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 /* ------------------------------------------------------------------------ */
  59
  60 /*
  61  *      Get the LAPB device for the ethernet device
  62  */
  63 static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
  64 {
  65         struct lapbethdev *lapbeth;
  66
  67         list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
  68                 if (lapbeth->ethdev == dev)
  69                         return lapbeth;
  70         }
  71         return NULL;
  72 }
  73
  74 static __inline__ int dev_is_ethdev(struct net_device *dev)
  75 {
  76         return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
  77 }
  78
  79 /* ------------------------------------------------------------------------ */
  80
  81 /*
  82  *      Receive a LAPB frame via an ethernet interface.
  83  */
  84 static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
  85 {
  86         int len, err;
  87         struct lapbethdev *lapbeth;
  88
  89         if (dev_net(dev) != &init_net)
  90                 goto drop;
  91
  92         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
  93                 return NET_RX_DROP;
  94
  95         if (!pskb_may_pull(skb, 2))
  96                 goto drop;
  97
  98         rcu_read_lock();
  99         lapbeth = lapbeth_get_x25_dev(dev);
 100         if (!lapbeth)
 101                 goto drop_unlock;
 102         if (!netif_running(lapbeth->axdev))
 103                 goto drop_unlock;
 104
 105         len = skb->data[0] + skb->data[1] * 256;
 106         dev->stats.rx_packets++;
 107         dev->stats.rx_bytes += len;
 108
 109         skb_pull(skb, 2);       /* Remove the length bytes */
 110         skb_trim(skb, len);     /* Set the length of the data */
 111
 112         if ((err = lapb_data_received(lapbeth->axdev, skb)) != LAPB_OK) {
 113                 printk(KERN_DEBUG "lapbether: lapb_data_received err - %d\n", err);
 114                 goto drop_unlock;
 115         }
 116 out:
 117         rcu_read_unlock();
 118         return 0;
 119 drop_unlock:
 120         kfree_skb(skb);
 121         goto out;
 122 drop:
 123         kfree_skb(skb);
 124         return 0;
 125 }
 126
 127 static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
 128 {
 129         unsigned char *ptr;
 130
 131         if (skb_cow(skb, 1)) {
 132                 kfree_skb(skb);
 133                 return NET_RX_DROP;
 134         }
 135
 136         skb_push(skb, 1);
 137
 138         ptr  = skb->data;
 139         *ptr = X25_IFACE_DATA;
 140
 141         skb->protocol = x25_type_trans(skb, dev);
 142         return netif_rx(skb);
 143 }
 144
 145 /*
 146  *      Send a LAPB frame via an ethernet interface
 147  */
 148 static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
 149                                       struct net_device *dev)
 150 {
 151         int err;
 152
 153         /*
 154          * Just to be *really* sure not to send anything if the interface
 155          * is down, the ethernet device may have gone.
 156          */
 157         if (!netif_running(dev))
 158                 goto drop;
 159
 160         /* There should be a pseudo header of 1 byte added by upper layers.
 161          * Check to make sure it is there before reading it.
