TF_NOPUSH
!(tp->t_flags & TF_NOPUSH)) {
tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY);
tp->t_flags |= TF_NOPUSH;
tp->t_flags &= ~TF_NOPUSH;
optval = tp->t_flags & TF_NOPUSH;