1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* net/sched/sch_teql.c "True" (or "trivial") link equalizer. 3 * 4 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> 5 */ 6 7 #include <linux/module.h> 8 #include <linux/types.h> 9 #include <linux/kernel.h> 10 #include <linux/slab.h> 11 #include <linux/string.h> 12 #include <linux/errno.h> 13 #include <linux/if_arp.h> 14 #include <linux/netdevice.h> 15 #include <linux/init.h> 16 #include <linux/skbuff.h> 17 #include <linux/moduleparam.h> 18 #include <net/dst.h> 19 #include <net/neighbour.h> 20 #include <net/pkt_sched.h> 21 22 /* 23 How to setup it. 24 ---------------- 25 26 After loading this module you will find a new device teqlN 27 and new qdisc with the same name. To join a slave to the equalizer 28 you should just set this qdisc on a device f.e. 29 30 # tc qdisc add dev eth0 root teql0 31 # tc qdisc add dev eth1 root teql0 32 33 That's all. Full PnP 8) 34 35 Applicability. 36 -------------- 37 38 1. Slave devices MUST be active devices, i.e., they must raise the tbusy 39 signal and generate EOI events. If you want to equalize virtual devices 40 like tunnels, use a normal eql device. 41 2. This device puts no limitations on physical slave characteristics 42 f.e. it will equalize 9600baud line and 100Mb ethernet perfectly :-) 43 Certainly, large difference in link speeds will make the resulting 44 eqalized link unusable, because of huge packet reordering. 45 I estimate an upper useful difference as ~10 times. 46 3. If the slave requires address resolution, only protocols using 47 neighbour cache (IPv4/IPv6) will work over the equalized link. 48 Other protocols are still allowed to use the slave device directly, 49 which will not break load balancing, though native slave 50 traffic will have the highest priority. */ 51 52 struct teql_master { 53 struct Qdisc_ops qops; 54 struct net_device *dev; 55 struct Qdisc __rcu *slaves; 56 spinlock_t slaves_lock; /* serializes writes to ->slaves */ 57 struct list_head master_list; 58 unsigned long tx_bytes; 59 unsigned long tx_packets; 60 unsigned long tx_errors; 61 unsigned long tx_dropped; 62 }; 63 64 struct teql_sched_data { 65 struct Qdisc __rcu *next; 66 struct teql_master *m; 67 struct sk_buff_head q; 68 }; 69 70 #define NEXT_SLAVE(q) (((struct teql_sched_data *)qdisc_priv(q))->next) 71 72 #define FMASK (IFF_BROADCAST | IFF_POINTOPOINT) 73 74 /* "teql*" qdisc routines */ 75 76 static int 77 teql_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) 78 { 79 struct net_device *dev = qdisc_dev(sch); 80 struct teql_sched_data *q = qdisc_priv(sch); 81 82 if (q->q.qlen < READ_ONCE(dev->tx_queue_len)) { 83 __skb_queue_tail(&q->q, skb); 84 return NET_XMIT_SUCCESS; 85 } 86 87 return qdisc_drop(skb, sch, to_free); 88 } 89 90 static struct sk_buff * 91 teql_dequeue(struct Qdisc *sch) 92 { 93 struct teql_sched_data *dat = qdisc_priv(sch); 94 struct netdev_queue *dat_queue; 95 struct sk_buff *skb; 96 struct Qdisc *q; 97 98 skb = __skb_dequeue(&dat->q); 99 dat_queue = netdev_get_tx_queue(dat->m->dev, 0); 100 q = rcu_dereference_bh(dat_queue->qdisc); 101 102 if (skb == NULL) { 103 struct net_device *m = qdisc_dev(q); 104 if (m) { 105 spin_lock_bh(&dat->m->slaves_lock); 106 rcu_assign_pointer(dat->m->slaves, sch); 107 spin_unlock_bh(&dat->m->slaves_lock); 108 netif_wake_queue(m); 109 } 110 } else { 111 qdisc_bstats_update(sch, skb); 112 } 113 WRITE_ONCE(sch->q.qlen, dat->q.qlen + READ_ONCE(q->q.qlen)); 114 return skb; 115 } 116 117 static struct sk_buff * 118 teql_peek(struct Qdisc *sch) 119 { 120 /* teql is meant to be used as root qdisc */ 121 return NULL; 122 } 123 124 static void 125 teql_reset(struct Qdisc *sch) 126 { 127 struct teql_sched_data *dat = qdisc_priv(sch); 128 129 skb_queue_purge(&dat->q); 130 } 131 132 static void 133 teql_destroy(struct Qdisc *sch) 134 { 135 struct Qdisc *q, *prev; 136 struct teql_sched_data *dat = qdisc_priv(sch); 137 struct teql_master *master = dat->m; 138 struct netdev_queue *txq = NULL; 139 bool reset_master_queue = false; 140 141 if (!master) 142 return; 143 144 spin_lock_bh(&master->slaves_lock); 145 prev = rcu_dereference_protected(master->slaves, 146 lockdep_is_held(&master->slaves_lock)); 147 if (prev) { 148 do { 149 struct Qdisc *head, *next; 150 151 q = rcu_dereference_protected(NEXT_SLAVE(prev), 152 lockdep_is_held(&master->slaves_lock)); 153 if (q != sch) { 154 prev = q; 155 continue; 156 } 157 158 next = rcu_dereference_protected(NEXT_SLAVE(q), 159 lockdep_is_held(&master->slaves_lock)); 160 rcu_assign_pointer(NEXT_SLAVE(prev), next); 161 162 head = rcu_dereference_protected(master->slaves, 163 lockdep_is_held(&master->slaves_lock)); 164 if (q == head) { 165 rcu_assign_pointer(master->slaves, next); 166 if (q == next) { 167 txq = netdev_get_tx_queue(master->dev, 0); 168 rcu_assign_pointer(master->slaves, NULL); 169 reset_master_queue = true; 170 } 171 } 172 skb_queue_purge(&dat->q); 173 break; 174 } while (prev != rcu_dereference_protected(master->slaves, 175 lockdep_is_held(&master->slaves_lock))); 176 } 177 spin_unlock_bh(&master->slaves_lock); 178 179 if (reset_master_queue) 180 dev_reset_queue(master->dev, txq, NULL); 181 } 182 183 static int teql_qdisc_init(struct Qdisc *sch, struct nlattr *opt, 184 struct netlink_ext_ack *extack) 185 { 186 struct net_device *dev = qdisc_dev(sch); 187 struct teql_master *m = (struct teql_master *)sch->ops; 188 struct teql_sched_data *q = qdisc_priv(sch); 189 struct Qdisc *first; 190 191 if (dev->hard_header_len > m->dev->hard_header_len) 192 return -EINVAL; 193 194 if (m->dev == dev) 195 return -ELOOP; 196 197 if (sch->parent != TC_H_ROOT) { 198 NL_SET_ERR_MSG_MOD(extack, "teql can only be used as root"); 199 return -EOPNOTSUPP; 200 } 201 202 q->m = m; 203 204 skb_queue_head_init(&q->q); 205 206 spin_lock_bh(&m->slaves_lock); 207 first = rcu_dereference_protected(m->slaves, lockdep_is_held(&m->slaves_lock)); 208 if (first) { 209 if (m->dev->flags & IFF_UP) { 210 if ((m->dev->flags & IFF_POINTOPOINT && 211 !(dev->flags & IFF_POINTOPOINT)) || 212 (m->dev->flags & IFF_BROADCAST && 213 !(dev->flags & IFF_BROADCAST)) || 214 (m->dev->flags & IFF_MULTICAST && 215 !(dev->flags & IFF_MULTICAST)) || 216 dev->mtu < m->dev->mtu) { 217 spin_unlock_bh(&m->slaves_lock); 218 return -EINVAL; 219 } 220 } else { 221 if (!(dev->flags&IFF_POINTOPOINT)) 222 m->dev->flags &= ~IFF_POINTOPOINT; 223 if (!(dev->flags&IFF_BROADCAST)) 224 m->dev->flags &= ~IFF_BROADCAST; 225 if (!(dev->flags&IFF_MULTICAST)) 226 m->dev->flags &= ~IFF_MULTICAST; 227 if (dev->mtu < m->dev->mtu) 228 m->dev->mtu = dev->mtu; 229 } 230 rcu_assign_pointer(q->next, 231 rcu_dereference_protected(NEXT_SLAVE(first), 232 lockdep_is_held(&m->slaves_lock))); 233 rcu_assign_pointer(NEXT_SLAVE(first), sch); 234 } else { 235 rcu_assign_pointer(q->next, sch); 236 rcu_assign_pointer(m->slaves, sch); 237 m->dev->mtu = dev->mtu; 238 m->dev->flags = (m->dev->flags&~FMASK)|(dev->flags&FMASK); 239 } 240 spin_unlock_bh(&m->slaves_lock); 241 return 0; 242 } 243 244 245 static int 246 __teql_resolve(struct sk_buff *skb, struct sk_buff *skb_res, 247 struct net_device *dev, struct netdev_queue *txq, 248 struct dst_entry *dst) 249 { 250 struct neighbour *n; 251 int err = 0; 252 253 n = dst_neigh_lookup_skb(dst, skb); 254 if (!n) 255 return -ENOENT; 256 257 if (dst->dev != dev) { 258 struct neighbour *mn; 259 260 mn = __neigh_lookup_errno(n->tbl, n->primary_key, dev); 261 neigh_release(n); 262 if (IS_ERR(mn)) 263 return PTR_ERR(mn); 264 n = mn; 265 } 266 267 if (neigh_event_send(n, skb_res) == 0) { 268 int err; 269 char haddr[MAX_ADDR_LEN]; 270 271 neigh_ha_snapshot(haddr, n, dev); 272 err = dev_hard_header(skb, dev, ntohs(skb_protocol(skb, false)), 273 haddr, NULL, skb->len); 274 275 if (err < 0) 276 err = -EINVAL; 277 } else { 278 err = (skb_res == NULL) ? -EAGAIN : 1; 279 } 280 neigh_release(n); 281 return err; 282 } 283 284 static inline int teql_resolve(struct sk_buff *skb, 285 struct sk_buff *skb_res, 286 struct net_device *dev, 287 struct netdev_queue *txq) 288 { 289 struct dst_entry *dst = skb_dst(skb); 290 int res; 291 292 if (rcu_access_pointer(txq->qdisc) == &noop_qdisc) 293 return -ENODEV; 294 295 if (!dev->header_ops || !dst) 296 return 0; 297 298 rcu_read_lock(); 299 res = __teql_resolve(skb, skb_res, dev, txq, dst); 300 rcu_read_unlock(); 301 302 return res; 303 } 304 305 static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev) 306 { 307 struct teql_master *master = netdev_priv(dev); 308 struct Qdisc *start, *q; 309 int busy; 310 int nores; 311 int subq = skb_get_queue_mapping(skb); 312 struct sk_buff *skb_res = NULL; 313 314 restart: 315 nores = 0; 316 busy = 0; 317 318 rcu_read_lock(); 319 320 start = rcu_dereference(master->slaves); 321 322 q = start; 323 if (!q) 324 goto drop; 325 326 do { 327 struct net_device *slave = qdisc_dev(q); 328 struct netdev_queue *slave_txq = netdev_get_tx_queue(slave, 0); 329 330 if (rcu_access_pointer(slave_txq->qdisc_sleeping) != q) 331 continue; 332 if (netif_xmit_stopped(netdev_get_tx_queue(slave, subq)) || 333 !netif_running(slave)) { 334 busy = 1; 335 continue; 336 } 337 338 switch (teql_resolve(skb, skb_res, slave, slave_txq)) { 339 case 0: 340 if (__netif_tx_trylock(slave_txq)) { 341 unsigned int length = qdisc_pkt_len(skb); 342 343 skb->dev = slave; 344 if (!netif_xmit_frozen_or_stopped(slave_txq) && 345 netdev_start_xmit(skb, slave, slave_txq, false) == 346 NETDEV_TX_OK) { 347 __netif_tx_unlock(slave_txq); 348 spin_lock(&master->slaves_lock); 349 if (rcu_dereference_protected(master->slaves, 350 lockdep_is_held(&master->slaves_lock)) == q) 351 rcu_assign_pointer(master->slaves, 352 rcu_dereference_protected(NEXT_SLAVE(q), 353 lockdep_is_held(&master->slaves_lock))); 354 spin_unlock(&master->slaves_lock); 355 netif_wake_queue(dev); 356 master->tx_packets++; 357 master->tx_bytes += length; 358 rcu_read_unlock(); 359 return NETDEV_TX_OK; 360 } 361 __netif_tx_unlock(slave_txq); 362 } 363 if (netif_xmit_stopped(netdev_get_tx_queue(dev, 0))) 364 busy = 1; 365 break; 366 case 1: 367 spin_lock(&master->slaves_lock); 368 if (rcu_dereference_protected(master->slaves, 369 lockdep_is_held(&master->slaves_lock)) == q) 370 rcu_assign_pointer(master->slaves, 371 rcu_dereference_protected(NEXT_SLAVE(q), 372 lockdep_is_held(&master->slaves_lock))); 373 spin_unlock(&master->slaves_lock); 374 rcu_read_unlock(); 375 return NETDEV_TX_OK; 376 default: 377 nores = 1; 378 break; 379 } 380 skb->dev = dev; 381 __skb_pull(skb, skb_network_offset(skb)); 382 } while ((q = rcu_dereference(NEXT_SLAVE(q))) != start); 383 384 if (nores && skb_res == NULL) { 385 skb_res = skb; 386 rcu_read_unlock(); 387 goto restart; 388 } 389 390 if (busy) { 391 netif_stop_queue(dev); 392 rcu_read_unlock(); 393 return NETDEV_TX_BUSY; 394 } 395 master->tx_errors++; 396 397 drop: 398 master->tx_dropped++; 399 rcu_read_unlock(); 400 dev_kfree_skb(skb); 401 return NETDEV_TX_OK; 402 } 403 404 static int teql_master_open(struct net_device *dev) 405 { 406 struct Qdisc *q, *first; 407 struct teql_master *m = netdev_priv(dev); 408 int mtu = 0xFFFE; 409 unsigned int flags = IFF_NOARP | IFF_MULTICAST; 410 411 first = rtnl_dereference(m->slaves); 412 if (!first) 413 return -EUNATCH; 414 415 flags = FMASK; 416 417 q = first; 418 do { 419 struct net_device *slave = qdisc_dev(q); 420 421 if (slave == NULL) 422 return -EUNATCH; 423 424 if (slave->mtu < mtu) 425 mtu = slave->mtu; 426 if (slave->hard_header_len > LL_MAX_HEADER) 427 return -EINVAL; 428 429 /* If all the slaves are BROADCAST, master is BROADCAST 430 If all the slaves are PtP, master is PtP 431 Otherwise, master is NBMA. 432 */ 433 if (!(slave->flags&IFF_POINTOPOINT)) 434 flags &= ~IFF_POINTOPOINT; 435 if (!(slave->flags&IFF_BROADCAST)) 436 flags &= ~IFF_BROADCAST; 437 if (!(slave->flags&IFF_MULTICAST)) 438 flags &= ~IFF_MULTICAST; 439 } while ((q = rtnl_dereference(NEXT_SLAVE(q))) != first); 440 441 m->dev->mtu = mtu; 442 m->dev->flags = (m->dev->flags&~FMASK) | flags; 443 netif_start_queue(m->dev); 444 return 0; 445 } 446 447 static int teql_master_close(struct net_device *dev) 448 { 449 netif_stop_queue(dev); 450 return 0; 451 } 452 453 static void teql_master_stats64(struct net_device *dev, 454 struct rtnl_link_stats64 *stats) 455 { 456 struct teql_master *m = netdev_priv(dev); 457 458 stats->tx_packets = m->tx_packets; 459 stats->tx_bytes = m->tx_bytes; 460 stats->tx_errors = m->tx_errors; 461 stats->tx_dropped = m->tx_dropped; 462 } 463 464 static int teql_master_mtu(struct net_device *dev, int new_mtu) 465 { 466 struct teql_master *m = netdev_priv(dev); 467 struct Qdisc *q, *first; 468 469 first = rtnl_dereference(m->slaves); 470 q = first; 471 if (q) { 472 do { 473 if (new_mtu > qdisc_dev(q)->mtu) 474 return -EINVAL; 475 } while ((q = rtnl_dereference(NEXT_SLAVE(q))) != first); 476 } 477 478 WRITE_ONCE(dev->mtu, new_mtu); 479 return 0; 480 } 481 482 static const struct net_device_ops teql_netdev_ops = { 483 .ndo_open = teql_master_open, 484 .ndo_stop = teql_master_close, 485 .ndo_start_xmit = teql_master_xmit, 486 .ndo_get_stats64 = teql_master_stats64, 487 .ndo_change_mtu = teql_master_mtu, 488 }; 489 490 static __init void teql_master_setup(struct net_device *dev) 491 { 492 struct teql_master *master = netdev_priv(dev); 493 struct Qdisc_ops *ops = &master->qops; 494 495 spin_lock_init(&master->slaves_lock); 496 master->dev = dev; 497 ops->priv_size = sizeof(struct teql_sched_data); 498 499 ops->enqueue = teql_enqueue; 500 ops->dequeue = teql_dequeue; 501 ops->peek = teql_peek; 502 ops->init = teql_qdisc_init; 503 ops->reset = teql_reset; 504 ops->destroy = teql_destroy; 505 ops->owner = THIS_MODULE; 506 507 dev->netdev_ops = &teql_netdev_ops; 508 dev->type = ARPHRD_VOID; 509 dev->mtu = 1500; 510 dev->min_mtu = 68; 511 dev->max_mtu = 65535; 512 dev->tx_queue_len = 100; 513 dev->flags = IFF_NOARP; 514 dev->hard_header_len = LL_MAX_HEADER; 515 netif_keep_dst(dev); 516 } 517 518 static LIST_HEAD(master_dev_list); 519 static int max_equalizers = 1; 520 module_param(max_equalizers, int, 0); 521 MODULE_PARM_DESC(max_equalizers, "Max number of link equalizers"); 522 523 static int __init teql_init(void) 524 { 525 int i; 526 int err = -ENODEV; 527 528 for (i = 0; i < max_equalizers; i++) { 529 struct net_device *dev; 530 struct teql_master *master; 531 532 dev = alloc_netdev(sizeof(struct teql_master), "teql%d", 533 NET_NAME_UNKNOWN, teql_master_setup); 534 if (!dev) { 535 err = -ENOMEM; 536 break; 537 } 538 539 if ((err = register_netdev(dev))) { 540 free_netdev(dev); 541 break; 542 } 543 544 master = netdev_priv(dev); 545 546 strscpy(master->qops.id, dev->name, IFNAMSIZ); 547 err = register_qdisc(&master->qops); 548 549 if (err) { 550 unregister_netdev(dev); 551 free_netdev(dev); 552 break; 553 } 554 555 list_add_tail(&master->master_list, &master_dev_list); 556 } 557 return i ? 0 : err; 558 } 559 560 static void __exit teql_exit(void) 561 { 562 struct teql_master *master, *nxt; 563 564 list_for_each_entry_safe(master, nxt, &master_dev_list, master_list) { 565 566 list_del(&master->master_list); 567 568 unregister_qdisc(&master->qops); 569 unregister_netdev(master->dev); 570 free_netdev(master->dev); 571 } 572 } 573 574 module_init(teql_init); 575 module_exit(teql_exit); 576 577 MODULE_LICENSE("GPL"); 578 MODULE_DESCRIPTION("True (or trivial) link equalizer qdisc"); 579