oracular (7) bio.7ssl.gz

Provided by: openssl_3.3.1-2ubuntu2.1_amd64 bug

NAME
       bio - Basic I/O abstraction


SYNOPSIS
        #include <openssl/bio.h>


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 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 BIO_s_ and a filter BIO
       with BIO_f_.

   TCP Fast Open
       TCP Fast Open (RFC7413), abbreviated "TFO", is supported by the BIO interface since OpenSSL 3.2. TFO is
       supported in the following operating systems:

       •   Linux kernel 3.13 and later, where TFO is enabled by default.

       •   Linux kernel 4.11 and later, using TCP_FASTOPEN_CONNECT.

       •   FreeBSD 10.3 to 11.4, supports server TFO only.

       •   FreeBSD 12.0 and later, supports both client and server TFO.

       •   macOS 10.14 and later.

       Each operating system has a slightly different API for TFO. Please refer to the operating systems' API
       documentation when using sockets directly.


EXAMPLES
       Create a memory BIO:

        BIO *mem = BIO_new(BIO_s_mem());


SEE ALSO
       BIO_ctrl(3), BIO_f_base64(3), BIO_f_buffer(3), BIO_f_cipher(3), BIO_f_md(3), BIO_f_null(3), BIO_f_ssl(3),
       BIO_f_readbuffer(3), BIO_find_type(3), BIO_get_conn_mode(3), BIO_new(3), BIO_new_bio_pair(3),
       BIO_push(3), BIO_read_ex(3), BIO_s_accept(3), BIO_s_bio(3), BIO_s_connect(3), BIO_s_fd(3), BIO_s_file(3),
       BIO_s_mem(3), BIO_s_null(3), BIO_s_socket(3), BIO_set_callback(3), BIO_set_conn_mode(3), BIO_set_tfo(3),
       BIO_set_tfo_accept(3), BIO_should_retry(3)


       Copyright 2000-2022 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>.