When I try to add an IP rule for IPv6 on my Linux system, it errors out:

$ ip -6 rule add fwmark 0xfab lookup 0xf
RTNETLINK answers: Address family not supported by protocol

I checked out the IP rule code; it issues a netlink message to the kernel. Probably I need to load some module, but I don't know which. What do I need to do to fix this?

I am using linux 2.6.37.3 built from kernel sources