diff --git a/include/common/standard.h b/include/common/standard.h
index cd422cd..9ed0668 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -237,6 +237,11 @@
  */
 int str2mask(const char *str, struct in_addr *mask);
 
+/* convert <cidr> to struct in_addr <mask>. It returns 1 if the conversion
+ * succeeds otherwise non-zero.
+ */
+int cidr2dotted(int cidr, struct in_addr *mask);
+
 /*
  * converts <str> to two struct in_addr* which must be pre-allocated.
  * The format is "addr[/mask]", where "addr" cannot be empty, and mask