1 files changed, 13 insertions, 0 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4c2dd9f863f7..62508a2f9b21 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4199,6 +4199,17 @@ static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
                 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
 }
 
+static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
+{
+        /* When the ACK path fails or drops most ACKs, the sender would
+         * timeout and spuriously retransmit the same segment repeatedly.
+         * The receiver remembers and reflects via DSACKs. Leverage the
+         * DSACK state and change the txhash to re-route speculatively.
+         */
+        if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq)
+                sk_rethink_txhash(sk);
+}
+
 static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
 {
         struct tcp_sock *tp = tcp_sk(sk);
@@ -4211,6 +4222,7 @@ static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
                 if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) {
                         u32 end_seq = TCP_SKB_CB(skb)->end_seq;
 
+                        tcp_rcv_spurious_retrans(sk, skb);
                         if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
                                 end_seq = tp->rcv_nxt;
                         tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
@@ -4755,6 +4767,7 @@ queue_and_out:
         }
 
         if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
+                tcp_rcv_spurious_retrans(sk, skb);
                 /* A retransmit, 2nd most common case.  Force an immediate ack. */
                 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
                 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);