Deletes FIP agent gw port when last VM is deleted

This patch deletes the FIP agent gateway port in
the plugin, when the last VM with FIP using this
FIP agent gw port on a Compute node gets deleted.

Closes-bug: #1367588

Change-Id: I71a9fa48544fa4bbd08ac6d83c99e6542c818009

neutron/db/l3_dvr_db.py

@@ -181,6 +181,26 @@ class L3_NAT_with_dvr_db_mixin(l3_db.L3_NAT_db_mixin,
         super(L3_NAT_with_dvr_db_mixin,
               self).delete_floatingip(context, id)
 
+    def _get_floatingip_on_port(self, context, port_id=None):
+        """Helper function to retrieve the fip associated with port."""
+        fip_qry = context.session.query(l3_db.FloatingIP)
+        floating_ip = fip_qry.filter_by(fixed_port_id=port_id)
+        return floating_ip.first()
+
+    def disassociate_floatingips(self, context, port_id, do_notify=True):
+        """Override disassociate floatingips to delete fip agent gw port."""
+        with context.session.begin(subtransactions=True):
+            fip = self._get_floatingip_on_port(
+                context, port_id=port_id)
+            if fip:
+                admin_ctx = context.elevated()
+                self.clear_unused_fip_agent_gw_port(
+                    admin_ctx, fip, id)
+        return super(L3_NAT_with_dvr_db_mixin,
+                     self).disassociate_floatingips(context,
+                                                    port_id,
+                                                    do_notify=do_notify)
+
     def add_router_interface(self, context, router_id, interface_info):
         add_by_port, add_by_sub = self._validate_interface_info(interface_info)
         router = self._get_router(context, router_id)

neutron/tests/unit/db/test_l3_dvr_db.py

@@ -23,7 +23,6 @@ from neutron import manager
 from neutron.openstack.common import uuidutils
 from neutron.tests.unit import testlib_api
 
-
 _uuid = uuidutils.generate_uuid
 
 
@@ -214,6 +213,32 @@ class L3DvrTestCase(testlib_api.SqlTestCase):
             self.mixin.delete_floatingip(self.ctx, fip_id)
             return vf
 
+    def _disassociate_floatingip_setup(self, port_id=None, floatingip=None):
+        with contextlib.nested(
+            mock.patch.object(self.mixin, '_get_floatingip_on_port'),
+            mock.patch.object(self.mixin,
+                              'clear_unused_fip_agent_gw_port'),
+                              ) as (gf, vf):
+            gf.return_value = floatingip
+            self.mixin.disassociate_floatingips(
+                self.ctx, port_id, do_notify=False)
+            return vf
+
+    def test_disassociate_floatingip_with_vm_port(self):
+        port_id = '1234'
+        floatingip = {
+            'id': _uuid(),
+            'fixed_port_id': 1234,
+            'floating_network_id': _uuid()
+        }
+        mock_disassociate_fip = self._disassociate_floatingip_setup(
+            port_id=port_id, floatingip=floatingip)
+        self.assertTrue(mock_disassociate_fip.called)
+
+    def test_disassociate_floatingip_with_no_vm_port(self):
+        mock_disassociate_fip = self._disassociate_floatingip_setup()
+        self.assertFalse(mock_disassociate_fip.called)
+
     def test_delete_floatingip_without_internal_port(self):
         floatingip = {
             'id': _uuid(),