netdev - [PATCH net-next 1/2] tcp: add max_quickacks param to tcp_incr_quickack and tcp_enter_quickack

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Message-Id: <20180521220857.229273-2-edumazet@google.com>
Date:   Mon, 21 May 2018 15:08:56 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>, Van Jacobson <vanj@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 1/2] 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@...gle.com>
---
 net/ipv4/tcp_input.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index aebb29ab2fdf2ceaa182cd11928f145a886149ff..2e970e9f4e09d966b703af2d14d521a4328eba7e 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 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 		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);
 
-- 
2.17.0.441.gb46fe60e1d-goog