text: /*
   * DTLS implementation written by Nagendra Modadugu
   * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
   */
  /* ====================================================================
   * Copyright (c) 1999-2005 The OpenSSL Project.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. All advertising materials mentioning features or use of this
   *    software must display the following acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
   *
   * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For written permission, please contact
   *    openssl-core@OpenSSL.org.
   *
   * 5. Products derived from this software may not be called "OpenSSL"
   *    nor may "OpenSSL" appear in their names without prior written
   *    permission of the OpenSSL Project.
   *
   * 6. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
   *
   * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
   * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   * ====================================================================
   *
   * This product includes cryptographic software written by Eric Young
   * (eay@cryptsoft.com).  This product includes software written by Tim
   * Hudson (tjh@cryptsoft.com). */
  
  #include <openssl/ssl.h>
  
  #include <assert.h>
  #include <string.h>
  
  #include <openssl/buf.h>
  #include <openssl/err.h>
  
  #include "../crypto/internal.h"
  #include "internal.h"
  
  
  using namespace bssl;
  
  static void dtls1_on_handshake_complete(SSL *ssl) {
    // Stop the reply timer left by the last flight we sent.
    dtls1_stop_timer(ssl);
    // If the final flight had a reply, we know the peer has received it. If not,
    // we must leave the flight around for post-handshake retransmission.
    if (ssl->d1->flight_has_reply) {
      dtls_clear_outgoing_messages(ssl);
    }
  }
  
  static bool dtls1_set_read_state(SSL *ssl, UniquePtr<SSLAEADContext> aead_ctx) {
    // Cipher changes are forbidden if the current epoch has leftover data.
    if (dtls_has_unprocessed_handshake_data(ssl)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFERED_MESSAGES_ON_CIPHER_CHANGE);
      ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
      return false;
    }
  
    ssl->d1->r_epoch++;
    OPENSSL_memset(&ssl->d1->bitmap, 0, sizeof(ssl->d1->bitmap));
    OPENSSL_memset(ssl->s3->read_sequence, 0, sizeof(ssl->s3->read_sequence));
  
    ssl->s3->aead_read_ctx = std::move(aead_ctx);
    return true;
  }
  
  static bool dtls1_set_write_state(SSL *ssl,
                                    UniquePtr<SSLAEADContext> aead_ctx) {
    ssl->d1->w_epoch++;
    OPENSSL_memcpy(ssl->d1->last_write_sequence, ssl->s3->write_sequence,
                   sizeof(ssl->s3->write_sequence));
    OPENSSL_memset(ssl->s3->write_sequence, 0, sizeof(ssl->s3->write_sequence));
  
    ssl->d1->last_aead_write_ctx = std::move(ssl->s3->aead_write_ctx);
    ssl->s3->aead_write_ctx = std::move(aead_ctx);
    return true;
  }
  
  static const SSL_PROTOCOL_METHOD kDTLSProtocolMethod = {
      true /* is_dtls */,
      dtls1_new,
      dtls1_free,
      dtls1_get_message,
      dtls1_next_message,
      dtls1_open_handshake,
      dtls1_open_change_cipher_spec,
      dtls1_open_app_data,
      dtls1_write_app_data,
      dtls1_dispatch_alert,
      dtls1_init_message,
      dtls1_finish_message,
      dtls1_add_message,
      dtls1_add_change_cipher_spec,
      dtls1_flush_flight,
      dtls1_on_handshake_complete,
      dtls1_set_read_state,
      dtls1_set_write_state,
  };
  
  const SSL_METHOD *DTLS_method(void) {
    static const SSL_METHOD kMethod = {
        0,
        &kDTLSProtocolMethod,
        &ssl_crypto_x509_method,
    };
    return &kMethod;
  }
  
  const SSL_METHOD *DTLS_with_buffers_method(void) {
    static const SSL_METHOD kMethod = {
        0,
        &kDTLSProtocolMethod,
        &ssl_noop_x509_method,
    };
    return &kMethod;
  }
  
  // Legacy version-locked methods.
  
  const SSL_METHOD *DTLSv1_2_method(void) {
    static const SSL_METHOD kMethod = {
        DTLS1_2_VERSION,
        &kDTLSProtocolMethod,
        &ssl_crypto_x509_method,
    };
    return &kMethod;
  }
  
  const SSL_METHOD *DTLSv1_method(void) {
    static const SSL_METHOD kMethod = {
        DTLS1_VERSION,
        &kDTLSProtocolMethod,
        &ssl_crypto_x509_method,
    };
    return &kMethod;
  }
  
  // Legacy side-specific methods.
  
  const SSL_METHOD *DTLSv1_2_server_method(void) {
    return DTLSv1_2_method();
  }
  
  const SSL_METHOD *DTLSv1_server_method(void) {
    return DTLSv1_method();
  }
  
  const SSL_METHOD *DTLSv1_2_client_method(void) {
    return DTLSv1_2_method();
  }
  
  const SSL_METHOD *DTLSv1_client_method(void) {
    return DTLSv1_method();
  }
  
  const SSL_METHOD *DTLS_server_method(void) {
    return DTLS_method();
  }
  
  const SSL_METHOD *DTLS_client_method(void) {
    return DTLS_method();
  }
  