[PATCH net-next 0/2] tcp: add NV congestion control

[PATCH net-next 0/2] tcp: add NV congestion control

[Lawrence Brakmo]

This version of NV does much better than previous versions when things are
very congested and also adds a couple of experimental features.

Tested in a rack using between 1 and 380 active TCP-NV flows.

Consists of the following patches:
[PATCH net-next 1/2] tcp: add in_flight to tcp_skb_cb
[PATCH net-next 2/2] tcp: add NV congestion control

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>

include/net/tcp.h     |   2 +
net/ipv4/Kconfig      |  16 ++
net/ipv4/Makefile     |   1 +
net/ipv4/tcp_input.c  |   5 +-
net/ipv4/tcp_nv.c     | 597 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
net/ipv4/tcp_output.c |   4 +-
6 files changed, 623 insertions(+), 2 deletions(-)

[PATCH net-next 1/2] tcp: add in_flight to tcp_skb_cb

[Lawrence Brakmo]

Add in_flight (bytes in flight when packet was sent) field
to tx component of tcp_skb_cb and make it available to
congestion modules' pkts_acked() function through the
ack_sample function argument.

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
---
 include/net/tcp.h     | 2 ++
 net/ipv4/tcp_input.c  | 5 ++++-
 net/ipv4/tcp_output.c | 4 +++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0bcc70f..a79894b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -767,6 +767,7 @@ struct tcp_skb_cb {
 	union {
 		struct {
 			/* There is space for up to 20 bytes */
+			__u32 in_flight;/* Bytes in flight when packet sent */
 		} tx;   /* only used for outgoing skbs */
 		union {
 			struct inet_skb_parm	h4;
@@ -859,6 +860,7 @@ union tcp_cc_info;
 struct ack_sample {
 	u32 pkts_acked;
 	s32 rtt_us;
+	u32 in_flight;
 };
 
 struct tcp_congestion_ops {
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d6c8f4cd0..c7f33f0 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3115,6 +3115,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 	long ca_rtt_us = -1L;
 	struct sk_buff *skb;
 	u32 pkts_acked = 0;
+	u32 last_in_flight = 0;
 	bool rtt_update;
 	int flag = 0;
 
@@ -3154,6 +3155,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 			if (!first_ackt.v64)
 				first_ackt = last_ackt;
 
+			last_in_flight = TCP_SKB_CB(skb)->tx.in_flight;
 			reord = min(pkts_acked, reord);
 			if (!after(scb->end_seq, tp->high_seq))
 				flag |= FLAG_ORIG_SACK_ACKED;
@@ -3250,7 +3252,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 
 	if (icsk->icsk_ca_ops->pkts_acked) {
 		struct ack_sample sample = { .pkts_acked = pkts_acked,
-					     .rtt_us = ca_rtt_us };
+					     .rtt_us = ca_rtt_us,
+					     .in_flight = last_in_flight };
 
 		icsk->icsk_ca_ops->pkts_acked(sk, &sample);
 	}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8bd9911..b1bcba0 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -911,9 +911,12 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 	int err;
 
 	BUG_ON(!skb || !tcp_skb_pcount(skb));
+	tp = tcp_sk(sk);
 
 	if (clone_it) {
 		skb_mstamp_get(&skb->skb_mstamp);
+		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
+			- tp->snd_una;
 
 		if (unlikely(skb_cloned(skb)))
 			skb = pskb_copy(skb, gfp_mask);
@@ -924,7 +927,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 	}
 
 	inet = inet_sk(sk);
-	tp = tcp_sk(sk);
 	tcb = TCP_SKB_CB(skb);
 	memset(&opts, 0, sizeof(opts));
 
-- 
2.8.0.rc2

[PATCH net-next 2/2] tcp: add NV congestion control

[Lawrence Brakmo]

TCP-NV (New Vegas) is a major update to TCP-Vegas.
An earlier version of NV was presented at 2010's LPC.
It is a delayed based congestion avoidance for the
data center. This version has been tested within a
10G rack where the HW RTTs are 20-50us.

A description of TCP-NV, including implementation
details as well as experimental results, can be found at:
http://www.brakmo.org/networking/tcp-nv/TCPNV.html

The current version includes many module parameters to support
experimentation with the parameters.

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
---
 net/ipv4/Kconfig  |  16 ++
 net/ipv4/Makefile |   1 +
 net/ipv4/tcp_nv.c | 597 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 614 insertions(+)
 create mode 100644 net/ipv4/tcp_nv.c

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 238225b..50d6a9b 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -532,6 +532,22 @@ config TCP_CONG_VEGAS
 	window. TCP Vegas should provide less packet loss, but it is
 	not as aggressive as TCP Reno.
 
