1/*-
2 * Copyright (c) 2008-2010 Lawrence Stewart <lstewart@freebsd.org>
3 * Copyright (c) 2010 The FreeBSD Foundation
4 * All rights reserved.
5 *
6 * This software was developed by Lawrence Stewart while studying at the Centre
7 * for Advanced Internet Architectures, Swinburne University of Technology, made
8 * possible in part by a grant from the Cisco University Research Program Fund
9 * at Community Foundation Silicon Valley.
10 *
11 * Portions of this software were developed at the Centre for Advanced
12 * Internet Architectures, Swinburne University of Technology, Melbourne,
13 * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
14 *
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
17 * are met:
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37/*
38 * An implementation of the CUBIC congestion control algorithm for FreeBSD,
39 * based on the Internet Draft "draft-rhee-tcpm-cubic-02" by Rhee, Xu and Ha.
40 * Originally released as part of the NewTCP research project at Swinburne
41 * University of Technology's Centre for Advanced Internet Architectures,
42 * Melbourne, Australia, which was made possible in part by a grant from the
43 * Cisco University Research Program Fund at Community Foundation Silicon
44 * Valley. More details are available at:
45 * http://caia.swin.edu.au/urp/newtcp/
46 */
47
48#include <sys/cdefs.h>
| 1/*-
2 * Copyright (c) 2008-2010 Lawrence Stewart <lstewart@freebsd.org>
3 * Copyright (c) 2010 The FreeBSD Foundation
4 * All rights reserved.
5 *
6 * This software was developed by Lawrence Stewart while studying at the Centre
7 * for Advanced Internet Architectures, Swinburne University of Technology, made
8 * possible in part by a grant from the Cisco University Research Program Fund
9 * at Community Foundation Silicon Valley.
10 *
11 * Portions of this software were developed at the Centre for Advanced
12 * Internet Architectures, Swinburne University of Technology, Melbourne,
13 * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
14 *
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
17 * are met:
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37/*
38 * An implementation of the CUBIC congestion control algorithm for FreeBSD,
39 * based on the Internet Draft "draft-rhee-tcpm-cubic-02" by Rhee, Xu and Ha.
40 * Originally released as part of the NewTCP research project at Swinburne
41 * University of Technology's Centre for Advanced Internet Architectures,
42 * Melbourne, Australia, which was made possible in part by a grant from the
43 * Cisco University Research Program Fund at Community Foundation Silicon
44 * Valley. More details are available at:
45 * http://caia.swin.edu.au/urp/newtcp/
46 */
47
48#include <sys/cdefs.h>
|
67#include <netinet/cc/cc_cubic.h>
68#include <netinet/cc/cc_module.h>
69
70static void cubic_ack_received(struct cc_var *ccv, uint16_t type);
71static void cubic_cb_destroy(struct cc_var *ccv);
72static int cubic_cb_init(struct cc_var *ccv);
73static void cubic_cong_signal(struct cc_var *ccv, uint32_t type);
74static void cubic_conn_init(struct cc_var *ccv);
75static int cubic_mod_init(void);
76static void cubic_post_recovery(struct cc_var *ccv);
77static void cubic_record_rtt(struct cc_var *ccv);
78static void cubic_ssthresh_update(struct cc_var *ccv);
79
80struct cubic {
81 /* Cubic K in fixed point form with CUBIC_SHIFT worth of precision. */
82 int64_t K;
83 /* Sum of RTT samples across an epoch in ticks. */
84 int64_t sum_rtt_ticks;
85 /* cwnd at the most recent congestion event. */
86 unsigned long max_cwnd;
87 /* cwnd at the previous congestion event. */
88 unsigned long prev_max_cwnd;
89 /* Number of congestion events. */
90 uint32_t num_cong_events;
91 /* Minimum observed rtt in ticks. */
92 int min_rtt_ticks;
93 /* Mean observed rtt between congestion epochs. */
94 int mean_rtt_ticks;
95 /* ACKs since last congestion event. */
96 int epoch_ack_count;
97 /* Time of last congestion event in ticks. */
98 int t_last_cong;
99};
100
101static MALLOC_DEFINE(M_CUBIC, "cubic data",
102 "Per connection data required for the CUBIC congestion control algorithm");
103
104struct cc_algo cubic_cc_algo = {
105 .name = "cubic",
106 .ack_received = cubic_ack_received,
107 .cb_destroy = cubic_cb_destroy,
108 .cb_init = cubic_cb_init,
109 .cong_signal = cubic_cong_signal,
110 .conn_init = cubic_conn_init,
111 .mod_init = cubic_mod_init,
112 .post_recovery = cubic_post_recovery,
113};
114
115static void
116cubic_ack_received(struct cc_var *ccv, uint16_t type)
117{
118 struct cubic *cubic_data;
119 unsigned long w_tf, w_cubic_next;
120 int ticks_since_cong;
121
122 cubic_data = ccv->cc_data;
123 cubic_record_rtt(ccv);
124
125 /*
126 * Regular ACK and we're not in cong/fast recovery and we're cwnd
127 * limited and we're either not doing ABC or are slow starting or are
128 * doing ABC and we've sent a cwnd's worth of bytes.
