ipfw3: accept fragmented packets

[Chuck Musser]

How do you use the "frag" keyword to accept fragmented packets? I think the
particular traffic I'm generating is resulting in large packets and fragmentation,
but I can't figure out how to accept fragments to test this hypothesis.

I tried:

ipfw3 add 130 set 2 allow ip frag via tun0

And some other similar variations. They all said "bad command". Does someone
have an example of valid syntax for this filter?

Chuck