MirOS Manual: inet6_rthdr_add(3), inet6_rthdr_getaddr(3), inet6_rthdr_getflags(3), inet6_rthdr_init(3), inet6_rthdr_lasthop(3), inet6_rthdr_reverse(3), inet6_rthdr_segments(3), inet6_rthdr_space(3)

INET6_RTHDR_SPACE(3)       BSD Programmer's Manual        INET6_RTHDR_SPACE(3)


     inet6_rthdr_space, inet6_rthdr_init, inet6_rthdr_add,
     inet6_rthdr_lasthop, inet6_rthdr_reverse, inet6_rthdr_segments,
     inet6_rthdr_getaddr, inet6_rthdr_getflags - IPv6 Routing Header Options


     #include <sys/types.h>
     #include <netinet/in.h>

     inet6_rthdr_space(int type, int segments);

     struct cmsghdr *
     inet6_rthdr_init(void *bp, int type);

     inet6_rthdr_add(struct cmsghdr *cmsg, const struct in6_addr *addr,
             unsigned int flags);

     inet6_rthdr_lasthop(struct cmsghdr *cmsg, unsigned int flags);

     inet6_rthdr_reverse(const struct cmsghdr *in, struct cmsghdr *out);

     inet6_rthdr_segments(const struct cmsghdr *cmsg);

     struct in6_addr *
     inet6_rthdr_getaddr(struct cmsghdr *cmsg, int index);

     inet6_rthdr_getflags(const struct cmsghdr *cmsg, int index);


     The RFC 2292 IPv6 Advanced API defined eight functions for applications
     to use for building and parsing routing headers. The eight functions are
     split into two groups, the first of which builds the header and the
     second of which can parse it. The function prototypes for these functions
     are all in the <netinet/in.h> header. Although direct manipulation of a
     routing header is possible, this set of APIs make it unnecessary and such
     direct manipulation should be avoided so that changes to the underlying
     structures do not break applications.

     Please note that RFC 2292 uses the term "segments" instead of the term
     "addresses" but they are considered equivalent for this manual page.


     The inet6_rthdr_space() function returns the number of bytes required to
     hold a routing header of the specified type and containing the specified
     number of segments. Only one type is supported, IPV6_RTHDR_TYPE_0, and it
     can hold from 1 to 23 segments. The return value includes the size of the
     cmsghdr structure that precedes the routing header and any required pad-

     A return value of 0 indicates an error. Either the type was specified in-
     correctly, or the number of segments was less than one or greater than

     Note: The inet6_rthdr_space() function only returns the size required by
     the routing header and does not allocate memory for the caller.


     The inet6_rthdr_init() function initializes a buffer, pointed to by bp
     with an appropriate cmsghdr structure followed by a routing header of the
     specified type.

     The caller must use the inet6_rthdr_space() function to determine the
     size of the buffer, and then allocate that buffer before calling

     The return value is a pointer to a cmsghdr structure, which is used as
     the first argument to the inet6_rthdr_add() and inet6_rthdr_lasthop()
     functions in order to construct the routing header. When an error occurs
     the return value is NULL.


     The inet6_rthdr_add() function adds the IPv6 address pointed to by addr
     to the end of the routing header being constructed and sets the type of
     this address to the value of flags. The flags must be either
     IPV6_RTHDR_LOOSE or IPV6_RTHDR_STRICT indicating whether loose or strict
     source routing is required.

     When the function succeeds it returns 0, otherwise -1 is returned.


     The inet6_rthdr_lasthop() function specifies the strict or loose flag for
     the final hop of a routing header. The flags argument must be either

     The return value of the function is 0 upon success, and -1 when an error
     has occurred.

     Please note that a routing header specifying N intermediate nodes re-
     quires N+1 strict or loose flags meaning that inet6_rthdr_add() must be
     called N times and then inet6_rthdr_lasthop() must be called once.


     This function was never implemented.

     The following three functions provide an API for parsing a received rout-
     ing header:


     The inet6_rthdr_segments() function returns the number of segments con-
     tained in the routing header pointed to by the cmsg argument. On success
     the return value is from 1 to 23. When an error occurs, -1 is returned.


     The inet6_rthdr_getaddr() function returns a pointer to the IPv6 address
     specified by the index argument from the routing header pointed to by
     cmsg. The index must be between 1 and the number returned by
     inet6_rthdr_segments(), described above. An application must call
     inet6_rthdr_segments() to obtain the number of segments in the routing

     If an error occurs, NULL is returned.


     The inet6_rthdr_getflags() function returns the flags value of the seg-
     ment specified by index of the routing header pointed to by cmsg. The
     index argument must be between 0 and the value returned by
     inet6_rthdr_segments(). The return value will be either IPV6_RTHDR_LOOSE
     or IPV6_RTHDR_STRICT indicating whether loose or strict source routing
     was requested for that segment.

     When an error occurs, -1 is returned.

     Note: Flags begin at index 0 while segments begin at index 1, to maintain
     consistency with the terminology and figures in RFC 2460.


     RFC 2292 gives comprehensive examples in chapter 8.


     The inet6_rthdr_space() function returns 0 when an error occurs.

     The inet6_rthdr_add() and inet6_rthdr_lasthop() functions return 0 on
     success, and -1 on error.

     The inet6_rthdr_init() and inet6_rthdr_getaddr() functions return NULL on

     The inet6_rthdr_segments() and inet6_rthdr_getflags() functions return -1
     on error.


     inet6(4), ip6(4)

     W. Stevens and M. Thomas, Advanced Sockets API for IPv6, RFC 2292,
     February 1998.

     S. Deering and R. Hinden, Internet Protocol, Version 6 (IPv6)
     Specification, RFC 2460, December 1998.


     This implementation first appeared in the KAME advanced networking kit.


     The inet6_rthdr_reverse() function was never implemented.

MirOS BSD #10-current         December 27, 2004                              2

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