drivers/net/slip/slip.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * slip.c       This module implements the SLIP protocol for kernel-based
   4  *              devices like TTY.  It interfaces between a raw TTY, and the
   5  *              kernel's INET protocol layers.
   6  *
   7  * Version:     @(#)slip.c      0.8.3   12/24/94
   8  *
   9  * Authors:     Laurence Culhane, <loz@holmes.demon.co.uk>
  10  *              Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
  11  *
  12  * Fixes:
  13  *              Alan Cox        :       Sanity checks and avoid tx overruns.
  14  *                                      Has a new sl->mtu field.
  15  *              Alan Cox        :       Found cause of overrun. ifconfig sl0
  16  *                                      mtu upwards. Driver now spots this
  17  *                                      and grows/shrinks its buffers(hack!).
  18  *                                      Memory leak if you run out of memory
  19  *                                      setting up a slip driver fixed.
  20  *              Matt Dillon     :       Printable slip (borrowed from NET2E)
  21  *      Pauline Middelink       :       Slip driver fixes.
  22  *              Alan Cox        :       Honours the old SL_COMPRESSED flag
  23  *              Alan Cox        :       KISS AX.25 and AXUI IP support
  24  *              Michael Riepe   :       Automatic CSLIP recognition added
  25  *              Charles Hedrick :       CSLIP header length problem fix.
  26  *              Alan Cox        :       Corrected non-IP cases of the above.
  27  *              Alan Cox        :       Now uses hardware type as per FvK.
  28  *              Alan Cox        :       Default to 192.168.0.0 (RFC 1597)
  29  *              A.N.Kuznetsov   :       dev_tint() recursion fix.
  30  *      Dmitry Gorodchanin      :       SLIP memory leaks
  31  *      Dmitry Gorodchanin      :       Code cleanup. Reduce tty driver
  32  *                                      buffering from 4096 to 256 bytes.
  33  *                                      Improving SLIP response time.
  34  *                                      CONFIG_SLIP_MODE_SLIP6.
  35  *                                      ifconfig sl? up & down now works
  36  *                                      correctly.
  37  *                                      Modularization.
  38  *              Alan Cox        :       Oops - fix AX.25 buffer lengths
  39  *      Dmitry Gorodchanin      :       Even more cleanups. Preserve CSLIP
  40  *                                      statistics. Include CSLIP code only
  41  *                                      if it really needed.
  42  *              Alan Cox        :       Free slhc buffers in the right place.
  43  *              Alan Cox        :       Allow for digipeated IP over AX.25
  44  *              Matti Aarnio    :       Dynamic SLIP devices, with ideas taken
  45  *                                      from Jim Freeman's <jfree@caldera.com>
  46  *                                      dynamic PPP devices.  We do NOT kfree()
  47  *                                      device entries, just reg./unreg. them
  48  *                                      as they are needed.  We kfree() them
  49  *                                      at module cleanup.
  50  *                                      With MODULE-loading ``insmod'', user
  51  *                                      can issue parameter:  slip_maxdev=1024
  52  *                                      (Or how much he/she wants.. Default
  53  *                                      is 256)
  54  *      Stanislav Voronyi       :       Slip line checking, with ideas taken
  55  *                                      from multislip BSDI driver which was
  56  *                                      written by Igor Chechik, RELCOM Corp.
  57  *                                      Only algorithms have been ported to
  58  *                                      Linux SLIP driver.
  59  *      Vitaly E. Lavrov        :       Sane behaviour on tty hangup.
  60  *      Alexey Kuznetsov        :       Cleanup interfaces to tty & netdevice
  61  *                                      modules.
  62  */
  63
  64 #define SL_CHECK_TRANSMIT
  65 #include <linux/module.h>
  66 #include <linux/moduleparam.h>
  67
  68 #include <linux/uaccess.h>
  69 #include <linux/bitops.h>
  70 #include <linux/sched/signal.h>
  71 #include <linux/string.h>
  72 #include <linux/mm.h>
  73 #include <linux/interrupt.h>
  74 #include <linux/in.h>
  75 #include <linux/tty.h>
  76 #include <linux/errno.h>
  77 #include <linux/netdevice.h>
  78 #include <linux/etherdevice.h>
  79 #include <linux/skbuff.h>
  80 #include <linux/rtnetlink.h>
  81 #include <linux/if_arp.h>
  82 #include <linux/if_slip.h>
  83 #include <linux/delay.h>
  84 #include <linux/init.h>
  85 #include <linux/slab.h>
  86 #include <linux/workqueue.h>
  87 #include "slip.h"
  88 #ifdef CONFIG_INET
  89 #include <linux/ip.h>
  90 #include <linux/tcp.h>
  91 #include <net/slhc_vj.h>
  92 #endif
  93
  94 #define SLIP_VERSION    "0.8.4-NET3.019-NEWTTY"
  95
  96 static struct net_device **slip_devs;
  97
  98 static int slip_maxdev = SL_NRUNIT;
  99 module_param(slip_maxdev, int, 0);
 100 MODULE_PARM_DESC(slip_maxdev, "Maximum number of slip devices");
 101
 102 static int slip_esc(unsigned char *p, unsigned char *d, int len);
 103 static void slip_unesc(struct slip *sl, unsigned char c);
 104 #ifdef CONFIG_SLIP_MODE_SLIP6
 105 static int slip_esc6(unsigned char *p, unsigned char *d, int len);
 106 static void slip_unesc6(struct slip *sl, unsigned char c);
 107 #endif
 108 #ifdef CONFIG_SLIP_SMART
 109 static void sl_keepalive(struct timer_list *t);
 110 static void sl_outfill(struct timer_list *t);
 111 static int sl_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
 112 #endif
 113
 114 /********************************
 115 *  Buffer administration routines:
 116 *       sl_alloc_bufs()
 117 *       sl_free_bufs()
 118 *       sl_realloc_bufs()
 119 *
 120 * NOTE: sl_realloc_bufs != sl_free_bufs + sl_alloc_bufs, because
 121 *       sl_realloc_bufs provides strong atomicity and reallocation
 122 *       on actively running device.
 123 *********************************/
 124
 125 /*
 126    Allocate channel buffers.
 127  */
 128
 129 static int sl_alloc_bufs(struct slip *sl, int mtu)
 130 {
 131         int err = -ENOBUFS;
 132         unsigned long len;
 133         char *rbuff = NULL;
 134         char *xbuff = NULL;
 135 #ifdef SL_INCLUDE_CSLIP
 136         char *cbuff = NULL;
 137         struct slcompress *slcomp = NULL;
 138 #endif
 139
 140         /*
 141          * Allocate the SLIP frame buffers:
 142          *
 143          * rbuff        Receive buffer.
