summaryrefslogtreecommitdiffstats
path: root/net/ipv4/tcp_veno.c
blob: a4d2d2d88dcae7c00cf4db83d8b13ce6b143b3b4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
/*
 * 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 http://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, u32 cnt, s32 rtt_us)
{
	struct veno *veno = inet_csk_ca(sk);
	u32 vrtt;

	if (rtt_us < 0)
		return;

	/* Never allow zero rtt or baseRTT */
	vrtt = 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)tp->snd_cwnd * veno->basertt;
		target_cwnd <<= V_PARAM_SHIFT;
		do_div(target_cwnd, rtt);

		veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;

		if (tp->snd_cwnd <= tp->snd_ssthresh) {
			/* Slow start.  */
			tcp_slow_start(tp, acked);
		} else {
			/* Congestion avoidance. */
			if (veno->diff < beta) {
				/* In the "non-congestive state", increase cwnd
				 *  every rtt.
				 */
				tcp_cong_avoid_ai(tp, tp->snd_cwnd);
			} else {
				/* In the "congestive state", increase cwnd
				 * every other rtt.
				 */
				if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
					if (veno->inc &&
					    tp->snd_cwnd < tp->snd_cwnd_clamp) {
						tp->snd_cwnd++;
						veno->inc = 0;
					} else
						veno->inc = 1;
					tp->snd_cwnd_cnt = 0;
				} else
					tp->snd_cwnd_cnt++;
			}
		}
		if (tp->snd_cwnd < 2)
			tp->snd_cwnd = 2;
		else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
			tp->snd_cwnd = 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(tp->snd_cwnd * 4 / 5, 2U);
	else
		/* in "congestive state", cut cwnd by 1/2 */
		return max(tp->snd_cwnd >> 1U, 2U);
}

static struct tcp_congestion_ops tcp_veno __read_mostly = {
	.init		= tcp_veno_init,
	.ssthresh	= tcp_veno_ssthresh,
	.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");
OpenPOWER on IntegriCloud