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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/if_ppp.h>
30#include <linux/ppp_channel.h>
31#include <linux/spinlock.h>
32#include <linux/init.h>
33#include <asm/uaccess.h>
Philippe De Muyter6722e782005-11-08 09:40:26 -080034#include <asm/string.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070035
36#define PPP_VERSION "2.4.2"
37
38#define OBUFSIZE 256
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 atomic_t refcnt;
69 struct semaphore dead_sem;
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 struct ppp_channel_ops async_ops = {
110 ppp_async_send,
111 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 atomic_inc(&ap->refcnt);
140 read_unlock(&disc_data_lock);
141 return ap;
142}
143
144static void ap_put(struct asyncppp *ap)
145{
146 if (atomic_dec_and_test(&ap->refcnt))
147 up(&ap->dead_sem);
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
160 err = -ENOMEM;
161 ap = kmalloc(sizeof(*ap), GFP_KERNEL);
162 if (ap == 0)
163 goto out;
164
165 /* initialize the asyncppp structure */
166 memset(ap, 0, sizeof(*ap));
167 ap->tty = tty;
168 ap->mru = PPP_MRU;
169 spin_lock_init(&ap->xmit_lock);
170 spin_lock_init(&ap->recv_lock);
171 ap->xaccm[0] = ~0U;
172 ap->xaccm[3] = 0x60000000U;
173 ap->raccm = ~0U;
174 ap->optr = ap->obuf;
175 ap->olim = ap->obuf;
176 ap->lcp_fcs = -1;
177
178 skb_queue_head_init(&ap->rqueue);
179 tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
180
181 atomic_set(&ap->refcnt, 1);
182 init_MUTEX_LOCKED(&ap->dead_sem);
183
184 ap->chan.private = ap;
185 ap->chan.ops = &async_ops;
186 ap->chan.mtu = PPP_MRU;
187 err = ppp_register_channel(&ap->chan);
188 if (err)
189 goto out_free;
190
191 tty->disc_data = ap;
192
193 return 0;
194
195 out_free:
196 kfree(ap);
197 out:
198 return err;
199}
200
201/*
202 * Called when the tty is put into another line discipline
203 * or it hangs up. We have to wait for any cpu currently
204 * executing in any of the other ppp_asynctty_* routines to
205 * finish before we can call ppp_unregister_channel and free
206 * the asyncppp struct. This routine must be called from
207 * process context, not interrupt or softirq context.
208 */
209static void
210ppp_asynctty_close(struct tty_struct *tty)
211{
212 struct asyncppp *ap;
213
214 write_lock_irq(&disc_data_lock);
215 ap = tty->disc_data;
216 tty->disc_data = NULL;
217 write_unlock_irq(&disc_data_lock);
218 if (ap == 0)
219 return;
220
221 /*
222 * We have now ensured that nobody can start using ap from now
223 * on, but we have to wait for all existing users to finish.
224 * Note that ppp_unregister_channel ensures that no calls to
225 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
226 * by the time it returns.
227 */
228 if (!atomic_dec_and_test(&ap->refcnt))
229 down(&ap->dead_sem);
230 tasklet_kill(&ap->tsk);
231
232 ppp_unregister_channel(&ap->chan);
233 if (ap->rpkt != 0)
234 kfree_skb(ap->rpkt);
235 skb_queue_purge(&ap->rqueue);
236 if (ap->tpkt != 0)
237 kfree_skb(ap->tpkt);
238 kfree(ap);
239}
240
241/*
242 * Called on tty hangup in process context.
243 *
244 * Wait for I/O to driver to complete and unregister PPP channel.
245 * This is already done by the close routine, so just call that.
246 */
247static int ppp_asynctty_hangup(struct tty_struct *tty)
248{
249 ppp_asynctty_close(tty);
250 return 0;
251}
252
253/*
254 * Read does nothing - no data is ever available this way.
255 * Pppd reads and writes packets via /dev/ppp instead.
256 */
257static ssize_t
258ppp_asynctty_read(struct tty_struct *tty, struct file *file,
259 unsigned char __user *buf, size_t count)
260{
261 return -EAGAIN;
262}
263
264/*
265 * Write on the tty does nothing, the packets all come in
266 * from the ppp generic stuff.
267 */
268static ssize_t
269ppp_asynctty_write(struct tty_struct *tty, struct file *file,
270 const unsigned char *buf, size_t count)
271{
272 return -EAGAIN;
273}
274
275/*
276 * Called in process context only. May be re-entered by multiple
277 * ioctl calling threads.
278 */
279
280static int
281ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
282 unsigned int cmd, unsigned long arg)
283{
284 struct asyncppp *ap = ap_get(tty);
285 int err, val;
286 int __user *p = (int __user *)arg;
287
288 if (ap == 0)
289 return -ENXIO;
290 err = -EFAULT;
291 switch (cmd) {
292 case PPPIOCGCHAN:
293 err = -ENXIO;
294 if (ap == 0)
295 break;
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 = -ENXIO;
304 if (ap == 0)
305 break;
306 err = -EFAULT;
307 if (put_user(ppp_unit_number(&ap->chan), p))
308 break;
309 err = 0;
310 break;
311
312 case TCGETS:
313 case TCGETA:
314 err = n_tty_ioctl(tty, file, cmd, arg);
315 break;
316
317 case TCFLSH:
318 /* flush our buffers and the serial port's buffer */
319 if (arg == TCIOFLUSH || arg == TCOFLUSH)
320 ppp_async_flush_output(ap);
321 err = n_tty_ioctl(tty, file, cmd, arg);
322 break;
323
324 case FIONREAD:
325 val = 0;
326 if (put_user(val, p))
327 break;
328 err = 0;
329 break;
330
331 default:
332 err = -ENOIOCTLCMD;
333 }
334
335 ap_put(ap);
336 return err;
337}
338
339/* No kernel lock - fine */
340static unsigned int
341ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
342{
343 return 0;
344}
345
346static int
347ppp_asynctty_room(struct tty_struct *tty)
348{
349 return 65535;
350}
351
352/*
353 * This can now be called from hard interrupt level as well
354 * as soft interrupt level or mainline.
355 */
356static void
357ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
358 char *cflags, int count)
359{
360 struct asyncppp *ap = ap_get(tty);
361 unsigned long flags;
362
363 if (ap == 0)
364 return;
365 spin_lock_irqsave(&ap->recv_lock, flags);
366 ppp_async_input(ap, buf, cflags, count);
367 spin_unlock_irqrestore(&ap->recv_lock, flags);
David S. Millerb03efcf2005-07-08 14:57:23 -0700368 if (!skb_queue_empty(&ap->rqueue))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 tasklet_schedule(&ap->tsk);
370 ap_put(ap);
371 if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
372 && tty->driver->unthrottle)
373 tty->driver->unthrottle(tty);
374}
375
376static void
377ppp_asynctty_wakeup(struct tty_struct *tty)
378{
379 struct asyncppp *ap = ap_get(tty);
380
381 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
382 if (ap == 0)
383 return;
384 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
385 tasklet_schedule(&ap->tsk);
386 ap_put(ap);
387}
388
389
390static struct tty_ldisc ppp_ldisc = {
391 .owner = THIS_MODULE,
392 .magic = TTY_LDISC_MAGIC,
393 .name = "ppp",
394 .open = ppp_asynctty_open,
395 .close = ppp_asynctty_close,
396 .hangup = ppp_asynctty_hangup,
397 .read = ppp_asynctty_read,
398 .write = ppp_asynctty_write,
399 .ioctl = ppp_asynctty_ioctl,
400 .poll = ppp_asynctty_poll,
401 .receive_room = ppp_asynctty_room,
402 .receive_buf = ppp_asynctty_receive,
403 .write_wakeup = ppp_asynctty_wakeup,
404};
405
406static int __init
407ppp_async_init(void)
408{
409 int err;
410
411 err = tty_register_ldisc(N_PPP, &ppp_ldisc);
412 if (err != 0)
413 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
414 err);
415 return err;
416}
417
418/*
419 * The following routines provide the PPP channel interface.
