xref: /openbmc/linux/net/sched/sch_tbf.c (revision 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2) 
1 /*
2  * net/sched/sch_tbf.c	Token Bucket Filter queue.
3  *
4  *		This program is free software; you can redistribute it and/or
5  *		modify it under the terms of the GNU General Public License
6  *		as published by the Free Software Foundation; either version
7  *		2 of the License, or (at your option) any later version.
8  *
9  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10  *		Dmitry Torokhov <dtor@mail.ru> - allow attaching inner qdiscs -
11  *						 original idea by Martin Devera
12  *
13  */
14 
15 #include <linux/config.h>
16 #include <linux/module.h>
17 #include <asm/uaccess.h>
18 #include <asm/system.h>
19 #include <linux/bitops.h>
20 #include <linux/types.h>
21 #include <linux/kernel.h>
22 #include <linux/jiffies.h>
23 #include <linux/string.h>
24 #include <linux/mm.h>
25 #include <linux/socket.h>
26 #include <linux/sockios.h>
27 #include <linux/in.h>
28 #include <linux/errno.h>
29 #include <linux/interrupt.h>
30 #include <linux/if_ether.h>
31 #include <linux/inet.h>
32 #include <linux/netdevice.h>
33 #include <linux/etherdevice.h>
34 #include <linux/notifier.h>
35 #include <net/ip.h>
36 #include <net/route.h>
37 #include <linux/skbuff.h>
38 #include <net/sock.h>
39 #include <net/pkt_sched.h>
40 
41 
42 /*	Simple Token Bucket Filter.
43 	=======================================
44 
45 	SOURCE.
46 	-------
47 
48 	None.
49 
50 	Description.
51 	------------
52 
53 	A data flow obeys TBF with rate R and depth B, if for any
54 	time interval t_i...t_f the number of transmitted bits
55 	does not exceed B + R*(t_f-t_i).
56 
57 	Packetized version of this definition:
58 	The sequence of packets of sizes s_i served at moments t_i
59 	obeys TBF, if for any i<=k:
60 
61 	s_i+....+s_k <= B + R*(t_k - t_i)
62 
63 	Algorithm.
64 	----------
65 
66 	Let N(t_i) be B/R initially and N(t) grow continuously with time as:
67 
68 	N(t+delta) = min{B/R, N(t) + delta}
69 
70 	If the first packet in queue has length S, it may be
71 	transmitted only at the time t_* when S/R <= N(t_*),
72 	and in this case N(t) jumps:
73 
74 	N(t_* + 0) = N(t_* - 0) - S/R.
75 
76 
77 
78 	Actually, QoS requires two TBF to be applied to a data stream.
79 	One of them controls steady state burst size, another
80 	one with rate P (peak rate) and depth M (equal to link MTU)
81 	limits bursts at a smaller time scale.
82 
83 	It is easy to see that P>R, and B>M. If P is infinity, this double
84 	TBF is equivalent to a single one.
85 
86 	When TBF works in reshaping mode, latency is estimated as:
87 
88 	lat = max ((L-B)/R, (L-M)/P)
89 
90 
91 	NOTES.
92 	------
93 
94 	If TBF throttles, it starts a watchdog timer, which will wake it up
95 	when it is ready to transmit.
96 	Note that the minimal timer resolution is 1/HZ.
97 	If no new packets arrive during this period,
98 	or if the device is not awaken by EOI for some previous packet,
99 	TBF can stop its activity for 1/HZ.
100 
101 
102 	This means, that with depth B, the maximal rate is
103 
104 	R_crit = B*HZ
105 
106 	F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
107 
108 	Note that the peak rate TBF is much more tough: with MTU 1500
109 	P_crit = 150Kbytes/sec. So, if you need greater peak
110 	rates, use alpha with HZ=1000 :-)
111 
112 	With classful TBF, limit is just kept for backwards compatibility.
113 	It is passed to the default bfifo qdisc - if the inner qdisc is
114 	changed the limit is not effective anymore.
115 */
116 
117 struct tbf_sched_data
118 {
119 /* Parameters */
120 	u32		limit;		/* Maximal length of backlog: bytes */
121 	u32		buffer;		/* Token bucket depth/rate: MUST BE >= MTU/B */
122 	u32		mtu;
123 	u32		max_size;
124 	struct qdisc_rate_table	*R_tab;
125 	struct qdisc_rate_table	*P_tab;
126 
127 /* Variables */
128 	long	tokens;			/* Current number of B tokens */
129 	long	ptokens;		/* Current number of P tokens */
130 	psched_time_t	t_c;		/* Time check-point */
131 	struct timer_list wd_timer;	/* Watchdog timer */
132 	struct Qdisc	*qdisc;		/* Inner qdisc, default - bfifo queue */
133 };
134 
135 #define L2T(q,L)   ((q)->R_tab->data[(L)>>(q)->R_tab->rate.cell_log])
136 #define L2T_P(q,L) ((q)->P_tab->data[(L)>>(q)->P_tab->rate.cell_log])
137 
138 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc* sch)
139 {
140 	struct tbf_sched_data *q = qdisc_priv(sch);
141 	int ret;
142 
143 	if (skb->len > q->max_size) {
144 		sch->qstats.drops++;
145 #ifdef CONFIG_NET_CLS_POLICE
146 		if (sch->reshape_fail == NULL || sch->reshape_fail(skb, sch))
147 #endif
148 			kfree_skb(skb);
149 
150 		return NET_XMIT_DROP;
151 	}
152 
153 	if ((ret = q->qdisc->enqueue(skb, q->qdisc)) != 0) {
154 		sch->qstats.drops++;
155 		return ret;
156 	}
157 
158 	sch->q.qlen++;
159 	sch->bstats.bytes += skb->len;
160 	sch->bstats.packets++;
161 	return 0;
162 }
163 
164 static int tbf_requeue(struct sk_buff *skb, struct Qdisc* sch)
165 {
166 	struct tbf_sched_data *q = qdisc_priv(sch);
167 	int ret;
168 
169 	if ((ret = q->qdisc->ops->requeue(skb, q->qdisc)) == 0) {
170 		sch->q.qlen++;
171 		sch->qstats.requeues++;
172 	}
173 
174 	return ret;
175 }
176 
177 static unsigned int tbf_drop(struct Qdisc* sch)
178 {
179 	struct tbf_sched_data *q = qdisc_priv(sch);
180 	unsigned int len;
181 
182 	if ((len = q->qdisc->ops->drop(q->qdisc)) != 0) {
183 		sch->q.qlen--;
184 		sch->qstats.drops++;
185 	}
186 	return len;
187 }
188 
189 static void tbf_watchdog(unsigned long arg)
190 {
191 	struct Qdisc *sch = (struct Qdisc*)arg;
192 
193 	sch->flags &= ~TCQ_F_THROTTLED;
194 	netif_schedule(sch->dev);
195 }
196 
197 static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
198 {
199 	struct tbf_sched_data *q = qdisc_priv(sch);
200 	struct sk_buff *skb;
201 
202 	skb = q->qdisc->dequeue(q->qdisc);
203 
204 	if (skb) {
205 		psched_time_t now;
206 		long toks, delay;
207 		long ptoks = 0;
208 		unsigned int len = skb->len;
209 
210 		PSCHED_GET_TIME(now);
211 
212 		toks = PSCHED_TDIFF_SAFE(now, q->t_c, q->buffer);
213 
214 		if (q->P_tab) {
215 			ptoks = toks + q->ptokens;
216 			if (ptoks > (long)q->mtu)
217 				ptoks = q->mtu;
218 			ptoks -= L2T_P(q, len);
219 		}
220 		toks += q->tokens;
221 		if (toks > (long)q->buffer)
222 			toks = q->buffer;
223 		toks -= L2T(q, len);
224 
225 		if ((toks|ptoks) >= 0) {
226 			q->t_c = now;
227 			q->tokens = toks;
228 			q->ptokens = ptoks;
229 			sch->q.qlen--;
230 			sch->flags &= ~TCQ_F_THROTTLED;
231 			return skb;
232 		}
233 
234 		delay = PSCHED_US2JIFFIE(max_t(long, -toks, -ptoks));
235 
236 		if (delay == 0)
237 			delay = 1;
238 
239 		mod_timer(&q->wd_timer, jiffies+delay);
240 
241 		/* Maybe we have a shorter packet in the queue,
242 		   which can be sent now. It sounds cool,
243 		   but, however, this is wrong in principle.
244 		   We MUST NOT reorder packets under these circumstances.
245 
246 		   Really, if we split the flow into independent
247 		   subflows, it would be a very good solution.
