I think this problem started after I upgraded my kernel from
NetBSD-1.4.1 to NetBSD-release.  ipnat was working previously, and I
had not made any changes to my kernel configuration file.

After installing the new kernel, when just about any ip___ command is
run, I get the following error:

ioctl(SIOCGETFS): Invalid argument

I thought that maybe the ip___ executables needed to be updated to
match the new kernel, so I downloaded usr.sbin.tar.gz ... but guess
what?  All of the sources under src/usr.sbin/ipf are missing!  (The
makefiles are still there, and the directory structure, but that's
all.)

--- Trevin Beattie
Violence is the last refuge of the incompetent.
                -- Salvor Hardin