1 files changed, 11 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d6edb98fd526..b54d9d37b636 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1842,9 +1842,16 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
                 }
 
-                /* Don't lost mark skbs that were fwd transmitted after RTO */
-                if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) &&
-                    !after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) {
+                /* Marking forward transmissions that were made after RTO lost
+                 * can cause unnecessary retransmissions in some scenarios,
+                 * SACK blocks will mitigate that in some but not in all cases.
+                 * We used to not mark them but it was causing break-ups with
+                 * receivers that do only in-order receival.
+                 *
+                 * TODO: we could detect presence of such receiver and select
+                 * different behavior per flow.
+                 */
+                if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
                         tp->lost_out += tcp_skb_pcount(skb);
                 }
@@ -1860,7 +1867,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
         tp->reordering = min_t(unsigned int, tp->reordering,
                                sysctl_tcp_reordering);
         tcp_set_ca_state(sk, TCP_CA_Loss);
-        tp->high_seq = tp->frto_highmark;
+        tp->high_seq = tp->snd_nxt;
         TCP_ECN_queue_cwr(tp);
 
         tcp_clear_retrans_hints_partial(tp);