bridge_basic.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2013 Digium, Inc.
 *
 * Richard Mudgett <[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 Basic bridge class.  It is a subclass of struct ast_bridge.
 *
 * \author Richard Mudgett <[email protected]>
 *
 * See Also:
 * \arg \ref AstCREDITS
 */


#include "asterisk.h"

#include "asterisk/channel.h"
#include "asterisk/utils.h"
#include "asterisk/linkedlists.h"
#include "asterisk/bridge.h"
#include "asterisk/bridge_internal.h"
#include "asterisk/bridge_basic.h"
#include "asterisk/bridge_after.h"
#include "asterisk/astobj2.h"
#include "asterisk/features_config.h"
#include "asterisk/pbx.h"
#include "asterisk/file.h"
#include "asterisk/app.h"
#include "asterisk/dial.h"
#include "asterisk/stasis_bridges.h"
#include "asterisk/stasis_channels.h"
#include "asterisk/features.h"
#include "asterisk/format_cache.h"
#include "asterisk/test.h"

#define NORMAL_FLAGS (AST_BRIDGE_FLAG_DISSOLVE_HANGUP | AST_BRIDGE_FLAG_DISSOLVE_EMPTY \
         | AST_BRIDGE_FLAG_SMART)

#define TRANSFER_FLAGS AST_BRIDGE_FLAG_SMART

struct attended_transfer_properties;

enum bridge_basic_personality_type {
   /*! Index for "normal" basic bridge personality */
   BRIDGE_BASIC_PERSONALITY_NORMAL,
   /*! Index for attended transfer basic bridge personality */
   BRIDGE_BASIC_PERSONALITY_ATXFER,
   /*! Indicates end of enum. Must always remain the last element */
   BRIDGE_BASIC_PERSONALITY_END,
};

/*!
 * \brief Change basic bridge personality
 *
 * Changing personalities allows for the bridge to remain in use but have
 * properties such as its v_table and its flags change.
 *
 * \param bridge The bridge
 * \param type The personality to change the bridge to
 * \user_data Private data to attach to the personality.
 */
static void bridge_basic_change_personality(struct ast_bridge *bridge,
      enum bridge_basic_personality_type type, void *user_data);

/* ------------------------------------------------------------------- */

static const struct ast_datastore_info dtmf_features_info = {
   .type = "bridge-dtmf-features",
   .destroy = ast_free_ptr,
};

/*!
 * \internal
 * \since 12.0.0
 * \brief read a feature code character and set it on for the give feature_flags struct
 *
 * \param feature_flags flags being modifed
 * \param feature feature code provided - should be an uppercase letter
 *
 * \retval 0 if the feature was set successfully
 * \retval -1 failure because the requested feature code isn't handled by this function
 */
static int set_feature_flag_from_char(struct ast_flags *feature_flags, char feature)
{
   switch (feature) {
   case 'T':
      ast_set_flag(feature_flags, AST_FEATURE_REDIRECT);
      return 0;
   case 'K':
      ast_set_flag(feature_flags, AST_FEATURE_PARKCALL);
      return 0;
   case 'H':
      ast_set_flag(feature_flags, AST_FEATURE_DISCONNECT);
      return 0;
   case 'W':
      ast_set_flag(feature_flags, AST_FEATURE_AUTOMON);
      return 0;
   case 'X':
      ast_set_flag(feature_flags, AST_FEATURE_AUTOMIXMON);
      return 0;
   default:
      return -1;
   }
}

/*!
 * \internal
 * \since 12.0.0
 * \brief Write a features string to a string buffer based on the feature flags provided
 *
 * \param feature_flags pointer to the feature flags to write from.
 * \param buffer pointer to a string buffer to write the features
 * \param buffer_size size of the buffer provided (should be able to fit all feature codes)
 *
 * \retval 0 on successful write
 * \retval -1 failure due to running out of buffer space
 */
static int dtmf_features_flags_to_string(struct ast_flags *feature_flags, char *buffer, size_t buffer_size)
{
   size_t buffer_expended = 0;
   unsigned int cur_feature;
   static const struct {
      char letter;
      unsigned int flag;
   } associations[] = {
      { 'T', AST_FEATURE_REDIRECT },
      { 'K', AST_FEATURE_PARKCALL },
      { 'H', AST_FEATURE_DISCONNECT },
      { 'W', AST_FEATURE_AUTOMON },
      { 'X', AST_FEATURE_AUTOMIXMON },
   };

   for (cur_feature = 0; cur_feature < ARRAY_LEN(associations); cur_feature++) {
      if (ast_test_flag(feature_flags, associations[cur_feature].flag)) {
         if (buffer_expended == buffer_size - 1) {
            buffer[buffer_expended] = '\0';
            return -1;
         }
         buffer[buffer_expended++] = associations[cur_feature].letter;
      }
   }

   buffer[buffer_expended] = '\0';
   return 0;
}

static int build_dtmf_features(struct ast_flags *flags, const char *features)
{
   const char *feature;

   char missing_features[strlen(features) + 1];
   size_t number_of_missing_features = 0;

   for (feature = features; *feature; feature++) {
      if (!isupper(*feature)) {
         ast_log(LOG_ERROR, "Features string '%s' rejected because it contains non-uppercase feature.\n", features);
         return -1;
      }

      if (set_feature_flag_from_char(flags, *feature)) {
         missing_features[number_of_missing_features++] = *feature;
      }
   }

   missing_features[number_of_missing_features] = '\0';

   if (number_of_missing_features) {
      ast_log(LOG_WARNING, "Features '%s' from features string '%s' can not be applied.\n", missing_features, features);
   }

   return 0;
}

int ast_bridge_features_ds_set_string(struct ast_channel *chan, const char *features)
{
   struct ast_flags flags = {0};

   if (build_dtmf_features(&flags, features)) {
      return -1;
   }

   ast_channel_lock(chan);
   if (ast_bridge_features_ds_set(chan, &flags)) {
      ast_channel_unlock(chan);
      ast_log(LOG_ERROR, "Failed to apply features datastore for '%s' to channel '%s'\n", features, ast_channel_name(chan));
      return -1;
   }
   ast_channel_unlock(chan);

   return 0;
}

int ast_bridge_features_ds_get_string(struct ast_channel *chan, char *buffer, size_t buf_size)
{
   struct ast_flags *channel_flags;
   struct ast_flags held_copy;

   ast_channel_lock(chan);
   if (!(channel_flags = ast_bridge_features_ds_get(chan))) {
      ast_channel_unlock(chan);
      return -1;
   }
   held_copy = *channel_flags;
   ast_channel_unlock(chan);

   return dtmf_features_flags_to_string(&held_copy, buffer, buf_size);
}

static int bridge_features_ds_set_full(struct ast_channel *chan, struct ast_flags *flags, int replace)
{
   struct ast_datastore *datastore;
   struct ast_flags *ds_flags;

   datastore = ast_channel_datastore_find(chan, &dtmf_features_info, NULL);
   if (datastore) {
      ds_flags = datastore->data;
      if (replace) {
         *ds_flags = *flags;
      } else {
         flags->flags = flags->flags | ds_flags->flags;
         *ds_flags = *flags;
      }
      return 0;
   }

   datastore = ast_datastore_alloc(&dtmf_features_info, NULL);
   if (!datastore) {
      return -1;
   }

   ds_flags = ast_malloc(sizeof(*ds_flags));
   if (!ds_flags) {
      ast_datastore_free(datastore);
      return -1;
   }

   *ds_flags = *flags;
   datastore->data = ds_flags;
   ast_channel_datastore_add(chan, datastore);
   return 0;
}

int ast_bridge_features_ds_set(struct ast_channel *chan, struct ast_flags *flags)
{
   return bridge_features_ds_set_full(chan, flags, 1);
}

int ast_bridge_features_ds_append(struct ast_channel *chan, struct ast_flags *flags)
{
   return bridge_features_ds_set_full(chan, flags, 0);
}

struct ast_flags *ast_bridge_features_ds_get(struct ast_channel *chan)
{
   struct ast_datastore *datastore;

   datastore = ast_channel_datastore_find(chan, &dtmf_features_info, NULL);
   if (!datastore) {
      return NULL;
   }
   return datastore->data;
}

/*!
 * \internal
 * \brief Determine if we should dissolve the bridge from a hangup.
 * \since 12.0.0
 *
 * \param bridge_channel Channel executing the feature
 * \param hook_pvt Private data passed in when the hook was created
 *
 * \retval 0 Keep the callback hook.
 * \retval -1 Remove the callback hook.
 */
static int basic_hangup_hook(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   int bridge_count = 0;
   struct ast_bridge_channel *iter;

   ast_bridge_channel_lock_bridge(bridge_channel);
   AST_LIST_TRAVERSE(&bridge_channel->bridge->channels, iter, entry) {
      if (iter != bridge_channel && iter->state == BRIDGE_CHANNEL_STATE_WAIT) {
         ++bridge_count;
      }
   }
   if (2 <= bridge_count) {
      /* Just allow this channel to leave the multi-party bridge. */
      ast_bridge_channel_leave_bridge(bridge_channel,
         BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, 0);
   }
   ast_bridge_unlock(bridge_channel->bridge);
   return 0;
}

/*!
 * \brief Details for specific basic bridge personalities
 */
struct personality_details {
   /*! The v_table to use for this personality */
   struct ast_bridge_methods *v_table;
   /*! Flags to set on this type of bridge */
   unsigned int bridge_flags;
   /*! User data for this personality. If used, must be an ao2 object */
   void *pvt;
   /*! Callback to be called when changing to the personality */
   void (*on_personality_change)(struct ast_bridge *bridge);
};

/*!
 * \brief structure that organizes different personalities for basic bridges.
 */
struct bridge_basic_personality {
   /*! The current bridge personality in use */
   enum bridge_basic_personality_type current;
   /*! Array of details for the types of bridge personalities supported */
   struct personality_details details[BRIDGE_BASIC_PERSONALITY_END];
};

/*
 * \internal
 * \brief Get the extension for a given builtin feature.
 *
 * \param chan Get the feature extension for this channel.
 * \param feature_name features.conf name of feature.
 * \param buf Where to put the extension.
 * \param len Length of the given extension buffer.
 *
 * \retval 0 success
 * \retval non-zero failiure
 */
static int builtin_feature_get_exten(struct ast_channel *chan, const char *feature_name, char *buf, size_t len)
{
   SCOPED_CHANNELLOCK(lock, chan);

   return ast_get_builtin_feature(chan, feature_name, buf, len);
}

/*!
 * \internal
 * \brief Helper to add a builtin DTMF feature hook to the features struct.
 * \since 12.0.0
 *
 * \param features Bridge features to setup.
 * \param chan Get features from this channel.
 * \param flags Feature flags on the channel.
 * \param feature_flag Feature flag to test.
 * \param feature_name features.conf name of feature.
 * \param feature_bridge Bridge feature enum to get hook callback.
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int builtin_features_helper(struct ast_bridge_features *features, struct ast_channel *chan,
   struct ast_flags *flags, unsigned int feature_flag, const char *feature_name, enum ast_bridge_builtin_feature feature_bridge)
{
   char dtmf[AST_FEATURE_MAX_LEN];
   int res;

   res = 0;
   if (ast_test_flag(flags, feature_flag)
      && !builtin_feature_get_exten(chan, feature_name, dtmf, sizeof(dtmf))
      && !ast_strlen_zero(dtmf)) {
      res = ast_bridge_features_enable(features, feature_bridge, dtmf, NULL, NULL,
         AST_BRIDGE_HOOK_REMOVE_ON_PULL | AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE);
      if (res) {
         ast_log(LOG_ERROR, "Channel %s: Requested DTMF feature %s not available.\n",
            ast_channel_name(chan), feature_name);
      }
   }

   return res;
}

/*!
 * \internal
 * \brief Setup bridge builtin features.
 * \since 12.0.0
 *
 * \param features Bridge features to setup.
 * \param chan Get features from this channel.
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int setup_bridge_features_builtin(struct ast_bridge_features *features, struct ast_channel *chan)
{
   struct ast_flags *flags;
   int res;

   ast_channel_lock(chan);
   flags = ast_bridge_features_ds_get(chan);
   ast_channel_unlock(chan);
   if (!flags) {
      return 0;
   }

   res = 0;
   res |= builtin_features_helper(features, chan, flags, AST_FEATURE_REDIRECT, "blindxfer", AST_BRIDGE_BUILTIN_BLINDTRANSFER);
   res |= builtin_features_helper(features, chan, flags, AST_FEATURE_REDIRECT, "atxfer", AST_BRIDGE_BUILTIN_ATTENDEDTRANSFER);
   res |= builtin_features_helper(features, chan, flags, AST_FEATURE_DISCONNECT, "disconnect", AST_BRIDGE_BUILTIN_HANGUP);
   res |= builtin_features_helper(features, chan, flags, AST_FEATURE_PARKCALL, "parkcall", AST_BRIDGE_BUILTIN_PARKCALL);
   res |= builtin_features_helper(features, chan, flags, AST_FEATURE_AUTOMON, "automon", AST_BRIDGE_BUILTIN_AUTOMON);
   res |= builtin_features_helper(features, chan, flags, AST_FEATURE_AUTOMIXMON, "automixmon", AST_BRIDGE_BUILTIN_AUTOMIXMON);

   return res ? -1 : 0;
}

struct dynamic_dtmf_hook_run {
   /*! Offset into app_name[] where the channel name that activated the hook starts. */
   int activated_offset;
   /*! Offset into app_name[] where the dynamic feature name starts. */
   int feature_offset;
   /*! Offset into app_name[] where the MOH class name starts.  (zero if no MOH) */
   int moh_offset;
   /*! Offset into app_name[] where the application argument string starts. (zero if no arguments) */
   int app_args_offset;
   /*! Application name to run. */
   char app_name[0];
};

static void dynamic_dtmf_hook_callback(struct ast_bridge_channel *bridge_channel,
   const void *payload, size_t payload_size)
{
   struct ast_channel *chan = bridge_channel->chan;
   const struct dynamic_dtmf_hook_run *run_data = payload;

   pbx_builtin_setvar_helper(chan, "DYNAMIC_FEATURENAME",
      &run_data->app_name[run_data->feature_offset]);
   pbx_builtin_setvar_helper(chan, "DYNAMIC_WHO_ACTIVATED",
      &run_data->app_name[run_data->activated_offset]);

   ast_bridge_channel_run_app(bridge_channel, run_data->app_name,
      run_data->app_args_offset ? &run_data->app_name[run_data->app_args_offset] : NULL,
      run_data->moh_offset ? &run_data->app_name[run_data->moh_offset] : NULL);
}

struct dynamic_dtmf_hook_data {
   /*! Which side of bridge to run app (AST_FEATURE_FLAG_ONSELF/AST_FEATURE_FLAG_ONPEER) */
   unsigned int flags;
   /*! Offset into app_name[] where the dynamic feature name starts. */
   int feature_offset;
   /*! Offset into app_name[] where the MOH class name starts.  (zero if no MOH) */
   int moh_offset;
   /*! Offset into app_name[] where the application argument string starts. (zero if no arguments) */
   int app_args_offset;
   /*! Application name to run. */
   char app_name[0];
};

/*!
 * \internal
 * \brief Activated dynamic DTMF feature hook.
 * \since 12.0.0
 *
 * \param bridge_channel Channel executing the feature
 * \param hook_pvt Private data passed in when the hook was created
 *
 * \retval 0 Keep the callback hook.
 * \retval -1 Remove the callback hook.
 */
static int dynamic_dtmf_hook_trip(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   struct dynamic_dtmf_hook_data *pvt = hook_pvt;
   struct dynamic_dtmf_hook_run *run_data;
   const char *activated_name;
   size_t len_name;
   size_t len_args;
   size_t len_moh;
   size_t len_feature;
   size_t len_activated;
   size_t len_data;

   /* Determine lengths of things. */
   len_name = strlen(pvt->app_name) + 1;
   len_args = pvt->app_args_offset ? strlen(&pvt->app_name[pvt->app_args_offset]) + 1 : 0;
   len_moh = pvt->moh_offset ? strlen(&pvt->app_name[pvt->moh_offset]) + 1 : 0;
   len_feature = strlen(&pvt->app_name[pvt->feature_offset]) + 1;
   ast_channel_lock(bridge_channel->chan);
   activated_name = ast_strdupa(ast_channel_name(bridge_channel->chan));
   ast_channel_unlock(bridge_channel->chan);
   len_activated = strlen(activated_name) + 1;
   len_data = sizeof(*run_data) + len_name + len_args + len_moh + len_feature + len_activated;