+config TCP_CONG_NV
+       tristate "TCP NV"
+       default n
+       ---help---
+       TCP NV is a follow up to TCP Vegas. It has been modified to deal with
+       10G networks, measurement noise introduced by LRO, GRO and interrupt
+       coalescence. In addition, it will decrease its cwnd multiplicatively
+       instead of linearly.
+
+       Note that in general congestion avoidance (cwnd decreased when # packets
+       queued grows) cannot coexist with congestion control (cwnd decreased only
+       when there is packet loss) due to fairness issues. One scenario when they
+       can coexist safely is when the CA flows have RTTs << CC flows RTTs.
+
+       For further details see http://www.brakmo.org/networking/tcp-nv/
+
 config TCP_CONG_SCALABLE
 	tristate "Scalable TCP"
 	default n
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index bfa1336..24629b6 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o
 obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o
 obj-$(CONFIG_TCP_CONG_HTCP) += tcp_htcp.o
 obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
+obj-$(CONFIG_TCP_CONG_NV) += tcp_nv.o
 obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
 obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
new file mode 100644
index 0000000..1a69215
--- /dev/null
+++ b/net/ipv4/tcp_nv.c
@@ -0,0 +1,597 @@
+/*
+ * TCP NV: TCP with Congestion Avoidance
+ *
+ * TCP-NV is a successor of TCP-Vegas that has been developed to
+ * deal with the issues that occur in modern networks.
+ * Like TCP-Vegas, TCP-NV supports true congestion avoidance,
+ * the ability to detect congestion before packet losses occur.
+ * When congestion (queue buildup) starts to occur, TCP-NV
+ * predicts what the cwnd size should be for the current
+ * throughput and it reduces the cwnd proportionally to
+ * the difference between the current cwnd and the predicted cwnd.
+ * TCP-NV behaves like Reno when no congestion is detected, or when
+ * recovering from packet losses.
+ *
+ * Note: High NIC coalescence values may lower the performance of NV
+ * due to the increased noise in RTT values. In particular, we have
+ * seen issues with rx-frames values greater than 8.
+ *
+ * TODO:
+ * 1) Add mechanism to deal with reverse congestion.
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/math64.h>
+#include <net/tcp.h>
+#include <linux/inet_diag.h>
+
+/* TCP NV parameters
+ *
+ * nv_enable		Behaves like Reno if disabled
+ * nv_pad		Packets queued to trigger congestion detection
+ * nv_pad_buffer	Below this packets queued trigger cwnd growth
+ * nv_reset_period	Who often (in) seconds)to reset min_rtt
+ * nv_min_cwnd		Don't decrease cwnd below this if there are no losses
+ * nv_cong_dec_mult	Decrease cwnd by X% (30%) of congestion when detected
+ * nv_ssthresh_factor	On congestion set ssthresh to this * <desired cwnd> / 8
+ * nv_rtt_factor	RTT averaging factor
+ * nv_rtt_cnt_dec_delta Periodically decrease cwnd for this many RTTs
+ * nv_dec_factor	  and this factor (temp cwnd = cwnd * this / 8)
+ * nv_loss_dec_factor	Decrease cwnd by this (50%) when losses occur
+ * nv_dec_eval_min_calls	Wait this many RTT measurements before dec cwnd
+ * nv_inc_eval_min_calls	Wait this many RTT measurements before inc cwnd
+ * nv_ssthresh_eval_min_calls	Wait this many RTT measurements before stopping
+ *				slow-start due to congestion
+ * nv_stop_rtt_cnt	Only grow cwnd for this many RTTs after non-congestion
+ * nv_rtt_min_cnt	Wait these many RTTs before making congesion decision
+ * nv_min_min_rtt	Lower bound for min_rtt
+ * nv_max_min_rtt	Upper bound for min_rtt
+ *	Experimental feature. NV is unlikely to converge to an accurate minRTT
+ *	in very congested networks. Both these parameters allow setting
+ *	appropriate bounds to minRTT based on apriori knowledge (such as
+ *	knowing the traffic is within a DC.
+ *	I am working on a mechanism to better support this feature,
+ * nv_cwnd_growth_rate_neg
+ * nv_cwnd_growth_rate_pos
+ *	How quickly to double growth rate (not rate) of cwnd when not congested.
+ *	One value (nv_cwnd_growth_rate_neg) for when rate < 1 pkt/RTT
+ *	(after losses). The other (nv_cwnd_growth_rate_pos) otherwise.
+ */
+
+static int nv_enable __read_mostly = 1;
+static int nv_pad __read_mostly = 10;
+static int nv_pad_buffer __read_mostly = 2;
+static int nv_reset_period __read_mostly = 5; /* in seconds */
+static int nv_min_cwnd __read_mostly = 2;
+static int nv_cong_dec_mult __read_mostly = 30 * 128 / 100; /* = 30% */
+static int nv_ssthresh_factor __read_mostly = 8; /* = 1 */
+static int nv_rtt_factor __read_mostly = 128; /* = 1/2*old + 1/2*new */
+static int nv_rtt_cnt_dec_delta __read_mostly; /* 0 => off */
+static int nv_dec_factor __read_mostly = 8;  /* tmp cwnd = cwnd * factor / 8 */
+static int nv_loss_dec_factor __read_mostly = 512; /* => 50% */
+static int nv_cwnd_growth_rate_neg __read_mostly = 8;
+static int nv_cwnd_growth_rate_pos __read_mostly; /* 0 => fixed like Reno */
+static int nv_dec_eval_min_calls __read_mostly = 60;
+static int nv_inc_eval_min_calls __read_mostly = 20;
+static int nv_ssthresh_eval_min_calls __read_mostly = 30;
+static int nv_stop_rtt_cnt __read_mostly = 10;
+static int nv_rtt_min_cnt __read_mostly = 2;
+static int nv_min_min_rtt __read_mostly; /* 0 => none */
+static int nv_max_min_rtt __read_mostly; /* 0 => none */
+
+module_param(nv_enable, int, 0644);
+MODULE_PARM_DESC(nv_enable, "enable NV (congestion avoidance) behavior");
+module_param(nv_pad, int, 0644);
+MODULE_PARM_DESC(nv_pad, "extra packets above congestion level");
+module_param(nv_pad_buffer, int, 0644);
+MODULE_PARM_DESC(nv_pad_buffer, "no growth buffer zone");
+module_param(nv_reset_period, int, 0644);
+MODULE_PARM_DESC(nv_reset_period, "nv_min_rtt reset period (secs)");
+module_param(nv_min_cwnd, int, 0644);
+MODULE_PARM_DESC(nv_min_cwnd, "NV will not decrease cwnd below this value"
+		 " without losses");
+module_param(nv_dec_eval_min_calls, int, 0644);
+MODULE_PARM_DESC(nv_dec_eval_min_calls, "Wait for this many data points"
+		 " before declaring congestion");
+module_param(nv_inc_eval_min_calls, int, 0644);
+MODULE_PARM_DESC(nv_inc_eval_min_calls, "Wait for this many data points"
+		 " before allowing cwnd growth");
+module_param(nv_stop_rtt_cnt, int, 0644);
+MODULE_PARM_DESC(nv_stop_rtt_cnt, "Wait for this many RTTs before stopping"
+		 " cwnd growth");
+module_param(nv_ssthresh_eval_min_calls, int, 0644);
+MODULE_PARM_DESC(nv_ssthresh_eval_min_calls, "Wait for this many data points"
+		 " before declaring congestion during initial slow-start");
+module_param(nv_rtt_min_cnt, int, 0644);
+MODULE_PARM_DESC(nv_rtt_min_cnt, "Wait for this many RTTs before declaring"
+		 " congestion");
+module_param(nv_cong_dec_mult, int, 0644);
+MODULE_PARM_DESC(nv_cong_dec_mult, "Congestion decrease factor");
+module_param(nv_ssthresh_factor, int, 0644);
+MODULE_PARM_DESC(nv_ssthresh_factor, "ssthresh factor");
+module_param(nv_rtt_factor, int, 0644);
+MODULE_PARM_DESC(nv_rtt_factor, "rtt averaging factor");
+module_param(nv_rtt_cnt_dec_delta, int, 0644);
+MODULE_PARM_DESC(nv_rtt_cnt_dec_delta, "decrease cwnd for this many RTTs"
+		 " every 100 RTTs");
+module_param(nv_dec_factor, int, 0644);
