The IPv6 Advanced API, RFC 3542, defines the functions that an
application calls to build and examine IPv6 Routing headers.
Routing headers are used to perform source routing in IPv6 networks.
The RFC uses the word
``segments''
to describe addresses and that is the term used here as well.
All of the functions are defined in the
#include <netinet/in.h>
header file.
The functions described in this manual page all operate
on routing header structures which are defined in
#include <netinet/ip6.h>
but which should not need to be modified outside the use of this API.
The size and shape of the route header structures may change, so using
the APIs is a more portable, long term, solution.
The functions in the API are split into two groups, those that build a
routing header and those that parse a received routing header.
We will describe the builder functions followed by the parser functions.
inet6_rth_space
The
inet6_rth_space ();
function returns the number of bytes required to hold a Routing Header
of the type, specified in the
Fa type
argument and containing the number of addresses specified in the
Fa segments
argument.
When the type is
IPV6_RTHDR_TYPE_0
the number of segments must be from 0 through 127.
Routing headers of type
IPV6_RTHDR_TYPE_2
contain only one segment, and are only used with Mobile IPv6.
The return value from this function is the number of bytes required to
store the routing header.
If the value 0 is returned then either the
route header type was not recognized or another error occurred.
inet6_rth_init
The
inet6_rth_init ();
function initializes the pre-allocated buffer pointed to by
Fa bp
to contain a routing header of the specified type The
Fa bp_len
argument is used to verify that the buffer is large enough.
The caller must allocate the buffer pointed to by bp.
The necessary buffer size should be determined by calling
inet6_rth_space ();
described in the previous sections.
The
inet6_rth_init ();
function returns a pointer to
Fa bp
on success and
NULL
when there is an error.
inet6_rth_add
The
inet6_rth_add ();
function adds the IPv6 address pointed to by
Fa addr
to the end of the routing header being constructed.
A successful addition results in the function returning 0, otherwise
-1 is returned.
inet6_rth_reverse
The
inet6_rth_reverse ();
function takes a routing header, pointed to by the
argument
Fa in ,
and writes a new routing header into the argument pointed to by
Fa out .
The routing header at that sends datagrams along the reverse of that
route.
Both arguments are allowed to point to the same buffer meaning
that the reversal can occur in place.
The return value of the function is 0 on success, or -1 when
there is an error.
The next set of functions operate on a routing header that the
application wants to parse.
In the usual case such a routing header
is received from the network, although these functions can also be
used with routing headers that the application itself created.
inet6_rth_segments
The
inet6_rth_segments ();
function returns the number of segments contained in the
routing header pointed to by
Fa bp .
The return value is the number of segments contained in the routing
header, or -1 if an error occurred.
It is not an error for 0 to be
returned as a routing header may contain 0 segments.
inet6_rth_getaddr
The
inet6_rth_getaddr ();
function is used to retrieve a single address from a routing header.
The
Fa index
is the location in the routing header from which the application wants
to retrieve an address.
The
Fa index
parameter must have a value between 0 and one less than the number of
segments present in the routing header.
The
inet6_rth_segments ();
function, described in the last section, should be used to determine
the total number of segments in the routing header.
The
inet6_rth_getaddr ();
function returns a pointer to an IPv6 address on success or
NULL
when an error has occurred.
EXAMPLES
RFC 3542 gives extensive examples in Section 21, Appendix B.
KAME also provides examples in the advapitest directory of its kit.
DIAGNOSTICS
The
inet6_rth_space ();
and
inet6_rth_getaddr ();
functions return 0 on errors.
The
inet6_rthdr_init ();
function returns
NULL
on error.
The
inet6_rth_add ();
and
inet6_rth_reverse ();
functions return 0 on success, or -1 upon an error.
SEE ALSO
W. Stevens
M. Thomas
E. Nordmark
T. Jinmei
"Advanced Sockets API for IPv6"
RFC 3542
May 2003
S. Deering
R. Hinden
"Internet Protocol, Version 6 (IPv6) Specification"
RFC2460
December 1998
HISTORY
The implementation first appeared in KAME advanced networking kit.