   /* Fill in dynamic feature run hook data. */
   run_data = ast_alloca(len_data);
   run_data->app_args_offset = len_args ? len_name : 0;
   run_data->moh_offset = len_moh ? len_name + len_args : 0;
   run_data->feature_offset = len_name + len_args + len_moh;
   run_data->activated_offset = len_name + len_args + len_moh + len_feature;
   strcpy(run_data->app_name, pvt->app_name);/* Safe */
   if (len_args) {
      strcpy(&run_data->app_name[run_data->app_args_offset],
         &pvt->app_name[pvt->app_args_offset]);/* Safe */
   }
   if (len_moh) {
      strcpy(&run_data->app_name[run_data->moh_offset],
         &pvt->app_name[pvt->moh_offset]);/* Safe */
   }
   strcpy(&run_data->app_name[run_data->feature_offset],
      &pvt->app_name[pvt->feature_offset]);/* Safe */
   strcpy(&run_data->app_name[run_data->activated_offset], activated_name);/* Safe */

   if (ast_test_flag(pvt, AST_FEATURE_FLAG_ONPEER)) {
      ast_bridge_channel_write_callback(bridge_channel,
         AST_BRIDGE_CHANNEL_CB_OPTION_MEDIA,
         dynamic_dtmf_hook_callback, run_data, len_data);
   } else {
      dynamic_dtmf_hook_callback(bridge_channel, run_data, len_data);
   }
   return 0;
}

/*!
 * \internal
 * \brief Add a dynamic DTMF feature hook to the bridge features.
 * \since 12.0.0
 *
 * \param features Bridge features to setup.
 * \param flags Which side of bridge to run app (AST_FEATURE_FLAG_ONSELF/AST_FEATURE_FLAG_ONPEER).
 * \param dtmf DTMF trigger sequence.
 * \param feature_name Name of the dynamic feature.
 * \param app_name Dialplan application name to run.
 * \param app_args Dialplan application arguments. (Empty or NULL if no arguments)
 * \param moh_class MOH class to play to peer. (Empty or NULL if no MOH played)
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int dynamic_dtmf_hook_add(struct ast_bridge_features *features, unsigned int flags, const char *dtmf, const char *feature_name, const char *app_name, const char *app_args, const char *moh_class)
{
   struct dynamic_dtmf_hook_data *hook_data;
   size_t len_name = strlen(app_name) + 1;
   size_t len_args = ast_strlen_zero(app_args) ? 0 : strlen(app_args) + 1;
   size_t len_moh = ast_strlen_zero(moh_class) ? 0 : strlen(moh_class) + 1;
   size_t len_feature = strlen(feature_name) + 1;
   size_t len_data = sizeof(*hook_data) + len_name + len_args + len_moh + len_feature;
   int res;

   /* Fill in application run hook data. */
   hook_data = ast_malloc(len_data);
   if (!hook_data) {
      return -1;
   }
   hook_data->flags = flags;
   hook_data->app_args_offset = len_args ? len_name : 0;
   hook_data->moh_offset = len_moh ? len_name + len_args : 0;
   hook_data->feature_offset = len_name + len_args + len_moh;
   strcpy(hook_data->app_name, app_name);/* Safe */
   if (len_args) {
      strcpy(&hook_data->app_name[hook_data->app_args_offset], app_args);/* Safe */
   }
   if (len_moh) {
      strcpy(&hook_data->app_name[hook_data->moh_offset], moh_class);/* Safe */
   }
   strcpy(&hook_data->app_name[hook_data->feature_offset], feature_name);/* Safe */

   res = ast_bridge_dtmf_hook(features, dtmf, dynamic_dtmf_hook_trip, hook_data,
      ast_free_ptr,
      AST_BRIDGE_HOOK_REMOVE_ON_PULL | AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE);
   if (res) {
      ast_free(hook_data);
   }
   return res;
}

static int setup_dynamic_feature(void *obj, void *arg, void *data, int flags)
{
   struct ast_applicationmap_item *item = obj;
   struct ast_bridge_features *features = arg;
   int *res = data;

   *res |= dynamic_dtmf_hook_add(features,
      item->activate_on_self ? AST_FEATURE_FLAG_ONSELF : AST_FEATURE_FLAG_ONPEER,
      item->dtmf, item->name, item->app, item->app_data, item->moh_class);

   return 0;
}

/*!
 * \internal
 * \brief Setup bridge dynamic features.
 * \since 12.0.0
 *
 * \param features Bridge features to setup.
 * \param chan Get features from this channel.
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int setup_bridge_features_dynamic(struct ast_bridge_features *features, struct ast_channel *chan)
{
   struct ao2_container *applicationmap;
   int res = 0;

   ast_channel_lock(chan);
   applicationmap = ast_get_chan_applicationmap(chan);
   ast_channel_unlock(chan);
   if (applicationmap) {
      ao2_callback_data(applicationmap, 0, setup_dynamic_feature, features, &res);
      ao2_ref(applicationmap, -1);
   }

   return res;
}

/*!
 * \internal
 * \brief Setup DTMF feature hooks using the channel features datastore property.
 * \since 12.0.0
 *
 * \param bridge_channel What to setup DTMF features on.
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int bridge_basic_setup_features(struct ast_bridge_channel *bridge_channel)
{
   int res = 0;

   res |= setup_bridge_features_builtin(bridge_channel->features, bridge_channel->chan);
   res |= setup_bridge_features_dynamic(bridge_channel->features, bridge_channel->chan);

   return res;
}

static int add_normal_hooks(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
{
   return ast_bridge_hangup_hook(bridge_channel->features, basic_hangup_hook,
         NULL, NULL, AST_BRIDGE_HOOK_REMOVE_ON_PULL)
      || bridge_basic_setup_features(bridge_channel);
}

/*!
 * \internal
 * \brief ast_bridge basic push method.
 * \since 12.0.0
 *
 * \param self Bridge to operate upon.
 * \param bridge_channel Bridge channel to push.
 * \param swap Bridge channel to swap places with if not NULL.
 *
 * \note On entry, self is already locked.
 *
 * \retval 0 on success
 * \retval -1 on failure
 */
static int bridge_personality_normal_push(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel, struct ast_bridge_channel *swap)
{
   if (add_normal_hooks(self, bridge_channel)) {
      return -1;
   }

   return 0;
}

static int bridge_basic_push(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel, struct ast_bridge_channel *swap)
{
   struct bridge_basic_personality *personality = self->personality;

   ast_assert(personality != NULL);

   if (personality->details[personality->current].v_table->push
      && personality->details[personality->current].v_table->push(self, bridge_channel, swap)) {
      return -1;
   }

   ast_bridge_channel_update_linkedids(bridge_channel, swap);
   ast_bridge_channel_update_accountcodes(bridge_channel, swap);

   return ast_bridge_base_v_table.push(self, bridge_channel, swap);
}

static void bridge_basic_pull(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel)
{
   struct bridge_basic_personality *personality = self->personality;

   ast_assert(personality != NULL);

   if (personality->details[personality->current].v_table->pull) {
      personality->details[personality->current].v_table->pull(self, bridge_channel);
   }

   ast_bridge_channel_update_accountcodes(NULL, bridge_channel);

   ast_bridge_base_v_table.pull(self, bridge_channel);
}

static void bridge_basic_destroy(struct ast_bridge *self)
{
   struct bridge_basic_personality *personality = self->personality;

   ao2_cleanup(personality);

   ast_bridge_base_v_table.destroy(self);
}

/*!
 * \brief Remove appropriate hooks when basic bridge personality changes
 *
 * Hooks that have the AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE flag
 * set will be removed from all bridge channels in the bridge.
 *
 * \param bridge Basic bridge undergoing personality change
 */
static void remove_hooks_on_personality_change(struct ast_bridge *bridge)
{
   struct ast_bridge_channel *iter;

   AST_LIST_TRAVERSE(&bridge->channels, iter, entry) {
      SCOPED_LOCK(lock, iter, ast_bridge_channel_lock, ast_bridge_channel_unlock);
      ast_bridge_features_remove(iter->features, AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE);
   }
}

/*!
 * \brief Attended transfer superstates.
 *
 * An attended transfer's progress is facilitated by a state machine.
 * The individual states of the state machine fall into the realm of
 * one of two superstates.
 */
enum attended_transfer_superstate {
   /*!
    * \brief Transfer superstate
    *
    * The attended transfer state machine begins in this superstate. The
    * goal of this state is for a transferer channel to facilitate a
    * transfer from a transferee to a transfer target.
    *
    * There are two bridges used in this superstate. The transferee bridge is
    * the bridge that the transferer and transferee channels originally
    * communicate in, and the target bridge is the bridge where the transfer
    * target is being dialed.
    *
    * The transferer channel is capable of moving between the bridges using
    * the DTMF swap sequence.
    */
   SUPERSTATE_TRANSFER,
   /*!
    * \brief Recall superstate
    *
    * The attended transfer state machine moves to this superstate if
    * atxferdropcall is set to "no" and the transferer channel hangs up
    * during a transfer. The goal in this superstate is to call back either
    * the transfer target or transferer and rebridge with the transferee
    * channel(s).
    *
    * In this superstate, there is only a single bridge used, the original
    * transferee bridge. Rather than distinguishing between a transferer
    * and transfer target, all outbound calls are toward a "recall_target"
    * channel.
    */
   SUPERSTATE_RECALL,
};

/*!
 * The states in the attended transfer state machine.
 */
enum attended_transfer_state {
   /*!
    * \brief Calling Target state
    *
    * This state describes the initial state of a transfer. The transferer
    * waits in the transfer target's bridge for the transfer target to answer.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transfer target is RINGING
    * 2) Transferer is in transferee bridge
    * 3) Transferee is on hold
    *
    * Transitions to TRANSFER_CALLING_TARGET:
    * 1) This is the initial state for an attended transfer.
    * 2) TRANSFER_HESITANT: Transferer presses DTMF swap sequence
    *
    * State operation:
    * The transferer is moved from the transferee bridge into the transfer
    * target bridge.
    *
    * Transitions from TRANSFER_CALLING_TARGET:
    * 1) TRANSFER_FAIL: Transferee hangs up.
    * 2) TRANSFER_BLOND: Transferer hangs up or presses DTMF swap sequence
    * and configured atxferdropcall setting is yes.
    * 3) TRANSFER_BLOND_NONFINAL: Transferer hangs up or presses DTMF swap
    * sequence and configured atxferdroppcall setting is no.
    * 4) TRANSFER_CONSULTING: Transfer target answers the call.
    * 5) TRANSFER_REBRIDGE: Transfer target hangs up, call to transfer target
    * times out, or transferer presses DTMF abort sequence.
    * 6) TRANSFER_THREEWAY: Transferer presses DTMF threeway sequence.
    * 7) TRANSFER_HESITANT: Transferer presses DTMF swap sequence.
    */
   TRANSFER_CALLING_TARGET,
   /*!
    * \brief Hesitant state
    *
    * This state only arises if when waiting for the transfer target to
    * answer, the transferer presses the DTMF swap sequence. This will
    * cause the transferer to be rebridged with the transferee temporarily.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transfer target is in ringing state
    * 2) Transferer is in transfer target bridge
    * 3) Transferee is on hold
    *
    * Transitions to TRANSFER_HESITANT:
    * 1) TRANSFER_CALLING_TARGET: Transferer presses DTMF swap sequence.
    *
    * State operation:
    * The transferer is moved from the transfer target bridge into the
    * transferee bridge, and the transferee is taken off hold.
    *
    * Transitions from TRANSFER_HESITANT:
    * 1) TRANSFER_FAIL: Transferee hangs up
    * 2) TRANSFER_BLOND: Transferer hangs up or presses DTMF swap sequence
    * and configured atxferdropcall setting is yes.
    * 3) TRANSFER_BLOND_NONFINAL: Transferer hangs up or presses DTMF swap
    * sequence and configured atxferdroppcall setting is no.
    * 4) TRANSFER_DOUBLECHECKING: Transfer target answers the call
    * 5) TRANSFER_RESUME: Transfer target hangs up, call to transfer target
    * times out, or transferer presses DTMF abort sequence.
    * 6) TRANSFER_THREEWAY: Transferer presses DTMF threeway sequence.
    * 7) TRANSFER_CALLING_TARGET: Transferer presses DTMF swap sequence.
    */
   TRANSFER_HESITANT,
   /*!
    * \brief Rebridge state
    *
    * This is a terminal state that indicates that the transferer needs
    * to move back to the transferee's bridge. This is a failed attended
    * transfer result.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transferer is in transfer target bridge
    * 2) Transferee is on hold
    *
    * Transitions to TRANSFER_REBRIDGE:
    * 1) TRANSFER_CALLING_TARGET: Transfer target hangs up, call to transfer target
    * times out, or transferer presses DTMF abort sequence.
    * 2) TRANSFER_STATE_CONSULTING: Transfer target hangs up, or transferer presses
    * DTMF abort sequence.
    *
    * State operation:
    * The transferer channel is moved from the transfer target bridge to the
    * transferee bridge. The transferee is taken off hold. A stasis transfer
    * message is published indicating a failed attended transfer.
    *
    * Transitions from TRANSFER_REBRIDGE:
    * None
    */
   TRANSFER_REBRIDGE,
   /*!
    * \brief Resume state
    *
    * This is a terminal state that indicates that the party bridged with the
    * transferee is the final party to be bridged with that transferee. This state
    * may come about due to a successful recall or due to a failed transfer.
    *
    * Superstate: Transfer or Recall
    *
    * Preconditions:
    * In Transfer Superstate:
    * 1) Transferer is in transferee bridge
    * 2) Transferee is not on hold
    * In Recall Superstate:
    * 1) The recall target is in the transferee bridge
    * 2) Transferee is not on hold
    *
    * Transitions to TRANSFER_RESUME:
    * TRANSFER_HESITANT: Transfer target hangs up, call to transfer target times out,
    * or transferer presses DTMF abort sequence.
    * TRANSFER_DOUBLECHECKING: Transfer target hangs up or transferer presses DTMF
    * abort sequence.
    * TRANSFER_BLOND_NONFINAL: Recall target answers
    * TRANSFER_RECALLING: Recall target answers
    * TRANSFER_RETRANSFER: Recall target answers
    *
    * State operations:
    * None
    *
    * Transitions from TRANSFER_RESUME:
    * None
    */
   TRANSFER_RESUME,
   /*!
    * \brief Threeway state
    *
    * This state results when the transferer wishes to have all parties involved
    * in a transfer to be in the same bridge together.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transfer target state is either RINGING or UP
    * 2) Transferer is in either bridge
    * 3) Transferee is not on hold
    *
    * Transitions to TRANSFER_THREEWAY:
    * 1) TRANSFER_CALLING_TARGET: Transferer presses DTMF threeway sequence.
    * 2) TRANSFER_HESITANT: Transferer presses DTMF threeway sequence.
    * 3) TRANSFER_CONSULTING: Transferer presses DTMF threeway sequence.
    * 4) TRANSFER_DOUBLECHECKING: Transferer presses DTMF threeway sequence.
    *
    * State operation:
    * The transfer target bridge is merged into the transferee bridge.
    *
    * Transitions from TRANSFER_THREEWAY:
    * None.
    */
   TRANSFER_THREEWAY,
   /*!
    * \brief Consulting state
    *
    * This state describes the case where the transferer and transfer target
    * are able to converse in the transfer target's bridge prior to completing
    * the transfer.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transfer target is UP
    * 2) Transferer is in target bridge
    * 3) Transferee is on hold
    *
    * Transitions to TRANSFER_CONSULTING:
    * 1) TRANSFER_CALLING_TARGET: Transfer target answers.
    * 2) TRANSFER_DOUBLECHECKING: Transferer presses DTMF swap sequence.
    *
    * State operations:
    * None.
    *
    * Transitions from TRANSFER_CONSULTING:
    * TRANSFER_COMPLETE: Transferer hangs up or transferer presses DTMF complete sequence.
    * TRANSFER_REBRIDGE: Transfer target hangs up or transferer presses DTMF abort sequence.
    * TRANSFER_THREEWAY: Transferer presses DTMF threeway sequence.
    * TRANSFER_DOUBLECHECKING: Transferer presses DTMF swap sequence.
    */
   TRANSFER_CONSULTING,
   /*!
    * \brief Double-checking state
    *
    * This state describes the case where the transferer and transferee are
    * able to converse in the transferee's bridge prior to completing the transfer. The
    * difference between this and TRANSFER_HESITANT is that the transfer target is
    * UP in this case.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transfer target is UP and on hold
    * 2) Transferer is in transferee bridge
    * 3) Transferee is off hold
    *
    * Transitions to TRANSFER_DOUBLECHECKING:
    * 1) TRANSFER_HESITANT: Transfer target answers.
    * 2) TRANSFER_CONSULTING: Transferer presses DTMF swap sequence.
    *
    * State operations:
    * None.
    *
    * Transitions from TRANSFER_DOUBLECHECKING:
    * 1) TRANSFER_FAIL: Transferee hangs up.
    * 2) TRANSFER_COMPLETE: Transferer hangs up or presses DTMF complete sequence.
    * 3) TRANSFER_RESUME: Transfer target hangs up or transferer presses DTMF abort sequence.
    * 4) TRANSFER_THREEWAY: Transferer presses DTMF threeway sequence.
    * 5) TRANSFER_CONSULTING: Transferer presses the DTMF swap sequence.
    */
   TRANSFER_DOUBLECHECKING,
   /*!
    * \brief Complete state
    *
    * This is a terminal state where a transferer has successfully completed an attended
    * transfer. This state's goal is to get the transfer target and transferee into
    * the same bridge and the transferer off the call.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transfer target is UP and off hold.
    * 2) Transferer is in either bridge.
    * 3) Transferee is off hold.
    *
    * Transitions to TRANSFER_COMPLETE:
    * 1) TRANSFER_CONSULTING: transferer hangs up or presses the DTMF complete sequence.
    * 2) TRANSFER_DOUBLECHECKING: transferer hangs up or presses the DTMF complete sequence.
    *
    * State operation:
    * The transfer target bridge is merged into the transferee bridge. The transferer
    * channel is kicked out of the bridges as part of the merge.
    *
    * State operations:
    * 1) Merge the transfer target bridge into the transferee bridge,
    * excluding the transferer channel from the merge.
    * 2) Publish a stasis transfer message.
    *
    * Exit operations:
    * This is a terminal state, so there are no exit operations.
    */
   TRANSFER_COMPLETE,
   /*!
    * \brief Blond state
    *
    * This is a terminal state where a transferer has completed an attended transfer prior
    * to the transfer target answering. This state is only entered if atxferdropcall
    * is set to 'yes'. This is considered to be a successful attended transfer.
    *
    * Superstate: Transfer
    *
    * Preconditions:
    * 1) Transfer target is RINGING.
    * 2) Transferer is in either bridge.
    * 3) Transferee is off hold.
    *
    * Transitions to TRANSFER_BLOND:
    * 1) TRANSFER_CALLING_TARGET: Transferer hangs up or presses the DTMF complete sequence.
    *    atxferdropcall is set to 'yes'.
    * 2) TRANSFER_HESITANT: Transferer hangs up or presses the DTMF complete sequence.
    *    atxferdropcall is set to 'yes'.
    *
    * State operations:
    * The transfer target bridge is merged into the transferee bridge. The transferer
    * channel is kicked out of the bridges as part of the merge. A stasis transfer
    * publication is sent indicating a successful transfer.
    *
    * Transitions from TRANSFER_BLOND:
    * None
    */
   TRANSFER_BLOND,
   /*!
    * \brief Blond non-final state
    *
    * This state is very similar to the TRANSFER_BLOND state, except that
    * this state is entered when atxferdropcall is set to 'no'. This is the
    * initial state of the Recall superstate, so state operations mainly involve
    * moving to the Recall superstate. This means that the transfer target, that
    * is currently ringing is now known as the recall target.
    *
    * Superstate: Recall
    *
    * Preconditions:
    * 1) Recall target is RINGING.
    * 2) Transferee is off hold.
    *
    * Transitions to TRANSFER_BLOND_NONFINAL:
    * 1) TRANSFER_CALLING_TARGET: Transferer hangs up or presses the DTMF complete sequence.
    *    atxferdropcall is set to 'no'.
    * 2) TRANSFER_HESITANT: Transferer hangs up or presses the DTMF complete sequence.
    *    atxferdropcall is set to 'no'.
    *
    * State operation:
    * The superstate of the attended transfer is changed from Transfer to Recall.
    * The transfer target bridge is merged into the transferee bridge. The transferer
    * channel is kicked out of the bridges as part of the merge.
    *
    * Transitions from TRANSFER_BLOND_NONFINAL:
    * 1) TRANSFER_FAIL: Transferee hangs up
    * 2) TRANSFER_RESUME: Recall target answers
    * 3) TRANSFER_RECALLING: Recall target hangs up or time expires.
    */
   TRANSFER_BLOND_NONFINAL,
   /*!
    * \brief Recalling state
    *
    * This state is entered if the recall target from the TRANSFER_BLOND_NONFINAL
    * or TRANSFER_RETRANSFER states hangs up or does not answer. The goal of this
    * state is to call back the original transferer in an attempt to recover the
    * original call.
    *
    * Superstate: Recall
    *
    * Preconditions:
    * 1) Recall target is down.
    * 2) Transferee is off hold.
    *
    * Transitions to TRANSFER_RECALLING:
    * 1) TRANSFER_BLOND_NONFINAL: Recall target hangs up or time expires.
    * 2) TRANSFER_RETRANSFER: Recall target hangs up or time expires.
    *    atxferloopdelay is non-zero.
    * 3) TRANSFER_WAIT_TO_RECALL: Time expires.
    *
    * State operation:
    * The original transferer becomes the recall target and is called using the Dialing API.
    * Ringing is indicated to the transferee.
    *
    * Transitions from TRANSFER_RECALLING:
    * 1) TRANSFER_FAIL:
    *    a) Transferee hangs up.
    *    b) Recall target hangs up or time expires, and number of recall attempts exceeds atxfercallbackretries
    * 2) TRANSFER_WAIT_TO_RETRANSFER: Recall target hangs up or time expires.
    *    atxferloopdelay is non-zero.
    * 3) TRANSFER_RETRANSFER: Recall target hangs up or time expires.
    *    atxferloopdelay is zero.
    * 4) TRANSFER_RESUME: Recall target answers.
    */
   TRANSFER_RECALLING,
   /*!
    * \brief Wait to Retransfer state
    *
    * This state is used simply to give a bit of breathing room between attempting
    * to call back the original transferer and attempting to call back the original
    * transfer target. The transferee hears music on hold during this state as an
    * auditory clue that no one is currently being dialed.
    *
    * Superstate: Recall
    *
    * Preconditions:
    * 1) Recall target is down.
    * 2) Transferee is off hold.
    *
    * Transitions to TRANSFER_WAIT_TO_RETRANSFER:
    * 1) TRANSFER_RECALLING: Recall target hangs up or time expires.
    *    atxferloopdelay is non-zero.
    *
    * State operation:
    * The transferee is placed on hold.
    *
    * Transitions from TRANSFER_WAIT_TO_RETRANSFER:
    * 1) TRANSFER_FAIL: Transferee hangs up.
    * 2) TRANSFER_RETRANSFER: Time expires.
    */
   TRANSFER_WAIT_TO_RETRANSFER,
   /*!
    * \brief Retransfer state
    *
    * This state is used in order to attempt to call back the original
    * transfer target channel from the transfer. The transferee hears
    * ringing during this state as an auditory cue that a party is being
    * dialed.
    *
    * Superstate: Recall
    *
    * Preconditions:
    * 1) Recall target is down.
    * 2) Transferee is off hold.
    *
    * Transitions to TRANSFER_RETRANSFER:
    * 1) TRANSFER_RECALLING: Recall target hangs up or time expires.
    *    atxferloopdelay is zero.
    * 2) TRANSFER_WAIT_TO_RETRANSFER: Time expires.
    *
    * State operation:
    * The original transfer target is requested and is set as the recall target.
    * The recall target is called and placed into the transferee bridge.
    *
    * Transitions from TRANSFER_RETRANSFER:
    * 1) TRANSFER_FAIL: Transferee hangs up.
    * 2) TRANSFER_WAIT_TO_RECALL: Recall target hangs up or time expires.
    *    atxferloopdelay is non-zero.
    * 3) TRANSFER_RECALLING: Recall target hangs up or time expires.
    *    atxferloopdelay is zero.
    */
   TRANSFER_RETRANSFER,
   /*!
    * \brief Wait to recall state
    *
    * This state is used simply to give a bit of breathing room between attempting
    * to call back the original transfer target and attempting to call back the
    * original transferer. The transferee hears music on hold during this state as an
    * auditory clue that no one is currently being dialed.
    *
    * Superstate: Recall
    *
    * Preconditions:
    * 1) Recall target is down.
    * 2) Transferee is off hold.
    *
    * Transitions to TRANSFER_WAIT_TO_RECALL:
    * 1) TRANSFER_RETRANSFER: Recall target hangs up or time expires.
    *    atxferloopdelay is non-zero.
    *
    * State operation:
    * Transferee is placed on hold.
    *
    * Transitions from TRANSFER_WAIT_TO_RECALL:
    * 1) TRANSFER_FAIL: Transferee hangs up
    * 2) TRANSFER_RECALLING: Time expires
    */
   TRANSFER_WAIT_TO_RECALL,
   /*!
    * \brief Fail state
    *
    * This state indicates that something occurred during the transfer that
    * makes a graceful completion impossible. The most common stimulus for this
    * state is when the transferee hangs up.
    *
    * Superstate: Transfer and Recall
    *
    * Preconditions:
    * None
    *
    * Transitions to TRANSFER_FAIL:
    * 1) TRANSFER_CALLING_TARGET: Transferee hangs up.
    * 2) TRANSFER_HESITANT: Transferee hangs up.
    * 3) TRANSFER_DOUBLECHECKING: Transferee hangs up.
    * 4) TRANSFER_BLOND_NONFINAL: Transferee hangs up.
    * 5) TRANSFER_RECALLING:
    *    a) Transferee hangs up.
    *    b) Recall target hangs up or time expires, and number of
    *       recall attempts exceeds atxfercallbackretries.
    * 6) TRANSFER_WAIT_TO_RETRANSFER: Transferee hangs up.
    * 7) TRANSFER_RETRANSFER: Transferee hangs up.
    * 8) TRANSFER_WAIT_TO_RECALL: Transferee hangs up.
    *
    * State operation:
    * A transfer stasis publication is made indicating a failed transfer.
    * The transferee bridge is destroyed.
    *
    * Transitions from TRANSFER_FAIL:
    * None.
    */
   TRANSFER_FAIL,
};

/*!
 * \brief Stimuli that can cause transfer state changes
 */
enum attended_transfer_stimulus {
   /*! No stimulus. This literally can never happen. */
   STIMULUS_NONE,
   /*! All of the transferee channels have been hung up. */
   STIMULUS_TRANSFEREE_HANGUP,
   /*! The transferer has hung up. */
   STIMULUS_TRANSFERER_HANGUP,
   /*! The transfer target channel has hung up. */
   STIMULUS_TRANSFER_TARGET_HANGUP,
   /*! The transfer target channel has answered. */
   STIMULUS_TRANSFER_TARGET_ANSWER,
   /*! The recall target channel has hung up. */
   STIMULUS_RECALL_TARGET_HANGUP,
   /*! The recall target channel has answered. */
   STIMULUS_RECALL_TARGET_ANSWER,
   /*! The current state's timer has expired. */
   STIMULUS_TIMEOUT,
   /*! The transferer pressed the abort DTMF sequence. */
   STIMULUS_DTMF_ATXFER_ABORT,
   /*! The transferer pressed the complete DTMF sequence. */
   STIMULUS_DTMF_ATXFER_COMPLETE,
   /*! The transferer pressed the three-way DTMF sequence. */
   STIMULUS_DTMF_ATXFER_THREEWAY,
   /*! The transferer pressed the swap DTMF sequence. */
   STIMULUS_DTMF_ATXFER_SWAP,
};

/*!
 * \brief String representations of the various stimuli
 *
 * Used for debugging purposes
 */
const char *stimulus_strs[] = {
   [STIMULUS_NONE] = "None",
   [STIMULUS_TRANSFEREE_HANGUP] = "Transferee Hangup",
   [STIMULUS_TRANSFERER_HANGUP] = "Transferer Hangup",
   [STIMULUS_TRANSFER_TARGET_HANGUP] = "Transfer Target Hangup",
   [STIMULUS_TRANSFER_TARGET_ANSWER] = "Transfer Target Answer",
   [STIMULUS_RECALL_TARGET_HANGUP] = "Recall Target Hangup",
   [STIMULUS_RECALL_TARGET_ANSWER] = "Recall Target Answer",
   [STIMULUS_TIMEOUT] = "Timeout",
   [STIMULUS_DTMF_ATXFER_ABORT] = "DTMF Abort",
   [STIMULUS_DTMF_ATXFER_COMPLETE] = "DTMF Complete",
   [STIMULUS_DTMF_ATXFER_THREEWAY] = "DTMF Threeway",
   [STIMULUS_DTMF_ATXFER_SWAP] = "DTMF Swap",
};

struct stimulus_list {
   enum attended_transfer_stimulus stimulus;
   AST_LIST_ENTRY(stimulus_list) next;
};

/*!
 * \brief Collection of data related to an attended transfer attempt
 */
struct attended_transfer_properties {
   AST_DECLARE_STRING_FIELDS (
      /*! Extension of transfer target */
      AST_STRING_FIELD(exten);
      /*! Context of transfer target */
      AST_STRING_FIELD(context);
      /*! Sound to play when transfer completes */
      AST_STRING_FIELD(xfersound);
      /*! The channel technology of the transferer channel */
      AST_STRING_FIELD(transferer_type);
      /*! The transferer channel address */
      AST_STRING_FIELD(transferer_addr);
   );
   /*! Condition used to synchronize when stimuli are reported to the monitor thread */
   ast_cond_t cond;
   /*! The bridge where the transferee resides. This bridge is also the bridge that
    * survives a successful attended transfer.
    */
   struct ast_bridge *transferee_bridge;
   /*! The bridge used to place an outbound call to the transfer target. This
    * bridge is merged with the transferee_bridge on a successful transfer.
    */
   struct ast_bridge *target_bridge;
   /*! The party that performs the attended transfer. */
   struct ast_channel *transferer;
   /*! The local channel dialed to reach the transfer target. */
   struct ast_channel *transfer_target;
   /*! The party that is currently being recalled. Depending on
    * the current state, this may be either the party that originally
    * was the transferer or the original transfer target.  This is
    * set with reference when entering the BLOND_NONFINAL, RECALLING,
    * and RETRANSFER states, and the reference released on state exit
    * if continuing with recall or retransfer to avoid leak.
    */
   struct ast_channel *recall_target;
   /*! The absolute starting time for running timers */
   struct timeval start;
   AST_LIST_HEAD_NOLOCK(,stimulus_list) stimulus_queue;
   /*! The current state of the attended transfer */
   enum attended_transfer_state state;
   /*! The current superstate of the attended transfer */
   enum attended_transfer_superstate superstate;
   /*! Configured atxferdropcall from features.conf */
   int atxferdropcall;
   /*! Configured atxfercallbackretries from features.conf */
   int atxfercallbackretries;
   /*! Configured atxferloopdelay from features.conf */
   int atxferloopdelay;
   /*! Configured atxfernoanswertimeout from features.conf */
   int atxfernoanswertimeout;
   /*! Count of the number of times that recalls have been attempted */
   int retry_attempts;
   /*! Framehook ID for outbounc call to transfer target or recall target */
   int target_framehook_id;
   /*! Dial structure used when recalling transferer channel */
   struct ast_dial *dial;
   /*! The bridging features the transferer has available */
   struct ast_flags transferer_features;
   /*! Saved transferer connected line data for recalling the transferer. */
   struct ast_party_connected_line original_transferer_colp;
};

static void attended_transfer_properties_destructor(void *obj)
{
   struct attended_transfer_properties *props = obj;

   ast_debug(1, "Destroy attended transfer properties %p\n", props);

   ao2_cleanup(props->target_bridge);
   ao2_cleanup(props->transferee_bridge);
   /* Use ast_channel_cleanup() instead of ast_channel_unref() for channels since they may be NULL */
   ast_channel_cleanup(props->transferer);
   ast_channel_cleanup(props->transfer_target);
   ast_channel_cleanup(props->recall_target);
   ast_party_connected_line_free(&props->original_transferer_colp);
   ast_string_field_free_memory(props);
   ast_cond_destroy(&props->cond);
}

/*!
 * \internal
 * \brief Determine the transfer context to use.
 * \since 12.0.0
 *
 * \param transferer Channel initiating the transfer.
 * \param context User supplied context if available.  May be NULL.
 *
 * \return The context to use for the transfer.
 */
static const char *get_transfer_context(struct ast_channel *transferer, const char *context)
{
   if (!ast_strlen_zero(context)) {
      return context;
   }
   context = pbx_builtin_getvar_helper(transferer, "TRANSFER_CONTEXT");
   if (!ast_strlen_zero(context)) {
      return context;
   }
   context = ast_channel_macrocontext(transferer);
   if (!ast_strlen_zero(context)) {
      return context;
   }
   context = ast_channel_context(transferer);
   if (!ast_strlen_zero(context)) {
      return context;
   }
   return "default";
}

/*!
 * \brief Allocate and initialize attended transfer properties
 *
 * \param transferer The channel performing the attended transfer
 * \param context Suggestion for what context the transfer target extension can be found in
 *
 * \retval NULL Failure to allocate or initialize
 * \retval non-NULL Newly allocated properties
 */
static struct attended_transfer_properties *attended_transfer_properties_alloc(
   struct ast_channel *transferer, const char *context)
{
   struct attended_transfer_properties *props;
   char *tech;
   char *addr;
   char *serial;
   struct ast_features_xfer_config *xfer_cfg;
   struct ast_flags *transferer_features;

   props = ao2_alloc(sizeof(*props), attended_transfer_properties_destructor);
   if (!props) {
      ast_log(LOG_ERROR, "Unable to create props - channel %s, context %s\n",
         ast_channel_name(transferer), context);
      return NULL;
   }

   ast_cond_init(&props->cond, NULL);

   if (ast_string_field_init(props, 64)) {
      ast_log(LOG_ERROR, "Unable to initialize prop fields - channel %s, context %s\n",
         ast_channel_name(transferer), context);
      ao2_ref(props, -1);
      return NULL;
   }

   props->target_framehook_id = -1;
   props->transferer = ast_channel_ref(transferer);

   ast_channel_lock(props->transferer);
   xfer_cfg = ast_get_chan_features_xfer_config(props->transferer);
   if (!xfer_cfg) {
      ast_log(LOG_ERROR, "Unable to get transfer configuration from channel %s\n", ast_channel_name(props->transferer));
      ast_channel_unlock(props->transferer);
      ao2_ref(props, -1);
      return NULL;
   }
   transferer_features = ast_bridge_features_ds_get(props->transferer);
   if (transferer_features) {
      props->transferer_features = *transferer_features;
   }
   props->atxferdropcall = xfer_cfg->atxferdropcall;
   props->atxfercallbackretries = xfer_cfg->atxfercallbackretries;
   props->atxfernoanswertimeout = xfer_cfg->atxfernoanswertimeout;
   props->atxferloopdelay = xfer_cfg->atxferloopdelay;
   ast_string_field_set(props, context, get_transfer_context(transferer, context));
   ast_string_field_set(props, xfersound, xfer_cfg->xfersound);
   ao2_ref(xfer_cfg, -1);

   /*
    * Save the transferee's party information for any recall calls.
    * This is the only piece of information needed that gets overwritten
    * on the transferer channel by the inital call to the transfer target.
    */
   ast_party_connected_line_copy(&props->original_transferer_colp,
      ast_channel_connected(props->transferer));

   tech = ast_strdupa(ast_channel_name(props->transferer));
   addr = strchr(tech, '/');
   if (!addr) {
      ast_log(LOG_ERROR, "Transferer channel name does not follow typical channel naming format (tech/address)\n");
      ast_channel_unlock(props->transferer);
      ao2_ref(props, -1);
      return NULL;
   }
   *addr++ = '\0';
   serial = strrchr(addr, '-');
   if (serial) {
      *serial = '\0';
   }
   ast_string_field_set(props, transferer_type, tech);
   ast_string_field_set(props, transferer_addr, addr);

   ast_channel_unlock(props->transferer);

   ast_debug(1, "Allocated attended transfer properties %p for transfer from %s\n",
         props, ast_channel_name(props->transferer));
   return props;
}

/*!
 * \brief Free backlog of stimuli in the queue
 */
static void clear_stimulus_queue(struct attended_transfer_properties *props)
{
   struct stimulus_list *list;
   SCOPED_AO2LOCK(lock, props);

   while ((list = AST_LIST_REMOVE_HEAD(&props->stimulus_queue, next))) {
      ast_free(list);
   }
}

/*!
 * \brief Initiate shutdown of attended transfer properties
 *
 * Calling this indicates that the attended transfer properties are no longer needed
 * because the transfer operation has concluded.
 */
static void attended_transfer_properties_shutdown(struct attended_transfer_properties *props)
{
   ast_debug(1, "Shutting down attended transfer %p\n", props);

   if (props->transferee_bridge) {
      bridge_basic_change_personality(props->transferee_bridge,
            BRIDGE_BASIC_PERSONALITY_NORMAL, NULL);
      ast_bridge_merge_inhibit(props->transferee_bridge, -1);
   }

   if (props->target_bridge) {
      ast_bridge_destroy(props->target_bridge, 0);
      props->target_bridge = NULL;
   }

   if (props->transferer) {
      ast_channel_remove_bridge_role(props->transferer, AST_TRANSFERER_ROLE_NAME);
   }

   clear_stimulus_queue(props);

   ao2_cleanup(props);
}

static void stimulate_attended_transfer(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   struct stimulus_list *list;

   list = ast_calloc(1, sizeof(*list));
   if (!list) {
      ast_log(LOG_ERROR, "Unable to push event to attended transfer queue. Expect transfer to fail\n");
      return;
   }

   list->stimulus = stimulus;
   ao2_lock(props);
   AST_LIST_INSERT_TAIL(&props->stimulus_queue, list, next);
   ast_cond_signal(&props->cond);
   ao2_unlock(props);
}

static void remove_attended_transfer_stimulus(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   struct stimulus_list *list;

   ao2_lock(props);
   AST_LIST_TRAVERSE_SAFE_BEGIN(&props->stimulus_queue, list, next) {
      if (list->stimulus == stimulus) {
         AST_LIST_REMOVE_CURRENT(next);
         ast_free(list);
         break;
      }
   }
   AST_LIST_TRAVERSE_SAFE_END;
   ao2_unlock(props);
}

/*!
 * \brief Get a desired transfer party for a bridge the transferer is not in.
 *
 * \param bridge The bridge to get the party from. May be NULL.
 * \param[out] party The lone channel in the bridge. Will be set NULL if bridge is NULL or multiple parties are present.
 */
static void get_transfer_party_non_transferer_bridge(struct ast_bridge *bridge,
      struct ast_channel **party)
{
   if (bridge && bridge->num_channels == 1) {
      *party = ast_channel_ref(AST_LIST_FIRST(&bridge->channels)->chan);
   } else {
      *party = NULL;
   }
}

/*!
 * \brief Get the transferee and transfer target when the transferer is in a bridge with
 * one of the desired parties.
 *
 * \param transferer_bridge The bridge the transferer is in
 * \param other_bridge The bridge the transferer is not in. May be NULL.
 * \param transferer The transferer party
 * \param[out] transferer_peer The party that is in the bridge with the transferer
 * \param[out] other_party The party that is in the other_bridge
 */
static void get_transfer_parties_transferer_bridge(struct ast_bridge *transferer_bridge,
      struct ast_bridge *other_bridge, struct ast_channel *transferer,
      struct ast_channel **transferer_peer, struct ast_channel **other_party)
{
   *transferer_peer = ast_bridge_peer(transferer_bridge, transferer);
   get_transfer_party_non_transferer_bridge(other_bridge, other_party);
}

/*!
 * \brief determine transferee and transfer target for an attended transfer
 *
 * In builtin attended transfers, there is a single transferer channel that jumps between
 * the two bridges involved. At the time the attended transfer occurs, the transferer could
 * be in either bridge, so determining the parties is a bit more complex than normal.
 *
 * The method used here is to determine which of the two bridges the transferer is in, and
 * grabbing the peer from that bridge. The other bridge, if it only has a single channel in it,
 * has the other desired channel.
 *
 * \param transferer The channel performing the transfer
 * \param transferee_bridge The bridge that the transferee is in
 * \param target_bridge The bridge that the transfer target is in
 * \param[out] transferee The transferee channel
 * \param[out] transfer_target The transfer target channel
 */
static void get_transfer_parties(struct ast_channel *transferer, struct ast_bridge *transferee_bridge,
      struct ast_bridge *target_bridge, struct ast_channel **transferee,
      struct ast_channel **transfer_target)
{
   struct ast_bridge *transferer_bridge;

   ast_channel_lock(transferer);
   transferer_bridge = ast_channel_get_bridge(transferer);
   ast_channel_unlock(transferer);

   if (transferer_bridge == transferee_bridge) {
      get_transfer_parties_transferer_bridge(transferee_bridge, target_bridge,
            transferer, transferee, transfer_target);
   } else if (transferer_bridge == target_bridge) {
      get_transfer_parties_transferer_bridge(target_bridge, transferee_bridge,
            transferer, transfer_target, transferee);
   } else {
      get_transfer_party_non_transferer_bridge(transferee_bridge, transferee);
      get_transfer_party_non_transferer_bridge(target_bridge, transfer_target);
   }

   ao2_cleanup(transferer_bridge);
}

/*!
 * \brief Send a stasis publication for a successful attended transfer
 */
static void publish_transfer_success(struct attended_transfer_properties *props,
      struct ast_channel *transferee_channel, struct ast_channel *target_channel)
{
   struct ast_attended_transfer_message *transfer_msg;

   transfer_msg = ast_attended_transfer_message_create(0, props->transferer,
         props->transferee_bridge, props->transferer, props->target_bridge,
         transferee_channel, target_channel);

   if (!transfer_msg) {
      ast_log(LOG_ERROR, "Unable to publish successful attended transfer from %s\n",
            ast_channel_name(props->transferer));
      return;
   }

   ast_attended_transfer_message_add_merge(transfer_msg, props->transferee_bridge);
   ast_bridge_publish_attended_transfer(transfer_msg);
   ao2_cleanup(transfer_msg);
}

/*!
 * \brief Send a stasis publication for an attended transfer that ends in a threeway call
 */
static void publish_transfer_threeway(struct attended_transfer_properties *props,
      struct ast_channel *transferee_channel, struct ast_channel *target_channel)
{
   struct ast_attended_transfer_message *transfer_msg;

   transfer_msg = ast_attended_transfer_message_create(0, props->transferer,
         props->transferee_bridge, props->transferer, props->target_bridge,
         transferee_channel, target_channel);

   if (!transfer_msg) {
      ast_log(LOG_ERROR, "Unable to publish successful three-way transfer from %s\n",
            ast_channel_name(props->transferer));
      return;
   }

   ast_attended_transfer_message_add_threeway(transfer_msg, props->transferer,
         props->transferee_bridge);
   ast_bridge_publish_attended_transfer(transfer_msg);
   ao2_cleanup(transfer_msg);
}

/*!
 * \brief Send a stasis publication for a failed attended transfer
 */
static void publish_transfer_fail(struct attended_transfer_properties *props)
{
   struct ast_attended_transfer_message *transfer_msg;

   transfer_msg = ast_attended_transfer_message_create(0, props->transferer,
         props->transferee_bridge, props->transferer, props->target_bridge,
         NULL, NULL);

   if (!transfer_msg) {
      ast_log(LOG_ERROR, "Unable to publish failed transfer from %s\n",
            ast_channel_name(props->transferer));
      return;
   }

   transfer_msg->result = AST_BRIDGE_TRANSFER_FAIL;
   ast_bridge_publish_attended_transfer(transfer_msg);
   ao2_cleanup(transfer_msg);
}

/*!
 * \brief Helper method to play a sound on a channel in a bridge
 *
 * \param chan The channel to play the sound to
 * \param sound The sound to play
 */
static void play_sound(struct ast_channel *chan, const char *sound)
{
   struct ast_bridge_channel *bridge_channel;

   ast_channel_lock(chan);
   bridge_channel = ast_channel_get_bridge_channel(chan);
   ast_channel_unlock(chan);

   if (bridge_channel) {
      ast_bridge_channel_queue_playfile(bridge_channel, NULL, sound, NULL);
      ao2_ref(bridge_channel, -1);
   }
}

/*!
 * \brief Helper method to play a fail sound on a channel in a bridge
 *
 * \param chan The channel to play the fail sound to
 */
static void play_failsound(struct ast_channel *chan)
{
   char *sound;

   ast_channel_lock(chan);
   sound = ast_get_chan_features_xferfailsound(chan);
   ast_channel_unlock(chan);

   if (sound) {
      play_sound(chan, sound);
      ast_free(sound);
   }
}

/*!
 * \brief Helper method to stream a fail sound on a channel
 *
 * \param chan The channel to stream the fail sound to
 */
static void stream_failsound(struct ast_channel *chan)
{
   char *sound;

   ast_channel_lock(chan);
   sound = ast_get_chan_features_xferfailsound(chan);
   ast_channel_unlock(chan);

   if (sound) {
      ast_stream_and_wait(chan, sound, AST_DIGIT_NONE);
      ast_free(sound);
   }
}

/*!
 * \brief Helper method to place a channel in a bridge on hold
 */
static void hold(struct ast_channel *chan)
{
   struct ast_bridge_channel *bridge_channel;

   if (!chan) {
      return;
   }

   ast_channel_lock(chan);
   bridge_channel = ast_channel_get_bridge_channel(chan);
   ast_channel_unlock(chan);

   if (bridge_channel) {
      ast_bridge_channel_write_hold(bridge_channel, NULL);
      ao2_ref(bridge_channel, -1);
   }
}

/*!
 * \brief Helper method to take a channel in a bridge off hold
 */
static void unhold(struct ast_channel *chan)
{
   struct ast_bridge_channel *bridge_channel;

   if (!chan) {
      return;
   }

   ast_channel_lock(chan);
   bridge_channel = ast_channel_get_bridge_channel(chan);
   ast_channel_unlock(chan);

   if (bridge_channel) {
      ast_bridge_channel_write_unhold(bridge_channel);
      ao2_ref(bridge_channel, -1);
   }
}

/*!
 * \brief Helper method to send a ringing indication to a channel in a bridge
 */
static void ringing(struct ast_channel *chan)
{
   struct ast_bridge_channel *bridge_channel;

   ast_channel_lock(chan);
   bridge_channel = ast_channel_get_bridge_channel(chan);
   ast_channel_unlock(chan);

   if (bridge_channel) {
      ast_bridge_channel_write_control_data(bridge_channel, AST_CONTROL_RINGING, NULL, 0);
      ao2_ref(bridge_channel, -1);
   }
}

