/*
 *Copyright (c) 2000-2002 Viola Systems Ltd.
 *All rights reserved.
 *
 *Redistribution and use in source and binary forms, with or without
 *modification, are permitted provided that the following conditions
 *are met:
 *
 *1. Redistributions of source code must retain the above copyright
 *notice, this list of conditions and the following disclaimer.
 *
 *2. Redistributions in binary form must reproduce the above copyright
 *notice, this list of conditions and the following disclaimer in the
 *documentation and/or other materials provided with the distribution.
 *
 *3. The end-user documentation included with the redistribution, if
 *any, must include the following acknowledgment:
 *	"This product includes software developed by Viola
 *	Systems (http://www.violasystems.com/)."
 *
 *Alternately, this acknowledgment may appear in the software itself,
 *if and wherever such third-party acknowledgments normally appear.
 *
 *4. The names "OpenTCP" and "Viola Systems" must not be used to
 *endorse or promote products derived from this software without prior
 *written permission. For written permission, please contact
 *opentcp@opentcp.org.
 *
 *5. Products derived from this software may not be called "OpenTCP",
 *nor may "OpenTCP" appear in their name, without prior written
 *permission of the Viola Systems Ltd.
 *
 *THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
 *WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *IN NO EVENT SHALL VIOLA SYSTEMS LTD. OR ITS CONTRIBUTORS BE LIABLE
 *FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 *BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 *WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 *OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 *EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *====================================================================
 *
 *OpenTCP is the unified open source TCP/IP stack available on a series
 *of 8/16-bit microcontrollers, please see <http://www.opentcp.org>.
 *
 *For more information on how to network-enable your devices, or how to
 *obtain commercial technical support for OpenTCP, please see
 *<http://www.violasystems.com/>.
 */


/** \file dns.c
 *	\brief OpenTCP DNS client implementation
 *	\author
 *		\li Vladan Jovanovic (vladan.jovanovic@violasystems.com)
 *	\version 1.0
 *	\date 10.10.2002
 *	\bug
 *	\warning
 *	\todo
 *		\li Probably should implement sending different ID with
 *		requests.
 *		\li Maybe create similar cache as for ARP ?
 *		\li <b>Definitely</b> implement DNS's IP address use as a
 *		parameter to get_host_by_name function. This would allow more
 *		flexible manipulation
 *
 *	OpenTCP DNS client implementation. API functions, data structures
 *	and constants may be found in dns.h
 */

#include "debug.h"
#include "datatypes.h"
#include "globalvariables.h"
#include "system.h"
#include "timers.h"
#include "tcp_ip.h"
#ifdef DNS_WANTED
#include "dns.h"


#define DNS_STATE_READY 	0
#define DNS_STATE_BUSY		1
#define DNS_STATE_RESEND	2	/* retransmit request */

UINT8 dns_state; /**< Current DNS state. Used to prevent multiple requests, issue retransmissions,... See DNS_STATE_* for possible values. */
INT8 dns_socket; /**< UDP socket used by the DNS resolver */
UINT8 dns_timer; /**< DNS timer handle used for retransmissions */
UINT8 dns_retries; /**< DNS retry counter used for detecting timeouts */

UINT32 dns_tmp_ip; /**< Used in many ways: as an IP address holder, for issuing requests to authorative name servers,.. */

UINT8 *dns_hostptr;	/**< Pointer to hostname that is beeing resolved. Needed for retransmissions.*/


void (*dns_event_listener)(UINT8 event, UINT32 data);

/** \brief Initialize resources needed for the DNS client
 * 	\author
 *		\li Vladan Jovanovic (vladan.jovanovic@violasystems.com)
 *	\date 10.10.2002
 *
 *	Invoke this function at startup to properly initialize DNS resources.
 *
 */
void dns_init(void){

	dns_state = DNS_STATE_READY;

	dns_socket=udp_getsocket(0 , dns_eventlistener , UDP_OPT_SEND_CS | UDP_OPT_CHECK_CS);

	if(dns_socket == -1){
		DEBUGOUT("DNS: No free UDP sockets!! \r\n");
		return;
	}

	/* open socket */
	(void)udp_open(dns_socket,DNS_UDP_PORT);

	/* now the timer. This will be used for retransmitting the requests */
	dns_timer=get_timer();

	/* TODO: if GetTimer is modified so that it doesn't reset system if
		no timers available, check return value! */

	DEBUGOUT("Initialized DNS client\r\n");

}

/** \brief Retransmits requests towards the DNS server
 * 	\author
 *		\li Vladan Jovanovic (vladan.jovanovic@violasystems.com)
 *	\date 10.10.2002
 *
 *	This is internal function and IS NOT INTENDED to be invoked by the
 *	user application. It simply checks if retransmissions should be done
 *	(when retransmissions not used yet) and if yes, sends one.
 *	Otherwise timeout error is sent to the event listener.
 */
void dns_retransmit(void){
	if(dns_retries!=0){
		dns_state=DNS_STATE_RESEND;
		dns_retries--;
		(void)get_host_by_name(dns_hostptr,dns_event_listener);
		init_timer(dns_timer,DNS_RESEND_PERIOD*TIMERTIC);
	}else{

