net/sched/sch_teql.c

   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 *slaves;
  56         struct list_head master_list;
  57         unsigned long   tx_bytes;
  58         unsigned long   tx_packets;
  59         unsigned long   tx_errors;
  60         unsigned long   tx_dropped;
  61 };
  62
  63 struct teql_sched_data {
  64         struct Qdisc *next;
  65         struct teql_master *m;
  66         struct sk_buff_head q;
  67 };
  68
  69 #define NEXT_SLAVE(q) (((struct teql_sched_data *)qdisc_priv(q))->next)
  70
  71 #define FMASK (IFF_BROADCAST | IFF_POINTOPOINT)
  72
  73 /* "teql*" qdisc routines */
  74
  75 static int
  76 teql_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
  77 {
  78         struct net_device *dev = qdisc_dev(sch);
  79         struct teql_sched_data *q = qdisc_priv(sch);
  80
  81         if (q->q.qlen < dev->tx_queue_len) {
  82                 __skb_queue_tail(&q->q, skb);
  83                 return NET_XMIT_SUCCESS;
  84         }
  85
  86         return qdisc_drop(skb, sch, to_free);
  87 }
  88
  89 static struct sk_buff *
  90 teql_dequeue(struct Qdisc *sch)
  91 {
  92         struct teql_sched_data *dat = qdisc_priv(sch);
  93         struct netdev_queue *dat_queue;
  94         struct sk_buff *skb;
  95         struct Qdisc *q;
  96
  97         skb = __skb_dequeue(&dat->q);
  98         dat_queue = netdev_get_tx_queue(dat->m->dev, 0);
  99         q = rcu_dereference_bh(dat_queue->qdisc);
 100
 101         if (skb == NULL) {
 102                 struct net_device *m = qdisc_dev(q);
 103                 if (m) {
 104                         dat->m->slaves = sch;
 105                         netif_wake_queue(m);
 106                 }
 107         } else {
 108                 qdisc_bstats_update(sch, skb);
 109         }
 110         sch->q.qlen = dat->q.qlen + q->q.qlen;
 111         return skb;
 112 }
 113
 114 static struct sk_buff *
 115 teql_peek(struct Qdisc *sch)
 116 {
 117         /* teql is meant to be used as root qdisc */
 118         return NULL;
 119 }
 120
 121 static void
 122 teql_reset(struct Qdisc *sch)
 123 {
 124         struct teql_sched_data *dat = qdisc_priv(sch);
 125
 126         skb_queue_purge(&dat->q);
 127         sch->q.qlen = 0;
 128 }
 129
 130 static void
 131 teql_destroy(struct Qdisc *sch)
 132 {
 133         struct Qdisc *q, *prev;
 134         struct teql_sched_data *dat = qdisc_priv(sch);
 135         struct teql_master *master = dat->m;
 136
 137         if (!master)
 138                 return;
 139
 140         prev = master->slaves;
 141         if (prev) {
 142                 do {
 143                         q = NEXT_SLAVE(prev);
 144                         if (q == sch) {
 145                                 NEXT_SLAVE(prev) = NEXT_SLAVE(q);
 146                                 if (q == master->slaves) {
 147                                         master->slaves = NEXT_SLAVE(q);
 148                                         if (q == master->slaves) {
 149                                                 struct netdev_queue *txq;
 150                                                 spinlock_t *root_lock;
 151
 152                                                 txq = netdev_get_tx_queue(master->dev, 0);
 153                                                 master->slaves = NULL;
 154
 155                                                 root_lock = qdisc_root_sleeping_lock(rtnl_dereference(txq->qdisc));
 156                                                 spin_lock_bh(root_lock);
 157                                                 qdisc_reset(rtnl_dereference(txq->qdisc));
 158                                                 spin_unlock_bh(root_lock);
 159                                         }
 160                                 }
 161                                 skb_queue_purge(&dat->q);
 162                                 break;
 163                         }
 164
 165                 } while ((prev = q) != master->slaves);
 166         }
 167 }
 168
 169 static int teql_qdisc_init(struct Qdisc *sch, struct nlattr *opt,
 170                            struct netlink_ext_ack *extack)
 171 {
 172         struct net_device *dev = qdisc_dev(sch);
 173         struct teql_master *m = (struct teql_master *)sch->ops;
 174         struct teql_sched_data *q = qdisc_priv(sch);
 175
 176         if (dev->hard_header_len > m->dev->hard_header_len)
 177                 return -EINVAL;
 178
 179         if (m->dev == dev)
 180                 return -ELOOP;
 181
 182         q->m = m;
 183
 184         skb_queue_head_init(&q->q);
 185
 186         if (m->slaves) {
 187                 if (m->dev->flags & IFF_UP) {
 188                         if ((m->dev->flags & IFF_POINTOPOINT &&
 189                              !(dev->flags & IFF_POINTOPOINT)) ||
 190                             (m->dev->flags & IFF_BROADCAST &&
 191                              !(dev->flags & IFF_BROADCAST)) ||
 192                             (m->dev->flags & IFF_MULTICAST &&
 193                              !(dev->flags & IFF_MULTICAST)) ||
 194                             dev->mtu < m->dev->mtu)
 195                                 return -EINVAL;
 196                 } else {
 197                         if (!(dev->flags&IFF_POINTOPOINT))
 198                                 m->dev->flags &= ~IFF_POINTOPOINT;
 199                         if (!(dev->flags&IFF_BROADCAST))
 200                                 m->dev->flags &= ~IFF_BROADCAST;
 201                         if (!(dev->flags&IFF_MULTICAST))
 202                                 m->dev->flags &= ~IFF_MULTICAST;
 203                         if (dev->mtu < m->dev->mtu)
 204                                 m->dev->mtu = dev->mtu;
 205                 }
 206                 q->next = NEXT_SLAVE(m->slaves);
 207                 NEXT_SLAVE(m->slaves) = sch;
 208         } else {
 209                 q->next = sch;
 210                 m->slaves = sch;
 211                 m->dev->mtu = dev->mtu;
 212                 m->dev->flags = (m->dev->flags&~FMASK)|(dev->flags&FMASK);
 213         }
 214         return 0;
 215 }
 216
 217
 218 static int
 219 __teql_resolve(struct sk_buff *skb, struct sk_buff *skb_res,
 220                struct net_device *dev, struct netdev_queue *txq,
 221                struct dst_entry *dst)
 222 {
 223         struct neighbour *n;
 224         int err = 0;
 225
 226         n = dst_neigh_lookup_skb(dst, skb);
 227         if (!n)
 228                 return -ENOENT;
 229
 230         if (dst->dev != dev) {
 231                 struct neighbour *mn;
 232
 233                 mn = __neigh_lookup_errno(n->tbl, n->primary_key, dev);
 234                 neigh_release(n);
 235                 if (IS_ERR(mn))
 236                         return PTR_ERR(mn);
 237                 n = mn;
 238         }
 239
 240         if (neigh_event_send(n, skb_res) == 0) {
 241                 int err;
 242                 char haddr[MAX_ADDR_LEN];
 243
 244                 neigh_ha_snapshot(haddr, n, dev);
 245                 err = dev_hard_header(skb, dev, ntohs(skb_protocol(skb, false)),
 246                                       haddr, NULL, skb->len);
 247
 248                 if (err < 0)
 249                         err = -EINVAL;
 250         } else {
 251                 err = (skb_res == NULL) ? -EAGAIN : 1;
 252         }
 253         neigh_release(n);
 254         return err;
 255 }
 256
 257 static inline int teql_resolve(struct sk_buff *skb,
 258                                struct sk_buff *skb_res,
 259                                struct net_device *dev,
 260                                struct netdev_queue *txq)
 261 {
 262         struct dst_entry *dst = skb_dst(skb);
 263         int res;
 264
 265         if (rcu_access_pointer(txq->qdisc) == &noop_qdisc)
 266                 return -ENODEV;
 267
 268         if (!dev->header_ops || !dst)
 269                 return 0;
 270
 271         rcu_read_lock();
 272         res = __teql_resolve(skb, skb_res, dev, txq, dst);
 273         rcu_read_unlock();
 274
 275         return res;
 276 }
 277
 278 static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev)
 279 {
 280         struct teql_master *master = netdev_priv(dev);
 281         struct Qdisc *start, *q;
 282         int busy;
 283         int nores;
 284         int subq = skb_get_queue_mapping(skb);
 285         struct sk_buff *skb_res = NULL;
 286
 287         start = master->slaves;
 288
 289 restart:
 290         nores = 0;
 291         busy = 0;
 292
 293         q = start;
 294         if (!q)
 295                 goto drop;
 296
 297         do {
 298                 struct net_device *slave = qdisc_dev(q);
 299                 struct netdev_queue *slave_txq = netdev_get_tx_queue(slave, 0);
 300
 301                 if (slave_txq->qdisc_sleeping != q)
 302                         continue;
 303                 if (netif_xmit_stopped(netdev_get_tx_queue(slave, subq)) ||
 304                     !netif_running(slave)) {
 305                         busy = 1;
 306                         continue;
 307                 }
 308
 309                 switch (teql_resolve(skb, skb_res, slave, slave_txq)) {
 310                 case 0:
 311                         if (__netif_tx_trylock(slave_txq)) {
 312                                 unsigned int length = qdisc_pkt_len(skb);
 313
 314                                 if (!netif_xmit_frozen_or_stopped(slave_txq) &&
 315                                     netdev_start_xmit(skb, slave, slave_txq, false) ==
 316                                     NETDEV_TX_OK) {
 317                                         __netif_tx_unlock(slave_txq);
 318                                         master->slaves = NEXT_SLAVE(q);
 319                                         netif_wake_queue(dev);
 320                                         master->tx_packets++;
 321                                         master->tx_bytes += length;
 322                                         return NETDEV_TX_OK;
 323                                 }
 324                                 __netif_tx_unlock(slave_txq);
 325                         }
 326                         if (netif_xmit_stopped(netdev_get_tx_queue(dev, 0)))
 327                                 busy = 1;
 328                         break;
 329                 case 1:
 330                         master->slaves = NEXT_SLAVE(q);
 331                         return NETDEV_TX_OK;
 332                 default:
 333                         nores = 1;
 334                         break;
 335                 }
 336                 __skb_pull(skb, skb_network_offset(skb));
 337         } while ((q = NEXT_SLAVE(q)) != start);
 338
 339         if (nores && skb_res == NULL) {
 340                 skb_res = skb;
 341                 goto restart;
 342         }
 343
 344         if (busy) {
 345                 netif_stop_queue(dev);
 346                 return NETDEV_TX_BUSY;
 347         }
 348         master->tx_errors++;
 349
 350 drop:
 351         master->tx_dropped++;
 352         dev_kfree_skb(skb);
 353         return NETDEV_TX_OK;
 354 }
 355
 356 static int teql_master_open(struct net_device *dev)
 357 {
 358         struct Qdisc *q;
 359         struct teql_master *m = netdev_priv(dev);
 360         int mtu = 0xFFFE;
 361         unsigned int flags = IFF_NOARP | IFF_MULTICAST;
 362
 363         if (m->slaves == NULL)
 364                 return -EUNATCH;
 365
 366         flags = FMASK;
 367
 368         q = m->slaves;
 369         do {
 370                 struct net_device *slave = qdisc_dev(q);
 371
 372                 if (slave == NULL)
 373                         return -EUNATCH;
 374
 375                 if (slave->mtu < mtu)
 376                         mtu = slave->mtu;
 377                 if (slave->hard_header_len > LL_MAX_HEADER)
 378                         return -EINVAL;
 379
 380                 /* If all the slaves are BROADCAST, master is BROADCAST
 381                    If all the slaves are PtP, master is PtP
 382                    Otherwise, master is NBMA.
 383                  */
 384                 if (!(slave->flags&IFF_POINTOPOINT))
 385                         flags &= ~IFF_POINTOPOINT;
 386                 if (!(slave->flags&IFF_BROADCAST))
 387                         flags &= ~IFF_BROADCAST;
 388                 if (!(slave->flags&IFF_MULTICAST))
 389                         flags &= ~IFF_MULTICAST;
 390         } while ((q = NEXT_SLAVE(q)) != m->slaves);
 391
 392         m->dev->mtu = mtu;
 393         m->dev->flags = (m->dev->flags&~FMASK) | flags;
 394         netif_start_queue(m->dev);
 395         return 0;
 396 }
 397
 398 static int teql_master_close(struct net_device *dev)
 399 {
 400         netif_stop_queue(dev);
 401         return 0;
 402 }
 403
 404 static void teql_master_stats64(struct net_device *dev,
 405                                 struct rtnl_link_stats64 *stats)
 406 {
 407         struct teql_master *m = netdev_priv(dev);
 408
 409         stats->tx_packets       = m->tx_packets;
 410         stats->tx_bytes         = m->tx_bytes;
 411         stats->tx_errors        = m->tx_errors;
 412         stats->tx_dropped       = m->tx_dropped;
 413 }
 414
 415 static int teql_master_mtu(struct net_device *dev, int new_mtu)
 416 {
 417         struct teql_master *m = netdev_priv(dev);
 418         struct Qdisc *q;
 419
 420         q = m->slaves;
 421         if (q) {
 422                 do {
 423                         if (new_mtu > qdisc_dev(q)->mtu)
 424                                 return -EINVAL;
 425                 } while ((q = NEXT_SLAVE(q)) != m->slaves);
 426         }
 427
 428         dev->mtu = new_mtu;
 429         return 0;
 430 }
 431
 432 static const struct net_device_ops teql_netdev_ops = {
 433         .ndo_open       = teql_master_open,
 434         .ndo_stop       = teql_master_close,
 435         .ndo_start_xmit = teql_master_xmit,
 436         .ndo_get_stats64 = teql_master_stats64,
 437         .ndo_change_mtu = teql_master_mtu,
 438 };
 439
 440 static __init void teql_master_setup(struct net_device *dev)
 441 {
 442         struct teql_master *master = netdev_priv(dev);
 443         struct Qdisc_ops *ops = &master->qops;
 444
 445         master->dev     = dev;
 446         ops->priv_size  = sizeof(struct teql_sched_data);
 447
 448         ops->enqueue    =       teql_enqueue;
 449         ops->dequeue    =       teql_dequeue;
 450         ops->peek       =       teql_peek;
 451         ops->init       =       teql_qdisc_init;
 452         ops->reset      =       teql_reset;
 453         ops->destroy    =       teql_destroy;
 454         ops->owner      =       THIS_MODULE;
 455
 456         dev->netdev_ops =       &teql_netdev_ops;
 457         dev->type               = ARPHRD_VOID;
 458         dev->mtu                = 1500;
 459         dev->min_mtu            = 68;
 460         dev->max_mtu            = 65535;
 461         dev->tx_queue_len       = 100;
 462         dev->flags              = IFF_NOARP;
 463         dev->hard_header_len    = LL_MAX_HEADER;
 464         netif_keep_dst(dev);
 465 }
 466
 467 static LIST_HEAD(master_dev_list);
 468 static int max_equalizers = 1;
 469 module_param(max_equalizers, int, 0);
 470 MODULE_PARM_DESC(max_equalizers, "Max number of link equalizers");
 471
 472 static int __init teql_init(void)
 473 {
 474         int i;
 475         int err = -ENODEV;
 476
 477         for (i = 0; i < max_equalizers; i++) {
 478                 struct net_device *dev;
 479                 struct teql_master *master;
 480
 481                 dev = alloc_netdev(sizeof(struct teql_master), "teql%d",
 482                                    NET_NAME_UNKNOWN, teql_master_setup);
 483                 if (!dev) {
 484                         err = -ENOMEM;
 485                         break;
 486                 }
 487
 488                 if ((err = register_netdev(dev))) {
 489                         free_netdev(dev);
 490                         break;
 491                 }
 492
 493                 master = netdev_priv(dev);
 494
 495                 strlcpy(master->qops.id, dev->name, IFNAMSIZ);
 496                 err = register_qdisc(&master->qops);
 497
 498                 if (err) {
 499                         unregister_netdev(dev);
 500                         free_netdev(dev);
 501                         break;
 502                 }
 503
 504                 list_add_tail(&master->master_list, &master_dev_list);
 505         }
 506         return i ? 0 : err;
 507 }
 508
 509 static void __exit teql_exit(void)
 510 {
 511         struct teql_master *master, *nxt;
 512
 513         list_for_each_entry_safe(master, nxt, &master_dev_list, master_list) {
 514
 515                 list_del(&master->master_list);
 516
 517                 unregister_qdisc(&master->qops);
 518                 unregister_netdev(master->dev);
 519                 free_netdev(master->dev);
 520         }
 521 }
 522
 523 module_init(teql_init);
 524 module_exit(teql_exit);
 525
 526 MODULE_LICENSE("GPL");