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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
d7ded13a MC |
5 | SSL_pending, SSL_has_pending - check for readable bytes buffered in an |
6 | SSL object | |
c19b6c92 RL |
7 | |
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include <openssl/ssl.h> | |
11 | ||
c3e64028 | 12 | int SSL_pending(const SSL *ssl); |
d7ded13a | 13 | int SSL_has_pending(const SSL *s); |
c19b6c92 RL |
14 | |
15 | =head1 DESCRIPTION | |
16 | ||
d7ded13a MC |
17 | Data is received in whole blocks known as records from the peer. A whole record |
18 | is processed (e.g. decrypted) in one go and is buffered by OpenSSL until it is | |
7714dc5e | 19 | read by the application via a call to L<SSL_read_ex(3)> or L<SSL_read(3)>. |
d7ded13a MC |
20 | |
21 | SSL_pending() returns the number of bytes which have been processed, buffered | |
22 | and are available inside B<ssl> for immediate read. | |
23 | ||
24 | If the B<SSL> object's I<read_ahead> flag is set (see | |
25 | L<SSL_CTX_set_read_ahead(3)>), additional protocol bytes (beyond the current | |
26 | record) may have been read containing more TLS/SSL records. This also applies to | |
27 | DTLS and pipelining (see L<SSL_CTX_set_split_send_fragment(3)>). These | |
28 | additional bytes will be buffered by OpenSSL but will remain unprocessed until | |
29 | they are needed. As these bytes are still in an unprocessed state SSL_pending() | |
30 | will ignore them. Therefore it is possible for no more bytes to be readable from | |
31 | the underlying BIO (because OpenSSL has already read them) and for SSL_pending() | |
32 | to return 0, even though readable application data bytes are available (because | |
33 | the data is in unprocessed buffered records). | |
34 | ||
35 | SSL_has_pending() returns 1 if B<s> has buffered data (whether processed or | |
36 | unprocessed) and 0 otherwise. Note that it is possible for SSL_has_pending() to | |
7714dc5e MC |
37 | return 1, and then a subsequent call to SSL_read_ex() or SSL_read() to return no |
38 | data because the unprocessed buffered data when processed yielded no application | |
39 | data (for example this can happen during renegotiation). It is also possible in | |
40 | this scenario for SSL_has_pending() to continue to return 1 even after an | |
41 | SSL_read_ex() or SSL_read() call because the buffered and unprocessed data is | |
42 | not yet processable (e.g. because OpenSSL has only received a partial record so | |
43 | far). | |
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44 | |
45 | =head1 RETURN VALUES | |
46 | ||
d7ded13a MC |
47 | SSL_pending() returns the number of buffered and processed application data |
48 | bytes that are pending and are available for immediate read. SSL_has_pending() | |
49 | returns 1 if there is buffered record data in the SSL object and 0 otherwise. | |
c19b6c92 | 50 | |
d7ded13a | 51 | =head1 SEE ALSO |
b7af080f | 52 | |
7714dc5e | 53 | L<SSL_read_ex(3)>, L<SSL_read(3)>, L<SSL_CTX_set_read_ahead(3)>, |
b97fdb57 | 54 | L<SSL_CTX_set_split_send_fragment(3)>, L<ssl(7)> |
b7af080f | 55 | |
d7ded13a | 56 | =head1 HISTORY |
b7af080f | 57 | |
d7ded13a | 58 | The SSL_has_pending() function was added in OpenSSL 1.1.0. |
c19b6c92 | 59 | |
e2f92610 RS |
60 | =head1 COPYRIGHT |
61 | ||
62 | Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. | |
63 | ||
4746f25a | 64 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
65 | this file except in compliance with the License. You can obtain a copy |
66 | in the file LICENSE in the source distribution or at | |
67 | L<https://www.openssl.org/source/license.html>. | |
68 | ||
69 | =cut |