1 files changed, 9 insertions, 2 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 1d56dfd9b4ea..62819cfd6d1d 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -351,8 +351,15 @@ cc_conn_init(struct tcpcb *tp)
 	if (V_tcp_do_rfc3390)
 		tp->snd_cwnd = min(4 * tp->t_maxseg,
 		    max(2 * tp->t_maxseg, 4380));
-	else
-		tp->snd_cwnd = tp->t_maxseg;
+	else {
+		/* Per RFC5681 Section 3.1 */
+		if (tp->t_maxseg > 2190)
+			tp->snd_cwnd = 2 * tp->t_maxseg;
+		else if (tp->t_maxseg > 1095)
+			tp->snd_cwnd = 3 * tp->t_maxseg;
+		else
+			tp->snd_cwnd = 4 * tp->t_maxseg;
+	}
 
 	if (CC_ALGO(tp)->conn_init != NULL)
 		CC_ALGO(tp)->conn_init(tp->ccv);