IPV6_FLOWINFO_FLOWLABEL
flow = ntohl(ip6h->ip6_vcf & IPV6_FLOWINFO_FLOWLABEL);
flow = iph->ip6_vcf & IPV6_FLOWINFO_FLOWLABEL;
ntohl(sin6->sin6_flowinfo & IPV6_FLOWINFO_FLOWLABEL));
ip6h->ip6_vcf &= ~IPV6_FLOWINFO_FLOWLABEL;
ip6h->ip6_vcf &= ~IPV6_FLOWINFO_FLOWLABEL;