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# inet6_rthdr_space

    INET6_RTHDR_SPACE(3)    System Library Functions Manual   INET6_RTHDR_SPACE(3)

    NAME
         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
         manipulation

    SYNOPSIS
         #include <netinet/in.h>

         size_t
         inet6_rthdr_space(int type, int segments);

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

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

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

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

         int
         inet6_rthdr_segments(const struct cmsghdr *cmsg);

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

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

    DESCRIPTION
         RFC2292 IPv6 advanced API defines eight functions that the application
         calls to build and examine a Routing header.  Four functions build a
         Routing header:

         inet6_rthdr_space() return #bytes required for ancillary data

         inet6_rthdr_init() initialize ancillary data for Routing header

         inet6_rthdr_add() add IPv6 address & flags to Routing header

         inet6_rthdr_lasthop() specify the flags for the final hop

         Four functions deal with a returned Routing header:

         inet6_rthdr_reverse() reverse a Routing header

         inet6_rthdr_segments() return #segments in a Routing header

         inet6_rthdr_getaddr() fetch one address from a Routing header

         inet6_rthdr_getflags() fetch one flag from a Routing header

         The function prototypes for these functions are all in the <netinet/in.h>
         header.

       inet6_rthdr_space
         This function returns the number of bytes required to hold a Routing
         header of the specified type containing the specified number of segments
         (addresses).  For an IPv6 Type 0 Routing header, the number of segments
         must be between 1 and 23, inclusive.  The return value includes the size
         of the cmsghdr structure that precedes the Routing header, and any
         required padding.

         If the return value is 0, then either the type of the Routing header is
         not supported by this implementation or the number of segments is invalid
         for this type of Routing header.

         Note: This function returns the size but does not allocate the space
         required for the ancillary data.  This allows an application to allocate
         a larger buffer, if other ancillary data objects are desired, since all
         the ancillary data objects must be specified to sendmsg(2) as a single
         msg_control buffer.

       inet6_rthdr_init
         This function initializes the buffer pointed to by bp to contain a
         cmsghdr structure followed by a Routing header of the specified type.
         The cmsg_len member of the cmsghdr structure is initialized to the size
         of the structure plus the amount of space required by the Routing header.
         The cmsg_level and cmsg_type members are also initialized as required.

         The caller must allocate the buffer and its size can be determined by
         calling inet6_rthdr_space().

         Upon success the return value is the pointer to the cmsghdr structure,
         and this is then used as the first argument to the next two functions.
         Upon an error the return value is NULL.

       inet6_rthdr_add
         This function adds the address pointed to by addr to the end of the Rout-
         ing header being constructed and sets the type of this hop to the value
         of flags.  For an IPv6 Type 0 Routing header, flags must be either
         IPV6_RTHDR_LOOSE or IPV6_RTHDR_STRICT.

         If successful, the cmsg_len member of the cmsghdr structure is updated to
         account for the new address in the Routing header and the return value of
         the function is 0.  Upon an error the return value of the function is -1.

       inet6_rthdr_lasthop
         This function specifies the Strict/Loose flag for the final hop of a
         Routing header.  For an IPv6 Type 0 Routing header, flags must be either
         IPV6_RTHDR_LOOSE or IPV6_RTHDR_STRICT.

         The return value of the function is 0 upon success, or -1 upon an error.

         Notice that a Routing header specifying N intermediate nodes requires N+1
         Strict/Loose flags.  This requires N calls to inet6_rthdr_add() followed
         by one call to inet6_rthdr_lasthop().

       inet6_rthdr_reverse
         This function takes a Routing header that was received as ancillary data
         (pointed to by the first argument, in) and writes a new Routing header
         that sends datagrams along the reverse of that route.  Both arguments are
         allowed to point to the same buffer (that is, the reversal can occur in
         place).

         The return value of the function is 0 on success, or -1 upon an error.

       inet6_rthdr_segments
         This function returns the number of segments (addresses) contained in the
         Routing header described by cmsg.  On success the return value is between
         1 and 23, inclusive.  The return value of the function is -1 upon an
         error.

       inet6_rthdr_getaddr
         This function returns a pointer to the IPv6 address specified by index
         (which must have a value between 1 and the value returned by
         inet6_rthdr_segments()) in the Routing header described by cmsg.  An
         application should first call inet6_rthdr_segments() to obtain the number
         of segments in the Routing header.

         Upon an error the return value of the function is NULL.

       inet6_rthdr_getflags
         This function returns the flags value specified by index (which must have
         a value between 0 and the value returned by inet6_rthdr_segments()) in
         the Routing header described by cmsg.  For an IPv6 Type 0 Routing header
         the return value will be either IPV6_RTHDR_LOOSE or IPV6_RTHDR_STRICT.

         Upon an error the return value of the function is -1.

         Note: Addresses are indexed starting at 1, and flags starting at 0, to
         maintain consistency with the terminology and figures in RFC2460.

    DIAGNOSTICS
         inet6_rthdr_space() returns 0 on errors.

         inet6_rthdr_add(), inet6_rthdr_lasthop() and inet6_rthdr_reverse() return
         0 on success, and returns -1 on error.

         inet6_rthdr_init() and inet6_rthdr_getaddr() return NULL on error.

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

    EXAMPLES
         RFC2292 gives comprehensive examples in chapter 8.

    SEE ALSO
         W. Stevens and M. Thomas, Advanced Sockets API for IPv6, RFC2292,
         February 1998.

         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''
         (RFC2292).

    BUGS
         The text was shamelessly copied from RFC2292.

         inet6_rthdr_reverse() is not implemented yet.

    BSD                            December 10, 1999                           BSD

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