1 files changed, 8 insertions, 1 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3d6156f07a8d..715d541b52dd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -247,8 +247,15 @@ static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
 
 static void tcp_ecn_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb)
 {
-        if (tcp_hdr(skb)->cwr)
+        if (tcp_hdr(skb)->cwr) {
                 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
+
+                /* If the sender is telling us it has entered CWR, then its
+                 * cwnd may be very low (even just 1 packet), so we should ACK
+                 * immediately.
+                 */
+                tcp_enter_quickack_mode((struct sock *)tp, 2);
+        }
 }
 
 static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp)