[TCP]: Eliminate spurious CWND restart on every new connection.

net/ipv4/tcp_input.c

@@ -3698,6 +3698,12 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 		tp->af_specific->rebuild_header(sk);
 
 		tcp_init_metrics(sk);
+
+		/* Prevent spurious tcp_cwnd_restart() on first data
+		 * packet.
+		 */
+		tp->lsndtime = tcp_time_stamp;
+
 		tcp_init_buffer_space(sk);
 
 		if (sock_flag(sk, SOCK_KEEPOPEN))
@@ -3969,6 +3975,12 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 				tp->af_specific->rebuild_header(sk);
 
 				tcp_init_metrics(sk);
+
+				/* Prevent spurious tcp_cwnd_restart() on
+				 * first data packet.
+				 */
+				tp->lsndtime = tcp_time_stamp;
+
 				tcp_initialize_rcv_mss(sk);
 				tcp_init_buffer_space(sk);
 				tcp_fast_path_on(tp);