=head1 NAME
-SSL_pending - obtain number of readable bytes buffered in an SSL object
+SSL_pending, SSL_has_pending - check for readable bytes buffered in an
+SSL object
=head1 SYNOPSIS
#include <openssl/ssl.h>
int SSL_pending(const SSL *ssl);
+ int SSL_has_pending(const SSL *s);
=head1 DESCRIPTION
-SSL_pending() returns the number of bytes which are available inside
-B<ssl> for immediate read.
+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 L<SSL_read(3)>.
+
+SSL_pending() returns the number of bytes which have been processed, buffered
+and are available inside B<ssl> for immediate read.
+
+If the B<SSL> object's I<read_ahead> flag is set (see
+L<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 L<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 B<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() 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()
+call because the buffered and unprocessed data is not yet processable (e.g.
+because OpenSSL has only received a partial record so far).
-=head1 NOTES
+=head1 RETURN VALUES
-Data are received in blocks from the peer. Therefore data can be buffered
-inside B<ssl> and are ready for immediate retrieval with
-L<SSL_read(3)|SSL_read(3)>.
+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.
-=head1 RETURN VALUES
+=head1 SEE ALSO
-The number of bytes pending is returned.
+L<SSL_read(3)>, L<SSL_CTX_set_read_ahead(3)>,
+L<SSL_CTX_set_split_send_fragment(3)>, L<ssl(3)>
-=head1 BUGS
+=head1 HISTORY
-SSL_pending() takes into account only bytes from the TLS/SSL record
-that is currently being processed (if any). If the B<SSL> object's
-I<read_ahead> flag is set, additional protocol bytes may have been
-read containing more TLS/SSL records; these are ignored by
-SSL_pending().
+The SSL_has_pending() function was added in OpenSSL 1.1.0.
-Up to OpenSSL 0.9.6, SSL_pending() does not check if the record type
-of pending data is application data.
+=head1 COPYRIGHT
-=head1 SEE ALSO
+Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
-L<SSL_read(3)|SSL_read(3)>, L<ssl(3)|ssl(3)>
+Licensed under the OpenSSL license (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
+L<https://www.openssl.org/source/license.html>.
=cut
projects / cassiopeia.git / blobdiff