[asterisk/asterisk.git] / main / bridge.c

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2007 - 2009, Digium, Inc.
 *
 * Joshua Colp <jcolp@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Bridging API
 *
 * \author Joshua Colp <jcolp@digium.com>
 */

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

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision$")

#include "asterisk/logger.h"
#include "asterisk/channel.h"
#include "asterisk/options.h"
#include "asterisk/utils.h"
#include "asterisk/lock.h"
#include "asterisk/linkedlists.h"
#include "asterisk/bridge.h"
#include "asterisk/bridge_internal.h"
#include "asterisk/bridge_channel_internal.h"
#include "asterisk/bridge_features.h"
#include "asterisk/bridge_basic.h"
#include "asterisk/bridge_technology.h"
#include "asterisk/bridge_channel.h"
#include "asterisk/bridge_after.h"
#include "asterisk/stasis_bridges.h"
#include "asterisk/stasis_channels.h"
#include "asterisk/stasis_cache_pattern.h"
#include "asterisk/app.h"
#include "asterisk/file.h"
#include "asterisk/module.h"
#include "asterisk/astobj2.h"
#include "asterisk/pbx.h"
#include "asterisk/test.h"
#include "asterisk/_private.h"
#include "asterisk/heap.h"
#include "asterisk/say.h"
#include "asterisk/timing.h"
#include "asterisk/stringfields.h"
#include "asterisk/musiconhold.h"
#include "asterisk/features.h"
#include "asterisk/cli.h"
#include "asterisk/parking.h"
#include "asterisk/core_local.h"
#include "asterisk/core_unreal.h"
#include "asterisk/causes.h"

/*! All bridges container. */
static struct ao2_container *bridges;

static AST_RWLIST_HEAD_STATIC(bridge_technologies, ast_bridge_technology);

static unsigned int optimization_id;

/* Initial starting point for the bridge array of channels */
#define BRIDGE_ARRAY_START 128

/* Grow rate of bridge array of channels */
#define BRIDGE_ARRAY_GROW 32

static void cleanup_video_mode(struct ast_bridge *bridge);
static int bridge_make_compatible(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel);

/*! Default DTMF keys for built in features */
static char builtin_features_dtmf[AST_BRIDGE_BUILTIN_END][MAXIMUM_DTMF_FEATURE_STRING];

/*! Function handlers for the built in features */
static ast_bridge_hook_callback builtin_features_handlers[AST_BRIDGE_BUILTIN_END];

/*! Function handlers for built in interval features */
static ast_bridge_builtin_set_limits_fn builtin_interval_handlers[AST_BRIDGE_BUILTIN_INTERVAL_END];

/*! Bridge manager service request */
struct bridge_manager_request {
        /*! List of bridge service requests. */
        AST_LIST_ENTRY(bridge_manager_request) node;
        /*! Refed bridge requesting service. */
        struct ast_bridge *bridge;
};

struct bridge_manager_controller {
        /*! Condition, used to wake up the bridge manager thread. */
        ast_cond_t cond;
        /*! Queue of bridge service requests. */
        AST_LIST_HEAD_NOLOCK(, bridge_manager_request) service_requests;
        /*! Manager thread */
        pthread_t thread;
        /*! TRUE if the manager needs to stop. */
        unsigned int stop:1;
};

/*! Bridge manager controller. */
static struct bridge_manager_controller *bridge_manager;

/*!
 * \internal
 * \brief Request service for a bridge from the bridge manager.
 * \since 12.0.0
 *
 * \param bridge Requesting service.
 *
 * \return Nothing
 */
static void bridge_manager_service_req(struct ast_bridge *bridge)
{
        struct bridge_manager_request *request;

        ao2_lock(bridge_manager);
        if (bridge_manager->stop) {
                ao2_unlock(bridge_manager);
                return;
        }

        /* Create the service request. */
        request = ast_calloc(1, sizeof(*request));
        if (!request) {
                /* Well. This isn't good. */
                ao2_unlock(bridge_manager);
                return;
        }
        ao2_ref(bridge, +1);
        request->bridge = bridge;

        /* Put request into the queue and wake the bridge manager. */
        AST_LIST_INSERT_TAIL(&bridge_manager->service_requests, request, node);
        ast_cond_signal(&bridge_manager->cond);
        ao2_unlock(bridge_manager);
}

int __ast_bridge_technology_register(struct ast_bridge_technology *technology, struct ast_module *module)
{
        struct ast_bridge_technology *current;

        /* Perform a sanity check to make sure the bridge technology conforms to our needed requirements */
        if (ast_strlen_zero(technology->name)
                || !technology->capabilities
                || !technology->write) {
                ast_log(LOG_WARNING, "Bridge technology %s failed registration sanity check.\n",
                        technology->name);
                return -1;
        }

        AST_RWLIST_WRLOCK(&bridge_technologies);

        /* Look for duplicate bridge technology already using this name, or already registered */
        AST_RWLIST_TRAVERSE(&bridge_technologies, current, entry) {
                if ((!strcasecmp(current->name, technology->name)) || (current == technology)) {
                        ast_log(LOG_WARNING, "A bridge technology of %s already claims to exist in our world.\n",
                                technology->name);
                        AST_RWLIST_UNLOCK(&bridge_technologies);
                        return -1;
                }
        }

        /* Copy module pointer so reference counting can keep the module from unloading */
        technology->mod = module;

        /* Insert our new bridge technology into the list and print out a pretty message */
        AST_RWLIST_INSERT_TAIL(&bridge_technologies, technology, entry);

        AST_RWLIST_UNLOCK(&bridge_technologies);

        ast_verb(2, "Registered bridge technology %s\n", technology->name);

        return 0;
}

int ast_bridge_technology_unregister(struct ast_bridge_technology *technology)
{
        struct ast_bridge_technology *current;

        AST_RWLIST_WRLOCK(&bridge_technologies);

        /* Ensure the bridge technology is registered before removing it */
        AST_RWLIST_TRAVERSE_SAFE_BEGIN(&bridge_technologies, current, entry) {
                if (current == technology) {
                        AST_RWLIST_REMOVE_CURRENT(entry);
                        ast_verb(2, "Unregistered bridge technology %s\n", technology->name);
                        break;
                }
        }
        AST_RWLIST_TRAVERSE_SAFE_END;

        AST_RWLIST_UNLOCK(&bridge_technologies);

        return current ? 0 : -1;
}

/*!
 * \internal
 * \brief Put an action onto the specified bridge. Don't dup the action frame.
 * \since 12.0.0
 *
 * \param bridge What to queue the action on.
 * \param action What to do.
 *
 * \return Nothing
 */
static void bridge_queue_action_nodup(struct ast_bridge *bridge, struct ast_frame *action)
{
        ast_debug(1, "Bridge %s: queueing action type:%d sub:%d\n",
                bridge->uniqueid, action->frametype, action->subclass.integer);

        ast_bridge_lock(bridge);
        AST_LIST_INSERT_TAIL(&bridge->action_queue, action, frame_list);
        ast_bridge_unlock(bridge);
        bridge_manager_service_req(bridge);
}

int ast_bridge_queue_action(struct ast_bridge *bridge, struct ast_frame *action)
{
        struct ast_frame *dup;

        dup = ast_frdup(action);
        if (!dup) {
                return -1;
        }
        bridge_queue_action_nodup(bridge, dup);
        return 0;
}

void bridge_dissolve(struct ast_bridge *bridge, int cause)
{
        struct ast_bridge_channel *bridge_channel;
        struct ast_frame action = {
                .frametype = AST_FRAME_BRIDGE_ACTION,
                .subclass.integer = BRIDGE_CHANNEL_ACTION_DEFERRED_DISSOLVING,
        };

        if (bridge->dissolved) {
                return;
        }
        bridge->dissolved = 1;

        if (cause <= 0) {
                cause = AST_CAUSE_NORMAL_CLEARING;
        }
        bridge->cause = cause;

        ast_debug(1, "Bridge %s: dissolving bridge with cause %d(%s)\n",
                bridge->uniqueid, cause, ast_cause2str(cause));

        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                ast_bridge_channel_leave_bridge(bridge_channel,
                        BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, cause);
        }

        /* Must defer dissolving bridge because it is already locked. */
        ast_bridge_queue_action(bridge, &action);
}

/*!
 * \internal
 * \brief Check if a bridge should dissolve because of a stolen channel and do it.
 * \since 12.0.0
 *
 * \param bridge Bridge to check.
 * \param bridge_channel Stolen channel causing the check.  It is not in the bridge to check and may be in another bridge.
 *
 * \note On entry, bridge and bridge_channel->bridge are already locked.
 *
 * \return Nothing
 */
static void bridge_dissolve_check_stolen(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
{
        if (bridge->dissolved) {
                return;
        }

        if (bridge_channel->features->usable
                && ast_test_flag(&bridge_channel->features->feature_flags,
                        AST_BRIDGE_CHANNEL_FLAG_DISSOLVE_HANGUP)) {
                /* The stolen channel controlled the bridge it was stolen from. */
                bridge_dissolve(bridge, 0);
                return;
        }
        if (bridge->num_channels < 2
                && ast_test_flag(&bridge->feature_flags, AST_BRIDGE_FLAG_DISSOLVE_HANGUP)) {
                /*
                 * The stolen channel has not left enough channels to keep the
                 * bridge alive.  Assume the stolen channel hung up.
                 */
                bridge_dissolve(bridge, 0);
                return;
        }
}

/*!
 * \internal
 * \brief Update connected line information after a bridge has been reconfigured.
 *
 * \param bridge The bridge itself.
 *
 * \return Nothing
 */
static void bridge_reconfigured_connected_line_update(struct ast_bridge *bridge)
{
        struct ast_party_connected_line connected;
        struct ast_bridge_channel *bridge_channel = AST_LIST_FIRST(&bridge->channels), *peer;
        unsigned char data[1024];
        size_t datalen;

        if (!bridge_channel ||
                !(bridge->technology->capabilities & (AST_BRIDGE_CAPABILITY_1TO1MIX | AST_BRIDGE_CAPABILITY_NATIVE)) ||
                !(peer = ast_bridge_channel_peer(bridge_channel)) ||
                ast_test_flag(ast_channel_flags(bridge_channel->chan), AST_FLAG_ZOMBIE) ||
                ast_test_flag(ast_channel_flags(peer->chan), AST_FLAG_ZOMBIE) ||
                ast_check_hangup_locked(bridge_channel->chan) ||
                ast_check_hangup_locked(peer->chan)) {
                return;
        }

        ast_party_connected_line_init(&connected);

        ast_channel_lock(bridge_channel->chan);
        ast_connected_line_copy_from_caller(&connected, ast_channel_caller(bridge_channel->chan));
        ast_channel_unlock(bridge_channel->chan);

        if ((datalen = ast_connected_line_build_data(data, sizeof(data), &connected, NULL)) != (size_t) -1) {
                ast_bridge_channel_queue_control_data(peer, AST_CONTROL_CONNECTED_LINE, data, datalen);
        }

        ast_channel_lock(peer->chan);
        ast_connected_line_copy_from_caller(&connected, ast_channel_caller(peer->chan));
        ast_channel_unlock(peer->chan);

        if ((datalen = ast_connected_line_build_data(data, sizeof(data), &connected, NULL)) != (size_t) -1) {
                ast_bridge_channel_queue_control_data(bridge_channel, AST_CONTROL_CONNECTED_LINE, data, datalen);
        }

        ast_party_connected_line_free(&connected);
}

/*!
 * \internal
 * \brief Complete joining a channel to the bridge.
 * \since 12.0.0
 *
 * \param bridge What to operate upon.
 * \param bridge_channel What is joining the bridge technology.
 *
 * \note On entry, bridge is already locked.
 *
 * \return Nothing
 */
static void bridge_channel_complete_join(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
{
        /* Make the channel compatible with the bridge */
        bridge_make_compatible(bridge, bridge_channel);

        /* Tell the bridge technology we are joining so they set us up */
        ast_debug(1, "Bridge %s: %p(%s) is joining %s technology\n",
                bridge->uniqueid, bridge_channel, ast_channel_name(bridge_channel->chan),
                bridge->technology->name);
        if (bridge->technology->join
                && bridge->technology->join(bridge, bridge_channel)) {
                ast_debug(1, "Bridge %s: %p(%s) failed to join %s technology\n",
                        bridge->uniqueid, bridge_channel, ast_channel_name(bridge_channel->chan),
                        bridge->technology->name);
                bridge_channel->just_joined = 1;
                return;
        }

        bridge_channel->just_joined = 0;
}

/*!
 * \internal
 * \brief Complete joining new channels to the bridge.
 * \since 12.0.0
 *
 * \param bridge Check for new channels on this bridge.
 *
 * \note On entry, bridge is already locked.
 *
 * \return Nothing
 */
static void bridge_complete_join(struct ast_bridge *bridge)
{
        struct ast_bridge_channel *bridge_channel;

        if (bridge->dissolved) {
                /*
                 * No sense in completing the join on channels for a dissolved
                 * bridge.  They are just going to be removed soon anyway.
                 * However, we do have reason to abort here because the bridge
                 * technology may not be able to handle the number of channels
                 * still in the bridge.
                 */
                return;
        }

        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                if (!bridge_channel->just_joined) {
                        continue;
                }
                bridge_channel_complete_join(bridge, bridge_channel);
        }
}

/*! \brief Helper function used to find the "best" bridge technology given specified capabilities */
static struct ast_bridge_technology *find_best_technology(uint32_t capabilities, struct ast_bridge *bridge)
{
        struct ast_bridge_technology *current;
        struct ast_bridge_technology *best = NULL;

        AST_RWLIST_RDLOCK(&bridge_technologies);
        AST_RWLIST_TRAVERSE(&bridge_technologies, current, entry) {
                if (current->suspended) {
                        ast_debug(1, "Bridge technology %s is suspended. Skipping.\n",
                                current->name);
                        continue;
                }
                if (!(current->capabilities & capabilities)) {
                        ast_debug(1, "Bridge technology %s does not have any capabilities we want.\n",
                                current->name);
                        continue;
                }
                if (best && current->preference <= best->preference) {
                        ast_debug(1, "Bridge technology %s has less preference than %s (%d <= %d). Skipping.\n",
                                current->name, best->name, current->preference, best->preference);
                        continue;
                }
                if (current->compatible && !current->compatible(bridge)) {
                        ast_debug(1, "Bridge technology %s is not compatible with properties of existing bridge.\n",
                                current->name);
                        continue;
                }
                best = current;
        }

        if (best) {
                /* Increment it's module reference count if present so it does not get unloaded while in use */
                ast_module_ref(best->mod);
                ast_debug(1, "Chose bridge technology %s\n", best->name);
        }

        AST_RWLIST_UNLOCK(&bridge_technologies);

        return best;
}

struct tech_deferred_destroy {
        struct ast_bridge_technology *tech;
        void *tech_pvt;
};

/*!
 * \internal
 * \brief Deferred destruction of bridge tech private structure.
 * \since 12.0.0
 *
 * \param bridge What to execute the action on.
 * \param action Deferred bridge tech destruction.
 *
 * \note On entry, bridge must not be locked.
 *
 * \return Nothing
 */
static void bridge_tech_deferred_destroy(struct ast_bridge *bridge, struct ast_frame *action)
{
        struct tech_deferred_destroy *deferred = action->data.ptr;
        struct ast_bridge dummy_bridge = {
                .technology = deferred->tech,
                .tech_pvt = deferred->tech_pvt,
                };

        ast_copy_string(dummy_bridge.uniqueid, bridge->uniqueid, sizeof(dummy_bridge.uniqueid));
        ast_debug(1, "Bridge %s: calling %s technology destructor (deferred, dummy)\n",
                dummy_bridge.uniqueid, dummy_bridge.technology->name);
        dummy_bridge.technology->destroy(&dummy_bridge);
        ast_module_unref(dummy_bridge.technology->mod);
}

/*!
 * \internal
 * \brief Handle bridge action frame.
 * \since 12.0.0
 *
 * \param bridge What to execute the action on.
 * \param action What to do.
 *
 * \note On entry, bridge is already locked.
 * \note Can be called by the bridge destructor.
 *
 * \return Nothing
 */
static void bridge_action_bridge(struct ast_bridge *bridge, struct ast_frame *action)
{
#if 0   /* In case we need to know when the destructor is calling us. */
        int in_destructor = !ao2_ref(bridge, 0);
#endif

        switch (action->subclass.integer) {
        case BRIDGE_CHANNEL_ACTION_DEFERRED_TECH_DESTROY:
                ast_bridge_unlock(bridge);
                bridge_tech_deferred_destroy(bridge, action);
                ast_bridge_lock(bridge);
                break;
        case BRIDGE_CHANNEL_ACTION_DEFERRED_DISSOLVING:
                ast_bridge_unlock(bridge);
                bridge->v_table->dissolving(bridge);
                ast_bridge_lock(bridge);
                break;
        default:
                /* Unexpected deferred action type.  Should never happen. */
                ast_assert(0);
                break;
        }
}

