1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * net/sched/sch_cbs.c Credit Based Shaper 4 * 5 * Authors: Vinicius Costa Gomes <vinicius.gomes@intel.com> 6 */ 7 8 /* Credit Based Shaper (CBS) 9 * ========================= 10 * 11 * This is a simple rate-limiting shaper aimed at TSN applications on 12 * systems with known traffic workloads. 13 * 14 * Its algorithm is defined by the IEEE 802.1Q-2014 Specification, 15 * Section 8.6.8.2, and explained in more detail in the Annex L of the 16 * same specification. 17 * 18 * There are four tunables to be considered: 19 * 20 * 'idleslope': Idleslope is the rate of credits that is 21 * accumulated (in kilobits per second) when there is at least 22 * one packet waiting for transmission. Packets are transmitted 23 * when the current value of credits is equal or greater than 24 * zero. When there is no packet to be transmitted the amount of 25 * credits is set to zero. This is the main tunable of the CBS 26 * algorithm. 27 * 28 * 'sendslope': 29 * Sendslope is the rate of credits that is depleted (it should be a 30 * negative number of kilobits per second) when a transmission is 31 * ocurring. It can be calculated as follows, (IEEE 802.1Q-2014 Section 32 * 8.6.8.2 item g): 33 * 34 * sendslope = idleslope - port_transmit_rate 35 * 36 * 'hicredit': Hicredit defines the maximum amount of credits (in 37 * bytes) that can be accumulated. Hicredit depends on the 38 * characteristics of interfering traffic, 39 * 'max_interference_size' is the maximum size of any burst of 40 * traffic that can delay the transmission of a frame that is 41 * available for transmission for this traffic class, (IEEE 42 * 802.1Q-2014 Annex L, Equation L-3): 43 * 44 * hicredit = max_interference_size * (idleslope / port_transmit_rate) 45 * 46 * 'locredit': Locredit is the minimum amount of credits that can 47 * be reached. It is a function of the traffic flowing through 48 * this qdisc (IEEE 802.1Q-2014 Annex L, Equation L-2): 49 * 50 * locredit = max_frame_size * (sendslope / port_transmit_rate) 51 */ 52 53 #include <linux/module.h> 54 #include <linux/types.h> 55 #include <linux/kernel.h> 56 #include <linux/string.h> 57 #include <linux/errno.h> 58 #include <linux/skbuff.h> 59 #include <net/netevent.h> 60 #include <net/netlink.h> 61 #include <net/sch_generic.h> 62 #include <net/pkt_sched.h> 63 64 static LIST_HEAD(cbs_list); 65 static DEFINE_SPINLOCK(cbs_list_lock); 66 67 #define BYTES_PER_KBIT (1000LL / 8) 68 69 struct cbs_sched_data { 70 bool offload; 71 int queue; 72 atomic64_t port_rate; /* in bytes/s */ 73 s64 last; /* timestamp in ns */ 74 s64 credits; /* in bytes */ 75 s32 locredit; /* in bytes */ 76 s32 hicredit; /* in bytes */ 77 s64 sendslope; /* in bytes/s */ 78 s64 idleslope; /* in bytes/s */ 79 struct qdisc_watchdog watchdog; 80 int (*enqueue)(struct sk_buff *skb, struct Qdisc *sch, 81 struct sk_buff **to_free); 82 struct sk_buff *(*dequeue)(struct Qdisc *sch); 83 struct Qdisc *qdisc; 84 struct list_head cbs_list; 85 }; 86 87 static int cbs_child_enqueue(struct sk_buff *skb, struct Qdisc *sch, 88 struct Qdisc *child, 89 struct