gio/gresolver.c

   1 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
   2
   3 /* GIO - GLib Input, Output and Streaming Library
   4  *
   5  * Copyright (C) 2008 Red Hat, Inc.
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General
  18  * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include "config.h"
  22 #include <glib.h>
  23 #include "glibintl.h"
  24
  25 #include "gresolver.h"
  26 #include "gnetworkingprivate.h"
  27 #include "gasyncresult.h"
  28 #include "ginetaddress.h"
  29 #include "gtask.h"
  30 #include "gsrvtarget.h"
  31 #include "gthreadedresolver.h"
  32 #include "gioerror.h"
  33
  34 #ifdef G_OS_UNIX
  35 #include <sys/stat.h>
  36 #endif
  37
  38 #include <stdlib.h>
  39
  40
  41 /**
  42  * SECTION:gresolver
  43  * @short_description: Asynchronous and cancellable DNS resolver
  44  * @include: gio/gio.h
  45  *
  46  * #GResolver provides cancellable synchronous and asynchronous DNS
  47  * resolution, for hostnames (g_resolver_lookup_by_address(),
  48  * g_resolver_lookup_by_name() and their async variants) and SRV
  49  * (service) records (g_resolver_lookup_service()).
  50  *
  51  * #GNetworkAddress and #GNetworkService provide wrappers around
  52  * #GResolver functionality that also implement #GSocketConnectable,
  53  * making it easy to connect to a remote host/service.
  54  */
  55
  56 enum {
  57   RELOAD,
  58   LAST_SIGNAL
  59 };
  60
  61 static guint signals[LAST_SIGNAL] = { 0 };
  62
  63 struct _GResolverPrivate {
  64 #ifdef G_OS_UNIX
  65   time_t resolv_conf_timestamp;
  66 #else
  67   int dummy;
  68 #endif
  69 };
  70
  71 /**
  72  * GResolver:
  73  *
  74  * The object that handles DNS resolution. Use g_resolver_get_default()
  75  * to get the default resolver.
  76  *
  77  * This is an abstract type; subclasses of it implement different resolvers for
  78  * different platforms and situations.
  79  */
  80 G_DEFINE_ABSTRACT_TYPE_WITH_CODE (GResolver, g_resolver, G_TYPE_OBJECT,
  81                                   G_ADD_PRIVATE (GResolver)
  82                                   g_networking_init ();)
  83
  84 static GList *
  85 srv_records_to_targets (GList *records)
  86 {
  87   const gchar *hostname;
  88   guint16 port, priority, weight;
  89   GSrvTarget *target;
  90   GList *l;
  91
  92   for (l = records; l != NULL; l = g_list_next (l))
  93     {
  94       g_variant_get (l->data, "(qqq&s)", &priority, &weight, &port, &hostname);
  95       target = g_srv_target_new (hostname, port, priority, weight);
  96       g_variant_unref (l->data);
  97       l->data = target;
  98     }
  99
 100   return g_srv_target_list_sort (records);
 101 }
 102
 103 static GList *
 104 g_resolver_real_lookup_service (GResolver            *resolver,
 105                                 const gchar          *rrname,
 106                                 GCancellable         *cancellable,
 107                                 GError              **error)
 108 {
 109   GList *records;
 110
 111   records = G_RESOLVER_GET_CLASS (resolver)->lookup_records (resolver,
 112                                                              rrname,
 113                                                              G_RESOLVER_RECORD_SRV,
 114                                                              cancellable,
 115                                                              error);
 116
 117   return srv_records_to_targets (records);
 118 }
 119
 120 static void
 121 g_resolver_real_lookup_service_async (GResolver            *resolver,
 122                                       const gchar          *rrname,
 123                                       GCancellable         *cancellable,
 124                                       GAsyncReadyCallback   callback,
 125                                       gpointer              user_data)
 126 {
 127   G_RESOLVER_GET_CLASS (resolver)->lookup_records_async (resolver,
 128                                                          rrname,
 129                                                          G_RESOLVER_RECORD_SRV,
 130                                                          cancellable,
 131                                                          callback,
 132                                                          user_data);
 133 }
 134
 135 static GList *
 136 g_resolver_real_lookup_service_finish (GResolver            *resolver,
 137                                        GAsyncResult         *result,
 138                                        GError              **error)
 139 {
 140   GList *records;
 141
 142   records = G_RESOLVER_GET_CLASS (resolver)->lookup_records_finish (resolver,
 143                                                                     result,
 144                                                                     error);
 145
 146   return srv_records_to_targets (records);
 147 }
 148
 149 static void
 150 g_resolver_class_init (GResolverClass *resolver_class)
 151 {
 152   /* Automatically pass these over to the lookup_records methods */
 153   resolver_class->lookup_service = g_resolver_real_lookup_service;
 154   resolver_class->lookup_service_async = g_resolver_real_lookup_service_async;
 155   resolver_class->lookup_service_finish = g_resolver_real_lookup_service_finish;
 156
 157   /**
 158    * GResolver::reload:
 159    * @resolver: a #GResolver
 160    *
 161    * Emitted when the resolver notices that the system resolver
 162    * configuration has changed.
