ip_print_inner(netdissect_options *ndo,
	       const u_char *bp,
	       u_int length, u_int nh,
	       const u_char *bp2)
{
	struct ip_print_demux_state  ipd;

	ipd.ip = (const struct ip *)bp2;
	ipd.cp = bp;
	ipd.len  = length;
	ipd.off  = 0;
	ipd.nh   = nh;
	ipd.advance = 0;

	ip_print_demux(ndo, &ipd);
}

The product reads data past the end, or before the beginning, of the intended buffer.