rl_start
task_set(&sc->rl_start, re_txstart, sc);
ifq_serialize(&ifp->if_snd, &sc->rl_start);
ifq_serialize(ifq, &sc->rl_start);
ifp->if_start = rl_start;
void rl_start(struct ifnet *);
rl_start(ifp);
struct task rl_start;