/*!
 * \internal
 * \brief Do any pending bridge actions.
 * \since 12.0.0
 *
 * \param bridge What to do actions on.
 *
 * \note On entry, bridge is already locked.
 * \note Can be called by the bridge destructor.
 *
 * \return Nothing
 */
static void bridge_handle_actions(struct ast_bridge *bridge)
{
        struct ast_frame *action;

        while ((action = AST_LIST_REMOVE_HEAD(&bridge->action_queue, frame_list))) {
                switch (action->frametype) {
                case AST_FRAME_BRIDGE_ACTION:
                        bridge_action_bridge(bridge, action);
                        break;
                default:
                        /* Unexpected deferred frame type.  Should never happen. */
                        ast_assert(0);
                        break;
                }
                ast_frfree(action);
        }
}

static struct stasis_message *create_bridge_snapshot_message(struct ast_bridge *bridge)
{
        RAII_VAR(struct ast_bridge_snapshot *, snapshot, NULL, ao2_cleanup);

        snapshot = ast_bridge_snapshot_create(bridge);
        if (!snapshot) {
                return NULL;
        }

        return stasis_message_create(ast_bridge_snapshot_type(), snapshot);
}

static void destroy_bridge(void *obj)
{
        struct ast_bridge *bridge = obj;

        ast_debug(1, "Bridge %s: actually destroying %s bridge, nobody wants it anymore\n",
                bridge->uniqueid, bridge->v_table->name);

        if (bridge->construction_completed) {
                RAII_VAR(struct stasis_message *, clear_msg, NULL, ao2_cleanup);

                clear_msg = create_bridge_snapshot_message(bridge);
                if (clear_msg) {
                        RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);

                        msg = stasis_cache_clear_create(clear_msg);
                        if (msg) {
                                stasis_publish(ast_bridge_topic(bridge), msg);
                        }
                }
        }

        /* Do any pending actions in the context of destruction. */
        ast_bridge_lock(bridge);
        bridge_handle_actions(bridge);
        ast_bridge_unlock(bridge);

        /* There should not be any channels left in the bridge. */
        ast_assert(AST_LIST_EMPTY(&bridge->channels));

        ast_debug(1, "Bridge %s: calling %s bridge destructor\n",
                bridge->uniqueid, bridge->v_table->name);
        bridge->v_table->destroy(bridge);

        /* Pass off the bridge to the technology to destroy if needed */
        if (bridge->technology) {
                ast_debug(1, "Bridge %s: calling %s technology stop\n",
                        bridge->uniqueid, bridge->technology->name);
                if (bridge->technology->stop) {
                        ast_bridge_lock(bridge);
                        bridge->technology->stop(bridge);
                        ast_bridge_unlock(bridge);
                }
                ast_debug(1, "Bridge %s: calling %s technology destructor\n",
                        bridge->uniqueid, bridge->technology->name);
                if (bridge->technology->destroy) {
                        bridge->technology->destroy(bridge);
                }
                ast_module_unref(bridge->technology->mod);
                bridge->technology = NULL;
        }

        if (bridge->callid) {
                bridge->callid = ast_callid_unref(bridge->callid);
        }

        cleanup_video_mode(bridge);

        stasis_cp_single_unsubscribe(bridge->topics);
}

struct ast_bridge *bridge_register(struct ast_bridge *bridge)
{
        if (bridge) {
                bridge->construction_completed = 1;
                ast_bridge_publish_state(bridge);
                if (!ao2_link(bridges, bridge)) {
                        ast_bridge_destroy(bridge, 0);
                        bridge = NULL;
                }
        }
        return bridge;
}

struct ast_bridge *bridge_alloc(size_t size, const struct ast_bridge_methods *v_table)
{
        struct ast_bridge *bridge;

        /* Check v_table that all methods are present. */
        if (!v_table
                || !v_table->name
                || !v_table->destroy
                || !v_table->dissolving
                || !v_table->push
                || !v_table->pull
                || !v_table->notify_masquerade
                || !v_table->get_merge_priority) {
                ast_log(LOG_ERROR, "Virtual method table for bridge class %s not complete.\n",
                        v_table && v_table->name ? v_table->name : "<unknown>");
                ast_assert(0);
                return NULL;
        }

        bridge = ao2_alloc(size, destroy_bridge);
        if (bridge) {
                bridge->v_table = v_table;
        }
        return bridge;
}

struct ast_bridge *bridge_base_init(struct ast_bridge *self, uint32_t capabilities, unsigned int flags)
{
        if (!self) {
                return NULL;
        }

        ast_uuid_generate_str(self->uniqueid, sizeof(self->uniqueid));
        ast_set_flag(&self->feature_flags, flags);
        self->allowed_capabilities = capabilities;

        if (bridge_topics_init(self) != 0) {
                ast_log(LOG_WARNING, "Bridge %s: Could not initialize topics\n",
                        self->uniqueid);
                ao2_ref(self, -1);
                return NULL;
        }

        /* Use our helper function to find the "best" bridge technology. */
        self->technology = find_best_technology(capabilities, self);
        if (!self->technology) {
                ast_log(LOG_WARNING, "Bridge %s: Could not create class %s.  No technology to support it.\n",
                        self->uniqueid, self->v_table->name);
                ao2_ref(self, -1);
                return NULL;
        }

        /* Pass off the bridge to the technology to manipulate if needed */
        ast_debug(1, "Bridge %s: calling %s technology constructor\n",
                self->uniqueid, self->technology->name);
        if (self->technology->create && self->technology->create(self)) {
                ast_log(LOG_WARNING, "Bridge %s: failed to setup bridge technology %s\n",
                        self->uniqueid, self->technology->name);
                ao2_ref(self, -1);
                return NULL;
        }
        ast_debug(1, "Bridge %s: calling %s technology start\n",
                self->uniqueid, self->technology->name);
        if (self->technology->start && self->technology->start(self)) {
                ast_log(LOG_WARNING, "Bridge %s: failed to start bridge technology %s\n",
                        self->uniqueid, self->technology->name);
                ao2_ref(self, -1);
                return NULL;
        }

        if (!ast_bridge_topic(self)) {
                ao2_ref(self, -1);
                return NULL;
        }

        return self;
}

/*!
 * \internal
 * \brief ast_bridge base class destructor.
 * \since 12.0.0
 *
 * \param self Bridge to operate upon.
 *
 * \note Stub because of nothing to do.
 *
 * \return Nothing
 */
static void bridge_base_destroy(struct ast_bridge *self)
{
}

/*!
 * \internal
 * \brief The bridge is being dissolved.
 * \since 12.0.0
 *
 * \param self Bridge to operate upon.
 *
 * \return Nothing
 */
static void bridge_base_dissolving(struct ast_bridge *self)
{
        ao2_unlink(bridges, self);
}

/*!
 * \internal
 * \brief ast_bridge base 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.
 * \note Stub because of nothing to do.
 *
 * \retval 0 on success
 * \retval -1 on failure
 */
static int bridge_base_push(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel, struct ast_bridge_channel *swap)
{
        return 0;
}

/*!
 * \internal
 * \brief ast_bridge base pull method.
 * \since 12.0.0
 *
 * \param self Bridge to operate upon.
 * \param bridge_channel Bridge channel to pull.
 *
 * \note On entry, self is already locked.
 *
 * \return Nothing
 */
static void bridge_base_pull(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel)
{
        ast_bridge_features_remove(bridge_channel->features, AST_BRIDGE_HOOK_REMOVE_ON_PULL);
}

/*!
 * \internal
 * \brief ast_bridge base notify_masquerade method.
 * \since 12.0.0
 *
 * \param self Bridge to operate upon.
 * \param bridge_channel Bridge channel that was masqueraded.
 *
 * \note On entry, self is already locked.
 *
 * \return Nothing
 */
static void bridge_base_notify_masquerade(struct ast_bridge *self, struct ast_bridge_channel *bridge_channel)
{
        self->reconfigured = 1;
}

/*!
 * \internal
 * \brief Get the merge priority of this bridge.
 * \since 12.0.0
 *
 * \param self Bridge to operate upon.
 *
 * \note On entry, self is already locked.
 *
 * \return Merge priority
 */
static int bridge_base_get_merge_priority(struct ast_bridge *self)
{
        return 0;
}

struct ast_bridge_methods ast_bridge_base_v_table = {
        .name = "base",
        .destroy = bridge_base_destroy,
        .dissolving = bridge_base_dissolving,
        .push = bridge_base_push,
        .pull = bridge_base_pull,
        .notify_masquerade = bridge_base_notify_masquerade,
        .get_merge_priority = bridge_base_get_merge_priority,
};

struct ast_bridge *ast_bridge_base_new(uint32_t capabilities, unsigned int flags)
{
        void *bridge;

        bridge = bridge_alloc(sizeof(struct ast_bridge), &ast_bridge_base_v_table);
        bridge = bridge_base_init(bridge, capabilities, flags);
        bridge = bridge_register(bridge);
        return bridge;
}

int ast_bridge_destroy(struct ast_bridge *bridge, int cause)
{
        ast_debug(1, "Bridge %s: telling all channels to leave the party\n", bridge->uniqueid);
        ast_bridge_lock(bridge);
        bridge_dissolve(bridge, cause);
        ast_bridge_unlock(bridge);

        ao2_ref(bridge, -1);

        return 0;
}

static int bridge_make_compatible(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
{
        struct ast_format read_format;
        struct ast_format write_format;
        struct ast_format best_format;
        char codec_buf[512];

        ast_format_copy(&read_format, ast_channel_readformat(bridge_channel->chan));
        ast_format_copy(&write_format, ast_channel_writeformat(bridge_channel->chan));

        /* Are the formats currently in use something this bridge can handle? */
        if (!ast_format_cap_iscompatible(bridge->technology->format_capabilities, ast_channel_readformat(bridge_channel->chan))) {
                ast_best_codec(bridge->technology->format_capabilities, &best_format);

                /* Read format is a no go... */
                ast_debug(1, "Bridge technology %s wants to read any of formats %s but channel has %s\n",
                        bridge->technology->name,
                        ast_getformatname_multiple(codec_buf, sizeof(codec_buf), bridge->technology->format_capabilities),
                        ast_getformatname(&read_format));

                /* Switch read format to the best one chosen */
                if (ast_set_read_format(bridge_channel->chan, &best_format)) {
                        ast_log(LOG_WARNING, "Failed to set channel %s to read format %s\n",
                                ast_channel_name(bridge_channel->chan), ast_getformatname(&best_format));
                        return -1;
                }
                ast_debug(1, "Bridge %s put channel %s into read format %s\n",
                        bridge->uniqueid, ast_channel_name(bridge_channel->chan),
                        ast_getformatname(&best_format));
        } else {
                ast_debug(1, "Bridge %s is happy that channel %s already has read format %s\n",
                        bridge->uniqueid, ast_channel_name(bridge_channel->chan),
                        ast_getformatname(&read_format));
        }

        if (!ast_format_cap_iscompatible(bridge->technology->format_capabilities, &write_format)) {
                ast_best_codec(bridge->technology->format_capabilities, &best_format);

                /* Write format is a no go... */
                ast_debug(1, "Bridge technology %s wants to write any of formats %s but channel has %s\n",
                        bridge->technology->name,
                        ast_getformatname_multiple(codec_buf, sizeof(codec_buf), bridge->technology->format_capabilities),
                        ast_getformatname(&write_format));

                /* Switch write format to the best one chosen */
                if (ast_set_write_format(bridge_channel->chan, &best_format)) {
                        ast_log(LOG_WARNING, "Failed to set channel %s to write format %s\n",
                                ast_channel_name(bridge_channel->chan), ast_getformatname(&best_format));
                        return -1;
                }
                ast_debug(1, "Bridge %s put channel %s into write format %s\n",
                        bridge->uniqueid, ast_channel_name(bridge_channel->chan),
                        ast_getformatname(&best_format));
        } else {
                ast_debug(1, "Bridge %s is happy that channel %s already has write format %s\n",
                        bridge->uniqueid, ast_channel_name(bridge_channel->chan),
                        ast_getformatname(&write_format));
        }

        return 0;
}

/*!
 * \internal
 * \brief Perform the smart bridge operation.
 * \since 12.0.0
 *
 * \param bridge Work on this bridge.
 *
 * \details
 * Basically see if a new bridge technology should be used instead
 * of the current one.
 *
 * \note On entry, bridge is already locked.
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int smart_bridge_operation(struct ast_bridge *bridge)
{
        uint32_t new_capabilities;
        struct ast_bridge_technology *new_technology;
        struct ast_bridge_technology *old_technology = bridge->technology;
        struct ast_bridge_channel *bridge_channel;
        struct ast_frame *deferred_action;
        struct ast_bridge dummy_bridge = {
                .technology = bridge->technology,
                .tech_pvt = bridge->tech_pvt,
        };

        if (bridge->dissolved) {
                ast_debug(1, "Bridge %s is dissolved, not performing smart bridge operation.\n",
                        bridge->uniqueid);
                return 0;
        }

        /* Determine new bridge technology capabilities needed. */
        if (2 < bridge->num_channels) {
                new_capabilities = AST_BRIDGE_CAPABILITY_MULTIMIX;
                new_capabilities &= bridge->allowed_capabilities;
        } else {
                new_capabilities = AST_BRIDGE_CAPABILITY_NATIVE | AST_BRIDGE_CAPABILITY_1TO1MIX;
                new_capabilities &= bridge->allowed_capabilities;
                if (!new_capabilities
                        && (bridge->allowed_capabilities & AST_BRIDGE_CAPABILITY_MULTIMIX)) {
                        /* Allow switching between different multimix bridge technologies. */
                        new_capabilities = AST_BRIDGE_CAPABILITY_MULTIMIX;
                }
        }

        /* Find a bridge technology to satisfy the new capabilities. */
        new_technology = find_best_technology(new_capabilities, bridge);
        if (!new_technology) {
                int is_compatible = 0;

                if (old_technology->compatible) {
                        is_compatible = old_technology->compatible(bridge);
                } else if (old_technology->capabilities & AST_BRIDGE_CAPABILITY_MULTIMIX) {
                        is_compatible = 1;
                } else if (bridge->num_channels <= 2
                        && (old_technology->capabilities & AST_BRIDGE_CAPABILITY_1TO1MIX)) {
                        is_compatible = 1;
                }

                if (is_compatible) {
                        ast_debug(1, "Bridge %s could not get a new technology, staying with old technology.\n",
                                bridge->uniqueid);
                        return 0;
                }
                ast_log(LOG_WARNING, "Bridge %s has no technology available to support it.\n",
                        bridge->uniqueid);
                return -1;
        }
        if (new_technology == old_technology) {
                ast_debug(1, "Bridge %s is already using the new technology.\n",
                        bridge->uniqueid);
                ast_module_unref(old_technology->mod);
                return 0;
        }

        ast_copy_string(dummy_bridge.uniqueid, bridge->uniqueid, sizeof(dummy_bridge.uniqueid));

        if (old_technology->destroy) {
                struct tech_deferred_destroy deferred_tech_destroy = {
                        .tech = dummy_bridge.technology,
                        .tech_pvt = dummy_bridge.tech_pvt,
                };
                struct ast_frame action = {
                        .frametype = AST_FRAME_BRIDGE_ACTION,
                        .subclass.integer = BRIDGE_CHANNEL_ACTION_DEFERRED_TECH_DESTROY,
                        .data.ptr = &deferred_tech_destroy,
                        .datalen = sizeof(deferred_tech_destroy),
                };

                /*
                 * We need to defer the bridge technology destroy callback
                 * because we have the bridge locked.
                 */
                deferred_action = ast_frdup(&action);
                if (!deferred_action) {
                        ast_module_unref(new_technology->mod);
                        return -1;
                }
        } else {
                deferred_action = NULL;
        }

        /*
         * We are now committed to changing the bridge technology.  We
         * must not release the bridge lock until we have installed the
         * new bridge technology.
         */
        ast_verb(4, "Bridge %s: switching from %s technology to %s\n",
                bridge->uniqueid, old_technology->name, new_technology->name);

        /*
         * Since we are soon going to pass this bridge to a new
         * technology we need to NULL out the tech_pvt pointer but
         * don't worry as it still exists in dummy_bridge, ditto for the
         * old technology.
         */
        bridge->tech_pvt = NULL;
        bridge->technology = new_technology;

        /* Setup the new bridge technology. */
        ast_debug(1, "Bridge %s: calling %s technology constructor\n",
                bridge->uniqueid, new_technology->name);
        if (new_technology->create && new_technology->create(bridge)) {
                ast_log(LOG_WARNING, "Bridge %s: failed to setup bridge technology %s\n",
                        bridge->uniqueid, new_technology->name);
                bridge->tech_pvt = dummy_bridge.tech_pvt;
                bridge->technology = dummy_bridge.technology;
                ast_module_unref(new_technology->mod);
                return -1;
        }

        ast_debug(1, "Bridge %s: calling %s technology stop\n",
                dummy_bridge.uniqueid, old_technology->name);
        if (old_technology->stop) {
                old_technology->stop(&dummy_bridge);
        }

