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 };
  57
  58 static LIST_HEAD(lapbeth_devices);
  59
  60 /* ------------------------------------------------------------------------ */
  61
  62 /*
  63  *      Get the LAPB device for the ethernet device
  64  */
  65 static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
  66 {
  67         struct lapbethdev *lapbeth;
  68
  69         list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
  70                 if (lapbeth->ethdev == dev)
  71                         return lapbeth;
  72         }
  73         return NULL;
  74 }
  75
  76 static __inline__ int dev_is_ethdev(struct net_device *dev)
  77 {
  78         return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
  79 }
  80
  81 /* ------------------------------------------------------------------------ */
  82
  83 /*
  84  *      Receive a LAPB frame via an ethernet interface.
  85  */
  86 static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
  87 {
  88         int len, err;
  89         struct lapbethdev *lapbeth;
  90
  91         if (dev_net(dev) != &init_net)
  92                 goto drop;
  93
  94         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
  95                 return NET_RX_DROP;
  96
  97         if (!pskb_may_pull(skb, 2))
  98                 goto drop;
  99
 100         rcu_read_lock();
 101         lapbeth = lapbeth_get_x25_dev(dev);
 102         if (!lapbeth)
 103                 goto drop_unlock_rcu;
 104         spin_lock_bh(&lapbeth->up_lock);
 105         if (!lapbeth->up)
 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         spin_unlock_bh(&lapbeth->up_lock);
 121         rcu_read_unlock();
 122         return 0;
 123 drop_unlock:
 124         kfree_skb(skb);
 125         goto out;
 126 drop_unlock_rcu:
 127         rcu_read_unlock();
 128 drop:
 129         kfree_skb(skb);
 130         return 0;
 131 }
 132
 133 static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
 134 {
 135         unsigned char *ptr;
 136
 137         if (skb_cow(skb, 1)) {
 138                 kfree_skb(skb);
 139                 return NET_RX_DROP;
 140         }
 141
 142         skb_push(skb, 1);
 143
 144         ptr  = skb->data;
 145         *ptr = X25_IFACE_DATA;
 146
 147         skb->protocol = x25_type_trans(skb, dev);
 148         return netif_rx(skb);
 149 }
 150
 151 /*
 152  *      Send a LAPB frame via an ethernet interface
 153  */
 154 static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
 155                                       struct net_device *dev)
 156 {
 157         struct lapbethdev *lapbeth = netdev_priv(dev);
 158         int err;
 159
 160         spin_lock_bh(&lapbeth->up_lock);
 161         if (!lapbeth->up)
 162                 goto drop;
 163
 164         /* There should be a pseudo header of 1 byte added by upper layers.
 165          * Check to make sure it is there before reading it.
 166          */
 167         if (skb->len < 1)
 168                 goto drop;
 169
 170         switch (skb->data[0]) {
 171         case X25_IFACE_DATA:
 172                 break;
 173         case X25_IFACE_CONNECT:
 174                 if ((err = lapb_connect_request(dev)) != LAPB_OK)
 175                         pr_err("lapb_connect_request error: %d\n", err);
 176                 goto drop;
 177         case X25_IFACE_DISCONNECT:
 178                 if ((err = lapb_disconnect_request(dev)) != LAPB_OK)
 179                         pr_err("lapb_disconnect_request err: %d\n", err);
 180                 fallthrough;
 181         default:
 182                 goto drop;
 183         }
 184
 185         skb_pull(skb, 1);
 186
 187         if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {
 188                 pr_err("lapb_data_request error - %d\n", err);
 189                 goto drop;
 190         }
 191 out:
 192         spin_unlock_bh(&lapbeth->up_lock);
 193         return NETDEV_TX_OK;
 194 drop:
 195         kfree_skb(skb);
 196         goto out;
 197 }
 198
 199 static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
 200 {
 201         struct lapbethdev *lapbeth = netdev_priv(ndev);
 202         unsigned char *ptr;
 203         struct net_device *dev;
 204         int size = skb->len;
 205
 206         ptr = skb_push(skb, 2);
 207
 208         *ptr++ = size % 256;
 209         *ptr++ = size / 256;
 210
 211         ndev->stats.tx_packets++;
 212         ndev->stats.tx_bytes += size;
