sres.c

sip协议栈

    query->q_hash = query->q_id * Q_PRIME /* + query->q_i_server */;
    sres_qtable_append(res->res_queries, query);
  }

  return query;
}

static inline
void 
sres_remove_query(sres_resolver_t *res, sres_query_t *q, int all)
{
  int i;

  if (q->q_hash) {
    sres_qtable_remove(res->res_queries, q), q->q_hash = 0;

    if (all)
      for (i = 0; i <= SRES_MAX_SEARCH; i++) {
	if (q->q_subqueries[i] && q->q_subqueries[i]->q_hash) {
	  sres_qtable_remove(res->res_queries, q->q_subqueries[i]);
	  q->q_subqueries[i]->q_hash = 0;
	}
      }
  }
}

/** Remove a query from hash table and free it. */
static
void sres_free_query(sres_resolver_t *res, sres_query_t *q)
{
  int i;

  if (q == NULL)
    return;

  if (q->q_hash)
    sres_qtable_remove(res->res_queries, q), q->q_hash = 0;

  for (i = 0; i <= SRES_MAX_SEARCH; i++) {
    sres_query_t *sq;

    sq = q->q_subqueries[i];
    q->q_subqueries[i] = NULL;
    if (sq)
      sres_free_query(res, sq);
    if (q->q_subanswers[i])
      sres_cache_free_answers(res->res_cache, q->q_subanswers[i]);
    q->q_subanswers[i] = NULL;
  }
 
  su_free(res->res_home, q);
}

static
sres_record_t **
sres_combine_results(sres_resolver_t *res,
		     sres_record_t **search_results[SRES_MAX_SEARCH + 1])
{
  sres_record_t **combined_result;
  int i, j, found;

  /* Combine the results into a single list. */
  for (i = 0, found = 0; i <= SRES_MAX_SEARCH; i++)
    if (search_results[i])
      for (j = 0; search_results[i][j]; j++)
	found++;

  combined_result = su_alloc((su_home_t *)res->res_cache, 
			     (found + 1) * (sizeof combined_result[0]));
  if (combined_result) {
    for (i = 0, found = 0; i <= SRES_MAX_SEARCH; i++)
      if (search_results[i])
	for (j = 0; search_results[i][j]; j++) {
	  combined_result[found++] = search_results[i][j];
	  search_results[i][j] = NULL;
	}

    combined_result[found] = NULL;
    sres_sort_answers(res, combined_result);
  }

  for (i = 0; i <= SRES_MAX_SEARCH; i++)
    if (search_results[i])
      sres_free_answers(res, search_results[i]), search_results[i] = NULL;

  return combined_result;
}

static
int
sres_sockaddr2string(sres_resolver_t *res,
		     char name[],
		     size_t namelen,
		     struct sockaddr const *addr)
{
  name[0] = '\0';

  if (addr->sa_family == AF_INET) {
    struct sockaddr_in const *sin = (struct sockaddr_in *)addr;
    uint8_t const *in_addr = (uint8_t*)&sin->sin_addr;
    return snprintf(name, namelen, "%u.%u.%u.%u.in-addr.arpa.",
		    in_addr[3], in_addr[2], in_addr[1], in_addr[0]);
  }
#if HAVE_SIN6
  else if (addr->sa_family == AF_INET6) {
    struct sockaddr_in6 const *sin6 = (struct sockaddr_in6 *)addr;
    int addrsize = sizeof(sin6->sin6_addr.s6_addr);
    char *postfix;
    int required;
    int i;

    if (res->res_config->c_opt.ip6int)
      postfix = "ip6.int.";
    else
      postfix = "ip6.arpa.";

    required = addrsize * 4 + strlen(postfix);

    if (namelen <= required)
      return required;

    for (i = 0; i < addrsize; i++) {
      uint8_t byte = sin6->sin6_addr.s6_addr[addrsize - i - 1];
      uint8_t hex;

      hex = byte & 0xf;
      name[4 * i] = hex > 9 ? hex + 'a' - 10 : hex + '0';
      name[4 * i + 1] = '.';
      hex = (byte >> 4) & 0xf;
      name[4 * i + 2] = hex > 9 ? hex + 'a' - 10 : hex + '0';
      name[4 * i + 3] = '.';
    }
    
    strcpy(name + 4 * i, postfix);

    return required;
  }
#endif
  else {
    su_seterrno(EAFNOSUPPORT);
    SU_DEBUG_3(("%s: %s\n", "sres_sockaddr2string", 
                su_strerror(EAFNOSUPPORT)));
    return 0;
  }
}

/** Make a domain name a top level domain name.
 *
 * The function sres_toplevel() returns a copies string @a domain and 
 * terminates it with a dot if it is not already terminated. 
 */
static
char const *
sres_toplevel(char buf[], size_t blen, char const *domain)
{
  size_t len;
  int already;

