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/pkt_sched.h>
25 /* Simple Token Bucket Filter.
26 =======================================
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).
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:
44 s_i+....+s_k <= B + R*(t_k - t_i)
49 Let N(t_i) be B/R initially and N(t) grow continuously with time as:
51 N(t+delta) = min{B/R, N(t) + delta}
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:
57 N(t_* + 0) = N(t_* - 0) - S/R.
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.
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.
69 When TBF works in reshaping mode, latency is estimated as:
71 lat = max ((L-B)/R, (L-M)/P)
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.
85 This means, that with depth B, the maximal rate is
89 F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
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 :-)
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.
100 struct tbf_sched_data
103 u32 limit; /* Maximal length of backlog: bytes */
104 u32 buffer; /* Token bucket depth/rate: MUST BE >= MTU/B */
107 struct qdisc_rate_table *R_tab;
108 struct qdisc_rate_table *P_tab;
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 */
118 #define L2T(q,L) qdisc_l2t((q)->R_tab,L)
119 #define L2T_P(q,L) qdisc_l2t((q)->P_tab,L)
121 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc* sch)
123 struct tbf_sched_data *q = qdisc_priv(sch);
126 if (qdisc_pkt_len(skb) > q->max_size)
127 return qdisc_reshape_fail(skb, sch);
129 ret = qdisc_enqueue(skb, q->qdisc);
131 if (net_xmit_drop_count(ret))
137 sch->bstats.bytes += qdisc_pkt_len(skb);
138 sch->bstats.packets++;
142 static unsigned int tbf_drop(struct Qdisc* sch)
144 struct tbf_sched_data *q = qdisc_priv(sch);
145 unsigned int len = 0;
147 if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
154 static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
156 struct tbf_sched_data *q = qdisc_priv(sch);
159 skb = q->qdisc->ops->peek(q->qdisc);
165 unsigned int len = qdisc_pkt_len(skb);
167 now = psched_get_time();
168 toks = psched_tdiff_bounded(now, q->t_c, q->buffer);
171 ptoks = toks + q->ptokens;
172 if (ptoks > (long)q->mtu)
174 ptoks -= L2T_P(q, len);
177 if (toks > (long)q->buffer)
181 if ((toks|ptoks) >= 0) {
182 skb = qdisc_dequeue_peeked(q->qdisc);
190 sch->flags &= ~TCQ_F_THROTTLED;
194 qdisc_watchdog_schedule(&q->watchdog,
195 now + max_t(long, -toks, -ptoks));
197 /* Maybe we have a shorter packet in the queue,
198 which can be sent now. It sounds cool,
199 but, however, this is wrong in principle.
200 We MUST NOT reorder packets under these circumstances.
202 Really, if we split the flow into independent
203 subflows, it would be a very good solution.
