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