dhcpd
-1)
	WARNING: the entire project is still pre alpha, work in progress
	WARNING: the entire project is still pre alpha, work in progress
	WARNING: the entire project is still pre alpha, work in progress
	WARNING: the entire project is still pre alpha, work in progress
	WARNING: the entire project is still pre alpha, work in progress
	WARNING: the entire project is still pre alpha, work in progress
	WARNING: the entire project is still pre alpha, work in progress

0) install:
	download: 
	$ wget -O dhcpd.tar.gz https://github.com/jackdoe/dhcpd/tarball/master
	# or fetch -o dhcpd.tar.gz ...
	
	$ tar -zvxf dhcpd.tar.gz 
	$ cd jackdoe-dhcpd-*
	
	edit Makefile and choose your decision maker 
			(dont forget to edit its config in decision-maker/$decision-maker/)
		change also the c compiler if you dont have llvm for example:
		CC= gcc
		$ make
	and then:
		$ cp dhcpd wherever-you-want
	
1) abstract
	the idea is very simple:
	client -+
		|
		| DHCPDISCOVER/DHCPREQUEST
		|
		server - pcap_loop()
			|
			packet_validate()
			|(inval)	| packet is valid
			|		|
			|		p_reply(&reply_packet) - external
			|		| (nop)	| (we have lease and filled reply_pkt)
			|		|	cksum && pcap_inject(reply_packet)
			+	____	+
				drop

	so, all the decisions can be based on whatever you want
	CHADDR, eh->ether_shost, GIADDR, or 60-80 byte of the packet

2) decision maker:
you need to have 6 functions
p_reply() 	called on each dhcp packet of type BOOTPREQUEST
p_release() called on DHCPRELEASE
p_log()		called on each packet input of any type
p_signal()	called every XX seconds, so you can do some lease related stuff
p_init()	called when the server starts
p_clean()	called when the server is about to exit

export.h:
/*
 * p_reply()
 * arguments:
 *	reply_packet - 
 *		poiter to a dhcp_reply structure, the decision maker must fill
 *		the whole structure, including ether_header, ip header,udp header
 *		dhcp fixed header, and dhcp options
 *	request_packet - is just a pointer to the DHCPDISCOVER/OFFER packet
 *
 * returns:
 *	SUCCESS	- if there is a lease available (server will reply)
 *	FAIL	- no free leases (server will do nothing)
 * 
 */
int p_reply(struct dhcp_reply *reply_packet,
		struct dhcp_packet *request_packet, 
		u8 reply_msg_type, u8 request_msg_type);

/*
 * p_release()
 * arguments:
 *	mac,ip,dhcp_packet - plugin has to make a decision if there IS a lease
 *				with the followinig parameters set in its database
 * returns:
 *	SUCCESS	- if there was a lease (the server will execute expiry() event)
 *	FAIL	- if there was no such lease (server will do nothing)
 */
int p_release(u8 *mac,struct in_addr ip,struct dhcp_packet *request_packet);


3) example decision-makers:
	3.1) dummy
		just an empty skeleton
	3.2) static
		this is an example to demonstrate framed/fixed ip address
		assignment, based on CHADDR in the BOOTPREQUEST packet.
		it uses db(3) hash(3) for backend, key is chaddr value is 
		this structure:
		struct lease {
			struct in_addr ip;
			struct in_addr subnet;
			struct in_addr dns[DNS_COUNT];
			struct in_addr gw;
			struct in_addr broadcast;
			u32 lease_time;
		};
		so the decision maker must fill the whole dhcp_reply structure
		including ether_header, ip header, udp header, dhcp header, dhcp options
		with the information it has from the BOOTPREQUEST packet plus this 
		simple lease structure.
	3.3) static-mysql
		same as static, but instead db(3) it uses mysql
		you can see the example tables in decision-maker/mysql-static/mysql-config.h.