sk_buff **to_free) 90 { 91 unsigned int len = qdisc_pkt_len(skb); 92 int err; 93 94 err = child->ops->enqueue(skb, child, to_free); 95 if (err != NET_XMIT_SUCCESS) 96 return err; 97 98 sch->qstats.backlog += len; 99 sch->q.qlen++; 100 101 return NET_XMIT_SUCCESS; 102 } 103 104 static int cbs_enqueue_offload(struct sk_buff *skb, struct Qdisc *sch, 105 struct sk_buff **to_free) 106 { 107 struct cbs_sched_data *q = qdisc_priv(sch); 108 struct Qdisc *qdisc = q->qdisc; 109 110 return cbs_child_enqueue(skb, sch, qdisc, to_free); 111 } 112 113 static int cbs_enqueue_soft(struct sk_buff *skb, struct Qdisc *sch, 114 struct sk_buff **to_free) 115 { 116 struct cbs_sched_data *q = qdisc_priv(sch); 117 struct Qdisc *qdisc = q->qdisc; 118 119 if (sch->q.qlen == 0 && q->credits > 0) { 120 /* We need to stop accumulating credits when there's 121 * no enqueued packets and q->credits is positive. 122 */ 123 q->credits = 0; 124 q->last = ktime_get_ns(); 125 } 126 127 return cbs_child_enqueue(skb, sch, qdisc, to_free); 128 } 129 130 static int cbs_enqueue(struct sk_buff *skb, struct Qdisc *sch, 131 struct sk_buff **to_free) 132 { 133 struct cbs_sched_data *q = qdisc_priv(sch); 134 135 return q->enqueue(skb, sch, to_free); 136 } 137 138 /* timediff is in ns, slope is in bytes/s */ 139 static s64 timediff_to_credits(s64 timediff, s64 slope) 140 { 141 return div64_s64(timediff * slope, NSEC_PER_SEC); 142 } 143 144 static s64 delay_from_credits(s64 credits, s64 slope) 145 { 146 if (unlikely(slope == 0)) 147 return S64_MAX; 148 149 return div64_s64(-credits * NSEC_PER_SEC, slope); 150 } 151 152 static s64 credits_from_len(unsigned int len, s64 slope, s64 port_rate) 153 { 154 if (unlikely(port_rate == 0)) 155 return S64_MAX; 156 157 return div64_s64(len * slope, port_rate); 158 } 159 160 static struct sk_buff *cbs_child_dequeue(struct Qdisc *sch, struct Qdisc *child) 161 { 162 struct sk_buff *skb; 163 164 skb = child->ops->dequeue(child); 165 if (!skb) 166 return NULL; 167 168 qdisc_qstats_backlog_dec(sch, skb); 169 qdisc_bstats_update(sch, skb); 170 sch->q.qlen--; 171 172 return skb; 173 } 174 175 static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch) 176 { 177 struct cbs_sched_data *q = qdisc_priv(sch); 178 struct Qdisc *qdisc = q->qdisc; 179 s64 now = ktime_get_ns(); 180 struct sk_buff *skb; 181 s64 credits; 182 int len; 183 184 /* The previous packet is still being sent */ 185 if (now < q->last) { 186 qdisc_watchdog_schedule_ns(&q->watchdog, q->last); 187 return NULL; 188 } 189 if (q->credits < 0) { 190 credits = timediff_to_credits(now - q->last, q->idleslope); 191 192 credits = q->credits + credits; 193 q->credits = min_t(s64, credits, q->hicredit); 194 195 if (q->credits < 0) { 196 s64 delay; 197 198 delay = delay_from_credits(q->credits, q->idleslope); 199 qdisc_watchdog_schedule_ns(&q->watchdog, now + delay); 200 201 q->last = now; 202 203 return NULL; 204 } 205 } 206 skb = cbs_child_dequeue(sch, qdisc); 207 if (!skb) 208 return NULL; 209 210 len = qdisc_pkt_len(skb); 211 212 /* As sendslope is a negative number, this will decrease the 213 * amount of q->credits. 