/// Bootp Header (DHCP is transported by BOOTP/UDP/IP)
struct netBootpHeader {
	unsigned char	op;		///< Message op-code / message type
	unsigned char	htype;		///< Hardware address type   (Ethernet=1)
	unsigned char	hlen;		///< Hardware address length (Ethernet=6 byte MAC addr)
	unsigned char	hops;		///< hop count (client set to zero)
	unsigned int	xid;		///< Transaction ID (randomly chosen by client, must remain same)
	unsigned short	secs;		///< Seconds elapsed since DHCP negotiation began (filled by client)
	unsigned short	flags;		///< Flags
	unsigned int    ciaddr;		///< Client IP address (filled only if already bound, renewing, or rebinding)
	unsigned int    yiaddr;		///< 'Your' IP address (client)
	unsigned int    siaddr;		///< Server IP address
	unsigned int    giaddr;		///< Gateway IP address
	unsigned char	chaddr[16];	///< Client Hardware Address
	unsigned char	sname[64];	///< Server Host Name
	unsigned char	file[128];	///< Boot file name (null-term string)
} __attribute__ ((packed));

#define BOOTP_HEADER_LEN	236	///< length of BOOTP header not including options

#define BOOTP_OP_BOOTREQUEST	1	///< BOOTP Request operation (message from client to server)
#define BOOTP_OP_BOOTREPLY	2	///< BOOTP Reply operation (message from server to client)

#define BOOTP_HTYPE_ETHERNET	1
#define BOOTP_HLEN_ETHERNET     6

/// DHCP Header
struct netDhcpHeader {
	struct netBootpHeader bootp;	///< BOOTP header
	unsigned int	cookie;		///< magic cookie value
	unsigned char	options[];	///< DHCP options
}__attribute__ ((packed));

#define DHCP_HEADER_LEN		240	///< length of DHCP header not including options

#define DHCP_UDP_SERVER_PORT	67	///< UDP port where DHCP requests should be sent
#define DHCP_UDP_CLIENT_PORT    68	///< UDP port clients will receive DHCP replies

#define DHCP_OPT_PAD		0   ///< token padding value (make be skipped)
#define DHCP_OPT_NETMASK        1   ///< subnet mask client should use (4 byte mask)
#define DHCP_OPT_ROUTERS        3   ///< routers client should use (IP addr list)
#define DHCP_OPT_TIMESERVERS    4   ///< time servers client should use (IP addr list)
#define DHCP_OPT_NAMESERVERS    5   ///< name servers client should use (IP addr list)
#define DHCP_OPT_DNSSERVERS     6   ///< DNS servers client should use (IP addr list)
#define DHCP_OPT_HOSTNAME       12  ///< host name client should use (string)
#define DHCP_OPT_DOMAINNAME     15  ///< domain name client should use (string)
#define DHCP_OPT_REQUESTEDIP    50  ///< IP address requested by client (IP address)
#define DHCP_OPT_LEASETIME      51  ///< DHCP Lease Time (uint32 seconds)
#define DHCP_OPT_DHCPMSGTYPE    53  ///< DHCP message type (1 byte)
#define DHCP_OPT_SERVERID       54  ///< Server Identifier (IP address)
#define DHCP_OPT_PARAMREQLIST   55  ///< Paramerter Request List (n OPT codes)
#define DHCP_OPT_RENEWALTIME    58  ///< DHCP Lease Renewal Time (uint32 seconds)
#define DHCP_OPT_REBINDTIME     59  ///< DHCP Lease Rebinding Time (uint32 seconds)
#define DHCP_OPT_CLIENT_IDENT   61  ///< DHCP Client identifer
#define DHCP_OPT_END            255 ///< token end value (marks end of options list)

#define DHCP_MSG_DHCPDISCOVER   1   ///< DISCOVER is broadcast by client to solicit OFFER from any/all DHCP servers.
#define DHCP_MSG_DHCPOFFER      2   ///< OFFER(s) are made to client by server to offer IP address and config info.
#define DHCP_MSG_DHCPREQUEST    3   ///< REQUEST is made my client in response to best/favorite OFFER message.
#define DHCP_MSG_DHCPDECLINE    4   ///< DECLINE may be sent by client to server to indicate IP already in use.
#define DHCP_MSG_DHCPACK        5   ///< ACK is sent to client by server in confirmation of REQUEST, contains config and IP.
#define DHCP_MSG_DHCPNAK        6   ///< NAK is sent to client by server to indicate problem with REQUEST.
#define DHCP_MSG_DHCPRELEASE    7   ///< RELEASE is sent by client to server to relinquish DHCP lease on IP address, etc.
#define DHCP_MSG_DHCPINFORM     8   ///< INFORM is sent by client to server to request config info, IP address configured locally.

/* Processes incoming DHCP packets from UDP port 68.
   This function is to be called by the stack when a DHCP packet
   arrives over the network.  The DHCP packet will be parsed, handled,
   and a response will be generated and sent if needed.  When the DHCP
   process completes, the IP addressing will be automatically updated. */
int dhcpIn(char*, int, int, struct netDhcpHeader*);

/* Request DHCP assigned network parameters.
   This function begins the DHCP process.  The remainder of operations
   are handled in dhcpIn(). */
int dhcpRequest(char*, int);

/* Periodic DHCP maintenance.
   This function is to be called once per second and will 
   expire the DHCP lease. */
void dhcpTimer(void);

/* Get a DHCP option from the option list.
   \param options is a pointer to the options field of a DHCP packet.
   \param optcode is the desired option number to retrieve.
   \param optlen is the maximum data length that should be retrieved (less data will be retrieved if option is shorter).
   \param optvalptr is a pointer to where the option value will be stored.
   \return actual length of the option data, as stored in the options list. */
unsigned char dhcpGetOption(unsigned char* options, unsigned char optcode, unsigned char optlen, void* optvalptr);

/* Set a DHCP option in the option list.
   \param options is a pointer to the options field of a DHCP packet.
   \param optcode is the option number to write.
   \param optlen is the data length of the option value.
   \param optvalptr is a pointer to the option data to be read.
   \return pointer to write location of the next option. */
unsigned char* dhcpSetOption(unsigned char* options, unsigned char optcode, unsigned char optlen, void* optvalptr);

/* Print diagnotic information about BOOTP/DHCP packet. */
void dhcpPrintHeader(struct netDhcpHeader* packet);