port-hint-ovs-tx-steering: shim extension

and a ML2 extension that does nothing, just loads the API extension.
All the real implementation is in the agent-side change.

To enable this:

* ml2_conf.ini:
  [ml2]
  extension_drivers += port_hint_ovs_tx_steering

Change-Id: I572072b3817484129a60ef68adf74ffd52b9eab8
Closes-Bug: #1990842
Related-Change (spec): https://review.opendev.org/c/openstack/neutron-specs/+/862133
Related-Change (n-lib api-def): https://review.opendev.org/c/openstack/neutron-lib/+/873112

neutron/extensions/port_hint_ovs_tx_steering.py

@@ -0,0 +1,21 @@
+# Copyright 2023 Ericsson Software Technology
+#
+# 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.api.definitions import port_hint_ovs_tx_steering \
+    as phint_txs_def
+from neutron_lib.api import extensions as api_extensions
+
+
+class Port_hint_ovs_tx_steering(api_extensions.APIExtensionDescriptor):
+    api_definition = phint_txs_def

neutron/plugins/ml2/extensions/port_hint_ovs_tx_steering.py

@@ -0,0 +1,35 @@
+# Copyright 2023 Ericsson Software Technology
+#
+# 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.plugins.ml2 import api
+from oslo_log import log as logging
+
+from neutron_lib.api.definitions import port_hint_ovs_tx_steering \
+    as phint_txs_def
+
+
+LOG = logging.getLogger(__name__)
+
+
+class PortHintOvsTxSteeringExtensionDriver(api.ExtensionDriver):
+
+    _supported_extension_alias = phint_txs_def.ALIAS
+
+    def initialize(self):
+        LOG.info(
+            'PortHintOvsTxSteeringExtensionDriver initialization complete')
+
+    @property
+    def extension_alias(self):
+        return self._supported_extension_alias

releasenotes/notes/port-hint-ovs-tx-steering-277a411933ed372b.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    The first hint using the new ``hints`` port attribute is the
+    ``ovs-tx-steering`` hint. The availability of this is marked
+    by the extension: ``port-hint-ovs-tx-steering``.  This hint is
+    specific to the ``openvswitch`` mechanism driver.  It enables
+    the control of Open vSwitch's Userspace Tx packet steering
+    feature. For details about the Open vSwitch feature please see:
+    https://docs.openvswitch.org/en/latest/topics/userspace-tx-steering/
+    The valid values for the ``hints`` attribute introduced by the 2nd
+    extension are:
+    ``{"openvswitch": {"other_config": {"tx-steering": "hash|thread"}}}``

releasenotes/notes/port-hints-d465bb2fa144537c.yaml

@@ -0,0 +1,12 @@
+---
+features:
+  - |
+    Ports now have a ``hints`` attribute, in which backend specific
+    tuning options can be passed to Neutron. The availability of the
+    ``hints`` attribute is signaled by the ``port-hints`` extension.
+    The ``hints`` attribute is admin-only by default. Its value is a
+    dict, keyed by mechanism driver aliases. The possible values are
+    defined by the mechanism drivers. An admin user can ask for a
+    hint in a port create or update request. As the name suggests a
+    hint is not a demand - Neutron applies the hint when it can, but
+    it is free to ignore it, when it can't.

setup.cfg

@@ -126,6 +126,7 @@ neutron.ml2.extension_drivers =
     subnet_dns_publish_fixed_ip = neutron.plugins.ml2.extensions.subnet_dns_publish_fixed_ip:SubnetDNSPublishFixedIPExtensionDriver
     dns_domain_keywords = neutron.plugins.ml2.extensions.dns_domain_keywords:DnsDomainKeywordsExtensionDriver
     port_hints = neutron.plugins.ml2.extensions.port_hints:PortHintsExtensionDriver
+    port_hint_ovs_tx_steering = neutron.plugins.ml2.extensions.port_hint_ovs_tx_steering:PortHintOvsTxSteeringExtensionDriver
 neutron.ipam_drivers =
     fake = neutron.tests.unit.ipam.fake_driver:FakeDriver
     internal = neutron.ipam.drivers.neutrondb_ipam.driver:NeutronDbPool