Merge "net_utils: Add a random mac generator"

neutron_lib/tests/unit/utils/test_net.py

@@ -11,6 +11,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import itertools
 import random
 import socket
 
@@ -46,6 +47,37 @@ class TestGetRandomMac(base.BaseTestCase):
         mock_rnd.assert_called_with(8)
 
 
+class TestRandomMacGenerator(base.BaseTestCase):
+
+    def test_all_macs_generated(self):
+        mac = ['aa', 'bb', 'cc', 'dd', 'ee', 'ff']
+        generator = itertools.islice(net.random_mac_generator(mac), 70000)
+        self.assertEqual(2**16, len(list(generator)))
+
+    @mock.patch.object(random, 'getrandbits', return_value=0xa2)
+    def test_first_generated_mac(self, mock_rnd):
+        mac = ['aa', 'bb', 'cc', '00', 'ee', 'ff']
+        generator = itertools.islice(net.random_mac_generator(mac), 1)
+        self.assertEqual(['aa:bb:cc:a2:a2:a2'], list(generator))
+        mock_rnd.assert_called_with(8)
+
+    @mock.patch.object(random, 'getrandbits', return_value=0xa2)
+    def test_respected_early_zeroes_generated_mac(self, mock_rnd):
+        mac1 = ['00', 'bb', 'cc', '00', 'ee', 'ff']
+
+        generator = itertools.islice(net.random_mac_generator(mac1), 1)
+        self.assertEqual(['00:bb:cc:a2:a2:a2'], list(generator))
+
+        mac2 = ['aa', '00', 'cc', '00', 'ee', 'ff']
+        generator = itertools.islice(net.random_mac_generator(mac2), 1)
+        self.assertEqual(['aa:00:cc:a2:a2:a2'], list(generator))
+
+        mac3 = ['aa', 'bb', '00', '00', 'ee', 'ff']
+        generator = itertools.islice(net.random_mac_generator(mac3), 1)
+        self.assertEqual(['aa:bb:00:a2:a2:a2'], list(generator))
+        mock_rnd.assert_called_with(8)
+
+
 class TestPortDeviceOwner(base.BaseTestCase):
 
     def test_is_port_trusted(self):

neutron_lib/utils/net.py

@@ -43,6 +43,36 @@ def get_random_mac(base_mac):
     return ':'.join(["%02x" % x for x in mac])
 
 
+def random_mac_generator(base_mac):
+    """Generates random mac addresses from a specified base format.
+
+    The first 3 octets of each MAC address will remain unchanged. If the 4th
+    octet is not 00, it will also be used. The others will be randomly
+    generated.
+
+    :param base_mac: Base mac address represented by an array of 6 strings.
+    :returns: A mac address string generator.
+    """
+    fixed = list(base_mac[0:3])
+    to_generate = 3
+    if base_mac[3] != '00':
+        fixed += base_mac[3]
+        to_generate = 2
+    beginning = ':'.join(fixed) + ':'
+
+    form = '{}' + ':'.join('{:02x}' for _ in range(to_generate))
+    max_macs = 2 ** (to_generate * 8)
+    seen = set()
+    while len(seen) < max_macs:
+        numbers = [random.getrandbits(8) for _ in range(to_generate)]
+        mac = form.format(beginning, *numbers)
+        if mac in seen:
+            continue
+        else:
+            seen.add(mac)
+            yield mac
+
+
 def is_port_trusted(port):
     """Used to determine if port can be trusted not to attack network.
 

releasenotes/notes/mac-generator-f927df2fe57300c0.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    Introduced ``neutron_lib.utils.net.random_mac_generator(basemac)``. It allows
+    you to get a mac address string Python generator from the same kind of
+    basemac that ``neutron_lib.utils.net.get_random_mac(basemac)`` expects. If
+    there are a lot of macs to get, this will speed the process up
+    significantly over generating single macs and testing for collisions.