248 		   This is the main idea of all FQ algorithms
249 		   (cf. CSZ, HPFQ, HFSC)
250 		 */
251 
252 		if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
253 			/* When requeue fails skb is dropped */
254 			sch->q.qlen--;
255 			sch->qstats.drops++;
256 		}
257 
258 		sch->flags |= TCQ_F_THROTTLED;
259 		sch->qstats.overlimits++;
260 	}
261 	return NULL;
262 }
263 
264 static void tbf_reset(struct Qdisc* sch)
265 {
266 	struct tbf_sched_data *q = qdisc_priv(sch);
267 
268 	qdisc_reset(q->qdisc);
269 	sch->q.qlen = 0;
270 	PSCHED_GET_TIME(q->t_c);
271 	q->tokens = q->buffer;
272 	q->ptokens = q->mtu;
273 	sch->flags &= ~TCQ_F_THROTTLED;
274 	del_timer(&q->wd_timer);
275 }
276 
277 static struct Qdisc *tbf_create_dflt_qdisc(struct net_device *dev, u32 limit)
278 {
279 	struct Qdisc *q = qdisc_create_dflt(dev, &bfifo_qdisc_ops);
280         struct rtattr *rta;
281 	int ret;
282 
283 	if (q) {
284 		rta = kmalloc(RTA_LENGTH(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
285 		if (rta) {
286 			rta->rta_type = RTM_NEWQDISC;
287 			rta->rta_len = RTA_LENGTH(sizeof(struct tc_fifo_qopt));
288 			((struct tc_fifo_qopt *)RTA_DATA(rta))->limit = limit;
289 
290 			ret = q->ops->change(q, rta);
291 			kfree(rta);
292 
293 			if (ret == 0)
294 				return q;
295 		}
296 		qdisc_destroy(q);
297 	}
298 
299 	return NULL;
300 }
301 
302 static int tbf_change(struct Qdisc* sch, struct rtattr *opt)
303 {
304 	int err = -EINVAL;
305 	struct tbf_sched_data *q = qdisc_priv(sch);
306 	struct rtattr *tb[TCA_TBF_PTAB];
307 	struct tc_tbf_qopt *qopt;
308 	struct qdisc_rate_table *rtab = NULL;
309 	struct qdisc_rate_table *ptab = NULL;
310 	struct Qdisc *child = NULL;
311 	int max_size,n;
312 
313 	if (rtattr_parse_nested(tb, TCA_TBF_PTAB, opt) ||
314 	    tb[TCA_TBF_PARMS-1] == NULL ||
315 	    RTA_PAYLOAD(tb[TCA_TBF_PARMS-1]) < sizeof(*qopt))
316 		goto done;
317 
318 	qopt = RTA_DATA(tb[TCA_TBF_PARMS-1]);
319 	rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB-1]);
320 	if (rtab == NULL)
321 		goto done;
322 
323 	if (qopt->peakrate.rate) {
324 		if (qopt->peakrate.rate > qopt->rate.rate)
325 			ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB-1]);
326 		if (ptab == NULL)
327 			goto done;
328 	}
329 
330 	for (n = 0; n < 256; n++)
331 		if (rtab->data[n] > qopt->buffer) break;
332 	max_size = (n << qopt->rate.cell_log)-1;
333 	if (ptab) {
334 		int size;
335 
336 		for (n = 0; n < 256; n++)
337 			if (ptab->data[n] > qopt->mtu) break;
338 		size = (n << qopt->peakrate.cell_log)-1;
339 		if (size < max_size) max_size = size;
340 	}
341 	if (max_size < 0)
342 		goto done;
343 
344 	if (q->qdisc == &noop_qdisc) {
345 		if ((child = tbf_create_dflt_qdisc(sch->dev, qopt->limit)) == NULL)
346 			goto done;
347 	}
348 
349 	sch_tree_lock(sch);
350 	if (child) q->qdisc = child;
351 	q->limit = qopt->limit;
352 	q->mtu = qopt->mtu;
353 	q->max_size = max_size;
354 	q->buffer = qopt->buffer;
355 	q->tokens = q->buffer;
356 	q->ptokens = q->mtu;
357 	rtab = xchg(&q->R_tab, rtab);
358 	ptab = xchg(&q->P_tab, ptab);
359 	sch_tree_unlock(sch);
360 	err = 0;
361 done:
362 	if (rtab)
363 		qdisc_put_rtab(rtab);
364 	if (ptab)
365 		qdisc_put_rtab(ptab);
366 	return err;
367 }
368 
369 static int tbf_init(struct Qdisc* sch, struct rtattr *opt)
370 {
371 	struct tbf_sched_data *q = qdisc_priv(sch);
372 
373 	if (opt == NULL)
374 		return -EINVAL;
375 
376 	PSCHED_GET_TIME(q->t_c);
377 	init_timer(&q->wd_timer);
378 	q->wd_timer.function = tbf_watchdog;
379 	q->wd_timer.data = (unsigned long)sch;
380 
381 	q->qdisc = &noop_qdisc;
382 
383 	return tbf_change(sch, opt);
384 }
385 
386 static void tbf_destroy(struct Qdisc *sch)