 163    **/
 164   signals[RELOAD] =
 165     g_signal_new (I_("reload"),
 166                   G_TYPE_RESOLVER,
 167                   G_SIGNAL_RUN_LAST,
 168                   G_STRUCT_OFFSET (GResolverClass, reload),
 169                   NULL, NULL,
 170                   g_cclosure_marshal_VOID__VOID,
 171                   G_TYPE_NONE, 0);
 172 }
 173
 174 static void
 175 g_resolver_init (GResolver *resolver)
 176 {
 177 #ifdef G_OS_UNIX
 178   struct stat st;
 179 #endif
 180
 181   resolver->priv = g_resolver_get_instance_private (resolver);
 182
 183 #ifdef G_OS_UNIX
 184   if (stat (_PATH_RESCONF, &st) == 0)
 185     resolver->priv->resolv_conf_timestamp = st.st_mtime;
 186 #endif
 187 }
 188
 189 G_LOCK_DEFINE_STATIC (default_resolver);
 190 static GResolver *default_resolver;
 191
 192 /**
 193  * g_resolver_get_default:
 194  *
 195  * Gets the default #GResolver. You should unref it when you are done
 196  * with it. #GResolver may use its reference count as a hint about how
 197  * many threads it should allocate for concurrent DNS resolutions.
 198  *
 199  * Returns: (transfer full): the default #GResolver.
 200  *
 201  * Since: 2.22
 202  */
 203 GResolver *
 204 g_resolver_get_default (void)
 205 {
 206   GResolver *ret;
 207
 208   G_LOCK (default_resolver);
 209   if (!default_resolver)
 210     default_resolver = g_object_new (G_TYPE_THREADED_RESOLVER, NULL);
 211   ret = g_object_ref (default_resolver);
 212   G_UNLOCK (default_resolver);
 213
 214   return ret;
 215 }
 216
 217 /**
 218  * g_resolver_set_default:
 219  * @resolver: the new default #GResolver
 220  *
 221  * Sets @resolver to be the application's default resolver (reffing
 222  * @resolver, and unreffing the previous default resolver, if any).
 223  * Future calls to g_resolver_get_default() will return this resolver.
 224  *
 225  * This can be used if an application wants to perform any sort of DNS
 226  * caching or "pinning"; it can implement its own #GResolver that
 227  * calls the original default resolver for DNS operations, and
 228  * implements its own cache policies on top of that, and then set
 229  * itself as the default resolver for all later code to use.
 230  *
 231  * Since: 2.22
 232  */
 233 void
 234 g_resolver_set_default (GResolver *resolver)
 235 {
 236   G_LOCK (default_resolver);
 237   if (default_resolver)
 238     g_object_unref (default_resolver);
 239   default_resolver = g_object_ref (resolver);
 240   G_UNLOCK (default_resolver);
 241 }
 242
 243 /* Bionic has res_init() but it's not in any header */
 244 #ifdef __BIONIC__
 245 int res_init (void);
 246 #endif
 247
 248 static void
 249 g_resolver_maybe_reload (GResolver *resolver)
 250 {
 251 #ifdef G_OS_UNIX
 252   struct stat st;
 253
 254   if (stat (_PATH_RESCONF, &st) == 0)
 255     {
 256       if (st.st_mtime != resolver->priv->resolv_conf_timestamp)
 257         {
 258           resolver->priv->resolv_conf_timestamp = st.st_mtime;
 259 #ifdef HAVE_RES_INIT
 260           res_init ();
 261 #endif
 262           g_signal_emit (resolver, signals[RELOAD], 0);
 263         }
 264     }
 265 #endif
 266 }
 267
 268 /* filter out duplicates, cf. https://bugzilla.gnome.org/show_bug.cgi?id=631379 */
 269 static void
 270 remove_duplicates (GList *addrs)
 271 {
 272   GList *l;
 273   GList *ll;
 274   GList *lll;
 275
 276   /* TODO: if this is too slow (it's O(n^2) but n is typically really
 277    * small), we can do something more clever but note that we must not
 278    * change the order of elements...
