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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/ppp-ioctl.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 <linux/refcount.h>
50#include <asm/unaligned.h>
51#include <linux/uaccess.h>
52
53#define PPP_VERSION "2.4.2"
54
55/* Structure for storing local state. */
56struct syncppp {
57 struct tty_struct *tty;
58 unsigned int flags;
59 unsigned int rbits;
60 int mru;
61 spinlock_t xmit_lock;
62 spinlock_t recv_lock;
63 unsigned long xmit_flags;
64 u32 xaccm[8];
65 u32 raccm;
66 unsigned int bytes_sent;
67 unsigned int bytes_rcvd;
68
69 struct sk_buff *tpkt;
70 unsigned long last_xmit;
71
72 struct sk_buff_head rqueue;
73
74 struct tasklet_struct tsk;
75
76 refcount_t refcnt;
77 struct completion dead_cmp;
78 struct ppp_channel chan; /* interface to generic ppp layer */
79};
80
81/* Bit numbers in xmit_flags */
82#define XMIT_WAKEUP 0
83#define XMIT_FULL 1
84
85/* Bits in rbits */
86#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
87
88#define PPPSYNC_MAX_RQLEN 32 /* arbitrary */
89
90/*
91 * Prototypes.
92 */
93static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *);
94static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb);
95static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
96 unsigned long arg);
97static void ppp_sync_process(unsigned long arg);
98static int ppp_sync_push(struct syncppp *ap);
99static void ppp_sync_flush_output(struct syncppp *ap);
100static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
101 char *flags, int count);
102
103static const struct ppp_channel_ops sync_ops = {
104 .start_xmit = ppp_sync_send,
105 .ioctl = ppp_sync_ioctl,
106};
107
108/*
109 * Utility procedure to print a buffer in hex/ascii
110 */
111static void
112ppp_print_buffer (const char *name, const __u8 *buf, int count)
113{
114 if (name != NULL)
115 printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);
116
117 print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, count);
118}
119
120
121/*
122 * Routines implementing the synchronous PPP line discipline.
123 */
124
125/*
126 * We have a potential race on dereferencing tty->disc_data,
127 * because the tty layer provides no locking at all - thus one
128 * cpu could be running ppp_synctty_receive while another
129 * calls ppp_synctty_close, which zeroes tty->disc_data and
130 * frees the memory that ppp_synctty_receive is using. The best
131 * way to fix this is to use a rwlock in the tty struct, but for now
132 * we use a single global rwlock for all ttys in ppp line discipline.
133 *
134 * FIXME: Fixed in tty_io nowadays.
135 */
136static DEFINE_RWLOCK(disc_data_lock);
137
138static struct syncppp *sp_get(struct tty_struct *tty)
139{
140 struct syncppp *ap;
141
142 read_lock(&disc_data_lock);
143 ap = tty->disc_data;
144 if (ap != NULL)
145 refcount_inc(&ap->refcnt);
146 read_unlock(&disc_data_lock);
147 return ap;
148}
149
150static void sp_put(struct syncppp *ap)
151{
152 if (refcount_dec_and_test(&ap->refcnt))
153 complete(&ap->dead_cmp);
154}
155
156/*
157 * Called when a tty is put into sync-PPP line discipline.