420 */
421static int
422ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
423{
424 struct asyncppp *ap = chan->private;
425 void __user *argp = (void __user *)arg;
426 int __user *p = argp;
427 int err, val;
428 u32 accm[8];
429
430 err = -EFAULT;
431 switch (cmd) {
432 case PPPIOCGFLAGS:
433 val = ap->flags | ap->rbits;
434 if (put_user(val, p))
435 break;
436 err = 0;
437 break;
438 case PPPIOCSFLAGS:
439 if (get_user(val, p))
440 break;
441 ap->flags = val & ~SC_RCV_BITS;
442 spin_lock_irq(&ap->recv_lock);
443 ap->rbits = val & SC_RCV_BITS;
444 spin_unlock_irq(&ap->recv_lock);
445 err = 0;
446 break;
447
448 case PPPIOCGASYNCMAP:
449 if (put_user(ap->xaccm[0], (u32 __user *)argp))
450 break;
451 err = 0;
452 break;
453 case PPPIOCSASYNCMAP:
454 if (get_user(ap->xaccm[0], (u32 __user *)argp))
455 break;
456 err = 0;
457 break;
458
459 case PPPIOCGRASYNCMAP:
460 if (put_user(ap->raccm, (u32 __user *)argp))
461 break;
462 err = 0;
463 break;
464 case PPPIOCSRASYNCMAP:
465 if (get_user(ap->raccm, (u32 __user *)argp))
466 break;
467 err = 0;
468 break;
469
470 case PPPIOCGXASYNCMAP:
471 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
472 break;
473 err = 0;
474 break;
475 case PPPIOCSXASYNCMAP:
476 if (copy_from_user(accm, argp, sizeof(accm)))
477 break;
478 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
479 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
480 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
481 err = 0;
482 break;
483
484 case PPPIOCGMRU:
485 if (put_user(ap->mru, p))
486 break;
487 err = 0;
488 break;
489 case PPPIOCSMRU:
490 if (get_user(val, p))
491 break;
492 if (val < PPP_MRU)
493 val = PPP_MRU;
494 ap->mru = val;
495 err = 0;
496 break;
497
498 default:
499 err = -ENOTTY;
500 }
501
502 return err;
503}
504
505/*
506 * This is called at softirq level to deliver received packets
507 * to the ppp_generic code, and to tell the ppp_generic code
508 * if we can accept more output now.
509 */
510static void ppp_async_process(unsigned long arg)
511{
512 struct asyncppp *ap = (struct asyncppp *) arg;
513 struct sk_buff *skb;
514
515 /* process received packets */
516 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
517 if (skb->cb[0])
518 ppp_input_error(&ap->chan, 0);
519 ppp_input(&ap->chan, skb);
520 }
521
522 /* try to push more stuff out */
523 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
524 ppp_output_wakeup(&ap->chan);
525}
526
527/*
528 * Procedures for encapsulation and framing.
529 */
530
531/*
532 * Procedure to encode the data for async serial transmission.
533 * Does octet stuffing (escaping), puts the address/control bytes
534 * on if A/C compression is disabled, and does protocol compression.
535 * Assumes ap->tpkt != 0 on entry.
536 * Returns 1 if we finished the current frame, 0 otherwise.
537 */
538
539#define PUT_BYTE(ap, buf, c, islcp) do { \
540 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
541 *buf++ = PPP_ESCAPE; \
542 *buf++ = c ^ 0x20; \
543 } else \
544 *buf++ = c; \
545} while (0)
546
547static int
548ppp_async_encode(struct asyncppp *ap)
549{
550 int fcs, i, count, c, proto;
551 unsigned char *buf, *buflim;
552 unsigned char *data;
553 int islcp;
554
555 buf = ap->obuf;
556 ap->olim = buf;
557 ap->optr = buf;
558 i = ap->tpkt_pos;
559 data = ap->tpkt->data;
560 count = ap->tpkt->len;
561 fcs = ap->tfcs;
562 proto = (data[0] << 8) + data[1];
563
564 /*
565 * LCP packets with code values between 1 (configure-reqest)
566 * and 7 (code-reject) must be sent as though no options
567 * had been negotiated.
568 */
569 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
570
571 if (i == 0) {
572 if (islcp)
573 async_lcp_peek(ap, data, count, 0);
574
575 /*
576 * Start of a new packet - insert the leading FLAG
577 * character if necessary.
578 */
579 if (islcp || flag_time == 0
580 || jiffies - ap->last_xmit >= flag_time)
581 *buf++ = PPP_FLAG;
582 ap->last_xmit = jiffies;
583 fcs = PPP_INITFCS;
584
585 /*
586 * Put in the address/control bytes if necessary
587 */
588 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
589 PUT_BYTE(ap, buf, 0xff, islcp);
590 fcs = PPP_FCS(fcs, 0xff);
591 PUT_BYTE(ap, buf, 0x03, islcp);
592 fcs = PPP_FCS(fcs, 0x03);
593 }
594 }
595
596 /*
597 * Once we put in the last byte, we need to put in the FCS
598 * and closing flag, so make sure there is at least 7 bytes
599 * of free space in the output buffer.
