sres.c

sip协议栈

su_log_t sresolv_log[] = { SU_LOG_INIT("sresolv", "SRESOLV_DEBUG", 3) };

/** Internal errors */
enum {
  SRES_EDNS0_ERR = 255		/**< Server did not support EDNS. */
};

/* ---------------------------------------------------------------------- */

/**Create a resolver.
 *
 * Allocate and initialize a new sres resolver object. The resolver object
 * contains the parsed resolv.conf file, a cache object containing past
 * answers from DNS, and a list of active queries. The default resolv.conf
 * file can be overriden by giving the name of the configuration file as @a
 * conf_file_path.
 *
 * @param conf_file_path name of the resolv.conf configuration file 
 *
 * @return A pointer to a newly created sres resolver object, or NULL upon
 * an error.
 */
sres_resolver_t *
sres_resolver_new(char const *conf_file_path)
{
  return sres_resolver_new_internal(NULL, NULL, conf_file_path, NULL);
}

/** Copy a resolver.
 *
 * Make a copy of resolver with old
 */
sres_resolver_t *sres_resolver_copy(sres_resolver_t *res)
{
  char const *cnffile;
  sres_config_t *config;
  sres_cache_t *cache;
  char const **options;

  if (!res)
    return NULL;

  cnffile = res->res_cnffile;
  config = su_home_ref(res->res_config->c_home);
  cache = res->res_cache;
  options = res->res_options;

  return sres_resolver_new_internal(cache, config, cnffile, options);
}

/**New resolver object.
 *
 * Allocate and initialize a new sres resolver object. The resolver object
 * contains the parsed resolv.conf file, a cache object containing past
 * answers from DNS, and a list of active queries. The default resolv.conf
 * file can be overriden by giving the name of the configuration file as @a
 * conf_file_path.
 *
 * It is also possible to override the values in the resolv.conf and
 * RES_OPTIONS by giving the directives in the NULL-terminated list.
 *
 * @param conf_file_path name of the resolv.conf configuration file 
 * @param cache          optional pointer to a resolver cache
 * @param option, ...    list of resolv.conf options directives 
 *                       (overriding options in conf_file)
 *
 * @par Environment Variables
 * - LOCALDOMAIN overrides @c domain or @c search directives
 * - RES_OPTIONS overrides values of @a options in resolv.conf
 * - SRES_OPTIONS overrides values of @a options in resolv.conf, RES_OPTIONS,
 *   and @a options, ... list given as argument for this function
 *
 * @return A pointer to a newly created sres resolver object, or NULL upon
 * an error.
 */
sres_resolver_t *
sres_resolver_new_with_cache(char const *conf_file_path,
			     sres_cache_t *cache,
			     char const *option, ...)
{
  sres_resolver_t *retval;
  va_list va;
  va_start(va, option);
  retval = sres_resolver_new_with_cache_va(conf_file_path, cache, option, va);
  va_end(va);
  return retval;
}

/**Create a resolver.
 *
 * Allocate and initialize a new sres resolver object. 
 *
 * This is a stdarg version of sres_resolver_new_with_cache().
 */
sres_resolver_t *
sres_resolver_new_with_cache_va(char const *conf_file_path,
				sres_cache_t *cache,
				char const *option,
				va_list va)
{
  va_list va0;
  size_t i;
  char const *o, *oarray[16], **olist = oarray;
  sres_resolver_t *res;

  va_copy(va0, va);
  
  for (i = 0, o = option; o; o = va_arg(va0, char const *)) {
    if (i < 16)
      olist[i] = o;
    i++;
  }

  if (i >= 16) {
    olist = malloc((i + 1) * sizeof *olist);
    if (!olist)
      return NULL;
    for (i = 0, o = option; o; o = va_arg(va, char const *)) {
      olist[i++] = o;
      i++;
    }
  }
  olist[i] = NULL;
  res = sres_resolver_new_internal(cache, NULL, conf_file_path, olist);
  if (olist != oarray)
    free(olist);

  return res;
}

sres_resolver_t *
sres_resolver_new_internal(sres_cache_t *cache,
			   sres_config_t const *config,
			   char const *conf_file_path,
			   char const **options)
{
  sres_resolver_t *res;
  size_t i, n, len;
  char **array, *o, *end;
 
  for (n = 0, len = 0; options && options[n]; n++)
    len += strlen(options[n]) + 1;

  res = su_home_new(sizeof(*res) + (n + 1) * (sizeof *options) + len);

  if (res == NULL)
    return NULL;

  array = (void *)(res + 1);
  o = (void *)(array + n + 1);
  end = o + len;

  for (i = 0; options && options[i]; i++)
    o = memccpy(array[i] = o, options[i], '\0', len - (end - o));
  assert(o == end);

  su_home_desctructor(res->res_home, sres_resolver_destructor);