 144          * xbuff        Transmit buffer.
 145          * cbuff        Temporary compression buffer.
 146          */
 147         len = mtu * 2;
 148
 149         /*
 150          * allow for arrival of larger UDP packets, even if we say not to
 151          * also fixes a bug in which SunOS sends 512-byte packets even with
 152          * an MSS of 128
 153          */
 154         if (len < 576 * 2)
 155                 len = 576 * 2;
 156         rbuff = kmalloc(len + 4, GFP_KERNEL);
 157         if (rbuff == NULL)
 158                 goto err_exit;
 159         xbuff = kmalloc(len + 4, GFP_KERNEL);
 160         if (xbuff == NULL)
 161                 goto err_exit;
 162 #ifdef SL_INCLUDE_CSLIP
 163         cbuff = kmalloc(len + 4, GFP_KERNEL);
 164         if (cbuff == NULL)
 165                 goto err_exit;
 166         slcomp = slhc_init(16, 16);
 167         if (IS_ERR(slcomp))
 168                 goto err_exit;
 169 #endif
 170         spin_lock_bh(&sl->lock);
 171         if (sl->tty == NULL) {
 172                 spin_unlock_bh(&sl->lock);
 173                 err = -ENODEV;
 174                 goto err_exit;
 175         }
 176         sl->mtu      = mtu;
 177         sl->buffsize = len;
 178         sl->rcount   = 0;
 179         sl->xleft    = 0;
 180         rbuff = xchg(&sl->rbuff, rbuff);
 181         xbuff = xchg(&sl->xbuff, xbuff);
 182 #ifdef SL_INCLUDE_CSLIP
 183         cbuff = xchg(&sl->cbuff, cbuff);
 184         slcomp = xchg(&sl->slcomp, slcomp);
 185 #endif
 186 #ifdef CONFIG_SLIP_MODE_SLIP6
 187         sl->xdata    = 0;
 188         sl->xbits    = 0;
 189 #endif
 190         spin_unlock_bh(&sl->lock);
 191         err = 0;
 192
 193         /* Cleanup */
 194 err_exit:
 195 #ifdef SL_INCLUDE_CSLIP
 196         kfree(cbuff);
 197         slhc_free(slcomp);
 198 #endif
 199         kfree(xbuff);
 200         kfree(rbuff);
 201         return err;
 202 }
 203
 204 /* Free a SLIP channel buffers. */
 205 static void sl_free_bufs(struct slip *sl)
 206 {
 207         /* Free all SLIP frame buffers. */
 208         kfree(xchg(&sl->rbuff, NULL));
 209         kfree(xchg(&sl->xbuff, NULL));
 210 #ifdef SL_INCLUDE_CSLIP
 211         kfree(xchg(&sl->cbuff, NULL));
 212         slhc_free(xchg(&sl->slcomp, NULL));
 213 #endif
 214 }
 215
 216 /*
 217    Reallocate slip channel buffers.
 218  */
 219
 220 static int sl_realloc_bufs(struct slip *sl, int mtu)
 221 {
 222         int err = 0;
 223         struct net_device *dev = sl->dev;
 224         unsigned char *xbuff, *rbuff;
 225 #ifdef SL_INCLUDE_CSLIP
 226         unsigned char *cbuff;
 227 #endif
 228         int len = mtu * 2;
 229
 230 /*
 231  * allow for arrival of larger UDP packets, even if we say not to
 232  * also fixes a bug in which SunOS sends 512-byte packets even with
 233  * an MSS of 128
 234  */
 235         if (len < 576 * 2)
 236                 len = 576 * 2;
 237
 238         xbuff = kmalloc(len + 4, GFP_ATOMIC);
 239         rbuff = kmalloc(len + 4, GFP_ATOMIC);
 240 #ifdef SL_INCLUDE_CSLIP
 241         cbuff = kmalloc(len + 4, GFP_ATOMIC);
 242 #endif
 243
 244
 245 #ifdef SL_INCLUDE_CSLIP
 246         if (xbuff == NULL || rbuff == NULL || cbuff == NULL)  {
 247 #else
 248         if (xbuff == NULL || rbuff == NULL)  {
 249 #endif
 250                 if (mtu > sl->mtu) {
 251                         printk(KERN_WARNING "%s: unable to grow slip buffers, MTU change cancelled.\n",
 252                                dev->name);
 253                         err = -ENOBUFS;
 254                 }
 255                 goto done;
 256         }
 257         spin_lock_bh(&sl->lock);
 258
 259         err = -ENODEV;
 260         if (sl->tty == NULL)
 261                 goto done_on_bh;
 262
 263         xbuff    = xchg(&sl->xbuff, xbuff);
 264         rbuff    = xchg(&sl->rbuff, rbuff);
 265 #ifdef SL_INCLUDE_CSLIP
 266         cbuff    = xchg(&sl->cbuff, cbuff);
 267 #endif
 268         if (sl->xleft)  {
 269                 if (sl->xleft <= len)  {
 270                         memcpy(sl->xbuff, sl->xhead, sl->xleft);
 271                 } else  {
 272                         sl->xleft = 0;
 273                         dev->stats.tx_dropped++;
 274                 }
 275         }
 276         sl->xhead = sl->xbuff;
 277
 278         if (sl->rcount)  {
 279                 if (sl->rcount <= len) {
 280                         memcpy(sl->rbuff, rbuff, sl->rcount);
 281                 } else  {
 282                         sl->rcount = 0;
 283                         dev->stats.rx_over_errors++;
 284                         set_bit(SLF_ERROR, &sl->flags);
 285                 }
 286         }
 287         sl->mtu      = mtu;
 288         dev->mtu      = mtu;
 289         sl->buffsize = len;
 290         err = 0;
 291
 292 done_on_bh:
 293         spin_unlock_bh(&sl->lock);
 294
 295 done:
 296         kfree(xbuff);
 297         kfree(rbuff);
 298 #ifdef SL_INCLUDE_CSLIP
 299         kfree(cbuff);
 300 #endif
 301         return err;
 302 }
 303
 304
 305 /* Set the "sending" flag.  This must be atomic hence the set_bit. */
 306 static inline void sl_lock(struct slip *sl)
 307 {
 308         netif_stop_queue(sl->dev);
 309 }
 310
 311
 312 /* Clear the "sending" flag.  This must be atomic, hence the ASM. */
 313 static inline void sl_unlock(struct slip *sl)
 314 {
 315         netif_wake_queue(sl->dev);
 316 }
 317
 318 /* Send one completely decapsulated IP datagram to the IP layer. */
 319 static void sl_bump(struct slip *sl)
 320 {
 321         struct net_device *dev = sl->dev;
 322         struct sk_buff *skb;
 323         int count;
 324
 325         count = sl->rcount;
 326 #ifdef SL_INCLUDE_CSLIP
 327         if (sl->mode & (SL_MODE_ADAPTIVE | SL_MODE_CSLIP)) {
 328                 unsigned char c = sl->rbuff[0];
 329                 if (c & SL_TYPE_COMPRESSED_TCP) {
 330                         /* ignore compressed packets when CSLIP is off */
 331                         if (!(sl->mode & SL_MODE_CSLIP)) {
 332                                 printk(KERN_WARNING "%s: compressed packet ignored\n", dev->name);
