struct in_addr* in_addr_prefixlen_to_netmask(struct in_addr *addr, unsigned char prefixlen);
int in_addr_default_prefixlen(const struct in_addr *addr, unsigned char *prefixlen);
int in_addr_default_subnet_mask(const struct in_addr *addr, struct in_addr *mask);
struct in_addr* in_addr_prefixlen_to_netmask(struct in_addr *addr, unsigned char prefixlen);
int in_addr_default_prefixlen(const struct in_addr *addr, unsigned char *prefixlen);
int in_addr_default_subnet_mask(const struct in_addr *addr, struct in_addr *mask);