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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * PPP async serial channel driver for Linux.
4 *
5 * Copyright 1999 Paul Mackerras.
6 *
7 * This driver provides the encapsulation and framing for sending
8 * and receiving PPP frames over async serial lines. It relies on
9 * the generic PPP layer to give it frames to send and to process
10 * received frames. It implements the PPP line discipline.
11 *
12 * Part of the code in this driver was inspired by the old async-only
13 * PPP driver, written by Michael Callahan and Al Longyear, and
14 * subsequently hacked by Paul Mackerras.
15 */
16
17#include <linux/module.h>
18#include <linux/kernel.h>
19#include <linux/skbuff.h>
20#include <linux/tty.h>
21#include <linux/netdevice.h>
22#include <linux/poll.h>
23#include <linux/crc-ccitt.h>
24#include <linux/ppp_defs.h>
25#include <linux/ppp-ioctl.h>
26#include <linux/ppp_channel.h>
27#include <linux/spinlock.h>
28#include <linux/init.h>
29#include <linux/interrupt.h>
30#include <linux/jiffies.h>
31#include <linux/slab.h>
32#include <linux/unaligned.h>
33#include <linux/uaccess.h>
34#include <asm/string.h>
35
36#define PPP_VERSION "2.4.2"
37
38#define OBUFSIZE 4096
39
40/* Structure for storing local state. */
41struct asyncppp {
42 struct tty_struct *tty;
43 unsigned int flags;
44 unsigned int state;
45 unsigned int rbits;
46 int mru;
47 spinlock_t xmit_lock;
48 spinlock_t recv_lock;
49 unsigned long xmit_flags;
50 u32 xaccm[8];
51 u32 raccm;
52 unsigned int bytes_sent;
53 unsigned int bytes_rcvd;
54
55 struct sk_buff *tpkt;
56 int tpkt_pos;
57 u16 tfcs;
58 unsigned char *optr;
59 unsigned char *olim;
60 unsigned long last_xmit;
61
62 struct sk_buff *rpkt;
63 int lcp_fcs;
64 struct sk_buff_head rqueue;
65
66 struct tasklet_struct tsk;
67
68 refcount_t refcnt;
69 struct completion dead;
70 struct ppp_channel chan; /* interface to generic ppp layer */
71 unsigned char obuf[OBUFSIZE];
72};
73
74/* Bit numbers in xmit_flags */
75#define XMIT_WAKEUP 0
76#define XMIT_FULL 1
77#define XMIT_BUSY 2
78
79/* State bits */
80#define SC_TOSS 1
81#define SC_ESCAPE 2
82#define SC_PREV_ERROR 4
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
87static int flag_time = HZ;
88module_param(flag_time, int, 0);
89MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
90MODULE_DESCRIPTION("PPP async serial channel module");
91MODULE_LICENSE("GPL");
92MODULE_ALIAS_LDISC(N_PPP);
93
94/*
95 * Prototypes.
96 */
97static int ppp_async_encode(struct asyncppp *ap);
98static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
99static int ppp_async_push(struct asyncppp *ap);
100static void ppp_async_flush_output(struct asyncppp *ap);
101static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
102 const u8 *flags, int count);
103static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
104 unsigned long arg);
105static void ppp_async_process(struct tasklet_struct *t);
106
107static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
108 int len, int inbound);
109
110static const struct ppp_channel_ops async_ops = {
111 .start_xmit = ppp_async_send,
112 .ioctl = ppp_async_ioctl,
113};
114
115/*
116 * Routines implementing the PPP line discipline.
117 */
118
119/*
120 * We have a potential race on dereferencing tty->disc_data,
121 * because the tty layer provides no locking at all - thus one
122 * cpu could be running ppp_asynctty_receive while another
123 * calls ppp_asynctty_close, which zeroes tty->disc_data and
124 * frees the memory that ppp_asynctty_receive is using. The best
125 * way to fix this is to use a rwlock in the tty struct, but for now
126 * we use a single global rwlock for all ttys in ppp line discipline.
127 *
128 * FIXME: this is no longer true. The _close path for the ldisc is
129 * now guaranteed to be sane.
130 */
131static DEFINE_RWLOCK(disc_data_lock);
132
133static struct asyncppp *ap_get(struct tty_struct *tty)
134{
135 struct asyncppp *ap;
136
137 read_lock(&disc_data_lock);
138 ap = tty->disc_data;
139 if (ap != NULL)
140 refcount_inc(&ap->refcnt);
141 read_unlock(&disc_data_lock);
142 return ap;
143}
144
145static void ap_put(struct asyncppp *ap)
146{
147 if (refcount_dec_and_test(&ap->refcnt))
148 complete(&ap->dead);
149}
150
151/*
152 * Called when a tty is put into PPP line discipline. Called in process
153 * context.
154 */
155static int
156ppp_asynctty_open(struct tty_struct *tty)
157{
158 struct asyncppp *ap;
159 int err;
160 int speed;
161
162 if (tty->ops->write == NULL)
163 return -EOPNOTSUPP;
164
165 err = -ENOMEM;
166 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
167 if (!ap)
168 goto out;
169
170 /* initialize the asyncppp structure */
171 ap->tty = tty;
172 ap->mru = PPP_MRU;
173 spin_lock_init(&ap->xmit_lock);
174 spin_lock_init(&ap->recv_lock);
175 ap->xaccm[0] = ~0U;
176 ap->xaccm[3] = 0x60000000U;
177 ap->raccm = ~0U;
178 ap->optr = ap->obuf;
179 ap->olim = ap->obuf;
180 ap->lcp_fcs = -1;
181
182 skb_queue_head_init(&ap->rqueue);
183 tasklet_setup(&ap->tsk, ppp_async_process);
184
185 refcount_set(&ap->refcnt, 1);
186 init_completion(&ap->dead);
187
188 ap->chan.private = ap;
189 ap->chan.ops = &async_ops;
190 ap->chan.mtu = PPP_MRU;
191 speed = tty_get_baud_rate(tty);
192 ap->chan.speed = speed;
193 err = ppp_register_channel(&ap->chan);
194 if (err)
195 goto out_free;
196
197 tty->disc_data = ap;
198 tty->receive_room = 65536;
199 return 0;
200
201 out_free:
202 kfree(ap);
203 out:
204 return err;
205}
206
207/*
208 * Called when the tty is put into another line discipline
209 * or it hangs up. We have to wait for any cpu currently
210 * executing in any of the other ppp_asynctty_* routines to
211 * finish before we can call ppp_unregister_channel and free
212 * the asyncppp struct. This routine must be called from
213 * process context, not interrupt or softirq context.
214 */
215static void
216ppp_asynctty_close(struct tty_struct *tty)
217{
218 struct asyncppp *ap;
219
220 write_lock_irq(&disc_data_lock);
221 ap = tty->disc_data;
222 tty->disc_data = NULL;
223 write_unlock_irq(&disc_data_lock);
224 if (!ap)
225 return;
226
227 /*
228 * We have now ensured that nobody can start using ap from now
229 * on, but we have to wait for all existing users to finish.
230 * Note that ppp_unregister_channel ensures that no calls to
231 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
232 * by the time it returns.
233 */
234 if (!refcount_dec_and_test(&ap->refcnt))
235 wait_for_completion(&ap->dead);
236 tasklet_kill(&ap->tsk);
237
238 ppp_unregister_channel(&ap->chan);
239 kfree_skb(ap->rpkt);
240 skb_queue_purge(&ap->rqueue);
241 kfree_skb(ap->tpkt);
242 kfree(ap);
243}
244
245/*
246 * Called on tty hangup in process context.