 279    */
 280   for (l = addrs; l != NULL; l = l->next)
 281     {
 282       GInetAddress *address = G_INET_ADDRESS (l->data);
 283       for (ll = l->next; ll != NULL; ll = lll)
 284         {
 285           GInetAddress *other_address = G_INET_ADDRESS (ll->data);
 286           lll = ll->next;
 287           if (g_inet_address_equal (address, other_address))
 288             {
 289               g_object_unref (other_address);
 290               /* we never return the first element */
 291               g_warn_if_fail (g_list_delete_link (addrs, ll) == addrs);
 292             }
 293         }
 294     }
 295 }
 296
 297 /* Note that this does not follow the "FALSE means @error is set"
 298  * convention. The return value tells the caller whether it should
 299  * return @addrs and @error to the caller right away, or if it should
 300  * continue and trying to resolve the name as a hostname.
 301  */
 302 static gboolean
 303 handle_ip_address (const char  *hostname,
 304                    GList      **addrs,
 305                    GError     **error)
 306 {
 307   GInetAddress *addr;
 308
 309 #ifndef G_OS_WIN32
 310   struct in_addr ip4addr;
 311 #endif
 312
 313   addr = g_inet_address_new_from_string (hostname);
 314   if (addr)
 315     {
 316       *addrs = g_list_append (NULL, addr);
 317       return TRUE;
 318     }
 319
 320   *addrs = NULL;
 321
 322 #ifdef G_OS_WIN32
 323
 324   /* Reject IPv6 addresses that have brackets ('[' or ']') and/or port numbers,
 325    * as no valid addresses should contain these at this point.
 326    * Non-standard IPv4 addresses would be rejected during the call to
 327    * getaddrinfo() later.
 328    */
 329   if (strrchr (hostname, '[') != NULL ||
 330       strrchr (hostname, ']') != NULL)
 331 #else
 332
 333   /* Reject non-standard IPv4 numbers-and-dots addresses.
 334    * g_inet_address_new_from_string() will have accepted any "real" IP
 335    * address, so if inet_aton() succeeds, then it's an address we want
 336    * to reject.
 337    */
 338   if (inet_aton (hostname, &ip4addr))
 339 #endif
 340     {
 341       g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_NOT_FOUND,
 342                    _("Error resolving “%s”: %s"),
 343                    hostname, gai_strerror (EAI_NONAME));
 344       return TRUE;
 345     }
 346
 347   return FALSE;
 348 }
 349
 350 /**
 351  * g_resolver_lookup_by_name:
 352  * @resolver: a #GResolver
 353  * @hostname: the hostname to look up
 354  * @cancellable: (nullable): a #GCancellable, or %NULL
 355  * @error: return location for a #GError, or %NULL
 356  *
 357  * Synchronously resolves @hostname to determine its associated IP
 358  * address(es). @hostname may be an ASCII-only or UTF-8 hostname, or
 359  * the textual form of an IP address (in which case this just becomes
 360  * a wrapper around g_inet_address_new_from_string()).
 361  *
 362  * On success, g_resolver_lookup_by_name() will return a non-empty #GList of
 363  * #GInetAddress, sorted in order of preference and guaranteed to not
 364  * contain duplicates. That is, if using the result to connect to
 365  * @hostname, you should attempt to connect to the first address
 366  * first, then the second if the first fails, etc. If you are using
 367  * the result to listen on a socket, it is appropriate to add each
 368  * result using e.g. g_socket_listener_add_address().
 369  *
 370  * If the DNS resolution fails, @error (if non-%NULL) will be set to a
 371  * value from #GResolverError and %NULL will be returned.
 372  *
 373  * If @cancellable is non-%NULL, it can be used to cancel the
 374  * operation, in which case @error (if non-%NULL) will be set to
 375  * %G_IO_ERROR_CANCELLED.
 376  *
 377  * If you are planning to connect to a socket on the resolved IP
 378  * address, it may be easier to create a #GNetworkAddress and use its
 379  * #GSocketConnectable interface.
 380  *
 381  * Returns: (element-type GInetAddress) (transfer full): a non-empty #GList
 382  * of #GInetAddress, or %NULL on error. You
 383  * must unref each of the addresses and free the list when you are
 384  * done with it. (You can use g_resolver_free_addresses() to do this.)
