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 segs->next = NULL; 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 int ret; 189 190 if (qdisc_pkt_len(skb) > q->max_size) { 191 if (skb_is_gso(skb) && 192 skb_gso_validate_mac_len(skb, q->max_size)) 193 return tbf_segment(skb, sch, to_free); 194 return qdisc_drop(skb, sch, to_free); 195 } 196 ret = qdisc_enqueue(skb, q->qdisc, to_free); 197 if (ret != NET_XMIT_SUCCESS) { 198 if (net_xmit_drop_count(ret)) 199 qdisc_qstats_drop(sch); 200 return ret; 201 } 202 203 qdisc_qstats_backlog_inc(sch, skb); 204 sch->q.qlen++; 205 return NET_XMIT_SUCCESS; 206 } 207 208 static bool tbf_peak_present(const struct tbf_sched_data *q) 209 { 210 return q->peak.rate_bytes_ps; 211 } 212 213 static struct sk_buff *tbf_dequeue(struct Qdisc *sch) 214 { 215 struct tbf_sched_data *q = qdisc_priv(sch); 216 struct sk_buff *skb; 217 218 skb = q->qdisc->ops->peek(q->qdisc); 219 220 if (skb) { 221 s64 now; 222 s64 toks; 223 s64 ptoks = 0; 224 unsigned int len = qdisc_pkt_len(skb); 225 226 now = ktime_get_ns(); 227 toks = min_t(s64, now - q->t_c, q->buffer); 228 229 if (tbf_peak_present(q)) { 230 ptoks = toks + q->ptokens; 231 if (ptoks > q->mtu) 232 ptoks = q->mtu; 233 ptoks -= (s64) psched_l2t_ns(&q->peak, len); 234 } 235 toks += q->tokens; 236 if (toks > q->buffer) 237 toks = q->buffer; 238 toks -= (s64) psched_l2t_ns(&q->rate, len); 239 240 if ((toks|ptoks) >= 0) { 241 skb = qdisc_dequeue_peeked(q->qdisc); 242 if (unlikely(!skb)) 243 return NULL; 244 245 q->t_c = now; 246 q->tokens = toks; 247 q->ptokens = ptoks; 248 qdisc_qstats_backlog_dec(sch, skb); 249 sch->q.qlen--; 250 qdisc_bstats_update(sch, skb); 251 return skb; 252 } 253 254 qdisc_watchdog_schedule_ns(&q->watchdog, 255 now + max_t(long, -toks, -ptoks)); 256 257 /* Maybe we have a shorter packet in the queue, 258 which can be sent now. It sounds cool, 259 but, however, this is wrong in principle. 260 We MUST NOT reorder packets under these circumstances. 261 262 Really, if we split the flow into independent 263 subflows, it would be a very good solution. 264 This is the main idea of all FQ algorithms 265 (cf. CSZ, HPFQ, HFSC) 266 */ 267 268 qdisc_qstats_overlimit(sch); 269 } 270 return NULL; 271 } 272 273 static void tbf_reset(struct Qdisc *sch) 274 { 275 struct tbf_sched_data *q = qdisc_priv(sch); 276 277 qdisc_reset(q->qdisc); 278 sch->qstats.backlog = 0; 279 sch->q.qlen = 0; 280 q->t_c = ktime_get_ns(); 281 q->tokens = q->buffer; 282 q->ptokens = q->mtu; 283 qdisc_watchdog_cancel(&q->watchdog); 284 } 285 286 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = { 287 [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) }, 288 [TCA_TBF_RTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE }, 289 [TCA_TBF_PTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE }, 290 [TCA_TBF_RATE64] = { .type = NLA_U64 }, 291 [TCA_TBF_PRATE64] = { .type = NLA_U64 }, 292 [TCA_TBF_BURST] = { .type = NLA_U32 }, 293 [TCA_TBF_PBURST] = { .type = NLA_U32 }, 294 }; 295 296 static int tbf_change(struct