discard the oldest packet, as specified in RFC2461 7.2.2.
it does not *make* anything.
current doesn't work.
* kame/kame/dhcp6/addrconf.c (update_address): make sure that the lifetimes of addresses are updated when the client receives a Reply in response to Renew or Rebind.
…ated or updated (otherwise, the valid/preferred lifetimes won't be updated).
whether the ID is provided, since it's mandatory for Solicit).
(by default, it is disabled)