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1/*
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.
9 *
10 * 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/completion.h>
46#include <linux/init.h>
47#include <linux/interrupt.h>
48#include <linux/slab.h>
49#include <asm/unaligned.h>
50#include <asm/uaccess.h>
51
52#define PPP_VERSION "2.4.2"
53
54/* Structure for storing local state. */
55struct syncppp {
56 struct tty_struct *tty;
57 unsigned int flags;
58 unsigned int rbits;
59 int mru;
60 spinlock_t xmit_lock;
61 spinlock_t recv_lock;
62 unsigned long xmit_flags;
63 u32 xaccm[8];
64 u32 raccm;
65 unsigned int bytes_sent;
66 unsigned int bytes_rcvd;
67
68 struct sk_buff *tpkt;
69 unsigned long last_xmit;
70
71 struct sk_buff_head rqueue;
72
73 struct tasklet_struct tsk;
74
75 atomic_t refcnt;
76 struct completion dead_cmp;
77 struct ppp_channel chan; /* interface to generic ppp layer */
78};
79
80/* Bit numbers in xmit_flags */
81#define XMIT_WAKEUP 0
82#define XMIT_FULL 1
83
84/* Bits in rbits */
85#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
86
87#define PPPSYNC_MAX_RQLEN 32 /* arbitrary */
88
89/*
90 * Prototypes.
91 */
92static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *);
93static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb);
94static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
95 unsigned long arg);
96static void ppp_sync_process(unsigned long arg);
97static int ppp_sync_push(struct syncppp *ap);
98static void ppp_sync_flush_output(struct syncppp *ap);
99static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
100 char *flags, int count);
101
102static const struct ppp_channel_ops sync_ops = {
103 .start_xmit = ppp_sync_send,
104 .ioctl = ppp_sync_ioctl,
105};
106
107/*
108 * Utility procedures to print a buffer in hex/ascii
109 */
110static void
111ppp_print_hex (register __u8 * out, const __u8 * in, int count)
112{
113 register __u8 next_ch;
114 static const char hex[] = "0123456789ABCDEF";
115
116 while (count-- > 0) {
117 next_ch = *in++;
118 *out++ = hex[(next_ch >> 4) & 0x0F];
119 *out++ = hex[next_ch & 0x0F];
120 ++out;
121 }
122}
123
124static void
125ppp_print_char (register __u8 * out, const __u8 * in, int count)
126{
127 register __u8 next_ch;
128
129 while (count-- > 0) {
130 next_ch = *in++;
131
132 if (next_ch < 0x20 || next_ch > 0x7e)
133 *out++ = '.';
134 else {
135 *out++ = next_ch;
136 if (next_ch == '%') /* printk/syslogd has a bug !! */
137 *out++ = '%';
138 }
139 }
140 *out = '\0';
141}
142
143static void
144ppp_print_buffer (const char *name, const __u8 *buf, int count)
145{
146 __u8 line[44];
147
148 if (name != NULL)
149 printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);
150
151 while (count > 8) {
152 memset (line, 32, 44);
153 ppp_print_hex (line, buf, 8);
154 ppp_print_char (&line[8 * 3], buf, 8);
155 printk(KERN_DEBUG "%s\n", line);
156 count -= 8;
157 buf += 8;
158 }
159
160 if (count > 0) {
161 memset (line, 32, 44);
162 ppp_print_hex (line, buf, count);
163 ppp_print_char (&line[8 * 3], buf, count);
164 printk(KERN_DEBUG "%s\n", line);
165 }
166}
167
168
169/*
170 * Routines implementing the synchronous PPP line discipline.
171 */
172
173/*
174 * We have a potential race on dereferencing tty->disc_data,
175 * because the tty layer provides no locking at all - thus one
176 * cpu could be running ppp_synctty_receive while another
177 * calls ppp_synctty_close, which zeroes tty->disc_data and
178 * frees the memory that ppp_synctty_receive is using. The best
179 * way to fix this is to use a rwlock in the tty struct, but for now
180 * we use a single global rwlock for all ttys in ppp line discipline.
181 *
182 * FIXME: Fixed in tty_io nowadays.