247 *
248 * Wait for I/O to driver to complete and unregister PPP channel.
249 * This is already done by the close routine, so just call that.
250 */
251static void ppp_asynctty_hangup(struct tty_struct *tty)
252{
253 ppp_asynctty_close(tty);
254}
255
256/*
257 * Read does nothing - no data is ever available this way.
258 * Pppd reads and writes packets via /dev/ppp instead.
259 */
260static ssize_t
261ppp_asynctty_read(struct tty_struct *tty, struct file *file, u8 *buf,
262 size_t count, void **cookie, unsigned long offset)
263{
264 return -EAGAIN;
265}
266
267/*
268 * Write on the tty does nothing, the packets all come in
269 * from the ppp generic stuff.
270 */
271static ssize_t
272ppp_asynctty_write(struct tty_struct *tty, struct file *file, const u8 *buf,
273 size_t count)
274{
275 return -EAGAIN;
276}
277
278/*
279 * Called in process context only. May be re-entered by multiple
280 * ioctl calling threads.
281 */
282
283static int
284ppp_asynctty_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
285{
286 struct asyncppp *ap = ap_get(tty);
287 int err, val;
288 int __user *p = (int __user *)arg;
289
290 if (!ap)
291 return -ENXIO;
292 err = -EFAULT;
293 switch (cmd) {
294 case PPPIOCGCHAN:
295 err = -EFAULT;
296 if (put_user(ppp_channel_index(&ap->chan), p))
297 break;
298 err = 0;
299 break;
300
301 case PPPIOCGUNIT:
302 err = -EFAULT;
303 if (put_user(ppp_unit_number(&ap->chan), p))
304 break;
305 err = 0;
306 break;
307
308 case TCFLSH:
309 /* flush our buffers and the serial port's buffer */
310 if (arg == TCIOFLUSH || arg == TCOFLUSH)
311 ppp_async_flush_output(ap);
312 err = n_tty_ioctl_helper(tty, cmd, arg);
313 break;
314
315 case FIONREAD:
316 val = 0;
317 if (put_user(val, p))
318 break;
319 err = 0;
320 break;
321
322 default:
323 /* Try the various mode ioctls */
324 err = tty_mode_ioctl(tty, cmd, arg);
325 }
326
327 ap_put(ap);
328 return err;
329}
330
331/* May sleep, don't call from interrupt level or with interrupts disabled */
332static void
333ppp_asynctty_receive(struct tty_struct *tty, const u8 *buf, const u8 *cflags,
334 size_t count)
335{
336 struct asyncppp *ap = ap_get(tty);
337 unsigned long flags;
338
339 if (!ap)
340 return;
341 spin_lock_irqsave(&ap->recv_lock, flags);
342 ppp_async_input(ap, buf, cflags, count);
343 spin_unlock_irqrestore(&ap->recv_lock, flags);
344 if (!skb_queue_empty(&ap->rqueue))
345 tasklet_schedule(&ap->tsk);
346 ap_put(ap);
347 tty_unthrottle(tty);
348}
349
350static void
351ppp_asynctty_wakeup(struct tty_struct *tty)
352{
353 struct asyncppp *ap = ap_get(tty);
354
355 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
356 if (!ap)
357 return;
358 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
359 tasklet_schedule(&ap->tsk);
360 ap_put(ap);
361}
362
363
364static struct tty_ldisc_ops ppp_ldisc = {
365 .owner = THIS_MODULE,
366 .num = N_PPP,
367 .name = "ppp",
368 .open = ppp_asynctty_open,
369 .close = ppp_asynctty_close,
370 .hangup = ppp_asynctty_hangup,
371 .read = ppp_asynctty_read,
372 .write = ppp_asynctty_write,
373 .ioctl = ppp_asynctty_ioctl,
374 .receive_buf = ppp_asynctty_receive,
375 .write_wakeup = ppp_asynctty_wakeup,
376};
377
378static int __init
379ppp_async_init(void)
380{
381 int err;
382
383 err = tty_register_ldisc(&ppp_ldisc);
384 if (err != 0)
385 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
386 err);
387 return err;
388}
389
390/*
391 * The following routines provide the PPP channel interface.
392 */
393static int
394ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
395{
396 struct asyncppp *ap = chan->private;
397 void __user *argp = (void __user *)arg;
398 int __user *p = argp;
399 int err, val;
400 u32 accm[8];
401
402 err = -EFAULT;
403 switch (cmd) {
404 case PPPIOCGFLAGS:
405 val = ap->flags | ap->rbits;
406 if (put_user(val, p))
407 break;
408 err = 0;
409 break;
410 case PPPIOCSFLAGS:
411 if (get_user(val, p))
412 break;
413 ap->flags = val & ~SC_RCV_BITS;
414 spin_lock_irq(&ap->recv_lock);
415 ap->rbits = val & SC_RCV_BITS;
416 spin_unlock_irq(&ap->recv_lock);
417 err = 0;
418 break;
419
420 case PPPIOCGASYNCMAP:
421 if (put_user(ap->xaccm[0], (u32 __user *)argp))
422 break;
423 err = 0;
424 break;
425 case PPPIOCSASYNCMAP:
426 if (get_user(ap->xaccm[0], (u32 __user *)argp))
427 break;
428 err = 0;
429 break;
430
431 case PPPIOCGRASYNCMAP:
432 if (put_user(ap->raccm, (u32 __user *)argp))
433 break;
434 err = 0;
435 break;
436 case PPPIOCSRASYNCMAP:
437 if (get_user(ap->raccm, (u32 __user *)argp))
438 break;
439 err = 0;
440 break;
441
442 case PPPIOCGXASYNCMAP:
443 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
444 break;
445 err = 0;
446 break;
447 case PPPIOCSXASYNCMAP:
448 if (copy_from_user(accm, argp, sizeof(accm)))
449 break;
450 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
451 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
452 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
453 err = 0;
454 break;
455
456 case PPPIOCGMRU:
457 if (put_user(ap->mru, p))
458 break;
459 err = 0;
460 break;
461 case PPPIOCSMRU:
462 if (get_user(val, p))
463 break;
464 if (val > U16_MAX) {
465 err = -EINVAL;
466 break;
467 }
468 if (val < PPP_MRU)
469 val = PPP_MRU;
470 ap->mru = val;
471 err = 0;
472 break;
473
474 default:
475 err = -ENOTTY;
476 }
477
478 return err;
479}
480
481/*
482 * This is called at softirq level to deliver received packets
483 * to the ppp_generic code, and to tell the ppp_generic code
484 * if we can accept more output now.
485 */
486static void ppp_async_process(struct tasklet_struct *t)
487{
488 struct asyncppp *ap = from_tasklet(ap, t, tsk);
489 struct sk_buff *skb;
490
491 /* process received packets */
492 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
493 if (skb->cb[0])
494 ppp_input_error(&ap->chan, 0);
495 ppp_input(&ap->chan, skb);
496 }
497
498 /* try to push more stuff out */
499 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
500 ppp_output_wakeup(&ap->chan);
501}
502
503/*
504 * Procedures for encapsulation and framing.
505 */
506
507/*
508 * Procedure to encode the data for async serial transmission.
509 * Does octet stuffing (escaping), puts the address/control bytes
510 * on if A/C compression is disabled, and does protocol compression.
511 * Assumes ap->tpkt != 0 on entry.
512 * Returns 1 if we finished the current frame, 0 otherwise.
