I reviewed the code:
 - I pushed a few cosmetics stuff, please pull and review them

 - I have a question which IMHO requires an answer:
  when T1 and T2 are not zero or derived from lifetimes
  I think they should be reduced? Note this is really specific
  to DHCPv6 as for DHCPv4 this is only one timer doing
  everything.

My concern is the the threshold is a bit high after a reuse
the returned T1/T2 can (mis)lead too far.