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         switch (skb->data[0]) {
 161         case X25_IFACE_DATA:
 162                 break;
 163         case X25_IFACE_CONNECT:
 164                 if ((err = lapb_connect_request(dev)) != LAPB_OK)
 165                         pr_err("lapb_connect_request error: %d\n", err);
 166                 goto drop;
 167         case X25_IFACE_DISCONNECT:
 168                 if ((err = lapb_disconnect_request(dev)) != LAPB_OK)
 169                         pr_err("lapb_disconnect_request err: %d\n", err);
 170                 /* Fall thru */
 171         default:
 172                 goto drop;
 173         }
 174
 175         skb_pull(skb, 1);
 176
 177         if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {
 178                 pr_err("lapb_data_request error - %d\n", err);
 179                 goto drop;
 180         }
 181 out:
 182         return NETDEV_TX_OK;
 183 drop:
 184         kfree_skb(skb);
 185         goto out;
 186 }
 187
 188 static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
 189 {
 190         struct lapbethdev *lapbeth = netdev_priv(ndev);
 191         unsigned char *ptr;
 192         struct net_device *dev;
 193         int size = skb->len;
 194
 195         skb->protocol = htons(ETH_P_X25);
 196
 197         ptr = skb_push(skb, 2);
 198
 199         *ptr++ = size % 256;
 200         *ptr++ = size / 256;
 201
 202         ndev->stats.tx_packets++;
 203         ndev->stats.tx_bytes += size;
 204
 205         skb->dev = dev = lapbeth->ethdev;
 206
 207         dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
 208
 209         dev_queue_xmit(skb);
 210 }
 211
 212 static void lapbeth_connected(struct net_device *dev, int reason)
 213 {
 214         unsigned char *ptr;
 215         struct sk_buff *skb = dev_alloc_skb(1);
 216
 217         if (!skb) {
 218                 pr_err("out of memory\n");
 219                 return;
 220         }
 221
 222         ptr  = skb_put(skb, 1);
 223         *ptr = X25_IFACE_CONNECT;
 224
 225         skb->protocol = x25_type_trans(skb, dev);
 226         netif_rx(skb);
 227 }
 228
 229 static void lapbeth_disconnected(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_DISCONNECT;
 241
 242         skb->protocol = x25_type_trans(skb, dev);
 243         netif_rx(skb);
 244 }
 245
 246 /*
 247  *      Set AX.25 callsign
 248  */
 249 static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
 250 {
 251         struct sockaddr *sa = addr;
 252         memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
 253         return 0;
 254 }
 255
 256
 257 static const struct lapb_register_struct lapbeth_callbacks = {
 258         .connect_confirmation    = lapbeth_connected,
 259         .connect_indication      = lapbeth_connected,
 260         .disconnect_confirmation = lapbeth_disconnected,
 261         .disconnect_indication   = lapbeth_disconnected,
 262         .data_indication         = lapbeth_data_indication,
 263         .data_transmit           = lapbeth_data_transmit,
 264 };
 265
 266 /*
 267  * open/close a device
 268  */
 269 static int lapbeth_open(struct net_device *dev)
 270 {
 271         int err;
 272
 273         if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
 274                 pr_err("lapb_register error: %d\n", err);
 275                 return -ENODEV;
 276         }
 277
 278         netif_start_queue(dev);
 279         return 0;
 280 }
 281
 282 static int lapbeth_close(struct net_device *dev)
 283 {
 284         int err;
 285
 286         netif_stop_queue(dev);
 287
 288         if ((err = lapb_unregister(dev)) != LAPB_OK)
 289                 pr_err("lapb_unregister error: %d\n", err);
 290
 291         return 0;
 292 }
 293
 294 /* ------------------------------------------------------------------------ */
 295
 296 static const struct net_device_ops lapbeth_netdev_ops = {
 297         .ndo_open            = lapbeth_open,
 298         .ndo_stop            = lapbeth_close,
 299         .ndo_start_xmit      = lapbeth_xmit,
 300         .ndo_set_mac_address = lapbeth_set_mac_address,
 301 };
 302
 303 static void lapbeth_setup(struct net_device *dev)
 304 {
 305         dev->netdev_ops      = &lapbeth_netdev_ops;
 306         dev->needs_free_netdev = true;
 307         dev->type            = ARPHRD_X25;
 308         dev->mtu             = 1000;
 309         dev->addr_len        = 0;
 310 }
 311
 312 /*
 313  *      Setup a new device.
