diff --git a/net/ipv4/tcp_highspeed.c b/net/ipv4/tcp_highspeed.c
index db78424..6d9879e 100644
--- a/net/ipv4/tcp_highspeed.c
+++ b/net/ipv4/tcp_highspeed.c
@@ -94,6 +94,7 @@
 
 struct hstcp {
 	u32	ai;
+	u32	loss_cwnd;
 };
 
 static void hstcp_init(struct sock *sk)
@@ -150,16 +151,24 @@
 static u32 hstcp_ssthresh(struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
-	const struct hstcp *ca = inet_csk_ca(sk);
+	struct hstcp *ca = inet_csk_ca(sk);
 
+	ca->loss_cwnd = tp->snd_cwnd;
 	/* Do multiplicative decrease */
 	return max(tp->snd_cwnd - ((tp->snd_cwnd * hstcp_aimd_vals[ca->ai].md) >> 8), 2U);
 }
 
+static u32 hstcp_cwnd_undo(struct sock *sk)
+{
+	const struct hstcp *ca = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
+}
 
 static struct tcp_congestion_ops tcp_highspeed __read_mostly = {
 	.init		= hstcp_init,
 	.ssthresh	= hstcp_ssthresh,
+	.undo_cwnd	= hstcp_cwnd_undo,
 	.cong_avoid	= hstcp_cong_avoid,
 
 	.owner		= THIS_MODULE,
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
index c8e6d86..60352ff 100644
--- a/net/ipv4/tcp_illinois.c
+++ b/net/ipv4/tcp_illinois.c
@@ -48,6 +48,7 @@
 	u32	end_seq;	/* right edge of current RTT */
 	u32	alpha;		/* Additive increase */
 	u32	beta;		/* Muliplicative decrease */
+	u32	loss_cwnd;	/* cwnd on loss */
 	u16	acked;		/* # packets acked by current ACK */
 	u8	rtt_above;	/* average rtt has gone above threshold */
 	u8	rtt_low;	/* # of rtts measurements below threshold */
@@ -296,10 +297,18 @@
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct illinois *ca = inet_csk_ca(sk);
 
+	ca->loss_cwnd = tp->snd_cwnd;
 	/* Multiplicative decrease */
 	return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->beta) >> BETA_SHIFT), 2U);
 }
 
+static u32 tcp_illinois_cwnd_undo(struct sock *sk)
+{
+	const struct illinois *ca = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
+}
+
 /* Extract info for Tcp socket info provided via netlink. */
 static size_t tcp_illinois_info(struct sock *sk, u32 ext, int *attr,
 				union tcp_cc_info *info)
@@ -327,6 +336,7 @@
 static struct tcp_congestion_ops tcp_illinois __read_mostly = {
 	.init		= tcp_illinois_init,
 	.ssthresh	= tcp_illinois_ssthresh,
+	.undo_cwnd	= tcp_illinois_cwnd_undo,
 	.cong_avoid	= tcp_illinois_cong_avoid,
 	.set_state	= tcp_illinois_state,
 	.get_info	= tcp_illinois_info,
diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c
index bf5ea9e..f212307 100644
--- a/net/ipv4/tcp_scalable.c
+++ b/net/ipv4/tcp_scalable.c
@@ -15,6 +15,10 @@
 #define TCP_SCALABLE_AI_CNT	50U
 #define TCP_SCALABLE_MD_SCALE	3
 
+struct scalable {
+	u32 loss_cwnd;
+};
+
 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -32,12 +36,23 @@
 static u32 tcp_scalable_ssthresh(struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
+	struct scalable *ca = inet_csk_ca(sk);
+
+	ca->loss_cwnd = tp->snd_cwnd;
 
 	return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
 }
 
+static u32 tcp_scalable_cwnd_undo(struct sock *sk)
+{
+	const struct scalable *ca = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
+}
+
 static struct tcp_congestion_ops tcp_scalable __read_mostly = {
 	.ssthresh	= tcp_scalable_ssthresh,
+	.undo_cwnd	= tcp_scalable_cwnd_undo,
 	.cong_avoid	= tcp_scalable_cong_avoid,
 
 	.owner		= THIS_MODULE,
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index 40171e1..76005d4 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -30,6 +30,7 @@
 	u32 basertt;		/* the min of all Veno rtt measurements seen (in usec) */
 	u32 inc;		/* decide whether to increase cwnd */
 	u32 diff;		/* calculate the diff rate */
+	u32 loss_cwnd;		/* cwnd when loss occured */
 };
 
 /* There are several situations when we must "re-start" Veno:
@@ -193,6 +194,7 @@
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct veno *veno = inet_csk_ca(sk);
 
+	veno->loss_cwnd = tp->snd_cwnd;
 	if (veno->diff < beta)
 		/* in "non-congestive state", cut cwnd by 1/5 */
 		return max(tp->snd_cwnd * 4 / 5, 2U);
@@ -201,9 +203,17 @@
 		return max(tp->snd_cwnd >> 1U, 2U);
 }
 
+static u32 tcp_veno_cwnd_undo(struct sock *sk)
+{
+	const struct veno *veno = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, veno->loss_cwnd);
+}
+
 static struct tcp_congestion_ops tcp_veno __read_mostly = {
 	.init		= tcp_veno_init,
 	.ssthresh	= tcp_veno_ssthresh,
+	.undo_cwnd	= tcp_veno_cwnd_undo,
 	.cong_avoid	= tcp_veno_cong_avoid,
 	.pkts_acked	= tcp_veno_pkts_acked,
 	.set_state	= tcp_veno_state,
diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c
index 9c5fc97..e6ff99c 100644
--- a/net/ipv4/tcp_yeah.c
+++ b/net/ipv4/tcp_yeah.c
@@ -37,6 +37,7 @@
 	u32 fast_count;
 
 	u32 pkts_acked;
+	u32 loss_cwnd;
 };
 
 static void tcp_yeah_init(struct sock *sk)
@@ -219,13 +220,22 @@
 
 	yeah->fast_count = 0;
 	yeah->reno_count = max(yeah->reno_count>>1, 2U);
+	yeah->loss_cwnd = tp->snd_cwnd;
 
 	return max_t(int, tp->snd_cwnd - reduction, 2);
 }
 
+static u32 tcp_yeah_cwnd_undo(struct sock *sk)
+{
+	const struct yeah *yeah = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, yeah->loss_cwnd);
+}
+
 static struct tcp_congestion_ops tcp_yeah __read_mostly = {
 	.init		= tcp_yeah_init,
 	.ssthresh	= tcp_yeah_ssthresh,
+	.undo_cwnd      = tcp_yeah_cwnd_undo,
 	.cong_avoid	= tcp_yeah_cong_avoid,
 	.set_state	= tcp_vegas_state,
 	.cwnd_event	= tcp_vegas_cwnd_event,