/*!
 * \brief Helper method to send a ringing indication to all channels in a bridge
 */
static void bridge_ringing(struct ast_bridge *bridge)
{
   struct ast_frame ringing = {
      .frametype = AST_FRAME_CONTROL,
      .subclass.integer = AST_CONTROL_RINGING,
   };

   ast_bridge_queue_everyone_else(bridge, NULL, &ringing);
}

/*!
 * \brief Helper method to send a hold frame to all channels in a bridge
 */
static void bridge_hold(struct ast_bridge *bridge)
{
   struct ast_frame hold = {
      .frametype = AST_FRAME_CONTROL,
      .subclass.integer = AST_CONTROL_HOLD,
   };

   ast_bridge_queue_everyone_else(bridge, NULL, &hold);
}

/*!
 * \brief Helper method to send an unhold frame to all channels in a bridge
 */
static void bridge_unhold(struct ast_bridge *bridge)
{
   struct ast_frame unhold = {
      .frametype = AST_FRAME_CONTROL,
      .subclass.integer = AST_CONTROL_UNHOLD,
   };

   ast_bridge_queue_everyone_else(bridge, NULL, &unhold);
}

/*!
 * \brief Wrapper for \ref bridge_do_move
 */
static void bridge_move(struct ast_bridge *dest, struct ast_bridge *src, struct ast_channel *channel, struct ast_channel *swap)
{
   struct ast_bridge_channel *bridge_channel;

   ast_bridge_lock_both(src, dest);

   ast_channel_lock(channel);
   bridge_channel = ast_channel_get_bridge_channel(channel);
   ast_channel_unlock(channel);

   if (bridge_channel) {
      ao2_lock(bridge_channel);
      bridge_channel->swap = swap;
      ao2_unlock(bridge_channel);

      bridge_do_move(dest, bridge_channel, 1, 0);
   }

   ast_bridge_unlock(dest);
   ast_bridge_unlock(src);

   ao2_cleanup(bridge_channel);
}

/*!
 * \brief Wrapper for \ref bridge_do_merge
 */
static void bridge_merge(struct ast_bridge *dest, struct ast_bridge *src, struct ast_channel **kick_channels, unsigned int num_channels)
{
   struct ast_bridge_channel **kick_bridge_channels = num_channels ?
      ast_alloca(num_channels * sizeof(*kick_bridge_channels)) : NULL;
   int i;
   int num_bridge_channels = 0;

   ast_bridge_lock_both(dest, src);

   for (i = 0; i < num_channels; ++i) {
      struct ast_bridge_channel *kick_bridge_channel;

      kick_bridge_channel = bridge_find_channel(src, kick_channels[i]);
      if (!kick_bridge_channel) {
         kick_bridge_channel = bridge_find_channel(dest, kick_channels[i]);
      }

      /* It's possible (and fine) for the bridge channel to be NULL at this point if the
       * channel has hung up already. If that happens, we can just remove it from the list
       * of bridge channels to kick from the bridge
       */
      if (!kick_bridge_channel) {
         continue;
      }

      kick_bridge_channels[num_bridge_channels++] = kick_bridge_channel;
   }

   bridge_do_merge(dest, src, kick_bridge_channels, num_bridge_channels, 0);
   ast_bridge_unlock(dest);
   ast_bridge_unlock(src);
}

/*!
 * \brief Flags that indicate properties of attended transfer states
 */
enum attended_transfer_state_flags {
   /*! This state requires that the timer be reset when entering the state */
   TRANSFER_STATE_FLAG_TIMER_RESET = (1 << 0),
   /*! This state's timer uses atxferloopdelay */
   TRANSFER_STATE_FLAG_TIMER_LOOP_DELAY = (1 << 1),
   /*! This state's timer uses atxfernoanswertimeout */
   TRANSFER_STATE_FLAG_ATXFER_NO_ANSWER = (1 << 2),
   /*! This state has a time limit associated with it */
   TRANSFER_STATE_FLAG_TIMED = (TRANSFER_STATE_FLAG_TIMER_RESET |
         TRANSFER_STATE_FLAG_TIMER_LOOP_DELAY | TRANSFER_STATE_FLAG_ATXFER_NO_ANSWER),
   /*! This state does not transition to any other states */
   TRANSFER_STATE_FLAG_TERMINAL = (1 << 3),
};

static int calling_target_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state calling_target_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int hesitant_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state hesitant_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int rebridge_enter(struct attended_transfer_properties *props);

static int resume_enter(struct attended_transfer_properties *props);

static int threeway_enter(struct attended_transfer_properties *props);

static int consulting_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state consulting_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int double_checking_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state double_checking_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int complete_enter(struct attended_transfer_properties *props);

static int blond_enter(struct attended_transfer_properties *props);

static int blond_nonfinal_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state blond_nonfinal_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int recalling_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state recalling_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int wait_to_retransfer_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state wait_to_retransfer_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int retransfer_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state retransfer_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int wait_to_recall_enter(struct attended_transfer_properties *props);
static enum attended_transfer_state wait_to_recall_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus);

static int fail_enter(struct attended_transfer_properties *props);

/*!
 * \brief Properties of an attended transfer state
 */
struct attended_transfer_state_properties {
   /*! The name of the state. Used for debugging */
   const char *state_name;
   /*! Function used to enter a state */
   int (*enter)(struct attended_transfer_properties *props);
   /*!
    * Function used to exit a state
    * This is used both to determine what the next state
    * to transition to will be and to perform any cleanup
    * necessary before exiting the current state.
    */
   enum attended_transfer_state (*exit)(struct attended_transfer_properties *props,
         enum attended_transfer_stimulus stimulus);
   /*! Flags associated with this state */
   enum attended_transfer_state_flags flags;
};

static const struct attended_transfer_state_properties state_properties[] = {
   [TRANSFER_CALLING_TARGET] = {
      .state_name = "Calling Target",
      .enter = calling_target_enter,
      .exit = calling_target_exit,
      .flags = TRANSFER_STATE_FLAG_ATXFER_NO_ANSWER | TRANSFER_STATE_FLAG_TIMER_RESET,
   },
   [TRANSFER_HESITANT] = {
      .state_name = "Hesitant",
      .enter = hesitant_enter,
      .exit = hesitant_exit,
      .flags = TRANSFER_STATE_FLAG_ATXFER_NO_ANSWER,
   },
   [TRANSFER_REBRIDGE] = {
      .state_name = "Rebridge",
      .enter = rebridge_enter,
      .flags = TRANSFER_STATE_FLAG_TERMINAL,
   },
   [TRANSFER_RESUME] = {
      .state_name = "Resume",
      .enter = resume_enter,
      .flags = TRANSFER_STATE_FLAG_TERMINAL,
   },
   [TRANSFER_THREEWAY] = {
      .state_name = "Threeway",
      .enter = threeway_enter,
      .flags = TRANSFER_STATE_FLAG_TERMINAL,
   },
   [TRANSFER_CONSULTING] = {
      .state_name = "Consulting",
      .enter = consulting_enter,
      .exit = consulting_exit,
   },
   [TRANSFER_DOUBLECHECKING] = {
      .state_name = "Double Checking",
      .enter = double_checking_enter,
      .exit = double_checking_exit,
   },
   [TRANSFER_COMPLETE] = {
      .state_name = "Complete",
      .enter = complete_enter,
      .flags = TRANSFER_STATE_FLAG_TERMINAL,
   },
   [TRANSFER_BLOND] = {
      .state_name = "Blond",
      .enter = blond_enter,
      .flags = TRANSFER_STATE_FLAG_TERMINAL,
   },
   [TRANSFER_BLOND_NONFINAL] = {
      .state_name = "Blond Non-Final",
      .enter = blond_nonfinal_enter,
      .exit = blond_nonfinal_exit,
      .flags = TRANSFER_STATE_FLAG_ATXFER_NO_ANSWER,
   },
   [TRANSFER_RECALLING] = {
      .state_name = "Recalling",
      .enter = recalling_enter,
      .exit = recalling_exit,
      .flags = TRANSFER_STATE_FLAG_ATXFER_NO_ANSWER | TRANSFER_STATE_FLAG_TIMER_RESET,
   },
   [TRANSFER_WAIT_TO_RETRANSFER] = {
      .state_name = "Wait to Retransfer",
      .enter = wait_to_retransfer_enter,
      .exit = wait_to_retransfer_exit,
      .flags = TRANSFER_STATE_FLAG_TIMER_RESET | TRANSFER_STATE_FLAG_TIMER_LOOP_DELAY,
   },
   [TRANSFER_RETRANSFER] = {
      .state_name = "Retransfer",
      .enter = retransfer_enter,
      .exit = retransfer_exit,
      .flags = TRANSFER_STATE_FLAG_ATXFER_NO_ANSWER | TRANSFER_STATE_FLAG_TIMER_RESET,
   },
   [TRANSFER_WAIT_TO_RECALL] = {
      .state_name = "Wait to Recall",
      .enter = wait_to_recall_enter,
      .exit = wait_to_recall_exit,
      .flags = TRANSFER_STATE_FLAG_TIMER_RESET | TRANSFER_STATE_FLAG_TIMER_LOOP_DELAY,
   },
   [TRANSFER_FAIL] = {
      .state_name = "Fail",
      .enter = fail_enter,
      .flags = TRANSFER_STATE_FLAG_TERMINAL,
   },
};

static int calling_target_enter(struct attended_transfer_properties *props)
{
   bridge_move(props->target_bridge, props->transferee_bridge, props->transferer, NULL);
   return 0;
}

static enum attended_transfer_state calling_target_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      play_failsound(props->transferer);
      publish_transfer_fail(props);
      return TRANSFER_FAIL;
   case STIMULUS_DTMF_ATXFER_COMPLETE:
   case STIMULUS_TRANSFERER_HANGUP:
      bridge_unhold(props->transferee_bridge);
      return props->atxferdropcall ? TRANSFER_BLOND : TRANSFER_BLOND_NONFINAL;
   case STIMULUS_TRANSFER_TARGET_ANSWER:
      return TRANSFER_CONSULTING;
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_TIMEOUT:
   case STIMULUS_DTMF_ATXFER_ABORT:
      play_failsound(props->transferer);
      return TRANSFER_REBRIDGE;
   case STIMULUS_DTMF_ATXFER_THREEWAY:
      bridge_unhold(props->transferee_bridge);
      return TRANSFER_THREEWAY;
   case STIMULUS_DTMF_ATXFER_SWAP:
      return TRANSFER_HESITANT;
   case STIMULUS_NONE:
   case STIMULUS_RECALL_TARGET_ANSWER:
   case STIMULUS_RECALL_TARGET_HANGUP:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int hesitant_enter(struct attended_transfer_properties *props)
{
   bridge_move(props->transferee_bridge, props->target_bridge, props->transferer, NULL);
   unhold(props->transferer);
   return 0;
}

static enum attended_transfer_state hesitant_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      play_failsound(props->transferer);
      publish_transfer_fail(props);
      return TRANSFER_FAIL;
   case STIMULUS_DTMF_ATXFER_COMPLETE:
   case STIMULUS_TRANSFERER_HANGUP:
      return props->atxferdropcall ? TRANSFER_BLOND : TRANSFER_BLOND_NONFINAL;
   case STIMULUS_TRANSFER_TARGET_ANSWER:
      return TRANSFER_DOUBLECHECKING;
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_TIMEOUT:
   case STIMULUS_DTMF_ATXFER_ABORT:
      play_failsound(props->transferer);
      return TRANSFER_RESUME;
   case STIMULUS_DTMF_ATXFER_THREEWAY:
      return TRANSFER_THREEWAY;
   case STIMULUS_DTMF_ATXFER_SWAP:
      hold(props->transferer);
      return TRANSFER_CALLING_TARGET;
   case STIMULUS_NONE:
   case STIMULUS_RECALL_TARGET_HANGUP:
   case STIMULUS_RECALL_TARGET_ANSWER:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int rebridge_enter(struct attended_transfer_properties *props)
{
   bridge_move(props->transferee_bridge, props->target_bridge, props->transferer, NULL);
   unhold(props->transferer);
   return 0;
}

static int resume_enter(struct attended_transfer_properties *props)
{
   return 0;
}

static int threeway_enter(struct attended_transfer_properties *props)
{
   struct ast_channel *transferee_channel;
   struct ast_channel *target_channel;

   get_transfer_parties(props->transferer, props->transferee_bridge, props->target_bridge,
         &transferee_channel, &target_channel);
   bridge_merge(props->transferee_bridge, props->target_bridge, NULL, 0);
   play_sound(props->transfer_target, props->xfersound);
   play_sound(props->transferer, props->xfersound);
   publish_transfer_threeway(props, transferee_channel, target_channel);

   ast_channel_cleanup(transferee_channel);
   ast_channel_cleanup(target_channel);
   return 0;
}

static int consulting_enter(struct attended_transfer_properties *props)
{
   return 0;
}

static enum attended_transfer_state consulting_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      /* This is a one-of-a-kind event. The transferer and transfer target are talking in
       * one bridge, and the transferee has hung up in a separate bridge. In this case, we
       * will change the personality of the transfer target bridge back to normal, and play
       * a sound to the transferer to indicate the transferee is gone.
       */
      bridge_basic_change_personality(props->target_bridge, BRIDGE_BASIC_PERSONALITY_NORMAL, NULL);
      play_failsound(props->transferer);
      ast_bridge_merge_inhibit(props->target_bridge, -1);
      /* These next two lines are here to ensure that our reference to the target bridge
       * is cleaned up properly and that the target bridge is not destroyed when the
       * monitor thread exits
       */
      ao2_ref(props->target_bridge, -1);
      props->target_bridge = NULL;
      return TRANSFER_FAIL;
   case STIMULUS_TRANSFERER_HANGUP:
   case STIMULUS_DTMF_ATXFER_COMPLETE:
      /* We know the transferer is in the target_bridge, so take the other bridge off hold */
      bridge_unhold(props->transferee_bridge);
      return TRANSFER_COMPLETE;
   case STIMULUS_TRANSFER_TARGET_HANGUP:
      return TRANSFER_REBRIDGE;
   case STIMULUS_DTMF_ATXFER_ABORT:
      play_failsound(props->transferer);
      return TRANSFER_REBRIDGE;
   case STIMULUS_DTMF_ATXFER_THREEWAY:
      bridge_unhold(props->transferee_bridge);
      return TRANSFER_THREEWAY;
   case STIMULUS_DTMF_ATXFER_SWAP:
      hold(props->transferer);
      bridge_move(props->transferee_bridge, props->target_bridge, props->transferer, NULL);
      unhold(props->transferer);
      return TRANSFER_DOUBLECHECKING;
   case STIMULUS_NONE:
   case STIMULUS_TIMEOUT:
   case STIMULUS_TRANSFER_TARGET_ANSWER:
   case STIMULUS_RECALL_TARGET_HANGUP:
   case STIMULUS_RECALL_TARGET_ANSWER:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int double_checking_enter(struct attended_transfer_properties *props)
{
   return 0;
}

static enum attended_transfer_state double_checking_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      play_failsound(props->transferer);
      publish_transfer_fail(props);
      return TRANSFER_FAIL;
   case STIMULUS_TRANSFERER_HANGUP:
   case STIMULUS_DTMF_ATXFER_COMPLETE:
      /* We know the transferer is in the transferee, so take the other bridge off hold */
      bridge_unhold(props->target_bridge);
      return TRANSFER_COMPLETE;
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_DTMF_ATXFER_ABORT:
      play_failsound(props->transferer);
      return TRANSFER_RESUME;
   case STIMULUS_DTMF_ATXFER_THREEWAY:
      bridge_unhold(props->target_bridge);
      return TRANSFER_THREEWAY;
   case STIMULUS_DTMF_ATXFER_SWAP:
      hold(props->transferer);
      bridge_move(props->target_bridge, props->transferee_bridge, props->transferer, NULL);
      unhold(props->transferer);
      return TRANSFER_CONSULTING;
   case STIMULUS_NONE:
   case STIMULUS_TIMEOUT:
   case STIMULUS_TRANSFER_TARGET_ANSWER:
   case STIMULUS_RECALL_TARGET_HANGUP:
   case STIMULUS_RECALL_TARGET_ANSWER:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int complete_enter(struct attended_transfer_properties *props)
{
   struct ast_channel *transferee_channel;
   struct ast_channel *target_channel;

   get_transfer_parties(props->transferer, props->transferee_bridge, props->target_bridge,
         &transferee_channel, &target_channel);
   bridge_merge(props->transferee_bridge, props->target_bridge, &props->transferer, 1);
   play_sound(props->transfer_target, props->xfersound);
   publish_transfer_success(props, transferee_channel, target_channel);

   ast_channel_cleanup(transferee_channel);
   ast_channel_cleanup(target_channel);
   return 0;
}

static int blond_enter(struct attended_transfer_properties *props)
{
   struct ast_channel *transferee_channel;
   struct ast_channel *target_channel;

   get_transfer_parties(props->transferer, props->transferee_bridge, props->target_bridge,
         &transferee_channel, &target_channel);
   bridge_merge(props->transferee_bridge, props->target_bridge, &props->transferer, 1);
   ringing(props->transfer_target);
   publish_transfer_success(props, transferee_channel, target_channel);

   ast_channel_cleanup(transferee_channel);
   ast_channel_cleanup(target_channel);
   return 0;
}

static int blond_nonfinal_enter(struct attended_transfer_properties *props)
{
   int res;
   props->superstate = SUPERSTATE_RECALL;
   /* move the transfer target to the recall target along with its reference */
   props->recall_target = ast_channel_ref(props->transfer_target);
   res = blond_enter(props);
   props->transfer_target = ast_channel_unref(props->transfer_target);
   return res;
}

static enum attended_transfer_state blond_nonfinal_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      return TRANSFER_FAIL;
   case STIMULUS_RECALL_TARGET_ANSWER:
      return TRANSFER_RESUME;
   case STIMULUS_TIMEOUT:
      ast_softhangup(props->recall_target, AST_SOFTHANGUP_EXPLICIT);
      /* It is possible before we hung them up that they queued up a recall target answer
       * so we remove it if present as it should not exist.
       */
      remove_attended_transfer_stimulus(props, STIMULUS_RECALL_TARGET_ANSWER);
   case STIMULUS_RECALL_TARGET_HANGUP:
      props->recall_target = ast_channel_unref(props->recall_target);
      return TRANSFER_RECALLING;
   case STIMULUS_NONE:
   case STIMULUS_DTMF_ATXFER_ABORT:
   case STIMULUS_DTMF_ATXFER_COMPLETE:
   case STIMULUS_DTMF_ATXFER_THREEWAY:
   case STIMULUS_DTMF_ATXFER_SWAP:
   case STIMULUS_TRANSFERER_HANGUP:
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_TRANSFER_TARGET_ANSWER:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

