1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * 6pack.c This module implements the 6pack protocol for kernel-based 4 * devices like TTY. It interfaces between a raw TTY and the 5 * kernel's AX.25 protocol layers. 6 * 7 * Authors: Andreas Könsgen <ajk@comnets.uni-bremen.de> 8 * Ralf Baechle DL5RB <ralf@linux-mips.org> 9 * 10 * Quite a lot of stuff "stolen" by Joerg Reuter from slip.c, written by 11 * 12 * Laurence Culhane, <loz@holmes.demon.co.uk> 13 * Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org> 14 */ 15 16 #include <linux/module.h> 17 #include <linux/uaccess.h> 18 #include <linux/bitops.h> 19 #include <linux/string.h> 20 #include <linux/mm.h> 21 #include <linux/interrupt.h> 22 #include <linux/in.h> 23 #include <linux/tty.h> 24 #include <linux/errno.h> 25 #include <linux/netdevice.h> 26 #include <linux/timer.h> 27 #include <linux/slab.h> 28 #include <net/ax25.h> 29 #include <linux/etherdevice.h> 30 #include <linux/skbuff.h> 31 #include <linux/rtnetlink.h> 32 #include <linux/spinlock.h> 33 #include <linux/if_arp.h> 34 #include <linux/init.h> 35 #include <linux/ip.h> 36 #include <linux/tcp.h> 37 #include <linux/semaphore.h> 38 #include <linux/refcount.h> 39 40 #define SIXPACK_VERSION "Revision: 0.3.0" 41 42 /* sixpack priority commands */ 43 #define SIXP_SEOF 0x40 /* start and end of a 6pack frame */ 44 #define SIXP_TX_URUN 0x48 /* transmit overrun */ 45 #define SIXP_RX_ORUN 0x50 /* receive overrun */ 46 #define SIXP_RX_BUF_OVL 0x58 /* receive buffer overflow */ 47 48 #define SIXP_CHKSUM 0xFF /* valid checksum of a 6pack frame */ 49 50 /* masks to get certain bits out of the status bytes sent by the TNC */ 51 52 #define SIXP_CMD_MASK 0xC0 53 #define SIXP_CHN_MASK 0x07 54 #define SIXP_PRIO_CMD_MASK 0x80 55 #define SIXP_STD_CMD_MASK 0x40 56 #define SIXP_PRIO_DATA_MASK 0x38 57 #define SIXP_TX_MASK 0x20 58 #define SIXP_RX_MASK 0x10 59 #define SIXP_RX_DCD_MASK 0x18 60 #define SIXP_LEDS_ON 0x78 61 #define SIXP_LEDS_OFF 0x60 62 #define SIXP_CON 0x08 63 #define SIXP_STA 0x10 64 65 #define SIXP_FOUND_TNC 0xe9 66 #define SIXP_CON_ON 0x68 67 #define SIXP_DCD_MASK 0x08 68 #define SIXP_DAMA_OFF 0 69 70 /* default level 2 parameters */ 71 #define SIXP_TXDELAY 25 /* 250 ms */ 72 #define SIXP_PERSIST 50 /* in 256ths */ 73 #define SIXP_SLOTTIME 10 /* 100 ms */ 74 #define SIXP_INIT_RESYNC_TIMEOUT (3*HZ/2) /* in 1 s */ 75 #define SIXP_RESYNC_TIMEOUT 5*HZ /* in 1 s */ 76 77 /* 6pack configuration. */ 78 #define SIXP_NRUNIT 31 /* MAX number of 6pack channels */ 79 #define SIXP_MTU 256 /* Default MTU */ 80 81 enum sixpack_flags { 82 SIXPF_ERROR, /* Parity, etc. error */ 83 }; 84 85 struct sixpack { 86 /* Various fields. */ 87 struct tty_struct *tty; /* ptr to TTY structure */ 88 struct net_device *dev; /* easy for intr handling */ 89 90 /* These are pointers to the malloc()ed frame buffers. */ 91 unsigned char *rbuff; /* receiver buffer */ 92 int rcount; /* received chars counter */ 93 unsigned char *xbuff; /* transmitter buffer */ 94 unsigned char *xhead; /* next byte to XMIT */ 95 int xleft; /* bytes left in XMIT queue */ 96 97 unsigned char raw_buf[4]; 98 unsigned char cooked_buf[400]; 99 100 unsigned int rx_count; 101 unsigned int rx_count_cooked; 102 103 int mtu; /* Our mtu (to spot changes!) */ 104 int buffsize; /* Max buffers sizes */ 105 106 unsigned long flags; /* Flag values/ mode etc */ 107 unsigned char mode; /* 6pack mode */ 108 109 /* 6pack stuff */ 110 unsigned char tx_delay; 111 unsigned char persistence; 112 unsigned char slottime; 113 unsigned char duplex; 114 unsigned char led_state; 115 unsigned char status; 116 unsigned char status1; 117 unsigned char status2; 118 unsigned char tx_enable; 119 unsigned char tnc_state; 120 121 struct timer_list tx_t; 122 struct timer_list resync_t; 123 refcount_t refcnt; 124 struct completion dead; 125 spinlock_t lock; 126 }; 127 128 #define AX25_6PACK_HEADER_LEN 0 129 130 static void sixpack_decode(struct sixpack *, const unsigned char[], int); 131 static int encode_sixpack(unsigned char *, unsigned char *, int, unsigned char); 132 133 /* 134 * Perform the persistence/slottime algorithm for CSMA access. If the 135 * persistence check was successful, write the data to the serial driver. 136 * Note that in case of DAMA operation, the data is not sent here. 137 */ 138 139 static void sp_xmit_on_air(struct timer_list *t) 140 { 141 struct sixpack *sp = from_timer(sp, t, tx_t); 142 int actual, when = sp->slottime; 143 static unsigned char random; 144 145 random = random * 17 + 41; 146 147 if (((sp->status1 & SIXP_DCD_MASK) == 0) && (random < sp->persistence)) { 148 sp->led_state = 0x70; 149 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 150 sp->tx_enable = 1; 151 actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2); 152 sp->xleft -= actual; 153 sp->xhead += actual; 154 sp->led_state = 0x60; 155 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 156 sp->status2 = 0; 157 } else 158 mod_timer(&sp->tx_t, jiffies + ((when + 1) * HZ) / 100); 159 } 160 161 /* ----> 6pack timer interrupt handler and friends. <---- */ 162 163 /* Encapsulate one AX.25 frame and stuff into a TTY queue. */ 164 static void sp_encaps(struct sixpack *sp, unsigned char *icp, int len) 165 { 166 unsigned char *msg, *p = icp; 167 int actual, count; 168 169 if (len > sp->mtu) { /* sp->mtu = AX25_MTU = max. PACLEN = 256 */ 170 msg = "oversized transmit packet!"; 171 goto out_drop; 172 } 173 174 if (p[0] > 5) { 175 msg = "invalid KISS command"; 176 goto out_drop; 177 } 178 179 if ((p[0] != 0) && (len > 2)) { 180 msg = "KISS control packet too long"; 181 goto out_drop; 182 } 183 184 if ((p[0] == 0) && (len < 15)) { 185 msg = "bad AX.25 packet to transmit"; 186 goto out_drop; 187 } 188 189 count = encode_sixpack(p, sp->xbuff, len, sp->tx_delay); 190 set_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags); 191 192 switch (p[0]) { 193 case 1: sp->tx_delay = p[1]; 194 return; 195 case 2: sp->persistence = p[1]; 196 return; 197 case 3: sp->slottime = p[1]; 198 return; 199 case 4: /* ignored */ 200 return; 201 case 5: sp->duplex = p[1]; 202 return; 203 } 204 205 if (p[0] != 0) 206 return; 207 208 /* 209 * In case of fullduplex or DAMA operation, we don't take care about the 210 * state of the DCD or of any timers, as the determination of the 211 * correct time to send is the job of the AX.25 layer. We send 212 * immediately after data has arrived. 213 */ 214 if (sp->duplex == 1) { 215 sp->led_state = 0x70; 216 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 217 sp->tx_enable = 1; 218 actual = sp->tty->ops->write(sp->tty, sp->xbuff, count); 219 sp->xleft = count - actual; 220 sp->xhead = sp->xbuff + actual; 221 sp->led_state = 0x60; 222 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 223 } else { 224 sp->xleft = count; 225 sp->xhead = sp->xbuff; 226 sp->status2 = count; 227 sp_xmit_on_air(&sp->tx_t); 228 } 229 230 return; 231 232 out_drop: 233 sp->dev->stats.tx_dropped++; 234 netif_start_queue(sp->dev); 235 if (net_ratelimit()) 236 printk(KERN_DEBUG "%s: %s - dropped.\n", sp->dev->name, msg); 237 } 238 239 /* Encapsulate an IP datagram and kick it into a TTY queue. */ 240 241 static netdev_tx_t sp_xmit(struct sk_buff *skb, struct net_device *dev) 242 { 243 struct sixpack *sp = netdev_priv(dev); 244 245 if (skb->protocol == htons(ETH_P_IP)) 246 return ax25_ip_xmit(skb); 247 248 spin_lock_bh(&sp->lock); 249 /* We were not busy, so we are now... :-) */ 250 netif_stop_queue(dev); 251 dev->stats.tx_bytes += skb->len; 252 sp_encaps(sp, skb->data, skb->len); 253 spin_unlock_bh(&sp->lock); 254 255 dev_kfree_skb(skb); 256 257 return NETDEV_TX_OK; 258 } 259 260 static int sp_open_dev(struct net_device *dev) 261 { 262 struct sixpack *sp = netdev_priv(dev); 263 264 if (sp->tty == NULL) 265 return -ENODEV; 266 return 0; 267 } 268 269 /* Close the low-level part of the 6pack channel. */ 270 static int sp_close(struct net_device *dev) 271 { 272 struct sixpack *sp = netdev_priv(dev); 273 274 spin_lock_bh(&sp->lock); 275 if (sp->tty) { 276 /* TTY discipline is running. */ 277 clear_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags); 278 } 279 netif_stop_queue(dev); 280 spin_unlock_bh(&sp->lock); 281 282 return 0; 283 } 284 285 static int sp_set_mac_address(struct net_device *dev, void *addr) 286 { 287 struct sockaddr_ax25 *sa = addr; 288 289 netif_tx_lock_bh(dev); 290 netif_addr_lock(dev); 291 __dev_addr_set(dev, &sa->sax25_call, AX25_ADDR_LEN); 292 netif_addr_unlock(dev); 293 netif_tx_unlock_bh(dev); 294 295 return 0; 296 } 297 298 static const struct net_device_ops sp_netdev_ops = { 299 .ndo_open = sp_open_dev, 300 .ndo_stop = sp_close, 301 .ndo_start_xmit = sp_xmit, 302 .ndo_set_mac_address = sp_set_mac_address, 303 }; 304 305 static void sp_setup(struct net_device *dev) 306 { 307 /* Finish setting up the DEVICE info. */ 308 dev->netdev_ops = &sp_netdev_ops; 309 dev->mtu = SIXP_MTU; 310 dev->hard_header_len = AX25_MAX_HEADER_LEN; 311 dev->header_ops = &ax25_header_ops; 312 313 dev->addr_len = AX25_ADDR_LEN; 314 dev->type = ARPHRD_AX25; 315 dev->tx_queue_len = 10; 316 317 /* Only activated in AX.25 mode */ 318 memcpy(dev->broadcast, &ax25_bcast, AX25_ADDR_LEN); 319 dev_addr_set(dev, (u8 *)&ax25_defaddr); 320 321 dev->flags = 0; 322 } 323 324 /* Send one completely decapsulated IP datagram to the IP layer. */ 325 326 /* 327 * This is the routine that sends the received data to the kernel AX.25. 328 * 'cmd' is the KISS command. For AX.25 data, it is zero. 329 */ 330 331 static void sp_bump(struct sixpack *sp, char cmd) 332 { 333 struct sk_buff *skb; 334 int count; 335 unsigned char *ptr; 336 337 count = sp->rcount + 1; 338 339 sp->dev->stats.rx_bytes += count; 340 341 if ((skb = dev_alloc_skb(count + 1)) == NULL) 342 goto out_mem; 343 344 ptr = skb_put(skb, count + 1); 345 *ptr++ = cmd; /* KISS command */ 346 347 memcpy(ptr, sp->cooked_buf + 1, count); 348 skb->protocol = ax25_type_trans(skb, sp->dev); 349 netif_rx(skb); 350 sp->dev->stats.rx_packets++; 351 352 return; 353 354 out_mem: 355 sp->dev->stats.rx_dropped++; 356 } 357 358 359 /* ----------------------------------------------------------------------- */ 360 361 /* 362 * We have a potential race on dereferencing tty->disc_data, because the tty 363 * layer provides no locking at all - thus one cpu could be running 364 * sixpack_receive_buf while another calls sixpack_close, which zeroes 365 * tty->disc_data and frees the memory that sixpack_receive_buf is using. The 366 * best way to fix this is to use a rwlock in the tty struct, but for now we 367 * use a single global rwlock for all ttys in ppp line discipline. 368 */ 369 static DEFINE_RWLOCK(disc_data_lock); 370 371 static struct sixpack *sp_get(struct tty_struct *tty) 372 { 373 struct sixpack *sp; 374 375 read_lock(&disc_data_lock); 376 sp = tty->disc_data; 377 if (sp) 378 refcount_inc(&sp->refcnt); 379 read_unlock(&disc_data_lock); 380 381 return sp; 382 } 383 384 static void sp_put(struct sixpack *sp) 385 { 386 if (refcount_dec_and_test(&sp->refcnt)) 387 complete(&sp->dead); 388 } 389 390 /* 391 * Called by the TTY driver when there's room for more data. If we have 392 * more packets to send, we send them here. 393 */ 394 static void sixpack_write_wakeup(struct tty_struct *tty) 395 { 396 struct sixpack *sp = sp_get(tty); 397 int actual; 398 399 if (!sp) 400 return; 401 if (sp->xleft <= 0) { 402 /* Now serial buffer is almost free & we can start 403 * transmission of another packet */ 404 sp->dev->stats.tx_packets++; 405 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 406 sp->tx_enable = 0; 407 netif_wake_queue(sp->dev); 408 goto out; 409 } 410 411 if (sp->tx_enable) { 412 actual = tty->ops->write(tty, sp->xhead, sp->xleft); 413 sp->xleft -= actual; 414 sp->xhead += actual; 415 } 416 417 out: 418 sp_put(sp); 419 } 420 421 /* ----------------------------------------------------------------------- */ 422 423 /* 424 * Handle the 'receiver data ready' interrupt. 425 * This function is called by the tty module in the kernel when 426 * a block of 6pack data has been received, which can now be decapsulated 427 * and sent on to some IP layer for further processing. 428 */ 429 static void sixpack_receive_buf(struct tty_struct *tty, 430 const unsigned char *cp, const char *fp, int count) 431 { 432 struct sixpack *sp; 433 int count1; 434 435 if (!count) 436 return; 437 438 sp = sp_get(tty); 439 if (!sp) 440 return; 441 442 /* Read the characters out of the buffer */ 443 count1 = count; 444 while (count) { 445 count--; 446 if (fp && *fp++) { 447 if (!test_and_set_bit(SIXPF_ERROR, &sp->flags)) 448 sp->dev->stats.rx_errors++; 449 continue; 450 } 451 } 452 sixpack_decode(sp, cp, count1); 453 454 sp_put(sp); 455 tty_unthrottle(tty); 456 } 457 458 /* 459 * Try to resync the TNC. Called by the resync timer defined in 460 * decode_prio_command 461 */ 462 463 #define TNC_UNINITIALIZED 0 464 #define TNC_UNSYNC_STARTUP 1 465 #define TNC_UNSYNCED 2 466 #define TNC_IN_SYNC 3 467 468 static void __tnc_set_sync_state(struct sixpack *sp, int new_tnc_state) 469 { 470 char *msg; 471 472 switch (new_tnc_state) { 473 default: /* gcc oh piece-o-crap ... */ 474 case TNC_UNSYNC_STARTUP: 475 msg = "Synchronizing with TNC"; 476 break; 477 case TNC_UNSYNCED: 478 msg = "Lost synchronization with TNC\n"; 479 break; 480 case TNC_IN_SYNC: 481 msg = "Found TNC"; 482 break; 483 } 484 485 sp->tnc_state = new_tnc_state; 486 printk(KERN_INFO "%s: %s\n", sp->dev->name, msg); 487 } 488 489 static inline void tnc_set_sync_state(struct sixpack *sp, int new_tnc_state) 490 { 491 int old_tnc_state = sp->tnc_state; 492 493 if (old_tnc_state != new_tnc_state) 494 __tnc_set_sync_state(sp, new_tnc_state); 495 } 496 497 static void resync_tnc(struct timer_list *t) 498 { 499 struct sixpack *sp = from_timer(sp, t, resync_t); 500 static char resync_cmd = 0xe8; 501 502 /* clear any data that might have been received */ 503 504 sp->rx_count = 0; 505 sp->rx_count_cooked = 0; 506 507 /* reset state machine */ 508 509 sp->status = 1; 510 sp->status1 = 1; 511 sp->status2 = 0; 512 513 /* resync the TNC */ 514 515 sp->led_state = 0x60; 516 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 517 sp->tty->ops->write(sp->tty, &resync_cmd, 1); 518 519 520 /* Start resync timer again -- the TNC might be still absent */ 521 mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT); 522 } 523 524 static inline int tnc_init(struct sixpack *sp) 525 { 526 unsigned char inbyte = 0xe8; 527 528 tnc_set_sync_state(sp, TNC_UNSYNC_STARTUP); 529 530 sp->tty->ops->write(sp->tty, &inbyte, 1); 531 532 mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT); 533 534 return 0; 535 } 536 537 /* 538 * Open the high-level part of the 6pack channel. 539 * This function is called by the TTY module when the 540 * 6pack line discipline is called for. Because we are 541 * sure the tty line exists, we only have to link it to 542 * a free 6pcack channel... 543 */ 544 static int sixpack_open(struct tty_struct *tty) 545 { 546 char *rbuff = NULL, *xbuff = NULL; 547 struct net_device *dev; 548 struct sixpack *sp; 549 unsigned long len; 550 int err = 0; 551 552 if (!capable(CAP_NET_ADMIN)) 553 return -EPERM; 554 if (tty->ops->write == NULL) 555 return -EOPNOTSUPP; 556 557 dev = alloc_netdev(sizeof(struct sixpack), "sp%d", NET_NAME_UNKNOWN, 558 sp_setup); 559 if (!dev) { 560 err = -ENOMEM; 561 goto out; 562 } 563 564 sp = netdev_priv(dev); 565 sp->dev = dev; 566 567 spin_lock_init(&sp->lock); 568 refcount_set(&sp->refcnt, 1); 569 init_completion(&sp->dead); 570 571 /* !!! length of the buffers. MTU is IP MTU, not PACLEN! */ 572 573 len = dev->mtu * 2; 574 575 rbuff = kmalloc(len + 4, GFP_KERNEL); 576 xbuff = kmalloc(len + 4, GFP_KERNEL); 577 578 if (rbuff == NULL || xbuff == NULL) { 579 err = -ENOBUFS; 580 goto out_free; 581 } 582 583 spin_lock_bh(&sp->lock); 584 585 sp->tty = tty; 586 587 sp->rbuff = rbuff; 588 sp->xbuff = xbuff; 589 590 sp->mtu = AX25_MTU + 73; 591 sp->buffsize = len; 592 sp->rcount = 0; 593 sp->rx_count = 0; 594 sp->rx_count_cooked = 0; 595 sp->xleft = 0; 596 597 sp->flags = 0; /* Clear ESCAPE & ERROR flags */ 598 599 sp->duplex = 0; 600 sp->tx_delay = SIXP_TXDELAY; 601 sp->persistence = SIXP_PERSIST; 602 sp->slottime = SIXP_SLOTTIME; 603 sp->led_state = 0x60; 604 sp->status = 1; 605 sp->status1 = 1; 606 sp->status2 = 0; 607 sp->tx_enable = 0; 608 609 netif_start_queue(dev); 610 611 timer_setup(&sp->tx_t, sp_xmit_on_air, 0); 612 613 timer_setup(&sp->resync_t, resync_tnc, 0); 614 615 spin_unlock_bh(&sp->lock); 616 617 /* Done. We have linked the TTY line to a channel. */ 618 tty->disc_data = sp; 619 tty->receive_room = 65536; 620 621 /* Now we're ready to register. */ 622 err = register_netdev(dev); 623 if (err) 624 goto out_free; 625 626 tnc_init(sp); 627 628 return 0; 629 630 out_free: 631 kfree(xbuff); 632 kfree(rbuff); 633 634 free_netdev(dev); 635 636 out: 637 return err; 638 } 639 640 641 /* 642 * Close down a 6pack channel. 643 * This means flushing out any pending queues, and then restoring the 644 * TTY line discipline to what it was before it got hooked to 6pack 645 * (which usually is TTY again). 646 */ 647 static void sixpack_close(struct tty_struct *tty) 648 { 649 struct sixpack *sp; 650 651 write_lock_irq(&disc_data_lock); 652 sp = tty->disc_data; 653 tty->disc_data = NULL; 654 write_unlock_irq(&disc_data_lock); 655 if (!sp) 656 return; 657 658 /* 659 * We have now ensured that nobody can start using ap from now on, but 660 * we have to wait for all existing users to finish. 661 */ 662 if (!refcount_dec_and_test(&sp->refcnt)) 663 wait_for_completion(&sp->dead); 664 665 /* We must stop the queue to avoid potentially scribbling 666 * on the free buffers. The sp->dead completion is not sufficient 667 * to protect us from sp->xbuff access. 668 */ 669 netif_stop_queue(sp->dev); 670 671 unregister_netdev(sp->dev); 672 673 del_timer_sync(&sp->tx_t); 674 del_timer_sync(&sp->resync_t); 675 676 /* Free all 6pack frame buffers after unreg. */ 677 kfree(sp->rbuff); 678 kfree(sp->xbuff); 679 680 free_netdev(sp->dev); 681 } 682 683 /* Perform I/O control on an active 6pack channel. */ 684 static int sixpack_ioctl(struct tty_struct *tty, unsigned int cmd, 685 unsigned long arg) 686 { 687 struct sixpack *sp = sp_get(tty); 688 struct net_device *dev; 689 unsigned int tmp, err; 690 691 if (!sp) 692 return -ENXIO; 693 dev = sp->dev; 694 695 switch(cmd) { 696 case SIOCGIFNAME: 697 err = copy_to_user((void __user *) arg, dev->name, 698 strlen(dev->name) + 1) ? -EFAULT : 0; 699 break; 700 701 case SIOCGIFENCAP: 702 err = put_user(0, (int __user *) arg); 703 break; 704 705 case SIOCSIFENCAP: 706 if (get_user(tmp, (int __user *) arg)) { 707 err = -EFAULT; 708 break; 709 } 710 711 sp->mode = tmp; 712 dev->addr_len = AX25_ADDR_LEN; 713 dev->hard_header_len = AX25_KISS_HEADER_LEN + 714 AX25_MAX_HEADER_LEN + 3; 715 dev->type = ARPHRD_AX25; 716 717 err = 0; 718 break; 719 720 case SIOCSIFHWADDR: { 721 char addr[AX25_ADDR_LEN]; 722 723 if (copy_from_user(&addr, 724 (void __user *)arg, AX25_ADDR_LEN)) { 725 err = -EFAULT; 726 break; 727 } 728 729 netif_tx_lock_bh(dev); 730 __dev_addr_set(dev, &addr, AX25_ADDR_LEN); 731 netif_tx_unlock_bh(dev); 732 err = 0; 733 break; 734 } 735 default: 736 err = tty_mode_ioctl(tty, cmd, arg); 737 } 738 739 sp_put(sp); 740 741 return err; 742 } 743 744 static struct tty_ldisc_ops sp_ldisc = { 745 .owner = THIS_MODULE, 746 .num = N_6PACK, 747 .name = "6pack", 748 .open = sixpack_open, 749 .close = sixpack_close, 750 .ioctl = sixpack_ioctl, 751 .receive_buf = sixpack_receive_buf, 752 .write_wakeup = sixpack_write_wakeup, 753 }; 754 755 /* Initialize 6pack control device -- register 6pack line discipline */ 756 757 static const char msg_banner[] __initconst = KERN_INFO \ 758 "AX.25: 6pack driver, " SIXPACK_VERSION "\n"; 759 static const char msg_regfail[] __initconst = KERN_ERR \ 760 "6pack: can't register line discipline (err = %d)\n"; 761 762 static int __init sixpack_init_driver(void) 763 { 764 int status; 765 766 printk(msg_banner); 767 768 /* Register the provided line protocol discipline */ 769 status = tty_register_ldisc(&sp_ldisc); 770 if (status) 771 printk(msg_regfail, status); 772 773 return status; 774 } 775 776 static void __exit sixpack_exit_driver(void) 777 { 778 tty_unregister_ldisc(&sp_ldisc); 779 } 780 781 /* encode an AX.25 packet into 6pack */ 782 783 static int encode_sixpack(unsigned char *tx_buf, unsigned char *tx_buf_raw, 784 int length, unsigned char tx_delay) 785 { 786 int count = 0; 787 unsigned char checksum = 0, buf[400]; 788 int raw_count = 0; 789 790 tx_buf_raw[raw_count++] = SIXP_PRIO_CMD_MASK | SIXP_TX_MASK; 791 tx_buf_raw[raw_count++] = SIXP_SEOF; 792 793 buf[0] = tx_delay; 794 for (count = 1; count < length; count++) 795 buf[count] = tx_buf[count]; 796 797 for (count = 0; count < length; count++) 798 checksum += buf[count]; 799 buf[length] = (unsigned char) 0xff - checksum; 800 801 for (count = 0; count <= length; count++) { 802 if ((count % 3) == 0) { 803 tx_buf_raw[raw_count++] = (buf[count] & 0x3f); 804 tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x30); 805 } else if ((count % 3) == 1) { 806 tx_buf_raw[raw_count++] |= (buf[count] & 0x0f); 807 tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x3c); 808 } else { 809 tx_buf_raw[raw_count++] |= (buf[count] & 0x03); 810 tx_buf_raw[raw_count++] = (buf[count] >> 2); 811 } 812 } 813 if ((length % 3) != 2) 814 raw_count++; 815 tx_buf_raw[raw_count++] = SIXP_SEOF; 816 return raw_count; 817 } 818 819 /* decode 4 sixpack-encoded bytes into 3 data bytes */ 820 821 static void decode_data(struct sixpack *sp, unsigned char inbyte) 822 { 823 unsigned char *buf; 824 825 if (sp->rx_count != 3) { 826 sp->raw_buf[sp->rx_count++] = inbyte; 827 828 return; 829 } 830 831 if (sp->rx_count_cooked + 2 >= sizeof(sp->cooked_buf)) { 832 pr_err("6pack: cooked buffer overrun, data loss\n"); 833 sp->rx_count = 0; 834 return; 835 } 836 837 buf = sp->raw_buf; 838 sp->cooked_buf[sp->rx_count_cooked++] = 839 buf[0] | ((buf[1] << 2) & 0xc0); 840 sp->cooked_buf[sp->rx_count_cooked++] = 841 (buf[1] & 0x0f) | ((buf[2] << 2) & 0xf0); 842 sp->cooked_buf[sp->rx_count_cooked++] = 843 (buf[2] & 0x03) | (inbyte << 2); 844 sp->rx_count = 0; 845 } 846 847 /* identify and execute a 6pack priority command byte */ 848 849 static void decode_prio_command(struct sixpack *sp, unsigned char cmd) 850 { 851 int actual; 852 853 if ((cmd & SIXP_PRIO_DATA_MASK) != 0) { /* idle ? */ 854 855 /* RX and DCD flags can only be set in the same prio command, 856 if the DCD flag has been set without the RX flag in the previous 857 prio command. If DCD has not been set before, something in the 858 transmission has gone wrong. In this case, RX and DCD are 859 cleared in order to prevent the decode_data routine from 860 reading further data that might be corrupt. */ 861 862 if (((sp->status & SIXP_DCD_MASK) == 0) && 863 ((cmd & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)) { 