The recurring unit test expects the user data on a DNS query created as a result of a recurring DNS query to be the recurring structure itself. This is true, mostly. When invoking the user provided callback this user data is changed to the user provided data. This presents a race condition where the data may or may not point to the recurring data. This change simplifies the callback of the user provided callback by creating a new query and populating it with the expected values. This leaves the recurring DNS query alone and fixes the race condition. This is more in line with how the API should be used overall. ASTERISK-25222 #close Change-Id: I10fb6deec025dff097157e7ec17e6e4921778478
158 lines
4.4 KiB
C
158 lines
4.4 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2015, Digium, Inc.
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*
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* Joshua Colp <jcolp@digium.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief DNS Recurring Query Support
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*
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* \author Joshua Colp <jcolp@digium.com>
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*/
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/*** MODULEINFO
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<support_level>core</support_level>
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***/
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#include "asterisk.h"
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ASTERISK_REGISTER_FILE()
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#include "asterisk/astobj2.h"
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#include "asterisk/linkedlists.h"
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#include "asterisk/sched.h"
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#include "asterisk/strings.h"
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#include "asterisk/dns_core.h"
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#include "asterisk/dns_recurring.h"
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#include "asterisk/dns_internal.h"
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#include <arpa/nameser.h>
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/*! \brief Destructor for a DNS query */
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static void dns_query_recurring_destroy(void *data)
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{
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struct ast_dns_query_recurring *recurring = data;
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ao2_cleanup(recurring->user_data);
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}
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static void dns_query_recurring_resolution_callback(const struct ast_dns_query *query);
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/*! \brief Scheduled recurring query callback */
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static int dns_query_recurring_scheduled_callback(const void *data)
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{
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struct ast_dns_query_recurring *recurring = (struct ast_dns_query_recurring *)data;
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ao2_lock(recurring);
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recurring->timer = -1;
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if (!recurring->cancelled) {
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recurring->active = ast_dns_resolve_async(recurring->name, recurring->rr_type, recurring->rr_class, dns_query_recurring_resolution_callback,
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recurring);
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}
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ao2_unlock(recurring);
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ao2_ref(recurring, -1);
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return 0;
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}
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/*! \brief Query resolution callback */
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static void dns_query_recurring_resolution_callback(const struct ast_dns_query *query)
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{
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struct ast_dns_query_recurring *recurring = ast_dns_query_get_data(query);
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struct ast_dns_query *callback_query;
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/* Create a separate query to invoke the user specific callback on as the
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* recurring query user data may get used externally (by the unit test)
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* and thus changing it is problematic
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*/
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callback_query = dns_query_alloc(query->name, query->rr_type, query->rr_class,
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recurring->callback, recurring->user_data);
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if (callback_query) {
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/* The result is immutable at this point and can be safely provided */
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callback_query->result = query->result;
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callback_query->callback(callback_query);
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callback_query->result = NULL;
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ao2_ref(callback_query, -1);
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}
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ao2_lock(recurring);
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/* So.. if something has not externally cancelled this we can reschedule based on the TTL */
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if (!recurring->cancelled) {
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const struct ast_dns_result *result = ast_dns_query_get_result(query);
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int ttl = MIN(ast_dns_result_get_lowest_ttl(result), INT_MAX / 1000);
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if (ttl) {
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recurring->timer = ast_sched_add(ast_dns_get_sched(), ttl * 1000, dns_query_recurring_scheduled_callback, ao2_bump(recurring));
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if (recurring->timer < 0) {
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/* It is impossible for this to be the last reference as the query has a reference to it */
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ao2_ref(recurring, -1);
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}
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}
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}
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ao2_replace(recurring->active, NULL);
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ao2_unlock(recurring);
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}
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struct ast_dns_query_recurring *ast_dns_resolve_recurring(const char *name, int rr_type, int rr_class, ast_dns_resolve_callback callback, void *data)
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{
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struct ast_dns_query_recurring *recurring;
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if (ast_strlen_zero(name) || !callback || !ast_dns_get_sched()) {
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return NULL;
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}
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recurring = ao2_alloc(sizeof(*recurring) + strlen(name) + 1, dns_query_recurring_destroy);
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if (!recurring) {
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return NULL;
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}
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recurring->callback = callback;
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recurring->user_data = ao2_bump(data);
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recurring->timer = -1;
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recurring->rr_type = rr_type;
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recurring->rr_class = rr_class;
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strcpy(recurring->name, name); /* SAFE */
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recurring->active = ast_dns_resolve_async(name, rr_type, rr_class, dns_query_recurring_resolution_callback, recurring);
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if (!recurring->active) {
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ao2_ref(recurring, -1);
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return NULL;
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}
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return recurring;
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}
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int ast_dns_resolve_recurring_cancel(struct ast_dns_query_recurring *recurring)
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{
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int res = 0;
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ao2_lock(recurring);
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recurring->cancelled = 1;
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AST_SCHED_DEL_UNREF(ast_dns_get_sched(), recurring->timer, ao2_ref(recurring, -1));
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if (recurring->active) {
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res = ast_dns_resolve_cancel(recurring->active);
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ao2_replace(recurring->active, NULL);
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}
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ao2_unlock(recurring);
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return res;
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}
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