TCPSACK_HAVED
if ((tp->rcv_sack_flags & TCPSACK_HAVED) != 0) {
tp->rcv_sack_flags &= ~TCPSACK_HAVED;
if ((tp->rcv_sack_flags & TCPSACK_HAVED) != 0) {
tp->rcv_sack_flags |= TCPSACK_HAVED;
numblks = (((tp->rcv_sack_flags & TCPSACK_HAVED) != 0) ? 1 : 0) +