framehook.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2010, Digium, Inc.
 *
 * David Vossel <dvossel@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 FrameHooks Architecture
 *
 * \author David Vossel <dvossel@digium.com>
 */
 
/*** MODULEINFO
    <support_level>core</support_level>
 ***/
 
#include "asterisk.h"
 
#include "asterisk/channel.h"
#include "asterisk/linkedlists.h"
#include "asterisk/framehook.h"
#include "asterisk/frame.h"
 
struct ast_framehook {
    struct ast_framehook_interface i;
    /*! This pointer to ast_channel the framehook is attached to. */
    struct ast_channel *chan;
    /*! the id representing this framehook on a channel */
    unsigned int id;
    /*! when set, this signals the read and write function to detach the hook */
    int detach_and_destroy_me;
    /*! list entry for ast_framehook_list object */
    AST_LIST_ENTRY(ast_framehook) list;
};
 
struct ast_framehook_list {
    /*! the number of hooks currently present */
    unsigned int count;
    /*! id for next framehook added */
    unsigned int id_count;
    AST_LIST_HEAD_NOLOCK(, ast_framehook) list;
};
 
enum framehook_detachment_mode
{
    /*! Destroy the framehook outright. */
    FRAMEHOOK_DETACH_DESTROY = 0,
    /*! Remove the framehook from the channel, but don't destroy the data since
     *  it will be used by a replacement framehook on another channel. */
    FRAMEHOOK_DETACH_PRESERVE,
};
 
static void framehook_detach(struct ast_framehook *framehook, enum framehook_detachment_mode mode)
{
    struct ast_frame *frame;
    frame = framehook->i.event_cb(framehook->chan, NULL, AST_FRAMEHOOK_EVENT_DETACHED, framehook->i.data);
    /* never assume anything about this function. If you can return a frame during
     * the detached event, then assume someone will. */
    if (frame) {
        ast_frfree(frame);
    }
    framehook->chan = NULL;
 
    if (mode == FRAMEHOOK_DETACH_DESTROY && framehook->i.destroy_cb) {
        framehook->i.destroy_cb(framehook->i.data);
    }
    ast_free(framehook);
}
 
static struct ast_frame *framehook_list_push_event(struct ast_framehook_list *framehooks, struct ast_frame *frame, enum ast_framehook_event event)
{
    struct ast_framehook *framehook;
    struct ast_frame *original_frame;
    int *skip;
    size_t skip_size;
 
    if (!framehooks) {
        return frame;
    }
 
    skip_size = sizeof(int) * framehooks->count;
    skip = ast_alloca(skip_size);
    memset(skip, 0, skip_size);
 
    do {
        unsigned int num = 0;
        original_frame = frame;
 
        AST_LIST_TRAVERSE_SAFE_BEGIN(&framehooks->list, framehook, list) {
            if (framehook->detach_and_destroy_me) {
                /* this guy is signaled for destruction */
                AST_LIST_REMOVE_CURRENT(list);
                framehook_detach(framehook, FRAMEHOOK_DETACH_DESTROY);
                continue;
            }
 
            /* If this framehook has been marked as needing to be skipped, do so */
            if (skip[num]) {
                num++;
                continue;
            }
 
            frame = framehook->i.event_cb(framehook->chan, frame, event, framehook->i.data);
 
            if (frame != original_frame) {
                /* To prevent looping we skip any framehooks that have already provided a modified frame */
                skip[num] = 1;
                break;
            }
 
            num++;
        }
        AST_LIST_TRAVERSE_SAFE_END;
    } while (frame != original_frame);
 
    return frame;
}
 
int ast_framehook_attach(struct ast_channel *chan, struct ast_framehook_interface *i)
{
    struct ast_framehook *framehook;
    struct ast_framehook_list *fh_list;
    struct ast_frame *frame;
    if (i->version != AST_FRAMEHOOK_INTERFACE_VERSION) {
        ast_log(LOG_ERROR, "Version '%hu' of framehook interface not what we compiled against (%i)\n",
            i->version, AST_FRAMEHOOK_INTERFACE_VERSION);
        return -1;
    }
    if (!i->event_cb || !(framehook = ast_calloc(1, sizeof(*framehook)))) {
        return -1;
    }
    framehook->i = *i;
    framehook->chan = chan;
 
    /* create the framehook list if it didn't already exist */
    if (!ast_channel_framehooks(chan)) {
        if (!(fh_list = ast_calloc(1, sizeof(*ast_channel_framehooks(chan))))) {
            ast_free(framehook);
            return -1;
        }
        ast_channel_framehooks_set(chan, fh_list);
    }
 
    ast_channel_framehooks(chan)->count++;
    framehook->id = ++ast_channel_framehooks(chan)->id_count;
    AST_LIST_INSERT_TAIL(&ast_channel_framehooks(chan)->list, framehook, list);
 
    /* Tell the event callback we're live and rocking */
    frame = framehook->i.event_cb(framehook->chan, NULL, AST_FRAMEHOOK_EVENT_ATTACHED, framehook->i.data);
 
    /* Never assume anything about this function. If you can return a frame during
     * the attached event, then assume someone will. */
    if (frame) {
        ast_frfree(frame);
    }
 
    if (ast_channel_is_bridged(chan)) {
        ast_channel_set_unbridged_nolock(chan, 1);
    }
 
    return framehook->id;
}
 
int ast_framehook_detach(struct ast_channel *chan, int id)
{
    struct ast_framehook *framehook;
    int res = -1;
 
    if (!ast_channel_framehooks(chan)) {
        return res;
    }
 
    AST_LIST_TRAVERSE_SAFE_BEGIN(&ast_channel_framehooks(chan)->list, framehook, list) {
        if (framehook->id == id) {
            /* we mark for detachment rather than doing explicitly here because
             * it needs to be safe for this function to be called within the
             * event callback.  If we allowed the hook to actually be destroyed
             * immediately here, the event callback would crash on exit. */
            framehook->detach_and_destroy_me = 1;
            res = 0;
            break;
        }
    }
    AST_LIST_TRAVERSE_SAFE_END;
 
    if (!res && ast_channel_is_bridged(chan)) {
        ast_channel_set_unbridged_nolock(chan, 1);
    }
 
    return res;
}
 
int ast_framehook_list_destroy(struct ast_channel *chan)
{
    struct ast_framehook *framehook;
 
    if (!ast_channel_framehooks(chan)) {
        return 0;
    }
    AST_LIST_TRAVERSE_SAFE_BEGIN(&ast_channel_framehooks(chan)->list, framehook, list) {
        AST_LIST_REMOVE_CURRENT(list);
        framehook_detach(framehook, FRAMEHOOK_DETACH_DESTROY);
    }
    AST_LIST_TRAVERSE_SAFE_END;
    ast_free(ast_channel_framehooks(chan));
    ast_channel_framehooks_set(chan, NULL);
    return 0;
}
 
void ast_framehook_list_fixup(struct ast_channel *old_chan, struct ast_channel *new_chan)
{
    struct ast_framehook *framehook;
    int moved_framehook_id;
 
    if (ast_channel_framehooks(new_chan)) {
        AST_LIST_TRAVERSE_SAFE_BEGIN(&ast_channel_framehooks(new_chan)->list, framehook, list) {
            if (framehook->i.disable_inheritance) {
                ast_framehook_detach(new_chan, framehook->id);
                continue;
            }
 
            if (framehook->i.chan_breakdown_cb) {
                framehook->i.chan_breakdown_cb(framehook->i.data, framehook->id,
                    old_chan, new_chan);
            }
        }
        AST_LIST_TRAVERSE_SAFE_END;
    }
 
    if (!ast_channel_framehooks(old_chan)) {
        return;
    }
 
    if (!AST_LIST_EMPTY(&ast_channel_framehooks(old_chan)->list)
        && ast_channel_is_bridged(old_chan)) {
        ast_channel_set_unbridged_nolock(old_chan, 1);
    }
    while ((framehook = AST_LIST_REMOVE_HEAD(&ast_channel_framehooks(old_chan)->list, list))) {
        /* If inheritance is not allowed for this framehook, just destroy it. */
        if (framehook->i.disable_inheritance) {
            framehook_detach(framehook, FRAMEHOOK_DETACH_DESTROY);
            continue;
        }
 
        /* Otherwise move it to the other channel and perform any fixups set by the framehook interface */
        moved_framehook_id = ast_framehook_attach(new_chan, &framehook->i);
        if (moved_framehook_id < 0) {
            ast_log(LOG_WARNING, "Failed framehook copy during masquerade. Expect loss of features.\n");
            framehook_detach(framehook, FRAMEHOOK_DETACH_DESTROY);
        } else {
            if (framehook->i.chan_fixup_cb) {
                framehook->i.chan_fixup_cb(framehook->i.data, moved_framehook_id,
                    old_chan, new_chan);
            }
 
            framehook_detach(framehook, FRAMEHOOK_DETACH_PRESERVE);
        }
    }
}
 
int ast_framehook_list_is_empty(struct ast_framehook_list *framehooks)
{
    if (!framehooks) {
        return 1;
    }
    return AST_LIST_EMPTY(&framehooks->list) ? 1 : 0;
}
 
int ast_framehook_list_contains_no_active(struct ast_framehook_list *framehooks)
{
    return ast_framehook_list_contains_no_active_of_type(framehooks, 0);
}
 
int ast_framehook_list_contains_no_active_of_type(struct ast_framehook_list *framehooks,
    enum ast_frame_type type)
{
    struct ast_framehook *cur;
 
    if (!framehooks) {
        return 1;
    }
 
    if (AST_LIST_EMPTY(&framehooks->list)) {
        return 1;
    }
 
    AST_LIST_TRAVERSE(&framehooks->list, cur, list) {
        if (cur->detach_and_destroy_me) {
            continue;
        }
        if (type && cur->i.consume_cb && !cur->i.consume_cb(cur->i.data, type)) {
            continue;
        }
        return 0;
    }
 
    return 1;
}
 
struct ast_frame *ast_framehook_list_write_event(struct ast_framehook_list *framehooks, struct ast_frame *frame)
{
    return framehook_list_push_event(framehooks, frame, AST_FRAMEHOOK_EVENT_WRITE);
}
 
struct ast_frame *ast_framehook_list_read_event(struct ast_framehook_list *framehooks, struct ast_frame *frame)
{
    return framehook_list_push_event(framehooks, frame, AST_FRAMEHOOK_EVENT_READ);
}