183 */
184static DEFINE_RWLOCK(disc_data_lock);
185
186static struct syncppp *sp_get(struct tty_struct *tty)
187{
188 struct syncppp *ap;
189
190 read_lock(&disc_data_lock);
191 ap = tty->disc_data;
192 if (ap != NULL)
193 atomic_inc(&ap->refcnt);
194 read_unlock(&disc_data_lock);
195 return ap;
196}
197
198static void sp_put(struct syncppp *ap)
199{
200 if (atomic_dec_and_test(&ap->refcnt))
201 complete(&ap->dead_cmp);
202}
203
204/*
205 * Called when a tty is put into sync-PPP line discipline.
206 */
207static int
208ppp_sync_open(struct tty_struct *tty)
209{
210 struct syncppp *ap;
211 int err;
212 int speed;
213
214 if (tty->ops->write == NULL)
215 return -EOPNOTSUPP;
216
217 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
218 err = -ENOMEM;
219 if (!ap)
220 goto out;
221
222 /* initialize the syncppp structure */
223 ap->tty = tty;
224 ap->mru = PPP_MRU;
225 spin_lock_init(&ap->xmit_lock);
226 spin_lock_init(&ap->recv_lock);
227 ap->xaccm[0] = ~0U;
228 ap->xaccm[3] = 0x60000000U;
229 ap->raccm = ~0U;
230
231 skb_queue_head_init(&ap->rqueue);
232 tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);
233
234 atomic_set(&ap->refcnt, 1);
235 init_completion(&ap->dead_cmp);
236
237 ap->chan.private = ap;
238 ap->chan.ops = &sync_ops;
239 ap->chan.mtu = PPP_MRU;
240 ap->chan.hdrlen = 2; /* for A/C bytes */
241 speed = tty_get_baud_rate(tty);
242 ap->chan.speed = speed;
243 err = ppp_register_channel(&ap->chan);
244 if (err)
245 goto out_free;
246
247 tty->disc_data = ap;
248 tty->receive_room = 65536;
249 return 0;
250
251 out_free:
252 kfree(ap);
253 out:
254 return err;
255}
256
257/*
258 * Called when the tty is put into another line discipline
259 * or it hangs up. We have to wait for any cpu currently
260 * executing in any of the other ppp_synctty_* routines to
261 * finish before we can call ppp_unregister_channel and free
262 * the syncppp struct. This routine must be called from
263 * process context, not interrupt or softirq context.
264 */
265static void
266ppp_sync_close(struct tty_struct *tty)
267{
268 struct syncppp *ap;
269
270 write_lock_irq(&disc_data_lock);
271 ap = tty->disc_data;
272 tty->disc_data = NULL;
273 write_unlock_irq(&disc_data_lock);
274 if (!ap)
275 return;
276
277 /*
278 * We have now ensured that nobody can start using ap from now
279 * on, but we have to wait for all existing users to finish.
280 * Note that ppp_unregister_channel ensures that no calls to
281 * our channel ops (i.e. ppp_sync_send/ioctl) are in progress
282 * by the time it returns.
283 */
284 if (!atomic_dec_and_test(&ap->refcnt))
285 wait_for_completion(&ap->dead_cmp);
286 tasklet_kill(&ap->tsk);
287
288 ppp_unregister_channel(&ap->chan);
289 skb_queue_purge(&ap->rqueue);
290 kfree_skb(ap->tpkt);
291 kfree(ap);
292}
293
294/*
295 * Called on tty hangup in process context.
296 *
297 * Wait for I/O to driver to complete and unregister PPP channel.
298 * This is already done by the close routine, so just call that.
299 */
300static int ppp_sync_hangup(struct tty_struct *tty)
301{
302 ppp_sync_close(tty);
303 return 0;
304}
305
306/*
307 * Read does nothing - no data is ever available this way.
308 * Pppd reads and writes packets via /dev/ppp instead.
309 */
310static ssize_t
311ppp_sync_read(struct tty_struct *tty, struct file *file,
312 unsigned char __user *buf, size_t count)
313{
314 return -EAGAIN;
315}
316
317/*
318 * Write on the tty does nothing, the packets all come in
319 * from the ppp generic stuff.
