NHF_MULTIPATH
_Static_assert(MPF_MULTIPATH == NHF_MULTIPATH,
#define NH_IS_NHGRP(_nh) ((_nh)->nh_flags & NHF_MULTIPATH)
if ((nh->nh_flags & NHF_MULTIPATH) != 0)
MPASS((nh_src->nh_flags & NHF_MULTIPATH) == 0);