 333                                 return;
 334                         }
 335                         /* make sure we've reserved enough space for uncompress
 336                            to use */
 337                         if (count + 80 > sl->buffsize) {
 338                                 dev->stats.rx_over_errors++;
 339                                 return;
 340                         }
 341                         count = slhc_uncompress(sl->slcomp, sl->rbuff, count);
 342                         if (count <= 0)
 343                                 return;
 344                 } else if (c >= SL_TYPE_UNCOMPRESSED_TCP) {
 345                         if (!(sl->mode & SL_MODE_CSLIP)) {
 346                                 /* turn on header compression */
 347                                 sl->mode |= SL_MODE_CSLIP;
 348                                 sl->mode &= ~SL_MODE_ADAPTIVE;
 349                                 printk(KERN_INFO "%s: header compression turned on\n", dev->name);
 350                         }
 351                         sl->rbuff[0] &= 0x4f;
 352                         if (slhc_remember(sl->slcomp, sl->rbuff, count) <= 0)
 353                                 return;
 354                 }
 355         }
 356 #endif  /* SL_INCLUDE_CSLIP */
 357
 358         dev->stats.rx_bytes += count;
 359
 360         skb = dev_alloc_skb(count);
 361         if (skb == NULL) {
 362                 printk(KERN_WARNING "%s: memory squeeze, dropping packet.\n", dev->name);
 363                 dev->stats.rx_dropped++;
 364                 return;
 365         }
 366         skb->dev = dev;
 367         skb_put_data(skb, sl->rbuff, count);
 368         skb_reset_mac_header(skb);
 369         skb->protocol = htons(ETH_P_IP);
 370         netif_rx_ni(skb);
 371         dev->stats.rx_packets++;
 372 }
 373
 374 /* Encapsulate one IP datagram and stuff into a TTY queue. */
 375 static void sl_encaps(struct slip *sl, unsigned char *icp, int len)
 376 {
 377         unsigned char *p;
 378         int actual, count;
 379
 380         if (len > sl->mtu) {            /* Sigh, shouldn't occur BUT ... */
 381                 printk(KERN_WARNING "%s: truncating oversized transmit packet!\n", sl->dev->name);
 382                 sl->dev->stats.tx_dropped++;
 383                 sl_unlock(sl);
 384                 return;
 385         }
 386
 387         p = icp;
 388 #ifdef SL_INCLUDE_CSLIP
 389         if (sl->mode & SL_MODE_CSLIP)
 390                 len = slhc_compress(sl->slcomp, p, len, sl->cbuff, &p, 1);
 391 #endif
 392 #ifdef CONFIG_SLIP_MODE_SLIP6
 393         if (sl->mode & SL_MODE_SLIP6)
 394                 count = slip_esc6(p, sl->xbuff, len);
 395         else
 396 #endif
 397                 count = slip_esc(p, sl->xbuff, len);
 398
 399         /* Order of next two lines is *very* important.
 400          * When we are sending a little amount of data,
 401          * the transfer may be completed inside the ops->write()
 402          * routine, because it's running with interrupts enabled.
 403          * In this case we *never* got WRITE_WAKEUP event,
 404          * if we did not request it before write operation.
 405          *       14 Oct 1994  Dmitry Gorodchanin.
 406          */
 407         set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 408         actual = sl->tty->ops->write(sl->tty, sl->xbuff, count);
 409 #ifdef SL_CHECK_TRANSMIT
 410         netif_trans_update(sl->dev);
 411 #endif
 412         sl->xleft = count - actual;
 413         sl->xhead = sl->xbuff + actual;
 414 #ifdef CONFIG_SLIP_SMART
 415         /* VSV */
 416         clear_bit(SLF_OUTWAIT, &sl->flags);     /* reset outfill flag */
 417 #endif
 418 }
 419
 420 /* Write out any remaining transmit buffer. Scheduled when tty is writable */
 421 static void slip_transmit(struct work_struct *work)
 422 {
 423         struct slip *sl = container_of(work, struct slip, tx_work);
 424         int actual;
 425
 426         spin_lock_bh(&sl->lock);
 427         /* First make sure we're connected. */
 428         if (!sl->tty || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) {
 429                 spin_unlock_bh(&sl->lock);
 430                 return;
 431         }
 432
 433         if (sl->xleft <= 0)  {
 434                 /* Now serial buffer is almost free & we can start
 435                  * transmission of another packet */
 436                 sl->dev->stats.tx_packets++;
 437                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 438                 spin_unlock_bh(&sl->lock);
 439                 sl_unlock(sl);
 440                 return;
 441         }
 442
 443         actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft);
 444         sl->xleft -= actual;
 445         sl->xhead += actual;
 446         spin_unlock_bh(&sl->lock);
 447 }
 448
 449 /*
 450  * Called by the driver when there's room for more data.
 451  * Schedule the transmit.
 452  */
 453 static void slip_write_wakeup(struct tty_struct *tty)
 454 {
 455         struct slip *sl = tty->disc_data;
 456
 457         schedule_work(&sl->tx_work);
 458 }
 459
 460 static void sl_tx_timeout(struct net_device *dev)
 461 {
 462         struct slip *sl = netdev_priv(dev);
 463
 464         spin_lock(&sl->lock);
 465
 466         if (netif_queue_stopped(dev)) {
 467                 if (!netif_running(dev))
 468                         goto out;
 469
 470                 /* May be we must check transmitter timeout here ?
 471                  *      14 Oct 1994 Dmitry Gorodchanin.
 472                  */
 473 #ifdef SL_CHECK_TRANSMIT
 474                 if (time_before(jiffies, dev_trans_start(dev) + 20 * HZ))  {
 475                         /* 20 sec timeout not reached */
 476                         goto out;
 477                 }
 478                 printk(KERN_WARNING "%s: transmit timed out, %s?\n",
 479                         dev->name,
 480                         (tty_chars_in_buffer(sl->tty) || sl->xleft) ?
