IPV6_FLOWLABEL_MASK
u_int32_t flow = ip6->ip6_flow & IPV6_FLOWLABEL_MASK;
flow = ip6->ip6_flow & IPV6_FLOWLABEL_MASK;
ip6->ip6_flow |= (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK;
htonl(sc->sc_iss) & IPV6_FLOWLABEL_MASK;
inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
(eip6->ip6_flow & IPV6_FLOWLABEL_MASK);
inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
(htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
flowinfo == (inp->inp_flow & IPV6_FLOWLABEL_MASK) &&
gi6->gi6_ip6.ip6_flow |= flowid & IPV6_FLOWLABEL_MASK;
#if !defined(IPV6_FLOWLABEL_MASK)
h6->ip6_flow &= IPV6_FLOWLABEL_MASK | IPV6_VERSION_MASK;