/*!
 * \brief Dial callback when attempting to recall the original transferer channel
 *
 * This is how we can monitor if the recall target has answered or has hung up.
 * If one of the two is detected, then an appropriate stimulus is sent to the
 * attended transfer monitor thread.
 */
static void recall_callback(struct ast_dial *dial)
{
   struct attended_transfer_properties *props = ast_dial_get_user_data(dial);

   switch (ast_dial_state(dial)) {
   default:
   case AST_DIAL_RESULT_INVALID:
   case AST_DIAL_RESULT_FAILED:
   case AST_DIAL_RESULT_TIMEOUT:
   case AST_DIAL_RESULT_HANGUP:
   case AST_DIAL_RESULT_UNANSWERED:
      /* Failure cases */
      stimulate_attended_transfer(props, STIMULUS_RECALL_TARGET_HANGUP);
      break;
   case AST_DIAL_RESULT_RINGING:
   case AST_DIAL_RESULT_PROGRESS:
   case AST_DIAL_RESULT_PROCEEDING:
   case AST_DIAL_RESULT_TRYING:
      /* Don't care about these cases */
      break;
   case AST_DIAL_RESULT_ANSWERED:
      /* We struck gold! */
      props->recall_target = ast_dial_answered_steal(dial);
      stimulate_attended_transfer(props, STIMULUS_RECALL_TARGET_ANSWER);
      break;
   }
}

/*!
 * \internal
 * \brief Setup common things to transferrer and transfer_target recall channels.
 *
 * \param recall Channel for recalling a party.
 * \param transferer Channel supplying recall information.
 *
 * \details
 * Setup callid, variables, datastores, accountcode, and peeraccount.
 *
 * \pre Both channels are locked on entry.
 *
 * \pre COLP and CLID on the recall channel are setup by the caller but not
 * explicitly published yet.
 *
 * \return Nothing
 */
static void common_recall_channel_setup(struct ast_channel *recall, struct ast_channel *transferer)
{
   ast_callid callid;

   callid = ast_read_threadstorage_callid();
   if (callid) {
      ast_channel_callid_set(recall, callid);
   }

   ast_channel_inherit_variables(transferer, recall);
   ast_channel_datastore_inherit(transferer, recall);

   /*
    * Stage a snapshot to ensure that a snapshot is always done
    * on the recall channel so earler COLP and CLID setup will
    * get published.
    */
   ast_channel_stage_snapshot(recall);
   ast_channel_req_accountcodes(recall, transferer, AST_CHANNEL_REQUESTOR_REPLACEMENT);
   ast_channel_stage_snapshot_done(recall);
}

static int recalling_enter(struct attended_transfer_properties *props)
{
   RAII_VAR(struct ast_format_cap *, cap, ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT), ao2_cleanup);
   struct ast_channel *recall;

   if (!cap) {
      return -1;
   }

   ast_format_cap_append(cap, ast_format_slin, 0);

   /* When we dial the transfer target, since we are communicating
    * with a local channel, we can place the local channel in a bridge
    * and then call out to it. When recalling the transferer, though, we
    * have to use the dialing API because the channel is not local.
    */
   props->dial = ast_dial_create();
   if (!props->dial) {
      return -1;
   }

   if (ast_dial_append(props->dial, props->transferer_type, props->transferer_addr, NULL)) {
      return -1;
   }

   if (ast_dial_prerun(props->dial, NULL, cap)) {
      return -1;
   }

   /*
    * Setup callid, variables, datastores, accountcode, peeraccount,
    * COLP, and CLID on the recalled transferrer.
    */
   recall = ast_dial_get_channel(props->dial, 0);
   if (!recall) {
      return -1;
   }
   ast_channel_lock_both(recall, props->transferer);

   ast_party_caller_copy(ast_channel_caller(recall),
      ast_channel_caller(props->transferer));
   ast_party_connected_line_copy(ast_channel_connected(recall),
      &props->original_transferer_colp);

   common_recall_channel_setup(recall, props->transferer);
   ast_channel_unlock(recall);
   ast_channel_unlock(props->transferer);

   ast_dial_set_state_callback(props->dial, recall_callback);

   ao2_ref(props, +1);
   ast_dial_set_user_data(props->dial, props);

   if (ast_dial_run(props->dial, NULL, 1) == AST_DIAL_RESULT_FAILED) {
      ao2_ref(props, -1);
      return -1;
   }

   bridge_ringing(props->transferee_bridge);
   return 0;
}

static enum attended_transfer_state recalling_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   /* No matter what the outcome was, we need to kill off the dial */
   ast_dial_join(props->dial);
   ast_dial_destroy(props->dial);
   props->dial = NULL;
   /* This reference is the one we incremented for the dial state callback (recall_callback) to use */
   ao2_ref(props, -1);

   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      return TRANSFER_FAIL;
   case STIMULUS_TIMEOUT:
   case STIMULUS_RECALL_TARGET_HANGUP:
      ++props->retry_attempts;
      if (props->retry_attempts >= props->atxfercallbackretries) {
         return TRANSFER_FAIL;
      }
      if (props->atxferloopdelay) {
         return TRANSFER_WAIT_TO_RETRANSFER;
      }
      return TRANSFER_RETRANSFER;
   case STIMULUS_RECALL_TARGET_ANSWER:
      /* Setting this datastore up will allow the transferer to have all of his
       * call features set up automatically when the bridge changes back to a
       * normal personality
       */
      ast_bridge_features_ds_set(props->recall_target, &props->transferer_features);
      ast_channel_ref(props->recall_target);
      if (ast_bridge_impart(props->transferee_bridge, props->recall_target, NULL, NULL,
         AST_BRIDGE_IMPART_CHAN_INDEPENDENT)) {
         ast_hangup(props->recall_target);
         ast_channel_unref(props->recall_target);
         return TRANSFER_FAIL;
      }
      return TRANSFER_RESUME;
   case STIMULUS_NONE:
   case STIMULUS_DTMF_ATXFER_ABORT:
   case STIMULUS_DTMF_ATXFER_COMPLETE:
   case STIMULUS_DTMF_ATXFER_THREEWAY:
   case STIMULUS_DTMF_ATXFER_SWAP:
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_TRANSFER_TARGET_ANSWER:
   case STIMULUS_TRANSFERER_HANGUP:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int wait_to_retransfer_enter(struct attended_transfer_properties *props)
{
   bridge_hold(props->transferee_bridge);
   return 0;
}

static enum attended_transfer_state wait_to_retransfer_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   bridge_unhold(props->transferee_bridge);
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      return TRANSFER_FAIL;
   case STIMULUS_TIMEOUT:
      return TRANSFER_RETRANSFER;
   case STIMULUS_NONE:
   case STIMULUS_DTMF_ATXFER_ABORT:
   case STIMULUS_DTMF_ATXFER_COMPLETE:
   case STIMULUS_DTMF_ATXFER_THREEWAY:
   case STIMULUS_DTMF_ATXFER_SWAP:
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_TRANSFER_TARGET_ANSWER:
   case STIMULUS_TRANSFERER_HANGUP:
   case STIMULUS_RECALL_TARGET_HANGUP:
   case STIMULUS_RECALL_TARGET_ANSWER:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int attach_framehook(struct attended_transfer_properties *props, struct ast_channel *channel);

static int retransfer_enter(struct attended_transfer_properties *props)
{
   RAII_VAR(struct ast_format_cap *, cap, ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT), ao2_cleanup);
   char destination[AST_MAX_EXTENSION + AST_MAX_CONTEXT + 2];
   int cause;

   if (!cap) {
      return -1;
   }

   snprintf(destination, sizeof(destination), "%s@%s", props->exten, props->context);

   ast_format_cap_append(cap, ast_format_slin, 0);

   /* Get a channel that is the destination we wish to call */
   props->recall_target = ast_request("Local", cap, NULL, NULL, destination, &cause);
   if (!props->recall_target) {
      ast_log(LOG_ERROR, "Unable to request outbound channel for recall target\n");
      return -1;
   }

   if (attach_framehook(props, props->recall_target)) {
      ast_log(LOG_ERROR, "Unable to attach framehook to recall target\n");
      ast_hangup(props->recall_target);
      props->recall_target = NULL;
      return -1;
   }

   /*
    * Setup callid, variables, datastores, accountcode, peeraccount,
    * and COLP on the recalled transfer target.
    */
   ast_channel_lock_both(props->recall_target, props->transferer);

   ast_party_connected_line_copy(ast_channel_connected(props->recall_target),
      &props->original_transferer_colp);
   ast_party_id_reset(&ast_channel_connected(props->recall_target)->priv);

   common_recall_channel_setup(props->recall_target, props->transferer);
   ast_channel_unlock(props->recall_target);
   ast_channel_unlock(props->transferer);

   if (ast_call(props->recall_target, destination, 0)) {
      ast_log(LOG_ERROR, "Unable to place outbound call to recall target\n");
      ast_hangup(props->recall_target);
      props->recall_target = NULL;
      return -1;
   }

   ast_channel_ref(props->recall_target);
   if (ast_bridge_impart(props->transferee_bridge, props->recall_target, NULL, NULL,
      AST_BRIDGE_IMPART_CHAN_INDEPENDENT)) {
      ast_log(LOG_ERROR, "Unable to place recall target into bridge\n");
      ast_hangup(props->recall_target);
      ast_channel_unref(props->recall_target);
      return -1;
   }

   return 0;
}

static enum attended_transfer_state retransfer_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      return TRANSFER_FAIL;
   case STIMULUS_TIMEOUT:
      ast_softhangup(props->recall_target, AST_SOFTHANGUP_EXPLICIT);
   case STIMULUS_RECALL_TARGET_HANGUP:
      props->recall_target = ast_channel_unref(props->recall_target);
      if (props->atxferloopdelay) {
         return TRANSFER_WAIT_TO_RECALL;
      }
      return TRANSFER_RECALLING;
   case STIMULUS_RECALL_TARGET_ANSWER:
      return TRANSFER_RESUME;
   case STIMULUS_NONE:
   case STIMULUS_DTMF_ATXFER_ABORT:
   case STIMULUS_DTMF_ATXFER_COMPLETE:
   case STIMULUS_DTMF_ATXFER_THREEWAY:
   case STIMULUS_DTMF_ATXFER_SWAP:
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_TRANSFER_TARGET_ANSWER:
   case STIMULUS_TRANSFERER_HANGUP:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int wait_to_recall_enter(struct attended_transfer_properties *props)
{
   bridge_hold(props->transferee_bridge);
   return 0;
}

static enum attended_transfer_state wait_to_recall_exit(struct attended_transfer_properties *props,
      enum attended_transfer_stimulus stimulus)
{
   bridge_unhold(props->transferee_bridge);
   switch (stimulus) {
   case STIMULUS_TRANSFEREE_HANGUP:
      return TRANSFER_FAIL;
   case STIMULUS_TIMEOUT:
      return TRANSFER_RECALLING;
   case STIMULUS_NONE:
   case STIMULUS_DTMF_ATXFER_ABORT:
   case STIMULUS_DTMF_ATXFER_COMPLETE:
   case STIMULUS_DTMF_ATXFER_THREEWAY:
   case STIMULUS_DTMF_ATXFER_SWAP:
   case STIMULUS_TRANSFER_TARGET_HANGUP:
   case STIMULUS_TRANSFER_TARGET_ANSWER:
   case STIMULUS_TRANSFERER_HANGUP:
   case STIMULUS_RECALL_TARGET_HANGUP:
   case STIMULUS_RECALL_TARGET_ANSWER:
   default:
      ast_log(LOG_WARNING, "Unexpected stimulus '%s' received in attended transfer state '%s'\n",
            stimulus_strs[stimulus], state_properties[props->state].state_name);
      return props->state;
   }
}

static int fail_enter(struct attended_transfer_properties *props)
{
   if (props->transferee_bridge) {
      ast_bridge_destroy(props->transferee_bridge, 0);
      props->transferee_bridge = NULL;
   }
   return 0;
}

/*!
 * \brief DTMF hook when transferer presses abort sequence.
 *
 * Sends a stimulus to the attended transfer monitor thread that the abort sequence has been pressed
 */
static int atxfer_abort(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   struct attended_transfer_properties *props = hook_pvt;

   ast_debug(1, "Transferer on attended transfer %p pressed abort sequence\n", props);
   stimulate_attended_transfer(props, STIMULUS_DTMF_ATXFER_ABORT);
   return 0;
}

/*!
 * \brief DTMF hook when transferer presses complete sequence.
 *
 * Sends a stimulus to the attended transfer monitor thread that the complete sequence has been pressed
 */
static int atxfer_complete(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   struct attended_transfer_properties *props = hook_pvt;

   ast_debug(1, "Transferer on attended transfer %p pressed complete sequence\n", props);
   stimulate_attended_transfer(props, STIMULUS_DTMF_ATXFER_COMPLETE);
   return 0;
}

/*!
 * \brief DTMF hook when transferer presses threeway sequence.
 *
 * Sends a stimulus to the attended transfer monitor thread that the threeway sequence has been pressed
 */
static int atxfer_threeway(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   struct attended_transfer_properties *props = hook_pvt;

   ast_debug(1, "Transferer on attended transfer %p pressed threeway sequence\n", props);
   stimulate_attended_transfer(props, STIMULUS_DTMF_ATXFER_THREEWAY);
   return 0;
}

/*!
 * \brief DTMF hook when transferer presses swap sequence.
 *
 * Sends a stimulus to the attended transfer monitor thread that the swap sequence has been pressed
 */
static int atxfer_swap(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   struct attended_transfer_properties *props = hook_pvt;

   ast_debug(1, "Transferer on attended transfer %p pressed swap sequence\n", props);
   stimulate_attended_transfer(props, STIMULUS_DTMF_ATXFER_SWAP);
   return 0;
}

/*!
 * \brief Hangup hook for transferer channel.
 *
 * Sends a stimulus to the attended transfer monitor thread that the transferer has hung up.
 */
static int atxfer_transferer_hangup(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   struct attended_transfer_properties *props = hook_pvt;

   ast_debug(1, "Transferer on attended transfer %p hung up\n", props);
   stimulate_attended_transfer(props, STIMULUS_TRANSFERER_HANGUP);
   return 0;
}

