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(r: &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(r: &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(list: &ap->rqueue);
183 tasklet_setup(t: &ap->tsk, callback: ppp_async_process);
184
185 refcount_set(r: &ap->refcnt, n: 1);
186 init_completion(x: &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(objp: 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(r: &ap->refcnt))
235 wait_for_completion(&ap->dead);
236 tasklet_kill(t: &ap->tsk);
237
238 ppp_unregister_channel(&ap->chan);
239 kfree_skb(skb: ap->rpkt);
240 skb_queue_purge(list: &ap->rqueue);
241 kfree_skb(skb: ap->tpkt);
242 kfree(objp: 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, flags: cflags, count);
343 spin_unlock_irqrestore(lock: &ap->recv_lock, flags);
344 if (!skb_queue_empty(list: &ap->rqueue))
345 tasklet_schedule(t: &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(nr: TTY_DO_WRITE_WAKEUP, addr: &tty->flags);
356 if (!ap)
357 return;
358 set_bit(XMIT_WAKEUP, addr: &ap->xmit_flags);
359 tasklet_schedule(t: &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(new_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(lock: &ap->recv_lock);
415 ap->rbits = val & SC_RCV_BITS;
416 spin_unlock_irq(lock: &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(to: argp, from: ap->xaccm, n: sizeof(ap->xaccm)))
444 break;
445 err = 0;
446 break;
447 case PPPIOCSXASYNCMAP:
448 if (copy_from_user(to: accm, from: argp, n: 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(list: &ap->rqueue)) != NULL) {
493 if (skb->cb[0])
494 ppp_input_error(&ap->chan, code: 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(p: 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, len: count, inbound: 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(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, addr: &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, addr: &ap->xmit_flags))
658 return 0;
659 spin_lock_bh(lock: &ap->xmit_lock);
660 for (;;) {
661 if (test_and_clear_bit(XMIT_WAKEUP, addr: &ap->xmit_flags))
662 tty_stuffed = 0;
663 if (!tty_stuffed && ap->optr < ap->olim) {
664 avail = ap->olim - ap->optr;
665 set_bit(nr: TTY_DO_WRITE_WAKEUP, addr: &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, addr: &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, addr: &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, addr: &ap->xmit_flags))
698 break;
699 }
700 spin_unlock_bh(lock: &ap->xmit_lock);
701 return done;
702
703flush:
704 clear_bit(XMIT_BUSY, addr: &ap->xmit_flags);
705 if (ap->tpkt) {
706 kfree_skb(skb: ap->tpkt);
707 ap->tpkt = NULL;
708 clear_bit(XMIT_FULL, addr: &ap->xmit_flags);
709 done = 1;
710 }
711 ap->optr = ap->olim;
712 spin_unlock_bh(lock: &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(lock: &ap->xmit_lock);
727 ap->optr = ap->olim;
728 if (ap->tpkt != NULL) {
729 kfree_skb(skb: ap->tpkt);
730 ap->tpkt = NULL;
731 clear_bit(XMIT_FULL, addr: &ap->xmit_flags);
732 done = 1;
733 }
734 spin_unlock_bh(lock: &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, len: 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, len: 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, data: p, len: skb->len, inbound: 1);
803 }
804
805 /* queue the frame to be processed */
806 skb->cb[0] = ap->state;
807 skb_queue_tail(list: &ap->rqueue, newsk: 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, len: 0);
818 skb_reserve(skb, len: - 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(length: 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, len: 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, data: buf, len: 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(tty: ap->tty);
908 else if (c == STOP_CHAR(ap->tty))
909 stop_tty(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(p: 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(p: 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(p: 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(ldisc: &ppp_ldisc);
1013}
1014
1015module_init(ppp_async_init);
1016module_exit(ppp_async_cleanup);
1017

source code of linux/drivers/net/ppp/ppp_async.c