unresolved symbol

Yang Hua yanghua@bigfoot.com
Tue, 19 Oct 1999 17:00:53 +0800 

I compiled kernel 2.3.20 with netfilter support.
And then I compiled netfilter 0.1.10.
These were done successfully.
But when I tried to insmod ***.o
I found these error message,
	unresolved symbol nf_register_hook
	unresolved symbol nf_unregister_hook
	.
	.
	.
I wonder how this happened. And what should I do.