ip6_flow
ipp->ipp_tclass = IPV6_FLOW_TCLASS(ip6h->ip6_flow);
ip6->ip6_flow = ((ip6_t *)fin->fin_ip)->ip6_flow;
ip6->ip6_flow = ((ip6_t *)fin->fin_ip)->ip6_flow;
frag->ipfr_tos = ip6->ip6_flow & IPV6_FLOWINFO_MASK;
#define ip6_vcf ip6_flow /* Version, tclass, flow-ID */