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v3.15
  1/*
  2 * TCP Veno congestion control
  3 *
  4 * This is based on the congestion detection/avoidance scheme described in
  5 *    C. P. Fu, S. C. Liew.
  6 *    "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."
  7 *    IEEE Journal on Selected Areas in Communication,
  8 *    Feb. 2003.
  9 * 	See http://www.ie.cuhk.edu.hk/fileadmin/staff_upload/soung/Journal/J3.pdf
 10 */
 11
 12#include <linux/mm.h>
 13#include <linux/module.h>
 14#include <linux/skbuff.h>
 15#include <linux/inet_diag.h>
 16
 17#include <net/tcp.h>
 18
 19/* Default values of the Veno variables, in fixed-point representation
 20 * with V_PARAM_SHIFT bits to the right of the binary point.
 21 */
 22#define V_PARAM_SHIFT 1
 23static const int beta = 3 << V_PARAM_SHIFT;
 24
 25/* Veno variables */
 26struct veno {
 27	u8 doing_veno_now;	/* if true, do veno for this rtt */
 28	u16 cntrtt;		/* # of rtts measured within last rtt */
 29	u32 minrtt;		/* min of rtts measured within last rtt (in usec) */
 30	u32 basertt;		/* the min of all Veno rtt measurements seen (in usec) */
 31	u32 inc;		/* decide whether to increase cwnd */
 32	u32 diff;		/* calculate the diff rate */
 33};
 34
 35/* There are several situations when we must "re-start" Veno:
 36 *
 37 *  o when a connection is established
 38 *  o after an RTO
 39 *  o after fast recovery
 40 *  o when we send a packet and there is no outstanding
 41 *    unacknowledged data (restarting an idle connection)
 42 *
 43 */
 44static inline void veno_enable(struct sock *sk)
 45{
 46	struct veno *veno = inet_csk_ca(sk);
 47
 48	/* turn on Veno */
 49	veno->doing_veno_now = 1;
 50
 51	veno->minrtt = 0x7fffffff;
 52}
 53
 54static inline void veno_disable(struct sock *sk)
 55{
 56	struct veno *veno = inet_csk_ca(sk);
 57
 58	/* turn off Veno */
 59	veno->doing_veno_now = 0;
 60}
 61
 62static void tcp_veno_init(struct sock *sk)
 63{
 64	struct veno *veno = inet_csk_ca(sk);
 65
 66	veno->basertt = 0x7fffffff;
 67	veno->inc = 1;
 68	veno_enable(sk);
 69}
 70
 71/* Do rtt sampling needed for Veno. */
 72static void tcp_veno_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us)
 
 73{
 74	struct veno *veno = inet_csk_ca(sk);
 75	u32 vrtt;
 76
 77	if (rtt_us < 0)
 78		return;
 79
 80	/* Never allow zero rtt or baseRTT */
 81	vrtt = rtt_us + 1;
 82
 83	/* Filter to find propagation delay: */
 84	if (vrtt < veno->basertt)
 85		veno->basertt = vrtt;
 86
 87	/* Find the min rtt during the last rtt to find
 88	 * the current prop. delay + queuing delay:
 89	 */
 90	veno->minrtt = min(veno->minrtt, vrtt);
 91	veno->cntrtt++;
 92}
 93
 94static void tcp_veno_state(struct sock *sk, u8 ca_state)
 95{
 96	if (ca_state == TCP_CA_Open)
 97		veno_enable(sk);
 98	else
 99		veno_disable(sk);
100}
101
102/*
103 * If the connection is idle and we are restarting,
104 * then we don't want to do any Veno calculations
105 * until we get fresh rtt samples.  So when we
106 * restart, we reset our Veno state to a clean
107 * state. After we get acks for this flight of
108 * packets, _then_ we can make Veno calculations
109 * again.