+MODULE_PARM_DESC(nv_dec_factor, "decrease cwnd every ~192 RTTS by factor/8");
+module_param(nv_loss_dec_factor, int, 0644);
+MODULE_PARM_DESC(nv_loss_dec_factor, "on loss new cwnd = cwnd * this / 1024");
+module_param(nv_cwnd_growth_rate_neg, int, 0644);
+MODULE_PARM_DESC(nv_cwnd_growth_rate_neg, "Applies when current cwnd growth"
+		 " rate < Reno");
+module_param(nv_cwnd_growth_rate_pos, int, 0644);
+MODULE_PARM_DESC(nv_cwnd_growth_rate_pos, "Applies when current cwnd growth"
+		 " rate >= Reno");
+module_param(nv_min_min_rtt, int, 0644);
+MODULE_PARM_DESC(nv_min_min_rtt, "lower bound for ca->nv_min_rtt");
+module_param(nv_max_min_rtt, int, 0644);
+MODULE_PARM_DESC(nv_max_min_rtt, "upper bound for ca->nv_min_rtt");
+
+/* TCP NV Parameters */
+struct tcpnv {
+	unsigned long nv_min_rtt_reset_jiffies;  /* when to switch to
+						  * nv_min_rtt_new */
+	s8  cwnd_growth_factor;	/* Current cwnd growth factor,
+				 * < 0 => less than 1 packet/RTT */
+	u8  available8;
+	u16 available16;
+	u32 loss_cwnd;	/* cwnd at last loss */
+	u8  nv_allow_cwnd_growth:1, /* whether cwnd can grow */
+		nv_reset:1,	    /* whether to reset values */
+		nv_catchup:1;	    /* whether we are growing because
+				     * of temporary cwnd decrease */
+	u8  nv_eval_call_cnt;	/* call count since last eval */
+	u8  nv_min_cwnd;	/* nv won't make a ca decision if cwnd is
+				 * smaller than this. It may grow to handle
+				 * TSO, LRO and interrupt coalescence because
+				 * with these a small cwnd cannot saturate
+				 * the link. Note that this is different from
+				 * the file local nv_min_cwnd */
+	u8  nv_rtt_cnt;		/* RTTs without making ca decision */;
+	u32 nv_last_rtt;	/* last rtt */
+	u32 nv_min_rtt;		/* active min rtt. Used to determine slope */
+	u32 nv_min_rtt_new;	/* min rtt for future use */
+	u32 nv_rtt_max_rate;	/* max rate seen during current RTT */
+	u32 nv_rtt_start_seq;	/* current RTT ends when packet arrives
+				 * acking beyond nv_rtt_start_seq */
+	u32 nv_last_snd_una;	/* Previous value of tp->snd_una. It is
+				 * used to determine bytes acked since last
+				 * call to bictcp_acked */
+	u32 nv_no_cong_cnt;	/* Consecutive no congestion decisions */
+	u32 nv_rtt_cnt_dec;	/* RTTs since last temporary cwnd decrease */
+};
+
+#define NV_INIT_RTT	  U32_MAX
+#define NV_MIN_CWND	  4
+#define NV_MIN_CWND_GROW  2
+#define NV_TSO_CWND_BOUND 80
+
+static inline void tcpnv_reset(struct tcpnv *ca, struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	ca->nv_reset = 0;
+	ca->loss_cwnd = 0;
+	ca->nv_no_cong_cnt = 0;
+	ca->nv_rtt_cnt = 0;
+	ca->nv_rtt_cnt_dec = 0;
+	ca->nv_last_rtt = 0;
+	ca->nv_rtt_max_rate = 0;
+	ca->nv_rtt_start_seq = tp->snd_una;
+	ca->nv_eval_call_cnt = 0;
+	ca->nv_last_snd_una = tp->snd_una;
+}
+
+inline u32 get_nv_min_rtt(u32 val)
+{
+	if (nv_min_min_rtt > 0 && val < nv_min_min_rtt)
+		return nv_min_min_rtt;
+	else if (nv_max_min_rtt > 0 && val > nv_max_min_rtt)
+		return nv_max_min_rtt;
+	else
+		return val;
+}
+
+static void tcpnv_init(struct sock *sk)
+{
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	tcpnv_reset(ca, sk);
+
+	ca->nv_allow_cwnd_growth = 1;
+	ca->nv_min_rtt_reset_jiffies = jiffies + 2 * HZ;
+	ca->nv_min_rtt = NV_INIT_RTT;
+	ca->nv_min_rtt_new = NV_INIT_RTT;
+	ca->nv_min_cwnd = NV_MIN_CWND;
+	ca->nv_catchup = 0;
+	ca->cwnd_growth_factor = 0;
+}
+
+static void tcpnv_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcpnv *ca = inet_csk_ca(sk);
+	u32 cnt;
+
+	if (!tcp_is_cwnd_limited(sk))
+		return;
+
+	/* Only grow cwnd if NV has not detected congestion */
+	if (nv_enable && !ca->nv_allow_cwnd_growth)
+		return;
+
+	if (tcp_in_slow_start(tp)) {
+		acked = tcp_slow_start(tp, acked);
+		if (!acked)
+			return;
+	}
+	if (!nv_enable)
+		ca->cwnd_growth_factor = 0;
+
+	if (ca->cwnd_growth_factor < 0) {
+		cnt = tp->snd_cwnd << -ca->cwnd_growth_factor;
+		tcp_cong_avoid_ai(tp, cnt, acked);
+	} else {
+		cnt = max(4U, tp->snd_cwnd >> ca->cwnd_growth_factor);
+		tcp_cong_avoid_ai(tp, cnt, acked);
+	}
+}
+
+static u32 tcpnv_recalc_ssthresh(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	ca->loss_cwnd = tp->snd_cwnd;
+	return max((tp->snd_cwnd * nv_loss_dec_factor) >> 10, 2U);
+}
+
+static u32 tcpnv_undo_cwnd(struct sock *sk)
+{
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
+}
+
+static void tcpnv_state(struct sock *sk, u8 new_state)
+{
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	if (new_state == TCP_CA_Open && ca->nv_reset) {
+		tcpnv_reset(ca, sk);
+	} else if (new_state == TCP_CA_Loss || new_state == TCP_CA_CWR ||
+		new_state == TCP_CA_Recovery) {
+		ca->nv_reset = 1;
+		ca->nv_allow_cwnd_growth = 0;
+		if (new_state == TCP_CA_Loss) {
+			/* Reset cwnd growth factor to Reno value */
+			if (ca->cwnd_growth_factor > 0)
+				ca->cwnd_growth_factor = 0;
+			/* Decrease growth rate if allowed */
+			if (nv_cwnd_growth_rate_neg > 0 &&
+			    ca->cwnd_growth_factor > -8)
+				ca->cwnd_growth_factor--;
+		}
+	}
+}
+
+/* Do congestion avoidance calculations for TCP-NV
+ */
+static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcpnv *ca = inet_csk_ca(sk);
+	unsigned long now = jiffies;
+	s64 rate64 = 0;
+	u32 rate, max_win, cwnd_by_slope;
+	u32 avg_rtt;
+	u32 bytes_acked = 0;
+
+	/* Some calls are for duplicates without timetamps */
+	if (sample->rtt_us < 0)
+		return;
+
+	/* If not in TCP_CA_Open or TCP_CA_Disorder states, skip. */
+	if (icsk->icsk_ca_state != TCP_CA_Open &&
+	    icsk->icsk_ca_state != TCP_CA_Disorder)
+		return;
+
+	/* If NV mode is not enabled, behave like Reno */
+	if (!nv_enable) {
+		ca->nv_allow_cwnd_growth = 1;
+		return;
+	}
+
+	/* Stop cwnd growth if we were in catch up mode */
+	if (ca->nv_catchup && tp->snd_cwnd >= nv_min_cwnd) {
+		ca->nv_catchup = 0;
+		ca->nv_allow_cwnd_growth = 0;
+	}
+
+	bytes_acked = tp->snd_una - ca->nv_last_snd_una;
+	ca->nv_last_snd_una = tp->snd_una;
+
+	if (sample->in_flight == 0)
+		return;
+
+	/* Calculate moving average of RTT */
+	if (nv_rtt_factor > 0) {
+		if (ca->nv_last_rtt > 0) {
+			avg_rtt = (((u64)sample->rtt_us) * nv_rtt_factor +
+				   ((u64)ca->nv_last_rtt)
+				   * (256 - nv_rtt_factor)) >> 8;
+		} else {
+			avg_rtt = sample->rtt_us;
+			ca->nv_min_rtt = get_nv_min_rtt(avg_rtt << 1);
+		}
+		ca->nv_last_rtt = avg_rtt;
+	} else {
+		avg_rtt = sample->rtt_us;
+	}
+
+	/* rate in 100's bits per second */
+	rate64 = ((u64)sample->in_flight) * 8000000;
+	rate = (u32)div64_u64(rate64, (u64)(avg_rtt * 100));
+
+	/* Remember the maximum rate seen during this RTT
+	 * Note: It may be more than one RTT. This function should be
+	 *       called at least nv_dec_eval_min_calls times.
+	 */
+	if (ca->nv_rtt_max_rate < rate)
+		ca->nv_rtt_max_rate = rate;
+
+	/* We have valid information, increment counter */
+	if (ca->nv_eval_call_cnt < 255)
+		ca->nv_eval_call_cnt++;
+
+	/* Apply bounds to rtt */
+	avg_rtt = get_nv_min_rtt(avg_rtt);
+
+	/* update min rtt if necessary */
+	if (avg_rtt < ca->nv_min_rtt)
+		ca->nv_min_rtt = avg_rtt;
+
+	/* update future min_rtt if necessary */
+	if (avg_rtt < ca->nv_min_rtt_new)
+		ca->nv_min_rtt_new = avg_rtt;
+
+	/* nv_min_rtt is updated with the minimum (possibley averaged) rtt
+	 * seen in the last sysctl_tcp_nv_reset_period seconds (i.e. a
+	 * warm reset). This new nv_min_rtt will be continued to be updated