        /*
         * Move existing channels over to the new technology and
         * complete joining any new channels to the bridge.
         */
        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                if (!bridge_channel->just_joined) {
                        /* Take existing channel from the old technology. */
                        ast_debug(1, "Bridge %s: %p(%s) is leaving %s technology (dummy)\n",
                                dummy_bridge.uniqueid, bridge_channel, ast_channel_name(bridge_channel->chan),
                                old_technology->name);
                        if (old_technology->leave) {
                                old_technology->leave(&dummy_bridge, bridge_channel);
                        }
                }

                /* Add any new channels or re-add an existing channel to the bridge. */
                bridge_channel_complete_join(bridge, bridge_channel);
        }

        ast_debug(1, "Bridge %s: calling %s technology start\n",
                bridge->uniqueid, new_technology->name);
        if (new_technology->start && new_technology->start(bridge)) {
                ast_log(LOG_WARNING, "Bridge %s: failed to start bridge technology %s\n",
                        bridge->uniqueid, new_technology->name);
        }

        /*
         * Now that all the channels have been moved over we need to get
         * rid of all the information the old technology may have left
         * around.
         */
        if (old_technology->destroy) {
                ast_debug(1, "Bridge %s: deferring %s technology destructor\n",
                        dummy_bridge.uniqueid, old_technology->name);
                bridge_queue_action_nodup(bridge, deferred_action);
        } else {
                ast_debug(1, "Bridge %s: calling %s technology destructor\n",
                        dummy_bridge.uniqueid, old_technology->name);
                ast_module_unref(old_technology->mod);
        }

        return 0;
}

/*!
 * \internal
 * \brief Bridge channel to check if a BRIDGE_PLAY_SOUND needs to be played.
 * \since 12.0.0
 *
 * \param bridge_channel What to check.
 *
 * \return Nothing
 */
static void check_bridge_play_sound(struct ast_bridge_channel *bridge_channel)
{
        const char *play_file;

        ast_channel_lock(bridge_channel->chan);
        play_file = pbx_builtin_getvar_helper(bridge_channel->chan, "BRIDGE_PLAY_SOUND");
        if (!ast_strlen_zero(play_file)) {
                play_file = ast_strdupa(play_file);
                pbx_builtin_setvar_helper(bridge_channel->chan, "BRIDGE_PLAY_SOUND", NULL);
        } else {
                play_file = NULL;
        }
        ast_channel_unlock(bridge_channel->chan);

        if (play_file) {
                ast_bridge_channel_queue_playfile(bridge_channel, NULL, play_file, NULL);
        }
}

/*!
 * \internal
 * \brief Check for any BRIDGE_PLAY_SOUND channel variables in the bridge.
 * \since 12.0.0
 *
 * \param bridge What to operate on.
 *
 * \note On entry, the bridge is already locked.
 *
 * \return Nothing
 */
static void check_bridge_play_sounds(struct ast_bridge *bridge)
{
        struct ast_bridge_channel *bridge_channel;

        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                check_bridge_play_sound(bridge_channel);
        }
}

static void update_bridge_vars_set(struct ast_channel *chan, const char *name, const char *pvtid)
{
        pbx_builtin_setvar_helper(chan, "BRIDGEPEER", name);
        pbx_builtin_setvar_helper(chan, "BRIDGEPVTCALLID", pvtid);
}

/*!
 * \internal
 * \brief Set BRIDGEPEER and BRIDGEPVTCALLID channel variables in a 2 party bridge.
 * \since 12.0.0
 *
 * \param c0 Party of the first part.
 * \param c1 Party of the second part.
 *
 * \note On entry, the bridge is already locked.
 * \note The bridge is expected to have exactly two parties.
 *
 * \return Nothing
 */
static void set_bridge_peer_vars_2party(struct ast_channel *c0, struct ast_channel *c1)
{
        const char *c0_name;
        const char *c1_name;
        const char *c0_pvtid = NULL;
        const char *c1_pvtid = NULL;
#define UPDATE_BRIDGE_VARS_GET(chan, name, pvtid)                                                                       \
        do {                                                                                                                                                    \
                name = ast_strdupa(ast_channel_name(chan));                                                                     \
                if (ast_channel_tech(chan)->get_pvt_uniqueid) {                                                         \
                        pvtid = ast_strdupa(ast_channel_tech(chan)->get_pvt_uniqueid(chan));    \
                }                                                                                                                                                       \
        } while (0)

        ast_channel_lock(c1);
        UPDATE_BRIDGE_VARS_GET(c1, c1_name, c1_pvtid);
        ast_channel_unlock(c1);

        ast_channel_lock(c0);
        update_bridge_vars_set(c0, c1_name, c1_pvtid);
        UPDATE_BRIDGE_VARS_GET(c0, c0_name, c0_pvtid);
        ast_channel_unlock(c0);

        ast_channel_lock(c1);
        update_bridge_vars_set(c1, c0_name, c0_pvtid);
        ast_channel_unlock(c1);
}

/*!
 * \internal
 * \brief Fill the BRIDGEPEER value buffer with a comma separated list of channel names.
 * \since 12.0.0
 *
 * \param buf Buffer to fill.  The caller must guarantee the buffer is large enough.
 * \param cur_idx Which index into names[] to skip.
 * \param names Channel names to put in the buffer.
 * \param num_names Number of names in the array.
 *
 * \return Nothing
 */
static void fill_bridgepeer_buf(char *buf, unsigned int cur_idx, const char *names[], unsigned int num_names)
{
        int need_separator = 0;
        unsigned int idx;
        const char *src;
        char *pos;

        pos = buf;
        for (idx = 0; idx < num_names; ++idx) {
                if (idx == cur_idx) {
                        continue;
                }

                if (need_separator) {
                        *pos++ = ',';
                }
                need_separator = 1;

                /* Copy name into buffer. */
                src = names[idx];
                while (*src) {
                        *pos++ = *src++;
                }
        }
        *pos = '\0';
}

/*!
 * \internal
 * \brief Set BRIDGEPEER and BRIDGEPVTCALLID channel variables in a multi-party bridge.
 * \since 12.0.0
 *
 * \param bridge What to operate on.
 *
 * \note On entry, the bridge is already locked.
 * \note The bridge is expected to have more than two parties.
 *
 * \return Nothing
 */
static void set_bridge_peer_vars_multiparty(struct ast_bridge *bridge)
{
/*
 * Set a maximum number of channel names for the BRIDGEPEER
 * list.  The plus one is for the current channel which is not
 * put in the list.
 */
#define MAX_BRIDGEPEER_CHANS    (10 + 1)

        unsigned int idx;
        unsigned int num_names;
        unsigned int len;
        const char **names;
        char *buf;
        struct ast_bridge_channel *bridge_channel;

        /* Get first MAX_BRIDGEPEER_CHANS channel names. */
        num_names = MIN(bridge->num_channels, MAX_BRIDGEPEER_CHANS);
        names = ast_alloca(num_names * sizeof(*names));
        idx = 0;
        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                if (num_names <= idx) {
                        break;
                }
                ast_channel_lock(bridge_channel->chan);
                names[idx++] = ast_strdupa(ast_channel_name(bridge_channel->chan));
                ast_channel_unlock(bridge_channel->chan);
        }

        /* Determine maximum buf size needed. */
        len = num_names;
        for (idx = 0; idx < num_names; ++idx) {
                len += strlen(names[idx]);
        }
        buf = ast_alloca(len);

        /* Set the bridge channel variables. */
        idx = 0;
        buf[0] = '\0';
        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                if (idx < num_names) {
                        fill_bridgepeer_buf(buf, idx, names, num_names);
                }
                ++idx;

                ast_channel_lock(bridge_channel->chan);
                update_bridge_vars_set(bridge_channel->chan, buf, NULL);
                ast_channel_unlock(bridge_channel->chan);
        }
}

/*!
 * \internal
 * \brief Set BRIDGEPEER and BRIDGEPVTCALLID channel variables in a holding bridge.
 * \since 12.0.0
 *
 * \param bridge What to operate on.
 *
 * \note On entry, the bridge is already locked.
 *
 * \return Nothing
 */
static void set_bridge_peer_vars_holding(struct ast_bridge *bridge)
{
        struct ast_bridge_channel *bridge_channel;

        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                ast_channel_lock(bridge_channel->chan);
                update_bridge_vars_set(bridge_channel->chan, NULL, NULL);
                ast_channel_unlock(bridge_channel->chan);
        }
}

/*!
 * \internal
 * \brief Set BRIDGEPEER and BRIDGEPVTCALLID channel variables in the bridge.
 * \since 12.0.0
 *
 * \param bridge What to operate on.
 *
 * \note On entry, the bridge is already locked.
 *
 * \return Nothing
 */
static void set_bridge_peer_vars(struct ast_bridge *bridge)
{
        if (bridge->technology->capabilities & AST_BRIDGE_CAPABILITY_HOLDING) {
                set_bridge_peer_vars_holding(bridge);
                return;
        }
        if (bridge->num_channels < 2) {
                return;
        }
        if (bridge->num_channels == 2) {
                set_bridge_peer_vars_2party(AST_LIST_FIRST(&bridge->channels)->chan,
                        AST_LIST_LAST(&bridge->channels)->chan);
        } else {
                set_bridge_peer_vars_multiparty(bridge);
        }
}

void bridge_reconfigured(struct ast_bridge *bridge, unsigned int colp_update)
{
        if (!bridge->reconfigured) {
                return;
        }
        bridge->reconfigured = 0;
        if (ast_test_flag(&bridge->feature_flags, AST_BRIDGE_FLAG_SMART)
                && smart_bridge_operation(bridge)) {
                /* Smart bridge failed. */
                bridge_dissolve(bridge, 0);
                return;
        }
        bridge_complete_join(bridge);

        if (bridge->dissolved) {
                return;
        }
        check_bridge_play_sounds(bridge);
        set_bridge_peer_vars(bridge);
        ast_bridge_publish_state(bridge);

        if (colp_update) {
                bridge_reconfigured_connected_line_update(bridge);
        }
}

struct ast_bridge_channel *bridge_find_channel(struct ast_bridge *bridge, struct ast_channel *chan)
{
        struct ast_bridge_channel *bridge_channel;

        AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
                if (bridge_channel->chan == chan) {
                        break;
                }
        }

        return bridge_channel;
}

void ast_bridge_notify_masquerade(struct ast_channel *chan)
{
        struct ast_bridge_channel *bridge_channel;
        struct ast_bridge *bridge;

        /* Safely get the bridge_channel pointer for the chan. */
        ast_channel_lock(chan);
        bridge_channel = ast_channel_get_bridge_channel(chan);
        ast_channel_unlock(chan);
        if (!bridge_channel) {
                /* Not in a bridge */
                return;
        }

        ast_bridge_channel_lock_bridge(bridge_channel);
        bridge = bridge_channel->bridge;
        if (bridge_channel == bridge_find_channel(bridge, chan)) {
/*
 * XXX ASTERISK-22366 this needs more work.  The channels need
 * to be made compatible again if the formats change. The
 * bridge_channel thread needs to monitor for this case.
 */
                /* The channel we want to notify is still in a bridge. */
                bridge->v_table->notify_masquerade(bridge, bridge_channel);
                bridge_reconfigured(bridge, 1);
        }
        ast_bridge_unlock(bridge);
        ao2_ref(bridge_channel, -1);
}

/*
 * XXX ASTERISK-21271 make ast_bridge_join() require features to be allocated just like ast_bridge_impart() and not expect the struct back.
 *
 * This change is really going to break ConfBridge.  All other
 * users are easily changed.  However, it is needed so the
 * bridging code can manipulate features on all channels
 * consistently no matter how they joined.
 *
 * Need to update the features parameter doxygen when this
 * change is made to be like ast_bridge_impart().
 */
int ast_bridge_join(struct ast_bridge *bridge,
        struct ast_channel *chan,
        struct ast_channel *swap,
        struct ast_bridge_features *features,
        struct ast_bridge_tech_optimizations *tech_args,
        int pass_reference)
{
        struct ast_bridge_channel *bridge_channel;
        int res = 0;

        bridge_channel = bridge_channel_internal_alloc(bridge);
        if (pass_reference) {
                ao2_ref(bridge, -1);
        }
        if (!bridge_channel) {
                res = -1;
                goto join_exit;
        }
/* XXX ASTERISK-21271 features cannot be NULL when passed in. When it is changed to allocated we can do like ast_bridge_impart() and allocate one. */
        ast_assert(features != NULL);
        if (!features) {
                ao2_ref(bridge_channel, -1);
                res = -1;
                goto join_exit;
        }
        if (tech_args) {
                bridge_channel->tech_args = *tech_args;
        }

        ast_channel_lock(chan);
        if (ast_test_flag(ast_channel_flags(chan), AST_FLAG_ZOMBIE)) {
                res = -1;
        } else {
                ast_channel_internal_bridge_channel_set(chan, bridge_channel);
        }
        ast_channel_unlock(chan);
        bridge_channel->thread = pthread_self();
        bridge_channel->chan = chan;
        bridge_channel->swap = swap;
        bridge_channel->features = features;

        if (!res) {
                res = bridge_channel_internal_join(bridge_channel);
        }

        /* Cleanup all the data in the bridge channel after it leaves the bridge. */
        ast_channel_lock(chan);
        ast_channel_internal_bridge_channel_set(chan, NULL);
        ast_channel_unlock(chan);
        bridge_channel->chan = NULL;
        bridge_channel->swap = NULL;
        bridge_channel->features = NULL;

        ao2_ref(bridge_channel, -1);

join_exit:;
        ast_bridge_run_after_callback(chan);
        if (!(ast_channel_softhangup_internal_flag(chan) & AST_SOFTHANGUP_ASYNCGOTO)
                && !ast_bridge_setup_after_goto(chan)) {
                /* Claim the after bridge goto is an async goto destination. */
                ast_channel_lock(chan);
                ast_softhangup_nolock(chan, AST_SOFTHANGUP_ASYNCGOTO);
                ast_channel_unlock(chan);
        }
        return res;
}

/*! \brief Thread responsible for imparted bridged channels to be departed */
static void *bridge_channel_depart_thread(void *data)
{
        struct ast_bridge_channel *bridge_channel = data;

        if (bridge_channel->callid) {
                ast_callid_threadassoc_add(bridge_channel->callid);
        }

        bridge_channel_internal_join(bridge_channel);

        /* cleanup */
        bridge_channel->swap = NULL;
        ast_bridge_features_destroy(bridge_channel->features);
        bridge_channel->features = NULL;

        ast_bridge_discard_after_callback(bridge_channel->chan, AST_BRIDGE_AFTER_CB_REASON_DEPART);
        ast_bridge_discard_after_goto(bridge_channel->chan);

        return NULL;
}

/*! \brief Thread responsible for independent imparted bridged channels */
static void *bridge_channel_ind_thread(void *data)
{
        struct ast_bridge_channel *bridge_channel = data;
        struct ast_channel *chan;

        if (bridge_channel->callid) {
                ast_callid_threadassoc_add(bridge_channel->callid);
        }

        bridge_channel_internal_join(bridge_channel);
        chan = bridge_channel->chan;

        /* cleanup */
        ast_channel_lock(chan);
        ast_channel_internal_bridge_channel_set(chan, NULL);
        ast_channel_unlock(chan);
        bridge_channel->chan = NULL;
        bridge_channel->swap = NULL;
        ast_bridge_features_destroy(bridge_channel->features);
        bridge_channel->features = NULL;

        ao2_ref(bridge_channel, -1);

        ast_bridge_run_after_callback(chan);
        ast_bridge_run_after_goto(chan);
        return NULL;
}

int ast_bridge_impart(struct ast_bridge *bridge, struct ast_channel *chan, struct ast_channel *swap, struct ast_bridge_features *features, int independent)
{
        int res = 0;
        struct ast_bridge_channel *bridge_channel;

        /* Imparted channels cannot have a PBX. */
        if (ast_channel_pbx(chan)) {
                ast_log(AST_LOG_WARNING, "Channel %s has a PBX thread and cannot be imparted into bridge %s\n",
                        ast_channel_name(chan), bridge->uniqueid);
                return -1;
        }

        /* Supply an empty features structure if the caller did not. */
        if (!features) {
                features = ast_bridge_features_new();
                if (!features) {
                        return -1;
                }
        }

        /* Try to allocate a structure for the bridge channel */
        bridge_channel = bridge_channel_internal_alloc(bridge);
        if (!bridge_channel) {
                ast_bridge_features_destroy(features);
                return -1;
        }

        ast_channel_lock(chan);
        if (ast_test_flag(ast_channel_flags(chan), AST_FLAG_ZOMBIE)) {
                ast_log(AST_LOG_NOTICE, "Channel %s is a zombie and cannot be imparted into bridge %s\n",
                        ast_channel_name(chan), bridge->uniqueid);
                res = -1;
        } else {
                ast_channel_internal_bridge_channel_set(chan, bridge_channel);
        }
        ast_channel_unlock(chan);
        bridge_channel->chan = chan;
        bridge_channel->swap = swap;
        bridge_channel->features = features;
        bridge_channel->depart_wait = independent ? 0 : 1;
        bridge_channel->callid = ast_read_threadstorage_callid();

