rt6_nh_nlmsg_size
nexthop_for_each_fib6_nh(f6i->nh, rt6_nh_nlmsg_size,
rt6_nh_nlmsg_size(nh, &nexthop_len);
rt6_nh_nlmsg_size(sibling->fib6_nh, &nexthop_len);