inet6_rth_space() — Return number of bytes for a routing header

Standards

Format

#define _OPEN_SYS_SOCK_IPV6
#include <netinet/in.h>

socklen_t inet6_rth_space(int type, int segments);

General description

inet6_rth_space() calculates the number of bytes required to hold a routing header for the specified type containing the specified number of segments (addresses).

Returned value

If successful, inet6_rth_space() returns the number of bytes, space required, for the routing header.

Upon failure, returns 0 and errno is set to one of the following:

EINVAL If one of the following is true:

Usage notes

1. 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, because all the ancillary data objects must be specified to sendmsg() as a single msg_control buffer.
2. For an IPv6 Type 0 routing header, the number of segments must be between 0 and 127, inclusive. When the application uses ancillary data it must pass the returned length to CMSG_SPACE() to determine how much memory is needed for the ancillary data object (including the cmsghdr structure).

Related information

• netinet/in.h
• inet6_rth_add() — Add an IPv6 address to end of the routing header
• inet6_rth_getaddr() — Return pointer to the IPv6 address specified
• inet6_rth_init() — Initialize an IPv6 routing header buffer
• inet6_rth_reverse() — Reverse the order of the addresses
• inet6_rth_segments() — Return number of segments contained in header