[RouteOrch] Publish route state for route to Loopback interface (#3013)

* [RouteOrch] Publish route state for route to Loopback interface
Route to loopback interface is not advertised to peers when FIB suppression is enabled.

Route is queued:
```
admin@sonic:~$ show ipv6 route |grep q
       > - selected route, * - FIB route, q - queued route, r - rejected route
S>qfc00:1::/64 [1/0] is directly connected, Loopback0, 00:02:00
```

With this change:
```
admin@sonic:~$ show ipv6 route | grep q
       > - selected route, * - FIB route, q - queued route, r - rejected route
```

The proper way would be to program route to HW and then publish the
route state, however to keep the existing behaviour this W/A is proposed
until a final solution.

orchagent/routeorch.cpp

@@ -751,6 +751,9 @@ void RouteOrch::doTask(Consumer& consumer)
                             it = consumer.m_toSync.erase(it);
                         else
                             it++;
+
+                        /* Publish route state to advertise routes to Loopback interface */
+                        publishRouteState(ctx);
                         continue;
                     }
 
@@ -2548,7 +2551,7 @@ bool RouteOrch::removeRoutePost(const RouteBulkContext& ctx)
 
     SWSS_LOG_INFO("Remove route %s with next hop(s) %s",
             ipPrefix.to_string().c_str(), it_route->second.nhg_key.to_string().c_str());
-    
+
     /* Publish removal status, removes route entry from APPL STATE DB */
     publishRouteState(ctx);
 

tests/mock_tests/routeorch_ut.cpp

@@ -282,6 +282,10 @@ namespace routeorch_test
             static_cast<Orch *>(gPortsOrch)->doTask();
 
             Table intfTable = Table(m_app_db.get(), APP_INTF_TABLE_NAME);
+            intfTable.set("Loopback0", { {"NULL", "NULL" },
+                                         {"mac_addr", "00:00:00:00:00:00" }});
+            intfTable.set("Loopback0:10.1.0.32/32", { { "scope", "global" },
+                                                      { "family", "IPv4" }});
             intfTable.set("Ethernet0", { {"NULL", "NULL" },
                                          {"mac_addr", "00:00:00:00:00:00" }});
             intfTable.set("Ethernet0:10.0.0.1/24", { { "scope", "global" },
@@ -484,4 +488,22 @@ namespace routeorch_test
 
         gMockResponsePublisher.reset();
     }
+
+    TEST_F(RouteOrchTest, RouteOrchLoopbackRoute)
+    {
+        gMockResponsePublisher = std::make_unique<MockResponsePublisher>();
+
+        std::deque<KeyOpFieldsValuesTuple> entries;
+        std::string key = "fc00:1::/64";
+        std::vector<FieldValueTuple> fvs{{"ifname", "Loopback"}, {"nexthop", "::"}, {"protocol", "static"}};
+        entries.push_back({key, "SET", fvs});
+
+        auto consumer = dynamic_cast<Consumer *>(gRouteOrch->getExecutor(APP_ROUTE_TABLE_NAME));
+        consumer->addToSync(entries);
+
+        EXPECT_CALL(*gMockResponsePublisher, publish(APP_ROUTE_TABLE_NAME, key, std::vector<FieldValueTuple>{{"protocol", "static"}}, ReturnCode(SAI_STATUS_SUCCESS), false)).Times(1);
+        static_cast<Orch *>(gRouteOrch)->doTask();
+
+        gMockResponsePublisher.reset();
+    }
 }