inet6_opt_initinet6_opt_appendinet6_opt_finishinet6_opt_set_valinet6_opt_nextinet6_opt_findinet6_opt_get_val
- IPv6 Hop-by-Hop and Destination Options manipulation
SYNOPSIS
#include <netinet/in.h> int
inet6_opt_init (void *extbuf socklen_t extlen); int
inet6_opt_append (void *extbuf socklen_t extlen int offset u_int8_t type socklen_t len u_int8_t align void **databufp); int
inet6_opt_finish (void *extbuf socklen_t extlen int offset); int
inet6_opt_set_val (void *databuf int offset void *val socklen_t vallen); int
inet6_opt_next (void *extbuf socklen_t extlen int offset u_int8_t *typep socklen_t *lenp void **databufp); int
inet6_opt_find (void *extbuf socklen_t extlen int offset u_int8_t type socklen_t *lenp void **databufp); int
inet6_opt_get_val (void *databuf int offset void *val socklen_t vallen);
DESCRIPTION
Building and parsing the Hop-by-Hop and Destination options is
complicated.
The advanced sockets API defines a set of functions to
help applications create and manipulate Hop-by-Hop and Destination
options.
This man page describes the functions specified in
IETF Draft RFC3542.
These functions use 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 contained in the
#include <netinet/in.h>
header file.
inet6_opt_init
The
inet6_opt_init ();
function
returns the number of bytes needed for an empty
extension header, one without any options.
If the
Fa extbuf
argument points to a valid section of memory
then the
inet6_opt_init ();
function also initializes the extension header's length field.
When attempting to initialize an extension buffer passed in the
Fa extbuf
argument,
Fa extlen
must be a positive multiple of 8 or else the function fails and
returns -1 to the caller.
inet6_opt_append
The
inet6_opt_append ();
function can perform two different jobs.
When a valid
Fa extbuf
argument is supplied it appends an option to the extension buffer and
returns the updated total length as well as a pointer to the newly
created option in
Fa databufp .
If the value
of
Fa extbuf
is
NULL
then the
inet6_opt_append ();
function only reports what the total length would
be if the option were actually appended.
The
Fa len
and
Fa align
arguments specify the length of the option and the required data
alignment which must be used when appending the option.
The
Fa offset
argument should be the length returned by the
inet6_opt_init ();
function or a previous call to
inet6_opt_append (.);
The
Fa type
argument is the 8-bit option type.
After
inet6_opt_append ();
has been called, the application can use the buffer pointed to by
Fa databufp
directly, or use
inet6_opt_set_val ();
to specify the data to be contained in the option.
Option types of
0
and
1
are reserved for the
Pad1
and
PadN
options.
All other values from 2 through 255 may be used by applications.
The length of the option data is contained in an 8-bit value and so
may contain any value from 0 through 255.
The
Fa align
parameter must have a value of 1, 2, 4, or 8 and cannot exceed the
value of
Fa len .
The alignment values represent no alignment, 16 bit, 32 bit and 64 bit
alignments, respectively.
inet6_opt_finish
The
inet6_opt_finish ();
function
calculates the final padding necessary to make the extension header a
multiple of 8 bytes, as required by the IPv6 extension header
specification, and returns the extension header's updated total
length.
The
Fa offset
argument should be the length returned by
inet6_opt_init ();
or
inet6_opt_append (.);
When
Fa extbuf
is not
NULL
the function also sets up the appropriate padding bytes by inserting a
Pad1 or PadN option of the proper length.
If the extension header is too small to contain the proper padding
then an error of -1 is returned to the caller.
inet6_opt_set_val
The
inet6_opt_set_val ();
function inserts data items of various sizes into the data portion of
the option.
The
Fa databuf
argument is a pointer to memory that was returned by the
inet6_opt_append ();
call and the
Fa offset
argument specifies where the option should be placed in the
data buffer.
The
Fa val
argument points to an area of memory containing the data to be
inserted into the extension header, and the
Fa vallen
argument indicates how much data to copy.
The caller should ensure that each field is aligned on its natural
boundaries as described in Appendix B of RFC2460.
The function returns the offset for the next field which is calculated as
Fa offset
+
Fa vallen
and is used when composing options with multiple fields.
inet6_opt_next
The
inet6_opt_next ();
function parses received extension headers.
The
Fa extbuf
and
Fa extlen
arguments specify the location and length of the extension header
being parsed.
The
Fa offset
argument should either be zero, for the first option, or the length value
returned by a previous call to
inet6_opt_next ();
or
inet6_opt_find (.);
The return value specifies the position where to continue scanning the
extension buffer.
The option is returned in the arguments
Fa typep , lenp ,
and
Fa databufp ,
which
point to the 8-bit option type, the 8-bit option length and the option
data, respectively.
This function does not return any PAD1 or PADN options.
When an error occurs or there are no more options, the return
value is -1.
inet6_opt_find
The
inet6_opt_find ();
function searches the extension buffer for a particular option type,
passed in through the
Fa type
argument.
If the option is found then the
Fa lenp
and
Fa databufp
arguments are updated to point to the option's length and data,
respectively.
The
Fa extbuf
and
Fa extlen
arguments
must point to a valid extension buffer and give its length.
The
Fa offset
argument can be used to search from a location anywhere in the
extension header.
inet6_opt_get_val
The
inet6_opt_get_val ();
function extracts data items of various sizes in the data portion of
the option.
The
Fa databuf
is a pointer returned by the
inet6_opt_next ();
or
inet6_opt_find ();
functions.
The
Fa val
argument points where the data will be extracted.
The
Fa offset
argument specifies from where in the data portion of the option the
value should be extracted; the first byte of option data is specified
by an offset of zero.
It is expected that each field is aligned on its natural boundaries as
described in Appendix B of RFC2460.
The function returns the offset for the next field
by calculating
Fa offset
+
Fa vallen
which can be used when extracting option content with multiple fields.
Robust receivers must verify alignment before calling this function.
RETURN VALUES
All the functions return
-1
on an error.
EXAMPLES
RFC3542 gives comprehensive examples in Section 23.
KAME also provides examples in the
advapitest
directory of its kit.
SEE ALSO
W. Stevens
M. Thomas
E. Nordmark
T. Jinmei
"Advanced Sockets API for IPv6"
RFC3542
October 2002
S. Deering
R. Hinden
"Internet Protocol, Version 6 (IPv6) Specification"
RFC2460
December 1998
STANDARDS
The functions are documented in
``Advanced Sockets API for IPv6''
(RFC3542)
HISTORY
The implementation first appeared in KAME advanced networking kit.
