SSL_clear - reset SSL object to allow another connection
 #include <openssl/ssl.h>
 int SSL_clear(SSL *ssl);
Reset ssl to allow another connection. All settings (method, ciphers,
  BIOs) are kept.
SSL_clear is used to prepare an SSL object for a new connection. While all
  settings are kept, a side effect is the handling of the current SSL session.
  If a session is still open, it is considered bad and will be removed
  from the session cache, as required by RFC2246. A session is considered open,
  if SSL_shutdown(3) was not called for the connection or at least
  SSL_set_shutdown(3) was used to set the SSL_SENT_SHUTDOWN state.
If a session was closed cleanly, the session object will be kept
    and all settings corresponding. This explicitly means, that e.g. the special
    method used during the session will be kept for the next handshake. So if
    the session was a TLSv1 session, a SSL client object will use a TLSv1 client
    method for the next handshake and a SSL server object will use a TLSv1
    server method, even if TLS_*_methods were chosen on startup. This will might
    lead to connection failures (see SSL_new(3)) for a description of the
    method's properties.
SSL_clear() resets the SSL object to allow for another connection. The
  reset operation however keeps several settings of the last sessions (some of
  these settings were made automatically during the last handshake). It only
  makes sense for a new connection with the exact same peer that shares these
  settings, and may fail if that peer changes its settings between connections.
  Use the sequence SSL_get_session(3); SSL_new(3);
  SSL_set_session(3); SSL_free(3) instead to avoid such failures
  (or simply SSL_free(3); SSL_new(3) if session reuse is not
  desired).
The following return values can occur:
  - 0
- The SSL_clear() operation could not be performed. Check the error
      stack to find out the reason.
- 1
- The SSL_clear() operation was successful.
SSL_new(3), SSL_free(3), SSL_shutdown(3),
    SSL_set_shutdown(3), SSL_CTX_set_options(3), ssl(7),
    SSL_CTX_set_client_cert_cb(3)
Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You
    may not use this file except in compliance with the License. You can obtain
    a copy in the file LICENSE in the source distribution or at
    <https://www.openssl.org/source/license.html>.