  while (res->res_id == 0) {
#if HAVE_DEV_URANDOM
    int fd;
    if ((fd = open("/dev/urandom", O_RDONLY, 0)) != -1) {
      read(fd, &res->res_id, (sizeof res->res_id));
      close(fd);
    }
    else
#endif
    res->res_id = time(NULL);
  }

  time(&res->res_now);

  if (cache)
    res->res_cache = sres_cache_ref(cache);
  else
    res->res_cache = sres_cache_new(0);

  res->res_config = config;

  if (conf_file_path && conf_file_path != sres_conf_file_path)
    res->res_cnffile = su_strdup(res->res_home, conf_file_path);
  else
    res->res_cnffile = conf_file_path = sres_conf_file_path;

  if (!res->res_cache || !res->res_cnffile) {
    perror("sres: malloc");
  }
  else if (sres_qtable_resize(res->res_home, res->res_queries, 0) < 0) {
    perror("sres: res_qtable_resize");
  }
  else if (sres_resolver_update(res, config == NULL) < 0) {
    perror("sres: sres_resolver_update");
  }
  else {
    return res;
  }

  sres_resolver_unref(res);

  return NULL;
}

/** Increase reference count on a resolver object. */
sres_resolver_t *
sres_resolver_ref(sres_resolver_t *res)
{
  return su_home_ref(res->res_home);
}
		     
/** Decrease the reference count on a resolver object.  */
void
sres_resolver_unref(sres_resolver_t *res)
{
  su_home_unref(res->res_home);
}

/** Set userdata pointer.
 *
 * @return New userdata pointer.
 * 
 * @ERRORS
 * @ERROR EFAULT @a res points outside the address space
 */
void *
sres_resolver_set_userdata(sres_resolver_t *res, 
			   void *userdata)
{
  void *old;

  if (!res)
    return su_seterrno(EFAULT), (void *)NULL;

  old = res->res_userdata, res->res_userdata = userdata;

  return old;
}

/**Get userdata pointer.
 *
 * @return Userdata pointer.
 * 
 * @ERRORS
 * @ERROR EFAULT @a res points outside the address space
 */
void *
sres_resolver_get_userdata(sres_resolver_t const *res)
{
  if (res == NULL)
    return su_seterrno(EFAULT), (void *)NULL;
  else
    return res->res_userdata;
}

/** Set async object.
 *
 * @return Set async object.
 * 
 * @ERRORS
 * @ERROR EFAULT @a res points outside the address space
 * @ERROR EALREADY different async callback already set
 */
sres_async_t *
sres_resolver_set_async(sres_resolver_t *res,
			sres_update_f *callback,
			sres_async_t *async, 
			int update_all)
{
  if (!res)
    return su_seterrno(EFAULT), (void *)NULL;

  if (res->res_updcb && res->res_updcb != callback)
    return su_seterrno(EALREADY), (void *)NULL;
    
  res->res_async = async;
  res->res_updcb = callback;
  res->res_update_all = callback && update_all != 0;

  return async;
}

sres_async_t *
sres_resolver_get_async(sres_resolver_t const *res,
			sres_update_f *callback)
{
  if (res == NULL)
    return su_seterrno(EFAULT), (void *)NULL;
  else if (callback == NULL)
    return res->res_async ? (sres_async_t *)-1 : 0;
  else if (res->res_updcb != callback)
    return NULL;
  else
    return res->res_async;
}

/**Send a DNS query.
 *
 * Sends a DNS query with specified @a type and @a domain to the DNS server. 
 * The sres resolver takes care of retransmitting the query if
 * sres_resolver_timer() is called in regular intervals. It generates an
 * error record with nonzero status if no response is received.
 *
 * @sa sres_search(), sres_blocking_query(), sres_query_make()
 *
 * @ERRORS
 * @ERROR EFAULT @a res or @a domain point outside the address space
 * @ERROR ENAMETOOLONG @a domain is longer than SRES_MAXDNAME
 * @ERROR ENOMEM memory exhausted
 */
sres_query_t *
sres_query(sres_resolver_t *res,
	   sres_answer_f *callback,
	   sres_context_t *context,
	   uint16_t type,
	   char const *domain)
{
  sres_query_t *query = NULL;
  size_t dlen;
  
  char b[8];
  SU_DEBUG_9(("sres_query(%p, %p, %p, %s, \"%s\") called\n",
	      res, callback, context, sres_record_type(type, b), domain));

  if (res == NULL || domain == NULL)
    return su_seterrno(EFAULT), (void *)NULL;

  dlen = strlen(domain);
  if (dlen > SRES_MAXDNAME ||
      (dlen == SRES_MAXDNAME && domain[dlen - 1] != '.')) {
    su_seterrno(ENAMETOOLONG);
    return NULL;
  }

