Get centralized FIP only on router's snat host

It may happen that L3 agent works in dvr_snat mode but
it handles some router as "normal" dvr router because
snat for this router is handled on other node.
In such case we shouldn't try to get floating IPs cidrs
from snat namespace as it doesn't exists on host.

Change-Id: Ib27dc223fcca56030ebb528625cc927fc60553e1
Related-Bug: #1717302

neutron/agent/l3/dvr_edge_router.py

@@ -270,7 +270,10 @@ class DvrEdgeRouter(dvr_local_router.DvrLocalRouter):
     def get_centralized_fip_cidr_set(self):
         """Returns the fip_cidr set for centralized floatingips."""
         ex_gw_port = self.get_ex_gw_port()
-        if not ex_gw_port:
+        # Don't look for centralized FIP cidrs if gw_port not exists or
+        # this is not snat host
+        if (not ex_gw_port or not self._is_this_snat_host() or
+                not self.snat_namespace.exists()):
             return set()
         interface_name = self.get_snat_external_device_interface_name(
                 ex_gw_port)
@@ -287,10 +290,7 @@ class DvrEdgeRouter(dvr_local_router.DvrLocalRouter):
         regular floatingip cidr list that are bound to fip namespace.
         """
         fip_cidrs = super(DvrEdgeRouter, self).get_router_cidrs(device)
-        centralized_cidrs = set()
-        # Call get_centralized_fip_cidr_set only when snat_namespace exists
-        if self.get_ex_gw_port() and self.snat_namespace.exists():
-            centralized_cidrs = self.get_centralized_fip_cidr_set()
+        centralized_cidrs = self.get_centralized_fip_cidr_set()
         return fip_cidrs | centralized_cidrs
 
     def remove_centralized_floatingip(self, fip_cidr):

neutron/tests/functional/agent/l3/test_dvr_router.py

@@ -1184,6 +1184,38 @@ class TestDvrRouter(framework.L3AgentTestFramework):
         self.assertFalse(self._fixed_ip_rule_exists(snat_ns, fixed_ip_cent))
         self.assertTrue(self._namespace_exists(fip_ns))
 
+    def _test_get_centralized_fip_cidr_set(self, router_info,
+                                           expected_result_empty):
+        self.agent.conf.agent_mode = lib_constants.L3_AGENT_MODE_DVR_SNAT
+        self.manage_router(self.agent, router_info)
+        router = self.agent.router_info[router_info['id']]
+        centralized_fips = router.get_centralized_fip_cidr_set()
+        if expected_result_empty:
+            self.assertEqual(set([]), centralized_fips)
+        else:
+            self.assertNotEqual(set([]), centralized_fips)
+
+    def test_get_centralized_fip_cidr_set(self):
+        router_info = self.generate_dvr_router_info(
+            enable_floating_ip=True, enable_centralized_fip=True,
+            enable_snat=True, snat_bound_fip=True)
+        self._test_get_centralized_fip_cidr_set(router_info, False)
+
+    def test_get_centralized_fip_cidr_set_not_snat_host(self):
+        router_info = self.generate_dvr_router_info(
+            enable_floating_ip=True, enable_centralized_fip=True,
+            enable_snat=True, snat_bound_fip=True)
+        router_info['gw_port_host'] = 'some-other-host'
+        self._test_get_centralized_fip_cidr_set(router_info, True)
+
+    def test_get_centralized_fip_cidr_set_no_ex_gw_port(self):
+        self.agent.conf.agent_mode = lib_constants.L3_AGENT_MODE_DVR_SNAT
+        router_info = self.generate_dvr_router_info(
+            enable_floating_ip=True, enable_centralized_fip=True,
+            enable_snat=True, snat_bound_fip=True)
+        router_info['gw_port'] = {}
+        self._test_get_centralized_fip_cidr_set(router_info, True)
+
     def test_floating_ip_not_deployed_on_dvr_no_external_agent(self):
         """Test to check floating ips not configured for dvr_no_external."""
         self.agent.conf.agent_mode = (