129 */
130 if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
131 (ccv->flags & CCF_CWND_LIMITED) && (!V_tcp_do_rfc3465 ||
132 CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) ||
133 (V_tcp_do_rfc3465 && ccv->flags & CCF_ABC_SENTAWND))) {
134 /* Use the logic in NewReno ack_received() for slow start. */
135 if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) ||
136 cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)
137 newreno_cc_algo.ack_received(ccv, type);
138 else {
139 ticks_since_cong = ticks - cubic_data->t_last_cong;
140
141 /*
142 * The mean RTT is used to best reflect the equations in
143 * the I-D. Using min_rtt in the tf_cwnd calculation
144 * causes w_tf to grow much faster than it should if the
145 * RTT is dominated by network buffering rather than
146 * propogation delay.
147 */
148 w_tf = tf_cwnd(ticks_since_cong,
149 cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
150 CCV(ccv, t_maxseg));
151
152 w_cubic_next = cubic_cwnd(ticks_since_cong +
153 cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
154 CCV(ccv, t_maxseg), cubic_data->K);
155
156 ccv->flags &= ~CCF_ABC_SENTAWND;
157
158 if (w_cubic_next < w_tf)
159 /*
160 * TCP-friendly region, follow tf
161 * cwnd growth.
162 */
163 CCV(ccv, snd_cwnd) = w_tf;
164
165 else if (CCV(ccv, snd_cwnd) < w_cubic_next) {
166 /*
167 * Concave or convex region, follow CUBIC
168 * cwnd growth.
169 */
170 if (V_tcp_do_rfc3465)
171 CCV(ccv, snd_cwnd) = w_cubic_next;
172 else
173 CCV(ccv, snd_cwnd) += ((w_cubic_next -
174 CCV(ccv, snd_cwnd)) *
175 CCV(ccv, t_maxseg)) /
176 CCV(ccv, snd_cwnd);
177 }
178
179 /*
180 * If we're not in slow start and we're probing for a
181 * new cwnd limit at the start of a connection
182 * (happens when hostcache has a relevant entry),
183 * keep updating our current estimate of the
184 * max_cwnd.
185 */
186 if (cubic_data->num_cong_events == 0 &&
187 cubic_data->max_cwnd < CCV(ccv, snd_cwnd))
188 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
189 }
190 }
191}
192
193static void
194cubic_cb_destroy(struct cc_var *ccv)
195{
196
197 if (ccv->cc_data != NULL)
198 free(ccv->cc_data, M_CUBIC);
199}
200
201static int
202cubic_cb_init(struct cc_var *ccv)
203{
204 struct cubic *cubic_data;
205
206 cubic_data = malloc(sizeof(struct cubic), M_CUBIC, M_NOWAIT|M_ZERO);
207
208 if (cubic_data == NULL)
209 return (ENOMEM);
210
211 /* Init some key variables with sensible defaults. */
212 cubic_data->t_last_cong = ticks;
213 cubic_data->min_rtt_ticks = TCPTV_SRTTBASE;
214 cubic_data->mean_rtt_ticks = 1;
215
216 ccv->cc_data = cubic_data;
217
218 return (0);
219}
220
221/*
222 * Perform any necessary tasks before we enter congestion recovery.
223 */
224static void
225cubic_cong_signal(struct cc_var *ccv, uint32_t type)
226{
227 struct cubic *cubic_data;
228
229 cubic_data = ccv->cc_data;
230
231 switch (type) {
232 case CC_NDUPACK:
233 if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
234 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
235 cubic_ssthresh_update(ccv);
236 cubic_data->num_cong_events++;
237 cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
238 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
239 }
240 ENTER_RECOVERY(CCV(ccv, t_flags));
241 }
242 break;
243
244 case CC_ECN:
245 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
246 cubic_ssthresh_update(ccv);
247 cubic_data->num_cong_events++;
248 cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
249 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
250 cubic_data->t_last_cong = ticks;
251 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
252 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
253 }
254 break;
255
256 case CC_RTO:
257 /*
258 * Grab the current time and record it so we know when the
259 * most recent congestion event was. Only record it when the
260 * timeout has fired more than once, as there is a reasonable
261 * chance the first one is a false alarm and may not indicate
262 * congestion.
