nd_opt_rdnss
struct nd_opt_rdnss *ndopt_rdnss;
packlen += sizeof(struct nd_opt_rdnss);
ndopt_rdnss = (struct nd_opt_rdnss *)buf;
buf += sizeof(struct nd_opt_rdnss);
(optlen - sizeof(struct nd_opt_rdnss)) % 16 == 0)
struct nd_opt_rdnss *rdnss;
rdnss = (struct nd_opt_rdnss *)raoptp;