158 */
159static int
160ppp_sync_open(struct tty_struct *tty)
161{
162 struct syncppp *ap;
163 int err;
164 int speed;
165
166 if (tty->ops->write == NULL)
167 return -EOPNOTSUPP;
168
169 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
170 err = -ENOMEM;
171 if (!ap)
172 goto out;
173
174 /* initialize the syncppp structure */
175 ap->tty = tty;
176 ap->mru = PPP_MRU;
177 spin_lock_init(&ap->xmit_lock);
178 spin_lock_init(&ap->recv_lock);
179 ap->xaccm[0] = ~0U;
180 ap->xaccm[3] = 0x60000000U;
181 ap->raccm = ~0U;
182
183 skb_queue_head_init(&ap->rqueue);
184 tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);
185
186 refcount_set(&ap->refcnt, 1);
187 init_completion(&ap->dead_cmp);
188
189 ap->chan.private = ap;
190 ap->chan.ops = &sync_ops;
191 ap->chan.mtu = PPP_MRU;
192 ap->chan.hdrlen = 2; /* for A/C bytes */
193 speed = tty_get_baud_rate(tty);
194 ap->chan.speed = speed;
195 err = ppp_register_channel(&ap->chan);
196 if (err)
197 goto out_free;
198
199 tty->disc_data = ap;
200 tty->receive_room = 65536;
201 return 0;
202
203 out_free:
204 kfree(ap);
205 out:
206 return err;
207}
208
209/*
210 * Called when the tty is put into another line discipline
211 * or it hangs up. We have to wait for any cpu currently
212 * executing in any of the other ppp_synctty_* routines to
213 * finish before we can call ppp_unregister_channel and free
214 * the syncppp struct. This routine must be called from
215 * process context, not interrupt or softirq context.
216 */
217static void
218ppp_sync_close(struct tty_struct *tty)
219{
220 struct syncppp *ap;
221
222 write_lock_irq(&disc_data_lock);
223 ap = tty->disc_data;
224 tty->disc_data = NULL;
225 write_unlock_irq(&disc_data_lock);
226 if (!ap)
227 return;
228
229 /*
230 * We have now ensured that nobody can start using ap from now
231 * on, but we have to wait for all existing users to finish.
232 * Note that ppp_unregister_channel ensures that no calls to
233 * our channel ops (i.e. ppp_sync_send/ioctl) are in progress
234 * by the time it returns.
235 */
236 if (!refcount_dec_and_test(&ap->refcnt))
237 wait_for_completion(&ap->dead_cmp);
238 tasklet_kill(&ap->tsk);
239
240 ppp_unregister_channel(&ap->chan);
241 skb_queue_purge(&ap->rqueue);
242 kfree_skb(ap->tpkt);
243 kfree(ap);
244}
245
246/*
247 * Called on tty hangup in process context.
248 *
249 * Wait for I/O to driver to complete and unregister PPP channel.
250 * This is already done by the close routine, so just call that.
251 */
252static int ppp_sync_hangup(struct tty_struct *tty)
253{
254 ppp_sync_close(tty);
255 return 0;
256}
257
258/*
259 * Read does nothing - no data is ever available this way.
260 * Pppd reads and writes packets via /dev/ppp instead.
261 */
262static ssize_t
263ppp_sync_read(struct tty_struct *tty, struct file *file,
264 unsigned char __user *buf, size_t count)
265{
266 return -EAGAIN;
267}
268
269/*
270 * Write on the tty does nothing, the packets all come in
271 * from the ppp generic stuff.
