--- a/util/ip.lua	Sat May 18 15:29:31 2013 +0100
+++ b/util/ip.lua	Sat May 18 16:45:29 2013 +0100
@@ -215,5 +215,28 @@
 	return private;
 end
 
+local function parse_cidr(cidr)
+	local bits;
+	local ip_len = cidr:find("/", 1, true);
+	if ip_len then
+		bits = tonumber(cidr:sub(ip_len+1, -1));
+		cidr = cidr:sub(1, ip_len-1);
+	end
+	return new_ip(cidr), bits;
+end
+
+local function match(ipA, ipB, bits)
+	local common_bits = commonPrefixLength(ipA, ipB);
+	if not bits then
+		return ipA == ipB;
+	end
+	if bits and ipB.proto == "IPv4" then
+		common_bits = common_bits - 96; -- v6 mapped addresses always share these bits
+	end
+	return common_bits >= bits;
+end
+
 return {new_ip = new_ip,
-	commonPrefixLength = commonPrefixLength};
+	commonPrefixLength = commonPrefixLength,
+	parse_cidr = parse_cidr,
+	match=match};