1 files changed, 7 insertions, 3 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ee1b0705321d..c4172c1fb198 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -160,7 +160,8 @@ static void tcp_event_data_sent(struct tcp_sock *tp,
 }
 
 /* Account for an ACK we sent. */
-static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
+static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
+                                      u32 rcv_nxt)
 {
         struct tcp_sock *tp = tcp_sk(sk);
 
@@ -171,6 +172,9 @@ static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
                 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
                         __sock_put(sk);
         }
+
+        if (unlikely(rcv_nxt != tp->rcv_nxt))
+                return;  /* Special ACK sent by DCTCP to reflect ECN */
         tcp_dec_quickack_mode(sk, pkts);
         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 }
@@ -1141,7 +1145,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
         icsk->icsk_af_ops->send_check(sk, skb);
 
         if (likely(tcb->tcp_flags & TCPHDR_ACK))
-                tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
+                tcp_event_ack_sent(sk, tcp_skb_pcount(skb), rcv_nxt);
 
         if (skb->len != tcp_header_size) {
                 tcp_event_data_sent(tp, sk);
@@ -3613,12 +3617,12 @@ void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
         /* Send it off, this clears delayed acks for us. */
         __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
 }
+EXPORT_SYMBOL_GPL(__tcp_send_ack);
 
 void tcp_send_ack(struct sock *sk)
 {
         __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
 }
-EXPORT_SYMBOL_GPL(tcp_send_ack);
 
 /* This routine sends a packet with an out of date sequence
  * number. It assumes the other end will try to ack it.