drivers/net/wan/lapbether.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      "LAPB via ethernet" driver release 001
   4  *
   5  *      This code REQUIRES 2.1.15 or higher/ NET3.038
   6  *
   7  *      This is a "pseudo" network driver to allow LAPB over Ethernet.
   8  *
   9  *      This driver can use any ethernet destination address, and can be
  10  *      limited to accept frames from one dedicated ethernet card only.
  11  *
  12  *      History
  13  *      LAPBETH 001     Jonathan Naylor         Cloned from bpqether.c
  14  *      2000-10-29      Henner Eisen    lapb_data_indication() return status.
  15  *      2000-11-14      Henner Eisen    dev_hold/put, NETDEV_GOING_DOWN support
  16  */
  17
  18 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  19
  20 #include <linux/errno.h>
  21 #include <linux/types.h>
  22 #include <linux/socket.h>
  23 #include <linux/in.h>
  24 #include <linux/slab.h>
  25 #include <linux/kernel.h>
  26 #include <linux/string.h>
  27 #include <linux/net.h>
  28 #include <linux/inet.h>
  29 #include <linux/netdevice.h>
  30 #include <linux/if_arp.h>
  31 #include <linux/skbuff.h>
  32 #include <net/sock.h>
  33 #include <linux/uaccess.h>
  34 #include <linux/mm.h>
  35 #include <linux/interrupt.h>
  36 #include <linux/notifier.h>
  37 #include <linux/stat.h>
  38 #include <linux/module.h>
  39 #include <linux/lapb.h>
  40 #include <linux/init.h>
  41
  42 #include <net/x25device.h>
  43
  44 static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
  45
  46 /* If this number is made larger, check that the temporary string buffer
  47  * in lapbeth_new_device is large enough to store the probe device name.*/
  48 #define MAXLAPBDEV 100
  49
  50 struct lapbethdev {
  51         struct list_head        node;
  52         struct net_device       *ethdev;        /* link to ethernet device */
  53         struct net_device       *axdev;         /* lapbeth device (lapb#) */
  54         bool                    up;
  55         spinlock_t              up_lock;        /* Protects "up" */
  56         struct sk_buff_head     rx_queue;
  57         struct napi_struct      napi;
  58 };
  59
  60 static LIST_HEAD(lapbeth_devices);
  61
  62 static void lapbeth_connected(struct net_device *dev, int reason);
  63 static void lapbeth_disconnected(struct net_device *dev, int reason);
  64
  65 /* ------------------------------------------------------------------------ */
  66
  67 /*
  68  *      Get the LAPB device for the ethernet device
  69  */
  70 static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
  71 {
  72         struct lapbethdev *lapbeth;
  73
  74         list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
  75                 if (lapbeth->ethdev == dev)
  76                         return lapbeth;
  77         }
  78         return NULL;
  79 }
  80
  81 static __inline__ int dev_is_ethdev(struct net_device *dev)
  82 {
  83         return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
  84 }
  85
  86 /* ------------------------------------------------------------------------ */
  87
  88 static int lapbeth_napi_poll(struct napi_struct *napi, int budget)
  89 {
  90         struct lapbethdev *lapbeth = container_of(napi, struct lapbethdev,
  91                                                   napi);
  92         struct sk_buff *skb;
  93         int processed = 0;
  94
  95         for (; processed < budget; ++processed) {
  96                 skb = skb_dequeue(&lapbeth->rx_queue);
  97                 if (!skb)
  98                         break;
  99                 netif_receive_skb_core(skb);
 100         }
 101
 102         if (processed < budget)
 103                 napi_complete(napi);
 104
 105         return processed;
 106 }
 107
 108 /*
 109  *      Receive a LAPB frame via an ethernet interface.