513 */
514
515#define PUT_BYTE(ap, buf, c, islcp) do { \
516 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
517 *buf++ = PPP_ESCAPE; \
518 *buf++ = c ^ PPP_TRANS; \
519 } else \
520 *buf++ = c; \
521} while (0)
522
523static int
524ppp_async_encode(struct asyncppp *ap)
525{
526 int fcs, i, count, c, proto;
527 unsigned char *buf, *buflim;
528 unsigned char *data;
529 int islcp;
530
531 buf = ap->obuf;
532 ap->olim = buf;
533 ap->optr = buf;
534 i = ap->tpkt_pos;
535 data = ap->tpkt->data;
536 count = ap->tpkt->len;
537 fcs = ap->tfcs;
538 proto = get_unaligned_be16(data);
539
540 /*
541 * LCP packets with code values between 1 (configure-request)
542 * and 7 (code-reject) must be sent as though no options
543 * had been negotiated.
544 */
545 islcp = proto == PPP_LCP && count >= 3 && 1 <= data[2] && data[2] <= 7;
546
547 if (i == 0) {
548 if (islcp)
549 async_lcp_peek(ap, data, count, 0);
550
551 /*
552 * Start of a new packet - insert the leading FLAG
553 * character if necessary.
554 */
555 if (islcp || flag_time == 0 ||
556 time_after_eq(jiffies, ap->last_xmit + flag_time))
557 *buf++ = PPP_FLAG;
558 ap->last_xmit = jiffies;
559 fcs = PPP_INITFCS;
560
561 /*
562 * Put in the address/control bytes if necessary
563 */
564 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
565 PUT_BYTE(ap, buf, 0xff, islcp);
566 fcs = PPP_FCS(fcs, 0xff);
567 PUT_BYTE(ap, buf, 0x03, islcp);
568 fcs = PPP_FCS(fcs, 0x03);
569 }
570 }
571
572 /*
573 * Once we put in the last byte, we need to put in the FCS
574 * and closing flag, so make sure there is at least 7 bytes
575 * of free space in the output buffer.
576 */
577 buflim = ap->obuf + OBUFSIZE - 6;
578 while (i < count && buf < buflim) {
579 c = data[i++];
580 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
581 continue; /* compress protocol field */
582 fcs = PPP_FCS(fcs, c);
583 PUT_BYTE(ap, buf, c, islcp);
584 }
585
586 if (i < count) {
587 /*
588 * Remember where we are up to in this packet.
589 */
590 ap->olim = buf;
591 ap->tpkt_pos = i;
592 ap->tfcs = fcs;
593 return 0;
594 }
595
596 /*
597 * We have finished the packet. Add the FCS and flag.
598 */
599 fcs = ~fcs;
600 c = fcs & 0xff;
601 PUT_BYTE(ap, buf, c, islcp);
602 c = (fcs >> 8) & 0xff;
603 PUT_BYTE(ap, buf, c, islcp);
604 *buf++ = PPP_FLAG;
605 ap->olim = buf;
606
607 consume_skb(ap->tpkt);
608 ap->tpkt = NULL;
609 return 1;
610}
611
612/*
613 * Transmit-side routines.
614 */
615
616/*
617 * Send a packet to the peer over an async tty line.
618 * Returns 1 iff the packet was accepted.
619 * If the packet was not accepted, we will call ppp_output_wakeup
620 * at some later time.
621 */
622static int
623ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
624{
625 struct asyncppp *ap = chan->private;
626
627 ppp_async_push(ap);
628
629 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
630 return 0; /* already full */
631 ap->tpkt = skb;
632 ap->tpkt_pos = 0;
633
634 ppp_async_push(ap);
635 return 1;
636}
637
638/*
639 * Push as much data as possible out to the tty.
640 */
641static int
642ppp_async_push(struct asyncppp *ap)
643{
644 int avail, sent, done = 0;
645 struct tty_struct *tty = ap->tty;
646 int tty_stuffed = 0;
647
648 /*
649 * We can get called recursively here if the tty write
650 * function calls our wakeup function. This can happen
651 * for example on a pty with both the master and slave
652 * set to PPP line discipline.
653 * We use the XMIT_BUSY bit to detect this and get out,
654 * leaving the XMIT_WAKEUP bit set to tell the other
655 * instance that it may now be able to write more now.
656 */
657 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
658 return 0;
659 spin_lock_bh(&ap->xmit_lock);
660 for (;;) {
661 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
662 tty_stuffed = 0;
663 if (!tty_stuffed && ap->optr < ap->olim) {
664 avail = ap->olim - ap->optr;
665 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
666 sent = tty->ops->write(tty, ap->optr, avail);
667 if (sent < 0)
668 goto flush; /* error, e.g. loss of CD */
669 ap->optr += sent;
670 if (sent < avail)
671 tty_stuffed = 1;
672 continue;
673 }
674 if (ap->optr >= ap->olim && ap->tpkt) {
675 if (ppp_async_encode(ap)) {
676 /* finished processing ap->tpkt */
677 clear_bit(XMIT_FULL, &ap->xmit_flags);
678 done = 1;
679 }
680 continue;
681 }
682 /*
683 * We haven't made any progress this time around.
684 * Clear XMIT_BUSY to let other callers in, but
685 * after doing so we have to check if anyone set
686 * XMIT_WAKEUP since we last checked it. If they
687 * did, we should try again to set XMIT_BUSY and go
688 * around again in case XMIT_BUSY was still set when
689 * the other caller tried.
690 */
691 clear_bit(XMIT_BUSY, &ap->xmit_flags);
692 /* any more work to do? if not, exit the loop */
693 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
694 (!tty_stuffed && ap->tpkt)))
695 break;
696 /* more work to do, see if we can do it now */
697 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
698 break;
699 }
700 spin_unlock_bh(&ap->xmit_lock);
701 return done;
702
703flush:
704 clear_bit(XMIT_BUSY, &ap->xmit_flags);
705 if (ap->tpkt) {
706 kfree_skb(ap->tpkt);
707 ap->tpkt = NULL;
708 clear_bit(XMIT_FULL, &ap->xmit_flags);
709 done = 1;
710 }
711 ap->optr = ap->olim;
712 spin_unlock_bh(&ap->xmit_lock);
713 return done;
714}
715
716/*
717 * Flush output from our internal buffers.
718 * Called for the TCFLSH ioctl. Can be entered in parallel
719 * but this is covered by the xmit_lock.
720 */
721static void
722ppp_async_flush_output(struct asyncppp *ap)
723{
724 int done = 0;
725
726 spin_lock_bh(&ap->xmit_lock);
727 ap->optr = ap->olim;
728 if (ap->tpkt != NULL) {
729 kfree_skb(ap->tpkt);
730 ap->tpkt = NULL;
731 clear_bit(XMIT_FULL, &ap->xmit_flags);
732 done = 1;
733 }
734 spin_unlock_bh(&ap->xmit_lock);
735 if (done)
736 ppp_output_wakeup(&ap->chan);
737}
738
739/*
740 * Receive-side routines.
741 */
742
743/* see how many ordinary chars there are at the start of buf */
744static inline int
745scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
746{
747 int i, c;
748
749 for (i = 0; i < count; ++i) {
750 c = buf[i];
751 if (c == PPP_ESCAPE || c == PPP_FLAG ||
752 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
753 break;
754 }
755 return i;
756}
757
758/* called when a flag is seen - do end-of-packet processing */
759static void
760process_input_packet(struct asyncppp *ap)
761{
762 struct sk_buff *skb;
763 unsigned char *p;
764 unsigned int len, fcs;
765
766 skb = ap->rpkt;
767 if (ap->state & (SC_TOSS | SC_ESCAPE))
768 goto err;
769
770 if (skb == NULL)
771 return; /* 0-length packet */
772
773 /* check the FCS */
774 p = skb->data;
775 len = skb->len;
776 if (len < 3)
777 goto err; /* too short */
778 fcs = PPP_INITFCS;
779 for (; len > 0; --len)
780 fcs = PPP_FCS(fcs, *p++);
781 if (fcs != PPP_GOODFCS)
782 goto err; /* bad FCS */
783 skb_trim(skb, skb->len - 2);
784
785 /* check for address/control and protocol compression */
786 p = skb->data;
787 if (p[0] == PPP_ALLSTATIONS) {
788 /* chop off address/control */
789 if (p[1] != PPP_UI || skb->len < 3)
790 goto err;
791 p = skb_pull(skb, 2);
792 }
793
794 /* If protocol field is not compressed, it can be LCP packet */
795 if (!(p[0] & 0x01)) {
796 unsigned int proto;
797
798 if (skb->len < 2)
799 goto err;
800 proto = (p[0] << 8) + p[1];
801 if (proto == PPP_LCP)
802 async_lcp_peek(ap, p, skb->len, 1);
803 }
804
805 /* queue the frame to be processed */
806 skb->cb[0] = ap->state;
807 skb_queue_tail(&ap->rqueue, skb);
808 ap->rpkt = NULL;
809 ap->state = 0;
810 return;
811
812 err:
813 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
814 ap->state = SC_PREV_ERROR;
815 if (skb) {
816 /* make skb appear as freshly allocated */
817 skb_trim(skb, 0);
818 skb_reserve(skb, - skb_headroom(skb));
819 }
820}
821
822/* Called when the tty driver has data for us. Runs parallel with the
823 other ldisc functions but will not be re-entered */
824
825static void
826ppp_async_input(struct asyncppp *ap, const u8 *buf, const u8 *flags, int count)
827{
828 struct sk_buff *skb;
829 int c, i, j, n, s, f;
830 unsigned char *sp;
831
832 /* update bits used for 8-bit cleanness detection */
833 if (~ap->rbits & SC_RCV_BITS) {
834 s = 0;
835 for (i = 0; i < count; ++i) {
836 c = buf[i];
837 if (flags && flags[i] != 0)
838 continue;
839 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
840 c = ((c >> 4) ^ c) & 0xf;
841 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
842 }
843 ap->rbits |= s;
844 }
845
846 while (count > 0) {
847 /* scan through and see how many chars we can do in bulk */
848 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
849 n = 1;
850 else
851 n = scan_ordinary(ap, buf, count);
852
853 f = 0;
854 if (flags && (ap->state & SC_TOSS) == 0) {
855 /* check the flags to see if any char had an error */
856 for (j = 0; j < n; ++j)
857 if ((f = flags[j]) != 0)
858 break;
859 }
860 if (f != 0) {
861 /* start tossing */
862 ap->state |= SC_TOSS;
863
864 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
865 /* stuff the chars in the skb */
866 skb = ap->rpkt;
867 if (!skb) {
868 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
869 if (!skb)
870 goto nomem;
871 ap->rpkt = skb;
872 }
873 if (skb->len == 0) {
874 /* Try to get the payload 4-byte aligned.
875 * This should match the
876 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
877 * process_input_packet, but we do not have
878 * enough chars here to test buf[1] and buf[2].
879 */
880 if (buf[0] != PPP_ALLSTATIONS)
881 skb_reserve(skb, 2 + (buf[0] & 1));
882 }
883 if (n > skb_tailroom(skb)) {
884 /* packet overflowed MRU */
885 ap->state |= SC_TOSS;
886 } else {
887 sp = skb_put_data(skb, buf, n);
888 if (ap->state & SC_ESCAPE) {
889 sp[0] ^= PPP_TRANS;
890 ap->state &= ~SC_ESCAPE;
891 }
892 }
893 }
894
895 if (n >= count)
896 break;
897
898 c = buf[n];
899 if (flags != NULL && flags[n] != 0) {
900 ap->state |= SC_TOSS;
901 } else if (c == PPP_FLAG) {
902 process_input_packet(ap);
903 } else if (c == PPP_ESCAPE) {
904 ap->state |= SC_ESCAPE;
905 } else if (I_IXON(ap->tty)) {
906 if (c == START_CHAR(ap->tty))
907 start_tty(ap->tty);
908 else if (c == STOP_CHAR(ap->tty))
909 stop_tty(ap->tty);
910 }
911 /* otherwise it's a char in the recv ACCM */
912 ++n;
913
914 buf += n;
915 if (flags)
916 flags += n;
917 count -= n;
918 }
919 return;
920
921 nomem:
922 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
923 ap->state |= SC_TOSS;
924}
925
926/*
927 * We look at LCP frames going past so that we can notice
928 * and react to the LCP configure-ack from the peer.
929 * In the situation where the peer has been sent a configure-ack
930 * already, LCP is up once it has sent its configure-ack
931 * so the immediately following packet can be sent with the
932 * configured LCP options. This allows us to process the following
933 * packet correctly without pppd needing to respond quickly.
934 *
935 * We only respond to the received configure-ack if we have just
936 * sent a configure-request, and the configure-ack contains the
937 * same data (this is checked using a 16-bit crc of the data).
938 */
939#define CONFREQ 1 /* LCP code field values */
940#define CONFACK 2
941#define LCP_MRU 1 /* LCP option numbers */
942#define LCP_ASYNCMAP 2
943
944static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
945 int len, int inbound)
946{
947 int dlen, fcs, i, code;
948 u32 val;
949
950 data += 2; /* skip protocol bytes */
951 len -= 2;
952 if (len < 4) /* 4 = code, ID, length */
953 return;
954 code = data[0];
955 if (code != CONFACK && code != CONFREQ)
956 return;
957 dlen = get_unaligned_be16(data + 2);
958 if (len < dlen)
959 return; /* packet got truncated or length is bogus */
960
961 if (code == (inbound? CONFACK: CONFREQ)) {
962 /*
963 * sent confreq or received confack:
964 * calculate the crc of the data from the ID field on.
965 */
966 fcs = PPP_INITFCS;
967 for (i = 1; i < dlen; ++i)
968 fcs = PPP_FCS(fcs, data[i]);
969
970 if (!inbound) {
971 /* outbound confreq - remember the crc for later */
972 ap->lcp_fcs = fcs;
973 return;
974 }
975
976 /* received confack, check the crc */
977 fcs ^= ap->lcp_fcs;
978 ap->lcp_fcs = -1;
979 if (fcs != 0)
980 return;
981 } else if (inbound)
982 return; /* not interested in received confreq */
983
984 /* process the options in the confack */
985 data += 4;
986 dlen -= 4;
987 /* data[0] is code, data[1] is length */
988 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
989 switch (data[0]) {
990 case LCP_MRU:
991 val = get_unaligned_be16(data + 2);
992 if (inbound)
993 ap->mru = val;
994 else
995 ap->chan.mtu = val;
996 break;
997 case LCP_ASYNCMAP:
998 val = get_unaligned_be32(data + 2);
999 if (inbound)
1000 ap->raccm = val;
1001 else
1002 ap->xaccm[0] = val;
1003 break;
1004 }
1005 dlen -= data[1];
1006 data += data[1];
1007 }
1008}
1009
1010static void __exit ppp_async_cleanup(void)
1011{
1012 tty_unregister_ldisc(&ppp_ldisc);
1013}
1014
1015module_init(ppp_async_init);
1016module_exit(ppp_async_cleanup);
1/*
2 * PPP async serial channel driver for Linux.
