chan_bridge.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2008, 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
 *
 * \author Joshua Colp <jcolp@digium.com>
 *
 * \brief Bridge Interaction Channel
 *
 * \ingroup channel_drivers
 */

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

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 358907 $")

#include <fcntl.h>
#include <sys/signal.h>

#include "asterisk/lock.h"
#include "asterisk/channel.h"
#include "asterisk/config.h"
#include "asterisk/module.h"
#include "asterisk/pbx.h"
#include "asterisk/sched.h"
#include "asterisk/io.h"
#include "asterisk/acl.h"
#include "asterisk/callerid.h"
#include "asterisk/file.h"
#include "asterisk/cli.h"
#include "asterisk/app.h"
#include "asterisk/bridging.h"
#include "asterisk/astobj2.h"

static struct ast_channel *bridge_request(const char *type, struct ast_format_cap *cap, const struct ast_channel *requestor, const char *data, int *cause);
static int bridge_call(struct ast_channel *ast, const char *dest, int timeout);
static int bridge_hangup(struct ast_channel *ast);
static struct ast_frame *bridge_read(struct ast_channel *ast);
static int bridge_write(struct ast_channel *ast, struct ast_frame *f);
static struct ast_channel *bridge_bridgedchannel(struct ast_channel *chan, struct ast_channel *bridge);

static struct ast_channel_tech bridge_tech = {
   .type = "Bridge",
   .description = "Bridge Interaction Channel",
   .requester = bridge_request,
   .call = bridge_call,
   .hangup = bridge_hangup,
   .read = bridge_read,
   .write = bridge_write,
   .write_video = bridge_write,
   .exception = bridge_read,
   .bridged_channel = bridge_bridgedchannel,
};

struct bridge_pvt {
   struct ast_channel *input;  /*!< Input channel - talking to source */
   struct ast_channel *output; /*!< Output channel - talking to bridge */
};

/*! \brief Called when the user of this channel wants to get the actual channel in the bridge */
static struct ast_channel *bridge_bridgedchannel(struct ast_channel *chan, struct ast_channel *bridge)
{
   struct bridge_pvt *p = ast_channel_tech_pvt(chan);
   return (chan == p->input) ? p->output : bridge;
}

/*! \brief Called when a frame should be read from the channel */
static struct ast_frame  *bridge_read(struct ast_channel *ast)
{
   return &ast_null_frame;
}

/*! \brief Called when a frame should be written out to a channel */
static int bridge_write(struct ast_channel *ast, struct ast_frame *f)
{
   struct bridge_pvt *p = ast_channel_tech_pvt(ast);
   struct ast_channel *other = NULL;

   ao2_lock(p);
   /* only write frames to output. */
   if (p->input == ast) {
      other = p->output;
      if (other) {
         ast_channel_ref(other);
      }
   }
   ao2_unlock(p);

   if (other) {
      ast_channel_unlock(ast);
      ast_queue_frame(other, f);
      ast_channel_lock(ast);
      other = ast_channel_unref(other);
   }

   return 0;
}

/*! \brief Called when the channel should actually be dialed */
static int bridge_call(struct ast_channel *ast, const char *dest, int timeout)
{
   struct bridge_pvt *p = ast_channel_tech_pvt(ast);

   /* If no bridge has been provided on the input channel, bail out */
   if (!ast_channel_internal_bridge(ast)) {
      return -1;
   }

   /* Impart the output channel upon the given bridge of the input channel */
   ast_bridge_impart(ast_channel_internal_bridge(p->input), p->output, NULL, NULL, 0);

   return 0;
}

/*! \brief Called when a channel should be hung up */
static int bridge_hangup(struct ast_channel *ast)
{
   struct bridge_pvt *p = ast_channel_tech_pvt(ast);

   if (!p) {
      return 0;
   }

   ao2_lock(p);
   if (p->input == ast) {
      p->input = NULL;
   } else if (p->output == ast) {
      p->output = NULL;
   }
   ao2_unlock(p);

   ast_channel_tech_pvt_set(ast, NULL);
   ao2_ref(p, -1);

   return 0;
}

/*! \brief Called when we want to place a call somewhere, but not actually call it... yet */
static struct ast_channel *bridge_request(const char *type, struct ast_format_cap *cap, const struct ast_channel *requestor, const char *data, int *cause)
{
   struct bridge_pvt *p = NULL;
   struct ast_format slin;

   /* Try to allocate memory for our very minimal pvt structure */
   if (!(p = ao2_alloc(sizeof(*p), NULL))) {
      return NULL;
   }

   /* Try to grab two Asterisk channels to use as input and output channels */
   if (!(p->input = ast_channel_alloc(1, AST_STATE_UP, 0, 0, "", "", "", requestor ? ast_channel_linkedid(requestor) : NULL, 0, "Bridge/%p-input", p))) {
      ao2_ref(p, -1);
      return NULL;
   }
   if (!(p->output = ast_channel_alloc(1, AST_STATE_UP, 0, 0, "", "", "", requestor ? ast_channel_linkedid(requestor) : NULL, 0, "Bridge/%p-output", p))) {
      p->input = ast_channel_release(p->input);
      ao2_ref(p, -1);
      return NULL;
   }

   /* Setup parameters on both new channels */
   ast_channel_tech_set(p->input, &bridge_tech);
   ast_channel_tech_set(p->output, &bridge_tech);

   ao2_ref(p, 2);
   ast_channel_tech_pvt_set(p->input, p);
   ast_channel_tech_pvt_set(p->output, p);

   ast_format_set(&slin, AST_FORMAT_SLINEAR, 0);

   ast_format_cap_add(ast_channel_nativeformats(p->input), &slin);
   ast_format_cap_add(ast_channel_nativeformats(p->output), &slin);
   ast_format_copy(ast_channel_readformat(p->input), &slin);
   ast_format_copy(ast_channel_readformat(p->output), &slin);
   ast_format_copy(ast_channel_rawreadformat(p->input), &slin);
   ast_format_copy(ast_channel_rawreadformat(p->output), &slin);
   ast_format_copy(ast_channel_writeformat(p->input), &slin);
   ast_format_copy(ast_channel_writeformat(p->output), &slin);
   ast_format_copy(ast_channel_rawwriteformat(p->input), &slin);
   ast_format_copy(ast_channel_rawwriteformat(p->output), &slin);

   ast_answer(p->output);
   ast_answer(p->input);

   /* remove the reference from the alloc. The channels now own the pvt. */
   ao2_ref(p, -1);
   return p->input;
}

/*! \brief Load module into PBX, register channel */
static int load_module(void)
{
   if (!(bridge_tech.capabilities = ast_format_cap_alloc())) {
      return AST_MODULE_LOAD_FAILURE;
   }

   ast_format_cap_add_all(bridge_tech.capabilities);
   /* Make sure we can register our channel type */
   if (ast_channel_register(&bridge_tech)) {
      ast_log(LOG_ERROR, "Unable to register channel class 'Bridge'\n");
      return AST_MODULE_LOAD_FAILURE;
   }
   return AST_MODULE_LOAD_SUCCESS;
}

/*! \brief Unload the bridge interaction channel from Asterisk */
static int unload_module(void)
{
   ast_channel_unregister(&bridge_tech);
   bridge_tech.capabilities = ast_format_cap_destroy(bridge_tech.capabilities);
   return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Bridge Interaction Channel",
   .load = load_module,
   .unload = unload_module,
   .load_pri = AST_MODPRI_CHANNEL_DRIVER,
);