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_pull(skb, skb_network_offset(skb)); 381 } while ((q = rcu_dereference(NEXT_SLAVE(q))) != start); 382 383 if (nores && skb_res == NULL) { 384 skb_res = skb; 385 rcu_read_unlock(); 386 goto restart; 387 } 388 389 if (busy) { 390 netif_stop_queue(dev); 391 rcu_read_unlock(); 392 return NETDEV_TX_BUSY; 393 } 394 master->tx_errors++; 395 396 drop: 397 master->tx_dropped++; 398 rcu_read_unlock(); 399 dev_kfree_skb(skb); 400 return NETDEV_TX_OK; 401 } 402 403 static int teql_master_open(struct net_device *dev) 404 { 405 struct Qdisc *q, *first; 406 struct teql_master *m = netdev_priv(dev); 407 int mtu = 0xFFFE; 408 unsigned int flags = IFF_NOARP | IFF_MULTICAST; 409 410 first = rtnl_dereference(m->slaves); 411 if (!first) 412 return -EUNATCH; 413 414 flags = FMASK; 415 416 q = first; 417 do { 418 struct net_device *slave = qdisc_dev(q); 419 420 if (slave == NULL) 421 return -EUNATCH; 422 423 if (slave->mtu < mtu) 424 mtu = slave->mtu; 425 if (slave->hard_header_len > LL_MAX_HEADER) 426 return -EINVAL; 427 428 /* If all the slaves are BROADCAST, master is BROADCAST 429 If all the slaves are PtP, master is PtP 430 Otherwise, master is NBMA. 431 */ 432 if (!(slave->flags&IFF_POINTOPOINT)) 433 flags &= ~IFF_POINTOPOINT; 434 if (!(slave->flags&IFF_BROADCAST)) 435 flags &= ~IFF_BROADCAST; 436 if (!(slave->flags&IFF_MULTICAST)) 437 flags &= ~IFF_MULTICAST; 438 } while ((q = rtnl_dereference(NEXT_SLAVE(q))) != first); 439 440 m->dev->mtu = mtu; 441 m->dev->flags = (m->dev->flags&~FMASK) | flags; 442 netif_start_queue(m->dev); 443 return 0; 444 } 445 446 static int teql_master_close(struct net_device *dev) 447 { 448 netif_stop_queue(dev); 449 return 0; 450 } 451 452 static void teql_master_stats64(struct net_device *dev, 453 struct rtnl_link_stats64 *stats) 454 { 455 struct teql_master *m = netdev_priv(dev); 456 457 stats->tx_packets = m->tx_packets; 458 stats->tx_bytes = m->tx_bytes; 459 stats->tx_errors = m->tx_errors; 460 stats->tx_dropped = m->tx_dropped; 461 } 462 463 static int teql_master_mtu(struct net_device *dev, int new_mtu) 464 { 465 struct teql_master *m = netdev_priv(dev); 466 struct Qdisc *q, *first; 467 468 first = rtnl_dereference(m->slaves); 469 q = first; 470 if (q) { 471 do { 472 if (new_mtu > qdisc_dev(q)->mtu) 473 return -EINVAL; 474 } while ((q = rtnl_dereference(NEXT_SLAVE(q))) != first); 475 } 476 477 WRITE_ONCE(dev->mtu, new_mtu); 478 return 0; 479 } 480 481 static const struct net_device_ops teql_netdev_ops = { 482 .ndo_open = teql_master_open, 483 .ndo_stop = teql_master_close, 484 .ndo_start_xmit = teql_master_xmit, 485 .ndo_get_stats64 = teql_master_stats64, 486 .ndo_change_mtu = teql_master_mtu, 487 }; 488 489 static __init void teql_master_setup(struct net_device *dev) 490 { 491 struct teql_master *master = netdev_priv(dev); 492 struct Qdisc_ops *ops = &master->qops; 493 494 spin_lock_init(&master->slaves_lock); 495 master->dev = dev; 496 ops->priv_size = sizeof(struct teql_sched_data); 497 498 ops->enqueue = teql_enqueue; 499 ops->dequeue = teql_dequeue; 500 ops->peek = teql_peek; 501 ops->init = teql_qdisc_init; 502 ops->reset = teql_reset; 503 ops->destroy = teql_destroy; 504 ops->owner = THIS_MODULE; 505 506 dev->netdev_ops = &teql_netdev_ops; 507 dev->type = ARPHRD_VOID; 508 dev->mtu = 1500; 509 dev->min_mtu = 68; 510 dev->max_mtu = 65535; 511 dev->tx_queue_len = 100; 512 dev->flags = IFF_NOARP; 513 dev->hard_header_len = LL_MAX_HEADER; 514 netif_keep_dst(dev); 515 } 516 517 static LIST_HEAD(master_dev_list); 518 static int max_equalizers = 1; 519 module_param(max_equalizers, int, 0); 520 MODULE_PARM_DESC(max_equalizers, "Max number of link equalizers"); 521 522 static int __init teql_init(void) 523 { 524 int i; 525 int err = -ENODEV; 526 527 for (i = 0; i < max_equalizers; i++) { 528 struct net_device *dev; 529 struct teql_master *master; 530 531 dev = alloc_netdev(sizeof(struct teql_master), "teql%d", 532 NET_NAME_UNKNOWN, teql_master_setup); 533 if (!dev) { 534 err = -ENOMEM; 535 break; 536 } 537 538 if ((err = register_netdev(dev))) { 539 free_netdev(dev); 540 break; 541 } 542 543 master = netdev_priv(dev); 544 545 strscpy(master->qops.id, dev->name, IFNAMSIZ); 546 err = register_qdisc(&master->qops); 547 548 if (err) { 549 unregister_netdev(dev); 550 free_netdev(dev); 551 break; 552 } 553 554 list_add_tail(&master->master_list, &master_dev_list); 555 } 556 return i ? 0 : err; 557 } 558 559 static void __exit teql_exit(void) 560 { 561 struct teql_master *master, *nxt; 562 563 list_for_each_entry_safe(master, nxt, &master_dev_list, master_list) { 564 565 list_del(&master->master_list); 566 567 unregister_qdisc(&master->qops); 568 unregister_netdev(master->dev); 569 free_netdev(master->dev); 570 } 571 } 572 573 module_init(teql_init); 574 module_exit(teql_exit); 575 576 MODULE_LICENSE("GPL"); 577 MODULE_DESCRIPTION("True (or trivial) link equalizer qdisc"); 578