/** * \addtogroup apps * @{ *//** * \defgroup resolv DNS resolver * @{ * * The uIP DNS resolver functions are used to lookup a hostname and * map it to a numerical IP address. It maintains a list of resolved * hostnames that can be queried with the resolv_lookup() * function. New hostnames can be resolved using the resolv_query() * function. * * When a hostname has been resolved (or found to be non-existant), * the resolver code calls a callback function called resolv_found() * that must be implemented by the module that uses the resolver. *//** * \file * DNS host name to IP address resolver. * \author Adam Dunkels <adam@dunkels.com> * * This file implements a DNS host name to IP address resolver. *//* * Copyright (c) 2002-2003, Adam Dunkels. * 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 name of the author may not be used to endorse or promote *    products derived from this software without specific prior *    written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS * 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 THE AUTHOR 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. * * This file is part of the uIP TCP/IP stack. * * $Id: resolv.c,v 1.5 2006/06/11 21:46:37 adam Exp $ * */#include "resolv.h"#include "uip.h"#include <string.h>#ifndef NULL#define NULL (void *)0#endif /* NULL *//** \internal The maximum number of retries when asking for a name. */#define MAX_RETRIES 8/** \internal The DNS message header. */struct dns_hdr {  u16_t id;  u8_t flags1, flags2;#define DNS_FLAG1_RESPONSE        0x80#define DNS_FLAG1_OPCODE_STATUS   0x10#define DNS_FLAG1_OPCODE_INVERSE  0x08#define DNS_FLAG1_OPCODE_STANDARD 0x00#define DNS_FLAG1_AUTHORATIVE     0x04#define DNS_FLAG1_TRUNC           0x02#define DNS_FLAG1_RD              0x01#define DNS_FLAG2_RA              0x80#define DNS_FLAG2_ERR_MASK        0x0f#define DNS_FLAG2_ERR_NONE        0x00#define DNS_FLAG2_ERR_NAME        0x03  u16_t numquestions;  u16_t numanswers;  u16_t numauthrr;  u16_t numextrarr;};/** \internal The DNS answer message structure. */struct dns_answer {  /* DNS answer record starts with either a domain name or a pointer     to a name already present somewhere in the packet. */  u16_t type;  u16_t class;  u16_t ttl[2];  u16_t len;  uip_ipaddr_t ipaddr;};struct namemap {#define STATE_UNUSED 0#define STATE_NEW    1#define STATE_ASKING 2#define STATE_DONE   3#define STATE_ERROR  4  u8_t state;  u8_t tmr;  u8_t retries;  u8_t seqno;  u8_t err;  char name[32];  uip_ipaddr_t ipaddr;};#ifndef UIP_CONF_RESOLV_ENTRIES#define RESOLV_ENTRIES 4#else /* UIP_CONF_RESOLV_ENTRIES */#define RESOLV_ENTRIES UIP_CONF_RESOLV_ENTRIES#endif /* UIP_CONF_RESOLV_ENTRIES */static struct namemap names[RESOLV_ENTRIES];static u8_t seqno;static struct uip_udp_conn *resolv_conn = NULL;/*---------------------------------------------------------------------------*//** \internal * Walk through a compact encoded DNS name and return the end of it. * * \return The end of the name. *//*---------------------------------------------------------------------------*/static unsigned char *parse_name(unsigned char *query){  unsigned char n;  do {    n = *query++;        while(n > 0) {      /*      printf("%c", *query);*/      ++query;      --n;    };    /*    printf(".");*/  } while(*query != 0);  /*  printf("\n");*/  return query + 1;}/*---------------------------------------------------------------------------*//** \internal * Runs through the list of names to see if there are any that have * not yet been queried and, if so, sends out a query. *//*---------------------------------------------------------------------------*/static voidcheck_entries(void){  register struct dns_hdr *hdr;  char *query, *nptr, *nameptr;  static u8_t i;  static u8_t n;  register struct namemap *namemapptr;    for(i = 0; i < RESOLV_ENTRIES; ++i) {    namemapptr = &names[i];    if(namemapptr->state == STATE_NEW ||       namemapptr->state == STATE_ASKING) {      if(namemapptr->state == STATE_ASKING) {	if(--namemapptr->tmr == 0) {	  if(++namemapptr->retries == MAX_RETRIES) {	    namemapptr->state = STATE_ERROR;	    resolv_found(namemapptr->name, NULL);	    continue;	  }	  namemapptr->tmr = namemapptr->retries;	} else {	  /*	  printf("Timer %d\n", namemapptr->tmr);*/	  /* Its timer has not run out, so we move on to next	     entry. */	  continue;	}      } else {	namemapptr->state = STATE_ASKING;	namemapptr->tmr = 1;	namemapptr->retries = 0;      }      hdr = (struct dns_hdr *)uip_appdata;      memset(hdr, 0, sizeof(struct dns_hdr));      hdr->id = htons(i);      hdr->flags1 = DNS_FLAG1_RD;      hdr->numquestions = HTONS(1);      query = (char *)uip_appdata + 12;      nameptr = namemapptr->name;      --nameptr;      /* Convert hostname into suitable query format. */      do {	++nameptr;	nptr = query;	++query;	for(n = 0; *nameptr != '.' && *nameptr != 0; ++nameptr) {	  *query = *nameptr;	  ++query;	  ++n;	}	*nptr = n;      } while(*nameptr != 0);      {	static unsigned char endquery[] =	  {0,0,1,0,1};	memcpy(query, endquery, 5);      }      uip_udp_send((unsigned char)(query + 5 - (char *)uip_appdata));      break;    }  }}/*---------------------------------------------------------------------------*//** \internal * Called when new UDP data arrives. *//*---------------------------------------------------------------------------*/static voidnewdata(void){  char *nameptr;  struct dns_answer *ans;  struct dns_hdr *hdr;  static u8_t nquestions, nanswers;  static u8_t i;  register struct namemap *namemapptr;    hdr = (struct dns_hdr *)uip_appdata;  /*  printf("ID %d\n", htons(hdr->id));      printf("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE);      printf("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK);      printf("Num questions %d, answers %d, authrr %d, extrarr %d\n",      htons(hdr->numquestions),      htons(hdr->numanswers),      htons(hdr->numauthrr),      htons(hdr->numextrarr));  */  /* The ID in the DNS header should be our entry into the name     table. */  i = htons(hdr->id);  namemapptr = &names[i];  if(i < RESOLV_ENTRIES &&     namemapptr->state == STATE_ASKING) {    /* This entry is now finished. */    namemapptr->state = STATE_DONE;    namemapptr->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;    /* Check for error. If so, call callback to inform. */    if(namemapptr->err != 0) {      namemapptr->state = STATE_ERROR;      resolv_found(namemapptr->name, NULL);      return;    }    /* We only care about the question(s) and the answers. The authrr       and the extrarr are simply discarded. */    nquestions = htons(hdr->numquestions);    nanswers = htons(hdr->numanswers);    /* Skip the name in the question. XXX: This should really be       checked agains the name in the question, to be sure that they       match. */    nameptr = parse_name((char *)uip_appdata + 12) + 4;    while(nanswers > 0) {      /* The first byte in the answer resource record determines if it	 is a compressed record or a normal one. */      if(*nameptr & 0xc0) {	/* Compressed name. */	nameptr +=2;	/*	printf("Compressed anwser\n");*/      } else {	/* Not compressed name. */	nameptr = parse_name((char *)nameptr);      }      ans = (struct dns_answer *)nameptr;      /*      printf("Answer: type %x, class %x, ttl %x, length %x\n",	     htons(ans->type), htons(ans->class), (htons(ans->ttl[0])	     << 16) | htons(ans->ttl[1]), htons(ans->len));*/      /* Check for IP address type and Internet class. Others are	 discarded. */      if(ans->type == HTONS(1) &&	 ans->class == HTONS(1) &&	 ans->len == HTONS(4)) {	/*	printf("IP address %d.%d.%d.