unsigned char in4_addr_netmask_to_prefixlen(const struct in_addr *addr);
struct in_addr* in4_addr_prefixlen_to_netmask(struct in_addr *addr, unsigned char prefixlen);
+struct in6_addr* in6_addr_prefixlen_to_netmask(struct in6_addr *addr, unsigned char prefixlen);
+int in_addr_prefixlen_to_netmask(int family, union in_addr_union *addr, unsigned char prefixlen);
int in4_addr_default_prefixlen(const struct in_addr *addr, unsigned char *prefixlen);
int in4_addr_default_subnet_mask(const struct in_addr *addr, struct in_addr *mask);
int in4_addr_mask(struct in_addr *addr, unsigned char prefixlen);