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/module.h>
16 #include <linux/types.h>
17 #include <linux/kernel.h>
18 #include <linux/string.h>
19 #include <linux/errno.h>
20 #include <linux/skbuff.h>
21 #include <net/netlink.h>
22 #include <net/pkt_sched.h>
23
24
25 /* Simple Token Bucket Filter.
26 =======================================
27
28 SOURCE.
29 -------
30
31 None.
32
33 Description.
34 ------------
35
36 A data flow obeys TBF with rate R and depth B, if for any
37 time interval t_i...t_f the number of transmitted bits
38 does not exceed B + R*(t_f-t_i).
39
40 Packetized version of this definition:
41 The sequence of packets of sizes s_i served at moments t_i
42 obeys TBF, if for any i<=k:
43
44 s_i+....+s_k <= B + R*(t_k - t_i)
45
46 Algorithm.
47 ----------
48
49 Let N(t_i) be B/R initially and N(t) grow continuously with time as:
50
51 N(t+delta) = min{B/R, N(t) + delta}
52
53 If the first packet in queue has length S, it may be
54 transmitted only at the time t_* when S/R <= N(t_*),
55 and in this case N(t) jumps:
56
57 N(t_* + 0) = N(t_* - 0) - S/R.
58
59
60
61 Actually, QoS requires two TBF to be applied to a data stream.
62 One of them controls steady state burst size, another
63 one with rate P (peak rate) and depth M (equal to link MTU)
64 limits bursts at a smaller time scale.
65
66 It is easy to see that P>R, and B>M. If P is infinity, this double
67 TBF is equivalent to a single one.
68
69 When TBF works in reshaping mode, latency is estimated as:
70
71 lat = max ((L-B)/R, (L-M)/P)
72
73
74 NOTES.
75 ------
76
77 If TBF throttles, it starts a watchdog timer, which will wake it up
78 when it is ready to transmit.
79 Note that the minimal timer resolution is 1/HZ.
80 If no new packets arrive during this period,
81 or if the device is not awaken by EOI for some previous packet,
82 TBF can stop its activity for 1/HZ.
83
84
85 This means, that with depth B, the maximal rate is
86
87 R_crit = B*HZ
88
89 F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
90
91 Note that the peak rate TBF is much more tough: with MTU 1500
92 P_crit = 150Kbytes/sec. So, if you need greater peak
93 rates, use alpha with HZ=1000 :-)
94
95 With classful TBF, limit is just kept for backwards compatibility.
96 It is passed to the default bfifo qdisc - if the inner qdisc is
97 changed the limit is not effective anymore.
98 */
99
100 struct tbf_sched_data
101 {
102 /* Parameters */
103 u32 limit; /* Maximal length of backlog: bytes */
104 u32 buffer; /* Token bucket depth/rate: MUST BE >= MTU/B */
105 u32 mtu;
106 u32 max_size;
107 struct qdisc_rate_table *R_tab;
108 struct qdisc_rate_table *P_tab;
109
110 /* Variables */
111 long tokens; /* Current number of B tokens */
112 long ptokens; /* Current number of P tokens */
113 psched_time_t t_c; /* Time check-point */
114 struct Qdisc *qdisc; /* Inner qdisc, default - bfifo queue */
115 struct qdisc_watchdog watchdog; /* Watchdog timer */
116 };
117
118 #define L2T(q,L) qdisc_l2t((q)->R_tab,L)
119 #define L2T_P(q,L) qdisc_l2t((q)->P_tab,L)
120
121 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc* sch)
122 {
123 struct tbf_sched_data *q = qdisc_priv(sch);
124 int ret;
125
126 if (skb->len > q->max_size) {
127 sch->qstats.drops++;
128 #ifdef CONFIG_NET_CLS_ACT
129 if (sch->reshape_fail == NULL || sch->reshape_fail(skb, sch))
130 #endif
131 kfree_skb(skb);
132
133 return NET_XMIT_DROP;
134 }
135
136 if ((ret = q->qdisc->enqueue(skb, q->qdisc)) != 0) {
137 sch->qstats.drops++;
138 return ret;
139 }
140
141 sch->q.qlen++;
142 sch->bstats.bytes += skb->len;
143 sch->bstats.packets++;
144 return 0;
145 }
146
147 static int tbf_requeue(struct sk_buff *skb, struct Qdisc* sch)
148 {
149 struct tbf_sched_data *q = qdisc_priv(sch);
150 int ret;
151
152 if ((ret = q->qdisc->ops->requeue(skb, q->qdisc)) == 0) {
153 sch->q.qlen++;
154 sch->qstats.requeues++;
155 }
156
157 return ret;
158 }
159
160 static unsigned int tbf_drop(struct Qdisc* sch)
161 {
162 struct tbf_sched_data *q = qdisc_priv(sch);
163 unsigned int len = 0;
164
165 if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
166 sch->q.qlen--;
167 sch->qstats.drops++;
168 }
169 return len;
170 }
171
172 static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
173 {
174 struct tbf_sched_data *q = qdisc_priv(sch);
175 struct sk_buff *skb;
176
177 skb = q->qdisc->dequeue(q->qdisc);
178
179 if (skb) {
180 psched_time_t now;
181 long toks;
182 long ptoks = 0;
183 unsigned int len = skb->len;
184
185 now = psched_get_time();
186 toks = psched_tdiff_bounded(now, q->t_c, q->buffer);
187
188 if (q->P_tab) {
189 ptoks = toks + q->ptokens;
190 if (ptoks > (long)q->mtu)
191 ptoks = q->mtu;
192 ptoks -= L2T_P(q, len);
193 }
194 toks += q->tokens;
195 if (toks > (long)q->buffer)
196 toks = q->buffer;
197 toks -= L2T(q, len);
198
199 if ((toks|ptoks) >= 0) {
200 q->t_c = now;
201 q->tokens = toks;
202 q->ptokens = ptoks;
203 sch->q.qlen--;
204 sch->flags &= ~TCQ_F_THROTTLED;
205 return skb;
206 }
207
208 qdisc_watchdog_schedule(&q->watchdog,
209 now + max_t(long, -toks, -ptoks));
210
211 /* Maybe we have a shorter packet in the queue,
212 which can be sent now. It sounds cool,
213 but, however, this is wrong in principle.
