+
+int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, uint8_t type,
+ uint16_t secs, uint8_t **opt, size_t *optlen);
+
+void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint8_t op, uint16_t len);
+
+int dhcp_packet_verify_headers(DHCPPacket *packet, uint8_t op, size_t len);