Fix update of trunk subports during live migration

During the live migration trunk subports where updated only based
on the "host_id" field. But when rpc message to update subports
is send trunk's port is still bound to the old host and has
"migrating_to" field in binding:profile set to the new host.
Because of that binding:host_id for the subport's port wasn't updated
proberly and port was set to DOWN on the new host.
That could even cause connectivity break if L2population is used in the
cloud.

This patch fixes that by updating subport's binding:host_id field based
on the migrating_to field if that is available and not empty.

Closes-Bug: #1914747
Change-Id: I98e55242d381ada642ca0729e9aefdea7628c945
(cherry picked from commit e05101c8ac)

neutron/services/trunk/rpc/server.py

@@ -128,6 +128,12 @@ class TrunkSkeleton(object):
         trunk_port_id = trunk.port_id
         trunk_port = self.core_plugin.get_port(context, trunk_port_id)
         trunk_host = trunk_port.get(portbindings.HOST_ID)
+        migrating_to_host = trunk_port.get(
+            portbindings.PROFILE, {}).get('migrating_to')
+        if migrating_to_host and trunk_host != migrating_to_host:
+            # Trunk is migrating now, so lets update host of the subports
+            # to the new host already
+            trunk_host = migrating_to_host
 
         # NOTE(status_police) Set the trunk in BUILD state before
         # processing subport bindings. The trunk will stay in BUILD

neutron/tests/unit/services/trunk/rpc/test_server.py

@@ -103,6 +103,43 @@ class TrunkSkeletonTest(test_plugin.Ml2PluginV2TestCase):
         for port in updated_subports[trunk['id']]:
             self.assertEqual('trunk_host_id', port[portbindings.HOST_ID])
 
+    def test_update_subport_bindings_during_migration(self):
+        with self.port() as _parent_port:
+            parent_port = _parent_port
+        trunk = self._create_test_trunk(parent_port)
+        subports = []
+        for vid in range(0, 3):
+            with self.port() as new_port:
+                obj = trunk_obj.SubPort(
+                    context=self.context,
+                    trunk_id=trunk['id'],
+                    port_id=new_port['port']['id'],
+                    segmentation_type='vlan',
+                    segmentation_id=vid)
+                subports.append(obj)
+
+        expected_calls = [
+            mock.call(
+                mock.ANY, subport['port_id'],
+                {'port': {portbindings.HOST_ID: 'new_trunk_host_id',
+                          'device_owner': constants.TRUNK_SUBPORT_OWNER}})
+            for subport in subports]
+
+        test_obj = server.TrunkSkeleton()
+        test_obj._trunk_plugin = self.trunk_plugin
+        test_obj._core_plugin = self.core_plugin
+        port_data = {
+            portbindings.HOST_ID: 'trunk_host_id',
+            portbindings.PROFILE: {'migrating_to': 'new_trunk_host_id'}}
+        with mock.patch.object(
+                self.core_plugin, "get_port",
+                return_value=port_data), \
+            mock.patch.object(
+                test_obj, "_safe_update_trunk"):
+            test_obj.update_subport_bindings(self.context, subports=subports)
+        for expected_call in expected_calls:
+            self.assertIn(expected_call, self.mock_update_port.mock_calls)
+
     def test__handle_port_binding_binding_error(self):
         with self.port() as _trunk_port:
             trunk = self._create_test_trunk(_trunk_port)