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

  len = strlen(domain);

  if (len >= blen)
    return su_seterrno(ENAMETOOLONG), (void *)NULL;

  already = len > 0 && domain[len - 1] == '.';

  if (already)
    return domain;

  if (len + 1 >= blen)
    return su_seterrno(ENAMETOOLONG), (void *)NULL;

  strcpy(buf, domain);
  buf[len] = '.'; buf[len + 1] = '\0';

  return buf;
}

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

static int sres_parse_config(sres_config_t *, FILE *);
static int sres_parse_options(sres_config_t *c, char const *value);
static int sres_parse_nameserver(sres_config_t *c, char const *server);
static time_t sres_config_timestamp(sres_config_t const *c);

/** Update configuration
 *
 */
int sres_resolver_update(sres_resolver_t *res, int always)
{
  sres_config_t *c = NULL;
  sres_config_t const *previous;
  sres_server_t **servers, **old_servers;

  previous = res->res_config;

  time(&res->res_now);

  if (!always && previous && res->res_now < res->res_checked)
    return 0;

  /* Try avoid checking for changes too often. */
  res->res_checked = res->res_now + SRES_UPDATE_INTERVAL_SECS; 
  
  if (!always && previous && 
      sres_config_timestamp(previous) == previous->c_modified)
    return 0;

  c = sres_parse_resolv_conf(res, res->res_options);
  if (!c)
    return -1;

  res->res_config = c;

  if (sres_config_changed_servers(c, previous)) {
    servers = sres_servers_new(res, c);
    if (!servers) {
      su_home_unref((void *)c->c_home);
      return -1;
    }

    old_servers = res->res_servers;

    res->res_i_server = 0;
    res->res_n_servers = sres_servers_count(servers);
    res->res_servers = servers;

    sres_servers_unref(res, old_servers);
  }

  su_home_unref((su_home_t *)previous->c_home);

  return 0;
}

#if _WIN32

/** Number of octets to read from a registry key at a time */
#define QUERY_DATALEN         1024
#define MAX_DATALEN           65535

/**
 * Parses name servers listed in registry key 'key+lpValueName'. The
 * key is expected to contain a whitespace separate list of
 * name server IP addresses.
 *
 * @return number of server addresses added
 */ 
static int sres_parse_win32_reg_parse_dnsserver(sres_config_t *c, HKEY key, LPCTSTR lpValueName)
{
  su_home_t *home = c->c_home;
  su_strlst_t *reg_dns_list;
  char *name_servers = su_alloc(home, QUERY_DATALEN);
  int name_servers_length = QUERY_DATALEN;
  int ret, servers_added = 0;

  /* get name servers and ... */
  while((ret = RegQueryValueEx(key, 
			       lpValueName, 
			       NULL, NULL, 
			       name_servers, 
			       &name_servers_length)) == ERROR_MORE_DATA) {
    name_servers_length += QUERY_DATALEN;

    /* sanity check, upper limit for memallocs */
    if (name_servers_length > MAX_DATALEN) break;

    name_servers = su_realloc(home, name_servers, name_servers_length);
  }

  /* if reading the key was succesful, continue */
  if (ret == ERROR_SUCCESS) {
    if (name_servers[0]){
      int i;

      /* add to list */
      reg_dns_list = su_strlst_split(home, name_servers, " ");
	    
      for(i = 0 ; i < su_strlst_len(reg_dns_list); i++) {
	const char *item = su_strlst_item(reg_dns_list, i);
	SU_DEBUG_3(("Adding nameserver: %s (key=%s)\n", item, (char*)lpValueName));
	sres_parse_nameserver(c, item);
	++servers_added;
      }
	    
      su_strlst_destroy(reg_dns_list);

    }
  }

  su_free(home, name_servers);

  return servers_added;
}

#endif /* _WIN32 */

/**
 * Discover system nameservers from Windows registry.
 *
 * Refs:
 *  - http://msdn.microsoft.com/library/default.asp?url=/library/en-us/sysinfo/base/regqueryvalueex.asp
 *  - http://support.microsoft.com/default.aspx?scid=kb;en-us;120642
 *  - http://support.microsoft.com/kb/314053/EN-US/
 */
static int sres_parse_win32_reg(sres_config_t *c)
{
  int ret = -1;

#ifdef _WIN32

#define MAX_KEY_LEN           255
#define MAX_VALUE_NAME_LEN    16383

  su_home_t *home = c->c_home;
  HKEY key_handle, interface_key_handle;  
  FILETIME ftime;
  int index, i, found = 0;
  char *interface_guid = su_alloc(home, MAX_VALUE_NAME_LEN);
  int guid_size = MAX_VALUE_NAME_LEN;

  /* step 1: find interface specific nameservers */

  /* open the 'Interfaces' registry Key */
  if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, 
		   "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces", 
		   0, KEY_READ, &key_handle)) {
    SU_DEBUG_2(("RegOpenKeyEx failed\n"));
  } else {
    index = 0;
    /* for each interface listed ... */
    while (RegEnumKeyEx(key_handle, index,
			interface_guid, &guid_size,
			NULL,NULL,0,&ftime) == ERROR_SUCCESS){
      if (RegOpenKeyEx(key_handle, interface_guid,
		       0, KEY_READ, 
		       &interface_key_handle) == ERROR_SUCCESS) {

