inet6_opt_init(3N) inet6_opt_init(3N)
NAME
inet6_opt_init(), inet6_opt_append(), inet6_opt_find(), inet6_opt_finish(), inet6_opt_get_val(), inet6_opt_next(), inet6_opt_set_val() -
IPv6 Hop-by-Hop and Destination options manipulation functions.
SYNOPSIS
DESCRIPTION
These functions can be used by applications to build and parse the IPv6 Hop-by-Hop and Destination options header. The Hop-by-Hop option
header is used to carry optional information that must be examined by every node along a packet's delivery path and the Destination option
header is used to carry optional information that needs to be examined only by a packet's destination node(s).
This function returns the number of bytes needed for the empty
extension header without any options. If extbuf is not NULL, it also initializes the extension header to have the correct length
field. If the extlen value is not a positive multiple of 8, the function fails and returns -1.
This function returns the updated total
length required to add an option with length len and alignment align. If extbuf is not NULL, then in addition to returning the
length, this function also inserts any needed pad option, initializes the option (sets the type and length fields), and returns a
pointer to the location for the option content in databufp. If the option specified by type does not fit in the extension header buf-
fer then the function returns -1.
The third parameter offset should be the length returned by or by a previous
The parameter type is the 8-bit option type and it must be a value from 2 to 255, inclusive. 0 and 1 are reserved for the Pad1 and
PadN options, respectively.
The parameter len is the length of the option data excluding the option type and option length fields. It must have a value between 0
and 255, inclusive, and it specifies the length of the option data that follows the option header.
The align parameter must have a value of 1, 2, 4, or 8. The align value can not exceed the value of len. If the len parameter is 0,
the align parameter is ignored.
Once has been called, the application can use databuf directly, or use to specify (set) the contents of the option.
This function returns the updated total length
including the final padding of the extension header to make the header a multiple of 8 bytes.
If extbuf is not NULL, the function also initializes the option by inserting a Pad1 or PadN option of the proper length. If the nec-
essary pad does not fit in the extension header buffer, the function returns -1.
The parameter offset should be the length returned by or
This function inserts data items of various sizes (1, 2, 4, or 8 bytes) in the data portion of the option. After inserting, the function
returns the offset for the next field (offset + vallen) which can be used when composing option content with multiple fields. The
parameter val points to the data to be inserted and the parameter offset 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.
The parameter databuf should be a pointer returned by
This function parses extension header options received by the
application and it returns the offset of the next option.
The parameters extbuf and extlen specify the extension header.
The parameter offset is either zero (for the first option) or the length returned by a previous call to or offset specifies the posi-
tion where to continue scanning the extension buffer. The next option is returned by updating the parameters databufp, typep, and
lenp. This function returns the updated "previous" length computed by advancing past the option that was returned. This returned
"previous" length can then be passed to subsequent calls to
This function does not return any Pad1 or PadN options. When there are no more options or if the option extension header is mal-
formed, the return value is -1.
This function is similar to the
function but this function lets the caller specify the option type to be searched for instead of always returning the next option in
the extension header.
If an option of the specified type is located, the function returns the updated "previous" total length. This "previous" total length
is computed by advancing past the option that was returned and past any options that did not match the type. This returned previous
length can then be passed to subsequent calls to for finding the next occurrence of the same option type.
If an option of the specified type is not located or the option extension header is malformed, the return value is -1.
This function extracts data items of various sizes
(1, 2, 4, or 8 bytes) in the data portion of the option. The function returns the offset for the next field (offset + vallen) which
can be used when extracting option content with multiple fields.
The first parameter databuf should be a pointer returned by or containing the data portion of the option.
offset parameter 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.
val points to the destination for the extracted data.
Notes
To use these functions, the application must be compiled with:
To receive Hop-by-Hop options, the application must enable the socket option:
To send a Hop-by-Hop options header, the application specifies the header either as ancillary data in a call to or using
The application can remove any sticky Hop-by-Hop extension header by calling for with a zero option length.
To receive Destination options appearing after a Routing header (or in a packet without a Routing header), the application must enable the
socket option:
To receive Destination options appearing before a Routing header, the application must enable the socket option:
To send a Destination options header, the application specifies it either as ancillary data in a call to or using
The application can remove any sticky Destination extension header by calling for with a zero option length.
RETURN VALUE
and return -1 on an error.
EXAMPLES
gives a comprehensive example in Appendix C.
SEE ALSO
ip6(7P), xopen_networking(7).
inet6_opt_init(3N)