Log how often DTLS negotiation failed because of incompatible ciphersuites.

webrtc/base/opensslstreamadapter.cc

 /*
  *  Copyright 2004 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 836 matching lines @@
       }
       break;
 
     case SSL_ERROR_WANT_WRITE:
       LOG(LS_VERBOSE) << " -- error want write";
       break;
 
     case SSL_ERROR_ZERO_RETURN:
     default:
       LOG(LS_VERBOSE) << " -- error " << code;
+      SSLHandshakeError ssl_handshake_err = SSLHandshakeError::ERR_OTHER;
+      int err_code = 0;
+      if ((err_code = ERR_peek_last_error()) != 0 &&

[honghaiz3, 2016/07/22 21:35:26]

you could do
int err_code = ERR_peek_last_error();
if (err_code != 0 && ...

[Zhi Huang, 2016/07/25 17:24:28]

Done.

+          ERR_GET_REASON(err_code) == SSL_R_NO_SHARED_CIPHER) {
+        ssl_handshake_err = SSLHandshakeError::ERR_INCOMPATIBLE_CIPHERSUITE;
+      }
+      SignalSSLHandshakeError(ssl_handshake_err);
       return (ssl_error != 0) ? ssl_error : -1;
   }
 
   return 0;
 }
 
 void OpenSSLStreamAdapter::Error(const char* context, int err, bool signal) {
   LOG(LS_WARNING) << "OpenSSLStreamAdapter::Error("
                   << context << ", " << err << ")";
   state_ = SSL_ERROR;
@@ skipping 352 matching lines @@
         return true;
     }
   }
 
   return false;
 }
 
 }  // namespace rtc
 
 #endif  // HAVE_OPENSSL_SSL_H