 385  *
 386  * Since: 2.22
 387  */
 388 GList *
 389 g_resolver_lookup_by_name (GResolver     *resolver,
 390                            const gchar   *hostname,
 391                            GCancellable  *cancellable,
 392                            GError       **error)
 393 {
 394   GList *addrs;
 395   gchar *ascii_hostname = NULL;
 396
 397   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 398   g_return_val_if_fail (hostname != NULL, NULL);
 399
 400   /* Check if @hostname is just an IP address */
 401   if (handle_ip_address (hostname, &addrs, error))
 402     return addrs;
 403
 404   if (g_hostname_is_non_ascii (hostname))
 405     hostname = ascii_hostname = g_hostname_to_ascii (hostname);
 406
 407   if (!hostname)
 408     {
 409       g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_FAILED,
 410                            _("Invalid hostname"));
 411       return NULL;
 412     }
 413
 414   g_resolver_maybe_reload (resolver);
 415   addrs = G_RESOLVER_GET_CLASS (resolver)->
 416     lookup_by_name (resolver, hostname, cancellable, error);
 417
 418   remove_duplicates (addrs);
 419
 420   g_free (ascii_hostname);
 421   return addrs;
 422 }
 423
 424 /**
 425  * g_resolver_lookup_by_name_async:
 426  * @resolver: a #GResolver
 427  * @hostname: the hostname to look up the address of
 428  * @cancellable: (nullable): a #GCancellable, or %NULL
 429  * @callback: (scope async): callback to call after resolution completes
 430  * @user_data: (closure): data for @callback
 431  *
 432  * Begins asynchronously resolving @hostname to determine its
 433  * associated IP address(es), and eventually calls @callback, which
 434  * must call g_resolver_lookup_by_name_finish() to get the result.
 435  * See g_resolver_lookup_by_name() for more details.
 436  *
 437  * Since: 2.22
 438  */
 439 void
 440 g_resolver_lookup_by_name_async (GResolver           *resolver,
 441                                  const gchar         *hostname,
 442                                  GCancellable        *cancellable,
 443                                  GAsyncReadyCallback  callback,
 444                                  gpointer             user_data)
 445 {
 446   gchar *ascii_hostname = NULL;
 447   GList *addrs;
 448   GError *error = NULL;
 449
 450   g_return_if_fail (G_IS_RESOLVER (resolver));
 451   g_return_if_fail (hostname != NULL);
 452
 453   /* Check if @hostname is just an IP address */
 454   if (handle_ip_address (hostname, &addrs, &error))
 455     {
 456       GTask *task;
 457
 458       task = g_task_new (resolver, cancellable, callback, user_data);
 459       g_task_set_source_tag (task, g_resolver_lookup_by_name_async);
 460       if (addrs)
 461         g_task_return_pointer (task, addrs, (GDestroyNotify) g_resolver_free_addresses);
 462       else
 463         g_task_return_error (task, error);
 464       g_object_unref (task);
 465       return;
 466     }
 467
 468   if (g_hostname_is_non_ascii (hostname))
 469     hostname = ascii_hostname = g_hostname_to_ascii (hostname);
 470
 471   if (!hostname)
 472     {
 473       GTask *task;
 474
 475       g_set_error_literal (&error, G_IO_ERROR, G_IO_ERROR_FAILED,
 476                            _("Invalid hostname"));
 477       task = g_task_new (resolver, cancellable, callback, user_data);
 478       g_task_set_source_tag (task, g_resolver_lookup_by_name_async);
 479       g_task_return_error (task, error);
 480       g_object_unref (task);
 481       return;
 482     }
 483
 484   g_resolver_maybe_reload (resolver);
 485   G_RESOLVER_GET_CLASS (resolver)->
 486     lookup_by_name_async (resolver, hostname, cancellable, callback, user_data);
 487
 488   g_free (ascii_hostname);
 489 }
 490
 491 /**
 492  * g_resolver_lookup_by_name_finish:
 493  * @resolver: a #GResolver
 494  * @result: the result passed to your #GAsyncReadyCallback
 495  * @error: return location for a #GError, or %NULL
 496  *
 497  * Retrieves the result of a call to
 498  * g_resolver_lookup_by_name_async().
 499  *
 500  * If the DNS resolution failed, @error (if non-%NULL) will be set to
 501  * a value from #GResolverError. If the operation was cancelled,
 502  * @error will be set to %G_IO_ERROR_CANCELLED.