/*!
 * \brief Frame hook for transfer target channel
 *
 * This is used to determine if the transfer target or recall target has answered
 * the outgoing call.
 *
 * When an answer is detected, a stimulus is sent to the attended transfer monitor
 * thread to indicate that the transfer target or recall target has answered.
 *
 * \param chan The channel the framehook is attached to.
 * \param frame The frame being read or written.
 * \param event What is being done with the frame.
 * \param data The attended transfer properties.
 */
static struct ast_frame *transfer_target_framehook_cb(struct ast_channel *chan,
      struct ast_frame *frame, enum ast_framehook_event event, void *data)
{
   struct attended_transfer_properties *props = data;

   if (event == AST_FRAMEHOOK_EVENT_READ &&
         frame && frame->frametype == AST_FRAME_CONTROL &&
         frame->subclass.integer == AST_CONTROL_ANSWER &&
         !ast_check_hangup(chan)) {

      ast_debug(1, "Detected an answer for recall attempt on attended transfer %p\n", props);
      if (props->superstate == SUPERSTATE_TRANSFER) {
         stimulate_attended_transfer(props, STIMULUS_TRANSFER_TARGET_ANSWER);
      } else {
         stimulate_attended_transfer(props, STIMULUS_RECALL_TARGET_ANSWER);
      }
      ast_framehook_detach(chan, props->target_framehook_id);
      props->target_framehook_id = -1;
   }

   return frame;
}

/*! \brief Callback function which informs upstream if we are consuming a frame of a specific type */
static int transfer_target_framehook_consume(void *data, enum ast_frame_type type)
{
   return (type == AST_FRAME_CONTROL ? 1 : 0);
}

static void transfer_target_framehook_destroy_cb(void *data)
{
   struct attended_transfer_properties *props = data;
   ao2_cleanup(props);
}

static int bridge_personality_atxfer_push(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel, struct ast_bridge_channel *swap)
{
   const char *abort_dtmf;
   const char *complete_dtmf;
   const char *threeway_dtmf;
   const char *swap_dtmf;
   struct bridge_basic_personality *personality = self->personality;

   if (!ast_channel_has_role(bridge_channel->chan, AST_TRANSFERER_ROLE_NAME)) {
      return 0;
   }

   abort_dtmf = ast_channel_get_role_option(bridge_channel->chan, AST_TRANSFERER_ROLE_NAME, "abort");
   complete_dtmf = ast_channel_get_role_option(bridge_channel->chan, AST_TRANSFERER_ROLE_NAME, "complete");
   threeway_dtmf = ast_channel_get_role_option(bridge_channel->chan, AST_TRANSFERER_ROLE_NAME, "threeway");
   swap_dtmf = ast_channel_get_role_option(bridge_channel->chan, AST_TRANSFERER_ROLE_NAME, "swap");

   if (!ast_strlen_zero(abort_dtmf) && ast_bridge_dtmf_hook(bridge_channel->features,
         abort_dtmf, atxfer_abort, personality->details[personality->current].pvt, NULL,
         AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE | AST_BRIDGE_HOOK_REMOVE_ON_PULL)) {
      return -1;
   }
   if (!ast_strlen_zero(complete_dtmf) && ast_bridge_dtmf_hook(bridge_channel->features,
         complete_dtmf, atxfer_complete, personality->details[personality->current].pvt, NULL,
         AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE | AST_BRIDGE_HOOK_REMOVE_ON_PULL)) {
      return -1;
   }
   if (!ast_strlen_zero(threeway_dtmf) && ast_bridge_dtmf_hook(bridge_channel->features,
         threeway_dtmf, atxfer_threeway, personality->details[personality->current].pvt, NULL,
         AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE | AST_BRIDGE_HOOK_REMOVE_ON_PULL)) {
      return -1;
   }
   if (!ast_strlen_zero(swap_dtmf) && ast_bridge_dtmf_hook(bridge_channel->features,
         swap_dtmf, atxfer_swap, personality->details[personality->current].pvt, NULL,
         AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE | AST_BRIDGE_HOOK_REMOVE_ON_PULL)) {
      return -1;
   }
   if (ast_bridge_hangup_hook(bridge_channel->features, atxfer_transferer_hangup,
         personality->details[personality->current].pvt, NULL,
         AST_BRIDGE_HOOK_REMOVE_ON_PERSONALITY_CHANGE | AST_BRIDGE_HOOK_REMOVE_ON_PULL)) {
      return -1;
   }

   return 0;
}

static void transfer_pull(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel, struct attended_transfer_properties *props)
{
   if (self->num_channels > 1 || bridge_channel->state == BRIDGE_CHANNEL_STATE_WAIT) {
      return;
   }

   if (self->num_channels == 1) {
      struct ast_bridge_channel *transferer_bridge_channel;
      int not_transferer;

      ast_channel_lock(props->transferer);
      transferer_bridge_channel = ast_channel_get_bridge_channel(props->transferer);
      ast_channel_unlock(props->transferer);

      if (!transferer_bridge_channel) {
         return;
      }

      not_transferer = AST_LIST_FIRST(&self->channels) != transferer_bridge_channel;
      ao2_ref(transferer_bridge_channel, -1);
      if (not_transferer) {
         return;
      }
   }

   /* Reaching this point means that either
    * 1) The bridge has no channels in it
    * 2) The bridge has one channel, and it's the transferer
    * In either case, it indicates that the non-transferer parties
    * are no longer in the bridge.
    */
   if (self == props->transferee_bridge) {
      stimulate_attended_transfer(props, STIMULUS_TRANSFEREE_HANGUP);
   } else {
      stimulate_attended_transfer(props, STIMULUS_TRANSFER_TARGET_HANGUP);
   }
}

static void recall_pull(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel, struct attended_transfer_properties *props)
{
   if (self == props->target_bridge) {
      /* Once we're in the recall superstate, we no longer care about this bridge */
      return;
   }

   if (bridge_channel->chan == props->recall_target) {
      stimulate_attended_transfer(props, STIMULUS_RECALL_TARGET_HANGUP);
      return;
   }

   if (self->num_channels == 0) {
      /* Empty bridge means all transferees are gone for sure */
      stimulate_attended_transfer(props, STIMULUS_TRANSFEREE_HANGUP);
      return;
   }

   if (self->num_channels == 1) {
      struct ast_bridge_channel *target_bridge_channel;

      if (!props->recall_target) {
         /* No recall target means that the pull happened on a transferee. If there's still
          * a channel left in the bridge, we don't need to send a stimulus
          */
         return;
      }

      ast_channel_lock(props->recall_target);
      target_bridge_channel = ast_channel_get_bridge_channel(props->recall_target);
      ast_channel_unlock(props->recall_target);

      if (target_bridge_channel) {
         if (AST_LIST_FIRST(&self->channels) == target_bridge_channel) {
            stimulate_attended_transfer(props, STIMULUS_TRANSFEREE_HANGUP);
         }
         ao2_ref(target_bridge_channel, -1);
      }
   }
}

static void bridge_personality_atxfer_pull(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel)
{
   struct bridge_basic_personality *personality = self->personality;
   struct attended_transfer_properties *props = personality->details[personality->current].pvt;

   switch (props->superstate) {
   case SUPERSTATE_TRANSFER:
      transfer_pull(self, bridge_channel, props);
      break;
   case SUPERSTATE_RECALL:
      recall_pull(self, bridge_channel, props);
      break;
   }
}

static enum attended_transfer_stimulus wait_for_stimulus(struct attended_transfer_properties *props)
{
   enum attended_transfer_stimulus stimulus;
   struct stimulus_list *list;
   SCOPED_MUTEX(lock, ao2_object_get_lockaddr(props));

   while (!(list = AST_LIST_REMOVE_HEAD(&props->stimulus_queue, next))) {
      if (!(state_properties[props->state].flags & TRANSFER_STATE_FLAG_TIMED)) {
         ast_cond_wait(&props->cond, lock);
      } else {
         struct timeval relative_timeout = { 0, };
         struct timeval absolute_timeout;
         struct timespec timeout_arg;

         if (state_properties[props->state].flags & TRANSFER_STATE_FLAG_TIMER_RESET) {
            props->start = ast_tvnow();
         }

         if (state_properties[props->state].flags & TRANSFER_STATE_FLAG_TIMER_LOOP_DELAY) {
            relative_timeout.tv_sec = props->atxferloopdelay;
         } else {
            /* Implied TRANSFER_STATE_FLAG_TIMER_ATXFER_NO_ANSWER */
            relative_timeout.tv_sec = props->atxfernoanswertimeout;
         }

         absolute_timeout = ast_tvadd(props->start, relative_timeout);
         timeout_arg.tv_sec = absolute_timeout.tv_sec;
         timeout_arg.tv_nsec = absolute_timeout.tv_usec * 1000;

         if (ast_cond_timedwait(&props->cond, lock, &timeout_arg) == ETIMEDOUT) {
            return STIMULUS_TIMEOUT;
         }
      }
   }
   stimulus = list->stimulus;
   ast_free(list);
   return stimulus;
}

/*!
 * \brief The main loop for the attended transfer monitor thread.
 *
 * This loop runs continuously until the attended transfer reaches
 * a terminal state. Stimuli for changes in the attended transfer
 * state are handled in this thread so that all factors in an
 * attended transfer can be handled in an orderly fashion.
 *
 * \param data The attended transfer properties
 */
static void *attended_transfer_monitor_thread(void *data)
{
   struct attended_transfer_properties *props = data;
   ast_callid callid;

   /*
    * Set thread callid to the transferer's callid because we
    * are doing all this on that channel's behalf.
    */
   ast_channel_lock(props->transferer);
   callid = ast_channel_callid(props->transferer);
   ast_channel_unlock(props->transferer);
   if (callid) {
      ast_callid_threadassoc_add(callid);
   }

   for (;;) {
      enum attended_transfer_stimulus stimulus;

      ast_debug(1, "About to enter state %s for attended transfer %p\n", state_properties[props->state].state_name, props);

      if (state_properties[props->state].enter &&
            state_properties[props->state].enter(props)) {
         ast_log(LOG_ERROR, "State %s enter function returned an error for attended transfer %p\n",
               state_properties[props->state].state_name, props);
         break;
      }

      if (state_properties[props->state].flags & TRANSFER_STATE_FLAG_TERMINAL) {
         ast_debug(1, "State %s is a terminal state. Ending attended transfer %p\n",
               state_properties[props->state].state_name, props);
         break;
      }

      stimulus = wait_for_stimulus(props);

      ast_debug(1, "Received stimulus %s on attended transfer %p\n", stimulus_strs[stimulus], props);

      ast_assert(state_properties[props->state].exit != NULL);

      props->state = state_properties[props->state].exit(props, stimulus);

      ast_debug(1, "Told to enter state %s exit on attended transfer %p\n", state_properties[props->state].state_name, props);
   }

   attended_transfer_properties_shutdown(props);

   if (callid) {
      ast_callid_threadassoc_remove();
   }

   return NULL;
}

static int attach_framehook(struct attended_transfer_properties *props, struct ast_channel *channel)
{
   struct ast_framehook_interface target_interface = {
      .version = AST_FRAMEHOOK_INTERFACE_VERSION,
      .event_cb = transfer_target_framehook_cb,
      .destroy_cb = transfer_target_framehook_destroy_cb,
      .consume_cb = transfer_target_framehook_consume,
      .disable_inheritance = 1,
   };

   ao2_ref(props, +1);
   target_interface.data = props;

   ast_channel_lock(channel);
   props->target_framehook_id = ast_framehook_attach(channel, &target_interface);
   ast_channel_unlock(channel);
   if (props->target_framehook_id == -1) {
      ao2_ref(props, -1);
      return -1;
   }
   return 0;
}

static int add_transferer_role(struct ast_channel *chan, struct ast_bridge_features_attended_transfer *attended_transfer)
{
   const char *atxfer_abort;
   const char *atxfer_threeway;
   const char *atxfer_complete;
   const char *atxfer_swap;
   struct ast_features_xfer_config *xfer_cfg;
   SCOPED_CHANNELLOCK(lock, chan);

   xfer_cfg = ast_get_chan_features_xfer_config(chan);
   if (!xfer_cfg) {
      return -1;
   }
   if (attended_transfer) {
      atxfer_abort = ast_strdupa(S_OR(attended_transfer->abort, xfer_cfg->atxferabort));
      atxfer_threeway = ast_strdupa(S_OR(attended_transfer->threeway, xfer_cfg->atxferthreeway));
      atxfer_complete = ast_strdupa(S_OR(attended_transfer->complete, xfer_cfg->atxfercomplete));
      atxfer_swap = ast_strdupa(S_OR(attended_transfer->swap, xfer_cfg->atxferswap));
   } else {
      atxfer_abort = ast_strdupa(xfer_cfg->atxferabort);
      atxfer_threeway = ast_strdupa(xfer_cfg->atxferthreeway);
      atxfer_complete = ast_strdupa(xfer_cfg->atxfercomplete);
      atxfer_swap = ast_strdupa(xfer_cfg->atxferswap);
   }
   ao2_ref(xfer_cfg, -1);

   return ast_channel_add_bridge_role(chan, AST_TRANSFERER_ROLE_NAME) ||
      ast_channel_set_bridge_role_option(chan, AST_TRANSFERER_ROLE_NAME, "abort", atxfer_abort) ||
      ast_channel_set_bridge_role_option(chan, AST_TRANSFERER_ROLE_NAME, "complete", atxfer_complete) ||
      ast_channel_set_bridge_role_option(chan, AST_TRANSFERER_ROLE_NAME, "threeway", atxfer_threeway) ||
      ast_channel_set_bridge_role_option(chan, AST_TRANSFERER_ROLE_NAME, "swap", atxfer_swap);
}

/*!
 * \brief Helper function that presents dialtone and grabs extension
 *
 * \retval 0 on success
 * \retval -1 on failure
 */
static int grab_transfer(struct ast_channel *chan, char *exten, size_t exten_len, const char *context)
{
   int res;
   int digit_timeout;
   int attempts = 0;
   int max_attempts;
   struct ast_features_xfer_config *xfer_cfg;
   char *retry_sound;
   char *invalid_sound;

   ast_channel_lock(chan);
   xfer_cfg = ast_get_chan_features_xfer_config(chan);
   if (!xfer_cfg) {
      ast_log(LOG_ERROR, "Channel %s: Unable to get transfer configuration\n",
         ast_channel_name(chan));
      ast_channel_unlock(chan);
      return -1;
   }
   digit_timeout = xfer_cfg->transferdigittimeout * 1000;
   max_attempts = xfer_cfg->transferdialattempts;
   retry_sound = ast_strdupa(xfer_cfg->transferretrysound);
   invalid_sound = ast_strdupa(xfer_cfg->transferinvalidsound);
   ao2_ref(xfer_cfg, -1);
   ast_channel_unlock(chan);

   /* Play the simple "transfer" prompt out and wait */
   res = ast_stream_and_wait(chan, "pbx-transfer", AST_DIGIT_ANY);
   ast_stopstream(chan);
   if (res < 0) {
      /* Hangup or error */
      return -1;
   }
   if (res) {
      /* Store the DTMF digit that interrupted playback of the file. */
      exten[0] = res;
   }

   /* Drop to dialtone so they can enter the extension they want to transfer to */
   do {
      ++attempts;

      ast_test_suite_event_notify("TRANSFER_BEGIN_DIAL",
            "Channel: %s\r\n"
            "Attempt: %d",
            ast_channel_name(chan), attempts);
      res = ast_app_dtget(chan, context, exten, exten_len, exten_len - 1, digit_timeout);
      ast_test_suite_event_notify("TRANSFER_DIALLED",
            "Channel: %s\r\n"
            "Attempt: %d\r\n"
            "Dialled: %s\r\n"
            "Result: %s",
            ast_channel_name(chan), attempts, exten, res > 0 ? "Success" : "Failure");
      if (res < 0) {
         /* Hangup or error */
         res = -1;
      } else if (!res) {
         /* 0 for invalid extension dialed. */
         if (ast_strlen_zero(exten)) {
            ast_verb(3, "Channel %s: Dialed no digits.\n", ast_channel_name(chan));
         } else {
            ast_verb(3, "Channel %s: Dialed '%s@%s' does not exist.\n",
               ast_channel_name(chan), exten, context);
         }
         if (attempts < max_attempts) {
            ast_stream_and_wait(chan, retry_sound, AST_DIGIT_NONE);
         } else {
            ast_stream_and_wait(chan, invalid_sound, AST_DIGIT_NONE);
         }
         memset(exten, 0, exten_len);
         res = 1;
      } else {
         /* Dialed extension is valid. */
         res = 0;
      }
   } while (res > 0 && attempts < max_attempts);

   ast_test_suite_event_notify("TRANSFER_DIAL_FINAL",
         "Channel: %s\r\n"
         "Result: %s",
         ast_channel_name(chan), res == 0 ? "Success" : "Failure");

   return res ? -1 : 0;
}

static void copy_caller_data(struct ast_channel *dest, struct ast_channel *caller)
{
   ast_channel_lock_both(caller, dest);
   ast_connected_line_copy_from_caller(ast_channel_connected(dest), ast_channel_caller(caller));
   ast_channel_inherit_variables(caller, dest);
   ast_channel_datastore_inherit(caller, dest);
   ast_channel_unlock(dest);
   ast_channel_unlock(caller);
}

