diff mbox series

[ovs-dev,v5] northd: Refactor build_lrouter_nat_flows_for_lb function

Message ID 20230123075952.71044-1-amusil@redhat.com
State Changes Requested
Delegated to: Dumitru Ceara
Headers show
Series [ovs-dev,v5] northd: Refactor build_lrouter_nat_flows_for_lb function | expand

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ovsrobot/apply-robot success apply and check: success
ovsrobot/github-robot-_Build_and_Test success github build: passed
ovsrobot/github-robot-_ovn-kubernetes fail github build: failed

Commit Message

Ales Musil Jan. 23, 2023, 7:59 a.m. UTC
To make it easier to add flows to this stage, refactor the function.
This also has the benefit that we should see fewer allocations due to
rearranging how we create flows and how we manipulate the match string.

Signed-off-by: Ales Musil <amusil@redhat.com>
---
v5: Rebase on top of current main.
    Add missing ");" if ct_lb_related feature is not supported.
---
 northd/northd.c     | 483 ++++++++++++++++++++------------------------
 tests/ovn-northd.at |   9 -
 2 files changed, 220 insertions(+), 272 deletions(-)

Comments

Dumitru Ceara Jan. 23, 2023, 2:50 p.m. UTC | #1
On 1/23/23 08:59, Ales Musil wrote:
> To make it easier to add flows to this stage, refactor the function.
> This also has the benefit that we should see fewer allocations due to
> rearranging how we create flows and how we manipulate the match string.
> 
> Signed-off-by: Ales Musil <amusil@redhat.com>
> ---

Hi Ales,

> v5: Rebase on top of current main.
>     Add missing ");" if ct_lb_related feature is not supported.

Thanks for this revision!

> ---
>  northd/northd.c     | 483 ++++++++++++++++++++------------------------
>  tests/ovn-northd.at |   9 -
>  2 files changed, 220 insertions(+), 272 deletions(-)
> 

[...]

> diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
> index 35f186ad6..32cbdb0de 100644
> --- a/tests/ovn-northd.at
> +++ b/tests/ovn-northd.at
> @@ -3772,15 +3772,6 @@ AT_CHECK([grep "lr_in_dnat" lr0flows | sort], [0], [dnl
>    table=7 (lr_in_dnat         ), priority=70   , match=(ct.rel && !ct.est && !ct.new && ct_mark.skip_snat == 1), action=(flags.skip_snat_for_lb = 1; ct_commit_nat;)
>  ])
>  
> -AT_CHECK([grep "lr_out_undnat" lr0flows | sed 's/table=./table=?/' | sort], [0], [dnl
> -  table=? (lr_out_undnat      ), priority=0    , match=(1), action=(next;)
> -  table=? (lr_out_undnat      ), priority=50   , match=(ip), action=(flags.loopback = 1; ct_dnat;)
> -])
> -
> -AT_CHECK([grep "lr_out_post_undnat" lr0flows | sed 's/table=./table=?/' | sort], [0], [dnl
> -  table=? (lr_out_post_undnat ), priority=0    , match=(1), action=(next;)
> -  table=? (lr_out_post_undnat ), priority=50   , match=(ip && ct.new), action=(ct_commit { } ; next; )
> -])
>  
>  check ovn-nbctl --wait=sb set logical_router lr0 options:lb_force_snat_ip="20.0.0.4 aef0::4"
>  

I'm guessing this got added by accident to the v5 version.

I was about to apply this patch to the main branch but I noticed we
might be introducing a regression.  OVN-kubernetes CI fails with this
patch applied:

https://github.com/ovsrobot/ovn/actions/runs/3984516025/jobs/6831150082

The failing test is:

"[It] should be able to preserve UDP traffic when server pod cycles for
a NodePort service"

And I think it might be more than a false positive.  Would you be able
to spend some time looking into this please?  Otherwise I can take a
stab at it in the coming days.  Until then I'll refrain from applying
the patch and I'll assign it to myself on patchwork.

