Introduce ovn_nb_global config section

The patch introduces a new config section ovn_nb_global. All options
from this section are passed to OVN Northbound NB_Global table to
configure Northbound OVN.

First option is ignore_lsp_down to override OVN default configuration.
This option was changed in OVN to `true` [1] but for Neutron it's better
to not answer ARP packets when ports are in DOWN status.

[1] https://www.mail-archive.com/ovs-dev@openvswitch.org/msg60064.html

Change-Id: I478249cae483fd2540a7ff3ab714e3d9c3e13f17
Signed-off-by: Jakub Libosvar <libosvar@redhat.com>

neutron/conf/plugins/ml2/drivers/ovn/ovn_conf.py

@@ -28,6 +28,8 @@ VLOG_LEVELS = {'CRITICAL': vlog.CRITICAL, 'ERROR': vlog.ERROR, 'WARNING':
 
 MIGRATE_MODE = "migrate"
 
+OVN_NB_GLOBAL = "ovn_nb_global"
+
 ovn_opts = [
     cfg.StrOpt('ovn_nb_connection',
                default='tcp:127.0.0.1:6641',
@@ -226,16 +228,33 @@ ovn_opts = [
                        'newer.')),
 ]
 
+nb_global_opts = [
+    cfg.BoolOpt('ignore_lsp_down',
+                default=False,
+                help=_('If set to False, ARP/ND reply flows for logical '
+                       'switch ports will be installed only if the port is '
+                       'UP, i.e. claimed by a Chassis. If set to True, these '
+                       'flows are installed regardless of the status of the '
+                       'port, which can result in a situation that an ARP '
+                       'request to an IP is resolved even before the relevant '
+                       'VM/container is running. For environments where this '
+                       'is not an issue, setting it to True can reduce '
+                       'the load and latency of the control plane. '
+                       'The default value is False.')),
+]
+
 
 def register_opts():
     cfg.CONF.register_opts(ovn_opts, group='ovn')
     ovs_conf.register_ovs_agent_opts()
+    cfg.CONF.register_opts(nb_global_opts, group=OVN_NB_GLOBAL)
 
 
 def list_opts():
     return [
         ('ovn', ovn_opts),
-        ('ovs', ovs_conf.OPTS)
+        ('ovs', ovs_conf.OPTS),
+        (OVN_NB_GLOBAL, nb_global_opts),
     ]
 
 

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

@@ -623,6 +623,10 @@ class API(api.API, metaclass=abc.ABCMeta):
         :returns: The NAT rule row or Load_Balancer row or None
         """
 
+    @abc.abstractmethod
+    def set_nb_global_options(self, key, value):
+        """Set NB_Global options configuration"""
+
 
 class SbAPI(api.API, metaclass=abc.ABCMeta):
 

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

@@ -848,6 +848,10 @@ class OvsdbNbOvnIdl(nb_impl_idl.OvnNbApiIdlImpl, Backend):
     def update_lb_external_ids(self, lb_name, values, if_exists=True):
         return cmd.UpdateLbExternalIds(self, lb_name, values, if_exists)
 
+    def set_nb_global_options(self, **options):
+        LOG.debug("Setting NB_Global options: %s", options)
+        return self.db_set("NB_Global", ".", options=options)
+
 
 class OvsdbSbOvnIdl(sb_impl_idl.OvnSbApiIdlImpl, Backend):
     def __init__(self, connection):

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

@@ -1079,6 +1079,22 @@ class DBInconsistenciesPeriodics(SchemaAwarePeriodicsBase):
         context = n_context.get_admin_context()
         hash_ring_db.cleanup_old_nodes(context, days=5)
 
+    @has_lock_periodic(spacing=86400, run_immediately=True)
+    def configure_nb_global(self):
+        """Configure Northbound OVN NB_Global options
+
+        The method goes over all config options from ovn_nb_global config
+        sections and configures same key/value pairs to the NB_Global:options
+        column.
+        """
+        options = {opt.name: str(cfg.CONF.ovn_nb_global.get(opt.name)).lower()
+                   for opt in ovn_conf.nb_global_opts}
+
+        self._nb_idl.set_nb_global_options(**options).execute(
+            check_error=True)
+
+        raise periodics.NeverAgain()
+
 
 class HashRingHealthCheckPeriodics(object):
 

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

@@ -1032,6 +1032,39 @@ class TestMaintenance(_TestMaintenanceHelper):
         # "Chassis_Private" register was missing.
         self.assertEqual(2, len(chassis_result))
 
+    def test_configure_nb_global(self):
+        def options_intersect(options1, options2):
+            return bool(set(
+                new_nb_global_options.keys()).intersection(nb_options.keys()))
+
+        new_nb_global_options = {
+            'foo': 'bar',
+            'baz': 'qux',
+        }
+
+        cfg_nb_global_options = [
+            ovn_config.cfg.StrOpt(key) for key in new_nb_global_options
+        ]
+
+        def get_opt(key):
+            return new_nb_global_options[key]
+
+        nb_options = self.nb_api.db_get('NB_Global', '.', 'options').execute(
+            check_error=True, log_errors=True)
+        self.assertFalse(options_intersect(new_nb_global_options, nb_options))
+
+        with mock.patch.object(
+                ovn_config, 'nb_global_opts', cfg_nb_global_options), \
+                mock.patch.object(
+                    ovn_config.cfg.CONF.ovn_nb_global, 'get',
+                    side_effect=get_opt):
+            self.assertRaises(periodics.NeverAgain,
+                              self.maint.configure_nb_global)
+
+        nb_options = self.nb_api.db_get('NB_Global', '.', 'options').execute(
+            check_error=True, log_errors=True)
+        self.assertTrue(options_intersect(new_nb_global_options, nb_options))
+
 
 class TestLogMaintenance(_TestMaintenanceHelper,
                          test_log_driver.LogApiTestCaseBase):

releasenotes/notes/OVN-not-responding-to-ARP-for-DOWN-ports-3620173f00089539.yaml

@@ -0,0 +1,11 @@
+---
+upgrade:
+  - |
+    Starting with OVN version v21.12.0, OVN replies to ARP requests for ports
+    that are in a DOWN status. It does not reply in versions older than
+    v21.12.0.  In order to keep the same behavior in Neutron, the default OVN
+    behavior is overridden by Neutron and Neutron ports will no longer reply to
+    ARP packets if the ports are in a DOWN state. If it is required to reply to
+    ARP for such ports, the config option ``ignore_lsp_down`` from
+    ``[ovn_nb_global]`` section can be set to True in the Neutron config. It is
+    set to False by default.