 481                                 "bad line quality" : "driver error");
 482                 sl->xleft = 0;
 483                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 484                 sl_unlock(sl);
 485 #endif
 486         }
 487 out:
 488         spin_unlock(&sl->lock);
 489 }
 490
 491
 492 /* Encapsulate an IP datagram and kick it into a TTY queue. */
 493 static netdev_tx_t
 494 sl_xmit(struct sk_buff *skb, struct net_device *dev)
 495 {
 496         struct slip *sl = netdev_priv(dev);
 497
 498         spin_lock(&sl->lock);
 499         if (!netif_running(dev)) {
 500                 spin_unlock(&sl->lock);
 501                 printk(KERN_WARNING "%s: xmit call when iface is down\n", dev->name);
 502                 dev_kfree_skb(skb);
 503                 return NETDEV_TX_OK;
 504         }
 505         if (sl->tty == NULL) {
 506                 spin_unlock(&sl->lock);
 507                 dev_kfree_skb(skb);
 508                 return NETDEV_TX_OK;
 509         }
 510
 511         sl_lock(sl);
 512         dev->stats.tx_bytes += skb->len;
 513         sl_encaps(sl, skb->data, skb->len);
 514         spin_unlock(&sl->lock);
 515
 516         dev_kfree_skb(skb);
 517         return NETDEV_TX_OK;
 518 }
 519
 520
 521 /******************************************
 522  *   Routines looking at netdevice side.
 523  ******************************************/
 524
 525 /* Netdevice UP -> DOWN routine */
 526
 527 static int
 528 sl_close(struct net_device *dev)
 529 {
 530         struct slip *sl = netdev_priv(dev);
 531
 532         spin_lock_bh(&sl->lock);
 533         if (sl->tty)
 534                 /* TTY discipline is running. */
 535                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 536         netif_stop_queue(dev);
 537         sl->rcount   = 0;
 538         sl->xleft    = 0;
 539         spin_unlock_bh(&sl->lock);
 540
 541         return 0;
 542 }
 543
 544 /* Netdevice DOWN -> UP routine */
 545
 546 static int sl_open(struct net_device *dev)
 547 {
 548         struct slip *sl = netdev_priv(dev);
 549
 550         if (sl->tty == NULL)
 551                 return -ENODEV;
 552
 553         sl->flags &= (1 << SLF_INUSE);
 554         netif_start_queue(dev);
 555         return 0;
 556 }
 557
 558 /* Netdevice change MTU request */
 559
 560 static int sl_change_mtu(struct net_device *dev, int new_mtu)
 561 {
 562         struct slip *sl = netdev_priv(dev);
 563
 564         return sl_realloc_bufs(sl, new_mtu);
 565 }
 566
 567 /* Netdevice get statistics request */
 568
 569 static void
 570 sl_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 571 {
 572         struct net_device_stats *devstats = &dev->stats;
 573 #ifdef SL_INCLUDE_CSLIP
 574         struct slip *sl = netdev_priv(dev);
 575         struct slcompress *comp = sl->slcomp;
 576 #endif
 577         stats->rx_packets     = devstats->rx_packets;
 578         stats->tx_packets     = devstats->tx_packets;
 579         stats->rx_bytes       = devstats->rx_bytes;
 580         stats->tx_bytes       = devstats->tx_bytes;
 581         stats->rx_dropped     = devstats->rx_dropped;
 582         stats->tx_dropped     = devstats->tx_dropped;
 583         stats->tx_errors      = devstats->tx_errors;
 584         stats->rx_errors      = devstats->rx_errors;
 585         stats->rx_over_errors = devstats->rx_over_errors;
 586
 587 #ifdef SL_INCLUDE_CSLIP
 588         if (comp) {
 589                 /* Generic compressed statistics */
 590                 stats->rx_compressed   = comp->sls_i_compressed;
 591                 stats->tx_compressed   = comp->sls_o_compressed;
 592
 593                 /* Are we really still needs this? */
 594                 stats->rx_fifo_errors += comp->sls_i_compressed;
 595                 stats->rx_dropped     += comp->sls_i_tossed;
 596                 stats->tx_fifo_errors += comp->sls_o_compressed;
 597                 stats->collisions     += comp->sls_o_misses;
 598         }
 599 #endif
 600 }
 601
 602 /* Netdevice register callback */
 603
 604 static int sl_init(struct net_device *dev)
 605 {
 606         struct slip *sl = netdev_priv(dev);
 607
 608         /*
 609          *      Finish setting up the DEVICE info.
 610          */
 611
 612         dev->mtu                = sl->mtu;
 613         dev->type               = ARPHRD_SLIP + sl->mode;
 614 #ifdef SL_CHECK_TRANSMIT
 615         dev->watchdog_timeo     = 20*HZ;
 616 #endif
 617         return 0;
 618 }
 619
 620
 621 static void sl_uninit(struct net_device *dev)
 622 {
 623         struct slip *sl = netdev_priv(dev);
 624
 625         sl_free_bufs(sl);
 626 }
 627
 628 /* Hook the destructor so we can free slip devices at the right point in time */
 629 static void sl_free_netdev(struct net_device *dev)
 630 {
 631         int i = dev->base_addr;
 632
 633         slip_devs[i] = NULL;
 634 }
 635
 636 static const struct net_device_ops sl_netdev_ops = {
 637         .ndo_init               = sl_init,
 638         .ndo_uninit             = sl_uninit,
 639         .ndo_open               = sl_open,
 640         .ndo_stop               = sl_close,
 641         .ndo_start_xmit         = sl_xmit,
 642         .ndo_get_stats64        = sl_get_stats64,
 643         .ndo_change_mtu         = sl_change_mtu,
 644         .ndo_tx_timeout         = sl_tx_timeout,
 645 #ifdef CONFIG_SLIP_SMART
 646         .ndo_do_ioctl           = sl_ioctl,
 647 #endif
 648 };
 649
 650
 651 static void sl_setup(struct net_device *dev)
 652 {
 653         dev->netdev_ops         = &sl_netdev_ops;
 654         dev->needs_free_netdev  = true;
 655         dev->priv_destructor    = sl_free_netdev;
 656
 657         dev->hard_header_len    = 0;
 658         dev->addr_len           = 0;
 659         dev->tx_queue_len       = 10;
 660
 661         /* MTU range: 68 - 65534 */
 662         dev->min_mtu = 68;
 663         dev->max_mtu = 65534;
 664
 665         /* New-style flags. */
 666         dev->flags              = IFF_NOARP|IFF_POINTOPOINT|IFF_MULTICAST;
 667 }
 668
 669 /******************************************
 670   Routines looking at TTY side.
 671  ******************************************/
 672
 673
 674 /*
 675  * Handle the 'receiver data ready' interrupt.
