Prevent the user from creating a single IP address sized network

If the user doesn't specify a mask when creating a subnet, the mask
defaults to /32 (IPv4) or /128 (IPv6) making it impossible to allocate
an IP address when later launching an instance. This patch prevents
creating a subnet with such a small mask.

Fixes bug #1102504

Change-Id: I4962e0a416b8ec9aca013e41783994f65c22a989

openstack_dashboard/dashboards/project/networks/tests.py

@@ -364,6 +364,21 @@ def test_network_create_post_with_subnet_nocidr(self):
         self.assertContains(res, escape('Specify "Network Address" or '
                                         'clear "Create Subnet" checkbox.'))
 
+    def test_network_create_post_with_subnet_cidr_without_mask(self):
+        network = self.networks.first()
+        subnet = self.subnets.first()
+
+        form_data = {'net_name': network.name,
+                     'admin_state': network.admin_state_up,
+                     'with_subnet': True}
+        form_data.update(form_data_subnet(subnet, cidr='10.0.0.0',
+                                          allocation_pools=[]))
+        url = reverse('horizon:project:networks:create')
+        res = self.client.post(url, form_data)
+
+        expected_msg = "The subnet in the Network Address is too small (/32)."
+        self.assertContains(res, expected_msg)
+
     def test_network_create_post_with_subnet_cidr_inconsistent(self):
         network = self.networks.first()
         subnet = self.subnets.first()

openstack_dashboard/dashboards/project/networks/workflows.py

@@ -104,9 +104,15 @@ def _check_subnet_data(self, cleaned_data, is_create=True):
                     'clear "Create Subnet" checkbox.')
             raise forms.ValidationError(msg)
         if cidr:
-            if netaddr.IPNetwork(cidr).version is not ip_version:
+            subnet = netaddr.IPNetwork(cidr)
+            if subnet.version != ip_version:
                 msg = _('Network Address and IP version are inconsistent.')
                 raise forms.ValidationError(msg)
+            if (ip_version == 4 and subnet.prefixlen == 32) or \
+                    (ip_version == 6 and subnet.prefixlen == 128):
+                msg = _("The subnet in the Network Address is too small (/%s)."
+                        % subnet.prefixlen)
+                raise forms.ValidationError(msg)
         if not no_gateway and gateway_ip:
             if netaddr.IPAddress(gateway_ip).version is not ip_version:
                 msg = _('Gateway IP and IP version are inconsistent.')