320 */
321static ssize_t
322ppp_sync_write(struct tty_struct *tty, struct file *file,
323 const unsigned char *buf, size_t count)
324{
325 return -EAGAIN;
326}
327
328static int
329ppp_synctty_ioctl(struct tty_struct *tty, struct file *file,
330 unsigned int cmd, unsigned long arg)
331{
332 struct syncppp *ap = sp_get(tty);
333 int __user *p = (int __user *)arg;
334 int err, val;
335
336 if (!ap)
337 return -ENXIO;
338 err = -EFAULT;
339 switch (cmd) {
340 case PPPIOCGCHAN:
341 err = -EFAULT;
342 if (put_user(ppp_channel_index(&ap->chan), p))
343 break;
344 err = 0;
345 break;
346
347 case PPPIOCGUNIT:
348 err = -EFAULT;
349 if (put_user(ppp_unit_number(&ap->chan), p))
350 break;
351 err = 0;
352 break;
353
354 case TCFLSH:
355 /* flush our buffers and the serial port's buffer */
356 if (arg == TCIOFLUSH || arg == TCOFLUSH)
357 ppp_sync_flush_output(ap);
358 err = tty_perform_flush(tty, arg);
359 break;
360
361 case FIONREAD:
362 val = 0;
363 if (put_user(val, p))
364 break;
365 err = 0;
366 break;
367
368 default:
369 err = tty_mode_ioctl(tty, file, cmd, arg);
370 break;
371 }
372
373 sp_put(ap);
374 return err;
375}
376
377/* No kernel lock - fine */
378static unsigned int
379ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
380{
381 return 0;
382}
383
384/* May sleep, don't call from interrupt level or with interrupts disabled */
385static void
386ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
387 char *cflags, int count)
388{
389 struct syncppp *ap = sp_get(tty);
390 unsigned long flags;
391
392 if (!ap)
393 return;
394 spin_lock_irqsave(&ap->recv_lock, flags);
395 ppp_sync_input(ap, buf, cflags, count);
396 spin_unlock_irqrestore(&ap->recv_lock, flags);
397 if (!skb_queue_empty(&ap->rqueue))
398 tasklet_schedule(&ap->tsk);
399 sp_put(ap);
400 tty_unthrottle(tty);
401}
402
403static void
404ppp_sync_wakeup(struct tty_struct *tty)
405{
406 struct syncppp *ap = sp_get(tty);
407
408 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
409 if (!ap)
410 return;
411 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
412 tasklet_schedule(&ap->tsk);
413 sp_put(ap);
414}
415
416
417static struct tty_ldisc_ops ppp_sync_ldisc = {
418 .owner = THIS_MODULE,
419 .magic = TTY_LDISC_MAGIC,
420 .name = "pppsync",
421 .open = ppp_sync_open,
422 .close = ppp_sync_close,
423 .hangup = ppp_sync_hangup,
424 .read = ppp_sync_read,
425 .write = ppp_sync_write,
426 .ioctl = ppp_synctty_ioctl,
427 .poll = ppp_sync_poll,
428 .receive_buf = ppp_sync_receive,
429 .write_wakeup = ppp_sync_wakeup,
430};
431
432static int __init
433ppp_sync_init(void)
434{
435 int err;
436
437 err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
438 if (err != 0)
439 printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
440 err);
441 return err;
442}
443
444/*
445 * The following routines provide the PPP channel interface.
