icmp-type rules not working

Hello,

I've been trying this for a long time now and it just doesn't work:

pass in quick on tun0 proto icmp from any to 20.20.20.0/24 icmp-type 0
pass in quick on tun0 proto icmp from any to 20.20.20.0/24 icmp-type 11
block in log quick on tun0 proto icmp from any to any

This is copied straight out of the manual (of course my numbers and
interfaces are different.) Even with only these lines in the ruleset,
pings get blocked. Until we remove the "block" line no pings get
through. The blocked packets show up in the logs.

If I take the "block" line out of the ruleset and just leave the "pass"
ones with logging...

pass in log quick on tun0 proto icmp from any to 20.20.20.0/24 icmp-type 0
pass in log quick on tun0 proto icmp from any to 20.20.20.0/24 icmp-type 11

....the machine responds to the ping, but no icmp packets are logged.

What exactly constitutes a icmp-type 0 or icmp-type 11? It would appear
that pings are not being interpreted by either of these.

I'm running NetBSD/mac68k -current (1.6ZG), ipfilter v3.4.29.
default=pass all

Can anyone replicate this problem or clarify what's really going on?

Any help would be great,

Louis