int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, uint8_t type,
uint8_t **opt, size_t *optlen);
+uint16_t dhcp_packet_checksum(void *buf, int len);
+
void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
uint16_t source, be32_t destination_addr,
uint16_t destination, uint16_t len);