110 */
111static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event)
112{
113	if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)
114		tcp_veno_init(sk);
115}
116
117static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked,
118				u32 in_flight)
119{
120	struct tcp_sock *tp = tcp_sk(sk);
121	struct veno *veno = inet_csk_ca(sk);
122
123	if (!veno->doing_veno_now) {
124		tcp_reno_cong_avoid(sk, ack, acked, in_flight);
125		return;
126	}
127
128	/* limited by applications */
129	if (!tcp_is_cwnd_limited(sk, in_flight))
130		return;
131
132	/* We do the Veno calculations only if we got enough rtt samples */
133	if (veno->cntrtt <= 2) {
134		/* We don't have enough rtt samples to do the Veno
135		 * calculation, so we'll behave like Reno.
136		 */
137		tcp_reno_cong_avoid(sk, ack, acked, in_flight);
138	} else {
139		u64 target_cwnd;
140		u32 rtt;
141
142		/* We have enough rtt samples, so, using the Veno
143		 * algorithm, we determine the state of the network.
144		 */
145
146		rtt = veno->minrtt;
147
148		target_cwnd = (tp->snd_cwnd * veno->basertt);
149		target_cwnd <<= V_PARAM_SHIFT;
150		do_div(target_cwnd, rtt);
151
152		veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;
153
154		if (tp->snd_cwnd <= tp->snd_ssthresh) {
155			/* Slow start.  */
156			tcp_slow_start(tp, acked);
157		} else {
158			/* Congestion avoidance. */
159			if (veno->diff < beta) {
160				/* In the "non-congestive state", increase cwnd
161				 *  every rtt.
162				 */
163				tcp_cong_avoid_ai(tp, tp->snd_cwnd);
164			} else {
165				/* In the "congestive state", increase cwnd
166				 * every other rtt.
167				 */
168				if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
169					if (veno->inc &&
170					    tp->snd_cwnd < tp->snd_cwnd_clamp) {
171						tp->snd_cwnd++;
172						veno->inc = 0;
173					} else
174						veno->inc = 1;
175					tp->snd_cwnd_cnt = 0;
176				} else
177					tp->snd_cwnd_cnt++;
178			}
179
180		}
181		if (tp->snd_cwnd < 2)
182			tp->snd_cwnd = 2;
183		else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
184			tp->snd_cwnd = tp->snd_cwnd_clamp;
185	}
186	/* Wipe the slate clean for the next rtt. */
187	/* veno->cntrtt = 0; */
188	veno->minrtt = 0x7fffffff;
189}
190
191/* Veno MD phase */
192static u32 tcp_veno_ssthresh(struct sock *sk)
193{
194	const struct tcp_sock *tp = tcp_sk(sk);
195	struct veno *veno = inet_csk_ca(sk);
196
197	if (veno->diff < beta)
198		/* in "non-congestive state", cut cwnd by 1/5 */
199		return max(tp->snd_cwnd * 4 / 5, 2U);
200	else
201		/* in "congestive state", cut cwnd by 1/2 */
202		return max(tp->snd_cwnd >> 1U, 2U);
203}
204
205static struct tcp_congestion_ops tcp_veno __read_mostly = {
206	.init		= tcp_veno_init,
207	.ssthresh	= tcp_veno_ssthresh,
 
208	.cong_avoid	= tcp_veno_cong_avoid,
209	.pkts_acked	= tcp_veno_pkts_acked,
210	.set_state	= tcp_veno_state,
211	.cwnd_event	= tcp_veno_cwnd_event,
212
213	.owner		= THIS_MODULE,
214	.name		= "veno",
215};
216
217static int __init tcp_veno_register(void)
218{
219	BUILD_BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE);
220	tcp_register_congestion_control(&tcp_veno);
221	return 0;
222}
223
224static void __exit tcp_veno_unregister(void)
225{
226	tcp_unregister_congestion_control(&tcp_veno);
227}
228
229module_init(tcp_veno_register);
230module_exit(tcp_veno_unregister);
231
232MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu");
233MODULE_LICENSE("GPL");
234MODULE_DESCRIPTION("TCP Veno");
v4.17
  1/*
  2 * TCP Veno congestion control
  3 *
  4 * This is based on the congestion detection/avoidance scheme described in
  5 *    C. P. Fu, S. C. Liew.
