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 qdisc_qstats_drop(sch); 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 qdisc_qstats_drop(sch); 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 qdisc_qstats_drop(sch); 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_get_ns(); 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 true); 273 274 /* Maybe we have a shorter packet in the queue, 275 which can be sent now. It sounds cool, 276 but, however, this is wrong in principle. 277 We MUST NOT reorder packets under these circumstances. 278 279 Really, if we split the flow into independent 280 subflows, it would be a very good solution. 281 This is the main idea of all FQ algorithms 282 (cf. CSZ, HPFQ, HFSC) 283 */ 284 285 qdisc_qstats_overlimit(sch); 286 } 287 return NULL; 288 } 289 290 static void tbf_reset(struct Qdisc *sch) 291 { 292 struct tbf_sched_data *q = qdisc_priv(sch); 293 294 qdisc_reset(q->qdisc); 295 sch->q.qlen = 0; 296 q->t_c = ktime_get_ns(); 297 q->tokens = q->buffer; 298 q->ptokens = q->mtu; 299 qdisc_watchdog_cancel(&q->watchdog); 300 } 301 302 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = { 303 [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) }, 304 [TCA_TBF_RTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE }, 305 [TCA_TBF_PTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE }, 306 [TCA_TBF_RATE64] = { .type = NLA_U64 }, 307 [TCA_TBF_PRATE64] = { .type = NLA_U64 }, 308 [TCA_TBF_BURST] = { .type = NLA_U32 }, 309 [TCA_TBF_PBURST] = { .type = NLA_U32 }, 310 }; 311 312 static int tbf_change(struct Qdisc *sch, struct nlattr *opt) 313 { 314 int err; 315 struct tbf_sched_data *q = qdisc_priv(sch); 316 struct nlattr *tb[TCA_TBF_MAX + 1]; 317 struct tc_tbf_qopt *qopt; 318 struct Qdisc *child = NULL; 319 struct psched_ratecfg rate; 320 struct psched_ratecfg peak; 321 u64 max_size; 322 s64 buffer, mtu; 323 u64 rate64 = 0, prate64 = 0; 324 325 err = nla_parse_nested(tb, TCA_TBF_MAX, opt, tbf_policy); 326 if (err < 0) 327 return err; 328 329 err = -EINVAL; 330 if (tb[TCA_TBF_PARMS] == NULL) 331 goto done; 332 333 qopt = nla_data(tb[TCA_TBF_PARMS]); 334 if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE) 335 qdisc_put_rtab(qdisc_get_rtab(&qopt->rate, 336 tb[TCA_TBF_RTAB])); 337 338 if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE) 339 qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate, 340 tb[TCA_TBF_PTAB])); 341 342 buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U); 343 mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U); 344 345 if (tb[TCA_TBF_RATE64]) 346 rate64 = nla_get_u64(tb[TCA_TBF_RATE64]); 347 psched_ratecfg_precompute(&rate, &qopt->rate, rate64); 348 349 if (tb[TCA_TBF_BURST]) { 350 max_size = nla_get_u32(tb[TCA_TBF_BURST]); 351 buffer = psched_l2t_ns(&rate, max_size); 352 } else { 353 max_size = min_t(u64, psched_ns_t2l(&rate, buffer), ~0U); 354 } 355 356 if (qopt->peakrate.rate) { 357 if (tb[TCA_TBF_PRATE64]) 358 prate64 = nla_get_u64(tb[TCA_TBF_PRATE64]); 359 psched_ratecfg_precompute(&peak, &qopt->peakrate, prate64); 360 if (peak.rate_bytes_ps <= rate.rate_bytes_ps) { 361 pr_warn_ratelimited("sch_tbf: peakrate %llu is lower than or equals to rate %llu !\n", 362 peak.rate_bytes_ps, rate.rate_bytes_ps); 363 err = -EINVAL; 364 goto done; 365 } 366 367 if (tb[TCA_TBF_PBURST]) { 368 u32 pburst = nla_get_u32(tb[TCA_TBF_PBURST]); 369 max_size = min_t(u32, max_size, pburst); 370 mtu = psched_l2t_ns(&peak, pburst); 371 } else { 372 max_size = min_t(u64, max_size, psched_ns_t2l(&peak, mtu)); 373 } 374 } else { 375 memset(&peak, 0, sizeof(peak)); 376 } 377 378 if (max_size < psched_mtu(qdisc_dev(sch))) 379 pr_warn_ratelimited("sch_tbf: burst %llu is lower than device %s mtu (%u) !