Thanks,
Dumitru
diff mbox series

Patch

diff --git a/northd/northd.c b/northd/northd.c
index 40a302579..16416563c 100644
--- a/northd/northd.c
+++ b/northd/northd.c
@@ -3866,10 +3866,13 @@  static bool
 build_lb_vip_actions(struct ovn_lb_vip *lb_vip,
                      struct ovn_northd_lb_vip *lb_vip_nb,
                      struct ds *action, char *selection_fields,
-                     bool ls_dp, bool ct_lb_mark)
+                     struct ds *skip_snat_action, struct ds *force_snat_action,
+                     bool ls_dp, const struct chassis_features *features)
 {
-    const char *ct_lb_action = ct_lb_mark ? "ct_lb_mark" : "ct_lb";
-    bool skip_hash_fields = false, reject = false;
+    const char *ct_lb_action =
+        features->ct_no_masked_label ? "ct_lb_mark" : "ct_lb";
+    bool reject = !lb_vip->n_backends && lb_vip->empty_backend_rej;
+    bool drop = false;
 
     if (lb_vip_nb->lb_health_check) {
         ds_put_format(action, "%s(backends=", ct_lb_action);
@@ -3890,23 +3893,12 @@  build_lb_vip_actions(struct ovn_lb_vip *lb_vip,
             ds_put_format(action, "%s:%"PRIu16",",
                           backend->ip_str, backend->port);
         }
+        ds_chomp(action, ',');
 
-        if (!n_active_backends) {
-            if (!lb_vip->empty_backend_rej) {
-                ds_clear(action);
-                ds_put_cstr(action, debug_drop_action());
-                skip_hash_fields = true;
-            } else {
-                reject = true;
-            }
-        } else {
-            ds_chomp(action, ',');
-            ds_put_cstr(action, ");");
-        }
-    } else if (lb_vip->empty_backend_rej && !lb_vip->n_backends) {
-        reject = true;
+        drop = !n_active_backends && !lb_vip->empty_backend_rej;
+        reject = !n_active_backends && lb_vip->empty_backend_rej;
     } else {
-        ds_put_format(action, "%s(backends=%s);", ct_lb_action,
+        ds_put_format(action, "%s(backends=%s", ct_lb_action,
                       lb_vip_nb->backend_ips);
     }
 
@@ -3915,12 +3907,29 @@  build_lb_vip_actions(struct ovn_lb_vip *lb_vip,
                           : ovn_stage_get_table(S_ROUTER_OUT_SNAT);
         ds_clear(action);
         ds_put_format(action, "reg0 = 0; reject { outport <-> inport; "
-                      "next(pipeline=egress,table=%d);};", stage);
-    } else if (!skip_hash_fields && selection_fields && selection_fields[0]) {
-        ds_chomp(action, ';');
-        ds_chomp(action, ')');
-        ds_put_format(action, "; hash_fields=\"%s\");", selection_fields);
+                              "next(pipeline=egress,table=%d);};", stage);
+    } else if (drop) {
+        ds_clear(action);
+        ds_put_cstr(action, debug_drop_action());
+    } else if (selection_fields && selection_fields[0]) {
+        ds_put_format(action, "; hash_fields=\"%s\"", selection_fields);
+    }
+
+    bool is_lb_action = !(reject || drop);
+
+    if (!ls_dp) {
+        bool flag_supported = is_lb_action && features->ct_lb_related;
+        ds_put_format(skip_snat_action, "flags.skip_snat_for_lb = 1; %s%s",
+                      ds_cstr(action),
+                      flag_supported ? "; skip_snat);" : ");");
+        ds_put_format(force_snat_action, "flags.force_snat_for_lb = 1; %s%s",
+                      ds_cstr(action),
+                      flag_supported ? "; force_snat);" : ");");
     }
+    if (is_lb_action) {
+        ds_put_cstr(action, ");");
+    }
+
     return reject;
 }
 
@@ -7480,9 +7489,9 @@  build_lb_affinity_default_flows(struct ovn_datapath *od, struct hmap *lflows)
 }
 
 static void
-build_lb_rules(struct hmap *lflows, struct ovn_northd_lb *lb, bool ct_lb_mark,
-               struct ds *match, struct ds *action,
-               const struct shash *meter_groups)
+build_lb_rules(struct hmap *lflows, struct ovn_northd_lb *lb,
+               const struct chassis_features *features, struct ds *match,
+               struct ds *action, const struct shash *meter_groups)
 {
     for (size_t i = 0; i < lb->n_vips; i++) {
         struct ovn_lb_vip *lb_vip = &lb->vips[i];
@@ -7505,8 +7514,8 @@  build_lb_rules(struct hmap *lflows, struct ovn_northd_lb *lb, bool ct_lb_mark,
         /* New connections in Ingress table. */
         const char *meter = NULL;
         bool reject = build_lb_vip_actions(lb_vip, lb_vip_nb, action,
-                                           lb->selection_fields, true,
-                                           ct_lb_mark);
+                                           lb->selection_fields, NULL,
+                                           NULL, true, features);
 
         ds_put_format(match, "ct.new && %s.dst == %s", ip_match,
                       lb_vip->vip_str);
@@ -10443,49 +10452,123 @@  get_force_snat_ip(struct ovn_datapath *od, const char *key_type,
     return true;
 }
 