        /* Actually create the thread that will handle the channel */
        if (!res) {
                if (independent) {
                        res = ast_pthread_create_detached(&bridge_channel->thread, NULL,
                                bridge_channel_ind_thread, bridge_channel);
                } else {
                        res = ast_pthread_create(&bridge_channel->thread, NULL,
                                bridge_channel_depart_thread, bridge_channel);
                }
        }

        if (res) {
                /* cleanup */
                ast_channel_lock(chan);
                ast_channel_internal_bridge_channel_set(chan, NULL);
                ast_channel_unlock(chan);
                bridge_channel->chan = NULL;
                bridge_channel->swap = NULL;
                ast_bridge_features_destroy(bridge_channel->features);
                bridge_channel->features = NULL;

                ao2_ref(bridge_channel, -1);
                return -1;
        }

        return 0;
}

int ast_bridge_depart(struct ast_channel *chan)
{
        struct ast_bridge_channel *bridge_channel;
        int departable;

        ast_channel_lock(chan);
        bridge_channel = ast_channel_internal_bridge_channel(chan);
        departable = bridge_channel && bridge_channel->depart_wait;
        ast_channel_unlock(chan);
        if (!departable) {
                ast_log(LOG_ERROR, "Channel %s cannot be departed.\n",
                        ast_channel_name(chan));
                /*
                 * Should never happen.  It likely means that
                 * ast_bridge_depart() is called by two threads for the same
                 * channel, the channel was never imparted to be departed, or it
                 * has already been departed.
                 */
                ast_assert(0);
                return -1;
        }

        /*
         * We are claiming the reference held by the depart bridge
         * channel thread.
         */

        ast_bridge_channel_leave_bridge(bridge_channel,
                BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, AST_CAUSE_NORMAL_CLEARING);

        /* Wait for the depart thread to die */
        ast_debug(1, "Waiting for %p(%s) bridge thread to die.\n",
                bridge_channel, ast_channel_name(bridge_channel->chan));
        pthread_join(bridge_channel->thread, NULL);

        ast_channel_lock(chan);
        ast_channel_internal_bridge_channel_set(chan, NULL);
        ast_channel_unlock(chan);

        /* We can get rid of the bridge_channel after the depart thread has died. */
        ao2_ref(bridge_channel, -1);
        return 0;
}

int ast_bridge_remove(struct ast_bridge *bridge, struct ast_channel *chan)
{
        struct ast_bridge_channel *bridge_channel;

        ast_bridge_lock(bridge);

        /* Try to find the channel that we want to remove */
        if (!(bridge_channel = bridge_find_channel(bridge, chan))) {
                ast_bridge_unlock(bridge);
                return -1;
        }

        ast_bridge_channel_leave_bridge(bridge_channel,
                BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, AST_CAUSE_NORMAL_CLEARING);

        ast_bridge_unlock(bridge);

        return 0;
}

static void kick_it(struct ast_bridge_channel *bridge_channel, const void *payload, size_t payload_size)
{
        ast_bridge_channel_kick(bridge_channel, AST_CAUSE_NORMAL_CLEARING);
}

int ast_bridge_kick(struct ast_bridge *bridge, struct ast_channel *chan)
{
        struct ast_bridge_channel *bridge_channel;
        int res;

        ast_bridge_lock(bridge);

        /* Try to find the channel that we want to kick. */
        if (!(bridge_channel = bridge_find_channel(bridge, chan))) {
                ast_bridge_unlock(bridge);
                return -1;
        }

        res = ast_bridge_channel_queue_callback(bridge_channel, 0, kick_it, NULL, 0);

        ast_bridge_unlock(bridge);

        return res;
}

/*!
 * \internal
 * \brief Point the bridge_channel to a new bridge.
 * \since 12.0.0
 *
 * \param bridge_channel What is to point to a new bridge.
 * \param new_bridge Where the bridge channel should point.
 *
 * \return Nothing
 */
static void bridge_channel_change_bridge(struct ast_bridge_channel *bridge_channel, struct ast_bridge *new_bridge)
{
        struct ast_bridge *old_bridge;

        ao2_ref(new_bridge, +1);
        ast_bridge_channel_lock(bridge_channel);
        ast_channel_lock(bridge_channel->chan);
        old_bridge = bridge_channel->bridge;
        bridge_channel->bridge = new_bridge;
        ast_channel_internal_bridge_set(bridge_channel->chan, new_bridge);
        ast_channel_unlock(bridge_channel->chan);
        ast_bridge_channel_unlock(bridge_channel);
        ao2_ref(old_bridge, -1);
}

void bridge_do_merge(struct ast_bridge *dst_bridge, struct ast_bridge *src_bridge, struct ast_bridge_channel **kick_me, unsigned int num_kick,
        unsigned int optimized)
{
        struct ast_bridge_channel *bridge_channel;
        unsigned int idx;

        ast_debug(1, "Merging bridge %s into bridge %s\n",
                src_bridge->uniqueid, dst_bridge->uniqueid);

        ast_bridge_publish_merge(dst_bridge, src_bridge);

        /*
         * Move channels from src_bridge over to dst_bridge.
         *
         * We must use AST_LIST_TRAVERSE_SAFE_BEGIN() because
         * bridge_channel_internal_pull() alters the list we are traversing.
         */
        AST_LIST_TRAVERSE_SAFE_BEGIN(&src_bridge->channels, bridge_channel, entry) {
                if (bridge_channel->state != BRIDGE_CHANNEL_STATE_WAIT) {
                        /*
                         * The channel is already leaving let it leave normally because
                         * pulling it may delete hooks that should run for this channel.
                         */
                        continue;
                }
                if (ast_test_flag(&bridge_channel->features->feature_flags,
                        AST_BRIDGE_CHANNEL_FLAG_IMMOVABLE)) {
                        continue;
                }

                if (kick_me) {
                        for (idx = 0; idx < num_kick; ++idx) {
                                if (bridge_channel == kick_me[idx]) {
                                        ast_bridge_channel_leave_bridge(bridge_channel,
                                                BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, AST_CAUSE_NORMAL_CLEARING);
                                        break;
                                }
                        }
                }
                bridge_channel_internal_pull(bridge_channel);
                if (bridge_channel->state != BRIDGE_CHANNEL_STATE_WAIT) {
                        /*
                         * The channel died as a result of being pulled or it was
                         * kicked.  Leave it pointing to the original bridge.
                         */
                        continue;
                }

                /* Point to new bridge.*/
                bridge_channel_change_bridge(bridge_channel, dst_bridge);

                if (bridge_channel_internal_push(bridge_channel)) {
                        ast_bridge_channel_leave_bridge(bridge_channel,
                                BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, bridge_channel->bridge->cause);
                }
        }
        AST_LIST_TRAVERSE_SAFE_END;

        if (kick_me) {
                /*
                 * Now we can kick any channels in the dst_bridge without
                 * potentially dissolving the bridge.
                 */
                for (idx = 0; idx < num_kick; ++idx) {
                        bridge_channel = kick_me[idx];
                        ast_bridge_channel_lock(bridge_channel);
                        if (bridge_channel->state == BRIDGE_CHANNEL_STATE_WAIT) {
                                ast_bridge_channel_leave_bridge_nolock(bridge_channel,
                                        BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, AST_CAUSE_NORMAL_CLEARING);
                                bridge_channel_internal_pull(bridge_channel);
                        }
                        ast_bridge_channel_unlock(bridge_channel);
                }
        }

        bridge_reconfigured(dst_bridge, !optimized);
        bridge_reconfigured(src_bridge, !optimized);

        ast_debug(1, "Merged bridge %s into bridge %s\n",
                src_bridge->uniqueid, dst_bridge->uniqueid);
}

struct merge_direction {
        /*! Destination merge bridge. */
        struct ast_bridge *dest;
        /*! Source merge bridge. */
        struct ast_bridge *src;
};

/*!
 * \internal
 * \brief Determine which bridge should merge into the other.
 * \since 12.0.0
 *
 * \param bridge1 A bridge for merging
 * \param bridge2 A bridge for merging
 *
 * \note The two bridges are assumed already locked.
 *
 * \return Which bridge merges into which or NULL bridges if cannot merge.
 */
static struct merge_direction bridge_merge_determine_direction(struct ast_bridge *bridge1, struct ast_bridge *bridge2)
{
        struct merge_direction merge = { NULL, NULL };
        int bridge1_priority;
        int bridge2_priority;

        if (!ast_test_flag(&bridge1->feature_flags,
                        AST_BRIDGE_FLAG_MERGE_INHIBIT_TO | AST_BRIDGE_FLAG_MERGE_INHIBIT_FROM)
                && !ast_test_flag(&bridge2->feature_flags,
                        AST_BRIDGE_FLAG_MERGE_INHIBIT_TO | AST_BRIDGE_FLAG_MERGE_INHIBIT_FROM)) {
                /*
                 * Can merge either way.  Merge to the higher priority merge
                 * bridge.  Otherwise merge to the larger bridge.
                 */
                bridge1_priority = bridge1->v_table->get_merge_priority(bridge1);
                bridge2_priority = bridge2->v_table->get_merge_priority(bridge2);
                if (bridge2_priority < bridge1_priority) {
                        merge.dest = bridge1;
                        merge.src = bridge2;
                } else if (bridge1_priority < bridge2_priority) {
                        merge.dest = bridge2;
                        merge.src = bridge1;
                } else {
                        /* Merge to the larger bridge. */
                        if (bridge2->num_channels <= bridge1->num_channels) {
                                merge.dest = bridge1;
                                merge.src = bridge2;
                        } else {
                                merge.dest = bridge2;
                                merge.src = bridge1;
                        }
                }
        } else if (!ast_test_flag(&bridge1->feature_flags, AST_BRIDGE_FLAG_MERGE_INHIBIT_TO)
                && !ast_test_flag(&bridge2->feature_flags, AST_BRIDGE_FLAG_MERGE_INHIBIT_FROM)) {
                /* Can merge only one way. */
                merge.dest = bridge1;
                merge.src = bridge2;
        } else if (!ast_test_flag(&bridge2->feature_flags, AST_BRIDGE_FLAG_MERGE_INHIBIT_TO)
                && !ast_test_flag(&bridge1->feature_flags, AST_BRIDGE_FLAG_MERGE_INHIBIT_FROM)) {
                /* Can merge only one way. */
                merge.dest = bridge2;
                merge.src = bridge1;
        }

        return merge;
}

/*!
 * \internal
 * \brief Merge two bridges together
 * \since 12.0.0
 *
 * \param dst_bridge Destination bridge of merge.
 * \param src_bridge Source bridge of merge.
 * \param merge_best_direction TRUE if don't care about which bridge merges into the other.
 * \param kick_me Array of channels to kick from the bridges.
 * \param num_kick Number of channels in the kick_me array.
 *
 * \note The dst_bridge and src_bridge are assumed already locked.
 *
 * \retval 0 on success
 * \retval -1 on failure
 */
static int bridge_merge_locked(struct ast_bridge *dst_bridge, struct ast_bridge *src_bridge, int merge_best_direction, struct ast_channel **kick_me, unsigned int num_kick)
{
        struct merge_direction merge;
        struct ast_bridge_channel **kick_them = NULL;

        /* Sanity check. */
        ast_assert(dst_bridge && src_bridge && dst_bridge != src_bridge && (!num_kick || kick_me));

        if (dst_bridge->dissolved || src_bridge->dissolved) {
                ast_debug(1, "Can't merge bridges %s and %s, at least one bridge is dissolved.\n",
                        src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }
        if (ast_test_flag(&dst_bridge->feature_flags, AST_BRIDGE_FLAG_MASQUERADE_ONLY)
                || ast_test_flag(&src_bridge->feature_flags, AST_BRIDGE_FLAG_MASQUERADE_ONLY)) {
                ast_debug(1, "Can't merge bridges %s and %s, masquerade only.\n",
                        src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }
        if (dst_bridge->inhibit_merge || src_bridge->inhibit_merge) {
                ast_debug(1, "Can't merge bridges %s and %s, merging temporarily inhibited.\n",
                        src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }

        if (merge_best_direction) {
                merge = bridge_merge_determine_direction(dst_bridge, src_bridge);
        } else {
                merge.dest = dst_bridge;
                merge.src = src_bridge;
        }

        if (!merge.dest
                || ast_test_flag(&merge.dest->feature_flags, AST_BRIDGE_FLAG_MERGE_INHIBIT_TO)
                || ast_test_flag(&merge.src->feature_flags, AST_BRIDGE_FLAG_MERGE_INHIBIT_FROM)) {
                ast_debug(1, "Can't merge bridges %s and %s, merging inhibited.\n",
                        src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }
        if (merge.src->num_channels < 2) {
                /*
                 * For a two party bridge, a channel may be temporarily removed
                 * from the source bridge or the initial bridge members have not
                 * joined yet.
                 */
                ast_debug(1, "Can't merge bridge %s into bridge %s, not enough channels in source bridge.\n",
                        merge.src->uniqueid, merge.dest->uniqueid);
                return -1;
        }
        if (2 + num_kick < merge.dest->num_channels + merge.src->num_channels
                && !(merge.dest->technology->capabilities & AST_BRIDGE_CAPABILITY_MULTIMIX)
                && (!ast_test_flag(&merge.dest->feature_flags, AST_BRIDGE_FLAG_SMART)
                        || !(merge.dest->allowed_capabilities & AST_BRIDGE_CAPABILITY_MULTIMIX))) {
                ast_debug(1, "Can't merge bridge %s into bridge %s, multimix is needed and it cannot be acquired.\n",
                        merge.src->uniqueid, merge.dest->uniqueid);
                return -1;
        }

        if (num_kick) {
                unsigned int num_to_kick = 0;
                unsigned int idx;

                kick_them = ast_alloca(num_kick * sizeof(*kick_them));
                for (idx = 0; idx < num_kick; ++idx) {
                        kick_them[num_to_kick] = bridge_find_channel(merge.src, kick_me[idx]);
                        if (!kick_them[num_to_kick]) {
                                kick_them[num_to_kick] = bridge_find_channel(merge.dest, kick_me[idx]);
                        }
                        if (kick_them[num_to_kick]) {
                                ++num_to_kick;
                        }
                }

                if (num_to_kick != num_kick) {
                        ast_debug(1, "Can't merge bridge %s into bridge %s, at least one kicked channel is not in either bridge.\n",
                                merge.src->uniqueid, merge.dest->uniqueid);
                        return -1;
                }
        }

        bridge_do_merge(merge.dest, merge.src, kick_them, num_kick, 0);
        return 0;
}

int ast_bridge_merge(struct ast_bridge *dst_bridge, struct ast_bridge *src_bridge, int merge_best_direction, struct ast_channel **kick_me, unsigned int num_kick)
{
        int res;

        /* Sanity check. */
        ast_assert(dst_bridge && src_bridge);

        ast_bridge_lock_both(dst_bridge, src_bridge);
        res = bridge_merge_locked(dst_bridge, src_bridge, merge_best_direction, kick_me, num_kick);
        ast_bridge_unlock(src_bridge);
        ast_bridge_unlock(dst_bridge);
        return res;
}

int bridge_do_move(struct ast_bridge *dst_bridge, struct ast_bridge_channel *bridge_channel, int attempt_recovery,
        unsigned int optimized)
{
        struct ast_bridge *orig_bridge;
        int was_in_bridge;
        int res = 0;

        if (bridge_channel->swap) {
                ast_debug(1, "Moving %p(%s) into bridge %s swapping with %s\n",
                        bridge_channel, ast_channel_name(bridge_channel->chan), dst_bridge->uniqueid,
                        ast_channel_name(bridge_channel->swap));
        } else {
                ast_debug(1, "Moving %p(%s) into bridge %s\n",
                        bridge_channel, ast_channel_name(bridge_channel->chan), dst_bridge->uniqueid);
        }

        orig_bridge = bridge_channel->bridge;
        was_in_bridge = bridge_channel->in_bridge;

        bridge_channel_internal_pull(bridge_channel);
        if (bridge_channel->state != BRIDGE_CHANNEL_STATE_WAIT) {
                /*
                 * The channel died as a result of being pulled.  Leave it
                 * pointing to the original bridge.
                 */
                bridge_reconfigured(orig_bridge, 0);
                return -1;
        }

        /* Point to new bridge.*/
        ao2_ref(orig_bridge, +1);/* Keep a ref in case the push fails. */
        bridge_channel_change_bridge(bridge_channel, dst_bridge);

        if (bridge_channel_internal_push(bridge_channel)) {
                /* Try to put the channel back into the original bridge. */
                if (attempt_recovery && was_in_bridge) {
                        /* Point back to original bridge. */
                        bridge_channel_change_bridge(bridge_channel, orig_bridge);

                        if (bridge_channel_internal_push(bridge_channel)) {
                                ast_bridge_channel_leave_bridge(bridge_channel,
                                        BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, bridge_channel->bridge->cause);
                                bridge_channel_settle_owed_events(orig_bridge, bridge_channel);
                        }
                } else {
                        ast_bridge_channel_leave_bridge(bridge_channel,
                                BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, bridge_channel->bridge->cause);
                        bridge_channel_settle_owed_events(orig_bridge, bridge_channel);
                }
                res = -1;
        } else {
                bridge_channel_settle_owed_events(orig_bridge, bridge_channel);
        }

        bridge_reconfigured(dst_bridge, !optimized);
        bridge_reconfigured(orig_bridge, !optimized);
        ao2_ref(orig_bridge, -1);
        return res;
}

