xref: /openbmc/linux/net/sched/sch_tbf.c (revision f59a3ee6) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * net/sched/sch_tbf.c	Token Bucket Filter queue.
4  *
5  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
6  *		Dmitry Torokhov <dtor@mail.ru> - allow attaching inner qdiscs -
7  *						 original idea by Martin Devera
8  */
9 
10 #include <linux/module.h>
11 #include <linux/types.h>
12 #include <linux/kernel.h>
13 #include <linux/string.h>
14 #include <linux/errno.h>
15 #include <linux/skbuff.h>
16 #include <net/netlink.h>
17 #include <net/sch_generic.h>
18 #include <net/pkt_cls.h>
19 #include <net/pkt_sched.h>
20 
21 
22 /*	Simple Token Bucket Filter.
23 	=======================================
24 
25 	SOURCE.
26 	-------
27 
28 	None.
29 
30 	Description.
31 	------------
32 
33 	A data flow obeys TBF with rate R and depth B, if for any
34 	time interval t_i...t_f the number of transmitted bits
35 	does not exceed B + R*(t_f-t_i).
36 
37 	Packetized version of this definition:
38 	The sequence of packets of sizes s_i served at moments t_i
39 	obeys TBF, if for any i<=k:
40 
41 	s_i+....+s_k <= B + R*(t_k - t_i)
42 
43 	Algorithm.
44 	----------
45 
46 	Let N(t_i) be B/R initially and N(t) grow continuously with time as:
47 
48 	N(t+delta) = min{B/R, N(t) + delta}
49 
50 	If the first packet in queue has length S, it may be
51 	transmitted only at the time t_* when S/R <= N(t_*),
52 	and in this case N(t) jumps:
53 
54 	N(t_* + 0) = N(t_* - 0) - S/R.
55 
56 
57 
58 	Actually, QoS requires two TBF to be applied to a data stream.
59 	One of them controls steady state burst size, another
60 	one with rate P (peak rate) and depth M (equal to link MTU)
61 	limits bursts at a smaller time scale.
62 
63 	It is easy to see that P>R, and B>M. If P is infinity, this double
64 	TBF is equivalent to a single one.
65 
66 	When TBF works in reshaping mode, latency is estimated as:
67 
68 	lat = max ((L-B)/R, (L-M)/P)
69 
70 
71 	NOTES.
72 	------
73 
74 	If TBF throttles, it starts a watchdog timer, which will wake it up
75 	when it is ready to transmit.
76 	Note that the minimal timer resolution is 1/HZ.
77 	If no new packets arrive during this period,
78 	or if the device is not awaken by EOI for some previous packet,
79 	TBF can stop its activity for 1/HZ.
80 
81 
82 	This means, that with depth B, the maximal rate is
83 
84 	R_crit = B*HZ
85 
86 	F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
87 
88 	Note that the peak rate TBF is much more tough: with MTU 1500
89 	P_crit = 150Kbytes/sec. So, if you need greater peak
90 	rates, use alpha with HZ=1000 :-)
91 
92 	With classful TBF, limit is just kept for backwards compatibility.
93 	It is passed to the default bfifo qdisc - if the inner qdisc is
94 	changed the limit is not effective anymore.
95 */
96 
97 struct tbf_sched_data {
98 /* Parameters */
99 	u32		limit;		/* Maximal length of backlog: bytes */
100 	u32		max_size;
101 	s64		buffer;		/* Token bucket depth/rate: MUST BE >= MTU/B */
102 	s64		mtu;
103 	struct psched_ratecfg rate;
104 	struct psched_ratecfg peak;
105 
106 /* Variables */
107 	s64	tokens;			/* Current number of B tokens */
108 	s64	ptokens;		/* Current number of P tokens */
109 	s64	t_c;			/* Time check-point */
110 	struct Qdisc	*qdisc;		/* Inner qdisc, default - bfifo queue */
111 	struct qdisc_watchdog watchdog;	/* Watchdog timer */
112 };
113 
114 
115 /* Time to Length, convert time in ns to length in bytes
116  * to determinate how many bytes can be sent in given time.