+#define LROUTER_NAT_LB_FLOW_INIT(MATCH, ACTION, PRIO) \
+        (struct lrouter_nat_lb_flow)                  \
+        { .action = (ACTION), .lflow_ref = NULL,      \
+          .hash = ovn_logical_flow_hash(              \
+          ovn_stage_get_table(S_ROUTER_IN_DNAT),      \
+          ovn_stage_get_pipeline(S_ROUTER_IN_DNAT),   \
+          (PRIO), ds_cstr(MATCH), (ACTION)) }
+
+enum lrouter_nat_lb_flow_type {
+    LROUTER_NAT_LB_FLOW_NORMAL = 0,
+    LROUTER_NAT_LB_FLOW_SKIP_SNAT,
+    LROUTER_NAT_LB_FLOW_FORCE_SNAT,
+    LROUTER_NAT_LB_FLOW_MAX,
+};
+
+struct lrouter_nat_lb_flow {
+    char *action;
+    struct ovn_lflow *lflow_ref;
+
+    uint32_t hash;
+};
+
+struct lrouter_nat_lb_flows_ctx {
+    struct lrouter_nat_lb_flow new[LROUTER_NAT_LB_FLOW_MAX];
+    struct lrouter_nat_lb_flow est[LROUTER_NAT_LB_FLOW_MAX];
+
+    struct ds *new_match;
+    struct ds *est_match;
+    struct ds *undnat_match;
+
+    struct ovn_lb_vip *lb_vip;
+    struct ovn_northd_lb *lb;
+    bool reject;
+
+    int prio;
+
+    struct hmap *lflows;
+    const struct shash *meter_groups;
+};
+
 static void
-build_gw_lrouter_nat_flows_for_lb(struct ovn_northd_lb *lb,
-                                  struct ovn_datapath **dplist, int n_dplist,
-                                  bool reject, char *new_match,
-                                  char *new_action, char *est_match,
-                                  char *est_action, struct hmap *lflows,
-                                  int prio, const struct shash *meter_groups)
-{
-    if (!n_dplist) {
+build_distr_lrouter_nat_flows_for_lb(struct lrouter_nat_lb_flows_ctx *ctx,
+                                     enum lrouter_nat_lb_flow_type type,
+                                     struct ovn_datapath *od)
+{
+    char *gw_action = od->is_gw_router ? "ct_dnat;" : "ct_dnat_in_czone;";
+    /* Store the match lengths, so we can reuse the ds buffer. */
+    size_t new_match_len = ctx->new_match->length;
+    size_t est_match_len = ctx->est_match->length;
+    size_t undnat_match_len = ctx->undnat_match->length;
+
+
+    const char *meter = NULL;
+
+    if (ctx->reject) {
+        meter = copp_meter_get(COPP_REJECT, od->nbr->copp, ctx->meter_groups);
+    }
+
+    if (ctx->lb_vip->n_backends || !ctx->lb_vip->empty_backend_rej) {
+        ds_put_format(ctx->new_match, " && is_chassis_resident(%s)",
+                      od->l3dgw_ports[0]->cr_port->json_key);
+        ds_put_format(ctx->est_match, " && is_chassis_resident(%s)",
+                      od->l3dgw_ports[0]->cr_port->json_key);
+    }
+
+    ovn_lflow_add_with_hint__(ctx->lflows, od, S_ROUTER_IN_DNAT, ctx->prio,
+                              ds_cstr(ctx->new_match), ctx->new[type].action,
+                              NULL, meter, &ctx->lb->nlb->header_);
+    ovn_lflow_add_with_hint(ctx->lflows, od, S_ROUTER_IN_DNAT, ctx->prio,
+                            ds_cstr(ctx->est_match), ctx->est[type].action,
+                            &ctx->lb->nlb->header_);
+
+    ds_truncate(ctx->new_match, new_match_len);
+    ds_truncate(ctx->est_match, est_match_len);
+
+    if (!ctx->lb_vip->n_backends) {
         return;
     }
 
-    struct ovn_lflow *lflow_ref_new = NULL, *lflow_ref_est = NULL;
-    uint32_t hash_new = ovn_logical_flow_hash(
-            ovn_stage_get_table(S_ROUTER_IN_DNAT),
-            ovn_stage_get_pipeline(S_ROUTER_IN_DNAT),
-            prio, new_match, new_action);
-    uint32_t hash_est = ovn_logical_flow_hash(
-            ovn_stage_get_table(S_ROUTER_IN_DNAT),
-            ovn_stage_get_pipeline(S_ROUTER_IN_DNAT),
-            prio, est_match, est_action);
+    char *action = type == LROUTER_NAT_LB_FLOW_NORMAL
+                   ? gw_action : ctx->est[type].action;
 