600 */
601 buflim = ap->obuf + OBUFSIZE - 6;
602 while (i < count && buf < buflim) {
603 c = data[i++];
604 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
605 continue; /* compress protocol field */
606 fcs = PPP_FCS(fcs, c);
607 PUT_BYTE(ap, buf, c, islcp);
608 }
609
610 if (i < count) {
611 /*
612 * Remember where we are up to in this packet.
613 */
614 ap->olim = buf;
615 ap->tpkt_pos = i;
616 ap->tfcs = fcs;
617 return 0;
618 }
619
620 /*
621 * We have finished the packet. Add the FCS and flag.
622 */
623 fcs = ~fcs;
624 c = fcs & 0xff;
625 PUT_BYTE(ap, buf, c, islcp);
626 c = (fcs >> 8) & 0xff;
627 PUT_BYTE(ap, buf, c, islcp);
628 *buf++ = PPP_FLAG;
629 ap->olim = buf;
630
631 kfree_skb(ap->tpkt);
632 ap->tpkt = NULL;
633 return 1;
634}
635
636/*
637 * Transmit-side routines.
638 */
639
640/*
641 * Send a packet to the peer over an async tty line.
642 * Returns 1 iff the packet was accepted.
643 * If the packet was not accepted, we will call ppp_output_wakeup
644 * at some later time.
645 */
646static int
647ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
648{
649 struct asyncppp *ap = chan->private;
650
651 ppp_async_push(ap);
652
653 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
654 return 0; /* already full */
655 ap->tpkt = skb;
656 ap->tpkt_pos = 0;
657
658 ppp_async_push(ap);
659 return 1;
660}
661
662/*
663 * Push as much data as possible out to the tty.
664 */
665static int
666ppp_async_push(struct asyncppp *ap)
667{
668 int avail, sent, done = 0;
669 struct tty_struct *tty = ap->tty;
670 int tty_stuffed = 0;
671
672 /*
673 * We can get called recursively here if the tty write
674 * function calls our wakeup function. This can happen
675 * for example on a pty with both the master and slave
676 * set to PPP line discipline.
677 * We use the XMIT_BUSY bit to detect this and get out,
678 * leaving the XMIT_WAKEUP bit set to tell the other
679 * instance that it may now be able to write more now.
680 */
681 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
682 return 0;
683 spin_lock_bh(&ap->xmit_lock);
684 for (;;) {
685 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
686 tty_stuffed = 0;
687 if (!tty_stuffed && ap->optr < ap->olim) {
688 avail = ap->olim - ap->optr;
689 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
690 sent = tty->driver->write(tty, ap->optr, avail);
691 if (sent < 0)
692 goto flush; /* error, e.g. loss of CD */
693 ap->optr += sent;
694 if (sent < avail)
695 tty_stuffed = 1;
696 continue;
697 }
698 if (ap->optr >= ap->olim && ap->tpkt != 0) {
699 if (ppp_async_encode(ap)) {
700 /* finished processing ap->tpkt */
701 clear_bit(XMIT_FULL, &ap->xmit_flags);
702 done = 1;
703 }
704 continue;
705 }
706 /*
707 * We haven't made any progress this time around.
708 * Clear XMIT_BUSY to let other callers in, but
709 * after doing so we have to check if anyone set
710 * XMIT_WAKEUP since we last checked it. If they
711 * did, we should try again to set XMIT_BUSY and go
712 * around again in case XMIT_BUSY was still set when
713 * the other caller tried.
714 */
715 clear_bit(XMIT_BUSY, &ap->xmit_flags);
716 /* any more work to do? if not, exit the loop */
717 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags)
718 || (!tty_stuffed && ap->tpkt != 0)))
719 break;
720 /* more work to do, see if we can do it now */
721 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
722 break;
723 }
724 spin_unlock_bh(&ap->xmit_lock);
725 return done;
726
727flush:
728 clear_bit(XMIT_BUSY, &ap->xmit_flags);
729 if (ap->tpkt != 0) {
730 kfree_skb(ap->tpkt);
731 ap->tpkt = NULL;
732 clear_bit(XMIT_FULL, &ap->xmit_flags);
733 done = 1;
734 }
735 ap->optr = ap->olim;
736 spin_unlock_bh(&ap->xmit_lock);
737 return done;
738}
739
740/*
741 * Flush output from our internal buffers.
742 * Called for the TCFLSH ioctl. Can be entered in parallel
743 * but this is covered by the xmit_lock.