214 We MUST NOT reorder packets under these circumstances.
215
216 Really, if we split the flow into independent
217 subflows, it would be a very good solution.
218 This is the main idea of all FQ algorithms
219 (cf. CSZ, HPFQ, HFSC)
220 */
221
222 if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
223 /* When requeue fails skb is dropped */
224 qdisc_tree_decrease_qlen(q->qdisc, 1);
225 sch->qstats.drops++;
226 }
227
228 sch->qstats.overlimits++;
229 }
230 return NULL;
231 }
232
233 static void tbf_reset(struct Qdisc* sch)
234 {
235 struct tbf_sched_data *q = qdisc_priv(sch);
236
237 qdisc_reset(q->qdisc);
238 sch->q.qlen = 0;
239 q->t_c = psched_get_time();
240 q->tokens = q->buffer;
241 q->ptokens = q->mtu;
242 qdisc_watchdog_cancel(&q->watchdog);
243 }
244
245 static struct Qdisc *tbf_create_dflt_qdisc(struct Qdisc *sch, u32 limit)
246 {
247 struct Qdisc *q;
248 struct nlattr *nla;
249 int ret;
250
251 q = qdisc_create_dflt(sch->dev, &bfifo_qdisc_ops,
252 TC_H_MAKE(sch->handle, 1));
253 if (q) {
254 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)),
255 GFP_KERNEL);
256 if (nla) {
257 nla->nla_type = RTM_NEWQDISC;
258 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
259 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
260
261 ret = q->ops->change(q, nla);
262 kfree(nla);
263
264 if (ret == 0)
265 return q;
266 }
267 qdisc_destroy(q);
268 }
269
270 return NULL;
271 }
272
273 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
274 [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) },
275 [TCA_TBF_RTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
276 [TCA_TBF_PTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
277 };
278
279 static int tbf_change(struct Qdisc* sch, struct nlattr *opt)
280 {
281 int err;
282 struct tbf_sched_data *q = qdisc_priv(sch);
283 struct nlattr *tb[TCA_TBF_PTAB + 1];
284 struct tc_tbf_qopt *qopt;
285 struct qdisc_rate_table *rtab = NULL;
286 struct qdisc_rate_table *ptab = NULL;
287 struct Qdisc *child = NULL;
288 int max_size,n;
289
290 err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, tbf_policy);
291 if (err < 0)
292 return err;
293
294 err = -EINVAL;
295 if (tb[TCA_TBF_PARMS] == NULL)
296 goto done;
297
298 qopt = nla_data(tb[TCA_TBF_PARMS]);
299 rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
300 if (rtab == NULL)
301 goto done;
302
303 if (qopt->peakrate.rate) {
304 if (qopt->peakrate.rate > qopt->rate.rate)
305 ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
306 if (ptab == NULL)
307 goto done;
308 }
309
310 for (n = 0; n < 256; n++)
311 if (rtab->data[n] > qopt->buffer) break;
312 max_size = (n << qopt->rate.cell_log)-1;
313 if (ptab) {
314 int size;
315
316 for (n = 0; n < 256; n++)
317 if (ptab->data[n] > qopt->mtu) break;
318 size = (n << qopt->peakrate.cell_log)-1;
319 if (size < max_size) max_size = size;
320 }
321 if (max_size < 0)
322 goto done;
323
324 if (qopt->limit > 0) {
325 if ((child = tbf_create_dflt_qdisc(sch, qopt->limit)) == NULL)
326 goto done;
327 }
328
329 sch_tree_lock(sch);
330 if (child) {
331 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
332 qdisc_destroy(xchg(&q->qdisc, child));
333 }
334 q->limit = qopt->limit;
335 q->mtu = qopt->mtu;
336 q->max_size = max_size;
337 q->buffer = qopt->buffer;
338 q->tokens = q->buffer;
339 q->ptokens = q->mtu;
340 rtab = xchg(&q->R_tab, rtab);
341 ptab = xchg(&q->P_tab, ptab);
342 sch_tree_unlock(sch);
343 err = 0;
344 done:
345 if (rtab)
346 qdisc_put_rtab(rtab);
347 if (ptab)
348 qdisc_put_rtab(ptab);
349 return err;
350 }
351
352 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
353 {
354 struct tbf_sched_data *q = qdisc_priv(sch);
355
356 if (opt == NULL)
357 return -EINVAL;
358
359 q->t_c = psched_get_time();
360 qdisc_watchdog_init(&q->watchdog, sch);
361 q->qdisc = &noop_qdisc;
362
363 return tbf_change(sch, opt);
364 }
365
366 static void tbf_destroy(struct Qdisc *sch)
367 {
368 struct tbf_sched_data *q = qdisc_priv(sch);
369
370 qdisc_watchdog_cancel(&q->watchdog);
371
372 if (q->P_tab)
373 qdisc_put_rtab(q->P_tab);
374 if (q->R_tab)
375 qdisc_put_rtab(q->R_tab);
376
377 qdisc_destroy(q->qdisc);
378 }
379
380 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
381 {
382 struct tbf_sched_data *q = qdisc_priv(sch);
383 struct nlattr *nest;
384 struct tc_tbf_qopt opt;
385
386 nest = nla_nest_start(skb, TCA_OPTIONS);
387 if (nest == NULL)
388 goto nla_put_failure;
389
390 opt.limit = q->limit;
391 opt.rate = q->R_tab->rate;
392 if (q->P_tab)
393 opt.peakrate = q->P_tab->rate;
394 else
395 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
396 opt.mtu = q->mtu;
397 opt.buffer = q->buffer;
398 NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
399
400 nla_nest_end(skb, nest);
401 return skb->len;
402
403 nla_put_failure:
404 nla_nest_cancel(skb, nest);
405 return -1;
406 }
407
408 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
409 struct sk_buff *skb, struct tcmsg *tcm)
410 {
411 struct tbf_sched_data *q = qdisc_priv(sch);
412
413 if (cl != 1) /* only one class */
414 return -ENOENT;
415
416 tcm->tcm_handle |= TC_H_MIN(1);
417 tcm->tcm_info = q->qdisc->handle;
418
419 return 0;
420 }
421
422 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
423 struct Qdisc **old)
424 {
425 struct tbf_sched_data *q = qdisc_priv(sch);
426
427 if (new == NULL)
428 new = &noop_qdisc;
429
430 sch_tree_lock(sch);
431 *old = xchg(&q->qdisc, new);
432 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
433 qdisc_reset(*old);
434 sch_tree_unlock(sch);
435
436 return 0;
437 }
438
439 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
440 {
441 struct tbf_sched_data *q = qdisc_priv(sch);
442 return q->qdisc;
443 }
444
445 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
446 {
447 return 1;
448 }
449
450 static void tbf_put(struct Qdisc *sch, unsigned long arg)
451 {
452 }
453
454 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
455 struct nlattr **tca, unsigned long *arg)
456 {
457 return -ENOSYS;
458 }
459
460 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
461 {
462 return -ENOSYS;
463 }
464
465 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
466 {
467 if (!walker->stop) {
468 if (walker->count >= walker->skip)
469 if (walker->fn(sch, 1, walker) < 0) {
470 walker->stop = 1;
471 return;
472 }
473 walker->count++;
474 }
475 }
476
477 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
478 {
479 return NULL;
480 }
481
482 static const struct Qdisc_class_ops tbf_class_ops =
483 {
484 .graft = tbf_graft,
485 .leaf = tbf_leaf,
486 .get = tbf_get,
487 .put = tbf_put,
488 .change = tbf_change_class,
489 .delete = tbf_delete,
490 .walk = tbf_walk,
491 .tcf_chain = tbf_find_tcf,
492 .dump = tbf_dump_class,
493 };
494
495 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
496 .next = NULL,
497 .cl_ops = &tbf_class_ops,
498 .id = "tbf",
499 .priv_size = sizeof(struct tbf_sched_data),
500 .enqueue = tbf_enqueue,
501 .dequeue = tbf_dequeue,
502 .requeue = tbf_requeue,
503 .drop = tbf_drop,
504 .init = tbf_init,
505 .reset = tbf_reset,
506 .destroy = tbf_destroy,
507 .change = tbf_change,
508 .dump = tbf_dump,
509 .owner = THIS_MODULE,
510 };
511
512 static int __init tbf_module_init(void)
513 {
514 return register_qdisc(&tbf_qdisc_ops);
515 }
516
517 static void __exit tbf_module_exit(void)
518 {
519 unregister_qdisc(&tbf_qdisc_ops);
520 }
521 module_init(tbf_module_init)
522 module_exit(tbf_module_exit)
523 MODULE_LICENSE("GPL");
524
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