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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>
Marcelo Feitoza Parisiff5688a2006-01-09 18:37:15 -080033#include <linux/jiffies.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070034#include <asm/uaccess.h>
Philippe De Muyter6722e782005-11-08 09:40:26 -080035#include <asm/string.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
37#define PPP_VERSION "2.4.2"
38
39#define OBUFSIZE 256
40
41/* Structure for storing local state. */
42struct asyncppp {
43 struct tty_struct *tty;
44 unsigned int flags;
45 unsigned int state;
46 unsigned int rbits;
47 int mru;
48 spinlock_t xmit_lock;
49 spinlock_t recv_lock;
50 unsigned long xmit_flags;
51 u32 xaccm[8];
52 u32 raccm;
53 unsigned int bytes_sent;
54 unsigned int bytes_rcvd;
55
56 struct sk_buff *tpkt;
57 int tpkt_pos;
58 u16 tfcs;
59 unsigned char *optr;
60 unsigned char *olim;
61 unsigned long last_xmit;
62
63 struct sk_buff *rpkt;
64 int lcp_fcs;
65 struct sk_buff_head rqueue;
66
67 struct tasklet_struct tsk;
68
69 atomic_t refcnt;
70 struct semaphore dead_sem;
71 struct ppp_channel chan; /* interface to generic ppp layer */
72 unsigned char obuf[OBUFSIZE];
73};
74
75/* Bit numbers in xmit_flags */
76#define XMIT_WAKEUP 0
77#define XMIT_FULL 1
78#define XMIT_BUSY 2
79
80/* State bits */
81#define SC_TOSS 1
82#define SC_ESCAPE 2
83#define SC_PREV_ERROR 4
84
85/* Bits in rbits */
86#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
87
88static int flag_time = HZ;
89module_param(flag_time, int, 0);
90MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
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 char *flags, int count);
103static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
104 unsigned long arg);
105static void ppp_async_process(unsigned long arg);
106
107static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
108 int len, int inbound);
109
110static struct ppp_channel_ops async_ops = {
111 ppp_async_send,
112 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 *
Jeff Garzik6aa20a22006-09-13 13:24:59 -0400128 * FIXME: this is no longer true. The _close path for the ldisc is
129 * now guaranteed to be sane.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 */
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 atomic_inc(&ap->refcnt);
141 read_unlock(&disc_data_lock);
142 return ap;
143}
144
145static void ap_put(struct asyncppp *ap)
146{
147 if (atomic_dec_and_test(&ap->refcnt))
148 up(&ap->dead_sem);
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
161 err = -ENOMEM;
162 ap = kmalloc(sizeof(*ap), GFP_KERNEL);
163 if (ap == 0)
164 goto out;
165
166 /* initialize the asyncppp structure */
167 memset(ap, 0, sizeof(*ap));
168 ap->tty = tty;
169 ap->mru = PPP_MRU;
170 spin_lock_init(&ap->xmit_lock);
171 spin_lock_init(&ap->recv_lock);
172 ap->xaccm[0] = ~0U;
173 ap->xaccm[3] = 0x60000000U;
174 ap->raccm = ~0U;
175 ap->optr = ap->obuf;
176 ap->olim = ap->obuf;
177 ap->lcp_fcs = -1;
178
179 skb_queue_head_init(&ap->rqueue);
180 tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
181
182 atomic_set(&ap->refcnt, 1);
183 init_MUTEX_LOCKED(&ap->dead_sem);
184
185 ap->chan.private = ap;
186 ap->chan.ops = &async_ops;
187 ap->chan.mtu = PPP_MRU;
188 err = ppp_register_channel(&ap->chan);
189 if (err)
190 goto out_free;
191
192 tty->disc_data = ap;
Alan Cox33f0f882006-01-09 20:54:13 -0800193 tty->receive_room = 65536;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 return 0;
195
196 out_free:
197 kfree(ap);
198 out:
199 return err;
200}
201
202/*
203 * Called when the tty is put into another line discipline
204 * or it hangs up. We have to wait for any cpu currently
205 * executing in any of the other ppp_asynctty_* routines to
206 * finish before we can call ppp_unregister_channel and free
207 * the asyncppp struct. This routine must be called from
208 * process context, not interrupt or softirq context.
209 */
210static void
211ppp_asynctty_close(struct tty_struct *tty)
212{
213 struct asyncppp *ap;
214
215 write_lock_irq(&disc_data_lock);
216 ap = tty->disc_data;
217 tty->disc_data = NULL;
218 write_unlock_irq(&disc_data_lock);
219 if (ap == 0)
220 return;
221
222 /*
223 * We have now ensured that nobody can start using ap from now
224 * on, but we have to wait for all existing users to finish.
225 * Note that ppp_unregister_channel ensures that no calls to
226 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
227 * by the time it returns.
228 */
229 if (!atomic_dec_and_test(&ap->refcnt))
230 down(&ap->dead_sem);
231 tasklet_kill(&ap->tsk);
232
233 ppp_unregister_channel(&ap->chan);
234 if (ap->rpkt != 0)
235 kfree_skb(ap->rpkt);
236 skb_queue_purge(&ap->rqueue);
237 if (ap->tpkt != 0)
238 kfree_skb(ap->tpkt);
239 kfree(ap);
240}
241
242/*
243 * Called on tty hangup in process context.
244 *
245 * Wait for I/O to driver to complete and unregister PPP channel.
246 * This is already done by the close routine, so just call that.
247 */
248static int ppp_asynctty_hangup(struct tty_struct *tty)
249{
250 ppp_asynctty_close(tty);
251 return 0;
252}
253
254/*
255 * Read does nothing - no data is ever available this way.
256 * Pppd reads and writes packets via /dev/ppp instead.
257 */
258static ssize_t
259ppp_asynctty_read(struct tty_struct *tty, struct file *file,
260 unsigned char __user *buf, size_t count)
261{
262 return -EAGAIN;
263}
264
265/*
266 * Write on the tty does nothing, the packets all come in
267 * from the ppp generic stuff.
268 */
269static ssize_t
270ppp_asynctty_write(struct tty_struct *tty, struct file *file,
271 const unsigned char *buf, size_t count)
272{
273 return -EAGAIN;
274}
275
276/*
277 * Called in process context only. May be re-entered by multiple
278 * ioctl calling threads.
279 */
Jeff Garzik6aa20a22006-09-13 13:24:59 -0400280
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281static int
282ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
283 unsigned int cmd, unsigned long arg)
284{
285 struct asyncppp *ap = ap_get(tty);
286 int err, val;
287 int __user *p = (int __user *)arg;
288
289 if (ap == 0)
290 return -ENXIO;
291 err = -EFAULT;
292 switch (cmd) {
293 case PPPIOCGCHAN:
294 err = -ENXIO;
295 if (ap == 0)
296 break;
297 err = -EFAULT;
298 if (put_user(ppp_channel_index(&ap->chan), p))
299 break;
300 err = 0;
301 break;
302
303 case PPPIOCGUNIT:
304 err = -ENXIO;
305 if (ap == 0)
306 break;
307 err = -EFAULT;
308 if (put_user(ppp_unit_number(&ap->chan), p))
309 break;
310 err = 0;
311 break;
312
313 case TCGETS:
314 case TCGETA:
315 err = n_tty_ioctl(tty, file, cmd, arg);
316 break;
317
318 case TCFLSH:
319 /* flush our buffers and the serial port's buffer */
320 if (arg == TCIOFLUSH || arg == TCOFLUSH)
321 ppp_async_flush_output(ap);
322 err = n_tty_ioctl(tty, file, cmd, arg);
323 break;
324
325 case FIONREAD:
326 val = 0;
327 if (put_user(val, p))
328 break;
329 err = 0;
330 break;
331
332 default:
333 err = -ENOIOCTLCMD;
334 }
335
336 ap_put(ap);
337 return err;
338}
339
340/* No kernel lock - fine */
341static unsigned int
342ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
343{
344 return 0;
345}
346
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347/*
348 * This can now be called from hard interrupt level as well
349 * as soft interrupt level or mainline.
