1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 41163ddc312c..378ca8a086a3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2112,7 +2112,10 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
-        int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
+        int is_dupack = (tp->snd_una == prior_snd_una &&
+                         (!(flag&FLAG_NOT_DUP) ||
+                          ((flag&FLAG_DATA_SACKED) &&
+                           (tp->fackets_out > tp->reordering))));
 
         /* Some technical things:
          * 1. Reno does not count dupacks (sacked_out) automatically. */