3 *
4 * Copyright 1999 Paul Mackerras.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 * This driver provides the encapsulation and framing for sending
12 * and receiving PPP frames over async serial lines. It relies on
13 * the generic PPP layer to give it frames to send and to process
14 * received frames. It implements the PPP line discipline.
15 *
16 * Part of the code in this driver was inspired by the old async-only
17 * PPP driver, written by Michael Callahan and Al Longyear, and
18 * subsequently hacked by Paul Mackerras.
19 */
20
21#include <linux/module.h>
22#include <linux/kernel.h>
23#include <linux/skbuff.h>
24#include <linux/tty.h>
25#include <linux/netdevice.h>
26#include <linux/poll.h>
27#include <linux/crc-ccitt.h>
28#include <linux/ppp_defs.h>
29#include <linux/ppp-ioctl.h>
30#include <linux/ppp_channel.h>
31#include <linux/spinlock.h>
32#include <linux/init.h>
33#include <linux/interrupt.h>
34#include <linux/jiffies.h>
35#include <linux/slab.h>
36#include <asm/unaligned.h>
37#include <asm/uaccess.h>
38#include <asm/string.h>
39
40#define PPP_VERSION "2.4.2"
41
42#define OBUFSIZE 4096
43
44/* Structure for storing local state. */
45struct asyncppp {
46 struct tty_struct *tty;
47 unsigned int flags;
48 unsigned int state;
49 unsigned int rbits;
50 int mru;
51 spinlock_t xmit_lock;
52 spinlock_t recv_lock;
53 unsigned long xmit_flags;
54 u32 xaccm[8];
55 u32 raccm;
56 unsigned int bytes_sent;
57 unsigned int bytes_rcvd;
58
59 struct sk_buff *tpkt;
60 int tpkt_pos;
61 u16 tfcs;
62 unsigned char *optr;
63 unsigned char *olim;
64 unsigned long last_xmit;
65
66 struct sk_buff *rpkt;
67 int lcp_fcs;
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 unsigned char obuf[OBUFSIZE];
76};
77
78/* Bit numbers in xmit_flags */
79#define XMIT_WAKEUP 0
80#define XMIT_FULL 1
81#define XMIT_BUSY 2
82
83/* State bits */
84#define SC_TOSS 1
85#define SC_ESCAPE 2
86#define SC_PREV_ERROR 4
87
88/* Bits in rbits */
89#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
90
91static int flag_time = HZ;
92module_param(flag_time, int, 0);
93MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
94MODULE_LICENSE("GPL");
95MODULE_ALIAS_LDISC(N_PPP);
96
97/*
98 * Prototypes.
99 */
100static int ppp_async_encode(struct asyncppp *ap);
101static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
102static int ppp_async_push(struct asyncppp *ap);
103static void ppp_async_flush_output(struct asyncppp *ap);
104static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
105 char *flags, int count);
106static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
107 unsigned long arg);
108static void ppp_async_process(unsigned long arg);
109
110static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
111 int len, int inbound);
112
113static const struct ppp_channel_ops async_ops = {
114 .start_xmit = ppp_async_send,
115 .ioctl = ppp_async_ioctl,
116};
117
118/*
119 * Routines implementing the PPP line discipline.
120 */
121
122/*
123 * We have a potential race on dereferencing tty->disc_data,
124 * because the tty layer provides no locking at all - thus one
125 * cpu could be running ppp_asynctty_receive while another
126 * calls ppp_asynctty_close, which zeroes tty->disc_data and
127 * frees the memory that ppp_asynctty_receive is using. The best
128 * way to fix this is to use a rwlock in the tty struct, but for now
129 * we use a single global rwlock for all ttys in ppp line discipline.
130 *
131 * FIXME: this is no longer true. The _close path for the ldisc is
132 * now guaranteed to be sane.
133 */
134static DEFINE_RWLOCK(disc_data_lock);
135
136static struct asyncppp *ap_get(struct tty_struct *tty)
137{
138 struct asyncppp *ap;
139
140 read_lock(&disc_data_lock);
141 ap = tty->disc_data;
142 if (ap != NULL)
143 atomic_inc(&ap->refcnt);
144 read_unlock(&disc_data_lock);
145 return ap;
146}
147
148static void ap_put(struct asyncppp *ap)
149{
150 if (atomic_dec_and_test(&ap->refcnt))
151 up(&ap->dead_sem);
152}
153
154/*
155 * Called when a tty is put into PPP line discipline. Called in process
156 * context.
157 */
158static int
159ppp_asynctty_open(struct tty_struct *tty)
160{
161 struct asyncppp *ap;
162 int err;
163 int speed;
164
165 if (tty->ops->write == NULL)
166 return -EOPNOTSUPP;
167
168 err = -ENOMEM;
169 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
170 if (!ap)
171 goto out;
172
173 /* initialize the asyncppp structure */
174 ap->tty = tty;
175 ap->mru = PPP_MRU;
176 spin_lock_init(&ap->xmit_lock);
177 spin_lock_init(&ap->recv_lock);
178 ap->xaccm[0] = ~0U;
179 ap->xaccm[3] = 0x60000000U;
180 ap->raccm = ~0U;
181 ap->optr = ap->obuf;
182 ap->olim = ap->obuf;
183 ap->lcp_fcs = -1;
184
185 skb_queue_head_init(&ap->rqueue);
186 tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
187
188 atomic_set(&ap->refcnt, 1);
189 sema_init(&ap->dead_sem, 0);
190
191 ap->chan.private = ap;
192 ap->chan.ops = &async_ops;
193 ap->chan.mtu = PPP_MRU;
194 speed = tty_get_baud_rate(tty);
195 ap->chan.speed = speed;
196 err = ppp_register_channel(&ap->chan);
197 if (err)
198 goto out_free;
199
200 tty->disc_data = ap;
201 tty->receive_room = 65536;
202 return 0;
203
204 out_free:
205 kfree(ap);
206 out:
207 return err;
208}
209
210/*
211 * Called when the tty is put into another line discipline
212 * or it hangs up. We have to wait for any cpu currently
213 * executing in any of the other ppp_asynctty_* routines to
214 * finish before we can call ppp_unregister_channel and free
215 * the asyncppp struct. This routine must be called from
216 * process context, not interrupt or softirq context.
217 */
218static void
219ppp_asynctty_close(struct tty_struct *tty)
220{
221 struct asyncppp *ap;
222
223 write_lock_irq(&disc_data_lock);
224 ap = tty->disc_data;
225 tty->disc_data = NULL;
226 write_unlock_irq(&disc_data_lock);
227 if (!ap)
228 return;
229
230 /*
231 * We have now ensured that nobody can start using ap from now
232 * on, but we have to wait for all existing users to finish.
233 * Note that ppp_unregister_channel ensures that no calls to
234 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
235 * by the time it returns.
236 */
237 if (!atomic_dec_and_test(&ap->refcnt))
238 down(&ap->dead_sem);
239 tasklet_kill(&ap->tsk);
240
241 ppp_unregister_channel(&ap->chan);
242 kfree_skb(ap->rpkt);
243 skb_queue_purge(&ap->rqueue);
244 kfree_skb(ap->tpkt);
245 kfree(ap);
246}
247
248/*
249 * Called on tty hangup in process context.
