INET6_RTH_SPACE(3) BSD Programmer's Manual INET6_RTH_SPACE(3)NAME
inet6_rth_space inet6_rth_init inet6_rth_add inet6_rth_reverse
inet6_rth_segments inet6_rth_getaddr - IPv6 Routing Header Options manip-
ulation
SYNOPSIS
#include <netinet/in.h>
size_t
inet6_rth_space(int, int);
void *
inet6_rth_init(void *, int, int, int);
int
inet6_rth_add(void *, const struct in6_addr *);
int
inet6_rth_reverse(const void *, void *);
int
inet6_rth_segments(const void *);
struct in6_addr *
inet6_rth_getaddr(const void *, int);
DESCRIPTION
The IPv6 advanced API defines six functions that the application calls to
build and examine a Routing header, and the ability to use sticky options
or ancillary data to communicate this information between the application
and the kernel using the IPV6_RTHDR option.
Three functions build a Routing header:
inet6_rth_space() returns #bytes required for Routing header
inet6_rth_init() initializes buffer data for Routing header
inet6_rth_add() adds one IPv6 address to the Routing header
Three functions deal with a returned Routing header:
inet6_rth_reverse() reverses a Routing header
inet6_rth_segments() returns #segments in a Routing header
inet6_rth_getaddr() fetches one address from a Routing header
The function prototypes for these functions are defined as a result of
including the <netinet/in.h> header.
inet6_rth_space
inet6_rth_space() 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 0 and 127, inclusive. The return value is just the space
for the Routing header. When the application uses ancillary data it must
pass the returned length to CMSG_LEN() to determine how much memory is
needed for the ancillary data object (including the cmsghdr structure.)
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 re-
quired 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() as a single
msg_control buffer.
inet6_rth_init
inet6_rth_init() 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. bp_len is only used to verify that the buffer is
large enough. The ip6r0_segleft field is set to zero; inet6_rth_add()
will increment it.
When the application uses ancillary data the application must initialize
any cmsghdr fields.
The caller must allocate the buffer and its size can be determined by
calling inet6_rth_space().
Upon success the return value is the pointer to the buffer bp, and this
is then used as the first argument to the next two functions. Upon an
error the return value is NULL.
inet6_rth_add
inet6_rth_add() adds the IPv6 address pointed to by addr to the end of
the Routing header being constructed.
If successful, the segleft member of the Routing Header is updated to ac-
count 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_rth_reverse
inet6_rth_reverse() takes a Routing header extension header (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_rth_segments
inet6_rth_segments() returns the number of segments (addresses) contained
in the Routing header described by bp. On success the return value is ze-
ro or greater. The return value of the function is -1 upon an error.
inet6_rth_getaddrinet6_rth_getaddr() returns a pointer to the IPv6 address specified by
index turned by inet6_rth_segments() (which must have a value between 0
and one less than the value re-) in the Routing header described by bp.
An application should first call inet6_rth_segments() to obtain the num-
ber of segments in the Routing header.
Upon an error the return value of the function is NULL.
DIAGNOSTICSinet6_rth_space() and return 0 on errors.
inet6_rthdr_init() returns NULL on error. inet6_rth_add() and
inet6_rth_reverse() return0 on success, or -1 upon an error.
EXAMPLES
draft-ietf-ipngwg-rfc2292bis-01.txt gives comprehensive examples in Sec-
tion 23.
KAME also provides examples in the advapi directry of its kit.
SEE ALSO
W. Stevens, M. Thomas, and E. Nordmark, Advanced Sockets API for IPv6,
draft-ietf-ipngwg-rfc2292bis-01, October 1999.
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''
(draft-ietf-ipngwg-rfc2292bis-01.txt).
BUGS
RFC2292bis is still under standardization procedure. The specification
of the functions described in this manual can be changed in the future.
The text was shamelessly copied from internet-drafts for RFC2292bis.
KAME February 5, 2000 3
