Updated: 2022/Sep/29

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SSL_CTX_set_read_ahead(3)           OpenSSL          SSL_CTX_set_read_ahead(3)



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

LIBRARY
       libcrypto, -lcrypto

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>.



3.0.12                            2023-05-07         SSL_CTX_set_read_ahead(3)