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chan_websocket: Fix codec validation and add passthrough option.

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* Fixed an issue in webchan_write() where we weren't detecting equivalent
  codecs properly.
* Added the "p" dialstring option that puts the channel driver in
  "passthrough" mode where it will not attempt to re-frame or re-time
  media coming in over the websocket from the remote app.  This can be used
  for any codec but MUST be used for codecs that use packet headers or whose
  data stream can't be broken up on arbitrary byte boundaries. In this case,
  the remote app is fully responsible for correctly framing and timing media
  sent to Asterisk and the MEDIA text commands that could be sent over the
  websocket are disabled.  Currently, passthrough mode is automatically set
  for the opus, speex and g729 codecs.
* Now calling ast_set_read_format() after ast_channel_set_rawreadformat() to
  ensure proper translation paths are set up when switching between native
  frames and slin silence frames.  This fixes an issue with codec errors
  when transcode_via_sln=yes.

Resolves: #1462
This commit is contained in:
George Joseph
2025-09-17 07:21:48 -06:00
parent 72032b9493
commit b624b92656
1 changed files with 99 additions and 14 deletions
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103
channels/chan_websocket.c
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@@ -59,6 +59,18 @@
/channels/answer ARI endpoint.
</para>
</enum>
<enum name="p - Passthrough mode">
<para>In passthrough mode, the channel driver won't attempt
to re-frame or re-time media coming in over the websocket from
the remote app. This can be used for any codec but MUST be used
for codecs that use packet headers or whose data stream can't be
broken up on arbitrary byte boundaries. In this case, the remote
app is fully responsible for correctly framing and timing media
sent to Asterisk and the MEDIA text commands that could be sent
over the websocket are disabled. Currently, passthrough mode is
automatically set for the opus, speex and g729 codecs.
</para>
</enum>
<enum name="v(uri_parameters) - Add parameters to the outbound URI">
<para>This option allows you to add additional parameters to the
outbound URI. The format is:
@@ -78,6 +90,9 @@
<example title="Make an outbound WebSocket connection using connection 'connection1' and the 'sln16' codec.">
same => n,Dial(WebSocket/connection1/c(sln16))
</example>
<example title="Make an outbound WebSocket connection using connection 'connection1' and the 'opus' codec. Passthrough mode will automatically be set.">
same => n,Dial(WebSocket/connection1/c(opus))
</example>
<example title="Listen for an incoming WebSocket connection and don't auto-answer it.">
same => n,Dial(WebSocket/INCOMING/n)
</example>
@@ -127,6 +142,7 @@ struct websocket_pvt {
char *uri_params;
char *leftover_data;
int no_auto_answer;
int passthrough;
int optimal_frame_size;
int bulk_media_in_progress;
int report_queue_drained;
@@ -188,6 +204,7 @@ static void set_channel_format(struct websocket_pvt * instance,
if (ast_format_cmp(ast_channel_rawreadformat(instance->channel), fmt)
== AST_FORMAT_CMP_NOT_EQUAL) {
ast_channel_set_rawreadformat(instance->channel, fmt);
ast_set_read_format(instance->channel, ast_channel_readformat(instance->channel));
ast_debug(4, "Switching readformat to %s\n", ast_format_get_name(fmt));
}
}
@@ -332,10 +349,10 @@ static struct ast_frame *webchan_read(struct ast_channel *ast)
}
/*
* If the frame length is already optimal_frame_size, we can just
* return it.
* If we're in passthrough mode or the frame length is already optimal_frame_size,
* we can just return it.
