What happened to ipt_physdev.c ?

[Paul Reilly]

In recent kernels, 2.6.16.x   there is no longer any

net/ipv4/netfilter/ipt_physdev.c

and no option in kernel config to enable CONFIG_NETFILTER_XT_MATCH_PHYSDEV
So I have no physdev in /proc/net/ip_tables_matches
and my rules which include a -m physdev fail with:

iptables: No chain/target/match by that name

Has PHYSDEV been moved somewhere else?
How do I enable it?

Paul