"tcp" will match both IPv4 TCP and IPv6 TCP.
"ip6" will match IPv6.
you can chase header chain by using "protochain" instead of "proto"
(but bpf code is not optimizable in this case)
commit to tcpdump will follow.
I've sent this fix to LBL guys to get no response. I wonder why it was.
Some of the stuff (e.g., rarpd, bootpd, dhcpd etc., libsa) still will
only support Ethernet. Tcpdump itself should be ok, but libpcap needs
lot of work.
For the detailed change history, look at the commit log entries for
the is-newarp branch.
itojun