RT_BLACKHOLE
if (ro != NULL && ro->ro_flags & (RT_REJECT|RT_BLACKHOLE)) {
return (ro->ro_flags & RT_BLACKHOLE ? 0 : EHOSTUNREACH);
ro->ro_flags &= ~ (RT_REJECT|RT_BLACKHOLE|RT_HAS_GW);
ro->ro_flags |= (nh_flags & NHF_BLACKHOLE) ? RT_BLACKHOLE : 0;