1 files changed, 238 insertions, 0 deletions
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
new file mode 100644
index 0000000000..366ff6f214
--- /dev/null
+++ b/net/ipv4/tcp_veno.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * TCP Veno congestion control
+ *
+ * This is based on the congestion detection/avoidance scheme described in
+ *    C. P. Fu, S. C. Liew.
+ *    "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."
+ *    IEEE Journal on Selected Areas in Communication,
+ *    Feb. 2003.
+ * 	See https://www.ie.cuhk.edu.hk/fileadmin/staff_upload/soung/Journal/J3.pdf
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet_diag.h>
+
+#include <net/tcp.h>
+
+/* Default values of the Veno variables, in fixed-point representation
+ * with V_PARAM_SHIFT bits to the right of the binary point.
+ */
+#define V_PARAM_SHIFT 1
+static const int beta = 3 << V_PARAM_SHIFT;
+
+/* Veno variables */
+struct veno {
+	u8 doing_veno_now;	/* if true, do veno for this rtt */
+	u16 cntrtt;		/* # of rtts measured within last rtt */
+	u32 minrtt;		/* min of rtts measured within last rtt (in usec) */
+	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 */
+};
+
+/* There are several situations when we must "re-start" Veno:
+ *
+ *  o when a connection is established
+ *  o after an RTO
+ *  o after fast recovery
+ *  o when we send a packet and there is no outstanding
+ *    unacknowledged data (restarting an idle connection)
+ *
+ */
+static inline void veno_enable(struct sock *sk)
+{
+	struct veno *veno = inet_csk_ca(sk);
+
+	/* turn on Veno */
+	veno->doing_veno_now = 1;
+
+	veno->minrtt = 0x7fffffff;
+}
+
+static inline void veno_disable(struct sock *sk)
+{
+	struct veno *veno = inet_csk_ca(sk);
+
+	/* turn off Veno */
+	veno->doing_veno_now = 0;
+}
+
+static void tcp_veno_init(struct sock *sk)
+{
+	struct veno *veno = inet_csk_ca(sk);
+
+	veno->basertt = 0x7fffffff;
+	veno->inc = 1;
+	veno_enable(sk);
+}
+
+/* Do rtt sampling needed for Veno. */
+static void tcp_veno_pkts_acked(struct sock *sk,
+				const struct ack_sample *sample)
+{
+	struct veno *veno = inet_csk_ca(sk);
+	u32 vrtt;
+
+	if (sample->rtt_us < 0)
+		return;
+
+	/* Never allow zero rtt or baseRTT */
+	vrtt = sample->rtt_us + 1;
+
+	/* Filter to find propagation delay: */
+	if (vrtt < veno->basertt)
+		veno->basertt = vrtt;
+
+	/* Find the min rtt during the last rtt to find
+	 * the current prop. delay + queuing delay:
+	 */
+	veno->minrtt = min(veno->minrtt, vrtt);
+	veno->cntrtt++;
+}
+
+static void tcp_veno_state(struct sock *sk, u8 ca_state)
+{
+	if (ca_state == TCP_CA_Open)
+		veno_enable(sk);
+	else
+		veno_disable(sk);
+}
+
+/*
+ * If the connection is idle and we are restarting,
+ * then we don't want to do any Veno calculations
+ * until we get fresh rtt samples.  So when we
+ * restart, we reset our Veno state to a clean
+ * state. After we get acks for this flight of
+ * packets, _then_ we can make Veno calculations
+ * again.
+ */
+static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event)
+{
+	if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)
+		tcp_veno_init(sk);
+}
+
+static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct veno *veno = inet_csk_ca(sk);
+
+	if (!veno->doing_veno_now) {
+		tcp_reno_cong_avoid(sk, ack, acked);
+		return;
+	}
+
+	/* limited by applications */
+	if (!tcp_is_cwnd_limited(sk))
+		return;
+
+	/* We do the Veno calculations only if we got enough rtt samples */
+	if (veno->cntrtt <= 2) {
+		/* We don't have enough rtt samples to do the Veno
+		 * calculation, so we'll behave like Reno.
+		 */
+		tcp_reno_cong_avoid(sk, ack, acked);
+	} else {
+		u64 target_cwnd;
+		u32 rtt;
+
+		/* We have enough rtt samples, so, using the Veno
+		 * algorithm, we determine the state of the network.
+		 */
+
+		rtt = veno->minrtt;
+
+		target_cwnd = (u64)tcp_snd_cwnd(tp) * veno->basertt;
+		target_cwnd <<= V_PARAM_SHIFT;
+		do_div(target_cwnd, rtt);
+
+		veno->diff = (tcp_snd_cwnd(tp) << V_PARAM_SHIFT) - target_cwnd;
+
+		if (tcp_in_slow_start(tp)) {
+			/* Slow start. */
+			acked = tcp_slow_start(tp, acked);
+			if (!acked)
+				goto done;
+		}
+
+		/* Congestion avoidance. */
+		if (veno->diff < beta) {
+			/* In the "non-congestive state", increase cwnd
+			 * every rtt.
+			 */
+			tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
+		} else {
+			/* In the "congestive state", increase cwnd
+			 * every other rtt.
+			 */
+			if (tp->snd_cwnd_cnt >= tcp_snd_cwnd(tp)) {
+				if (veno->inc &&
+				    tcp_snd_cwnd(tp) < tp->snd_cwnd_clamp) {
+					tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
+					veno->inc = 0;
+				} else
+					veno->inc = 1;
+				tp->snd_cwnd_cnt = 0;
+			} else
+				tp->snd_cwnd_cnt += acked;
+		}
+done:
+		if (tcp_snd_cwnd(tp) < 2)
+			tcp_snd_cwnd_set(tp, 2);
+		else if (tcp_snd_cwnd(tp) > tp->snd_cwnd_clamp)
+			tcp_snd_cwnd_set(tp, tp->snd_cwnd_clamp);
+	}
+	/* Wipe the slate clean for the next rtt. */
+	/* veno->cntrtt = 0; */
+	veno->minrtt = 0x7fffffff;
+}
+
+/* Veno MD phase */
+static u32 tcp_veno_ssthresh(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct veno *veno = inet_csk_ca(sk);
+
+	if (veno->diff < beta)
+		/* in "non-congestive state", cut cwnd by 1/5 */
+		return max(tcp_snd_cwnd(tp) * 4 / 5, 2U);
+	else
+		/* in "congestive state", cut cwnd by 1/2 */
+		return max(tcp_snd_cwnd(tp) >> 1U, 2U);
+}
+
+static struct tcp_congestion_ops tcp_veno __read_mostly = {
+	.init		= tcp_veno_init,
+	.ssthresh	= tcp_veno_ssthresh,
+	.undo_cwnd	= tcp_reno_undo_cwnd,
+	.cong_avoid	= tcp_veno_cong_avoid,
+	.pkts_acked	= tcp_veno_pkts_acked,
+	.set_state	= tcp_veno_state,
+	.cwnd_event	= tcp_veno_cwnd_event,
+
+	.owner		= THIS_MODULE,
+	.name		= "veno",
+};
+
+static int __init tcp_veno_register(void)
+{
+	BUILD_BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE);
+	tcp_register_congestion_control(&tcp_veno);
+	return 0;
+}
+
+static void __exit tcp_veno_unregister(void)
+{
+	tcp_unregister_congestion_control(&tcp_veno);
+}
+
+module_init(tcp_veno_register);
+module_exit(tcp_veno_unregister);
+
+MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Veno");