On Sat, 24 Feb 1996, Brad Salai wrote:

> On a MacII, trying to make a kernel from recently supped sources, I get:
> 
> ld ...... vers.o
> idp_usrreq.o: undefined symbol 'ns_cksum' referenced from text segment
> ns_error.o:  (same thing)
> ns_error.o:  (same thing)
> spp_usrreq.o (same thing)
> ***Error Code 1

config(8) your kernel, then rebuild.  This should fix the problem.