+	 * and be used for another sysctl_tcp_nv_reset_period seconds,
+	 * when it will be updated again.
+	 * In practice we introduce some randomness, so the actual period used
+	 * is chosen randomly from the range:
+	 *   [sysctl_tcp_nv_reset_period*3/4, sysctl_tcp_nv_reset_period*5/4)
+	 */
+	if (time_after_eq(now, ca->nv_min_rtt_reset_jiffies)) {
+		unsigned char rand;
+
+		ca->nv_min_rtt = ca->nv_min_rtt_new;
+		ca->nv_min_rtt_new = NV_INIT_RTT;
+		get_random_bytes(&rand, 1);
+		ca->nv_min_rtt_reset_jiffies =
+			now + ((nv_reset_period * (384 + rand) * HZ) >> 9);
+		/* Every so often we decrease nv_min_cwnd in case previous
+		 *  value is no longer accurate.
+		 */
+		ca->nv_min_cwnd = max(ca->nv_min_cwnd / 2, NV_MIN_CWND);
+	}
+
+	/* Once per RTT check if we need to do congestion avoidance */
+	if (before(ca->nv_rtt_start_seq, tp->snd_una)) {
+		ca->nv_rtt_start_seq = tp->snd_nxt;
+		if (ca->nv_rtt_cnt < 0xff)
+			/* Increase counter for RTTs without CA decision */
+			ca->nv_rtt_cnt++;
+		if (ca->nv_rtt_cnt_dec < 0xffff)
+			/* Increase counter for temporary cwnd decrease */
+			ca->nv_rtt_cnt_dec++;
+
+		/* If this function is only called once within an RTT
+		 * the cwnd is probably too small (in some cases due to
+		 * tso, lro or interrupt coalescence), so we increase
+		 * nv_min_cwnd.
+		 */
+		if (ca->nv_eval_call_cnt == 1 &&
+		    bytes_acked >= (ca->nv_min_cwnd - 1) * tp->mss_cache &&
+		    ca->nv_min_cwnd < (NV_TSO_CWND_BOUND + 1) &&
+		    ca->nv_rtt_cnt_dec < 192) {
+			ca->nv_min_cwnd = min(ca->nv_min_cwnd
+					      + NV_MIN_CWND_GROW,
+					      NV_TSO_CWND_BOUND + 1);
+			ca->nv_rtt_start_seq = tp->snd_nxt +
+				ca->nv_min_cwnd * tp->mss_cache;
+			ca->nv_eval_call_cnt = 0;
+			ca->nv_allow_cwnd_growth = 1;
+			return;
+		}
+
+		/* Every 192 to 320 RTTs decrease cwnd to get better min RTT
+		 * measurement. In practice we accomplish this by initializing
+		 * nv_rtt_cnd_dec randomly form the range [0, 128) and
+		 * stopping at 320.
+		 * We keep the value low for nv_rtt_cnt_dec_delta RTTs and then
+		 * we restore cwnd to its previous value (by setting
+		 * ssthresh to the previous value).
+		 */
+		if (ca->nv_rtt_cnt_dec < 320 && tp->snd_cwnd < nv_min_cwnd) {
+			ca->nv_allow_cwnd_growth = 1;
+			ca->nv_catchup = 1;
+			return;
+		} else if (ca->nv_rtt_cnt_dec == 320) {
+			if (nv_rtt_cnt_dec_delta == 0) {
+				ca->nv_rtt_cnt_dec = 0;
+			} else {
+				/* decrease cwnd and ssthresh */
+				tp->snd_cwnd = max((unsigned int)nv_min_cwnd,
+						   ((tp->snd_cwnd *
+						     nv_dec_factor) >> 3));
+				tp->snd_ssthresh =
+					max(tp->snd_cwnd,
+					    ((tp->snd_ssthresh * nv_dec_factor)
+					     >> 3));
+				ca->nv_allow_cwnd_growth = 0;
+				return;
+			}
+		} else if (ca->nv_rtt_cnt_dec > 320) {
+			if (ca->nv_rtt_cnt_dec - 320 >= nv_rtt_cnt_dec_delta) {
+				/* Restore ssthresh to restore cwnd */
+				unsigned char rand;
+
+				get_random_bytes(&rand, 1);
+				ca->nv_rtt_cnt_dec = rand >> 1;
+				tp->snd_ssthresh = (tp->snd_ssthresh << 3)
+					/ nv_dec_factor;
+				ca->nv_allow_cwnd_growth = 1;
+				ca->nv_no_cong_cnt = 0;
+			}
+			return;
+		}
+
+		/* Find the ideal cwnd for current rate from slope
+		 * slope = 80000.0 * mss / nv_min_rtt
+		 * cwnd_by_slope = nv_rtt_max_rate / slope
+		 */
+		cwnd_by_slope = (u32)
+			div64_u64(((u64)ca->nv_rtt_max_rate) * ca->nv_min_rtt,
+				  (u64)(80000 * tp->mss_cache));
+		max_win = cwnd_by_slope + nv_pad;
+
+		/* If cwnd > max_win, decrease cwnd
+		 * if cwnd < max_win, grow cwnd
+		 * else leave the same
+		 */
+		if (tp->snd_cwnd > max_win) {
+			/* there is congestion, check that it is ok
+			 * to make a CA decision
+			 * 1. We should have at least nv_dec_eval_min_calls
+			 *    data points before making a CA  decision
+			 * 2. We only make a congesion decision after
+			 *    nv_rtt_min_cnt RTTs
+			 */
+			if (ca->nv_rtt_cnt < nv_rtt_min_cnt) {
+				return;
+			} else if (tp->snd_ssthresh == TCP_INFINITE_SSTHRESH) {
+				if (ca->nv_eval_call_cnt <
+				    nv_ssthresh_eval_min_calls)
+					return;
+				/* otherwise we will decrease cwnd */
+			} else if (ca->nv_eval_call_cnt <
+				   nv_dec_eval_min_calls) {
+				if (ca->nv_allow_cwnd_growth &&
+				    ca->nv_rtt_cnt > nv_stop_rtt_cnt)
+					ca->nv_allow_cwnd_growth = 0;
+				return;
+			}
+
+			/* We have enough data to determine we are congested */
+			ca->nv_allow_cwnd_growth = 0;
+			tp->snd_ssthresh =
+				(nv_ssthresh_factor * max_win) >> 3;
+			if (tp->snd_cwnd - max_win > 2) {
+				/* gap > 2, we do exponential cwnd decrease */
+				int dec;
+
+				dec = max(2U, ((tp->snd_cwnd - max_win) *
+					       nv_cong_dec_mult) >> 7);
+				tp->snd_cwnd -= dec;
+			} else if (nv_cong_dec_mult > 0) {
+				tp->snd_cwnd = max_win;
+			}
+			if (ca->cwnd_growth_factor > 0)
+				ca->cwnd_growth_factor = 0;
+			ca->nv_no_cong_cnt = 0;
+		} else if (tp->snd_cwnd <= max_win - nv_pad_buffer) {
+			/* There is no congestion, wait before growing cwnd */
+			if (ca->nv_eval_call_cnt < nv_inc_eval_min_calls)
+				return;
+
+			ca->nv_allow_cwnd_growth = 1;
+			ca->nv_no_cong_cnt++;
+			if (ca->cwnd_growth_factor < 0 &&
+			    nv_cwnd_growth_rate_neg > 0 &&
+			    ca->nv_no_cong_cnt > nv_cwnd_growth_rate_neg) {
+				ca->cwnd_growth_factor++;
+				ca->nv_no_cong_cnt = 0;
+			} else if (ca->cwnd_growth_factor >= 0 &&
+				   nv_cwnd_growth_rate_pos > 0 &&
+				   ca->nv_no_cong_cnt >
+				   nv_cwnd_growth_rate_pos) {
+				ca->cwnd_growth_factor++;
+				ca->nv_no_cong_cnt = 0;
+			}
+		} else {
+			/* cwnd is in-between, so do nothing */
+			return;
+		}
+
+		/* update state */
+		ca->nv_eval_call_cnt = 0;
+		ca->nv_rtt_cnt = 0;
+		ca->nv_rtt_max_rate = 0;
+
+		/* Don't want to make cwnd < nv_min_cwnd
+		 * (it wasn't before, if it is now is because nv
+		 *  decreased it).
+		 */
+		if (tp->snd_cwnd < nv_min_cwnd)
+			tp->snd_cwnd = nv_min_cwnd;
+	}
+}
+
+/* Extract info for Tcp socket info provided via netlink */
+size_t tcpnv_get_info(struct sock *sk, u32 ext, int *attr,
+		      union tcp_cc_info *info)
+{
+	const struct tcpnv *ca = inet_csk_ca(sk);
+
+	if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
+		info->vegas.tcpv_enabled = nv_enable;
+		info->vegas.tcpv_rttcnt = ca->nv_rtt_cnt;
+		info->vegas.tcpv_rtt = ca->nv_last_rtt;
+		info->vegas.tcpv_minrtt = ca->nv_min_rtt;
+
+		*attr = INET_DIAG_VEGASINFO;
+		return sizeof(struct tcpvegas_info);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tcpnv_get_info);
+
+static struct tcp_congestion_ops tcpnv __read_mostly = {
+	.init		= tcpnv_init,
+	.ssthresh	= tcpnv_recalc_ssthresh,
+	.cong_avoid	= tcpnv_cong_avoid,
+	.set_state	= tcpnv_state,
+	.undo_cwnd	= tcpnv_undo_cwnd,
+	.pkts_acked     = tcpnv_acked,
+	.get_info	= tcpnv_get_info,
+
+	.owner		= THIS_MODULE,
+	.name		= "nv",
+};
+
+static int __init tcpnv_register(void)
+{
+	BUILD_BUG_ON(sizeof(struct tcpnv) > ICSK_CA_PRIV_SIZE);
+
+	return tcp_register_congestion_control(&tcpnv);
+}
+
+static void __exit tcpnv_unregister(void)
+{
+	tcp_unregister_congestion_control(&tcpnv);
+}
+
+module_init(tcpnv_register);
+module_exit(tcpnv_unregister);
+
+MODULE_AUTHOR("Lawrence Brakmo");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP NV");
+MODULE_VERSION("1.0");
-- 
2.8.0.rc2