204 This is the main idea of all FQ algorithms
205 (cf. CSZ, HPFQ, HFSC)
208 sch->qstats.overlimits++;
213 static void tbf_reset(struct Qdisc* sch)
215 struct tbf_sched_data *q = qdisc_priv(sch);
217 qdisc_reset(q->qdisc);
219 q->t_c = psched_get_time();
220 q->tokens = q->buffer;
222 qdisc_watchdog_cancel(&q->watchdog);
225 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
226 [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) },
227 [TCA_TBF_RTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
228 [TCA_TBF_PTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
231 static int tbf_change(struct Qdisc* sch, struct nlattr *opt)
234 struct tbf_sched_data *q = qdisc_priv(sch);
235 struct nlattr *tb[TCA_TBF_PTAB + 1];
236 struct tc_tbf_qopt *qopt;
237 struct qdisc_rate_table *rtab = NULL;
238 struct qdisc_rate_table *ptab = NULL;
239 struct Qdisc *child = NULL;
242 err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, tbf_policy);
247 if (tb[TCA_TBF_PARMS] == NULL)
250 qopt = nla_data(tb[TCA_TBF_PARMS]);
251 rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
255 if (qopt->peakrate.rate) {
256 if (qopt->peakrate.rate > qopt->rate.rate)
257 ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
262 for (n = 0; n < 256; n++)
263 if (rtab->data[n] > qopt->buffer) break;
264 max_size = (n << qopt->rate.cell_log)-1;
268 for (n = 0; n < 256; n++)
269 if (ptab->data[n] > qopt->mtu) break;
270 size = (n << qopt->peakrate.cell_log)-1;
271 if (size < max_size) max_size = size;
276 if (qopt->limit > 0) {
277 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit);
279 err = PTR_ERR(child);
286 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
287 qdisc_destroy(q->qdisc);
290 q->limit = qopt->limit;
292 q->max_size = max_size;
293 q->buffer = qopt->buffer;
294 q->tokens = q->buffer;
297 swap(q->R_tab, rtab);
298 swap(q->P_tab, ptab);
300 sch_tree_unlock(sch);
304 qdisc_put_rtab(rtab);
306 qdisc_put_rtab(ptab);
310 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
312 struct tbf_sched_data *q = qdisc_priv(sch);
317 q->t_c = psched_get_time();
318 qdisc_watchdog_init(&q->watchdog, sch);
319 q->qdisc = &noop_qdisc;
321 return tbf_change(sch, opt);
324 static void tbf_destroy(struct Qdisc *sch)
326 struct tbf_sched_data *q = qdisc_priv(sch);
328 qdisc_watchdog_cancel(&q->watchdog);
331 qdisc_put_rtab(q->P_tab);
333 qdisc_put_rtab(q->R_tab);
335 qdisc_destroy(q->qdisc);
338 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
340 struct tbf_sched_data *q = qdisc_priv(sch);
342 struct tc_tbf_qopt opt;
344 nest = nla_nest_start(skb, TCA_OPTIONS);
346 goto nla_put_failure;
348 opt.limit = q->limit;
349 opt.rate = q->R_tab->rate;
351 opt.peakrate = q->P_tab->rate;
353 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
355 opt.buffer = q->buffer;
356 NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
358 nla_nest_end(skb, nest);
362 nla_nest_cancel(skb, nest);
366 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
367 struct sk_buff *skb, struct tcmsg *tcm)
369 struct tbf_sched_data *q = qdisc_priv(sch);
371 if (cl != 1) /* only one class */
374 tcm->tcm_handle |= TC_H_MIN(1);
375 tcm->tcm_info = q->qdisc->handle;
380 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
383 struct tbf_sched_data *q = qdisc_priv(sch);
391 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
393 sch_tree_unlock(sch);
398 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
400 struct tbf_sched_data *q = qdisc_priv(sch);
404 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
409 static void tbf_put(struct Qdisc *sch, unsigned long arg)
413 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
414 struct nlattr **tca, unsigned long *arg)
419 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
424 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
427 if (walker->count >= walker->skip)
428 if (walker->fn(sch, 1, walker) < 0) {
436 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
441 static const struct Qdisc_class_ops tbf_class_ops =
447 .change = tbf_change_class,
448 .delete = tbf_delete,
450 .tcf_chain = tbf_find_tcf,
451 .dump = tbf_dump_class,
454 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
456 .cl_ops = &tbf_class_ops,
458 .priv_size = sizeof(struct tbf_sched_data),
459 .enqueue = tbf_enqueue,
460 .dequeue = tbf_dequeue,
461 .peek = qdisc_peek_dequeued,
465 .destroy = tbf_destroy,
466 .change = tbf_change,
468 .owner = THIS_MODULE,
471 static int __init tbf_module_init(void)
473 return register_qdisc(&tbf_qdisc_ops);
476 static void __exit tbf_module_exit(void)
478 unregister_qdisc(&tbf_qdisc_ops);
480 module_init(tbf_module_init)
481 module_exit(tbf_module_exit)
482 MODULE_LICENSE("GPL");