  6 *    "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."
  7 *    IEEE Journal on Selected Areas in Communication,
  8 *    Feb. 2003.
  9 * 	See http://www.ie.cuhk.edu.hk/fileadmin/staff_upload/soung/Journal/J3.pdf
 10 */
 11
 12#include <linux/mm.h>
 13#include <linux/module.h>
 14#include <linux/skbuff.h>
 15#include <linux/inet_diag.h>
 16
 17#include <net/tcp.h>
 18
 19/* Default values of the Veno variables, in fixed-point representation
 20 * with V_PARAM_SHIFT bits to the right of the binary point.
 21 */
 22#define V_PARAM_SHIFT 1
 23static const int beta = 3 << V_PARAM_SHIFT;
 24
 25/* Veno variables */
 26struct veno {
 27	u8 doing_veno_now;	/* if true, do veno for this rtt */
 28	u16 cntrtt;		/* # of rtts measured within last rtt */
 29	u32 minrtt;		/* min of rtts measured within last rtt (in usec) */
 30	u32 basertt;		/* the min of all Veno rtt measurements seen (in usec) */
 31	u32 inc;		/* decide whether to increase cwnd */
 32	u32 diff;		/* calculate the diff rate */
 33};
 34
 35/* There are several situations when we must "re-start" Veno:
 36 *
 37 *  o when a connection is established
 38 *  o after an RTO
 39 *  o after fast recovery
 40 *  o when we send a packet and there is no outstanding
 41 *    unacknowledged data (restarting an idle connection)
 42 *
 43 */
 44static inline void veno_enable(struct sock *sk)
 45{
 46	struct veno *veno = inet_csk_ca(sk);
 47
 48	/* turn on Veno */
 49	veno->doing_veno_now = 1;
 50
 51	veno->minrtt = 0x7fffffff;
 52}
 53
 54static inline void veno_disable(struct sock *sk)
 55{
 56	struct veno *veno = inet_csk_ca(sk);
 57
 58	/* turn off Veno */
 59	veno->doing_veno_now = 0;
 60}
 61
 62static void tcp_veno_init(struct sock *sk)
 63{
 64	struct veno *veno = inet_csk_ca(sk);
 65
 66	veno->basertt = 0x7fffffff;
 67	veno->inc = 1;
 68	veno_enable(sk);
 69}
 70
 71/* Do rtt sampling needed for Veno. */
 72static void tcp_veno_pkts_acked(struct sock *sk,
 73				const struct ack_sample *sample)
 74{
 75	struct veno *veno = inet_csk_ca(sk);
 76	u32 vrtt;
 77
 78	if (sample->rtt_us < 0)
 79		return;
 80
 81	/* Never allow zero rtt or baseRTT */
 82	vrtt = sample->rtt_us + 1;
 83
 84	/* Filter to find propagation delay: */
 85	if (vrtt < veno->basertt)
 86		veno->basertt = vrtt;
 87
 88	/* Find the min rtt during the last rtt to find
 89	 * the current prop. delay + queuing delay:
 90	 */
 91	veno->minrtt = min(veno->minrtt, vrtt);
 92	veno->cntrtt++;
 93}
 94
 95static void tcp_veno_state(struct sock *sk, u8 ca_state)
 96{
 97	if (ca_state == TCP_CA_Open)
 98		veno_enable(sk);
 99	else
100		veno_disable(sk);
101}
102
103/*
104 * If the connection is idle and we are restarting,
105 * then we don't want to do any Veno calculations
106 * until we get fresh rtt samples.  So when we
107 * restart, we reset our Veno state to a clean
108 * state. After we get acks for this flight of
109 * packets, _then_ we can make Veno calculations
110 * again.