214 */ 215 credits = credits_from_len(len, q->sendslope, 216 atomic64_read(&q->port_rate)); 217 credits += q->credits; 218 219 q->credits = max_t(s64, credits, q->locredit); 220 /* Estimate of the transmission of the last byte of the packet in ns */ 221 if (unlikely(atomic64_read(&q->port_rate) == 0)) 222 q->last = now; 223 else 224 q->last = now + div64_s64(len * NSEC_PER_SEC, 225 atomic64_read(&q->port_rate)); 226 227 return skb; 228 } 229 230 static struct sk_buff *cbs_dequeue_offload(struct Qdisc *sch) 231 { 232 struct cbs_sched_data *q = qdisc_priv(sch); 233 struct Qdisc *qdisc = q->qdisc; 234 235 return cbs_child_dequeue(sch, qdisc); 236 } 237 238 static struct sk_buff *cbs_dequeue(struct Qdisc *sch) 239 { 240 struct cbs_sched_data *q = qdisc_priv(sch); 241 242 return q->dequeue(sch); 243 } 244 245 static const struct nla_policy cbs_policy[TCA_CBS_MAX + 1] = { 246 [TCA_CBS_PARMS] = { .len = sizeof(struct tc_cbs_qopt) }, 247 }; 248 249 static void cbs_disable_offload(struct net_device *dev, 250 struct cbs_sched_data *q) 251 { 252 struct tc_cbs_qopt_offload cbs = { }; 253 const struct net_device_ops *ops; 254 int err; 255 256 if (!q->offload) 257 return; 258 259 q->enqueue = cbs_enqueue_soft; 260 q->dequeue = cbs_dequeue_soft; 261 262 ops = dev->netdev_ops; 263 if (!ops->ndo_setup_tc) 264 return; 265 266 cbs.queue = q->queue; 267 cbs.enable = 0; 268 269 err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs); 270 if (err < 0) 271 pr_warn("Couldn't disable CBS offload for queue %d\n", 272 cbs.queue); 273 } 274 275 static int cbs_enable_offload(struct net_device *dev, struct cbs_sched_data *q, 276 const struct tc_cbs_qopt *opt, 277 struct netlink_ext_ack *extack) 278 { 279 const struct net_device_ops *ops = dev->netdev_ops; 280 struct tc_cbs_qopt_offload cbs = { }; 281 int err; 282 283 if (!ops->ndo_setup_tc) { 284 NL_SET_ERR_MSG(extack, "Specified device does not support cbs offload"); 285 return -EOPNOTSUPP; 286 } 287 288 cbs.queue = q->queue; 289 290 cbs.enable = 1; 291 cbs.hicredit = opt->hicredit; 292 cbs.locredit = opt->locredit; 293 cbs.idleslope = opt->idleslope; 294 cbs.sendslope = opt->sendslope; 295 296 err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs); 297 if (err < 0) { 298 NL_SET_ERR_MSG(extack, "Specified device failed to setup cbs hardware offload"); 299 return err; 300 } 301 302 q->enqueue = cbs_enqueue_offload; 303 q->dequeue = cbs_dequeue_offload; 304 305 return 0; 306 } 307 308 static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q) 309 { 310 struct ethtool_link_ksettings ecmd; 311 int speed = SPEED_10; 312 int port_rate; 313 int err; 314 315 err = __ethtool_get_link_ksettings(dev, &ecmd); 316 if (err < 0) 317 goto skip; 318 319 if (ecmd.base.speed && ecmd.base.speed != SPEED_UNKNOWN) 320 speed = ecmd.base.speed; 321 322 skip: 323 port_rate = speed * 1000 * BYTES_PER_KBIT; 324 325 atomic64_set(&q->port_rate, port_rate); 326 netdev_dbg(dev, "cbs: set %s's port_rate to: %lld, linkspeed: %d\n", 327 dev->name, (long long)atomic64_read(&q->port_rate), 328 ecmd.base.speed); 329 } 330 331 static int cbs_dev_notifier(struct