744 */
745static void
746ppp_async_flush_output(struct asyncppp *ap)
747{
748 int done = 0;
749
750 spin_lock_bh(&ap->xmit_lock);
751 ap->optr = ap->olim;
752 if (ap->tpkt != NULL) {
753 kfree_skb(ap->tpkt);
754 ap->tpkt = NULL;
755 clear_bit(XMIT_FULL, &ap->xmit_flags);
756 done = 1;
757 }
758 spin_unlock_bh(&ap->xmit_lock);
759 if (done)
760 ppp_output_wakeup(&ap->chan);
761}
762
763/*
764 * Receive-side routines.
765 */
766
767/* see how many ordinary chars there are at the start of buf */
768static inline int
769scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
770{
771 int i, c;
772
773 for (i = 0; i < count; ++i) {
774 c = buf[i];
775 if (c == PPP_ESCAPE || c == PPP_FLAG
776 || (c < 0x20 && (ap->raccm & (1 << c)) != 0))
777 break;
778 }
779 return i;
780}
781
782/* called when a flag is seen - do end-of-packet processing */
783static void
784process_input_packet(struct asyncppp *ap)
785{
786 struct sk_buff *skb;
787 unsigned char *p;
788 unsigned int len, fcs, proto;
789
790 skb = ap->rpkt;
791 if (ap->state & (SC_TOSS | SC_ESCAPE))
792 goto err;
793
794 if (skb == NULL)
795 return; /* 0-length packet */
796
797 /* check the FCS */
798 p = skb->data;
799 len = skb->len;
800 if (len < 3)
801 goto err; /* too short */
802 fcs = PPP_INITFCS;
803 for (; len > 0; --len)
804 fcs = PPP_FCS(fcs, *p++);
805 if (fcs != PPP_GOODFCS)
806 goto err; /* bad FCS */
807 skb_trim(skb, skb->len - 2);
808
809 /* check for address/control and protocol compression */
810 p = skb->data;
811 if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
812 /* chop off address/control */
813 if (skb->len < 3)
814 goto err;
815 p = skb_pull(skb, 2);
816 }
817 proto = p[0];
818 if (proto & 1) {
819 /* protocol is compressed */
820 skb_push(skb, 1)[0] = 0;
821 } else {
822 if (skb->len < 2)
823 goto err;
824 proto = (proto << 8) + p[1];
825 if (proto == PPP_LCP)
826 async_lcp_peek(ap, p, skb->len, 1);
827 }
828
829 /* queue the frame to be processed */
830 skb->cb[0] = ap->state;
831 skb_queue_tail(&ap->rqueue, skb);
832 ap->rpkt = NULL;
833 ap->state = 0;
834 return;
835
836 err:
837 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
838 ap->state = SC_PREV_ERROR;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800839 if (skb) {
840 /* make skb appear as freshly allocated */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700841 skb_trim(skb, 0);
Philippe De Muyter6722e782005-11-08 09:40:26 -0800842 skb_reserve(skb, - skb_headroom(skb));
843 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700844}
845
846/* Called when the tty driver has data for us. Runs parallel with the
847 other ldisc functions but will not be re-entered */
848
849static void
850ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
851 char *flags, int count)
852{
853 struct sk_buff *skb;
854 int c, i, j, n, s, f;
855 unsigned char *sp;
856
857 /* update bits used for 8-bit cleanness detection */
858 if (~ap->rbits & SC_RCV_BITS) {
859 s = 0;
860 for (i = 0; i < count; ++i) {
861 c = buf[i];
862 if (flags != 0 && flags[i] != 0)
863 continue;
864 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
865 c = ((c >> 4) ^ c) & 0xf;
866 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
867 }
868 ap->rbits |= s;
869 }
870
871 while (count > 0) {
872 /* scan through and see how many chars we can do in bulk */
873 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
874 n = 1;
875 else
876 n = scan_ordinary(ap, buf, count);
877
878 f = 0;
879 if (flags != 0 && (ap->state & SC_TOSS) == 0) {
880 /* check the flags to see if any char had an error */
881 for (j = 0; j < n; ++j)
882 if ((f = flags[j]) != 0)
883 break;
884 }
885 if (f != 0) {
886 /* start tossing */
887 ap->state |= SC_TOSS;
888
889 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
890 /* stuff the chars in the skb */
891 skb = ap->rpkt;
892 if (skb == 0) {
893 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
894 if (skb == 0)
895 goto nomem;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800896 ap->rpkt = skb;
897 }
898 if (skb->len == 0) {
899 /* Try to get the payload 4-byte aligned.
900 * This should match the
901 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
902 * process_input_packet, but we do not have
903 * enough chars here to test buf[1] and buf[2].
