Support encrypted RTP extensions (RFC 6904)

webrtc/media/engine/webrtcmediaengine.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 181 matching lines @@
 
   // Ignore any extensions that we don't recognize.
   for (const auto& extension : extensions) {
     if (supported(extension.uri)) {
       result.push_back(extension);
     } else {
       LOG(LS_WARNING) << "Unsupported RTP extension: " << extension.ToString();
     }
   }
 
-  // Sort by name, ascending, so that we don't reset extensions if they were
-  // specified in a different order (also allows us to use std::unique below).
+  // Sort by name, ascending (prioritise encryption), so that we don't reset
+  // extensions if they were specified in a different order (also allows us
+  // to use std::unique below).
   std::sort(result.begin(), result.end(),
             [](const webrtc::RtpExtension& rhs,
-               const webrtc::RtpExtension& lhs) { return rhs.uri < lhs.uri; });
+               const webrtc::RtpExtension& lhs) {
+                return rhs.encrypt == lhs.encrypt ? rhs.uri < lhs.uri
+                                                  : rhs.encrypt > lhs.encrypt;
+              });
 
   // Remove unnecessary extensions (used on send side).
   if (filter_redundant_extensions) {
     auto it = std::unique(
         result.begin(), result.end(),
         [](const webrtc::RtpExtension& rhs, const webrtc::RtpExtension& lhs) {
-          return rhs.uri == lhs.uri;
+          return rhs.uri == lhs.uri && rhs.encrypt == lhs.encrypt;
         });
     result.erase(it, result.end());
 
     // Keep just the highest priority extension of any in the following list.
     static const char* kBweExtensionPriorities[] = {
         webrtc::RtpExtension::kTransportSequenceNumberUri,
         webrtc::RtpExtension::kAbsSendTimeUri,
         webrtc::RtpExtension::kTimestampOffsetUri};
     DiscardRedundantExtensions(&result, kBweExtensionPriorities);
   }
@@ skipping 20 matching lines @@
   }
   if (codec.GetParam(kCodecParamMaxBitrate, &bitrate_kbps) &&
       bitrate_kbps > 0) {
     config.max_bitrate_bps = bitrate_kbps * 1000;
   } else {
     config.max_bitrate_bps = -1;
   }
   return config;
 }
 }  // namespace cricket