Commit 0c39068c authored by Sebastian Dröge's avatar Sebastian Dröge 🍵 Committed by GStreamer Merge Bot

webrtcbin: Start datachannel SCTP elements only after the DTLS connection is established

Otherwise we would start sending data to the DTLS connection before, and
the DTLS elements consider this an error.

Also RFC 8261 mentions:
  o A DTLS connection MUST be established before an SCTP association can
    be set up.
parent 2798a80e
......@@ -1784,6 +1784,66 @@ _on_sctp_state_notify (GstWebRTCSCTPTransport * sctp, GParamSpec * pspec,
/* Forward declaration so we can easily disconnect the signal handler */
static void _on_sctp_notify_dtls_state (GstWebRTCDTLSTransport * transport,
GParamSpec * pspec, GstWebRTCBin * webrtc);
static void
_sctp_check_dtls_state_task (GstWebRTCBin * webrtc, gpointer unused)
TransportStream *stream;
GstWebRTCDTLSTransport *transport;
GstWebRTCDTLSTransportState dtls_state;
GstWebRTCSCTPTransport *sctp_transport;
stream = webrtc->priv->data_channel_transport;
transport = stream->transport;
g_object_get (transport, "state", &dtls_state, NULL);
/* Not connected yet so just return */
"Data channel DTLS connection is not ready yet: %d", dtls_state);
GST_DEBUG_OBJECT (webrtc, "Data channel DTLS connection is now ready");
sctp_transport = webrtc->priv->sctp_transport;
/* Not locked state anymore so this was already taken care of before */
if (!gst_element_is_locked_state (sctp_transport->sctpdec))
/* Start up the SCTP elements now that the DTLS connection is established */
gst_element_set_locked_state (sctp_transport->sctpdec, FALSE);
gst_element_set_locked_state (sctp_transport->sctpenc, FALSE);
gst_element_sync_state_with_parent (GST_ELEMENT (sctp_transport->sctpdec));
gst_element_sync_state_with_parent (GST_ELEMENT (sctp_transport->sctpenc));
g_signal_handlers_disconnect_by_func (transport, _on_sctp_notify_dtls_state,
static void
_on_sctp_notify_dtls_state (GstWebRTCDTLSTransport * transport,
GParamSpec * pspec, GstWebRTCBin * webrtc)
GstWebRTCDTLSTransportState dtls_state;
g_object_get (transport, "state", &dtls_state, NULL);
GST_TRACE_OBJECT (webrtc, "Data channel DTLS state changed to %d",
/* Connected now, so schedule a task to update the state of the SCTP
* elements */
gst_webrtc_bin_enqueue_task (webrtc,
(GstWebRTCBinFunc) _sctp_check_dtls_state_task, NULL, NULL);
static TransportStream *
_get_or_create_data_channel_transports (GstWebRTCBin * webrtc, guint session_id)
......@@ -1811,6 +1871,11 @@ _get_or_create_data_channel_transports (GstWebRTCBin * webrtc, guint session_id)
g_object_ref (webrtc->priv->data_channel_transport->transport);
sctp_transport->webrtcbin = webrtc;
/* Don't automatically start SCTP elements as part of webrtcbin. We
* need to delay this until the DTLS transport is fully connected! */
gst_element_set_locked_state (sctp_transport->sctpdec, TRUE);
gst_element_set_locked_state (sctp_transport->sctpenc, TRUE);
gst_bin_add (GST_BIN (webrtc), sctp_transport->sctpdec);
gst_bin_add (GST_BIN (webrtc), sctp_transport->sctpenc);
......@@ -1843,10 +1908,16 @@ _get_or_create_data_channel_transports (GstWebRTCBin * webrtc, guint session_id)
gst_element_sync_state_with_parent (GST_ELEMENT (stream->receive_bin));
if (!webrtc->priv->sctp_transport) {
gst_element_sync_state_with_parent (GST_ELEMENT
gst_element_sync_state_with_parent (GST_ELEMENT
/* Connect to the notify::state signal to get notified when the DTLS
* connection is established. Only then can we start the SCTP elements */
g_signal_connect (stream->transport, "notify::state",
G_CALLBACK (_on_sctp_notify_dtls_state), webrtc);
/* As this would be racy otherwise, also schedule a task that checks the
* current state of the connection already without getting the signal
* called */
gst_webrtc_bin_enqueue_task (webrtc,
(GstWebRTCBinFunc) _sctp_check_dtls_state_task, NULL, NULL);
webrtc->priv->sctp_transport = sctp_transport;
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