Qdisc *sch, struct nlattr *opt, 297 struct netlink_ext_ack *extack) 298 { 299 int err; 300 struct tbf_sched_data *q = qdisc_priv(sch); 301 struct nlattr *tb[TCA_TBF_MAX + 1]; 302 struct tc_tbf_qopt *qopt; 303 struct Qdisc *child = NULL; 304 struct psched_ratecfg rate; 305 struct psched_ratecfg peak; 306 u64 max_size; 307 s64 buffer, mtu; 308 u64 rate64 = 0, prate64 = 0; 309 310 err = nla_parse_nested(tb, TCA_TBF_MAX, opt, tbf_policy, NULL); 311 if (err < 0) 312 return err; 313 314 err = -EINVAL; 315 if (tb[TCA_TBF_PARMS] == NULL) 316 goto done; 317 318 qopt = nla_data(tb[TCA_TBF_PARMS]); 319 if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE) 320 qdisc_put_rtab(qdisc_get_rtab(&qopt->rate, 321 tb[TCA_TBF_RTAB], 322 NULL)); 323 324 if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE) 325 qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate, 326 tb[TCA_TBF_PTAB], 327 NULL)); 328 329 buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U); 330 mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U); 331 332 if (tb[TCA_TBF_RATE64]) 333 rate64 = nla_get_u64(tb[TCA_TBF_RATE64]); 334 psched_ratecfg_precompute(&rate, &qopt->rate, rate64); 335 336 if (tb[TCA_TBF_BURST]) { 337 max_size = nla_get_u32(tb[TCA_TBF_BURST]); 338 buffer = psched_l2t_ns(&rate, max_size); 339 } else { 340 max_size = min_t(u64, psched_ns_t2l(&rate, buffer), ~0U); 341 } 342 343 if (qopt->peakrate.rate) { 344 if (tb[TCA_TBF_PRATE64]) 345 prate64 = nla_get_u64(tb[TCA_TBF_PRATE64]); 346 psched_ratecfg_precompute(&peak, &qopt->peakrate, prate64); 347 if (peak.rate_bytes_ps <= rate.rate_bytes_ps) { 348 pr_warn_ratelimited("sch_tbf: peakrate %llu is lower than or equals to rate %llu !\n", 349 peak.rate_bytes_ps, rate.rate_bytes_ps); 350 err = -EINVAL; 351 goto done; 352 } 353 354 if (tb[TCA_TBF_PBURST]) { 355 u32 pburst = nla_get_u32(tb[TCA_TBF_PBURST]); 356 max_size = min_t(u32, max_size, pburst); 357 mtu = psched_l2t_ns(&peak, pburst); 358 } else { 359 max_size = min_t(u64, max_size, psched_ns_t2l(&peak, mtu)); 360 } 361 } else { 362 memset(&peak, 0, sizeof(peak)); 363 } 364 365 if (max_size < psched_mtu(qdisc_dev(sch))) 366 pr_warn_ratelimited("sch_tbf: burst %llu is lower than device %s mtu (%u) !\n", 367 max_size, qdisc_dev(sch)->name, 368 psched_mtu(qdisc_dev(sch))); 369 370 if (!max_size) { 371 err = -EINVAL; 372 goto done; 373 } 374 375 if (q->qdisc != &noop_qdisc) { 376 err = fifo_set_limit(q->qdisc, qopt->limit); 377 if (err) 378 goto done; 379 } else if (qopt->limit > 0) { 380 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit, 381 extack); 382 if (IS_ERR(child)) { 383 err = PTR_ERR(child); 384 goto done; 385 } 386 387 /* child is fifo, no need to check for noop_qdisc */ 388 qdisc_hash_add(child, true); 389 } 390 391 sch_tree_lock(sch); 392 if (child) { 393 qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen, 394 q->qdisc->qstats.backlog); 395 qdisc_destroy(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_destroy(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