamic_routing) {
> +            return true;
> +        }
> +
> +        const struct nbrec_logical_router *nbr = lrp->od->nbr;
> +        for (size_t i = 0; i < nbr->n_nat; i++) {
> +            const struct nbrec_nat *nat = nbr->nat[i];
> +            if (nat->logical_port && !strcmp(nat->logical_port, lport) &&
> +                is_nat_distributed(nat, lrp->od)) {
> +                return true;
> +            }
> +        }
> +    }
> +    return false;
> +}
> +
>  static bool
>  ls_port_has_changed(const struct nbrec_logical_switch_port *new)
>  {
> @@ -4963,6 +5011,13 @@ ls_handle_lsp_changes(struct ovsdb_idl_txn 
> *ovnsb_idl_txn,
>                  if (!lsp_can_be_inc_processed(new_nbsp)) {
>                      goto fail;
>                  }
> +                if (lsp_is_virtual(new_nbsp) &&
> +                    virtual_lsp_needs_recompute(od, new_nbsp->name)) {
> +                    /* The new virtual port has a dependency on a connected
> +                     * router that can't be handled incrementally.  Fall back
> +                     * to recompute. */
> +                    goto fail;
> +                }
>                  op = ls_port_create(ovnsb_idl_txn, &nd->ls_ports,
>                                      new_nbsp->name, new_nbsp, od,
>                                      ni->sbrec_mirror_table,
> @@ -4981,6 +5036,15 @@ ls_handle_lsp_changes(struct ovsdb_idl_txn 
> *ovnsb_idl_txn,
>                      !lsp_can_be_inc_processed(new_nbsp)) {
>                      goto fail;
>                  }
> +                if (lsp_is_virtual(new_nbsp) &&
> +                    virtual_lsp_needs_recompute(od, new_nbsp->name)) {
> +                    /* This virtual port has a dependency on a connected 
> router
> +                     * that can't be handled incrementally.  In particular a
> +                     * claim (which reaches northd as an "up"-only change) 
> must
> +                     * re-run the advertised-route engine.  Fall back to
> +                     * recompute. */
> +                    goto fail;
> +                }
>                  const struct sbrec_port_binding *sb = op->sb;
>                  if (sset_contains(&nd->svc_monitor_lsps, new_nbsp->name)) {
>                      /* This port is used for svc monitor, which may be 
> impacted
> @@ -5038,6 +5102,13 @@ ls_handle_lsp_changes(struct ovsdb_idl_txn 
> *ovnsb_idl_txn,
>              if (!op->lsp_can_be_inc_processed) {
>                  goto fail;
>              }
> +            if (lsp_is_virtual(op->nbsp) &&
> +                virtual_lsp_needs_recompute(op->od, op->key)) {
> +                /* This virtual port has a dependency on a connected router
> +                 * that can't be regenerated incrementally.  Fall back to
> +                 * recompute. */
> +                goto fail;
> +            }
>              if (sset_contains(&nd->svc_monitor_lsps, op->key)) {
>                  /* This port was used for svc monitor, which may be
>                   * impacted by this deletion. Fallback to recompute. */
> diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
> index 86cab3d5b..ed7aef72f 100644
> --- a/tests/ovn-northd.at
> +++ b/tests/ovn-northd.at
> @@ -12043,6 +12043,135 @@ ignored_dp=ls0
>  AT_CLEANUP
>  ])
>
> +AT_SETUP([Virtual port incremental processing])
> +AT_KEYWORDS([incremental processing])
> +ovn_start
> +
> +check ovn-nbctl ls-add sw0
> +check ovn-nbctl --wait=sb lsp-add sw0 vif0 \
> +    -- lsp-set-addresses vif0 "00:00:00:00:00:01 10.0.0.4"
> +
> +# Creating a virtual port should be incrementally processed.
> +check as northd ovn-appctl -t ovn-northd inc-engine/clear-stats
> +check ovn-nbctl --wait=sb lsp-add sw0 vip0 \
> +    -- lsp-set-type vip0 virtual \
> +    -- set Logical_Switch_Port vip0 \
> +        options:virtual-ip=10.0.0.10 options:virtual-parents=vif0
> +check_engine_compute northd incremental
> +check_engine_compute lflow incremental
> +
> +# The bind_vport flow for the virtual port is present.
> +AT_CHECK([ovn-sbctl dump-flows sw0 | grep ls_in_arp_rsp | grep bind_vport \
> +    | ovn_strip_lflows], [0], [dnl
> +  table=??(ls_in_arp_rsp      ), priority=100  , match=(inport == "vif0" && 
> ((arp.op == 1 && arp.spa == 10.0.0.10 && arp.tpa == 10.0.0.10) || (arp.op == 
> 2 && arp.spa == 10.0.0.10))), action=(bind_vport("vip0", inport); next;)
> +])
> +
> +CHECK_NO_CHANGE_AFTER_RECOMPUTE
> +
> +# Deleting a virtual port should be incrementally processed.
> +check as northd ovn-appctl -t ovn-northd inc-engine/clear-stats
> +check ovn-nbctl --wait=sb lsp-del vip0
> +check_engine_compute northd incremental
> +check_engine_compute lflow incremental
> +
> +# The bind_vport flow for the virtual port is gone.