117  */
118 static u64 psched_ns_t2l(const struct psched_ratecfg *r,
119 			 u64 time_in_ns)
120 {
121 	/* The formula is :
122 	 * len = (time_in_ns * r->rate_bytes_ps) / NSEC_PER_SEC
123 	 */
124 	u64 len = time_in_ns * r->rate_bytes_ps;
125 
126 	do_div(len, NSEC_PER_SEC);
127 
128 	if (unlikely(r->linklayer == TC_LINKLAYER_ATM)) {
129 		do_div(len, 53);
130 		len = len * 48;
131 	}
132 
133 	if (len > r->overhead)
134 		len -= r->overhead;
135 	else
136 		len = 0;
137 
138 	return len;
139 }
140 
141 static void tbf_offload_change(struct Qdisc *sch)
142 {
143 	struct tbf_sched_data *q = qdisc_priv(sch);
144 	struct net_device *dev = qdisc_dev(sch);
145 	struct tc_tbf_qopt_offload qopt;
146 
147 	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
148 		return;
149 
150 	qopt.command = TC_TBF_REPLACE;
151 	qopt.handle = sch->handle;
152 	qopt.parent = sch->parent;
153 	qopt.replace_params.rate = q->rate;
154 	qopt.replace_params.max_size = q->max_size;
155 	qopt.replace_params.qstats = &sch->qstats;
156 
157 	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_TBF, &qopt);
158 }
159 
160 static void tbf_offload_destroy(struct Qdisc *sch)
161 {
162 	struct net_device *dev = qdisc_dev(sch);
163 	struct tc_tbf_qopt_offload qopt;
164 
165 	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
166 		return;
167 
168 	qopt.command = TC_TBF_DESTROY;
169 	qopt.handle = sch->handle;
170 	qopt.parent = sch->parent;
171 	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_TBF, &qopt);
172 }
173 
174 static int tbf_offload_dump(struct Qdisc *sch)
175 {
176 	struct tc_tbf_qopt_offload qopt;
177 
178 	qopt.command = TC_TBF_STATS;
179 	qopt.handle = sch->handle;
180 	qopt.parent = sch->parent;
181 	qopt.stats.bstats = &sch->bstats;
182 	qopt.stats.qstats = &sch->qstats;
183 
184 	return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_TBF, &qopt);
185 }
186 
187 static void tbf_offload_graft(struct Qdisc *sch, struct Qdisc *new,
188 			      struct Qdisc *old, struct netlink_ext_ack *extack)
189 {
190 	struct tc_tbf_qopt_offload graft_offload = {
191 		.handle		= sch->handle,
192 		.parent		= sch->parent,
193 		.child_handle	= new->handle,
194 		.command	= TC_TBF_GRAFT,
195 	};
196 
197 	qdisc_offload_graft_helper(qdisc_dev(sch), sch, new, old,
198 				   TC_SETUP_QDISC_TBF, &graft_offload, extack);
199 }
200 
201 /* GSO packet is too big, segment it so that tbf can transmit
202  * each segment in time
203  */
204 static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch,
205 		       struct sk_buff **to_free)
206 {
207 	struct tbf_sched_data *q = qdisc_priv(sch);
208 	struct sk_buff *segs, *nskb;
209 	netdev_features_t features = netif_skb_features(skb);
210 	unsigned int len = 0, prev_len = qdisc_pkt_len(skb);
211 	int ret, nb;
212 
213 	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
214 
215 	if (IS_ERR_OR_NULL(segs))
216 		return qdisc_drop(skb, sch, to_free);
217 
218 	nb = 0;
219 	skb_list_walk_safe(segs, segs, nskb) {
220 		skb_mark_not_on_list(segs);
221 		qdisc_skb_cb(segs)->pkt_len = segs->len;
222 		len += segs->len;
223 		ret = qdisc_enqueue(segs, q->qdisc, to_free);
224 		if (ret != NET_XMIT_SUCCESS) {
225 			if (net_xmit_drop_count(ret))
226 				qdisc_qstats_drop(sch);
227 		} else {
228 			nb++;
229 		}
230 	}
231 	sch->q.qlen += nb;
232 	if (nb > 1)
233 		qdisc_tree_reduce_backlog(sch, 1 - nb, prev_len - len);
234 	consume_skb(skb);
235 	return nb > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
236 }
237 
238 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
239 		       struct sk_buff **to_free)