notifier_block *nb, unsigned long event, 332 void *ptr) 333 { 334 struct net_device *dev = netdev_notifier_info_to_dev(ptr); 335 struct cbs_sched_data *q; 336 struct net_device *qdev; 337 bool found = false; 338 339 ASSERT_RTNL(); 340 341 if (event != NETDEV_UP && event != NETDEV_CHANGE) 342 return NOTIFY_DONE; 343 344 spin_lock(&cbs_list_lock); 345 list_for_each_entry(q, &cbs_list, cbs_list) { 346 qdev = qdisc_dev(q->qdisc); 347 if (qdev == dev) { 348 found = true; 349 break; 350 } 351 } 352 spin_unlock(&cbs_list_lock); 353 354 if (found) 355 cbs_set_port_rate(dev, q); 356 357 return NOTIFY_DONE; 358 } 359 360 static int cbs_change(struct Qdisc *sch, struct nlattr *opt, 361 struct netlink_ext_ack *extack) 362 { 363 struct cbs_sched_data *q = qdisc_priv(sch); 364 struct net_device *dev = qdisc_dev(sch); 365 struct nlattr *tb[TCA_CBS_MAX + 1]; 366 struct tc_cbs_qopt *qopt; 367 int err; 368 369 err = nla_parse_nested_deprecated(tb, TCA_CBS_MAX, opt, cbs_policy, 370 extack); 371 if (err < 0) 372 return err; 373 374 if (!tb[TCA_CBS_PARMS]) { 375 NL_SET_ERR_MSG(extack, "Missing CBS parameter which are mandatory"); 376 return -EINVAL; 377 } 378 379 qopt = nla_data(tb[TCA_CBS_PARMS]); 380 381 if (!qopt->offload) { 382 cbs_set_port_rate(dev, q); 383 cbs_disable_offload(dev, q); 384 } else { 385 err = cbs_enable_offload(dev, q, qopt, extack); 386 if (err < 0) 387 return err; 388 } 389 390 /* Everything went OK, save the parameters used. */ 391 q->hicredit = qopt->hicredit; 392 q->locredit = qopt->locredit; 393 q->idleslope = qopt->idleslope * BYTES_PER_KBIT; 394 q->sendslope = qopt->sendslope * BYTES_PER_KBIT; 395 q->offload = qopt->offload; 396 397 return 0; 398 } 399 400 static int cbs_init(struct Qdisc *sch, struct nlattr *opt, 401 struct netlink_ext_ack *extack) 402 { 403 struct cbs_sched_data *q = qdisc_priv(sch); 404 struct net_device *dev = qdisc_dev(sch); 405 406 if (!opt) { 407 NL_SET_ERR_MSG(extack, "Missing CBS qdisc options which are mandatory"); 408 return -EINVAL; 409 } 410 411 q->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, 412 sch->handle, extack); 413 if (!q->qdisc) 414 return -ENOMEM; 415 416 spin_lock(&cbs_list_lock); 417 list_add(&q->cbs_list, &cbs_list); 418 spin_unlock(&cbs_list_lock); 419 420 qdisc_hash_add(q->qdisc, false); 421 422 q->queue = sch->dev_queue - netdev_get_tx_queue(dev, 0); 423 424 q->enqueue = cbs_enqueue_soft; 425 q->dequeue = cbs_dequeue_soft; 426 427 qdisc_watchdog_init(&q->watchdog, sch); 428 429 return cbs_change(sch, opt, extack); 430 } 431 432 static void cbs_destroy(struct Qdisc *sch) 433 { 434 struct cbs_sched_data *q = qdisc_priv(sch); 435 struct net_device *dev = qdisc_dev(sch); 436 437 /* Nothing to do if we couldn't create the underlying qdisc */ 438 if (!q->qdisc) 439 return; 440 441 qdisc_watchdog_cancel(&q->watchdog); 442 cbs_disable_offload(dev, q); 443 444 spin_lock(&cbs_list_lock); 445 list_del(&q->cbs_list); 446 spin_unlock(&cbs_list_lock); 447 448 qdisc_put(q->qdisc); 449 } 450 451 static int cbs_dump(struct Qdisc *sch, struct sk_buff *skb) 452 { 453 struct cbs_sched_data *q = qdisc_priv(sch); 454 struct