904 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700905 if (buf[0] != PPP_ALLSTATIONS)
906 skb_reserve(skb, 2 + (buf[0] & 1));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907 }
908 if (n > skb_tailroom(skb)) {
909 /* packet overflowed MRU */
910 ap->state |= SC_TOSS;
911 } else {
912 sp = skb_put(skb, n);
913 memcpy(sp, buf, n);
914 if (ap->state & SC_ESCAPE) {
915 sp[0] ^= 0x20;
916 ap->state &= ~SC_ESCAPE;
917 }
918 }
919 }
920
921 if (n >= count)
922 break;
923
924 c = buf[n];
925 if (flags != NULL && flags[n] != 0) {
926 ap->state |= SC_TOSS;
927 } else if (c == PPP_FLAG) {
928 process_input_packet(ap);
929 } else if (c == PPP_ESCAPE) {
930 ap->state |= SC_ESCAPE;
931 } else if (I_IXON(ap->tty)) {
932 if (c == START_CHAR(ap->tty))
933 start_tty(ap->tty);
934 else if (c == STOP_CHAR(ap->tty))
935 stop_tty(ap->tty);
936 }
937 /* otherwise it's a char in the recv ACCM */
938 ++n;
939
940 buf += n;
941 if (flags != 0)
942 flags += n;
943 count -= n;
944 }
945 return;
946
947 nomem:
948 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
949 ap->state |= SC_TOSS;
950}
951
952/*
953 * We look at LCP frames going past so that we can notice
954 * and react to the LCP configure-ack from the peer.
955 * In the situation where the peer has been sent a configure-ack
956 * already, LCP is up once it has sent its configure-ack
957 * so the immediately following packet can be sent with the
958 * configured LCP options. This allows us to process the following
959 * packet correctly without pppd needing to respond quickly.
960 *
961 * We only respond to the received configure-ack if we have just
962 * sent a configure-request, and the configure-ack contains the
963 * same data (this is checked using a 16-bit crc of the data).
964 */
965#define CONFREQ 1 /* LCP code field values */
966#define CONFACK 2
967#define LCP_MRU 1 /* LCP option numbers */
968#define LCP_ASYNCMAP 2
969
970static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
971 int len, int inbound)
972{
973 int dlen, fcs, i, code;
974 u32 val;
975
976 data += 2; /* skip protocol bytes */
977 len -= 2;
978 if (len < 4) /* 4 = code, ID, length */
979 return;
980 code = data[0];
981 if (code != CONFACK && code != CONFREQ)
982 return;
983 dlen = (data[2] << 8) + data[3];
984 if (len < dlen)
985 return; /* packet got truncated or length is bogus */
986
987 if (code == (inbound? CONFACK: CONFREQ)) {
988 /*
989 * sent confreq or received confack:
990 * calculate the crc of the data from the ID field on.
991 */
992 fcs = PPP_INITFCS;
993 for (i = 1; i < dlen; ++i)
994 fcs = PPP_FCS(fcs, data[i]);
995
996 if (!inbound) {
997 /* outbound confreq - remember the crc for later */
998 ap->lcp_fcs = fcs;
999 return;
1000 }
1001
1002 /* received confack, check the crc */
1003 fcs ^= ap->lcp_fcs;
1004 ap->lcp_fcs = -1;
1005 if (fcs != 0)
1006 return;
1007 } else if (inbound)
1008 return; /* not interested in received confreq */
1009
1010 /* process the options in the confack */
1011 data += 4;
1012 dlen -= 4;
1013 /* data[0] is code, data[1] is length */
1014 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
1015 switch (data[0]) {
1016 case LCP_MRU:
1017 val = (data[2] << 8) + data[3];
1018 if (inbound)
1019 ap->mru = val;
1020 else
1021 ap->chan.mtu = val;
1022 break;
1023 case LCP_ASYNCMAP:
1024 val = (data[2] << 24) + (data[3] << 16)
1025 + (data[4] << 8) + data[5];
1026 if (inbound)
1027 ap->raccm = val;
1028 else
1029 ap->xaccm[0] = val;
1030 break;
1031 }
1032 dlen -= data[1];
1033 data += data[1];
1034 }
1035}
1036
1037static void __exit ppp_async_cleanup(void)
1038{
Alexey Dobriyan64ccd712005-06-23 00:10:33 -07001039 if (tty_unregister_ldisc(N_PPP) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1041}
1042
1043module_init(ppp_async_init);
1044module_exit(ppp_async_cleanup);