446 lines
10 KiB
Groff
446 lines
10 KiB
Groff
.\" Copyright (c) 1983, 1987, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $Id: inet6_option_space.3,v 1.4 2000/02/05 10:32:24 jinmei Exp $
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.\" $FreeBSD$
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.\"
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.Dd December 10, 1999
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.Dt INET6_OPTION_SPACE 3
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.Os
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.\"
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.Sh NAME
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.Nm inet6_option_space ,
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.Nm inet6_option_init ,
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.Nm inet6_option_append ,
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.Nm inet6_option_alloc ,
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.Nm inet6_option_next ,
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.Nm inet6_option_find
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.Nd IPv6 Hop-by-Hop and Destination Options manipulation
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.\"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In netinet/in.h
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.Ft "int"
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.Fn inet6_option_space "int nbytes"
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.Ft "int"
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.Fn inet6_option_init "void *bp" "struct cmsghdr **cmsgp" "int type"
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.Ft "int"
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.Fn inet6_option_append "struct cmsghdr *cmsg" "const u_int8_t *typep" "int multx" "int plusy"
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.Ft "u_int8_t *"
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.Fn inet6_option_alloc "struct cmsghdr *cmsg" "int datalen" "int multx" "int plusy"
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.Ft "int"
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.Fn inet6_option_next "const struct cmsghdr *cmsg" "u_int8_t **tptrp"
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.Ft "int"
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.Fn inet6_option_find "const struct cmsghdr *cmsg" "u_int8_t **tptrp" "int type"
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.\"
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.Sh DESCRIPTION
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.\"
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Building and parsing the Hop-by-Hop and Destination options is
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complicated due to alignment constranints, padding and
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ancillary data manipulation.
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RFC2292 defines a set of functions to help the application.
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The function prototypes for
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these functions are all in the
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.Aq Li netinet/in.h
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header.
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.\"
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.Ss inet6_option_space
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.Fn inet6_option_space
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returns the number of bytes required to hold an option when it is stored as
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ancillary data, including the
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.Li cmsghdr
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structure at the beginning,
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and any padding at the end
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(to make its size a multiple of 8 bytes).
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The argument is the size of the structure defining the option,
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which must include any pad bytes at the beginning
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(the value
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.Li y
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in the alignment term
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.Dq Li "xn + y" ) ,
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the type byte, the length byte, and the option data.
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.Pp
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Note: If multiple options are stored in a single ancillary data
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object, which is the recommended technique, this function
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overestimates the amount of space required by the size of
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.Li N-1
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.Li cmsghdr
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structures,
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where
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.Li N
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is the number of options to be stored in the object.
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This is of little consequence, since it is assumed that most
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Hop-by-Hop option headers and Destination option headers carry only
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one option
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(appendix B of [RFC-2460]).
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.\"
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.Ss inet6_option_init
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.Fn inet6_option_init
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is called once per ancillary data object that will
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contain either Hop-by-Hop or Destination options.
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It returns
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.Li 0
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on success or
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.Li -1
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on an error.
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.Pp
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.Fa bp
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is a pointer to previously allocated space that will contain the
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ancillary data object.
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It must be large enough to contain all the
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individual options to be added by later calls to
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.Fn inet6_option_append
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and
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.Fn inet6_option_alloc .
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.Pp
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.Fa cmsgp
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is a pointer to a pointer to a
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.Li cmsghdr
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structure.
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.Fa *cmsgp
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is initialized by this function to point to the
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.Li cmsghdr
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structure constructed by this function in the buffer pointed to by
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.Fa bp .
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.Pp
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.Fa type
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is either
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.Dv IPV6_HOPOPTS
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or
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.Dv IPV6_DSTOPTS .
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This
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.Fa type
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is stored in the
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.Li cmsg_type
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member of the
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.Li cmsghdr
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structure pointed to by
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.Fa *cmsgp .
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.\"
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.Ss inet6_option_append
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This function appends a Hop-by-Hop option or a Destination option
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into an ancillary data object that has been initialized by
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.Fn inet6_option_init .
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This function returns
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.Li 0
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if it succeeds or
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.Li -1
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on an error.
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.Pp
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.Fa cmsg
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is a pointer to the
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.Li cmsghdr
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structure that must have been
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initialized by
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.Fn inet6_option_init .
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.Pp
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.Fa typep
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is a pointer to the 8-bit option type.
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It is assumed that this
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field is immediately followed by the 8-bit option data length field,
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which is then followed immediately by the option data.
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The caller
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initializes these three fields
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(the type-length-value, or TLV)
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before calling this function.
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.Pp
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The option type must have a value from
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.Li 2
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to
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.Li 255 ,
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inclusive.
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.Li ( 0
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and
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.Li 1
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are reserved for the
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.Li Pad1
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and
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.Li PadN
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options, respectively.)
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.Pp
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The option data length must have a value between
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.Li 0
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and
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.Li 255 ,
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inclusive, and is the length of the option data that follows.
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.Pp
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.Fa multx
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is the value
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.Li x
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in the alignment term
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.Dq Li xn + y .
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It must have a value of
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.Li 1 ,
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.Li 2 ,
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.Li 4 ,
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or
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.Li 8 .
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.Pp
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.Fa plusy
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is the value
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.Li y
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in the alignment term
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.Dq Li xn + y .
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It must have a value between
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.Li 0
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and
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.Li 7 ,
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inclusive.
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.\"
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.Ss inet6_option_alloc
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This function appends a Hop-by-Hop option or a Destination option
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into an ancillary data object that has been initialized by
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.Fn inet6_option_init .
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This function returns a pointer to the 8-bit
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option type field that starts the option on success, or
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.Dv NULL
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on an error.
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.Pp
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The difference between this function and
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.Fn inet6_option_append
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is that the latter copies the contents of a previously built option into
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the ancillary data object while the current function returns a
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pointer to the space in the data object where the option's TLV must
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then be built by the caller.
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.Pp
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.Fa cmsg
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is a pointer to the
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.Li cmsghdr
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structure that must have been
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initialized by
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.Fn inet6_option_init .
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.Pp
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.Fa datalen
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is the value of the option data length byte for this option.
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This value is required as an argument to allow the function to
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determine if padding must be appended at the end of the option.
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(The
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.Fn inet6_option_append
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function does not need a data length argument
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since the option data length must already be stored by the caller.)
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.Pp
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.Fa multx
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is the value
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.Li x
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in the alignment term
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.Dq Li xn + y .
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It must have a value of
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.Li 1 ,
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.Li 2 ,
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.Li 4 ,
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or
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.Li 8 .
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.Pp
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.Fa plusy
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is the value
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.Li y
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in the alignment term
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.Dq Li xn + y .
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It must have a value between
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.Li 0
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and
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.Li 7 ,
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inclusive.
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.\"
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.Ss inet6_option_next
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This function processes the next Hop-by-Hop option or Destination
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option in an ancillary data object.
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If another option remains to be
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processed, the return value of the function is
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.Li 0
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and
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.Fa *tptrp
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points to
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the 8-bit option type field
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(which is followed by the 8-bit option
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data length, followed by the option data).
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If no more options remain
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to be processed, the return value is
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.Li -1
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and
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.Fa *tptrp
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is
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.Dv NULL .
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If an error occurs, the return value is
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.Li -1
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and
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.Fa *tptrp
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is not
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.Dv NULL .
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.Pp
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.Fa cmsg
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is a pointer to
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.Li cmsghdr
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structure of which
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.Li cmsg_level
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equals
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.Dv IPPROTO_IPV6
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and
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.Li cmsg_type
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equals either
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.Dv IPV6_HOPOPTS
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or
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.Dv IPV6_DSTOPTS .
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.Pp
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.Fa tptrp
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is a pointer to a pointer to an 8-bit byte and
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.Fa *tptrp
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is used
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by the function to remember its place in the ancillary data object
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each time the function is called.
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The first time this function is
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called for a given ancillary data object,
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.Fa *tptrp
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must be set to
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.Dv NULL .
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.Pp
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Each time this function returns success,
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.Fa *tptrp
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points to the 8-bit
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option type field for the next option to be processed.
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.\"
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.Ss inet6_option_find
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This function is similar to the previously described
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.Fn inet6_option_next
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function, except this function lets the caller
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specify the option type to be searched for, instead of always
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returning the next option in the ancillary data object.
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.Fa cmsg
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is a
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pointer to
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.Li cmsghdr
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structure of which
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.Li cmsg_level
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equals
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.Dv IPPROTO_IPV6
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and
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.Li cmsg_type
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equals either
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.Dv IPV6_HOPOPTS
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or
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.Dv IPV6_DSTOPTS .
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.Pp
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.Fa tptrp
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is a pointer to a pointer to an 8-bit byte and
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.Fa *tptrp
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is used
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by the function to remember its place in the ancillary data object
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each time the function is called.
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The first time this function is
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called for a given ancillary data object,
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.Fa *tptrp
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must be set to
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.Dv NULL .
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.Pa
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This function starts searching for an option of the specified type
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beginning after the value of
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.Fa *tptrp .
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If an option of the specified
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type is located, this function returns
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.Li 0
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and
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.Fa *tptrp
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points to the 8-
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bit option type field for the option of the specified type.
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If an
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option of the specified type is not located, the return value is
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.Li -1
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and
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.Fa *tptrp
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is
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.Dv NULL .
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If an error occurs, the return value is
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.Li -1
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and
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.Fa *tptrp
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is not
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.Dv NULL .
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.\"
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.Sh DIAGNOSTICS
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.Fn inet6_option_init
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and
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.Fn inet6_option_append
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return
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.Li 0
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on success or
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.Li -1
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on an error.
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.Pp
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.Fn inet6_option_alloc
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returns
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.Dv NULL
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on an error.
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.Pp
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On errors,
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.Fn inet6_option_next
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and
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.Fn inet6_option_find
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return
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.Li -1
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setting
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.Fa *tptrp
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to non
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.Dv NULL
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value.
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.\"
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.Sh EXAMPLES
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RFC2292 gives comprehensive examples in chapter 6.
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.\"
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.Sh SEE ALSO
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.Rs
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.%A W. Stevens
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.%A M. Thomas
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.%T "Advanced Sockets API for IPv6"
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.%N RFC2292
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.%D February 1998
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.Re
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.Rs
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.%A S. Deering
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.%A R. Hinden
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.%T "Internet Protocol, Version 6 (IPv6) Specification"
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.%N RFC2460
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.%D December 1998
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.Re
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.\"
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.Sh HISTORY
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The implementation first appeared in KAME advanced networking kit.
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.\"
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.Sh STANDARDS
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The functions
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are documented in
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.Dq Advanced Sockets API for IPv6
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(RFC2292).
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.\"
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.Sh BUGS
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The text was shamelessly copied from RFC2292.
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