It seems that under NetBSD 1.4.1, at least, when you set up a gre tunnel
between two machines, the `real' interface that the tunnel's packets pass
over is showing de-encapsulated incoming packets to bpf, ipfilter, etc.
(Outgoing are shown encapsulated.) Here's an example:

16:33:38.755359 fmh.blink.com > 192.168.10.32: icmp: echo request (gre encap)
16:33:38.788769 192.168.10.32 > fmh.blink.com: icmp: echo reply

What's up with this? Does current still do it?

cjs
-- 
Curt Sampson  <cjs@cynic.net>   917 532 4208   De gustibus, aut bene aut nihil.
The most widely ported operating system in the world: http://www.netbsd.org