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

LIBRARY
libc

SYNOPSIS
#include <sys/types.h>
#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
The RFC 2292 IPv6 Advanced API defined eight functions for applications to use for building and parsing routing headers. The eight functions are split into two groups, the first of which builds the header and the second of which can parse it. The function prototypes for these functions are all in the <netinet/in.h> header. Although direct manipulation of a routing header is possible this set of APIs make it unnecessary and such direct manipulation should be avoided so that changes to the underlying structures do not break applications.

Please note that RFC 2292 uses the term “segments” instead of the term “addresses” but they are considered equivalent for this manual page.

  inet6_rthdr_space
The inet6_rthdr_space() function returns the number of bytes required to hold a routing header of the specified type and containing the specified number of segments. Only one type is supported, IPV6_RTHDR_TYPE_0, and it can hold from 1 to 23 segments. The return value includes the size of the cmsghdr structure that precedes the routing header, and any required padding.

A return value of 0 indicates an error. Either the type was specified incorrectly, or the number of segments was less than one or greater than 23.

Note: The inet6_rthdr_space() function only returns the size required by the routing header and does not allocate memory for the caller.

  inet6_rthdr_init
The inet6_rthdr_init() function initializes a buffer, pointed to by bp with an appropriate cmsghdr structure followed by a routing header of the specified type.

The caller must use the inet6_rthdr_space() function to determine the size of the buffer, and then allocate that buffer before calling inet6_rthdr_init().

The return value is a pointer to a cmsghdr structure, which is used as the first argument to the inet6_rthdr_add() and inet6_rthdr_lasthop() functions in order to construct the routing header. When an error occurs the return value is NULL.

  inet6_rthdr_add
The inet6_rthdr_add() function adds the IPv6 address pointed to by addr to the end of the routing header being constructed and sets the type of this address to the value of flags. The flags must be either IPV6_RTHDR_LOOSE or IPV6_RTHDR_STRICT indicating whether loose or strict source routing is required.

When the function succeeds it returns 0, otherwise -1 is returned.

  inet6_rthdr_lasthop
The inet6_rthdr_lasthop() function specifies the strict or loose flag for the final hop of a routing header. The flags must be either IPV6_RTHDR_LOOSE or IPV6_RTHDR_STRICT.

The return value of the function is 0 upon success, and -1 when an error has occurred.

Please note that a routing header specifying N intermediate nodes requires N+1 strict or loose flags meaning that inet6_rthdr_add() must be called N times and then inet6_rthdr_lasthop() must be called once.

  inet6_rthdr_reverse
This function was never implemented.

The following four functions provide an API for parsing a received routing header.

  inet6_rthdr_segments
The inet6_rthdr_segments() function returns the number of segments contained in the Routing header pointed to by the cmsg argument. On success the return value is from 1 to 23. When an error occurs -1 is returned.

  inet6_rthdr_getaddr
The inet6_rthdr_getaddr() function returns a pointer to the IPv6 address specified by the index argument from the routing header pointed to by cmsg. The index must be between 1 and the number returned by inet6_rthdr_segments() described above. An application must call inet6_rthdr_segments() to obtain the number of segments in the routing header.

If an error occurs the NULL is returned.

  inet6_rthdr_getflags
The inet6_rthdr_getflags() function returns the flags value of the segment specified by index of the routing header pointed to by cmsg. The index argument must be between 0 and the value returned by inet6_rthdr_segments(). The return value will be either IPV6_RTHDR_LOOSE or IPV6_RTHDR_STRICT indicating whether loose or strict source routing was requested for that segment.

When an error occurs -1 is returned.

Note: Flags begin at index 0 while segments begin at index 1, to maintain consistency with the terminology and figures in RFC2460.

DIAGNOSTICS
The inet6_rthdr_space() function returns 0 when an error occurs.

The inet6_rthdr_add(), inet6_rthdr_lasthop() functions return 0 on success, and -1 on error.

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

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

EXAMPLES
RFC2292 gives comprehensive examples in chapter 8.

SEE ALSO
W. Stevens, M. Thomas, Advanced Sockets API for IPv6, RFC2292, February 1998. S. Deering, R. Hinden, Internet Protocol, Version 6 (IPv6) Specification, RFC2460, December 1998.

HISTORY
The implementation first appeared in KAME advanced networking kit.

BUGS
The inet6_rthdr_reverse() function was never implemented.