1/*-
2 * Copyright (c) 2007-2008
3 * Swinburne University of Technology, Melbourne, Australia
4 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
5 * Copyright (c) 2014 Midori Kato <katoon@sfc.wide.ad.jp>
6 * Copyright (c) 2014 The FreeBSD Foundation
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31/*
32 * An implementation of the DCTCP algorithm for FreeBSD, based on
33 * "Data Center TCP (DCTCP)" by M. Alizadeh, A. Greenberg, D. A. Maltz,
34 * J. Padhye, P. Patel, B. Prabhakar, S. Sengupta, and M. Sridharan.,
35 * in ACM Conference on SIGCOMM 2010, New York, USA,
36 * Originally released as the contribution of Microsoft Research project.
37 */
38
39#include <sys/cdefs.h>
| 1/*-
2 * Copyright (c) 2007-2008
3 * Swinburne University of Technology, Melbourne, Australia
4 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
5 * Copyright (c) 2014 Midori Kato <katoon@sfc.wide.ad.jp>
6 * Copyright (c) 2014 The FreeBSD Foundation
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31/*
32 * An implementation of the DCTCP algorithm for FreeBSD, based on
33 * "Data Center TCP (DCTCP)" by M. Alizadeh, A. Greenberg, D. A. Maltz,
34 * J. Padhye, P. Patel, B. Prabhakar, S. Sengupta, and M. Sridharan.,
35 * in ACM Conference on SIGCOMM 2010, New York, USA,
36 * Originally released as the contribution of Microsoft Research project.
37 */
38
39#include <sys/cdefs.h>
|
57#include <netinet/cc/cc_module.h>
58
59#define CAST_PTR_INT(X) (*((int*)(X)))
60
61#define MAX_ALPHA_VALUE 1024
62static VNET_DEFINE(uint32_t, dctcp_alpha) = 0;
63#define V_dctcp_alpha VNET(dctcp_alpha)
64static VNET_DEFINE(uint32_t, dctcp_shift_g) = 4;
65#define V_dctcp_shift_g VNET(dctcp_shift_g)
66static VNET_DEFINE(uint32_t, dctcp_slowstart) = 0;
67#define V_dctcp_slowstart VNET(dctcp_slowstart)
68
69struct dctcp {
70 int bytes_ecn; /* # of marked bytes during a RTT */
71 int bytes_total; /* # of acked bytes during a RTT */
72 int alpha; /* the fraction of marked bytes */
73 int ce_prev; /* CE state of the last segment */
74 int save_sndnxt; /* end sequence number of the current window */
75 int ece_curr; /* ECE flag in this segment */
76 int ece_prev; /* ECE flag in the last segment */
77 uint32_t num_cong_events; /* # of congestion events */
78};
79
80static MALLOC_DEFINE(M_dctcp, "dctcp data",
81 "Per connection data required for the dctcp algorithm");
82
83static void dctcp_ack_received(struct cc_var *ccv, uint16_t type);
84static void dctcp_after_idle(struct cc_var *ccv);
85static void dctcp_cb_destroy(struct cc_var *ccv);
86static int dctcp_cb_init(struct cc_var *ccv);
87static void dctcp_cong_signal(struct cc_var *ccv, uint32_t type);
88static void dctcp_conn_init(struct cc_var *ccv);
89static void dctcp_post_recovery(struct cc_var *ccv);
90static void dctcp_ecnpkt_handler(struct cc_var *ccv);
91static void dctcp_update_alpha(struct cc_var *ccv);
92
93struct cc_algo dctcp_cc_algo = {
94 .name = "dctcp",
95 .ack_received = dctcp_ack_received,
96 .cb_destroy = dctcp_cb_destroy,
97 .cb_init = dctcp_cb_init,
98 .cong_signal = dctcp_cong_signal,
99 .conn_init = dctcp_conn_init,
100 .post_recovery = dctcp_post_recovery,
101 .ecnpkt_handler = dctcp_ecnpkt_handler,
102 .after_idle = dctcp_after_idle,
103};
104
105static void
106dctcp_ack_received(struct cc_var *ccv, uint16_t type)
107{
108 struct dctcp *dctcp_data;
109 int bytes_acked = 0;
110
111 dctcp_data = ccv->cc_data;
112
113 if (CCV(ccv, t_flags) & TF_ECN_PERMIT) {
114 /*
115 * DCTCP doesn't treat receipt of ECN marked packet as a
116 * congestion event. Thus, DCTCP always executes the ACK
117 * processing out of congestion recovery.
118 */
119 if (IN_CONGRECOVERY(CCV(ccv, t_flags))) {
120 EXIT_CONGRECOVERY(CCV(ccv, t_flags));
121 newreno_cc_algo.ack_received(ccv, type);
122 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
123 } else
124 newreno_cc_algo.ack_received(ccv, type);
125
126 if (type == CC_DUPACK)
127 bytes_acked = CCV(ccv, t_maxseg);
128
129 if (type == CC_ACK)
130 bytes_acked = ccv->bytes_this_ack;
131
132 /* Update total bytes. */
133 dctcp_data->bytes_total += bytes_acked;
134
135 /* Update total marked bytes. */
136 if (dctcp_data->ece_curr) {
137 if (!dctcp_data->ece_prev
138 && bytes_acked > CCV(ccv, t_maxseg)) {
139 dctcp_data->bytes_ecn +=
140 (bytes_acked - CCV(ccv, t_maxseg));
141 } else
142 dctcp_data->bytes_ecn += bytes_acked;
143 dctcp_data->ece_prev = 1;
144 } else {
145 if (dctcp_data->ece_prev
146 && bytes_acked > CCV(ccv, t_maxseg))
147 dctcp_data->bytes_ecn += CCV(ccv, t_maxseg);
148 dctcp_data->ece_prev = 0;
149 }
150 dctcp_data->ece_curr = 0;
151
152 /*
153 * Update the fraction of marked bytes at the end of
154 * current window size.
155 */
156 if ((IN_FASTRECOVERY(CCV(ccv, t_flags)) &&
157 SEQ_GEQ(ccv->curack, CCV(ccv, snd_recover))) ||
158 (!IN_FASTRECOVERY(CCV(ccv, t_flags)) &&
159 SEQ_GT(ccv->curack, dctcp_data->save_sndnxt)))
160 dctcp_update_alpha(ccv);
161 } else
162 newreno_cc_algo.ack_received(ccv, type);
163}
164
165static void
166dctcp_after_idle(struct cc_var *ccv)
167{
168 struct dctcp *dctcp_data;
169
170 dctcp_data = ccv->cc_data;
171
172 /* Initialize internal parameters after idle time */
173 dctcp_data->bytes_ecn = 0;
174 dctcp_data->bytes_total = 0;
175 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
176 dctcp_data->alpha = V_dctcp_alpha;
177 dctcp_data->ece_curr = 0;
178 dctcp_data->ece_prev = 0;
179 dctcp_data->num_cong_events = 0;
180
181 dctcp_cc_algo.after_idle = newreno_cc_algo.after_idle;
182}
183
184static void
185dctcp_cb_destroy(struct cc_var *ccv)
186{
187 if (ccv->cc_data != NULL)
188 free(ccv->cc_data, M_dctcp);
189}
190
191static int
192dctcp_cb_init(struct cc_var *ccv)
193{
194 struct dctcp *dctcp_data;
195
196 dctcp_data = malloc(sizeof(struct dctcp), M_dctcp, M_NOWAIT|M_ZERO);
197
198 if (dctcp_data == NULL)
199 return (ENOMEM);
200
201 /* Initialize some key variables with sensible defaults. */
202 dctcp_data->bytes_ecn = 0;
203 dctcp_data->bytes_total = 0;
204 /*
205 * When alpha is set to 0 in the beggining, DCTCP sender transfers as
206 * much data as possible until the value converges which may expand the
207 * queueing delay at the switch. When alpha is set to 1, queueing delay
208 * is kept small.
209 * Throughput-sensitive applications should have alpha = 0
210 * Latency-sensitive applications should have alpha = 1
211 *
212 * Note: DCTCP draft suggests initial alpha to be 1 but we've decided to
213 * keep it 0 as default.
214 */
215 dctcp_data->alpha = V_dctcp_alpha;
216 dctcp_data->save_sndnxt = 0;
217 dctcp_data->ce_prev = 0;
218 dctcp_data->ece_curr = 0;
219 dctcp_data->ece_prev = 0;
220 dctcp_data->num_cong_events = 0;
221
222 ccv->cc_data = dctcp_data;
223 return (0);
224}
225
226/*
227 * Perform any necessary tasks before we enter congestion recovery.
228 */
229static void
230dctcp_cong_signal(struct cc_var *ccv, uint32_t type)
231{
232 struct dctcp *dctcp_data;
233 u_int win, mss;
234
235 dctcp_data = ccv->cc_data;
236 win = CCV(ccv, snd_cwnd);
237 mss = CCV(ccv, t_maxseg);
238
239 switch (type) {
240 case CC_NDUPACK:
241 if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
242 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
243 CCV(ccv, snd_ssthresh) = mss *
244 max(win / 2 / mss, 2);
245 dctcp_data->num_cong_events++;
246 } else {
247 /* cwnd has already updated as congestion
248 * recovery. Reverse cwnd value using
249 * snd_cwnd_prev and recalculate snd_ssthresh
250 */
251 win = CCV(ccv, snd_cwnd_prev);
252 CCV(ccv, snd_ssthresh) =
253 max(win / 2 / mss, 2) * mss;
254 }
255 ENTER_RECOVERY(CCV(ccv, t_flags));
256 }
257 break;
258 case CC_ECN:
259 /*
260 * Save current snd_cwnd when the host encounters both
261 * congestion recovery and fast recovery.
262 */
263 CCV(ccv, snd_cwnd_prev) = win;
264 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
265 if (V_dctcp_slowstart &&
266 dctcp_data->num_cong_events++ == 0) {
267 CCV(ccv, snd_ssthresh) =
268 mss * max(win / 2 / mss, 2);
269 dctcp_data->alpha = MAX_ALPHA_VALUE;
270 dctcp_data->bytes_ecn = 0;
271 dctcp_data->bytes_total = 0;
272 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
273 } else
274 CCV(ccv, snd_ssthresh) = max((win - ((win *
275 dctcp_data->alpha) >> 11)) / mss, 2) * mss;
276 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
277 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
278 }
279 dctcp_data->ece_curr = 1;
280 break;
281 case CC_RTO:
282 if (CCV(ccv, t_flags) & TF_ECN_PERMIT) {
283 CCV(ccv, t_flags) |= TF_ECN_SND_CWR;
284 dctcp_update_alpha(ccv);
285 dctcp_data->save_sndnxt += CCV(ccv, t_maxseg);
286 dctcp_data->num_cong_events++;
287 }
288 break;
289 }
290}
291
292static void
293dctcp_conn_init(struct cc_var *ccv)
294{
295 struct dctcp *dctcp_data;
296
297 dctcp_data = ccv->cc_data;
298
299 if (CCV(ccv, t_flags) & TF_ECN_PERMIT)
300 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
301}
302
303/*
304 * Perform any necessary tasks before we exit congestion recovery.
305 */
306static void
307dctcp_post_recovery(struct cc_var *ccv)
308{
309 dctcp_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
310
311 if (CCV(ccv, t_flags) & TF_ECN_PERMIT)
312 dctcp_update_alpha(ccv);
313}
314
315/*
316 * Execute an additional ECN processing using ECN field in IP header and the CWR
317 * bit in TCP header.
318 *
319 * delay_ack == 0 - Delayed ACK disabled
320 * delay_ack == 1 - Delayed ACK enabled
321 */
322
323static void
324dctcp_ecnpkt_handler(struct cc_var *ccv)
325{
326 struct dctcp *dctcp_data;
327 uint32_t ccflag;
328 int delay_ack;
329
330 dctcp_data = ccv->cc_data;
331 ccflag = ccv->flags;
332 delay_ack = 1;
333
334 /*
335 * DCTCP responses an ACK immediately when the CE state
336 * in between this segment and the last segment is not same.
337 */
338 if (ccflag & CCF_IPHDR_CE) {
339 if (!dctcp_data->ce_prev && (ccflag & CCF_DELACK))
340 delay_ack = 0;
341 dctcp_data->ce_prev = 1;
342 CCV(ccv, t_flags) |= TF_ECN_SND_ECE;
343 } else {
344 if (dctcp_data->ce_prev && (ccflag & CCF_DELACK))
345 delay_ack = 0;
346 dctcp_data->ce_prev = 0;
347 CCV(ccv, t_flags) &= ~TF_ECN_SND_ECE;
348 }
349
350 /* DCTCP sets delayed ack when this segment sets the CWR flag. */
351 if ((ccflag & CCF_DELACK) && (ccflag & CCF_TCPHDR_CWR))
352 delay_ack = 1;
353
354 if (delay_ack == 0)
355 ccv->flags |= CCF_ACKNOW;
356 else
357 ccv->flags &= ~CCF_ACKNOW;
358}
359
360/*
361 * Update the fraction of marked bytes represented as 'alpha'.
362 * Also initialize several internal parameters at the end of this function.
363 */
364static void
365dctcp_update_alpha(struct cc_var *ccv)
366{
367 struct dctcp *dctcp_data;
368 int alpha_prev;
369
370 dctcp_data = ccv->cc_data;
371 alpha_prev = dctcp_data->alpha;
372 dctcp_data->bytes_total = max(dctcp_data->bytes_total, 1);
373
374 /*
375 * Update alpha: alpha = (1 - g) * alpha + g * F.
376 * Here:
377 * g is weight factor
378 * recommaded to be set to 1/16
379 * small g = slow convergence between competitive DCTCP flows
380 * large g = impacts low utilization of bandwidth at switches
381 * F is fraction of marked segments in last RTT
382 * updated every RTT
383 * Alpha must be round to 0 - MAX_ALPHA_VALUE.
384 */
385 dctcp_data->alpha = min(alpha_prev - (alpha_prev >> V_dctcp_shift_g) +
386 (dctcp_data->bytes_ecn << (10 - V_dctcp_shift_g)) /
387 dctcp_data->bytes_total, MAX_ALPHA_VALUE);
388
389 /* Initialize internal parameters for next alpha calculation */
390 dctcp_data->bytes_ecn = 0;
391 dctcp_data->bytes_total = 0;
392 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
393}
394
395static int
396dctcp_alpha_handler(SYSCTL_HANDLER_ARGS)
397{
398 uint32_t new;
399 int error;
400
401 new = V_dctcp_alpha;
402 error = sysctl_handle_int(oidp, &new, 0, req);
403 if (error == 0 && req->newptr != NULL) {
404 if (CAST_PTR_INT(req->newptr) > 1)
405 error = EINVAL;
406 else {
407 if (new > MAX_ALPHA_VALUE)
408 V_dctcp_alpha = MAX_ALPHA_VALUE;
409 else
410 V_dctcp_alpha = new;
411 }
412 }
413
414 return (error);
415}
416
417static int
418dctcp_shift_g_handler(SYSCTL_HANDLER_ARGS)
419{
420 uint32_t new;
421 int error;
422
423 new = V_dctcp_shift_g;
424 error = sysctl_handle_int(oidp, &new, 0, req);
425 if (error == 0 && req->newptr != NULL) {
426 if (CAST_PTR_INT(req->newptr) > 1)
427 error = EINVAL;
428 else
429 V_dctcp_shift_g = new;
430 }
431
432 return (error);
433}
434
435static int
436dctcp_slowstart_handler(SYSCTL_HANDLER_ARGS)
437{
438 uint32_t new;
439 int error;
440
441 new = V_dctcp_slowstart;
442 error = sysctl_handle_int(oidp, &new, 0, req);
443 if (error == 0 && req->newptr != NULL) {
444 if (CAST_PTR_INT(req->newptr) > 1)
445 error = EINVAL;
446 else
447 V_dctcp_slowstart = new;
448 }
449
450 return (error);
451}
452
453SYSCTL_DECL(_net_inet_tcp_cc_dctcp);
454SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, dctcp, CTLFLAG_RW, NULL,
455 "dctcp congestion control related settings");
456
457SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, alpha,
458 CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_alpha), 0,
459 &dctcp_alpha_handler,
460 "IU", "dctcp alpha parameter");
461
462SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, shift_g,
463 CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_shift_g), 4,
464 &dctcp_shift_g_handler,
465 "IU", "dctcp shift parameter");
466
467SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, slowstart,
468 CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_slowstart), 0,
469 &dctcp_slowstart_handler,
470 "IU", "half CWND reduction after the first slow start");
471
472DECLARE_CC_MODULE(dctcp, &dctcp_cc_algo);
| 57#include <netinet/cc/cc_module.h>
58
59#define CAST_PTR_INT(X) (*((int*)(X)))
60
61#define MAX_ALPHA_VALUE 1024
62static VNET_DEFINE(uint32_t, dctcp_alpha) = 0;
63#define V_dctcp_alpha VNET(dctcp_alpha)
64static VNET_DEFINE(uint32_t, dctcp_shift_g) = 4;
65#define V_dctcp_shift_g VNET(dctcp_shift_g)
66static VNET_DEFINE(uint32_t, dctcp_slowstart) = 0;
67#define V_dctcp_slowstart VNET(dctcp_slowstart)
68
69struct dctcp {
70 int bytes_ecn; /* # of marked bytes during a RTT */
71 int bytes_total; /* # of acked bytes during a RTT */
72 int alpha; /* the fraction of marked bytes */
73 int ce_prev; /* CE state of the last segment */
74 int save_sndnxt; /* end sequence number of the current window */
75 int ece_curr; /* ECE flag in this segment */
76 int ece_prev; /* ECE flag in the last segment */
77 uint32_t num_cong_events; /* # of congestion events */
78};
79
80static MALLOC_DEFINE(M_dctcp, "dctcp data",
81 "Per connection data required for the dctcp algorithm");
82
83static void dctcp_ack_received(struct cc_var *ccv, uint16_t type);
84static void dctcp_after_idle(struct cc_var *ccv);
85static void dctcp_cb_destroy(struct cc_var *ccv);
86static int dctcp_cb_init(struct cc_var *ccv);
87static void dctcp_cong_signal(struct cc_var *ccv, uint32_t type);
88static void dctcp_conn_init(struct cc_var *ccv);
89static void dctcp_post_recovery(struct cc_var *ccv);
90static void dctcp_ecnpkt_handler(struct cc_var *ccv);
91static void dctcp_update_alpha(struct cc_var *ccv);
92
93struct cc_algo dctcp_cc_algo = {
94 .name = "dctcp",
95 .ack_received = dctcp_ack_received,
96 .cb_destroy = dctcp_cb_destroy,
97 .cb_init = dctcp_cb_init,
98 .cong_signal = dctcp_cong_signal,
99 .conn_init = dctcp_conn_init,
100 .post_recovery = dctcp_post_recovery,
101 .ecnpkt_handler = dctcp_ecnpkt_handler,
102 .after_idle = dctcp_after_idle,
103};
104
105static void
106dctcp_ack_received(struct cc_var *ccv, uint16_t type)
107{
108 struct dctcp *dctcp_data;
109 int bytes_acked = 0;
110
111 dctcp_data = ccv->cc_data;
112
113 if (CCV(ccv, t_flags) & TF_ECN_PERMIT) {
114 /*
115 * DCTCP doesn't treat receipt of ECN marked packet as a
116 * congestion event. Thus, DCTCP always executes the ACK
117 * processing out of congestion recovery.
118 */
119 if (IN_CONGRECOVERY(CCV(ccv, t_flags))) {
120 EXIT_CONGRECOVERY(CCV(ccv, t_flags));
121 newreno_cc_algo.ack_received(ccv, type);
122 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
123 } else
124 newreno_cc_algo.ack_received(ccv, type);
125
126 if (type == CC_DUPACK)
127 bytes_acked = CCV(ccv, t_maxseg);
128
129 if (type == CC_ACK)
130 bytes_acked = ccv->bytes_this_ack;
131
132 /* Update total bytes. */
133 dctcp_data->bytes_total += bytes_acked;
134
135 /* Update total marked bytes. */
136 if (dctcp_data->ece_curr) {
137 if (!dctcp_data->ece_prev
138 && bytes_acked > CCV(ccv, t_maxseg)) {
139 dctcp_data->bytes_ecn +=
140 (bytes_acked - CCV(ccv, t_maxseg));
141 } else
142 dctcp_data->bytes_ecn += bytes_acked;
143 dctcp_data->ece_prev = 1;
144 } else {
145 if (dctcp_data->ece_prev
146 && bytes_acked > CCV(ccv, t_maxseg))
147 dctcp_data->bytes_ecn += CCV(ccv, t_maxseg);
148 dctcp_data->ece_prev = 0;
149 }
150 dctcp_data->ece_curr = 0;
151
152 /*
153 * Update the fraction of marked bytes at the end of
154 * current window size.
155 */
156 if ((IN_FASTRECOVERY(CCV(ccv, t_flags)) &&
157 SEQ_GEQ(ccv->curack, CCV(ccv, snd_recover))) ||
158 (!IN_FASTRECOVERY(CCV(ccv, t_flags)) &&
159 SEQ_GT(ccv->curack, dctcp_data->save_sndnxt)))
160 dctcp_update_alpha(ccv);
161 } else
162 newreno_cc_algo.ack_received(ccv, type);
163}
164
165static void
166dctcp_after_idle(struct cc_var *ccv)
167{
168 struct dctcp *dctcp_data;
169
170 dctcp_data = ccv->cc_data;
171
172 /* Initialize internal parameters after idle time */
173 dctcp_data->bytes_ecn = 0;
174 dctcp_data->bytes_total = 0;
175 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
176 dctcp_data->alpha = V_dctcp_alpha;
177 dctcp_data->ece_curr = 0;
178 dctcp_data->ece_prev = 0;
179 dctcp_data->num_cong_events = 0;
180
181 dctcp_cc_algo.after_idle = newreno_cc_algo.after_idle;
182}
183
184static void
185dctcp_cb_destroy(struct cc_var *ccv)
186{
187 if (ccv->cc_data != NULL)
188 free(ccv->cc_data, M_dctcp);
189}
190
191static int
192dctcp_cb_init(struct cc_var *ccv)
193{
194 struct dctcp *dctcp_data;
195
196 dctcp_data = malloc(sizeof(struct dctcp), M_dctcp, M_NOWAIT|M_ZERO);
197
198 if (dctcp_data == NULL)
199 return (ENOMEM);
200
201 /* Initialize some key variables with sensible defaults. */
202 dctcp_data->bytes_ecn = 0;
203 dctcp_data->bytes_total = 0;
204 /*
205 * When alpha is set to 0 in the beggining, DCTCP sender transfers as
206 * much data as possible until the value converges which may expand the
207 * queueing delay at the switch. When alpha is set to 1, queueing delay
208 * is kept small.
209 * Throughput-sensitive applications should have alpha = 0
210 * Latency-sensitive applications should have alpha = 1
211 *
212 * Note: DCTCP draft suggests initial alpha to be 1 but we've decided to
213 * keep it 0 as default.
214 */
215 dctcp_data->alpha = V_dctcp_alpha;
216 dctcp_data->save_sndnxt = 0;
217 dctcp_data->ce_prev = 0;
218 dctcp_data->ece_curr = 0;
219 dctcp_data->ece_prev = 0;
220 dctcp_data->num_cong_events = 0;
221
222 ccv->cc_data = dctcp_data;
223 return (0);
224}
225
226/*
227 * Perform any necessary tasks before we enter congestion recovery.
228 */
229static void
230dctcp_cong_signal(struct cc_var *ccv, uint32_t type)
231{
232 struct dctcp *dctcp_data;
233 u_int win, mss;
234
235 dctcp_data = ccv->cc_data;
236 win = CCV(ccv, snd_cwnd);
237 mss = CCV(ccv, t_maxseg);
238
239 switch (type) {
240 case CC_NDUPACK:
241 if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
242 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
243 CCV(ccv, snd_ssthresh) = mss *
244 max(win / 2 / mss, 2);
245 dctcp_data->num_cong_events++;
246 } else {
247 /* cwnd has already updated as congestion
248 * recovery. Reverse cwnd value using
249 * snd_cwnd_prev and recalculate snd_ssthresh
250 */
251 win = CCV(ccv, snd_cwnd_prev);
252 CCV(ccv, snd_ssthresh) =
253 max(win / 2 / mss, 2) * mss;
254 }
255 ENTER_RECOVERY(CCV(ccv, t_flags));
256 }
257 break;
258 case CC_ECN:
259 /*
260 * Save current snd_cwnd when the host encounters both
261 * congestion recovery and fast recovery.
262 */
263 CCV(ccv, snd_cwnd_prev) = win;
264 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
265 if (V_dctcp_slowstart &&
266 dctcp_data->num_cong_events++ == 0) {
267 CCV(ccv, snd_ssthresh) =
268 mss * max(win / 2 / mss, 2);
269 dctcp_data->alpha = MAX_ALPHA_VALUE;
270 dctcp_data->bytes_ecn = 0;
271 dctcp_data->bytes_total = 0;
272 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
273 } else
274 CCV(ccv, snd_ssthresh) = max((win - ((win *
275 dctcp_data->alpha) >> 11)) / mss, 2) * mss;
276 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
277 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
278 }
279 dctcp_data->ece_curr = 1;
280 break;
281 case CC_RTO:
282 if (CCV(ccv, t_flags) & TF_ECN_PERMIT) {
283 CCV(ccv, t_flags) |= TF_ECN_SND_CWR;
284 dctcp_update_alpha(ccv);
285 dctcp_data->save_sndnxt += CCV(ccv, t_maxseg);
286 dctcp_data->num_cong_events++;
287 }
288 break;
289 }
290}
291
292static void
293dctcp_conn_init(struct cc_var *ccv)
294{
295 struct dctcp *dctcp_data;
296
297 dctcp_data = ccv->cc_data;
298
299 if (CCV(ccv, t_flags) & TF_ECN_PERMIT)
300 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
301}
302
303/*
304 * Perform any necessary tasks before we exit congestion recovery.
305 */
306static void
307dctcp_post_recovery(struct cc_var *ccv)
308{
309 dctcp_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
310
311 if (CCV(ccv, t_flags) & TF_ECN_PERMIT)
312 dctcp_update_alpha(ccv);
313}
314
315/*
316 * Execute an additional ECN processing using ECN field in IP header and the CWR
317 * bit in TCP header.
318 *
319 * delay_ack == 0 - Delayed ACK disabled
320 * delay_ack == 1 - Delayed ACK enabled
321 */
322
323static void
324dctcp_ecnpkt_handler(struct cc_var *ccv)
325{
326 struct dctcp *dctcp_data;
327 uint32_t ccflag;
328 int delay_ack;
329
330 dctcp_data = ccv->cc_data;
331 ccflag = ccv->flags;
332 delay_ack = 1;
333
334 /*
335 * DCTCP responses an ACK immediately when the CE state
336 * in between this segment and the last segment is not same.
337 */
338 if (ccflag & CCF_IPHDR_CE) {
339 if (!dctcp_data->ce_prev && (ccflag & CCF_DELACK))
340 delay_ack = 0;
341 dctcp_data->ce_prev = 1;
342 CCV(ccv, t_flags) |= TF_ECN_SND_ECE;
343 } else {
344 if (dctcp_data->ce_prev && (ccflag & CCF_DELACK))
345 delay_ack = 0;
346 dctcp_data->ce_prev = 0;
347 CCV(ccv, t_flags) &= ~TF_ECN_SND_ECE;
348 }
349
350 /* DCTCP sets delayed ack when this segment sets the CWR flag. */
351 if ((ccflag & CCF_DELACK) && (ccflag & CCF_TCPHDR_CWR))
352 delay_ack = 1;
353
354 if (delay_ack == 0)
355 ccv->flags |= CCF_ACKNOW;
356 else
357 ccv->flags &= ~CCF_ACKNOW;
358}
359
360/*
361 * Update the fraction of marked bytes represented as 'alpha'.
362 * Also initialize several internal parameters at the end of this function.
363 */
364static void
365dctcp_update_alpha(struct cc_var *ccv)
366{
367 struct dctcp *dctcp_data;
368 int alpha_prev;
369
370 dctcp_data = ccv->cc_data;
371 alpha_prev = dctcp_data->alpha;
372 dctcp_data->bytes_total = max(dctcp_data->bytes_total, 1);
373
374 /*
375 * Update alpha: alpha = (1 - g) * alpha + g * F.
376 * Here:
377 * g is weight factor
378 * recommaded to be set to 1/16
379 * small g = slow convergence between competitive DCTCP flows
380 * large g = impacts low utilization of bandwidth at switches
381 * F is fraction of marked segments in last RTT
382 * updated every RTT
383 * Alpha must be round to 0 - MAX_ALPHA_VALUE.
384 */
385 dctcp_data->alpha = min(alpha_prev - (alpha_prev >> V_dctcp_shift_g) +
386 (dctcp_data->bytes_ecn << (10 - V_dctcp_shift_g)) /
387 dctcp_data->bytes_total, MAX_ALPHA_VALUE);
388
389 /* Initialize internal parameters for next alpha calculation */
390 dctcp_data->bytes_ecn = 0;
391 dctcp_data->bytes_total = 0;
392 dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
393}
394
395static int
396dctcp_alpha_handler(SYSCTL_HANDLER_ARGS)
397{
398 uint32_t new;
399 int error;
400
401 new = V_dctcp_alpha;
402 error = sysctl_handle_int(oidp, &new, 0, req);
403 if (error == 0 && req->newptr != NULL) {
404 if (CAST_PTR_INT(req->newptr) > 1)
405 error = EINVAL;
406 else {
407 if (new > MAX_ALPHA_VALUE)
408 V_dctcp_alpha = MAX_ALPHA_VALUE;
409 else
410 V_dctcp_alpha = new;
411 }
412 }
413
414 return (error);
415}
416
417static int
418dctcp_shift_g_handler(SYSCTL_HANDLER_ARGS)
419{
420 uint32_t new;
421 int error;
422
423 new = V_dctcp_shift_g;
424 error = sysctl_handle_int(oidp, &new, 0, req);
425 if (error == 0 && req->newptr != NULL) {
426 if (CAST_PTR_INT(req->newptr) > 1)
427 error = EINVAL;
428 else
429 V_dctcp_shift_g = new;
430 }
431
432 return (error);
433}
434
435static int
436dctcp_slowstart_handler(SYSCTL_HANDLER_ARGS)
437{
438 uint32_t new;
439 int error;
440
441 new = V_dctcp_slowstart;
442 error = sysctl_handle_int(oidp, &new, 0, req);
443 if (error == 0 && req->newptr != NULL) {
444 if (CAST_PTR_INT(req->newptr) > 1)
445 error = EINVAL;
446 else
447 V_dctcp_slowstart = new;
448 }
449
450 return (error);
451}
452
453SYSCTL_DECL(_net_inet_tcp_cc_dctcp);
454SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, dctcp, CTLFLAG_RW, NULL,
455 "dctcp congestion control related settings");
456
457SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, alpha,
458 CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_alpha), 0,
459 &dctcp_alpha_handler,
460 "IU", "dctcp alpha parameter");
461
462SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, shift_g,
463 CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_shift_g), 4,
464 &dctcp_shift_g_handler,
465 "IU", "dctcp shift parameter");
466
467SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, slowstart,
468 CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_slowstart), 0,
469 &dctcp_slowstart_handler,
470 "IU", "half CWND reduction after the first slow start");
471
472DECLARE_CC_MODULE(dctcp, &dctcp_cc_algo);
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