 162          */
 163         if (skb->len < 1)
 164                 goto drop;
 165
 166         switch (skb->data[0]) {
 167         case X25_IFACE_DATA:
 168                 break;
 169         case X25_IFACE_CONNECT:
 170                 if ((err = lapb_connect_request(dev)) != LAPB_OK)
 171                         pr_err("lapb_connect_request error: %d\n", err);
 172                 goto drop;
 173         case X25_IFACE_DISCONNECT:
 174                 if ((err = lapb_disconnect_request(dev)) != LAPB_OK)
 175                         pr_err("lapb_disconnect_request err: %d\n", err);
 176                 /* Fall thru */
 177         default:
 178                 goto drop;
 179         }
 180
 181         skb_pull(skb, 1);
 182
 183         if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {
 184                 pr_err("lapb_data_request error - %d\n", err);
 185                 goto drop;
 186         }
 187 out:
 188         return NETDEV_TX_OK;
 189 drop:
 190         kfree_skb(skb);
 191         goto out;
 192 }
 193
 194 static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
 195 {
 196         struct lapbethdev *lapbeth = netdev_priv(ndev);
 197         unsigned char *ptr;
 198         struct net_device *dev;
 199         int size = skb->len;
 200
 201         skb->protocol = htons(ETH_P_X25);
 202
 203         ptr = skb_push(skb, 2);
 204
 205         *ptr++ = size % 256;
 206         *ptr++ = size / 256;
 207
 208         ndev->stats.tx_packets++;
 209         ndev->stats.tx_bytes += size;
 210
 211         skb->dev = dev = lapbeth->ethdev;
 212
 213         dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
 214
 215         dev_queue_xmit(skb);
 216 }
 217
 218 static void lapbeth_connected(struct net_device *dev, int reason)
 219 {
 220         unsigned char *ptr;
 221         struct sk_buff *skb = dev_alloc_skb(1);
 222
 223         if (!skb) {
 224                 pr_err("out of memory\n");
 225                 return;
 226         }
 227
 228         ptr  = skb_put(skb, 1);
 229         *ptr = X25_IFACE_CONNECT;
 230
 231         skb->protocol = x25_type_trans(skb, dev);
 232         netif_rx(skb);
 233 }
 234
 235 static void lapbeth_disconnected(struct net_device *dev, int reason)
 236 {
 237         unsigned char *ptr;
 238         struct sk_buff *skb = dev_alloc_skb(1);
 239
 240         if (!skb) {
 241                 pr_err("out of memory\n");
 242                 return;
 243         }
 244
 245         ptr  = skb_put(skb, 1);
 246         *ptr = X25_IFACE_DISCONNECT;
 247
 248         skb->protocol = x25_type_trans(skb, dev);
 249         netif_rx(skb);
 250 }
 251
 252 /*
 253  *      Set AX.25 callsign
 254  */
 255 static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
 256 {
 257         struct sockaddr *sa = addr;
 258         memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
 259         return 0;
 260 }
 261
 262
 263 static const struct lapb_register_struct lapbeth_callbacks = {
 264         .connect_confirmation    = lapbeth_connected,
 265         .connect_indication      = lapbeth_connected,
 266         .disconnect_confirmation = lapbeth_disconnected,
 267         .disconnect_indication   = lapbeth_disconnected,
 268         .data_indication         = lapbeth_data_indication,
 269         .data_transmit           = lapbeth_data_transmit,
 270 };
 271
 272 /*
 273  * open/close a device
 274  */
 275 static int lapbeth_open(struct net_device *dev)
 276 {
 277         int err;
 278
 279         if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
 280                 pr_err("lapb_register error: %d\n", err);
 281                 return -ENODEV;
 282         }
 283
 284         netif_start_queue(dev);
 285         return 0;
 286 }
 287
 288 static int lapbeth_close(struct net_device *dev)
 289 {
 290         int err;
 291
 292         netif_stop_queue(dev);
 293
 294         if ((err = lapb_unregister(dev)) != LAPB_OK)
 295                 pr_err("lapb_unregister error: %d\n", err);
 296
 297         return 0;
 298 }
 299
 300 /* ------------------------------------------------------------------------ */
 301
 302 static const struct net_device_ops lapbeth_netdev_ops = {
 303         .ndo_open            = lapbeth_open,
 304         .ndo_stop            = lapbeth_close,
 305         .ndo_start_xmit      = lapbeth_xmit,
 306         .ndo_set_mac_address = lapbeth_set_mac_address,
 307 };
 308
 309 static void lapbeth_setup(struct net_device *dev)
 310 {
 311         dev->netdev_ops      = &lapbeth_netdev_ops;
 312         dev->needs_free_netdev = true;
 313         dev->type            = ARPHRD_X25;
 314         dev->hard_header_len = 0;
 315         dev->mtu             = 1000;
 316         dev->addr_len        = 0;
 317 }
 318
 319 /*
 320  *      Setup a new device.
 321  */
 322 static int lapbeth_new_device(struct net_device *dev)
 323 {
 324         struct net_device *ndev;
 325         struct lapbethdev *lapbeth;
 326         int rc = -ENOMEM;
 327
 328         ASSERT_RTNL();
 329
 330         ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
 331                             lapbeth_setup);
 332         if (!ndev)
 333                 goto out;
 334
 335         /* When transmitting data:
 336          * first this driver removes a pseudo header of 1 byte,
 337          * then the lapb module prepends an LAPB header of at most 3 bytes,
 338          * then this driver prepends a length field of 2 bytes,
 339          * then the underlying Ethernet device prepends its own header.
 340          */
 341         ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
 342                                            + dev->needed_headroom;
 343
 344         lapbeth = netdev_priv(ndev);
 345         lapbeth->axdev = ndev;
 346
 347         dev_hold(dev);
 348         lapbeth->ethdev = dev;
 349
 350         rc = -EIO;
 351         if (register_netdevice(ndev))
 352                 goto fail;
 353
 354         list_add_rcu(&lapbeth->node, &lapbeth_devices);
 355         rc = 0;
 356 out:
 357         return rc;
 358 fail:
 359         dev_put(dev);
 360         free_netdev(ndev);
 361         goto out;
 362 }
 363
 364 /*
 365  *      Free a lapb network device.
 366  */
 367 static void lapbeth_free_device(struct lapbethdev *lapbeth)
 368 {
 369         dev_put(lapbeth->ethdev);
 370         list_del_rcu(&lapbeth->node);
 371         unregister_netdevice(lapbeth->axdev);
 372 }
 373
 374 /*
 375  *      Handle device status changes.
 376  *
 377  * Called from notifier with RTNL held.
 378  */
 379 static int lapbeth_device_event(struct notifier_block *this,
 380                                 unsigned long event, void *ptr)
 381 {
 382         struct lapbethdev *lapbeth;
 383         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 384
 385         if (dev_net(dev) != &init_net)
 386                 return NOTIFY_DONE;
 387
 388         if (!dev_is_ethdev(dev))
 389                 return NOTIFY_DONE;
 390
 391         switch (event) {
 392         case NETDEV_UP:
 393                 /* New ethernet device -> new LAPB interface     */
 394                 if (lapbeth_get_x25_dev(dev) == NULL)
 395                         lapbeth_new_device(dev);
 396                 break;
 397         case NETDEV_DOWN:
 398                 /* ethernet device closed -> close LAPB interface */
 399                 lapbeth = lapbeth_get_x25_dev(dev);
 400                 if (lapbeth)
 401                         dev_close(lapbeth->axdev);
 402                 break;
 403         case NETDEV_UNREGISTER:
 404                 /* ethernet device disappears -> remove LAPB interface */
 405                 lapbeth = lapbeth_get_x25_dev(dev);
 406                 if (lapbeth)
 407                         lapbeth_free_device(lapbeth);
 408                 break;
 409         }
 410
 411         return NOTIFY_DONE;
 412 }
 413
 414 /* ------------------------------------------------------------------------ */
 415
 416 static struct packet_type lapbeth_packet_type __read_mostly = {
 417         .type = cpu_to_be16(ETH_P_DEC),
 418         .func = lapbeth_rcv,
 419 };
 420
 421 static struct notifier_block lapbeth_dev_notifier = {
 422         .notifier_call = lapbeth_device_event,
 423 };
 424
 425 static const char banner[] __initconst =
 426         KERN_INFO "LAPB Ethernet driver version 0.02\n";
 427
 428 static int __init lapbeth_init_driver(void)
 429 {
 430         dev_add_pack(&lapbeth_packet_type);
 431
 432         register_netdevice_notifier(&lapbeth_dev_notifier);
 433
 434         printk(banner);
 435
 436         return 0;
 437 }
 438 module_init(lapbeth_init_driver);
 439
 440 static void __exit lapbeth_cleanup_driver(void)
 441 {
 442         struct lapbethdev *lapbeth;
 443         struct list_head *entry, *tmp;
 444
 445         dev_remove_pack(&lapbeth_packet_type);
 446         unregister_netdevice_notifier(&lapbeth_dev_notifier);
 447
 448         rtnl_lock();
 449         list_for_each_safe(entry, tmp, &lapbeth_devices) {
 450                 lapbeth = list_entry(entry, struct lapbethdev, node);
 451
 452                 dev_put(lapbeth->ethdev);
 453                 unregister_netdevice(lapbeth->axdev);
 454         }
 455         rtnl_unlock();
 456 }
 457 module_exit(lapbeth_cleanup_driver);
 458
 459 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
 460 MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
 461 MODULE_LICENSE("GPL");