OVN: fix DVR Floating IP support

When DVR is enabled FIP traffic need to be forwarded directly using
external connection to the underlay network and not be distributed
through geneve tunnels.
Fix this adding new logical flows to take care of distributed DNAT/SNAT

Acked-by: Mark Michelson <mmichels@redhat.com>
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

Author: Lorenzo Bianconi

northd/ovn-northd.8.xml

@@ -1861,6 +1861,37 @@ output;
     </p>
 
     <ul>
+      <li>
+        <p>
+          For distributed logical routers where one of the logical router
+          ports specifies a <code>redirect-chassis</code>, a priority-400
+          logical flow for each ip source/destination couple that matches the
+          <code>dnat_and_snat</code> NAT rules configured. These flows will
+          allow to properly forward traffic to the external connections if
+          available and avoid sending it through the tunnel.
+          Assuming the two following NAT rules have been configured:
+        </p>
+
+        <pre>
+external_ip{0,1} = <var>EIP{0,1}</var>;
+external_mac{0,1} = <var>MAC{0,1}</var>;
+logical_ip{0,1} = <var>LIP{0,1}</var>;
+        </pre>
+
+        <p>
+            the following action will be applied:
+        </p>
+
+        <pre>
+eth.dst = <var>MAC0</var>;
+eth.src = <var>MAC1</var>;
+reg0 = ip4.dst;
+reg1 = <var>EIP1</var>;
+outport = <code>redirect-chassis-port</code>;
+<code>REGBIT_DISTRIBUTED_NAT = 1; next;</code>.
+        </pre>
+      </li>
+
       <li>
         <p>
           For distributed logical routers where one of the logical router
@@ -1957,6 +1988,12 @@ next;
 
     <ul>
       <li>
+        <p>
+          For distributed logical routers where one of the logical router
+          ports specifies a <code>redirect-chassis</code>, a priority-400
+          logical flow with match <code>REGBIT_DISTRIBUTED_NAT == 1</code>
+          has action <code>next;</code>
+        </p>
         <p>
           For distributed logical routers where one of the logical router
           ports specifies a <code>redirect-chassis</code>, a priority-200
@@ -2045,6 +2082,11 @@ next;
     </p>
 
     <ul>
+      <li>
+        A priority-300 logical flow with match
+        <code>REGBIT_DISTRIBUTED_NAT == 1</code> has action
+        <code>next;</code>
+      </li>
       <li>
         A priority-200 logical flow with match
         <code>REGBIT_NAT_REDIRECT == 1</code> has actions
@@ -2354,6 +2396,15 @@ nd_ns {
 
     <ul>
       <li>
+        <p>
+          For each <code>dnat_and_snat</code> NAT rule couple in the
+          OVN Northbound database on a distributed router,
+          a priority-200 logical with match
+          <code>ip4.dst == <var>external_ip0</var> &amp;&amp;
+          ip4.src == <var>external_ip1</var></code>, has action
+          <code>next;</code>
+        </p>
+
         <p>
           For each NAT rule in the OVN Northbound database on a
           distributed router, a priority-100 logical flow with match

northd/ovn-northd.c

@@ -181,6 +181,7 @@ enum ovn_stage {
  * logical router dropping packets with source IP address equals
  * one of the logical router's own IP addresses. */
 #define REGBIT_EGRESS_LOOPBACK  "reg9[1]"
+#define REGBIT_DISTRIBUTED_NAT  "reg9[2]"
 
 /* Returns an "enum ovn_stage" built from the arguments. */
 static enum ovn_stage
@@ -5009,6 +5010,66 @@ find_lrp_member_ip(const struct ovn_port *op, const char *ip_s)
     return NULL;
 }
 
