INET6_OPT_INIT(3)					   BSD Library Functions Manual 					 INET6_OPT_INIT(3)

NAME

     inet6_opt_init, inet6_opt_append, inet6_opt_finish, inet6_opt_set_val, inet6_opt_next, inet6_opt_find, inet6_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, socklen_t 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-Hope and Destination options.  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
     <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 extbuf argu-
     ment 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 extbuf argument 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 to different jobs.  When a valid extbuf argument is supplied it appends an option to the exten-
     sion buffer and returns the updated total length as well as a pointer to the newly created option in databufp.  If the value of extbuf is
     NULL then the inet6_opt_append(function, only, reports, what, the, total, length, would) be if the option were actually appended.	The len
     and align arguments specify the length of the option and the required data alignment which must be used when appending the option.  The
     offset argument should be the length returned by the inet6_opt_init() function or a previous call to inet6_opt_append().

     The type argument is the 8-bit option type.

     After inet6_opt_append() has been called, the application can use the buffer pointed to by 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 align parameter must have a value of 1, 2, 4, or 8 and cannot exceed the value of len.  The alignment values represent no alignment, 16
     bit, 32 bit and 64 bit alignments respectively.

   inet6_opt_finish
     The inet6_opt_finish() 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 offset argument should be the length returned
     by inet6_opt_init() or inet6_opt_append().  When 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 databuf argument is a pointer
     to memory that was returned by the inet6_opt_append() call and the offset argument specifies where the option should be placed in the data
     buffer.  The val argument points to an area of memory containing the data to be inserted into the extension header, and the 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 offset + vallen and is used when composing options with multiple
     fields.

   inet6_opt_next
     The inet6_opt_next() function parses received extension headers.  The extbuf and extlen arguments specify the location and length of the
     extension header being parsed.  The 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 typep, lenp, and databufp.  typep, lenp, and databufp 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 type argument.  If the option
     is found then the lenp and databufp arguments are updated to point to the option's length and data respectively.  extbuf and extlen must
     point to a valid extension buffer and give its length.  The 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 databuf is a pointer returned
     by the inet6_opt_next() or inet6_opt_find() functions.  The val argument points where the data will be extracted.	The offset argument speci-
     fies 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 offset + vallen which can be used when extracting option content with mul-
     tiple fields.  Robust receivers must verify alignment before calling this function.

DIAGNOSTICS

     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, and T. Jinmei, Advanced Sockets API for IPv6, RFC3542, October 2002.

     S. Deering and R. Hinden, Internet Protocol, Version 6 (IPv6) Specification, RFC2460, December 1998.

HISTORY

     The implementation first appeared in KAME advanced networking kit.

STANDARDS

     The functions are documented in ``Advanced Sockets API for IPv6'' (RFC3542).

BSD
								 December 23, 2004							       BSD