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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *
4 * YeAH TCP
5 *
6 * For further details look at:
7 * https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
8 *
9 */
10#include <linux/mm.h>
11#include <linux/module.h>
12#include <linux/skbuff.h>
13#include <linux/inet_diag.h>
14
15#include <net/tcp.h>
16
17#include "tcp_vegas.h"
18
19#define TCP_YEAH_ALPHA 80 /* number of packets queued at the bottleneck */
20#define TCP_YEAH_GAMMA 1 /* fraction of queue to be removed per rtt */
21#define TCP_YEAH_DELTA 3 /* log minimum fraction of cwnd to be removed on loss */
22#define TCP_YEAH_EPSILON 1 /* log maximum fraction to be removed on early decongestion */
23#define TCP_YEAH_PHY 8 /* maximum delta from base */
24#define TCP_YEAH_RHO 16 /* minimum number of consecutive rtt to consider competition on loss */
25#define TCP_YEAH_ZETA 50 /* minimum number of state switches to reset reno_count */
26
27#define TCP_SCALABLE_AI_CNT 100U
28
29/* YeAH variables */
30struct yeah {
31 struct vegas vegas; /* must be first */
32
33 /* YeAH */
34 u32 lastQ;
35 u32 doing_reno_now;
36
37 u32 reno_count;
38 u32 fast_count;
39
40 u32 pkts_acked;
41};
42
43static void tcp_yeah_init(struct sock *sk)
44{
45 struct tcp_sock *tp = tcp_sk(sk);
46 struct yeah *yeah = inet_csk_ca(sk);
47
48 tcp_vegas_init(sk);
49
50 yeah->doing_reno_now = 0;
51 yeah->lastQ = 0;
52
53 yeah->reno_count = 2;
54
55 /* Ensure the MD arithmetic works. This is somewhat pedantic,
56 * since I don't think we will see a cwnd this large. :) */
57 tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
58}
59
60static void tcp_yeah_pkts_acked(struct sock *sk,
61 const struct ack_sample *sample)
62{
63 const struct inet_connection_sock *icsk = inet_csk(sk);
64 struct yeah *yeah = inet_csk_ca(sk);
65
66 if (icsk->icsk_ca_state == TCP_CA_Open)
67 yeah->pkts_acked = sample->pkts_acked;
68
69 tcp_vegas_pkts_acked(sk, sample);
70}
71
72static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
73{
74 struct tcp_sock *tp = tcp_sk(sk);
75 struct yeah *yeah = inet_csk_ca(sk);
76
77 if (!tcp_is_cwnd_limited(sk))
78 return;
79
80 if (tcp_in_slow_start(tp))
81 tcp_slow_start(tp, acked);
82
83 else if (!yeah->doing_reno_now) {
84 /* Scalable */
85
86 tp->snd_cwnd_cnt += yeah->pkts_acked;
87 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)) {
88 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
89 tp->snd_cwnd++;
90 tp->snd_cwnd_cnt = 0;
91 }
92
93 yeah->pkts_acked = 1;
94
95 } else {
96 /* Reno */
97 tcp_cong_avoid_ai(tp, tp->snd_cwnd, 1);
98 }
99
100 /* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
101 *
102 * These are so named because they represent the approximate values
103 * of snd_una and snd_nxt at the beginning of the current RTT. More
104 * precisely, they represent the amount of data sent during the RTT.
105 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
106 * we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
107 * bytes of data have been ACKed during the course of the RTT, giving
108 * an "actual" rate of:
109 *
110 * (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
111 *
112 * Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
113 * because delayed ACKs can cover more than one segment, so they
114 * don't line up yeahly with the boundaries of RTTs.
115 *
116 * Another unfortunate fact of life is that delayed ACKs delay the
117 * advance of the left edge of our send window, so that the number
118 * of bytes we send in an RTT is often less than our cwnd will allow.
119 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
120 */
121
122 if (after(ack, yeah->vegas.beg_snd_nxt)) {
123 /* We do the Vegas calculations only if we got enough RTT
124 * samples that we can be reasonably sure that we got
125 * at least one RTT sample that wasn't from a delayed ACK.
126 * If we only had 2 samples total,
127 * then that means we're getting only 1 ACK per RTT, which
128 * means they're almost certainly delayed ACKs.
129 * If we have 3 samples, we should be OK.
130 */
131
132 if (yeah->vegas.cntRTT > 2) {
133 u32 rtt, queue;
134 u64 bw;
135
136 /* We have enough RTT samples, so, using the Vegas
137 * algorithm, we determine if we should increase or
138 * decrease cwnd, and by how much.
139 */
140
141 /* Pluck out the RTT we are using for the Vegas
142 * calculations. This is the min RTT seen during the
143 * last RTT. Taking the min filters out the effects
144 * of delayed ACKs, at the cost of noticing congestion
145 * a bit later.
146 */
147 rtt = yeah->vegas.minRTT;
148
149 /* Compute excess number of packets above bandwidth
150 * Avoid doing full 64 bit divide.
151 */
152 bw = tp->snd_cwnd;
153 bw *= rtt - yeah->vegas.baseRTT;
154 do_div(bw, rtt);
155 queue = bw;
156
157 if (queue > TCP_YEAH_ALPHA ||
158 rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
159 if (queue > TCP_YEAH_ALPHA &&
160 tp->snd_cwnd > yeah->reno_count) {
161 u32 reduction = min(queue / TCP_YEAH_GAMMA ,
162 tp->snd_cwnd >> TCP_YEAH_EPSILON);
163
164 tp->snd_cwnd -= reduction;
165
166 tp->snd_cwnd = max(tp->snd_cwnd,
167 yeah->reno_count);
168
169 tp->snd_ssthresh = tp->snd_cwnd;
170 }
171
172 if (yeah->reno_count <= 2)
173 yeah->reno_count = max(tp->snd_cwnd>>1, 2U);
174 else
175 yeah->reno_count++;
176
177 yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
178 0xffffffU);
179 } else {
180 yeah->fast_count++;
181
182 if (yeah->fast_count > TCP_YEAH_ZETA) {
183 yeah->reno_count = 2;
184 yeah->fast_count = 0;
185 }
186
187 yeah->doing_reno_now = 0;
188 }
189
190 yeah->lastQ = queue;
191 }
192
193 /* Save the extent of the current window so we can use this
194 * at the end of the next RTT.
195 */
196 yeah->vegas.beg_snd_una = yeah->vegas.beg_snd_nxt;
197 yeah->vegas.beg_snd_nxt = tp->snd_nxt;
198 yeah->vegas.beg_snd_cwnd = tp->snd_cwnd;
199
200 /* Wipe the slate clean for the next RTT. */
201 yeah->vegas.cntRTT = 0;
202 yeah->vegas.minRTT = 0x7fffffff;
203 }
204}
205
206static u32 tcp_yeah_ssthresh(struct sock *sk)
207{
208 const struct tcp_sock *tp = tcp_sk(sk);
209 struct yeah *yeah = inet_csk_ca(sk);
210 u32 reduction;
211
212 if (yeah->doing_reno_now < TCP_YEAH_RHO) {
213 reduction = yeah->lastQ;
214
215 reduction = min(reduction, max(tp->snd_cwnd>>1, 2U));
216
217 reduction = max(reduction, tp->snd_cwnd >> TCP_YEAH_DELTA);
218 } else
219 reduction = max(tp->snd_cwnd>>1, 2U);
220
221 yeah->fast_count = 0;
222 yeah->reno_count = max(yeah->reno_count>>1, 2U);
223
224 return max_t(int, tp->snd_cwnd - reduction, 2);
225}
226
227static struct tcp_congestion_ops tcp_yeah __read_mostly = {
228 .init = tcp_yeah_init,
229 .ssthresh = tcp_yeah_ssthresh,
230 .undo_cwnd = tcp_reno_undo_cwnd,
231 .cong_avoid = tcp_yeah_cong_avoid,
232 .set_state = tcp_vegas_state,
233 .cwnd_event = tcp_vegas_cwnd_event,
234 .get_info = tcp_vegas_get_info,
235 .pkts_acked = tcp_yeah_pkts_acked,
236
237 .owner = THIS_MODULE,
238 .name = "yeah",
239};
240
241static int __init tcp_yeah_register(void)
242{
243 BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
244 tcp_register_congestion_control(&tcp_yeah);
245 return 0;
246}
247
248static void __exit tcp_yeah_unregister(void)
249{
250 tcp_unregister_congestion_control(&tcp_yeah);
251}
252
253module_init(tcp_yeah_register);
254module_exit(tcp_yeah_unregister);
255
256MODULE_AUTHOR("Angelo P. Castellani");
257MODULE_LICENSE("GPL");
258MODULE_DESCRIPTION("YeAH TCP");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *
4 * YeAH TCP
5 *
6 * For further details look at:
7 * https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
8 *
9 */
10#include <linux/mm.h>
