tcp: add max_quickacks param to tcp_incr_quickack and tcp_enter_quickack_mode

We want to add finer control of the number of ACK packets sent after
ECN events.

This patch is not changing current behavior, it only enables following
change.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 11 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index aebb29ab2fdf..2e970e9f4e09 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -203,21 +203,23 @@ static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
         }
 }
 
-static void tcp_incr_quickack(struct sock *sk)
+static void tcp_incr_quickack(struct sock *sk, unsigned int max_quickacks)
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
         unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
 
         if (quickacks == 0)
                 quickacks = 2;
+        quickacks = min(quickacks, max_quickacks);
         if (quickacks > icsk->icsk_ack.quick)
-                icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
+                icsk->icsk_ack.quick = quickacks;
 }
 
-static void tcp_enter_quickack_mode(struct sock *sk)
+static void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks)
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
-        tcp_incr_quickack(sk);
+
+        tcp_incr_quickack(sk, max_quickacks);
         icsk->icsk_ack.pingpong = 0;
         icsk->icsk_ack.ato = TCP_ATO_MIN;
 }
@@ -261,7 +263,7 @@ static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
                  * it is probably a retransmit.
                  */
                 if (tp->ecn_flags & TCP_ECN_SEEN)
-                        tcp_enter_quickack_mode((struct sock *)tp);
+                        tcp_enter_quickack_mode((struct sock *)tp, TCP_MAX_QUICKACKS);
                 break;
         case INET_ECN_CE:
                 if (tcp_ca_needs_ecn((struct sock *)tp))
@@ -269,7 +271,7 @@ static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
 
                 if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {
                         /* Better not delay acks, sender can have a very low cwnd */
-                        tcp_enter_quickack_mode((struct sock *)tp);
+                        tcp_enter_quickack_mode((struct sock *)tp, TCP_MAX_QUICKACKS);
                         tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
                 }
                 tp->ecn_flags |= TCP_ECN_SEEN;
@@ -686,7 +688,7 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
                 /* The _first_ data packet received, initialize
                  * delayed ACK engine.
                  */
-                tcp_incr_quickack(sk);
+                tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);
                 icsk->icsk_ack.ato = TCP_ATO_MIN;
         } else {
                 int m = now - icsk->icsk_ack.lrcvtime;
@@ -702,7 +704,7 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
                         /* Too long gap. Apparently sender failed to
                          * restart window, so that we send ACKs quickly.
                          */
-                        tcp_incr_quickack(sk);
+                        tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);
                         sk_mem_reclaim(sk);
                 }
         }
@@ -4179,7 +4181,7 @@ static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
             before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
                 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
-                tcp_enter_quickack_mode(sk);
+                tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
 
                 if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) {
                         u32 end_seq = TCP_SKB_CB(skb)->end_seq;
@@ -4706,7 +4708,7 @@ queue_and_out:
                 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
 
 out_of_window:
-                tcp_enter_quickack_mode(sk);
+                tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
                 inet_csk_schedule_ack(sk);
 drop:
                 tcp_drop(sk, skb);
@@ -5790,7 +5792,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
                          * to stand against the temptation 8)     --ANK
                          */
                         inet_csk_schedule_ack(sk);
-                        tcp_enter_quickack_mode(sk);
+                        tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
                                                   TCP_DELACK_MAX, TCP_RTO_MAX);