2 * net/sched/sch_tbf.c Token Bucket Filter queue.
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.
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
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/sch_generic.h>
23 #include <net/pkt_sched.h>
26 /* Simple Token Bucket Filter.
27 =======================================
37 A data flow obeys TBF with rate R and depth B, if for any
38 time interval t_i...t_f the number of transmitted bits
39 does not exceed B + R*(t_f-t_i).
41 Packetized version of this definition:
42 The sequence of packets of sizes s_i served at moments t_i
43 obeys TBF, if for any i<=k:
45 s_i+....+s_k <= B + R*(t_k - t_i)
50 Let N(t_i) be B/R initially and N(t) grow continuously with time as:
52 N(t+delta) = min{B/R, N(t) + delta}
54 If the first packet in queue has length S, it may be
55 transmitted only at the time t_* when S/R <= N(t_*),
56 and in this case N(t) jumps:
58 N(t_* + 0) = N(t_* - 0) - S/R.
62 Actually, QoS requires two TBF to be applied to a data stream.
63 One of them controls steady state burst size, another
64 one with rate P (peak rate) and depth M (equal to link MTU)
65 limits bursts at a smaller time scale.
67 It is easy to see that P>R, and B>M. If P is infinity, this double
68 TBF is equivalent to a single one.
70 When TBF works in reshaping mode, latency is estimated as:
72 lat = max ((L-B)/R, (L-M)/P)
78 If TBF throttles, it starts a watchdog timer, which will wake it up
79 when it is ready to transmit.
80 Note that the minimal timer resolution is 1/HZ.
81 If no new packets arrive during this period,
82 or if the device is not awaken by EOI for some previous packet,
83 TBF can stop its activity for 1/HZ.
86 This means, that with depth B, the maximal rate is
90 F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
92 Note that the peak rate TBF is much more tough: with MTU 1500
93 P_crit = 150Kbytes/sec. So, if you need greater peak
94 rates, use alpha with HZ=1000 :-)
96 With classful TBF, limit is just kept for backwards compatibility.
97 It is passed to the default bfifo qdisc - if the inner qdisc is
98 changed the limit is not effective anymore.
101 struct tbf_sched_data {
103 u32 limit; /* Maximal length of backlog: bytes */
105 s64 buffer; /* Token bucket depth/rate: MUST BE >= MTU/B */
107 struct psched_ratecfg rate;
108 struct psched_ratecfg peak;
111 s64 tokens; /* Current number of B tokens */
112 s64 ptokens; /* Current number of P tokens */
113 s64 t_c; /* Time check-point */
114 struct Qdisc *qdisc; /* Inner qdisc, default - bfifo queue */
115 struct qdisc_watchdog watchdog; /* Watchdog timer */
119 /* Time to Length, convert time in ns to length in bytes
120 * to determinate how many bytes can be sent in given time.
122 static u64 psched_ns_t2l(const struct psched_ratecfg *r,
126 * len = (time_in_ns * r->rate_bytes_ps) / NSEC_PER_SEC
128 u64 len = time_in_ns * r->rate_bytes_ps;
130 do_div(len, NSEC_PER_SEC);
132 if (unlikely(r->linklayer == TC_LINKLAYER_ATM)) {
137 if (len > r->overhead)
145 /* GSO packet is too big, segment it so that tbf can transmit
146 * each segment in time
148 static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch,
149 struct sk_buff **to_free)
151 struct tbf_sched_data *q = qdisc_priv(sch);
152 struct sk_buff *segs, *nskb;
153 netdev_features_t features = netif_skb_features(skb);
154 unsigned int len = 0, prev_len = qdisc_pkt_len(skb);
157 segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
159 if (IS_ERR_OR_NULL(segs))
160 return qdisc_drop(skb, sch, to_free);
165 skb_mark_not_on_list(segs);
166 qdisc_skb_cb(segs)->pkt_len = segs->len;
168 ret = qdisc_enqueue(segs, q->qdisc, to_free);
169 if (ret != NET_XMIT_SUCCESS) {
170 if (net_xmit_drop_count(ret))
171 qdisc_qstats_drop(sch);
179 qdisc_tree_reduce_backlog(sch, 1 - nb, prev_len - len);
181 return nb > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
184 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
185 struct sk_buff **to_free)
