1 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
3 /* GIO - GLib Input, Output and Streaming Library
5 * Copyright (C) 2008 Red Hat, Inc.
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.
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.
17 * You should have received a copy of the GNU Lesser General
18 * Public License along with this library; if not, write to the
19 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
20 * Boston, MA 02111-1307, USA.
27 #include "gsrvtarget.h"
35 * @short_description: DNS SRV record target
38 * SRV (service) records are used by some network protocols to provide
39 * service-specific aliasing and load-balancing. For example, XMPP
40 * (Jabber) uses SRV records to locate the XMPP server for a domain;
41 * rather than connecting directly to "example.com" or assuming a
42 * specific server hostname like "xmpp.example.com", an XMPP client
43 * would look up the "xmpp-client" SRV record for "example.com", and
44 * then connect to whatever host was pointed to by that record.
46 * You can use g_resolver_lookup_service() or
47 * g_resolver_lookup_service_async() to find the #GSrvTarget<!-- -->s
48 * for a given service. However, if you are simply planning to connect
49 * to the remote service, you can use #GNetworkService's
50 * #GSocketConnectable interface and not need to worry about
65 * A single target host/port that a network service is running on.
69 g_srv_target_get_type (void)
71 static volatile gsize type_volatile = 0;
73 if (g_once_init_enter (&type_volatile))
75 GType type = g_boxed_type_register_static (
76 g_intern_static_string ("GSrvTarget"),
77 (GBoxedCopyFunc) g_srv_target_copy,
78 (GBoxedFreeFunc) g_srv_target_free);
79 g_once_init_leave (&type_volatile, type);
86 * @hostname: the host that the service is running on
87 * @port: the port that the service is running on
88 * @priority: the target's priority
89 * @weight: the target's weight
91 * Creates a new #GSrvTarget with the given parameters.
93 * You should not need to use this; normally #GSrvTarget<!-- -->s are
94 * created by #GResolver.
96 * Return value: a new #GSrvTarget.
101 g_srv_target_new (const gchar *hostname,
106 GSrvTarget *target = g_slice_new0 (GSrvTarget);
108 target->hostname = g_strdup (hostname);
110 target->priority = priority;
111 target->weight = weight;
118 * @target: a #GSrvTarget
122 * Return value: a copy of @target
127 g_srv_target_copy (GSrvTarget *target)
129 return g_srv_target_new (target->hostname, target->port,
130 target->priority, target->weight);
135 * @target: a #GSrvTarget
142 g_srv_target_free (GSrvTarget *target)
144 g_free (target->hostname);
145 g_slice_free (GSrvTarget, target);
149 * g_srv_target_get_hostname:
150 * @target: a #GSrvTarget
152 * Gets @target's hostname (in ASCII form; if you are going to present
153 * this to the user, you should use g_hostname_is_ascii_encoded() to
154 * check if it contains encoded Unicode segments, and use
155 * g_hostname_to_unicode() to convert it if it does.)
157 * Return value: @target's hostname
162 g_srv_target_get_hostname (GSrvTarget *target)
164 return target->hostname;
168 * g_srv_target_get_port:
169 * @target: a #GSrvTarget
171 * Gets @target's port
173 * Return value: @target's port
178 g_srv_target_get_port (GSrvTarget *target)
184 * g_srv_target_get_priority:
185 * @target: a #GSrvTarget
187 * Gets @target's priority. You should not need to look at this;
188 * #GResolver already sorts the targets according to the algorithm in
191 * Return value: @target's priority
196 g_srv_target_get_priority (GSrvTarget *target)
198 return target->priority;
202 * g_srv_target_get_weight:
203 * @target: a #GSrvTarget
205 * Gets @target's weight. You should not need to look at this;
206 * #GResolver already sorts the targets according to the algorithm in
209 * Return value: @target's weight
214 g_srv_target_get_weight (GSrvTarget *target)
216 return target->weight;
220 compare_target (gconstpointer a, gconstpointer b)
222 GSrvTarget *ta = (GSrvTarget *)a;
223 GSrvTarget *tb = (GSrvTarget *)b;
225 if (ta->priority == tb->priority)
227 /* Arrange targets of the same priority "in any order, except
228 * that all those with weight 0 are placed at the beginning of
231 return ta->weight - tb->weight;
234 return ta->priority - tb->priority;
238 * g_srv_target_list_sort:
239 * @targets: a #GList of #GSrvTarget
241 * Sorts @targets in place according to the algorithm in RFC 2782.
243 * Return value: the head of the sorted list.
248 g_srv_target_list_sort (GList *targets)
250 gint sum, num, val, priority, weight;
251 GList *t, *out, *tail;
259 target = targets->data;
260 if (!strcmp (target->hostname, "."))
262 /* 'A Target of "." means that the service is decidedly not
263 * available at this domain.'
265 g_srv_target_free (target);
266 g_list_free (targets);
271 /* Sort input list by priority, and put the 0-weight targets first
272 * in each priority group. Initialize output list to %NULL.
274 targets = g_list_sort (targets, compare_target);
277 /* For each group of targets with the same priority, remove them
278 * from @targets and append them to @out in a valid order.
282 priority = ((GSrvTarget *)targets->data)->priority;
284 /* Count the number of targets at this priority level, and
285 * compute the sum of their weights.
288 for (t = targets; t; t = t->next)
290 target = (GSrvTarget *)t->data;
291 if (target->priority != priority)
293 sum += target->weight;
297 /* While there are still targets at this priority level... */
300 /* Randomly select from the targets at this priority level,
301 * giving precedence to the ones with higher weight,
302 * according to the rules from RFC 2782.
304 val = g_random_int_range (0, sum + 1);
305 for (t = targets; ; t = t->next)
307 weight = ((GSrvTarget *)t->data)->weight;
313 targets = g_list_remove_link (targets, t);