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 };
  55
  56 static LIST_HEAD(lapbeth_devices);
  57
  58 static void lapbeth_connected(struct net_device *dev, int reason);
  59 static void lapbeth_disconnected(struct net_device *dev, int reason);
  60
  61 /* ------------------------------------------------------------------------ */
  62
  63 /*
  64  *      Get the LAPB device for the ethernet device
  65  */
  66 static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
  67 {
  68         struct lapbethdev *lapbeth;
  69
  70         list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
  71                 if (lapbeth->ethdev == dev)
  72                         return lapbeth;
  73         }
  74         return NULL;
  75 }
  76
  77 static __inline__ int dev_is_ethdev(struct net_device *dev)
  78 {
  79         return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
  80 }
  81
  82 /* ------------------------------------------------------------------------ */
  83
  84 /*
  85  *      Receive a LAPB frame via an ethernet interface.
  86  */
  87 static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
  88 {
  89         int len, err;
  90         struct lapbethdev *lapbeth;
  91
  92         if (dev_net(dev) != &init_net)
  93                 goto drop;
  94
  95         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
  96                 return NET_RX_DROP;
  97
  98         if (!pskb_may_pull(skb, 2))
  99                 goto drop;
 100
 101         rcu_read_lock();
 102         lapbeth = lapbeth_get_x25_dev(dev);
 103         if (!lapbeth)
 104                 goto drop_unlock;
 105         if (!netif_running(lapbeth->axdev))
 106                 goto drop_unlock;
 107
 108         len = skb->data[0] + skb->data[1] * 256;
 109         dev->stats.rx_packets++;
 110         dev->stats.rx_bytes += len;
 111
 112         skb_pull(skb, 2);       /* Remove the length bytes */
 113         skb_trim(skb, len);     /* Set the length of the data */
 114
 115         if ((err = lapb_data_received(lapbeth->axdev, skb)) != LAPB_OK) {
 116                 printk(KERN_DEBUG "lapbether: lapb_data_received err - %d\n", err);
 117                 goto drop_unlock;
 118         }
 119 out:
 120         rcu_read_unlock();
 121         return 0;
 122 drop_unlock:
 123         kfree_skb(skb);
 124         goto out;
 125 drop:
 126         kfree_skb(skb);
 127         return 0;
 128 }
 129
 130 static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
 131 {
 132         unsigned char *ptr;
 133
 134         if (skb_cow(skb, 1)) {
 135                 kfree_skb(skb);
 136                 return NET_RX_DROP;
 137         }
 138
 139         skb_push(skb, 1);
 140
 141         ptr  = skb->data;
 142         *ptr = X25_IFACE_DATA;
 143
 144         skb->protocol = x25_type_trans(skb, dev);
 145         return netif_rx(skb);
 146 }
 147
 148 /*
 149  *      Send a LAPB frame via an ethernet interface
 150  */
 151 static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
 152                                       struct net_device *dev)
 153 {
 154         int err;
 155
 156         /*
 157          * Just to be *really* sure not to send anything if the interface
 158          * is down, the ethernet device may have gone.
 159          */
 160         if (!netif_running(dev))
 161                 goto drop;
 162
 163         /* There should be a pseudo header of 1 byte added by upper layers.
 164          * Check to make sure it is there before reading it.
