Other InetUtils tools fails when passed a -6 and IPv6 is not working, for example:
jas@latte:~$ telnet gnu.org Trying 140.186.70.148... ^C jas@latte:~$ telnet -6 gnu.org gnu.org/telnet: lookup failure: No address associated with hostname jas@latte:~$ Generally, it feels more natural for a tool to fail when it cannot do what it is asked to, rather than give a warning and do something else. Typically users won't use --ipv4 or --ipv6 but rather use a hostname, and let the getaddrinfo() do its magic of selecting ipv4 vs ipv6, right? That is a good point, you've convinced me atleast that a hard error is better for --ipv6, and simply `work' for normal lookups.
