Pick the DTLS handshake timeout based on the ICE RTT estimate

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 505 matching lines @@
 void OpenSSLStreamAdapter::SetMode(SSLMode mode) {
   RTC_DCHECK(state_ == SSL_NONE);
   ssl_mode_ = mode;
 }
 
 void OpenSSLStreamAdapter::SetMaxProtocolVersion(SSLProtocolVersion version) {
   RTC_DCHECK(ssl_ctx_ == NULL);
   ssl_max_version_ = version;
 }
 
+void OpenSSLStreamAdapter::SetHandshakeTimeout(int timeout_ms) {
+  RTC_DCHECK(ssl_ctx_ == NULL);

[Taylor Brandstetter, 2017/02/02 18:07:41]

Should leave a comment in the header file saying that this can only be called
before StartSSL.

[skvlad, 2017/02/02 22:19:33]

Done.

+  dtls_handshake_timeout_ms_ = timeout_ms;
+}
+
 //
 // StreamInterface Implementation
 //
 
 StreamResult OpenSSLStreamAdapter::Write(const void* data, size_t data_len,
                                          size_t* written, int* error) {
   LOG(LS_VERBOSE) << "OpenSSLStreamAdapter::Write(" << data_len << ")";
 
   switch (state_) {
   case SSL_NONE:
@@ skipping 257 matching lines @@
   if (!ssl_) {
     BIO_free(bio);
     return -1;
   }
 
   SSL_set_app_data(ssl_, this);
 
   SSL_set_bio(ssl_, bio, bio);  // the SSL object owns the bio now.
   if (ssl_mode_ == SSL_MODE_DTLS) {
 #ifdef OPENSSL_IS_BORINGSSL
-    // Change the initial retransmission timer from 1 second to 50ms.
-    // This will likely result in some spurious retransmissions, but
-    // it's useful for ensuring a timely handshake when there's packet
-    // loss.
-    DTLSv1_set_initial_timeout_duration(ssl_, 50);
+    // Change the initial retransmission timer to the value selected to match
+    // the connection RTT. This ensures fast connection setup without excessive
+    // bandwidth usage.

[Taylor Brandstetter, 2017/02/02 18:07:41]

This comment is a little out of place here; this class doesn't know how the
timer value was selected.

[skvlad, 2017/02/02 22:19:33]

Acknowledged.

+    DTLSv1_set_initial_timeout_duration(ssl_, dtls_handshake_timeout_ms_);
 #else
     // Enable read-ahead for DTLS so whole packets are read from internal BIO
     // before parsing. This is done internally by BoringSSL for DTLS.
     SSL_set_read_ahead(ssl_, 1);
 #endif
   }
 
   SSL_set_mode(ssl_, SSL_MODE_ENABLE_PARTIAL_WRITE |
                SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
@@ skipping 409 matching lines @@
   }
 
   return false;
 }
 
 void OpenSSLStreamAdapter::enable_time_callback_for_testing() {
   g_use_time_callback_for_testing = true;
 }
 
 }  // namespace rtc