-    for (size_t i = 0; i < n_dplist; i++) {
-        struct ovn_datapath *od = dplist[i];
-        const char *meter = NULL;
+    ds_put_format(ctx->undnat_match,
+                  ") && outport == %s && is_chassis_resident(%s)",
+                  od->l3dgw_ports[0]->json_key,
+                  od->l3dgw_ports[0]->cr_port->json_key);
+    ovn_lflow_add_with_hint(ctx->lflows, od, S_ROUTER_OUT_UNDNAT, 120,
+                            ds_cstr(ctx->undnat_match), action,
+                            &ctx->lb->nlb->header_);
+    ds_truncate(ctx->undnat_match, undnat_match_len);
+}
 
-        if (reject) {
-            meter = copp_meter_get(COPP_REJECT, od->nbr->copp, meter_groups);
-        }
-        if (meter || !ovn_dp_group_add_with_reference(lflow_ref_new, od)) {
-            struct ovn_lflow *lflow = ovn_lflow_add_at_with_hash(lflows, od,
-                    S_ROUTER_IN_DNAT, prio, new_match, new_action,
-                    NULL, meter, &lb->nlb->header_, OVS_SOURCE_LOCATOR,
-                    hash_new);
-            lflow_ref_new = meter ? NULL : lflow;
-        }
+static void
+build_gw_lrouter_nat_flows_for_lb(struct lrouter_nat_lb_flows_ctx *ctx,
+                                  enum lrouter_nat_lb_flow_type type,
+                                  struct ovn_datapath *od)
+{
+    const char *meter = NULL;
+    struct lrouter_nat_lb_flow *new_flow = &ctx->new[type];
+    struct lrouter_nat_lb_flow *est_flow = &ctx->est[type];
 
-        if (!ovn_dp_group_add_with_reference(lflow_ref_est, od)) {
-            lflow_ref_est = ovn_lflow_add_at_with_hash(lflows, od,
-                    S_ROUTER_IN_DNAT, prio, est_match, est_action,
-                    NULL, NULL, &lb->nlb->header_,
-                    OVS_SOURCE_LOCATOR, hash_est);
-        }
+    if (ctx->reject) {
+        meter = copp_meter_get(COPP_REJECT, od->nbr->copp, ctx->meter_groups);
+    }
+    if (meter || !ovn_dp_group_add_with_reference(new_flow->lflow_ref, od)) {
+        struct ovn_lflow *lflow = ovn_lflow_add_at_with_hash(ctx->lflows, od,
+                S_ROUTER_IN_DNAT, ctx->prio, ds_cstr(ctx->new_match),
+                new_flow->action, NULL, meter, &ctx->lb->nlb->header_,
+                OVS_SOURCE_LOCATOR, new_flow->hash);
+        new_flow->lflow_ref = meter ? NULL : lflow;
+    }
+
+    if (!ovn_dp_group_add_with_reference(est_flow->lflow_ref, od)) {
+        est_flow->lflow_ref = ovn_lflow_add_at_with_hash(ctx->lflows, od,
+                S_ROUTER_IN_DNAT, ctx->prio, ds_cstr(ctx->est_match),
+                est_flow->action, NULL, NULL, &ctx->lb->nlb->header_,
+                OVS_SOURCE_LOCATOR, est_flow->hash);
     }
 }
 
@@ -10501,22 +10584,25 @@  build_lrouter_nat_flows_for_lb(struct ovn_lb_vip *lb_vip,
     const char *ct_natted = features->ct_no_masked_label
                             ? "ct_mark.natted"
                             : "ct_label.natted";
-    char *skip_snat_new_action = NULL;
-    char *skip_snat_est_action = NULL;
-    char *new_match;
-    char *est_match;
+
+    bool ipv4 = lb_vip->address_family == AF_INET;
+    const char *ip_match = ipv4 ? "ip4" : "ip6";
+    const char *ip_reg = ipv4 ? REG_NEXT_HOP_IPV4 : REG_NEXT_HOP_IPV6;
+
+    int prio = 110;
+
+    struct ds skip_snat_act = DS_EMPTY_INITIALIZER;
+    struct ds force_snat_act = DS_EMPTY_INITIALIZER;
+    struct ds est_match = DS_EMPTY_INITIALIZER;
+    struct ds undnat_match = DS_EMPTY_INITIALIZER;
+    struct ds unsnat_match = DS_EMPTY_INITIALIZER;
 
     ds_clear(match);
     ds_clear(action);
 
     bool reject = build_lb_vip_actions(lb_vip, vips_nb, action,
-                                       lb->selection_fields, false,
-                                       features->ct_no_masked_label);
-    bool drop = !!strncmp(ds_cstr(action), "ct_lb", strlen("ct_lb"));
-    if (!drop) {
-        /* Remove the trailing ");". */
-        ds_truncate(action, action->length - 2);
-    }
+                                       lb->selection_fields, &skip_snat_act,
+                                       &force_snat_act, false, features);
 
