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
#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);
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().
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.
SSL_get_read_ahead() and
SSL_CTX_get_read_ahead() return 0 if
reading ahead is off, and non zero otherwise.
ssl(7),
SSL_pending(3)
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>.