Re: [PATCH net-next 2/2] tcp: add NV congestion control

[David Miller]

From: Lawrence Brakmo <brakmo@fb.com>
Date: Fri, 3 Jun 2016 13:37:58 -0700

> +module_param(nv_enable, int, 0644);
> +MODULE_PARM_DESC(nv_enable, "enable NV (congestion avoidance) behavior");
> +module_param(nv_pad, int, 0644);
> +MODULE_PARM_DESC(nv_pad, "extra packets above congestion level");
> +module_param(nv_pad_buffer, int, 0644);
> +MODULE_PARM_DESC(nv_pad_buffer, "no growth buffer zone");
> +module_param(nv_reset_period, int, 0644);
> +MODULE_PARM_DESC(nv_reset_period, "nv_min_rtt reset period (secs)");
> +module_param(nv_min_cwnd, int, 0644);
> +MODULE_PARM_DESC(nv_min_cwnd, "NV will not decrease cwnd below this value"
> +		 " without losses");
> +module_param(nv_dec_eval_min_calls, int, 0644);
> +MODULE_PARM_DESC(nv_dec_eval_min_calls, "Wait for this many data points"
> +		 " before declaring congestion");
> +module_param(nv_inc_eval_min_calls, int, 0644);
> +MODULE_PARM_DESC(nv_inc_eval_min_calls, "Wait for this many data points"
> +		 " before allowing cwnd growth");
> +module_param(nv_stop_rtt_cnt, int, 0644);
> +MODULE_PARM_DESC(nv_stop_rtt_cnt, "Wait for this many RTTs before stopping"
> +		 " cwnd growth");
> +module_param(nv_ssthresh_eval_min_calls, int, 0644);
> +MODULE_PARM_DESC(nv_ssthresh_eval_min_calls, "Wait for this many data points"
> +		 " before declaring congestion during initial slow-start");
> +module_param(nv_rtt_min_cnt, int, 0644);
> +MODULE_PARM_DESC(nv_rtt_min_cnt, "Wait for this many RTTs before declaring"
> +		 " congestion");
> +module_param(nv_cong_dec_mult, int, 0644);
> +MODULE_PARM_DESC(nv_cong_dec_mult, "Congestion decrease factor");
> +module_param(nv_ssthresh_factor, int, 0644);
> +MODULE_PARM_DESC(nv_ssthresh_factor, "ssthresh factor");
> +module_param(nv_rtt_factor, int, 0644);
> +MODULE_PARM_DESC(nv_rtt_factor, "rtt averaging factor");
> +module_param(nv_rtt_cnt_dec_delta, int, 0644);
> +MODULE_PARM_DESC(nv_rtt_cnt_dec_delta, "decrease cwnd for this many RTTs"
> +		 " every 100 RTTs");
> +module_param(nv_dec_factor, int, 0644);
> +MODULE_PARM_DESC(nv_dec_factor, "decrease cwnd every ~192 RTTS by factor/8");
> +module_param(nv_loss_dec_factor, int, 0644);
> +MODULE_PARM_DESC(nv_loss_dec_factor, "on loss new cwnd = cwnd * this / 1024");
> +module_param(nv_cwnd_growth_rate_neg, int, 0644);
> +MODULE_PARM_DESC(nv_cwnd_growth_rate_neg, "Applies when current cwnd growth"
> +		 " rate < Reno");
> +module_param(nv_cwnd_growth_rate_pos, int, 0644);
> +MODULE_PARM_DESC(nv_cwnd_growth_rate_pos, "Applies when current cwnd growth"
> +		 " rate >= Reno");
> +module_param(nv_min_min_rtt, int, 0644);
> +MODULE_PARM_DESC(nv_min_min_rtt, "lower bound for ca->nv_min_rtt");
> +module_param(nv_max_min_rtt, int, 0644);
> +MODULE_PARM_DESC(nv_max_min_rtt, "upper bound for ca->nv_min_rtt");

That's a disturbingly huge number of module parameters.  Even the first
one "nv_enable" is superfluous, just hook up another congestion control
algorithm.

