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/interface.py

@@ -18,6 +18,7 @@ import config.loopback as loopback
 import config.vxlan_tunnel as vxlan_tunnel
 import config.lcp as lcp
 import config.address as address
+import config.mac as mac
 
 def get_qinx_parent_by_name(yaml, ifname):
     """ Returns the sub-interface which matches a QinAD or QinQ outer tag, or None,None
@@ -424,6 +425,10 @@ def validate_interfaces(yaml):
         if not 'state' in iface:
             iface['state'] = 'up'
 
+        if 'mac' in iface and mac.is_multicast(iface['mac']):
+            msgs.append("interface %s MAC address %s cannot be multicast" % (ifname, iface['mac']))
+            result = False
+
         iface_mtu = get_mtu(yaml, ifname)
         iface_lcp = get_lcp(yaml, ifname)
         iface_address = has_address(yaml, ifname)