blob: ce64032a465af512dae7b961ce80f1cc2203a4de [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * PPP synchronous tty channel driver for Linux.
3 *
4 * This is a ppp channel driver that can be used with tty device drivers
5 * that are frame oriented, such as synchronous HDLC devices.
6 *
7 * Complete PPP frames without encoding/decoding are exchanged between
8 * the channel driver and the device driver.
Jeff Garzik6aa20a22006-09-13 13:24:59 -04009 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 * The async map IOCTL codes are implemented to keep the user mode
11 * applications happy if they call them. Synchronous PPP does not use
12 * the async maps.
13 *
14 * Copyright 1999 Paul Mackerras.
15 *
16 * Also touched by the grubby hands of Paul Fulghum paulkf@microgate.com
17 *
18 * This program is free software; you can redistribute it and/or
19 * modify it under the terms of the GNU General Public License
20 * as published by the Free Software Foundation; either version
21 * 2 of the License, or (at your option) any later version.
22 *
23 * This driver provides the encapsulation and framing for sending
24 * and receiving PPP frames over sync serial lines. It relies on
25 * the generic PPP layer to give it frames to send and to process
26 * received frames. It implements the PPP line discipline.
27 *
28 * Part of the code in this driver was inspired by the old async-only
29 * PPP driver, written by Michael Callahan and Al Longyear, and
30 * subsequently hacked by Paul Mackerras.
31 *
32 * ==FILEVERSION 20040616==
33 */
34
35#include <linux/module.h>
36#include <linux/kernel.h>
37#include <linux/skbuff.h>
38#include <linux/tty.h>
39#include <linux/netdevice.h>
40#include <linux/poll.h>
41#include <linux/ppp_defs.h>
42#include <linux/if_ppp.h>
43#include <linux/ppp_channel.h>
44#include <linux/spinlock.h>
45#include <linux/init.h>
46#include <asm/uaccess.h>
47#include <asm/semaphore.h>
48
49#define PPP_VERSION "2.4.2"
50
51/* Structure for storing local state. */
52struct syncppp {
53 struct tty_struct *tty;
54 unsigned int flags;
55 unsigned int rbits;
56 int mru;
57 spinlock_t xmit_lock;
58 spinlock_t recv_lock;
59 unsigned long xmit_flags;
60 u32 xaccm[8];
61 u32 raccm;
62 unsigned int bytes_sent;
63 unsigned int bytes_rcvd;
64
65 struct sk_buff *tpkt;
66 unsigned long last_xmit;
67
68 struct sk_buff_head rqueue;
69
70 struct tasklet_struct tsk;
71
72 atomic_t refcnt;
73 struct semaphore dead_sem;
74 struct ppp_channel chan; /* interface to generic ppp layer */
75};
76
77/* Bit numbers in xmit_flags */
78#define XMIT_WAKEUP 0
79#define XMIT_FULL 1
80
81/* Bits in rbits */
82#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
83
84#define PPPSYNC_MAX_RQLEN 32 /* arbitrary */
85
86/*
87 * Prototypes.
