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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * TCP Veno congestion control
4 *
5 * This is based on the congestion detection/avoidance scheme described in
6 * C. P. Fu, S. C. Liew.
7 * "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."
8 * IEEE Journal on Selected Areas in Communication,
9 * Feb. 2003.
10 * See https://www.ie.cuhk.edu.hk/fileadmin/staff_upload/soung/Journal/J3.pdf
11 */
12
13#include <linux/mm.h>
14#include <linux/module.h>
15#include <linux/skbuff.h>
16#include <linux/inet_diag.h>
17
18#include <net/tcp.h>
19
20/* Default values of the Veno variables, in fixed-point representation
21 * with V_PARAM_SHIFT bits to the right of the binary point.
22 */
23#define V_PARAM_SHIFT 1
24static const int beta = 3 << V_PARAM_SHIFT;
25
26/* Veno variables */
27struct veno {
28 u8 doing_veno_now; /* if true, do veno for this rtt */
29 u16 cntrtt; /* # of rtts measured within last rtt */
30 u32 minrtt; /* min of rtts measured within last rtt (in usec) */
31 u32 basertt; /* the min of all Veno rtt measurements seen (in usec) */
32 u32 inc; /* decide whether to increase cwnd */
33 u32 diff; /* calculate the diff rate */
34};
35
36/* There are several situations when we must "re-start" Veno:
37 *
38 * o when a connection is established
39 * o after an RTO
40 * o after fast recovery
41 * o when we send a packet and there is no outstanding
42 * unacknowledged data (restarting an idle connection)
43 *
44 */
45static inline void veno_enable(struct sock *sk)
46{
47 struct veno *veno = inet_csk_ca(sk);
48
49 /* turn on Veno */
50 veno->doing_veno_now = 1;
51
52 veno->minrtt = 0x7fffffff;
53}
54
55static inline void veno_disable(struct sock *sk)
56{
57 struct veno *veno = inet_csk_ca(sk);
58
59 /* turn off Veno */
60 veno->doing_veno_now = 0;
61}
62
63static void tcp_veno_init(struct sock *sk)
64{
65 struct veno *veno = inet_csk_ca(sk);
66
67 veno->basertt = 0x7fffffff;
68 veno->inc = 1;
69 veno_enable(sk);
70}
71
72/* Do rtt sampling needed for Veno. */
73static void tcp_veno_pkts_acked(struct sock *sk,
74 const struct ack_sample *sample)
75{
76 struct veno *veno = inet_csk_ca(sk);
77 u32 vrtt;
78
79 if (sample->rtt_us < 0)
80 return;
81
82 /* Never allow zero rtt or baseRTT */
83 vrtt = sample->rtt_us + 1;
84
85 /* Filter to find propagation delay: */
86 if (vrtt < veno->basertt)
87 veno->basertt = vrtt;
88
89 /* Find the min rtt during the last rtt to find
90 * the current prop. delay + queuing delay:
91 */
92 veno->minrtt = min(veno->minrtt, vrtt);
93 veno->cntrtt++;
94}
95
96static void tcp_veno_state(struct sock *sk, u8 ca_state)
97{
98 if (ca_state == TCP_CA_Open)
99 veno_enable(sk);
100 else
101 veno_disable(sk);
102}
103
104/*
105 * If the connection is idle and we are restarting,
106 * then we don't want to do any Veno calculations
107 * until we get fresh rtt samples. So when we
108 * restart, we reset our Veno state to a clean
109 * state. After we get acks for this flight of
110 * packets, _then_ we can make Veno calculations
111 * again.
112 */
113static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event)
114{
115 if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)
116 tcp_veno_init(sk);
117}
118
119static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
120{
121 struct tcp_sock *tp = tcp_sk(sk);
122 struct veno *veno = inet_csk_ca(sk);
123
124 if (!veno->doing_veno_now) {
125 tcp_reno_cong_avoid(sk, ack, acked);
126 return;
127 }
128
129 /* limited by applications */
130 if (!tcp_is_cwnd_limited(sk))
131 return;
132
133 /* We do the Veno calculations only if we got enough rtt samples */
134 if (veno->cntrtt <= 2) {
135 /* We don't have enough rtt samples to do the Veno
136 * calculation, so we'll behave like Reno.
137 */
138 tcp_reno_cong_avoid(sk, ack, acked);
139 } else {
140 u64 target_cwnd;
141 u32 rtt;
142
143 /* We have enough rtt samples, so, using the Veno
144 * algorithm, we determine the state of the network.
145 */
146
147 rtt = veno->minrtt;
148
149 target_cwnd = (u64)tcp_snd_cwnd(tp) * veno->basertt;
150 target_cwnd <<= V_PARAM_SHIFT;
151 do_div(target_cwnd, rtt);
152
153 veno->diff = (tcp_snd_cwnd(tp) << V_PARAM_SHIFT) - target_cwnd;
154
155 if (tcp_in_slow_start(tp)) {
156 /* Slow start. */
157 acked = tcp_slow_start(tp, acked);
158 if (!acked)
159 goto done;
160 }
161
162 /* Congestion avoidance. */
163 if (veno->diff < beta) {
164 /* In the "non-congestive state", increase cwnd
165 * every rtt.
