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Diffstat (limited to 'lib/libc/net/inet6_option_space.3')
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diff --git a/lib/libc/net/inet6_option_space.3 b/lib/libc/net/inet6_option_space.3 new file mode 100644 index 00000000000..9b5cac95e8e --- /dev/null +++ b/lib/libc/net/inet6_option_space.3 @@ -0,0 +1,434 @@ +.\" $OpenBSD: inet6_option_space.3,v 1.15 2005/01/06 03:50:46 itojun Exp $ +.\" $KAME: inet6_option_space.3,v 1.11 2005/01/05 03:00:44 itojun Exp $ +.\" +.\" Copyright (C) 2004 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. +.\" +.Dd December 23, 2004 +.Dt INET6_OPTION_SPACE 3 +.Os +.\" +.Sh NAME +.Nm inet6_option_space , +.Nm inet6_option_init , +.Nm inet6_option_append , +.Nm inet6_option_alloc , +.Nm inet6_option_next , +.Nm inet6_option_find +.Nd IPv6 Hop-by-Hop and Destination Option Manipulation +.\" +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/types.h +.In netinet/in.h +.Ft "int" +.Fn inet6_option_space "int nbytes" +.Ft "int" +.Fn inet6_option_init "void *bp" "struct cmsghdr **cmsgp" "int type" +.Ft "int" +.Fn inet6_option_append "struct cmsghdr *cmsg" "const u_int8_t *typep" "int multx" "int plusy" +.Ft "u_int8_t *" +.Fn inet6_option_alloc "struct cmsghdr *cmsg" "int datalen" "int multx" "int plusy" +.Ft "int" +.Fn inet6_option_next "const struct cmsghdr *cmsg" "u_int8_t **tptrp" +.Ft "int" +.Fn inet6_option_find "const struct cmsghdr *cmsg" "u_int8_t **tptrp" "int type" +.\" +.Sh DESCRIPTION +.\" +Manipulating and parsing IPv6's Hop-by-Hop and Destination options is +complicated by the need to properly align and pad data as well as the +need to manipulate ancillary information that is not part of the data +stream. +RFC2292 defines a set of functions, which are implemented as +part of the Kame libraries, to support help developers create, change, +and parse Hop-by-Hope and Destination options. +All of the prototypes +for the option functions are defined in the +.In netinet/in.h +header file. +.\" +.Ss inet6_option_space +In order to determine the amount of space necessary to hold any option +the +.Fn inet6_option_space +function is called. +It returns the number of bytes required to hold +an option when it is stored as ancillary data, including the +.Li cmsghdr +structure at the beginning, and any necessary padding at the end. +The +.Li nbytes +argument indicates the size of the structure defining the option, +and must include any pad bytes at the beginning (the value +.Li y +in the alignment term +.Dq Li "xn + y" ) , +the type byte, the length byte, and the option data. +.Pp +Note: If multiple options are stored in a single ancillary data +object, which is the recommended technique, the +.Fn inet6_option_space +function overestimates the amount of space required by the size of +.Li N-1 +.Li cmsghdr +structures, where +.Li N +is the number of options to be stored in the object. +Usually this has +no impact because it is assumed that most Hop-by-Hop and Destination +option headers carry only one option as indicated in appendix B of RFC2460. +.\" +.Ss inet6_option_init +The +.Fn inet6_option_init +function is called to initialize any ancillary data object that will contain +a Hop-by-Hop or Destination option. +It returns +.Li 0 +on success and +.Li -1 +when an error occurs. +.Pp +The +.Fa bp +argument points to a previously allocated area of memory which must be +large enough to contain all the arguments that the application indents +to add later via +.Fn inet6_option_append +and +.Fn inet6_option_alloc +routines. +.Pp +The +.Fa cmsgp +argument is a pointer to a pointer to a +.Li cmsghdr +structure. +The +.Fa *cmsgp +argument +points to a +.Li cmsghdr +structure which is constructed by this function and stored in the +area of memory pointed to by +.Fa bp . +.Pp +The +.Fa type +is either +.Dv IPV6_HOPOPTS +or +.Dv IPV6_DSTOPTS +and is stored in the +.Li cmsg_type +member of the +.Li cmsghdr +structure mentioned above. +.\" +.Ss inet6_option_append +This function appends a Hop-by-Hop option or a Destination option into +an ancillary data object previously initialized by a call to +.Fn inet6_option_init . +The +.Fn inet6_option_append function returns +.Li 0 +if it succeeds or +.Li -1 +when an error occurs. +.Pp +The +.Fa cmsg +argument is a pointer to the +.Li cmsghdr +structure that was initialized by a call to +.Fn inet6_option_init . +.Pp +The +.Fa typep +argument is a pointer to the 8-bit option type. +All options are +encoded as type-length-value tuples and it is assumed that +the +.Fa typep +field is immediately followed by the 8-bit option data length field, +which is then followed by the option data. +.Pp +The option types of +.Li 0 +and +.Li 1 are reserved for the +.Li Pad1 +and +.Li PadN +options respectively. +All other values from +.Li 2 +through +.Li 255 +are available for applications to use. +.Pp +The option data length, since it is stored in 8 bites, must have a +value between +.Li 0 +and +.Li 255 , +inclusive. +.Pp +The +.Fa multx +argument +is the value +.Li x +in the alignment term +.Dq Li xn + y +and indicates the byte alignment necessary for the data. +Alignments may be specified as +.Li 1 , +.Li 2 , +.Li 4 , +or +.Li 8 +bytes, which is no alignment, 16 bit, 32 bit and 64 bit alignments +respectively. +.Pp +The +.Fa plusy +argument +is the value +.Li y +in the alignment term +.Dq Li xn + y +and must have a value between +.Li 0 +and +.Li 7 , +inclusive, indicating the amount of padding that is necessary for an +option. +.