func_periodic_hook.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2014, Russell Bryant
 *
 * Russell Bryant <[email protected]>
 *
 * 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 Periodic dialplan hooks.
 *
 * \author Russell Bryant <[email protected]>
 *
 * \ingroup functions
 */

/*** MODULEINFO
   <depend>app_chanspy</depend>
   <depend>func_cut</depend>
   <depend>func_groupcount</depend>
   <depend>func_uri</depend>
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/module.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/app.h"
#include "asterisk/audiohook.h"
#define AST_API_MODULE
#include "asterisk/beep.h"

/*** DOCUMENTATION
   <function name="PERIODIC_HOOK" language="en_US">
      <synopsis>
         Execute a periodic dialplan hook into the audio of a call.
      </synopsis>
      <syntax>
         <parameter name="context" required="true">
            <para>(On Read Only) Context for the hook extension.</para>
         </parameter>
         <parameter name="extension" required="true">
            <para>(On Read Only) The hook extension.</para>
         </parameter>
         <parameter name="interval" required="true">
            <para>(On Read Only) Number of seconds in between hook runs.
            Whole seconds only.</para>
         </parameter>
         <parameter name="hook_id" required="true">
            <para>(On Write Only) The hook ID.</para>
         </parameter>
      </syntax>
      <description>
         <para>For example, you could use this function to enable playing
         a periodic <literal>beep</literal> sound in a call.</para>
         <para/>
         <para>To turn on:</para>
         <para>  Set(BEEPID=${PERIODIC_HOOK(hooks,beep,180)})</para>
         <para/>
         <para>To turn off:</para>
         <para>  Set(PERIODIC_HOOK(${BEEPID})=off)</para>
         <para/>
         <para>To turn back on again later:</para>
         <para>Set(PERIODIC_HOOK(${BEEPID})=on)</para>
         <para/>
         <para>It is important to note that the hook does not actually
         run on the channel itself.  It runs asynchronously on a new channel.
         Any audio generated by the hook gets injected into the call for
         the channel PERIODIC_HOOK() was set on.</para>
         <para/>
         <para>The hook dialplan will have two variables available.
         <variable>HOOK_CHANNEL</variable> is the channel the hook is
         enabled on.  <variable>HOOK_ID</variable> is the hook ID for
         enabling or disabling the hook.</para>
      </description>
   </function>
 ***/

static const char context_name[] = "__func_periodic_hook_context__";
static const char exten_name[] = "hook";
static const char full_exten_name[] = "hook@__func_periodic_hook_context__";

static const char beep_exten[] = "beep";

/*!
 * \brief Last used hook ID
 *
 * This is incremented each time a hook is created to give each hook a unique
 * ID.
 */
static unsigned int global_hook_id;

/*! State put in a datastore to track the state of the hook */
struct hook_state {
   /*!
    * \brief audiohook used as a callback into this module
    *
    * \note The code assumes this is the first element in the struct
    */
   struct ast_audiohook audiohook;
   /*! Seconds between each hook run */
   unsigned int interval;
   /*! The last time the hook ran */
   struct timeval last_hook;
   /*! Dialplan context for the hook */
   char *context;
   /*! Dialplan extension for the hook */
   char *exten;
   /*! Hook ID */
   unsigned int hook_id;
   /*! Non-zero if the hook is currently disabled */
   unsigned char disabled;
};

static void hook_datastore_destroy_callback(void *data)
{
   struct hook_state *state = data;

   ast_audiohook_lock(&state->audiohook);
   ast_audiohook_detach(&state->audiohook);
   ast_audiohook_unlock(&state->audiohook);
   ast_audiohook_destroy(&state->audiohook);

   ast_free(state->context);
   ast_free(state->exten);
   ast_free(state);
}

static const struct ast_datastore_info hook_datastore = {
   .type = AST_MODULE,
   .destroy = hook_datastore_destroy_callback,
};

/*! Arguments to the thread that launches the hook */
struct hook_thread_arg {
   /*! Hook ID */
   char *hook_id;
   /*! Name of the channel the hook was set on */
   char *chan_name;
   /*! Dialplan context for the hook */
   char *context;
   /*! Dialplan extension for the hook */
   char *exten;
};

static void hook_thread_arg_destroy(struct hook_thread_arg *arg)
{
   ast_free(arg->hook_id);
   ast_free(arg->chan_name);
   ast_free(arg->context);
   ast_free(arg->exten);
   ast_free(arg);
}

static void *hook_launch_thread(void *data)
{
   struct hook_thread_arg *arg = data;
   struct ast_variable hook_id = {
      .name = "HOOK_ID",
      .value = arg->hook_id,
   };
   struct ast_variable chan_name_var = {
      .name = "HOOK_CHANNEL",
      .value = arg->chan_name,
      .next = &hook_id,
   };

   ast_pbx_outgoing_exten("Local", NULL, full_exten_name, 60,
         arg->context, arg->exten, 1, NULL, AST_OUTGOING_NO_WAIT,
         NULL, NULL, &chan_name_var, NULL, NULL, 1, NULL);

   hook_thread_arg_destroy(arg);

   return NULL;
}

static struct hook_thread_arg *hook_thread_arg_alloc(struct ast_channel *chan,
      struct hook_state *state)
{
   struct hook_thread_arg *arg;

   if (!(arg = ast_calloc(1, sizeof(*arg)))) {
      return NULL;
   }

   ast_channel_lock(chan);
   arg->chan_name = ast_strdup(ast_channel_name(chan));
   ast_channel_unlock(chan);
   if (!arg->chan_name) {
      hook_thread_arg_destroy(arg);
      return NULL;
   }

   if (ast_asprintf(&arg->hook_id, "%u", state->hook_id) == -1) {
      hook_thread_arg_destroy(arg);
      return NULL;
   }

   if (!(arg->context = ast_strdup(state->context))) {
      hook_thread_arg_destroy(arg);
      return NULL;
   }

   if (!(arg->exten = ast_strdup(state->exten))) {
      hook_thread_arg_destroy(arg);
      return NULL;
   }

   return arg;
}

static int do_hook(struct ast_channel *chan, struct hook_state *state)
{
   pthread_t t;
   struct hook_thread_arg *arg;
   int res;

   if (!(arg = hook_thread_arg_alloc(chan, state))) {
      return -1;
   }

   /*
    * We don't want to block normal frame processing *at all* while we kick
    * this off, so do it in a new thread.
    */
   res = ast_pthread_create_detached_background(&t, NULL, hook_launch_thread, arg);
   if (res != 0) {
      hook_thread_arg_destroy(arg);
   }

   return res;
}

static int hook_callback(struct ast_audiohook *audiohook, struct ast_channel *chan,
      struct ast_frame *frame, enum ast_audiohook_direction direction)
{
   struct hook_state *state = (struct hook_state *) audiohook; /* trust me. */
   struct timeval now;
   int res = 0;

   if (audiohook->status == AST_AUDIOHOOK_STATUS_DONE || state->disabled) {
      return 0;
   }

   now = ast_tvnow();
   if (ast_tvdiff_ms(now, state->last_hook) > state->interval * 1000) {
      if ((res = do_hook(chan, state))) {
         const char *name;
         ast_channel_lock(chan);
         name = ast_strdupa(ast_channel_name(chan));
         ast_channel_unlock(chan);
         ast_log(LOG_WARNING, "Failed to run hook on '%s'\n", name);
      }
      state->last_hook = now;
   }

   return res;
}

static struct hook_state *hook_state_alloc(const char *context, const char *exten,
      unsigned int interval, unsigned int hook_id)
{
   struct hook_state *state;

   if (!(state = ast_calloc(1, sizeof(*state)))) {
      return NULL;
   }

   state->context = ast_strdup(context);
   state->exten = ast_strdup(exten);
   state->interval = interval;
   state->hook_id = hook_id;

   ast_audiohook_init(&state->audiohook, AST_AUDIOHOOK_TYPE_MANIPULATE,
         AST_MODULE, AST_AUDIOHOOK_MANIPULATE_ALL_RATES);
   state->audiohook.manipulate_callback = hook_callback;

   return state;
}

static int init_hook(struct ast_channel *chan, const char *context, const char *exten,
      unsigned int interval, unsigned int hook_id)
{
   struct hook_state *state;
   struct ast_datastore *datastore;
   char uid[32];

   snprintf(uid, sizeof(uid), "%u", hook_id);

   if (!(datastore = ast_datastore_alloc(&hook_datastore, uid))) {
      return -1;
   }

   if (!(state = hook_state_alloc(context, exten, interval, hook_id))) {
      ast_datastore_free(datastore);
      return -1;
   }
   datastore->data = state;

   ast_channel_lock(chan);
   ast_channel_datastore_add(chan, datastore);
   ast_audiohook_attach(chan, &state->audiohook);
   ast_channel_unlock(chan);

   return 0;
}

static int hook_on(struct ast_channel *chan, const char *data, unsigned int hook_id)
{
   char *parse = ast_strdupa(S_OR(data, ""));
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(context);
      AST_APP_ARG(exten);
      AST_APP_ARG(interval);
   );
   unsigned int interval;

   AST_STANDARD_APP_ARGS(args, parse);

   if (ast_strlen_zero(args.interval) ||
         sscanf(args.interval, "%30u", &interval) != 1 || interval == 0) {
      ast_log(LOG_WARNING, "Invalid hook interval: '%s'\n", S_OR(args.interval, ""));
      return -1;
   }

   if (ast_strlen_zero(args.context) || ast_strlen_zero(args.exten)) {
      ast_log(LOG_WARNING, "A context and extension are required for PERIODIC_HOOK().\n");
      return -1;
   }

   ast_debug(1, "hook to %s@%s enabled on %s with interval of %u seconds\n",
         args.exten, args.context, ast_channel_name(chan), interval);

   return init_hook(chan, args.context, args.exten, interval, hook_id);
}

static int hook_off(struct ast_channel *chan, const char *hook_id)
{
   struct ast_datastore *datastore;
   struct hook_state *state;

   if (ast_strlen_zero(hook_id)) {
      return -1;
   }

   ast_channel_lock(chan);

   if (!(datastore = ast_channel_datastore_find(chan, &hook_datastore, hook_id))) {
      ast_log(LOG_WARNING, "Hook with ID '%s' not found on channel '%s'\n", hook_id,
            ast_channel_name(chan));
      ast_channel_unlock(chan);
      return -1;
   }

   state = datastore->data;
   state->disabled = 1;

   ast_channel_unlock(chan);

   return 0;
}

static int hook_read(struct ast_channel *chan, const char *cmd, char *data,
          char *buf, size_t len)
{
   unsigned int hook_id;

   if (!chan) {
      return -1;
   }

   hook_id = (unsigned int) ast_atomic_fetchadd_int((int *) &global_hook_id, 1);

   snprintf(buf, len, "%u", hook_id);

   return hook_on(chan, data, hook_id);
}

static int hook_re_enable(struct ast_channel *chan, const char *uid)
{
   struct ast_datastore *datastore;
   struct hook_state *state;

   if (ast_strlen_zero(uid)) {
      return -1;
   }

   ast_channel_lock(chan);

   if (!(datastore = ast_channel_datastore_find(chan, &hook_datastore, uid))) {
      ast_log(LOG_WARNING, "Hook with ID '%s' not found on '%s'\n",
            uid, ast_channel_name(chan));
      ast_channel_unlock(chan);
      return -1;
   }