240 {
241 	struct tbf_sched_data *q = qdisc_priv(sch);
242 	unsigned int len = qdisc_pkt_len(skb);
243 	int ret;
244 
245 	if (qdisc_pkt_len(skb) > q->max_size) {
246 		if (skb_is_gso(skb) &&
247 		    skb_gso_validate_mac_len(skb, q->max_size))
248 			return tbf_segment(skb, sch, to_free);
249 		return qdisc_drop(skb, sch, to_free);
250 	}
251 	ret = qdisc_enqueue(skb, q->qdisc, to_free);
252 	if (ret != NET_XMIT_SUCCESS) {
253 		if (net_xmit_drop_count(ret))
254 			qdisc_qstats_drop(sch);
255 		return ret;
256 	}
257 
258 	sch->qstats.backlog += len;
259 	sch->q.qlen++;
260 	return NET_XMIT_SUCCESS;
261 }
262 
263 static bool tbf_peak_present(const struct tbf_sched_data *q)
264 {
265 	return q->peak.rate_bytes_ps;
266 }
267 
268 static struct sk_buff *tbf_dequeue(struct Qdisc *sch)
269 {
270 	struct tbf_sched_data *q = qdisc_priv(sch);
271 	struct sk_buff *skb;
272 
273 	skb = q->qdisc->ops->peek(q->qdisc);
274 
275 	if (skb) {
276 		s64 now;
277 		s64 toks;
278 		s64 ptoks = 0;
279 		unsigned int len = qdisc_pkt_len(skb);
280 
281 		now = ktime_get_ns();
282 		toks = min_t(s64, now - q->t_c, q->buffer);
283 
284 		if (tbf_peak_present(q)) {
285 			ptoks = toks + q->ptokens;
286 			if (ptoks > q->mtu)
287 				ptoks = q->mtu;
288 			ptoks -= (s64) psched_l2t_ns(&q->peak, len);
289 		}
290 		toks += q->tokens;
291 		if (toks > q->buffer)
292 			toks = q->buffer;
293 		toks -= (s64) psched_l2t_ns(&q->rate, len);
294 
295 		if ((toks|ptoks) >= 0) {
296 			skb = qdisc_dequeue_peeked(q->qdisc);
297 			if (unlikely(!skb))
298 				return NULL;
299 
300 			q->t_c = now;
301 			q->tokens = toks;
302 			q->ptokens = ptoks;
303 			qdisc_qstats_backlog_dec(sch, skb);
304 			sch->q.qlen--;
305 			qdisc_bstats_update(sch, skb);
306 			return skb;
307 		}
308 
309 		qdisc_watchdog_schedule_ns(&q->watchdog,
310 					   now + max_t(long, -toks, -ptoks));
311 
312 		/* Maybe we have a shorter packet in the queue,
313 		   which can be sent now. It sounds cool,
314 		   but, however, this is wrong in principle.
315 		   We MUST NOT reorder packets under these circumstances.
316 
317 		   Really, if we split the flow into independent
318 		   subflows, it would be a very good solution.
319 		   This is the main idea of all FQ algorithms
320 		   (cf. CSZ, HPFQ, HFSC)
321 		 */
322 
323 		qdisc_qstats_overlimit(sch);
324 	}
325 	return NULL;
326 }
327 
328 static void tbf_reset(struct Qdisc *sch)
329 {
330 	struct tbf_sched_data *q = qdisc_priv(sch);
331 
332 	qdisc_reset(q->qdisc);
333 	q->t_c = ktime_get_ns();
334 	q->tokens = q->buffer;
335 	q->ptokens = q->mtu;
336 	qdisc_watchdog_cancel(&q->watchdog);
337 }
338 
339 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
340 	[TCA_TBF_PARMS]	= { .len = sizeof(struct tc_tbf_qopt) },
341 	[TCA_TBF_RTAB]	= { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
342 	[TCA_TBF_PTAB]	= { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
343 	[TCA_TBF_RATE64]	= { .type = NLA_U64 },
344 	[TCA_TBF_PRATE64]	= { .type = NLA_U64 },
345 	[TCA_TBF_BURST] = { .type = NLA_U32 },
346 	[TCA_TBF_PBURST] = { .type = NLA_U32 },
347 };
348 
349 static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
350 		      struct netlink_ext_ack *extack)
351 {
352 	int err;
353 	struct tbf_sched_data *q = qdisc_priv(sch);
354 	struct nlattr *tb[TCA_TBF_MAX + 1];
355 	struct tc_tbf_qopt *qopt;
356 	struct Qdisc *child = NULL;
357 	struct Qdisc *old = NULL;
358 	struct psched_ratecfg rate;
359 	struct psched_ratecfg peak;
360 	u64 max_size;
361 	s64 buffer, mtu;
362 	u64 rate64 = 0, prate64 = 0;
363 
