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ET6_RTHDR_SPACE(3)
Contents
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IN 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
#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);
RFC 2292 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 Routing
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 RFC
2460.
RFC 2292 gives comprehensive examples in chapter 8.
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.
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.
The functions are documented in ``Advanced Sockets API for
IPv6'' (RFC
2292).
The implementation first appeared in KAME advanced networking kit.
The text was shamelessly copied from RFC 2292.
inet6_rthdr_reverse() is not implemented yet.
OpenBSD 3.6 December 10, 1999
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