Add MTU attribute for OS::Neutron::Net

MTU(Maximum Transmission Unit), add a read-only attribute which hasn't been
supported by HEAT yet.

Change-Id: I4aaa6df15bae3995ab683f7e8f71f52b023e1c47
Closes-Bug: #1447806

heat/engine/resources/openstack/neutron/net.py

@@ -29,10 +29,10 @@ class Net(neutron.NeutronResource):
 
     ATTRIBUTES = (
         STATUS, NAME_ATTR, SUBNETS, ADMIN_STATE_UP_ATTR, TENANT_ID_ATTR, SHOW,
-        PORT_SECURITY_ENABLED_ATTR,
+        PORT_SECURITY_ENABLED_ATTR, MTU_ATTR,
     ) = (
         "status", "name", "subnets", "admin_state_up", "tenant_id", "show",
-        "port_security_enabled",
+        "port_security_enabled", "mtu",
     )
 
     properties_schema = {
@@ -118,6 +118,11 @@ class Net(neutron.NeutronResource):
             support_status=support.SupportStatus(version='5.0.0'),
             type=attributes.Schema.BOOLEAN
         ),
+        MTU_ATTR: attributes.Schema(
+            _("The maximum transmission unit size(in bytes) for the network."),
+            support_status=support.SupportStatus(version='5.0.0'),
+            type=attributes.Schema.INTEGER
+        ),
     }
 
     def handle_create(self):

heat/tests/neutron/test_neutron_net.py

@@ -112,7 +112,8 @@ class NeutronNetTest(common.HeatTestCase):
             "admin_state_up": True,
             "shared": True,
             "tenant_id": "c1210485b2424d48804aad5d39c61b8f",
-            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766"
+            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766",
+            "mtu": 0
         }})
 
         neutronclient.Client.list_dhcp_agent_hosting_networks(
@@ -133,7 +134,8 @@ class NeutronNetTest(common.HeatTestCase):
             "admin_state_up": True,
             "shared": True,
             "tenant_id": "c1210485b2424d48804aad5d39c61b8f",
-            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766"
+            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766",
+            "mtu": 0
         }})
 
         neutronclient.Client.show_network(
@@ -145,7 +147,8 @@ class NeutronNetTest(common.HeatTestCase):
             "admin_state_up": True,
             "shared": True,
             "tenant_id": "c1210485b2424d48804aad5d39c61b8f",
-            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766"
+            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766",
+            "mtu": 0
         }})
 
         neutronclient.Client.show_network(
@@ -161,7 +164,8 @@ class NeutronNetTest(common.HeatTestCase):
             "admin_state_up": True,
             "shared": True,
             "tenant_id": "c1210485b2424d48804aad5d39c61b8f",
-            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766"
+            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766",
+            "mtu": 0
         }})
 
         neutronclient.Client.show_network(
@@ -173,7 +177,8 @@ class NeutronNetTest(common.HeatTestCase):
             "admin_state_up": True,
             "shared": True,
             "tenant_id": "c1210485b2424d48804aad5d39c61b8f",
-            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766"
+            "id": "fc68ea2c-b60b-4b4f-bd82-94ec81110766",
+            "mtu": 0
         }})
 
         # Update script
@@ -254,6 +259,7 @@ class NeutronNetTest(common.HeatTestCase):
 
         self.assertIsNone(rsrc.FnGetAtt('status'))
         self.assertEqual('ACTIVE', rsrc.FnGetAtt('status'))
+        self.assertEqual(0, rsrc.FnGetAtt('mtu'))
         self.assertRaises(
             exception.InvalidTemplateAttribute, rsrc.FnGetAtt, 'Foo')
         prop_diff = {