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 /* GSO packet is too big, segment it so that tbf can transmit 146 * each segment in time 147 */ 148 static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch, 149 struct sk_buff **to_free) 150 { 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); 155 int ret, nb; 156 157 segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK); 158 159 if (IS_ERR_OR_NULL(segs)) 160 return qdisc_drop(skb, sch, to_free); 161 162 nb = 0; 163 while (segs) { 164 nskb = segs->next; 165 skb_mark_not_on_list(segs); 166 qdisc_skb_cb(segs)->pkt_len = segs->len; 167 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); 172 } else { 173 nb++; 174 } 175 segs = nskb; 176 } 177 sch->q.qlen += nb; 178 if (nb > 1) 179 qdisc_tree_reduce_backlog(sch, 1 - nb, prev_len - len); 180 consume_skb(skb); 181 return nb > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP; 182 } 183 184 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch, 185 struct sk_buff **to_free) 186 { 187 struct tbf_sched_data *q = qdisc_priv(sch); 188 unsigned int len = qdisc_pkt_len(skb); 189 int ret; 190 191 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); 196 } 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); 201 return ret; 202 } 203 204 sch->qstats.backlog += len; 205 sch->q.qlen++; 206 return NET_XMIT_SUCCESS; 207 } 208 209 static bool tbf_peak_present(const struct tbf_sched_data *q) 210 { 211 return q->peak.rate_bytes_ps; 212 } 213 214 static struct sk_buff *tbf_dequeue(struct Qdisc *sch) 215 { 216 struct tbf_sched_data *q = qdisc_priv(sch); 217 struct sk_buff *skb; 218 219 skb = q->qdisc->ops->peek(q->qdisc); 220 221 if (skb) { 222 s64 now; 223 s64 toks; 224 s64 ptoks = 0; 225 unsigned int len = qdisc_pkt_len(skb); 226 227 now = ktime_get_ns(); 228 toks = min_t(s64, now - q->t_c, q->buffer); 229 230 if (tbf_peak_present(q)) { 231 ptoks = toks + q->ptokens; 232 if (ptoks > q->mtu) 233 ptoks = q->mtu; 234 ptoks -= (s64) psched_l2t_ns(&q->peak, len); 235 } 236 toks += q->tokens; 237 if (toks > q->buffer) 238 toks = q->buffer; 239 toks -= (s64) psched_l2t_ns(&q->rate, len); 240 241 if ((toks|ptoks) >= 0) { 242 skb = qdisc_dequeue_peeked(q->qdisc); 243 if (unlikely(!skb)) 244 return NULL; 245 246 q->t_c = now; 247 q->tokens = toks; 248 q->ptokens = ptoks; 249 qdisc_qstats_backlog_dec(sch, skb); 250 sch->q.qlen--; 251 qdisc_bstats_update(sch, skb); 252 return skb; 253 } 254 255 qdisc_watchdog_schedule_ns(&q->watchdog, 256 now + max_t(long, -toks, -ptoks)); 257 258 /* 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. 262 263 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) 267 */ 268 269 qdisc_qstats_overlimit(sch); 270 } 271 return NULL; 272 } 273 274 static void tbf_reset(struct Qdisc *sch) 275 { 276 struct tbf_sched_data *q = qdisc_priv(sch); 277 278 qdisc_reset(q->qdisc); 279 sch->qstats.backlog = 0; 280 sch->q.qlen = 0; 281 q->t_c = ktime_get_ns(); 282 q->tokens = q->buffer; 283 q->ptokens = q->mtu; 284 qdisc_watchdog_cancel(&q->watchdog); 285 } 286 287 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 }, 295 }; 296 297 static int tbf_change(struct Qdisc *sch, struct nlattr *opt, 298 struct netlink_ext_ack *extack) 299 { 300 int err; 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; 307 u64 max_size; 308 s64 buffer, mtu; 309 u64 rate64 = 0, prate64 = 0; 310 311 err = nla_parse_nested(tb, TCA_TBF_MAX, opt, tbf_policy, NULL); 312 if (err < 0) 313 return err; 314 315 err = -EINVAL; 316 if (tb[TCA_TBF_PARMS] == NULL) 317 goto done; 318 319 qopt = nla_data(tb[TCA_TBF_PARMS]); 320 if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE) 321 qdisc_put_rtab(qdisc_get_rtab(&qopt->rate, 322 tb[TCA_TBF_RTAB], 323 NULL)); 324 325 if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE) 326 qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate, 327 tb[TCA_TBF_PTAB], 328 NULL)); 329 330 buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U); 331 mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U); 332 333 if (tb[TCA_TBF_RATE64]) 334 rate64 = nla_get_u64(tb[TCA_TBF_RATE64]); 335 psched_ratecfg_precompute(&rate, &qopt->rate, rate64); 336 337 if (tb[TCA_TBF_BURST]) { 338 max_size = nla_get_u32(tb[TCA_TBF_BURST]); 339 buffer = psched_l2t_ns(&rate, max_size); 340 } else { 341 max_size = min_t(u64, psched_ns_t2l(&rate, buffer), ~0U); 342 } 343 344 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); 351 err = -EINVAL; 352 goto done; 353 } 354 355 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); 