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         return 0;
 296 }
 297
 298 static int lapbeth_close(struct net_device *dev)
 299 {
 300         int err;
 301
 302         if ((err = lapb_unregister(dev)) != LAPB_OK)
 303                 pr_err("lapb_unregister error: %d\n", err);
 304
 305         return 0;
 306 }
 307
 308 /* ------------------------------------------------------------------------ */
 309
 310 static const struct net_device_ops lapbeth_netdev_ops = {
 311         .ndo_open            = lapbeth_open,
 312         .ndo_stop            = lapbeth_close,
 313         .ndo_start_xmit      = lapbeth_xmit,
 314         .ndo_set_mac_address = lapbeth_set_mac_address,
 315 };
 316
 317 static void lapbeth_setup(struct net_device *dev)
 318 {
 319         dev->netdev_ops      = &lapbeth_netdev_ops;
 320         dev->needs_free_netdev = true;
 321         dev->type            = ARPHRD_X25;
 322         dev->hard_header_len = 0;
 323         dev->mtu             = 1000;
 324         dev->addr_len        = 0;
 325 }
 326
 327 /*
 328  *      Setup a new device.
 329  */
 330 static int lapbeth_new_device(struct net_device *dev)
 331 {
 332         struct net_device *ndev;
 333         struct lapbethdev *lapbeth;
 334         int rc = -ENOMEM;
 335
 336         ASSERT_RTNL();
 337
 338         ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
 339                             lapbeth_setup);
 340         if (!ndev)
 341                 goto out;
 342
 343         /* When transmitting data:
 344          * first this driver removes a pseudo header of 1 byte,
 345          * then the lapb module prepends an LAPB header of at most 3 bytes,
 346          * then this driver prepends a length field of 2 bytes,
 347          * then the underlying Ethernet device prepends its own header.
 348          */
 349         ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
 350                                            + dev->needed_headroom;
 351         ndev->needed_tailroom = dev->needed_tailroom;
 352
 353         lapbeth = netdev_priv(ndev);
 354         lapbeth->axdev = ndev;
 355
 356         dev_hold(dev);
 357         lapbeth->ethdev = dev;
 358
 359         rc = -EIO;
 360         if (register_netdevice(ndev))
 361                 goto fail;
 362
 363         list_add_rcu(&lapbeth->node, &lapbeth_devices);
 364         rc = 0;
 365 out:
 366         return rc;
 367 fail:
 368         dev_put(dev);
 369         free_netdev(ndev);
 370         goto out;
 371 }
 372
 373 /*
 374  *      Free a lapb network device.
 375  */
 376 static void lapbeth_free_device(struct lapbethdev *lapbeth)
 377 {
 378         dev_put(lapbeth->ethdev);
 379         list_del_rcu(&lapbeth->node);
 380         unregister_netdevice(lapbeth->axdev);
 381 }
 382
 383 /*
 384  *      Handle device status changes.
 385  *
 386  * Called from notifier with RTNL held.
 387  */
 388 static int lapbeth_device_event(struct notifier_block *this,
 389                                 unsigned long event, void *ptr)
 390 {
 391         struct lapbethdev *lapbeth;
 392         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 393
 394         if (dev_net(dev) != &init_net)
 395                 return NOTIFY_DONE;
 396
 397         if (!dev_is_ethdev(dev))
 398                 return NOTIFY_DONE;
 399
 400         switch (event) {
 401         case NETDEV_UP:
 402                 /* New ethernet device -> new LAPB interface     */
 403                 if (lapbeth_get_x25_dev(dev) == NULL)
 404                         lapbeth_new_device(dev);
 405                 break;
 406         case NETDEV_DOWN:
 407                 /* ethernet device closed -> close LAPB interface */
 408                 lapbeth = lapbeth_get_x25_dev(dev);
 409                 if (lapbeth)
 410                         dev_close(lapbeth->axdev);
 411                 break;
 412         case NETDEV_UNREGISTER:
 413                 /* ethernet device disappears -> remove LAPB interface */
 414                 lapbeth = lapbeth_get_x25_dev(dev);
 415                 if (lapbeth)
 416                         lapbeth_free_device(lapbeth);
 417                 break;
 418         }
 419
 420         return NOTIFY_DONE;
 421 }
 422
 423 /* ------------------------------------------------------------------------ */
 424
 425 static struct packet_type lapbeth_packet_type __read_mostly = {
 426         .type = cpu_to_be16(ETH_P_DEC),
 427         .func = lapbeth_rcv,
 428 };
 429
 430 static struct notifier_block lapbeth_dev_notifier = {
 431         .notifier_call = lapbeth_device_event,
 432 };
 433
 434 static const char banner[] __initconst =
 435         KERN_INFO "LAPB Ethernet driver version 0.02\n";
 436
 437 static int __init lapbeth_init_driver(void)
 438 {
 439         dev_add_pack(&lapbeth_packet_type);
 440
 441         register_netdevice_notifier(&lapbeth_dev_notifier);
 442
 443         printk(banner);
 444
 445         return 0;
 446 }
 447 module_init(lapbeth_init_driver);
 448
 449 static void __exit lapbeth_cleanup_driver(void)
 450 {
 451         struct lapbethdev *lapbeth;
 452         struct list_head *entry, *tmp;
 453
 454         dev_remove_pack(&lapbeth_packet_type);
 455         unregister_netdevice_notifier(&lapbeth_dev_notifier);
 456
 457         rtnl_lock();
 458         list_for_each_safe(entry, tmp, &lapbeth_devices) {
 459                 lapbeth = list_entry(entry, struct lapbethdev, node);
 460
 461                 dev_put(lapbeth->ethdev);
 462                 unregister_netdevice(lapbeth->axdev);
 463         }
 464         rtnl_unlock();
 465 }
 466 module_exit(lapbeth_cleanup_driver);
 467
 468 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
 469 MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
 470 MODULE_LICENSE("GPL");