     /* Higher priority rules are added for load-balancing in DNAT
      * table.  For every match (on a VIP[:port]), we add two flows.
@@ -10524,52 +10610,23 @@  build_lrouter_nat_flows_for_lb(struct ovn_lb_vip *lb_vip,
      * of "ct_lb_mark($targets);". The other flow is for ct.est with
      * an action of "next;".
      */
-    if (lb_vip->address_family == AF_INET) {
-        ds_put_format(match, "ip4 && "REG_NEXT_HOP_IPV4" == %s",
-                      lb_vip->vip_str);
-    } else {
-        ds_put_format(match, "ip6 && "REG_NEXT_HOP_IPV6" == %s",
-                      lb_vip->vip_str);
-    }
-
-    if (lb->skip_snat) {
-        const char *skip_snat = features->ct_lb_related && !drop
-                                ? "; skip_snat);"
-                                : "";
-        skip_snat_new_action = xasprintf("flags.skip_snat_for_lb = 1; %s%s",
-                                         ds_cstr(action), skip_snat);
-        skip_snat_est_action = xasprintf("flags.skip_snat_for_lb = 1; "
-                                         "next;");
-    }
-
-    int prio = 110;
-    if (lb_vip->port_str) {
+    ds_put_format(match, "ct.new && !ct.rel && %s && %s == %s",
+                  ip_match, ip_reg, lb_vip->vip_str);
+    if (lb_vip->vip_port) {
         prio = 120;
-        new_match = xasprintf("ct.new && !ct.rel && %s && %s && "
-                              REG_ORIG_TP_DPORT_ROUTER" == %s",
-                              ds_cstr(match), lb->proto, lb_vip->port_str);
-        est_match = xasprintf("ct.est && !ct.rel && %s && %s && "
-                              REG_ORIG_TP_DPORT_ROUTER" == %s && %s == 1",
-                              ds_cstr(match), lb->proto, lb_vip->port_str,
-                              ct_natted);
-    } else {
-        new_match = xasprintf("ct.new && !ct.rel && %s", ds_cstr(match));
-        est_match = xasprintf("ct.est && !ct.rel && %s && %s == 1",
-                          ds_cstr(match), ct_natted);
+        ds_put_format(match, " && %s && "REG_ORIG_TP_DPORT_ROUTER" == %d",
+                      lb->proto, lb_vip->vip_port);
     }
 
-    const char *ip_match = NULL;
-    if (lb_vip->address_family == AF_INET) {
-        ip_match = "ip4";
-    } else {
-        ip_match = "ip6";
-    }
+    ds_put_cstr(&est_match, "ct.est");
+    /* Clone the match after initial "ct.new" (6 bytes). */
+    ds_put_cstr(&est_match, ds_cstr(match) + 6);
+    ds_put_format(&est_match, " && %s == 1", ct_natted);
 
     /* Add logical flows to UNDNAT the load balanced reverse traffic in
      * the router egress pipleine stage - S_ROUTER_OUT_UNDNAT if the logical
      * router has a gateway router port associated.
      */
-    struct ds undnat_match = DS_EMPTY_INITIALIZER;
     ds_put_format(&undnat_match, "%s && (", ip_match);
 
     for (size_t i = 0; i < lb_vip->n_backends; i++) {
@@ -10584,12 +10641,9 @@  build_lrouter_nat_flows_for_lb(struct ovn_lb_vip *lb_vip,
             ds_put_cstr(&undnat_match, ") || ");
         }
     }
-    ds_chomp(&undnat_match, ' ');
-    ds_chomp(&undnat_match, '|');
-    ds_chomp(&undnat_match, '|');
-    ds_chomp(&undnat_match, ' ');
+    /* Remove the trailing " || ". */
+    ds_truncate(&undnat_match, undnat_match.length - 4);
 