Please trim this down to something reasonable.  The more of these you have,
the more of them people will start wanting to use and depend upon, and then
you're stuck with them whether you like it or not.

Re: [PATCH net-next 2/2] tcp: add NV congestion control

[Lawrence Brakmo]

On 6/6/16, 4:01 PM, "David Miller" <davem@davemloft.net> wrote:

>From: Lawrence Brakmo <brakmo@fb.com>
>Date: Fri, 3 Jun 2016 13:37:58 -0700
>
>> +module_param(nv_enable, int, 0644);
>> +MODULE_PARM_DESC(nv_enable, "enable NV (congestion avoidance)
>>behavior");
>> +module_param(nv_pad, int, 0644);
>> +MODULE_PARM_DESC(nv_pad, "extra packets above congestion level");
>> +module_param(nv_pad_buffer, int, 0644);
>> +MODULE_PARM_DESC(nv_pad_buffer, "no growth buffer zone");
>> +module_param(nv_reset_period, int, 0644);
>> +MODULE_PARM_DESC(nv_reset_period, "nv_min_rtt reset period (secs)");
>> +module_param(nv_min_cwnd, int, 0644);
>> +MODULE_PARM_DESC(nv_min_cwnd, "NV will not decrease cwnd below this
>>value"
>> +		 " without losses");
>> +module_param(nv_dec_eval_min_calls, int, 0644);
>> +MODULE_PARM_DESC(nv_dec_eval_min_calls, "Wait for this many data
>>points"
>> +		 " before declaring congestion");
>> +module_param(nv_inc_eval_min_calls, int, 0644);
>> +MODULE_PARM_DESC(nv_inc_eval_min_calls, "Wait for this many data
>>points"
>> +		 " before allowing cwnd growth");
>> +module_param(nv_stop_rtt_cnt, int, 0644);
>> +MODULE_PARM_DESC(nv_stop_rtt_cnt, "Wait for this many RTTs before
>>stopping"
>> +		 " cwnd growth");
>> +module_param(nv_ssthresh_eval_min_calls, int, 0644);
>> +MODULE_PARM_DESC(nv_ssthresh_eval_min_calls, "Wait for this many data
>>points"
>> +		 " before declaring congestion during initial slow-start");
>> +module_param(nv_rtt_min_cnt, int, 0644);
>> +MODULE_PARM_DESC(nv_rtt_min_cnt, "Wait for this many RTTs before
>>declaring"
>> +		 " congestion");
>> +module_param(nv_cong_dec_mult, int, 0644);
>> +MODULE_PARM_DESC(nv_cong_dec_mult, "Congestion decrease factor");
>> +module_param(nv_ssthresh_factor, int, 0644);
>> +MODULE_PARM_DESC(nv_ssthresh_factor, "ssthresh factor");
>> +module_param(nv_rtt_factor, int, 0644);
>> +MODULE_PARM_DESC(nv_rtt_factor, "rtt averaging factor");
>> +module_param(nv_rtt_cnt_dec_delta, int, 0644);
>> +MODULE_PARM_DESC(nv_rtt_cnt_dec_delta, "decrease cwnd for this many
>>RTTs"
>> +		 " every 100 RTTs");
>> +module_param(nv_dec_factor, int, 0644);
>> +MODULE_PARM_DESC(nv_dec_factor, "decrease cwnd every ~192 RTTS by
>>factor/8");
>> +module_param(nv_loss_dec_factor, int, 0644);
>> +MODULE_PARM_DESC(nv_loss_dec_factor, "on loss new cwnd = cwnd * this /
>>1024");
>> +module_param(nv_cwnd_growth_rate_neg, int, 0644);
>> +MODULE_PARM_DESC(nv_cwnd_growth_rate_neg, "Applies when current cwnd
>>growth"
>> +		 " rate < Reno");
>> +module_param(nv_cwnd_growth_rate_pos, int, 0644);
>> +MODULE_PARM_DESC(nv_cwnd_growth_rate_pos, "Applies when current cwnd
>>growth"
>> +		 " rate >= Reno");
>> +module_param(nv_min_min_rtt, int, 0644);
>> +MODULE_PARM_DESC(nv_min_min_rtt, "lower bound for ca->nv_min_rtt");
>> +module_param(nv_max_min_rtt, int, 0644);
>> +MODULE_PARM_DESC(nv_max_min_rtt, "upper bound for ca->nv_min_rtt");
>
>That's a disturbingly huge number of module parameters.  Even the first
>one "nv_enable" is superfluous, just hook up another congestion control
>algorithm.
>
>Please trim this down to something reasonable.  The more of these you
>have,
>the more of them people will start wanting to use and depend upon, and
>then
>you're stuck with them whether you like it or not.

I will trim them down to something much smaller. My original intent was to
support experimentation, but those interested can use this version of the
patch to play with a larger number of parameters/tunables.

In regards to the parameter ³nv_enable², its function is to quickly allow
existing NV flows to revert to Reno behavior (by ³echo 0 >
/sys/module/tcp_nv/parameters/nv_enable²). The reason why this may be
necessary, is that under some conditions NV flows competing with more
aggressive flows will perform poorly. People may be more willing to test
NV if there is a quick and simple way to revert if necessary (without
having to restart the flows).

As to why NV could perform poorly, it has to do with the inherent
unfairness between flows that only decrease their cwnd when there are
losses (congestion control) and flows that decrease their cwnd when they
detect queue buildup (congestion avoidance) unless there is network
support. This is specially true when the RTTs for both types are small
(traffic within a DC), but the unfairness decreases as the RTTs of the
congestion control flows increases.

So, is it okay if I leave the parameter ³nv_enable² or would you still
prefer that I remove it?

Re: [PATCH net-next 2/2] tcp: add NV congestion control

[David Miller]

From: Lawrence Brakmo <brakmo@fb.com>
Date: Tue, 7 Jun 2016 01:04:06 +0000

> The reason why this may be necessary, is that under some conditions
> NV flows competing with more aggressive flows will perform
> poorly. People may be more willing to test NV if there is a quick
> and simple way to revert if necessary (without having to restart the
> flows).

This is a property that may apply to any congestion control algorithm
whatsoever, not just NV.

[PATCH net-next 0/2] tcp: add NV congestion control

[Lawrence Brakmo]

This patchset adds support for NV congestion control.

This version of NV does much better than previous versions when things are
very congested. 

Tested in a rack using between 1 and 380 active TCP-NV flows.

Consists of the following patches:
[PATCH net-next 1/2] tcp: add in_flight to tcp_skb_cb
[PATCH net-next 2/2] tcp: add NV congestion control

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>

include/net/tcp.h     |   2 +
net/ipv4/Kconfig      |  16 ++
net/ipv4/Makefile     |   1 +
net/ipv4/tcp_input.c  |   6 +-
net/ipv4/tcp_nv.c     | 592 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
net/ipv4/tcp_output.c |   4 +-
6 files changed, 619 insertions(+), 2 deletions(-)

[PATCH net-next 2/2] tcp: add NV congestion control

[Lawrence Brakmo]

TCP-NV (New Vegas) is a major update to TCP-Vegas.
An earlier version of NV was presented at 2010's LPC.
It is a delayed based congestion avoidance for the
data center. This version has been tested within a
10G rack where the HW RTTs are 20-50us.

A description of TCP-NV, including implementation
details as well as experimental results, can be found at:
http://www.brakmo.org/networking/tcp-nv/TCPNV.html

The current version includes many module parameters to support
experimentation with the parameters.

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
---
 net/ipv4/Kconfig  |  16 ++
 net/ipv4/Makefile |   1 +
 net/ipv4/tcp_nv.c | 592 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 609 insertions(+)
 create mode 100644 net/ipv4/tcp_nv.c

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 238225b..50d6a9b 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -532,6 +532,22 @@ config TCP_CONG_VEGAS
 	window. TCP Vegas should provide less packet loss, but it is
 	not as aggressive as TCP Reno.
 
