IP Address validator

Returns True if there is at most one occurence of the ip_interface (an IPv4/IPv6 prefix+len)
in the entire config. That said, we need the 'iface_addresses' because VPP is a bit fickle in
this regard.

IP addresses from the same prefix/len can be added to a given interface (ie 192.0.2.1/24 and
192.0.2.2/24), but other than that, any prefix can not occur as a more-specific or less-specific
of any other interface.

So, we will allow:
- any ip_interface that is of equal network/len of existing one(s) _on the same interface_

And, we will reject
- any ip_interface that is a more specific of any existing one
- any ip_interface that is a less specific of any existing one

Update unit tests to ensure ip_interfaces are allowed in all cases.

validator/loopback.py

@@ -13,6 +13,7 @@
 #
 import logging
 import validator.lcp as lcp
+import validator.address as address
 
 class NullHandler(logging.Handler):
     def emit(self, record):
@@ -46,5 +47,10 @@ def validate_loopbacks(yaml):
         if 'lcp' in iface and not lcp.is_unique(yaml, iface['lcp']):
             msgs.append("loopback %s does not have a unique LCP name %s" % (ifname, iface['lcp']))
             result = False
+        if 'addresses' in iface:
+            for a in iface['addresses']:
+                if not address.is_allowed(yaml, ifname, iface['addresses'], a):
+                    msgs.append("loopback %s IP address %s is not allowed" % (ifname, a))
+                    result = False
 
     return result, msgs