166 */
167 tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
168 } else {
169 /* In the "congestive state", increase cwnd
170 * every other rtt.
171 */
172 if (tp->snd_cwnd_cnt >= tcp_snd_cwnd(tp)) {
173 if (veno->inc &&
174 tcp_snd_cwnd(tp) < tp->snd_cwnd_clamp) {
175 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
176 veno->inc = 0;
177 } else
178 veno->inc = 1;
179 tp->snd_cwnd_cnt = 0;
180 } else
181 tp->snd_cwnd_cnt += acked;
182 }
183done:
184 if (tcp_snd_cwnd(tp) < 2)
185 tcp_snd_cwnd_set(tp, 2);
186 else if (tcp_snd_cwnd(tp) > tp->snd_cwnd_clamp)
187 tcp_snd_cwnd_set(tp, tp->snd_cwnd_clamp);
188 }
189 /* Wipe the slate clean for the next rtt. */
190 /* veno->cntrtt = 0; */
191 veno->minrtt = 0x7fffffff;
192}
193
194/* Veno MD phase */
195static u32 tcp_veno_ssthresh(struct sock *sk)
196{
197 const struct tcp_sock *tp = tcp_sk(sk);
198 struct veno *veno = inet_csk_ca(sk);
199
200 if (veno->diff < beta)
201 /* in "non-congestive state", cut cwnd by 1/5 */
202 return max(tcp_snd_cwnd(tp) * 4 / 5, 2U);
203 else
204 /* in "congestive state", cut cwnd by 1/2 */
205 return max(tcp_snd_cwnd(tp) >> 1U, 2U);
206}
207
208static struct tcp_congestion_ops tcp_veno __read_mostly = {
209 .init = tcp_veno_init,
210 .ssthresh = tcp_veno_ssthresh,
211 .undo_cwnd = tcp_reno_undo_cwnd,
212 .cong_avoid = tcp_veno_cong_avoid,
213 .pkts_acked = tcp_veno_pkts_acked,
214 .set_state = tcp_veno_state,
215 .cwnd_event = tcp_veno_cwnd_event,
216
217 .owner = THIS_MODULE,
218 .name = "veno",
219};
220
221static int __init tcp_veno_register(void)
222{
223 BUILD_BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE);
224 tcp_register_congestion_control(&tcp_veno);
225 return 0;
226}
227
228static void __exit tcp_veno_unregister(void)
229{
230 tcp_unregister_congestion_control(&tcp_veno);
231}
232
233module_init(tcp_veno_register);
234module_exit(tcp_veno_unregister);
235
236MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu");
237MODULE_LICENSE("GPL");
238MODULE_DESCRIPTION("TCP Veno");
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 in_flight)
118{
119 struct tcp_sock *tp = tcp_sk(sk);
120 struct veno *veno = inet_csk_ca(sk);
121
122 if (!veno->doing_veno_now) {
123 tcp_reno_cong_avoid(sk, ack, in_flight);
124 return;
125 }
126
127 /* limited by applications */
128 if (!tcp_is_cwnd_limited(sk, in_flight))
129 return;
130
131 /* We do the Veno calculations only if we got enough rtt samples */
132 if (veno->cntrtt <= 2) {
133 /* We don't have enough rtt samples to do the Veno
134 * calculation, so we'll behave like Reno.
135 */
136 tcp_reno_cong_avoid(sk, ack, in_flight);
137 } else {
138 u64 target_cwnd;
139 u32 rtt;
140
141 /* We have enough rtt samples, so, using the Veno
142 * algorithm, we determine the state of the network.
143 */
144
145 rtt = veno->minrtt;
146
147 target_cwnd = (tp->snd_cwnd * veno->basertt);
148 target_cwnd <<= V_PARAM_SHIFT;
149 do_div(target_cwnd, rtt);
150
151 veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;
152
153 if (tp->snd_cwnd <= tp->snd_ssthresh) {
154 /* Slow start. */
155 tcp_slow_start(tp);
156 } else {
157 /* Congestion avoidance. */
158 if (veno->diff < beta) {
159 /* In the "non-congestive state", increase cwnd
160 * every rtt.
161 */
162 tcp_cong_avoid_ai(tp, tp->snd_cwnd);
163 } else {
164 /* In the "congestive state", increase cwnd
165 * every other rtt.
166 */
167 if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
168 if (veno->inc &&
169 tp->snd_cwnd < tp->snd_cwnd_clamp) {
170 tp->snd_cwnd++;
171 veno->inc = 0;
172 } else
173 veno->inc = 1;
174 tp->snd_cwnd_cnt = 0;
175 } else
176 tp->snd_cwnd_cnt++;
177 }
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 .flags = TCP_CONG_RTT_STAMP,
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");