 503  *
 504  * Returns: (element-type GInetAddress) (transfer full): a #GList
 505  * of #GInetAddress, or %NULL on error. See g_resolver_lookup_by_name()
 506  * for more details.
 507  *
 508  * Since: 2.22
 509  */
 510 GList *
 511 g_resolver_lookup_by_name_finish (GResolver     *resolver,
 512                                   GAsyncResult  *result,
 513                                   GError       **error)
 514 {
 515   GList *addrs;
 516
 517   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 518
 519   if (g_async_result_legacy_propagate_error (result, error))
 520     return NULL;
 521   else if (g_async_result_is_tagged (result, g_resolver_lookup_by_name_async))
 522     {
 523       /* Handle the stringified-IP-addr case */
 524       return g_task_propagate_pointer (G_TASK (result), error);
 525     }
 526
 527   addrs = G_RESOLVER_GET_CLASS (resolver)->
 528     lookup_by_name_finish (resolver, result, error);
 529
 530   remove_duplicates (addrs);
 531
 532   return addrs;
 533 }
 534
 535 /**
 536  * g_resolver_free_addresses: (skip)
 537  * @addresses: a #GList of #GInetAddress
 538  *
 539  * Frees @addresses (which should be the return value from
 540  * g_resolver_lookup_by_name() or g_resolver_lookup_by_name_finish()).
 541  * (This is a convenience method; you can also simply free the results
 542  * by hand.)
 543  *
 544  * Since: 2.22
 545  */
 546 void
 547 g_resolver_free_addresses (GList *addresses)
 548 {
 549   GList *a;
 550
 551   for (a = addresses; a; a = a->next)
 552     g_object_unref (a->data);
 553   g_list_free (addresses);
 554 }
 555
 556 /**
 557  * g_resolver_lookup_by_address:
 558  * @resolver: a #GResolver
 559  * @address: the address to reverse-resolve
 560  * @cancellable: (nullable): a #GCancellable, or %NULL
 561  * @error: return location for a #GError, or %NULL
 562  *
 563  * Synchronously reverse-resolves @address to determine its
 564  * associated hostname.
 565  *
 566  * If the DNS resolution fails, @error (if non-%NULL) will be set to
 567  * a value from #GResolverError.
 568  *
 569  * If @cancellable is non-%NULL, it can be used to cancel the
 570  * operation, in which case @error (if non-%NULL) will be set to
 571  * %G_IO_ERROR_CANCELLED.
 572  *
 573  * Returns: a hostname (either ASCII-only, or in ASCII-encoded
 574  *     form), or %NULL on error.
 575  *
 576  * Since: 2.22
 577  */
 578 gchar *
 579 g_resolver_lookup_by_address (GResolver     *resolver,
 580                               GInetAddress  *address,
 581                               GCancellable  *cancellable,
 582                               GError       **error)
 583 {
 584   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 585   g_return_val_if_fail (G_IS_INET_ADDRESS (address), NULL);
 586
 587   g_resolver_maybe_reload (resolver);
 588   return G_RESOLVER_GET_CLASS (resolver)->
 589     lookup_by_address (resolver, address, cancellable, error);
 590 }
 591
 592 /**
 593  * g_resolver_lookup_by_address_async:
 594  * @resolver: a #GResolver
 595  * @address: the address to reverse-resolve
 596  * @cancellable: (nullable): a #GCancellable, or %NULL
 597  * @callback: (scope async): callback to call after resolution completes
 598  * @user_data: (closure): data for @callback
 599  *
 600  * Begins asynchronously reverse-resolving @address to determine its
 601  * associated hostname, and eventually calls @callback, which must
 602  * call g_resolver_lookup_by_address_finish() to get the final result.
 603  *
 604  * Since: 2.22
 605  */
 606 void
 607 g_resolver_lookup_by_address_async (GResolver           *resolver,
 608                                     GInetAddress        *address,
 609                                     GCancellable        *cancellable,
 610                                     GAsyncReadyCallback  callback,
 611                                     gpointer             user_data)
 612 {
 613   g_return_if_fail (G_IS_RESOLVER (resolver));
 614   g_return_if_fail (G_IS_INET_ADDRESS (address));
 615
 616   g_resolver_maybe_reload (resolver);
 617   G_RESOLVER_GET_CLASS (resolver)->
 618     lookup_by_address_async (resolver, address, cancellable, callback, user_data);
 619 }
 620
 621 /**
 622  * g_resolver_lookup_by_address_finish:
 623  * @resolver: a #GResolver
 624  * @result: the result passed to your #GAsyncReadyCallback
 625  * @error: return location for a #GError, or %NULL
 626  *
 627  * Retrieves the result of a previous call to
 628  * g_resolver_lookup_by_address_async().