   state = datastore->data;
   state->disabled = 0;

   ast_channel_unlock(chan);

   return 0;
}

static int hook_write(struct ast_channel *chan, const char *cmd, char *data,
      const char *value)
{
   int res;

   if (!chan) {
      return -1;
   }

   if (ast_false(value)) {
      res = hook_off(chan, data);
   } else if (ast_true(value)) {
      res = hook_re_enable(chan, data);
   } else {
      ast_log(LOG_WARNING, "Invalid value for PERIODIC_HOOK function: '%s'\n", value);
      res = -1;
   }

   return res;
}

static struct ast_custom_function hook_function = {
   .name = "PERIODIC_HOOK",
   .read = hook_read,
   .write = hook_write,
};

static int unload_module(void)
{
   ast_context_destroy(NULL, AST_MODULE);

   ast_custom_function_unregister(&hook_function);
   return 0;
}

static int load_module(void)
{
   int res;

   if (!ast_context_find_or_create(NULL, NULL, context_name, AST_MODULE)) {
      ast_log(LOG_ERROR, "Failed to create %s dialplan context.\n", context_name);
      return AST_MODULE_LOAD_DECLINE;
   }

   /*
    * Based on a handy recipe from the Asterisk Cookbook.
    */
   res = ast_add_extension(context_name, 1, exten_name, 1, "", "",
         "Set", "EncodedChannel=${CUT(HOOK_CHANNEL,-,1-2)}",
         NULL, AST_MODULE);
   res |= ast_add_extension(context_name, 1, exten_name, 2, "", "",
         "Set", "GROUP_NAME=${EncodedChannel}${HOOK_ID}",
         NULL, AST_MODULE);
   res |= ast_add_extension(context_name, 1, exten_name, 3, "", "",
         "Set", "GROUP(periodic-hook)=${GROUP_NAME}",
         NULL, AST_MODULE);
   res |= ast_add_extension(context_name, 1, exten_name, 4, "", "", "ExecIf",
         "$[${GROUP_COUNT(${GROUP_NAME}@periodic-hook)} > 1]?Hangup()",
         NULL, AST_MODULE);
   res |= ast_add_extension(context_name, 1, exten_name, 5, "", "",
         "Set", "ChannelToSpy=${URIDECODE(${EncodedChannel})}",
         NULL, AST_MODULE);
   res |= ast_add_extension(context_name, 1, exten_name, 6, "", "",
         "ChanSpy", "${ChannelToSpy},qEB", NULL, AST_MODULE);

   res |= ast_add_extension(context_name, 1, beep_exten, 1, "", "",
         "Answer", "", NULL, AST_MODULE);
   res |= ast_add_extension(context_name, 1, beep_exten, 2, "", "",
         "Playback", "beep", NULL, AST_MODULE);

   res |= ast_custom_function_register_escalating(&hook_function, AST_CFE_BOTH);

   if (res) {
      unload_module();
      return AST_MODULE_LOAD_DECLINE;
   }
   return AST_MODULE_LOAD_SUCCESS;
}

int AST_OPTIONAL_API_NAME(ast_beep_start)(struct ast_channel *chan,
      unsigned int interval, char *beep_id, size_t len)
{
   char args[AST_MAX_EXTENSION + AST_MAX_CONTEXT + 32];

   snprintf(args, sizeof(args), "%s,%s,%u",
         context_name, beep_exten, interval);

   if (hook_read(chan, NULL, args, beep_id, len)) {
      ast_log(LOG_WARNING, "Failed to enable periodic beep.\n");
      return -1;
   }

   return 0;
}

int AST_OPTIONAL_API_NAME(ast_beep_stop)(struct ast_channel *chan, const char *beep_id)
{
   return hook_write(chan, NULL, (char *) beep_id, "off");
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS, "Periodic dialplan hooks.",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .requires = "app_chanspy,func_cut,func_groupcount,func_uri",
);