1SSL_CTX_SET_READ_AHEAD(3)           OpenSSL          SSL_CTX_SET_READ_AHEAD(3)
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NAME

6       SSL_CTX_set_read_ahead, SSL_CTX_get_read_ahead, SSL_set_read_ahead,
7       SSL_get_read_ahead, SSL_CTX_get_default_read_ahead - manage whether to
8       read as many input bytes as possible
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SYNOPSIS

11        #include <openssl/ssl.h>
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13        void SSL_set_read_ahead(SSL *s, int yes);
14        int SSL_get_read_ahead(const SSL *s);
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16        SSL_CTX_set_read_ahead(SSL_CTX *ctx, int yes);
17        long SSL_CTX_get_read_ahead(SSL_CTX *ctx);
18        long SSL_CTX_get_default_read_ahead(SSL_CTX *ctx);
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DESCRIPTION

21       SSL_CTX_set_read_ahead() and SSL_set_read_ahead() set whether we should
22       read as many input bytes as possible (for nonblocking reads) or not.
23       For example if x bytes are currently required by OpenSSL, but y bytes
24       are available from the underlying BIO (where y > x), then OpenSSL will
25       read all y bytes into its buffer (providing that the buffer is large
26       enough) if reading ahead is on, or x bytes otherwise.  Setting the
27       parameter yes to 0 turns reading ahead is off, other values turn it on.
28       SSL_CTX_set_default_read_ahead() is identical to
29       SSL_CTX_set_read_ahead().
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31       SSL_CTX_get_read_ahead() and SSL_get_read_ahead() indicate whether
32       reading ahead has been set or not.  SSL_CTX_get_default_read_ahead() is
33       identical to SSL_CTX_get_read_ahead().
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NOTES

36       These functions have no impact when used with DTLS. The return values
37       for SSL_CTX_get_read_head() and SSL_get_read_ahead() are undefined for
38       DTLS. Setting read_ahead can impact the behaviour of the SSL_pending()
39       function (see SSL_pending(3)).
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41       Since SSL_read() can return SSL_ERROR_WANT_READ for non-application
42       data records, and SSL_has_pending() can't tell the difference between
43       processed and unprocessed data, it's recommended that if read ahead is
44       turned on that SSL_MODE_AUTO_RETRY is not turned off using
45       SSL_CTX_clear_mode().  That will prevent getting SSL_ERROR_WANT_READ
46       when there is still a complete record available that hasn't been
47       processed.
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49       If the application wants to continue to use the underlying transport
50       (e.g. TCP connection) after the SSL connection is finished using
51       SSL_shutdown() reading ahead should be turned off.  Otherwise the SSL
52       structure might read data that it shouldn't.
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RETURN VALUES

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

59       ssl(7), SSL_pending(3)
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62       Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
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64       Licensed under the OpenSSL license (the "License").  You may not use
65       this file except in compliance with the License.  You can obtain a copy
66       in the file LICENSE in the source distribution or at
67       <https://www.openssl.org/source/license.html>.
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711.1.1i                            2021-07-22         SSL_CTX_SET_READ_AHEAD(3)
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