TF_NODELAY
tp->t_flags = intotcpcb(listeninp)->t_flags & (TF_NOPUSH|TF_NODELAY);
if ((idle || (tp->t_flags & TF_NODELAY)) &&
tp->t_flags |= TF_NODELAY;
tp->t_flags &= ~TF_NODELAY;
*mtod(m, int *) = tp->t_flags & TF_NODELAY;