250 *
251 * Wait for I/O to driver to complete and unregister PPP channel.
252 * This is already done by the close routine, so just call that.
253 */
254static int ppp_asynctty_hangup(struct tty_struct *tty)
255{
256 ppp_asynctty_close(tty);
257 return 0;
258}
259
260/*
261 * Read does nothing - no data is ever available this way.
262 * Pppd reads and writes packets via /dev/ppp instead.
263 */
264static ssize_t
265ppp_asynctty_read(struct tty_struct *tty, struct file *file,
266 unsigned char __user *buf, size_t count)
267{
268 return -EAGAIN;
269}
270
271/*
272 * Write on the tty does nothing, the packets all come in
273 * from the ppp generic stuff.
274 */
275static ssize_t
276ppp_asynctty_write(struct tty_struct *tty, struct file *file,
277 const unsigned char *buf, size_t count)
278{
279 return -EAGAIN;
280}
281
282/*
283 * Called in process context only. May be re-entered by multiple
284 * ioctl calling threads.
285 */
286
287static int
288ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
289 unsigned int cmd, unsigned long arg)
290{
291 struct asyncppp *ap = ap_get(tty);
292 int err, val;
293 int __user *p = (int __user *)arg;
294
295 if (!ap)
296 return -ENXIO;
297 err = -EFAULT;
298 switch (cmd) {
299 case PPPIOCGCHAN:
300 err = -EFAULT;
301 if (put_user(ppp_channel_index(&ap->chan), p))
302 break;
303 err = 0;
304 break;
305
306 case PPPIOCGUNIT:
307 err = -EFAULT;
308 if (put_user(ppp_unit_number(&ap->chan), p))
309 break;
310 err = 0;
311 break;
312
313 case TCFLSH:
314 /* flush our buffers and the serial port's buffer */
315 if (arg == TCIOFLUSH || arg == TCOFLUSH)
316 ppp_async_flush_output(ap);
317 err = n_tty_ioctl_helper(tty, file, cmd, arg);
318 break;
319
320 case FIONREAD:
321 val = 0;
322 if (put_user(val, p))
323 break;
324 err = 0;
325 break;
326
327 default:
328 /* Try the various mode ioctls */
329 err = tty_mode_ioctl(tty, file, cmd, arg);
330 }
331
332 ap_put(ap);
333 return err;
334}
335
336/* No kernel lock - fine */
337static unsigned int
338ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
339{
340 return 0;
341}
342
343/* May sleep, don't call from interrupt level or with interrupts disabled */
344static void
345ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
346 char *cflags, int count)
347{
348 struct asyncppp *ap = ap_get(tty);
349 unsigned long flags;
350
351 if (!ap)
352 return;
353 spin_lock_irqsave(&ap->recv_lock, flags);
354 ppp_async_input(ap, buf, cflags, count);
355 spin_unlock_irqrestore(&ap->recv_lock, flags);
356 if (!skb_queue_empty(&ap->rqueue))
357 tasklet_schedule(&ap->tsk);
358 ap_put(ap);
359 tty_unthrottle(tty);
360}
361
362static void
363ppp_asynctty_wakeup(struct tty_struct *tty)
364{
365 struct asyncppp *ap = ap_get(tty);
366
367 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
368 if (!ap)
369 return;
370 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
371 tasklet_schedule(&ap->tsk);
372 ap_put(ap);
373}
374
375
376static struct tty_ldisc_ops ppp_ldisc = {
377 .owner = THIS_MODULE,
378 .magic = TTY_LDISC_MAGIC,
379 .name = "ppp",
380 .open = ppp_asynctty_open,
381 .close = ppp_asynctty_close,
382 .hangup = ppp_asynctty_hangup,
383 .read = ppp_asynctty_read,
384 .write = ppp_asynctty_write,
385 .ioctl = ppp_asynctty_ioctl,
386 .poll = ppp_asynctty_poll,
387 .receive_buf = ppp_asynctty_receive,
388 .write_wakeup = ppp_asynctty_wakeup,
389};
390
391static int __init
392ppp_async_init(void)
393{
394 int err;
395
396 err = tty_register_ldisc(N_PPP, &ppp_ldisc);
397 if (err != 0)
398 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
399 err);
400 return err;
401}
402
403/*
404 * The following routines provide the PPP channel interface.
405 */
406static int
407ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
408{
409 struct asyncppp *ap = chan->private;
410 void __user *argp = (void __user *)arg;
411 int __user *p = argp;
412 int err, val;
413 u32 accm[8];
414
415 err = -EFAULT;
416 switch (cmd) {
417 case PPPIOCGFLAGS:
418 val = ap->flags | ap->rbits;
419 if (put_user(val, p))
420 break;
421 err = 0;
422 break;
423 case PPPIOCSFLAGS:
424 if (get_user(val, p))
425 break;
426 ap->flags = val & ~SC_RCV_BITS;
427 spin_lock_irq(&ap->recv_lock);
428 ap->rbits = val & SC_RCV_BITS;
429 spin_unlock_irq(&ap->recv_lock);
430 err = 0;
431 break;
432
433 case PPPIOCGASYNCMAP:
434 if (put_user(ap->xaccm[0], (u32 __user *)argp))
435 break;
436 err = 0;
437 break;
438 case PPPIOCSASYNCMAP:
439 if (get_user(ap->xaccm[0], (u32 __user *)argp))
440 break;
441 err = 0;
442 break;
443
444 case PPPIOCGRASYNCMAP:
445 if (put_user(ap->raccm, (u32 __user *)argp))
446 break;
447 err = 0;
448 break;
449 case PPPIOCSRASYNCMAP:
450 if (get_user(ap->raccm, (u32 __user *)argp))
451 break;
452 err = 0;
453 break;
454
455 case PPPIOCGXASYNCMAP:
456 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
457 break;
458 err = 0;
459 break;
460 case PPPIOCSXASYNCMAP:
461 if (copy_from_user(accm, argp, sizeof(accm)))
462 break;
463 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
464 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
465 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
466 err = 0;
467 break;
468
469 case PPPIOCGMRU:
470 if (put_user(ap->mru, p))
471 break;
472 err = 0;
473 break;
474 case PPPIOCSMRU:
475 if (get_user(val, p))
476 break;
477 if (val < PPP_MRU)
478 val = PPP_MRU;
479 ap->mru = val;
480 err = 0;
481 break;
482
483 default:
484 err = -ENOTTY;
485 }
486
487 return err;
488}
489
490/*
491 * This is called at softirq level to deliver received packets
492 * to the ppp_generic code, and to tell the ppp_generic code
493 * if we can accept more output now.
494 */
495static void ppp_async_process(unsigned long arg)
496{
497 struct asyncppp *ap = (struct asyncppp *) arg;
498 struct sk_buff *skb;
499
500 /* process received packets */
501 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
502 if (skb->cb[0])
503 ppp_input_error(&ap->chan, 0);
504 ppp_input(&ap->chan, skb);
505 }
506
507 /* try to push more stuff out */
508 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
509 ppp_output_wakeup(&ap->chan);
510}
511
512/*
513 * Procedures for encapsulation and framing.
514 */
515
516/*
517 * Procedure to encode the data for async serial transmission.
518 * Does octet stuffing (escaping), puts the address/control bytes
519 * on if A/C compression is disabled, and does protocol compression.
520 * Assumes ap->tpkt != 0 on entry.
521 * Returns 1 if we finished the current frame, 0 otherwise.
