Manual Pages for UNIX Operating System command usage for man inet6_rth

Sockets Library Functions                      inet6_rth(3SOCKET)



NAME
     inet6_rth, inet6_rth_space,  inet6_rth_init,  inet6_rth_add,
     inet6_rth_reverse,  inet6_rth_segments,  inet6_rth_getaddr -
     Routing header manipulation

SYNOPSIS
     cc [ flag ... ] file ... -lsocket [library]
     #include 

     socklen_t inet6_rth_space(int type, int segments);


     void *inet6_rth_init(void *bp, socklen_t bp_len, int type, int segments);


     int inet6_rth_add(void *bp, const struct, in6_addr *addr);


     int inet6_rth_reverse(const void *in, void *out);


     int inet6_rth_segments(const void *bp);


     struct in6_addr *inet6_rth_getaddr(const void *bp, int index);


DESCRIPTION
     The inet6_rth functions enable users to  manipulate  routing
     headers without having knowledge of their structure.


     The iet6_rth_init() function initializes the buffer  pointed
     to  by  bp to contain a routing header of the specified type
     and sets ip6r_len  based  on  the  segments  parameter.  The
     bp_len  argument  is  used only to verify that the buffer is
     large enough. The ip6r_segleft field  is  set  to  zero  and
     inet6_rth_add()  increments  it.  The  caller  allocates the
     buffer  and  its  size  can   be   determined   by   calling
     inet6_rth_space().


     The inet6_rth_add() function adds the IPv6  address  pointed
     to  by  addr  to the end of the routing header that is being
     constructed.


     The inet6_rth_reverse()  function  takes  a  routing  header
     extension header pointed to by the first argument and writes
     a new routing header that sends datagrams along the  reverse
     of  the  route.  The  function  reverses  the  order  of the
     addresses and sets the segleft member  in  the  new  routing



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Sockets Library Functions                      inet6_rth(3SOCKET)



     header  to  the number of segments. Both arguments can point
     to the same buffer (that  is,  the  reversal  can  occur  in
     place).


     The inet6_rth_segments() function returns the number of seg-
     ments  (addresses) contained in the routing header described
     by bp.


     The inet6_rth_getaddr() function returns a  pointer  to  the
     IPv6  address  specified  by  index, which must have a value
     between  0  and  one  less  than  the  value   returned   by
     inet6_rth_segments()  in the routing header described by bp.
     Applications  should  first  call  inet6_rth_segments()   to
     obtain the number of segments in the routing header.


     The inet6_rth_space() function returns  the  size,  but  the
     function does not allocate the space required for the ancil-
     lary data routing header.

ROUTING HEADERS
     To receive a routing header, the application must enable the
     IPV6_RECVRTHDR socket option:

       int  on = 1;
       setsockopt (fd, IPPROTO_IPV6, IPV6_RECVRTHDR, &on, sizeof(on));



     Each received routing header is returned  as  one  ancillary
     data  object described by a cmsghdr structure with cmsg_type
     set to IPV6_RTHDR.


     To send a  routing  header,  the  application  specifies  it
     either  as ancillary data in a call to sendmsg() or by using
     setsockopt(). For the sending side,  this  API  assumes  the
     number  of occurrences of the routing header as described in
     RFC-2460. Applications can specify no more than one outgoing
     routing header.


     The application can remove any sticky routing header by cal-
     ling setsockopt() for IPV6_RTHDR with a zero option length.


     When using  ancillary  data,  a  routing  header  is  passed
     between  the  application  and  the  kernel  as follows: The
     cmsg_level member  has  a  value  of  IPPROTO_IPV6  and  the
     cmsg_type  member has a value of IPV6_RTHDR. The contents of



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Sockets Library Functions                      inet6_rth(3SOCKET)



     the cmsg_data member is implementation-dependent and  should
     not  be  accessed directly by the application, but should be
     accessed using the inet6_rth functions.


     The following constant is defined as a result  of  including
     the :

       #define IPV6_RTHDR_TYPE_0   0 /* IPv6 Routing header type 0 */


  ROUTING HEADER OPTION
     Source routing in IPv6 is accomplished by specifying a rout-
     ing  header  as  an  extension header. There are a number of
     different routing headers, but IPv6 currently  defines  only
     the  Type 0 header. See RFC-2460. The Type 0 header supports
     up to 127 intermediate nodes, limited by the length field in
     the extension header. With this maximum number of intermedi-
     ate nodes, a source, and a destination, there are 128 hops.

RETURN VALUES
     The inet6_rth_init()  function  returns  a  pointer  to  the
     buffer (bp) upon success.


     For the inet6_rth_add() function, the segleft member of  the
     routing  header is updated to account for the new address in
     the routing header. The function returns 0 upon success  and
     -1 upon failure.


     The inet6_rth_reverse() function returns 0 upon  success  or
     -1 upon an error.


     The inet6_rth_segments() function returns 0 or greater  upon
     success and -1 upon an error.


     The inet6_rth_getaddr() function returns NULL upon an error.


     The inet6_rth_space()  function  returns  the  size  of  the
     buffer needed for the routing header.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:







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Sockets Library Functions                      inet6_rth(3SOCKET)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | Safe                        |
    |_____________________________|_____________________________|
    | Standard                    | See standards(5).           |
    |_____________________________|_____________________________|


SEE ALSO
     RFC 3542- Advanced Sockets Application Programming Interface
     (API) for IPv6, The Internet Society. May 2003









































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