Add a few MAC checks

Notably mac.is_multicast() which is needed for TAPs / LCPs and
interfaces.

Add a test for interface MAC addresses being non-multicast.

config/test_mac.py

@@ -0,0 +1,21 @@
+import unittest
+import config.mac as mac
+
+class TestMACMethods(unittest.TestCase):
+    def test_is_valid(self):
+        self.assertTrue(mac.is_valid("00:01:02:03:04:05"))
+        self.assertTrue(mac.is_valid("00-01-02-03-04-05"))
+        self.assertTrue(mac.is_valid("0001.0203.0405"))
+        self.assertFalse(mac.is_valid("hoi"))
+
+    def test_is_local(self):
+        self.assertTrue(mac.is_local("02:00:00:00:00:00"))
+        self.assertFalse(mac.is_local("00:00:00:00:00:00"))
+
+    def test_is_multicast(self):
+        self.assertTrue(mac.is_multicast("01:00:00:00:00:00"))
+        self.assertFalse(mac.is_multicast("00:00:00:00:00:00"))
+
+    def test_is_unicast(self):
+        self.assertFalse(mac.is_unicast("01:00:00:00:00:00"))
+        self.assertTrue(mac.is_unicast("00:00:00:00:00:00"))