> +AT_CHECK([ovn-sbctl dump-flows sw0 | grep ls_in_arp_rsp | grep bind_vport \
> +    | ovn_strip_lflows], [0], [])
> +
> +CHECK_NO_CHANGE_AFTER_RECOMPUTE
> +
> +OVN_CLEANUP_NORTHD
> +AT_CLEANUP
> +
> +AT_SETUP([Virtual port incremental processing fallback with distributed NAT])
> +AT_KEYWORDS([incremental processing])
> +ovn_start
> +
> +check ovn-sbctl chassis-add gw1 geneve 127.0.0.1
> +
> +check ovn-nbctl ls-add sw0
> +check ovn-nbctl lr-add lr0
> +check ovn-nbctl lrp-add lr0 lr0-sw0 00:00:00:00:ff:01 10.0.0.1/24
> +check ovn-nbctl --wait=sb lsp-add-router-port sw0 sw0-lr0 lr0-sw0
> +
> +# Distributed gateway port so that dnat_and_snat NATs become distributed.
> +check ovn-nbctl ls-add public
> +check ovn-nbctl lrp-add lr0 lr0-public 00:00:20:20:12:13 172.168.0.100/24
> +check ovn-nbctl --wait=sb lsp-add-router-port public public-lr0 lr0-public
> +check ovn-nbctl lsp-add-localnet-port public ln-public public
> +check ovn-nbctl --wait=sb lrp-set-gateway-chassis lr0-public gw1 20
> +
> +# Parent VIF and the virtual port.  No NAT references it yet, so creating it 
> is
> +# incrementally processed.
> +check ovn-nbctl --wait=sb lsp-add sw0 vif0 \
> +    -- lsp-set-addresses vif0 "00:00:20:20:12:01 10.0.0.4"
> +check ovn-nbctl --wait=sb lsp-add sw0 vip0 \
> +    -- lsp-set-type vip0 virtual \
> +    -- set Logical_Switch_Port vip0 \
> +        options:virtual-ip=10.0.0.5 options:virtual-parents=vif0
> +
> +# Distributed dnat_and_snat whose logical_port is the virtual port 'vip0'.
> +# The router's S_ROUTER_IN_GW_REDIRECT drop flow for this NAT depends on
> +# 'vip0' being a virtual port, but that flow is owned by the router 
> datapath's
> +# lflow_ref, not by 'vip0'.
> +check ovn-nbctl --wait=sb lr-nat-add lr0 dnat_and_snat \
> +    172.168.0.110 10.0.0.5 vip0 30:54:00:00:00:03
> +
> +# Deleting the virtual port must fall back to recompute.
> +check as northd ovn-appctl -t ovn-northd inc-engine/clear-stats
> +check ovn-nbctl --wait=sb lsp-del vip0
> +check_engine_compute northd recompute
> +
> +# Re-creating the virtual port (still referenced by the NAT) must also fall
> +# back to recompute.
> +check as northd ovn-appctl -t ovn-northd inc-engine/clear-stats
> +check ovn-nbctl --wait=sb lsp-add sw0 vip0 \
> +    -- lsp-set-type vip0 virtual \
> +    -- set Logical_Switch_Port vip0 \
> +        options:virtual-ip=10.0.0.5 options:virtual-parents=vif0
> +check_engine_compute northd recompute
> +
> +CHECK_NO_CHANGE_AFTER_RECOMPUTE
> +
> +OVN_CLEANUP_NORTHD
> +AT_CLEANUP
> +
> +AT_SETUP([Virtual port incremental processing fallback with dynamic routing])
> +AT_KEYWORDS([incremental processing])
> +ovn_start
> +
> +check ovn-nbctl ls-add sw0
> +check ovn-nbctl lr-add lr0 \
> +    -- set Logical_Router lr0 options:dynamic-routing=true
> +check ovn-nbctl lrp-add lr0 lr0-sw0 00:00:00:00:ff:01 10.0.0.1/24 \
> +    -- set Logical_Router_Port lr0-sw0 \
> +        options:dynamic-routing-redistribute=connected-as-host
> +check ovn-nbctl --wait=sb lsp-add-router-port sw0 sw0-lr0 lr0-sw0
> +
> +check ovn-nbctl --wait=sb lsp-add sw0 vif0 \
> +    -- lsp-set-addresses vif0 "00:00:00:00:00:01 10.0.0.4"
> +
> +# Creating a virtual port on a switch connected to a dynamic-routing router
> +# must fall back to recompute: advertised host routes for virtual ports 
> depend
> +# on the SB "virtual_parent" (claim), which the incremental path does not
> +# track.
> +check as northd ovn-appctl -t ovn-northd inc-engine/clear-stats
> +check ovn-nbctl --wait=sb lsp-add sw0 vip0 \
> +    -- lsp-set-type vip0 virtual \
> +    -- set Logical_Switch_Port vip0 \
> +        options:virtual-ip=10.0.0.5 options:virtual-parents=vif0
> +check_engine_compute northd recompute
> +
> +# Deleting it must also fall back to recompute.
> +check as northd ovn-appctl -t ovn-northd inc-engine/clear-stats
> +check ovn-nbctl --wait=sb lsp-del vip0
> +check_engine_compute northd recompute
> +
> +CHECK_NO_CHANGE_AFTER_RECOMPUTE
> +
> +OVN_CLEANUP_NORTHD
> +AT_CLEANUP
> +
>  OVN_FOR_EACH_NORTHD_NO_HV([
>  AT_SETUP([SB Port binding incremental processing])
>  ovn_start
> --
> 2.43.0
>
>
> --
>
>
>
>
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