 629  *
 630  * If the DNS resolution failed, @error (if non-%NULL) will be set to
 631  * a value from #GResolverError. If the operation was cancelled,
 632  * @error will be set to %G_IO_ERROR_CANCELLED.
 633  *
 634  * Returns: a hostname (either ASCII-only, or in ASCII-encoded
 635  * form), or %NULL on error.
 636  *
 637  * Since: 2.22
 638  */
 639 gchar *
 640 g_resolver_lookup_by_address_finish (GResolver     *resolver,
 641                                      GAsyncResult  *result,
 642                                      GError       **error)
 643 {
 644   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 645
 646   if (g_async_result_legacy_propagate_error (result, error))
 647     return NULL;
 648
 649   return G_RESOLVER_GET_CLASS (resolver)->
 650     lookup_by_address_finish (resolver, result, error);
 651 }
 652
 653 static gchar *
 654 g_resolver_get_service_rrname (const char *service,
 655                                const char *protocol,
 656                                const char *domain)
 657 {
 658   gchar *rrname, *ascii_domain = NULL;
 659
 660   if (g_hostname_is_non_ascii (domain))
 661     domain = ascii_domain = g_hostname_to_ascii (domain);
 662
 663   rrname = g_strdup_printf ("_%s._%s.%s", service, protocol, domain);
 664
 665   g_free (ascii_domain);
 666   return rrname;
 667 }
 668
 669 /**
 670  * g_resolver_lookup_service:
 671  * @resolver: a #GResolver
 672  * @service: the service type to look up (eg, "ldap")
 673  * @protocol: the networking protocol to use for @service (eg, "tcp")
 674  * @domain: the DNS domain to look up the service in
 675  * @cancellable: (nullable): a #GCancellable, or %NULL
 676  * @error: return location for a #GError, or %NULL
 677  *
 678  * Synchronously performs a DNS SRV lookup for the given @service and
 679  * @protocol in the given @domain and returns an array of #GSrvTarget.
 680  * @domain may be an ASCII-only or UTF-8 hostname. Note also that the
 681  * @service and @protocol arguments do not include the leading underscore
 682  * that appears in the actual DNS entry.
 683  *
 684  * On success, g_resolver_lookup_service() will return a non-empty #GList of
 685  * #GSrvTarget, sorted in order of preference. (That is, you should
 686  * attempt to connect to the first target first, then the second if
 687  * the first fails, etc.)
 688  *
 689  * If the DNS resolution fails, @error (if non-%NULL) will be set to
 690  * a value from #GResolverError and %NULL will be returned.
 691  *
 692  * If @cancellable is non-%NULL, it can be used to cancel the
 693  * operation, in which case @error (if non-%NULL) will be set to
 694  * %G_IO_ERROR_CANCELLED.
 695  *
 696  * If you are planning to connect to the service, it is usually easier
 697  * to create a #GNetworkService and use its #GSocketConnectable
 698  * interface.
 699  *
 700  * Returns: (element-type GSrvTarget) (transfer full): a non-empty #GList of
 701  * #GSrvTarget, or %NULL on error. You must free each of the targets and the
 702  * list when you are done with it. (You can use g_resolver_free_targets() to do
 703  * this.)
 704  *
 705  * Since: 2.22
 706  */
 707 GList *
 708 g_resolver_lookup_service (GResolver     *resolver,
 709                            const gchar   *service,
 710                            const gchar   *protocol,
 711                            const gchar   *domain,
 712                            GCancellable  *cancellable,
 713                            GError       **error)
 714 {
 715   GList *targets;
 716   gchar *rrname;
 717
 718   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 719   g_return_val_if_fail (service != NULL, NULL);
 720   g_return_val_if_fail (protocol != NULL, NULL);
 721   g_return_val_if_fail (domain != NULL, NULL);
 722
 723   rrname = g_resolver_get_service_rrname (service, protocol, domain);
 724
 725   g_resolver_maybe_reload (resolver);
 726   targets = G_RESOLVER_GET_CLASS (resolver)->
 727     lookup_service (resolver, rrname, cancellable, error);
 728
 729   g_free (rrname);
 730   return targets;
 731 }
 732
 733 /**
 734  * g_resolver_lookup_service_async:
 735  * @resolver: a #GResolver
 736  * @service: the service type to look up (eg, "ldap")
 737  * @protocol: the networking protocol to use for @service (eg, "tcp")
 738  * @domain: the DNS domain to look up the service in
 739  * @cancellable: (nullable): a #GCancellable, or %NULL
 740  * @callback: (scope async): callback to call after resolution completes
 741  * @user_data: (closure): data for @callback
 742  *
 743  * Begins asynchronously performing a DNS SRV lookup for the given
 744  * @service and @protocol in the given @domain, and eventually calls
 745  * @callback, which must call g_resolver_lookup_service_finish() to
 746  * get the final result. See g_resolver_lookup_service() for more
 747  * details.
