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freebsd/crypto/openssl/doc/man7/bio.pod
Pierre Pronchery b077aed33b Merge OpenSSL 3.0.9
Migrate to OpenSSL 3.0 in advance of FreeBSD 14.0.  OpenSSL 1.1.1 (the
version we were previously using) will be EOL as of 2023-09-11.

Most of the base system has already been updated for a seamless switch
to OpenSSL 3.0.  For many components we've added
`-DOPENSSL_API_COMPAT=0x10100000L` to CFLAGS to specify the API version,
which avoids deprecation warnings from OpenSSL 3.0.  Changes have also
been made to avoid OpenSSL APIs that were already deprecated in OpenSSL
1.1.1.  The process of updating to contemporary APIs can continue after
this merge.

Additional changes are still required for libarchive and Kerberos-
related libraries or tools; workarounds will immediately follow this
commit.  Fixes are in progress in the upstream projects and will be
incorporated when those are next updated.

There are some performance regressions in benchmarks (certain tests in
`openssl speed`) and in some OpenSSL consumers in ports (e.g.  haproxy).
Investigation will continue for these.

Netflix's testing showed no functional regression and a rather small,
albeit statistically significant, increase in CPU consumption with
OpenSSL 3.0.

Thanks to ngie@ and des@ for updating base system components, to
antoine@ and bofh@ for ports exp-runs and port fixes/workarounds, and to
Netflix and everyone who tested prior to commit or contributed to this
update in other ways.

PR:		271615
PR:		271656 [exp-run]
Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation
2023-06-23 18:53:36 -04:00

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=pod
=head1 NAME
bio - Basic I/O abstraction
=head1 SYNOPSIS
=for openssl generic
#include <openssl/bio.h>
=head1 DESCRIPTION
A BIO is an I/O abstraction, it hides many of the underlying I/O
details from an application. If an application uses a BIO for its
I/O it can transparently handle SSL connections, unencrypted network
connections and file I/O.
There are two types of BIO, a source/sink BIO and a filter BIO.
As its name implies a source/sink BIO is a source and/or sink of data,
examples include a socket BIO and a file BIO.
A filter BIO takes data from one BIO and passes it through to
another, or the application. The data may be left unmodified (for
example a message digest BIO) or translated (for example an
encryption BIO). The effect of a filter BIO may change according
to the I/O operation it is performing: for example an encryption
BIO will encrypt data if it is being written to and decrypt data
if it is being read from.
BIOs can be joined together to form a chain (a single BIO is a chain
with one component). A chain normally consists of one source/sink
BIO and one or more filter BIOs. Data read from or written to the
first BIO then traverses the chain to the end (normally a source/sink
BIO).
Some BIOs (such as memory BIOs) can be used immediately after calling
BIO_new(). Others (such as file BIOs) need some additional initialization,
and frequently a utility function exists to create and initialize such BIOs.
If BIO_free() is called on a BIO chain it will only free one BIO resulting
in a memory leak.
Calling BIO_free_all() on a single BIO has the same effect as calling
BIO_free() on it other than the discarded return value.
Normally the I<type> argument is supplied by a function which returns a
pointer to a BIO_METHOD. There is a naming convention for such functions:
a source/sink BIO typically starts with I<BIO_s_> and
a filter BIO with I<BIO_f_>.
=head1 EXAMPLES
Create a memory BIO:
BIO *mem = BIO_new(BIO_s_mem());
=head1 SEE ALSO
L<BIO_ctrl(3)>,
L<BIO_f_base64(3)>, L<BIO_f_buffer(3)>,
L<BIO_f_cipher(3)>, L<BIO_f_md(3)>,
L<BIO_f_null(3)>, L<BIO_f_ssl(3)>,
L<BIO_f_readbuffer(3)>,
L<BIO_find_type(3)>, L<BIO_new(3)>,
L<BIO_new_bio_pair(3)>,
L<BIO_push(3)>, L<BIO_read_ex(3)>,
L<BIO_s_accept(3)>, L<BIO_s_bio(3)>,
L<BIO_s_connect(3)>, L<BIO_s_fd(3)>,
L<BIO_s_file(3)>, L<BIO_s_mem(3)>,
L<BIO_s_null(3)>, L<BIO_s_socket(3)>,
L<BIO_set_callback(3)>,
L<BIO_should_retry(3)>
=head1 COPYRIGHT
Copyright 2000-2021 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
L<https://www.openssl.org/source/license.html>.
=cut