Check vif exists before releasing ip

 * adds test to make sure code doesn't raise
 * fixes bug 968457

Change-Id: I7110cb18a45fb955769247a9a0c5fb721ab3935a

nova/network/manager.py

@@ -1223,7 +1223,8 @@ def deallocate_fixed_ip(self, context, address, **kwargs):
                     context, instance_id, network['id'])
             # NOTE(vish): This forces a packet so that the release_fixed_ip
             #             callback will get called by nova-dhcpbridge.
-            self.driver.release_dhcp(dev, address, vif['address'])
+            if vif:
+                self.driver.release_dhcp(dev, address, vif['address'])
 
     def lease_fixed_ip(self, context, address):
         """Called by dhcp-bridge when ip is leased."""

nova/tests/network/test_manager.py

@@ -873,6 +873,32 @@ def network_get(_context, network_id):
         db.floating_ip_destroy(context1.elevated(), float_addr)
         db.fixed_ip_disassociate(context1.elevated(), fix_addr)
 
+    def test_deallocate_fixed_no_vif(self):
+        """Verify that deallocate doesn't raise when no vif is returned.
+
+        Ensures https://bugs.launchpad.net/nova/+bug/968457 doesn't return"""
+
+        def network_get(_context, network_id):
+            return networks[network_id]
+
+        self.stubs.Set(db, 'network_get', network_get)
+
+        def vif_get(_context, _instance_id, _network_id):
+            return None
+
+        self.stubs.Set(db, 'virtual_interface_get_by_instance_and_network',
+                       vif_get)
+        context1 = context.RequestContext('user', 'project1')
+
+        instance = db.instance_create(context1,
+                {'project_id': 'project1'})
+
+        fix_addr = db.fixed_ip_associate_pool(context1.elevated(),
+                1, instance['id'])
+
+        self.flags(force_dhcp_release=True)
+        self.network.deallocate_fixed_ip(context1, fix_addr, 'fake')
+
 
 class CommonNetworkTestCase(test.TestCase):