From 51821644bae58d5c87eca2551e51bda78560e029 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olivier=20Cr=C3=AAte?= <olivier.crete@collabora.com>
Date: Tue, 18 May 2021 20:18:28 -0400
Subject: [PATCH] webrtc: Wait until ICE is connected to start DTLS handshake
 process

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2260>
---
 ext/webrtc/transportsendbin.c | 50 +++++++++++++++++++++++++++++------
 ext/webrtc/transportsendbin.h |  2 ++
 2 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/ext/webrtc/transportsendbin.c b/ext/webrtc/transportsendbin.c
index bf6ce359b5..d5de83ecee 100644
--- a/ext/webrtc/transportsendbin.c
+++ b/ext/webrtc/transportsendbin.c
@@ -173,6 +173,7 @@ transport_send_bin_change_state (GstElement * element,
       TSB_LOCK (send);
       gst_element_set_locked_state (send->rtp_ctx.dtlssrtpenc, TRUE);
       send->active = TRUE;
+      send->rtp_ctx.has_clientness = FALSE;
       TSB_UNLOCK (send);
       break;
     }
@@ -260,14 +261,32 @@ done:
   TSB_UNLOCK (send);
 }
 
+static void
+maybe_start_enc (TransportSendBin * send)
+{
+  GstWebRTCICEConnectionState state;
+
+  if (!send->rtp_ctx.has_clientness) {
+    GST_LOG_OBJECT (send, "Can't start DTLS because doesn't know client-ness");
+    return;
+  }
+
+  g_object_get (send->stream->transport->transport, "state", &state, NULL);
+  if (state != GST_WEBRTC_ICE_CONNECTION_STATE_CONNECTED &&
+      state != GST_WEBRTC_ICE_CONNECTION_STATE_COMPLETED) {
+    GST_LOG_OBJECT (send, "Can't start DTLS yet because ICE is not connected.");
+    return;
+  }
+
+  gst_element_set_locked_state (send->rtp_ctx.dtlssrtpenc, FALSE);
+  gst_element_sync_state_with_parent (send->rtp_ctx.dtlssrtpenc);
+}
+
 static void
 _on_notify_dtls_client_status (GstElement * dtlssrtpenc,
     GParamSpec * pspec, TransportSendBin * send)
 {
-  TransportSendBinDTLSContext *ctx;
-  if (dtlssrtpenc == send->rtp_ctx.dtlssrtpenc)
-    ctx = &send->rtp_ctx;
-  else {
+  if (dtlssrtpenc != send->rtp_ctx.dtlssrtpenc) {
     GST_WARNING_OBJECT (send,
         "Received dtls-enc client mode for unknown element %" GST_PTR_FORMAT,
         dtlssrtpenc);
@@ -281,15 +300,26 @@ _on_notify_dtls_client_status (GstElement * dtlssrtpenc,
     goto done;
   }
 
+  send->rtp_ctx.has_clientness = TRUE;
   GST_DEBUG_OBJECT (send,
-      "DTLS-SRTP encoder configured. Unlocking it and changing state %"
-      GST_PTR_FORMAT, ctx->dtlssrtpenc);
-  gst_element_set_locked_state (ctx->dtlssrtpenc, FALSE);
-  gst_element_sync_state_with_parent (ctx->dtlssrtpenc);
+      "DTLS-SRTP encoder configured. Unlocking it and maybe changing state %"
+      GST_PTR_FORMAT, dtlssrtpenc);
+  maybe_start_enc (send);
+
 done:
   TSB_UNLOCK (send);
 }
 
+static void
+_on_notify_ice_connection_state (GstWebRTCICETransport * transport,
+    GParamSpec * pspec, TransportSendBin * send)
+{
+  TSB_LOCK (send);
+  maybe_start_enc (send);
+  TSB_UNLOCK (send);
+}
+
+
 static void
 tsb_setup_ctx (TransportSendBin * send, TransportSendBinDTLSContext * ctx,
     GstWebRTCDTLSTransport * transport)
@@ -305,6 +335,10 @@ tsb_setup_ctx (TransportSendBin * send, TransportSendBinDTLSContext * ctx,
   /* Bring the encoder up to current state only once the is-client prop is set */
   g_signal_connect (dtlssrtpenc, "notify::is-client",
       G_CALLBACK (_on_notify_dtls_client_status), send);
+  /* unblock ice sink once it signals a connection */
+  g_signal_connect (transport->transport, "notify::state",
+      G_CALLBACK (_on_notify_ice_connection_state), send);
+
   gst_bin_add (GST_BIN (send), GST_ELEMENT (dtlssrtpenc));
   gst_bin_add (GST_BIN (send), GST_ELEMENT (nicesink));
 
diff --git a/ext/webrtc/transportsendbin.h b/ext/webrtc/transportsendbin.h
index c66183bde6..6821e05c2c 100644
--- a/ext/webrtc/transportsendbin.h
+++ b/ext/webrtc/transportsendbin.h
@@ -38,6 +38,8 @@ struct _TransportSendBinDTLSContext {
   GstElement *dtlssrtpenc;
   GstElement *nicesink;
 
+  gboolean has_clientness;
+
   /* Block on the dtlssrtpenc RTP sink pad, if any */
   struct pad_block          *rtp_block;
   /* Block on the dtlssrtpenc RTCP sink pad, if any */