int dhcp6_option_append_ia(uint8_t **buf, size_t *buflen, DHCP6IA *ia);
int dhcp6_option_parse(uint8_t **buf, size_t *buflen, uint16_t *optcode,
size_t *optlen, uint8_t **optvalue);
int dhcp6_option_append_ia(uint8_t **buf, size_t *buflen, DHCP6IA *ia);
int dhcp6_option_parse(uint8_t **buf, size_t *buflen, uint16_t *optcode,
size_t *optlen, uint8_t **optvalue);