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/compat.h> 66 #include <linux/module.h> 67 #include <linux/moduleparam.h> 68 69 #include <linux/uaccess.h> 70 #include <linux/bitops.h> 71 #include <linux/sched/signal.h> 72 #include <linux/string.h> 73 #include <linux/mm.h> 74 #include <linux/interrupt.h> 75 #include <linux/in.h> 76 #include <linux/tty.h> 77 #include <linux/errno.h> 78 #include <linux/netdevice.h> 79 #include <linux/etherdevice.h> 80 #include <linux/skbuff.h> 81 #include <linux/rtnetlink.h> 82 #include <linux/if_arp.h> 83 #include <linux/if_slip.h> 84 #include <linux/delay.h> 85 #include <linux/init.h> 86 #include <linux/slab.h> 87 #include <linux/workqueue.h> 88 #include "slip.h" 89 #ifdef CONFIG_INET 90 #include <linux/ip.h> 91 #include <linux/tcp.h> 92 #include <net/slhc_vj.h> 93 #endif 94 95 #define SLIP_VERSION "0.8.4-NET3.019-NEWTTY" 96 97 static struct net_device **slip_devs; 98 99 static int slip_maxdev = SL_NRUNIT; 100 module_param(slip_maxdev, int, 0); 101 MODULE_PARM_DESC(slip_maxdev, "Maximum number of slip devices"); 102 103 static int slip_esc(unsigned char *p, unsigned char *d, int len); 104 static void slip_unesc(struct slip *sl, unsigned char c); 105 #ifdef CONFIG_SLIP_MODE_SLIP6 106 static int slip_esc6(unsigned char *p, unsigned char *d, int len); 107 static void slip_unesc6(struct slip *sl, unsigned char c); 108 #endif 109 #ifdef CONFIG_SLIP_SMART 110 static void sl_keepalive(struct timer_list *t); 111 static void sl_outfill(struct timer_list *t); 112 static int sl_siocdevprivate(struct net_device *dev, struct ifreq *rq, void __user *data, int cmd); 113 #endif 114 115 /******************************** 116 * Buffer administration routines: 117 * sl_alloc_bufs() 118 * sl_free_bufs() 119 * sl_realloc_bufs() 120 * 121 * NOTE: sl_realloc_bufs != sl_free_bufs + sl_alloc_bufs, because 122 * sl_realloc_bufs provides strong atomicity and reallocation 123 * on actively running device. 124 *********************************/ 125 126 /* 127 Allocate channel buffers. 128 */ 129 130 static int sl_alloc_bufs(struct slip *sl, int mtu) 131 { 132 int err = -ENOBUFS; 133 unsigned long len; 134 char *rbuff = NULL; 135 char *xbuff = NULL; 136 #ifdef SL_INCLUDE_CSLIP 137 char *cbuff = NULL; 138 struct slcompress *slcomp = NULL; 139 #endif 140 141 /* 142 * Allocate the SLIP frame buffers: 143 * 144 * rbuff Receive buffer. 145 * xbuff Transmit buffer. 146 * cbuff Temporary compression buffer. 147 */ 148 len = mtu * 2; 149 150 /* 151 * allow for arrival of larger UDP packets, even if we say not to 152 * also fixes a bug in which SunOS sends 512-byte packets even with 153 * an MSS of 128 154 */ 155 if (len < 576 * 2) 156 len = 576 * 2; 157 rbuff = kmalloc(len + 4, GFP_KERNEL); 158 if (rbuff == NULL) 159 goto err_exit; 160 xbuff = kmalloc(len + 4, GFP_KERNEL); 161 if (xbuff == NULL) 162 goto err_exit; 163 #ifdef SL_INCLUDE_CSLIP 164 cbuff = kmalloc(len + 4, GFP_KERNEL); 165 if (cbuff == NULL) 166 goto err_exit; 167 slcomp = slhc_init(16, 16); 168 if (IS_ERR(slcomp)) 169 goto err_exit; 170 #endif 171 spin_lock_bh(&sl->lock); 172 if (sl->tty == NULL) { 173 spin_unlock_bh(&sl->lock); 174 err = -ENODEV; 175 goto err_exit; 176 } 177 sl->mtu = mtu; 178 sl->buffsize = len; 179 sl->rcount = 0; 180 sl->xleft = 0; 181 rbuff = xchg(&sl->rbuff, rbuff); 182 xbuff = xchg(&sl->xbuff, xbuff); 183 #ifdef SL_INCLUDE_CSLIP 184 cbuff = xchg(&sl->cbuff, cbuff); 185 slcomp = xchg(&sl->slcomp, slcomp); 186 #endif 187 #ifdef CONFIG_SLIP_MODE_SLIP6 188 sl->xdata = 0; 189 sl->xbits = 0; 190 #endif 191 spin_unlock_bh(&sl->lock); 192 err = 0; 193 194 /* Cleanup */ 195 err_exit: 196 #ifdef SL_INCLUDE_CSLIP 197 kfree(cbuff); 198 slhc_free(slcomp); 199 #endif 200 kfree(xbuff); 201 kfree(rbuff); 202 return err; 203 } 204 205 /* Free a SLIP channel buffers. */ 206 static void sl_free_bufs(struct slip *sl) 207 { 208 /* Free all SLIP frame buffers. */ 209 kfree(xchg(&sl->rbuff, NULL)); 210 kfree(xchg(&sl->xbuff, NULL)); 211 #ifdef SL_INCLUDE_CSLIP 212 kfree(xchg(&sl->cbuff, NULL)); 213 slhc_free(xchg(&sl->slcomp, NULL)); 214 #endif 215 } 216 217 /* 218 Reallocate slip channel buffers. 219 */ 220 221 static int sl_realloc_bufs(struct slip *sl, int mtu) 222 { 223 int err = 0; 224 struct net_device *dev = sl->dev; 225 unsigned char *xbuff, *rbuff; 226 #ifdef SL_INCLUDE_CSLIP 227 unsigned char *cbuff; 228 #endif 229 int len = mtu * 2; 230 231 /* 232 * allow for arrival of larger UDP packets, even if we say not to 233 * also fixes a bug in which SunOS sends 512-byte packets even with 234 * an MSS of 128 235 */ 236 if (len < 576 * 2) 237 len = 576 * 2; 238 239 xbuff = kmalloc(len + 4, GFP_ATOMIC); 240 rbuff = kmalloc(len + 4, GFP_ATOMIC); 241 #ifdef SL_INCLUDE_CSLIP 242 cbuff = kmalloc(len + 4, GFP_ATOMIC); 243 #endif 244 245 246 #ifdef SL_INCLUDE_CSLIP 247 if (xbuff == NULL || rbuff == NULL || cbuff == NULL) { 248 #else 249 if (xbuff == NULL || rbuff == NULL) { 250 #endif 251 if (mtu > sl->mtu) { 252 printk(KERN_WARNING "%s: unable to grow slip buffers, MTU change cancelled.\n", 253 dev->name); 254 err = -ENOBUFS; 255 } 256 goto done; 257 } 258 spin_lock_bh(&sl->lock); 259 260 err = -ENODEV; 261 if (sl->tty == NULL) 262 goto done_on_bh; 263 264 xbuff = xchg(&sl->xbuff, xbuff); 265 rbuff = xchg(&sl->rbuff, rbuff); 266 #ifdef SL_INCLUDE_CSLIP 267 cbuff = xchg(&sl->cbuff, cbuff); 268 #endif 269 if (sl->xleft) { 270 if (sl->xleft <= len) { 271 memcpy(sl->xbuff, sl->xhead, sl->xleft); 272 } else { 273 sl->xleft = 0; 274 dev->stats.tx_dropped++; 275 } 276 } 277 sl->xhead = sl->xbuff; 278 279 if (sl->rcount) { 280 if (sl->rcount <= len) { 281 memcpy(sl->rbuff, rbuff, sl->rcount); 282 } else { 283 sl->rcount = 0; 284 dev->stats.rx_over_errors++; 285 set_bit(SLF_ERROR, &sl->flags); 286 } 287 } 288 sl->mtu = mtu; 289 WRITE_ONCE(dev->mtu, mtu); 290 sl->buffsize = len; 291 err = 0; 292 293 done_on_bh: 294 spin_unlock_bh(&sl->lock); 295 296 done: 297 kfree(xbuff); 298 kfree(rbuff); 299 #ifdef SL_INCLUDE_CSLIP 300 kfree(cbuff); 301 #endif 302 return err; 303 } 304 305 306 /* Set the "sending" flag. This must be atomic hence the set_bit. */ 307 static inline void sl_lock(struct slip *sl) 308 { 309 netif_stop_queue(sl->dev); 310 } 311 312 313 /* Clear the "sending" flag. This must be atomic, hence the ASM. */ 314 static inline void sl_unlock(struct slip *sl) 315 { 316 netif_wake_queue(sl->dev); 317 } 318 319 /* Send one completely decapsulated IP datagram to the IP layer. */ 320 static void sl_bump(struct slip *sl) 321 { 322 struct net_device *dev = sl->dev; 323 struct sk_buff *skb; 324 int count; 325 326 count = sl->rcount; 327 #ifdef SL_INCLUDE_CSLIP 328 if (sl->mode & (SL_MODE_ADAPTIVE | SL_MODE_CSLIP)) { 329 unsigned char c = sl->rbuff[0]; 330 if (c & SL_TYPE_COMPRESSED_TCP) { 331 /* ignore compressed packets when CSLIP is off */ 332 if (!(sl->mode & SL_MODE_CSLIP)) { 333 printk(KERN_WARNING "%s: compressed packet ignored\n", dev->name); 334 return; 335 } 336 /* make sure we've reserved enough space for uncompress 337 to use */ 338 if (count + 80 > sl->buffsize) { 339 dev->stats.rx_over_errors++; 340 return; 341 } 342 count = slhc_uncompress(sl->slcomp, sl->rbuff, count); 343 if (count <= 0) 344 return; 345 } else if (c >= SL_TYPE_UNCOMPRESSED_TCP) { 346 if (!(sl->mode & SL_MODE_CSLIP)) { 347 /* turn on header compression */ 348 sl->mode |= SL_MODE_CSLIP; 349 sl->mode &= ~SL_MODE_ADAPTIVE; 350 printk(KERN_INFO "%s: header compression turned on\n", dev->name); 351 } 352 sl->rbuff[0] &= 0x4f; 353 if (slhc_remember(sl->slcomp, sl->rbuff, count) <= 0) 354 return; 355 } 356 } 357 #endif /* SL_INCLUDE_CSLIP */ 358 359 dev->stats.rx_bytes += count; 360 361 skb = dev_alloc_skb(count); 362 if (skb == NULL) { 363 printk(KERN_WARNING "%s: memory squeeze, dropping packet.\n", dev->name); 364 dev->stats.rx_dropped++; 365 return; 366 } 367 skb->dev = dev; 368 skb_put_data(skb, sl->rbuff, count); 369 skb_reset_mac_header(skb); 370 skb->protocol = htons(ETH_P_IP); 371 netif_rx(skb); 372 dev->stats.rx_packets++; 373 } 374 375 /* Encapsulate one IP datagram and stuff into a TTY queue. */ 376 static void sl_encaps(struct slip *sl, unsigned char *icp, int len) 377 { 378 unsigned char *p; 379 int actual, count; 380 381 if (len > sl->mtu) { /* Sigh, shouldn't occur BUT ... */ 382 printk(KERN_WARNING "%s: truncating oversized transmit packet!\n", sl->dev->name); 383 sl->dev->stats.tx_dropped++; 384 sl_unlock(sl); 385 return; 386 } 387 388 p = icp; 389 #ifdef SL_INCLUDE_CSLIP 390 if (sl->mode & SL_MODE_CSLIP) 391 len = slhc_compress(sl->slcomp, p, len, sl->cbuff, &p, 1); 392 #endif 393 #ifdef CONFIG_SLIP_MODE_SLIP6 394 if (sl->mode & SL_MODE_SLIP6) 395 count = slip_esc6(p, sl->xbuff, len); 396 else 397 #endif 398 count = slip_esc(p, sl->xbuff, len); 399 400 /* Order of next two lines is *very* important. 401 * When we are sending a little amount of data, 402 * the transfer may be completed inside the ops->write() 403 * routine, because it's running with interrupts enabled. 404 * In this case we *never* got WRITE_WAKEUP event, 405 * if we did not request it before write operation. 406 * 14 Oct 1994 Dmitry Gorodchanin. 407 */ 408 set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags); 409 actual = sl->tty->ops->write(sl->tty, sl->xbuff, count); 410 #ifdef SL_CHECK_TRANSMIT 411 netif_trans_update(sl->dev); 412 #endif 413 sl->xleft = count - actual; 414 sl->xhead = sl->xbuff + actual; 415 #ifdef CONFIG_SLIP_SMART 416 /* VSV */ 417 clear_bit(SLF_OUTWAIT, &sl->flags); /* reset outfill flag */ 418 #endif 419 } 420 421 /* Write out any remaining transmit buffer. Scheduled when tty is writable */ 422 static void slip_transmit(struct work_struct *work) 423 { 424 struct slip *sl = container_of(work, struct slip, tx_work); 425 int actual; 426 427 spin_lock_bh(&sl->lock); 428 /* First make sure we're connected. */ 429 if (!sl->tty || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) { 430 spin_unlock_bh(&sl->lock); 431 return; 432 } 433 434 if (sl->xleft <= 0) { 435 /* Now serial buffer is almost free & we can start 436 * transmission of another packet */ 437 sl->dev->stats.tx_packets++; 438 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags); 439 spin_unlock_bh(&sl->lock); 440 sl_unlock(sl); 441 return; 442 } 443 444 actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft); 445 sl->xleft -= actual; 446 sl->xhead += actual; 447 spin_unlock_bh(&sl->lock); 448 } 449 450 /* 451 * Called by the driver when there's room for more data. 452 * Schedule the transmit. 453 */ 454 static void slip_write_wakeup(struct tty_struct *tty) 455 { 456 struct slip *sl; 457 458 rcu_read_lock(); 459 sl = rcu_dereference(tty->disc_data); 460 if (sl) 461 schedule_work(&sl->tx_work); 462 rcu_read_unlock(); 463 } 464 465 static void sl_tx_timeout(struct net_device *dev, unsigned int txqueue) 466 { 467 struct slip *sl = netdev_priv(dev); 468 469 spin_lock(&sl->lock); 470 471 if (netif_queue_stopped(dev)) { 472 if (!netif_running(dev) || !sl->tty) 473 goto out; 474 475 /* May be we must check transmitter timeout here ? 476 * 14 Oct 1994 Dmitry Gorodchanin. 477 */ 478 #ifdef SL_CHECK_TRANSMIT 479 if (time_before(jiffies, dev_trans_start(dev) + 20 * HZ)) { 480 /* 20 sec timeout not reached */ 481 goto out; 482 } 483 printk(KERN_WARNING "%s: transmit timed out, %s?\n", 484 dev->name, 485 (tty_chars_in_buffer(sl->tty) || sl->xleft) ? 486 "bad line quality" : "driver error"); 487 sl->xleft = 0; 488 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags); 489 sl_unlock(sl); 490 #endif 491 } 492 out: 493 spin_unlock(&sl->lock); 494 } 495 496 497 /* Encapsulate an IP datagram and kick it into a TTY queue. */ 498 static netdev_tx_t 499 sl_xmit(struct sk_buff *skb, struct net_device *dev) 500 { 501 struct slip *sl = netdev_priv(dev); 502 503 spin_lock(&sl->lock); 504 if (!netif_running(dev)) { 505 spin_unlock(&sl->lock); 506 printk(KERN_WARNING "%s: xmit call when iface is down\n", dev->name); 507 dev_kfree_skb(skb); 508 return NETDEV_TX_OK; 509 } 510 if (sl->tty == NULL) { 511 spin_unlock(&sl->lock); 512 dev_kfree_skb(skb); 513 return NETDEV_TX_OK; 514 } 515 516 sl_lock(sl); 517 dev->stats.tx_bytes += skb->len; 518 sl_encaps(sl, skb->data, skb->len); 519 spin_unlock(&sl->lock); 520 521 dev_kfree_skb(skb); 522 return NETDEV_TX_OK; 523 } 524 525 526 /****************************************** 527 * Routines looking at netdevice side. 528 ******************************************/ 529 530 /* Netdevice UP -> DOWN routine */ 531 532 static int 533 sl_close(struct net_device *dev) 534 { 535 struct slip *sl = netdev_priv(dev); 536 537 spin_lock_bh(&sl->lock); 538 if (sl->tty) 539 /* TTY discipline is running. */ 540 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags); 541 netif_stop_queue(dev); 542 sl->rcount = 0; 543 sl->xleft = 0; 544 spin_unlock_bh(&sl->lock); 545 546 return 0; 547 } 548 549 /* Netdevice DOWN -> UP routine */ 550 551 static int sl_open(struct net_device *dev) 552 { 553 struct slip *sl = netdev_priv(dev); 554 555 if (sl->tty == NULL) 556 return -ENODEV; 557 558 sl->flags &= (1 << SLF_INUSE); 559 netif_start_queue(dev); 560 return 0; 561 } 562 563 /* Netdevice change MTU request */ 564 565 static int sl_change_mtu(struct net_device *dev, int new_mtu) 566 { 567 struct slip *sl = netdev_priv(dev); 568 569 return sl_realloc_bufs(sl, new_mtu); 570 } 571 572 /* Netdevice get statistics request */ 573 574 static void 575 sl_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats) 576 { 577 struct net_device_stats *devstats = &dev->stats; 578 #ifdef SL_INCLUDE_CSLIP 579 struct slip *sl = netdev_priv(dev); 580 struct slcompress *comp = sl->slcomp; 581 #endif 582 stats->rx_packets = devstats->rx_packets; 583 stats->tx_packets = devstats->tx_packets; 584 stats->rx_bytes = devstats->rx_bytes; 585 stats->tx_bytes = devstats->tx_bytes; 586 stats->rx_dropped = devstats->rx_dropped; 587 stats->tx_dropped = devstats->tx_dropped; 588 stats->tx_errors = devstats->tx_errors; 589 stats->rx_errors = devstats->rx_errors; 590 stats->rx_over_errors = devstats->rx_over_errors; 591 592 #ifdef SL_INCLUDE_CSLIP 593 if (comp) { 594 /* Generic compressed statistics */ 595 stats->rx_compressed = comp->sls_i_compressed; 596 stats->tx_compressed = comp->sls_o_compressed; 597 598 /* Are we really still needs this? */ 599 stats->rx_fifo_errors += comp->sls_i_compressed; 600 stats->rx_dropped += comp->sls_i_tossed; 601 stats->tx_fifo_errors += comp->sls_o_compressed; 602 stats->collisions += comp->sls_o_misses; 603 } 604 #endif 605 } 606 607 /* Netdevice register callback */ 608 609 static int sl_init(struct net_device *dev) 610 { 611 struct slip *sl = netdev_priv(dev); 612 613 /* 614 * Finish setting up the DEVICE info. 615 */ 616 617 dev->mtu = sl->mtu; 618 dev->type = ARPHRD_SLIP + sl->mode; 619 #ifdef SL_CHECK_TRANSMIT 620 dev->watchdog_timeo = 20*HZ; 621 #endif 622 return 0; 623 } 624 625 626 static void sl_uninit(struct net_device *dev) 627 { 628 struct slip *sl = netdev_priv(dev); 629 630 sl_free_bufs(sl); 631 /* Drop the slip_devs[] entry here rather than from the destructor: 632 * ndo_uninit runs under RTNL, so it cannot race sl_sync(). 633 */ 634 slip_devs[dev->base_addr] = NULL; 635 } 636 637 /* Only for the slip_open() error path: register_netdevice() can fail before 638 * ndo_init, and then ndo_uninit is not called either. 639 */ 640 static void sl_free_netdev(struct net_device *dev) 641 { 642 int i = dev->base_addr; 643 644 slip_devs[i] = NULL; 645 } 646 647 static const struct net_device_ops sl_netdev_ops = { 648 .ndo_init = sl_init, 649 .ndo_uninit = sl_uninit, 650 .ndo_open = sl_open, 651 .ndo_stop = sl_close, 652 .ndo_start_xmit = sl_xmit, 653 .ndo_get_stats64 = sl_get_stats64, 654 .ndo_change_mtu = sl_change_mtu, 655 .ndo_tx_timeout = sl_tx_timeout, 656 #ifdef CONFIG_SLIP_SMART 657 .ndo_siocdevprivate = sl_siocdevprivate, 658 #endif 659 }; 660 661 662 static void sl_setup(struct net_device *dev) 663 { 664 dev->netdev_ops = &sl_netdev_ops; 665 dev->needs_free_netdev = true; 666 667 dev->hard_header_len = 0; 668 dev->addr_len = 0; 669 dev->tx_queue_len = 10; 670 671 /* MTU range: 68 - 65534 */ 672 dev->min_mtu = 68; 673 dev->max_mtu = 65534; 674 675 /* New-style flags. */ 676 dev->flags = IFF_NOARP|IFF_POINTOPOINT|IFF_MULTICAST; 677 } 678 679 /****************************************** 680 Routines looking at TTY side. 681 ******************************************/ 682 683 684 /* 685 * Handle the 'receiver data ready' interrupt. 686 * This function is called by the 'tty_io' module in the kernel when 687 * a block of SLIP data has been received, which can now be decapsulated 688 * and sent on to some IP layer for further processing. This will not 689 * be re-entered while running but other ldisc functions may be called 690 * in parallel 691 */ 692 693 static void slip_receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp, 694 size_t count) 695 { 696 struct slip *sl = tty->disc_data; 697 698 if (!sl || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) 699 return; 700 701 spin_lock_bh(&sl->lock); 702 703 /* Read the characters out of the buffer */ 704 while (count--) { 705 if (fp && *fp++) { 706 if (!test_and_set_bit(SLF_ERROR, &sl->flags)) 707 sl->dev->stats.rx_errors++; 708 cp++; 709 continue; 710 } 711 #ifdef CONFIG_SLIP_MODE_SLIP6 712 if (sl->mode & SL_MODE_SLIP6) 713 slip_unesc6(sl, *cp++); 714 else 715 #endif 716 slip_unesc(sl, *cp++); 717 } 718 719 spin_unlock_bh(&sl->lock); 720 } 721 722 /************************************ 723 * slip_open helper routines. 724 ************************************/ 725 726 /* Collect hanged up channels */ 727 static void sl_sync(void) 728 { 729 int i; 730 struct net_device *dev; 731 struct slip *sl; 732 733 for (i = 0; i < slip_maxdev; i++) { 734 dev = slip_devs[i]; 735 if (dev == NULL) 736 break; 737 738 sl = netdev_priv(dev); 739 if (sl->tty || sl->leased) 740 continue; 741 if (dev->flags & IFF_UP) 742 dev_close(dev); 743 } 744 } 745 746 747 /* Find a free SLIP channel, and link in this `tty' line. */ 748 static struct slip *sl_alloc(void) 749 { 750 int i; 751 char name[IFNAMSIZ]; 752 struct net_device *dev = NULL; 753 struct slip *sl; 754 755 for (i = 0; i < slip_maxdev; i++) { 756 dev = slip_devs[i]; 757 if (dev == NULL) 758 break; 759 } 760 /* Sorry, too many, all slots in use */ 761 if (i >= slip_maxdev) 762 return NULL; 763 764 sprintf(name, "sl%d", i); 765 dev = alloc_netdev(sizeof(*sl), name, NET_NAME_UNKNOWN, sl_setup); 766 if (!dev) 767 return NULL; 768 769 dev->base_addr = i; 770 sl = netdev_priv(dev); 771 772 /* Initialize channel control data */ 773 sl->magic = SLIP_MAGIC; 774 sl->dev = dev; 775 spin_lock_init(&sl->lock); 776 INIT_WORK(&sl->tx_work, slip_transmit); 777 sl->mode = SL_MODE_DEFAULT; 778 #ifdef CONFIG_SLIP_SMART 779 /* initialize timer_list struct */ 780 timer_setup(&sl->keepalive_timer, sl_keepalive, 0); 781 timer_setup(&sl->outfill_timer, sl_outfill, 0); 782 #endif 783 slip_devs[i] = dev; 784 return sl; 785 } 786 787 /* 788 * Open the high-level part of the SLIP channel. 789 * This function is called by the TTY module when the 790 * SLIP line discipline is called for. Because we are 791 * sure the tty line exists, we only have to link it to 792 * a free SLIP channel... 793 * 794 * Called in process context serialized from other ldisc calls. 795 */ 796 797 static int slip_open(struct tty_struct *tty) 798 { 799 struct slip *sl; 800 int err; 801 802 if (!capable(CAP_NET_ADMIN)) 803 return -EPERM; 804 805 if (tty->ops->write == NULL) 806 return -EOPNOTSUPP; 807 808 /* RTnetlink lock is misused here to serialize concurrent 809 opens of slip channels. There are better ways, but it is 810 the simplest one. 811 */ 812 rtnl_lock(); 813 814 /* Collect hanged up channels. */ 815 sl_sync(); 816 817 sl = tty->disc_data; 818 819 err = -EEXIST; 820 /* First make sure we're not already connected. */ 821 if (sl && sl->magic == SLIP_MAGIC) 822 goto err_exit; 823 824 /* OK. Find a free SLIP channel to use. */ 825 err = -ENFILE; 826 sl = sl_alloc(); 827 if (sl == NULL) 828 goto err_exit; 829 830 sl->tty = tty; 831 tty->disc_data = sl; 832 sl->pid = current->pid; 833 834 if (!test_bit(SLF_INUSE, &sl->flags)) { 835 /* Perform the low-level SLIP initialization. */ 836 err = sl_alloc_bufs(sl, SL_MTU); 837 if (err) 838 goto err_free_chan; 839 840 set_bit(SLF_INUSE, &sl->flags); 841 842 err = register_netdevice(sl->dev); 843 if (err) 844 goto err_free_bufs; 845 } 846 847 #ifdef CONFIG_SLIP_SMART 848 if (sl->keepalive) { 849 sl->keepalive_timer.expires = jiffies + sl->keepalive * HZ; 850 add_timer(&sl->keepalive_timer); 851 } 852 if (sl->outfill) { 853 sl->outfill_timer.expires = jiffies + sl->outfill * HZ; 854 add_timer(&sl->outfill_timer); 855 } 856 #endif 857 858 /* Done. We have linked the TTY line to a channel. */ 859 rtnl_unlock(); 860 tty->receive_room = 65536; /* We don't flow control */ 861 862 /* TTY layer expects 0 on success */ 863 return 0; 864 865 err_free_bufs: 866 sl_free_bufs(sl); 867 868 err_free_chan: 869 sl->tty = NULL; 870 tty->disc_data = NULL; 871 clear_bit(SLF_INUSE, &sl->flags); 872 sl_free_netdev(sl->dev); 873 /* do not call free_netdev before rtnl_unlock */ 874 rtnl_unlock(); 875 free_netdev(sl->dev); 876 return err; 877 878 err_exit: 879 rtnl_unlock(); 880 881 /* Count references from TTY module */ 882 return err; 883 } 884 885 /* 886 * Close down a SLIP channel. 887 * This means flushing out any pending queues, and then returning. This 888 * call is serialized against other ldisc functions. 889 */ 890 891 static void slip_close(struct tty_struct *tty) 892 { 893 struct slip *sl = tty->disc_data; 894 895 /* First make sure we're connected. */ 896 if (!sl || sl->magic != SLIP_MAGIC || sl->tty != tty) 897 return; 898 899 spin_lock_bh(&sl->lock); 900 rcu_assign_pointer(tty->disc_data, NULL); 901 sl->tty = NULL; 902 spin_unlock_bh(&sl->lock); 903 904 synchronize_rcu(); 905 flush_work(&sl->tx_work); 906 907 /* VSV = very important to remove timers */ 908 #ifdef CONFIG_SLIP_SMART 909 timer_delete_sync(&sl->keepalive_timer); 910 timer_delete_sync(&sl->outfill_timer); 911 #endif 912 /* Flush network side */ 913 unregister_netdev(sl->dev); 914 /* sl_uninit() has dropped the slip_devs[] entry by now */ 915 } 916 /************************************************************************ 917 * STANDARD SLIP ENCAPSULATION * 918 ************************************************************************/ 919 920 static int slip_esc(unsigned char *s, unsigned char *d, int len) 921 { 922 unsigned char *ptr = d; 923 unsigned char c; 924 925 /* 926 * Send an initial END character to flush out any 927 * data that may have accumulated in the receiver 928 * due to line noise. 929 */ 930 931 *ptr++ = END; 932 933 /* 934 * For each byte in the packet, send the appropriate 935 * character sequence, according to the SLIP protocol. 936 */ 937 938 while (len-- > 0) { 939 switch (c = *s++) { 940 case END: 941 *ptr++ = ESC; 942 *ptr++ = ESC_END; 943 break; 944 case ESC: 945 *ptr++ = ESC; 946 *ptr++ = ESC_ESC; 947 break; 948 default: 949 *ptr++ = c; 950 break; 951 } 952 } 953 *ptr++ = END; 954 return ptr - d; 955 } 956 957 static void slip_unesc(struct slip *sl, unsigned char s) 958 { 959 960 switch (s) { 961 case END: 962 #ifdef CONFIG_SLIP_SMART 963 /* drop keeptest bit = VSV */ 964 if (test_bit(SLF_KEEPTEST, &sl->flags)) 965 clear_bit(SLF_KEEPTEST, &sl->flags); 966 #endif 967 968 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) && 969 (sl->rcount > 2)) 970 sl_bump(sl); 971 clear_bit(SLF_ESCAPE, &sl->flags); 972 sl->rcount = 0; 973 return; 974 975 case ESC: 976 set_bit(SLF_ESCAPE, &sl->flags); 977 return; 978 case ESC_ESC: 979 if (test_and_clear_bit(SLF_ESCAPE, &sl->flags)) 980 s = ESC; 981 break; 982 case ESC_END: 983 if (test_and_clear_bit(SLF_ESCAPE, &sl->flags)) 984 s = END; 985 break; 986 } 987 if (!test_bit(SLF_ERROR, &sl->flags)) { 988 if (sl->rcount < sl->buffsize) { 989 sl->rbuff[sl->rcount++] = s; 990 return; 991 } 992 sl->dev->stats.rx_over_errors++; 993 set_bit(SLF_ERROR, &sl->flags); 994 } 995 } 996 997 998 #ifdef CONFIG_SLIP_MODE_SLIP6 999 /************************************************************************ 1000 * 6 BIT SLIP ENCAPSULATION * 1001 ************************************************************************/ 1002 1003 static int slip_esc6(unsigned char *s, unsigned char *d, int len) 1004 { 1005 unsigned char *ptr = d; 1006 unsigned char c; 1007 int i; 1008 unsigned short v = 0; 1009 short bits = 0; 1010 1011 /* 1012 * Send an initial END character to flush out any 1013 * data that may have accumulated in the receiver 1014 * due to line noise. 1015 */ 1016 1017 *ptr++ = 0x70; 1018 1019 /* 1020 * Encode the packet into printable ascii characters 1021 */ 1022 1023 for (i = 0; i < len; ++i) { 1024 v = (v << 8) | s[i]; 1025 bits += 8; 1026 while (bits >= 6) { 1027 bits -= 6; 1028 c = 0x30 + ((v >> bits) & 0x3F); 1029 *ptr++ = c; 1030 } 1031 } 1032 if (bits) { 1033 c = 0x30 + ((v << (6 - bits)) & 0x3F); 1034 *ptr++ = c; 1035 } 1036 *ptr++ = 0x70; 1037 return ptr - d; 1038 } 1039 1040 static void slip_unesc6(struct slip *sl, unsigned char s) 1041 { 1042 unsigned char c; 1043 1044 if (s == 0x70) { 1045 #ifdef CONFIG_SLIP_SMART 1046 /* drop keeptest bit = VSV */ 1047 if (test_bit(SLF_KEEPTEST, &sl->flags)) 1048 clear_bit(SLF_KEEPTEST, &sl->flags); 1049 #endif 1050 1051 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) && 1052 (sl->rcount > 2)) 1053 sl_bump(sl); 1054 sl->rcount = 0; 1055 sl->xbits = 0; 1056 sl->xdata = 0; 1057 } else if (s >= 0x30 && s < 0x70) { 1058 sl->xdata = (sl->xdata << 6) | ((s - 0x30) & 0x3F); 1059 sl->xbits += 6; 1060 if (sl->xbits >= 8) { 1061 sl->xbits -= 8; 1062 c = (unsigned char)(sl->xdata >> sl->xbits); 1063 if (!test_bit(SLF_ERROR, &sl->flags)) { 1064 if (sl->rcount < sl->buffsize) { 1065 sl->rbuff[sl->rcount++] = c; 1066 return; 1067 } 1068 sl->dev->stats.rx_over_errors++; 1069 set_bit(SLF_ERROR, &sl->flags); 1070 } 1071 } 1072 } 1073 } 1074 #endif /* CONFIG_SLIP_MODE_SLIP6 */ 1075 1076 /* Perform I/O control on an active SLIP channel. */ 1077 static int slip_ioctl(struct tty_struct *tty, unsigned int cmd, 1078 unsigned long arg) 1079 { 1080 struct slip *sl = tty->disc_data; 1081 unsigned int tmp; 1082 int __user *p = (int __user *)arg; 1083 1084 /* First make sure we're connected. */ 1085 if (!sl || sl->magic != SLIP_MAGIC) 1086 return -EINVAL; 1087 1088 switch (cmd) { 1089 case SIOCGIFNAME: 1090 tmp = strlen(sl->dev->name) + 1; 1091 if (copy_to_user((void __user *)arg, sl->dev->name, tmp)) 1092 return -EFAULT; 1093 return 0; 1094 1095 case SIOCGIFENCAP: 1096 if (put_user(sl->mode, p)) 1097 return -EFAULT; 1098 return 0; 1099 1100 case SIOCSIFENCAP: 1101 if (get_user(tmp, p)) 1102 return -EFAULT; 1103 #ifndef SL_INCLUDE_CSLIP 1104 if (tmp & (SL_MODE_CSLIP|SL_MODE_ADAPTIVE)) 1105 return -EINVAL; 1106 #else 1107 if ((tmp & (SL_MODE_ADAPTIVE | SL_MODE_CSLIP)) == 1108 (SL_MODE_ADAPTIVE | SL_MODE_CSLIP)) 1109 /* return -EINVAL; */ 1110 tmp &= ~SL_MODE_ADAPTIVE; 1111 #endif 1112 #ifndef CONFIG_SLIP_MODE_SLIP6 1113 if (tmp & SL_MODE_SLIP6) 1114 return -EINVAL; 1115 #endif 1116 sl->mode = tmp; 1117 sl->dev->type = ARPHRD_SLIP + sl->mode; 1118 return 0; 1119 1120 case SIOCSIFHWADDR: 1121 return -EINVAL; 1122 1123 #ifdef CONFIG_SLIP_SMART 1124 /* VSV changes start here */ 1125 case SIOCSKEEPALIVE: 1126 if (get_user(tmp, p)) 1127 return -EFAULT; 1128 if (tmp > 255) /* max for unchar */ 1129 return -EINVAL; 1130 1131 spin_lock_bh(&sl->lock); 1132 if (!sl->tty) { 1133 spin_unlock_bh(&sl->lock); 1134 return -ENODEV; 1135 } 1136 sl->keepalive = (u8)tmp; 1137 if (sl->keepalive != 0) { 1138 mod_timer(&sl->keepalive_timer, 1139 jiffies + sl->keepalive * HZ); 1140 set_bit(SLF_KEEPTEST, &sl->flags); 1141 } else 1142 timer_delete(&sl->keepalive_timer); 1143 spin_unlock_bh(&sl->lock); 1144 return 0; 1145 1146 case SIOCGKEEPALIVE: 1147 if (put_user(sl->keepalive, p)) 1148 return -EFAULT; 1149 return 0; 1150 1151 case SIOCSOUTFILL: 1152 if (get_user(tmp, p)) 1153 return -EFAULT; 1154 if (tmp > 255) /* max for unchar */ 1155 return -EINVAL; 1156 spin_lock_bh(&sl->lock); 1157 if (!sl->tty) { 1158 spin_unlock_bh(&sl->lock); 1159 return -ENODEV; 1160 } 1161 sl->outfill = (u8)tmp; 1162 if (sl->outfill != 0) { 1163 mod_timer(&sl->outfill_timer, 1164 jiffies + sl->outfill * HZ); 1165 set_bit(SLF_OUTWAIT, &sl->flags); 1166 } else 1167 timer_delete(&sl->outfill_timer); 1168 spin_unlock_bh(&sl->lock); 1169 return 0; 1170 1171 case SIOCGOUTFILL: 1172 if (put_user(sl->outfill, p)) 1173 return -EFAULT; 1174 return 0; 1175 /* VSV changes end */ 1176 #endif 1177 default: 1178 return tty_mode_ioctl(tty, cmd, arg); 1179 } 1180 } 1181 1182 /* VSV changes start here */ 1183 #ifdef CONFIG_SLIP_SMART 1184 /* function sl_siocdevprivate called from net/core/dev.c 1185 to allow get/set outfill/keepalive parameter 1186 by ifconfig */ 1187 1188 static int sl_siocdevprivate(struct net_device *dev, struct ifreq *rq, 1189 void __user *data, int cmd) 1190 { 1191 struct slip *sl = netdev_priv(dev); 1192 unsigned long *p = (unsigned long *)&rq->ifr_ifru; 1193 1194 if (sl == NULL) /* Allocation failed ?? */ 1195 return -ENODEV; 1196 1197 if (in_compat_syscall()) 1198 return -EOPNOTSUPP; 1199 1200 spin_lock_bh(&sl->lock); 1201 1202 if (!sl->tty) { 1203 spin_unlock_bh(&sl->lock); 1204 return -ENODEV; 1205 } 1206 1207 switch (cmd) { 1208 case SIOCSKEEPALIVE: 1209 /* max for unchar */ 1210 if ((unsigned)*p > 255) { 1211 spin_unlock_bh(&sl->lock); 1212 return -EINVAL; 1213 } 1214 sl->keepalive = (u8)*p; 1215 if (sl->keepalive != 0) { 1216 sl->keepalive_timer.expires = 1217 jiffies + sl->keepalive * HZ; 1218 mod_timer(&sl->keepalive_timer, 1219 jiffies + sl->keepalive * HZ); 1220 set_bit(SLF_KEEPTEST, &sl->flags); 1221 } else 1222 timer_delete(&sl->keepalive_timer); 1223 break; 1224 1225 case SIOCGKEEPALIVE: 1226 *p = sl->keepalive; 1227 break; 1228 1229 case SIOCSOUTFILL: 1230 if ((unsigned)*p > 255) { /* max for unchar */ 1231 spin_unlock_bh(&sl->lock); 1232 return -EINVAL; 1233 } 1234 sl->outfill = (u8)*p; 1235 if (sl->outfill != 0) { 1236 mod_timer(&sl->outfill_timer, 1237 jiffies + sl->outfill * HZ); 1238 set_bit(SLF_OUTWAIT, &sl->flags); 1239 } else 1240 timer_delete(&sl->outfill_timer); 1241 break; 1242 1243 case SIOCGOUTFILL: 1244 *p = sl->outfill; 1245 break; 1246 1247 case SIOCSLEASE: 1248 /* Resolve race condition, when ioctl'ing hanged up 1249 and opened by another process device. 