		/* timeout happened */
		dns_state=DNS_STATE_READY;

		dns_event_listener(DNS_EVENT_ERROR,DNS_ERROR_TIMEOUT);

	}

}

/** \brief DNS client main loop
 * 	\author
 *		\li Vladan Jovanovic (vladan.jovanovic@violasystems.com)
 *	\date 10.10.2002
 *
 *	Simple main loop that checks whether DNS requests should be sent or
 *	not (based on timer timeout). If yes, and DNS is in appropriate state,
 *	dns_retransmit() function is invoked.
 */
void dns_run(void){
	if((dns_state==DNS_STATE_BUSY)||(dns_state==DNS_STATE_RESEND)){
		/* checking retransmission timer */
		if(!check_timer(dns_timer)){

			DEBUGOUT("DNS: retransmitting the request \r\n");
			/* timeout, send another one */
			dns_retransmit();

		}
	}
}

/** \brief DNS client event listener
 * 	\author
 *		\li Vladan Jovanovic (vladan.jovanovic@violasystems.com)
 *	\date 10.10.2002
 *	\param cbhandle handle of the socket this packet is intended for.
 * 	\param event event that is notified. For UDP, only UDP_EVENT_DATA.
 * 	\param ipaddr IP address of remote host who sent the UDP datagram
 * 	\param port port number of remote host who sent the UDP datagram
 * 	\param buffindex buffer index in RTL8019AS
 *	\return
 *		\li - 1 - error in processing
 *		\li 0 - DNS reply successfully processed
 *	\note
 *		\li Event listeners are NOT to be invoked directly. They are
 *		callback functions invoked by the TCP/IP stack to notify events.
 *
 *	This, of course, is where responses from DNS server are processed and
 *	checked whether they contain the IP address we requested or if they
 *	contain authorative name server to which we should proceed.
 *
 *	If we received the IP address we requested, #DNS_EVENT_SUCCESS is
 *	reported to application DNS event listener. Otherwise #DNS_EVENT_ERROR
 *	is reported.
 */
INT32 dns_eventlistener(INT8 cbhandle, UINT8 event, UINT32 ipaddr, UINT16 port, UINT16 buffindex, UINT16 datalen){
	UINT8 tmp_byte;
	UINT16 tmp_int;
	UINT8 *tmp_ptr;
	UINT8 count;
	/* it will fit in 8bits most of the time but... */
	UINT16 dns_ancount;
	UINT16 dns_nscount;
  buffindex=0;
  port=0;
  count=0;

	if(cbhandle!=dns_socket){
		DEBUGOUT("DNS: not my handle!!!!");
		return (-1);
	}

	if(ipaddr!=dns_tmp_ip){
		DEBUGOUT("DNS: received DNS but IP addr not OK!\r\n");
	}

	switch(event){
		case UDP_EVENT_DATA:
			/* only process data while not in ready state */
			if(dns_state==DNS_STATE_READY){
				DEBUGOUT("DNS: Received answer in wrong state\r\n");
				return (-1);
			}

			/* inital size checking. Every DNS reply will be bigger
				than 16 bytes */
			if(datalen<16){
				DEBUGOUT("DNS: UDP packet way to short for DNS!\r\n");
				return (-1);
			}

			/* some data received, check if it's what we're waiting for */
			tmp_int=RECEIVE_NETWORK_B();
			tmp_int=(tmp_int<<8)+RECEIVE_NETWORK_B();
			if(tmp_int!=0xaaaa){
				DEBUGOUT("DNS: ERROR: ID wrong!\r\n");
				return (-1);
			}

			tmp_byte=RECEIVE_NETWORK_B();

			if(!(tmp_byte&0x80)){
				DEBUGOUT("DNS: THIS IS NOT AN ANSWER! WE'RE NOT A DNS SERVER!\r\n");
				return (-1);
			}

			/* opcode or truncated ? */
			if(tmp_byte&0x7a){
				DEBUGOUT("DNS: Opcode not zero or message truncated. \r\n");
				dns_event_listener(DNS_EVENT_ERROR,DNS_ERROR_GENERAL);
				return (-1);
			}

			tmp_byte=RECEIVE_NETWORK_B();

			/* check RCODE */
			if((tmp_byte&0x7f)&&(tmp_byte&0x80)){
				/* RCODE not zero, and recursion is available	*/
				/* There was an error. Inform listener 			*/
				DEBUGOUT("DNS: RCODE not zero and recursion available! \r\n");
				dns_event_listener(DNS_EVENT_ERROR,tmp_byte&0x7f);
				return (-1);
			}

			/* question count == 1 ? */
			tmp_int=(((UINT16)RECEIVE_NETWORK_B())<<8);
			tmp_int+=RECEIVE_NETWORK_B();
			if(tmp_int != 1){
				DEBUGOUT("DNS: we only sent one question and received a couple of answers!!\r\n");