 676  * This function is called by the 'tty_io' module in the kernel when
 677  * a block of SLIP data has been received, which can now be decapsulated
 678  * and sent on to some IP layer for further processing. This will not
 679  * be re-entered while running but other ldisc functions may be called
 680  * in parallel
 681  */
 682
 683 static void slip_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 684                                                         char *fp, int count)
 685 {
 686         struct slip *sl = tty->disc_data;
 687
 688         if (!sl || sl->magic != SLIP_MAGIC || !netif_running(sl->dev))
 689                 return;
 690
 691         /* Read the characters out of the buffer */
 692         while (count--) {
 693                 if (fp && *fp++) {
 694                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
 695                                 sl->dev->stats.rx_errors++;
 696                         cp++;
 697                         continue;
 698                 }
 699 #ifdef CONFIG_SLIP_MODE_SLIP6
 700                 if (sl->mode & SL_MODE_SLIP6)
 701                         slip_unesc6(sl, *cp++);
 702                 else
 703 #endif
 704                         slip_unesc(sl, *cp++);
 705         }
 706 }
 707
 708 /************************************
 709  *  slip_open helper routines.
 710  ************************************/
 711
 712 /* Collect hanged up channels */
 713 static void sl_sync(void)
 714 {
 715         int i;
 716         struct net_device *dev;
 717         struct slip       *sl;
 718
 719         for (i = 0; i < slip_maxdev; i++) {
 720                 dev = slip_devs[i];
 721                 if (dev == NULL)
 722                         break;
 723
 724                 sl = netdev_priv(dev);
 725                 if (sl->tty || sl->leased)
 726                         continue;
 727                 if (dev->flags & IFF_UP)
 728                         dev_close(dev);
 729         }
 730 }
 731
 732
 733 /* Find a free SLIP channel, and link in this `tty' line. */
 734 static struct slip *sl_alloc(void)
 735 {
 736         int i;
 737         char name[IFNAMSIZ];
 738         struct net_device *dev = NULL;
 739         struct slip       *sl;
 740
 741         for (i = 0; i < slip_maxdev; i++) {
 742                 dev = slip_devs[i];
 743                 if (dev == NULL)
 744                         break;
 745         }
 746         /* Sorry, too many, all slots in use */
 747         if (i >= slip_maxdev)
 748                 return NULL;
 749
 750         sprintf(name, "sl%d", i);
 751         dev = alloc_netdev(sizeof(*sl), name, NET_NAME_UNKNOWN, sl_setup);
 752         if (!dev)
 753                 return NULL;
 754
 755         dev->base_addr  = i;
 756         sl = netdev_priv(dev);
 757
 758         /* Initialize channel control data */
 759         sl->magic       = SLIP_MAGIC;
 760         sl->dev         = dev;
 761         spin_lock_init(&sl->lock);
 762         INIT_WORK(&sl->tx_work, slip_transmit);
 763         sl->mode        = SL_MODE_DEFAULT;
 764 #ifdef CONFIG_SLIP_SMART
 765         /* initialize timer_list struct */
 766         timer_setup(&sl->keepalive_timer, sl_keepalive, 0);
 767         timer_setup(&sl->outfill_timer, sl_outfill, 0);
 768 #endif
 769         slip_devs[i] = dev;
 770         return sl;
 771 }
 772
 773 /*
 774  * Open the high-level part of the SLIP channel.
 775  * This function is called by the TTY module when the
 776  * SLIP line discipline is called for.  Because we are
 777  * sure the tty line exists, we only have to link it to
 778  * a free SLIP channel...
 779  *
 780  * Called in process context serialized from other ldisc calls.
 781  */
 782
 783 static int slip_open(struct tty_struct *tty)
 784 {
 785         struct slip *sl;
 786         int err;
 787
 788         if (!capable(CAP_NET_ADMIN))
 789                 return -EPERM;
 790
 791         if (tty->ops->write == NULL)
 792                 return -EOPNOTSUPP;
 793
 794         /* RTnetlink lock is misused here to serialize concurrent
 795            opens of slip channels. There are better ways, but it is
 796            the simplest one.
 797          */
 798         rtnl_lock();
 799
 800         /* Collect hanged up channels. */
 801         sl_sync();
 802
 803         sl = tty->disc_data;
 804
 805         err = -EEXIST;
 806         /* First make sure we're not already connected. */
 807         if (sl && sl->magic == SLIP_MAGIC)
 808                 goto err_exit;
 809
 810         /* OK.  Find a free SLIP channel to use. */
 811         err = -ENFILE;
 812         sl = sl_alloc();
 813         if (sl == NULL)
 814                 goto err_exit;
 815
 816         sl->tty = tty;
 817         tty->disc_data = sl;
 818         sl->pid = current->pid;
 819
 820         if (!test_bit(SLF_INUSE, &sl->flags)) {
 821                 /* Perform the low-level SLIP initialization. */
 822                 err = sl_alloc_bufs(sl, SL_MTU);
 823                 if (err)
 824                         goto err_free_chan;
 825
 826                 set_bit(SLF_INUSE, &sl->flags);
 827
 828                 err = register_netdevice(sl->dev);
 829                 if (err)
 830                         goto err_free_bufs;
 831         }
 832
 833 #ifdef CONFIG_SLIP_SMART
 834         if (sl->keepalive) {
 835                 sl->keepalive_timer.expires = jiffies + sl->keepalive * HZ;
 836                 add_timer(&sl->keepalive_timer);
 837         }
 838         if (sl->outfill) {
 839                 sl->outfill_timer.expires = jiffies + sl->outfill * HZ;
 840                 add_timer(&sl->outfill_timer);
 841         }
 842 #endif
 843
 844         /* Done.  We have linked the TTY line to a channel. */
 845         rtnl_unlock();
 846         tty->receive_room = 65536;      /* We don't flow control */
 847
 848         /* TTY layer expects 0 on success */
 849         return 0;
 850
 851 err_free_bufs:
 852         sl_free_bufs(sl);
 853
 854 err_free_chan:
 855         sl->tty = NULL;
 856         tty->disc_data = NULL;
 857         clear_bit(SLF_INUSE, &sl->flags);
 858         sl_free_netdev(sl->dev);
 859         free_netdev(sl->dev);
 860
 861 err_exit:
 862         rtnl_unlock();
 863
 864         /* Count references from TTY module */
 865         return err;
 866 }
 867
 868 /*
 869  * Close down a SLIP channel.
 870  * This means flushing out any pending queues, and then returning. This
 871  * call is serialized against other ldisc functions.