272 */
273static ssize_t
274ppp_sync_write(struct tty_struct *tty, struct file *file,
275 const unsigned char *buf, size_t count)
276{
277 return -EAGAIN;
278}
279
280static int
281ppp_synctty_ioctl(struct tty_struct *tty, struct file *file,
282 unsigned int cmd, unsigned long arg)
283{
284 struct syncppp *ap = sp_get(tty);
285 int __user *p = (int __user *)arg;
286 int err, val;
287
288 if (!ap)
289 return -ENXIO;
290 err = -EFAULT;
291 switch (cmd) {
292 case PPPIOCGCHAN:
293 err = -EFAULT;
294 if (put_user(ppp_channel_index(&ap->chan), p))
295 break;
296 err = 0;
297 break;
298
299 case PPPIOCGUNIT:
300 err = -EFAULT;
301 if (put_user(ppp_unit_number(&ap->chan), p))
302 break;
303 err = 0;
304 break;
305
306 case TCFLSH:
307 /* flush our buffers and the serial port's buffer */
308 if (arg == TCIOFLUSH || arg == TCOFLUSH)
309 ppp_sync_flush_output(ap);
310 err = n_tty_ioctl_helper(tty, file, cmd, arg);
311 break;
312
313 case FIONREAD:
314 val = 0;
315 if (put_user(val, p))
316 break;
317 err = 0;
318 break;
319
320 default:
321 err = tty_mode_ioctl(tty, file, cmd, arg);
322 break;
323 }
324
325 sp_put(ap);
326 return err;
327}
328
329/* No kernel lock - fine */
330static __poll_t
331ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
332{
333 return 0;
334}
335
336/* May sleep, don't call from interrupt level or with interrupts disabled */
337static void
338ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
339 char *cflags, int count)
340{
341 struct syncppp *ap = sp_get(tty);
342 unsigned long flags;
343
344 if (!ap)
345 return;
346 spin_lock_irqsave(&ap->recv_lock, flags);
347 ppp_sync_input(ap, buf, cflags, count);
348 spin_unlock_irqrestore(&ap->recv_lock, flags);
349 if (!skb_queue_empty(&ap->rqueue))
350 tasklet_schedule(&ap->tsk);
351 sp_put(ap);
352 tty_unthrottle(tty);
353}
354
355static void
356ppp_sync_wakeup(struct tty_struct *tty)
357{
358 struct syncppp *ap = sp_get(tty);
359
360 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
361 if (!ap)
362 return;
363 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
364 tasklet_schedule(&ap->tsk);
365 sp_put(ap);
366}
367
368
369static struct tty_ldisc_ops ppp_sync_ldisc = {
370 .owner = THIS_MODULE,
371 .magic = TTY_LDISC_MAGIC,
372 .name = "pppsync",
373 .open = ppp_sync_open,
374 .close = ppp_sync_close,
375 .hangup = ppp_sync_hangup,
376 .read = ppp_sync_read,
377 .write = ppp_sync_write,
378 .ioctl = ppp_synctty_ioctl,
379 .poll = ppp_sync_poll,
380 .receive_buf = ppp_sync_receive,
381 .write_wakeup = ppp_sync_wakeup,
382};
383
384static int __init
385ppp_sync_init(void)
386{
387 int err;
388
389 err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
390 if (err != 0)
391 printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
392 err);
393 return err;
394}
395
396/*
397 * The following routines provide the PPP channel interface.
398 */
399static int
400ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
401{
402 struct syncppp *ap = chan->private;
403 int err, val;
404 u32 accm[8];
405 void __user *argp = (void __user *)arg;
406 u32 __user *p = argp;
407
408 err = -EFAULT;
409 switch (cmd) {
410 case PPPIOCGFLAGS:
411 val = ap->flags | ap->rbits;
412 if (put_user(val, (int __user *) argp))
413 break;
414 err = 0;
415 break;
416 case PPPIOCSFLAGS:
417 if (get_user(val, (int __user *) argp))
418 break;
419 ap->flags = val & ~SC_RCV_BITS;
420 spin_lock_irq(&ap->recv_lock);
421 ap->rbits = val & SC_RCV_BITS;
422 spin_unlock_irq(&ap->recv_lock);
423 err = 0;
424 break;
425
426 case PPPIOCGASYNCMAP:
427 if (put_user(ap->xaccm[0], p))
428 break;
429 err = 0;
430 break;
431 case PPPIOCSASYNCMAP:
432 if (get_user(ap->xaccm[0], p))
433 break;
434 err = 0;
435 break;
436
437 case PPPIOCGRASYNCMAP:
438 if (put_user(ap->raccm, p))
439 break;
440 err = 0;
441 break;
442 case PPPIOCSRASYNCMAP:
443 if (get_user(ap->raccm, p))
444 break;
445 err = 0;
446 break;
447
448 case PPPIOCGXASYNCMAP:
449 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
450 break;
451 err = 0;
452 break;
453 case PPPIOCSXASYNCMAP:
454 if (copy_from_user(accm, argp, sizeof(accm)))
455 break;
456 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
457 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
458 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
459 err = 0;
460 break;
461
462 case PPPIOCGMRU:
463 if (put_user(ap->mru, (int __user *) argp))
464 break;
465 err = 0;
466 break;
467 case PPPIOCSMRU:
468 if (get_user(val, (int __user *) argp))
469 break;
470 if (val < PPP_MRU)
471 val = PPP_MRU;
472 ap->mru = val;
473 err = 0;
474 break;
475
476 default:
477 err = -ENOTTY;
478 }
479 return err;
480}
481
482/*
483 * This is called at softirq level to deliver received packets
484 * to the ppp_generic code, and to tell the ppp_generic code
485 * if we can accept more output now.