 165          */
 166         if (skb->len < 1)
 167                 goto drop;
 168
 169         switch (skb->data[0]) {
 170         case X25_IFACE_DATA:
 171                 break;
 172         case X25_IFACE_CONNECT:
 173                 err = lapb_connect_request(dev);
 174                 if (err == LAPB_CONNECTED)
 175                         lapbeth_connected(dev, LAPB_OK);
 176                 else if (err != LAPB_OK)
 177                         pr_err("lapb_connect_request error: %d\n", err);
 178                 goto drop;
 179         case X25_IFACE_DISCONNECT:
 180                 err = lapb_disconnect_request(dev);
 181                 if (err == LAPB_NOTCONNECTED)
 182                         lapbeth_disconnected(dev, LAPB_OK);
 183                 else if (err != LAPB_OK)
 184                         pr_err("lapb_disconnect_request err: %d\n", err);
 185                 fallthrough;
 186         default:
 187                 goto drop;
 188         }
 189
 190         skb_pull(skb, 1);
 191
 192         if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {
 193                 pr_err("lapb_data_request error - %d\n", err);
 194                 goto drop;
 195         }
 196 out:
 197         return NETDEV_TX_OK;
 198 drop:
 199         kfree_skb(skb);
 200         goto out;
 201 }
 202
 203 static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
 204 {
 205         struct lapbethdev *lapbeth = netdev_priv(ndev);
 206         unsigned char *ptr;
 207         struct net_device *dev;
 208         int size = skb->len;
 209
 210         ptr = skb_push(skb, 2);
 211
 212         *ptr++ = size % 256;
 213         *ptr++ = size / 256;
 214
 215         ndev->stats.tx_packets++;
 216         ndev->stats.tx_bytes += size;
 217
 218         skb->dev = dev = lapbeth->ethdev;
 219
 220         skb->protocol = htons(ETH_P_DEC);
 221
 222         skb_reset_network_header(skb);
 223
 224         dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
 225
 226         dev_queue_xmit(skb);
 227 }
 228
 229 static void lapbeth_connected(struct net_device *dev, int reason)
 230 {
 231         unsigned char *ptr;
 232         struct sk_buff *skb = dev_alloc_skb(1);
 233
 234         if (!skb) {
 235                 pr_err("out of memory\n");
 236                 return;
 237         }
 238
 239         ptr  = skb_put(skb, 1);
 240         *ptr = X25_IFACE_CONNECT;
 241
 242         skb->protocol = x25_type_trans(skb, dev);
 243         netif_rx(skb);
 244 }
 245
 246 static void lapbeth_disconnected(struct net_device *dev, int reason)
 247 {
 248         unsigned char *ptr;
 249         struct sk_buff *skb = dev_alloc_skb(1);
 250
 251         if (!skb) {
 252                 pr_err("out of memory\n");
 253                 return;
 254         }
 255
 256         ptr  = skb_put(skb, 1);
 257         *ptr = X25_IFACE_DISCONNECT;
 258
 259         skb->protocol = x25_type_trans(skb, dev);
 260         netif_rx(skb);
 261 }
 262
 263 /*
 264  *      Set AX.25 callsign
 265  */
 266 static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
 267 {
 268         struct sockaddr *sa = addr;
 269         memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
 270         return 0;
 271 }
 272
 273
 274 static const struct lapb_register_struct lapbeth_callbacks = {
 275         .connect_confirmation    = lapbeth_connected,
 276         .connect_indication      = lapbeth_connected,
 277         .disconnect_confirmation = lapbeth_disconnected,
 278         .disconnect_indication   = lapbeth_disconnected,
 279         .data_indication         = lapbeth_data_indication,
 280         .data_transmit           = lapbeth_data_transmit,
 281 };
 282
 283 /*
 284  * open/close a device
 285  */
 286 static int lapbeth_open(struct net_device *dev)
 287 {
 288         int err;
 289
 290         if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
 291                 pr_err("lapb_register error: %d\n", err);
 292                 return -ENODEV;
 293         }
 294
 295         netif_start_queue(dev);
 296         return 0;
 297 }
 298
 299 static int lapbeth_close(struct net_device *dev)
 300 {
 301         int err;
 302
 303         netif_stop_queue(dev);
 304
 305         if ((err = lapb_unregister(dev)) != LAPB_OK)
 306                 pr_err("lapb_unregister error: %d\n", err);
 307
 308         return 0;
 309 }
 310
 311 /* ------------------------------------------------------------------------ */
 312
 313 static const struct net_device_ops lapbeth_netdev_ops = {
 314         .ndo_open            = lapbeth_open,
 315         .ndo_stop            = lapbeth_close,
 316         .ndo_start_xmit      = lapbeth_xmit,
 317         .ndo_set_mac_address = lapbeth_set_mac_address,
 318 };
 319
 320 static void lapbeth_setup(struct net_device *dev)
 321 {
 322         dev->netdev_ops      = &lapbeth_netdev_ops;
 323         dev->needs_free_netdev = true;
 324         dev->type            = ARPHRD_X25;
 325         dev->hard_header_len = 0;
 326         dev->mtu             = 1000;
 327         dev->addr_len        = 0;
 328 }
 329
 330 /*
 331  *      Setup a new device.
 332  */
 333 static int lapbeth_new_device(struct net_device *dev)
 334 {
 335         struct net_device *ndev;
 336         struct lapbethdev *lapbeth;
 337         int rc = -ENOMEM;
 338
 339         ASSERT_RTNL();
 340
 341         ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
 342                             lapbeth_setup);
 343         if (!ndev)
 344                 goto out;
 345
 346         /* When transmitting data:
 347          * first this driver removes a pseudo header of 1 byte,
 348          * then the lapb module prepends an LAPB header of at most 3 bytes,
 349          * then this driver prepends a length field of 2 bytes,
 350          * then the underlying Ethernet device prepends its own header.
 351          */
 352         ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
 353                                            + dev->needed_headroom;
 354         ndev->needed_tailroom = dev->needed_tailroom;
 355
 356         lapbeth = netdev_priv(ndev);
 357         lapbeth->axdev = ndev;
 358
 359         dev_hold(dev);
 360         lapbeth->ethdev = dev;
 361
 362         rc = -EIO;
 363         if (register_netdevice(ndev))
 364                 goto fail;
 365
 366         list_add_rcu(&lapbeth->node, &lapbeth_devices);
 367         rc = 0;
 368 out:
 369         return rc;
 370 fail:
 371         dev_put(dev);
 372         free_netdev(ndev);
 373         goto out;
 374 }
 375
 376 /*
 377  *      Free a lapb network device.
 378  */
 379 static void lapbeth_free_device(struct lapbethdev *lapbeth)
 380 {
 381         dev_put(lapbeth->ethdev);
 382         list_del_rcu(&lapbeth->node);
 383         unregister_netdevice(lapbeth->axdev);
 384 }
 385
 386 /*
 387  *      Handle device status changes.
 388  *
 389  * Called from notifier with RTNL held.
 390  */
 391 static int lapbeth_device_event(struct notifier_block *this,
 392                                 unsigned long event, void *ptr)
 393 {
 394         struct lapbethdev *lapbeth;
 395         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 396
 397         if (dev_net(dev) != &init_net)
 398                 return NOTIFY_DONE;
 399
 400         if (!dev_is_ethdev(dev))
 401                 return NOTIFY_DONE;
 402
 403         switch (event) {
 404         case NETDEV_UP:
 405                 /* New ethernet device -> new LAPB interface     */
 406                 if (lapbeth_get_x25_dev(dev) == NULL)
 407                         lapbeth_new_device(dev);
 408                 break;
 409         case NETDEV_DOWN:
 410                 /* ethernet device closed -> close LAPB interface */
 411                 lapbeth = lapbeth_get_x25_dev(dev);
 412                 if (lapbeth)
 413                         dev_close(lapbeth->axdev);
 414                 break;
 415         case NETDEV_UNREGISTER:
 416                 /* ethernet device disappears -> remove LAPB interface */
 417                 lapbeth = lapbeth_get_x25_dev(dev);
 418                 if (lapbeth)
 419                         lapbeth_free_device(lapbeth);
 420                 break;
 421         }
 422
 423         return NOTIFY_DONE;
 424 }
 425
 426 /* ------------------------------------------------------------------------ */
 427
 428 static struct packet_type lapbeth_packet_type __read_mostly = {
 429         .type = cpu_to_be16(ETH_P_DEC),
 430         .func = lapbeth_rcv,
 431 };
 432
 433 static struct notifier_block lapbeth_dev_notifier = {
 434         .notifier_call = lapbeth_device_event,
 435 };
 436
 437 static const char banner[] __initconst =
 438         KERN_INFO "LAPB Ethernet driver version 0.02\n";
 439
 440 static int __init lapbeth_init_driver(void)
 441 {
 442         dev_add_pack(&lapbeth_packet_type);
 443
 444         register_netdevice_notifier(&lapbeth_dev_notifier);
 445
 446         printk(banner);
 447
 448         return 0;
 449 }
 450 module_init(lapbeth_init_driver);
 451
 452 static void __exit lapbeth_cleanup_driver(void)
 453 {
 454         struct lapbethdev *lapbeth;
 455         struct list_head *entry, *tmp;
 456
 457         dev_remove_pack(&lapbeth_packet_type);
 458         unregister_netdevice_notifier(&lapbeth_dev_notifier);
 459
 460         rtnl_lock();
 461         list_for_each_safe(entry, tmp, &lapbeth_devices) {
 462                 lapbeth = list_entry(entry, struct lapbethdev, node);
 463
 464                 dev_put(lapbeth->ethdev);
 465                 unregister_netdevice(lapbeth->axdev);
 466         }
 467         rtnl_unlock();
 468 }
 469 module_exit(lapbeth_cleanup_driver);
 470
 471 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
 472 MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
 473 MODULE_LICENSE("GPL");