diff --git a/include/net/tcp.h b/include/net/tcp.h
index 364426a..309801f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1165,6 +1165,19 @@
 }
 
 u32 tcp_default_init_rwnd(u32 mss);
+void tcp_cwnd_restart(struct sock *sk, s32 delta);
+
+static inline void tcp_slow_start_after_idle_check(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	s32 delta;
+
+	if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
+		return;
+	delta = tcp_time_stamp - tp->lsndtime;
+	if (delta > inet_csk(sk)->icsk_rto)
+		tcp_cwnd_restart(sk, delta);
+}
 
 /* Determine a window scaling and initial window to offer. */
 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,