2 files changed, 8 insertions, 6 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index b5c23756965a..40639c288dc2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1106,7 +1106,7 @@ static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
         }
 
         /* D-SACK for already forgotten data... Do dumb counting. */
-        if (dup_sack && tp->undo_marker && tp->undo_retrans &&
+        if (dup_sack && tp->undo_marker && tp->undo_retrans > 0 &&
             !after(end_seq_0, prior_snd_una) &&
             after(end_seq_0, tp->undo_marker))
                 tp->undo_retrans--;
@@ -1187,7 +1187,7 @@ static u8 tcp_sacktag_one(struct sock *sk,
 
         /* Account D-SACK for retransmitted packet. */
         if (dup_sack && (sacked & TCPCB_RETRANS)) {
-                if (tp->undo_marker && tp->undo_retrans &&
+                if (tp->undo_marker && tp->undo_retrans > 0 &&
                     after(end_seq, tp->undo_marker))
                         tp->undo_retrans--;
                 if (sacked & TCPCB_SACKED_ACKED)
@@ -1893,7 +1893,7 @@ static void tcp_clear_retrans_partial(struct tcp_sock *tp)
         tp->lost_out = 0;
 
         tp->undo_marker = 0;
-        tp->undo_retrans = 0;
+        tp->undo_retrans = -1;
 }
 
 void tcp_clear_retrans(struct tcp_sock *tp)
@@ -2665,7 +2665,7 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
 
         tp->prior_ssthresh = 0;
         tp->undo_marker = tp->snd_una;
-        tp->undo_retrans = tp->retrans_out;
+        tp->undo_retrans = tp->retrans_out ? : -1;
 
         if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
                 if (!ece_ack)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d92bce0ea24e..179b51e6bda3 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2525,8 +2525,6 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
                 if (!tp->retrans_stamp)
                         tp->retrans_stamp = TCP_SKB_CB(skb)->when;
 
-                tp->undo_retrans += tcp_skb_pcount(skb);
-
                 /* snd_nxt is stored to detect loss of retransmitted segment,
                  * see tcp_input.c tcp_sacktag_write_queue().
                  */
@@ -2534,6 +2532,10 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
         } else if (err != -EBUSY) {
                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
         }
+
+        if (tp->undo_retrans < 0)
+                tp->undo_retrans = 0;
+        tp->undo_retrans += tcp_skb_pcount(skb);
         return err;
 }