Support getting external HMAC auth context with libsrtp 2.1.0.

webrtc/pc/srtpfilter.cc

 /*
  *  Copyright 2009 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 547 matching lines @@
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   RTC_DCHECK(IsExternalAuthActive());
   if (!IsExternalAuthActive()) {
     return false;
   }
 
   ExternalHmacContext* external_hmac = nullptr;
   // stream_template will be the reference context for other streams.
   // Let's use it for getting the keys.
   srtp_stream_ctx_t* srtp_context = session_->stream_template;
+#if defined(SRTP_MAX_MKI_LEN)

[joachim, 2017/06/27 21:15:16]

The #define has been introduced in libsrtp 2.1.0

+  // libsrtp 2.1.0
+  if (srtp_context && srtp_context->session_keys &&
+      srtp_context->session_keys->rtp_auth) {
+    external_hmac = reinterpret_cast<ExternalHmacContext*>(
+        srtp_context->session_keys->rtp_auth->state);
+  }
+#else
+  // libsrtp 2.0.0
+  // TODO(jbauch): Remove after switching to libsrtp 2.1.0
   if (srtp_context && srtp_context->rtp_auth) {
     external_hmac = reinterpret_cast<ExternalHmacContext*>(
         srtp_context->rtp_auth->state);
   }
+#endif
 
   if (!external_hmac) {
     LOG(LS_ERROR) << "Failed to get auth keys from libsrtp!.";
     return false;
   }
 
   *key = external_hmac->key;
   *key_len = external_hmac->key_length;
   *tag_len = rtp_auth_tag_len_;
   return true;
@@ skipping 180 matching lines @@
   // Callback will be executed from same thread that calls the "srtp_protect"
   // and "srtp_unprotect" functions.
   SrtpSession* session = static_cast<SrtpSession*>(
       srtp_get_user_data(ev->session));
   if (session) {
     session->HandleEvent(ev);
   }
 }
 
 }  // namespace cricket