Section: OpenSSL (3)
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
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);
set whether we should read as
many input bytes as possible (for non-blocking reads) or not. For example if
bytes are currently required by OpenSSL, but y
bytes are available from
the underlying BIO
), then OpenSSL will read all y
into its buffer (providing that the buffer is large enough) if reading ahead is
on, or x
Setting the parameter yes
to 0 turns reading ahead is off, other values turn
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
are undefined for DTLS.
can impact the behaviour of the SSL_pending()
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 0 if reading ahead is off,
and non zero otherwise.
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