/*!
 * \internal
 * \brief Move a channel from one bridge to another.
 * \since 12.0.0
 *
 * \param dst_bridge Destination bridge of bridge channel move.
 * \param src_bridge Source bridge of bridge channel move.
 * \param chan Channel to move.
 * \param swap Channel to replace in dst_bridge.
 * \param attempt_recovery TRUE if failure attempts to push channel back into original bridge.
 *
 * \note The dst_bridge and src_bridge are assumed already locked.
 *
 * \retval 0 on success.
 * \retval -1 on failure.
 */
static int bridge_move_locked(struct ast_bridge *dst_bridge, struct ast_bridge *src_bridge, struct ast_channel *chan, struct ast_channel *swap, int attempt_recovery)
{
        struct ast_bridge_channel *bridge_channel;

        if (dst_bridge->dissolved || src_bridge->dissolved) {
                ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, at least one bridge is dissolved.\n",
                        ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }
        if (ast_test_flag(&dst_bridge->feature_flags, AST_BRIDGE_FLAG_MASQUERADE_ONLY)
                || ast_test_flag(&src_bridge->feature_flags, AST_BRIDGE_FLAG_MASQUERADE_ONLY)) {
                ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, masquerade only.\n",
                        ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }
        if (dst_bridge->inhibit_merge || src_bridge->inhibit_merge) {
                ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, temporarily inhibited.\n",
                        ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }

        bridge_channel = bridge_find_channel(src_bridge, chan);
        if (!bridge_channel) {
                ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, channel not in bridge.\n",
                        ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }
        if (bridge_channel->state != BRIDGE_CHANNEL_STATE_WAIT) {
                ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, channel leaving bridge.\n",
                        ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }
        if (ast_test_flag(&bridge_channel->features->feature_flags,
                AST_BRIDGE_CHANNEL_FLAG_IMMOVABLE)) {
                ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, channel immovable.\n",
                        ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid);
                return -1;
        }

        if (swap) {
                struct ast_bridge_channel *bridge_channel_swap;

                bridge_channel_swap = bridge_find_channel(dst_bridge, swap);
                if (!bridge_channel_swap) {
                        ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, swap channel %s not in bridge.\n",
                                ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid,
                                ast_channel_name(swap));
                        return -1;
                }
                if (bridge_channel_swap->state != BRIDGE_CHANNEL_STATE_WAIT) {
                        ast_debug(1, "Can't move channel %s from bridge %s into bridge %s, swap channel %s leaving bridge.\n",
                                ast_channel_name(chan), src_bridge->uniqueid, dst_bridge->uniqueid,
                                ast_channel_name(swap));
                        return -1;
                }
        }

        bridge_channel->swap = swap;
        return bridge_do_move(dst_bridge, bridge_channel, attempt_recovery, 0);
}

int ast_bridge_move(struct ast_bridge *dst_bridge, struct ast_bridge *src_bridge, struct ast_channel *chan, struct ast_channel *swap, int attempt_recovery)
{
        int res;

        ast_bridge_lock_both(dst_bridge, src_bridge);
        res = bridge_move_locked(dst_bridge, src_bridge, chan, swap, attempt_recovery);
        ast_bridge_unlock(src_bridge);
        ast_bridge_unlock(dst_bridge);
        return res;
}

int ast_bridge_add_channel(struct ast_bridge *bridge, struct ast_channel *chan,
        struct ast_bridge_features *features, int play_tone, const char *xfersound)
{
        RAII_VAR(struct ast_bridge *, chan_bridge, NULL, ao2_cleanup);
        RAII_VAR(struct ast_channel *, yanked_chan, NULL, ao2_cleanup);

        ast_channel_lock(chan);
        chan_bridge = ast_channel_get_bridge(chan);
        ast_channel_unlock(chan);

        if (chan_bridge) {
                struct ast_bridge_channel *bridge_channel;

                ast_bridge_lock_both(bridge, chan_bridge);
                bridge_channel = bridge_find_channel(chan_bridge, chan);

                if (bridge_move_locked(bridge, chan_bridge, chan, NULL, 1)) {
                        ast_bridge_unlock(chan_bridge);
                        ast_bridge_unlock(bridge);
                        return -1;
                }

                /*
                 * bridge_move_locked() will implicitly ensure that
                 * bridge_channel is not NULL.
                 */
                ast_assert(bridge_channel != NULL);

                /*
                 * Additional checks if the channel we just stole dissolves the
                 * original bridge.
                 */
                bridge_dissolve_check_stolen(chan_bridge, bridge_channel);
                ast_bridge_unlock(chan_bridge);
                ast_bridge_unlock(bridge);

                /* The channel was in a bridge so it is not getting any new features. */
                ast_bridge_features_destroy(features);
        } else {
                /* Slightly less easy case. We need to yank channel A from
                 * where he currently is and impart him into our bridge.
                 */
                yanked_chan = ast_channel_yank(chan);
                if (!yanked_chan) {
                        ast_log(LOG_WARNING, "Could not gain control of channel %s\n", ast_channel_name(chan));
                        return -1;
                }
                if (ast_channel_state(yanked_chan) != AST_STATE_UP) {
                        ast_answer(yanked_chan);
                }
                ast_channel_ref(yanked_chan);
                if (ast_bridge_impart(bridge, yanked_chan, NULL, features, 1)) {
                        /* It is possible for us to yank a channel and have some other
                         * thread start a PBX on the channl after we yanked it. In particular,
                         * this can theoretically happen on the ;2 of a Local channel if we
                         * yank it prior to the ;1 being answered. Make sure that it isn't
                         * executing a PBX before hanging it up.
                         */
                        if (ast_channel_pbx(yanked_chan)) {
                                ast_channel_unref(yanked_chan);
                        } else {
                                ast_hangup(yanked_chan);
                        }
                        return -1;
                }
        }

        if (play_tone && !ast_strlen_zero(xfersound)) {
                struct ast_channel *play_chan = yanked_chan ?: chan;
                RAII_VAR(struct ast_bridge_channel *, play_bridge_channel, NULL, ao2_cleanup);

                ast_channel_lock(play_chan);
                play_bridge_channel = ast_channel_get_bridge_channel(play_chan);
                ast_channel_unlock(play_chan);

                if (!play_bridge_channel) {
                        ast_log(LOG_WARNING, "Unable to play tone for channel %s. No longer in a bridge.\n",
                                ast_channel_name(play_chan));
                } else {
                        ast_bridge_channel_queue_playfile(play_bridge_channel, NULL, xfersound, NULL);
                }
        }
        return 0;
}

static int bridge_allows_optimization(struct ast_bridge *bridge)
{
        return !(bridge->inhibit_merge
                || bridge->dissolved
                || ast_test_flag(&bridge->feature_flags, AST_BRIDGE_FLAG_MASQUERADE_ONLY));
}

/*!
 * \internal
 * \brief Lock the unreal channel stack for chan and prequalify it.
 * \since 12.0.0
 *
 * \param chan Unreal channel writing a frame into the channel driver.
 *
 * \note It is assumed that chan is already locked.
 *
 * \retval bridge on success with bridge and bridge_channel locked.
 * \retval NULL if cannot do optimization now.
 */
static struct ast_bridge *optimize_lock_chan_stack(struct ast_channel *chan)
{
        struct ast_bridge *bridge;
        struct ast_bridge_channel *bridge_channel;

        if (!AST_LIST_EMPTY(ast_channel_readq(chan))) {
                return NULL;
        }
        if (ast_test_flag(ast_channel_flags(chan), AST_FLAG_EMULATE_DTMF)) {
                return NULL;
        }
        if (ast_channel_has_audio_frame_or_monitor(chan)) {
                /* Channel has an active monitor, audiohook, or framehook. */
                return NULL;
        }
        bridge_channel = ast_channel_internal_bridge_channel(chan);
        if (!bridge_channel || ast_bridge_channel_trylock(bridge_channel)) {
                return NULL;
        }
        bridge = bridge_channel->bridge;
        if (bridge_channel->activity != BRIDGE_CHANNEL_THREAD_SIMPLE
                || bridge_channel->state != BRIDGE_CHANNEL_STATE_WAIT
                || ast_bridge_trylock(bridge)) {
                ast_bridge_channel_unlock(bridge_channel);
                return NULL;
        }
        if (!bridge_channel_internal_allows_optimization(bridge_channel) ||
                        !bridge_allows_optimization(bridge)) {
                ast_bridge_unlock(bridge);
                ast_bridge_channel_unlock(bridge_channel);
                return NULL;
        }
        return bridge;
}

/*!
 * \internal
 * \brief Lock the unreal channel stack for peer and prequalify it.
 * \since 12.0.0
 *
 * \param peer Other unreal channel in the pair.
 *
 * \retval bridge on success with bridge, bridge_channel, and peer locked.
 * \retval NULL if cannot do optimization now.
 */
static struct ast_bridge *optimize_lock_peer_stack(struct ast_channel *peer)
{
        struct ast_bridge *bridge;
        struct ast_bridge_channel *bridge_channel;

        if (ast_channel_trylock(peer)) {
                return NULL;
        }
        if (!AST_LIST_EMPTY(ast_channel_readq(peer))) {
                ast_channel_unlock(peer);
                return NULL;
        }
        if (ast_test_flag(ast_channel_flags(peer), AST_FLAG_EMULATE_DTMF)) {
                ast_channel_unlock(peer);
                return NULL;
        }
        if (ast_channel_has_audio_frame_or_monitor(peer)) {
                /* Peer has an active monitor, audiohook, or framehook. */
                ast_channel_unlock(peer);
                return NULL;
        }
        bridge_channel = ast_channel_internal_bridge_channel(peer);
        if (!bridge_channel || ast_bridge_channel_trylock(bridge_channel)) {
                ast_channel_unlock(peer);
                return NULL;
        }
        bridge = bridge_channel->bridge;
        if (bridge_channel->activity != BRIDGE_CHANNEL_THREAD_IDLE
                || bridge_channel->state != BRIDGE_CHANNEL_STATE_WAIT
                || ast_bridge_trylock(bridge)) {
                ast_bridge_channel_unlock(bridge_channel);
                ast_channel_unlock(peer);
                return NULL;
        }
        if (!bridge_allows_optimization(bridge) ||
                        !bridge_channel_internal_allows_optimization(bridge_channel)) {
                ast_bridge_unlock(bridge);
                ast_bridge_channel_unlock(bridge_channel);
                ast_channel_unlock(peer);
                return NULL;
        }
        return bridge;
}

/*!
 * \internal
 * \brief Indicates allowability of a swap optimization
 */
enum bridge_allow_swap {
        /*! Bridges cannot allow for a swap optimization to occur */
        SWAP_PROHIBITED,
        /*! Bridge swap optimization can occur into the chan_bridge */
        SWAP_TO_CHAN_BRIDGE,
        /*! Bridge swap optimization can occur into the peer_bridge */
        SWAP_TO_PEER_BRIDGE,
};

/*!
 * \internal
 * \brief Determine if two bridges allow for swap optimization to occur
 *
 * \param chan_bridge First bridge being tested
 * \param peer_bridge Second bridge being tested
 * \return Allowability of swap optimization
 */
static enum bridge_allow_swap bridges_allow_swap_optimization(struct ast_bridge *chan_bridge,
                struct ast_bridge *peer_bridge)
{
        int chan_priority;
        int peer_priority;

        if (!ast_test_flag(&chan_bridge->feature_flags,
                        AST_BRIDGE_FLAG_SWAP_INHIBIT_TO | AST_BRIDGE_FLAG_SWAP_INHIBIT_FROM |
                        AST_BRIDGE_FLAG_TRANSFER_BRIDGE_ONLY)
                && !ast_test_flag(&peer_bridge->feature_flags,
                        AST_BRIDGE_FLAG_SWAP_INHIBIT_TO | AST_BRIDGE_FLAG_SWAP_INHIBIT_FROM |
                        AST_BRIDGE_FLAG_TRANSFER_BRIDGE_ONLY)) {
                /*
                 * Can swap either way.  Swap to the higher priority merge
                 * bridge.
                 */
                chan_priority = chan_bridge->v_table->get_merge_priority(chan_bridge);
                peer_priority = peer_bridge->v_table->get_merge_priority(peer_bridge);
                if (chan_bridge->num_channels == 2
                        && chan_priority <= peer_priority) {
                        return SWAP_TO_PEER_BRIDGE;
                } else if (peer_bridge->num_channels == 2
                        && peer_priority <= chan_priority) {
                        return SWAP_TO_CHAN_BRIDGE;
                }
        } else if (chan_bridge->num_channels == 2
                && !ast_test_flag(&chan_bridge->feature_flags, AST_BRIDGE_FLAG_SWAP_INHIBIT_FROM | AST_BRIDGE_FLAG_TRANSFER_BRIDGE_ONLY)
                && !ast_test_flag(&peer_bridge->feature_flags, AST_BRIDGE_FLAG_SWAP_INHIBIT_TO)) {
                /* Can swap optimize only one way. */
                return SWAP_TO_PEER_BRIDGE;
        } else if (peer_bridge->num_channels == 2
                && !ast_test_flag(&peer_bridge->feature_flags, AST_BRIDGE_FLAG_SWAP_INHIBIT_FROM | AST_BRIDGE_FLAG_TRANSFER_BRIDGE_ONLY)
                && !ast_test_flag(&chan_bridge->feature_flags, AST_BRIDGE_FLAG_SWAP_INHIBIT_TO)) {
                /* Can swap optimize only one way. */
                return SWAP_TO_CHAN_BRIDGE;
        }

        return SWAP_PROHIBITED;
}

/*!
 * \internal
 * \brief Check and attempt to swap optimize out the unreal channels.
 * \since 12.0.0
 *
 * \param chan_bridge
 * \param chan_bridge_channel
 * \param peer_bridge
 * \param peer_bridge_channel
 * \param pvt Unreal data containing callbacks to call if the optimization actually
 * happens
 *
 * \retval 1 if unreal channels failed to optimize out.
 * \retval 0 if unreal channels were not optimized out.
 * \retval -1 if unreal channels were optimized out.
 */
static int try_swap_optimize_out(struct ast_bridge *chan_bridge,
        struct ast_bridge_channel *chan_bridge_channel, struct ast_bridge *peer_bridge,
        struct ast_bridge_channel *peer_bridge_channel,
        struct ast_unreal_pvt *pvt)
{
        struct ast_bridge *dst_bridge;
        struct ast_bridge_channel *dst_bridge_channel;
        struct ast_bridge_channel *src_bridge_channel;
        struct ast_bridge_channel *other;
        int res = 1;

        switch (bridges_allow_swap_optimization(chan_bridge, peer_bridge)) {
        case SWAP_TO_CHAN_BRIDGE:
                dst_bridge = chan_bridge;
                dst_bridge_channel = chan_bridge_channel;
                src_bridge_channel = peer_bridge_channel;
                break;
        case SWAP_TO_PEER_BRIDGE:
                dst_bridge = peer_bridge;
                dst_bridge_channel = peer_bridge_channel;
                src_bridge_channel = chan_bridge_channel;
                break;
        case SWAP_PROHIBITED:
        default:
                return 0;
        }

        other = ast_bridge_channel_peer(src_bridge_channel);
        if (other && other->state == BRIDGE_CHANNEL_STATE_WAIT) {
                unsigned int id = ast_atomic_fetchadd_int((int *) &optimization_id, +1);

                ast_verb(3, "Move-swap optimizing %s <-- %s.\n",
                        ast_channel_name(dst_bridge_channel->chan),
                        ast_channel_name(other->chan));

                if (pvt && !ast_test_flag(pvt, AST_UNREAL_OPTIMIZE_BEGUN) && pvt->callbacks
                                && pvt->callbacks->optimization_started) {
                        pvt->callbacks->optimization_started(pvt, other->chan,
                                        dst_bridge_channel->chan == pvt->owner ? AST_UNREAL_OWNER : AST_UNREAL_CHAN,
                                        id);
                        ast_set_flag(pvt, AST_UNREAL_OPTIMIZE_BEGUN);
                }
                other->swap = dst_bridge_channel->chan;
                if (!bridge_do_move(dst_bridge, other, 1, 1)) {
                        ast_bridge_channel_leave_bridge(src_bridge_channel,
                                BRIDGE_CHANNEL_STATE_END_NO_DISSOLVE, AST_CAUSE_NORMAL_CLEARING);
                        res = -1;
                }
                if (pvt && pvt->callbacks && pvt->callbacks->optimization_finished) {
                        pvt->callbacks->optimization_finished(pvt, res == 1, id);
                }
        }
        return res;
}

/*!
 * \internal
 * \brief Indicates allowability of a merge optimization
 */
enum bridge_allow_merge {
        /*! Bridge properties prohibit merge optimization */
        MERGE_PROHIBITED,
        /*! Merge optimization cannot occur because the source bridge has too few channels */
        MERGE_NOT_ENOUGH_CHANNELS,
        /*! Merge optimization cannot occur because multimix capability could not be requested */
        MERGE_NO_MULTIMIX,
        /*! Merge optimization allowed between bridges */
        MERGE_ALLOWED,
};

