func_srv and explicit specification of a remote IP for SIP.

From Review Board:
There are two interrelated changes here.

First, there is the introduction of func_srv. This adds two new read-only
dialplan functions, SRVQUERY and SRVRESULT. They work very similarly to the
ENUMQUERY and ENUMRESULT functions, except that this allows one to query SRV
records instead. In order to facilitate this work, I added a couple of new API
calls to srv.h. ast_srv_get_record_count tells the number of records returned
by an SRV lookup. This number is calculated at the time of the SRV lookup.
ast_srv_get_nth_record allows one to get a numbered SRV record.

Second, there is the modification to chan_sip that allows one to specify a
hostname or IP address (along with a port) to send an outgoing INVITE to when
dialing a SIP peer. This goes hand-in-hand with func_srv. You can query SRV
records and then use the host and port from the results to dial via a specific
host instead of what is configured in sip.conf.

Review: https://reviewboard.asterisk.org/r/608
SWP-1200



git-svn-id: http://svn.digium.com/svn/asterisk/trunk@256485 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 254 insertions, 0 deletions

diff --git a/funcs/func_srv.c b/funcs/func_srv.c
new file mode 100644
index 000000000..339a0284b
--- /dev/null
+++ b/funcs/func_srv.c
@@ -0,0 +1,254 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 1999 - 2006 Digium, Inc.
+ *
+ * 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 SRV Functions
+ *
+ * \author Mark Michelson <mmichelson@digium.com>
+ *
+ * \ingroup functions
+ */
+
+#include "asterisk.h"
+
+ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
+
+#include "asterisk/module.h"
+#include "asterisk/srv.h"
+#include "asterisk/pbx.h"
+#include "asterisk/app.h"
+
+/*** DOCUMENTATION
+	<function name="SRVQUERY" language="en_US">
+		<synopsis>
+			Initiate an SRV query.
+		</synopsis>
+		<syntax>
+			<parameter name="service" required="true">
+				<para>The service for which to look up SRV records. An example would be something
+				like <literal>_sip._udp.example.com</literal></para>
+			</parameter>
+		</syntax>
+		<description>
+			<para>This will do an SRV lookup of the given service.</para>
+		</description>
+	</function>
+	<function name="SRVRESULT" language="en_US">
+		<synopsis>
+			Retrieve results from an SRVQUERY.
+		</synopsis>
+		<syntax>
+			<parameter name="id" required="true">
+				<para>The identifier returned by the SRVQUERY function.</para>
+			</parameter>
+			<parameter name="resultnum" required="true">
+				<para>The number of the result that you want to retrieve.</para>
+				<para>Results start at <literal>1</literal>. If this argument is specified
+				as <literal>getnum</literal>, then it will return the total number of results
+				that are available.</para>
+			</parameter>
+		</syntax>
+		<description>
+			<para>This function will retrieve results from a previous use
+			of the SRVQUERY function.</para>
+		</description>
+	</function>
+ ***/
+
+struct srv_result_datastore {
+	struct srv_context *context;
+	char id[1];
+};
+
+static void srds_destroy_cb(void *data)
+{
+	struct srv_result_datastore *datastore = data;
+	ast_srv_cleanup(&datastore->context);
+	ast_free(datastore);
+}
+
+static const struct ast_datastore_info srv_result_datastore_info = {
+	.type = "SRVQUERY",
+	.destroy = srds_destroy_cb,
+};
+
+static struct srv_context *srv_datastore_setup(const char *service, struct ast_channel *chan)
+{
+	struct srv_result_datastore *srds;
+	struct ast_datastore *datastore;
+	const char *host;
+	unsigned short port;
+
+	if (!(srds = ast_calloc(1, sizeof(*srds) + strlen(service)))) {
+		return NULL;
+	}
+
+	if (ast_srv_lookup(&srds->context, service, &host, &port) < 0) {
+		ast_log(LOG_NOTICE, "Error performing lookup of service '%s'\n", service);
