TSACK_F_SACKLEFT
tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT);
~(TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT);
(TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT)) ||
if (tcp_do_smartsack && (tp->sack_flags & TSACK_F_SACKLEFT)) {
~(TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT);