+ if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
+ if (flag & FLAG_ORIG_SACK_ACKED) {
+ /* Step 3.b. A timeout is spurious if not all data are
+ * lost, i.e., never-retransmitted data are (s)acked.
+ */
+ tcp_try_undo_loss(sk, true);
+ return;
+ }
+ if (after(tp->snd_nxt, tp->high_seq) &&
+ (flag & FLAG_DATA_SACKED || is_dupack)) {
+ tp->frto = 0; /* Loss was real: 2nd part of step 3.a */
+ } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
+ tp->high_seq = tp->snd_nxt;
+ __tcp_push_pending_frames(sk, tcp_current_mss(sk),
+ TCP_NAGLE_OFF);
+ if (after(tp->snd_nxt, tp->high_seq))
+ return; /* Step 2.b */
+ tp->frto = 0;
+ }
+ }
+
+ if (recovered) {
+ /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */