Add bridge-domain support.

Refactor validator main function to avoid 'interface' symbol clash.
Add get_mtu() for interfaces, returns the sub-int's MTU or its parent's MTU, defaulting to 1500.
Ensure MTU for all bridge-domain members is set to the same value.
Ensure all bridge-domain members are L2 (have no LCP, have no address)

validator/bridgedomain.py

@@ -1,15 +1,55 @@
 import logging
+import validator.interface as interface
 
 class NullHandler(logging.Handler):
     def emit(self, record):
         pass
 
 
-def bridgedomain(args, yaml):
+def get_by_name(yaml, ifname):
+    """ Return the BridgeDomain by name, if it exists. Return None otherwise. """
+    try:
+        if ifname in yaml['bridgedomains']:
+            return yaml['bridgedomains'][ifname]
+    except:
+        pass
+    return None
+
+
+def validate_bridgedomains(args, yaml):
     result = True
     msgs = []
     logger = logging.getLogger('vppcfg.validator')
     logger.addHandler(NullHandler())
 
+    if not 'bridgedomains' in yaml:
+        return result, msgs
+
     logger.debug("Validating bridgedomains...")
+    for ifname, iface in yaml['bridgedomains'].items():
+        logger.debug("bridgedomain %s" % iface)
+        bd_mtu = 1500
+        if 'mtu' in iface:
+            bd_mtu = iface['mtu']
+
+        if 'interfaces' in iface:
+            for member in iface['interfaces']:
+                member_iface = interface.get_by_name(yaml, member)
+                if not member_iface:
+                    msgs.append("bondethernet %s member %s doesn't exist" % (ifname, member))
+                    result = False
+                    continue
+
+                if interface.has_lcp(yaml, member):
+                    msgs.append("bridgedomain %s member %s has an LCP" % (ifname, member))
+                    result = False
+                if interface.has_address(yaml, member):
+                    msgs.append("bridgedomain %s member %s has an address" % (ifname, member))
+                    result = False
+                member_mtu = interface.get_mtu(yaml, member)
+                if member_mtu != bd_mtu:
+                    msgs.append("bridgedomain %s member %s has MTU %d, while bridge has %d" % (ifname, member, member_mtu, bd_mtu))
+                    result = False
+
+
     return result, msgs