diff --git a/sys/netinet/cc/cc_newreno.c b/sys/netinet/cc/cc_newreno.c
index 988cdb087f3b..50c0b79660e2 100644
--- a/sys/netinet/cc/cc_newreno.c
+++ b/sys/netinet/cc/cc_newreno.c
@@ -199,7 +199,7 @@ newreno_ack_received(struct cc_var *ccv, uint16_t type)
 static void
 newreno_after_idle(struct cc_var *ccv)
 {
-	int rw;
+	uint32_t rw;
 
 	/*
 	 * If we've been idle for more than one retransmit timeout the old
@@ -214,11 +214,7 @@ newreno_after_idle(struct cc_var *ccv)
 	 *
 	 * See RFC5681 Section 4.1. "Restarting Idle Connections".
 	 */
-	if (V_tcp_do_rfc3390)
-		rw = min(4 * CCV(ccv, t_maxseg),
-		    max(2 * CCV(ccv, t_maxseg), 4380));
-	else
-		rw = CCV(ccv, t_maxseg) * 2;
+	rw = tcp_compute_initwnd(tcp_maxseg(ccv->ccvc.tcp));
 
 	CCV(ccv, snd_cwnd) = min(rw, CCV(ccv, snd_cwnd));
 }
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index c4a4746d4218..750046407fbd 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -371,31 +371,14 @@ cc_conn_init(struct tcpcb *tp)
 	/*
 	 * Set the initial slow-start flight size.
 	 *
-	 * RFC5681 Section 3.1 specifies the default conservative values.
-	 * RFC3390 specifies slightly more aggressive values.
-	 * RFC6928 increases it to ten segments.
-	 * Support for user specified value for initial flight size.
-	 *
 	 * If a SYN or SYN/ACK was lost and retransmitted, we have to
 	 * reduce the initial CWND to one segment as congestion is likely
 	 * requiring us to be cautious.
 	 */
 	if (tp->snd_cwnd == 1)
 		tp->snd_cwnd = maxseg;		/* SYN(-ACK) lost */
-	else if (V_tcp_initcwnd_segments)
-		tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg,
-		    max(2 * maxseg, V_tcp_initcwnd_segments * 1460));
-	else if (V_tcp_do_rfc3390)
-		tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380));
-	else {
-		/* Per RFC5681 Section 3.1 */
-		if (maxseg > 2190)
-			tp->snd_cwnd = 2 * maxseg;
-		else if (maxseg > 1095)
-			tp->snd_cwnd = 3 * maxseg;
-		else
-			tp->snd_cwnd = 4 * maxseg;
-	}
+	else
+		tp->snd_cwnd = tcp_compute_initwnd(maxseg);
 
 	if (CC_ALGO(tp)->conn_init != NULL)
 		CC_ALGO(tp)->conn_init(tp->ccv);
@@ -3818,3 +3801,30 @@ tcp_compute_pipe(struct tcpcb *tp)
 		tp->sackhint.sack_bytes_rexmit -
 		tp->sackhint.sacked_bytes);
 }
+
+uint32_t
+tcp_compute_initwnd(uint32_t maxseg)
+{
+	/*
+	 * Calculate the Initial Window, also used as Restart Window
+	 *
+	 * RFC5681 Section 3.1 specifies the default conservative values.
+	 * RFC3390 specifies slightly more aggressive values.
+	 * RFC6928 increases it to ten segments.
+	 * Support for user specified value for initial flight size.
+	 */
+	if (V_tcp_initcwnd_segments)
+		return min(V_tcp_initcwnd_segments * maxseg,
+		    max(2 * maxseg, V_tcp_initcwnd_segments * 1460));
+	else if (V_tcp_do_rfc3390)
+		return min(4 * maxseg, max(2 * maxseg, 4380));
+	else {
+		/* Per RFC5681 Section 3.1 */
+		if (maxseg > 2190)
+			return (2 * maxseg);
+		else if (maxseg > 1095)
+			return (3 * maxseg);
+		else
+			return (4 * maxseg);
+	}
+}
diff --git a/sys/netinet/tcp_stacks/rack.c b/sys/netinet/tcp_stacks/rack.c
index d2db801b1f85..8201dc514bf0 100644
--- a/sys/netinet/tcp_stacks/rack.c
+++ b/sys/netinet/tcp_stacks/rack.c
@@ -1425,21 +1425,9 @@ rack_cc_after_idle(struct tcpcb *tp, int reduce_largest)
 
 	if (tp->snd_cwnd == 1)
 		i_cwnd = tp->t_maxseg;		/* SYN(-ACK) lost */
-	else if (V_tcp_initcwnd_segments)
-		i_cwnd = min((V_tcp_initcwnd_segments * tp->t_maxseg),
-		    max(2 * tp->t_maxseg, V_tcp_initcwnd_segments * 1460));
-	else if (V_tcp_do_rfc3390)
-		i_cwnd = min(4 * tp->t_maxseg,
-		    max(2 * tp->t_maxseg, 4380));
-	else {
-		/* Per RFC5681 Section 3.1 */
-		if (tp->t_maxseg > 2190)
-			i_cwnd = 2 * tp->t_maxseg;
-		else if (tp->t_maxseg > 1095)
-			i_cwnd = 3 * tp->t_maxseg;
-		else
-			i_cwnd = 4 * tp->t_maxseg;
-	}
+	else 
+		i_cwnd = tcp_compute_initwnd(tcp_maxseg(tp));
+
 	if (reduce_largest) {
 		/*
 		 * Do we reduce the largest cwnd to make 
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 2fbe07ade5dc..09316343cb2a 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -942,6 +942,7 @@ void	 tcp_sack_partialack(struct tcpcb *, struct tcphdr *);
 void	 tcp_free_sackholes(struct tcpcb *tp);
 int	 tcp_newreno(struct tcpcb *, struct tcphdr *);
 int	 tcp_compute_pipe(struct tcpcb *);
+uint32_t tcp_compute_initwnd(uint32_t);
 void	 tcp_sndbuf_autoscale(struct tcpcb *, struct socket *, uint32_t);
 struct mbuf *
 	 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen,