sync type of mtu (ifp->if_mtu uses u_long, so it makes more sense to use u_long)
sync type of mtu (ifp->if_mtu uses u_long, so it makes more sense to use u_long)

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame