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, 149 insertions, 0 deletions

diff --git a/main/dns_recurring.c b/main/dns_recurring.c
new file mode 100644
index 000000000..3ebbab070
--- /dev/null
+++ b/main/dns_recurring.c
@@ -0,0 +1,149 @@
+/*
+ * 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 Query Support
+ *
+ * \author Joshua Colp <jcolp@digium.com>
+ */
+
+/*** MODULEINFO
+	<support_level>core</support_level>
+ ***/
+
+#include "asterisk.h"
+
+ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
+
+#include "asterisk/astobj2.h"
+#include "asterisk/linkedlists.h"
+#include "asterisk/sched.h"
+#include "asterisk/strings.h"
+#include "asterisk/dns_core.h"
+#include "asterisk/dns_recurring.h"
+#include "asterisk/dns_internal.h"
+
+#include <arpa/nameser.h>
+
+/*! \brief Destructor for a DNS query */
+static void dns_query_recurring_destroy(void *data)
+{
+	struct ast_dns_query_recurring *recurring = data;
+
+	ao2_cleanup(recurring->user_data);
+}
+
+static void dns_query_recurring_resolution_callback(const struct ast_dns_query *query);
+
+/*! \brief Scheduled recurring query callback */
+static int dns_query_recurring_scheduled_callback(const void *data)
+{
+	struct ast_dns_query_recurring *recurring = (struct ast_dns_query_recurring *)data;
+
+	ao2_lock(recurring);
+	recurring->timer = -1;
+	if (!recurring->cancelled) {
+		recurring->active = ast_dns_resolve_async(recurring->name, recurring->rr_type, recurring->rr_class, dns_query_recurring_resolution_callback,
+			recurring);
+	}
+	ao2_unlock(recurring);
+
+	ao2_ref(recurring, -1);
+
+	return 0;
+}
+
+/*! \brief Query resolution callback */
+static void dns_query_recurring_resolution_callback(const struct ast_dns_query *query)
+{
+	struct ast_dns_query_recurring *recurring = ast_dns_query_get_data(query);
+
+	/* Replace the user data so the actual callback sees what it provided */
+	((struct ast_dns_query*)query)->user_data = ao2_bump(recurring->user_data);
+	recurring->callback(query);
+
+	ao2_lock(recurring);
+	/* So.. if something has not externally cancelled this we can reschedule based on the TTL */
+	if (!recurring->cancelled) {
+		const struct ast_dns_result *result = ast_dns_query_get_result(query);
+		int ttl = MIN(ast_dns_result_get_lowest_ttl(result), INT_MAX / 1000);
+
+		if (ttl) {
+			recurring->timer = ast_sched_add(ast_dns_get_sched(), ttl * 1000, dns_query_recurring_scheduled_callback, ao2_bump(recurring));
+			if (recurring->timer < 0) {
+				/* It is impossible for this to be the last reference as this callback function holds a reference itself */
+				ao2_ref(recurring, -1);
+			}
+		}
+	}
+
+	ao2_replace(recurring->active, NULL);
+	ao2_unlock(recurring);
+
+	/* Since we stole the reference from the query we need to drop it ourselves */
+	ao2_ref(recurring, -1);
+}
+
+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)
+{
+	struct ast_dns_query_recurring *recurring;
+
+	if (ast_strlen_zero(name) || !callback || !ast_dns_get_sched()) {
+		return NULL;
+	}
+
+	recurring = ao2_alloc(sizeof(*recurring) + strlen(name) + 1, dns_query_recurring_destroy);
+	if (!recurring) {
+		return NULL;
+	}
+
+	recurring->callback = callback;
+	recurring->user_data = ao2_bump(data);
+	recurring->timer = -1;
+	recurring->rr_type = rr_type;
+	recurring->rr_class = rr_class;
+	strcpy(recurring->name, name); /* SAFE */
+
+	recurring->active = ast_dns_resolve_async(name, rr_type, rr_class, dns_query_recurring_resolution_callback, recurring);
+	if (!recurring->active) {
+		ao2_ref(recurring, -1);
+		return NULL;
+	}
+
+	return recurring;
+}
+
+int ast_dns_resolve_recurring_cancel(struct ast_dns_query_recurring *recurring)
+{
+	int res = 0;
+
+	ao2_lock(recurring);
+
+	recurring->cancelled = 1;
+	AST_SCHED_DEL_UNREF(ast_dns_get_sched(), recurring->timer, ao2_ref(recurring, -1));
+
+	if (recurring->active) {
+		res = ast_dns_resolve_cancel(recurring->active);
+		ao2_replace(recurring->active, NULL);
+	}
+
+	ao2_unlock(recurring);
+
+	return res;
+}