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

include/asterisk/dns_query_set.h

@@ -0,0 +1,136 @@
+/*
+ * 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 Query Set API
+ * \author Joshua Colp <jcolp@digium.com>
+ */
+
+#ifndef _ASTERISK_DNS_QUERY_SET_H
+#define _ASTERISK_DNS_QUERY_SET_H
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+/*! \brief Opaque structure for a set of DNS queries */
+struct ast_dns_query_set;
+
+/*!
+ * \brief Callback invoked when a query set completes
+ *
+ * \param query_set The DNS query set that was invoked
+ */
+typedef void (*ast_dns_query_set_callback)(const struct ast_dns_query_set *query_set);
+
+/*!
+ * \brief Create a query set to hold queries
+ *
+ * \retval non-NULL success
+ * \retval NULL failure
+ */
+struct ast_dns_query_set *ast_dns_query_set_create(void);
+
+/*!
+ * \brief Add a query to a query set
+ *
+ * \param query_set A DNS query set
+ * \param name The name of what to resolve
+ * \param rr_type Resource record type
+ * \param rr_class Resource record class
+ *
+ * \retval 0 success
+ * \retval -1 failure
+ */
+int ast_dns_query_set_add(struct ast_dns_query_set *query_set, const char *name, int rr_type, int rr_class);
+
+/*!
+ * \brief Retrieve the number of queries in a query set
+ *
+ * \param query_set A DNS query set
+ *
+ * \return the number of queries
+ */
+size_t ast_dns_query_set_num_queries(const struct ast_dns_query_set *query_set);
+
+/*!
+ * \brief Retrieve a query from a query set
+ *
+ * \param query_set A DNS query set
+ * \param index The index of the query to retrieve
+ *
+ * \retval non-NULL success
+ * \retval NULL failure
+ */
+struct ast_dns_query *ast_dns_query_set_get(const struct ast_dns_query_set *query_set, unsigned int index);
+
+/*!
+ * \brief Retrieve user specific data from a query set
+ *
+ * \param query_set A DNS query set
+ *
+ * \return user specific data
+ */
+void *ast_dns_query_set_get_data(const struct ast_dns_query_set *query_set);
+
+/*!
+ * \brief Asynchronously resolve queries in a query set
+ *
+ * \param query_set The query set
+ * \param callback The callback to invoke upon completion
+ * \param data User data to make available on the query set
+ *
+ * \note The callback will be invoked when all queries have completed
+ *
+ * \note The user data passed in to this function must be ao2 allocated
+ */
+void ast_dns_query_set_resolve_async(struct ast_dns_query_set *query_set, ast_dns_query_set_callback callback, void *data);
+
+/*!
+ * \brief Synchronously resolve queries in a query set
+ *
+ * \param query_set The query set
+ *
+ * \note This function will return when all queries have been completed
+ */
+void ast_query_set_resolve(struct ast_dns_query_set *query_set);
+
+/*!
+ * \brief Cancel an asynchronous DNS query set resolution
+ *
+ * \param query_set The DNS query set
+ *
+ * \retval 0 success
+ * \retval -1 failure
+ *
+ * \note If successfully cancelled the callback will not be invoked
+ */
+int ast_dns_query_set_resolve_cancel(struct ast_dns_query_set *query_set);
+
+/*!
+ * \brief Free a query set
+ *
+ * \param query_set A DNS query set
+ */
+void ast_dns_query_set_free(struct ast_dns_query_set *query_set);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}
+#endif
+
+#endif /* _ASTERISK_DNS_QUERY_SET_H */