%d\n",	       htons(ans->ipaddr[0]) >> 8,	       htons(ans->ipaddr[0]) & 0xff,	       htons(ans->ipaddr[1]) >> 8,	       htons(ans->ipaddr[1]) & 0xff);*/	/* XXX: we should really check that this IP address is the one	   we want. */	namemapptr->ipaddr[0] = ans->ipaddr[0];	namemapptr->ipaddr[1] = ans->ipaddr[1];		resolv_found(namemapptr->name, namemapptr->ipaddr);	return;      } else {	nameptr = nameptr + 10 + htons(ans->len);      }      --nanswers;    }  }}/*---------------------------------------------------------------------------*//** \internal * The main UDP function. *//*---------------------------------------------------------------------------*/voidresolv_appcall(void){  if(uip_udp_conn->rport == HTONS(53)) {    if(uip_poll()) {      check_entries();    }    if(uip_newdata()) {      newdata();    }  }}/*---------------------------------------------------------------------------*//** * Queues a name so that a question for the name will be sent out. * * \param name The hostname that is to be queried. *//*---------------------------------------------------------------------------*/voidresolv_query(char *name){  static u8_t i;  static u8_t lseq, lseqi;  register struct namemap *nameptr;        lseq = lseqi = 0;    for(i = 0; i < RESOLV_ENTRIES; ++i) {    nameptr = &names[i];    if(nameptr->state == STATE_UNUSED) {      break;    }    if(seqno - nameptr->seqno > lseq) {      lseq = seqno - nameptr->seqno;      lseqi = i;    }  }  if(i == RESOLV_ENTRIES) {    i = lseqi;    nameptr = &names[i];  }  /*  printf("Using entry %d\n", i);*/  strcpy(nameptr->name, name);  nameptr->state = STATE_NEW;  nameptr->seqno = seqno;  ++seqno;}/*---------------------------------------------------------------------------*//** * Look up a hostname in the array of known hostnames. * * \note This function only looks in the internal array of known * hostnames, it does not send out a query for the hostname if none * was found. The function resolv_query() can be used to send a query * for a hostname. * * \return A pointer to a 4-byte representation of the hostname's IP * address, or NULL if the hostname was not found in the array of * hostnames. *//*---------------------------------------------------------------------------*/u16_t *resolv_lookup(char *name){  static u8_t i;  struct namemap *nameptr;    /* Walk through the list to see if the name is in there. If it is     not, we return NULL. */  for(i = 0; i < RESOLV_ENTRIES; ++i) {    nameptr = &names[i];    if(nameptr->state == STATE_DONE &&       strcmp(name, nameptr->name) == 0) {      return nameptr->ipaddr;    }  }  return NULL;}/*---------------------------------------------------------------------------*//** * Obtain the currently configured DNS server. * * \return A pointer to a 4-byte representation of the IP address of * the currently configured DNS server or NULL if no DNS server has * been configured. *//*---------------------------------------------------------------------------*/u16_t *resolv_getserver(void){  if(resolv_conn == NULL) {    return NULL;  }  return resolv_conn->ripaddr;}/*---------------------------------------------------------------------------*//** * Configure which DNS server to use for queries. * * \param dnsserver A pointer to a 4-byte representation of the IP * address of the DNS server to be configured. *//*---------------------------------------------------------------------------*/voidresolv_conf(u16_t *dnsserver){  if(resolv_conn != NULL) {    uip_udp_remove(resolv_conn);  }    resolv_conn = uip_udp_new(dnsserver, HTONS(53));}/*---------------------------------------------------------------------------*//** * Initalize the resolver. *//*---------------------------------------------------------------------------*/voidresolv_init(void){  static u8_t i;    for(i = 0; i < RESOLV_ENTRIES; ++i) {    names[i].state = STATE_DONE;  }}/*---------------------------------------------------------------------------*//** @} *//** @} */