There are three cases for sending packets:
 - explicit sends from an application on the node itself
 - kernel reflection (ie ICMP Echo & all)
 - forwarding

With a strong model and an explicit local index in all the direct
routes (note an indirect route uses a direct route for its gateway):
 - unbound UDP server application must use in6_pktinfo
 - reflection has no problem (just a bit strict :-)
 - forwarding is no more useable!

If the strong model is restricted to link-local addresses then
forwarding works again (note forwarding for link-local destinations
is very restricted).

The current proposal is to document the NOARP flag for ll0 interface
in order to avoid the main case of failure of the (too) weak model,
ie selection of a bad link when it is not known. Kernel reflection should
be a bit more strict too (and more user friendly).

Question: the case where the same link-local address is used on more than
*one* link is a needed case ???