522 */
523
524#define PUT_BYTE(ap, buf, c, islcp) do { \
525 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
526 *buf++ = PPP_ESCAPE; \
527 *buf++ = c ^ PPP_TRANS; \
528 } else \
529 *buf++ = c; \
530} while (0)
531
532static int
533ppp_async_encode(struct asyncppp *ap)
534{
535 int fcs, i, count, c, proto;
536 unsigned char *buf, *buflim;
537 unsigned char *data;
538 int islcp;
539
540 buf = ap->obuf;
541 ap->olim = buf;
542 ap->optr = buf;
543 i = ap->tpkt_pos;
544 data = ap->tpkt->data;
545 count = ap->tpkt->len;
546 fcs = ap->tfcs;
547 proto = get_unaligned_be16(data);
548
549 /*
550 * LCP packets with code values between 1 (configure-reqest)
551 * and 7 (code-reject) must be sent as though no options
552 * had been negotiated.
553 */
554 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
555
556 if (i == 0) {
557 if (islcp)
558 async_lcp_peek(ap, data, count, 0);
559
560 /*
561 * Start of a new packet - insert the leading FLAG
562 * character if necessary.
563 */
564 if (islcp || flag_time == 0 ||
565 time_after_eq(jiffies, ap->last_xmit + flag_time))
566 *buf++ = PPP_FLAG;
567 ap->last_xmit = jiffies;
568 fcs = PPP_INITFCS;
569
570 /*
571 * Put in the address/control bytes if necessary
572 */
573 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
574 PUT_BYTE(ap, buf, 0xff, islcp);
575 fcs = PPP_FCS(fcs, 0xff);
576 PUT_BYTE(ap, buf, 0x03, islcp);
577 fcs = PPP_FCS(fcs, 0x03);
578 }
579 }
580
581 /*
582 * Once we put in the last byte, we need to put in the FCS
583 * and closing flag, so make sure there is at least 7 bytes
584 * of free space in the output buffer.
585 */
586 buflim = ap->obuf + OBUFSIZE - 6;
587 while (i < count && buf < buflim) {
588 c = data[i++];
589 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
590 continue; /* compress protocol field */
591 fcs = PPP_FCS(fcs, c);
592 PUT_BYTE(ap, buf, c, islcp);
593 }
594
595 if (i < count) {
596 /*
597 * Remember where we are up to in this packet.
598 */
599 ap->olim = buf;
600 ap->tpkt_pos = i;
601 ap->tfcs = fcs;
602 return 0;
603 }
604
605 /*
606 * We have finished the packet. Add the FCS and flag.
607 */
608 fcs = ~fcs;
609 c = fcs & 0xff;
610 PUT_BYTE(ap, buf, c, islcp);
611 c = (fcs >> 8) & 0xff;
612 PUT_BYTE(ap, buf, c, islcp);
613 *buf++ = PPP_FLAG;
614 ap->olim = buf;
615
616 consume_skb(ap->tpkt);
617 ap->tpkt = NULL;
618 return 1;
619}
620
621/*
622 * Transmit-side routines.
623 */
624
625/*
626 * Send a packet to the peer over an async tty line.
627 * Returns 1 iff the packet was accepted.
628 * If the packet was not accepted, we will call ppp_output_wakeup
629 * at some later time.
630 */
631static int
632ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
633{
634 struct asyncppp *ap = chan->private;
635
636 ppp_async_push(ap);
637
638 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
639 return 0; /* already full */
640 ap->tpkt = skb;
641 ap->tpkt_pos = 0;
642
643 ppp_async_push(ap);
644 return 1;
645}
646
647/*
648 * Push as much data as possible out to the tty.
649 */
650static int
651ppp_async_push(struct asyncppp *ap)
652{
653 int avail, sent, done = 0;
654 struct tty_struct *tty = ap->tty;
655 int tty_stuffed = 0;
656
657 /*
658 * We can get called recursively here if the tty write
659 * function calls our wakeup function. This can happen
660 * for example on a pty with both the master and slave
661 * set to PPP line discipline.
662 * We use the XMIT_BUSY bit to detect this and get out,
663 * leaving the XMIT_WAKEUP bit set to tell the other
664 * instance that it may now be able to write more now.
665 */
666 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
667 return 0;
668 spin_lock_bh(&ap->xmit_lock);
669 for (;;) {
670 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
671 tty_stuffed = 0;
672 if (!tty_stuffed && ap->optr < ap->olim) {
673 avail = ap->olim - ap->optr;
674 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
675 sent = tty->ops->write(tty, ap->optr, avail);
676 if (sent < 0)
677 goto flush; /* error, e.g. loss of CD */
678 ap->optr += sent;
679 if (sent < avail)
680 tty_stuffed = 1;
681 continue;
682 }
683 if (ap->optr >= ap->olim && ap->tpkt) {
684 if (ppp_async_encode(ap)) {
685 /* finished processing ap->tpkt */
686 clear_bit(XMIT_FULL, &ap->xmit_flags);
687 done = 1;
688 }
689 continue;
690 }
691 /*
692 * We haven't made any progress this time around.
693 * Clear XMIT_BUSY to let other callers in, but
694 * after doing so we have to check if anyone set
695 * XMIT_WAKEUP since we last checked it. If they
696 * did, we should try again to set XMIT_BUSY and go
697 * around again in case XMIT_BUSY was still set when
698 * the other caller tried.
699 */
700 clear_bit(XMIT_BUSY, &ap->xmit_flags);
701 /* any more work to do? if not, exit the loop */
702 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
703 (!tty_stuffed && ap->tpkt)))
704 break;
705 /* more work to do, see if we can do it now */
706 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
707 break;
708 }
709 spin_unlock_bh(&ap->xmit_lock);
710 return done;
711
712flush:
713 clear_bit(XMIT_BUSY, &ap->xmit_flags);
714 if (ap->tpkt) {
715 kfree_skb(ap->tpkt);
716 ap->tpkt = NULL;
717 clear_bit(XMIT_FULL, &ap->xmit_flags);
718 done = 1;
719 }
720 ap->optr = ap->olim;
721 spin_unlock_bh(&ap->xmit_lock);
722 return done;
723}
724
725/*
726 * Flush output from our internal buffers.
727 * Called for the TCFLSH ioctl. Can be entered in parallel
728 * but this is covered by the xmit_lock.
729 */
730static void
731ppp_async_flush_output(struct asyncppp *ap)
732{
733 int done = 0;
734
735 spin_lock_bh(&ap->xmit_lock);
736 ap->optr = ap->olim;
737 if (ap->tpkt != NULL) {
738 kfree_skb(ap->tpkt);
739 ap->tpkt = NULL;
740 clear_bit(XMIT_FULL, &ap->xmit_flags);
741 done = 1;
742 }
743 spin_unlock_bh(&ap->xmit_lock);
744 if (done)
745 ppp_output_wakeup(&ap->chan);
746}
747
748/*
749 * Receive-side routines.
