IPV6_FLOWLABEL_MASK
u_int32_t flow = ip6->ip6_flow & IPV6_FLOWLABEL_MASK;
flow = ip6->ip6_flow & IPV6_FLOWLABEL_MASK;
(eip6->ip6_flow & IPV6_FLOWLABEL_MASK);
inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK;
(htonl(ip6_flow_seq++) & IPV6_FLOWLABEL_MASK);
inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK;
flowinfo == (inp->in6p_flowinfo & IPV6_FLOWLABEL_MASK) &&