Updated: October 26, 2022

Find the next IPv6 hop-by-hop or destination option


#include <netinet/in.h>

int inet6_option_next(const struct cmsghdr *cmsg, 
                      u_int8_t **tptrp);


A pointer to the cmsghdr structure that must have been initialized by inet6_option_init().
A pointer to a pointer to an 8-bit byte.



Use the -l socket option to qcc to link against this library.


This inet6_option_next() function finds the next hop-by-hop option or destination option in an ancillary data object. If another option remains to be processed, the return value of the function is 0 and *tptrp points to the 8-bit option type field the option data.

The cmsg variable is a pointer to cmsghdr structure for which cmsg_level equals IPPROTO_IPV6 and cmsg_type equals either IPV6_HOPOPTS or IPV6_DSTOPTS.

The tptrp is a pointer to a pointer to an 8-bit byte, and *tptrp is used by the function to remember its place in the ancillary data object each time the function is called. The first time you call this function for a given ancillary data object, you must set *tptrp to NULL.

Each time this function returns success, *tptrp points to the 8-bit option type field for the next option to be processed.

Based on:


The option is located and the *tptrp points to the 8-bit option type field.
-1 with *tptrp pointing to NULL
No more options to process.
-1 with *tptrp pointing to non-NULL
An error occurred.


RFC 2292

Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes