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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/* sixpack priority commands */
41#define SIXP_SEOF 0x40 /* start and end of a 6pack frame */
42#define SIXP_TX_URUN 0x48 /* transmit overrun */
43#define SIXP_RX_ORUN 0x50 /* receive overrun */
44#define SIXP_RX_BUF_OVL 0x58 /* receive buffer overflow */
45
46#define SIXP_CHKSUM 0xFF /* valid checksum of a 6pack frame */
47
48/* masks to get certain bits out of the status bytes sent by the TNC */
49
50#define SIXP_CMD_MASK 0xC0
51#define SIXP_CHN_MASK 0x07
52#define SIXP_PRIO_CMD_MASK 0x80
53#define SIXP_STD_CMD_MASK 0x40
54#define SIXP_PRIO_DATA_MASK 0x38
55#define SIXP_TX_MASK 0x20
56#define SIXP_RX_MASK 0x10
57#define SIXP_RX_DCD_MASK 0x18
58#define SIXP_LEDS_ON 0x78
59#define SIXP_LEDS_OFF 0x60
60#define SIXP_CON 0x08
61#define SIXP_STA 0x10
62
63#define SIXP_FOUND_TNC 0xe9
64#define SIXP_CON_ON 0x68
65#define SIXP_DCD_MASK 0x08
66#define SIXP_DAMA_OFF 0
67
68/* default level 2 parameters */
69#define SIXP_TXDELAY 25 /* 250 ms */
70#define SIXP_PERSIST 50 /* in 256ths */
71#define SIXP_SLOTTIME 10 /* 100 ms */
72#define SIXP_INIT_RESYNC_TIMEOUT (3*HZ/2) /* in 1 s */
73#define SIXP_RESYNC_TIMEOUT 5*HZ /* in 1 s */
74
75/* 6pack configuration. */
76#define SIXP_NRUNIT 31 /* MAX number of 6pack channels */
77#define SIXP_MTU 256 /* Default MTU */
78
79enum sixpack_flags {
80 SIXPF_ERROR, /* Parity, etc. error */
81};
82
83struct sixpack {
84 /* Various fields. */
85 struct tty_struct *tty; /* ptr to TTY structure */
86 struct net_device *dev; /* easy for intr handling */
87
88 /* These are pointers to the malloc()ed frame buffers. */
89 int rcount; /* received chars counter */
90 unsigned char *xbuff; /* transmitter buffer */
91 unsigned char *xhead; /* next byte to XMIT */
92 int xleft; /* bytes left in XMIT queue */
93
94 u8 raw_buf[4];
95 u8 cooked_buf[400];
96
97 unsigned int rx_count;
98 unsigned int rx_count_cooked;
99 spinlock_t rxlock;
100
101 unsigned long flags; /* Flag values/ mode etc */
102 unsigned char mode; /* 6pack mode */
103
104 /* 6pack stuff */
105 unsigned char tx_delay;
106 unsigned char persistence;
107 unsigned char slottime;
108 unsigned char duplex;
109 unsigned char led_state;
110 u8 status;
111 u8 status1;
112 unsigned char status2;
113 unsigned char tx_enable;
114 unsigned char tnc_state;
115
116 struct timer_list tx_t;
117 struct timer_list resync_t;
118 refcount_t refcnt;
119 struct completion dead;
120 spinlock_t lock;
121};
122
123#define AX25_6PACK_HEADER_LEN 0
124
125static void sixpack_decode(struct sixpack *, const u8 *, size_t);
126static int encode_sixpack(unsigned char *, unsigned char *, int, unsigned char);
127
128/*
129 * Perform the persistence/slottime algorithm for CSMA access. If the
130 * persistence check was successful, write the data to the serial driver.
131 * Note that in case of DAMA operation, the data is not sent here.
132 */
133
134static void sp_xmit_on_air(struct timer_list *t)
135{
136 struct sixpack *sp = from_timer(sp, t, tx_t);
137 int actual, when = sp->slottime;
138 static unsigned char random;
139
140 random = random * 17 + 41;
141
142 if (((sp->status1 & SIXP_DCD_MASK) == 0) && (random < sp->persistence)) {
143 sp->led_state = 0x70;
144 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
145 sp->tx_enable = 1;
146 actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
147 sp->xleft -= actual;
148 sp->xhead += actual;
149 sp->led_state = 0x60;
150 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
151 sp->status2 = 0;
152 } else
153 mod_timer(&sp->tx_t, jiffies + ((when + 1) * HZ) / 100);
154}
155
156/* ----> 6pack timer interrupt handler and friends. <---- */
157
158/* Encapsulate one AX.25 frame and stuff into a TTY queue. */
159static void sp_encaps(struct sixpack *sp, unsigned char *icp, int len)
160{
161 unsigned char *msg, *p = icp;
162 int actual, count;
163
164 if (len > AX25_MTU + 73) {
165 msg = "oversized transmit packet!";
166 goto out_drop;
167 }
168
169 if (p[0] > 5) {
170 msg = "invalid KISS command";
171 goto out_drop;
172 }
173
174 if ((p[0] != 0) && (len > 2)) {
175 msg = "KISS control packet too long";
176 goto out_drop;
177 }
178
179 if ((p[0] == 0) && (len < 15)) {
180 msg = "bad AX.25 packet to transmit";
181 goto out_drop;
182 }
183
184 count = encode_sixpack(p, sp->xbuff, len, sp->tx_delay);
185 set_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
186
187 switch (p[0]) {
188 case 1: sp->tx_delay = p[1];
189 return;
190 case 2: sp->persistence = p[1];
191 return;
192 case 3: sp->slottime = p[1];
193 return;
194 case 4: /* ignored */
195 return;
196 case 5: sp->duplex = p[1];
197 return;
198 }
199
200 if (p[0] != 0)
201 return;
202
203 /*
204 * In case of fullduplex or DAMA operation, we don't take care about the
205 * state of the DCD or of any timers, as the determination of the
206 * correct time to send is the job of the AX.25 layer. We send
207 * immediately after data has arrived.
208 */
209 if (sp->duplex == 1) {
210 sp->led_state = 0x70;
211 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
212 sp->tx_enable = 1;
213 actual = sp->tty->ops->write(sp->tty, sp->xbuff, count);
214 sp->xleft = count - actual;
215 sp->xhead = sp->xbuff + actual;
216 sp->led_state = 0x60;
217 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
218 } else {
219 sp->xleft = count;
220 sp->xhead = sp->xbuff;
221 sp->status2 = count;
222 sp_xmit_on_air(&sp->tx_t);
223 }
224
225 return;
226
227out_drop:
228 sp->dev->stats.tx_dropped++;
229 netif_start_queue(sp->dev);
230 if (net_ratelimit())
231 printk(KERN_DEBUG "%s: %s - dropped.\n", sp->dev->name, msg);
232}
233
234/* Encapsulate an IP datagram and kick it into a TTY queue. */
235
236static netdev_tx_t sp_xmit(struct sk_buff *skb, struct net_device *dev)
237{
238 struct sixpack *sp = netdev_priv(dev);
239
240 if (skb->protocol == htons(ETH_P_IP))
241 return ax25_ip_xmit(skb);
242
243 spin_lock_bh(&sp->lock);
244 /* We were not busy, so we are now... :-) */
245 netif_stop_queue(dev);
246 dev->stats.tx_bytes += skb->len;
247 sp_encaps(sp, skb->data, skb->len);
248 spin_unlock_bh(&sp->lock);
249
250 dev_kfree_skb(skb);
251
252 return NETDEV_TX_OK;
253}
254
255static int sp_open_dev(struct net_device *dev)
256{
257 struct sixpack *sp = netdev_priv(dev);
258
259 if (sp->tty == NULL)
260 return -ENODEV;
261 return 0;
262}
263
264/* Close the low-level part of the 6pack channel. */
265static int sp_close(struct net_device *dev)
266{
267 struct sixpack *sp = netdev_priv(dev);
268
269 spin_lock_bh(&sp->lock);
270 if (sp->tty) {
271 /* TTY discipline is running. */
272 clear_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
273 }
274 netif_stop_queue(dev);
275 spin_unlock_bh(&sp->lock);
276
277 return 0;
278}
279
280static int sp_set_mac_address(struct net_device *dev, void *addr)
281{
282 struct sockaddr_ax25 *sa = addr;
283
284 netif_tx_lock_bh(dev);
285 netif_addr_lock(dev);
286 __dev_addr_set(dev, &sa->sax25_call, AX25_ADDR_LEN);
287 netif_addr_unlock(dev);
288 netif_tx_unlock_bh(dev);
289
290 return 0;
291}
292
293static const struct net_device_ops sp_netdev_ops = {
294 .ndo_open = sp_open_dev,
295 .ndo_stop = sp_close,
296 .ndo_start_xmit = sp_xmit,
297 .ndo_set_mac_address = sp_set_mac_address,
298};
299
300static void sp_setup(struct net_device *dev)
301{
302 /* Finish setting up the DEVICE info. */
303 dev->netdev_ops = &sp_netdev_ops;
304 dev->mtu = SIXP_MTU;
305 dev->hard_header_len = AX25_MAX_HEADER_LEN;
306 dev->header_ops = &ax25_header_ops;
307
308 dev->addr_len = AX25_ADDR_LEN;
309 dev->type = ARPHRD_AX25;
310 dev->tx_queue_len = 10;
311
312 /* Only activated in AX.25 mode */
313 memcpy(dev->broadcast, &ax25_bcast, AX25_ADDR_LEN);
314 dev_addr_set(dev, (u8 *)&ax25_defaddr);
315
316 dev->flags = 0;
317}
318
319/* Send one completely decapsulated IP datagram to the IP layer. */
320
321/*
322 * This is the routine that sends the received data to the kernel AX.25.
323 * 'cmd' is the KISS command. For AX.25 data, it is zero.
324 */
325
326static void sp_bump(struct sixpack *sp, char cmd)
327{
328 struct sk_buff *skb;
329 int count;
330 u8 *ptr;
331
332 count = sp->rcount + 1;
333
334 sp->dev->stats.rx_bytes += count;
335
336 if ((skb = dev_alloc_skb(count + 1)) == NULL)
337 goto out_mem;
338
339 ptr = skb_put(skb, count + 1);
340 *ptr++ = cmd; /* KISS command */
341
342 memcpy(ptr, sp->cooked_buf + 1, count);
343 skb->protocol = ax25_type_trans(skb, sp->dev);
344 netif_rx(skb);
345 sp->dev->stats.rx_packets++;
346
347 return;
348
349out_mem:
350 sp->dev->stats.rx_dropped++;
351}
352
353
354/* ----------------------------------------------------------------------- */
355
356/*
357 * We have a potential race on dereferencing tty->disc_data, because the tty
358 * layer provides no locking at all - thus one cpu could be running
359 * sixpack_receive_buf while another calls sixpack_close, which zeroes
360 * tty->disc_data and frees the memory that sixpack_receive_buf is using. The
361 * best way to fix this is to use a rwlock in the tty struct, but for now we
362 * use a single global rwlock for all ttys in ppp line discipline.
363 */
364static DEFINE_RWLOCK(disc_data_lock);
365
366static struct sixpack *sp_get(struct tty_struct *tty)
367{
368 struct sixpack *sp;
369
370 read_lock(&disc_data_lock);
371 sp = tty->disc_data;
372 if (sp)
373 refcount_inc(&sp->refcnt);
374 read_unlock(&disc_data_lock);
375
376 return sp;
377}
378
379static void sp_put(struct sixpack *sp)
380{
381 if (refcount_dec_and_test(&sp->refcnt))
382 complete(&sp->dead);
383}
384
385/*
386 * Called by the TTY driver when there's room for more data. If we have
387 * more packets to send, we send them here.
388 */
389static void sixpack_write_wakeup(struct tty_struct *tty)
390{
391 struct sixpack *sp = sp_get(tty);
392 int actual;
393
394 if (!sp)
395 return;
396 if (sp->xleft <= 0) {
397 /* Now serial buffer is almost free & we can start
398 * transmission of another packet */
399 sp->dev->stats.tx_packets++;
400 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
401 sp->tx_enable = 0;
402 netif_wake_queue(sp->dev);
403 goto out;
404 }
405
406 if (sp->tx_enable) {
407 actual = tty->ops->write(tty, sp->xhead, sp->xleft);
408 sp->xleft -= actual;
409 sp->xhead += actual;
410 }
411
412out:
413 sp_put(sp);
414}
415
416/* ----------------------------------------------------------------------- */
417
418/*
419 * Handle the 'receiver data ready' interrupt.
420 * This function is called by the tty module in the kernel when
421 * a block of 6pack data has been received, which can now be decapsulated
422 * and sent on to some IP layer for further processing.
423 */
424static void sixpack_receive_buf(struct tty_struct *tty, const u8 *cp,
425 const u8 *fp, size_t count)
426{
427 struct sixpack *sp;
428 size_t count1;
429
430 if (!count)
431 return;
432
433 sp = sp_get(tty);
434 if (!sp)
435 return;
436
437 /* Read the characters out of the buffer */
438 count1 = count;
439 while (count) {
440 count--;
441 if (fp && *fp++) {
442 if (!test_and_set_bit(SIXPF_ERROR, &sp->flags))
443 sp->dev->stats.rx_errors++;
444 continue;
445 }
446 }
447 sixpack_decode(sp, cp, count1);
448
449 sp_put(sp);
450 tty_unthrottle(tty);
451}
452
453/*
454 * Try to resync the TNC. Called by the resync timer defined in
455 * decode_prio_command
456 */
457
458#define TNC_UNINITIALIZED 0
459#define TNC_UNSYNC_STARTUP 1
460#define TNC_UNSYNCED 2
461#define TNC_IN_SYNC 3
462
463static void __tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
464{
465 char *msg;
466
467 switch (new_tnc_state) {
468 default: /* gcc oh piece-o-crap ... */
469 case TNC_UNSYNC_STARTUP:
470 msg = "Synchronizing with TNC";
471 break;
472 case TNC_UNSYNCED:
473 msg = "Lost synchronization with TNC\n";
474 break;
475 case TNC_IN_SYNC:
476 msg = "Found TNC";
477 break;
478 }
479
480 sp->tnc_state = new_tnc_state;
481 printk(KERN_INFO "%s: %s\n", sp->dev->name, msg);
482}
483
484static inline void tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
485{
486 int old_tnc_state = sp->tnc_state;
487
488 if (old_tnc_state != new_tnc_state)
489 __tnc_set_sync_state(sp, new_tnc_state);
490}
491
492static void resync_tnc(struct timer_list *t)
493{
494 struct sixpack *sp = from_timer(sp, t, resync_t);
495 static char resync_cmd = 0xe8;
496
497 /* clear any data that might have been received */
498
499 sp->rx_count = 0;
500 sp->rx_count_cooked = 0;
501
502 /* reset state machine */
503
504 sp->status = 1;
505 sp->status1 = 1;
506 sp->status2 = 0;
507
508 /* resync the TNC */
509
510 sp->led_state = 0x60;
511 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
512 sp->tty->ops->write(sp->tty, &resync_cmd, 1);
513
514
515 /* Start resync timer again -- the TNC might be still absent */
516 mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT);
517}
518
519static inline int tnc_init(struct sixpack *sp)
520{
521 unsigned char inbyte = 0xe8;
522
523 tnc_set_sync_state(sp, TNC_UNSYNC_STARTUP);
524
525 sp->tty->ops->write(sp->tty, &inbyte, 1);
526
527 mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT);
528
529 return 0;
530}
531
532/*
533 * Open the high-level part of the 6pack channel.
534 * This function is called by the TTY module when the
535 * 6pack line discipline is called for. Because we are
536 * sure the tty line exists, we only have to link it to
537 * a free 6pcack channel...
538 */
539static int sixpack_open(struct tty_struct *tty)
540{
541 char *xbuff = NULL;
542 struct net_device *dev;
543 struct sixpack *sp;
544 unsigned long len;
545 int err = 0;
546
547 if (!capable(CAP_NET_ADMIN))
548 return -EPERM;
549 if (tty->ops->write == NULL)
550 return -EOPNOTSUPP;
551
552 dev = alloc_netdev(sizeof(struct sixpack), "sp%d", NET_NAME_UNKNOWN,
553 sp_setup);
554 if (!dev) {
555 err = -ENOMEM;
556 goto out;
557 }
558
559 sp = netdev_priv(dev);
560 sp->dev = dev;
561
562 spin_lock_init(&sp->lock);
563 spin_lock_init(&sp->rxlock);
564 refcount_set(&sp->refcnt, 1);
565 init_completion(&sp->dead);
566
567 /* !!! length of the buffers. MTU is IP MTU, not PACLEN! */
568
569 len = dev->mtu * 2;
570
571 xbuff = kmalloc(len + 4, GFP_KERNEL);
572 if (xbuff == NULL) {
573 err = -ENOBUFS;
574 goto out_free;
575 }
576
577 spin_lock_bh(&sp->lock);
578
579 sp->tty = tty;
580
581 sp->xbuff = xbuff;
582
583 sp->rcount = 0;
584 sp->rx_count = 0;
585 sp->rx_count_cooked = 0;
586 sp->xleft = 0;
587
588 sp->flags = 0; /* Clear ESCAPE & ERROR flags */
589
590 sp->duplex = 0;
591 sp->tx_delay = SIXP_TXDELAY;
592 sp->persistence = SIXP_PERSIST;
593 sp->slottime = SIXP_SLOTTIME;
594 sp->led_state = 0x60;
595 sp->status = 1;
596 sp->status1 = 1;
597 sp->status2 = 0;
598 sp->tx_enable = 0;
599
600 netif_start_queue(dev);
601
602 timer_setup(&sp->tx_t, sp_xmit_on_air, 0);
603
604 timer_setup(&sp->resync_t, resync_tnc, 0);
605
606 spin_unlock_bh(&sp->lock);
607
608 /* Done. We have linked the TTY line to a channel. */
609 tty->disc_data = sp;
610 tty->receive_room = 65536;
611
612 /* Now we're ready to register. */
613 err = register_netdev(dev);
614 if (err)
615 goto out_free;
616
617 tnc_init(sp);
618
619 return 0;
620
621out_free:
622 kfree(xbuff);
623
624 free_netdev(dev);
625
626out:
627 return err;
628}
629
630
631/*
632 * Close down a 6pack channel.
633 * This means flushing out any pending queues, and then restoring the
634 * TTY line discipline to what it was before it got hooked to 6pack
635 * (which usually is TTY again).
636 */
637static void sixpack_close(struct tty_struct *tty)
638{
639 struct sixpack *sp;
640
641 write_lock_irq(&disc_data_lock);
642 sp = tty->disc_data;
643 tty->disc_data = NULL;
644 write_unlock_irq(&disc_data_lock);
645 if (!sp)
646 return;
647
648 /*
649 * We have now ensured that nobody can start using ap from now on, but
650 * we have to wait for all existing users to finish.
651 */
652 if (!refcount_dec_and_test(&sp->refcnt))
653 wait_for_completion(&sp->dead);
654
655 /* We must stop the queue to avoid potentially scribbling
656 * on the free buffers. The sp->dead completion is not sufficient
657 * to protect us from sp->xbuff access.
658 */
659 netif_stop_queue(sp->dev);
660
661 unregister_netdev(sp->dev);
662
663 del_timer_sync(&sp->tx_t);
664 del_timer_sync(&sp->resync_t);
665
666 /* Free all 6pack frame buffers after unreg. */
667 kfree(sp->xbuff);
668
669 free_netdev(sp->dev);
670}
671
672/* Perform I/O control on an active 6pack channel. */
673static int sixpack_ioctl(struct tty_struct *tty, unsigned int cmd,
674 unsigned long arg)
675{
676 struct sixpack *sp = sp_get(tty);
677 struct net_device *dev;
678 unsigned int tmp, err;
679
680 if (!sp)
681 return -ENXIO;
682 dev = sp->dev;
683
684 switch(cmd) {
685 case SIOCGIFNAME:
686 err = copy_to_user((void __user *) arg, dev->name,
687 strlen(dev->name) + 1) ? -EFAULT : 0;
688 break;
689
690 case SIOCGIFENCAP:
691 err = put_user(0, (int __user *) arg);
692 break;
693
694 case SIOCSIFENCAP:
695 if (get_user(tmp, (int __user *) arg)) {
696 err = -EFAULT;
697 break;
698 }
699
700 sp->mode = tmp;
701 dev->addr_len = AX25_ADDR_LEN;
702 dev->hard_header_len = AX25_KISS_HEADER_LEN +
703 AX25_MAX_HEADER_LEN + 3;
704 dev->type = ARPHRD_AX25;
705
706 err = 0;
707 break;
708
709 case SIOCSIFHWADDR: {
710 char addr[AX25_ADDR_LEN];
711
712 if (copy_from_user(&addr,
713 (void __user *)arg, AX25_ADDR_LEN)) {
714 err = -EFAULT;
715 break;
716 }
717
718 netif_tx_lock_bh(dev);
719 __dev_addr_set(dev, &addr, AX25_ADDR_LEN);
720 netif_tx_unlock_bh(dev);
721 err = 0;
722 break;
723 }
724 default:
725 err = tty_mode_ioctl(tty, cmd, arg);
726 }
727
728 sp_put(sp);
729
730 return err;
731}
732
733static struct tty_ldisc_ops sp_ldisc = {
734 .owner = THIS_MODULE,
735 .num = N_6PACK,
736 .name = "6pack",
737 .open = sixpack_open,
738 .close = sixpack_close,
739 .ioctl = sixpack_ioctl,
740 .receive_buf = sixpack_receive_buf,
741 .write_wakeup = sixpack_write_wakeup,
742};
743
744/* Initialize 6pack control device -- register 6pack line discipline */
745
746static int __init sixpack_init_driver(void)
747{
748 int status;
749
750 /* Register the provided line protocol discipline */
751 status = tty_register_ldisc(&sp_ldisc);
752 if (status)
753 pr_err("6pack: can't register line discipline (err = %d)\n", status);
754
755 return status;
756}
757
758static void __exit sixpack_exit_driver(void)
759{
760 tty_unregister_ldisc(&sp_ldisc);
761}
762
763/* encode an AX.25 packet into 6pack */
764
765static int encode_sixpack(unsigned char *tx_buf, unsigned char *tx_buf_raw,
766 int length, unsigned char tx_delay)
767{
768 int count = 0;
769 unsigned char checksum = 0, buf[400];
770 int raw_count = 0;
771
772 tx_buf_raw[raw_count++] = SIXP_PRIO_CMD_MASK | SIXP_TX_MASK;
773 tx_buf_raw[raw_count++] = SIXP_SEOF;
774
775 buf[0] = tx_delay;
776 for (count = 1; count < length; count++)
777 buf[count] = tx_buf[count];
778
779 for (count = 0; count < length; count++)
780 checksum += buf[count];
781 buf[length] = (unsigned char) 0xff - checksum;
782
783 for (count = 0; count <= length; count++) {
784 if ((count % 3) == 0) {
785 tx_buf_raw[raw_count++] = (buf[count] & 0x3f);
786 tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x30);
787 } else if ((count % 3) == 1) {
788 tx_buf_raw[raw_count++] |= (buf[count] & 0x0f);
789 tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x3c);
790 } else {
791 tx_buf_raw[raw_count++] |= (buf[count] & 0x03);
792 tx_buf_raw[raw_count++] = (buf[count] >> 2);
793 }
794 }
795 if ((length % 3) != 2)
796 raw_count++;
797 tx_buf_raw[raw_count++] = SIXP_SEOF;
798 return raw_count;
799}
800
801/* decode 4 sixpack-encoded bytes into 3 data bytes */
802
803static void decode_data(struct sixpack *sp, u8 inbyte)
804{
805 u8 *buf;
806
807 if (sp->rx_count != 3) {
808 sp->raw_buf[sp->rx_count++] = inbyte;
809
810 return;
811 }
812
813 if (sp->rx_count_cooked + 2 >= sizeof(sp->cooked_buf)) {
814 pr_err("6pack: cooked buffer overrun, data loss\n");
815 sp->rx_count = 0;
816 return;
817 }
818
819 buf = sp->raw_buf;
820 sp->cooked_buf[sp->rx_count_cooked++] =
821 buf[0] | ((buf[1] << 2) & 0xc0);
822 sp->cooked_buf[sp->rx_count_cooked++] =
823 (buf[1] & 0x0f) | ((buf[2] << 2) & 0xf0);
824 sp->cooked_buf[sp->rx_count_cooked++] =
825 (buf[2] & 0x03) | (inbyte << 2);
826 sp->rx_count = 0;
827}
828
829/* identify and execute a 6pack priority command byte */
830
831static void decode_prio_command(struct sixpack *sp, u8 cmd)
832{
833 ssize_t actual;
834
835 if ((cmd & SIXP_PRIO_DATA_MASK) != 0) { /* idle ? */
836
837 /* RX and DCD flags can only be set in the same prio command,
838 if the DCD flag has been set without the RX flag in the previous
839 prio command. If DCD has not been set before, something in the
840 transmission has gone wrong. In this case, RX and DCD are
841 cleared in order to prevent the decode_data routine from
842 reading further data that might be corrupt. */
843
844 if (((sp->status & SIXP_DCD_MASK) == 0) &&
845 ((cmd & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)) {
846 if (sp->status != 1)
847 printk(KERN_DEBUG "6pack: protocol violation\n");
848 else
849 sp->status = 0;
850 cmd &= ~SIXP_RX_DCD_MASK;
851 }
852 sp->status = cmd & SIXP_PRIO_DATA_MASK;
853 } else { /* output watchdog char if idle */
854 if ((sp->status2 != 0) && (sp->duplex == 1)) {
855 sp->led_state = 0x70;
856 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
857 sp->tx_enable = 1;
858 actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
859 sp->xleft -= actual;
860 sp->xhead += actual;
861 sp->led_state = 0x60;
862 sp->status2 = 0;
863
864 }
865 }
866
867 /* needed to trigger the TNC watchdog */
868 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
869
870 /* if the state byte has been received, the TNC is present,
871 so the resync timer can be reset. */
872
873 if (sp->tnc_state == TNC_IN_SYNC)
874 mod_timer(&sp->resync_t, jiffies + SIXP_INIT_RESYNC_TIMEOUT);
875
876 sp->status1 = cmd & SIXP_PRIO_DATA_MASK;
877}
878
879/* identify and execute a standard 6pack command byte */
880
881static void decode_std_command(struct sixpack *sp, u8 cmd)
882{
883 u8 checksum = 0, rest = 0;
884 short i;
885
886 switch (cmd & SIXP_CMD_MASK) { /* normal command */
887 case SIXP_SEOF:
888 if ((sp->rx_count == 0) && (sp->rx_count_cooked == 0)) {
889 if ((sp->status & SIXP_RX_DCD_MASK) ==
890 SIXP_RX_DCD_MASK) {
891 sp->led_state = 0x68;
892 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
893 }
894 } else {
895 sp->led_state = 0x60;
896 /* fill trailing bytes with zeroes */
897 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
898 spin_lock_bh(&sp->rxlock);
899 rest = sp->rx_count;
900 if (rest != 0)
901 for (i = rest; i <= 3; i++)
902 decode_data(sp, 0);
903 if (rest == 2)
904 sp->rx_count_cooked -= 2;
905 else if (rest == 3)
906 sp->rx_count_cooked -= 1;
907 for (i = 0; i < sp->rx_count_cooked; i++)
908 checksum += sp->cooked_buf[i];
909 if (checksum != SIXP_CHKSUM) {
910 printk(KERN_DEBUG "6pack: bad checksum %2.2x\n", checksum);
911 } else {
912 sp->rcount = sp->rx_count_cooked-2;
913 sp_bump(sp, 0);
914 }
915 sp->rx_count_cooked = 0;
916 spin_unlock_bh(&sp->rxlock);
917 }
918 break;
919 case SIXP_TX_URUN: printk(KERN_DEBUG "6pack: TX underrun\n");
920 break;
921 case SIXP_RX_ORUN: printk(KERN_DEBUG "6pack: RX overrun\n");
922 break;
923 case SIXP_RX_BUF_OVL:
924 printk(KERN_DEBUG "6pack: RX buffer overflow\n");
925 }
926}
927
928/* decode a 6pack packet */
929
930static void
931sixpack_decode(struct sixpack *sp, const u8 *pre_rbuff, size_t count)
932{
933 size_t count1;
934 u8 inbyte;
935
936 for (count1 = 0; count1 < count; count1++) {
937 inbyte = pre_rbuff[count1];
938 if (inbyte == SIXP_FOUND_TNC) {
939 tnc_set_sync_state(sp, TNC_IN_SYNC);
940 del_timer(&sp->resync_t);
941 }
942 if ((inbyte & SIXP_PRIO_CMD_MASK) != 0)
943 decode_prio_command(sp, inbyte);
944 else if ((inbyte & SIXP_STD_CMD_MASK) != 0)
945 decode_std_command(sp, inbyte);
946 else if ((sp->status & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK) {
947 spin_lock_bh(&sp->rxlock);
948 decode_data(sp, inbyte);
949 spin_unlock_bh(&sp->rxlock);
950 }
951 }
952}
953
954MODULE_AUTHOR("Ralf Baechle DO1GRB <ralf@linux-mips.org>");
955MODULE_DESCRIPTION("6pack driver for AX.25");
956MODULE_LICENSE("GPL");
957MODULE_ALIAS_LDISC(N_6PACK);
958
959module_init(sixpack_init_driver);
960module_exit(sixpack_exit_driver);
1/*
2 * 6pack.c This module implements the 6pack protocol for kernel-based
3 * devices like TTY. It interfaces between a raw TTY and the
4 * kernel's AX.25 protocol layers.
5 *
6 * Authors: Andreas Könsgen <ajk@comnets.uni-bremen.de>
7 * Ralf Baechle DL5RB <ralf@linux-mips.org>
8 *
9 * Quite a lot of stuff "stolen" by Joerg Reuter from slip.c, written by
10 *
11 * Laurence Culhane, <loz@holmes.demon.co.uk>
12 * Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
13 */
14
15#include <linux/module.h>
16#include <asm/uaccess.h>
17#include <linux/bitops.h>
18#include <linux/string.h>
19#include <linux/mm.h>
20#include <linux/interrupt.h>
21#include <linux/in.h>
22#include <linux/tty.h>
23#include <linux/errno.h>
24#include <linux/netdevice.h>
25#include <linux/timer.h>
26#include <linux/slab.h>
27#include <net/ax25.h>
28#include <linux/etherdevice.h>
29#include <linux/skbuff.h>
30#include <linux/rtnetlink.h>
31#include <linux/spinlock.h>
32#include <linux/if_arp.h>
33#include <linux/init.h>
34#include <linux/ip.h>
35#include <linux/tcp.h>
36#include <linux/semaphore.h>
37#include <linux/compat.h>
38#include <linux/atomic.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 (HZ/4) /* in 1 s */
72#define SIXP_PERSIST 50 /* in 256ths */
73#define SIXP_SLOTTIME (HZ/10) /* in 1 s */
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
81enum sixpack_flags {
82 SIXPF_ERROR, /* Parity, etc. error */
83};
84
85struct 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 atomic_t refcnt;
124 struct semaphore dead_sem;
125 spinlock_t lock;
126};
127
128#define AX25_6PACK_HEADER_LEN 0
129
130static void sixpack_decode(struct sixpack *, unsigned char[], int);
131static 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
139static void sp_xmit_on_air(unsigned long channel)
140{
141 struct sixpack *sp = (struct sixpack *) channel;
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. */
164static 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 (len > sp->mtu) { /* sp->mtu = AX25_MTU = max. PACLEN = 256 */
175 msg = "oversized transmit packet!";
176 goto out_drop;
177 }
178
179 if (p[0] > 5) {
180 msg = "invalid KISS command";
181 goto out_drop;
182 }
183
184 if ((p[0] != 0) && (len > 2)) {
185 msg = "KISS control packet too long";
186 goto out_drop;
187 }
188
189 if ((p[0] == 0) && (len < 15)) {
190 msg = "bad AX.25 packet to transmit";
191 goto out_drop;
192 }
193
194 count = encode_sixpack(p, sp->xbuff, len, sp->tx_delay);
195 set_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
196
197 switch (p[0]) {
198 case 1: sp->tx_delay = p[1];
199 return;
200 case 2: sp->persistence = p[1];
201 return;
202 case 3: sp->slottime = p[1];
203 return;
204 case 4: /* ignored */
205 return;
206 case 5: sp->duplex = p[1];
207 return;
208 }
209
210 if (p[0] != 0)
211 return;
212
213 /*
214 * In case of fullduplex or DAMA operation, we don't take care about the
215 * state of the DCD or of any timers, as the determination of the
216 * correct time to send is the job of the AX.25 layer. We send
217 * immediately after data has arrived.
218 */
219 if (sp->duplex == 1) {
220 sp->led_state = 0x70;
221 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
222 sp->tx_enable = 1;
223 actual = sp->tty->ops->write(sp->tty, sp->xbuff, count);
224 sp->xleft = count - actual;
225 sp->xhead = sp->xbuff + actual;
226 sp->led_state = 0x60;
227 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
228 } else {
229 sp->xleft = count;
230 sp->xhead = sp->xbuff;
231 sp->status2 = count;
232 sp_xmit_on_air((unsigned long)sp);
233 }
234
235 return;
236
237out_drop:
238 sp->dev->stats.tx_dropped++;
239 netif_start_queue(sp->dev);
240 if (net_ratelimit())
241 printk(KERN_DEBUG "%s: %s - dropped.\n", sp->dev->name, msg);
242}
243
244/* Encapsulate an IP datagram and kick it into a TTY queue. */
245
246static netdev_tx_t sp_xmit(struct sk_buff *skb, struct net_device *dev)
247{
248 struct sixpack *sp = netdev_priv(dev);
249
250 if (skb->protocol == htons(ETH_P_IP))
251 return ax25_ip_xmit(skb);
252
253 spin_lock_bh(&sp->lock);
254 /* We were not busy, so we are now... :-) */
255 netif_stop_queue(dev);
256 dev->stats.tx_bytes += skb->len;
257 sp_encaps(sp, skb->data, skb->len);
258 spin_unlock_bh(&sp->lock);
259
260 dev_kfree_skb(skb);
261
262 return NETDEV_TX_OK;
263}
264
265static int sp_open_dev(struct net_device *dev)
266{
267 struct sixpack *sp = netdev_priv(dev);
268
269 if (sp->tty == NULL)
270 return -ENODEV;
271 return 0;
272}
273
274/* Close the low-level part of the 6pack channel. */
275static int sp_close(struct net_device *dev)
276{
277 struct sixpack *sp = netdev_priv(dev);
278
279 spin_lock_bh(&sp->lock);
280 if (sp->tty) {
281 /* TTY discipline is running. */
282 clear_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
283 }
284 netif_stop_queue(dev);
285 spin_unlock_bh(&sp->lock);
286
287 return 0;
288}
289
290static int sp_set_mac_address(struct net_device *dev, void *addr)
291{
292 struct sockaddr_ax25 *sa = addr;
293
294 netif_tx_lock_bh(dev);
295 netif_addr_lock(dev);
296 memcpy(dev->dev_addr, &sa->sax25_call, AX25_ADDR_LEN);
297 netif_addr_unlock(dev);
298 netif_tx_unlock_bh(dev);
299
300 return 0;
301}
302
303static const struct net_device_ops sp_netdev_ops = {
304 .ndo_open = sp_open_dev,
305 .ndo_stop = sp_close,
306 .ndo_start_xmit = sp_xmit,
307 .ndo_set_mac_address = sp_set_mac_address,
308};
309
310static void sp_setup(struct net_device *dev)
311{
312 /* Finish setting up the DEVICE info. */
313 dev->netdev_ops = &sp_netdev_ops;
314 dev->destructor = free_netdev;
315 dev->mtu = SIXP_MTU;
316 dev->hard_header_len = AX25_MAX_HEADER_LEN;
317 dev->header_ops = &ax25_header_ops;
318
319 dev->addr_len = AX25_ADDR_LEN;
320 dev->type = ARPHRD_AX25;
321 dev->tx_queue_len = 10;
322
323 /* Only activated in AX.25 mode */
324 memcpy(dev->broadcast, &ax25_bcast, AX25_ADDR_LEN);
325 memcpy(dev->dev_addr, &ax25_defaddr, AX25_ADDR_LEN);
326
327 dev->flags = 0;
328}
329
330/* Send one completely decapsulated IP datagram to the IP layer. */
331
332/*
333 * This is the routine that sends the received data to the kernel AX.25.
334 * 'cmd' is the KISS command. For AX.25 data, it is zero.
335 */
336
337static void sp_bump(struct sixpack *sp, char cmd)
338{
339 struct sk_buff *skb;
340 int count;
341 unsigned char *ptr;
342
343 count = sp->rcount + 1;
344
345 sp->dev->stats.rx_bytes += count;
346
347 if ((skb = dev_alloc_skb(count)) == NULL)
348 goto out_mem;
349
350 ptr = skb_put(skb, count);
351 *ptr++ = cmd; /* KISS command */
352
353 memcpy(ptr, sp->cooked_buf + 1, count);
354 skb->protocol = ax25_type_trans(skb, sp->dev);
355 netif_rx(skb);
356 sp->dev->stats.rx_packets++;
357
358 return;
359
360out_mem:
361 sp->dev->stats.rx_dropped++;
362}
363
364
365/* ----------------------------------------------------------------------- */
366
367/*
368 * We have a potential race on dereferencing tty->disc_data, because the tty
369 * layer provides no locking at all - thus one cpu could be running
370 * sixpack_receive_buf while another calls sixpack_close, which zeroes
371 * tty->disc_data and frees the memory that sixpack_receive_buf is using. The
372 * best way to fix this is to use a rwlock in the tty struct, but for now we
373 * use a single global rwlock for all ttys in ppp line discipline.
374 */
375static DEFINE_RWLOCK(disc_data_lock);
376
377static struct sixpack *sp_get(struct tty_struct *tty)
378{
379 struct sixpack *sp;
380
381 read_lock(&disc_data_lock);
382 sp = tty->disc_data;
383 if (sp)
384 atomic_inc(&sp->refcnt);
385 read_unlock(&disc_data_lock);
386
387 return sp;
388}
389
390static void sp_put(struct sixpack *sp)
391{
392 if (atomic_dec_and_test(&sp->refcnt))
393 up(&sp->dead_sem);
394}
395
396/*
397 * Called by the TTY driver when there's room for more data. If we have
398 * more packets to send, we send them here.
399 */
400static void sixpack_write_wakeup(struct tty_struct *tty)
401{
402 struct sixpack *sp = sp_get(tty);
403 int actual;
404
405 if (!sp)
406 return;
407 if (sp->xleft <= 0) {
408 /* Now serial buffer is almost free & we can start
409 * transmission of another packet */
410 sp->dev->stats.tx_packets++;
411 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
412 sp->tx_enable = 0;
413 netif_wake_queue(sp->dev);
414 goto out;
415 }
416
417 if (sp->tx_enable) {
418 actual = tty->ops->write(tty, sp->xhead, sp->xleft);
419 sp->xleft -= actual;
420 sp->xhead += actual;
421 }
422
423out:
424 sp_put(sp);
425}
426
427/* ----------------------------------------------------------------------- */
428
429/*
430 * Handle the 'receiver data ready' interrupt.
431 * This function is called by the 'tty_io' module in the kernel when
432 * a block of 6pack data has been received, which can now be decapsulated
433 * and sent on to some IP layer for further processing.
434 */
435static void sixpack_receive_buf(struct tty_struct *tty,
436 const unsigned char *cp, char *fp, int count)
437{
438 struct sixpack *sp;
439 unsigned char buf[512];
440 int count1;
441
442 if (!count)
443 return;
444
445 sp = sp_get(tty);
446 if (!sp)
447 return;
448
449 memcpy(buf, cp, count < sizeof(buf) ? count : sizeof(buf));
450
451 /* Read the characters out of the buffer */
452
453 count1 = count;
454 while (count) {
455 count--;
456 if (fp && *fp++) {
457 if (!test_and_set_bit(SIXPF_ERROR, &sp->flags))
458 sp->dev->stats.rx_errors++;
459 continue;
460 }
461 }
462 sixpack_decode(sp, buf, count1);
463
464 sp_put(sp);
465 tty_unthrottle(tty);
466}
467
468/*
469 * Try to resync the TNC. Called by the resync timer defined in
470 * decode_prio_command
471 */
472
473#define TNC_UNINITIALIZED 0
474#define TNC_UNSYNC_STARTUP 1
475#define TNC_UNSYNCED 2
476#define TNC_IN_SYNC 3
477
478static void __tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
479{
480 char *msg;
481
482 switch (new_tnc_state) {
483 default: /* gcc oh piece-o-crap ... */
484 case TNC_UNSYNC_STARTUP:
485 msg = "Synchronizing with TNC";
486 break;
487 case TNC_UNSYNCED:
488 msg = "Lost synchronization with TNC\n";
489 break;
490 case TNC_IN_SYNC:
491 msg = "Found TNC";
492 break;
493 }
494
495 sp->tnc_state = new_tnc_state;
496 printk(KERN_INFO "%s: %s\n", sp->dev->name, msg);
497}
498
499static inline void tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
500{
501 int old_tnc_state = sp->tnc_state;
502
503 if (old_tnc_state != new_tnc_state)
504 __tnc_set_sync_state(sp, new_tnc_state);
505}
506
507static void resync_tnc(unsigned long channel)
508{
509 struct sixpack *sp = (struct sixpack *) channel;
510 static char resync_cmd = 0xe8;
511
512 /* clear any data that might have been received */
513
514 sp->rx_count = 0;
515 sp->rx_count_cooked = 0;
516
517 /* reset state machine */
518
519 sp->status = 1;
520 sp->status1 = 1;
521 sp->status2 = 0;
522
523 /* resync the TNC */
524
525 sp->led_state = 0x60;
526 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
527 sp->tty->ops->write(sp->tty, &resync_cmd, 1);
528
529
530 /* Start resync timer again -- the TNC might be still absent */
531
532 del_timer(&sp->resync_t);
533 sp->resync_t.data = (unsigned long) sp;
534 sp->resync_t.function = resync_tnc;
535 sp->resync_t.expires = jiffies + SIXP_RESYNC_TIMEOUT;
536 add_timer(&sp->resync_t);
537}
538
539static inline int tnc_init(struct sixpack *sp)
540{
541 unsigned char inbyte = 0xe8;
542
543 tnc_set_sync_state(sp, TNC_UNSYNC_STARTUP);
544
545 sp->tty->ops->write(sp->tty, &inbyte, 1);
546
547 del_timer(&sp->resync_t);
548 sp->resync_t.data = (unsigned long) sp;
549 sp->resync_t.function = resync_tnc;
550 sp->resync_t.expires = jiffies + SIXP_RESYNC_TIMEOUT;
551 add_timer(&sp->resync_t);
552
553 return 0;
554}
555
556/*
557 * Open the high-level part of the 6pack channel.
558 * This function is called by the TTY module when the
559 * 6pack line discipline is called for. Because we are
560 * sure the tty line exists, we only have to link it to
561 * a free 6pcack channel...
562 */
563static int sixpack_open(struct tty_struct *tty)
564{
565 char *rbuff = NULL, *xbuff = NULL;
566 struct net_device *dev;
567 struct sixpack *sp;
568 unsigned long len;
569 int err = 0;
570
571 if (!capable(CAP_NET_ADMIN))
572 return -EPERM;
573 if (tty->ops->write == NULL)
574 return -EOPNOTSUPP;
575
576 dev = alloc_netdev(sizeof(struct sixpack), "sp%d", NET_NAME_UNKNOWN,
577 sp_setup);
578 if (!dev) {
579 err = -ENOMEM;
580 goto out;
581 }
582
583 sp = netdev_priv(dev);
584 sp->dev = dev;
585
586 spin_lock_init(&sp->lock);
587 atomic_set(&sp->refcnt, 1);
588 sema_init(&sp->dead_sem, 0);
589
590 /* !!! length of the buffers. MTU is IP MTU, not PACLEN! */
591
592 len = dev->mtu * 2;
593
594 rbuff = kmalloc(len + 4, GFP_KERNEL);
595 xbuff = kmalloc(len + 4, GFP_KERNEL);
596
597 if (rbuff == NULL || xbuff == NULL) {
598 err = -ENOBUFS;
599 goto out_free;
600 }
601
602 spin_lock_bh(&sp->lock);
603
604 sp->tty = tty;
605
606 sp->rbuff = rbuff;
607 sp->xbuff = xbuff;
608
609 sp->mtu = AX25_MTU + 73;
610 sp->buffsize = len;
611 sp->rcount = 0;
612 sp->rx_count = 0;
613 sp->rx_count_cooked = 0;
614 sp->xleft = 0;
615
616 sp->flags = 0; /* Clear ESCAPE & ERROR flags */
617
618 sp->duplex = 0;
619 sp->tx_delay = SIXP_TXDELAY;
620 sp->persistence = SIXP_PERSIST;
621 sp->slottime = SIXP_SLOTTIME;
622 sp->led_state = 0x60;
623 sp->status = 1;
624 sp->status1 = 1;
625 sp->status2 = 0;
626 sp->tx_enable = 0;
627
628 netif_start_queue(dev);
629
630 init_timer(&sp->tx_t);
631 sp->tx_t.function = sp_xmit_on_air;
632 sp->tx_t.data = (unsigned long) sp;
633
634 init_timer(&sp->resync_t);
635
636 spin_unlock_bh(&sp->lock);
637
638 /* Done. We have linked the TTY line to a channel. */
639 tty->disc_data = sp;
640 tty->receive_room = 65536;
641
642 /* Now we're ready to register. */
643 err = register_netdev(dev);
644 if (err)
645 goto out_free;
646
647 tnc_init(sp);
648
649 return 0;
650
651out_free:
652 kfree(xbuff);
653 kfree(rbuff);
654
655 free_netdev(dev);
656
657out:
658 return err;
659}
660
661
662/*
663 * Close down a 6pack channel.
664 * This means flushing out any pending queues, and then restoring the
665 * TTY line discipline to what it was before it got hooked to 6pack
666 * (which usually is TTY again).
667 */
668static void sixpack_close(struct tty_struct *tty)
669{
670 struct sixpack *sp;
671
672 write_lock_bh(&disc_data_lock);
673 sp = tty->disc_data;
674 tty->disc_data = NULL;
675 write_unlock_bh(&disc_data_lock);
676 if (!sp)
677 return;
678
679 /*
680 * We have now ensured that nobody can start using ap from now on, but
681 * we have to wait for all existing users to finish.
682 */
683 if (!atomic_dec_and_test(&sp->refcnt))
684 down(&sp->dead_sem);
685
686 /* We must stop the queue to avoid potentially scribbling
687 * on the free buffers. The sp->dead_sem is not sufficient
688 * to protect us from sp->xbuff access.
689 */
690 netif_stop_queue(sp->dev);
691
692 del_timer_sync(&sp->tx_t);
693 del_timer_sync(&sp->resync_t);
694
695 /* Free all 6pack frame buffers. */
696 kfree(sp->rbuff);
697 kfree(sp->xbuff);
698
699 unregister_netdev(sp->dev);
700}
701
702/* Perform I/O control on an active 6pack channel. */
703static int sixpack_ioctl(struct tty_struct *tty, struct file *file,
704 unsigned int cmd, unsigned long arg)
705{
706 struct sixpack *sp = sp_get(tty);
707 struct net_device *dev;
708 unsigned int tmp, err;
709
710 if (!sp)
711 return -ENXIO;
712 dev = sp->dev;
713
714 switch(cmd) {
715 case SIOCGIFNAME:
716 err = copy_to_user((void __user *) arg, dev->name,
717 strlen(dev->name) + 1) ? -EFAULT : 0;
718 break;
719
720 case SIOCGIFENCAP:
721 err = put_user(0, (int __user *) arg);
722 break;
723
724 case SIOCSIFENCAP:
725 if (get_user(tmp, (int __user *) arg)) {
726 err = -EFAULT;
727 break;
728 }
729
730 sp->mode = tmp;
731 dev->addr_len = AX25_ADDR_LEN;
732 dev->hard_header_len = AX25_KISS_HEADER_LEN +
733 AX25_MAX_HEADER_LEN + 3;
734 dev->type = ARPHRD_AX25;
735
736 err = 0;
737 break;
738
739 case SIOCSIFHWADDR: {
740 char addr[AX25_ADDR_LEN];
741
742 if (copy_from_user(&addr,
743 (void __user *) arg, AX25_ADDR_LEN)) {
744 err = -EFAULT;
745 break;
746 }
747
748 netif_tx_lock_bh(dev);
749 memcpy(dev->dev_addr, &addr, AX25_ADDR_LEN);
750 netif_tx_unlock_bh(dev);
751
752 err = 0;
753 break;
754 }
755
756 default:
757 err = tty_mode_ioctl(tty, file, cmd, arg);
758 }
759
760 sp_put(sp);
761
762 return err;
763}
764
765#ifdef CONFIG_COMPAT
766static long sixpack_compat_ioctl(struct tty_struct * tty, struct file * file,
767 unsigned int cmd, unsigned long arg)
768{
769 switch (cmd) {
770 case SIOCGIFNAME:
771 case SIOCGIFENCAP:
772 case SIOCSIFENCAP:
773 case SIOCSIFHWADDR:
774 return sixpack_ioctl(tty, file, cmd,
775 (unsigned long)compat_ptr(arg));
776 }
777
778 return -ENOIOCTLCMD;
779}
780#endif
781
782static struct tty_ldisc_ops sp_ldisc = {
783 .owner = THIS_MODULE,
784 .magic = TTY_LDISC_MAGIC,
785 .name = "6pack",
786 .open = sixpack_open,
787 .close = sixpack_close,
788 .ioctl = sixpack_ioctl,
789#ifdef CONFIG_COMPAT
790 .compat_ioctl = sixpack_compat_ioctl,
791#endif
792 .receive_buf = sixpack_receive_buf,
793 .write_wakeup = sixpack_write_wakeup,
794};
795
796/* Initialize 6pack control device -- register 6pack line discipline */
797
798static const char msg_banner[] __initconst = KERN_INFO \
799 "AX.25: 6pack driver, " SIXPACK_VERSION "\n";
800static const char msg_regfail[] __initconst = KERN_ERR \
801 "6pack: can't register line discipline (err = %d)\n";
802
803static int __init sixpack_init_driver(void)
804{
805 int status;
806
807 printk(msg_banner);
808
809 /* Register the provided line protocol discipline */
810 if ((status = tty_register_ldisc(N_6PACK, &sp_ldisc)) != 0)
811 printk(msg_regfail, status);
812
813 return status;
814}
815
816static const char msg_unregfail[] = KERN_ERR \
817 "6pack: can't unregister line discipline (err = %d)\n";
818
819static void __exit sixpack_exit_driver(void)
820{
821 int ret;
822
823 if ((ret = tty_unregister_ldisc(N_6PACK)))
824 printk(msg_unregfail, ret);
825}
826
827/* encode an AX.25 packet into 6pack */
828
829static int encode_sixpack(unsigned char *tx_buf, unsigned char *tx_buf_raw,
830 int length, unsigned char tx_delay)
831{
832 int count = 0;
833 unsigned char checksum = 0, buf[400];
834 int raw_count = 0;
835
836 tx_buf_raw[raw_count++] = SIXP_PRIO_CMD_MASK | SIXP_TX_MASK;
837 tx_buf_raw[raw_count++] = SIXP_SEOF;
838
839 buf[0] = tx_delay;
840 for (count = 1; count < length; count++)
841 buf[count] = tx_buf[count];
842
843 for (count = 0; count < length; count++)
844 checksum += buf[count];
845 buf[length] = (unsigned char) 0xff - checksum;
846
847 for (count = 0; count <= length; count++) {
848 if ((count % 3) == 0) {
849 tx_buf_raw[raw_count++] = (buf[count] & 0x3f);
850 tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x30);
851 } else if ((count % 3) == 1) {
852 tx_buf_raw[raw_count++] |= (buf[count] & 0x0f);
853 tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x3c);
854 } else {
855 tx_buf_raw[raw_count++] |= (buf[count] & 0x03);
856 tx_buf_raw[raw_count++] = (buf[count] >> 2);
857 }
858 }
859 if ((length % 3) != 2)
860 raw_count++;
861 tx_buf_raw[raw_count++] = SIXP_SEOF;
862 return raw_count;
863}
864
865/* decode 4 sixpack-encoded bytes into 3 data bytes */
866
867static void decode_data(struct sixpack *sp, unsigned char inbyte)
868{
869 unsigned char *buf;
870
871 if (sp->rx_count != 3) {
872 sp->raw_buf[sp->rx_count++] = inbyte;
873
874 return;
875 }
876
877 buf = sp->raw_buf;
878 sp->cooked_buf[sp->rx_count_cooked++] =
879 buf[0] | ((buf[1] << 2) & 0xc0);
880 sp->cooked_buf[sp->rx_count_cooked++] =
881 (buf[1] & 0x0f) | ((buf[2] << 2) & 0xf0);
882 sp->cooked_buf[sp->rx_count_cooked++] =
883 (buf[2] & 0x03) | (inbyte << 2);
884 sp->rx_count = 0;
885}
886
887/* identify and execute a 6pack priority command byte */
888
889static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
890{
891 unsigned char channel;
892 int actual;
893
894 channel = cmd & SIXP_CHN_MASK;
895 if ((cmd & SIXP_PRIO_DATA_MASK) != 0) { /* idle ? */
896
897 /* RX and DCD flags can only be set in the same prio command,
898 if the DCD flag has been set without the RX flag in the previous
899 prio command. If DCD has not been set before, something in the
900 transmission has gone wrong. In this case, RX and DCD are
901 cleared in order to prevent the decode_data routine from
902 reading further data that might be corrupt. */
903
904 if (((sp->status & SIXP_DCD_MASK) == 0) &&
905 ((cmd & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)) {
906 if (sp->status != 1)
907 printk(KERN_DEBUG "6pack: protocol violation\n");
908 else
909 sp->status = 0;
910 cmd &= ~SIXP_RX_DCD_MASK;
911 }
912 sp->status = cmd & SIXP_PRIO_DATA_MASK;
913 } else { /* output watchdog char if idle */
914 if ((sp->status2 != 0) && (sp->duplex == 1)) {
915 sp->led_state = 0x70;
916 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
917 sp->tx_enable = 1;
918 actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
919 sp->xleft -= actual;
920 sp->xhead += actual;
921 sp->led_state = 0x60;
922 sp->status2 = 0;
923
924 }
925 }
926
927 /* needed to trigger the TNC watchdog */
928 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
929
930 /* if the state byte has been received, the TNC is present,
931 so the resync timer can be reset. */
932
933 if (sp->tnc_state == TNC_IN_SYNC) {
934 del_timer(&sp->resync_t);
935 sp->resync_t.data = (unsigned long) sp;
936 sp->resync_t.function = resync_tnc;
937 sp->resync_t.expires = jiffies + SIXP_INIT_RESYNC_TIMEOUT;
938 add_timer(&sp->resync_t);
939 }
940
941 sp->status1 = cmd & SIXP_PRIO_DATA_MASK;
942}
943
944/* identify and execute a standard 6pack command byte */
945
946static void decode_std_command(struct sixpack *sp, unsigned char cmd)
947{
948 unsigned char checksum = 0, rest = 0, channel;
949 short i;
950
951 channel = cmd & SIXP_CHN_MASK;
952 switch (cmd & SIXP_CMD_MASK) { /* normal command */
953 case SIXP_SEOF:
954 if ((sp->rx_count == 0) && (sp->rx_count_cooked == 0)) {
955 if ((sp->status & SIXP_RX_DCD_MASK) ==
956 SIXP_RX_DCD_MASK) {
957 sp->led_state = 0x68;
958 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
959 }
960 } else {
961 sp->led_state = 0x60;
962 /* fill trailing bytes with zeroes */
963 sp->tty->ops->write(sp->tty, &sp->led_state, 1);
964 rest = sp->rx_count;
965 if (rest != 0)
966 for (i = rest; i <= 3; i++)
967 decode_data(sp, 0);
968 if (rest == 2)
969 sp->rx_count_cooked -= 2;
970 else if (rest == 3)
971 sp->rx_count_cooked -= 1;
972 for (i = 0; i < sp->rx_count_cooked; i++)
973 checksum += sp->cooked_buf[i];
974 if (checksum != SIXP_CHKSUM) {
975 printk(KERN_DEBUG "6pack: bad checksum %2.2x\n", checksum);
976 } else {
977 sp->rcount = sp->rx_count_cooked-2;
978 sp_bump(sp, 0);
979 }
980 sp->rx_count_cooked = 0;
981 }
982 break;
983 case SIXP_TX_URUN: printk(KERN_DEBUG "6pack: TX underrun\n");
984 break;
985 case SIXP_RX_ORUN: printk(KERN_DEBUG "6pack: RX overrun\n");
986 break;
987 case SIXP_RX_BUF_OVL:
988 printk(KERN_DEBUG "6pack: RX buffer overflow\n");
989 }
990}
991
992/* decode a 6pack packet */
993
994static void
995sixpack_decode(struct sixpack *sp, unsigned char *pre_rbuff, int count)
996{
997 unsigned char inbyte;
998 int count1;
999
1000 for (count1 = 0; count1 < count; count1++) {
1001 inbyte = pre_rbuff[count1];
1002 if (inbyte == SIXP_FOUND_TNC) {
1003 tnc_set_sync_state(sp, TNC_IN_SYNC);
1004 del_timer(&sp->resync_t);
1005 }
1006 if ((inbyte & SIXP_PRIO_CMD_MASK) != 0)
1007 decode_prio_command(sp, inbyte);
1008 else if ((inbyte & SIXP_STD_CMD_MASK) != 0)
1009 decode_std_command(sp, inbyte);
1010 else if ((sp->status & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)
1011 decode_data(sp, inbyte);
1012 }
1013}
1014
1015MODULE_AUTHOR("Ralf Baechle DO1GRB <ralf@linux-mips.org>");
1016MODULE_DESCRIPTION("6pack driver for AX.25");
1017MODULE_LICENSE("GPL");
1018MODULE_ALIAS_LDISC(N_6PACK);
1019
1020module_init(sixpack_init_driver);
1021module_exit(sixpack_exit_driver);