 872  *
 873  * We also use this method fo a hangup event
 874  */
 875
 876 static void slip_close(struct tty_struct *tty)
 877 {
 878         struct slip *sl = tty->disc_data;
 879
 880         /* First make sure we're connected. */
 881         if (!sl || sl->magic != SLIP_MAGIC || sl->tty != tty)
 882                 return;
 883
 884         spin_lock_bh(&sl->lock);
 885         tty->disc_data = NULL;
 886         sl->tty = NULL;
 887         spin_unlock_bh(&sl->lock);
 888
 889         flush_work(&sl->tx_work);
 890
 891         /* VSV = very important to remove timers */
 892 #ifdef CONFIG_SLIP_SMART
 893         del_timer_sync(&sl->keepalive_timer);
 894         del_timer_sync(&sl->outfill_timer);
 895 #endif
 896         /* Flush network side */
 897         unregister_netdev(sl->dev);
 898         /* This will complete via sl_free_netdev */
 899 }
 900
 901 static int slip_hangup(struct tty_struct *tty)
 902 {
 903         slip_close(tty);
 904         return 0;
 905 }
 906  /************************************************************************
 907   *                     STANDARD SLIP ENCAPSULATION                      *
 908   ************************************************************************/
 909
 910 static int slip_esc(unsigned char *s, unsigned char *d, int len)
 911 {
 912         unsigned char *ptr = d;
 913         unsigned char c;
 914
 915         /*
 916          * Send an initial END character to flush out any
 917          * data that may have accumulated in the receiver
 918          * due to line noise.
 919          */
 920
 921         *ptr++ = END;
 922
 923         /*
 924          * For each byte in the packet, send the appropriate
 925          * character sequence, according to the SLIP protocol.
 926          */
 927
 928         while (len-- > 0) {
 929                 switch (c = *s++) {
 930                 case END:
 931                         *ptr++ = ESC;
 932                         *ptr++ = ESC_END;
 933                         break;
 934                 case ESC:
 935                         *ptr++ = ESC;
 936                         *ptr++ = ESC_ESC;
 937                         break;
 938                 default:
 939                         *ptr++ = c;
 940                         break;
 941                 }
 942         }
 943         *ptr++ = END;
 944         return ptr - d;
 945 }
 946
 947 static void slip_unesc(struct slip *sl, unsigned char s)
 948 {
 949
 950         switch (s) {
 951         case END:
 952 #ifdef CONFIG_SLIP_SMART
 953                 /* drop keeptest bit = VSV */
 954                 if (test_bit(SLF_KEEPTEST, &sl->flags))
 955                         clear_bit(SLF_KEEPTEST, &sl->flags);
 956 #endif
 957
 958                 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
 959                     (sl->rcount > 2))
 960                         sl_bump(sl);
 961                 clear_bit(SLF_ESCAPE, &sl->flags);
 962                 sl->rcount = 0;
 963                 return;
 964
 965         case ESC:
 966                 set_bit(SLF_ESCAPE, &sl->flags);
 967                 return;
 968         case ESC_ESC:
 969                 if (test_and_clear_bit(SLF_ESCAPE, &sl->flags))
 970                         s = ESC;
 971                 break;
 972         case ESC_END:
 973                 if (test_and_clear_bit(SLF_ESCAPE, &sl->flags))
 974                         s = END;
 975                 break;
 976         }
 977         if (!test_bit(SLF_ERROR, &sl->flags))  {
 978                 if (sl->rcount < sl->buffsize)  {
 979                         sl->rbuff[sl->rcount++] = s;
 980                         return;
 981                 }
 982                 sl->dev->stats.rx_over_errors++;
 983                 set_bit(SLF_ERROR, &sl->flags);
 984         }
 985 }
 986
 987
 988 #ifdef CONFIG_SLIP_MODE_SLIP6
 989 /************************************************************************
 990  *                       6 BIT SLIP ENCAPSULATION                       *
 991  ************************************************************************/
 992
 993 static int slip_esc6(unsigned char *s, unsigned char *d, int len)
 994 {
 995         unsigned char *ptr = d;
 996         unsigned char c;
 997         int i;
 998         unsigned short v = 0;
 999         short bits = 0;
1000
1001         /*
1002          * Send an initial END character to flush out any
1003          * data that may have accumulated in the receiver
1004          * due to line noise.
1005          */
1006
1007         *ptr++ = 0x70;
1008
1009         /*
1010          * Encode the packet into printable ascii characters
1011          */
1012
1013         for (i = 0; i < len; ++i) {
1014                 v = (v << 8) | s[i];
1015                 bits += 8;
1016                 while (bits >= 6) {
1017                         bits -= 6;
1018                         c = 0x30 + ((v >> bits) & 0x3F);
1019                         *ptr++ = c;
1020                 }
1021         }
1022         if (bits) {
1023                 c = 0x30 + ((v << (6 - bits)) & 0x3F);
1024                 *ptr++ = c;
1025         }
1026         *ptr++ = 0x70;
1027         return ptr - d;
1028 }
1029
1030 static void slip_unesc6(struct slip *sl, unsigned char s)
1031 {
1032         unsigned char c;
1033
1034         if (s == 0x70) {
1035 #ifdef CONFIG_SLIP_SMART
1036                 /* drop keeptest bit = VSV */
1037                 if (test_bit(SLF_KEEPTEST, &sl->flags))
1038                         clear_bit(SLF_KEEPTEST, &sl->flags);
1039 #endif
1040
1041                 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
1042                     (sl->rcount > 2))
1043                         sl_bump(sl);
1044                 sl->rcount = 0;
1045                 sl->xbits = 0;
1046                 sl->xdata = 0;
1047         } else if (s >= 0x30 && s < 0x70) {
1048                 sl->xdata = (sl->xdata << 6) | ((s - 0x30) & 0x3F);
1049                 sl->xbits += 6;
1050                 if (sl->xbits >= 8) {
1051                         sl->xbits -= 8;
1052                         c = (unsigned char)(sl->xdata >> sl->xbits);
1053                         if (!test_bit(SLF_ERROR, &sl->flags))  {
1054                                 if (sl->rcount < sl->buffsize)  {
1055                                         sl->rbuff[sl->rcount++] = c;
1056                                         return;
1057                                 }
1058                                 sl->dev->stats.rx_over_errors++;
1059                                 set_bit(SLF_ERROR, &sl->flags);
1060                         }
1061                 }
1062         }
1063 }
1064 #endif /* CONFIG_SLIP_MODE_SLIP6 */