486 */
487static void ppp_sync_process(unsigned long arg)
488{
489 struct syncppp *ap = (struct syncppp *) arg;
490 struct sk_buff *skb;
491
492 /* process received packets */
493 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
494 if (skb->len == 0) {
495 /* zero length buffers indicate error */
496 ppp_input_error(&ap->chan, 0);
497 kfree_skb(skb);
498 }
499 else
500 ppp_input(&ap->chan, skb);
501 }
502
503 /* try to push more stuff out */
504 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
505 ppp_output_wakeup(&ap->chan);
506}
507
508/*
509 * Procedures for encapsulation and framing.
510 */
511
512static struct sk_buff*
513ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
514{
515 int proto;
516 unsigned char *data;
517 int islcp;
518
519 data = skb->data;
520 proto = get_unaligned_be16(data);
521
522 /* LCP packets with codes between 1 (configure-request)
523 * and 7 (code-reject) must be sent as though no options
524 * have been negotiated.
525 */
526 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
527
528 /* compress protocol field if option enabled */
529 if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
530 skb_pull(skb,1);
531
532 /* prepend address/control fields if necessary */
533 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
534 if (skb_headroom(skb) < 2) {
535 struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
536 if (npkt == NULL) {
537 kfree_skb(skb);
538 return NULL;
539 }
540 skb_reserve(npkt,2);
541 skb_copy_from_linear_data(skb,
542 skb_put(npkt, skb->len), skb->len);
543 consume_skb(skb);
544 skb = npkt;
545 }
546 skb_push(skb,2);
547 skb->data[0] = PPP_ALLSTATIONS;
548 skb->data[1] = PPP_UI;
549 }
550
551 ap->last_xmit = jiffies;
552
553 if (skb && ap->flags & SC_LOG_OUTPKT)
554 ppp_print_buffer ("send buffer", skb->data, skb->len);
555
556 return skb;
557}
558
559/*
560 * Transmit-side routines.
561 */
562
563/*
564 * Send a packet to the peer over an sync tty line.
565 * Returns 1 iff the packet was accepted.
566 * If the packet was not accepted, we will call ppp_output_wakeup
567 * at some later time.
568 */
569static int
570ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb)
571{
572 struct syncppp *ap = chan->private;
573
574 ppp_sync_push(ap);
575
576 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
577 return 0; /* already full */
578 skb = ppp_sync_txmunge(ap, skb);
579 if (skb != NULL)
580 ap->tpkt = skb;
581 else
582 clear_bit(XMIT_FULL, &ap->xmit_flags);
583
584 ppp_sync_push(ap);
585 return 1;
586}
587
588/*
589 * Push as much data as possible out to the tty.
