1 files changed, 29 insertions, 6 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f5622b250665..cc2ac5346b92 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4249,6 +4249,8 @@ static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
          * If the sack array is full, forget about the last one.
          */
         if (this_sack >= TCP_NUM_SACKS) {
+                if (tp->compressed_ack)
+                        tcp_send_ack(sk);
                 this_sack--;
                 tp->rx_opt.num_sacks--;
                 sp--;
@@ -5081,6 +5083,7 @@ static inline void tcp_data_snd_check(struct sock *sk)
 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
 {
         struct tcp_sock *tp = tcp_sk(sk);
+        unsigned long rtt, delay;
 
             /* More than one full frame received... */
         if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
@@ -5092,15 +5095,35 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
             (tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat ||
              __tcp_select_window(sk) >= tp->rcv_wnd)) ||
             /* We ACK each frame or... */
-            tcp_in_quickack_mode(sk) ||
-            /* We have out of order data. */
-            (ofo_possible && !RB_EMPTY_ROOT(&tp->out_of_order_queue))) {
-                /* Then ack it now */
+            tcp_in_quickack_mode(sk)) {
+send_now:
                 tcp_send_ack(sk);
-        } else {
-                /* Else, send delayed ack. */
+                return;
+        }
+
+        if (!ofo_possible || RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
                 tcp_send_delayed_ack(sk);
+                return;
         }
+
+        if (!tcp_is_sack(tp) || tp->compressed_ack >= 44)
+                goto send_now;
+        tp->compressed_ack++;
+
+        if (hrtimer_is_queued(&tp->compressed_ack_timer))
+                return;
+
+        /* compress ack timer : 5 % of rtt, but no more than 1 ms */
+
+        rtt = tp->rcv_rtt_est.rtt_us;
+        if (tp->srtt_us && tp->srtt_us < rtt)
+                rtt = tp->srtt_us;
+
+        delay = min_t(unsigned long, NSEC_PER_MSEC,
+                      rtt * (NSEC_PER_USEC >> 3)/20);
+        sock_hold(sk);
+        hrtimer_start(&tp->compressed_ack_timer, ns_to_ktime(delay),
+                      HRTIMER_MODE_REL_PINNED_SOFT);
 }
 
 static inline void tcp_ack_snd_check(struct sock *sk)