Fix Windows IPDevice.device_has_ip racefulness

get_device_by_ip gets all devices on the system,
then iterates on them and checks if the given IP
is configured on each device. Ths method does
not account for devices that are deleted after
the devices are listed.

Change-Id: Ibada2b4ed60f02539e00021cdc7b3ddb97f1840c
Closes-Bug: #1567608

neutron/agent/windows/ip_lib.py

@@ -48,10 +48,14 @@ class IPDevice(object):
         self.device_name = name
 
     def device_has_ip(self, ip):
+        try:
+            device_addresses = netifaces.ifaddresses(self.device_name)
+        except ValueError:  # The device does not exist on the system
+            return False
+
         try:
             addresses = [ip_addr['addr'] for ip_addr in
-                netifaces.ifaddresses(self.device_name).get(
-                    netifaces.AF_INET, [])]
+                         device_addresses.get(netifaces.AF_INET, [])]
             return ip in addresses
         except OSError:
             LOG.error(_LE("Failed to get ip addresses for interface: %s."),

neutron/tests/functional/agent/windows/test_ip_lib.py

@@ -28,3 +28,7 @@ class IpLibTestCase(base.BaseTestCase):
     def test_ipwrapper_get_device_by_ip(self):
         ip_dev = ip_lib.IPWrapper().get_device_by_ip(TEST_IP)
         self.assertEqual('lo', ip_dev.device_name)
+
+    def test_device_has_ip(self):
+        not_a_device = ip_lib.IPDevice('#!#._not_a_device_bleargh!!@@@')
+        self.assertFalse(not_a_device.device_has_ip(TEST_IP))