FreeBSD-5.3/lib/libc/net/inet6_opt_init.3

.\"	$KAME: inet6_opt_init.3,v 1.5 2002/10/17 14:13:47 jinmei Exp $
.\"
.\" Copyright (C) 2000 WIDE Project.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the project nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/lib/libc/net/inet6_opt_init.3,v 1.4 2004/07/05 07:21:55 ru Exp $
.\"
.Dd February 5, 2000
.Dt INET6_OPT_INIT 3
.Os
.\"
.Sh NAME
.Nm inet6_opt_init ,
.Nm inet6_opt_append ,
.Nm inet6_opt_finish ,
.Nm inet6_opt_set_val ,
.Nm inet6_opt_next ,
.Nm inet6_opt_find ,
.Nm inet6_opt_get_val
.Nd IPv6 Hop-by-Hop and Destination Options manipulation
.\"
.Sh SYNOPSIS
.In netinet/in.h
.Ft "int"
.Fn inet6_opt_init "void *extbuf" "socklen_t extlen"
.Ft "int"
.Fn inet6_opt_append "void *extbuf" "socklen_t extlen" "int offset" "u_int8_t type" "socklen_t len" "u_int8_t align" "void **databufp"
.Ft "int"
.Fn inet6_opt_finish "void *extbuf" "socklen_t extlen" "int offset"
.Ft "int"
.Fn inet6_opt_set_val "void *databuf" "int offset" "void *val" "socklen_t vallen"
.Ft "int"
.Fn inet6_opt_next "void *extbuf" "socklen_t extlen" "int offset" "u_int8_t *typep" "socklen_t *lenp" "void **databufp"
.Ft "int"
.Fn inet6_opt_find "void *extbuf" "socklen_t extlen" "int offset" "u_int8_t type" "socklen_t *lenp" "void **databufp"
.Ft "int"
.Fn inet6_opt_get_val "void *databuf" "socklen_t offset" "void *val" "socklen_t vallen"
.\"
.Sh DESCRIPTION
Building and parsing the Hop-by-Hop and Destination options is
complicated.
The advanced API therefore defines a set
of functions to help applications.
These functions assume the
formatting rules specified in Appendix B in RFC2460, i.e., that the
largest field is placed last in the option.
The function prototypes for
these functions are all in the
.In netinet/in.h
header.
.\"
.Ss inet6_opt_init
The
.Fn inet6_opt_init
function
returns the number of bytes needed for the empty
extension header, i.e., without any options.
If
.Va extbuf
is not
.Dv NULL
it also initializes the extension header to have the correct length
field.
In that case if the
.Fa extlen
value is not a positive
(i.e., non-zero)
multiple of 8 the function fails and returns \-1.
.\"
.Ss inet6_opt_append
The
.Fn inet6_opt_append
function
returns the updated total length taking into account
adding an option with length
.Fa len
and alignment
.Fa align .
The
.Fa offset
argument
should be the length returned by
.Fn inet6_opt_init
or a previous
.Fn inet6_opt_append .
If
.Fa extbuf
is not
.Dv NULL
then, in addition to returning the length,
the function inserts any needed pad option, initializes the option
(setting the type and length fields)
and returns a pointer to the location for the option content in
.Fa databufp .
.Pp
The
.Fa type
argument
is the 8-bit option type.
The
.Fa len
argument
is the length of the option data
(i.e., excluding the option type and option length fields).
.Pp
Once
.Fn inet6_opt_append
has been called, the application can use the
databuf directly, or use
.Fn inet6_opt_set_val
to specify the content of the option.
.Pp
The option type must have a value from 2 to 255, inclusive.
(0 and 1 are reserved for the Pad1 and PadN options, respectively.)
.Pp
The option data length must have a value between 0 and 255,
inclusive, and is the length of the option data that follows.
.Pp
The
.Fa align
parameter must have a value of 1, 2, 4, or 8.
The align value can not exceed the value of
.Fa len .
