tcp: Refactor pingpong code

Instead of using pingpong as a single bit information, we refactor the
code to treat it as a counter. When interactive session is detected,
we set pingpong count to TCP_PINGPONG_THRESH. And when pingpong count
is >= TCP_PINGPONG_THRESH, we consider the session in pingpong mode.

This patch is a pure refactor and sets foundation for the next patch.
This patch itself does not change any pingpong logic.
Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_connection_sock.h

@@ -314,4 +314,21 @@ int inet_csk_compat_setsockopt(struct sock *sk, int level, int optname,
 			       char __user *optval, unsigned int optlen);
 
 struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu);
+
+#define TCP_PINGPONG_THRESH	1
+
+static inline void inet_csk_enter_pingpong_mode(struct sock *sk)
+{
+	inet_csk(sk)->icsk_ack.pingpong = TCP_PINGPONG_THRESH;
+}
+
+static inline void inet_csk_exit_pingpong_mode(struct sock *sk)
+{
+	inet_csk(sk)->icsk_ack.pingpong = 0;
+}
+
+static inline bool inet_csk_in_pingpong_mode(struct sock *sk)
+{
+	return inet_csk(sk)->icsk_ack.pingpong >= TCP_PINGPONG_THRESH;
+}
 #endif /* _INET_CONNECTION_SOCK_H */

net/dccp/input.c

@@ -480,7 +480,7 @@ static int dccp_rcv_request_sent_state_process(struct sock *sk,
 			sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 		}
 
-		if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
+		if (sk->sk_write_pending || inet_csk_in_pingpong_mode(sk) ||
 		    icsk->icsk_accept_queue.rskq_defer_accept) {
 			/* Save one ACK. Data will be ready after
 			 * several ticks, if write_pending is set.

net/dccp/timer.c

@@ -199,7 +199,7 @@ static void dccp_delack_timer(struct timer_list *t)
 	icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 
 	if (inet_csk_ack_scheduled(sk)) {
-		if (!icsk->icsk_ack.pingpong) {
+		if (!inet_csk_in_pingpong_mode(sk)) {
 			/* Delayed ACK missed: inflate ATO. */
 			icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
 						 icsk->icsk_rto);
@@ -207,7 +207,7 @@ static void dccp_delack_timer(struct timer_list *t)
 			/* Delayed ACK missed: leave pingpong mode and
 			 * deflate ATO.
 			 */
-			icsk->icsk_ack.pingpong = 0;
+			inet_csk_exit_pingpong_mode(sk);
 			icsk->icsk_ack.ato = TCP_ATO_MIN;
 		}
 		dccp_send_ack(sk);

net/ipv4/tcp.c

@@ -1551,7 +1551,7 @@ static void tcp_cleanup_rbuf(struct sock *sk, int copied)
 		    (copied > 0 &&
 		     ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED2) ||
 		      ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED) &&
-		       !icsk->icsk_ack.pingpong)) &&
+		       !inet_csk_in_pingpong_mode(sk))) &&
 		      !atomic_read(&sk->sk_rmem_alloc)))
 			time_to_ack = true;
 	}
@@ -2984,16 +2984,16 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
 
 	case TCP_QUICKACK:
 		if (!val) {
-			icsk->icsk_ack.pingpong = 1;
+			inet_csk_enter_pingpong_mode(sk);
 		} else {
-			icsk->icsk_ack.pingpong = 0;
+			inet_csk_exit_pingpong_mode(sk);
 			if ((1 << sk->sk_state) &
 			    (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT) &&
 			    inet_csk_ack_scheduled(sk)) {
 				icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
 				tcp_cleanup_rbuf(sk, 1);
 				if (!(val & 1))
-					icsk->icsk_ack.pingpong = 1;
+					inet_csk_enter_pingpong_mode(sk);
 			}
 		}
 		break;
@@ -3407,7 +3407,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
 		return 0;
 	}
 	case TCP_QUICKACK:
-		val = !icsk->icsk_ack.pingpong;
+		val = !inet_csk_in_pingpong_mode(sk);
 		break;
 
 	case TCP_CONGESTION:

