1 files changed, 5 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index aaf6f66677f9..69f9f1ef3ef6 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -953,7 +953,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
         int prior_fackets;
         u32 lost_retrans = 0;
         int flag = 0;
-        int dup_sack = 0;
+        int found_dup_sack = 0;
         int cached_fack_count;
         int i;
         int first_sack_index;
@@ -964,20 +964,20 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 
         /* Check for D-SACK. */
         if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) {
-                dup_sack = 1;
+                found_dup_sack = 1;
                 tp->rx_opt.sack_ok |= 4;
                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
         } else if (num_sacks > 1 &&
                         !after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) &&
                         !before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) {
-                dup_sack = 1;
+                found_dup_sack = 1;
                 tp->rx_opt.sack_ok |= 4;
                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
         }
 
         /* D-SACK for already forgotten data...
          * Do dumb counting. */
-        if (dup_sack &&
+        if (found_dup_sack &&
                         !after(ntohl(sp[0].end_seq), prior_snd_una) &&
                         after(ntohl(sp[0].end_seq), tp->undo_marker))
                 tp->undo_retrans--;
@@ -1058,6 +1058,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                 __u32 start_seq = ntohl(sp->start_seq);
                 __u32 end_seq = ntohl(sp->end_seq);
                 int fack_count;
+                int dup_sack = (found_dup_sack && (i == first_sack_index));
 
                 skb = cached_skb;
                 fack_count = cached_fack_count;