263 */
264 if (CCV(ccv, t_rxtshift) >= 2)
265 cubic_data->num_cong_events++;
266 cubic_data->t_last_cong = ticks;
267 break;
268 }
269}
270
271static void
272cubic_conn_init(struct cc_var *ccv)
273{
274 struct cubic *cubic_data;
275
276 cubic_data = ccv->cc_data;
277
278 /*
279 * Ensure we have a sane initial value for max_cwnd recorded. Without
280 * this here bad things happen when entries from the TCP hostcache
281 * get used.
282 */
283 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
284}
285
286static int
287cubic_mod_init(void)
288{
289
290 cubic_cc_algo.after_idle = newreno_cc_algo.after_idle;
291
292 return (0);
293}
294
295/*
296 * Perform any necessary tasks before we exit congestion recovery.
297 */
298static void
299cubic_post_recovery(struct cc_var *ccv)
300{
301 struct cubic *cubic_data;
302 int pipe;
303
304 cubic_data = ccv->cc_data;
305 pipe = 0;
306
307 /* Fast convergence heuristic. */
308 if (cubic_data->max_cwnd < cubic_data->prev_max_cwnd)
309 cubic_data->max_cwnd = (cubic_data->max_cwnd * CUBIC_FC_FACTOR)
310 >> CUBIC_SHIFT;
311
312 if (IN_FASTRECOVERY(CCV(ccv, t_flags))) {
313 /*
314 * If inflight data is less than ssthresh, set cwnd
315 * conservatively to avoid a burst of data, as suggested in
316 * the NewReno RFC. Otherwise, use the CUBIC method.
317 *
318 * XXXLAS: Find a way to do this without needing curack
319 */
320 if (V_tcp_do_rfc6675_pipe)
321 pipe = tcp_compute_pipe(ccv->ccvc.tcp);
322 else
323 pipe = CCV(ccv, snd_max) - ccv->curack;
324
325 if (pipe < CCV(ccv, snd_ssthresh))
326 CCV(ccv, snd_cwnd) = pipe + CCV(ccv, t_maxseg);
327 else
328 /* Update cwnd based on beta and adjusted max_cwnd. */
329 CCV(ccv, snd_cwnd) = max(1, ((CUBIC_BETA *
330 cubic_data->max_cwnd) >> CUBIC_SHIFT));
331 }
332 cubic_data->t_last_cong = ticks;
333
334 /* Calculate the average RTT between congestion epochs. */
335 if (cubic_data->epoch_ack_count > 0 &&
336 cubic_data->sum_rtt_ticks >= cubic_data->epoch_ack_count) {
337 cubic_data->mean_rtt_ticks = (int)(cubic_data->sum_rtt_ticks /
338 cubic_data->epoch_ack_count);
339 }
340
341 cubic_data->epoch_ack_count = 0;
342 cubic_data->sum_rtt_ticks = 0;
343 cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, t_maxseg));
344}
345
346/*
347 * Record the min RTT and sum samples for the epoch average RTT calculation.
348 */
349static void
350cubic_record_rtt(struct cc_var *ccv)
351{
352 struct cubic *cubic_data;
353 int t_srtt_ticks;
354
355 /* Ignore srtt until a min number of samples have been taken. */
356 if (CCV(ccv, t_rttupdated) >= CUBIC_MIN_RTT_SAMPLES) {
357 cubic_data = ccv->cc_data;
358 t_srtt_ticks = CCV(ccv, t_srtt) / TCP_RTT_SCALE;
359
360 /*
361 * Record the current SRTT as our minrtt if it's the smallest
362 * we've seen or minrtt is currently equal to its initialised
363 * value.
364 *
365 * XXXLAS: Should there be some hysteresis for minrtt?
366 */
367 if ((t_srtt_ticks < cubic_data->min_rtt_ticks ||
368 cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)) {
369 cubic_data->min_rtt_ticks = max(1, t_srtt_ticks);
370
371 /*
372 * If the connection is within its first congestion
373 * epoch, ensure we prime mean_rtt_ticks with a
374 * reasonable value until the epoch average RTT is
375 * calculated in cubic_post_recovery().
376 */
377 if (cubic_data->min_rtt_ticks >
378 cubic_data->mean_rtt_ticks)
379 cubic_data->mean_rtt_ticks =
380 cubic_data->min_rtt_ticks;
381 }
382
383 /* Sum samples for epoch average RTT calculation. */
384 cubic_data->sum_rtt_ticks += t_srtt_ticks;
385 cubic_data->epoch_ack_count++;
386 }
387}
388
389/*
390 * Update the ssthresh in the event of congestion.
391 */
392static void
393cubic_ssthresh_update(struct cc_var *ccv)
394{
395 struct cubic *cubic_data;
396
397 cubic_data = ccv->cc_data;
398
399 /*
400 * On the first congestion event, set ssthresh to cwnd * 0.5, on
401 * subsequent congestion events, set it to cwnd * beta.
402 */
403 if (cubic_data->num_cong_events == 0)
404 CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd) >> 1;
405 else
406 CCV(ccv, snd_ssthresh) = (CCV(ccv, snd_cwnd) * CUBIC_BETA)
407 >> CUBIC_SHIFT;
408}
409
410
411DECLARE_CC_MODULE(cubic, &cubic_cc_algo);
| 67#include <netinet/cc/cc_cubic.h>
68#include <netinet/cc/cc_module.h>
69
70static void cubic_ack_received(struct cc_var *ccv, uint16_t type);
71static void cubic_cb_destroy(struct cc_var *ccv);
72static int cubic_cb_init(struct cc_var *ccv);
73static void cubic_cong_signal(struct cc_var *ccv, uint32_t type);
74static void cubic_conn_init(struct cc_var *ccv);
75static int cubic_mod_init(void);
76static void cubic_post_recovery(struct cc_var *ccv);
77static void cubic_record_rtt(struct cc_var *ccv);
78static void cubic_ssthresh_update(struct cc_var *ccv);
79
80struct cubic {
81 /* Cubic K in fixed point form with CUBIC_SHIFT worth of precision. */
82 int64_t K;
83 /* Sum of RTT samples across an epoch in ticks. */
84 int64_t sum_rtt_ticks;
85 /* cwnd at the most recent congestion event. */
86 unsigned long max_cwnd;
87 /* cwnd at the previous congestion event. */
88 unsigned long prev_max_cwnd;
89 /* Number of congestion events. */
90 uint32_t num_cong_events;
91 /* Minimum observed rtt in ticks. */
92 int min_rtt_ticks;
93 /* Mean observed rtt between congestion epochs. */
94 int mean_rtt_ticks;
95 /* ACKs since last congestion event. */
96 int epoch_ack_count;
97 /* Time of last congestion event in ticks. */
98 int t_last_cong;
99};
100
101static MALLOC_DEFINE(M_CUBIC, "cubic data",
102 "Per connection data required for the CUBIC congestion control algorithm");
103
104struct cc_algo cubic_cc_algo = {
105 .name = "cubic",
106 .ack_received = cubic_ack_received,
107 .cb_destroy = cubic_cb_destroy,
108 .cb_init = cubic_cb_init,
109 .cong_signal = cubic_cong_signal,
110 .conn_init = cubic_conn_init,
111 .mod_init = cubic_mod_init,
112 .post_recovery = cubic_post_recovery,
113};
114
115static void
116cubic_ack_received(struct cc_var *ccv, uint16_t type)
117{
118 struct cubic *cubic_data;
119 unsigned long w_tf, w_cubic_next;
120 int ticks_since_cong;
121
122 cubic_data = ccv->cc_data;
123 cubic_record_rtt(ccv);
124
125 /*
126 * Regular ACK and we're not in cong/fast recovery and we're cwnd
127 * limited and we're either not doing ABC or are slow starting or are
128 * doing ABC and we've sent a cwnd's worth of bytes.
129 */
130 if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
131 (ccv->flags & CCF_CWND_LIMITED) && (!V_tcp_do_rfc3465 ||
132 CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) ||
133 (V_tcp_do_rfc3465 && ccv->flags & CCF_ABC_SENTAWND))) {
134 /* Use the logic in NewReno ack_received() for slow start. */
135 if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) ||
136 cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)
137 newreno_cc_algo.ack_received(ccv, type);
138 else {
139 ticks_since_cong = ticks - cubic_data->t_last_cong;
140
141 /*
142 * The mean RTT is used to best reflect the equations in
143 * the I-D. Using min_rtt in the tf_cwnd calculation
144 * causes w_tf to grow much faster than it should if the
145 * RTT is dominated by network buffering rather than
146 * propogation delay.
