SSL_CTX_ctrl, SSL_CTX_callback_ctrl, SSL_ctrl, SSL_callback_ctrl - internal
  handling functions for SSL_CTX and SSL objects
 #include <openssl/ssl.h>
 long SSL_CTX_ctrl(SSL_CTX *ctx, int cmd, long larg, void *parg);
 long SSL_CTX_callback_ctrl(SSL_CTX *, int cmd, void (*fp)());
 long SSL_ctrl(SSL *ssl, int cmd, long larg, void *parg);
 long SSL_callback_ctrl(SSL *, int cmd, void (*fp)());
The SSL_*_ctrl() family of functions is used to manipulate settings of
  the SSL_CTX and SSL objects. Depending on the command cmd the arguments
  larg, parg, or fp are evaluated. These functions should
  never be called directly. All functionalities needed are made available via
  other functions or macros.
The return values of the SSL*_ctrl() functions depend on the command
  supplied via the cmd parameter.
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Licensed under the Apache License 2.0 (the "License").
    You may not use this file except in compliance with the License. You can
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    <https://www.openssl.org/source/license.html>.