Log how often DTLS negotiation failed because of incompatible ciphersuites.

webrtc/base/opensslstreamadapter.cc

Index: webrtc/base/opensslstreamadapter.cc
diff --git a/webrtc/base/opensslstreamadapter.cc b/webrtc/base/opensslstreamadapter.cc
index e04eb04d67c8d05eee38938f406484ccbe5d5247..50753cade2bb0f2b880f915414c022ef4049b858 100644
--- a/webrtc/base/opensslstreamadapter.cc
+++ b/webrtc/base/opensslstreamadapter.cc
@@ -854,6 +854,12 @@ int OpenSSLStreamAdapter::ContinueSSL() {
     case SSL_ERROR_ZERO_RETURN:
     default:
       LOG(LS_VERBOSE) << " -- error " << code;
+      int err_code = ERR_peek_last_error();
+      int err_reason = 0;

[Zhi Huang, 2016/07/27 21:04:14]

I can leave a comment, like "Use 0 to represent unknown error.", here before
submitting.

+      if (err_code != 0 && ERR_GET_REASON(err_code) == SSL_R_NO_SHARED_CIPHER) {
+        err_reason = SSL_R_NO_SHARED_CIPHER;
+      }
+      SignalSSLHandshakeError(err_reason);

[honghaiz3, 2016/07/29 15:49:54]

Should this just be 
int err_reason = ERR_GET_REASON(err_code);
SignalSSLHandshakeError(err_reason);  
?

[honghaiz3, 2016/08/01 17:19:19]

If you only want to log the error SSL_R_NO_SHARED_CIPHER, that is fine. 

       return (ssl_error != 0) ? ssl_error : -1;
   }