icmp6_datagram_len
icmp6_hdr(skb)->icmp6_datagram_len * 8);
if (icmp6h->icmp6_datagram_len)
icmp6h->icmp6_datagram_len = ICMP_EXT_ORIG_DGRAM_MIN_LEN / sizeof(u64);
icmph->icmp6_datagram_len = (len - sizeof(*icmph)) / sizeof(uint64_t);