tc_cbs_qopt opt = { }; 455 struct nlattr *nest; 456 457 nest = nla_nest_start_noflag(skb, TCA_OPTIONS); 458 if (!nest) 459 goto nla_put_failure; 460 461 opt.hicredit = q->hicredit; 462 opt.locredit = q->locredit; 463 opt.sendslope = div64_s64(q->sendslope, BYTES_PER_KBIT); 464 opt.idleslope = div64_s64(q->idleslope, BYTES_PER_KBIT); 465 opt.offload = q->offload; 466 467 if (nla_put(skb, TCA_CBS_PARMS, sizeof(opt), &opt)) 468 goto nla_put_failure; 469 470 return nla_nest_end(skb, nest); 471 472 nla_put_failure: 473 nla_nest_cancel(skb, nest); 474 return -1; 475 } 476 477 static int cbs_dump_class(struct Qdisc *sch, unsigned long cl, 478 struct sk_buff *skb, struct tcmsg *tcm) 479 { 480 struct cbs_sched_data *q = qdisc_priv(sch); 481 482 if (cl != 1 || !q->qdisc) /* only one class */ 483 return -ENOENT; 484 485 tcm->tcm_handle |= TC_H_MIN(1); 486 tcm->tcm_info = q->qdisc->handle; 487 488 return 0; 489 } 490 491 static int cbs_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new, 492 struct Qdisc **old, struct netlink_ext_ack *extack) 493 { 494 struct cbs_sched_data *q = qdisc_priv(sch); 495 496 if (!new) { 497 new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, 498 sch->handle, NULL); 499 if (!new) 500 new = &noop_qdisc; 501 } 502 503 *old = qdisc_replace(sch, new, &q->qdisc); 504 return 0; 505 } 506 507 static struct Qdisc *cbs_leaf(struct Qdisc *sch, unsigned long arg) 508 { 509 struct cbs_sched_data *q = qdisc_priv(sch); 510 511 return q->qdisc; 512 } 513 514 static unsigned long cbs_find(struct Qdisc *sch, u32 classid) 515 { 516 return 1; 517 } 518 519 static void cbs_walk(struct Qdisc *sch, struct qdisc_walker *walker) 520 { 521 if (!walker->stop) { 522 if (walker->count >= walker->skip) { 523 if (walker->fn(sch, 1, walker) < 0) { 524 walker->stop = 1; 525 return; 526 } 527 } 528 walker->count++; 529 } 530 } 531 532 static const struct Qdisc_class_ops cbs_class_ops = { 533 .graft = cbs_graft, 534 .leaf = cbs_leaf, 535 .find = cbs_find, 536 .walk = cbs_walk, 537 .dump = cbs_dump_class, 538 }; 539 540 static struct Qdisc_ops cbs_qdisc_ops __read_mostly = { 541 .id = "cbs", 542 .cl_ops = &cbs_class_ops, 543 .priv_size = sizeof(struct cbs_sched_data), 544 .enqueue = cbs_enqueue, 545 .dequeue = cbs_dequeue, 546 .peek = qdisc_peek_dequeued, 547 .init = cbs_init, 548 .reset = qdisc_reset_queue, 549 .destroy = cbs_destroy, 550 .change = cbs_change, 551 .dump = cbs_dump, 552 .owner = THIS_MODULE, 553 }; 554 555 static struct notifier_block cbs_device_notifier = { 556 .notifier_call = cbs_dev_notifier, 557 }; 558 559 static int __init cbs_module_init(void) 560 { 561 int err; 562 563 err = register_netdevice_notifier(&cbs_device_notifier); 564 if (err) 565 return err; 566 567 err = register_qdisc(&cbs_qdisc_ops); 568 if (err) 569 unregister_netdevice_notifier(&cbs_device_notifier); 570 571 return err; 572 } 573 574 static void __exit cbs_module_exit(void) 575 { 576 unregister_qdisc(&cbs_qdisc_ops); 577 unregister_netdevice_notifier(&cbs_device_notifier); 578 } 579 module_init(cbs_module_init) 580 module_exit(cbs_module_exit) 581 MODULE_LICENSE("GPL"); 582