tcp: move tcp_enter_cwr()

To prepare replacing rate halving with PRR algorithm in CWR state.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -743,29 +743,6 @@ __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst)
 	return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
 }
 
-/* Set slow start threshold and cwnd not falling to slow start */
-void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-	const struct inet_connection_sock *icsk = inet_csk(sk);
-
-	tp->prior_ssthresh = 0;
-	tp->bytes_acked = 0;
-	if (icsk->icsk_ca_state < TCP_CA_CWR) {
-		tp->undo_marker = 0;
-		if (set_ssthresh)
-			tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
-		tp->snd_cwnd = min(tp->snd_cwnd,
-				   tcp_packets_in_flight(tp) + 1U);
-		tp->snd_cwnd_cnt = 0;
-		tp->high_seq = tp->snd_nxt;
-		tp->snd_cwnd_stamp = tcp_time_stamp;
-		TCP_ECN_queue_cwr(tp);
-
-		tcp_set_ca_state(sk, TCP_CA_CWR);
-	}
-}
-
 /*
  * Packet counting of FACK is based on in-order assumptions, therefore TCP
  * disables it when reordering is detected
@@ -2741,6 +2718,29 @@ static inline void tcp_complete_cwr(struct sock *sk)
 	tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
 }
 
+/* Set slow start threshold and cwnd not falling to slow start */
+void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	tp->prior_ssthresh = 0;
+	tp->bytes_acked = 0;
+	if (icsk->icsk_ca_state < TCP_CA_CWR) {
+		tp->undo_marker = 0;
+		if (set_ssthresh)
+			tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
+		tp->snd_cwnd = min(tp->snd_cwnd,
+				   tcp_packets_in_flight(tp) + 1U);
+		tp->snd_cwnd_cnt = 0;
+		tp->high_seq = tp->snd_nxt;
+		tp->snd_cwnd_stamp = tcp_time_stamp;
+		TCP_ECN_queue_cwr(tp);
+
+		tcp_set_ca_state(sk, TCP_CA_CWR);
+	}
+}
+
 static void tcp_try_keep_open(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);