.\"
.Ss inet6_opt_finish
The
.Fn inet6_opt_finish
function
returns the updated total length
taking into account the final padding of the extension header to make
it a multiple of 8 bytes.
The
.Fa offset
argument
should be the length returned by
.Fn inet6_opt_init
or
.Fn inet6_opt_append .
If
.Fa extbuf
is not
.Dv NULL
the function also
initializes the option by inserting a Pad1 or PadN option of the
proper length.
.Pp
If the necessary pad does not fit in the extension header buffer the
function returns \-1.
.\"
.Ss inet6_opt_set_val
The
.Fn inet6_opt_set_val
function
inserts data items of various sizes in the data portion of the option.
The
.Fa databuf
argument
should be a pointer returned by
.Fn inet6_opt_append .
The
.Fa val
argument
should point to the data to be
inserted.
The
.Fa offset
argument
specifies where in the data portion of the option
the value should be inserted; the first byte after the option type
and length is accessed by specifying an offset of zero.
.Pp
The caller should ensure that each field is aligned on its natural
boundaries as described in Appendix B of RFC2460, but the function
must not rely on the caller's behavior.
Even when the alignment requirement is not satisfied,
the function should just copy the data as required.
.Pp
The function returns the offset for the next field
(i.e.,
.Fa offset
+
.Fa vallen )
which can be used when composing option content with multiple fields.
.\"
.Ss inet6_opt_next
The
.Fn inet6_opt_next
function
parses received extension headers returning the next
option.
The
.Fa extbuf
and
.Fa extlen
arguments specify the extension header.
The
.Fa offset
argument
should either be zero (for the first option), or the length returned
by a previous call to
.Fn inet6_opt_next
or
.Fn inet6_opt_find .
It specifies the position where to continue scanning the extension
buffer.
The next option is returned by updating
.Fa typep , lenp ,
and
.Fa databufp .
This function returns the updated
.Dq previous
length
computed by advancing past the option that was returned.
This returned
.Dq previous
length can then be passed to subsequent calls to
.Fn inet6_opt_next .
This function does not return any PAD1 or PADN options.
When there are no more options the return value is \-1.
.\"
.Ss inet6_opt_get_val
The
.Fn inet6_opt_get_val
function extracts data items of various sizes
in the data portion of the option.
The
.Fa databuf
argument
should be a pointer returned by
.Fn inet6_opt_next
or
.Fn inet6_opt_find .
The
.Fa val
argument
should point to the destination for the extracted data.
The
.Fa offset
argument
specifies from where in the data portion of the option the value should be
extracted; the first byte after the option type and length is
accessed by specifying an offset of zero.
.Pp
It is expected that each field is aligned on its natural boundaries
as described in Appendix B of RFC2460, but the function must not
rely on the alignment.
.Pp
The function returns the offset for the next field
(i.e.,
.Fa offset
+
.Fa vallen )
which can be used when extracting option content with
multiple fields.
Robust receivers might want to verify alignment before calling
this function.
.\"
.Sh DIAGNOSTICS
All the functions return
\-1
on an error.
.\"
.Sh EXAMPLES
draft-ietf-ipngwg-rfc2292bis-08.txt
gives comprehensive examples in Section 23.
.Pp
KAME also provides examples in the advapitest directory of its kit.
.\"
.Sh SEE ALSO
.Rs
.%A W. Stevens
.%A M. Thomas
.%A E. Nordmark
.%A T. Jinmei
.%T "Advanced Sockets API for IPv6"
.%N draft-ietf-ipngwg-rfc2292bis-08
.%D October 2002
.Re
.Rs
.%A S. Deering
.%A R. Hinden
.%T "Internet Protocol, Version 6 (IPv6) Specification"
.%N RFC2460
.%D December 1998
.Re
.Sh HISTORY
The implementation first appeared in KAME advanced networking kit.
.Sh STANDARDS
The functions
are documented in
.Dq Advanced Sockets API for IPv6
.Pq draft-ietf-ipngwg-rfc2292bis-08.txt .
.\"
.Sh BUGS
The text was shamelessly copied from internet-drafts for RFC2292bis.