1=pod 2 3=head1 NAME 4 5SSL_CTX_set_read_ahead, SSL_CTX_get_read_ahead, 6SSL_set_read_ahead, SSL_get_read_ahead, 7SSL_CTX_get_default_read_ahead 8- manage whether to read as many input bytes as possible 9 10=head1 SYNOPSIS 11 12 #include <openssl/ssl.h> 13 14 void SSL_set_read_ahead(SSL *s, int yes); 15 int SSL_get_read_ahead(const SSL *s); 16 17 SSL_CTX_set_read_ahead(SSL_CTX *ctx, int yes); 18 long SSL_CTX_get_read_ahead(SSL_CTX *ctx); 19 long SSL_CTX_get_default_read_ahead(SSL_CTX *ctx); 20 21=head1 DESCRIPTION 22 23SSL_CTX_set_read_ahead() and SSL_set_read_ahead() set whether we should read as 24many input bytes as possible (for nonblocking reads) or not. For example if 25B<x> bytes are currently required by OpenSSL, but B<y> bytes are available from 26the underlying BIO (where B<y> > B<x>), then OpenSSL will read all B<y> bytes 27into its buffer (providing that the buffer is large enough) if reading ahead is 28on, or B<x> bytes otherwise. 29Setting the parameter B<yes> to 0 turns reading ahead is off, other values turn 30it on. 31SSL_CTX_set_default_read_ahead() is identical to SSL_CTX_set_read_ahead(). 32 33SSL_CTX_get_read_ahead() and SSL_get_read_ahead() indicate whether reading 34ahead has been set or not. 35SSL_CTX_get_default_read_ahead() is identical to SSL_CTX_get_read_ahead(). 36 37=head1 NOTES 38 39These functions have no impact when used with DTLS. The return values for 40SSL_CTX_get_read_head() and SSL_get_read_ahead() are undefined for DTLS. Setting 41B<read_ahead> can impact the behaviour of the SSL_pending() function 42(see L<SSL_pending(3)>). 43 44Since SSL_read() can return B<SSL_ERROR_WANT_READ> for non-application data 45records, and SSL_has_pending() can't tell the difference between processed and 46unprocessed data, it's recommended that if read ahead is turned on that 47B<SSL_MODE_AUTO_RETRY> is not turned off using SSL_CTX_clear_mode(). 48That will prevent getting B<SSL_ERROR_WANT_READ> when there is still a complete 49record available that hasn't been processed. 50 51If the application wants to continue to use the underlying transport (e.g. TCP 52connection) after the SSL connection is finished using SSL_shutdown() reading 53ahead should be turned off. 54Otherwise the SSL structure might read data that it shouldn't. 55 56=head1 RETURN VALUES 57 58SSL_get_read_ahead() and SSL_CTX_get_read_ahead() return 0 if reading ahead is off, 59and non zero otherwise. 60 61=head1 SEE ALSO 62 63L<ssl(7)>, L<SSL_pending(3)> 64 65=head1 COPYRIGHT 66 67Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved. 68 69Licensed under the Apache License 2.0 (the "License"). You may not use 70this file except in compliance with the License. You can obtain a copy 71in the file LICENSE in the source distribution or at 72L<https://www.openssl.org/source/license.html>. 73 74=cut 75