ovn-controller: Datapath based conntrack zone for load-balancing.

Currently ct_lb() logical action is only added for a logical switch and
we use the conntrack zone allocated for the logical port.  A future commit
will use ct_lb() for a logical router too.  In that case, use the allocated
DNAT zone.

Rationale for not passing zone as an argument for ct_lb():
One way to look at it would be that a "zone" is an internal implementation
detail and should not be seen in a action of logical flow.  But we can then
say that we could rename "zone" as "datapath" in the logical action.  But,
then we would be limiting it to 2 anyway (datapath=lswitch or
datapath=lrouter) - in which case we are inferring it with the current patch.

Signed-off-by: Gurucharan Shetty <guru@ovn.org>
Acked-by: Ben Pfaff <blp@ovn.org>

include/ovn/actions.h

@@ -397,6 +397,9 @@ struct ovnact_encode_params {
                         unsigned int *portp);
     const void *aux;
 
+    /* 'true' if the flow is for a switch. */
+    bool is_switch;
+
     /* A map from a port name to its connection tracking zone. */
     const struct simap *ct_zones;
 

ovn/controller/lflow.c

@@ -251,6 +251,7 @@ consider_logical_flow(const struct lport_index *lports,
     struct ovnact_encode_params ep = {
         .lookup_port = lookup_port_cb,
         .aux = &aux,
+        .is_switch = is_switch(ldp),
         .ct_zones = ct_zones,
         .group_table = group_table,
 

ovn/lib/actions.c

@@ -912,7 +912,8 @@ encode_CT_LB(const struct ovnact_ct_lb *cl,
         struct ofpact_conntrack *ct = ofpact_put_CT(ofpacts);
         struct ofpact_nat *nat;
         size_t nat_offset;
-        ct->zone_src.field = mf_from_id(MFF_LOG_CT_ZONE);
+        ct->zone_src.field = ep->is_switch ? mf_from_id(MFF_LOG_CT_ZONE)
+                                : mf_from_id(MFF_LOG_DNAT_ZONE);
         ct->zone_src.ofs = 0;
         ct->zone_src.n_bits = 16;
         ct->flags = 0;
@@ -936,12 +937,16 @@ encode_CT_LB(const struct ovnact_ct_lb *cl,
     uint32_t group_id = 0, hash;
     struct group_info *group_info;
     struct ofpact_group *og;
+    uint32_t zone_reg = ep->is_switch ? MFF_LOG_CT_ZONE - MFF_REG0
+                            : MFF_LOG_DNAT_ZONE - MFF_REG0;
 
     struct ds ds = DS_EMPTY_INITIALIZER;
     ds_put_format(&ds, "type=select");
 
     BUILD_ASSERT(MFF_LOG_CT_ZONE >= MFF_REG0);
     BUILD_ASSERT(MFF_LOG_CT_ZONE < MFF_REG0 + FLOW_N_REGS);
+    BUILD_ASSERT(MFF_LOG_DNAT_ZONE >= MFF_REG0);
+    BUILD_ASSERT(MFF_LOG_DNAT_ZONE < MFF_REG0 + FLOW_N_REGS);
     for (size_t bucket_id = 0; bucket_id < cl->n_dsts; bucket_id++) {
         const struct ovnact_ct_lb_dst *dst = &cl->dsts[bucket_id];
         ds_put_format(&ds, ",bucket=bucket_id=%"PRIuSIZE",weight:100,actions="
@@ -950,7 +955,7 @@ encode_CT_LB(const struct ovnact_ct_lb *cl,
             ds_put_format(&ds, ":%"PRIu16, dst->port);
         }
         ds_put_format(&ds, "),commit,table=%d,zone=NXM_NX_REG%d[0..15])",
-                      recirc_table, MFF_LOG_CT_ZONE - MFF_REG0);
+                      recirc_table, zone_reg);
     }
 
     hash = hash_string(ds_cstr(&ds), 0);

ovn/ovn-sb.xml

@@ -1345,8 +1345,10 @@
             DNAT address.  Processing automatically moves on to the next table,
             as if <code>next;</code> were specified, and later tables act on
             the packet as modified by the connection tracker.  Connection
-            tracking state is scoped by the logical port, so overlapping
-            addresses may be used.
+            tracking state is scoped by the logical port when the action is
+            used in a flow for a logical switch, so overlapping
+            addresses may be used.  Connection tracking state is scoped by the
+            logical topology when the action is used in a flow for a router.
           </p>
           <p>
             Without arguments, <code>ct_lb</code> sends the packet to the

tests/test-ovn.c

@@ -1182,6 +1182,7 @@ test_parse_actions(struct ovs_cmdl_context *ctx OVS_UNUSED)
             const struct ovnact_encode_params ep = {
                 .lookup_port = lookup_port_cb,
                 .aux = &ports,
+                .is_switch = true,
                 .ct_zones = &ct_zones,
                 .group_table = &group_table,