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/sch_generic.h> 23 #include <net/pkt_sched.h> 24 25 26 /* Simple Token Bucket Filter. 27 ======================================= 28 29 SOURCE. 30 ------- 31 32 None. 33 34 Description. 35 ------------ 36 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). 40 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: 44 45 s_i+....+s_k <= B + R*(t_k - t_i) 46 47 Algorithm. 48 ---------- 49 50 Let N(t_i) be B/R initially and N(t) grow continuously with time as: 51 52 N(t+delta) = min{B/R, N(t) + delta} 53 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: 57 58 N(t_* + 0) = N(t_* - 0) - S/R. 59 60 61 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. 66 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. 69 70 When TBF works in reshaping mode, latency is estimated as: 71 72 lat = max ((L-B)/R, (L-M)/P) 73 74 75 NOTES. 76 ------ 77 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. 84 85 86 This means, that with depth B, the maximal rate is 87 88 R_crit = B*HZ 89 90 F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes. 91 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 :-) 95 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. 99 */ 100 101 struct tbf_sched_data { 102 /* Parameters */ 103 u32 limit; /* Maximal length of backlog: bytes */ 104 u32 max_size; 105 s64 buffer; /* Token bucket depth/rate: MUST BE >= MTU/B */ 106 s64 mtu; 107 struct psched_ratecfg rate; 108 struct psched_ratecfg peak; 109 110 /* Variables */ 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 */ 116 }; 117 118 119 /* Time to Length, convert time in ns to length in bytes 120 * to determinate how many bytes can be sent in given time. 121 */ 122 static u64 psched_ns_t2l(const struct psched_ratecfg *r, 123 u64 time_in_ns) 124 { 125 /* The formula is : 126 * len = (time_in_ns * r->rate_bytes_ps) / NSEC_PER_SEC 127 */ 128 u64 len = time_in_ns * r->rate_bytes_ps; 129 130 do_div(len, NSEC_PER_SEC); 131 132 if (unlikely(r->linklayer == TC_LINKLAYER_ATM)) { 133 do_div(len, 53); 134 len = len * 48; 135 } 136 137 if (len > r->overhead) 138 len -= r->overhead; 139 else 140 len = 0; 141 142 return len; 143 } 144 145 /* 146 * Return length of individual segments of a gso packet, 147 * including all headers (MAC, IP, TCP/UDP) 148 */ 149 static unsigned int skb_gso_mac_seglen(const struct sk_buff *skb) 150 { 151 unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb); 152 return hdr_len + skb_gso_transport_seglen(skb); 153 } 154 155 /* GSO packet is too big, segment it so that tbf can transmit 156 * each segment in time 157 */ 158 static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch) 159 { 160 struct tbf_sched_data *q = qdisc_priv(sch); 161 struct sk_buff *segs, *nskb; 162 netdev_features_t features = netif_skb_features(skb); 163 int ret, nb; 164 165 segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK); 166 167 if (IS_ERR_OR_NULL(segs)) 168 return qdisc_reshape_fail(skb, sch); 169 170 nb = 0; 171 while (segs) { 172 nskb = segs->next; 173 segs->next = NULL; 174 qdisc_skb_cb(segs)->pkt_len = segs->len; 175 ret = qdisc_enqueue(segs, q->qdisc); 176 if (ret != NET_XMIT_SUCCESS) { 177 if (net_xmit_drop_count(ret)) 178 sch->qstats.drops++; 179 } else { 180 nb++; 181 } 182 segs = nskb; 183 } 184 sch->q.qlen += nb; 185 if (nb > 1) 186 qdisc_tree_decrease_qlen(sch, 1 - nb); 187 consume_skb(skb); 188 return nb > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP; 189 } 190 191 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch) 192 { 193 struct tbf_sched_data *q = qdisc_priv(sch); 194 int ret; 195 196 if (qdisc_pkt_len(skb) > q->max_size) { 197 if (skb_is_gso(skb) && skb_gso_mac_seglen(skb) <= q->max_size) 198 return tbf_segment(skb, sch); 199 return qdisc_reshape_fail(skb, sch); 200 } 201 ret = qdisc_enqueue(skb, q->qdisc); 202 if (ret != NET_XMIT_SUCCESS) { 203 if (net_xmit_drop_count(ret)) 204 sch->qstats.drops++; 205 return ret; 206 } 207 208 sch->q.qlen++; 209 return NET_XMIT_SUCCESS; 210 } 211 212 static unsigned int tbf_drop(struct Qdisc *sch) 213 { 214 struct tbf_sched_data *q = qdisc_priv(sch); 215 unsigned int len = 0; 216 217 if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) { 218 sch->q.qlen--; 219 sch->qstats.drops++; 220 } 221 return len; 222 } 223 224 static bool tbf_peak_present(const struct tbf_sched_data *q) 225 { 226 return q->peak.rate_bytes_ps; 227 } 228 229 static struct sk_buff *tbf_dequeue(struct Qdisc *sch) 230 { 231 struct tbf_sched_data *q = qdisc_priv(sch); 232 struct sk_buff *skb; 233 234 skb = q->qdisc->ops->peek(q->qdisc); 235 236 if (skb) { 237 s64 now; 238 s64 toks; 239 s64 ptoks = 0; 240 unsigned int len = qdisc_pkt_len(skb); 241 242 now = ktime_to_ns(ktime_get()); 243 toks = min_t(s64, now - q->t_c, q->buffer); 244 245 if (tbf_peak_present(q)) { 246 ptoks = toks + q->ptokens; 247 if (ptoks > q->mtu) 248 ptoks = q->mtu; 249 ptoks -= (s64) psched_l2t_ns(&q->peak, len); 250 } 251 toks += q->tokens; 252 if (toks > q->buffer) 253 toks = q->buffer; 254 toks -= (s64) psched_l2t_ns(&q->rate, len); 255 256 if ((toks|ptoks) >= 0) { 257 skb = qdisc_dequeue_peeked(q->qdisc); 258 if (unlikely(!skb)) 259 return NULL; 260 261 q->t_c = now; 262 q->tokens = toks; 263 q->ptokens = ptoks; 264 sch->q.qlen--; 265 qdisc_unthrottled(sch); 266 qdisc_bstats_update(sch, skb); 267 return skb; 268 } 269 270 qdisc_watchdog_schedule_ns(&q->watchdog, 271 now + max_t(long, -toks, -ptoks)); 272 273 /* Maybe we have a shorter packet in the queue, 274 which can be sent now. It sounds cool, 275 but, however, this is wrong in principle. 276 We MUST NOT reorder packets under these circumstances. 277 278 Really, if we split the flow into independent 279 subflows, it would be a very good solution. 280 This is the main idea of all FQ algorithms 281 (cf. CSZ, HPFQ, HFSC) 282 */ 283 284 sch->qstats.overlimits++; 285 } 286 return NULL; 287 } 288 289 static void tbf_reset(struct Qdisc *sch) 290 { 291 struct tbf_sched_data *q = qdisc_priv(sch); 292 293 qdisc_reset(q->qdisc); 294 sch->q.qlen = 0; 295 q->t_c = ktime_to_ns(ktime_get()); 296 q->tokens = q->buffer; 297 q->ptokens = q->mtu; 298 qdisc_watchdog_cancel(&q->watchdog); 299 } 300 301 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = { 302 [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) }, 303 [TCA_TBF_RTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE }, 304 [TCA_TBF_PTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE }, 305 [TCA_TBF_RATE64] = { .type = NLA_U64 }, 306 [TCA_TBF_PRATE64] = { .type = NLA_U64 }, 307 [TCA_TBF_BURST] = { .type = NLA_U32 }, 308 [TCA_TBF_PBURST] = { .type = NLA_U32 }, 309 }; 310 311 static int tbf_change(struct Qdisc *sch, struct nlattr *opt) 312 { 313 int err; 314 struct tbf_sched_data *q = qdisc_priv(sch); 315 struct nlattr *tb[TCA_TBF_MAX + 1]; 316 struct tc_tbf_qopt *qopt; 317 struct Qdisc *child = NULL; 318 struct psched_ratecfg rate; 319 struct psched_ratecfg peak; 320 u64 max_size; 321 s64 buffer, mtu; 322 u64 rate64 = 0, prate64 = 0; 323 324 err = nla_parse_nested(tb, TCA_TBF_MAX, opt, tbf_policy); 325 if (err < 0) 326 return err; 327 328 err = -EINVAL; 329 if (tb[TCA_TBF_PARMS] == NULL) 330 goto done; 331 332 qopt = nla_data(tb[TCA_TBF_PARMS]); 333 if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE) 334 qdisc_put_rtab(qdisc_get_rtab(&qopt->rate, 335 tb[TCA_TBF_RTAB])); 336 337 if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE) 338 qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate, 339 tb[TCA_TBF_PTAB])); 340 341 buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U); 342 mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U); 343 344 if (tb[TCA_TBF_RATE64]) 345 rate64 = nla_get_u64(tb[TCA_TBF_RATE64]); 346 psched_ratecfg_precompute(&rate, &qopt->rate, rate64); 347 348 if (tb[TCA_TBF_BURST]) { 349 max_size = nla_get_u32(tb[TCA_TBF_BURST]); 350 buffer = psched_l2t_ns(&rate, max_size); 351 } else { 352 max_size = min_t(u64, psched_ns_t2l(&rate, buffer), ~0U); 353 } 354 355 if (qopt->peakrate.rate) { 356 if (tb[TCA_TBF_PRATE64]) 357 prate64 = nla_get_u64(tb[TCA_TBF_PRATE64]); 358 psched_ratecfg_precompute(&peak, &qopt->peakrate, prate64); 359 if (peak.rate_bytes_ps <= rate.rate_bytes_ps) { 360 pr_warn_ratelimited("sch_tbf: peakrate %llu is lower than or equals to rate %llu !\n", 361 peak.rate_bytes_ps, rate.rate_bytes_ps); 362 err = -EINVAL; 363 goto done; 364 } 365 366 if (tb[TCA_TBF_PBURST]) { 367 u32 pburst = nla_get_u32(tb[TCA_TBF_PBURST]); 368 max_size = min_t(u32, max_size, pburst); 369 mtu = psched_l2t_ns(&peak, pburst); 370 } else { 371 max_size = min_t(u64, max_size, psched_ns_t2l(&peak, mtu)); 372 } 373 } else { 374 memset(&peak, 0, sizeof(peak)); 375 } 376 377 if (max_size < psched_mtu(qdisc_dev(sch))) 378 pr_warn_ratelimited("sch_tbf: burst %llu is lower than device %s mtu (%u) !\n", 379 max_size, qdisc_dev(sch)->name, 380 psched_mtu(qdisc_dev(sch))); 381 382 if (!max_size) { 383 err = -EINVAL; 384 goto done; 385 } 386 387 if (q->qdisc != &noop_qdisc) { 388 err = fifo_set_limit(q->qdisc, qopt->limit); 389 if (err) 390 goto done; 391 } else if (qopt->limit > 0) { 392 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit); 393 if (IS_ERR(child)) { 394 err = PTR_ERR(child); 395 goto done; 396 } 397 } 398 399 sch_tree_lock(sch); 400 if (child) { 401 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen); 402 qdisc_destroy(q->qdisc); 403 q->qdisc = child; 404 } 405 q->limit = qopt->limit; 406 if (tb[TCA_TBF_PBURST]) 407 q->mtu = mtu; 408 else 409 q->mtu = PSCHED_TICKS2NS(qopt->mtu); 410 q->max_size = max_size; 411 if (tb[TCA_TBF_BURST]) 412 q->buffer = buffer; 413 else 414 q->buffer = PSCHED_TICKS2NS(qopt->buffer); 415 q->tokens = q->buffer; 416 q->ptokens = q->mtu; 417 418 memcpy(&q->rate, &rate, sizeof(struct psched_ratecfg)); 419 memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg)); 420 421 sch_tree_unlock(sch); 422 err = 0; 423 done: 424 return err; 425 } 426 427 static int tbf_init(struct Qdisc *sch, struct nlattr *opt) 428 { 429 struct tbf_sched_data *q = qdisc_priv(sch); 430 431 if (opt == NULL) 432 return -EINVAL; 433 434 q->t_c = ktime_to_ns(ktime_get()); 435 qdisc_watchdog_init(&q->watchdog, sch); 436 q->qdisc = &noop_qdisc; 437 438 return tbf_change(sch, opt); 439 } 440 441 static void tbf_destroy(struct Qdisc *sch) 442 { 443 struct tbf_sched_data *q = qdisc_priv(sch); 444 445 qdisc_watchdog_cancel(&q->watchdog); 446 qdisc_destroy(q->qdisc); 447 } 448 449 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb) 450 { 451 struct tbf_sched_data *q = qdisc_priv(sch); 452 struct nlattr *nest; 453 struct tc_tbf_qopt opt; 454 455 sch->qstats.backlog = q->qdisc->qstats.backlog; 456 nest = nla_nest_start(skb, TCA_OPTIONS); 457 if (nest == NULL) 458 goto nla_put_failure; 459 460 opt.limit = q->limit; 461 psched_ratecfg_getrate(&opt.rate, &q->rate); 462 if (tbf_peak_present(q)) 463 psched_ratecfg_getrate(&opt.peakrate, &q->peak); 464 else 465 memset(&opt.peakrate, 0, sizeof(opt.peakrate)); 466 opt.mtu = PSCHED_NS2TICKS(q->mtu); 467 opt.buffer = PSCHED_NS2TICKS(q->buffer); 468 if (nla_put(skb, TCA_TBF_PARMS, sizeof(opt), &opt)) 469 goto nla_put_failure; 470 if (q->rate.rate_bytes_ps >= (1ULL << 32) && 471 nla_put_u64(skb, TCA_TBF_RATE64, q->rate.rate_bytes_ps)) 472 goto nla_put_failure; 473 if (tbf_peak_present(q) && 474 q->peak.rate_bytes_ps >= (1ULL << 32) && 475 nla_put_u64(skb, TCA_TBF_PRATE64, q->peak.rate_bytes_ps)) 476 goto nla_put_failure; 477 478 return nla_nest_end(skb, nest); 479 480 nla_put_failure: 481 nla_nest_cancel(skb, nest); 482 return -1; 483 } 484 485 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl, 486 struct sk_buff *skb, struct tcmsg *tcm) 487 { 488 struct tbf_sched_data *q = qdisc_priv(sch); 489 490 tcm->tcm_handle |= TC_H_MIN(1); 491 tcm->tcm_info = q->qdisc->handle; 492 493 return 0; 494 } 495 496 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new, 497 struct Qdisc **old) 498 { 499 struct tbf_sched_data *q = qdisc_priv(sch); 500 501 if (new == NULL) 502 new = &noop_qdisc; 503 504 sch_tree_lock(sch); 505 *old = q->qdisc; 506 q->qdisc = new; 507 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen); 508 qdisc_reset(*old); 509 sch_tree_unlock(sch); 510 511 return 0; 512 } 513 514 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg) 515 { 516 struct tbf_sched_data *q = qdisc_priv(sch); 517 return q->qdisc; 518 } 519 520 static unsigned long tbf_get(struct Qdisc *sch, u32 classid) 521 { 522 return 1; 523 } 524 525 static void tbf_put(struct Qdisc *sch, unsigned long arg) 526 { 527 } 528 529 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker) 530 { 531 if (!walker->stop) { 532 if (walker->count >= walker->skip) 533 if (walker->fn(sch, 1, walker) < 0) { 534 walker->stop = 1; 535 return; 536 } 537 walker->count++; 538 } 539 } 540 541 static const struct Qdisc_class_ops tbf_class_ops = { 542 .graft = tbf_graft, 543 .leaf = tbf_leaf, 544 .get = tbf_get, 545 .put = tbf_put, 546 .walk = tbf_walk, 547 .dump = tbf_dump_class, 548 }; 549 550 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = { 551 .next = NULL, 552 .cl_ops = &tbf_class_ops, 553 .id = "tbf", 554 .priv_size = sizeof(struct tbf_sched_data), 555 .enqueue = tbf_enqueue, 556 .dequeue = tbf_dequeue, 557 .peek = qdisc_peek_dequeued, 558 .drop = tbf_drop, 559 .init = tbf_init, 560 .reset = tbf_reset, 561 .destroy = tbf_destroy, 562 .change = tbf_change, 563 .dump = tbf_dump, 564 .owner = THIS_MODULE, 565 }; 566 567 static int __init tbf_module_init(void) 568 { 569 return register_qdisc(&tbf_qdisc_ops); 570 } 571 572 static void __exit tbf_module_exit(void) 573 { 574 unregister_qdisc(&tbf_qdisc_ops); 575 } 576 module_init(tbf_module_init) 577 module_exit(tbf_module_exit) 578 MODULE_LICENSE("GPL"); 579