 110  */
 111 static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
 112 {
 113         int len, err;
 114         struct lapbethdev *lapbeth;
 115
 116         if (dev_net(dev) != &init_net)
 117                 goto drop;
 118
 119         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
 120                 return NET_RX_DROP;
 121
 122         if (!pskb_may_pull(skb, 2))
 123                 goto drop;
 124
 125         rcu_read_lock();
 126         lapbeth = lapbeth_get_x25_dev(dev);
 127         if (!lapbeth)
 128                 goto drop_unlock_rcu;
 129         spin_lock_bh(&lapbeth->up_lock);
 130         if (!lapbeth->up)
 131                 goto drop_unlock;
 132
 133         len = skb->data[0] + skb->data[1] * 256;
 134         dev->stats.rx_packets++;
 135         dev->stats.rx_bytes += len;
 136
 137         skb_pull(skb, 2);       /* Remove the length bytes */
 138         skb_trim(skb, len);     /* Set the length of the data */
 139
 140         if ((err = lapb_data_received(lapbeth->axdev, skb)) != LAPB_OK) {
 141                 printk(KERN_DEBUG "lapbether: lapb_data_received err - %d\n", err);
 142                 goto drop_unlock;
 143         }
 144 out:
 145         spin_unlock_bh(&lapbeth->up_lock);
 146         rcu_read_unlock();
 147         return 0;
 148 drop_unlock:
 149         kfree_skb(skb);
 150         goto out;
 151 drop_unlock_rcu:
 152         rcu_read_unlock();
 153 drop:
 154         kfree_skb(skb);
 155         return 0;
 156 }
 157
 158 static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
 159 {
 160         struct lapbethdev *lapbeth = netdev_priv(dev);
 161         unsigned char *ptr;
 162
 163         if (skb_cow(skb, 1)) {
 164                 kfree_skb(skb);
 165                 return NET_RX_DROP;
 166         }
 167
 168         skb_push(skb, 1);
 169
 170         ptr  = skb->data;
 171         *ptr = X25_IFACE_DATA;
 172
 173         skb->protocol = x25_type_trans(skb, dev);
 174
 175         skb_queue_tail(&lapbeth->rx_queue, skb);
 176         napi_schedule(&lapbeth->napi);
 177         return NET_RX_SUCCESS;
 178 }
 179
 180 /*
 181  *      Send a LAPB frame via an ethernet interface
 182  */
 183 static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
 184                                       struct net_device *dev)
 185 {
 186         struct lapbethdev *lapbeth = netdev_priv(dev);
 187         int err;
 188
 189         spin_lock_bh(&lapbeth->up_lock);
 190         if (!lapbeth->up)
 191                 goto drop;
 192
 193         /* There should be a pseudo header of 1 byte added by upper layers.
 194          * Check to make sure it is there before reading it.
 195          */
 196         if (skb->len < 1)
 197                 goto drop;
 198
 199         switch (skb->data[0]) {
 200         case X25_IFACE_DATA:
 201                 break;
 202         case X25_IFACE_CONNECT:
 203                 err = lapb_connect_request(dev);
 204                 if (err == LAPB_CONNECTED)
 205                         lapbeth_connected(dev, LAPB_OK);
 206                 else if (err != LAPB_OK)
 207                         pr_err("lapb_connect_request error: %d\n", err);
 208                 goto drop;
 209         case X25_IFACE_DISCONNECT:
 210                 err = lapb_disconnect_request(dev);
 211                 if (err == LAPB_NOTCONNECTED)
 212                         lapbeth_disconnected(dev, LAPB_OK);
 213                 else if (err != LAPB_OK)
 214                         pr_err("lapb_disconnect_request err: %d\n", err);
 215                 fallthrough;
 216         default:
 217                 goto drop;
 218         }
 219
 220         skb_pull(skb, 1);
 221
 222         if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {
 223                 pr_err("lapb_data_request error - %d\n", err);
 224                 goto drop;
 225         }
 226 out:
 227         spin_unlock_bh(&lapbeth->up_lock);
 228         return NETDEV_TX_OK;
 229 drop:
 230         kfree_skb(skb);
 231         goto out;
 232 }
 233
 234 static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
 235 {
 236         struct lapbethdev *lapbeth = netdev_priv(ndev);
 237         unsigned char *ptr;
 238         struct net_device *dev;
 239         int size = skb->len;
 240
 241         ptr = skb_push(skb, 2);
 242
 243         *ptr++ = size % 256;
 244         *ptr++ = size / 256;
 245
 246         ndev->stats.tx_packets++;
 247         ndev->stats.tx_bytes += size;
 248
 249         skb->dev = dev = lapbeth->ethdev;
 250
 251         skb->protocol = htons(ETH_P_DEC);
 252
 253         skb_reset_network_header(skb);
 254
