1.\" $OpenBSD: BIO_f_null.3,v 1.12 2023/04/11 16:58:43 schwarze Exp $ 2.\" full merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100 3.\" 4.\" This file was written by Dr. Stephen Henson <steve@openssl.org>. 5.\" Copyright (c) 2000 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: April 11 2023 $ 52.Dt BIO_F_NULL 3 53.Os 54.Sh NAME 55.Nm BIO_f_null 56.\" .Nm BIO_f_nbio_test is intentionally undocumented 57.\" because it exposes absurd functionality that is unused 58.\" except in openssl(1) s_client/s_server -nbio_test. 59.Nd null filter 60.Sh SYNOPSIS 61.In openssl/bio.h 62.Ft const BIO_METHOD * 63.Fo BIO_f_null 64.Fa void 65.Fc 66.Sh DESCRIPTION 67.Fn BIO_f_null 68returns the null filter BIO method. 69This is a filter BIO that does nothing. 70As may be apparent, a null filter BIO is not particularly useful. 71.Pp 72All requests to a null filter BIO are passed through to the next BIO 73in the chain: this means that a BIO chain containing a null filter BIO 74behaves just as though the BIO was not there. 75.Pp 76A chain containing a null filter BIO cannot be copied with 77.Xr BIO_dup_chain 3 , 78and any attempt to do so fails and returns 79.Dv NULL . 80.Sh RETURN VALUES 81.Fn BIO_f_null 82returns the null filter BIO method. 83.Pp 84When called on a null filter BIO object, 85.Xr BIO_method_type 3 86returns the constant 87.Dv BIO_TYPE_NULL_FILTER 88and 89.Xr BIO_method_name 3 90returns a pointer to the static string 91.Qq NULL filter , 92not to be confused with a NUL string nor with a 93.Dv NULL pointer . 94.Sh SEE ALSO 95.Xr BIO_new 3 96.Sh HISTORY 97.Fn BIO_f_null 98first appeared in SSLeay 0.8.0 and has been available since 99.Ox 2.4 . 100