750 */
751
752/* see how many ordinary chars there are at the start of buf */
753static inline int
754scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
755{
756 int i, c;
757
758 for (i = 0; i < count; ++i) {
759 c = buf[i];
760 if (c == PPP_ESCAPE || c == PPP_FLAG ||
761 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
762 break;
763 }
764 return i;
765}
766
767/* called when a flag is seen - do end-of-packet processing */
768static void
769process_input_packet(struct asyncppp *ap)
770{
771 struct sk_buff *skb;
772 unsigned char *p;
773 unsigned int len, fcs, proto;
774
775 skb = ap->rpkt;
776 if (ap->state & (SC_TOSS | SC_ESCAPE))
777 goto err;
778
779 if (skb == NULL)
780 return; /* 0-length packet */
781
782 /* check the FCS */
783 p = skb->data;
784 len = skb->len;
785 if (len < 3)
786 goto err; /* too short */
787 fcs = PPP_INITFCS;
788 for (; len > 0; --len)
789 fcs = PPP_FCS(fcs, *p++);
790 if (fcs != PPP_GOODFCS)
791 goto err; /* bad FCS */
792 skb_trim(skb, skb->len - 2);
793
794 /* check for address/control and protocol compression */
795 p = skb->data;
796 if (p[0] == PPP_ALLSTATIONS) {
797 /* chop off address/control */
798 if (p[1] != PPP_UI || skb->len < 3)
799 goto err;
800 p = skb_pull(skb, 2);
801 }
802 proto = p[0];
803 if (proto & 1) {
804 /* protocol is compressed */
805 skb_push(skb, 1)[0] = 0;
806 } else {
807 if (skb->len < 2)
808 goto err;
809 proto = (proto << 8) + p[1];
810 if (proto == PPP_LCP)
811 async_lcp_peek(ap, p, skb->len, 1);
812 }
813
814 /* queue the frame to be processed */
815 skb->cb[0] = ap->state;
816 skb_queue_tail(&ap->rqueue, skb);
817 ap->rpkt = NULL;
818 ap->state = 0;
819 return;
820
821 err:
822 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
823 ap->state = SC_PREV_ERROR;
824 if (skb) {
825 /* make skb appear as freshly allocated */
826 skb_trim(skb, 0);
827 skb_reserve(skb, - skb_headroom(skb));
828 }
829}
830
831/* Called when the tty driver has data for us. Runs parallel with the
832 other ldisc functions but will not be re-entered */
833
834static void
835ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
836 char *flags, int count)
837{
838 struct sk_buff *skb;
839 int c, i, j, n, s, f;
840 unsigned char *sp;
841
842 /* update bits used for 8-bit cleanness detection */
843 if (~ap->rbits & SC_RCV_BITS) {
844 s = 0;
845 for (i = 0; i < count; ++i) {
846 c = buf[i];
847 if (flags && flags[i] != 0)
848 continue;
849 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
850 c = ((c >> 4) ^ c) & 0xf;
851 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
852 }
853 ap->rbits |= s;
854 }
855
856 while (count > 0) {
857 /* scan through and see how many chars we can do in bulk */
858 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
859 n = 1;
860 else
861 n = scan_ordinary(ap, buf, count);
862
863 f = 0;
864 if (flags && (ap->state & SC_TOSS) == 0) {
865 /* check the flags to see if any char had an error */
866 for (j = 0; j < n; ++j)
867 if ((f = flags[j]) != 0)
868 break;
869 }
870 if (f != 0) {
871 /* start tossing */
872 ap->state |= SC_TOSS;
873
874 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
875 /* stuff the chars in the skb */
876 skb = ap->rpkt;
877 if (!skb) {
878 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
879 if (!skb)
880 goto nomem;
881 ap->rpkt = skb;
882 }
883 if (skb->len == 0) {
884 /* Try to get the payload 4-byte aligned.
885 * This should match the
886 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
887 * process_input_packet, but we do not have
888 * enough chars here to test buf[1] and buf[2].
889 */
890 if (buf[0] != PPP_ALLSTATIONS)
891 skb_reserve(skb, 2 + (buf[0] & 1));
892 }
893 if (n > skb_tailroom(skb)) {
894 /* packet overflowed MRU */
895 ap->state |= SC_TOSS;
896 } else {
897 sp = skb_put(skb, n);
898 memcpy(sp, buf, n);
899 if (ap->state & SC_ESCAPE) {
900 sp[0] ^= PPP_TRANS;
901 ap->state &= ~SC_ESCAPE;
902 }
903 }
904 }
905
906 if (n >= count)
907 break;
908
909 c = buf[n];
910 if (flags != NULL && flags[n] != 0) {
911 ap->state |= SC_TOSS;
912 } else if (c == PPP_FLAG) {
913 process_input_packet(ap);
914 } else if (c == PPP_ESCAPE) {
915 ap->state |= SC_ESCAPE;
916 } else if (I_IXON(ap->tty)) {
917 if (c == START_CHAR(ap->tty))
918 start_tty(ap->tty);
919 else if (c == STOP_CHAR(ap->tty))
920 stop_tty(ap->tty);
921 }
922 /* otherwise it's a char in the recv ACCM */
923 ++n;
924
925 buf += n;
926 if (flags)
927 flags += n;
928 count -= n;
929 }
930 return;
931
932 nomem:
933 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
934 ap->state |= SC_TOSS;
935}
936
937/*
938 * We look at LCP frames going past so that we can notice
939 * and react to the LCP configure-ack from the peer.
940 * In the situation where the peer has been sent a configure-ack
941 * already, LCP is up once it has sent its configure-ack
942 * so the immediately following packet can be sent with the
943 * configured LCP options. This allows us to process the following
944 * packet correctly without pppd needing to respond quickly.
945 *
946 * We only respond to the received configure-ack if we have just
947 * sent a configure-request, and the configure-ack contains the
948 * same data (this is checked using a 16-bit crc of the data).
949 */
950#define CONFREQ 1 /* LCP code field values */
951#define CONFACK 2
952#define LCP_MRU 1 /* LCP option numbers */
953#define LCP_ASYNCMAP 2
954
955static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
956 int len, int inbound)
957{
958 int dlen, fcs, i, code;
959 u32 val;
960
961 data += 2; /* skip protocol bytes */
962 len -= 2;
963 if (len < 4) /* 4 = code, ID, length */
964 return;
965 code = data[0];
966 if (code != CONFACK && code != CONFREQ)
967 return;
968 dlen = get_unaligned_be16(data + 2);
969 if (len < dlen)
970 return; /* packet got truncated or length is bogus */
971
972 if (code == (inbound? CONFACK: CONFREQ)) {
973 /*
974 * sent confreq or received confack:
975 * calculate the crc of the data from the ID field on.
976 */
977 fcs = PPP_INITFCS;
978 for (i = 1; i < dlen; ++i)
979 fcs = PPP_FCS(fcs, data[i]);
980
981 if (!inbound) {
982 /* outbound confreq - remember the crc for later */
983 ap->lcp_fcs = fcs;
984 return;
985 }
986
987 /* received confack, check the crc */
988 fcs ^= ap->lcp_fcs;
989 ap->lcp_fcs = -1;
990 if (fcs != 0)
991 return;
992 } else if (inbound)
993 return; /* not interested in received confreq */
994
995 /* process the options in the confack */
996 data += 4;
997 dlen -= 4;
998 /* data[0] is code, data[1] is length */
999 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
1000 switch (data[0]) {
1001 case LCP_MRU:
1002 val = get_unaligned_be16(data + 2);
1003 if (inbound)
1004 ap->mru = val;
1005 else
1006 ap->chan.mtu = val;
1007 break;
1008 case LCP_ASYNCMAP:
1009 val = get_unaligned_be32(data + 2);
1010 if (inbound)
1011 ap->raccm = val;
1012 else
1013 ap->xaccm[0] = val;
1014 break;
1015 }
1016 dlen -= data[1];
1017 data += data[1];
1018 }
1019}
1020
1021static void __exit ppp_async_cleanup(void)
1022{
1023 if (tty_unregister_ldisc(N_PPP) != 0)
1024 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1025}
1026
1027module_init(ppp_async_init);
1028module_exit(ppp_async_cleanup);