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 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()
.
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 2015-2019 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.