 748  *
 749  * Since: 2.22
 750  */
 751 void
 752 g_resolver_lookup_service_async (GResolver           *resolver,
 753                                  const gchar         *service,
 754                                  const gchar         *protocol,
 755                                  const gchar         *domain,
 756                                  GCancellable        *cancellable,
 757                                  GAsyncReadyCallback  callback,
 758                                  gpointer             user_data)
 759 {
 760   gchar *rrname;
 761
 762   g_return_if_fail (G_IS_RESOLVER (resolver));
 763   g_return_if_fail (service != NULL);
 764   g_return_if_fail (protocol != NULL);
 765   g_return_if_fail (domain != NULL);
 766
 767   rrname = g_resolver_get_service_rrname (service, protocol, domain);
 768
 769   g_resolver_maybe_reload (resolver);
 770   G_RESOLVER_GET_CLASS (resolver)->
 771     lookup_service_async (resolver, rrname, cancellable, callback, user_data);
 772
 773   g_free (rrname);
 774 }
 775
 776 /**
 777  * g_resolver_lookup_service_finish:
 778  * @resolver: a #GResolver
 779  * @result: the result passed to your #GAsyncReadyCallback
 780  * @error: return location for a #GError, or %NULL
 781  *
 782  * Retrieves the result of a previous call to
 783  * g_resolver_lookup_service_async().
 784  *
 785  * If the DNS resolution failed, @error (if non-%NULL) will be set to
 786  * a value from #GResolverError. If the operation was cancelled,
 787  * @error will be set to %G_IO_ERROR_CANCELLED.
 788  *
 789  * Returns: (element-type GSrvTarget) (transfer full): a non-empty #GList of
 790  * #GSrvTarget, or %NULL on error. See g_resolver_lookup_service() for more
 791  * details.
 792  *
 793  * Since: 2.22
 794  */
 795 GList *
 796 g_resolver_lookup_service_finish (GResolver     *resolver,
 797                                   GAsyncResult  *result,
 798                                   GError       **error)
 799 {
 800   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 801
 802   if (g_async_result_legacy_propagate_error (result, error))
 803     return NULL;
 804
 805   return G_RESOLVER_GET_CLASS (resolver)->
 806     lookup_service_finish (resolver, result, error);
 807 }
 808
 809 /**
 810  * g_resolver_free_targets: (skip)
 811  * @targets: a #GList of #GSrvTarget
 812  *
 813  * Frees @targets (which should be the return value from
 814  * g_resolver_lookup_service() or g_resolver_lookup_service_finish()).
 815  * (This is a convenience method; you can also simply free the
 816  * results by hand.)
 817  *
 818  * Since: 2.22
 819  */
 820 void
 821 g_resolver_free_targets (GList *targets)
 822 {
 823   GList *t;
 824
 825   for (t = targets; t; t = t->next)
 826     g_srv_target_free (t->data);
 827   g_list_free (targets);
 828 }
 829
 830 /**
 831  * g_resolver_lookup_records:
 832  * @resolver: a #GResolver
 833  * @rrname: the DNS name to lookup the record for
 834  * @record_type: the type of DNS record to lookup
 835  * @cancellable: (nullable): a #GCancellable, or %NULL
 836  * @error: return location for a #GError, or %NULL
 837  *
 838  * Synchronously performs a DNS record lookup for the given @rrname and returns
 839  * a list of records as #GVariant tuples. See #GResolverRecordType for
 840  * information on what the records contain for each @record_type.
 841  *
 842  * If the DNS resolution fails, @error (if non-%NULL) will be set to
 843  * a value from #GResolverError and %NULL will be returned.
 844  *
 845  * If @cancellable is non-%NULL, it can be used to cancel the
 846  * operation, in which case @error (if non-%NULL) will be set to
 847  * %G_IO_ERROR_CANCELLED.
