webrtc: Merge ICE candidates to local descriptions

When emitting ICE candidates, also merge them to the local and
pending description so they show up in the SDP if those are
retrieved from the current-local-description and
pending-local-description properties.

https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/issues/676

diff --git a/ext/webrtc/gstwebrtcbin.c b/ext/webrtc/gstwebrtcbin.c
index 9c2cb40..e12617b 100644 (file)
--- a/ext/webrtc/gstwebrtcbin.c
+++ b/ext/webrtc/gstwebrtcbin.c
@@ -3567,6 +3567,31 @@ _add_ice_candidates_from_sdp (GstWebRTCBin * webrtc, gint mlineindex,
   }
 }
 
+static void
+_add_ice_candidate_to_sdp (GstWebRTCBin * webrtc,
+    GstSDPMessage * sdp, gint mline_index, const gchar * candidate)
+{
+  GstSDPMedia *media = NULL;
+
+  if (mline_index < sdp->medias->len) {
+    media = &g_array_index (sdp->medias, GstSDPMedia, mline_index);
+  }
+
+  if (media == NULL) {
+    GST_WARNING_OBJECT (webrtc, "Couldn't find mline %d to merge ICE candidate",
+        mline_index);
+    return;
+  }
+  // Add the candidate as an attribute, first stripping off the existing
+  // candidate: key from the string description
+  if (strlen (candidate) < 10) {
+    GST_WARNING_OBJECT (webrtc,
+        "Dropping invalid ICE candidate for mline %d: %s", mline_index,
+        candidate);
+    return;
+  }
+  gst_sdp_media_add_attribute (media, "candidate", candidate + 10);
+}
 
 static gboolean
 _filter_sdp_fields (GQuark field_id, const GValue * value,
@@ -4581,6 +4606,20 @@ _on_ice_candidate_task (GstWebRTCBin * webrtc, IceCandidateItem * item)
   GST_TRACE_OBJECT (webrtc, "produced ICE candidate for mline:%u and %s",
       item->mlineindex, cand);
 
+  /* First, merge this ice candidate into the appropriate mline
+   * in the local-description SDP.
+   * Second, emit the on-ice-candidate signal for the app.
+   *
+   * FIXME: This ICE candidate should be stored somewhere with
+   * the associated mid and also merged back into any subsequent
+   * local descriptions on renegotiation */
+  if (webrtc->current_local_description)
+    _add_ice_candidate_to_sdp (webrtc, webrtc->current_local_description->sdp,
+        item->mlineindex, cand);
+  if (webrtc->pending_local_description)
+    _add_ice_candidate_to_sdp (webrtc, webrtc->pending_local_description->sdp,
+        item->mlineindex, cand);
+
   PC_UNLOCK (webrtc);
   g_signal_emit (webrtc, gst_webrtc_bin_signals[ON_ICE_CANDIDATE_SIGNAL],
       0, item->mlineindex, cand);