446 */
447static int
448ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
449{
450 struct syncppp *ap = chan->private;
451 int err, val;
452 u32 accm[8];
453 void __user *argp = (void __user *)arg;
454 u32 __user *p = argp;
455
456 err = -EFAULT;
457 switch (cmd) {
458 case PPPIOCGFLAGS:
459 val = ap->flags | ap->rbits;
460 if (put_user(val, (int __user *) argp))
461 break;
462 err = 0;
463 break;
464 case PPPIOCSFLAGS:
465 if (get_user(val, (int __user *) argp))
466 break;
467 ap->flags = val & ~SC_RCV_BITS;
468 spin_lock_irq(&ap->recv_lock);
469 ap->rbits = val & SC_RCV_BITS;
470 spin_unlock_irq(&ap->recv_lock);
471 err = 0;
472 break;
473
474 case PPPIOCGASYNCMAP:
475 if (put_user(ap->xaccm[0], p))
476 break;
477 err = 0;
478 break;
479 case PPPIOCSASYNCMAP:
480 if (get_user(ap->xaccm[0], p))
481 break;
482 err = 0;
483 break;
484
485 case PPPIOCGRASYNCMAP:
486 if (put_user(ap->raccm, p))
487 break;
488 err = 0;
489 break;
490 case PPPIOCSRASYNCMAP:
491 if (get_user(ap->raccm, p))
492 break;
493 err = 0;
494 break;
495
496 case PPPIOCGXASYNCMAP:
497 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
498 break;
499 err = 0;
500 break;
501 case PPPIOCSXASYNCMAP:
502 if (copy_from_user(accm, argp, sizeof(accm)))
503 break;
504 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
505 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
506 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
507 err = 0;
508 break;
509
510 case PPPIOCGMRU:
511 if (put_user(ap->mru, (int __user *) argp))
512 break;
513 err = 0;
514 break;
515 case PPPIOCSMRU:
516 if (get_user(val, (int __user *) argp))
517 break;
518 if (val < PPP_MRU)
519 val = PPP_MRU;
520 ap->mru = val;
521 err = 0;
522 break;
523
524 default:
525 err = -ENOTTY;
526 }
527 return err;
528}
529
530/*
531 * This is called at softirq level to deliver received packets
532 * to the ppp_generic code, and to tell the ppp_generic code
533 * if we can accept more output now.
534 */
535static void ppp_sync_process(unsigned long arg)
536{
537 struct syncppp *ap = (struct syncppp *) arg;
538 struct sk_buff *skb;
539
540 /* process received packets */
541 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
542 if (skb->len == 0) {
543 /* zero length buffers indicate error */
544 ppp_input_error(&ap->chan, 0);
545 kfree_skb(skb);
546 }
547 else
548 ppp_input(&ap->chan, skb);
549 }
550
551 /* try to push more stuff out */
552 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
553 ppp_output_wakeup(&ap->chan);
554}
555
556/*
557 * Procedures for encapsulation and framing.
558 */
559
560static struct sk_buff*
561ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
562{
563 int proto;
564 unsigned char *data;
565 int islcp;
566
567 data = skb->data;
568 proto = get_unaligned_be16(data);
569
570 /* LCP packets with codes between 1 (configure-request)
571 * and 7 (code-reject) must be sent as though no options
572 * have been negotiated.
573 */
574 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
575
576 /* compress protocol field if option enabled */
577 if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
578 skb_pull(skb,1);
579
580 /* prepend address/control fields if necessary */
581 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
582 if (skb_headroom(skb) < 2) {
583 struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
584 if (npkt == NULL) {
585 kfree_skb(skb);
586 return NULL;
587 }
588 skb_reserve(npkt,2);
589 skb_copy_from_linear_data(skb,
590 skb_put(npkt, skb->len), skb->len);
591 kfree_skb(skb);
592 skb = npkt;
593 }
594 skb_push(skb,2);
595 skb->data[0] = PPP_ALLSTATIONS;
596 skb->data[1] = PPP_UI;
597 }
598
599 ap->last_xmit = jiffies;
600
601 if (skb && ap->flags & SC_LOG_OUTPKT)
602 ppp_print_buffer ("send buffer", skb->data, skb->len);
603
604 return skb;
605}
606
607/*
608 * Transmit-side routines.
609 */
610
611/*
612 * Send a packet to the peer over an sync tty line.
613 * Returns 1 iff the packet was accepted.
614 * If the packet was not accepted, we will call ppp_output_wakeup
615 * at some later time.
616 */
617static int
618ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb)
619{
620 struct syncppp *ap = chan->private;
621
622 ppp_sync_push(ap);
623
624 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
625 return 0; /* already full */
626 skb = ppp_sync_txmunge(ap, skb);
627 if (skb != NULL)
628 ap->tpkt = skb;
629 else
630 clear_bit(XMIT_FULL, &ap->xmit_flags);
631
632 ppp_sync_push(ap);
633 return 1;
634}
635
636/*
637 * Push as much data as possible out to the tty.
