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
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* net/sched/sch_cbs.c Credit Based Shaper
*
* Authors: Vinicius Costa Gomes <vinicius.gomes@intel.com>
*/
/* Credit Based Shaper (CBS)
* =========================
*
* This is a simple rate-limiting shaper aimed at TSN applications on
* systems with known traffic workloads.
*
* Its algorithm is defined by the IEEE 802.1Q-2014 Specification,
* Section 8.6.8.2, and explained in more detail in the Annex L of the
* same specification.
*
* There are four tunables to be considered:
*
* 'idleslope': Idleslope is the rate of credits that is
* accumulated (in kilobits per second) when there is at least
* one packet waiting for transmission. Packets are transmitted
* when the current value of credits is equal or greater than
* zero. When there is no packet to be transmitted the amount of
* credits is set to zero. This is the main tunable of the CBS
* algorithm.
*
* 'sendslope':
* Sendslope is the rate of credits that is depleted (it should be a
* negative number of kilobits per second) when a transmission is
* ocurring. It can be calculated as follows, (IEEE 802.1Q-2014 Section
* 8.6.8.2 item g):
*
* sendslope = idleslope - port_transmit_rate
*
* 'hicredit': Hicredit defines the maximum amount of credits (in
* bytes) that can be accumulated. Hicredit depends on the
* characteristics of interfering traffic,
* 'max_interference_size' is the maximum size of any burst of
* traffic that can delay the transmission of a frame that is
* available for transmission for this traffic class, (IEEE
* 802.1Q-2014 Annex L, Equation L-3):
*
* hicredit = max_interference_size * (idleslope / port_transmit_rate)
*
* 'locredit': Locredit is the minimum amount of credits that can
* be reached. It is a function of the traffic flowing through
* this qdisc (IEEE 802.1Q-2014 Annex L, Equation L-2):
*
* locredit = max_frame_size * (sendslope / port_transmit_rate)
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <net/netevent.h>
#include <net/netlink.h>
#include <net/sch_generic.h>
#include <net/pkt_sched.h>
static LIST_HEAD(cbs_list);
static DEFINE_SPINLOCK(cbs_list_lock);
#define BYTES_PER_KBIT (1000LL / 8)
struct cbs_sched_data {
bool offload;
int queue;
atomic64_t port_rate; /* in bytes/s */
s64 last; /* timestamp in ns */
s64 credits; /* in bytes */
s32 locredit; /* in bytes */
s32 hicredit; /* in bytes */
s64 sendslope; /* in bytes/s */
s64 idleslope; /* in bytes/s */
struct qdisc_watchdog watchdog;
int (*enqueue)(struct sk_buff *skb, struct Qdisc *sch, spinlock_t *root_lock,
struct sk_buff **to_free);
struct sk_buff *(*dequeue)(struct Qdisc *sch);
struct Qdisc *qdisc;
struct list_head cbs_list;
};
static int cbs_child_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct Qdisc *child, spinlock_t *root_lock,
struct sk_buff **to_free)
{
unsigned int len = qdisc_pkt_len(skb);
int err;
err = child->ops->enqueue(skb, child, root_lock, to_free);
if (err != NET_XMIT_SUCCESS)
return err;
sch->qstats.backlog += len;
sch->q.qlen++;
return NET_XMIT_SUCCESS;
}
static int cbs_enqueue_offload(struct sk_buff *skb, struct Qdisc *sch, spinlock_t *root_lock,
struct sk_buff **to_free)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct Qdisc *qdisc = q->qdisc;
return cbs_child_enqueue(skb, sch, qdisc, root_lock, to_free);
}
static int cbs_enqueue_soft(struct sk_buff *skb, struct Qdisc *sch, spinlock_t *root_lock,
struct sk_buff **to_free)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct Qdisc *qdisc = q->qdisc;
if (sch->q.qlen == 0 && q->credits > 0) {
/* We need to stop accumulating credits when there's
* no enqueued packets and q->credits is positive.
