webrtcbin: use the latest self-generated SDP as the basis for renegotiations

Fixes multiple errors when a webrtcbin renegotiation can switch between the
offerer and the answerer.

ext/webrtc/gstwebrtcbin.c

@@ -2040,7 +2040,7 @@ sdp_media_from_transceiver (GstWebRTCBin * webrtc, GstSDPMedia * media,
    * dtls fingerprints
    * multiple dtls fingerprints https://tools.ietf.org/html/draft-ietf-mmusic-4572-update-05
    */
-  GstSDPMessage *last_offer = _get_latest_offer (webrtc);
+  GstSDPMessage *last_offer = _get_latest_self_generated_sdp (webrtc);
   gchar *direction, *sdp_mid, *ufrag, *pwd;
   gboolean bundle_only;
   GstCaps *caps;
@@ -2239,7 +2239,7 @@ _add_data_channel_offer (GstWebRTCBin * webrtc, GstSDPMessage * msg,
     GstSDPMedia * media, GString * bundled_mids, guint bundle_idx,
     gchar * bundle_ufrag, gchar * bundle_pwd)
 {
-  GstSDPMessage *last_offer = _get_latest_offer (webrtc);
+  GstSDPMessage *last_offer = _get_latest_self_generated_sdp (webrtc);
   gchar *ufrag, *pwd, *sdp_mid;
   gboolean bundle_only = bundled_mids
       && webrtc->bundle_policy == GST_WEBRTC_BUNDLE_POLICY_MAX_BUNDLE
@@ -2330,7 +2330,7 @@ _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
   gchar *bundle_ufrag = NULL;
   gchar *bundle_pwd = NULL;
   GArray *reserved_pts = NULL;
-  GstSDPMessage *last_offer = _get_latest_offer (webrtc);
+  GstSDPMessage *last_offer = _get_latest_self_generated_sdp (webrtc);
   GList *seen_transceivers = NULL;
   guint media_idx = 0;
   int i;
@@ -2524,6 +2524,18 @@ _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
 
   g_list_free (seen_transceivers);
 
+  if (webrtc->priv->last_generated_answer)
+    gst_webrtc_session_description_free (webrtc->priv->last_generated_answer);
+  webrtc->priv->last_generated_answer = NULL;
+  if (webrtc->priv->last_generated_offer)
+    gst_webrtc_session_description_free (webrtc->priv->last_generated_offer);
+  {
+    GstSDPMessage *copy;
+    gst_sdp_message_copy (ret, &copy);
+    webrtc->priv->last_generated_offer =
+        gst_webrtc_session_description_new (GST_WEBRTC_SDP_TYPE_OFFER, copy);
+  }
+
   return ret;
 }
 
@@ -2650,7 +2662,7 @@ _create_answer_task (GstWebRTCBin * webrtc, const GstStructure * options)
   gchar *bundle_ufrag = NULL;
   gchar *bundle_pwd = NULL;
   GList *seen_transceivers = NULL;
-  GstSDPMessage *last_answer = _get_latest_answer (webrtc);
+  GstSDPMessage *last_answer = _get_latest_self_generated_sdp (webrtc);
 
   if (!webrtc->pending_remote_description) {
     GST_ERROR_OBJECT (webrtc,
@@ -3034,6 +3046,18 @@ out:
 
   g_list_free (seen_transceivers);
 
+  if (webrtc->priv->last_generated_offer)
+    gst_webrtc_session_description_free (webrtc->priv->last_generated_offer);
+  webrtc->priv->last_generated_offer = NULL;
+  if (webrtc->priv->last_generated_answer)
+    gst_webrtc_session_description_free (webrtc->priv->last_generated_answer);
+  {
+    GstSDPMessage *copy;
+    gst_sdp_message_copy (ret, &copy);
+    webrtc->priv->last_generated_answer =
+        gst_webrtc_session_description_new (GST_WEBRTC_SDP_TYPE_ANSWER, copy);
+  }
+
   return ret;
 }
 
@@ -5454,6 +5478,13 @@ gst_webrtc_bin_finalize (GObject * object)
     gst_webrtc_session_description_free (webrtc->pending_remote_description);
   webrtc->pending_remote_description = NULL;
 
+  if (webrtc->priv->last_generated_answer)
+    gst_webrtc_session_description_free (webrtc->priv->last_generated_answer);
+  webrtc->priv->last_generated_answer = NULL;
+  if (webrtc->priv->last_generated_offer)
+    gst_webrtc_session_description_free (webrtc->priv->last_generated_offer);
+  webrtc->priv->last_generated_offer = NULL;
+
   if (webrtc->priv->stats)
     gst_structure_free (webrtc->priv->stats);
   webrtc->priv->stats = NULL;

ext/webrtc/gstwebrtcbin.h

@@ -133,6 +133,8 @@ struct _GstWebRTCBinPrivate
   guint media_counter;
   /* the number of times create_offer has been called for the version field */
   guint offer_count;
+  GstWebRTCSessionDescription *last_generated_offer;
+  GstWebRTCSessionDescription *last_generated_answer;
 
   GstStructure *stats;
 };

ext/webrtc/utils.c

@@ -97,6 +97,17 @@ _get_latest_sdp (GstWebRTCBin * webrtc)
   return NULL;
 }
 
+GstSDPMessage *
+_get_latest_self_generated_sdp (GstWebRTCBin * webrtc)
+{
+  if (webrtc->priv->last_generated_answer)
+    return webrtc->priv->last_generated_answer->sdp;
+  if (webrtc->priv->last_generated_offer)
+    return webrtc->priv->last_generated_offer->sdp;
+
+  return NULL;
+}
+
 struct pad_block *
 _create_pad_block (GstElement * element, GstPad * pad, gulong block_id,
     gpointer user_data, GDestroyNotify notify)

ext/webrtc/utils.h

@@ -49,6 +49,7 @@ GstPadTemplate *        _find_pad_template          (GstElement * element,
 GstSDPMessage *         _get_latest_sdp             (GstWebRTCBin * webrtc);
 GstSDPMessage *         _get_latest_offer           (GstWebRTCBin * webrtc);
 GstSDPMessage *         _get_latest_answer          (GstWebRTCBin * webrtc);
+GstSDPMessage *         _get_latest_self_generated_sdp (GstWebRTCBin * webrtc);
 
 GstWebRTCICEStream *    _find_ice_stream_for_session            (GstWebRTCBin * webrtc,
                                                                  guint session_id);