	/* note: 'NameServer' is preferred over 'DhcpNameServer' */
	found += sres_parse_win32_reg_parse_dnsserver(c, interface_key_handle, "NameServer");
	if (found == 0) 
	  found += sres_parse_win32_reg_parse_dnsserver(c, interface_key_handle, "DhcpNameServer");

	RegCloseKey(interface_key_handle);
      } else{
	SU_DEBUG_2(("interface RegOpenKeyEx failed\n"));
      }
      index++;
      guid_size = 64;
    }
    RegCloseKey(key_handle);
  }

  /* step 2: if no interface-specific nameservers are found, 
   *         check for system-wide nameservers */
  if (found == 0) {
    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, 
		     "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters", 
		     0, KEY_READ, &key_handle)) {
      SU_DEBUG_2(("RegOpenKeyEx failed (2)\n"));
    } else {
      found += sres_parse_win32_reg_parse_dnsserver(c, key_handle, "NameServer");
      if (found == 0) 
	found += sres_parse_win32_reg_parse_dnsserver(c, key_handle, "DhcpNameServer");
      RegCloseKey(key_handle);
    }
  }

  SU_DEBUG_3(("Total of %d name servers found from win32 registry.\n", found));

  /* return success if servers found */
  if (found) ret = 0;

  su_free(home, interface_guid);

#endif /* _WIN32 */

  return ret;
}

/** Parse /etc/resolv.conf file.
 *
 * @retval #sres_config_t structure when successful 
 * @retval NULL upon an error
 *
 * @todo The resolv.conf directives @b sortlist and most of the options 
 *       are currently ignored.
 */
static 
sres_config_t *sres_parse_resolv_conf(sres_resolver_t *res,
				      char const **options)
{
  sres_config_t *c = su_home_clone(res->res_home, (sizeof *c));

  if (c) {
    FILE *f;
    int i, success = 0;
    
    f = fopen(c->c_filename = res->res_cnffile, "r");

    sres_parse_config(c, f);

    if (f)
      fclose(f);
    
    /* on win32, query the registry for nameservers */
    if (sres_parse_win32_reg(c) == 0) 
      ++success;

#ifndef _WIN32
    /* note: no 127.0.0.1 on win32 systems */
    if (c->c_nameservers[0] == NULL)
      sres_parse_nameserver(c, "127.0.0.1");
#endif
      
    for (i = 0; c->c_nameservers[i] && i < SRES_MAX_NAMESERVERS; i++) {
      struct sockaddr_in *sin = (void *)c->c_nameservers[i]->ns_addr;
      sin->sin_port = htons(c->c_port);
    }

    sres_parse_options(c, getenv("RES_OPTIONS"));
    
    if (options)
      for (i = 0; options[i]; i++)
	sres_parse_options(c, options[i]);

    sres_parse_options(c, getenv("SRES_OPTIONS"));

    su_home_threadsafe(c->c_home);
  }

  return c;
}

/** Parse config file. 
 *
 * @return Number of search domains, if successful.
 * @retval -1 upon an error (never happens).
 */
static
int sres_parse_config(sres_config_t *c, FILE *f)
{
  su_home_t *home = c->c_home;
  int line;
  char const *localdomain;
  char *search = NULL, *domain = NULL;
  char buf[1025];
  int i = 0;

  localdomain = getenv("LOCALDOMAIN");

  /* Default values */
  c->c_opt.ndots = 1;
  c->c_opt.check_names = 1;
  c->c_opt.timeout = SRES_RETRY_INTERVAL;
  c->c_opt.attempts = SRES_MAX_RETRY_COUNT;
  c->c_port = 53;

  if (f != NULL) {  
    for (line = 1; fgets(buf, sizeof(buf), f); line++) {
      int len;
      char *value, *b;

      /* Skip whitespace at the beginning ...*/
      b = buf + strspn(buf, " \t");

      /* ... and at the end of line */
      for (len = strlen(b); len > 0 && strchr(" \t\r\n", b[len - 1]); len--)
	;

      if (len == 0 || b[0] == '#') 	/* Empty line or comment */
	continue;

      b[len] = '\0';

      len = strcspn(b, " \t");
      value = b + len; value += strspn(value, " \t");

#define MATCH(token) (len == strlen(token) && strncasecmp(token, b, len) == 0)

      if (MATCH("nameserver")) {
	if (sres_parse_nameserver(c, value) < 0)
	  return -1;
      }
      else if (MATCH("domain")) {
	if (localdomain)	/* LOCALDOMAIN overrides */
	  continue;
	if (search)
	  su_free(home, search), search = NULL;
	if (domain)
	  su_free(home, domain), domain = NULL;
	domain = su_strdup(home, value);
	if (!domain)
	  return -1;