Updating onos-gen-partitions to take IPs via CLI args

Also, moving to SHA256 hash for onos-gen-partitions

Change-Id: Id2a56401cebf75345660059e16144426d4ae89c3

@@ -23,9 +23,11 @@ def get_OC_vars():
       vars.append(var)
   return sorted(vars, key=alphanum_key)
 
-def get_nodes(vars, port=9876):
+def get_nodes(ips=None, port=9876):
   node = lambda k: { 'id': k, 'ip': k, 'port': port }
-  return [ node(environ[v]) for v in vars ]
+  if not ips:
+    ips = [ environ[v] for v in get_OC_vars() ]
+  return [ node(v) for v in ips ]
 
 def generate_base_partition(nodes):
   return {
@@ -46,16 +48,16 @@ def generate_extended_partitions(nodes, k):
   return perms
 
 if __name__ == '__main__':
-  vars = get_OC_vars()
-  nodes = get_nodes(vars)
+  nodes = get_nodes(sys.argv[1:])
   base_partition = generate_base_partition([v.get('id') for v in nodes])
   extended_partitions = generate_extended_partitions([v.get('id') for v in nodes], 3)
   partitions = []
   partitions.append(base_partition)
   partitions.extend(extended_partitions)
-  name = 0
+  m = hashlib.sha256()
   for node in nodes:
-    name = name ^ hash(node['ip'])
+    m.update(node['ip'])
+  name = int(m.hexdigest()[:8], base=16) # 32-bit int based on SHA256 digest
   data = {
            'name': name,
            'nodes': nodes,