88 */
89static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *);
90static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb);
91static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
92 unsigned long arg);
93static void ppp_sync_process(unsigned long arg);
94static int ppp_sync_push(struct syncppp *ap);
95static void ppp_sync_flush_output(struct syncppp *ap);
96static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
97 char *flags, int count);
98
99static struct ppp_channel_ops sync_ops = {
100 ppp_sync_send,
101 ppp_sync_ioctl
102};
103
104/*
105 * Utility procedures to print a buffer in hex/ascii
106 */
107static void
108ppp_print_hex (register __u8 * out, const __u8 * in, int count)
109{
110 register __u8 next_ch;
Arjan van de Venf71e1302006-03-03 21:33:57 -0500111 static const char hex[] = "0123456789ABCDEF";
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112
113 while (count-- > 0) {
114 next_ch = *in++;
115 *out++ = hex[(next_ch >> 4) & 0x0F];
116 *out++ = hex[next_ch & 0x0F];
117 ++out;
118 }
119}
120
121static void
122ppp_print_char (register __u8 * out, const __u8 * in, int count)
123{
124 register __u8 next_ch;
125
126 while (count-- > 0) {
127 next_ch = *in++;
128
129 if (next_ch < 0x20 || next_ch > 0x7e)
130 *out++ = '.';
131 else {
132 *out++ = next_ch;
133 if (next_ch == '%') /* printk/syslogd has a bug !! */
134 *out++ = '%';
135 }
136 }
137 *out = '\0';
138}
139
140static void
141ppp_print_buffer (const char *name, const __u8 *buf, int count)
142{
143 __u8 line[44];
144
145 if (name != NULL)
146 printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);
147
148 while (count > 8) {
149 memset (line, 32, 44);
150 ppp_print_hex (line, buf, 8);
151 ppp_print_char (&line[8 * 3], buf, 8);
152 printk(KERN_DEBUG "%s\n", line);
153 count -= 8;
154 buf += 8;
155 }
156
157 if (count > 0) {
158 memset (line, 32, 44);
159 ppp_print_hex (line, buf, count);
160 ppp_print_char (&line[8 * 3], buf, count);
161 printk(KERN_DEBUG "%s\n", line);
162 }
163}
164
165
166/*
167 * Routines implementing the synchronous PPP line discipline.
168 */
169
170/*
171 * We have a potential race on dereferencing tty->disc_data,
172 * because the tty layer provides no locking at all - thus one
173 * cpu could be running ppp_synctty_receive while another
174 * calls ppp_synctty_close, which zeroes tty->disc_data and
175 * frees the memory that ppp_synctty_receive is using. The best
176 * way to fix this is to use a rwlock in the tty struct, but for now
177 * we use a single global rwlock for all ttys in ppp line discipline.
178 *
179 * FIXME: Fixed in tty_io nowdays.
180 */
181static DEFINE_RWLOCK(disc_data_lock);
182
183static struct syncppp *sp_get(struct tty_struct *tty)
184{
185 struct syncppp *ap;
186
187 read_lock(&disc_data_lock);
188 ap = tty->disc_data;
189 if (ap != NULL)
190 atomic_inc(&ap->refcnt);
191 read_unlock(&disc_data_lock);
192 return ap;
193}
194
195static void sp_put(struct syncppp *ap)
196{
197 if (atomic_dec_and_test(&ap->refcnt))
198 up(&ap->dead_sem);
199}
200
201/*
202 * Called when a tty is put into sync-PPP line discipline.
203 */
204static int
205ppp_sync_open(struct tty_struct *tty)
206{
207 struct syncppp *ap;
208 int err;
209
Yoann Padioleaudd00cc42007-07-19 01:49:03 -0700210 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211 err = -ENOMEM;
212 if (ap == 0)
213 goto out;
214
215 /* initialize the syncppp structure */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216 ap->tty = tty;
217 ap->mru = PPP_MRU;
218 spin_lock_init(&ap->xmit_lock);
219 spin_lock_init(&ap->recv_lock);
220 ap->xaccm[0] = ~0U;
221 ap->xaccm[3] = 0x60000000U;
222 ap->raccm = ~0U;
223
224 skb_queue_head_init(&ap->rqueue);
225 tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);
226
227 atomic_set(&ap->refcnt, 1);
228 init_MUTEX_LOCKED(&ap->dead_sem);
229
230 ap->chan.private = ap;
231 ap->chan.ops = &sync_ops;
232 ap->chan.mtu = PPP_MRU;
233 ap->chan.hdrlen = 2; /* for A/C bytes */
234 err = ppp_register_channel(&ap->chan);
235 if (err)
236 goto out_free;
237
238 tty->disc_data = ap;
Alan Cox33f0f882006-01-09 20:54:13 -0800239 tty->receive_room = 65536;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240 return 0;
241
242 out_free:
243 kfree(ap);
244 out:
245 return err;
246}
247
248/*
249 * Called when the tty is put into another line discipline
250 * or it hangs up. We have to wait for any cpu currently
251 * executing in any of the other ppp_synctty_* routines to
252 * finish before we can call ppp_unregister_channel and free
253 * the syncppp struct. This routine must be called from
254 * process context, not interrupt or softirq context.
255 */
256static void
257ppp_sync_close(struct tty_struct *tty)
258{
259 struct syncppp *ap;
260
261 write_lock_irq(&disc_data_lock);
262 ap = tty->disc_data;
263 tty->disc_data = NULL;
264 write_unlock_irq(&disc_data_lock);
265 if (ap == 0)
266 return;
267
268 /*
269 * We have now ensured that nobody can start using ap from now
270 * on, but we have to wait for all existing users to finish.
271 * Note that ppp_unregister_channel ensures that no calls to
272 * our channel ops (i.e. ppp_sync_send/ioctl) are in progress
273 * by the time it returns.
274 */
275 if (!atomic_dec_and_test(&ap->refcnt))
276 down(&ap->dead_sem);
277 tasklet_kill(&ap->tsk);
278
279 ppp_unregister_channel(&ap->chan);
280 skb_queue_purge(&ap->rqueue);
281 if (ap->tpkt != 0)
282 kfree_skb(ap->tpkt);
283 kfree(ap);
284}
285
286/*
287 * Called on tty hangup in process context.
288 *
289 * Wait for I/O to driver to complete and unregister PPP channel.
290 * This is already done by the close routine, so just call that.
291 */
292static int ppp_sync_hangup(struct tty_struct *tty)
293{
294 ppp_sync_close(tty);
295 return 0;
296}
297
298/*
299 * Read does nothing - no data is ever available this way.
300 * Pppd reads and writes packets via /dev/ppp instead.
301 */
302static ssize_t
303ppp_sync_read(struct tty_struct *tty, struct file *file,
304 unsigned char __user *buf, size_t count)
305{
306 return -EAGAIN;
307}
308
309/*
310 * Write on the tty does nothing, the packets all come in
311 * from the ppp generic stuff.
312 */
313static ssize_t
314ppp_sync_write(struct tty_struct *tty, struct file *file,
315 const unsigned char *buf, size_t count)
316{
317 return -EAGAIN;
318}
319
320static int
321ppp_synctty_ioctl(struct tty_struct *tty, struct file *file,
322 unsigned int cmd, unsigned long arg)
323{
324 struct syncppp *ap = sp_get(tty);
325 int __user *p = (int __user *)arg;
326 int err, val;
327
328 if (ap == 0)
329 return -ENXIO;
330 err = -EFAULT;
331 switch (cmd) {
332 case PPPIOCGCHAN:
333 err = -ENXIO;
334 if (ap == 0)
335 break;
336 err = -EFAULT;
337 if (put_user(ppp_channel_index(&ap->chan), p))
338 break;
339 err = 0;
340 break;
341
342 case PPPIOCGUNIT:
343 err = -ENXIO;
344 if (ap == 0)
345 break;
346 err = -EFAULT;
347 if (put_user(ppp_unit_number(&ap->chan), p))
348 break;
349 err = 0;
350 break;
351
352 case TCGETS:
353 case TCGETA:
354 err = n_tty_ioctl(tty, file, cmd, arg);
355 break;
356
357 case TCFLSH:
358 /* flush our buffers and the serial port's buffer */
359 if (arg == TCIOFLUSH || arg == TCOFLUSH)
360 ppp_sync_flush_output(ap);
361 err = n_tty_ioctl(tty, file, cmd, arg);
362 break;
363
364 case FIONREAD:
365 val = 0;
366 if (put_user(val, p))
367 break;
368 err = 0;
369 break;
370
371 default:
372 err = -ENOIOCTLCMD;
373 }
374
375 sp_put(ap);
376 return err;
377}
378
379/* No kernel lock - fine */
380static unsigned int
381ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
382{
383 return 0;
384}
385
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386/*
387 * This can now be called from hard interrupt level as well
388 * as soft interrupt level or mainline.
389 */
390static void
391ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
392 char *cflags, int count)
393{
394 struct syncppp *ap = sp_get(tty);
395 unsigned long flags;
396
397 if (ap == 0)
398 return;
399 spin_lock_irqsave(&ap->recv_lock, flags);
400 ppp_sync_input(ap, buf, cflags, count);
401 spin_unlock_irqrestore(&ap->recv_lock, flags);
David S. Millerb03efcf2005-07-08 14:57:23 -0700402 if (!skb_queue_empty(&ap->rqueue))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 tasklet_schedule(&ap->tsk);
404 sp_put(ap);
405 if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
406 && tty->driver->unthrottle)
407 tty->driver->unthrottle(tty);
408}
409
410static void
411ppp_sync_wakeup(struct tty_struct *tty)
412{
413 struct syncppp *ap = sp_get(tty);
414
415 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
416 if (ap == 0)
417 return;
418 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
419 tasklet_schedule(&ap->tsk);
420 sp_put(ap);
421}
422
423
424static struct tty_ldisc ppp_sync_ldisc = {
425 .owner = THIS_MODULE,
426 .magic = TTY_LDISC_MAGIC,
427 .name = "pppsync",
428 .open = ppp_sync_open,
429 .close = ppp_sync_close,
430 .hangup = ppp_sync_hangup,
431 .read = ppp_sync_read,
432 .write = ppp_sync_write,
433 .ioctl = ppp_synctty_ioctl,
434 .poll = ppp_sync_poll,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435 .receive_buf = ppp_sync_receive,
436 .write_wakeup = ppp_sync_wakeup,
437};
438
439static int __init
440ppp_sync_init(void)
441{
442 int err;
443
444 err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
445 if (err != 0)
446 printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
447 err);
448 return err;
449}
450
451/*
452 * The following routines provide the PPP channel interface.
453 */
454static int
455ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
456{
457 struct syncppp *ap = chan->private;
458 int err, val;
459 u32 accm[8];
460 void __user *argp = (void __user *)arg;
461 u32 __user *p = argp;
462
463 err = -EFAULT;
464 switch (cmd) {
465 case PPPIOCGFLAGS:
466 val = ap->flags | ap->rbits;
467 if (put_user(val, (int __user *) argp))
468 break;
469 err = 0;
470 break;
471 case PPPIOCSFLAGS:
472 if (get_user(val, (int __user *) argp))
473 break;
474 ap->flags = val & ~SC_RCV_BITS;
475 spin_lock_irq(&ap->recv_lock);
476 ap->rbits = val & SC_RCV_BITS;
477 spin_unlock_irq(&ap->recv_lock);
478 err = 0;
479 break;
480
481 case PPPIOCGASYNCMAP:
482 if (put_user(ap->xaccm[0], p))
483 break;
484 err = 0;
485 break;
486 case PPPIOCSASYNCMAP:
487 if (get_user(ap->xaccm[0], p))
488 break;
489 err = 0;
490 break;
491
492 case PPPIOCGRASYNCMAP:
493 if (put_user(ap->raccm, p))
494 break;
495 err = 0;
496 break;
497 case PPPIOCSRASYNCMAP:
498 if (get_user(ap->raccm, p))
499 break;
500 err = 0;
501 break;
502
503 case PPPIOCGXASYNCMAP:
504 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
505 break;
506 err = 0;
507 break;
508 case PPPIOCSXASYNCMAP:
509 if (copy_from_user(accm, argp, sizeof(accm)))
510 break;
511 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
512 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
513 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
514 err = 0;
515 break;
516
517 case PPPIOCGMRU:
518 if (put_user(ap->mru, (int __user *) argp))
519 break;
520 err = 0;
521 break;
522 case PPPIOCSMRU:
523 if (get_user(val, (int __user *) argp))
524 break;
525 if (val < PPP_MRU)
526 val = PPP_MRU;
527 ap->mru = val;
528 err = 0;
529 break;
530
531 default:
532 err = -ENOTTY;
533 }
534 return err;
535}
536
537/*
538 * This is called at softirq level to deliver received packets
539 * to the ppp_generic code, and to tell the ppp_generic code
540 * if we can accept more output now.
541 */
542static void ppp_sync_process(unsigned long arg)
543{
544 struct syncppp *ap = (struct syncppp *) arg;
545 struct sk_buff *skb;
546
547 /* process received packets */
548 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
549 if (skb->len == 0) {
550 /* zero length buffers indicate error */
551 ppp_input_error(&ap->chan, 0);
552 kfree_skb(skb);
553 }
554 else
555 ppp_input(&ap->chan, skb);
556 }
557
558 /* try to push more stuff out */
559 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
560 ppp_output_wakeup(&ap->chan);
561}
562
563/*
564 * Procedures for encapsulation and framing.
565 */
566
567struct sk_buff*
568ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
569{
570 int proto;
571 unsigned char *data;
572 int islcp;
573
574 data = skb->data;
575 proto = (data[0] << 8) + data[1];
576
577 /* LCP packets with codes between 1 (configure-request)
578 * and 7 (code-reject) must be sent as though no options
579 * have been negotiated.
580 */
581 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
582
583 /* compress protocol field if option enabled */
584 if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
585 skb_pull(skb,1);
586
587 /* prepend address/control fields if necessary */
588 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
589 if (skb_headroom(skb) < 2) {
590 struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
591 if (npkt == NULL) {
592 kfree_skb(skb);
593 return NULL;
594 }
595 skb_reserve(npkt,2);
Arnaldo Carvalho de Melod626f622007-03-27 18:55:52 -0300596 skb_copy_from_linear_data(skb,
597 skb_put(npkt, skb->len), skb->len);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598 kfree_skb(skb);
599 skb = npkt;
600 }
601 skb_push(skb,2);
602 skb->data[0] = PPP_ALLSTATIONS;
603 skb->data[1] = PPP_UI;
604 }
605
606 ap->last_xmit = jiffies;
607
608 if (skb && ap->flags & SC_LOG_OUTPKT)
609 ppp_print_buffer ("send buffer", skb->data, skb->len);
610
611 return skb;
612}
613
614/*
615 * Transmit-side routines.
616 */
617
618/*
619 * Send a packet to the peer over an sync tty line.
620 * Returns 1 iff the packet was accepted.
621 * If the packet was not accepted, we will call ppp_output_wakeup
622 * at some later time.
623 */
624static int
625ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb)
626{
627 struct syncppp *ap = chan->private;
628
629 ppp_sync_push(ap);
630
631 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
632 return 0; /* already full */
633 skb = ppp_sync_txmunge(ap, skb);
634 if (skb != NULL)
635 ap->tpkt = skb;
636 else
637 clear_bit(XMIT_FULL, &ap->xmit_flags);
638
639 ppp_sync_push(ap);
640 return 1;
641}
642
643/*
644 * Push as much data as possible out to the tty.
645 */
646static int
647ppp_sync_push(struct syncppp *ap)
648{
649 int sent, done = 0;
650 struct tty_struct *tty = ap->tty;
651 int tty_stuffed = 0;
652
653 if (!spin_trylock_bh(&ap->xmit_lock))
654 return 0;
655 for (;;) {
656 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
657 tty_stuffed = 0;
658 if (!tty_stuffed && ap->tpkt != 0) {
659 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
660 sent = tty->driver->write(tty, ap->tpkt->data, ap->tpkt->len);
661 if (sent < 0)
662 goto flush; /* error, e.g. loss of CD */
663 if (sent < ap->tpkt->len) {
664 tty_stuffed = 1;
665 } else {
666 kfree_skb(ap->tpkt);
667 ap->tpkt = NULL;
668 clear_bit(XMIT_FULL, &ap->xmit_flags);
669 done = 1;
670 }
671 continue;
672 }
673 /* haven't made any progress */
674 spin_unlock_bh(&ap->xmit_lock);
675 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags)
676 || (!tty_stuffed && ap->tpkt != 0)))
677 break;
678 if (!spin_trylock_bh(&ap->xmit_lock))
679 break;
680 }
681 return done;
682
683flush:
684 if (ap->tpkt != 0) {
685 kfree_skb(ap->tpkt);
686 ap->tpkt = NULL;
687 clear_bit(XMIT_FULL, &ap->xmit_flags);
688 done = 1;
689 }
690 spin_unlock_bh(&ap->xmit_lock);
691 return done;
692}
693
694/*
695 * Flush output from our internal buffers.
696 * Called for the TCFLSH ioctl.
697 */
698static void
699ppp_sync_flush_output(struct syncppp *ap)
700{
701 int done = 0;
702
703 spin_lock_bh(&ap->xmit_lock);
704 if (ap->tpkt != NULL) {
705 kfree_skb(ap->tpkt);
706 ap->tpkt = NULL;
707 clear_bit(XMIT_FULL, &ap->xmit_flags);
708 done = 1;
709 }
710 spin_unlock_bh(&ap->xmit_lock);
711 if (done)
712 ppp_output_wakeup(&ap->chan);
713}
714
715/*
716 * Receive-side routines.
717 */
718
719/* called when the tty driver has data for us.
720 *
721 * Data is frame oriented: each call to ppp_sync_input is considered
722 * a whole frame. If the 1st flag byte is non-zero then the whole
723 * frame is considered to be in error and is tossed.
724 */
725static void
726ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
727 char *flags, int count)
728{
729 struct sk_buff *skb;
730 unsigned char *p;
731
732 if (count == 0)
733 return;
734
735 if (ap->flags & SC_LOG_INPKT)
736 ppp_print_buffer ("receive buffer", buf, count);
737
738 /* stuff the chars in the skb */
739 if ((skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2)) == 0) {
740 printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
741 goto err;
742 }
743 /* Try to get the payload 4-byte aligned */
744 if (buf[0] != PPP_ALLSTATIONS)
745 skb_reserve(skb, 2 + (buf[0] & 1));
746
747 if (flags != 0 && *flags) {
748 /* error flag set, ignore frame */
749 goto err;
750 } else if (count > skb_tailroom(skb)) {
751 /* packet overflowed MRU */
752 goto err;
753 }
754
755 p = skb_put(skb, count);
756 memcpy(p, buf, count);
757
758 /* strip address/control field if present */
759 p = skb->data;
760 if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
761 /* chop off address/control */
762 if (skb->len < 3)
763 goto err;
764 p = skb_pull(skb, 2);
765 }
766
767 /* decompress protocol field if compressed */
768 if (p[0] & 1) {
769 /* protocol is compressed */
770 skb_push(skb, 1)[0] = 0;
771 } else if (skb->len < 2)
772 goto err;
773
774 /* queue the frame to be processed */
775 skb_queue_tail(&ap->rqueue, skb);
776 return;
777
778err:
779 /* queue zero length packet as error indication */
780 if (skb || (skb = dev_alloc_skb(0))) {
781 skb_trim(skb, 0);
782 skb_queue_tail(&ap->rqueue, skb);
783 }
784}
785
786static void __exit
787ppp_sync_cleanup(void)
788{
Alexey Dobriyan64ccd712005-06-23 00:10:33 -0700789 if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700790 printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
791}
792
793module_init(ppp_sync_init);
794module_exit(ppp_sync_cleanup);
795MODULE_LICENSE("GPL");
796MODULE_ALIAS_LDISC(N_SYNC_PPP);