+config TCP_CONG_NV
+       tristate "TCP NV"
+       default n
+       ---help---
+       TCP NV is a follow up to TCP Vegas. It has been modified to deal with
+       10G networks, measurement noise introduced by LRO, GRO and interrupt
+       coalescence. In addition, it will decrease its cwnd multiplicatively
+       instead of linearly.
+
+       Note that in general congestion avoidance (cwnd decreased when # packets
+       queued grows) cannot coexist with congestion control (cwnd decreased only
+       when there is packet loss) due to fairness issues. One scenario when they
+       can coexist safely is when the CA flows have RTTs << CC flows RTTs.
+
+       For further details see http://www.brakmo.org/networking/tcp-nv/
+
 config TCP_CONG_SCALABLE
 	tristate "Scalable TCP"
 	default n
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index bfa1336..24629b6 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o
 obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o
 obj-$(CONFIG_TCP_CONG_HTCP) += tcp_htcp.o
 obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
+obj-$(CONFIG_TCP_CONG_NV) += tcp_nv.o
 obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
 obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
new file mode 100644
index 0000000..f658947
--- /dev/null
+++ b/net/ipv4/tcp_nv.c
@@ -0,0 +1,592 @@
+/*
+ * TCP NV: TCP with Congestion Avoidance
+ *
+ * TCP-NV is a successor of TCP-Vegas that has been developed to
+ * deal with the issues that occur in modern networks.
+ * Like TCP-Vegas, TCP-NV supports true congestion avoidance,
+ * the ability to detect congestion before packet losses occur.
+ * When congestion (queue buildup) starts to occur, TCP-NV
+ * predicts what the cwnd size should be for the current
+ * throughput and it reduces the cwnd proportionally to
+ * the difference between the current cwnd and the predicted cwnd.
+ * TCP-NV behaves like Reno when no congestion is detected, or when
+ * recovering from packet losses.
+ *
+ * Note: High NIC coalescence values may lower the performance of NV
+ * due to the increased noise in RTT values. In particular, we have
+ * seen issues with rx-frames values greater than 8.
+ *
+ * TODO:
+ * 1) Add mechanism to deal with reverse congestion.
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/math64.h>
+#include <net/tcp.h>
+#include <linux/inet_diag.h>
+
+/* TCP NV parameters
+ *
+ * nv_enable		Behaves like Reno if disabled
+ * nv_pad		Packets queued to trigger congestion detection
+ * nv_pad_buffer	Below this packets queued trigger cwnd growth
+ * nv_reset_period	Who often (in) seconds)to reset min_rtt
+ * nv_min_cwnd		Don't decrease cwnd below this if there are no losses
+ * nv_cong_dec_mult	Decrease cwnd by X% (30%) of congestion when detected
+ * nv_ssthresh_factor	On congestion set ssthresh to this * <desired cwnd> / 8
+ * nv_rtt_factor	RTT averaging factor
+ * nv_rtt_cnt_dec_delta Periodically decrease cwnd for this many RTTs
+ * nv_dec_factor	  and this factor (temp cwnd = cwnd * this / 8)
+ * nv_loss_dec_factor	Decrease cwnd by this (50%) when losses occur
+ * nv_dec_eval_min_calls	Wait this many RTT measurements before dec cwnd
+ * nv_inc_eval_min_calls	Wait this many RTT measurements before inc cwnd
+ * nv_ssthresh_eval_min_calls	Wait this many RTT measurements before stopping
+ *				slow-start due to congestion
+ * nv_stop_rtt_cnt	Only grow cwnd for this many RTTs after non-congestion
+ * nv_rtt_min_cnt	Wait these many RTTs before making congesion decision
+ * nv_min_min_rtt	Lower bound for min_rtt
+ * nv_max_min_rtt	Upper bound for min_rtt
+ *	How quickly to double growth rate (not rate) of cwnd when not congested.
+ *	One value (nv_cwnd_growth_rate_neg) for when rate < 1 pkt/RTT (losses)
+ *	the other (nv_cwnd_growth_rate_pos) otherwise.
+ * nv_cwnd_growth_rate_neg
+ * nv_cwnd_growth_rate_pos
+ */
+
+static int nv_enable __read_mostly = 1;
+static int nv_pad __read_mostly = 10;
+static int nv_pad_buffer __read_mostly = 2;
+static int nv_reset_period __read_mostly = 5; /* in seconds */
+static int nv_min_cwnd __read_mostly = 2;
+static int nv_cong_dec_mult __read_mostly = 30 * 128 / 100; /* = 30% */
+static int nv_ssthresh_factor __read_mostly = 8; /* = 1 */
+static int nv_rtt_factor __read_mostly = 128; /* = 1/2*old + 1/2*new */
+static int nv_rtt_cnt_dec_delta __read_mostly; /* 0 => off */
+static int nv_dec_factor __read_mostly = 8;  /* tmp cwnd = cwnd * factor / 8 */
+static int nv_loss_dec_factor __read_mostly = 512; /* => 50% */
+static int nv_cwnd_growth_rate_neg __read_mostly = 8;
+static int nv_cwnd_growth_rate_pos __read_mostly; /* 0 => fixed like Reno */
+static int nv_dec_eval_min_calls __read_mostly = 60;
+static int nv_inc_eval_min_calls __read_mostly = 20;
+static int nv_ssthresh_eval_min_calls __read_mostly = 30;
+static int nv_stop_rtt_cnt __read_mostly = 10;
+static int nv_rtt_min_cnt __read_mostly = 2;
+static int nv_min_min_rtt __read_mostly; /* 0 => none */
+static int nv_max_min_rtt __read_mostly; /* 0 => none */
+
+module_param(nv_enable, int, 0644);
+MODULE_PARM_DESC(nv_enable, "enable NV (congestion avoidance) behavior");
+module_param(nv_pad, int, 0644);
+MODULE_PARM_DESC(nv_pad, "extra packets above congestion level");
+module_param(nv_pad_buffer, int, 0644);
+MODULE_PARM_DESC(nv_pad_buffer, "no growth buffer zone");
+module_param(nv_reset_period, int, 0644);
+MODULE_PARM_DESC(nv_reset_period, "nv_min_rtt reset period (secs)");
+module_param(nv_min_cwnd, int, 0644);
+MODULE_PARM_DESC(nv_min_cwnd, "NV will not decrease cwnd below this value"
+		 " without losses");
+module_param(nv_dec_eval_min_calls, int, 0644);
+MODULE_PARM_DESC(nv_dec_eval_min_calls, "Wait for this many data points"
+		 " before declaring congestion");
+module_param(nv_inc_eval_min_calls, int, 0644);
+MODULE_PARM_DESC(nv_inc_eval_min_calls, "Wait for this many data points"
+		 " before allowing cwnd growth");
+module_param(nv_stop_rtt_cnt, int, 0644);
+MODULE_PARM_DESC(nv_stop_rtt_cnt, "Wait for this many RTTs before stopping"
+		 " cwnd growth");
+module_param(nv_ssthresh_eval_min_calls, int, 0644);
+MODULE_PARM_DESC(nv_ssthresh_eval_min_calls, "Wait for this many data points"
+		 " before declaring congestion during initial slow-start");
+module_param(nv_rtt_min_cnt, int, 0644);
+MODULE_PARM_DESC(nv_rtt_min_cnt, "Wait for this many RTTs before declaring"
+		 " congestion");
+module_param(nv_cong_dec_mult, int, 0644);
+MODULE_PARM_DESC(nv_cong_dec_mult, "Congestion decrease factor");
+module_param(nv_ssthresh_factor, int, 0644);
+MODULE_PARM_DESC(nv_ssthresh_factor, "ssthresh factor");
+module_param(nv_rtt_factor, int, 0644);
+MODULE_PARM_DESC(nv_rtt_factor, "rtt averaging factor");
+module_param(nv_rtt_cnt_dec_delta, int, 0644);
+MODULE_PARM_DESC(nv_rtt_cnt_dec_delta, "decrease cwnd for this many RTTs"
+		 " every 100 RTTs");
+module_param(nv_dec_factor, int, 0644);
+MODULE_PARM_DESC(nv_dec_factor, "decrease cwnd every ~192 RTTS by factor/8");
+module_param(nv_loss_dec_factor, int, 0644);
+MODULE_PARM_DESC(nv_loss_dec_factor, "on loss new cwnd = cwnd * this / 1024");
+module_param(nv_cwnd_growth_rate_neg, int, 0644);
+MODULE_PARM_DESC(nv_cwnd_growth_rate_neg, "Applies when current cwnd growth"
+		 " rate < Reno");
+module_param(nv_cwnd_growth_rate_pos, int, 0644);
+MODULE_PARM_DESC(nv_cwnd_growth_rate_pos, "Applies when current cwnd growth"
+		 " rate >= Reno");
+module_param(nv_min_min_rtt, int, 0644);
+MODULE_PARM_DESC(nv_min_min_rtt, "lower bound for ca->nv_min_rtt");
+module_param(nv_max_min_rtt, int, 0644);
+MODULE_PARM_DESC(nv_max_min_rtt, "upper bound for ca->nv_min_rtt");
+
+/* TCP NV Parameters */
+struct tcpnv {
+	unsigned long nv_min_rtt_reset_jiffies;  /* when to switch to
+						  * nv_min_rtt_new */
+	s8  cwnd_growth_factor;	/* Current cwnd growth factor,
+				 * < 0 => less than 1 packet/RTT */
+	u8  available8;
+	u16 available16;
+	u32 loss_cwnd;	/* cwnd at last loss */
+	u8  nv_allow_cwnd_growth:1, /* whether cwnd can grow */
+		nv_reset:1,	    /* whether to reset values */
+		nv_catchup:1;	    /* whether we are growing because
+				     * of temporary cwnd decrease */
+	u8  nv_eval_call_cnt;	/* call count since last eval */
+	u8  nv_min_cwnd;	/* nv won't make a ca decision if cwnd is
+				 * smaller than this. It may grow to handle
+				 * TSO, LRO and interrupt coalescence because
+				 * with these a small cwnd cannot saturate
+				 * the link. Note that this is different from
+				 * the file local nv_min_cwnd */
+	u8  nv_rtt_cnt;		/* RTTs without making ca decision */;
+	u32 nv_last_rtt;	/* last rtt */
+	u32 nv_min_rtt;		/* active min rtt. Used to determine slope */
+	u32 nv_min_rtt_new;	/* min rtt for future use */
+	u32 nv_rtt_max_rate;	/* max rate seen during current RTT */
+	u32 nv_rtt_start_seq;	/* current RTT ends when packet arrives
+				 * acking beyond nv_rtt_start_seq */
+	u32 nv_last_snd_una;	/* Previous value of tp->snd_una. It is
+				 * used to determine bytes acked since last
+				 * call to bictcp_acked */
+	u32 nv_no_cong_cnt;	/* Consecutive no congestion decisions */
+	u32 nv_rtt_cnt_dec;	/* RTTs since last temporary cwnd decrease */
+};
+
+#define NV_INIT_RTT	  U32_MAX
+#define NV_MIN_CWND	  4
+#define NV_MIN_CWND_GROW  2
+#define NV_TSO_CWND_BOUND 80
+
+static inline void tcpnv_reset(struct tcpnv *ca, struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	ca->nv_reset = 0;
+	ca->loss_cwnd = 0;
+	ca->nv_no_cong_cnt = 0;
+	ca->nv_rtt_cnt = 0;
+	ca->nv_rtt_cnt_dec = 0;
+	ca->nv_last_rtt = 0;
+	ca->nv_rtt_max_rate = 0;
+	ca->nv_rtt_start_seq = tp->snd_una;
+	ca->nv_eval_call_cnt = 0;
+	ca->nv_last_snd_una = tp->snd_una;
+}
+
+inline u32 get_nv_min_rtt(u32 val)
+{
+	if (nv_min_min_rtt > 0 && val < nv_min_min_rtt)
+		return nv_min_min_rtt;
+	else if (nv_max_min_rtt > 0 && val > nv_max_min_rtt)
+		return nv_max_min_rtt;
+	else
+		return val;
+}
+
+static void tcpnv_init(struct sock *sk)
+{
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	tcpnv_reset(ca, sk);
+
+	ca->nv_allow_cwnd_growth = 1;
+	ca->nv_min_rtt_reset_jiffies = jiffies + 2 * HZ;
+	ca->nv_min_rtt = NV_INIT_RTT;
+	ca->nv_min_rtt_new = NV_INIT_RTT;
+	ca->nv_min_cwnd = NV_MIN_CWND;
+	ca->nv_catchup = 0;
+	ca->cwnd_growth_factor = 0;
+}
+
+static void tcpnv_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcpnv *ca = inet_csk_ca(sk);
+	u32 cnt;
+
+	if (!tcp_is_cwnd_limited(sk))
+		return;
+
+	/* Only grow cwnd if NV has not detected congestion */
+	if (nv_enable && !ca->nv_allow_cwnd_growth)
+		return;
+
+	if (tcp_in_slow_start(tp)) {
+		acked = tcp_slow_start(tp, acked);
+		if (!acked)
+			return;
+	}
+	if (!nv_enable)
+		ca->cwnd_growth_factor = 0;
+
+	if (ca->cwnd_growth_factor < 0) {
