TF_NODELAY
((idle || tp->t_flags & TF_NODELAY) &&
tp->t_flags = sototcpcb(oso)->t_flags & TF_NODELAY;
tp->t_flags |= TF_NODELAY;
tp->t_flags &= ~TF_NODELAY;
optval = tp->t_flags & TF_NODELAY;