/*!
 * \internal
 * \brief Determines allowability of a merge optimization
 *
 * \note The merge output parameter is undefined if MERGE_PROHIBITED is returned. For success
 * and other failure returns, a merge direction was determined, and the parameter is safe to
 * access.
 *
 * \param chan_bridge First bridge being tested
 * \param peer_bridge Second bridge being tested
 * \param num_kick_channels The number of channels to remove from the bridges during merging
 * \param[out] merge Indicates the recommended direction for the bridge merge
 */
static enum bridge_allow_merge bridges_allow_merge_optimization(struct ast_bridge *chan_bridge,
                struct ast_bridge *peer_bridge, int num_kick_channels, struct merge_direction *merge)
{
        *merge = bridge_merge_determine_direction(chan_bridge, peer_bridge);
        if (!merge->dest) {
                return MERGE_PROHIBITED;
        }
        if (merge->src->num_channels < 2) {
                return MERGE_NOT_ENOUGH_CHANNELS;
        } else if ((2 + num_kick_channels) < merge->dest->num_channels + merge->src->num_channels
                && !(merge->dest->technology->capabilities & AST_BRIDGE_CAPABILITY_MULTIMIX)
                && (!ast_test_flag(&merge->dest->feature_flags, AST_BRIDGE_FLAG_SMART)
                        || !(merge->dest->allowed_capabilities & AST_BRIDGE_CAPABILITY_MULTIMIX))) {
                return MERGE_NO_MULTIMIX;
        }

        return MERGE_ALLOWED;
}

/*!
 * \internal
 * \brief Check and attempt to merge optimize out the unreal channels.
 * \since 12.0.0
 *
 * \param chan_bridge
 * \param chan_bridge_channel
 * \param peer_bridge
 * \param peer_bridge_channel
 * \param pvt Unreal data containing callbacks to call if the optimization actually
 * happens
 *
 * \retval 0 if unreal channels were not optimized out.
 * \retval -1 if unreal channels were optimized out.
 */
static int try_merge_optimize_out(struct ast_bridge *chan_bridge,
        struct ast_bridge_channel *chan_bridge_channel, struct ast_bridge *peer_bridge,
        struct ast_bridge_channel *peer_bridge_channel,
        struct ast_unreal_pvt *pvt)
{
        struct merge_direction merge;
        struct ast_bridge_channel *kick_me[] = {
                chan_bridge_channel,
                peer_bridge_channel,
        };
        unsigned int id;

        switch (bridges_allow_merge_optimization(chan_bridge, peer_bridge, ARRAY_LEN(kick_me), &merge)) {
        case MERGE_ALLOWED:
                break;
        case MERGE_PROHIBITED:
                return 0;
        case MERGE_NOT_ENOUGH_CHANNELS:
                ast_debug(4, "Can't optimize %s -- %s out, not enough channels in bridge %s.\n",
                        ast_channel_name(chan_bridge_channel->chan),
                        ast_channel_name(peer_bridge_channel->chan),
                        merge.src->uniqueid);
                return 0;
        case MERGE_NO_MULTIMIX:
                ast_debug(4, "Can't optimize %s -- %s out, multimix is needed and it cannot be acquired.\n",
                        ast_channel_name(chan_bridge_channel->chan),
                        ast_channel_name(peer_bridge_channel->chan));
                return 0;
        }

        ast_verb(3, "Merge optimizing %s -- %s out.\n",
                ast_channel_name(chan_bridge_channel->chan),
                ast_channel_name(peer_bridge_channel->chan));

        id = ast_atomic_fetchadd_int((int *) &optimization_id, +1);

        if (pvt && !ast_test_flag(pvt, AST_UNREAL_OPTIMIZE_BEGUN) && pvt->callbacks
                        && pvt->callbacks->optimization_started) {
                pvt->callbacks->optimization_started(pvt, NULL,
                                merge.dest == ast_channel_internal_bridge(pvt->owner) ? AST_UNREAL_OWNER : AST_UNREAL_CHAN,
                                id);
                ast_set_flag(pvt, AST_UNREAL_OPTIMIZE_BEGUN);
        }
        bridge_do_merge(merge.dest, merge.src, kick_me, ARRAY_LEN(kick_me), 1);
        if (pvt && pvt->callbacks && pvt->callbacks->optimization_finished) {
                pvt->callbacks->optimization_finished(pvt, 1, id);
        }

        return -1;
}

int ast_bridge_unreal_optimize_out(struct ast_channel *chan, struct ast_channel *peer, struct ast_unreal_pvt *pvt)
{
        struct ast_bridge *chan_bridge;
        struct ast_bridge *peer_bridge;
        struct ast_bridge_channel *chan_bridge_channel;
        struct ast_bridge_channel *peer_bridge_channel;
        int res = 0;

        chan_bridge = optimize_lock_chan_stack(chan);
        if (!chan_bridge) {
                return res;
        }
        chan_bridge_channel = ast_channel_internal_bridge_channel(chan);

        peer_bridge = optimize_lock_peer_stack(peer);
        if (peer_bridge) {
                peer_bridge_channel = ast_channel_internal_bridge_channel(peer);

                res = try_swap_optimize_out(chan_bridge, chan_bridge_channel,
                        peer_bridge, peer_bridge_channel, pvt);
                if (!res) {
                        res = try_merge_optimize_out(chan_bridge, chan_bridge_channel,
                                peer_bridge, peer_bridge_channel, pvt);
                } else if (0 < res) {
                        res = 0;
                }

                /* Release peer locks. */
                ast_bridge_unlock(peer_bridge);
                ast_bridge_channel_unlock(peer_bridge_channel);
                ast_channel_unlock(peer);
        }

        /* Release chan locks. */
        ast_bridge_unlock(chan_bridge);
        ast_bridge_channel_unlock(chan_bridge_channel);

        return res;
}

enum ast_bridge_optimization ast_bridges_allow_optimization(struct ast_bridge *chan_bridge,
                struct ast_bridge *peer_bridge)
{
        struct merge_direction merge;

        if (!bridge_allows_optimization(chan_bridge) || !bridge_allows_optimization(peer_bridge)) {
                return AST_BRIDGE_OPTIMIZE_PROHIBITED;
        }

        switch (bridges_allow_swap_optimization(chan_bridge, peer_bridge)) {
        case SWAP_TO_CHAN_BRIDGE:
                return AST_BRIDGE_OPTIMIZE_SWAP_TO_CHAN_BRIDGE;
        case SWAP_TO_PEER_BRIDGE:
                return AST_BRIDGE_OPTIMIZE_SWAP_TO_PEER_BRIDGE;
        case SWAP_PROHIBITED:
        default:
                break;
        }

        /* Two channels will be kicked from the bridges, the unreal;1 and unreal;2 channels */
        if (bridges_allow_merge_optimization(chan_bridge, peer_bridge, 2, &merge) != MERGE_ALLOWED) {
                return AST_BRIDGE_OPTIMIZE_PROHIBITED;
        }

        if (merge.dest == chan_bridge) {
                return AST_BRIDGE_OPTIMIZE_MERGE_TO_CHAN_BRIDGE;
        } else {
                return AST_BRIDGE_OPTIMIZE_MERGE_TO_PEER_BRIDGE;
        }
}

/*!
 * \internal
 * \brief Adjust the bridge merge inhibit request count.
 * \since 12.0.0
 *
 * \param bridge What to operate on.
 * \param request Inhibit request increment.
 *     (Positive to add requests.  Negative to remove requests.)
 *
 * \note This function assumes bridge is locked.
 *
 * \return Nothing
 */
void bridge_merge_inhibit_nolock(struct ast_bridge *bridge, int request)
{
        int new_request;

        new_request = bridge->inhibit_merge + request;
        ast_assert(0 <= new_request);
        bridge->inhibit_merge = new_request;
}

void ast_bridge_merge_inhibit(struct ast_bridge *bridge, int request)
{
        ast_bridge_lock(bridge);
        bridge_merge_inhibit_nolock(bridge, request);
        ast_bridge_unlock(bridge);
}

int ast_bridge_suspend(struct ast_bridge *bridge, struct ast_channel *chan)
{
        struct ast_bridge_channel *bridge_channel;
/* XXX ASTERISK-21271 the case of a disolved bridge while channel is suspended is not handled. */
/* XXX ASTERISK-21271 suspend/unsuspend needs to be rethought. The caller must block until it has successfully suspended the channel for temporary control. */
/* XXX ASTERISK-21271 external suspend/unsuspend needs to be eliminated. The channel may be playing a file at the time and stealing it then is not good. */

        ast_bridge_lock(bridge);

        if (!(bridge_channel = bridge_find_channel(bridge, chan))) {
                ast_bridge_unlock(bridge);
                return -1;
        }

        bridge_channel_internal_suspend_nolock(bridge_channel);

        ast_bridge_unlock(bridge);

        return 0;
}

int ast_bridge_unsuspend(struct ast_bridge *bridge, struct ast_channel *chan)
{
        struct ast_bridge_channel *bridge_channel;
/* XXX ASTERISK-21271 the case of a disolved bridge while channel is suspended is not handled. */

        ast_bridge_lock(bridge);

        if (!(bridge_channel = bridge_find_channel(bridge, chan))) {
                ast_bridge_unlock(bridge);
                return -1;
        }

        bridge_channel_internal_unsuspend_nolock(bridge_channel);

        ast_bridge_unlock(bridge);

        return 0;
}

void ast_bridge_technology_suspend(struct ast_bridge_technology *technology)
{
        technology->suspended = 1;
}

void ast_bridge_technology_unsuspend(struct ast_bridge_technology *technology)
{
        /*
         * XXX We may want the act of unsuspending a bridge technology
         * to prod all existing bridges to see if they should start
         * using it.
         */
        technology->suspended = 0;
}

int ast_bridge_features_register(enum ast_bridge_builtin_feature feature, ast_bridge_hook_callback callback, const char *dtmf)
{
        if (ARRAY_LEN(builtin_features_handlers) <= feature
                || builtin_features_handlers[feature]) {
                return -1;
        }

        if (!ast_strlen_zero(dtmf)) {
                ast_copy_string(builtin_features_dtmf[feature], dtmf, sizeof(builtin_features_dtmf[feature]));
        }

        builtin_features_handlers[feature] = callback;

        return 0;
}

int ast_bridge_features_unregister(enum ast_bridge_builtin_feature feature)
{
        if (ARRAY_LEN(builtin_features_handlers) <= feature
                || !builtin_features_handlers[feature]) {
                return -1;
        }

        builtin_features_handlers[feature] = NULL;

        return 0;
}

int ast_bridge_features_do(enum ast_bridge_builtin_feature feature, struct ast_bridge_channel *bridge_channel, void *hook_pvt)
{
        ast_bridge_hook_callback callback;

        if (ARRAY_LEN(builtin_features_handlers) <= feature) {
                return -1;
        }

        callback = builtin_features_handlers[feature];
        if (!callback) {
                return -1;
        }
        callback(bridge_channel, hook_pvt);

        return 0;
}

int ast_bridge_interval_register(enum ast_bridge_builtin_interval interval, ast_bridge_builtin_set_limits_fn callback)
{
        if (ARRAY_LEN(builtin_interval_handlers) <= interval
                || builtin_interval_handlers[interval]) {
                return -1;
        }

        builtin_interval_handlers[interval] = callback;

        return 0;
}

int ast_bridge_interval_unregister(enum ast_bridge_builtin_interval interval)
{
        if (ARRAY_LEN(builtin_interval_handlers) <= interval
                || !builtin_interval_handlers[interval]) {
                return -1;
        }

        builtin_interval_handlers[interval] = NULL;

        return 0;

}

/*!
 * \internal
 * \brief Bridge hook destructor.
 * \since 12.0.0
 *
 * \param vhook Object to destroy.
 *
 * \return Nothing
 */
static void bridge_hook_destroy(void *vhook)
{
        struct ast_bridge_hook *hook = vhook;

        if (hook->destructor) {
                hook->destructor(hook->hook_pvt);
        }
}

/*!
 * \internal
 * \brief Allocate and setup a generic bridge hook.
 * \since 12.0.0
 *
 * \param size How big an object to allocate.
 * \param callback Function to execute upon activation
 * \param hook_pvt Unique data
 * \param destructor Optional destructor callback for hook_pvt data
 * \param remove_flags Dictates what situations the hook should be removed.
 *
 * \retval hook on success.
 * \retval NULL on error.
 */
static struct ast_bridge_hook *bridge_hook_generic(size_t size,
        ast_bridge_hook_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        struct ast_bridge_hook *hook;

        /* Allocate new hook and setup it's basic variables */
        hook = ao2_alloc_options(size, bridge_hook_destroy, AO2_ALLOC_OPT_LOCK_NOLOCK);
        if (hook) {
                hook->callback = callback;
                hook->destructor = destructor;
                hook->hook_pvt = hook_pvt;
                ast_set_flag(&hook->remove_flags, remove_flags);
        }

        return hook;
}

int ast_bridge_dtmf_hook(struct ast_bridge_features *features,
        const char *dtmf,
        ast_bridge_hook_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        struct ast_bridge_hook_dtmf *hook;
        int res;

        /* Allocate new hook and setup it's various variables */
        hook = (struct ast_bridge_hook_dtmf *) bridge_hook_generic(sizeof(*hook), callback,
                hook_pvt, destructor, remove_flags);
        if (!hook) {
                return -1;
        }
        hook->generic.type = AST_BRIDGE_HOOK_TYPE_DTMF;
        ast_copy_string(hook->dtmf.code, dtmf, sizeof(hook->dtmf.code));

        /* Once done we put it in the container. */
        res = ao2_link(features->dtmf_hooks, hook) ? 0 : -1;
        if (res) {
                /*
                 * Could not link the hook into the container.
                 *
                 * Remove the hook_pvt destructor call from the hook since we
                 * are returning failure to install the hook.
                 */
                hook->generic.destructor = NULL;
        }
        ao2_ref(hook, -1);

        return res;
}

/*!
 * \internal
 * \brief Attach an other hook to a bridge features structure
 *
 * \param features Bridge features structure
 * \param callback Function to execute upon activation
 * \param hook_pvt Unique data
 * \param destructor Optional destructor callback for hook_pvt data
 * \param remove_flags Dictates what situations the hook should be removed.
 * \param type What type of hook is being attached.
 *
 * \retval 0 on success
 * \retval -1 on failure (The caller must cleanup any hook_pvt resources.)
 */
static int bridge_other_hook(struct ast_bridge_features *features,
        ast_bridge_hook_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags,
        enum ast_bridge_hook_type type)
{
        struct ast_bridge_hook *hook;
        int res;

        /* Allocate new hook and setup it's various variables */
        hook = bridge_hook_generic(sizeof(*hook), callback, hook_pvt, destructor,
                remove_flags);
        if (!hook) {
                return -1;
        }
        hook->type = type;

        /* Once done we put it in the container. */
        res = ao2_link(features->other_hooks, hook) ? 0 : -1;
        if (res) {
                /*
                 * Could not link the hook into the container.
                 *
                 * Remove the hook_pvt destructor call from the hook since we
                 * are returning failure to install the hook.
                 */
                hook->destructor = NULL;
        }
        ao2_ref(hook, -1);

        return res;
}

int ast_bridge_hangup_hook(struct ast_bridge_features *features,
        ast_bridge_hook_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        return bridge_other_hook(features, callback, hook_pvt, destructor, remove_flags,
                AST_BRIDGE_HOOK_TYPE_HANGUP);
}

int ast_bridge_join_hook(struct ast_bridge_features *features,
        ast_bridge_hook_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        return bridge_other_hook(features, callback, hook_pvt, destructor, remove_flags,
                AST_BRIDGE_HOOK_TYPE_JOIN);
}

int ast_bridge_leave_hook(struct ast_bridge_features *features,
        ast_bridge_hook_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        return bridge_other_hook(features, callback, hook_pvt, destructor, remove_flags,
                AST_BRIDGE_HOOK_TYPE_LEAVE);
}

int ast_bridge_talk_detector_hook(struct ast_bridge_features *features,
        ast_bridge_talking_indicate_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        ast_bridge_hook_callback hook_cb = (ast_bridge_hook_callback) callback;

        return bridge_other_hook(features, hook_cb, hook_pvt, destructor, remove_flags,
                AST_BRIDGE_HOOK_TYPE_TALK);
}

int ast_bridge_interval_hook(struct ast_bridge_features *features,
        enum ast_bridge_hook_timer_option flags,
        unsigned int interval,
        ast_bridge_hook_callback callback,
        void *hook_pvt,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        struct ast_bridge_hook_timer *hook;
        int res;

        if (!features ||!interval || !callback) {
                return -1;
        }

        /* Allocate new hook and setup it's various variables */
        hook = (struct ast_bridge_hook_timer *) bridge_hook_generic(sizeof(*hook), callback,
                hook_pvt, destructor, remove_flags);
        if (!hook) {
                return -1;
        }
        hook->generic.type = AST_BRIDGE_HOOK_TYPE_TIMER;
        hook->timer.interval = interval;
        hook->timer.trip_time = ast_tvadd(ast_tvnow(), ast_samp2tv(interval, 1000));
        hook->timer.seqno = ast_atomic_fetchadd_int((int *) &features->interval_sequence, +1);
        hook->timer.flags = flags;

        ast_debug(1, "Putting interval hook %p with interval %u in the heap on features %p\n",
                hook, hook->timer.interval, features);
        ast_heap_wrlock(features->interval_hooks);
        res = ast_heap_push(features->interval_hooks, hook);
        ast_heap_unlock(features->interval_hooks);
        if (res) {
                /*
                 * Could not push the hook into the heap
                 *
                 * Remove the hook_pvt destructor call from the hook since we
                 * are returning failure to install the hook.
                 */
                hook->generic.destructor = NULL;
                ao2_ref(hook, -1);
        }

        return res ? -1 : 0;
}

int ast_bridge_features_enable(struct ast_bridge_features *features,
        enum ast_bridge_builtin_feature feature,
        const char *dtmf,
        void *config,
        ast_bridge_hook_pvt_destructor destructor,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        if (ARRAY_LEN(builtin_features_handlers) <= feature
                || !builtin_features_handlers[feature]) {
                return -1;
        }

