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>

9 files changed, 35 insertions, 18 deletions

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index fe0d9b44d6fc..179609d1d1ea 100644
--- a/include/net/inet_connection_sock.h
+++ b/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 */
diff --git a/net/dccp/input.c b/net/dccp/input.c
index 85d6c879383d..8d03707abdac 100644
--- a/net/dccp/input.c
+++ b/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.
diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index 1501a20a94ca..74e138495d67 100644
--- a/net/dccp/timer.c
+++ b/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);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 12ba21433dd0..6f8d292ad501 100644
--- a/net/ipv4/tcp.c
+++ b/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:
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 76858b14ebe9..7a027dec649b 100644
--- a/net/ipv4/tcp_input.c
+++ b/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.
                          *
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index efc6fef692ff..662b034f1795 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/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 :
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 26a2948dca95..06228e2d010e 100644
--- a/net/ipv4/tcp_output.c
+++ b/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;
 
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index d7399a89469d..f0c86398e6a7 100644
--- a/net/ipv4/tcp_timer.c
+++ b/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));
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index b81eb7cb815e..e51cda79f0cc 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/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 :