-    struct ds unsnat_match = DS_EMPTY_INITIALIZER;
     ds_put_format(&unsnat_match, "%s && %s.dst == %s && %s",
                   ip_match, ip_match, lb_vip->vip_str, lb->proto);
     if (lb_vip->port_str) {
@@ -10597,21 +10651,34 @@  build_lrouter_nat_flows_for_lb(struct ovn_lb_vip *lb_vip,
                       lb_vip->port_str);
     }
 
-    struct ovn_datapath **gw_router_skip_snat =
-        xcalloc(lb->n_nb_lr, sizeof *gw_router_skip_snat);
-    int n_gw_router_skip_snat = 0;
+    struct lrouter_nat_lb_flows_ctx ctx = {
+        .lb_vip = lb_vip,
+        .lb = lb,
+        .reject = reject,
+        .prio = prio,
+        .lflows = lflows,
+        .meter_groups = meter_groups,
+        .new_match = match,
+        .est_match = &est_match,
+        .undnat_match = &undnat_match
+    };
 
-    struct ovn_datapath **gw_router_force_snat =
-        xcalloc(lb->n_nb_lr, sizeof *gw_router_force_snat);
-    int n_gw_router_force_snat = 0;
+    ctx.new[LROUTER_NAT_LB_FLOW_NORMAL] =
+        LROUTER_NAT_LB_FLOW_INIT(match, ds_cstr(action), prio);
+    ctx.est[LROUTER_NAT_LB_FLOW_NORMAL] =
+        LROUTER_NAT_LB_FLOW_INIT(&est_match, "next;", prio);
 
-    struct ovn_datapath **gw_router =
-        xcalloc(lb->n_nb_lr, sizeof *gw_router);
-    int n_gw_router = 0;
+    ctx.new[LROUTER_NAT_LB_FLOW_SKIP_SNAT] =
+        LROUTER_NAT_LB_FLOW_INIT(match, ds_cstr(&skip_snat_act), prio);
+    ctx.est[LROUTER_NAT_LB_FLOW_SKIP_SNAT] =
+        LROUTER_NAT_LB_FLOW_INIT(&est_match,
+                                 "flags.skip_snat_for_lb = 1; next;", prio);
 
-    struct ovn_datapath **distributed_router =
-        xcalloc(lb->n_nb_lr, sizeof *distributed_router);
-    int n_distributed_router = 0;
+    ctx.new[LROUTER_NAT_LB_FLOW_FORCE_SNAT] =
+        LROUTER_NAT_LB_FLOW_INIT(match, ds_cstr(&force_snat_act), prio);
+    ctx.est[LROUTER_NAT_LB_FLOW_FORCE_SNAT] =
+        LROUTER_NAT_LB_FLOW_INIT(&est_match,
+                                 "flags.force_snat_for_lb = 1; next;", prio);
 
     struct ovn_datapath **lb_aff_force_snat_router =
         xcalloc(lb->n_nb_lr, sizeof *lb_aff_force_snat_router);
@@ -10625,18 +10692,22 @@  build_lrouter_nat_flows_for_lb(struct ovn_lb_vip *lb_vip,
      * lflow generation for them.
      */
     for (size_t i = 0; i < lb->n_nb_lr; i++) {
+        enum lrouter_nat_lb_flow_type type;
         struct ovn_datapath *od = lb->nb_lr[i];
+
+        if (lb->skip_snat) {
+            type = LROUTER_NAT_LB_FLOW_SKIP_SNAT;
+        } else if (!lport_addresses_is_empty(&od->lb_force_snat_addrs) ||
+                   od->lb_force_snat_router_ip) {
+            type = LROUTER_NAT_LB_FLOW_FORCE_SNAT;
+        } else {
+            type = LROUTER_NAT_LB_FLOW_NORMAL;
+        }
+
         if (!od->n_l3dgw_ports) {
-            if (lb->skip_snat) {
-                gw_router_skip_snat[n_gw_router_skip_snat++] = od;
-            } else if (!lport_addresses_is_empty(&od->lb_force_snat_addrs) ||
-                       od->lb_force_snat_router_ip) {
-                gw_router_force_snat[n_gw_router_force_snat++] = od;
-            } else {
-                gw_router[n_gw_router++] = od;
-            }
+            build_gw_lrouter_nat_flows_for_lb(&ctx, type, od);
         } else {
-            distributed_router[n_distributed_router++] = od;
+            build_distr_lrouter_nat_flows_for_lb(&ctx, type, od);
         }
 
         if (!lport_addresses_is_empty(&od->lb_force_snat_addrs) ||
@@ -10658,149 +10729,36 @@  build_lrouter_nat_flows_for_lb(struct ovn_lb_vip *lb_vip,
              * unsnat stage, the conntrack flags are not set properly, and
              * it doesn't hit the established state flows in
              * S_ROUTER_IN_DNAT stage. */
-             ovn_lflow_add_with_hint(lflows, od, S_ROUTER_IN_UNSNAT, 120,
-                                     ds_cstr(&unsnat_match), "next;",
-                                     &lb->nlb->header_);
+            ovn_lflow_add_with_hint(lflows, od, S_ROUTER_IN_UNSNAT, 120,
+                                    ds_cstr(&unsnat_match), "next;",
+                                    &lb->nlb->header_);
         }
     }
 
-    /* GW router logic */
-    build_gw_lrouter_nat_flows_for_lb(lb, gw_router_skip_snat,
-            n_gw_router_skip_snat, reject, new_match,
-            skip_snat_new_action, est_match,
-            skip_snat_est_action, lflows, prio, meter_groups);
-
-    const char *force_snat = features->ct_lb_related && !drop
-                             ? "; force_snat);"
-                             : "";
-    char *new_actions = xasprintf("flags.force_snat_for_lb = 1; %s%s",
-                                  ds_cstr(action), force_snat);
-    build_gw_lrouter_nat_flows_for_lb(lb, gw_router_force_snat,
-            n_gw_router_force_snat, reject, new_match,
-            new_actions, est_match,
-            "flags.force_snat_for_lb = 1; next;",
-            lflows, prio, meter_groups);
-
     /* LB affinity flows for datapaths where CMS has specified
      * force_snat_for_lb floag option.
      */
-    build_lb_affinity_lr_flows(lflows, lb, lb_vip, new_match,
+    build_lb_affinity_lr_flows(lflows, lb, lb_vip, ds_cstr(match),
                                "flags.force_snat_for_lb = 1; ",
                                lb_aff_force_snat_router,
                                n_lb_aff_force_snat_router);
 
-    if (!drop) {
-        ds_put_cstr(action, ");");
-    }
-
-    build_gw_lrouter_nat_flows_for_lb(lb, gw_router, n_gw_router,
-            reject, new_match, ds_cstr(action), est_match,
-            "next;", lflows, prio, meter_groups);
-
     /* LB affinity flows for datapaths where CMS has specified
      * skip_snat_for_lb floag option or regular datapaths.
      */
     char *lb_aff_action =
         lb->skip_snat ? "flags.skip_snat_for_lb = 1; " : NULL;
-    build_lb_affinity_lr_flows(lflows, lb, lb_vip, new_match, lb_aff_action,
-                               lb_aff_router, n_lb_aff_router);
-
-    /* Distributed router logic */
-    for (size_t i = 0; i < n_distributed_router; i++) {
-        struct ovn_datapath *od = distributed_router[i];
-        char *new_match_p = new_match;
-        char *est_match_p = est_match;
-        const char *meter = NULL;
-        bool is_dp_lb_force_snat =
-            !lport_addresses_is_empty(&od->lb_force_snat_addrs) ||
-            od->lb_force_snat_router_ip;
-
-        if (reject) {
-            meter = copp_meter_get(COPP_REJECT, od->nbr->copp, meter_groups);
-        }
-
-        if (lb_vip->n_backends || !lb_vip->empty_backend_rej) {
-            new_match_p = xasprintf("%s && is_chassis_resident(%s)",
-                                    new_match,
-                                    od->l3dgw_ports[0]->cr_port->json_key);
-            est_match_p = xasprintf("%s && is_chassis_resident(%s)",
-                                    est_match,
-                                    od->l3dgw_ports[0]->cr_port->json_key);
-        }
-
-        if (lb->skip_snat) {
-            ovn_lflow_add_with_hint__(lflows, od, S_ROUTER_IN_DNAT, prio,
-                                      new_match_p, skip_snat_new_action,
-                                      NULL, meter, &lb->nlb->header_);
-            ovn_lflow_add_with_hint(lflows, od, S_ROUTER_IN_DNAT, prio,
-                                    est_match_p, skip_snat_est_action,
-                                    &lb->nlb->header_);
-        } else if (is_dp_lb_force_snat) {
-            ovn_lflow_add_with_hint__(lflows, od, S_ROUTER_IN_DNAT, prio,
-                                      new_match_p, new_actions, NULL,
-                                      meter, &lb->nlb->header_);
-            ovn_lflow_add_with_hint(lflows, od, S_ROUTER_IN_DNAT, prio,
-                                    est_match_p,
-                                    "flags.force_snat_for_lb = 1; next;",
-                                    &lb->nlb->header_);
-        } else {
-            ovn_lflow_add_with_hint__(lflows, od, S_ROUTER_IN_DNAT, prio,
-                                      new_match_p, ds_cstr(action), NULL,
-                                      meter, &lb->nlb->header_);
-            ovn_lflow_add_with_hint(lflows, od, S_ROUTER_IN_DNAT, prio,
-                                    est_match_p, "next;",
-                                    &lb->nlb->header_);
-        }
-
-        if (new_match_p != new_match) {
-            free(new_match_p);
-        }
-        if (est_match_p != est_match) {
-            free(est_match_p);
-        }
-
-        if (!lb_vip->n_backends) {
-            continue;
-        }
-
-        char *undnat_match_p = xasprintf(
-            "%s) && outport == %s && is_chassis_resident(%s)",
-            ds_cstr(&undnat_match),
-            od->l3dgw_ports[0]->json_key,
-            od->l3dgw_ports[0]->cr_port->json_key);
-        if (lb->skip_snat) {
-            ovn_lflow_add_with_hint(lflows, od, S_ROUTER_OUT_UNDNAT, 120,
-                                    undnat_match_p, skip_snat_est_action,
-                                    &lb->nlb->header_);
-        } else if (is_dp_lb_force_snat) {
-            ovn_lflow_add_with_hint(lflows, od, S_ROUTER_OUT_UNDNAT, 120,
-                                    undnat_match_p,
-                                    "flags.force_snat_for_lb = 1; next;",
-                                    &lb->nlb->header_);
-        } else {
-            ovn_lflow_add_with_hint(
-                lflows, od, S_ROUTER_OUT_UNDNAT, 120, undnat_match_p,
-                od->is_gw_router ? "ct_dnat;" : "ct_dnat_in_czone;",
-                &lb->nlb->header_);
-        }
-        free(undnat_match_p);
-    }
+    build_lb_affinity_lr_flows(lflows, lb, lb_vip, ds_cstr(match),
+                               lb_aff_action, lb_aff_router, n_lb_aff_router);
 
