ip6_rthdr
struct ip6_rthdr *rh = (struct ip6_rthdr *)extbuf;
hlen = (((struct ip6_rthdr *)cp)->ip6r_len+1) << 3;
nh = ((struct ip6_rthdr *)cp)->ip6r_nxt;
struct ip6_rthdr *rthdr = NULL;
rthdr = (struct ip6_rthdr *)CMSG_DATA(scmsgp);
struct ip6_rthdr *rth;
if (*lenp < (int)CMSG_SPACE(sizeof(struct ip6_rthdr) +