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
teql_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)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 *
teql_dequeue(struct Qdisc * sch)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 *
teql_peek(struct Qdisc * sch)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
teql_reset(struct Qdisc * sch)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
teql_destroy(struct Qdisc * sch)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
teql_qdisc_init(struct Qdisc * sch,struct nlattr * opt,struct netlink_ext_ack * extack)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
__teql_resolve(struct sk_buff * skb,struct sk_buff * skb_res,struct net_device * dev,struct netdev_queue * txq,struct dst_entry * dst)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
teql_resolve(struct sk_buff * skb,struct sk_buff * skb_res,struct net_device * dev,struct netdev_queue * txq)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
teql_master_xmit(struct sk_buff * skb,struct net_device * dev)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
teql_master_open(struct net_device * dev)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
teql_master_close(struct net_device * dev)446 static int teql_master_close(struct net_device *dev)
447 {
448 netif_stop_queue(dev);
449 return 0;
450 }
451
teql_master_stats64(struct net_device * dev,struct rtnl_link_stats64 * stats)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
teql_master_mtu(struct net_device * dev,int new_mtu)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
teql_master_setup(struct net_device * dev)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
teql_init(void)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
teql_exit(void)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