590 */
591static int
592ppp_sync_push(struct syncppp *ap)
593{
594 int sent, done = 0;
595 struct tty_struct *tty = ap->tty;
596 int tty_stuffed = 0;
597
598 if (!spin_trylock_bh(&ap->xmit_lock))
599 return 0;
600 for (;;) {
601 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
602 tty_stuffed = 0;
603 if (!tty_stuffed && ap->tpkt) {
604 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
605 sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
606 if (sent < 0)
607 goto flush; /* error, e.g. loss of CD */
608 if (sent < ap->tpkt->len) {
609 tty_stuffed = 1;
610 } else {
611 consume_skb(ap->tpkt);
612 ap->tpkt = NULL;
613 clear_bit(XMIT_FULL, &ap->xmit_flags);
614 done = 1;
615 }
616 continue;
617 }
618 /* haven't made any progress */
619 spin_unlock_bh(&ap->xmit_lock);
620 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
621 (!tty_stuffed && ap->tpkt)))
622 break;
623 if (!spin_trylock_bh(&ap->xmit_lock))
624 break;
625 }
626 return done;
627
628flush:
629 if (ap->tpkt) {
630 kfree_skb(ap->tpkt);
631 ap->tpkt = NULL;
632 clear_bit(XMIT_FULL, &ap->xmit_flags);
633 done = 1;
634 }
635 spin_unlock_bh(&ap->xmit_lock);
636 return done;
637}
638
639/*
640 * Flush output from our internal buffers.
641 * Called for the TCFLSH ioctl.
642 */
643static void
644ppp_sync_flush_output(struct syncppp *ap)
645{
646 int done = 0;
647
648 spin_lock_bh(&ap->xmit_lock);
649 if (ap->tpkt != NULL) {
650 kfree_skb(ap->tpkt);
651 ap->tpkt = NULL;
652 clear_bit(XMIT_FULL, &ap->xmit_flags);
653 done = 1;
654 }
655 spin_unlock_bh(&ap->xmit_lock);
656 if (done)
657 ppp_output_wakeup(&ap->chan);
658}
659
660/*
661 * Receive-side routines.
662 */
663
664/* called when the tty driver has data for us.
665 *
666 * Data is frame oriented: each call to ppp_sync_input is considered
667 * a whole frame. If the 1st flag byte is non-zero then the whole
668 * frame is considered to be in error and is tossed.
669 */
670static void
671ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
672 char *flags, int count)
673{
674 struct sk_buff *skb;
675 unsigned char *p;
676
677 if (count == 0)
678 return;
679
680 if (ap->flags & SC_LOG_INPKT)
681 ppp_print_buffer ("receive buffer", buf, count);
682
683 /* stuff the chars in the skb */
684 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
685 if (!skb) {
686 printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
687 goto err;
688 }
689 /* Try to get the payload 4-byte aligned */
690 if (buf[0] != PPP_ALLSTATIONS)
691 skb_reserve(skb, 2 + (buf[0] & 1));
692
693 if (flags && *flags) {
694 /* error flag set, ignore frame */
695 goto err;
696 } else if (count > skb_tailroom(skb)) {
697 /* packet overflowed MRU */
698 goto err;
699 }
700
701 skb_put_data(skb, buf, count);
702
703 /* strip address/control field if present */
704 p = skb->data;
705 if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
706 /* chop off address/control */
707 if (skb->len < 3)
708 goto err;
709 p = skb_pull(skb, 2);
710 }
711
712 /* decompress protocol field if compressed */
713 if (p[0] & 1) {
714 /* protocol is compressed */
715 *(u8 *)skb_push(skb, 1) = 0;
716 } else if (skb->len < 2)
717 goto err;
718
719 /* queue the frame to be processed */
720 skb_queue_tail(&ap->rqueue, skb);
721 return;
722
723err:
724 /* queue zero length packet as error indication */
725 if (skb || (skb = dev_alloc_skb(0))) {
726 skb_trim(skb, 0);
727 skb_queue_tail(&ap->rqueue, skb);
728 }
729}
730
731static void __exit
732ppp_sync_cleanup(void)
733{
734 if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
735 printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
736}
737
738module_init(ppp_sync_init);
739module_exit(ppp_sync_cleanup);
740MODULE_LICENSE("GPL");
741MODULE_ALIAS_LDISC(N_SYNC_PPP);