 255         dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
 256
 257         dev_queue_xmit(skb);
 258 }
 259
 260 static void lapbeth_connected(struct net_device *dev, int reason)
 261 {
 262         struct lapbethdev *lapbeth = netdev_priv(dev);
 263         unsigned char *ptr;
 264         struct sk_buff *skb = __dev_alloc_skb(1, GFP_ATOMIC | __GFP_NOMEMALLOC);
 265
 266         if (!skb) {
 267                 pr_err("out of memory\n");
 268                 return;
 269         }
 270
 271         ptr  = skb_put(skb, 1);
 272         *ptr = X25_IFACE_CONNECT;
 273
 274         skb->protocol = x25_type_trans(skb, dev);
 275
 276         skb_queue_tail(&lapbeth->rx_queue, skb);
 277         napi_schedule(&lapbeth->napi);
 278 }
 279
 280 static void lapbeth_disconnected(struct net_device *dev, int reason)
 281 {
 282         struct lapbethdev *lapbeth = netdev_priv(dev);
 283         unsigned char *ptr;
 284         struct sk_buff *skb = __dev_alloc_skb(1, GFP_ATOMIC | __GFP_NOMEMALLOC);
 285
 286         if (!skb) {
 287                 pr_err("out of memory\n");
 288                 return;
 289         }
 290
 291         ptr  = skb_put(skb, 1);
 292         *ptr = X25_IFACE_DISCONNECT;
 293
 294         skb->protocol = x25_type_trans(skb, dev);
 295
 296         skb_queue_tail(&lapbeth->rx_queue, skb);
 297         napi_schedule(&lapbeth->napi);
 298 }
 299
 300 /*
 301  *      Set AX.25 callsign
 302  */
 303 static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
 304 {
 305         struct sockaddr *sa = addr;
 306         memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
 307         return 0;
 308 }
 309
 310
 311 static const struct lapb_register_struct lapbeth_callbacks = {
 312         .connect_confirmation    = lapbeth_connected,
 313         .connect_indication      = lapbeth_connected,
 314         .disconnect_confirmation = lapbeth_disconnected,
 315         .disconnect_indication   = lapbeth_disconnected,
 316         .data_indication         = lapbeth_data_indication,
 317         .data_transmit           = lapbeth_data_transmit,
 318 };
 319
 320 /*
 321  * open/close a device
 322  */
 323 static int lapbeth_open(struct net_device *dev)
 324 {
 325         struct lapbethdev *lapbeth = netdev_priv(dev);
 326         int err;
 327
 328         napi_enable(&lapbeth->napi);
 329
 330         if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
 331                 pr_err("lapb_register error: %d\n", err);
 332                 return -ENODEV;
 333         }
 334
 335         spin_lock_bh(&lapbeth->up_lock);
 336         lapbeth->up = true;
 337         spin_unlock_bh(&lapbeth->up_lock);
 338
 339         return 0;
 340 }
 341
 342 static int lapbeth_close(struct net_device *dev)
 343 {
 344         struct lapbethdev *lapbeth = netdev_priv(dev);
 345         int err;
 346
 347         spin_lock_bh(&lapbeth->up_lock);
 348         lapbeth->up = false;
 349         spin_unlock_bh(&lapbeth->up_lock);
 350
 351         if ((err = lapb_unregister(dev)) != LAPB_OK)
 352                 pr_err("lapb_unregister error: %d\n", err);
 353
 354         napi_disable(&lapbeth->napi);
 355
 356         return 0;
 357 }
 358
 359 /* ------------------------------------------------------------------------ */
 360
 361 static const struct net_device_ops lapbeth_netdev_ops = {
 362         .ndo_open            = lapbeth_open,
 363         .ndo_stop            = lapbeth_close,
 364         .ndo_start_xmit      = lapbeth_xmit,
 365         .ndo_set_mac_address = lapbeth_set_mac_address,
 366 };
 367
 368 static void lapbeth_setup(struct net_device *dev)
 369 {
 370         dev->netdev_ops      = &lapbeth_netdev_ops;
 371         dev->needs_free_netdev = true;
 372         dev->type            = ARPHRD_X25;
 373         dev->hard_header_len = 0;
 374         dev->mtu             = 1000;
 375         dev->addr_len        = 0;
 376 }
 377
 378 /*
 379  *      Setup a new device.
 380  */
 381 static int lapbeth_new_device(struct net_device *dev)
 382 {
 383         struct net_device *ndev;
 384         struct lapbethdev *lapbeth;
 385         int rc = -ENOMEM;
 386
 387         ASSERT_RTNL();
 388
 389         ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
 390                             lapbeth_setup);
 391         if (!ndev)
 392                 goto out;
 393
 394         /* When transmitting data:
 395          * first this driver removes a pseudo header of 1 byte,
 396          * then the lapb module prepends an LAPB header of at most 3 bytes,
 397          * then this driver prepends a length field of 2 bytes,
 398          * then the underlying Ethernet device prepends its own header.
 399          */
 400         ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
 401                                            + dev->needed_headroom;
 402         ndev->needed_tailroom = dev->needed_tailroom;
 403
 404         lapbeth = netdev_priv(ndev);
 405         lapbeth->axdev = ndev;
 406
 407         dev_hold(dev);
 408         lapbeth->ethdev = dev;
 409
 410         lapbeth->up = false;
 411         spin_lock_init(&lapbeth->up_lock);
 412
 413         skb_queue_head_init(&lapbeth->rx_queue);
 414         netif_napi_add(ndev, &lapbeth->napi, lapbeth_napi_poll, 16);
 415
 416         rc = -EIO;
 417         if (register_netdevice(ndev))
 418                 goto fail;
 419
 420         list_add_rcu(&lapbeth->node, &lapbeth_devices);
 421         rc = 0;
 422 out:
 423         return rc;
 424 fail:
 425         dev_put(dev);
 426         free_netdev(ndev);
 427         goto out;
 428 }
 429
 430 /*
 431  *      Free a lapb network device.
 432  */
 433 static void lapbeth_free_device(struct lapbethdev *lapbeth)
 434 {
 435         dev_put(lapbeth->ethdev);
 436         list_del_rcu(&lapbeth->node);
 437         unregister_netdevice(lapbeth->axdev);
 438 }
 439
 440 /*
 441  *      Handle device status changes.
 442  *
 443  * Called from notifier with RTNL held.
 444  */
 445 static int lapbeth_device_event(struct notifier_block *this,
 446                                 unsigned long event, void *ptr)
 447 {
 448         struct lapbethdev *lapbeth;
 449         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 450
 451         if (dev_net(dev) != &init_net)
 452                 return NOTIFY_DONE;
 453
 454         if (!dev_is_ethdev(dev))
 455                 return NOTIFY_DONE;
 456
 457         switch (event) {
 458         case NETDEV_UP:
 459                 /* New ethernet device -> new LAPB interface     */
 460                 if (lapbeth_get_x25_dev(dev) == NULL)
 461                         lapbeth_new_device(dev);
 462                 break;
 463         case NETDEV_GOING_DOWN:
 464                 /* ethernet device closes -> close LAPB interface */
 465                 lapbeth = lapbeth_get_x25_dev(dev);
 466                 if (lapbeth)
 467                         dev_close(lapbeth->axdev);
 468                 break;
 469         case NETDEV_UNREGISTER:
 470                 /* ethernet device disappears -> remove LAPB interface */
 471                 lapbeth = lapbeth_get_x25_dev(dev);
 472                 if (lapbeth)
 473                         lapbeth_free_device(lapbeth);
 474                 break;
 475         }
 476
 477         return NOTIFY_DONE;
 478 }
 479
 480 /* ------------------------------------------------------------------------ */
 481
 482 static struct packet_type lapbeth_packet_type __read_mostly = {
 483         .type = cpu_to_be16(ETH_P_DEC),
 484         .func = lapbeth_rcv,
 485 };
 486
 487 static struct notifier_block lapbeth_dev_notifier = {
 488         .notifier_call = lapbeth_device_event,
 489 };
 490
 491 static const char banner[] __initconst =
 492         KERN_INFO "LAPB Ethernet driver version 0.02\n";
 493
 494 static int __init lapbeth_init_driver(void)
 495 {
 496         dev_add_pack(&lapbeth_packet_type);
 497
 498         register_netdevice_notifier(&lapbeth_dev_notifier);
 499
 500         printk(banner);
 501
 502         return 0;
 503 }
 504 module_init(lapbeth_init_driver);
 505
 506 static void __exit lapbeth_cleanup_driver(void)
 507 {
 508         struct lapbethdev *lapbeth;
 509         struct list_head *entry, *tmp;
 510
 511         dev_remove_pack(&lapbeth_packet_type);
 512         unregister_netdevice_notifier(&lapbeth_dev_notifier);
 513
 514         rtnl_lock();
 515         list_for_each_safe(entry, tmp, &lapbeth_devices) {
 516                 lapbeth = list_entry(entry, struct lapbethdev, node);
 517
 518                 dev_put(lapbeth->ethdev);
 519                 unregister_netdevice(lapbeth->axdev);
 520         }
 521         rtnl_unlock();
 522 }
 523 module_exit(lapbeth_cleanup_driver);
 524
 525 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
 526 MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
 527 MODULE_LICENSE("GPL");