+		cnt = tp->snd_cwnd << -ca->cwnd_growth_factor;
+		tcp_cong_avoid_ai(tp, cnt, acked);
+	} else {
+		cnt = max(4U, tp->snd_cwnd >> ca->cwnd_growth_factor);
+		tcp_cong_avoid_ai(tp, cnt, acked);
+	}
+}
+
+static u32 tcpnv_recalc_ssthresh(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	ca->loss_cwnd = tp->snd_cwnd;
+	return max((tp->snd_cwnd * nv_loss_dec_factor) >> 10, 2U);
+}
+
+static u32 tcpnv_undo_cwnd(struct sock *sk)
+{
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
+}
+
+static void tcpnv_state(struct sock *sk, u8 new_state)
+{
+	struct tcpnv *ca = inet_csk_ca(sk);
+
+	if (new_state == TCP_CA_Open && ca->nv_reset) {
+		tcpnv_reset(ca, sk);
+	} else if (new_state == TCP_CA_Loss || new_state == TCP_CA_CWR ||
+		new_state == TCP_CA_Recovery) {
+		ca->nv_reset = 1;
+		ca->nv_allow_cwnd_growth = 0;
+		if (new_state == TCP_CA_Loss) {
+			/* Reset cwnd growth factor to Reno value */
+			if (ca->cwnd_growth_factor > 0)
+				ca->cwnd_growth_factor = 0;
+			/* Decrease growth rate if allowed */
+			if (nv_cwnd_growth_rate_neg > 0 &&
+			    ca->cwnd_growth_factor > -8)
+				ca->cwnd_growth_factor--;
+		}
+	}
+}
+
+/* Do congestion avoidance calculations for TCP-NV
+ */
+static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcpnv *ca = inet_csk_ca(sk);
+	unsigned long now = jiffies;
+	s64 rate64 = 0;
+	u32 rate, max_win, cwnd_by_slope;
+	u32 avg_rtt;
+	u32 bytes_acked = 0;
+
+	/* Some calls are for duplicates without timetamps */
+	if (sample->rtt_us < 0)
+		return;
+
+	/* If not in TCP_CA_Open or TCP_CA_Disorder states, skip. */
+	if (icsk->icsk_ca_state != TCP_CA_Open &&
+	    icsk->icsk_ca_state != TCP_CA_Disorder)
+		return;
+
+	/* If NV mode is not enabled, behave like Reno */
+	if (!nv_enable) {
+		ca->nv_allow_cwnd_growth = 1;
+		return;
+	}
+
+	/* Stop cwnd growth if we were in catch up mode */
+	if (ca->nv_catchup && tp->snd_cwnd >= nv_min_cwnd) {
+		ca->nv_catchup = 0;
+		ca->nv_allow_cwnd_growth = 0;
+	}
+
+	bytes_acked = tp->snd_una - ca->nv_last_snd_una;
+	ca->nv_last_snd_una = tp->snd_una;
+
+	if (sample->in_flight == 0)
+		return;
+
+	/* Calculate moving average of RTT */
+	if (nv_rtt_factor > 0) {
+		if (ca->nv_last_rtt > 0) {
+			avg_rtt = (((u64)sample->rtt_us) * nv_rtt_factor +
+				   ((u64)ca->nv_last_rtt)
+				   * (256 - nv_rtt_factor)) >> 8;
+		} else {
+			avg_rtt = sample->rtt_us;
+			ca->nv_min_rtt = get_nv_min_rtt(avg_rtt << 1);
+		}
+		ca->nv_last_rtt = avg_rtt;
+	} else {
+		avg_rtt = sample->rtt_us;
+	}
+
+	/* rate in 100's bits per second */
+	rate64 = ((u64)sample->in_flight) * 8000000;
+	rate = (u32)div64_u64(rate64, (u64)(avg_rtt * 100));
+
+	/* Remember the maximum rate seen during this RTT
+	 * Note: It may be more than one RTT. This function should be
+	 *       called at least nv_dec_eval_min_calls times.
+	 */
+	if (ca->nv_rtt_max_rate < rate)
+		ca->nv_rtt_max_rate = rate;
+
+	/* We have valid information, increment counter */
+	if (ca->nv_eval_call_cnt < 255)
+		ca->nv_eval_call_cnt++;
+
+	/* Apply bounds to rtt */
+	avg_rtt = get_nv_min_rtt(avg_rtt);
+
+	/* update min rtt if necessary */
+	if (avg_rtt < ca->nv_min_rtt)
+		ca->nv_min_rtt = avg_rtt;
+
+	/* update future min_rtt if necessary */
+	if (avg_rtt < ca->nv_min_rtt_new)
+		ca->nv_min_rtt_new = avg_rtt;
+
+	/* nv_min_rtt is updated with the minimum (possibley averaged) rtt
+	 * seen in the last sysctl_tcp_nv_reset_period seconds (i.e. a
+	 * warm reset). This new nv_min_rtt will be continued to be updated
+	 * and be used for another sysctl_tcp_nv_reset_period seconds,
+	 * when it will be updated again.
+	 * In practice we introduce some randomness, so the actual period used
+	 * is chosen randomly from the range:
+	 *   [sysctl_tcp_nv_reset_period*3/4, sysctl_tcp_nv_reset_period*5/4)
+	 */
+	if (time_after_eq(now, ca->nv_min_rtt_reset_jiffies)) {
+		unsigned char rand;
+
+		ca->nv_min_rtt = ca->nv_min_rtt_new;
+		ca->nv_min_rtt_new = NV_INIT_RTT;
+		get_random_bytes(&rand, 1);
+		ca->nv_min_rtt_reset_jiffies =
+			now + ((nv_reset_period * (384 + rand) * HZ) >> 9);
+		/* Every so often we decrease nv_min_cwnd in case previous
+		 *  value is no longer accurate.
+		 */
+		ca->nv_min_cwnd = max(ca->nv_min_cwnd / 2, NV_MIN_CWND);
+	}
+
+	/* Once per RTT check if we need to do congestion avoidance */
+	if (before(ca->nv_rtt_start_seq, tp->snd_una)) {
+		ca->nv_rtt_start_seq = tp->snd_nxt;
+		if (ca->nv_rtt_cnt < 0xff)
+			/* Increase counter for RTTs without CA decision */
+			ca->nv_rtt_cnt++;
+		if (ca->nv_rtt_cnt_dec < 0xffff)
+			/* Increase counter for temporary cwnd decrease */
+			ca->nv_rtt_cnt_dec++;
+
+		/* If this function is only called once within an RTT
+		 * the cwnd is probably too small (in some cases due to
+		 * tso, lro or interrupt coalescence), so we increase
+		 * nv_min_cwnd.
+		 */
+		if (ca->nv_eval_call_cnt == 1 &&
+		    bytes_acked >= (ca->nv_min_cwnd - 1) * tp->mss_cache &&
+		    ca->nv_min_cwnd < (NV_TSO_CWND_BOUND + 1) &&
+		    ca->nv_rtt_cnt_dec < 192) {
+			ca->nv_min_cwnd = min(ca->nv_min_cwnd
+					      + NV_MIN_CWND_GROW,
+					      NV_TSO_CWND_BOUND + 1);
+			ca->nv_rtt_start_seq = tp->snd_nxt +
+				ca->nv_min_cwnd * tp->mss_cache;
+			ca->nv_eval_call_cnt = 0;
+			ca->nv_allow_cwnd_growth = 1;
+			return;
+		}
+
+		/* Every 192 to 320 RTTs decrease cwnd to get better min RTT
+		 * measurement. In practice we accomplish this by initializing
+		 * nv_rtt_cnd_dec randomly form the range [0, 128) and
+		 * stopping at 320.
+		 * We keep the value low for nv_rtt_cnt_dec_delta RTTs and then
+		 * we restore cwnd to its previous value (by setting
+		 * ssthresh to the previous value).
+		 */
+		if (ca->nv_rtt_cnt_dec < 320 && tp->snd_cwnd < nv_min_cwnd) {
+			ca->nv_allow_cwnd_growth = 1;
+			ca->nv_catchup = 1;
+			return;
+		} else if (ca->nv_rtt_cnt_dec == 320) {
+			if (nv_rtt_cnt_dec_delta == 0) {
+				ca->nv_rtt_cnt_dec = 0;
+			} else {
+				/* decrease cwnd and ssthresh */
+				tp->snd_cwnd = max((unsigned int)nv_min_cwnd,
+						   ((tp->snd_cwnd *
+						     nv_dec_factor) >> 3));
+				tp->snd_ssthresh =
+					max(tp->snd_cwnd,
+					    ((tp->snd_ssthresh * nv_dec_factor)
+					     >> 3));
+				ca->nv_allow_cwnd_growth = 0;
+				return;
+			}
+		} else if (ca->nv_rtt_cnt_dec > 320) {
+			if (ca->nv_rtt_cnt_dec - 320 >= nv_rtt_cnt_dec_delta) {
+				/* Restore ssthresh to restore cwnd */
+				unsigned char rand;
+
+				get_random_bytes(&rand, 1);
+				ca->nv_rtt_cnt_dec = rand >> 1;
+				tp->snd_ssthresh = (tp->snd_ssthresh << 3)
+					/ nv_dec_factor;
+				ca->nv_allow_cwnd_growth = 1;
+				ca->nv_no_cong_cnt = 0;
+			}
+			return;
+		}
+
+		/* Find the ideal cwnd for current rate from slope
+		 * slope = 80000.0 * mss / nv_min_rtt
+		 * cwnd_by_slope = nv_rtt_max_rate / slope
+		 */
+		cwnd_by_slope = (u32)
+			div64_u64(((u64)ca->nv_rtt_max_rate) * ca->nv_min_rtt,
+				  (u64)(80000 * tp->mss_cache));
+		max_win = cwnd_by_slope + nv_pad;
+
+		/* If cwnd > max_win, decrease cwnd
+		 * if cwnd < max_win, grow cwnd
+		 * else leave the same
+		 */
+		if (tp->snd_cwnd > max_win) {
+			/* there is congestion, check that it is ok
+			 * to make a CA decision
+			 * 1. We should have at least nv_dec_eval_min_calls
+			 *    data points before making a CA  decision
+			 * 2. We only make a congesion decision after
+			 *    nv_rtt_min_cnt RTTs
+			 */
+			if (ca->nv_rtt_cnt < nv_rtt_min_cnt) {
+				return;
+			} else if (tp->snd_ssthresh == TCP_INFINITE_SSTHRESH) {
+				if (ca->nv_eval_call_cnt <
+				    nv_ssthresh_eval_min_calls)
+					return;
+				/* otherwise we will decrease cwnd */
+			} else if (ca->nv_eval_call_cnt <
+				   nv_dec_eval_min_calls) {
+				if (ca->nv_allow_cwnd_growth &&
+				    ca->nv_rtt_cnt > nv_stop_rtt_cnt)
+					ca->nv_allow_cwnd_growth = 0;
+				return;
+			}
+
+			/* We have enough data to determine we are congested */
+			ca->nv_allow_cwnd_growth = 0;
+			tp->snd_ssthresh =
+				(nv_ssthresh_factor * max_win) >> 3;
+			if (tp->snd_cwnd - max_win > 2) {
+				/* gap > 2, we do exponential cwnd decrease */
+				int dec;
+
+				dec = max(2U, ((tp->snd_cwnd - max_win) *
+					       nv_cong_dec_mult) >> 7);
+				tp->snd_cwnd -= dec;
+			} else if (nv_cong_dec_mult > 0) {
+				tp->snd_cwnd = max_win;
+			}
+			if (ca->cwnd_growth_factor > 0)
+				ca->cwnd_growth_factor = 0;
+			ca->nv_no_cong_cnt = 0;
+		} else if (tp->snd_cwnd <= max_win - nv_pad_buffer) {
+			/* There is no congestion, wait before growing cwnd */
+			if (ca->nv_eval_call_cnt < nv_inc_eval_min_calls)
+				return;
+
+			ca->nv_allow_cwnd_growth = 1;
+			ca->nv_no_cong_cnt++;
+			if (ca->cwnd_growth_factor < 0 &&
+			    nv_cwnd_growth_rate_neg > 0 &&
+			    ca->nv_no_cong_cnt > nv_cwnd_growth_rate_neg) {
+				ca->cwnd_growth_factor++;
+				ca->nv_no_cong_cnt = 0;
+			} else if (ca->cwnd_growth_factor >= 0 &&
+				   nv_cwnd_growth_rate_pos > 0 &&
+				   ca->nv_no_cong_cnt >
+				   nv_cwnd_growth_rate_pos) {
+				ca->cwnd_growth_factor++;
+				ca->nv_no_cong_cnt = 0;
+			}
+		} else {
+			/* cwnd is in-between, so do nothing */
+			return;
+		}
+
+		/* update state */
+		ca->nv_eval_call_cnt = 0;
+		ca->nv_rtt_cnt = 0;
+		ca->nv_rtt_max_rate = 0;
+
+		/* Don't want to make cwnd < nv_min_cwnd
+		 * (it wasn't before, if it is now is because nv
+		 *  decreased it).
+		 */
+		if (tp->snd_cwnd < nv_min_cwnd)
+			tp->snd_cwnd = nv_min_cwnd;
+	}
+}
+
+/* Extract info for Tcp socket info provided via netlink */
+size_t tcpnv_get_info(struct sock *sk, u32 ext, int *attr,
+		      union tcp_cc_info *info)
+{
+	const struct tcpnv *ca = inet_csk_ca(sk);
+
+	if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
+		info->vegas.tcpv_enabled = nv_enable;
+		info->vegas.tcpv_rttcnt = ca->nv_rtt_cnt;
+		info->vegas.tcpv_rtt = ca->nv_last_rtt;
+		info->vegas.tcpv_minrtt = ca->nv_min_rtt;
+
+		*attr = INET_DIAG_VEGASINFO;
+		return sizeof(struct tcpvegas_info);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tcpnv_get_info);
+
+static struct tcp_congestion_ops tcpnv __read_mostly = {
+	.init		= tcpnv_init,
+	.ssthresh	= tcpnv_recalc_ssthresh,
+	.cong_avoid	= tcpnv_cong_avoid,
+	.set_state	= tcpnv_state,
+	.undo_cwnd	= tcpnv_undo_cwnd,
+	.pkts_acked     = tcpnv_acked,
+	.get_info	= tcpnv_get_info,
+
+	.owner		= THIS_MODULE,
+	.name		= "nv",
+};
+
+static int __init tcpnv_register(void)
+{
+	BUILD_BUG_ON(sizeof(struct tcpnv) > ICSK_CA_PRIV_SIZE);
+
+	return tcp_register_congestion_control(&tcpnv);
+}
+
+static void __exit tcpnv_unregister(void)
+{
+	tcp_unregister_congestion_control(&tcpnv);
+}
+
+module_init(tcpnv_register);
+module_exit(tcpnv_unregister);
+
+MODULE_AUTHOR("Lawrence Brakmo");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP NV");
+MODULE_VERSION("1.0");
-- 
2.8.0.rc2