 848  *
 849  * Returns: (element-type GVariant) (transfer full): a non-empty #GList of
 850  * #GVariant, or %NULL on error. You must free each of the records and the list
 851  * when you are done with it. (You can use g_list_free_full() with
 852  * g_variant_unref() to do this.)
 853  *
 854  * Since: 2.34
 855  */
 856 GList *
 857 g_resolver_lookup_records (GResolver            *resolver,
 858                            const gchar          *rrname,
 859                            GResolverRecordType   record_type,
 860                            GCancellable         *cancellable,
 861                            GError              **error)
 862 {
 863   GList *records;
 864
 865   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 866   g_return_val_if_fail (rrname != NULL, NULL);
 867
 868   g_resolver_maybe_reload (resolver);
 869   records = G_RESOLVER_GET_CLASS (resolver)->
 870     lookup_records (resolver, rrname, record_type, cancellable, error);
 871
 872   return records;
 873 }
 874
 875 /**
 876  * g_resolver_lookup_records_async:
 877  * @resolver: a #GResolver
 878  * @rrname: the DNS name to lookup the record for
 879  * @record_type: the type of DNS record to lookup
 880  * @cancellable: (nullable): a #GCancellable, or %NULL
 881  * @callback: (scope async): callback to call after resolution completes
 882  * @user_data: (closure): data for @callback
 883  *
 884  * Begins asynchronously performing a DNS lookup for the given
 885  * @rrname, and eventually calls @callback, which must call
 886  * g_resolver_lookup_records_finish() to get the final result. See
 887  * g_resolver_lookup_records() for more details.
 888  *
 889  * Since: 2.34
 890  */
 891 void
 892 g_resolver_lookup_records_async (GResolver           *resolver,
 893                                  const gchar         *rrname,
 894                                  GResolverRecordType  record_type,
 895                                  GCancellable        *cancellable,
 896                                  GAsyncReadyCallback  callback,
 897                                  gpointer             user_data)
 898 {
 899   g_return_if_fail (G_IS_RESOLVER (resolver));
 900   g_return_if_fail (rrname != NULL);
 901
 902   g_resolver_maybe_reload (resolver);
 903   G_RESOLVER_GET_CLASS (resolver)->
 904     lookup_records_async (resolver, rrname, record_type, cancellable, callback, user_data);
 905 }
 906
 907 /**
 908  * g_resolver_lookup_records_finish:
 909  * @resolver: a #GResolver
 910  * @result: the result passed to your #GAsyncReadyCallback
 911  * @error: return location for a #GError, or %NULL
 912  *
 913  * Retrieves the result of a previous call to
 914  * g_resolver_lookup_records_async(). Returns a non-empty list of records as
 915  * #GVariant tuples. See #GResolverRecordType for information on what the
 916  * records contain.
 917  *
 918  * If the DNS resolution failed, @error (if non-%NULL) will be set to
 919  * a value from #GResolverError. If the operation was cancelled,
 920  * @error will be set to %G_IO_ERROR_CANCELLED.
 921  *
 922  * Returns: (element-type GVariant) (transfer full): a non-empty #GList of
 923  * #GVariant, or %NULL on error. You must free each of the records and the list
 924  * when you are done with it. (You can use g_list_free_full() with
 925  * g_variant_unref() to do this.)
 926  *
 927  * Since: 2.34
 928  */
 929 GList *
 930 g_resolver_lookup_records_finish (GResolver     *resolver,
 931                                   GAsyncResult  *result,
 932                                   GError       **error)
 933 {
 934   g_return_val_if_fail (G_IS_RESOLVER (resolver), NULL);
 935   return G_RESOLVER_GET_CLASS (resolver)->
 936     lookup_records_finish (resolver, result, error);
 937 }
 938
 939 guint64
 940 g_resolver_get_serial (GResolver *resolver)
 941 {
 942   g_return_val_if_fail (G_IS_RESOLVER (resolver), 0);
 943
 944   g_resolver_maybe_reload (resolver);
 945
 946 #ifdef G_OS_UNIX
 947   return (guint64) resolver->priv->resolv_conf_timestamp;
 948 #else
 949   return 1;
 950 #endif
 951 }
 952
 953 /**
 954  * g_resolver_error_quark:
 955  *
 956  * Gets the #GResolver Error Quark.
 957  *
 958  * Returns: a #GQuark.
 959  *
 960  * Since: 2.22
 961  */
 962 G_DEFINE_QUARK (g-resolver-error-quark, g_resolver_error)