364 	err = nla_parse_nested_deprecated(tb, TCA_TBF_MAX, opt, tbf_policy,
365 					  NULL);
366 	if (err < 0)
367 		return err;
368 
369 	err = -EINVAL;
370 	if (tb[TCA_TBF_PARMS] == NULL)
371 		goto done;
372 
373 	qopt = nla_data(tb[TCA_TBF_PARMS]);
374 	if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE)
375 		qdisc_put_rtab(qdisc_get_rtab(&qopt->rate,
376 					      tb[TCA_TBF_RTAB],
377 					      NULL));
378 
379 	if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE)
380 			qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate,
381 						      tb[TCA_TBF_PTAB],
382 						      NULL));
383 
384 	buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U);
385 	mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U);
386 
387 	if (tb[TCA_TBF_RATE64])
388 		rate64 = nla_get_u64(tb[TCA_TBF_RATE64]);
389 	psched_ratecfg_precompute(&rate, &qopt->rate, rate64);
390 
391 	if (tb[TCA_TBF_BURST]) {
392 		max_size = nla_get_u32(tb[TCA_TBF_BURST]);
393 		buffer = psched_l2t_ns(&rate, max_size);
394 	} else {
395 		max_size = min_t(u64, psched_ns_t2l(&rate, buffer), ~0U);
396 	}
397 
398 	if (qopt->peakrate.rate) {
399 		if (tb[TCA_TBF_PRATE64])
400 			prate64 = nla_get_u64(tb[TCA_TBF_PRATE64]);
401 		psched_ratecfg_precompute(&peak, &qopt->peakrate, prate64);
402 		if (peak.rate_bytes_ps <= rate.rate_bytes_ps) {
403 			pr_warn_ratelimited("sch_tbf: peakrate %llu is lower than or equals to rate %llu !\n",
404 					peak.rate_bytes_ps, rate.rate_bytes_ps);
405 			err = -EINVAL;
406 			goto done;
407 		}
408 
409 		if (tb[TCA_TBF_PBURST]) {
410 			u32 pburst = nla_get_u32(tb[TCA_TBF_PBURST]);
411 			max_size = min_t(u32, max_size, pburst);
412 			mtu = psched_l2t_ns(&peak, pburst);
413 		} else {
414 			max_size = min_t(u64, max_size, psched_ns_t2l(&peak, mtu));
415 		}
416 	} else {
417 		memset(&peak, 0, sizeof(peak));
418 	}
419 
420 	if (max_size < psched_mtu(qdisc_dev(sch)))
421 		pr_warn_ratelimited("sch_tbf: burst %llu is lower than device %s mtu (%u) !\n",
422 				    max_size, qdisc_dev(sch)->name,
423 				    psched_mtu(qdisc_dev(sch)));
424 
425 	if (!max_size) {
426 		err = -EINVAL;
427 		goto done;
428 	}
429 
430 	if (q->qdisc != &noop_qdisc) {
431 		err = fifo_set_limit(q->qdisc, qopt->limit);
432 		if (err)
433 			goto done;
434 	} else if (qopt->limit > 0) {
435 		child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit,
436 					 extack);
437 		if (IS_ERR(child)) {
438 			err = PTR_ERR(child);
439 			goto done;
440 		}
441 
442 		/* child is fifo, no need to check for noop_qdisc */
443 		qdisc_hash_add(child, true);
444 	}
445 
446 	sch_tree_lock(sch);
447 	if (child) {
448 		qdisc_tree_flush_backlog(q->qdisc);
449 		old = q->qdisc;
450 		q->qdisc = child;
451 	}
452 	q->limit = qopt->limit;
453 	if (tb[TCA_TBF_PBURST])
454 		q->mtu = mtu;
455 	else
456 		q->mtu = PSCHED_TICKS2NS(qopt->mtu);
457 	q->max_size = max_size;
458 	if (tb[TCA_TBF_BURST])
459 		q->buffer = buffer;
460 	else
461 		q->buffer = PSCHED_TICKS2NS(qopt->buffer);
462 	q->tokens = q->buffer;
463 	q->ptokens = q->mtu;
464 
465 	memcpy(&q->rate, &rate, sizeof(struct psched_ratecfg));
466 	memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg));
467 
468 	sch_tree_unlock(sch);
469 	qdisc_put(old);
470 	err = 0;
471 
472 	tbf_offload_change(sch);
473 done:
474 	return err;
475 }
476 
477 static int tbf_init(struct Qdisc *sch, struct nlattr *opt,
478 		    struct netlink_ext_ack *extack)
479 {
480 	struct tbf_sched_data *q = qdisc_priv(sch);
481 
482 	qdisc_watchdog_init(&q->watchdog, sch);
483 	q->qdisc = &noop_qdisc;
484 
485 	if (!opt)