  /* Reread resolv.conf if needed */
  sres_resolver_update(res, 0);

  query = sres_query_alloc(res, callback, context, type, domain);

  if (query && sres_send_dns_query(res, query) != 0)
    sres_free_query(res, query), query = NULL;

  return query;
}

/**Search DNS.
 *
 * Sends DNS queries with specified @a type and @a name to the DNS server. 
 * If the @a name does not contain enought dots, the search domains are
 * appended to the name and resulting domain name are also queried.
 *
 * The sres resolver takes care of retransmitting the queries if
 * sres_resolver_timer() is called in regular intervals. It generates an
 * error record with nonzero status if no response is received.
 *
 * @param res pointer to resolver object
 * @param callback pointer to completion function
 * @param context argument given to the completion function
 * @param type record type to search (or sres_qtype_any for any record)
 * @param name host or domain name to search from DNS
 *
 * @ERRORS
 * @ERROR EFAULT @a res or @a domain point outside the address space
 * @ERROR ENAMETOOLONG @a domain is longer than SRES_MAXDNAME
 * @ERROR ENOMEM memory exhausted
 *
 * @sa sres_query(), sres_blocking_search()
 */
sres_query_t *
sres_search(sres_resolver_t *res,
	    sres_answer_f *callback,
	    sres_context_t *context,
	    uint16_t type,
	    char const *name)
{
  char const *domain = name;
  sres_query_t *query = NULL;
  size_t dlen;
  unsigned dots; char const *dot;
  char b[8];

  SU_DEBUG_9(("sres_search(%p, %p, %p, %s, \"%s\") called\n",
	      res, callback, context, sres_record_type(type, b), domain));

  if (res == NULL || domain == NULL)
    return su_seterrno(EFAULT), (void *)NULL;

  dlen = strlen(domain);
  if (dlen > SRES_MAXDNAME ||
      (dlen == SRES_MAXDNAME && domain[dlen - 1] != '.')) {
    su_seterrno(ENAMETOOLONG);
    return NULL;
  }

  sres_resolver_update(res, 0);

  if (sres_has_search_domain(res))
    for (dots = 0, dot = strchr(domain, '.');
	 dots < res->res_config->c_opt.ndots && dot; 
	 dots++, dot = strchr(dot + 1, '.'))
      ;
  else
    dots = 0;

  query = sres_query_alloc(res, callback, context, type, domain);

  if (query) {
    /* Create sub-query for each search domain */
    if (dots < res->res_config->c_opt.ndots) {
      sres_query_t *sub;
      int i, subs, len;
      char const **domains = res->res_config->c_search;
      char search[SRES_MAXDNAME + 1];

      memcpy(search, domain, dlen);
      search[dlen++] = '.';
      search[dlen] = '\0';

      for (i = 0, subs = 0; i <= SRES_MAX_SEARCH; i++) {
	if (domains[i]) {
	  len = strlen(domains[i]);
	  
	  if (dlen + len + 1 > SRES_MAXDNAME)
	    continue;

	  memcpy(search + dlen, domains[i], len);
	  search[dlen + len] = '.';
	  search[dlen + len + 1] = '\0';
	  sub = sres_query_alloc(res, sres_answer_subquery, (void *)query,
				 type, search);

	  if (sres_send_dns_query(res, sub) == 0) {
	    query->q_subqueries[i] = sub;
	  }
	  else {
	    sres_free_query(res, sub), sub = NULL;
	  }
	  subs += sub != NULL;
	}
      }

      query->q_n_subs = subs;
    }

    if (sres_send_dns_query(res, query) != 0) {
      if (!query->q_n_subs)
	sres_free_query(res, query), query = NULL;
      else
	query->q_id = 0;
    }
  }

  return query;
}

/** Make a reverse DNS query.
 *
 * Send a query to DNS server with specified @a type and domain name formed
 * from the socket address @a addr. The sres resolver takes care of
 * retransmitting the query if sres_resolver_timer() is called in regular
 * intervals. It generates an error record with nonzero status if no
 * response is received.
 */
sres_query_t *
sres_query_sockaddr(sres_resolver_t *res,
		    sres_answer_f *callback,
		    sres_context_t *context,
		    uint16_t type,
		    struct sockaddr const *addr)
{
  char name[80]; 

  if (!res || !addr)
    return su_seterrno(EFAULT), (void *)NULL;

  if (!sres_sockaddr2string(res, name, sizeof(name), addr))
    return NULL;

  return sres_query(res, callback, context, type, name);
}


/** Make a DNS query.
 *
 * Sends a DNS query with specified @a type and @a domain to the DNS server. 
 * The sres resolver takes care of retransmitting the query if
 * sres_resolver_timer() is called in regular intervals. It generates an
 * error record with nonzero status if no response is received.
 *
 * This function just makes sure that we have the @a socket is valid,
 * otherwise it behaves exactly like sres_query().
 */
sres_query_t *
sres_query_make(sres_resolver_t *res,
		sres_answer_f *callback,
		sres_context_t *context,
		int socket,
		uint16_t type,