SSL_pending, SSL_has_pending - check for readable bytes buffered in an SSL
object
#include <openssl/ssl.h>
int SSL_pending(const SSL *ssl);
int SSL_has_pending(const SSL *s);
Data is received in whole blocks known as records from the peer. A whole record
is processed (e.g. decrypted) in one go and is buffered by OpenSSL until it is
read by the application via a call to
SSL_read_ex(3) or
SSL_read(3).
SSL_pending() returns the number of bytes which have been processed,
buffered and are available inside
ssl for immediate read.
If the
SSL object's
read_ahead flag is set (see
SSL_CTX_set_read_ahead(3)), additional protocol bytes (beyond the
current record) may have been read containing more TLS/SSL records. This also
applies to DTLS and pipelining (see
SSL_CTX_set_split_send_fragment(3)). These additional bytes will be
buffered by OpenSSL but will remain unprocessed until they are needed. As
these bytes are still in an unprocessed state
SSL_pending() will ignore
them. Therefore, it is possible for no more bytes to be readable from the
underlying BIO (because OpenSSL has already read them) and for
SSL_pending() to return 0, even though readable application data bytes
are available (because the data is in unprocessed buffered records).
SSL_has_pending() returns 1 if
s has buffered data (whether
processed or unprocessed) and 0 otherwise. Note that it is possible for
SSL_has_pending() to return 1, and then a subsequent call to
SSL_read_ex() or
SSL_read() to return no data because the
unprocessed buffered data when processed yielded no application data (for
example this can happen during renegotiation). It is also possible in this
scenario for
SSL_has_pending() to continue to return 1 even after an
SSL_read_ex() or
SSL_read() call because the buffered and
unprocessed data is not yet processable (e.g. because OpenSSL has only
received a partial record so far).
SSL_pending() returns the number of buffered and processed application
data bytes that are pending and are available for immediate read.
SSL_has_pending() returns 1 if there is buffered record data in the SSL
object and 0 otherwise.
SSL_read_ex(3),
SSL_read(3),
SSL_CTX_set_read_ahead(3),
SSL_CTX_set_split_send_fragment(3),
ssl(7)
The
SSL_has_pending() function was added in OpenSSL 1.1.0.
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy in the
file LICENSE in the source distribution or at
<
https://www.openssl.org/source/license.html>.