nd_opt_rd_hdr_t
nd_opt_rd_hdr_t *rdh;
len = sizeof (nd_redirect_t) + sizeof (nd_opt_rd_hdr_t) + ll_opt_len;
rdh = (nd_opt_rd_hdr_t *)(buf + sizeof (nd_redirect_t) + ll_opt_len);
sizeof (nd_opt_rd_hdr_t))/8;
rdh->nd_opt_rh_len = (pkt_len + sizeof (nd_opt_rd_hdr_t))/8;