rack_update_entry
rack_update_entry(struct tcpcb *tp, struct tcp_rack *rack,
seq_out = rack_update_entry(tp, rack, rsm, cts, &len, add_flag, segsiz);
seq_out = rack_update_entry(tp, rack, rsm, cts, &len, add_flag, segsiz);
seq_out = rack_update_entry(tp, rack, nrsm, cts, &len, add_flag, segsiz);