387 {
388 	struct tbf_sched_data *q = qdisc_priv(sch);
389 
390 	del_timer(&q->wd_timer);
391 
392 	if (q->P_tab)
393 		qdisc_put_rtab(q->P_tab);
394 	if (q->R_tab)
395 		qdisc_put_rtab(q->R_tab);
396 
397 	qdisc_destroy(q->qdisc);
398 }
399 
400 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
401 {
402 	struct tbf_sched_data *q = qdisc_priv(sch);
403 	unsigned char	 *b = skb->tail;
404 	struct rtattr *rta;
405 	struct tc_tbf_qopt opt;
406 
407 	rta = (struct rtattr*)b;
408 	RTA_PUT(skb, TCA_OPTIONS, 0, NULL);
409 
410 	opt.limit = q->limit;
411 	opt.rate = q->R_tab->rate;
412 	if (q->P_tab)
413 		opt.peakrate = q->P_tab->rate;
414 	else
415 		memset(&opt.peakrate, 0, sizeof(opt.peakrate));
416 	opt.mtu = q->mtu;
417 	opt.buffer = q->buffer;
418 	RTA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
419 	rta->rta_len = skb->tail - b;
420 
421 	return skb->len;
422 
423 rtattr_failure:
424 	skb_trim(skb, b - skb->data);
425 	return -1;
426 }
427 
428 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
429 			  struct sk_buff *skb, struct tcmsg *tcm)
430 {
431 	struct tbf_sched_data *q = qdisc_priv(sch);
432 
433 	if (cl != 1) 	/* only one class */
434 		return -ENOENT;
435 
436 	tcm->tcm_handle |= TC_H_MIN(1);
437 	tcm->tcm_info = q->qdisc->handle;
438 
439 	return 0;
440 }
441 
442 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
443 		     struct Qdisc **old)
444 {
445 	struct tbf_sched_data *q = qdisc_priv(sch);
446 
447 	if (new == NULL)
448 		new = &noop_qdisc;
449 
450 	sch_tree_lock(sch);
451 	*old = xchg(&q->qdisc, new);
452 	qdisc_reset(*old);
453 	sch->q.qlen = 0;
454 	sch_tree_unlock(sch);
455 
456 	return 0;
457 }
458 
459 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
460 {
461 	struct tbf_sched_data *q = qdisc_priv(sch);
462 	return q->qdisc;
463 }
464 
465 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
466 {
467 	return 1;
468 }
469 
470 static void tbf_put(struct Qdisc *sch, unsigned long arg)
471 {
472 }
473 
474 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
475 			    struct rtattr **tca, unsigned long *arg)
476 {
477 	return -ENOSYS;
478 }
479 
480 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
481 {
482 	return -ENOSYS;
483 }
484 
485 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
486 {
487 	if (!walker->stop) {
488 		if (walker->count >= walker->skip)
489 			if (walker->fn(sch, 1, walker) < 0) {
490 				walker->stop = 1;
491 				return;
492 			}
493 		walker->count++;
494 	}
495 }
496 
497 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
498 {
499 	return NULL;
500 }
501 
502 static struct Qdisc_class_ops tbf_class_ops =
503 {
504 	.graft		=	tbf_graft,
505 	.leaf		=	tbf_leaf,
506 	.get		=	tbf_get,
507 	.put		=	tbf_put,
508 	.change		=	tbf_change_class,
509 	.delete		=	tbf_delete,
510 	.walk		=	tbf_walk,
511 	.tcf_chain	=	tbf_find_tcf,
512 	.dump		=	tbf_dump_class,
513 };
514 
515 static struct Qdisc_ops tbf_qdisc_ops = {
516 	.next		=	NULL,
517 	.cl_ops		=	&tbf_class_ops,
518 	.id		=	"tbf",
519 	.priv_size	=	sizeof(struct tbf_sched_data),
520 	.enqueue	=	tbf_enqueue,
521 	.dequeue	=	tbf_dequeue,
522 	.requeue	=	tbf_requeue,
523 	.drop		=	tbf_drop,
524 	.init		=	tbf_init,
525 	.reset		=	tbf_reset,
526 	.destroy	=	tbf_destroy,
527 	.change		=	tbf_change,
528 	.dump		=	tbf_dump,
529 	.owner		=	THIS_MODULE,
530 };
531 
532 static int __init tbf_module_init(void)
533 {
534 	return register_qdisc(&tbf_qdisc_ops);
535 }
536 
537 static void __exit tbf_module_exit(void)
538 {
539 	unregister_qdisc(&tbf_qdisc_ops);
540 }
541 module_init(tbf_module_init)
542 module_exit(tbf_module_exit)
543 MODULE_LICENSE("GPL");
544