Set mtu for DTLS to 1280

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 242 matching lines @@
   switch (cmd) {
     case BIO_CTRL_RESET:
       return 0;
     case BIO_CTRL_EOF:
       return b->num;
     case BIO_CTRL_WPENDING:
     case BIO_CTRL_PENDING:
       return 0;
     case BIO_CTRL_FLUSH:
       return 1;
+    case BIO_CTRL_DGRAM_QUERY_MTU:
+      // openssl defaults to mtu=256 unless we return something here.
+      // The handshake doesn't actually need to send packets above 1k,
+      // so this seems like a sensible value that should work in most cases.
+      // Webrtc uses the same value for video packets.
+      return 1200;
     default:
       return 0;
   }
 }
 
 /////////////////////////////////////////////////////////////////////////////
 // OpenSSLStreamAdapter
 /////////////////////////////////////////////////////////////////////////////
 
 OpenSSLStreamAdapter::OpenSSLStreamAdapter(StreamInterface* stream)
@@ skipping 854 matching lines @@
       }
 #else  // !OPENSSL_IS_BORINGSSL
       return kDefaultSslCipher12;
 #endif
   }
 }
 
 }  // namespace rtc
 
 #endif  // HAVE_OPENSSL_SSL_H