 314  */
 315 static int lapbeth_new_device(struct net_device *dev)
 316 {
 317         struct net_device *ndev;
 318         struct lapbethdev *lapbeth;
 319         int rc = -ENOMEM;
 320
 321         ASSERT_RTNL();
 322
 323         ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
 324                             lapbeth_setup);
 325         if (!ndev)
 326                 goto out;
 327
 328         /* When transmitting data:
 329          * first this driver removes a pseudo header of 1 byte,
 330          * then the lapb module prepends an LAPB header of at most 3 bytes,
 331          * then this driver prepends a length field of 2 bytes,
 332          * then the underlying Ethernet device prepends its own header.
 333          */
 334         ndev->hard_header_len = -1 + 3 + 2 + dev->hard_header_len;
 335
 336         lapbeth = netdev_priv(ndev);
 337         lapbeth->axdev = ndev;
 338
 339         dev_hold(dev);
 340         lapbeth->ethdev = dev;
 341
 342         rc = -EIO;
 343         if (register_netdevice(ndev))
 344                 goto fail;
 345
 346         list_add_rcu(&lapbeth->node, &lapbeth_devices);
 347         rc = 0;
 348 out:
 349         return rc;
 350 fail:
 351         dev_put(dev);
 352         free_netdev(ndev);
 353         goto out;
 354 }
 355
 356 /*
 357  *      Free a lapb network device.
 358  */
 359 static void lapbeth_free_device(struct lapbethdev *lapbeth)
 360 {
 361         dev_put(lapbeth->ethdev);
 362         list_del_rcu(&lapbeth->node);
 363         unregister_netdevice(lapbeth->axdev);
 364 }
 365
 366 /*
 367  *      Handle device status changes.
 368  *
 369  * Called from notifier with RTNL held.
 370  */
 371 static int lapbeth_device_event(struct notifier_block *this,
 372                                 unsigned long event, void *ptr)
 373 {
 374         struct lapbethdev *lapbeth;
 375         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 376
 377         if (dev_net(dev) != &init_net)
 378                 return NOTIFY_DONE;
 379
 380         if (!dev_is_ethdev(dev))
 381                 return NOTIFY_DONE;
 382
 383         switch (event) {
 384         case NETDEV_UP:
 385                 /* New ethernet device -> new LAPB interface     */
 386                 if (lapbeth_get_x25_dev(dev) == NULL)
 387                         lapbeth_new_device(dev);
 388                 break;
 389         case NETDEV_DOWN:
 390                 /* ethernet device closed -> close LAPB interface */
 391                 lapbeth = lapbeth_get_x25_dev(dev);
 392                 if (lapbeth)
 393                         dev_close(lapbeth->axdev);
 394                 break;
 395         case NETDEV_UNREGISTER:
 396                 /* ethernet device disappears -> remove LAPB interface */
 397                 lapbeth = lapbeth_get_x25_dev(dev);
 398                 if (lapbeth)
 399                         lapbeth_free_device(lapbeth);
 400                 break;
 401         }
 402
 403         return NOTIFY_DONE;
 404 }
 405
 406 /* ------------------------------------------------------------------------ */
 407
 408 static struct packet_type lapbeth_packet_type __read_mostly = {
 409         .type = cpu_to_be16(ETH_P_DEC),
 410         .func = lapbeth_rcv,
 411 };
 412
 413 static struct notifier_block lapbeth_dev_notifier = {
 414         .notifier_call = lapbeth_device_event,
 415 };
 416
 417 static const char banner[] __initconst =
 418         KERN_INFO "LAPB Ethernet driver version 0.02\n";
 419
 420 static int __init lapbeth_init_driver(void)
 421 {
 422         dev_add_pack(&lapbeth_packet_type);
 423
 424         register_netdevice_notifier(&lapbeth_dev_notifier);
 425
 426         printk(banner);
 427
 428         return 0;
 429 }
 430 module_init(lapbeth_init_driver);
 431
 432 static void __exit lapbeth_cleanup_driver(void)
 433 {
 434         struct lapbethdev *lapbeth;
 435         struct list_head *entry, *tmp;
 436
 437         dev_remove_pack(&lapbeth_packet_type);
 438         unregister_netdevice_notifier(&lapbeth_dev_notifier);
 439
 440         rtnl_lock();
 441         list_for_each_safe(entry, tmp, &lapbeth_devices) {
 442                 lapbeth = list_entry(entry, struct lapbethdev, node);
 443
 444                 dev_put(lapbeth->ethdev);
 445                 unregister_netdevice(lapbeth->axdev);
 446         }
 447         rtnl_unlock();
 448 }
 449 module_exit(lapbeth_cleanup_driver);
 450
 451 MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
 452 MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
 453 MODULE_LICENSE("GPL");