 213
 214         skb->dev = dev = lapbeth->ethdev;
 215
 216         skb->protocol = htons(ETH_P_DEC);
 217
 218         skb_reset_network_header(skb);
 219
 220         dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
 221
 222         dev_queue_xmit(skb);
 223 }
 224
 225 static void lapbeth_connected(struct net_device *dev, int reason)
 226 {
 227         unsigned char *ptr;
 228         struct sk_buff *skb = dev_alloc_skb(1);
 229
 230         if (!skb) {
 231                 pr_err("out of memory\n");
 232                 return;
 233         }
 234
 235         ptr  = skb_put(skb, 1);
 236         *ptr = X25_IFACE_CONNECT;
 237
 238         skb->protocol = x25_type_trans(skb, dev);
 239         netif_rx(skb);
 240 }
 241
 242 static void lapbeth_disconnected(struct net_device *dev, int reason)
 243 {
 244         unsigned char *ptr;
 245         struct sk_buff *skb = dev_alloc_skb(1);
 246
 247         if (!skb) {
 248                 pr_err("out of memory\n");
 249                 return;
 250         }
 251
 252         ptr  = skb_put(skb, 1);
 253         *ptr = X25_IFACE_DISCONNECT;
 254
 255         skb->protocol = x25_type_trans(skb, dev);
 256         netif_rx(skb);
 257 }
 258
 259 /*
 260  *      Set AX.25 callsign
 261  */
 262 static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
 263 {
 264         struct sockaddr *sa = addr;
 265         memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
 266         return 0;
 267 }
 268
 269
 270 static const struct lapb_register_struct lapbeth_callbacks = {
 271         .connect_confirmation    = lapbeth_connected,
 272         .connect_indication      = lapbeth_connected,
 273         .disconnect_confirmation = lapbeth_disconnected,
 274         .disconnect_indication   = lapbeth_disconnected,
 275         .data_indication         = lapbeth_data_indication,
 276         .data_transmit           = lapbeth_data_transmit,
 277 };
 278
 279 /*
 280  * open/close a device
 281  */
 282 static int lapbeth_open(struct net_device *dev)
 283 {
 284         struct lapbethdev *lapbeth = netdev_priv(dev);
 285         int err;
 286
 287         if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
 288                 pr_err("lapb_register error: %d\n", err);
 289                 return -ENODEV;
 290         }
 291
 292         spin_lock_bh(&lapbeth->up_lock);
 293         lapbeth->up = true;
 294         spin_unlock_bh(&lapbeth->up_lock);
 295
 296         return 0;
 297 }
 298
 299 static int lapbeth_close(struct net_device *dev)
 300 {
 301         struct lapbethdev *lapbeth = netdev_priv(dev);
 302         int err;
 303
 304         spin_lock_bh(&lapbeth->up_lock);
 305         lapbeth->up = false;
 306         spin_unlock_bh(&lapbeth->up_lock);
 307
 308         if ((err = lapb_unregister(dev)) != LAPB_OK)
 309                 pr_err("lapb_unregister error: %d\n", err);
 310
 311         return 0;
 312 }
 313
 314 /* ------------------------------------------------------------------------ */
 315
 316 static const struct net_device_ops lapbeth_netdev_ops = {
 317         .ndo_open            = lapbeth_open,
 318         .ndo_stop            = lapbeth_close,
 319         .ndo_start_xmit      = lapbeth_xmit,
 320         .ndo_set_mac_address = lapbeth_set_mac_address,
 321 };
 322
 323 static void lapbeth_setup(struct net_device *dev)
 324 {
 325         dev->netdev_ops      = &lapbeth_netdev_ops;
 326         dev->needs_free_netdev = true;
 327         dev->type            = ARPHRD_X25;
 328         dev->hard_header_len = 0;
 329         dev->mtu             = 1000;
 330         dev->addr_len        = 0;
 331 }
 332
 333 /*
 334  *      Setup a new device.
 335  */
 336 static int lapbeth_new_device(struct net_device *dev)
 337 {
 338         struct net_device *ndev;
 339         struct lapbethdev *lapbeth;
 340         int rc = -ENOMEM;
 341
 342         ASSERT_RTNL();
 343
 344         ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
 345                             lapbeth_setup);
 346         if (!ndev)
 347                 goto out;
 348
 349         /* When transmitting data:
 350          * first this driver removes a pseudo header of 1 byte,
 351          * then the lapb module prepends an LAPB header of at most 3 bytes,
 352          * then this driver prepends a length field of 2 bytes,
 353          * then the underlying Ethernet device prepends its own header.
 354          */
 355         ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
 356                                            + dev->needed_headroom;
 357         ndev->needed_tailroom = dev->needed_tailroom;
 358
 359         lapbeth = netdev_priv(ndev);
 360         lapbeth->axdev = ndev;
 361
 362         dev_hold(dev);
 363         lapbeth->ethdev = dev;
 364
 365         lapbeth->up = false;
 366         spin_lock_init(&lapbeth->up_lock);
 367
 368         rc = -EIO;
 369         if (register_netdevice(ndev))
 370                 goto fail;
 371
 372         list_add_rcu(&lapbeth->node, &lapbeth_devices);
 373         rc = 0;
 374 out:
 375         return rc;
 376 fail:
 377         dev_put(dev);
 378         free_netdev(ndev);
 379         goto out;
 380 }
 381
 382 /*
 383  *      Free a lapb network device.
 384  */
 385 static void lapbeth_free_device(struct lapbethdev *lapbeth)
 386 {
 387         dev_put(lapbeth->ethdev);
 388         list_del_rcu(&lapbeth->node);
 389         unregister_netdevice(lapbeth->axdev);
 390 }
 391
 392 /*
 393  *      Handle device status changes.
 394  *
 395  * Called from notifier with RTNL held.
 396  */
 397 static int lapbeth_device_event(struct notifier_block *this,
 398                                 unsigned long event, void *ptr)
 399 {
 400         struct lapbethdev *lapbeth;
 401         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 402
 403         if (dev_net(dev) != &init_net)
 404                 return NOTIFY_DONE;
 405
 406         if (!dev_is_ethdev(dev))
 407                 return NOTIFY_DONE;
 408
 409         switch (event) {
 410         case NETDEV_UP:
 411                 /* New ethernet device -> new LAPB interface     */
 412                 if (lapbeth_get_x25_dev(dev) == NULL)
 413                         lapbeth_new_device(dev);
 414                 break;
 415         case NETDEV_DOWN:
 416                 /* ethernet device closed -> close LAPB interface */
 417                 lapbeth = lapbeth_get_x25_dev(dev);
 418                 if (lapbeth)
 419                         dev_close(lapbeth->axdev);
 420                 break;
 421         case NETDEV_UNREGISTER:
 422                 /* ethernet device disappears -> remove LAPB interface */
 423                 lapbeth = lapbeth_get_x25_dev(dev);
 424                 if (lapbeth)
 425                         lapbeth_free_device(lapbeth);
 426                 break;
 427         }
 428
 429         return NOTIFY_DONE;
 430 }
 431
 432 /* ------------------------------------------------------------------------ */
 433
 434 static struct packet_type lapbeth_packet_type __read_mostly = {
 435         .type = cpu_to_be16(ETH_P_DEC),
 436         .func = lapbeth_rcv,
 437 };
 438
 439 static struct notifier_block lapbeth_dev_notifier = {
 440         .notifier_call = lapbeth_device_event,
 441 };
 442
 443 static const char banner[] __initconst =
 444         KERN_INFO "LAPB Ethernet driver version 0.02\n";
 445
 446 static int __init lapbeth_init_driver(void)
 447 {
 448         dev_add_pack(&lapbeth_packet_type);
 449
 450         register_netdevice_notifier(&lapbeth_dev_notifier);
 451
 452         printk(banner);
 453
 454         return 0;
 455 }
 456 module_init(lapbeth_init_driver);
 457
 458 static void __exit lapbeth_cleanup_driver(void)
 459 {
 460         struct lapbethdev *lapbeth;
 461         struct list_head *entry, *tmp;
 462
 463         dev_remove_pack(&lapbeth_packet_type);
 464         unregister_netdevice_notifier(&lapbeth_dev_notifier);
 465
 466         rtnl_lock();
 467         list_for_each_safe(entry, tmp, &lapbeth_devices) {
 468                 lapbeth = list_entry(entry, struct lapbethdev, node);
 469
 470                 dev_put(lapbeth->ethdev);
 471                 unregister_netdevice(lapbeth->axdev);
 472         }
 473         rtnl_unlock();
 474 }
 475 module_exit(lapbeth_cleanup_driver);
 476
 477 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
 478 MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
 479 MODULE_LICENSE("GPL");