147 */
148 w_tf = tf_cwnd(ticks_since_cong,
149 cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
150 CCV(ccv, t_maxseg));
151
152 w_cubic_next = cubic_cwnd(ticks_since_cong +
153 cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
154 CCV(ccv, t_maxseg), cubic_data->K);
155
156 ccv->flags &= ~CCF_ABC_SENTAWND;
157
158 if (w_cubic_next < w_tf)
159 /*
160 * TCP-friendly region, follow tf
161 * cwnd growth.
162 */
163 CCV(ccv, snd_cwnd) = w_tf;
164
165 else if (CCV(ccv, snd_cwnd) < w_cubic_next) {
166 /*
167 * Concave or convex region, follow CUBIC
168 * cwnd growth.
169 */
170 if (V_tcp_do_rfc3465)
171 CCV(ccv, snd_cwnd) = w_cubic_next;
172 else
173 CCV(ccv, snd_cwnd) += ((w_cubic_next -
174 CCV(ccv, snd_cwnd)) *
175 CCV(ccv, t_maxseg)) /
176 CCV(ccv, snd_cwnd);
177 }
178
179 /*
180 * If we're not in slow start and we're probing for a
181 * new cwnd limit at the start of a connection
182 * (happens when hostcache has a relevant entry),
183 * keep updating our current estimate of the
184 * max_cwnd.
185 */
186 if (cubic_data->num_cong_events == 0 &&
187 cubic_data->max_cwnd < CCV(ccv, snd_cwnd))
188 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
189 }
190 }
191}
192
193static void
194cubic_cb_destroy(struct cc_var *ccv)
195{
196
197 if (ccv->cc_data != NULL)
198 free(ccv->cc_data, M_CUBIC);
199}
200
201static int
202cubic_cb_init(struct cc_var *ccv)
203{
204 struct cubic *cubic_data;
205
206 cubic_data = malloc(sizeof(struct cubic), M_CUBIC, M_NOWAIT|M_ZERO);
207
208 if (cubic_data == NULL)
209 return (ENOMEM);
210
211 /* Init some key variables with sensible defaults. */
212 cubic_data->t_last_cong = ticks;
213 cubic_data->min_rtt_ticks = TCPTV_SRTTBASE;
214 cubic_data->mean_rtt_ticks = 1;
215
216 ccv->cc_data = cubic_data;
217
218 return (0);
219}
220
221/*
222 * Perform any necessary tasks before we enter congestion recovery.
223 */
224static void
225cubic_cong_signal(struct cc_var *ccv, uint32_t type)
226{
227 struct cubic *cubic_data;
228
229 cubic_data = ccv->cc_data;
230
231 switch (type) {
232 case CC_NDUPACK:
233 if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
234 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
235 cubic_ssthresh_update(ccv);
236 cubic_data->num_cong_events++;
237 cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
238 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
239 }
240 ENTER_RECOVERY(CCV(ccv, t_flags));
241 }
242 break;
243
244 case CC_ECN:
245 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
246 cubic_ssthresh_update(ccv);
247 cubic_data->num_cong_events++;
248 cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
249 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
250 cubic_data->t_last_cong = ticks;
251 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
252 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
253 }
254 break;
255
256 case CC_RTO:
257 /*
258 * Grab the current time and record it so we know when the
259 * most recent congestion event was. Only record it when the
260 * timeout has fired more than once, as there is a reasonable
261 * chance the first one is a false alarm and may not indicate
262 * congestion.
263 */
264 if (CCV(ccv, t_rxtshift) >= 2)
265 cubic_data->num_cong_events++;
266 cubic_data->t_last_cong = ticks;
267 break;
268 }
269}
270
271static void
272cubic_conn_init(struct cc_var *ccv)
273{
274 struct cubic *cubic_data;
275
276 cubic_data = ccv->cc_data;
277
278 /*
279 * Ensure we have a sane initial value for max_cwnd recorded. Without
280 * this here bad things happen when entries from the TCP hostcache
281 * get used.
282 */
283 cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
284}
285
286static int
287cubic_mod_init(void)
288{
289
290 cubic_cc_algo.after_idle = newreno_cc_algo.after_idle;
291
292 return (0);
293}
294
295/*
296 * Perform any necessary tasks before we exit congestion recovery.