187 struct tbf_sched_data *q = qdisc_priv(sch);
188 unsigned int len = qdisc_pkt_len(skb);
191 if (qdisc_pkt_len(skb) > q->max_size) {
192 if (skb_is_gso(skb) &&
193 skb_gso_validate_mac_len(skb, q->max_size))
194 return tbf_segment(skb, sch, to_free);
195 return qdisc_drop(skb, sch, to_free);
197 ret = qdisc_enqueue(skb, q->qdisc, to_free);
198 if (ret != NET_XMIT_SUCCESS) {
199 if (net_xmit_drop_count(ret))
200 qdisc_qstats_drop(sch);
204 sch->qstats.backlog += len;
206 return NET_XMIT_SUCCESS;
209 static bool tbf_peak_present(const struct tbf_sched_data *q)
211 return q->peak.rate_bytes_ps;
214 static struct sk_buff *tbf_dequeue(struct Qdisc *sch)
216 struct tbf_sched_data *q = qdisc_priv(sch);
219 skb = q->qdisc->ops->peek(q->qdisc);
225 unsigned int len = qdisc_pkt_len(skb);
227 now = ktime_get_ns();
228 toks = min_t(s64, now - q->t_c, q->buffer);
230 if (tbf_peak_present(q)) {
231 ptoks = toks + q->ptokens;
234 ptoks -= (s64) psched_l2t_ns(&q->peak, len);
237 if (toks > q->buffer)
239 toks -= (s64) psched_l2t_ns(&q->rate, len);
241 if ((toks|ptoks) >= 0) {
242 skb = qdisc_dequeue_peeked(q->qdisc);
249 qdisc_qstats_backlog_dec(sch, skb);
251 qdisc_bstats_update(sch, skb);
255 qdisc_watchdog_schedule_ns(&q->watchdog,
256 now + max_t(long, -toks, -ptoks));
258 /* Maybe we have a shorter packet in the queue,
259 which can be sent now. It sounds cool,
260 but, however, this is wrong in principle.
261 We MUST NOT reorder packets under these circumstances.
263 Really, if we split the flow into independent
264 subflows, it would be a very good solution.
265 This is the main idea of all FQ algorithms
266 (cf. CSZ, HPFQ, HFSC)
269 qdisc_qstats_overlimit(sch);
274 static void tbf_reset(struct Qdisc *sch)
276 struct tbf_sched_data *q = qdisc_priv(sch);
278 qdisc_reset(q->qdisc);
279 sch->qstats.backlog = 0;
281 q->t_c = ktime_get_ns();
282 q->tokens = q->buffer;
284 qdisc_watchdog_cancel(&q->watchdog);
287 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
288 [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) },
289 [TCA_TBF_RTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
290 [TCA_TBF_PTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
291 [TCA_TBF_RATE64] = { .type = NLA_U64 },
292 [TCA_TBF_PRATE64] = { .type = NLA_U64 },
293 [TCA_TBF_BURST] = { .type = NLA_U32 },
294 [TCA_TBF_PBURST] = { .type = NLA_U32 },
297 static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
298 struct netlink_ext_ack *extack)
301 struct tbf_sched_data *q = qdisc_priv(sch);
302 struct nlattr *tb[TCA_TBF_MAX + 1];
303 struct tc_tbf_qopt *qopt;
304 struct Qdisc *child = NULL;
305 struct psched_ratecfg rate;
306 struct psched_ratecfg peak;
309 u64 rate64 = 0, prate64 = 0;
311 err = nla_parse_nested(tb, TCA_TBF_MAX, opt, tbf_policy, NULL);
316 if (tb[TCA_TBF_PARMS] == NULL)
319 qopt = nla_data(tb[TCA_TBF_PARMS]);
320 if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE)
321 qdisc_put_rtab(qdisc_get_rtab(&qopt->rate,
325 if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE)
326 qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate,
330 buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U);
331 mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U);
333 if (tb[TCA_TBF_RATE64])
334 rate64 = nla_get_u64(tb[TCA_TBF_RATE64]);
335 psched_ratecfg_precompute(&rate, &qopt->rate, rate64);
337 if (tb[TCA_TBF_BURST]) {
338 max_size = nla_get_u32(tb[TCA_TBF_BURST]);
339 buffer = psched_l2t_ns(&rate, max_size);
341 max_size = min_t(u64, psched_ns_t2l(&rate, buffer), ~0U);
344 if (qopt->peakrate.rate) {
345 if (tb[TCA_TBF_PRATE64])
346 prate64 = nla_get_u64(tb[TCA_TBF_PRATE64]);
347 psched_ratecfg_precompute(&peak, &qopt->peakrate, prate64);
348 if (peak.rate_bytes_ps <= rate.rate_bytes_ps) {
349 pr_warn_ratelimited("sch_tbf: peakrate %llu is lower than or equals to rate %llu !\n",
350 peak.rate_bytes_ps, rate.rate_bytes_ps);
355 if (tb[TCA_TBF_PBURST]) {
356 u32 pburst = nla_get_u32(tb[TCA_TBF_PBURST]);
