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d0638fd5f0
Reviewed-by: Tomas Mraz <tomas@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> Reviewed-by: Paul Dale <pauli@openssl.org> (Merged from https://github.com/openssl/openssl/pull/20061)
77 lines
2.7 KiB
Plaintext
77 lines
2.7 KiB
Plaintext
=pod
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=head1 NAME
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SSL_CTX_set_read_ahead, SSL_CTX_get_read_ahead,
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SSL_set_read_ahead, SSL_get_read_ahead,
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SSL_CTX_get_default_read_ahead
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- manage whether to read as many input bytes as possible
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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void SSL_set_read_ahead(SSL *s, int yes);
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int SSL_get_read_ahead(const SSL *s);
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SSL_CTX_set_read_ahead(SSL_CTX *ctx, int yes);
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long SSL_CTX_get_read_ahead(SSL_CTX *ctx);
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long SSL_CTX_get_default_read_ahead(SSL_CTX *ctx);
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=head1 DESCRIPTION
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SSL_CTX_set_read_ahead() and SSL_set_read_ahead() set whether we should read as
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many input bytes as possible (for nonblocking reads) or not. For example if
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B<x> bytes are currently required by OpenSSL, but B<y> bytes are available from
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the underlying BIO (where B<y> > B<x>), then OpenSSL will read all B<y> bytes
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into its buffer (providing that the buffer is large enough) if reading ahead is
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on, or B<x> bytes otherwise.
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Setting the parameter B<yes> to 0 turns reading ahead is off, other values turn
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it on.
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SSL_CTX_set_default_read_ahead() is identical to SSL_CTX_set_read_ahead().
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SSL_CTX_get_read_ahead() and SSL_get_read_ahead() indicate whether reading
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ahead has been set or not.
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SSL_CTX_get_default_read_ahead() is identical to SSL_CTX_get_read_ahead().
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These functions cannot be used with QUIC SSL objects.
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=head1 NOTES
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These functions have no impact when used with DTLS. The return values for
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SSL_CTX_get_read_head() and SSL_get_read_ahead() are undefined for DTLS. Setting
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B<read_ahead> can impact the behaviour of the SSL_pending() function
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(see L<SSL_pending(3)>).
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Since SSL_read() can return B<SSL_ERROR_WANT_READ> for non-application data
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records, and SSL_has_pending() can't tell the difference between processed and
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unprocessed data, it's recommended that if read ahead is turned on that
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B<SSL_MODE_AUTO_RETRY> is not turned off using SSL_CTX_clear_mode().
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That will prevent getting B<SSL_ERROR_WANT_READ> when there is still a complete
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record available that hasn't been processed.
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If the application wants to continue to use the underlying transport (e.g. TCP
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connection) after the SSL connection is finished using SSL_shutdown() reading
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ahead should be turned off.
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Otherwise the SSL structure might read data that it shouldn't.
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=head1 RETURN VALUES
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SSL_get_read_ahead() and SSL_CTX_get_read_ahead() return 0 if reading ahead is off,
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and non zero otherwise.
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=head1 SEE ALSO
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L<ssl(7)>, L<SSL_pending(3)>
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=head1 COPYRIGHT
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Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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