486 		return -EINVAL;
487 
488 	q->t_c = ktime_get_ns();
489 
490 	return tbf_change(sch, opt, extack);
491 }
492 
493 static void tbf_destroy(struct Qdisc *sch)
494 {
495 	struct tbf_sched_data *q = qdisc_priv(sch);
496 
497 	qdisc_watchdog_cancel(&q->watchdog);
498 	tbf_offload_destroy(sch);
499 	qdisc_put(q->qdisc);
500 }
501 
502 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
503 {
504 	struct tbf_sched_data *q = qdisc_priv(sch);
505 	struct nlattr *nest;
506 	struct tc_tbf_qopt opt;
507 	int err;
508 
509 	err = tbf_offload_dump(sch);
510 	if (err)
511 		return err;
512 
513 	nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
514 	if (nest == NULL)
515 		goto nla_put_failure;
516 
517 	opt.limit = q->limit;
518 	psched_ratecfg_getrate(&opt.rate, &q->rate);
519 	if (tbf_peak_present(q))
520 		psched_ratecfg_getrate(&opt.peakrate, &q->peak);
521 	else
522 		memset(&opt.peakrate, 0, sizeof(opt.peakrate));
523 	opt.mtu = PSCHED_NS2TICKS(q->mtu);
524 	opt.buffer = PSCHED_NS2TICKS(q->buffer);
525 	if (nla_put(skb, TCA_TBF_PARMS, sizeof(opt), &opt))
526 		goto nla_put_failure;
527 	if (q->rate.rate_bytes_ps >= (1ULL << 32) &&
528 	    nla_put_u64_64bit(skb, TCA_TBF_RATE64, q->rate.rate_bytes_ps,
529 			      TCA_TBF_PAD))
530 		goto nla_put_failure;
531 	if (tbf_peak_present(q) &&
532 	    q->peak.rate_bytes_ps >= (1ULL << 32) &&
533 	    nla_put_u64_64bit(skb, TCA_TBF_PRATE64, q->peak.rate_bytes_ps,
534 			      TCA_TBF_PAD))
535 		goto nla_put_failure;
536 
537 	return nla_nest_end(skb, nest);
538 
539 nla_put_failure:
540 	nla_nest_cancel(skb, nest);
541 	return -1;
542 }
543 
544 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
545 			  struct sk_buff *skb, struct tcmsg *tcm)
546 {
547 	struct tbf_sched_data *q = qdisc_priv(sch);
548 
549 	tcm->tcm_handle |= TC_H_MIN(1);
550 	tcm->tcm_info = q->qdisc->handle;
551 
552 	return 0;
553 }
554 
555 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
556 		     struct Qdisc **old, struct netlink_ext_ack *extack)
557 {
558 	struct tbf_sched_data *q = qdisc_priv(sch);
559 
560 	if (new == NULL)
561 		new = &noop_qdisc;
562 
563 	*old = qdisc_replace(sch, new, &q->qdisc);
564 
565 	tbf_offload_graft(sch, new, *old, extack);
566 	return 0;
567 }
568 
569 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
570 {
571 	struct tbf_sched_data *q = qdisc_priv(sch);
572 	return q->qdisc;
573 }
574 
575 static unsigned long tbf_find(struct Qdisc *sch, u32 classid)
576 {
577 	return 1;
578 }
579 
580 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
581 {
582 	if (!walker->stop) {
583 		tc_qdisc_stats_dump(sch, 1, walker);
584 	}
585 }
586 
587 static const struct Qdisc_class_ops tbf_class_ops = {
588 	.graft		=	tbf_graft,
589 	.leaf		=	tbf_leaf,
590 	.find		=	tbf_find,
591 	.walk		=	tbf_walk,
592 	.dump		=	tbf_dump_class,
593 };
594 
595 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
596 	.next		=	NULL,
597 	.cl_ops		=	&tbf_class_ops,
598 	.id		=	"tbf",
599 	.priv_size	=	sizeof(struct tbf_sched_data),
600 	.enqueue	=	tbf_enqueue,
601 	.dequeue	=	tbf_dequeue,
602 	.peek		=	qdisc_peek_dequeued,
603 	.init		=	tbf_init,
604 	.reset		=	tbf_reset,
605 	.destroy	=	tbf_destroy,
606 	.change		=	tbf_change,
607 	.dump		=	tbf_dump,
608 	.owner		=	THIS_MODULE,
609 };
610 
611 static int __init tbf_module_init(void)
612 {
613 	return register_qdisc(&tbf_qdisc_ops);
614 }
615 
616 static void __exit tbf_module_exit(void)
617 {
618 	unregister_qdisc(&tbf_qdisc_ops);
619 }
620 module_init(tbf_module_init)
621 module_exit(tbf_module_exit)
622 MODULE_LICENSE("GPL");
623