1065
1066 /* Perform I/O control on an active SLIP channel. */
1067 static int slip_ioctl(struct tty_struct *tty, struct file *file,
1068                                         unsigned int cmd, unsigned long arg)
1069 {
1070         struct slip *sl = tty->disc_data;
1071         unsigned int tmp;
1072         int __user *p = (int __user *)arg;
1073
1074         /* First make sure we're connected. */
1075         if (!sl || sl->magic != SLIP_MAGIC)
1076                 return -EINVAL;
1077
1078         switch (cmd) {
1079         case SIOCGIFNAME:
1080                 tmp = strlen(sl->dev->name) + 1;
1081                 if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
1082                         return -EFAULT;
1083                 return 0;
1084
1085         case SIOCGIFENCAP:
1086                 if (put_user(sl->mode, p))
1087                         return -EFAULT;
1088                 return 0;
1089
1090         case SIOCSIFENCAP:
1091                 if (get_user(tmp, p))
1092                         return -EFAULT;
1093 #ifndef SL_INCLUDE_CSLIP
1094                 if (tmp & (SL_MODE_CSLIP|SL_MODE_ADAPTIVE))
1095                         return -EINVAL;
1096 #else
1097                 if ((tmp & (SL_MODE_ADAPTIVE | SL_MODE_CSLIP)) ==
1098                     (SL_MODE_ADAPTIVE | SL_MODE_CSLIP))
1099                         /* return -EINVAL; */
1100                         tmp &= ~SL_MODE_ADAPTIVE;
1101 #endif
1102 #ifndef CONFIG_SLIP_MODE_SLIP6
1103                 if (tmp & SL_MODE_SLIP6)
1104                         return -EINVAL;
1105 #endif
1106                 sl->mode = tmp;
1107                 sl->dev->type = ARPHRD_SLIP + sl->mode;
1108                 return 0;
1109
1110         case SIOCSIFHWADDR:
1111                 return -EINVAL;
1112
1113 #ifdef CONFIG_SLIP_SMART
1114         /* VSV changes start here */
1115         case SIOCSKEEPALIVE:
1116                 if (get_user(tmp, p))
1117                         return -EFAULT;
1118                 if (tmp > 255) /* max for unchar */
1119                         return -EINVAL;
1120
1121                 spin_lock_bh(&sl->lock);
1122                 if (!sl->tty) {
1123                         spin_unlock_bh(&sl->lock);
1124                         return -ENODEV;
1125                 }
1126                 sl->keepalive = (u8)tmp;
1127                 if (sl->keepalive != 0) {
1128                         mod_timer(&sl->keepalive_timer,
1129                                         jiffies + sl->keepalive * HZ);
1130                         set_bit(SLF_KEEPTEST, &sl->flags);
1131                 } else
1132                         del_timer(&sl->keepalive_timer);
1133                 spin_unlock_bh(&sl->lock);
1134                 return 0;
1135
1136         case SIOCGKEEPALIVE:
1137                 if (put_user(sl->keepalive, p))
1138                         return -EFAULT;
1139                 return 0;
1140
1141         case SIOCSOUTFILL:
1142                 if (get_user(tmp, p))
1143                         return -EFAULT;
1144                 if (tmp > 255) /* max for unchar */
1145                         return -EINVAL;
1146                 spin_lock_bh(&sl->lock);
1147                 if (!sl->tty) {
1148                         spin_unlock_bh(&sl->lock);
1149                         return -ENODEV;
1150                 }
1151                 sl->outfill = (u8)tmp;
1152                 if (sl->outfill != 0) {
1153                         mod_timer(&sl->outfill_timer,
1154                                                 jiffies + sl->outfill * HZ);
1155                         set_bit(SLF_OUTWAIT, &sl->flags);
1156                 } else
1157                         del_timer(&sl->outfill_timer);
1158                 spin_unlock_bh(&sl->lock);
1159                 return 0;
1160
1161         case SIOCGOUTFILL:
1162                 if (put_user(sl->outfill, p))
1163                         return -EFAULT;
1164                 return 0;
1165         /* VSV changes end */
1166 #endif
1167         default:
1168                 return tty_mode_ioctl(tty, file, cmd, arg);
1169         }
1170 }
1171
1172 /* VSV changes start here */
1173 #ifdef CONFIG_SLIP_SMART
1174 /* function do_ioctl called from net/core/dev.c
1175    to allow get/set outfill/keepalive parameter
1176    by ifconfig                                 */
1177
1178 static int sl_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
1179 {
1180         struct slip *sl = netdev_priv(dev);
1181         unsigned long *p = (unsigned long *)&rq->ifr_ifru;
1182
1183         if (sl == NULL)         /* Allocation failed ?? */
1184                 return -ENODEV;
1185
1186         spin_lock_bh(&sl->lock);
1187
1188         if (!sl->tty) {
1189                 spin_unlock_bh(&sl->lock);
1190                 return -ENODEV;
1191         }
1192
1193         switch (cmd) {
1194         case SIOCSKEEPALIVE:
1195                 /* max for unchar */
1196                 if ((unsigned)*p > 255) {
1197                         spin_unlock_bh(&sl->lock);
1198                         return -EINVAL;
1199                 }
1200                 sl->keepalive = (u8)*p;
1201                 if (sl->keepalive != 0) {
1202                         sl->keepalive_timer.expires =
1203                                                 jiffies + sl->keepalive * HZ;
1204                         mod_timer(&sl->keepalive_timer,
1205                                                 jiffies + sl->keepalive * HZ);
1206                         set_bit(SLF_KEEPTEST, &sl->flags);
1207                 } else
1208                         del_timer(&sl->keepalive_timer);
1209                 break;
1210
1211         case SIOCGKEEPALIVE:
1212                 *p = sl->keepalive;
1213                 break;
1214
1215         case SIOCSOUTFILL:
1216                 if ((unsigned)*p > 255) { /* max for unchar */
1217                         spin_unlock_bh(&sl->lock);
1218                         return -EINVAL;
1219                 }
1220                 sl->outfill = (u8)*p;
1221                 if (sl->outfill != 0) {
1222                         mod_timer(&sl->outfill_timer,
1223                                                 jiffies + sl->outfill * HZ);
1224                         set_bit(SLF_OUTWAIT, &sl->flags);
1225                 } else
1226                         del_timer(&sl->outfill_timer);
1227                 break;
1228
1229         case SIOCGOUTFILL:
1230                 *p = sl->outfill;
1231                 break;
1232
1233         case SIOCSLEASE:
1234                 /* Resolve race condition, when ioctl'ing hanged up
1235                    and opened by another process device.