638 */
639static int
640ppp_sync_push(struct syncppp *ap)
641{
642 int sent, done = 0;
643 struct tty_struct *tty = ap->tty;
644 int tty_stuffed = 0;
645
646 if (!spin_trylock_bh(&ap->xmit_lock))
647 return 0;
648 for (;;) {
649 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
650 tty_stuffed = 0;
651 if (!tty_stuffed && ap->tpkt) {
652 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
653 sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
654 if (sent < 0)
655 goto flush; /* error, e.g. loss of CD */
656 if (sent < ap->tpkt->len) {
657 tty_stuffed = 1;
658 } else {
659 kfree_skb(ap->tpkt);
660 ap->tpkt = NULL;
661 clear_bit(XMIT_FULL, &ap->xmit_flags);
662 done = 1;
663 }
664 continue;
665 }
666 /* haven't made any progress */
667 spin_unlock_bh(&ap->xmit_lock);
668 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
669 (!tty_stuffed && ap->tpkt)))
670 break;
671 if (!spin_trylock_bh(&ap->xmit_lock))
672 break;
673 }
674 return done;
675
676flush:
677 if (ap->tpkt) {
678 kfree_skb(ap->tpkt);
679 ap->tpkt = NULL;
680 clear_bit(XMIT_FULL, &ap->xmit_flags);
681 done = 1;
682 }
683 spin_unlock_bh(&ap->xmit_lock);
684 return done;
685}
686
687/*
688 * Flush output from our internal buffers.
689 * Called for the TCFLSH ioctl.
690 */
691static void
692ppp_sync_flush_output(struct syncppp *ap)
693{
694 int done = 0;
695
696 spin_lock_bh(&ap->xmit_lock);
697 if (ap->tpkt != NULL) {
698 kfree_skb(ap->tpkt);
699 ap->tpkt = NULL;
700 clear_bit(XMIT_FULL, &ap->xmit_flags);
701 done = 1;
702 }
703 spin_unlock_bh(&ap->xmit_lock);
704 if (done)
705 ppp_output_wakeup(&ap->chan);
706}
707
708/*
709 * Receive-side routines.
710 */
711
712/* called when the tty driver has data for us.
713 *
714 * Data is frame oriented: each call to ppp_sync_input is considered
715 * a whole frame. If the 1st flag byte is non-zero then the whole
716 * frame is considered to be in error and is tossed.
717 */
718static void
719ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
720 char *flags, int count)
721{
722 struct sk_buff *skb;
723 unsigned char *p;
724
725 if (count == 0)
726 return;
727
728 if (ap->flags & SC_LOG_INPKT)
729 ppp_print_buffer ("receive buffer", buf, count);
730
731 /* stuff the chars in the skb */
732 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
733 if (!skb) {
734 printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
735 goto err;
736 }
737 /* Try to get the payload 4-byte aligned */
738 if (buf[0] != PPP_ALLSTATIONS)
739 skb_reserve(skb, 2 + (buf[0] & 1));
740
741 if (flags && *flags) {
742 /* error flag set, ignore frame */
743 goto err;
744 } else if (count > skb_tailroom(skb)) {
745 /* packet overflowed MRU */
746 goto err;
747 }
748
749 p = skb_put(skb, count);
750 memcpy(p, buf, count);
751
752 /* strip address/control field if present */
753 p = skb->data;
754 if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
755 /* chop off address/control */
756 if (skb->len < 3)
757 goto err;
758 p = skb_pull(skb, 2);
759 }
760
761 /* decompress protocol field if compressed */
762 if (p[0] & 1) {
763 /* protocol is compressed */
764 skb_push(skb, 1)[0] = 0;
765 } else if (skb->len < 2)
766 goto err;
767
768 /* queue the frame to be processed */
769 skb_queue_tail(&ap->rqueue, skb);
770 return;
771
772err:
773 /* queue zero length packet as error indication */
774 if (skb || (skb = dev_alloc_skb(0))) {
775 skb_trim(skb, 0);
776 skb_queue_tail(&ap->rqueue, skb);
777 }
778}
779
780static void __exit
781ppp_sync_cleanup(void)
782{
783 if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
784 printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
785}
786
787module_init(ppp_sync_init);
788module_exit(ppp_sync_cleanup);
789MODULE_LICENSE("GPL");
790MODULE_ALIAS_LDISC(N_SYNC_PPP);