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<?xml version="1.0" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>SSL_CTX_set_read_ahead</title> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <link rev="made" href="mailto:root@hsxx.drive.ne.jp" /> </head> <body style="background-color: white"> <!-- INDEX BEGIN --> <div name="index"> <p><a name="__index__"></a></p> <ul> <li><a href="#name">NAME</a></li> <li><a href="#synopsis">SYNOPSIS</a></li> <li><a href="#description">DESCRIPTION</a></li> <li><a href="#notes">NOTES</a></li> <li><a href="#return_values">RETURN VALUES</a></li> <li><a href="#see_also">SEE ALSO</a></li> <li><a href="#copyright">COPYRIGHT</a></li> </ul> <hr name="index" /> </div> <!-- INDEX END --> <p> </p> <hr /> <h1><a name="name">NAME</a></h1> <p>SSL_CTX_set_read_ahead, SSL_CTX_get_read_ahead, SSL_set_read_ahead, SSL_get_read_ahead, SSL_CTX_get_default_read_ahead - manage whether to read as many input bytes as possible</p> <p> </p> <hr /> <h1><a name="synopsis">SYNOPSIS</a></h1> <pre> #include <openssl/ssl.h></pre> <pre> void SSL_set_read_ahead(SSL *s, int yes); int SSL_get_read_ahead(const SSL *s);</pre> <pre> SSL_CTX_set_read_ahead(SSL_CTX *ctx, int yes); long SSL_CTX_get_read_ahead(SSL_CTX *ctx); long SSL_CTX_get_default_read_ahead(SSL_CTX *ctx);</pre> <p> </p> <hr /> <h1><a name="description">DESCRIPTION</a></h1> <p><code>SSL_CTX_set_read_ahead()</code> and <code>SSL_set_read_ahead()</code> set whether we should read as many input bytes as possible (for nonblocking reads) or not. For example if <strong>x</strong> bytes are currently required by OpenSSL, but <strong>y</strong> bytes are available from the underlying BIO (where <strong>y</strong> > <strong>x</strong>), then OpenSSL will read all <strong>y</strong> bytes into its buffer (providing that the buffer is large enough) if reading ahead is on, or <strong>x</strong> bytes otherwise. Setting the parameter <strong>yes</strong> to 0 turns reading ahead is off, other values turn it on. <code>SSL_CTX_set_default_read_ahead()</code> is identical to <code>SSL_CTX_set_read_ahead()</code>.</p> <p><code>SSL_CTX_get_read_ahead()</code> and <code>SSL_get_read_ahead()</code> indicate whether reading ahead has been set or not. <code>SSL_CTX_get_default_read_ahead()</code> is identical to <code>SSL_CTX_get_read_ahead()</code>.</p> <p> </p> <hr /> <h1><a name="notes">NOTES</a></h1> <p>These functions have no impact when used with DTLS. The return values for <code>SSL_CTX_get_read_head()</code> and <code>SSL_get_read_ahead()</code> are undefined for DTLS. Setting <strong>read_ahead</strong> can impact the behaviour of the <code>SSL_pending()</code> function (see <em>SSL_pending(3)</em>).</p> <p>Since <code>SSL_read()</code> can return <strong>SSL_ERROR_WANT_READ</strong> for non-application data records, and <code>SSL_has_pending()</code> can't tell the difference between processed and unprocessed data, it's recommended that if read ahead is turned on that <strong>SSL_MODE_AUTO_RETRY</strong> is not turned off using <code>SSL_CTX_clear_mode()</code>. That will prevent getting <strong>SSL_ERROR_WANT_READ</strong> when there is still a complete record available that hasn't been processed.</p> <p>If the application wants to continue to use the underlying transport (e.g. TCP connection) after the SSL connection is finished using <code>SSL_shutdown()</code> reading ahead should be turned off. Otherwise the SSL structure might read data that it shouldn't.</p> <p> </p> <hr /> <h1><a name="return_values">RETURN VALUES</a></h1> <p><code>SSL_get_read_ahead()</code> and <code>SSL_CTX_get_read_ahead()</code> return 0 if reading ahead is off, and non zero otherwise.</p> <p> </p> <hr /> <h1><a name="see_also">SEE ALSO</a></h1> <p><em>ssl(7)</em>, <em>SSL_pending(3)</em></p> <p> </p> <hr /> <h1><a name="copyright">COPYRIGHT</a></h1> <p>Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.</p> <p>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 <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p> </body> </html>