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