func_srv.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2010 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 <[email protected]>
 *
 * \ingroup functions
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/module.h"
#include "asterisk/srv.h"
#include "asterisk/pbx.h"
#include "asterisk/app.h"
#include "asterisk/datastore.h"
#include "asterisk/channel.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;
   }

   ast_autoservice_start(chan);
   if (ast_srv_lookup(&srds->context, service, &host, &port) < 0) {
      ast_autoservice_stop(chan);
      ast_log(LOG_NOTICE, "Error performing lookup of service '%s'\n", service);
      ast_free(srds);
      return NULL;
   }
   ast_autoservice_stop(chan);

   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)
{
   struct ast_datastore *datastore;

   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 they already called SRVQUERY for this service once,
    * we need to kill the old datastore.
    */
   ast_channel_lock(chan);
   datastore = ast_channel_datastore_find(chan, &srv_result_datastore_info, data);
   ast_channel_unlock(chan);

   if (datastore) {
      ast_channel_datastore_remove(chan, datastore);
      ast_datastore_free(datastore);
   }

   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, "%d", port);
   } else if (!strcasecmp(args.field, "priority")) {
      snprintf(buf, len, "%d", priority);
   } else if (!strcasecmp(args.field, "weight")) {
      snprintf(buf, len, "%d", 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_custom_function_register(&srv_query_function);
   if (res < 0) {
      return AST_MODULE_LOAD_DECLINE;
   }
   res = ast_custom_function_register(&srv_result_function);
   if (res < 0) {
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;;
}

AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "SRV related dialplan functions");