1236                  */
1237                 if (sl->tty != current->signal->tty &&
1238                                                 sl->pid != current->pid) {
1239                         spin_unlock_bh(&sl->lock);
1240                         return -EPERM;
1241                 }
1242                 sl->leased = 0;
1243                 if (*p)
1244                         sl->leased = 1;
1245                 break;
1246
1247         case SIOCGLEASE:
1248                 *p = sl->leased;
1249         }
1250         spin_unlock_bh(&sl->lock);
1251         return 0;
1252 }
1253 #endif
1254 /* VSV changes end */
1255
1256 static struct tty_ldisc_ops sl_ldisc = {
1257         .owner          = THIS_MODULE,
1258         .magic          = TTY_LDISC_MAGIC,
1259         .name           = "slip",
1260         .open           = slip_open,
1261         .close          = slip_close,
1262         .hangup         = slip_hangup,
1263         .ioctl          = slip_ioctl,
1264         .receive_buf    = slip_receive_buf,
1265         .write_wakeup   = slip_write_wakeup,
1266 };
1267
1268 static int __init slip_init(void)
1269 {
1270         int status;
1271
1272         if (slip_maxdev < 4)
1273                 slip_maxdev = 4; /* Sanity */
1274
1275         printk(KERN_INFO "SLIP: version %s (dynamic channels, max=%d)"
1276 #ifdef CONFIG_SLIP_MODE_SLIP6
1277                " (6 bit encapsulation enabled)"
1278 #endif
1279                ".\n",
1280                SLIP_VERSION, slip_maxdev);
1281 #if defined(SL_INCLUDE_CSLIP)
1282         printk(KERN_INFO "CSLIP: code copyright 1989 Regents of the University of California.\n");
1283 #endif
1284 #ifdef CONFIG_SLIP_SMART
1285         printk(KERN_INFO "SLIP linefill/keepalive option.\n");
1286 #endif
1287
1288         slip_devs = kcalloc(slip_maxdev, sizeof(struct net_device *),
1289                                                                 GFP_KERNEL);
1290         if (!slip_devs)
1291                 return -ENOMEM;
1292
1293         /* Fill in our line protocol discipline, and register it */
1294         status = tty_register_ldisc(N_SLIP, &sl_ldisc);
1295         if (status != 0) {
1296                 printk(KERN_ERR "SLIP: can't register line discipline (err = %d)\n", status);
1297                 kfree(slip_devs);
1298         }
1299         return status;
1300 }
1301
1302 static void __exit slip_exit(void)
1303 {
1304         int i;
1305         struct net_device *dev;
1306         struct slip *sl;
1307         unsigned long timeout = jiffies + HZ;
1308         int busy = 0;
1309
1310         if (slip_devs == NULL)
1311                 return;
1312
1313         /* First of all: check for active disciplines and hangup them.
1314          */
1315         do {
1316                 if (busy)
1317                         msleep_interruptible(100);
1318
1319                 busy = 0;
1320                 for (i = 0; i < slip_maxdev; i++) {
1321                         dev = slip_devs[i];
1322                         if (!dev)
1323                                 continue;
1324                         sl = netdev_priv(dev);
1325                         spin_lock_bh(&sl->lock);
1326                         if (sl->tty) {
1327                                 busy++;
1328                                 tty_hangup(sl->tty);
1329                         }
1330                         spin_unlock_bh(&sl->lock);
1331                 }
1332         } while (busy && time_before(jiffies, timeout));
1333
1334         /* FIXME: hangup is async so we should wait when doing this second
1335            phase */
1336
1337         for (i = 0; i < slip_maxdev; i++) {
1338                 dev = slip_devs[i];
1339                 if (!dev)
1340                         continue;
1341                 slip_devs[i] = NULL;
1342
1343                 sl = netdev_priv(dev);
1344                 if (sl->tty) {
1345                         printk(KERN_ERR "%s: tty discipline still running\n",
1346                                dev->name);
1347                 }
1348
1349                 unregister_netdev(dev);
1350         }
1351
1352         kfree(slip_devs);
1353         slip_devs = NULL;
1354
1355         i = tty_unregister_ldisc(N_SLIP);
1356         if (i != 0)
1357                 printk(KERN_ERR "SLIP: can't unregister line discipline (err = %d)\n", i);
1358 }
1359
1360 module_init(slip_init);
1361 module_exit(slip_exit);
1362
1363 #ifdef CONFIG_SLIP_SMART
1364 /*
1365  * This is start of the code for multislip style line checking
1366  * added by Stanislav Voronyi. All changes before marked VSV
1367  */
1368
1369 static void sl_outfill(struct timer_list *t)
1370 {
1371         struct slip *sl = from_timer(sl, t, outfill_timer);
1372
1373         spin_lock(&sl->lock);
1374
1375         if (sl->tty == NULL)
1376                 goto out;
1377
1378         if (sl->outfill) {
1379                 if (test_bit(SLF_OUTWAIT, &sl->flags)) {
1380                         /* no packets were transmitted, do outfill */
1381 #ifdef CONFIG_SLIP_MODE_SLIP6
1382                         unsigned char s = (sl->mode & SL_MODE_SLIP6)?0x70:END;
1383 #else
1384                         unsigned char s = END;
1385 #endif
1386                         /* put END into tty queue. Is it right ??? */
1387                         if (!netif_queue_stopped(sl->dev)) {
1388                                 /* if device busy no outfill */
1389                                 sl->tty->ops->write(sl->tty, &s, 1);
1390                         }
1391                 } else
1392                         set_bit(SLF_OUTWAIT, &sl->flags);
1393
1394                 mod_timer(&sl->outfill_timer, jiffies+sl->outfill*HZ);
1395         }
1396 out:
1397         spin_unlock(&sl->lock);
1398 }
1399
1400 static void sl_keepalive(struct timer_list *t)
1401 {
1402         struct slip *sl = from_timer(sl, t, keepalive_timer);
1403
1404         spin_lock(&sl->lock);
1405
1406         if (sl->tty == NULL)
1407                 goto out;
1408
1409         if (sl->keepalive) {
1410                 if (test_bit(SLF_KEEPTEST, &sl->flags)) {
1411                         /* keepalive still high :(, we must hangup */
1412                         if (sl->outfill)
1413                                 /* outfill timer must be deleted too */
1414                                 (void)del_timer(&sl->outfill_timer);
1415                         printk(KERN_DEBUG "%s: no packets received during keepalive timeout, hangup.\n", sl->dev->name);
1416                         /* this must hangup tty & close slip */
1417                         tty_hangup(sl->tty);
1418                         /* I think we need not something else */
1419                         goto out;
1420                 } else
1421                         set_bit(SLF_KEEPTEST, &sl->flags);
1422
1423                 mod_timer(&sl->keepalive_timer, jiffies+sl->keepalive*HZ);
1424         }
1425 out:
1426         spin_unlock(&sl->lock);
1427 }
1428
1429 #endif
1430 MODULE_LICENSE("GPL");
1431 MODULE_ALIAS_LDISC(N_SLIP);