/*! \brief Helper function that creates an outgoing channel and returns it immediately */
static struct ast_channel *dial_transfer(struct ast_channel *caller, const char *destination)
{
   struct ast_channel *chan;
   int cause;

   /* Now we request a local channel to prepare to call the destination */
   chan = ast_request("Local", ast_channel_nativeformats(caller), NULL, caller, destination,
      &cause);
   if (!chan) {
      return NULL;
   }

   ast_channel_lock_both(chan, caller);

   ast_channel_req_accountcodes(chan, caller, AST_CHANNEL_REQUESTOR_BRIDGE_PEER);

   /* Who is transferring the call. */
   pbx_builtin_setvar_helper(chan, "TRANSFERERNAME", ast_channel_name(caller));

   ast_bridge_set_transfer_variables(chan, ast_channel_name(caller), 1);

   ast_channel_unlock(chan);
   ast_channel_unlock(caller);

   /* Before we actually dial out let's inherit appropriate information. */
   copy_caller_data(chan, caller);

   return chan;
}

/*!
 * \brief Internal built in feature for attended transfers
 *
 * This hook will set up a thread for monitoring the progress of
 * an attended transfer. For more information about attended transfer
 * progress, see documentation on the transfer state machine.
 *
 * \param bridge_channel The channel that pressed the attended transfer DTMF sequence
 * \param hook_pvt Structure with further information about the attended transfer
 */
static int feature_attended_transfer(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   struct ast_bridge_features_attended_transfer *attended_transfer = hook_pvt;
   struct attended_transfer_properties *props;
   struct ast_bridge *bridge;
   char destination[AST_MAX_EXTENSION + AST_MAX_CONTEXT + 1];
   char exten[AST_MAX_EXTENSION] = "";
   pthread_t thread;

   /* Inhibit the bridge before we do anything else. */
   bridge = ast_bridge_channel_merge_inhibit(bridge_channel, +1);

   ast_verb(3, "Channel %s: Started DTMF attended transfer.\n",
      ast_channel_name(bridge_channel->chan));

   if (strcmp(bridge->v_table->name, "basic")) {
      ast_log(LOG_ERROR, "Channel %s: Attended transfer attempted on unsupported bridge type '%s'.\n",
         ast_channel_name(bridge_channel->chan), bridge->v_table->name);
      ast_bridge_merge_inhibit(bridge, -1);
      ao2_ref(bridge, -1);
      return 0;
   }

   /* Was the bridge inhibited before we inhibited it? */
   if (1 < bridge->inhibit_merge) {
      /*
       * The peer likely initiated attended transfer at the same time
       * and we lost the race.
       */
      ast_verb(3, "Channel %s: Bridge '%s' does not permit merging at this time.\n",
         ast_channel_name(bridge_channel->chan), bridge->uniqueid);
      ast_bridge_merge_inhibit(bridge, -1);
      ao2_ref(bridge, -1);
      return 0;
   }

   props = attended_transfer_properties_alloc(bridge_channel->chan,
      attended_transfer ? attended_transfer->context : NULL);
   if (!props) {
      ast_log(LOG_ERROR, "Channel %s: Unable to allocate control structure for performing attended transfer.\n",
         ast_channel_name(bridge_channel->chan));
      ast_bridge_merge_inhibit(bridge, -1);
      ao2_ref(bridge, -1);
      return 0;
   }

   props->transferee_bridge = bridge;

   if (add_transferer_role(props->transferer, attended_transfer)) {
      ast_log(LOG_ERROR, "Channel %s: Unable to set transferrer bridge role.\n",
         ast_channel_name(bridge_channel->chan));
      attended_transfer_properties_shutdown(props);
      return 0;
   }

   ast_bridge_channel_write_hold(bridge_channel, NULL);

   /* Grab the extension to transfer to */
   if (grab_transfer(bridge_channel->chan, exten, sizeof(exten), props->context)) {
      /*
       * XXX The warning here really should be removed.  While the
       * message is accurate, this is a normal exit for when the user
       * fails to specify a valid transfer target.  e.g., The user
       * hungup, didn't dial any digits, or dialed an invalid
       * extension.
       */
      ast_log(LOG_WARNING, "Channel %s: Unable to acquire target extension for attended transfer.\n",
         ast_channel_name(bridge_channel->chan));
      ast_bridge_channel_write_unhold(bridge_channel);
      attended_transfer_properties_shutdown(props);
      return 0;
   }

   ast_string_field_set(props, exten, exten);

   /* Fill the variable with the extension and context we want to call */
   snprintf(destination, sizeof(destination), "%s@%s", props->exten, props->context);

   ast_debug(1, "Channel %s: Attended transfer target '%s'\n",
      ast_channel_name(bridge_channel->chan), destination);

   /* Get a channel that is the destination we wish to call */
   props->transfer_target = dial_transfer(bridge_channel->chan, destination);
   if (!props->transfer_target) {
      ast_log(LOG_ERROR, "Channel %s: Unable to request outbound channel for attended transfer target.\n",
         ast_channel_name(bridge_channel->chan));
      stream_failsound(props->transferer);
      ast_bridge_channel_write_unhold(bridge_channel);
      attended_transfer_properties_shutdown(props);
      return 0;
   }


   /* Create a bridge to use to talk to the person we are calling */
   props->target_bridge = ast_bridge_basic_new();
   if (!props->target_bridge) {
      ast_log(LOG_ERROR, "Channel %s: Unable to create bridge for attended transfer target.\n",
         ast_channel_name(bridge_channel->chan));
      stream_failsound(props->transferer);
      ast_bridge_channel_write_unhold(bridge_channel);
      ast_hangup(props->transfer_target);
      props->transfer_target = NULL;
      attended_transfer_properties_shutdown(props);
      return 0;
   }
   ast_bridge_merge_inhibit(props->target_bridge, +1);

   if (attach_framehook(props, props->transfer_target)) {
      ast_log(LOG_ERROR, "Channel %s: Unable to attach framehook to transfer target.\n",
         ast_channel_name(bridge_channel->chan));
      stream_failsound(props->transferer);
      ast_bridge_channel_write_unhold(bridge_channel);
      ast_hangup(props->transfer_target);
      props->transfer_target = NULL;
      attended_transfer_properties_shutdown(props);
      return 0;
   }

   bridge_basic_change_personality(props->target_bridge,
         BRIDGE_BASIC_PERSONALITY_ATXFER, props);
   bridge_basic_change_personality(bridge,
         BRIDGE_BASIC_PERSONALITY_ATXFER, props);

   if (ast_call(props->transfer_target, destination, 0)) {
      ast_log(LOG_ERROR, "Channel %s: Unable to place outbound call to transfer target.\n",
         ast_channel_name(bridge_channel->chan));
      stream_failsound(props->transferer);
      ast_bridge_channel_write_unhold(bridge_channel);
      ast_hangup(props->transfer_target);
      props->transfer_target = NULL;
      attended_transfer_properties_shutdown(props);
      return 0;
   }

   /* We increase the refcount of the transfer target because ast_bridge_impart() will
    * steal the reference we already have. We need to keep a reference, so the only
    * choice is to give it a bump
    */
   ast_channel_ref(props->transfer_target);
   if (ast_bridge_impart(props->target_bridge, props->transfer_target, NULL, NULL,
      AST_BRIDGE_IMPART_CHAN_INDEPENDENT)) {
      ast_log(LOG_ERROR, "Channel %s: Unable to place transfer target into bridge.\n",
         ast_channel_name(bridge_channel->chan));
      stream_failsound(props->transferer);
      ast_bridge_channel_write_unhold(bridge_channel);
      ast_hangup(props->transfer_target);
      props->transfer_target = NULL;
      attended_transfer_properties_shutdown(props);
      return 0;
   }

   if (ast_pthread_create_detached(&thread, NULL, attended_transfer_monitor_thread, props)) {
      ast_log(LOG_ERROR, "Channel %s: Unable to create monitoring thread for attended transfer.\n",
         ast_channel_name(bridge_channel->chan));
      stream_failsound(props->transferer);
      ast_bridge_channel_write_unhold(bridge_channel);
      attended_transfer_properties_shutdown(props);
      return 0;
   }

   /* Once the monitoring thread has been created, it is responsible for destroying all
    * of the necessary components.
    */
   return 0;
}

static void blind_transfer_cb(struct ast_channel *new_channel, struct transfer_channel_data *user_data_wrapper,
      enum ast_transfer_type transfer_type)
{
   struct ast_channel *transferer_channel = user_data_wrapper->data;

   if (transfer_type == AST_BRIDGE_TRANSFER_MULTI_PARTY) {
      copy_caller_data(new_channel, transferer_channel);
   }
}

/*! \brief Internal built in feature for blind transfers */
static int feature_blind_transfer(struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
   char xfer_exten[AST_MAX_EXTENSION] = "";
   struct ast_bridge_features_blind_transfer *blind_transfer = hook_pvt;
   const char *xfer_context;
   char *goto_on_blindxfr;

   ast_verb(3, "Channel %s: Started DTMF blind transfer.\n",
      ast_channel_name(bridge_channel->chan));

   ast_bridge_channel_write_hold(bridge_channel, NULL);

   ast_channel_lock(bridge_channel->chan);
   xfer_context = ast_strdupa(get_transfer_context(bridge_channel->chan,
      blind_transfer ? blind_transfer->context : NULL));
   goto_on_blindxfr = ast_strdupa(S_OR(pbx_builtin_getvar_helper(bridge_channel->chan,
      "GOTO_ON_BLINDXFR"), ""));
   ast_channel_unlock(bridge_channel->chan);

   /* Grab the extension to transfer to */
   if (grab_transfer(bridge_channel->chan, xfer_exten, sizeof(xfer_exten), xfer_context)) {
      ast_bridge_channel_write_unhold(bridge_channel);
      return 0;
   }

   ast_debug(1, "Channel %s: Blind transfer target '%s@%s'\n",
      ast_channel_name(bridge_channel->chan), xfer_exten, xfer_context);

   if (!ast_strlen_zero(goto_on_blindxfr)) {
      const char *chan_context;
      const char *chan_exten;
      int chan_priority;

      ast_debug(1, "Channel %s: After transfer, transferrer goes to %s\n",
         ast_channel_name(bridge_channel->chan), goto_on_blindxfr);

      ast_channel_lock(bridge_channel->chan);
      chan_context = ast_strdupa(ast_channel_context(bridge_channel->chan));
      chan_exten = ast_strdupa(ast_channel_exten(bridge_channel->chan));
      chan_priority = ast_channel_priority(bridge_channel->chan);
      ast_channel_unlock(bridge_channel->chan);
      ast_bridge_set_after_go_on(bridge_channel->chan,
         chan_context, chan_exten, chan_priority, goto_on_blindxfr);
   }

   if (ast_bridge_transfer_blind(0, bridge_channel->chan, xfer_exten, xfer_context,
      blind_transfer_cb, bridge_channel->chan) != AST_BRIDGE_TRANSFER_SUCCESS
      && !ast_strlen_zero(goto_on_blindxfr)) {
      ast_bridge_discard_after_goto(bridge_channel->chan);
   }

   return 0;
}

struct ast_bridge_methods ast_bridge_basic_v_table;
struct ast_bridge_methods personality_normal_v_table;
struct ast_bridge_methods personality_atxfer_v_table;

static void bridge_basic_change_personality(struct ast_bridge *bridge,
      enum bridge_basic_personality_type type, void *user_data)
{
   struct bridge_basic_personality *personality = bridge->personality;
   SCOPED_LOCK(lock, bridge, ast_bridge_lock, ast_bridge_unlock);

   remove_hooks_on_personality_change(bridge);

   ao2_cleanup(personality->details[personality->current].pvt);
   personality->details[personality->current].pvt = NULL;
   ast_clear_flag(&bridge->feature_flags, AST_FLAGS_ALL);

   personality->current = type;
   if (user_data) {
      ao2_ref(user_data, +1);
   }
   personality->details[personality->current].pvt = user_data;
   ast_set_flag(&bridge->feature_flags, personality->details[personality->current].bridge_flags);
   if (personality->details[personality->current].on_personality_change) {
      personality->details[personality->current].on_personality_change(bridge);
   }
}

static void personality_destructor(void *obj)
{
   struct bridge_basic_personality *personality = obj;
   int i;

   for (i = 0; i < BRIDGE_BASIC_PERSONALITY_END; ++i) {
      ao2_cleanup(personality->details[i].pvt);
   }
}

static void on_personality_change_normal(struct ast_bridge *bridge)
{
   struct ast_bridge_channel *iter;

   AST_LIST_TRAVERSE(&bridge->channels, iter, entry) {
      if (add_normal_hooks(bridge, iter)) {
         ast_log(LOG_WARNING, "Unable to set up bridge hooks for channel %s. Features may not work properly\n",
               ast_channel_name(iter->chan));
      }
   }
}

static void init_details(struct personality_details *details,
      enum bridge_basic_personality_type type)
{
   switch (type) {
   case BRIDGE_BASIC_PERSONALITY_NORMAL:
      details->v_table = &personality_normal_v_table;
      details->bridge_flags = NORMAL_FLAGS;
      details->on_personality_change = on_personality_change_normal;
      break;
   case BRIDGE_BASIC_PERSONALITY_ATXFER:
      details->v_table = &personality_atxfer_v_table;
      details->bridge_flags = TRANSFER_FLAGS;
      break;
   default:
      ast_log(LOG_WARNING, "Asked to initialize unexpected basic bridge personality type.\n");
      break;
   }
}

static struct ast_bridge *bridge_basic_personality_alloc(struct ast_bridge *bridge)
{
   struct bridge_basic_personality *personality;
   int i;

   if (!bridge) {
      return NULL;
   }

   personality = ao2_alloc(sizeof(*personality), personality_destructor);
   if (!personality) {
      ao2_ref(bridge, -1);
      return NULL;
   }
   for (i = 0; i < BRIDGE_BASIC_PERSONALITY_END; ++i) {
      init_details(&personality->details[i], i);
   }
   personality->current = BRIDGE_BASIC_PERSONALITY_NORMAL;
   bridge->personality = personality;

   return bridge;
}

struct ast_bridge *ast_bridge_basic_new(void)
{
   struct ast_bridge *bridge;

   bridge = bridge_alloc(sizeof(struct ast_bridge), &ast_bridge_basic_v_table);
   bridge = bridge_base_init(bridge,
      AST_BRIDGE_CAPABILITY_NATIVE | AST_BRIDGE_CAPABILITY_1TO1MIX
         | AST_BRIDGE_CAPABILITY_MULTIMIX, NORMAL_FLAGS, NULL, NULL, NULL);
   bridge = bridge_basic_personality_alloc(bridge);
   bridge = bridge_register(bridge);
   return bridge;
}

void ast_bridge_basic_set_flags(struct ast_bridge *bridge, unsigned int flags)
{
   SCOPED_LOCK(lock, bridge, ast_bridge_lock, ast_bridge_unlock);
   struct bridge_basic_personality *personality = bridge->personality;

   personality->details[personality->current].bridge_flags |= flags;
   ast_set_flag(&bridge->feature_flags, flags);
}

void ast_bridging_init_basic(void)
{
   /* Setup bridge basic subclass v_table. */
   ast_bridge_basic_v_table = ast_bridge_base_v_table;
   ast_bridge_basic_v_table.name = "basic";
   ast_bridge_basic_v_table.push = bridge_basic_push;
   ast_bridge_basic_v_table.pull = bridge_basic_pull;
   ast_bridge_basic_v_table.destroy = bridge_basic_destroy;

   /*
    * Personality vtables don't have the same rules as
    * normal bridge vtables.  These vtable functions are
    * used as alterations to the ast_bridge_basic_v_table
    * method functionality and are checked for NULL before
    * calling.
    */
   personality_normal_v_table.name = "normal";
   personality_normal_v_table.push = bridge_personality_normal_push;

   personality_atxfer_v_table.name = "attended transfer";
   personality_atxfer_v_table.push = bridge_personality_atxfer_push;
   personality_atxfer_v_table.pull = bridge_personality_atxfer_pull;

   ast_bridge_features_register(AST_BRIDGE_BUILTIN_ATTENDEDTRANSFER, feature_attended_transfer, NULL);
   ast_bridge_features_register(AST_BRIDGE_BUILTIN_BLINDTRANSFER, feature_blind_transfer, NULL);
}