NAME

       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

SYNOPSIS

        #include <openssl/ssl.h>

        void SSL_set_read_ahead(SSL *s, int yes);
        int SSL_get_read_ahead(const SSL *s);

        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);

DESCRIPTION

       SSL_CTX_set_read_ahead() and SSL_set_read_ahead() set whether we should read as many input
       bytes as possible (for nonblocking reads) or not. For example if x bytes are currently
       required by OpenSSL, but y bytes are available from the underlying BIO (where y > x), then
       OpenSSL will read all y bytes into its buffer (providing that the buffer is large enough)
       if reading ahead is on, or x bytes otherwise.  Setting the parameter yes to 0 turns
       reading ahead is off, other values turn it on.  SSL_CTX_set_default_read_ahead() is
       identical to SSL_CTX_set_read_ahead().

       SSL_CTX_get_read_ahead() and SSL_get_read_ahead() indicate whether reading ahead has been
       set or not.  SSL_CTX_get_default_read_ahead() is identical to SSL_CTX_get_read_ahead().

NOTES

       These functions have no impact when used with DTLS. The return values for
       SSL_CTX_get_read_head() and SSL_get_read_ahead() are undefined for DTLS. Setting
       read_ahead can impact the behaviour of the SSL_pending() function (see SSL_pending(3)).

       Since SSL_read() can return SSL_ERROR_WANT_READ for non-application data records, and
       SSL_has_pending() can't tell the difference between processed and unprocessed data, it's
       recommended that if read ahead is turned on that SSL_MODE_AUTO_RETRY is not turned off
       using SSL_CTX_clear_mode().  That will prevent getting SSL_ERROR_WANT_READ when there is
       still a complete record available that hasn't been processed.

       If the application wants to continue to use the underlying transport (e.g. TCP connection)
       after the SSL connection is finished using SSL_shutdown() reading ahead should be turned
       off.  Otherwise the SSL structure might read data that it shouldn't.

RETURN VALUES

       SSL_get_read_ahead() and SSL_CTX_get_read_ahead() return 0 if reading ahead is off, and
       non zero otherwise.

SEE ALSO

       ssl(7), SSL_pending(3)

COPYRIGHT

       Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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>.