TCP_ECN_DEMAND_CWR
tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR) &&
tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;