net/ipv4/tcp_input.c

@@ -221,7 +221,7 @@ void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks)
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
 	tcp_incr_quickack(sk, max_quickacks);
-	icsk->icsk_ack.pingpong = 0;
+	inet_csk_exit_pingpong_mode(sk);
 	icsk->icsk_ack.ato = TCP_ATO_MIN;
 }
 EXPORT_SYMBOL(tcp_enter_quickack_mode);
@@ -236,7 +236,7 @@ static bool tcp_in_quickack_mode(struct sock *sk)
 	const struct dst_entry *dst = __sk_dst_get(sk);
 
 	return (dst && dst_metric(dst, RTAX_QUICKACK)) ||
-		(icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong);
+		(icsk->icsk_ack.quick && !inet_csk_in_pingpong_mode(sk));
 }
 
 static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
@@ -4094,7 +4094,7 @@ void tcp_fin(struct sock *sk)
 	case TCP_ESTABLISHED:
 		/* Move to CLOSE_WAIT */
 		tcp_set_state(sk, TCP_CLOSE_WAIT);
-		inet_csk(sk)->icsk_ack.pingpong = 1;
+		inet_csk_enter_pingpong_mode(sk);
 		break;
 
 	case TCP_CLOSE_WAIT:
@@ -5889,7 +5889,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 			return -1;
 		if (sk->sk_write_pending ||
 		    icsk->icsk_accept_queue.rskq_defer_accept ||
-		    icsk->icsk_ack.pingpong) {
+		    inet_csk_in_pingpong_mode(sk)) {
 			/* Save one ACK. Data will be ready after
 			 * several ticks, if write_pending is set.
 			 *

net/ipv4/tcp_ipv4.c

@@ -2437,7 +2437,7 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i)
 		refcount_read(&sk->sk_refcnt), sk,
 		jiffies_to_clock_t(icsk->icsk_rto),
 		jiffies_to_clock_t(icsk->icsk_ack.ato),
-		(icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
+		(icsk->icsk_ack.quick << 1) | inet_csk_in_pingpong_mode(sk),
 		tp->snd_cwnd,
 		state == TCP_LISTEN ?
 		    fastopenq->max_qlen :

net/ipv4/tcp_output.c

@@ -171,7 +171,7 @@ static void tcp_event_data_sent(struct tcp_sock *tp,
 	 * packet, enter pingpong mode.
 	 */
 	if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
-		icsk->icsk_ack.pingpong = 1;
+		inet_csk_enter_pingpong_mode(sk);
 }
 
 /* Account for an ACK we sent. */
@@ -3569,7 +3569,7 @@ void tcp_send_delayed_ack(struct sock *sk)
 		const struct tcp_sock *tp = tcp_sk(sk);
 		int max_ato = HZ / 2;
 
-		if (icsk->icsk_ack.pingpong ||
+		if (inet_csk_in_pingpong_mode(sk) ||
 		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
 			max_ato = TCP_DELACK_MAX;
 

net/ipv4/tcp_timer.c

@@ -277,14 +277,14 @@ void tcp_delack_timer_handler(struct sock *sk)
 	icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 
 	if (inet_csk_ack_scheduled(sk)) {
-		if (!icsk->icsk_ack.pingpong) {
+		if (!inet_csk_in_pingpong_mode(sk)) {
 			/* Delayed ACK missed: inflate ATO. */
 			icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
 		} else {
 			/* Delayed ACK missed: leave pingpong mode and
 			 * deflate ATO.
 			 */
-			icsk->icsk_ack.pingpong = 0;
+			inet_csk_exit_pingpong_mode(sk);
 			icsk->icsk_ack.ato      = TCP_ATO_MIN;
 		}
 		tcp_mstamp_refresh(tcp_sk(sk));

net/ipv6/tcp_ipv6.c

@@ -1864,7 +1864,7 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
 		   refcount_read(&sp->sk_refcnt), sp,
 		   jiffies_to_clock_t(icsk->icsk_rto),
 		   jiffies_to_clock_t(icsk->icsk_ack.ato),
-		   (icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
+		   (icsk->icsk_ack.quick << 1) | inet_csk_in_pingpong_mode(sp),
 		   tp->snd_cwnd,
 		   state == TCP_LISTEN ?
 			fastopenq->max_qlen :