From 249b2d54d7068c6ea2943c7e2c9834716ceb3552 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olivier=20Cr=C3=AAte?= <olivier.crete@collabora.com>
Date: Fri, 26 Mar 2021 15:23:34 -0400
Subject: [PATCH] webrtcbin: Enforce compatible caps on pad request

If a pad is requested with certain caps and there is already a
transceiver, reject the pad request if the caps don't match.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2104>
---
 ext/webrtc/gstwebrtcbin.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/ext/webrtc/gstwebrtcbin.c b/ext/webrtc/gstwebrtcbin.c
index e1dcaeeffe..fe4cff2f94 100644
--- a/ext/webrtc/gstwebrtcbin.c
+++ b/ext/webrtc/gstwebrtcbin.c
@@ -6234,6 +6234,16 @@ gst_webrtc_bin_request_new_pad (GstElement * element, GstPadTemplate * templ,
         gst_object_unref (pad2);
         return NULL;
       }
+
+      if (caps && trans->codec_preferences) {
+        if (!gst_caps_can_intersect (caps, trans->codec_preferences)) {
+          GST_ERROR_OBJECT (element, "Tried to request a new sink pad %s for"
+              " existing m-line %d, but requested caps %" GST_PTR_FORMAT
+              " don't match existing codec preferences %" GST_PTR_FORMAT,
+              name, serial, caps, trans->codec_preferences);
+          return NULL;
+        }
+      }
     }
   }