864 if (sp->status != 1) 865 printk(KERN_DEBUG "6pack: protocol violation\n"); 866 else 867 sp->status = 0; 868 cmd &= ~SIXP_RX_DCD_MASK; 869 } 870 sp->status = cmd & SIXP_PRIO_DATA_MASK; 871 } else { /* output watchdog char if idle */ 872 if ((sp->status2 != 0) && (sp->duplex == 1)) { 873 sp->led_state = 0x70; 874 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 875 sp->tx_enable = 1; 876 actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2); 877 sp->xleft -= actual; 878 sp->xhead += actual; 879 sp->led_state = 0x60; 880 sp->status2 = 0; 881 882 } 883 } 884 885 /* needed to trigger the TNC watchdog */ 886 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 887 888 /* if the state byte has been received, the TNC is present, 889 so the resync timer can be reset. */ 890 891 if (sp->tnc_state == TNC_IN_SYNC) 892 mod_timer(&sp->resync_t, jiffies + SIXP_INIT_RESYNC_TIMEOUT); 893 894 sp->status1 = cmd & SIXP_PRIO_DATA_MASK; 895 } 896 897 /* identify and execute a standard 6pack command byte */ 898 899 static void decode_std_command(struct sixpack *sp, unsigned char cmd) 900 { 901 unsigned char checksum = 0, rest = 0; 902 short i; 903 904 switch (cmd & SIXP_CMD_MASK) { /* normal command */ 905 case SIXP_SEOF: 906 if ((sp->rx_count == 0) && (sp->rx_count_cooked == 0)) { 907 if ((sp->status & SIXP_RX_DCD_MASK) == 908 SIXP_RX_DCD_MASK) { 909 sp->led_state = 0x68; 910 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 911 } 912 } else { 913 sp->led_state = 0x60; 914 /* fill trailing bytes with zeroes */ 915 sp->tty->ops->write(sp->tty, &sp->led_state, 1); 916 rest = sp->rx_count; 917 if (rest != 0) 918 for (i = rest; i <= 3; i++) 919 decode_data(sp, 0); 920 if (rest == 2) 921 sp->rx_count_cooked -= 2; 922 else if (rest == 3) 923 sp->rx_count_cooked -= 1; 924 for (i = 0; i < sp->rx_count_cooked; i++) 925 checksum += sp->cooked_buf[i]; 926 if (checksum != SIXP_CHKSUM) { 927 printk(KERN_DEBUG "6pack: bad checksum %2.2x\n", checksum); 928 } else { 929 sp->rcount = sp->rx_count_cooked-2; 930 sp_bump(sp, 0); 931 } 932 sp->rx_count_cooked = 0; 933 } 934 break; 935 case SIXP_TX_URUN: printk(KERN_DEBUG "6pack: TX underrun\n"); 936 break; 937 case SIXP_RX_ORUN: printk(KERN_DEBUG "6pack: RX overrun\n"); 938 break; 939 case SIXP_RX_BUF_OVL: 940 printk(KERN_DEBUG "6pack: RX buffer overflow\n"); 941 } 942 } 943 944 /* decode a 6pack packet */ 945 946 static void 947 sixpack_decode(struct sixpack *sp, const unsigned char *pre_rbuff, int count) 948 { 949 unsigned char inbyte; 950 int count1; 951 952 for (count1 = 0; count1 < count; count1++) { 953 inbyte = pre_rbuff[count1]; 954 if (inbyte == SIXP_FOUND_TNC) { 955 tnc_set_sync_state(sp, TNC_IN_SYNC); 956 del_timer(&sp->resync_t); 957 } 958 if ((inbyte & SIXP_PRIO_CMD_MASK) != 0) 959 decode_prio_command(sp, inbyte); 960 else if ((inbyte & SIXP_STD_CMD_MASK) != 0) 961 decode_std_command(sp, inbyte); 962 else if ((sp->status & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK) 963 decode_data(sp, inbyte); 964 } 965 } 966 967 MODULE_AUTHOR("Ralf Baechle DO1GRB <ralf@linux-mips.org>"); 968 MODULE_DESCRIPTION("6pack driver for AX.25"); 969 MODULE_LICENSE("GPL"); 970 MODULE_ALIAS_LDISC(N_6PACK); 971 972 module_init(sixpack_init_driver); 973 module_exit(sixpack_exit_driver); 974