| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | SSL_pending, SSL_has_pending - check for readable bytes buffered in an
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| 6 | SSL object
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| 7 |
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| 8 | =head1 SYNOPSIS
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| 9 |
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| 10 | #include <openssl/ssl.h>
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| 11 |
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| 12 | int SSL_pending(const SSL *ssl);
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| 13 | int SSL_has_pending(const SSL *s);
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| 14 |
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| 15 | =head1 DESCRIPTION
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| 16 |
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| 17 | Data is received in whole blocks known as records from the peer. A whole record
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| 18 | is processed (e.g. decrypted) in one go and is buffered by OpenSSL until it is
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| 19 | read by the application via a call to L<SSL_read_ex(3)> or L<SSL_read(3)>.
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| 20 |
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| 21 | SSL_pending() returns the number of bytes which have been processed, buffered
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| 22 | and are available inside B<ssl> for immediate read.
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| 23 |
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| 24 | If the B<SSL> object's I<read_ahead> flag is set (see
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| 25 | L<SSL_CTX_set_read_ahead(3)>), additional protocol bytes (beyond the current
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| 26 | record) may have been read containing more TLS/SSL records. This also applies to
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| 27 | DTLS and pipelining (see L<SSL_CTX_set_split_send_fragment(3)>). These
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| 28 | additional bytes will be buffered by OpenSSL but will remain unprocessed until
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| 29 | they are needed. As these bytes are still in an unprocessed state SSL_pending()
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| 30 | will ignore them. Therefore, it is possible for no more bytes to be readable from
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| 31 | the underlying BIO (because OpenSSL has already read them) and for SSL_pending()
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| 32 | to return 0, even though readable application data bytes are available (because
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| 33 | the data is in unprocessed buffered records).
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| 34 |
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| 35 | SSL_has_pending() returns 1 if B<s> has buffered data (whether processed or
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| 36 | unprocessed) and 0 otherwise. Note that it is possible for SSL_has_pending() to
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| 37 | return 1, and then a subsequent call to SSL_read_ex() or SSL_read() to return no
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| 38 | data because the unprocessed buffered data when processed yielded no application
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| 39 | data (for example this can happen during renegotiation). It is also possible in
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| 40 | this scenario for SSL_has_pending() to continue to return 1 even after an
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| 41 | SSL_read_ex() or SSL_read() call because the buffered and unprocessed data is
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| 42 | not yet processable (e.g. because OpenSSL has only received a partial record so
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| 43 | far).
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| 44 |
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| 45 | =head1 RETURN VALUES
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| 46 |
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| 47 | SSL_pending() returns the number of buffered and processed application data
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| 48 | bytes that are pending and are available for immediate read. SSL_has_pending()
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| 49 | returns 1 if there is buffered record data in the SSL object and 0 otherwise.
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| 50 |
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| 51 | =head1 SEE ALSO
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| 52 |
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| 53 | L<SSL_read_ex(3)>, L<SSL_read(3)>, L<SSL_CTX_set_read_ahead(3)>,
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| 54 | L<SSL_CTX_set_split_send_fragment(3)>, L<ssl(7)>
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| 55 |
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| 56 | =head1 HISTORY
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| 57 |
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| 58 | The SSL_has_pending() function was added in OpenSSL 1.1.0.
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| 59 |
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| 60 | =head1 COPYRIGHT
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| 61 |
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| 62 | Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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| 63 |
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| 64 | Licensed under the OpenSSL license (the "License"). You may not use
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| 65 | this file except in compliance with the License. You can obtain a copy
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| 66 | in the file LICENSE in the source distribution or at
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| 67 | L<https://www.openssl.org/source/license.html>.
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| 68 |
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| 69 | =cut
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