I thought the short-circuit interface route was only necessary in older
   implementations (I have measured improvements on SunOS-4), but
   explicitly not necessary in 4.4 based implementations....


i think that this is incorrect.

many moons ago, i found that i could not connect to the address of
my ppp interface, from my ppp interface.  it took me a while to
figure out WTF was going on (it didn't happen often that i was doing
this), but, the deal was:
	- i was filtering incoming traffic on ppp0 that had a source
	  address of my local network.
	- i didn't have a route for that interface to localhost.

as soon as i did 'route add <pppip> localhost', things were happy.


these observations make me believe that the kernel does not short
cut local interfaces automatically, and that we still require that
route's be added for every local address.