\" +.Ss inet6_option_alloc +The +.Fn inet6_option_alloc +function appends a Hop-by-Hop option or a Destination option into an +ancillary data object that has previously been initialized by a call to +.Fn inet6_option_init . +The +.Fn inet6_option_alloc +function returns a pointer to the 8-bit option type field that at the +beginning of the allocated the option on success, or +.Dv NULL +on an error. +.Pp +The difference between the +.Fn inet6_option_alloc +and +.Fn inet6_option_append +functions is that the latter copies the contents of a previously built +option into the ancillary data object while the former returns a +pointer to the place in the data object where the option's TLV must +then be built by the application. +.Pp +The +.Fa cmsg +argument is a pointer to a +.Li cmsghdr +structure that was initialized by +.Fn inet6_option_init . +.Pp +The +.Fa datalen +argument is the value of the option data length byte for this option. +This value is required as an argument to allow the function to +determine if padding must be appended at the end of the option. +(The +.Fn inet6_option_append +function does not need a data length argument +since the option data length must already be stored by the caller) +.Pp +The +.Fa multx +and +.Fa plusy +arguments +are identical to the arguments of the same name described in the +.Fn inet6_option_init +function above. +.\" +.Ss inet6_option_next +The +.Fn inet6_option_next +function is used to process Hop-by-Hop and Destination options that +are present in an ancillary data object. +When an option remains to +be processed, the return value of the +.Fn inet6_option_next +function is +.Li 0 +and the +.Fa *tptrp +argument points to the 8-bit option type field, which is followed by +the 8-bit option data length, and then the option data. +When no more +options remain to be processed, the return value is +.Li -1 +and +.Fa *tptrp +is +.Dv NULL +and when an error occurs, the return value is +.Li -1 +but the +.Fa *tptrp +argument is not +.Dv NULL . +This set of return values allows a program to easily loop through all +the options in an ancillary data object, checking for the error and +end of stream conditions along the way. +.Pp +When a valid option is returned the +.Fa cmsg +argument points to a +.Li cmsghdr +where the +.Li cmsg_level +equals +.Dv IPPROTO_IPV6 +and +.Li cmsg_type +is either +.Dv IPV6_HOPOPTS +or +.Dv IPV6_DSTOPTS . +.Pp +The +.Fa tptrp +argument is a pointer to a pointer to an 8-bit byte and +.Fa *tptrp +is used by the function to remember its place in the ancillary data +object each time the function is called. +When the +.Fn inet6_option_next +function is called for the first time on a given ancillary data object, +.Fa *tptrp +must be set to +.Dv NULL . +.Pp +Each time the function returns success, +the +.Fa *tptrp +argument points to the 8-bit option type field for the next option to +be processed. +.\" +.Ss inet6_option_find +The +.Fn inet6_option_find +function allows an application to search for a particular option type +in an ancillary data object. +The +.Fa cmsg +argument is a pointer to +.Li cmsghdr +structure in which the +.Li cmsg_level +element equals +.Dv IPPROTO_IPV6 +and the +.Li cmsg_type +element is either +.Dv IPV6_HOPOPTS +or +.Dv IPV6_DSTOPTS . +.Pp +The +.Fa tptrp +argument is handled exactly as in the +.Fn inet6_option_next +function described above. +.Pa +The +.fn inet6_option_find +function starts searching for an option of the specified type +beginning after the value of +.Fa *tptrp . +.\" +.Sh DIAGNOSTICS +The +.Fn inet6_option_init +and +.Fn inet6_option_append +functions return +.Li 0 +on success or +.Li -1 +on an error. +.Pp +The +.Fn inet6_option_alloc +function returns +.Dv NULL +on an error. +.Pp +When +.Fn inet6_option_next +or +.Fn inet6_option_find +detect an error they return +.Li -1 +setting +.Fa *tptrp +to non +.Dv NULL +value. +.\" +.Sh EXAMPLES +RFC2292 gives comprehensive examples in chapter 6. +.\" +.Sh SEE ALSO +.Rs +.%A W. Stevens +.%A M. Thomas +.%T "Advanced Sockets API for IPv6" +.%N RFC2292 +.%D February 1998 +.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 +(RFC2292). +.\" |