297 */
298static void
299cubic_post_recovery(struct cc_var *ccv)
300{
301 struct cubic *cubic_data;
302 int pipe;
303
304 cubic_data = ccv->cc_data;
305 pipe = 0;
306
307 /* Fast convergence heuristic. */
308 if (cubic_data->max_cwnd < cubic_data->prev_max_cwnd)
309 cubic_data->max_cwnd = (cubic_data->max_cwnd * CUBIC_FC_FACTOR)
310 >> CUBIC_SHIFT;
311
312 if (IN_FASTRECOVERY(CCV(ccv, t_flags))) {
313 /*
314 * If inflight data is less than ssthresh, set cwnd
315 * conservatively to avoid a burst of data, as suggested in
316 * the NewReno RFC. Otherwise, use the CUBIC method.
317 *
318 * XXXLAS: Find a way to do this without needing curack
319 */
320 if (V_tcp_do_rfc6675_pipe)
321 pipe = tcp_compute_pipe(ccv->ccvc.tcp);
322 else
323 pipe = CCV(ccv, snd_max) - ccv->curack;
324
325 if (pipe < CCV(ccv, snd_ssthresh))
326 CCV(ccv, snd_cwnd) = pipe + CCV(ccv, t_maxseg);
327 else
328 /* Update cwnd based on beta and adjusted max_cwnd. */
329 CCV(ccv, snd_cwnd) = max(1, ((CUBIC_BETA *
330 cubic_data->max_cwnd) >> CUBIC_SHIFT));
331 }
332 cubic_data->t_last_cong = ticks;
333
334 /* Calculate the average RTT between congestion epochs. */
335 if (cubic_data->epoch_ack_count > 0 &&
336 cubic_data->sum_rtt_ticks >= cubic_data->epoch_ack_count) {
337 cubic_data->mean_rtt_ticks = (int)(cubic_data->sum_rtt_ticks /
338 cubic_data->epoch_ack_count);
339 }
340
341 cubic_data->epoch_ack_count = 0;
342 cubic_data->sum_rtt_ticks = 0;
343 cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, t_maxseg));
344}
345
346/*
347 * Record the min RTT and sum samples for the epoch average RTT calculation.
348 */
349static void
350cubic_record_rtt(struct cc_var *ccv)
351{
352 struct cubic *cubic_data;
353 int t_srtt_ticks;
354
355 /* Ignore srtt until a min number of samples have been taken. */
356 if (CCV(ccv, t_rttupdated) >= CUBIC_MIN_RTT_SAMPLES) {
357 cubic_data = ccv->cc_data;
358 t_srtt_ticks = CCV(ccv, t_srtt) / TCP_RTT_SCALE;
359
360 /*
361 * Record the current SRTT as our minrtt if it's the smallest
362 * we've seen or minrtt is currently equal to its initialised
363 * value.
364 *
365 * XXXLAS: Should there be some hysteresis for minrtt?
366 */
367 if ((t_srtt_ticks < cubic_data->min_rtt_ticks ||
368 cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)) {
369 cubic_data->min_rtt_ticks = max(1, t_srtt_ticks);
370
371 /*
372 * If the connection is within its first congestion
373 * epoch, ensure we prime mean_rtt_ticks with a
374 * reasonable value until the epoch average RTT is
375 * calculated in cubic_post_recovery().
376 */
377 if (cubic_data->min_rtt_ticks >
378 cubic_data->mean_rtt_ticks)
379 cubic_data->mean_rtt_ticks =
380 cubic_data->min_rtt_ticks;
381 }
382
383 /* Sum samples for epoch average RTT calculation. */
384 cubic_data->sum_rtt_ticks += t_srtt_ticks;
385 cubic_data->epoch_ack_count++;
386 }
387}
388
389/*
390 * Update the ssthresh in the event of congestion.
391 */
392static void
393cubic_ssthresh_update(struct cc_var *ccv)
394{
395 struct cubic *cubic_data;
396
397 cubic_data = ccv->cc_data;
398
399 /*
400 * On the first congestion event, set ssthresh to cwnd * 0.5, on
401 * subsequent congestion events, set it to cwnd * beta.
402 */
403 if (cubic_data->num_cong_events == 0)
404 CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd) >> 1;
405 else
406 CCV(ccv, snd_ssthresh) = (CCV(ccv, snd_cwnd) * CUBIC_BETA)
407 >> CUBIC_SHIFT;
408}
409
410
411DECLARE_CC_MODULE(cubic, &cubic_cc_algo);
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