1250 */ 1251 if (sl->tty != current->signal->tty && 1252 sl->pid != current->pid) { 1253 spin_unlock_bh(&sl->lock); 1254 return -EPERM; 1255 } 1256 sl->leased = 0; 1257 if (*p) 1258 sl->leased = 1; 1259 break; 1260 1261 case SIOCGLEASE: 1262 *p = sl->leased; 1263 } 1264 spin_unlock_bh(&sl->lock); 1265 return 0; 1266 } 1267 #endif 1268 /* VSV changes end */ 1269 1270 static struct tty_ldisc_ops sl_ldisc = { 1271 .owner = THIS_MODULE, 1272 .num = N_SLIP, 1273 .name = "slip", 1274 .open = slip_open, 1275 .close = slip_close, 1276 .ioctl = slip_ioctl, 1277 .receive_buf = slip_receive_buf, 1278 .write_wakeup = slip_write_wakeup, 1279 }; 1280 1281 static int __init slip_init(void) 1282 { 1283 int status; 1284 1285 if (slip_maxdev < 4) 1286 slip_maxdev = 4; /* Sanity */ 1287 1288 printk(KERN_INFO "SLIP: version %s (dynamic channels, max=%d)" 1289 #ifdef CONFIG_SLIP_MODE_SLIP6 1290 " (6 bit encapsulation enabled)" 1291 #endif 1292 ".\n", 1293 SLIP_VERSION, slip_maxdev); 1294 #if defined(SL_INCLUDE_CSLIP) 1295 printk(KERN_INFO "CSLIP: code copyright 1989 Regents of the University of California.\n"); 1296 #endif 1297 #ifdef CONFIG_SLIP_SMART 1298 printk(KERN_INFO "SLIP linefill/keepalive option.\n"); 1299 #endif 1300 1301 slip_devs = kzalloc_objs(struct net_device *, slip_maxdev); 1302 if (!slip_devs) 1303 return -ENOMEM; 1304 1305 /* Fill in our line protocol discipline, and register it */ 1306 status = tty_register_ldisc(&sl_ldisc); 1307 if (status != 0) { 1308 printk(KERN_ERR "SLIP: can't register line discipline (err = %d)\n", status); 1309 kfree(slip_devs); 1310 } 1311 return status; 1312 } 1313 1314 static void __exit slip_exit(void) 1315 { 1316 int i; 1317 struct net_device *dev; 1318 struct slip *sl; 1319 unsigned long timeout = jiffies + HZ; 1320 int busy = 0; 1321 1322 if (slip_devs == NULL) 1323 return; 1324 1325 /* First of all: check for active disciplines and hangup them. 1326 */ 1327 do { 1328 if (busy) 1329 msleep_interruptible(100); 1330 1331 busy = 0; 1332 for (i = 0; i < slip_maxdev; i++) { 1333 dev = slip_devs[i]; 1334 if (!dev) 1335 continue; 1336 sl = netdev_priv(dev); 1337 spin_lock_bh(&sl->lock); 1338 if (sl->tty) { 1339 busy++; 1340 tty_hangup(sl->tty); 1341 } 1342 spin_unlock_bh(&sl->lock); 1343 } 1344 } while (busy && time_before(jiffies, timeout)); 1345 1346 /* FIXME: hangup is async so we should wait when doing this second 1347 phase */ 1348 1349 for (i = 0; i < slip_maxdev; i++) { 1350 dev = slip_devs[i]; 1351 if (!dev) 1352 continue; 1353 slip_devs[i] = NULL; 1354 1355 sl = netdev_priv(dev); 1356 if (sl->tty) { 1357 printk(KERN_ERR "%s: tty discipline still running\n", 1358 dev->name); 1359 } 1360 1361 unregister_netdev(dev); 1362 } 1363 1364 kfree(slip_devs); 1365 slip_devs = NULL; 1366 1367 tty_unregister_ldisc(&sl_ldisc); 1368 } 1369 1370 module_init(slip_init); 1371 module_exit(slip_exit); 1372 1373 #ifdef CONFIG_SLIP_SMART 1374 /* 1375 * This is start of the code for multislip style line checking 1376 * added by Stanislav Voronyi. All changes before marked VSV 1377 */ 1378 1379 static void sl_outfill(struct timer_list *t) 1380 { 1381 struct slip *sl = timer_container_of(sl, t, outfill_timer); 1382 1383 spin_lock(&sl->lock); 1384 1385 if (sl->tty == NULL) 1386 goto out; 1387 1388 if (sl->outfill) { 1389 if (test_bit(SLF_OUTWAIT, &sl->flags)) { 1390 /* no packets were transmitted, do outfill */ 1391 #ifdef CONFIG_SLIP_MODE_SLIP6 1392 unsigned char s = (sl->mode & SL_MODE_SLIP6)?0x70:END; 1393 #else 1394 unsigned char s = END; 1395 #endif 1396 /* put END into tty queue. Is it right ??? */ 1397 if (!netif_queue_stopped(sl->dev)) { 1398 /* if device busy no outfill */ 1399 sl->tty->ops->write(sl->tty, &s, 1); 1400 } 1401 } else 1402 set_bit(SLF_OUTWAIT, &sl->flags); 1403 1404 mod_timer(&sl->outfill_timer, jiffies+sl->outfill*HZ); 1405 } 1406 out: 1407 spin_unlock(&sl->lock); 1408 } 1409 1410 static void sl_keepalive(struct timer_list *t) 1411 { 1412 struct slip *sl = timer_container_of(sl, t, keepalive_timer); 1413 1414 spin_lock(&sl->lock); 1415 1416 if (sl->tty == NULL) 1417 goto out; 1418 1419 if (sl->keepalive) { 1420 if (test_bit(SLF_KEEPTEST, &sl->flags)) { 1421 /* keepalive still high :(, we must hangup */ 1422 if (sl->outfill) 1423 /* outfill timer must be deleted too */ 1424 (void) timer_delete(&sl->outfill_timer); 1425 printk(KERN_DEBUG "%s: no packets received during keepalive timeout, hangup.\n", sl->dev->name); 1426 /* this must hangup tty & close slip */ 1427 tty_hangup(sl->tty); 1428 /* I think we need not something else */ 1429 goto out; 1430 } else 1431 set_bit(SLF_KEEPTEST, &sl->flags); 1432 1433 mod_timer(&sl->keepalive_timer, jiffies+sl->keepalive*HZ); 1434 } 1435 out: 1436 spin_unlock(&sl->lock); 1437 } 1438 1439 #endif 1440 MODULE_DESCRIPTION("SLIP (serial line) protocol module"); 1441 MODULE_LICENSE("GPL"); 1442 MODULE_ALIAS_LDISC(N_SLIP); 1443