/*
   * DNS support driver
   *
   * Copyright (c) 2008 Pieter Voorthuijsen <pieter.voorthuijsen@prodrive.nl>
   * Copyright (c) 2009 Robin Getz <rgetz@blackfin.uclinux.org>
   *
   * This is a simple DNS implementation for U-Boot. It will use the first IP
   * in the DNS response as NetServerIP. This can then be used for any other
   * network related activities.
   *
   * The packet handling is partly based on TADNS, original copyrights
   * follow below.
   *
   */
  
  /*
   * Copyright (c) 2004-2005 Sergey Lyubka <valenok@gmail.com>
   *
   * "THE BEER-WARE LICENSE" (Revision 42):
   * Sergey Lyubka wrote this file.  As long as you retain this notice you
   * can do whatever you want with this stuff. If we meet some day, and you think
   * this stuff is worth it, you can buy me a beer in return.
   */
  
  #include <common.h>
  #include <command.h>
  #include <net.h>

  #include <asm/unaligned.h>

  
  #include "dns.h"
  
  char *NetDNSResolve;	/* The host to resolve  */
  char *NetDNSenvvar;	/* The envvar to store the answer in */
  
  static int DnsOurPort;
  
  static void
  DnsSend(void)
  {
  	struct header *header;
  	int n, name_len;
  	uchar *p, *pkt;
  	const char *s;
  	const char *name;
  	enum dns_query_type qtype = DNS_A_RECORD;
  
  	name = NetDNSResolve;

  	pkt = p = (uchar *)(NetTxPacket + NetEthHdrSize() + IP_UDP_HDR_SIZE);

  
  	/* Prepare DNS packet header */
  	header           = (struct header *) pkt;
  	header->tid      = 1;
  	header->flags    = htons(0x100);	/* standard query */
  	header->nqueries = htons(1);		/* Just one query */
  	header->nanswers = 0;
  	header->nauth    = 0;
  	header->nother   = 0;
  
  	/* Encode DNS name */
  	name_len = strlen(name);
  	p = (uchar *) &header->data;	/* For encoding host name into packet */
  
  	do {
  		s = strchr(name, '.');
  		if (!s)
  			s = name + name_len;
  
  		n = s - name;			/* Chunk length */
  		*p++ = n;			/* Copy length  */
  		memcpy(p, name, n);		/* Copy chunk   */
  		p += n;
  
  		if (*s == '.')
  			n++;
  
  		name += n;
  		name_len -= n;
  	} while (*s != '\0');
  
  	*p++ = 0;			/* Mark end of host name */
  	*p++ = 0;			/* Some servers require double null */
  	*p++ = (unsigned char) qtype;	/* Query Type */
  
  	*p++ = 0;
  	*p++ = 1;				/* Class: inet, 0x0001 */
  
  	n = p - pkt;				/* Total packet length */
  	debug("Packet size %d
  ", n);
  
  	DnsOurPort = random_port();
  
  	NetSendUDPPacket(NetServerEther, NetOurDNSIP, DNS_SERVICE_PORT,
  		DnsOurPort, n);
  	debug("DNS packet sent
  ");
  }
  
  static void
  DnsTimeout(void)
  {
  	puts("Timeout
  ");

  	net_set_state(NETLOOP_FAIL);

  }
  
  static void

  DnsHandler(uchar *pkt, unsigned dest, IPaddr_t sip, unsigned src, unsigned len)

  {
  	struct header *header;
  	const unsigned char *p, *e, *s;
  	u16 type, i;
  	int found, stop, dlen;
  	char IPStr[22];
  	IPaddr_t IPAddress;

  
  
  	debug("%s
  ", __func__);
  	if (dest != DnsOurPort)
  		return;
  
  	for (i = 0; i < len; i += 4)
  		debug("0x%p - 0x%.2x  0x%.2x  0x%.2x  0x%.2x
  ",
  			pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]);

  	/* We sent one query. We want to have a single answer: */

  	header = (struct header *) pkt;
  	if (ntohs(header->nqueries) != 1)
  		return;
  
  	/* Received 0 answers */
  	if (header->nanswers == 0) {

  		puts("DNS: host not found
  ");

  		net_set_state(NETLOOP_SUCCESS);

  		return;
  	}
  
  	/* Skip host name */
  	s = &header->data[0];
  	e = pkt + len;
  	for (p = s; p < e && *p != '\0'; p++)
  		continue;
  
  	/* We sent query class 1, query type 1 */

  	if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) {
  		puts("DNS: response was not an A record
  ");

  		net_set_state(NETLOOP_SUCCESS);

  		return;
  	}
  
  	/* Go to the first answer section */
  	p += 5;
  
  	/* Loop through the answers, we want A type answer */
  	for (found = stop = 0; !stop && &p[12] < e; ) {
  
  		/* Skip possible name in CNAME answer */
  		if (*p != 0xc0) {
  			while (*p && &p[12] < e)
  				p++;
  			p--;
  		}
  		debug("Name (Offset in header): %d
  ", p[1]);

  		type = get_unaligned_be16(p+2);

  		debug("type = %d
  ", type);
  		if (type == DNS_CNAME_RECORD) {
  			/* CNAME answer. shift to the next section */
  			debug("Found canonical name
  ");

  			dlen = get_unaligned_be16(p+10);

  			debug("dlen = %d
  ", dlen);
  			p += 12 + dlen;
  		} else if (type == DNS_A_RECORD) {
  			debug("Found A-record
  ");
  			found = stop = 1;
  		} else {
  			debug("Unknown type
  ");
  			stop = 1;
  		}
  	}
  
  	if (found && &p[12] < e) {

  		dlen = get_unaligned_be16(p+10);

  		p += 12;
  		memcpy(&IPAddress, p, 4);
  
  		if (p + dlen <= e) {
  			ip_to_string(IPAddress, IPStr);
  			printf("%s
  ", IPStr);
  			if (NetDNSenvvar)
  				setenv(NetDNSenvvar, IPStr);
  		} else
  			puts("server responded with invalid IP number
  ");
  	}

  	net_set_state(NETLOOP_SUCCESS);

  }
  
  void
  DnsStart(void)
  {
  	debug("%s
  ", __func__);
  
  	NetSetTimeout(DNS_TIMEOUT, DnsTimeout);

  	net_set_udp_handler(DnsHandler);

  
  	DnsSend();
  }