Add function cidr_to_netmask to utils

cidr_to_netmask util function to returns netmask
from cidr subnet notation.

Change-Id: Id76d0aa698bbd844376075dfc2ff0d9add67cf83
Closes-Bug: #1273663

manila/tests/test_utils.py

@@ -729,3 +729,53 @@ class SSHPoolTestCase(test.TestCase):
             third_id = ssh.id
 
         self.assertNotEqual(first_id, third_id)
+
+
+class CidrToNetmaskTestCase(test.TestCase):
+    """Unit test for cidr to netmask."""
+
+    def test_cidr_to_netmask_01(self):
+        cidr = '10.0.0.0/0'
+        expected_netmask = '0.0.0.0'
+        result = utils.cidr_to_netmask(cidr)
+        self.assertEqual(expected_netmask, result)
+
+    def test_cidr_to_netmask_02(self):
+        cidr = '10.0.0.0/24'
+        expected_netmask = '255.255.255.0'
+        result = utils.cidr_to_netmask(cidr)
+        self.assertEqual(expected_netmask, result)
+
+    def test_cidr_to_netmask_03(self):
+        cidr = '10.0.0.0/5'
+        expected_netmask = '248.0.0.0'
+        result = utils.cidr_to_netmask(cidr)
+        self.assertEqual(expected_netmask, result)
+
+    def test_cidr_to_netmask_04(self):
+        cidr = '10.0.0.0/32'
+        expected_netmask = '255.255.255.255'
+        result = utils.cidr_to_netmask(cidr)
+        self.assertEqual(expected_netmask, result)
+
+    def test_cidr_to_netmask_05(self):
+        cidr = '10.0.0.1'
+        expected_netmask = '255.255.255.255'
+        result = utils.cidr_to_netmask(cidr)
+        self.assertEqual(expected_netmask, result)
+
+    def test_cidr_to_netmask_invalid_01(self):
+        cidr = '10.0.0.0/33'
+        self.assertRaises(exception.InvalidInput, utils.cidr_to_netmask, cidr)
+
+    def test_cidr_to_netmask_invalid_02(self):
+        cidr = ''
+        self.assertRaises(exception.InvalidInput, utils.cidr_to_netmask, cidr)
+
+    def test_cidr_to_netmask_invalid_03(self):
+        cidr = '10.0.0.0/33'
+        self.assertRaises(exception.InvalidInput, utils.cidr_to_netmask, cidr)
+
+    def test_cidr_to_netmask_invalid_04(self):
+        cidr = '10.0.0.555/33'
+        self.assertRaises(exception.InvalidInput, utils.cidr_to_netmask, cidr)

manila/utils.py

@@ -25,6 +25,7 @@ import errno
 import functools
 import hashlib
 import inspect
+import netaddr
 import os
 import paramiko
 import pyclbr
@@ -1214,14 +1215,9 @@ def to_bytes(text, default=0):
 
 
 def cidr_to_netmask(cidr):
-    """
-    Convert cidr notation to the netmask string
-
-    :param cidr: integer which represents cidr notation
-    :rtype: string
-    """
-    cidr = int(cidr)
-    bits = 0
-    for i in xrange(32 - cidr, 32):
-        bits |= (1 << i)
-    return socket.inet_ntoa(struct.pack('>I', bits))
+    """Convert cidr to netmask."""
+    try:
+        network = netaddr.IPNetwork(cidr)
+        return str(network.netmask)
+    except netaddr.AddrFormatError:
+        raise exception.InvalidInput(_("Invalid cidr supplied %s") % cidr)