framehook.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2010, Digium, Inc.
 *
 * David Vossel <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief FrameHooks Architecture
 *
 * \author David Vossel <[email protected]>
 */

/*** 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);
}