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/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2015, Digium, Inc.
*
* Joshua Colp <jcolp@digium.com>
*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
* any of the maintainers of this project for assistance;
* the project provides a web site, mailing lists and IRC
* channels for your use.
*
* This program is free software, distributed under the terms of
* the GNU General Public License Version 2. See the LICENSE file
* at the top of the source tree.
*/
/*! \file
* \brief DNS Recurring Resolution API
* \author Joshua Colp <jcolp@digium.com>
*/
#ifndef _ASTERISK_DNS_RECURRING_H
#define _ASTERISK_DNS_RECURRING_H
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
/*! \brief Opaque structure for a recurring DNS query */
struct ast_dns_query_recurring;
/*!
* \brief Asynchronously resolve a DNS query, and continue resolving it according to the lowest TTL available
*
* \param name The name of what to resolve
* \param rr_type Resource record type
* \param rr_class Resource record class
* \param callback The callback to invoke upon completion
* \param data User data to make available on the query
*
* \retval non-NULL success - query has been sent for resolution
* \retval NULL failure
*
* \note The user data passed in to this function must be ao2 allocated
*
* \note This query will continue to happen according to the lowest TTL unless cancelled using ast_dns_resolve_recurring_cancel
*
* \note It is NOT possible for the callback to be invoked concurrently for the query multiple times
*
* \note The query will occur when the TTL expires, not before. This means that there is a period of time where the previous
* information can be considered stale.
*
* \note If the TTL is determined to be 0 (the record specifies 0, or no records exist) this will cease doing a recurring query.
* It is the responsibility of the caller to resume querying at an interval they determine.
*/
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);
/*!
* \brief Cancel an asynchronous recurring DNS resolution
*
* \param query The DNS query returned from ast_dns_resolve_recurring
*
* \retval 0 success - any active query has been cancelled and the query will no longer occur
* \retval -1 failure - an active query was in progress and could not be cancelled
*
* \note If successfully cancelled the callback will not be invoked
*
* \note This function does NOT drop your reference to the recurring query, this should be dropped using ao2_ref
*/
int ast_dns_resolve_recurring_cancel(struct ast_dns_query_recurring *recurring);
#if defined(__cplusplus) || defined(c_plusplus)
}
#endif
#endif /* _ASTERISK_DNS_RECURRING_H */
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