[OVN] Method to retrieve the LRP chassis list

Added a new method in ``OvsdbNbOvnIdl`` to retrieve the
gateway ``Logical_Router_Port`` chassis list with priorities, stored in
the ``HA_Chassis_Group`` register associated to the router.

Partial-Bug: #2092271
Change-Id: I6b2bc7a3e80a906f146da3645c530d175f31a8dd

Author: ralonsoh

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

@@ -520,6 +520,30 @@ def _get_logical_router_port_gateway_chassis(self, lrp, priorities=None):
         # make sure that chassis are sorted by priority
         return sorted(chassis, reverse=True, key=lambda x: x[1])
 
+    @staticmethod
+    def _get_logical_router_port_ha_chassis_group(lrp, priorities=None):
+        """Get the list of chassis hosting this gateway port.
+
+        @param   lrp: logical router port
+        @type    lrp: Logical_Router_Port row
+        @param   priorities: a list of gateway chassis priorities to search for
+        @type    priorities: list of int
+        @return: List of tuples (chassis_name, priority) sorted by priority. If
+                 ``priorities`` is set then only chassis matching of these
+                 priorities are returned.
+        """
+        chassis = []
+        hcg = getattr(lrp, 'ha_chassis_group', None)
+        if not hcg:
+            return chassis
+
+        for hc in hcg[0].ha_chassis:
+            if priorities is not None and hc.priority not in priorities:
+                continue
+            chassis.append((hc.chassis_name, hc.priority))
+        # Make sure that chassis are sorted by priority (highest prio first)
+        return sorted(chassis, reverse=True, key=lambda x: x[1])
+
     def get_all_chassis_gateway_bindings(self,
                                          chassis_candidate_list=None,
                                          priorities=None):

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

@@ -19,6 +19,7 @@
 
 import netaddr
 from neutron_lib import constants
+from neutron_lib.utils import net as net_utils
 from oslo_utils import netutils
 from oslo_utils import uuidutils
 from ovsdbapp.backend.ovs_idl import connection
@@ -779,6 +780,45 @@ def test_ha_chassis_group_with_hc_add_two_hcg(self):
         self._check_hcg(hcg1, hcg_name1, chassis_priority1)
         self._check_hcg(hcg2, hcg_name2, chassis_priority2)
 
+    def _add_lrp_with_gw(self, chassis_priority=None, is_gw=True):
+        if is_gw:
+            hcg_name = uuidutils.generate_uuid()
+            hcg = self.nbapi.ha_chassis_group_with_hc_add(
+                hcg_name, chassis_priority).execute(check_error=True)
+            kwargs = {'ha_chassis_group': hcg.uuid}
+        else:
+            hcg = None
+            kwargs = {}
+
+        mac = next(net_utils.random_mac_generator(['ca', 'fe', 'ca', 'fe']))
+        networks = ['192.0.2.0/24']
+        lr = self.nbapi.lr_add(uuidutils.generate_uuid()).execute(
+            check_error=True)
+
+        lrp = self.nbapi.lrp_add(
+            lr.uuid, uuidutils.generate_uuid(), mac, networks,
+            **kwargs).execute(check_error=True)
+        return lr, lrp, hcg
+
+    def test__get_logical_router_port_ha_chassis_group(self):
+        chassis_priority = {'ch1': 1, 'ch2': 2, 'ch3': 3, 'ch4': 4}
+        lr, lrp, hcg = self._add_lrp_with_gw(chassis_priority)
+        cprio_res = self.nbapi._get_logical_router_port_ha_chassis_group(lrp)
+        self.assertEqual([('ch4', 4), ('ch3', 3), ('ch2', 2), ('ch1', 1)],
+                         cprio_res)
+
+    def test__get_logical_router_port_ha_chassis_group_with_priorities(self):
+        chassis_priority = {'ch1': 1, 'ch2': 2, 'ch3': 3, 'ch4': 4}
+        lr, lrp, hcg = self._add_lrp_with_gw(chassis_priority)
+        cprio_res = self.nbapi._get_logical_router_port_ha_chassis_group(
+            lrp, priorities=(1, 3, 4))
+        self.assertEqual([('ch4', 4), ('ch3', 3), ('ch1', 1)], cprio_res)
+
+    def test__get_logical_router_port_ha_chassis_group_no_hcg(self):
+        lr, lrp, hcg = self._add_lrp_with_gw(is_gw=False)
+        cprio_res = self.nbapi._get_logical_router_port_ha_chassis_group(lrp)
+        self.assertEqual([], cprio_res)
+
 
 class TestIgnoreConnectionTimeout(BaseOvnIdlTest):
     @classmethod