        /* If no alternate DTMF stream was provided use the default one */
        if (ast_strlen_zero(dtmf)) {
                dtmf = builtin_features_dtmf[feature];
                /* If no DTMF is still available (ie: it has been disabled) then error out now */
                if (ast_strlen_zero(dtmf)) {
                        ast_debug(1, "Failed to enable built in feature %d on %p, no DTMF string is available for it.\n",
                                feature, features);
                        return -1;
                }
        }

        /*
         * The rest is basically pretty easy.  We create another hook
         * using the built in feature's DTMF callback.  Easy as pie.
         */
        return ast_bridge_dtmf_hook(features, dtmf, builtin_features_handlers[feature],
                config, destructor, remove_flags);
}

int ast_bridge_features_limits_construct(struct ast_bridge_features_limits *limits)
{
        memset(limits, 0, sizeof(*limits));

        if (ast_string_field_init(limits, 256)) {
                return -1;
        }

        return 0;
}

void ast_bridge_features_limits_destroy(struct ast_bridge_features_limits *limits)
{
        ast_string_field_free_memory(limits);
}

int ast_bridge_features_set_limits(struct ast_bridge_features *features,
        struct ast_bridge_features_limits *limits,
        enum ast_bridge_hook_remove_flags remove_flags)
{
        if (builtin_interval_handlers[AST_BRIDGE_BUILTIN_INTERVAL_LIMITS]) {
                ast_bridge_builtin_set_limits_fn callback;

                callback = builtin_interval_handlers[AST_BRIDGE_BUILTIN_INTERVAL_LIMITS];
                return callback(features, limits, remove_flags);
        }

        ast_log(LOG_ERROR, "Attempted to set limits without an AST_BRIDGE_BUILTIN_INTERVAL_LIMITS callback registered.\n");
        return -1;
}

void ast_bridge_features_set_flag(struct ast_bridge_features *features, unsigned int flag)
{
        ast_set_flag(&features->feature_flags, flag);
        features->usable = 1;
}

/*!
 * \internal
 * \brief ao2 object match hooks with appropriate remove_flags.
 * \since 12.0.0
 *
 * \param obj Feature hook object.
 * \param arg Removal flags
 * \param flags Not used
 *
 * \retval CMP_MATCH if hook's remove_flags match the removal flags set.
 * \retval 0 if not match.
 */
static int hook_remove_match(void *obj, void *arg, int flags)
{
        struct ast_bridge_hook *hook = obj;
        enum ast_bridge_hook_remove_flags *remove_flags = arg;

        if (ast_test_flag(&hook->remove_flags, *remove_flags)) {
                return CMP_MATCH;
        } else {
                return 0;
        }
}

/*!
 * \internal
 * \brief Remove all hooks with appropriate remove_flags in the container.
 * \since 12.0.0
 *
 * \param hooks Hooks container to work on.
 * \param remove_flags Determinator for whether hook is removed
 *
 * \return Nothing
 */
static void hooks_remove_container(struct ao2_container *hooks, enum ast_bridge_hook_remove_flags remove_flags)
{
        ao2_callback(hooks, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE,
                hook_remove_match, &remove_flags);
}

/*!
 * \internal
 * \brief Remove all hooks in the heap with appropriate remove_flags set.
 * \since 12.0.0
 *
 * \param hooks Hooks heap to work on.
 * \param remove_flags Determinator for whether hook is removed
 *
 * \return Nothing
 */
static void hooks_remove_heap(struct ast_heap *hooks, enum ast_bridge_hook_remove_flags remove_flags)
{
        struct ast_bridge_hook *hook;
        int changed;

        ast_heap_wrlock(hooks);
        do {
                int idx;

                changed = 0;
                for (idx = ast_heap_size(hooks); idx; --idx) {
                        hook = ast_heap_peek(hooks, idx);
                        if (ast_test_flag(&hook->remove_flags, remove_flags)) {
                                ast_heap_remove(hooks, hook);
                                ao2_ref(hook, -1);
                                changed = 1;
                        }
                }
        } while (changed);
        ast_heap_unlock(hooks);
}

void ast_bridge_features_remove(struct ast_bridge_features *features, enum ast_bridge_hook_remove_flags remove_flags)
{
        hooks_remove_container(features->dtmf_hooks, remove_flags);
        hooks_remove_container(features->other_hooks, remove_flags);
        hooks_remove_heap(features->interval_hooks, remove_flags);
}

static int interval_hook_time_cmp(void *a, void *b)
{
        struct ast_bridge_hook_timer *hook_a = a;
        struct ast_bridge_hook_timer *hook_b = b;
        int cmp;

        cmp = ast_tvcmp(hook_b->timer.trip_time, hook_a->timer.trip_time);
        if (cmp) {
                return cmp;
        }

        cmp = hook_b->timer.seqno - hook_a->timer.seqno;
        return cmp;
}

/*!
 * \internal
 * \brief DTMF hook container sort comparison function.
 * \since 12.0.0
 *
 * \param obj_left pointer to the (user-defined part) of an object.
 * \param obj_right pointer to the (user-defined part) of an object.
 * \param flags flags from ao2_callback()
 *   OBJ_POINTER - if set, 'obj_right', is an object.
 *   OBJ_KEY - if set, 'obj_right', is a search key item that is not an object.
 *   OBJ_PARTIAL_KEY - if set, 'obj_right', is a partial search key item that is not an object.
 *
 * \retval <0 if obj_left < obj_right
 * \retval =0 if obj_left == obj_right
 * \retval >0 if obj_left > obj_right
 */
static int bridge_dtmf_hook_sort(const void *obj_left, const void *obj_right, int flags)
{
        const struct ast_bridge_hook_dtmf *hook_left = obj_left;
        const struct ast_bridge_hook_dtmf *hook_right = obj_right;
        const char *right_key = obj_right;
        int cmp;

        switch (flags & (OBJ_POINTER | OBJ_KEY | OBJ_PARTIAL_KEY)) {
        default:
        case OBJ_POINTER:
                right_key = hook_right->dtmf.code;
                /* Fall through */
        case OBJ_KEY:
                cmp = strcasecmp(hook_left->dtmf.code, right_key);
                break;
        case OBJ_PARTIAL_KEY:
                cmp = strncasecmp(hook_left->dtmf.code, right_key, strlen(right_key));
                break;
        }
        return cmp;
}

/* XXX ASTERISK-21271 make ast_bridge_features_init() static when make ast_bridge_join() requires features to be allocated. */
int ast_bridge_features_init(struct ast_bridge_features *features)
{
        /* Zero out the structure */
        memset(features, 0, sizeof(*features));

        /* Initialize the DTMF hooks container */
        features->dtmf_hooks = ao2_container_alloc_list(AO2_ALLOC_OPT_LOCK_MUTEX,
                AO2_CONTAINER_ALLOC_OPT_DUPS_REPLACE, bridge_dtmf_hook_sort, NULL);
        if (!features->dtmf_hooks) {
                return -1;
        }

        /* Initialize the miscellaneous other hooks container */
        features->other_hooks = ao2_container_alloc_list(AO2_ALLOC_OPT_LOCK_MUTEX, 0, NULL,
                NULL);
        if (!features->other_hooks) {
                return -1;
        }

        /* Initialize the interval hooks heap */
        features->interval_hooks = ast_heap_create(8, interval_hook_time_cmp,
                offsetof(struct ast_bridge_hook_timer, timer.heap_index));
        if (!features->interval_hooks) {
                return -1;
        }

        features->dtmf_passthrough = 1;

        return 0;
}

/* XXX ASTERISK-21271 make ast_bridge_features_cleanup() static when make ast_bridge_join() requires features to be allocated. */
void ast_bridge_features_cleanup(struct ast_bridge_features *features)
{
        struct ast_bridge_hook_timer *hook;

        /* Destroy the interval hooks heap. */
        if (features->interval_hooks) {
                while ((hook = ast_heap_pop(features->interval_hooks))) {
                        ao2_ref(hook, -1);
                }
                features->interval_hooks = ast_heap_destroy(features->interval_hooks);
        }

        /* Destroy the miscellaneous other hooks container. */
        ao2_cleanup(features->other_hooks);
        features->other_hooks = NULL;

        /* Destroy the DTMF hooks container. */
        ao2_cleanup(features->dtmf_hooks);
        features->dtmf_hooks = NULL;
}

void ast_bridge_features_destroy(struct ast_bridge_features *features)
{
        if (!features) {
                return;
        }
        ast_bridge_features_cleanup(features);
        ast_free(features);
}

struct ast_bridge_features *ast_bridge_features_new(void)
{
        struct ast_bridge_features *features;

        features = ast_malloc(sizeof(*features));
        if (features) {
                if (ast_bridge_features_init(features)) {
                        ast_bridge_features_destroy(features);
                        features = NULL;
                }
        }

        return features;
}

void ast_bridge_set_mixing_interval(struct ast_bridge *bridge, unsigned int mixing_interval)
{
        ast_bridge_lock(bridge);
        bridge->softmix.internal_mixing_interval = mixing_interval;
        ast_bridge_unlock(bridge);
}

void ast_bridge_set_internal_sample_rate(struct ast_bridge *bridge, unsigned int sample_rate)
{
        ast_bridge_lock(bridge);
        bridge->softmix.internal_sample_rate = sample_rate;
        ast_bridge_unlock(bridge);
}

static void cleanup_video_mode(struct ast_bridge *bridge)
{
        switch (bridge->softmix.video_mode.mode) {
        case AST_BRIDGE_VIDEO_MODE_NONE:
                break;
        case AST_BRIDGE_VIDEO_MODE_SINGLE_SRC:
                if (bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc) {
                        ast_channel_unref(bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc);
                }
                break;
        case AST_BRIDGE_VIDEO_MODE_TALKER_SRC:
                if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc) {
                        ast_channel_unref(bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc);
                }
                if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc) {
                        ast_channel_unref(bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc);
                }
        }
        memset(&bridge->softmix.video_mode, 0, sizeof(bridge->softmix.video_mode));
}

void ast_bridge_set_single_src_video_mode(struct ast_bridge *bridge, struct ast_channel *video_src_chan)
{
        ast_bridge_lock(bridge);
        cleanup_video_mode(bridge);
        bridge->softmix.video_mode.mode = AST_BRIDGE_VIDEO_MODE_SINGLE_SRC;
        bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc = ast_channel_ref(video_src_chan);
        ast_test_suite_event_notify("BRIDGE_VIDEO_MODE", "Message: video mode set to single source\r\nVideo Mode: %d\r\nVideo Channel: %s",
                bridge->softmix.video_mode.mode, ast_channel_name(video_src_chan));
        ast_indicate(video_src_chan, AST_CONTROL_VIDUPDATE);
        ast_bridge_unlock(bridge);
}

void ast_bridge_set_talker_src_video_mode(struct ast_bridge *bridge)
{
        ast_bridge_lock(bridge);
        cleanup_video_mode(bridge);
        bridge->softmix.video_mode.mode = AST_BRIDGE_VIDEO_MODE_TALKER_SRC;
        ast_test_suite_event_notify("BRIDGE_VIDEO_MODE", "Message: video mode set to talker source\r\nVideo Mode: %d",
                bridge->softmix.video_mode.mode);
        ast_bridge_unlock(bridge);
}

void ast_bridge_update_talker_src_video_mode(struct ast_bridge *bridge, struct ast_channel *chan, int talker_energy, int is_keyframe)
{
        struct ast_bridge_video_talker_src_data *data;

        /* If the channel doesn't support video, we don't care about it */
        if (!ast_format_cap_has_type(ast_channel_nativeformats(chan), AST_FORMAT_TYPE_VIDEO)) {
                return;
        }

        ast_bridge_lock(bridge);
        data = &bridge->softmix.video_mode.mode_data.talker_src_data;

        if (data->chan_vsrc == chan) {
                data->average_talking_energy = talker_energy;
        } else if ((data->average_talking_energy < talker_energy) && is_keyframe) {
                if (data->chan_old_vsrc) {
                        ast_channel_unref(data->chan_old_vsrc);
                }
                if (data->chan_vsrc) {
                        data->chan_old_vsrc = data->chan_vsrc;
                        ast_indicate(data->chan_old_vsrc, AST_CONTROL_VIDUPDATE);
                }
                data->chan_vsrc = ast_channel_ref(chan);
                data->average_talking_energy = talker_energy;
                ast_test_suite_event_notify("BRIDGE_VIDEO_SRC", "Message: video source updated\r\nVideo Channel: %s", ast_channel_name(data->chan_vsrc));
                ast_indicate(data->chan_vsrc, AST_CONTROL_VIDUPDATE);
        } else if ((data->average_talking_energy < talker_energy) && !is_keyframe) {
                ast_indicate(chan, AST_CONTROL_VIDUPDATE);
        } else if (!data->chan_vsrc && is_keyframe) {
                data->chan_vsrc = ast_channel_ref(chan);
                data->average_talking_energy = talker_energy;
                ast_test_suite_event_notify("BRIDGE_VIDEO_SRC", "Message: video source updated\r\nVideo Channel: %s", ast_channel_name(data->chan_vsrc));
                ast_indicate(chan, AST_CONTROL_VIDUPDATE);
        } else if (!data->chan_old_vsrc && is_keyframe) {
                data->chan_old_vsrc = ast_channel_ref(chan);
                ast_indicate(chan, AST_CONTROL_VIDUPDATE);
        }
        ast_bridge_unlock(bridge);
}

int ast_bridge_number_video_src(struct ast_bridge *bridge)
{
        int res = 0;

        ast_bridge_lock(bridge);
        switch (bridge->softmix.video_mode.mode) {
        case AST_BRIDGE_VIDEO_MODE_NONE:
                break;
        case AST_BRIDGE_VIDEO_MODE_SINGLE_SRC:
                if (bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc) {
                        res = 1;
                }
                break;
        case AST_BRIDGE_VIDEO_MODE_TALKER_SRC:
                if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc) {
                        res++;
                }
                if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc) {
                        res++;
                }
        }
        ast_bridge_unlock(bridge);
        return res;
}

int ast_bridge_is_video_src(struct ast_bridge *bridge, struct ast_channel *chan)
{
        int res = 0;

        ast_bridge_lock(bridge);
        switch (bridge->softmix.video_mode.mode) {
        case AST_BRIDGE_VIDEO_MODE_NONE:
                break;
        case AST_BRIDGE_VIDEO_MODE_SINGLE_SRC:
                if (bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc == chan) {
                        res = 1;
                }
                break;
        case AST_BRIDGE_VIDEO_MODE_TALKER_SRC:
                if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc == chan) {
                        res = 1;
                } else if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc == chan) {
                        res = 2;
                }

