154 lines
5.0 KiB
Groff
154 lines
5.0 KiB
Groff
.\" $NetBSD: sockopt.9,v 1.11 2018/01/04 01:42:25 christos Exp $
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.\"
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.\" Copyright (c) 2008 Iain Hibbert
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd January 3, 2018
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.Dt SOCKOPT 9
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.Os
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.Sh NAME
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.Nm sockopt_init ,
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.Nm sockopt_destroy ,
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.Nm sockopt_get ,
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.Nm sockopt_getint ,
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.Nm sockopt_set ,
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.Nm sockopt_setint
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.Nd socket options handling
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.Sh SYNOPSIS
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.In sys/socketvar.h
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.Ft void
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.Fn sockopt_init "struct sockopt *sopt" "int level" "int name" "size_t size"
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.Ft void
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.Fn sockopt_destroy "struct sockopt *sopt"
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.Ft int
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.Fn sockopt_get "struct sockopt *sopt" "void *value" "size_t size"
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.Ft int
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.Fn sockopt_getint "struct sockopt *sopt" "int *value"
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.Ft int
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.Fn sockopt_set "struct sockopt *sopt" "const void *value" "size_t size"
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.Ft int
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.Fn sockopt_setint "struct sockopt *sopt" "int value"
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.Sh DESCRIPTION
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The
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.Ft sockopt
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structure is used to pass a socket option and associated value:
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.Bd -literal -offset indent
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struct sockopt {
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int sopt_level; /* option level */
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int sopt_name; /* option name */
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size_t sopt_size; /* data length */
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size_t sopt_retsize; /* returned data length */
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void * sopt_data; /* data pointer */
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uint8_t sopt_buf[sizeof(int)]; /* internal storage */
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};
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.Ed
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.Pp
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The internal storage is used for the common case of values up to integer
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size so that memory allocation is not required and sopt_data will point
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to this in that case.
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.Pp
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Rather than provide accessor functions, the
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.Ft sockopt
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structure is public and the contents are expected to be internally
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consistent, but the normal practice would be to use the appropriate methods
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for storage and retrieval of values where a known datatype is expected,
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as the size will be verified.
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.Pp
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Note: a sockopt structure may only be used for a single level/name/size
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combination.
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If the structure is to be re-used, it must be destroyed and re-initialized
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with the new values.
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.Sh OPTIONS
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.Bl -tag -width xxxx
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.It Cd "options DIAGNOSTIC"
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Kernels compiled with the
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.Dv DIAGNOSTIC
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option will perform basic sanity checks on socket options operations.
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.El
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.Sh FUNCTIONS
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.Bl -tag -width xxxx
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.It Fn sockopt_init "sopt" "level" "name" "size"
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Initialise sockopt storage.
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If
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.Ar size
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is given,
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.Fn sockopt_init
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will arrange for sopt_data to point to a buffer of
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.Ar size
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bytes for the sockopt value.
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Where memory needs to be allocated to satisfy this,
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.Fn sockopt_init
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may sleep.
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.It Fn sockopt_destroy "sopt"
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Destroy sockopt storage, releasing any allocated memory.
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.It Fn sockopt_get "sopt" "value" "size"
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Copy out sockopt value.
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Will return
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.Er EINVAL
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if an incorrect data size is given.
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.It Fn sockopt_getint "sopt" "value"
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Common case of get sockopt integer value.
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Will return
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.Er EINVAL
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if sockopt does not contain an integer sized value.
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.It Fn sockopt_set "sopt" "value" "size"
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Copy in sockopt value.
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The sockopt structure must contain a data field of
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.Ar size
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bytes or be previously unset, in which case a data buffer may be
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allocated using
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.Xr kmem_alloc 9
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with the
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.Dv KM_NOSLEEP
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flag which may cause
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.Fn sockopt_set
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to return
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.Er ENOMEM .
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.Pp
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Note: If you need to use
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.Fn sockopt_set
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in a context where memory allocation may be required and you do not wish to
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contemplate failure, the sockopt structure can be initialised in a more suitable
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context using
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.Fn sockopt_init
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which will not fail.
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.It Fn sockopt_setint "sopt" "value"
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Common case of set sockopt integer value.
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The sockopt structure must contain an int sized data field or be previously
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unset, in which case the data pointer will be set to the internal storage.
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.El
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.Sh CODE REFERENCES
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The function prototypes and sockopt structure are defined in the
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.Pa sys/sys/socketvar.h
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header file, and the socket options implementation is in
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.Pa sys/kern/uipc_socket.c .
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.Sh SEE ALSO
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.Xr errno 2 ,
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.Xr kmem 9
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.Sh HISTORY
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The socket options KPI was inspired by a similar KPI in
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.Fx
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and
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first appeared in
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.Nx 5.0 .
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