357 max_size = min_t(u32, max_size, pburst);
358 mtu = psched_l2t_ns(&peak, pburst);
360 max_size = min_t(u64, max_size, psched_ns_t2l(&peak, mtu));
363 memset(&peak, 0, sizeof(peak));
366 if (max_size < psched_mtu(qdisc_dev(sch)))
367 pr_warn_ratelimited("sch_tbf: burst %llu is lower than device %s mtu (%u) !\n",
368 max_size, qdisc_dev(sch)->name,
369 psched_mtu(qdisc_dev(sch)));
376 if (q->qdisc != &noop_qdisc) {
377 err = fifo_set_limit(q->qdisc, qopt->limit);
380 } else if (qopt->limit > 0) {
381 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit,
384 err = PTR_ERR(child);
388 /* child is fifo, no need to check for noop_qdisc */
389 qdisc_hash_add(child, true);
394 qdisc_tree_flush_backlog(q->qdisc);
398 q->limit = qopt->limit;
399 if (tb[TCA_TBF_PBURST])
402 q->mtu = PSCHED_TICKS2NS(qopt->mtu);
403 q->max_size = max_size;
404 if (tb[TCA_TBF_BURST])
407 q->buffer = PSCHED_TICKS2NS(qopt->buffer);
408 q->tokens = q->buffer;
411 memcpy(&q->rate, &rate, sizeof(struct psched_ratecfg));
412 memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg));
414 sch_tree_unlock(sch);
420 static int tbf_init(struct Qdisc *sch, struct nlattr *opt,
421 struct netlink_ext_ack *extack)
423 struct tbf_sched_data *q = qdisc_priv(sch);
425 qdisc_watchdog_init(&q->watchdog, sch);
426 q->qdisc = &noop_qdisc;
431 q->t_c = ktime_get_ns();
433 return tbf_change(sch, opt, extack);
436 static void tbf_destroy(struct Qdisc *sch)
438 struct tbf_sched_data *q = qdisc_priv(sch);
440 qdisc_watchdog_cancel(&q->watchdog);
444 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
446 struct tbf_sched_data *q = qdisc_priv(sch);
448 struct tc_tbf_qopt opt;
450 sch->qstats.backlog = q->qdisc->qstats.backlog;
451 nest = nla_nest_start(skb, TCA_OPTIONS);
453 goto nla_put_failure;
455 opt.limit = q->limit;
456 psched_ratecfg_getrate(&opt.rate, &q->rate);
457 if (tbf_peak_present(q))
458 psched_ratecfg_getrate(&opt.peakrate, &q->peak);
460 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
461 opt.mtu = PSCHED_NS2TICKS(q->mtu);
462 opt.buffer = PSCHED_NS2TICKS(q->buffer);
463 if (nla_put(skb, TCA_TBF_PARMS, sizeof(opt), &opt))
464 goto nla_put_failure;
465 if (q->rate.rate_bytes_ps >= (1ULL << 32) &&
466 nla_put_u64_64bit(skb, TCA_TBF_RATE64, q->rate.rate_bytes_ps,
468 goto nla_put_failure;
469 if (tbf_peak_present(q) &&
470 q->peak.rate_bytes_ps >= (1ULL << 32) &&
471 nla_put_u64_64bit(skb, TCA_TBF_PRATE64, q->peak.rate_bytes_ps,
473 goto nla_put_failure;
475 return nla_nest_end(skb, nest);
478 nla_nest_cancel(skb, nest);
482 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
483 struct sk_buff *skb, struct tcmsg *tcm)
485 struct tbf_sched_data *q = qdisc_priv(sch);
487 tcm->tcm_handle |= TC_H_MIN(1);
488 tcm->tcm_info = q->qdisc->handle;
493 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
494 struct Qdisc **old, struct netlink_ext_ack *extack)
496 struct tbf_sched_data *q = qdisc_priv(sch);
501 *old = qdisc_replace(sch, new, &q->qdisc);
505 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
507 struct tbf_sched_data *q = qdisc_priv(sch);
511 static unsigned long tbf_find(struct Qdisc *sch, u32 classid)
516 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
519 if (walker->count >= walker->skip)
520 if (walker->fn(sch, 1, walker) < 0) {
528 static const struct Qdisc_class_ops tbf_class_ops = {
533 .dump = tbf_dump_class,
536 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
538 .cl_ops = &tbf_class_ops,
540 .priv_size = sizeof(struct tbf_sched_data),
541 .enqueue = tbf_enqueue,
542 .dequeue = tbf_dequeue,
543 .peek = qdisc_peek_dequeued,
546 .destroy = tbf_destroy,
547 .change = tbf_change,
549 .owner = THIS_MODULE,
552 static int __init tbf_module_init(void)
554 return register_qdisc(&tbf_qdisc_ops);
557 static void __exit tbf_module_exit(void)
559 unregister_qdisc(&tbf_qdisc_ops);
561 module_init(tbf_module_init)
562 module_exit(tbf_module_exit)
563 MODULE_LICENSE("GPL");