Fix segment-aware scheduling permissions error

Resolves a bug encountered when setting the Nova scheduler to
be aware of Neutron routed provider network segments, by using
'query_placement_for_routed_network_aggregates'.

Non-admin users attempting to access the 'segment_id' attribute
of a subnet caused a traceback, resulting in instance creation
failure.

This patch ensures the Neutron client is initialised with an
administrative context no matter what the requesting user's
permissions are.

Conflicts:
   nova/network/neutron.py
   nova/tests/unit/network/test_neutron.py
Both conflicts are due to I8058902df167239fa455396d3595a56bcf472b2b
We just picked the needed modifications then.

Change-Id: Ic0f25e4d2395560fc2b68f3b469e266ac59abaa2
Closes-Bug: #1970383
(cherry picked from commit ee32934f34)
(cherry picked from commit 60548e8042)

nova/network/neutron.py

@@ -3764,7 +3764,7 @@ class API:
         if not self._has_segment_extension(context):
             return []
 
-        client = get_client(context)
+        client = get_client(context, admin=True)
         try:
             # NOTE(sbauza): We can't use list_segments() directly because the
             # API is borked and returns both segments but also segmentation IDs
@@ -3794,7 +3794,7 @@ class API:
         if not self._has_segment_extension(context):
             return None
 
-        client = get_client(context)
+        client = get_client(context, admin=True)
         try:
             subnet = client.show_subnet(subnet_id)['subnet']
         except neutron_client_exc.NeutronClientException as e:

nova/tests/unit/network/test_neutron.py

@@ -7342,6 +7342,7 @@ class TestAPI(TestAPIBase):
             res = self.api.get_segment_ids_for_network(
                 self.context, uuids.network_id)
         self.assertEqual([uuids.segment_id], res)
+        mock_client.assert_called_once_with(self.context, admin=True)
         mocked_client.list_subnets.assert_called_once_with(
             network_id=uuids.network_id, fields='segment_id')
 
@@ -7357,6 +7358,7 @@ class TestAPI(TestAPIBase):
             res = self.api.get_segment_ids_for_network(
                 self.context, uuids.network_id)
         self.assertEqual([], res)
+        mock_client.assert_called_once_with(self.context, admin=True)
         mocked_client.list_subnets.assert_called_once_with(
             network_id=uuids.network_id, fields='segment_id')
 
@@ -7372,6 +7374,7 @@ class TestAPI(TestAPIBase):
             self.assertRaises(exception.InvalidRoutedNetworkConfiguration,
                               self.api.get_segment_ids_for_network,
                               self.context, uuids.network_id)
+            mock_client.assert_called_once_with(self.context, admin=True)
 
     def test_get_segment_id_for_subnet_no_segment_ext(self):
         with mock.patch.object(
@@ -7393,6 +7396,7 @@ class TestAPI(TestAPIBase):
             res = self.api.get_segment_id_for_subnet(
                 self.context, uuids.subnet_id)
         self.assertEqual(uuids.segment_id, res)
+        mock_client.assert_called_once_with(self.context, admin=True)
         mocked_client.show_subnet.assert_called_once_with(uuids.subnet_id)
 
     @mock.patch.object(neutronapi, 'get_client')
@@ -7407,6 +7411,7 @@ class TestAPI(TestAPIBase):
             self.assertIsNone(
                 self.api.get_segment_id_for_subnet(self.context,
                                                    uuids.subnet_id))
+            mock_client.assert_called_once_with(self.context, admin=True)
 
     @mock.patch.object(neutronapi, 'get_client')
     def test_get_segment_id_for_subnet_fails(self, mock_client):
@@ -7420,6 +7425,7 @@ class TestAPI(TestAPIBase):
             self.assertRaises(exception.InvalidRoutedNetworkConfiguration,
                               self.api.get_segment_id_for_subnet,
                               self.context, uuids.subnet_id)
+            mock_client.assert_called_once_with(self.context, admin=True)
 
     @mock.patch.object(neutronapi.LOG, 'debug')
     def test_get_port_pci_dev(self, mock_debug):

releasenotes/notes/bug-1970383-segment-scheduling-permissions-92ba907b10a9eb1c.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    `Bug #1970383 <https://bugs.launchpad.net/nova/+bug/1970383>`_: Fixes a
+    permissions error when using the
+    'query_placement_for_routed_network_aggregates' scheduler variable, which
+    caused a traceback on instance creation for non-admin users.