     ds_destroy(&unsnat_match);
     ds_destroy(&undnat_match);
+    ds_destroy(&est_match);
+    ds_destroy(&skip_snat_act);
+    ds_destroy(&force_snat_act);
 
-    free(skip_snat_new_action);
-    free(skip_snat_est_action);
-    free(est_match);
-    free(new_match);
-    free(new_actions);
-
-    free(gw_router_force_snat);
-    free(gw_router_skip_snat);
-    free(distributed_router);
     free(lb_aff_force_snat_router);
     free(lb_aff_router);
-    free(gw_router);
 }
 
 static void
@@ -10845,8 +10803,7 @@  build_lswitch_flows_for_lb(struct ovn_northd_lb *lb, struct hmap *lflows,
      * REGBIT_CONNTRACK_COMMIT. */
     build_lb_rules_pre_stateful(lflows, lb, features->ct_no_masked_label,
                                 match, action);
-    build_lb_rules(lflows, lb, features->ct_no_masked_label,
-                   match, action, meter_groups);
+    build_lb_rules(lflows, lb, features, match, action, meter_groups);
 }
 
 /* If there are any load balancing rules, we should send the packet to
diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
index 35f186ad6..32cbdb0de 100644
--- a/tests/ovn-northd.at
+++ b/tests/ovn-northd.at
@@ -3772,15 +3772,6 @@  AT_CHECK([grep "lr_in_dnat" lr0flows | sort], [0], [dnl
   table=7 (lr_in_dnat         ), priority=70   , match=(ct.rel && !ct.est && !ct.new && ct_mark.skip_snat == 1), action=(flags.skip_snat_for_lb = 1; ct_commit_nat;)
 ])
 
-AT_CHECK([grep "lr_out_undnat" lr0flows | sed 's/table=./table=?/' | sort], [0], [dnl
-  table=? (lr_out_undnat      ), priority=0    , match=(1), action=(next;)
-  table=? (lr_out_undnat      ), priority=50   , match=(ip), action=(flags.loopback = 1; ct_dnat;)
-])
-
-AT_CHECK([grep "lr_out_post_undnat" lr0flows | sed 's/table=./table=?/' | sort], [0], [dnl
-  table=? (lr_out_post_undnat ), priority=0    , match=(1), action=(next;)
-  table=? (lr_out_post_undnat ), priority=50   , match=(ip && ct.new), action=(ct_commit { } ; next; )
-])
 
 check ovn-nbctl --wait=sb set logical_router lr0 options:lb_force_snat_ip="20.0.0.4 aef0::4"