| yuezonghe | 824eb0c | 2024-06-27 02:32:26 -0700 | [diff] [blame] | 1 | =pod |
| 2 | |
| 3 | =head1 NAME |
| 4 | |
| 5 | SSL_pending, SSL_has_pending - check for readable bytes buffered in an |
| 6 | SSL object |
| 7 | |
| 8 | =head1 SYNOPSIS |
| 9 | |
| 10 | #include <openssl/ssl.h> |
| 11 | |
| 12 | int SSL_pending(const SSL *ssl); |
| 13 | int SSL_has_pending(const SSL *s); |
| 14 | |
| 15 | =head1 DESCRIPTION |
| 16 | |
| 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 |
| 19 | read by the application via a call to L<SSL_read_ex(3)> or L<SSL_read(3)>. |
| 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 |
| 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). |
| 44 | |
| 45 | =head1 RETURN VALUES |
| 46 | |
| 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. |
| 50 | |
| 51 | =head1 SEE ALSO |
| 52 | |
| 53 | L<SSL_read_ex(3)>, L<SSL_read(3)>, L<SSL_CTX_set_read_ahead(3)>, |
| 54 | L<SSL_CTX_set_split_send_fragment(3)>, L<ssl(7)> |
| 55 | |
| 56 | =head1 HISTORY |
| 57 | |
| 58 | The SSL_has_pending() function was added in OpenSSL 1.1.0. |
| 59 | |
| 60 | =head1 COPYRIGHT |
| 61 | |
| 62 | Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved. |
| 63 | |
| 64 | Licensed under the OpenSSL license (the "License"). You may not use |
| 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 |