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                 fallthrough;
 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         ptr = skb_push(skb, 2);
 202
 203         *ptr++ = size % 256;
 204         *ptr++ = size / 256;
 205
 206         ndev->stats.tx_packets++;
 207         ndev->stats.tx_bytes += size;
 208
 209         skb->dev = dev = lapbeth->ethdev;
 210
 211         skb->protocol = htons(ETH_P_DEC);
 212
 213         skb_reset_network_header(skb);
 214
 215         dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
 216
 217         dev_queue_xmit(skb);
 218 }
 219
 220 static void lapbeth_connected(struct net_device *dev, int reason)
 221 {
 222         unsigned char *ptr;
 223         struct sk_buff *skb = dev_alloc_skb(1);
 224
 225         if (!skb) {
 226                 pr_err("out of memory\n");
 227                 return;
 228         }
 229
 230         ptr  = skb_put(skb, 1);
 231         *ptr = X25_IFACE_CONNECT;
 232
 233         skb->protocol = x25_type_trans(skb, dev);
 234         netif_rx(skb);
 235 }
 236
 237 static void lapbeth_disconnected(struct net_device *dev, int reason)
 238 {
 239         unsigned char *ptr;
 240         struct sk_buff *skb = dev_alloc_skb(1);
 241
 242         if (!skb) {
 243                 pr_err("out of memory\n");
 244                 return;
 245         }
 246
 247         ptr  = skb_put(skb, 1);
 248         *ptr = X25_IFACE_DISCONNECT;
 249
 250         skb->protocol = x25_type_trans(skb, dev);
 251         netif_rx(skb);
 252 }
 253
 254 /*
 255  *      Set AX.25 callsign
 256  */
 257 static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
 258 {
 259         struct sockaddr *sa = addr;
 260         memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
 261         return 0;
 262 }
 263
 264
 265 static const struct lapb_register_struct lapbeth_callbacks = {
 266         .connect_confirmation    = lapbeth_connected,
 267         .connect_indication      = lapbeth_connected,
 268         .disconnect_confirmation = lapbeth_disconnected,
 269         .disconnect_indication   = lapbeth_disconnected,
 270         .data_indication         = lapbeth_data_indication,
 271         .data_transmit           = lapbeth_data_transmit,
 272 };
 273
 274 /*
 275  * open/close a device
 276  */
 277 static int lapbeth_open(struct net_device *dev)
 278 {
 279         int err;
 280
 281         if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
 282                 pr_err("lapb_register error: %d\n", err);
 283                 return -ENODEV;
 284         }
 285
 286         netif_start_queue(dev);
 287         return 0;
 288 }
 289
 290 static int lapbeth_close(struct net_device *dev)
 291 {
 292         int err;
 293
 294         netif_stop_queue(dev);
 295
 296         if ((err = lapb_unregister(dev)) != LAPB_OK)
 297                 pr_err("lapb_unregister error: %d\n", err);
 298
 299         return 0;
 300 }
 301
 302 /* ------------------------------------------------------------------------ */
 303
 304 static const struct net_device_ops lapbeth_netdev_ops = {
 305         .ndo_open            = lapbeth_open,
 306         .ndo_stop            = lapbeth_close,
 307         .ndo_start_xmit      = lapbeth_xmit,
 308         .ndo_set_mac_address = lapbeth_set_mac_address,
 309 };
 310
 311 static void lapbeth_setup(struct net_device *dev)
 312 {
 313         dev->netdev_ops      = &lapbeth_netdev_ops;
 314         dev->needs_free_netdev = true;
 315         dev->type            = ARPHRD_X25;
 316         dev->hard_header_len = 0;
 317         dev->mtu             = 1000;
 318         dev->addr_len        = 0;
 319 }
 320
 321 /*
 322  *      Setup a new device.
 323  */
 324 static int lapbeth_new_device(struct net_device *dev)
 325 {
 326         struct net_device *ndev;
 327         struct lapbethdev *lapbeth;
 328         int rc = -ENOMEM;
 329
 330         ASSERT_RTNL();
 331
 332         ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
 333                             lapbeth_setup);
 334         if (!ndev)
 335                 goto out;
 336
 337         /* When transmitting data:
 338          * first this driver removes a pseudo header of 1 byte,
 339          * then the lapb module prepends an LAPB header of at most 3 bytes,
 340          * then this driver prepends a length field of 2 bytes,
 341          * then the underlying Ethernet device prepends its own header.
 342          */
 343         ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
 344                                            + dev->needed_headroom;
 345         ndev->needed_tailroom = dev->needed_tailroom;
 346
 347         lapbeth = netdev_priv(ndev);
 348         lapbeth->axdev = ndev;
 349
 350         dev_hold(dev);
 351         lapbeth->ethdev = dev;
 352
 353         rc = -EIO;
 354         if (register_netdevice(ndev))
 355                 goto fail;
 356
 357         list_add_rcu(&lapbeth->node, &lapbeth_devices);
 358         rc = 0;
 359 out:
 360         return rc;
 361 fail:
 362         dev_put(dev);
 363         free_netdev(ndev);
 364         goto out;
 365 }
 366
 367 /*
 368  *      Free a lapb network device.
 369  */
 370 static void lapbeth_free_device(struct lapbethdev *lapbeth)
 371 {
 372         dev_put(lapbeth->ethdev);
 373         list_del_rcu(&lapbeth->node);
 374         unregister_netdevice(lapbeth->axdev);
 375 }
 376
 377 /*
 378  *      Handle device status changes.
 379  *
 380  * Called from notifier with RTNL held.
 381  */
 382 static int lapbeth_device_event(struct notifier_block *this,
 383                                 unsigned long event, void *ptr)
 384 {
 385         struct lapbethdev *lapbeth;
 386         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 387
 388         if (dev_net(dev) != &init_net)
 389                 return NOTIFY_DONE;
 390
 391         if (!dev_is_ethdev(dev))
 392                 return NOTIFY_DONE;
 393
 394         switch (event) {
 395         case NETDEV_UP:
 396                 /* New ethernet device -> new LAPB interface     */
 397                 if (lapbeth_get_x25_dev(dev) == NULL)
 398                         lapbeth_new_device(dev);
 399                 break;
 400         case NETDEV_DOWN:
 401                 /* ethernet device closed -> close LAPB interface */
 402                 lapbeth = lapbeth_get_x25_dev(dev);
 403                 if (lapbeth)
 404                         dev_close(lapbeth->axdev);
 405                 break;
 406         case NETDEV_UNREGISTER:
 407                 /* ethernet device disappears -> remove LAPB interface */
 408                 lapbeth = lapbeth_get_x25_dev(dev);
 409                 if (lapbeth)
 410                         lapbeth_free_device(lapbeth);
 411                 break;
 412         }
 413
 414         return NOTIFY_DONE;
 415 }
 416
 417 /* ------------------------------------------------------------------------ */
 418
 419 static struct packet_type lapbeth_packet_type __read_mostly = {
 420         .type = cpu_to_be16(ETH_P_DEC),
 421         .func = lapbeth_rcv,
 422 };
 423
 424 static struct notifier_block lapbeth_dev_notifier = {
 425         .notifier_call = lapbeth_device_event,
 426 };
 427
 428 static const char banner[] __initconst =
 429         KERN_INFO "LAPB Ethernet driver version 0.02\n";
 430
 431 static int __init lapbeth_init_driver(void)
 432 {
 433         dev_add_pack(&lapbeth_packet_type);
 434
 435         register_netdevice_notifier(&lapbeth_dev_notifier);
 436
 437         printk(banner);
 438
 439         return 0;
 440 }
 441 module_init(lapbeth_init_driver);
 442
 443 static void __exit lapbeth_cleanup_driver(void)
 444 {
 445         struct lapbethdev *lapbeth;
 446         struct list_head *entry, *tmp;
 447
 448         dev_remove_pack(&lapbeth_packet_type);
 449         unregister_netdevice_notifier(&lapbeth_dev_notifier);
 450
 451         rtnl_lock();
 452         list_for_each_safe(entry, tmp, &lapbeth_devices) {
 453                 lapbeth = list_entry(entry, struct lapbethdev, node);
 454
 455                 dev_put(lapbeth->ethdev);
 456                 unregister_netdevice(lapbeth->axdev);
 457         }
 458         rtnl_unlock();
 459 }
 460 module_exit(lapbeth_cleanup_driver);
 461
 462 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
 463 MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
 464 MODULE_LICENSE("GPL");