sres.c

Sofia SIP is an open-source SIP User-Agent library, compliant with the IETF RFC3261 specification.

			       char const *info);

static
void sres_log_response(sres_resolver_t const *res, 
		       sres_message_t const *m,
		       struct sockaddr_storage const *from,
		       sres_query_t const *query,
		       sres_record_t * const *reply);

static int sres_decode_msg(sres_resolver_t *res, 
			   sres_message_t *m,
			   sres_query_t **,
			   sres_record_t ***aanswers);

static char const *sres_toplevel(char buf[], size_t bsize, char const *domain);

static sres_record_t *sres_create_record(sres_resolver_t *, sres_message_t *m);

static sres_record_t *sres_init_rr_soa(sres_cache_t *cache,
				       sres_soa_record_t *,
				       sres_message_t *m);
static sres_record_t *sres_init_rr_a(sres_cache_t *cache,
				     sres_a_record_t *,
				     sres_message_t *m);
static sres_record_t *sres_init_rr_a6(sres_cache_t *cache,
				      sres_a6_record_t *,
				      sres_message_t *m);
static sres_record_t *sres_init_rr_aaaa(sres_cache_t *cache,
					sres_aaaa_record_t *,
					sres_message_t *m);
static sres_record_t *sres_init_rr_cname(sres_cache_t *cache,
					 sres_cname_record_t *,
					 sres_message_t *m);
static sres_record_t *sres_init_rr_ptr(sres_cache_t *cache,
				       sres_ptr_record_t *,
				       sres_message_t *m);
static sres_record_t *sres_init_rr_srv(sres_cache_t *cache,
				       sres_srv_record_t *,
				       sres_message_t *m);
static sres_record_t *sres_init_rr_naptr(sres_cache_t *cache,
					 sres_naptr_record_t *,
					 sres_message_t *m);
static sres_record_t *sres_init_rr_unknown(sres_cache_t *cache,
					   sres_common_t *r,
					   sres_message_t *m);

static sres_record_t *sres_create_error_rr(sres_cache_t *cache,
                                           sres_query_t const *q,
                                           uint16_t errcode);

static void m_put_uint16(sres_message_t *m, uint16_t h);
static void m_put_uint32(sres_message_t *m, uint32_t w);

static uint16_t m_put_domain(sres_message_t *m, 
                             char const *domain, 
                             uint16_t top, 
                             char const *topdomain);

static uint32_t m_get_uint32(sres_message_t *m);
static uint16_t m_get_uint16(sres_message_t *m);
static uint8_t m_get_uint8(sres_message_t *m);

static int m_get_string(char *d, int n, sres_message_t *m, uint16_t offset);
static int m_get_domain(char *d, int n, sres_message_t *m, uint16_t offset);

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

#define SU_LOG sresolv_log

#include <sofia-sip/su_debug.h>

#ifdef HAVE_WIN32
#include <winreg.h>
#endif

/**@ingroup sresolv_env
 *
 * Environment variable determining the debug log level for @b sresolv
 * module.
 *
 * The SRESOLV_DEBUG environment variable is used to determine the debug
 * logging level for @b sresolv module. The default level is 3.
 * 
 * @sa <sofia-sip/su_debug.h>, sresolv_log, SOFIA_DEBUG
 */
#ifdef DOXYGEN
extern char const SRESOLV_DEBUG[]; /* dummy declaration for Doxygen */
#endif

#ifndef SU_DEBUG
#define SU_DEBUG 3
#endif

/**Debug log for @b sresolv module. 
 * 
 * The sresolv_log is the log object used by @b sresolv module. The level of
 * #sresolv_log is set using #SRESOLV_DEBUG environment variable.
 */
su_log_t sresolv_log[] = { SU_LOG_INIT("sresolv", "SRESOLV_DEBUG", SU_DEBUG) };

/** 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 sharing the configuration and cache with old
 * resolver.
 */
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 (may be NULL)
 * @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_destructor(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) {
      size_t len = read(fd, &res->res_id, (sizeof res->res_id)); (void)len;
      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;
}

/** Get async object */
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;
}

/** Register resolver timer callback. */
int sres_resolver_set_timer_cb(sres_resolver_t *res,
			       sres_schedule_f *callback,
			       sres_async_t *async)
{
  if (res == NULL)
    return su_seterrno(EFAULT);
  if (res->res_async != async)
    return su_seterrno(EALREADY);

  res->res_schedulecb = callback;
  return 0;
}

/**Send a DNS query.
 *
 * Sends a DNS query with specified @a type and @a domain to the DNS server.
 * When an answer is received, the @a callback function is called with
 * @a context and returned records as arguments.
 *
 * The sres resolver takes care of retransmitting the query if a root object
 * is associate with the resolver or 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
 * @param callback function called when query is answered or times out
 * @param context pointer given as an extra argument to @a callback function
 * @param type record type to query (see #sres_qtypes)
 * @param domain name to query
 *
 * Query types also indicate the record type of the result.
 * Any record can be queried with #sres_qtype_any.
 * Well-known query types understood and decoded by @b sres include
 * #sres_type_a, 
 * #sres_type_aaaa,
 * #sres_type_cname,
 * #sres_type_ptr 
 * #sres_type_soa, 
 * #sres_type_aaaa, 
 * #sres_type_srv, and
 * #sres_type_naptr.
 *
 * Deprecated query type #sres_type_a6 is also decoded.
 *
 * @note The domain name is @b not concatenated with the domains from seach
 * path or with the local domain. Use sres_search() in order to try domains
 * in search path.
 *
 * @sa sres_search(), sres_blocking_query(), sres_cached_answers(),
 * sres_query_sockaddr()
 *
 * @ERRORS
 * @ERROR EFAULT @a res or @a domain point outside the address space
 * @ERROR ENAMETOOLONG @a domain is longer than SRES_MAXDNAME
 * @ERROR ENETDOWN no DNS servers configured
 * @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, %s, \"%s\") called\n",
			  (void *)res, (void *)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);

  if (res->res_n_servers == 0)