+static void
+add_distributed_nat_routes(struct hmap *lflows, const struct ovn_port *op)
+{
+    struct ds actions = DS_EMPTY_INITIALIZER;
+    struct ds match = DS_EMPTY_INITIALIZER;
+
+    if (!op->od->l3dgw_port) {
+        return;
+    }
+
+    if (!op->peer || !op->peer->od->nbs) {
+        return;
+    }
+
+    for (size_t i = 0; i < op->od->nbr->n_nat; i++) {
+        const struct nbrec_nat *nat = op->od->nbr->nat[i];
+        bool found = false;
+
+        if (strcmp(nat->type, "dnat_and_snat") ||
+            !nat->external_mac  || !nat->external_ip) {
+            continue;
+        }
+
+        const struct ovn_datapath *peer_dp = op->peer->od;
+        for (size_t j = 0; j < peer_dp->nbs->n_ports; j++) {
+            if (!strcmp(peer_dp->nbs->ports[j]->name, nat->logical_port)) {
+                found = true;
+                break;
+            }
+        }
+        if (!found) {
+            continue;
+        }
+
+        for (size_t j = 0; j < op->od->nbr->n_nat; j++) {
+            const struct nbrec_nat *nat2 = op->od->nbr->nat[j];
+
+            if (nat == nat2 || strcmp(nat2->type, "dnat_and_snat") ||
+                !nat2->external_mac || !nat2->external_ip)
+                continue;
+
+            ds_put_format(&match, "inport == %s && "
+                          "ip4.src == %s && ip4.dst == %s",
+                          op->json_key, nat->logical_ip, nat2->external_ip);
+            ds_put_format(&actions, "outport = %s; "
+                          "eth.src = %s; eth.dst = %s; "
+                          "reg0 = ip4.dst; reg1 = %s; "
+                          REGBIT_DISTRIBUTED_NAT" = 1; "
+                          REGBIT_NAT_REDIRECT" = 0; next;",
+                          op->od->l3dgw_port->json_key,
+                          op->od->l3dgw_port->lrp_networks.ea_s,
+                          nat2->external_mac, nat->external_ip);
+            ovn_lflow_add(lflows, op->od, S_ROUTER_IN_IP_ROUTING, 400,
+                          ds_cstr(&match), ds_cstr(&actions));
+            ds_clear(&match);
+            ds_clear(&actions);
+        }
+    }
+}
+
 static void
 add_route(struct hmap *lflows, const struct ovn_port *op,
           const char *lrp_addr_s, const char *network_s, int plen,
@@ -6392,6 +6453,41 @@ build_lrouter_flows(struct hmap *datapaths, struct hmap *ports,
              * ingress pipeline with inport = outport. */
             if (od->l3dgw_port) {
                 /* Distributed router. */
+                if (!strcmp(nat->type, "dnat_and_snat") &&
+                    nat->external_mac && nat->external_ip) {
+                    for (int j = 0; j < od->nbr->n_nat; j++) {
+                        const struct nbrec_nat *nat2 = od->nbr->nat[j];
+
+                        if (nat2 == nat ||
+                            strcmp(nat2->type, "dnat_and_snat") ||
+                            !nat2->external_mac || !nat2->external_ip) {
+                            continue;
+                        }
+
+                        ds_clear(&match);
+                        ds_put_format(&match, "is_chassis_resident(\"%s\") && "
+                                      "ip4.src == %s && ip4.dst == %s",
+                                      nat->logical_port, nat2->external_ip,
+                                      nat->external_ip);
+                        ds_clear(&actions);
+                        ds_put_format(&actions,
+                                      "inport = outport; outport = \"\"; "
+                                      "flags = 0; flags.loopback = 1; "
+                                      REGBIT_EGRESS_LOOPBACK" = 1; "
+                                      "next(pipeline=ingress, table=0); ");
+                        ovn_lflow_add(lflows, od, S_ROUTER_OUT_EGR_LOOP, 300,
+                                      ds_cstr(&match),  ds_cstr(&actions));
+
+                        ds_clear(&match);
+                        ds_put_format(&match,
+                                      "ip4.src == %s && ip4.dst == %s",
+                                      nat2->external_ip, nat->external_ip);
+                        ovn_lflow_add(lflows, od, S_ROUTER_OUT_EGR_LOOP, 200,
+                                      ds_cstr(&match), "next;");
+                        ds_clear(&match);
+                    }
+                }
+
                 ds_clear(&match);
                 ds_put_format(&match, "ip4.dst == %s && outport == %s",
                               nat->external_ip,
@@ -6463,6 +6559,9 @@ build_lrouter_flows(struct hmap *datapaths, struct hmap *ports,
             ovn_lflow_add(lflows, od, S_ROUTER_IN_DNAT, 50,
                           "ip", "flags.loopback = 1; ct_dnat;");
         } else {
+            ovn_lflow_add(lflows, od, S_ROUTER_IN_ARP_RESOLVE, 400,
+                          REGBIT_DISTRIBUTED_NAT" == 1", "next;");
+
             /* For NAT on a distributed router, add flows to Ingress
              * IP Routing table, Ingress ARP Resolution table, and
              * Ingress Gateway Redirect Table that are not specific to a
@@ -6698,6 +6797,9 @@ build_lrouter_flows(struct hmap *datapaths, struct hmap *ports,
             continue;
         }
 
+        /* create logical flows for DVR floating IPs */
+        add_distributed_nat_routes(lflows, op);
+
         for (int i = 0; i < op->lrp_networks.n_ipv4_addrs; i++) {
             add_route(lflows, op, op->lrp_networks.ipv4_addrs[i].addr_s,
                       op->lrp_networks.ipv4_addrs[i].network_s,
@@ -6938,6 +7040,9 @@ build_lrouter_flows(struct hmap *datapaths, struct hmap *ports,
             continue;
         }
         if (od->l3dgw_port && od->l3redirect_port) {
+            ovn_lflow_add(lflows, od, S_ROUTER_IN_GW_REDIRECT, 300,
+                          REGBIT_DISTRIBUTED_NAT" == 1", "next;");
+
             /* For traffic with outport == l3dgw_port, if the
              * packet did not match any higher priority redirect
              * rule, then the traffic is redirected to the central