111 */
112static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event)
113{
114	if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)
115		tcp_veno_init(sk);
116}
117
118static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 
119{
120	struct tcp_sock *tp = tcp_sk(sk);
121	struct veno *veno = inet_csk_ca(sk);
122
123	if (!veno->doing_veno_now) {
124		tcp_reno_cong_avoid(sk, ack, acked);
125		return;
126	}
127
128	/* limited by applications */
129	if (!tcp_is_cwnd_limited(sk))
130		return;
131
132	/* We do the Veno calculations only if we got enough rtt samples */
133	if (veno->cntrtt <= 2) {
134		/* We don't have enough rtt samples to do the Veno
135		 * calculation, so we'll behave like Reno.
136		 */
137		tcp_reno_cong_avoid(sk, ack, acked);
138	} else {
139		u64 target_cwnd;
140		u32 rtt;
141
142		/* We have enough rtt samples, so, using the Veno
143		 * algorithm, we determine the state of the network.
144		 */
145
146		rtt = veno->minrtt;
147
148		target_cwnd = (u64)tp->snd_cwnd * veno->basertt;
149		target_cwnd <<= V_PARAM_SHIFT;
150		do_div(target_cwnd, rtt);
151
152		veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;
153
154		if (tcp_in_slow_start(tp)) {
155			/* Slow start.  */
156			tcp_slow_start(tp, acked);
157		} else {
158			/* Congestion avoidance. */
159			if (veno->diff < beta) {
160				/* In the "non-congestive state", increase cwnd
161				 *  every rtt.
162				 */
163				tcp_cong_avoid_ai(tp, tp->snd_cwnd, 1);
164			} else {
165				/* In the "congestive state", increase cwnd
166				 * every other rtt.
167				 */
168				if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
169					if (veno->inc &&
170					    tp->snd_cwnd < tp->snd_cwnd_clamp) {
171						tp->snd_cwnd++;
172						veno->inc = 0;
173					} else
174						veno->inc = 1;
175					tp->snd_cwnd_cnt = 0;
176				} else
177					tp->snd_cwnd_cnt++;
178			}
 
179		}
180		if (tp->snd_cwnd < 2)
181			tp->snd_cwnd = 2;
182		else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
183			tp->snd_cwnd = tp->snd_cwnd_clamp;
184	}
185	/* Wipe the slate clean for the next rtt. */
186	/* veno->cntrtt = 0; */
187	veno->minrtt = 0x7fffffff;
188}
189
190/* Veno MD phase */
191static u32 tcp_veno_ssthresh(struct sock *sk)
192{
193	const struct tcp_sock *tp = tcp_sk(sk);
194	struct veno *veno = inet_csk_ca(sk);
195
196	if (veno->diff < beta)
197		/* in "non-congestive state", cut cwnd by 1/5 */
198		return max(tp->snd_cwnd * 4 / 5, 2U);
199	else
200		/* in "congestive state", cut cwnd by 1/2 */
201		return max(tp->snd_cwnd >> 1U, 2U);
202}
203
204static struct tcp_congestion_ops tcp_veno __read_mostly = {
205	.init		= tcp_veno_init,
206	.ssthresh	= tcp_veno_ssthresh,
207	.undo_cwnd	= tcp_reno_undo_cwnd,
208	.cong_avoid	= tcp_veno_cong_avoid,
209	.pkts_acked	= tcp_veno_pkts_acked,
210	.set_state	= tcp_veno_state,
211	.cwnd_event	= tcp_veno_cwnd_event,
212
213	.owner		= THIS_MODULE,
214	.name		= "veno",
215};
216
217static int __init tcp_veno_register(void)
218{
219	BUILD_BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE);
220	tcp_register_congestion_control(&tcp_veno);
221	return 0;
222}
223
224static void __exit tcp_veno_unregister(void)
225{
226	tcp_unregister_congestion_control(&tcp_veno);
227}
228
229module_init(tcp_veno_register);
230module_exit(tcp_veno_unregister);
231
232MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu");
233MODULE_LICENSE("GPL");
234MODULE_DESCRIPTION("TCP Veno");