359 } else { 360 max_size = min_t(u64, max_size, psched_ns_t2l(&peak, mtu)); 361 } 362 } else { 363 memset(&peak, 0, sizeof(peak)); 364 } 365 366 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))); 370 371 if (!max_size) { 372 err = -EINVAL; 373 goto done; 374 } 375 376 if (q->qdisc != &noop_qdisc) { 377 err = fifo_set_limit(q->qdisc, qopt->limit); 378 if (err) 379 goto done; 380 } else if (qopt->limit > 0) { 381 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit, 382 extack); 383 if (IS_ERR(child)) { 384 err = PTR_ERR(child); 385 goto done; 386 } 387 388 /* child is fifo, no need to check for noop_qdisc */ 389 qdisc_hash_add(child, true); 390 } 391 392 sch_tree_lock(sch); 393 if (child) { 394 qdisc_tree_flush_backlog(q->qdisc); 395 qdisc_put(q->qdisc); 396 q->qdisc = child; 397 } 398 q->limit = qopt->limit; 399 if (tb[TCA_TBF_PBURST]) 400 q->mtu = mtu; 401 else 402 q->mtu = PSCHED_TICKS2NS(qopt->mtu); 403 q->max_size = max_size; 404 if (tb[TCA_TBF_BURST]) 405 q->buffer = buffer; 406 else 407 q->buffer = PSCHED_TICKS2NS(qopt->buffer); 408 q->tokens = q->buffer; 409 q->ptokens = q->mtu; 410 411 memcpy(&q->rate, &rate, sizeof(struct psched_ratecfg)); 412 memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg)); 413 414 sch_tree_unlock(sch); 415 err = 0; 416 done: 417 return err; 418 } 419 420 static int tbf_init(struct Qdisc *sch, struct nlattr *opt, 421 struct netlink_ext_ack *extack) 422 { 423 struct tbf_sched_data *q = qdisc_priv(sch); 424 425 qdisc_watchdog_init(&q->watchdog, sch); 426 q->qdisc = &noop_qdisc; 427 428 if (!opt) 429 return -EINVAL; 430 431 q->t_c = ktime_get_ns(); 432 433 return tbf_change(sch, opt, extack); 434 } 435 436 static void tbf_destroy(struct Qdisc *sch) 437 { 438 struct tbf_sched_data *q = qdisc_priv(sch); 439 440 qdisc_watchdog_cancel(&q->watchdog); 441 qdisc_put(q->qdisc); 442 } 443 444 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb) 445 { 446 struct tbf_sched_data *q = qdisc_priv(sch); 447 struct nlattr *nest; 448 struct tc_tbf_qopt opt; 449 450 sch->qstats.backlog = q->qdisc->qstats.backlog; 451 nest = nla_nest_start(skb, TCA_OPTIONS); 452 if (nest == NULL) 453 goto nla_put_failure; 454 455 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); 459 else 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, 467 TCA_TBF_PAD)) 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, 472 TCA_TBF_PAD)) 473 goto nla_put_failure; 474 475 return nla_nest_end(skb, nest); 476 477 nla_put_failure: 478 nla_nest_cancel(skb, nest); 479 return -1; 480 } 481 482 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl, 483 struct sk_buff *skb, struct tcmsg *tcm) 484 { 485 struct tbf_sched_data *q = qdisc_priv(sch); 486 487 tcm->tcm_handle |= TC_H_MIN(1); 488 tcm->tcm_info = q->qdisc->handle; 489 490 return 0; 491 } 492 493 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new, 494 struct Qdisc **old, struct netlink_ext_ack *extack) 495 { 496 struct tbf_sched_data *q = qdisc_priv(sch); 497 498 if (new == NULL) 499 new = &noop_qdisc; 500 501 *old = qdisc_replace(sch, new, &q->qdisc); 502 return 0; 503 } 504 505 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg) 506 { 507 struct tbf_sched_data *q = qdisc_priv(sch); 508 return q->qdisc; 509 } 510 511 static unsigned long tbf_find(struct Qdisc *sch, u32 classid) 512 { 513 return 1; 514 } 515 516 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker) 517 { 518 if (!walker->stop) { 519 if (walker->count >= walker->skip) 520 if (walker->fn(sch, 1, walker) < 0) { 521 walker->stop = 1; 522 return; 523 } 524 walker->count++; 525 } 526 } 527 528 static const struct Qdisc_class_ops tbf_class_ops = { 529 .graft = tbf_graft, 530 .leaf = tbf_leaf, 531 .find = tbf_find, 532 .walk = tbf_walk, 533 .dump = tbf_dump_class, 534 }; 535 536 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = { 537 .next = NULL, 538 .cl_ops = &tbf_class_ops, 539 .id = "tbf", 540 .priv_size = sizeof(struct tbf_sched_data), 541 .enqueue = tbf_enqueue, 542 .dequeue = tbf_dequeue, 543 .peek = qdisc_peek_dequeued, 544 .init = tbf_init, 545 .reset = tbf_reset, 546 .destroy = tbf_destroy, 547 .change = tbf_change, 548 .dump = tbf_dump, 549 .owner = THIS_MODULE, 550 }; 551 552 static int __init tbf_module_init(void) 553 { 554 return register_qdisc(&tbf_qdisc_ops); 555 } 556 557 static void __exit tbf_module_exit(void) 558 { 559 unregister_qdisc(&tbf_qdisc_ops); 560 } 561 module_init(tbf_module_init) 562 module_exit(tbf_module_exit) 563 MODULE_LICENSE("GPL"); 564