11#include <linux/module.h>
12#include <linux/skbuff.h>
13#include <linux/inet_diag.h>
14
15#include <net/tcp.h>
16
17#include "tcp_vegas.h"
18
19#define TCP_YEAH_ALPHA 80 /* number of packets queued at the bottleneck */
20#define TCP_YEAH_GAMMA 1 /* fraction of queue to be removed per rtt */
21#define TCP_YEAH_DELTA 3 /* log minimum fraction of cwnd to be removed on loss */
22#define TCP_YEAH_EPSILON 1 /* log maximum fraction to be removed on early decongestion */
23#define TCP_YEAH_PHY 8 /* maximum delta from base */
24#define TCP_YEAH_RHO 16 /* minimum number of consecutive rtt to consider competition on loss */
25#define TCP_YEAH_ZETA 50 /* minimum number of state switches to reset reno_count */
26
27#define TCP_SCALABLE_AI_CNT 100U
28
29/* YeAH variables */
30struct yeah {
31 struct vegas vegas; /* must be first */
32
33 /* YeAH */
34 u32 lastQ;
35 u32 doing_reno_now;
36
37 u32 reno_count;
38 u32 fast_count;
39};
40
41static void tcp_yeah_init(struct sock *sk)
42{
43 struct tcp_sock *tp = tcp_sk(sk);
44 struct yeah *yeah = inet_csk_ca(sk);
45
46 tcp_vegas_init(sk);
47
48 yeah->doing_reno_now = 0;
49 yeah->lastQ = 0;
50
51 yeah->reno_count = 2;
52
53 /* Ensure the MD arithmetic works. This is somewhat pedantic,
54 * since I don't think we will see a cwnd this large. :) */
55 tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
56}
57
58static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
59{
60 struct tcp_sock *tp = tcp_sk(sk);
61 struct yeah *yeah = inet_csk_ca(sk);
62
63 if (!tcp_is_cwnd_limited(sk))
64 return;
65
66 if (tcp_in_slow_start(tp)) {
67 acked = tcp_slow_start(tp, acked);
68 if (!acked)
69 goto do_vegas;
70 }
71
72 if (!yeah->doing_reno_now) {
73 /* Scalable */
74 tcp_cong_avoid_ai(tp, min(tcp_snd_cwnd(tp), TCP_SCALABLE_AI_CNT),
75 acked);
76 } else {
77 /* Reno */
78 tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
79 }
80
81 /* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
82 *
83 * These are so named because they represent the approximate values
84 * of snd_una and snd_nxt at the beginning of the current RTT. More
85 * precisely, they represent the amount of data sent during the RTT.
86 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
87 * we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
88 * bytes of data have been ACKed during the course of the RTT, giving
89 * an "actual" rate of:
90 *
91 * (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
92 *
93 * Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
94 * because delayed ACKs can cover more than one segment, so they
95 * don't line up yeahly with the boundaries of RTTs.
96 *
97 * Another unfortunate fact of life is that delayed ACKs delay the
98 * advance of the left edge of our send window, so that the number
99 * of bytes we send in an RTT is often less than our cwnd will allow.
100 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
101 */
102do_vegas:
103 if (after(ack, yeah->vegas.beg_snd_nxt)) {
104 /* We do the Vegas calculations only if we got enough RTT
105 * samples that we can be reasonably sure that we got
106 * at least one RTT sample that wasn't from a delayed ACK.
107 * If we only had 2 samples total,
108 * then that means we're getting only 1 ACK per RTT, which
109 * means they're almost certainly delayed ACKs.
110 * If we have 3 samples, we should be OK.
111 */
112
113 if (yeah->vegas.cntRTT > 2) {
114 u32 rtt, queue;
115 u64 bw;
116
117 /* We have enough RTT samples, so, using the Vegas
118 * algorithm, we determine if we should increase or
119 * decrease cwnd, and by how much.
120 */
121
122 /* Pluck out the RTT we are using for the Vegas
123 * calculations. This is the min RTT seen during the
124 * last RTT. Taking the min filters out the effects
125 * of delayed ACKs, at the cost of noticing congestion
126 * a bit later.
127 */
128 rtt = yeah->vegas.minRTT;
129
130 /* Compute excess number of packets above bandwidth
131 * Avoid doing full 64 bit divide.
132 */
133 bw = tcp_snd_cwnd(tp);
134 bw *= rtt - yeah->vegas.baseRTT;
135 do_div(bw, rtt);
136 queue = bw;
137
138 if (queue > TCP_YEAH_ALPHA ||
139 rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
140 if (queue > TCP_YEAH_ALPHA &&
141 tcp_snd_cwnd(tp) > yeah->reno_count) {
142 u32 reduction = min(queue / TCP_YEAH_GAMMA ,
143 tcp_snd_cwnd(tp) >> TCP_YEAH_EPSILON);
144
145 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) - reduction);
146
147 tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp),
148 yeah->reno_count));
149
150 tp->snd_ssthresh = tcp_snd_cwnd(tp);
151 }
152
153 if (yeah->reno_count <= 2)
154 yeah->reno_count = max(tcp_snd_cwnd(tp)>>1, 2U);
155 else
156 yeah->reno_count++;
157
158 yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
159 0xffffffU);
160 } else {
161 yeah->fast_count++;
162
163 if (yeah->fast_count > TCP_YEAH_ZETA) {
164 yeah->reno_count = 2;
165 yeah->fast_count = 0;
166 }
167
168 yeah->doing_reno_now = 0;
169 }
170
171 yeah->lastQ = queue;
172 }
173
174 /* Save the extent of the current window so we can use this
175 * at the end of the next RTT.
176 */
177 yeah->vegas.beg_snd_una = yeah->vegas.beg_snd_nxt;
178 yeah->vegas.beg_snd_nxt = tp->snd_nxt;
179 yeah->vegas.beg_snd_cwnd = tcp_snd_cwnd(tp);
180
181 /* Wipe the slate clean for the next RTT. */
182 yeah->vegas.cntRTT = 0;
183 yeah->vegas.minRTT = 0x7fffffff;
184 }
185}
186
187static u32 tcp_yeah_ssthresh(struct sock *sk)
188{
189 const struct tcp_sock *tp = tcp_sk(sk);
190 struct yeah *yeah = inet_csk_ca(sk);
191 u32 reduction;
192
193 if (yeah->doing_reno_now < TCP_YEAH_RHO) {
194 reduction = yeah->lastQ;
195
196 reduction = min(reduction, max(tcp_snd_cwnd(tp)>>1, 2U));
197
198 reduction = max(reduction, tcp_snd_cwnd(tp) >> TCP_YEAH_DELTA);
199 } else
200 reduction = max(tcp_snd_cwnd(tp)>>1, 2U);
201
202 yeah->fast_count = 0;
203 yeah->reno_count = max(yeah->reno_count>>1, 2U);
204
205 return max_t(int, tcp_snd_cwnd(tp) - reduction, 2);
206}
207
208static struct tcp_congestion_ops tcp_yeah __read_mostly = {
209 .init = tcp_yeah_init,
210 .ssthresh = tcp_yeah_ssthresh,
211 .undo_cwnd = tcp_reno_undo_cwnd,
212 .cong_avoid = tcp_yeah_cong_avoid,
213 .set_state = tcp_vegas_state,
214 .cwnd_event = tcp_vegas_cwnd_event,
215 .get_info = tcp_vegas_get_info,
216 .pkts_acked = tcp_vegas_pkts_acked,
217
218 .owner = THIS_MODULE,
219 .name = "yeah",
220};
221
222static int __init tcp_yeah_register(void)
223{
224 BUILD_BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
225 tcp_register_congestion_control(&tcp_yeah);
226 return 0;
227}
228
229static void __exit tcp_yeah_unregister(void)
230{
231 tcp_unregister_congestion_control(&tcp_yeah);
232}
233
234module_init(tcp_yeah_register);
235module_exit(tcp_yeah_unregister);
236
237MODULE_AUTHOR("Angelo P. Castellani");
238MODULE_LICENSE("GPL");
239MODULE_DESCRIPTION("YeAH TCP");