ipv6calc is a small utility in C to manipulate IPv6 addresses. The intentions were to convert a given IPv6 address into compressed format, convert a given IPv6 address into the same format like shown in Linux' /proc/net/if_inet6 and (because it was not difficulty) migrate ip6_int into. Now only one utility is needed to do a lot (perhaps the features grow on demand in the future). This utility will be used in the future to extend features on network-functions-ipv6.