dns: Add core DNS API + unit tests and res_resolver_unbound module + unit tests.

This change adds an abstracted core DNS API which resembles the API described
here[1]. The API provides a pluggable mechanism for resolvers and also a
consistent view for records. Both synchronous and asynchronous queries are
supported.

This change also adds a res_resolver_unbound module which uses the libunbound
library to provide resolution.

Unit tests have also been written for all of the above to confirm the API and
functionality.

ASTERISK-24834 #close
Reported by: Matt Jordan

ASTERISK-24836 #close
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/4474/
Review: https://reviewboard.asterisk.org/r/4512/

[1] https://wiki.asterisk.org/wiki/display/AST/Asterisk+DNS+API


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@433370 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 78 insertions, 0 deletions

diff --git a/include/asterisk/dns_recurring.h b/include/asterisk/dns_recurring.h
new file mode 100644
index 000000000..c5c1af1ac
--- /dev/null
+++ b/include/asterisk/dns_recurring.h
@@ -0,0 +1,78 @@
+/*
+ * 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 */