This option should be tied to IPFORWARDING, in the following way:

If you're a router (IPFORWARDING=1), then you should accept a packet 
with your IP address on it, regardless of what interface it came in, 
i.e. strict checking should be OFF.

If you're not a router (IPFORWARDING=0), then the strict destination 
code should be on, and packets that came in from the wrong interface 
should be rejected.

I think those defaults will serve the majority effectively. We might 
still want to think about this in the context of multi-homed hosts 
(in the traditional definition of that term, please) a little more.

	Erik <fair@clock.org>