*/
q->credits = 0;
q->last = ktime_get_ns();
}
return cbs_child_enqueue(skb, sch, qdisc, root_lock, to_free);
}
static int cbs_enqueue(struct sk_buff *skb, struct Qdisc *sch, spinlock_t *root_lock,
struct sk_buff **to_free)
{
struct cbs_sched_data *q = qdisc_priv(sch);
return q->enqueue(skb, sch, root_lock, to_free);
}
/* timediff is in ns, slope is in bytes/s */
static s64 timediff_to_credits(s64 timediff, s64 slope)
{
return div64_s64(timediff * slope, NSEC_PER_SEC);
}
static s64 delay_from_credits(s64 credits, s64 slope)
{
if (unlikely(slope == 0))
return S64_MAX;
return div64_s64(-credits * NSEC_PER_SEC, slope);
}
static s64 credits_from_len(unsigned int len, s64 slope, s64 port_rate)
{
if (unlikely(port_rate == 0))
return S64_MAX;
return div64_s64(len * slope, port_rate);
}
static struct sk_buff *cbs_child_dequeue(struct Qdisc *sch, struct Qdisc *child)
{
struct sk_buff *skb;
skb = child->ops->dequeue(child);
if (!skb)
return NULL;
qdisc_qstats_backlog_dec(sch, skb);
qdisc_bstats_update(sch, skb);
sch->q.qlen--;
return skb;
}
static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct Qdisc *qdisc = q->qdisc;
s64 now = ktime_get_ns();
struct sk_buff *skb;
s64 credits;
int len;
/* The previous packet is still being sent */
if (now < q->last) {
qdisc_watchdog_schedule_ns(&q->watchdog, q->last);
return NULL;
}
if (q->credits < 0) {
credits = timediff_to_credits(now - q->last, q->idleslope);
credits = q->credits + credits;
q->credits = min_t(s64, credits, q->hicredit);
if (q->credits < 0) {
s64 delay;
delay = delay_from_credits(q->credits, q->idleslope);
qdisc_watchdog_schedule_ns(&q->watchdog, now + delay);
q->last = now;
return NULL;
}
}
skb = cbs_child_dequeue(sch, qdisc);
if (!skb)
return NULL;
len = qdisc_pkt_len(skb);
/* As sendslope is a negative number, this will decrease the
* amount of q->credits.
*/
credits = credits_from_len(len, q->sendslope,
atomic64_read(&q->port_rate));
credits += q->credits;
q->credits = max_t(s64, credits, q->locredit);
/* Estimate of the transmission of the last byte of the packet in ns */
if (unlikely(atomic64_read(&q->port_rate) == 0))
q->last = now;
else
q->last = now + div64_s64(len * NSEC_PER_SEC,
atomic64_read(&q->port_rate));
return skb;
}
static struct sk_buff *cbs_dequeue_offload(struct Qdisc *sch)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct Qdisc *qdisc = q->qdisc;
return cbs_child_dequeue(sch, qdisc);
}
static struct sk_buff *cbs_dequeue(struct Qdisc *sch)
{
struct cbs_sched_data *q = qdisc_priv(sch);
return q->dequeue(sch);
}
static const struct nla_policy cbs_policy[TCA_CBS_MAX + 1] = {
[TCA_CBS_PARMS] = { .len = sizeof(struct tc_cbs_qopt) },
};
static void cbs_disable_offload(struct net_device *dev,
struct cbs_sched_data *q)
{
struct tc_cbs_qopt_offload cbs = { };
const struct net_device_ops *ops;
int err;
if (!q->offload)
return;
q->enqueue = cbs_enqueue_soft;
q->dequeue = cbs_dequeue_soft;
ops = dev->netdev_ops;
if (!ops->ndo_setup_tc)
return;
cbs.queue = q->queue;
cbs.enable = 0;
err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs);
if (err < 0)
pr_warn("Couldn't disable CBS offload for queue %d\n",
cbs.queue);
}
static int cbs_enable_offload(struct net_device *dev, struct cbs_sched_data *q,
const struct tc_cbs_qopt *opt,
struct netlink_ext_ack *extack)
{
const struct net_device_ops *ops = dev->netdev_ops;
struct tc_cbs_qopt_offload cbs = { };
int err;
if (!ops->ndo_setup_tc) {
NL_SET_ERR_MSG(extack, "Specified device does not support cbs offload");
return -EOPNOTSUPP;
}
cbs.queue = q->queue;
cbs.enable = 1;
cbs.hicredit = opt->hicredit;
cbs.locredit = opt->locredit;
cbs.idleslope = opt->idleslope;
cbs.sendslope = opt->sendslope;
err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs);
if (err < 0) {
NL_SET_ERR_MSG(extack, "Specified device failed to setup cbs hardware offload");
return err;
}
q->enqueue = cbs_enqueue_offload;
q->dequeue = cbs_dequeue_offload;
return 0;
}
static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q)
{
struct ethtool_link_ksettings ecmd;
int speed = SPEED_10;
int port_rate;
int err;
err = __ethtool_get_link_ksettings(dev, &ecmd);
if (err < 0)
goto skip;
if (ecmd.base.speed && ecmd.base.speed != SPEED_UNKNOWN)
speed = ecmd.base.speed;
skip:
port_rate = speed * 1000 * BYTES_PER_KBIT;
atomic64_set(&q->port_rate, port_rate);
netdev_dbg(dev, "cbs: set %s's port_rate to: %lld, linkspeed: %d\n",
dev->name, (long long)atomic64_read(&q->port_rate),
ecmd.base.speed);
}
static int cbs_dev_notifier(struct notifier_block *nb, unsigned long event,
void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct cbs_sched_data *q;
struct net_device *qdev;
bool found = false;
ASSERT_RTNL();
if (event != NETDEV_UP && event != NETDEV_CHANGE)
return NOTIFY_DONE;
spin_lock(&cbs_list_lock);
list_for_each_entry(q, &cbs_list, cbs_list) {
qdev = qdisc_dev(q->qdisc);
if (qdev == dev) {
found = true;
break;
}
}
spin_unlock(&cbs_list_lock);
if (found)
cbs_set_port_rate(dev, q);
return NOTIFY_DONE;
}
static int cbs_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct net_device *dev = qdisc_dev(sch);
struct nlattr *tb[TCA_CBS_MAX + 1];
struct tc_cbs_qopt *qopt;
int err;
err = nla_parse_nested_deprecated(tb, TCA_CBS_MAX, opt, cbs_policy,
extack);
if (err < 0)
return err;
if (!tb[TCA_CBS_PARMS]) {
NL_SET_ERR_MSG(extack, "Missing CBS parameter which are mandatory");
return -EINVAL;
}
qopt = nla_data(tb[TCA_CBS_PARMS]);
if (!qopt->offload) {
cbs_set_port_rate(dev, q);
cbs_disable_offload(dev, q);
} else {
err = cbs_enable_offload(dev, q, qopt, extack);
if (err < 0)
return err;
}
/* Everything went OK, save the parameters used. */
q->hicredit = qopt->hicredit;
q->locredit = qopt->locredit;
q->idleslope = qopt->idleslope * BYTES_PER_KBIT;
q->sendslope = qopt->sendslope * BYTES_PER_KBIT;
q->offload = qopt->offload;
return 0;
}
static int cbs_init(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct net_device *dev = qdisc_dev(sch);
if (!opt) {
NL_SET_ERR_MSG(extack, "Missing CBS qdisc options which are mandatory");
return -EINVAL;
}
q->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
sch->handle, extack);
if (!q->qdisc)
return -ENOMEM;
spin_lock(&cbs_list_lock);
list_add(&q->cbs_list, &cbs_list);
spin_unlock(&cbs_list_lock);
qdisc_hash_add(q->qdisc, false);
q->queue = sch->dev_queue - netdev_get_tx_queue(dev, 0);
q->enqueue = cbs_enqueue_soft;
q->dequeue = cbs_dequeue_soft;
qdisc_watchdog_init(&q->watchdog, sch);
return cbs_change(sch, opt, extack);
}
static void cbs_destroy(struct Qdisc *sch)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct net_device *dev = qdisc_dev(sch);
/* Nothing to do if we couldn't create the underlying qdisc */
if (!q->qdisc)
return;
qdisc_watchdog_cancel(&q->watchdog);
cbs_disable_offload(dev, q);
spin_lock(&cbs_list_lock);
list_del(&q->cbs_list);
spin_unlock(&cbs_list_lock);
qdisc_put(q->qdisc);
}
static int cbs_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct cbs_sched_data *q = qdisc_priv(sch);
struct tc_cbs_qopt opt = { };
struct nlattr *nest;
nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
if (!nest)
goto nla_put_failure;
opt.hicredit = q->hicredit;
opt.locredit = q->locredit;
opt.sendslope = div64_s64(q->sendslope, BYTES_PER_KBIT);
opt.idleslope = div64_s64(q->idleslope, BYTES_PER_KBIT);
opt.offload = q->offload;
if (nla_put(skb, TCA_CBS_PARMS, sizeof(opt), &opt))
goto nla_put_failure;
return nla_nest_end(skb, nest);
nla_put_failure:
nla_nest_cancel(skb, nest);
return -1;
}
static int cbs_dump_class(struct Qdisc *sch, unsigned long cl,
struct sk_buff *skb, struct tcmsg *tcm)
{
struct cbs_sched_data *q = qdisc_priv(sch);
if (cl != 1 || !q->qdisc) /* only one class */
return -ENOENT;
tcm->tcm_handle |= TC_H_MIN(1);
tcm->tcm_info = q->qdisc->handle;
return 0;
}
static int cbs_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
struct Qdisc **old, struct netlink_ext_ack *extack)
{
struct cbs_sched_data *q = qdisc_priv(sch);
if (!new) {
new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
sch->handle, NULL);
if (!new)
new = &noop_qdisc;
}
*old = qdisc_replace(sch, new, &q->qdisc);
return 0;
}
static struct Qdisc *cbs_leaf(struct Qdisc *sch, unsigned long arg)
{
struct cbs_sched_data *q = qdisc_priv(sch);
return q->qdisc;
}
static unsigned long cbs_find(struct Qdisc *sch, u32 classid)
{
return 1;
}
static void cbs_walk(struct Qdisc *sch, struct qdisc_walker *walker)
{
if (!walker->stop) {
if (walker->count >= walker->skip) {
if (walker->fn(sch, 1, walker) < 0) {
walker->stop = 1;
return;
}
}
walker->count++;
}
}
static const struct Qdisc_class_ops cbs_class_ops = {
.graft = cbs_graft,
.leaf = cbs_leaf,
.find = cbs_find,
.walk = cbs_walk,
.dump = cbs_dump_class,
};
static struct Qdisc_ops cbs_qdisc_ops __read_mostly = {
.id = "cbs",
.cl_ops = &cbs_class_ops,
.priv_size = sizeof(struct cbs_sched_data),
.enqueue = cbs_enqueue,
.dequeue = cbs_dequeue,
.peek = qdisc_peek_dequeued,
.init = cbs_init,
.reset = qdisc_reset_queue,
.destroy = cbs_destroy,
.change = cbs_change,
.dump = cbs_dump,
.owner = THIS_MODULE,
};
static struct notifier_block cbs_device_notifier = {
.notifier_call = cbs_dev_notifier,
};
static int __init cbs_module_init(void)
{
int err;
err = register_netdevice_notifier(&cbs_device_notifier);
if (err)
return err;
err = register_qdisc(&cbs_qdisc_ops);
if (err)
unregister_netdevice_notifier(&cbs_device_notifier);
return err;
}
static void __exit cbs_module_exit(void)
{
unregister_qdisc(&cbs_qdisc_ops);
unregister_netdevice_notifier(&cbs_device_notifier);
}
module_init(cbs_module_init)
module_exit(cbs_module_exit)
MODULE_LICENSE("GPL");
|