Allow non-admins to define "external" extra-routes

Currently non-admin users can create extra-routes when the nexthop is on
router-interfaces subnets but not on external-network subnet. Indeed
user permissions are used to get router ports in order to validate
nexthops BUT non-admin users don't "see" router port on its external
network.

This change uses an elevated context instead of user context to enable
non-admins to create "external" extra-routes.

APIImpact
Closes-Bug: #1538767
Change-Id: I08b1d8586a4cd241a3589e8cb7151b77ab679124

neutron/db/extraroute_db.py

@@ -104,7 +104,7 @@ class ExtraRoute_dbonly_mixin(l3_db.L3_NAT_dbonly_mixin):
                 quota=cfg.CONF.max_routes)
 
         filters = {'device_id': [router_id]}
-        ports = self._core_plugin.get_ports(context, filters)
+        ports = self._core_plugin.get_ports(context.elevated(), filters)
         cidrs = []
         ips = []
         for port in ports:

neutron/tests/unit/extensions/test_extraroute.py

@@ -81,6 +81,16 @@ class ExtraRouteDBTestCaseBase(object):
                     self._routes_update_cleanup(p['port']['id'],
                                                 None, r['router']['id'], [])
 
+    def test_route_update_with_external_route(self):
+        routes = [{'destination': '135.207.0.0/16', 'nexthop': '10.0.1.3'}]
+        with self.subnet(cidr='10.0.1.0/24') as ext_subnet:
+            self._set_net_external(ext_subnet['subnet']['network_id'])
+            ext_info = {'network_id': ext_subnet['subnet']['network_id']}
+            with self.router(external_gateway_info=ext_info) as r:
+                body = self._routes_update_prepare(
+                    r['router']['id'], None, None, routes, skip_add=True)
+                self.assertEqual(routes, body['router']['routes'])
+
     def test_route_clear_routes_with_None(self):
         routes = [{'destination': '135.207.0.0/16',
                    'nexthop': '10.0.1.3'},

releasenotes/notes/allow-non-admins-to-define-external-extra-routes-0d541fc356a5c546.yaml

@@ -0,0 +1,3 @@
+---
+features:
+  - Allow non-admin users to define "external" extra-routes.