*/
if (native_frame->datalen == instance->optimal_frame_size) {
if (instance->passthrough || native_frame->datalen == instance->optimal_frame_size) {
set_channel_format(instance, instance->native_format);
return native_frame;
}
@@ -499,6 +516,11 @@ static int process_text_message(struct websocket_pvt *instance,
ast_queue_control(instance->channel, AST_CONTROL_HANGUP);
} else if (ast_strings_equal(command, START_MEDIA_BUFFERING)) {
if (instance->passthrough) {
ast_debug(4, "%s: WebSocket in passthrough mode. Ignoring %s command.\n",
ast_channel_name(instance->channel), command);
return 0;
}
AST_LIST_LOCK(&instance->frame_queue);
instance->bulk_media_in_progress = 1;
AST_LIST_UNLOCK(&instance->frame_queue);
@@ -511,6 +533,12 @@ static int process_text_message(struct websocket_pvt *instance,
id = ast_strip(command + strlen(STOP_MEDIA_BUFFERING));
if (instance->passthrough) {
ast_debug(4, "%s: WebSocket in passthrough mode. Ignoring %s command.\n",
ast_channel_name(instance->channel), command);
return 0;
}
ast_debug(4, "%s: WebSocket %s '%s' with %d bytes in leftover_data.\n",
ast_channel_name(instance->channel), STOP_MEDIA_BUFFERING, id,
(int)instance->leftover_len);
@@ -533,6 +561,13 @@ static int process_text_message(struct websocket_pvt *instance,
} else if (ast_strings_equal(command, FLUSH_MEDIA)) {
struct ast_frame *frame = NULL;
if (instance->passthrough) {
ast_debug(4, "%s: WebSocket in passthrough mode. Ignoring %s command.\n",
ast_channel_name(instance->channel), command);
return 0;
}
AST_LIST_LOCK(&instance->frame_queue);
while ((frame = AST_LIST_REMOVE_HEAD(&instance->frame_queue, frame_list))) {
ast_frfree(frame);
@@ -543,6 +578,12 @@ static int process_text_message(struct websocket_pvt *instance,
AST_LIST_UNLOCK(&instance->frame_queue);
} else if (ast_strings_equal(payload, REPORT_QUEUE_DRAINED)) {
if (instance->passthrough) {
ast_debug(4, "%s: WebSocket in passthrough mode. Ignoring %s command.\n",
ast_channel_name(instance->channel), command);
return 0;
}
AST_LIST_LOCK(&instance->frame_queue);
instance->report_queue_drained = 1;
AST_LIST_UNLOCK(&instance->frame_queue);
@@ -569,11 +610,21 @@ static int process_text_message(struct websocket_pvt *instance,
}
} else if (ast_strings_equal(payload, PAUSE_MEDIA)) {
if (instance->passthrough) {
ast_debug(4, "%s: WebSocket in passthrough mode. Ignoring %s command.\n",
ast_channel_name(instance->channel), command);
return 0;
}
AST_LIST_LOCK(&instance->frame_queue);
instance->queue_paused = 1;
AST_LIST_UNLOCK(&instance->frame_queue);
} else if (ast_strings_equal(payload, CONTINUE_MEDIA)) {
if (instance->passthrough) {
ast_debug(4, "%s: WebSocket in passthrough mode. Ignoring %s command.\n",
ast_channel_name(instance->channel), command);
return 0;
}
AST_LIST_LOCK(&instance->frame_queue);
instance->queue_paused = 0;
AST_LIST_UNLOCK(&instance->frame_queue);
@@ -607,6 +658,11 @@ static int process_binary_message(struct websocket_pvt *instance,
next_frame_ptr = payload;
instance->bytes_read += payload_len;
if (instance->passthrough) {
res = queue_frame_from_buffer(instance, payload, payload_len);
return res;
}
if (instance->bulk_media_in_progress && instance->leftover_len > 0) {
/*
* We have leftover data from a previous websocket message.
@@ -791,10 +847,10 @@ static void *read_thread_handler(void *obj)
* This is especially important for outbound connections otherwise
* the app won't know who the media is for.
*/
res = ast_asprintf(&command, "%s connection_id:%s channel:%s format:%s optimal_frame_size:%d", MEDIA_START,
res = ast_asprintf(&command, "%s connection_id:%s channel:%s format:%s optimal_frame_size:%d ptime:%d", MEDIA_START,
instance->connection_id, ast_channel_name(instance->channel),
ast_format_get_name(instance->native_format),
instance->optimal_frame_size);
instance->optimal_frame_size, instance->native_codec->default_ms);
if (res <= 0 || !command) {
ast_queue_control(instance->channel, AST_CONTROL_HANGUP);
ast_log(LOG_ERROR, "%s: Failed to create MEDIA_START\n", ast_channel_name(instance->channel));
@@ -843,9 +899,11 @@ static int webchan_write(struct ast_channel *ast, struct ast_frame *f)
ast_channel_name(ast));
return -1;
}
if (f->subclass.format != instance->native_format) {
ast_log(LOG_WARNING, "%s: This WebSocket channel only supports the '%s' format\n",
ast_channel_name(ast), ast_format_get_name(instance->native_format));
if (ast_format_cmp(f->subclass.format, instance->native_format) == AST_FORMAT_CMP_NOT_EQUAL) {
ast_log(LOG_WARNING, "%s: This WebSocket channel only supports the '%s' format, not '%s'\n",
ast_channel_name(ast), ast_format_get_name(instance->native_format),
ast_format_get_name(f->subclass.format));
return -1;
}
@@ -1044,14 +1102,35 @@ static struct websocket_pvt* websocket_new(const char *chan_name,
* References for native_format and native_codec are now held by the
* instance and will be released when the instance is destroyed.
*/
/*
* It's not possible for us to re-time or re-frame media if the data
* stream can't be broken up on arbitrary byte boundaries. This is usually
* indicated by the codec's minimum_bytes being small (10 bytes or less).
* We need to force passthrough mode in this case.
*/
if (instance->native_codec->minimum_bytes <= 10) {
instance->passthrough = 1;
instance->optimal_frame_size = 0;
} else {
instance->optimal_frame_size =
(instance->native_codec->default_ms * instance->native_codec->minimum_bytes)
/ instance->native_codec->minimum_ms;
instance->leftover_data = ast_calloc(1, instance->optimal_frame_size);
if (!instance->leftover_data) {
return NULL;
}
}
ast_debug(3,
"%s: WebSocket channel native format '%s' Sample rate: %d ptime: %dms minms: %u minbytes: %u passthrough: %d optimal_frame_size: %d\n",
chan_name, ast_format_get_name(instance->native_format),
ast_format_get_sample_rate(instance->native_format),
ast_format_get_default_ms(instance->native_format),
ast_format_get_minimum_ms(instance->native_format),
ast_format_get_minimum_bytes(instance->native_format),
instance->passthrough,
instance->optimal_frame_size);
/* We have exclusive access to proxy and sorcery, no need for locking here. */
if (ao2_weakproxy_set_object(proxy, instance, OBJ_NOLOCK)) {
@@ -1195,12 +1274,14 @@ enum {
OPT_WS_CODEC = (1 << 0),
OPT_WS_NO_AUTO_ANSWER = (1 << 1),
OPT_WS_URI_PARAM = (1 << 2),
OPT_WS_PASSTHROUGH = (1 << 3),
};
enum {
OPT_ARG_WS_CODEC,
OPT_ARG_WS_NO_AUTO_ANSWER,
OPT_ARG_WS_URI_PARAM,
OPT_ARG_WS_PASSTHROUGH,
OPT_ARG_ARRAY_SIZE
};
@@ -1208,6 +1289,7 @@ AST_APP_OPTIONS(websocket_options, BEGIN_OPTIONS
AST_APP_OPTION_ARG('c', OPT_WS_CODEC, OPT_ARG_WS_CODEC),
AST_APP_OPTION('n', OPT_WS_NO_AUTO_ANSWER),
AST_APP_OPTION_ARG('v', OPT_WS_URI_PARAM, OPT_ARG_WS_URI_PARAM),
AST_APP_OPTION('p', OPT_WS_PASSTHROUGH),
END_OPTIONS );
static struct ast_channel *webchan_request(const char *type,
@@ -1281,6 +1363,9 @@ static struct ast_channel *webchan_request(const char *type,
}
instance->no_auto_answer = ast_test_flag(&opts, OPT_WS_NO_AUTO_ANSWER);
if (!instance->passthrough) {
instance->passthrough = ast_test_flag(&opts, OPT_WS_PASSTHROUGH);
}
if (ast_test_flag(&opts, OPT_WS_URI_PARAM)
&& !ast_strlen_zero(opt_args[OPT_ARG_WS_URI_PARAM])) {