        }
        ast_bridge_unlock(bridge);
        return res;
}

void ast_bridge_remove_video_src(struct ast_bridge *bridge, struct ast_channel *chan)
{
        ast_bridge_lock(bridge);
        switch (bridge->softmix.video_mode.mode) {
        case AST_BRIDGE_VIDEO_MODE_NONE:
                break;
        case AST_BRIDGE_VIDEO_MODE_SINGLE_SRC:
                if (bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc == chan) {
                        if (bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc) {
                                ast_channel_unref(bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc);
                        }
                        bridge->softmix.video_mode.mode_data.single_src_data.chan_vsrc = NULL;
                }
                break;
        case AST_BRIDGE_VIDEO_MODE_TALKER_SRC:
                if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc == chan) {
                        if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc) {
                                ast_channel_unref(bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc);
                        }
                        bridge->softmix.video_mode.mode_data.talker_src_data.chan_vsrc = NULL;
                        bridge->softmix.video_mode.mode_data.talker_src_data.average_talking_energy = 0;
                }
                if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc == chan) {
                        if (bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc) {
                                ast_channel_unref(bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc);
                        }
                        bridge->softmix.video_mode.mode_data.talker_src_data.chan_old_vsrc = NULL;
                }
        }
        ast_bridge_unlock(bridge);
}

static int channel_hash(const void *obj, int flags)
{
        const struct ast_channel *chan = obj;
        const char *name = obj;
        int hash;

        switch (flags & (OBJ_POINTER | OBJ_KEY | OBJ_PARTIAL_KEY)) {
        default:
        case OBJ_POINTER:
                name = ast_channel_name(chan);
                /* Fall through */
        case OBJ_KEY:
                hash = ast_str_hash(name);
                break;
        case OBJ_PARTIAL_KEY:
                /* Should never happen in hash callback. */
                ast_assert(0);
                hash = 0;
                break;
        }
        return hash;
}

static int channel_cmp(void *obj, void *arg, int flags)
{
        const struct ast_channel *left = obj;
        const struct ast_channel *right = arg;
        const char *right_name = arg;
        int cmp;

        switch (flags & (OBJ_POINTER | OBJ_KEY | OBJ_PARTIAL_KEY)) {
        default:
        case OBJ_POINTER:
                right_name = ast_channel_name(right);
                /* Fall through */
        case OBJ_KEY:
                cmp = strcmp(ast_channel_name(left), right_name);
                break;
        case OBJ_PARTIAL_KEY:
                cmp = strncmp(ast_channel_name(left), right_name, strlen(right_name));
                break;
        }
        return cmp ? 0 : CMP_MATCH;
}

struct ao2_container *ast_bridge_peers_nolock(struct ast_bridge *bridge)
{
        struct ao2_container *channels;
        struct ast_bridge_channel *iter;

        channels = ao2_container_alloc_options(AO2_ALLOC_OPT_LOCK_NOLOCK,
                13, channel_hash, channel_cmp);
        if (!channels) {
                return NULL;
        }

        AST_LIST_TRAVERSE(&bridge->channels, iter, entry) {
                ao2_link(channels, iter->chan);
        }

        return channels;
}

struct ao2_container *ast_bridge_peers(struct ast_bridge *bridge)
{
        struct ao2_container *channels;

        ast_bridge_lock(bridge);
        channels = ast_bridge_peers_nolock(bridge);
        ast_bridge_unlock(bridge);

        return channels;
}

struct ast_channel *ast_bridge_peer_nolock(struct ast_bridge *bridge, struct ast_channel *chan)
{
        struct ast_channel *peer = NULL;
        struct ast_bridge_channel *iter;

        /* Asking for the peer channel only makes sense on a two-party bridge. */
        if (bridge->num_channels == 2
                && bridge->technology->capabilities
                        & (AST_BRIDGE_CAPABILITY_NATIVE | AST_BRIDGE_CAPABILITY_1TO1MIX)) {
                int in_bridge = 0;

                AST_LIST_TRAVERSE(&bridge->channels, iter, entry) {
                        if (iter->chan != chan) {
                                peer = iter->chan;
                        } else {
                                in_bridge = 1;
                        }
                }
                if (in_bridge && peer) {
                        ast_channel_ref(peer);
                } else {
                        peer = NULL;
                }
        }

        return peer;
}

struct ast_channel *ast_bridge_peer(struct ast_bridge *bridge, struct ast_channel *chan)
{
        struct ast_channel *peer;

        ast_bridge_lock(bridge);
        peer = ast_bridge_peer_nolock(bridge, chan);
        ast_bridge_unlock(bridge);

        return peer;
}

/*!
 * \internal
 * \brief Transfer an entire bridge to a specific destination.
 *
 * This creates a local channel to dial out and swaps the called local channel
 * with the transferer channel. By doing so, all participants in the bridge are
 * connected to the specified destination.
 *
 * While this means of transferring would work for both two-party and multi-party
 * bridges, this method is only used for multi-party bridges since this method would
 * be less efficient for two-party bridges.
 *
 * \param transferer The channel performing a transfer
 * \param bridge The bridge where the transfer is being performed
 * \param exten The destination extension for the blind transfer
 * \param context The destination context for the blind transfer
 * \param hook Framehook to attach to local channel
 * \return The success or failure of the operation
 */
static enum ast_transfer_result blind_transfer_bridge(struct ast_channel *transferer,
                struct ast_bridge *bridge, const char *exten, const char *context,
                transfer_channel_cb new_channel_cb, void *user_data)
{
        struct ast_channel *local;
        char chan_name[AST_MAX_EXTENSION + AST_MAX_CONTEXT + 2];
        int cause;

        snprintf(chan_name, sizeof(chan_name), "%s@%s", exten, context);
        local = ast_request("Local", ast_channel_nativeformats(transferer), transferer,
                        chan_name, &cause);
        if (!local) {
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        if (new_channel_cb) {
                new_channel_cb(local, user_data, AST_BRIDGE_TRANSFER_MULTI_PARTY);
        }

        if (ast_call(local, chan_name, 0)) {
                ast_hangup(local);
                return AST_BRIDGE_TRANSFER_FAIL;
        }
        if (ast_bridge_impart(bridge, local, transferer, NULL, 1)) {
                ast_hangup(local);
                return AST_BRIDGE_TRANSFER_FAIL;
        }
        return AST_BRIDGE_TRANSFER_SUCCESS;
}

/*!
 * \internal
 * \brief Base data to publish for stasis attended transfer messages
 */
struct stasis_attended_transfer_publish_data {
        /* The bridge between the transferer and transferee, and the transferer channel in this bridge */
        struct ast_bridge_channel_pair to_transferee;
        /* The bridge between the transferer and transfer target, and the transferer channel in this bridge */
        struct ast_bridge_channel_pair to_transfer_target;
};

static void stasis_publish_data_cleanup(struct stasis_attended_transfer_publish_data *publication)
{
        ast_channel_unref(publication->to_transferee.channel);
        ast_channel_unref(publication->to_transfer_target.channel);
        ao2_cleanup(publication->to_transferee.bridge);
        ao2_cleanup(publication->to_transfer_target.bridge);
}

/*!
 * \internal
 * \brief Set up base data for an attended transfer stasis publication
 *
 * \param to_transferee The original transferer channel, which may be bridged to a transferee
 * \param to_transferee_bridge The bridge that to_transferee is in.
 * \param to_transfer_target The second transferer channel, which may be bridged to a transfer target
 * \param to_target_bridge The bridge that to_transfer_target_is in.
 * \param[out] publication A structure to hold the other parameters
 */
static void stasis_publish_data_init(struct ast_channel *to_transferee,
                struct ast_bridge *to_transferee_bridge, struct ast_channel *to_transfer_target,
                struct ast_bridge *to_target_bridge,
                struct stasis_attended_transfer_publish_data *publication)
{
        memset(publication, 0, sizeof(*publication));
        publication->to_transferee.channel = ast_channel_ref(to_transferee);
        if (to_transferee_bridge) {
                ao2_ref(to_transferee_bridge, +1);
                publication->to_transferee.bridge = to_transferee_bridge;
        }

        publication->to_transfer_target.channel = ast_channel_ref(to_transfer_target);
        if (to_target_bridge) {
                ao2_ref(to_target_bridge, +1);
                publication->to_transfer_target.bridge = to_target_bridge;
        }
}

/*
 * \internal
 * \brief Publish a stasis attended transfer resulting in a bridge merge
 *
 * \param publication Base data about the attended transfer
 * \param final_bridge The surviving bridge of the attended transfer
 */
static void publish_attended_transfer_bridge_merge(struct stasis_attended_transfer_publish_data *publication,
                struct ast_bridge *final_bridge)
{
        ast_bridge_publish_attended_transfer_bridge_merge(1, AST_BRIDGE_TRANSFER_SUCCESS,
                        &publication->to_transferee, &publication->to_transfer_target, final_bridge);
}

/*
 * \internal
 * \brief Publish a stasis attended transfer to an application
 *
 * \param publication Base data about the attended transfer
 * \param app The app that is running at the conclusion of the transfer
 */
static void publish_attended_transfer_app(struct stasis_attended_transfer_publish_data *publication,
                const char *app)
{
        ast_bridge_publish_attended_transfer_app(1, AST_BRIDGE_TRANSFER_SUCCESS,
                        &publication->to_transferee, &publication->to_transfer_target, app);
}

/*
 * \internal
 * \brief Publish a stasis attended transfer showing a link between bridges
 *
 * \param publication Base data about the attended transfer
 * \param local_channel1 Local channel in the original bridge
 * \param local_channel2 Local channel in the second bridge
 */
static void publish_attended_transfer_link(struct stasis_attended_transfer_publish_data *publication,
                struct ast_channel *local_channel1, struct ast_channel *local_channel2)
{
        struct ast_channel *locals[2] = { local_channel1, local_channel2 };

        ast_bridge_publish_attended_transfer_link(1, AST_BRIDGE_TRANSFER_SUCCESS,
                        &publication->to_transferee, &publication->to_transfer_target, locals);
}

/*
 * \internal
 * \brief Publish a stasis attended transfer failure
 *
 * \param publication Base data about the attended transfer
 * \param result The transfer result
 */
static void publish_attended_transfer_fail(struct stasis_attended_transfer_publish_data *publication,
                enum ast_transfer_result result)
{
        ast_bridge_publish_attended_transfer_fail(1, result, &publication->to_transferee,
                        &publication->to_transfer_target);
}

/*!
 * \brief Perform an attended transfer of a bridge
 *
 * This performs an attended transfer of an entire bridge to a target.
 * The target varies, depending on what bridges exist during the transfer
 * attempt.
 *
 * If two bridges exist, then a local channel is created to link the two
 * bridges together.
 *
 * If only one bridge exists, then a local channel is created with one end
 * placed into the existing bridge and the other end masquerading into
 * the unbridged channel.
 *
 * \param chan1 Transferer channel. Guaranteed to be bridged.
 * \param chan2 Other transferer channel. May or may not be bridged.
 * \param bridge1 Bridge that chan1 is in. Guaranteed to be non-NULL.
 * \param bridge2 Bridge that chan2 is in. If NULL, then chan2 is not bridged.
 * \param publication Data to publish for a stasis attended transfer message.
 * \retval AST_BRIDGE_TRANSFER_FAIL Internal error occurred
 * \retval AST_BRIDGE_TRANSFER_SUCCESS Succesfully transferred the bridge
 */
static enum ast_transfer_result attended_transfer_bridge(struct ast_channel *chan1,
                struct ast_channel *chan2, struct ast_bridge *bridge1, struct ast_bridge *bridge2,
                struct stasis_attended_transfer_publish_data *publication)
{
        static const char *dest = "_attended@transfer/m";
        struct ast_channel *local_chan;
        int cause;
        int res;
        const char *app = NULL;

        local_chan = ast_request("Local", ast_channel_nativeformats(chan1), chan1,
                        dest, &cause);

        if (!local_chan) {
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        if (bridge2) {
                res = ast_local_setup_bridge(local_chan, bridge2, chan2, NULL);
        } else {
                app = ast_strdupa(ast_channel_appl(chan2));
                res = ast_local_setup_masquerade(local_chan, chan2);
        }

        if (res) {
                ast_hangup(local_chan);
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        if (ast_call(local_chan, dest, 0)) {
                ast_hangup(local_chan);
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        if (ast_bridge_impart(bridge1, local_chan, chan1, NULL, 1)) {
                ast_hangup(local_chan);
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        if (bridge2) {
                RAII_VAR(struct ast_channel *, local_chan2, NULL, ao2_cleanup);

                ast_channel_lock(local_chan);
                local_chan2 = ast_local_get_peer(local_chan);
                ast_channel_unlock(local_chan);

                ast_assert(local_chan2 != NULL);

                publish_attended_transfer_link(publication,
                                local_chan, local_chan2);
        } else {
                publish_attended_transfer_app(publication, app);
        }
        return AST_BRIDGE_TRANSFER_SUCCESS;
}

/*!
 * \internal
 * \brief Get the transferee channel
 *
 * This is only applicable to cases where a transfer is occurring on a
 * two-party bridge. The channels container passed in is expected to only
 * contain two channels, the transferer and the transferee. The transferer
 * channel is passed in as a parameter to ensure we don't return it as
 * the transferee channel.
 *
 * \param channels A two-channel container containing the transferer and transferee
 * \param transferer The party that is transfering the call
 * \return The party that is being transferred
 */
static struct ast_channel *get_transferee(struct ao2_container *channels, struct ast_channel *transferer)
{
        struct ao2_iterator channel_iter;
        struct ast_channel *transferee;

        for (channel_iter = ao2_iterator_init(channels, 0);
                        (transferee = ao2_iterator_next(&channel_iter));
                        ao2_cleanup(transferee)) {
                if (transferee != transferer) {
                        break;
                }
        }

        ao2_iterator_destroy(&channel_iter);
        return transferee;
}

static enum ast_transfer_result try_parking(struct ast_channel *transferer, const char *context, const char *exten)
{
        RAII_VAR(struct ast_bridge_channel *, transferer_bridge_channel, NULL, ao2_cleanup);

        if (!ast_parking_provider_registered()) {
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        ast_channel_lock(transferer);
        transferer_bridge_channel = ast_channel_get_bridge_channel(transferer);
        ast_channel_unlock(transferer);

        if (!transferer_bridge_channel) {
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        if (ast_parking_blind_transfer_park(transferer_bridge_channel,
                context, exten)) {
                return AST_BRIDGE_TRANSFER_FAIL;
        }

        return AST_BRIDGE_TRANSFER_SUCCESS;
}

/*!
 * \internal
 * \brief Set the BLINDTRANSFER variable as appropriate on channels involved in the transfer
 *
 * The transferer channel will have its BLINDTRANSFER variable set the same as its BRIDGEPEER
 * variable. This will account for all channels that it is bridged to. The other channels
 * involved in the transfer will have their BLINDTRANSFER variable set to the transferer
 * channel's name.
 *
 * \param transferer The channel performing the blind transfer
 * \param channels The channels belonging to the bridge
 */
static void set_blind_transfer_variables(struct ast_channel *transferer, struct ao2_container *channels)
{
        struct ao2_iterator iter;
        struct ast_channel *chan;
        const char *transferer_name;
        const char *transferer_bridgepeer;

        ast_channel_lock(transferer);
        transferer_name = ast_strdupa(ast_channel_name(transferer));
        transferer_bridgepeer = ast_strdupa(S_OR(pbx_builtin_getvar_helper(transferer, "BRIDGEPEER"), ""));
        ast_channel_unlock(transferer);

        for (iter = ao2_iterator_init(channels, 0);
                        (chan = ao2_iterator_next(&iter));
                        ao2_cleanup(chan)) {
                if (chan == transferer) {
                        pbx_builtin_setvar_helper(chan, "BLINDTRANSFER", transferer_bridgepeer);
                } else {
                        pbx_builtin_setvar_helper(chan, "BLINDTRANSFER", transferer_name);
                }
        }

        ao2_iterator_destroy(&iter);
}

static struct ast_bridge *acquire_bridge(struct ast_channel *chan)
{
        struct ast_bridge *bridge;

        ast_channel_lock(chan);
        bridge = ast_channel_get_bridge(chan);
        ast_channel_unlock(chan);

        if (bridge
                && ast_test_flag(&bridge->feature_flags, AST_BRIDGE_FLAG_MASQUERADE_ONLY)) {
                ao2_ref(bridge, -1);
                bridge = NULL;
        }

        return bridge;
}

static void publish_blind_transfer(int is_external, enum ast_transfer_result result,
                struct ast_channel *transferer, struct ast_bridge *bridge,
                const char *context, const char *exten)
{
        struct ast_bridge_channel_pair pair;
        pair.channel = transferer;
        pair.bridge = bridge;
        ast_bridge_publish_blind_transfer(is_external, result, &pair, context, exten);
}

enum ast_transfer_result ast_bridge_transfer_blind(int is_external,
                struct ast_channel *transferer, const char *exten, const char *context,
                transfer_channel_cb new_channel_cb, void *user_data)
{
        RAII_VAR(struct ast_bridge *, bridge, NULL, ao2_cleanup);
        RAII_VAR(struct ast_bridge_channel *, bridge_channel, NULL, ao2_cleanup);
        RAII_VAR(struct ao2_container *, channels, NULL, ao2_cleanup);
        RAII_VAR(struct ast_channel *, transferee, NULL, ast_channel_cleanup);
        int do_bridge_transfer;
        int transfer_prohibited;
        enum ast_transfer_result transfer_result;

        bridge = acquire_bridge(transferer);
        if (!bridge) {
                transfer_result = AST_BRIDGE_TRANSFER_INVALID;
                goto publish;
        }
        ast_channel_lock(transferer);
        bridge_channel = ast_channel_get_bridge_channel(transferer);
        ast_channel_unlock(transferer);
        if (!bridge_channel) {
                transfer_result = AST_BRIDGE_TRANSFER_INVALID;
                goto publish;
        }

        /* Take off hold if they are on hold. */
        ast_bridge_channel_write_unhold(bridge_channel);

        transfer_result = try_parking(transferer, context, exten);
        if (transfer_result == AST_BRIDGE_TRANSFER_SUCCESS) {
                goto publish;
        }

        {