against rules. It definitely doesn't need to know about kernel internals,
such as 'struct ifaddr'. What it does with ifaddr, is that it only takes
ifa_addr member of it, and treats it as sockaddr, while it is only a pointer
to sockaddr. Fortunately, sizeof(struct ifaddr) > sizeof(struct sockaddr_in6),
so no problems arise.
Fix that declaring a private struct ifaddr in ipftest(1) and stop including
if_var.h.
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