res_format_attr_ilbc.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2016, Alexander Traud
 *
 * Alexander Traud <[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 iLBC format attribute interface
 *
 * \author Alexander Traud <[email protected]>
 *
 * \note http://tools.ietf.org/html/rfc3952
 */

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

#include "asterisk.h"

#include <ctype.h>                      /* for tolower */

#include "asterisk/module.h"
#include "asterisk/format.h"
#include "asterisk/strings.h"           /* for ast_str_append */
#include "asterisk/utils.h"             /* for ast_free */

#include "asterisk/ilbc.h"

static struct ilbc_attr default_ilbc_attr = {
   .mode = 20,
};

static void ilbc_destroy(struct ast_format *format)
{
   struct ilbc_attr *attr = ast_format_get_attribute_data(format);

   ast_free(attr);
}

static int ilbc_clone(const struct ast_format *src, struct ast_format *dst)
{
   struct ilbc_attr *original = ast_format_get_attribute_data(src);
   struct ilbc_attr *attr = ast_malloc(sizeof(*attr));

   if (!attr) {
      return -1;
   }

   if (original) {
      *attr = *original;
   } else {
      *attr = default_ilbc_attr;
   }

   ast_format_set_attribute_data(dst, attr);

   return 0;
}

static struct ast_format *ilbc_parse_sdp_fmtp(const struct ast_format *format, const char *attributes)
{
   char *attribs = ast_strdupa(attributes), *attrib;
   struct ast_format *cloned;
   struct ilbc_attr *attr;
   const char *kvp;
   unsigned int val;

   cloned = ast_format_clone(format);
   if (!cloned) {
      return NULL;
   }
   attr = ast_format_get_attribute_data(cloned);

   /* lower-case everything, so we are case-insensitive */
   for (attrib = attribs; *attrib; ++attrib) {
      *attrib = tolower(*attrib);
   } /* based on channels/chan_sip.c:process_a_sdp_image() */

   if ((kvp = strstr(attribs, "mode")) && sscanf(kvp, "mode=%30u", &val) == 1) {
      attr->mode = val;
   } else {
      attr->mode = 30; /* optional attribute; 30 is default value */
   }

   return cloned;
}

static void ilbc_generate_sdp_fmtp(const struct ast_format *format, unsigned int payload, struct ast_str **str)
{
   struct ilbc_attr *attr = ast_format_get_attribute_data(format);

   if (!attr) {
      attr = &default_ilbc_attr;
   }

   /* When the VoIP/SIP client Zoiper calls Asterisk and its
    * iLBC 20 is disabled but iLBC 30 enabled, Zoiper still
    * falls back to iLBC 20, when there is no mode=30 in the
    * answer. Consequently, Zoiper defaults to iLBC 20. To
    * make that client happy, Asterisk sends mode always.
    * tested in June 2016, Zoiper Premium 1.13.2 for iPhone
    */
   /* if (attr->mode != 30) */ {
      ast_str_append(str, 0, "a=fmtp:%u mode=%u\r\n", payload, attr->mode);
   }
}

static struct ast_format *ilbc_getjoint(const struct ast_format *format1, const struct ast_format *format2)
{
   struct ast_format *jointformat;
   struct ilbc_attr *attr1 = ast_format_get_attribute_data(format1);
   struct ilbc_attr *attr2 = ast_format_get_attribute_data(format2);
   struct ilbc_attr *attr_res;

   if (!attr1) {
      attr1 = &default_ilbc_attr;
   }

   if (!attr2) {
      attr2 = &default_ilbc_attr;
   }

   jointformat = ast_format_clone(format1);
   if (!jointformat) {
      return NULL;
   }
   attr_res = ast_format_get_attribute_data(jointformat);

   if (attr1->mode != attr2->mode) {
      attr_res->mode = 30;
   }

   return jointformat;
}

static struct ast_format_interface ilbc_interface = {
   .format_destroy = ilbc_destroy,
   .format_clone = ilbc_clone,
   .format_cmp = NULL,
   .format_get_joint = ilbc_getjoint,
   .format_attribute_set = NULL,
   .format_parse_sdp_fmtp = ilbc_parse_sdp_fmtp,
   .format_generate_sdp_fmtp = ilbc_generate_sdp_fmtp,
};

static int load_module(void)
{
   if (ast_format_interface_register("ilbc", &ilbc_interface)) {
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "iLBC Format Attribute Module",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .load_pri = AST_MODPRI_CHANNEL_DEPEND,
);