\n", 380 max_size, qdisc_dev(sch)->name, 381 psched_mtu(qdisc_dev(sch))); 382 383 if (!max_size) { 384 err = -EINVAL; 385 goto done; 386 } 387 388 if (q->qdisc != &noop_qdisc) { 389 err = fifo_set_limit(q->qdisc, qopt->limit); 390 if (err) 391 goto done; 392 } else if (qopt->limit > 0) { 393 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit); 394 if (IS_ERR(child)) { 395 err = PTR_ERR(child); 396 goto done; 397 } 398 } 399 400 sch_tree_lock(sch); 401 if (child) { 402 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen); 403 qdisc_destroy(q->qdisc); 404 q->qdisc = child; 405 } 406 q->limit = qopt->limit; 407 if (tb[TCA_TBF_PBURST]) 408 q->mtu = mtu; 409 else 410 q->mtu = PSCHED_TICKS2NS(qopt->mtu); 411 q->max_size = max_size; 412 if (tb[TCA_TBF_BURST]) 413 q->buffer = buffer; 414 else 415 q->buffer = PSCHED_TICKS2NS(qopt->buffer); 416 q->tokens = q->buffer; 417 q->ptokens = q->mtu; 418 419 memcpy(&q->rate, &rate, sizeof(struct psched_ratecfg)); 420 memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg)); 421 422 sch_tree_unlock(sch); 423 err = 0; 424 done: 425 return err; 426 } 427 428 static int tbf_init(struct Qdisc *sch, struct nlattr *opt) 429 { 430 struct tbf_sched_data *q = qdisc_priv(sch); 431 432 if (opt == NULL) 433 return -EINVAL; 434 435 q->t_c = ktime_get_ns(); 436 qdisc_watchdog_init(&q->watchdog, sch); 437 q->qdisc = &noop_qdisc; 438 439 return tbf_change(sch, opt); 440 } 441 442 static void tbf_destroy(struct Qdisc *sch) 443 { 444 struct tbf_sched_data *q = qdisc_priv(sch); 445 446 qdisc_watchdog_cancel(&q->watchdog); 447 qdisc_destroy(q->qdisc); 448 } 449 450 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb) 451 { 452 struct tbf_sched_data *q = qdisc_priv(sch); 453 struct nlattr *nest; 454 struct tc_tbf_qopt opt; 455 456 sch->qstats.backlog = q->qdisc->qstats.backlog; 457 nest = nla_nest_start(skb, TCA_OPTIONS); 458 if (nest == NULL) 459 goto nla_put_failure; 460 461 opt.limit = q->limit; 462 psched_ratecfg_getrate(&opt.rate, &q->rate); 463 if (tbf_peak_present(q)) 464 psched_ratecfg_getrate(&opt.peakrate, &q->peak); 465 else 466 memset(&opt.peakrate, 0, sizeof(opt.peakrate)); 467 opt.mtu = PSCHED_NS2TICKS(q->mtu); 468 opt.buffer = PSCHED_NS2TICKS(q->buffer); 469 if (nla_put(skb, TCA_TBF_PARMS, sizeof(opt), &opt)) 470 goto nla_put_failure; 471 if (q->rate.rate_bytes_ps >= (1ULL << 32) && 472 nla_put_u64(skb, TCA_TBF_RATE64, q->rate.rate_bytes_ps)) 473 goto nla_put_failure; 474 if (tbf_peak_present(q) && 475 q->peak.rate_bytes_ps >= (1ULL << 32) && 476 nla_put_u64(skb, TCA_TBF_PRATE64, q->peak.rate_bytes_ps)) 477 goto nla_put_failure; 478 479 return nla_nest_end(skb, nest); 480 481 nla_put_failure: 482 nla_nest_cancel(skb, nest); 483 return -1; 484 } 485 486 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl, 487 struct sk_buff *skb, struct tcmsg *tcm) 488 { 489 struct tbf_sched_data *q = qdisc_priv(sch); 490 491 tcm->tcm_handle |= TC_H_MIN(1); 492 tcm->tcm_info = q->qdisc->handle; 493 494 return 0; 495 } 496 497 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new, 498 struct Qdisc **old) 499 { 500 struct tbf_sched_data *q = qdisc_priv(sch); 501 502 if (new == NULL) 503 new = &noop_qdisc; 504 505 sch_tree_lock(sch); 506 *old = q->qdisc; 507 q->qdisc = new; 508 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen); 509 qdisc_reset(*old); 510 sch_tree_unlock(sch); 511 512 return 0; 513 } 514 515 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg) 516 { 517 struct tbf_sched_data *q = qdisc_priv(sch); 518 return q->qdisc; 519 } 520 521 static unsigned long tbf_get(struct Qdisc *sch, u32 classid) 522 { 523 return 1; 524 } 525 526 static void tbf_put(struct Qdisc *sch, unsigned long arg) 527 { 528 } 529 530 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker) 531 { 532 if (!walker->stop) { 533 if (walker->count >= walker->skip) 534 if (walker->fn(sch, 1, walker) < 0) { 535 walker->stop = 1; 536 return; 537 } 538 walker->count++; 539 } 540 } 541 542 static const struct Qdisc_class_ops tbf_class_ops = { 543 .graft = tbf_graft, 544 .leaf = tbf_leaf, 545 .get = tbf_get, 546 .put = tbf_put, 547 .walk = tbf_walk, 548 .dump = tbf_dump_class, 549 }; 550 551 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = { 552 .next = NULL, 553 .cl_ops = &tbf_class_ops, 554 .id = "tbf", 555 .priv_size = sizeof(struct tbf_sched_data), 556 .enqueue = tbf_enqueue, 557 .dequeue = tbf_dequeue, 558 .peek = qdisc_peek_dequeued, 559 .drop = tbf_drop, 560 .init = tbf_init, 561 .reset = tbf_reset, 562 .destroy = tbf_destroy, 563 .change = tbf_change, 564 .dump = tbf_dump, 565 .owner = THIS_MODULE, 566 }; 567 568 static int __init tbf_module_init(void) 569 { 570 return register_qdisc(&tbf_qdisc_ops); 571 } 572 573 static void __exit tbf_module_exit(void) 574 { 575 unregister_qdisc(&tbf_qdisc_ops); 576 } 577 module_init(tbf_module_init) 578 module_exit(tbf_module_exit) 579 MODULE_LICENSE("GPL"); 580