+		ast_free(srds);
+		return NULL;
+	}
+
+	strcpy(srds->id, service);
+	
+	if (!(datastore = ast_datastore_alloc(&srv_result_datastore_info, srds->id))) {
+		ast_srv_cleanup(&srds->context);
+		ast_free(srds);
+		return NULL;
+	}
+
+	datastore->data = srds;
+	ast_channel_lock(chan);
+	ast_channel_datastore_add(chan, datastore);
+	ast_channel_unlock(chan);
+	return srds->context;
+}
+
+static int srv_query_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
+{
+	if (!chan) {
+		ast_log(LOG_WARNING, "%s cannot be used without a channel\n", cmd);
+		return -1;
+	}
+
+	if (ast_strlen_zero(data)) {
+		ast_log(LOG_WARNING, "%s requires a service as an argument\n", cmd);
+		return -1;
+	}
+
+	if (!srv_datastore_setup(data, chan)) {
+		return -1;
+	}
+
+	ast_copy_string(buf, data, len);
+
+	return 0;
+}
+
+static struct ast_custom_function srv_query_function = {
+	.name = "SRVQUERY",
+	.read = srv_query_read,
+};
+
+static int srv_result_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
+{
+	struct srv_result_datastore *srds;
+	struct ast_datastore *datastore;
+	struct srv_context *srv_context;
+	char *parse;
+	const char *host;
+	unsigned short port, priority, weight;
+	unsigned int num;
+	AST_DECLARE_APP_ARGS(args,
+		AST_APP_ARG(id);
+		AST_APP_ARG(resultnum);
+		AST_APP_ARG(field);
+	);
+
+	if (!chan) {
+		ast_log(LOG_WARNING, "%s cannot be used without a channel\n", cmd);
+		return -1;
+	}
+
+	if (ast_strlen_zero(data)) {
+		ast_log(LOG_WARNING, "%s requires two arguments (id and resultnum)\n", cmd);
+		return -1;
+	}
+
+	parse = ast_strdupa(data);
+
+	AST_STANDARD_APP_ARGS(args, parse);
+
+	ast_channel_lock(chan);
+	datastore = ast_channel_datastore_find(chan, &srv_result_datastore_info, args.id);
+	ast_channel_unlock(chan);
+
+	if (!datastore) {
+		/* They apparently decided to call SRVRESULT without first calling SRVQUERY.
+		 * No problem, we'll do the SRV lookup now.
+		 */
+		srv_context = srv_datastore_setup(args.id, chan);
+		if (!srv_context) {
+			return -1;
+		}
+	} else {
+		srds = datastore->data;
+		srv_context = srds->context;
+	}
+
+	if (!strcasecmp(args.resultnum, "getnum")) {
+		snprintf(buf, len, "%u", ast_srv_get_record_count(srv_context));
+		return 0;
+	}
+
+	if (ast_strlen_zero(args.field)) {
+		ast_log(LOG_ERROR, "A field must be provided when requesting SRV data\n");
+		return -1;
+	}
+
+	if (sscanf(args.resultnum, "%30u", &num) != 1) {
+		ast_log(LOG_ERROR, "Invalid value '%s' for resultnum to %s\n", args.resultnum, cmd);
+		return -1;
+	}
+
+	if (ast_srv_get_nth_record(srv_context, num, &host, &port, &priority, &weight)) {
+		ast_log(LOG_ERROR, "Failed to get record number %u for %s\n", num, cmd);
+		return -1;
+	}
+
+	if (!strcasecmp(args.field, "host")) {
+		ast_copy_string(buf, host, len);
+	} else if (!strcasecmp(args.field, "port")) {
+		snprintf(buf, len, "%u", port);
+	} else if (!strcasecmp(args.field, "priority")) {
+		snprintf(buf, len, "%u", priority);
+	} else if (!strcasecmp(args.field, "weight")) {
+		snprintf(buf, len, "%u", weight);
+	} else {
+		ast_log(LOG_WARNING, "Unrecognized SRV field '%s'\n", args.field);
+		return -1;
+	}
+
+	return 0;
+}
+
+static struct ast_custom_function srv_result_function = {
+	.name = "SRVRESULT",
+	.read = srv_result_read,
+};
+
+static int unload_module(void)
+{
+	int res = 0;
+
+	res |= ast_custom_function_unregister(&srv_query_function);
+	res |= ast_custom_function_unregister(&srv_result_function);
+
+	return res;
+}
+
+static int load_module(void)
+{
+	int res = AST_MODULE_LOAD_SUCCESS;
+
+	res |= ast_custom_function_register(&srv_query_function);
+	res |= ast_custom_function_register(&srv_result_function);
+
+	return res;
+}
+
+AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "SRV related dialplan functions");