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\"
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Dd December 10, 1999
Dt INET6_RTHDR_SPACE 3
Os
\"
Sh NAME
Nm inet6_rthdr_space ,
Nm inet6_rthdr_init ,
Nm inet6_rthdr_add ,
Nm inet6_rthdr_lasthop ,
Nm inet6_rthdr_reverse ,
Nm inet6_rthdr_segments ,
Nm inet6_rthdr_getaddr ,
Nm inet6_rthdr_getflags
Nd IPv6 Routing Header Options manipulation
\"
Sh SYNOPSIS
In netinet/in.h
Ft size_t
Fn inet6_rthdr_space "int type" "int segments"
Ft "struct cmsghdr *"
Fn inet6_rthdr_init "void *bp" "int type"
Ft int
Fn inet6_rthdr_add "struct cmsghdr *cmsg" "const struct in6_addr *addr" "unsigned int flags"
Ft int
Fn inet6_rthdr_lasthop "struct cmsghdr *cmsg" "unsigned int flags"
Ft int
Fn inet6_rthdr_reverse "const struct cmsghdr *in" "struct cmsghdr *out"
Ft int
Fn inet6_rthdr_segments "const struct cmsghdr *cmsg"
Ft "struct in6_addr *"
Fn inet6_rthdr_getaddr "struct cmsghdr *cmsg" "int index"
Ft int
Fn inet6_rthdr_getflags "const struct cmsghdr *cmsg" "int index"
\"
Sh DESCRIPTION
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:
Bl -hang
It Fn inet6_rthdr_space
return #bytes required for ancillary data
It Fn inet6_rthdr_init
initialize ancillary data for Routing header
It Fn inet6_rthdr_add
add IPv6 address & flags to Routing header
It Fn inet6_rthdr_lasthop
specify the flags for the final hop
El
Pp
Four functions deal with a returned Routing header:
Bl -hang
It Fn inet6_rthdr_reverse
reverse a Routing header
It Fn inet6_rthdr_segments
return #segments in a Routing header
It Fn inet6_rthdr_getaddr
fetch one address from a Routing header
It Fn inet6_rthdr_getflags
fetch one flag from a Routing header
El
Pp
The function prototypes for these functions are all in the
In netinet/in.h
header.
\"
Ss inet6_rthdr_space
This function returns the number of bytes required to hold a Routing
header of the specified
Fa type
containing the specified number of
Fa segments
Pq 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.
Pp
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.
Pp
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
Xr sendmsg 2
as a single
Li msg_control
buffer.
\"
Ss inet6_rthdr_init
This function initializes the buffer pointed to by
Fa bp
to contain a
Li cmsghdr
structure followed by a Routing header of the specified
Fa type .
The
Li cmsg_len
member of the
Li cmsghdr
structure is initialized to the
size of the structure plus the amount of space required by the
Routing header.
The
Li cmsg_level
and
Li cmsg_type
members are also initialized as required.
Pp
The caller must allocate the buffer and its size can be determined by
calling
Fn inet6_rthdr_space .
Pp
Upon success the return value is the pointer to the
Li cmsghdr
structure, and this is then used as the first argument to the next
two functions.
Upon an error the return value is
Dv NULL .
\"
Ss inet6_rthdr_add
This function adds the address pointed to by
Fa addr
to the end of the
Routing header being constructed and sets the type of this hop to the
value of
Fa flags .
For an IPv6 Type 0 Routing header,
Fa flags
must be
either
Dv IPV6_RTHDR_LOOSE
or
Dv IPV6_RTHDR_STRICT .
Pp
If successful, the
Li cmsg_len
member of the
Li 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.
\"
Ss 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,
Fa flags
must be either
Dv IPV6_RTHDR_LOOSE
or
Dv IPV6_RTHDR_STRICT .
Pp
The return value of the function is 0 upon success, or -1 upon an error.
Pp
Notice that a Routing header specifying
Li N
intermediate nodes requires
Li N+1
Strict/Loose flags.
This requires
Li N
calls to
Fn inet6_rthdr_add
followed by one call to
Fn inet6_rthdr_lasthop .
\"
Ss inet6_rthdr_reverse
This function takes a Routing header that was received as ancillary
data
Po
pointed to by the first argument,
Fa in
Pc
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
Pq that is, the reversal can occur in place .
Pp
The return value of the function is 0 on success, or -1 upon an
error.
\"
Ss inet6_rthdr_segments
This function returns the number of segments
Pq addresses
contained in
the Routing header described by
Fa cmsg .
On success the return value is
between 1 and 23, inclusive.
The return value of the function is -1 upon an error.
\"
Ss inet6_rthdr_getaddr
This function returns a pointer to the IPv6 address specified by
Fa index
Po
which must have a value between 1 and the value returned by
Fn inet6_rthdr_segments
Pc
in the Routing header described by
Fa cmsg .
An
application should first call
Fn inet6_rthdr_segments
to obtain the number of segments in the Routing header.
Pp
Upon an error the return value of the function is
Dv NULL .
\"
Ss inet6_rthdr_getflags
This function returns the flags value specified by
Fa index
Po
which must
have a value between 0 and the value returned by
Fn inet6_rthdr_segments
Pc
in the Routing header described by
Fa cmsg .
For an IPv6 Type 0 Routing header the return value will be either
Dv IPV6_RTHDR_LOOSE
or
Dv IPV6_RTHDR_STRICT .
Pp
Upon an error the return value of the function is -1.
Pp
Note: Addresses are indexed starting at 1, and flags starting at 0,
to maintain consistency with the terminology and figures in RFC 2460.
\"
Sh EXAMPLES
RFC 2292 gives comprehensive examples in chapter 8.
\"
Sh RETURN VALUES
Fn inet6_rthdr_space
returns 0 on errors.
Pp
Fn inet6_rthdr_add ,
Fn inet6_rthdr_lasthop
and
Fn inet6_rthdr_reverse
return 0 on success, and returns -1 on error.
Pp
Fn inet6_rthdr_init
and
Fn inet6_rthdr_getaddr
return
Dv NULL
on error.
Pp
Fn inet6_rthdr_segments
and
Fn inet6_rthdr_getflags
return -1 on error.
\"
Sh SEE ALSO
Rs
%A W. Stevens
%A M. Thomas
%T "Advanced Sockets API for IPv6"
%N RFC 2292
%D February 1998
Re
Rs
%A S. Deering
%A R. Hinden
%T "Internet Protocol, Version 6 (IPv6) Specification"
%N RFC 2460
%D December 1998
Re
\"
Sh STANDARDS
The functions
are documented in
Dq Advanced Sockets API for IPv6
Pq RFC 2292 .
\"
Sh HISTORY
The implementation first appeared in KAME advanced networking kit.
\"
Sh BUGS
The text was shamelessly copied from RFC 2292.
Pp
Fn inet6_rthdr_reverse
is not implemented yet.

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