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