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 non-blocking 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 2015-2019 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>.