[OVN] Explicitly define the fixed IPs for the metadata port

The metadata port fixed IPs depend on the subnets "enabled_dhcp" flag.
If the subnet has this flag disabled, the metadata port doesn't receive
an IP on the subnet CIDR.

The method ``create_metadata_port`` should explicitly define what fixed
IPs should request the metadata port during the creating depending on
the subnets "enabled_dhcp" flag.

Closes-Bug: #2011724
Change-Id: If362fab20ac03f8b62471b60c031f9349171ce93
(cherry picked from commit 9704dca84e)

neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py

@@ -2395,17 +2395,26 @@ class OVNClient(object):
                     return fixed_ip['ip_address']
 
     def create_metadata_port(self, context, network):
-        if ovn_conf.is_ovn_metadata_enabled():
-            metadata_port = self._find_metadata_port(context, network['id'])
-            if not metadata_port:
-                # Create a neutron port for DHCP/metadata services
-                port = {'port':
-                        {'network_id': network['id'],
+        if not ovn_conf.is_ovn_metadata_enabled():
+            return
+
+        if self._find_metadata_port(context, network['id']):
+            return
+
+        # Create a neutron port for DHCP/metadata services
+        filters = {'network_id': [network['id']]}
+        subnets = self._plugin.get_subnets(context, filters=filters)
+        fixed_ips = [{'subnet_id': s['id']}
+                     for s in subnets if s['enable_dhcp']]
+        port = {'port': {'network_id': network['id'],
                          'tenant_id': network['project_id'],
                          'device_owner': const.DEVICE_OWNER_DISTRIBUTED,
-                         'device_id': 'ovnmeta-%s' % network['id']}}
-                # TODO(boden): rehome create_port into neutron-lib
-                p_utils.create_port(self._plugin, context, port)
+                         'device_id': 'ovnmeta-%s' % network['id'],
+                         'fixed_ips': fixed_ips,
+                         }
+                }
+        # TODO(boden): rehome create_port into neutron-lib
+        p_utils.create_port(self._plugin, context, port)
 
     def update_metadata_port(self, context, network_id, subnet=None):
         """Update metadata port.

neutron/tests/functional/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_ovn_client.py

@@ -0,0 +1,68 @@
+# Copyright 2023 Red Hat, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from neutron_lib import constants
+
+from neutron.conf.plugins.ml2.drivers.ovn import ovn_conf as ovn_config
+from neutron.tests.functional import base
+
+
+class TestOVNClient(base.TestOVNFunctionalBase):
+
+    def test_create_metadata_port(self):
+        def check_metadata_port(enable_dhcp):
+            ports = self.plugin.get_ports(
+                self.context, filters={'network_id': [network['id']]})
+            self.assertEqual(1, len(ports))
+            if enable_dhcp:
+                self.assertEqual(1, len(ports[0]['fixed_ips']))
+            else:
+                self.assertEqual(0, len(ports[0]['fixed_ips']))
+            return ports
+
+        ovn_config.cfg.CONF.set_override('ovn_metadata_enabled', True,
+                                         group='ovn')
+        ovn_client = self.mech_driver._ovn_client
+        for enable_dhcp in (True, False):
+            network_args = {'tenant_id': 'project_1',
+                            'name': 'test_net_1',
+                            'admin_state_up': True,
+                            'shared': False,
+                            'status': constants.NET_STATUS_ACTIVE}
+            network = self.plugin.create_network(self.context,
+                                                 {'network': network_args})
+            subnet_args = {'tenant_id': 'project_1',
+                           'name': 'test_snet_1',
+                           'network_id': network['id'],
+                           'ip_version': constants.IP_VERSION_4,
+                           'cidr': '10.210.10.0/28',
+                           'enable_dhcp': enable_dhcp,
+                           'gateway_ip': constants.ATTR_NOT_SPECIFIED,
+                           'allocation_pools': constants.ATTR_NOT_SPECIFIED,
+                           'dns_nameservers': constants.ATTR_NOT_SPECIFIED,
+                           'host_routes': constants.ATTR_NOT_SPECIFIED}
+            self.plugin.create_subnet(self.context, {'subnet': subnet_args})
+
+            # The metadata port has been created during the network creation.
+            ports = check_metadata_port(enable_dhcp)
+
+            # Force the deletion and creation the metadata port.
+            self.plugin.delete_port(self.context, ports[0]['id'])
+            ovn_client.create_metadata_port(self.context, network)
+            check_metadata_port(enable_dhcp)
+
+            # Call again the "create_metadata_port" method as is idempotent
+            # because it checks first if the metadata port exists.
+            ovn_client.create_metadata_port(self.context, network)
+            check_metadata_port(enable_dhcp)