350 */
351static void
352ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
353 char *cflags, int count)
354{
355 struct asyncppp *ap = ap_get(tty);
356 unsigned long flags;
357
358 if (ap == 0)
359 return;
360 spin_lock_irqsave(&ap->recv_lock, flags);
361 ppp_async_input(ap, buf, cflags, count);
362 spin_unlock_irqrestore(&ap->recv_lock, flags);
David S. Millerb03efcf2005-07-08 14:57:23 -0700363 if (!skb_queue_empty(&ap->rqueue))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364 tasklet_schedule(&ap->tsk);
365 ap_put(ap);
366 if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
367 && tty->driver->unthrottle)
368 tty->driver->unthrottle(tty);
369}
370
371static void
372ppp_asynctty_wakeup(struct tty_struct *tty)
373{
374 struct asyncppp *ap = ap_get(tty);
375
376 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
377 if (ap == 0)
378 return;
379 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
380 tasklet_schedule(&ap->tsk);
381 ap_put(ap);
382}
383
384
385static struct tty_ldisc ppp_ldisc = {
386 .owner = THIS_MODULE,
387 .magic = TTY_LDISC_MAGIC,
388 .name = "ppp",
389 .open = ppp_asynctty_open,
390 .close = ppp_asynctty_close,
391 .hangup = ppp_asynctty_hangup,
392 .read = ppp_asynctty_read,
393 .write = ppp_asynctty_write,
394 .ioctl = ppp_asynctty_ioctl,
395 .poll = ppp_asynctty_poll,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396 .receive_buf = ppp_asynctty_receive,
397 .write_wakeup = ppp_asynctty_wakeup,
398};
399
400static int __init
401ppp_async_init(void)
402{
403 int err;
404
405 err = tty_register_ldisc(N_PPP, &ppp_ldisc);
406 if (err != 0)
407 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
408 err);
409 return err;
410}
411
412/*
413 * The following routines provide the PPP channel interface.
414 */
415static int
416ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
417{
418 struct asyncppp *ap = chan->private;
419 void __user *argp = (void __user *)arg;
420 int __user *p = argp;
421 int err, val;
422 u32 accm[8];
423
424 err = -EFAULT;
425 switch (cmd) {
426 case PPPIOCGFLAGS:
427 val = ap->flags | ap->rbits;
428 if (put_user(val, p))
429 break;
430 err = 0;
431 break;
432 case PPPIOCSFLAGS:
433 if (get_user(val, p))
434 break;
435 ap->flags = val & ~SC_RCV_BITS;
436 spin_lock_irq(&ap->recv_lock);
437 ap->rbits = val & SC_RCV_BITS;
438 spin_unlock_irq(&ap->recv_lock);
439 err = 0;
440 break;
441
442 case PPPIOCGASYNCMAP:
443 if (put_user(ap->xaccm[0], (u32 __user *)argp))
444 break;
445 err = 0;
446 break;
447 case PPPIOCSASYNCMAP:
448 if (get_user(ap->xaccm[0], (u32 __user *)argp))
449 break;
450 err = 0;
451 break;
452
453 case PPPIOCGRASYNCMAP:
454 if (put_user(ap->raccm, (u32 __user *)argp))
455 break;
456 err = 0;
457 break;
458 case PPPIOCSRASYNCMAP:
459 if (get_user(ap->raccm, (u32 __user *)argp))
460 break;
461 err = 0;
462 break;
463
464 case PPPIOCGXASYNCMAP:
465 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
466 break;
467 err = 0;
468 break;
469 case PPPIOCSXASYNCMAP:
470 if (copy_from_user(accm, argp, sizeof(accm)))
471 break;
472 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
473 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
474 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
475 err = 0;
476 break;
477
478 case PPPIOCGMRU:
479 if (put_user(ap->mru, p))
480 break;
481 err = 0;
482 break;
483 case PPPIOCSMRU:
484 if (get_user(val, p))
485 break;
486 if (val < PPP_MRU)
487 val = PPP_MRU;
488 ap->mru = val;
489 err = 0;
490 break;
491
492 default:
493 err = -ENOTTY;
494 }
495
496 return err;
497}
498
499/*
500 * This is called at softirq level to deliver received packets
501 * to the ppp_generic code, and to tell the ppp_generic code
502 * if we can accept more output now.
503 */
504static void ppp_async_process(unsigned long arg)
505{
506 struct asyncppp *ap = (struct asyncppp *) arg;
507 struct sk_buff *skb;
508
509 /* process received packets */
510 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
511 if (skb->cb[0])
512 ppp_input_error(&ap->chan, 0);
513 ppp_input(&ap->chan, skb);
514 }
515
516 /* try to push more stuff out */
517 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
518 ppp_output_wakeup(&ap->chan);
519}
520
521/*
522 * Procedures for encapsulation and framing.
523 */
524
525/*
526 * Procedure to encode the data for async serial transmission.
527 * Does octet stuffing (escaping), puts the address/control bytes
528 * on if A/C compression is disabled, and does protocol compression.
529 * Assumes ap->tpkt != 0 on entry.
530 * Returns 1 if we finished the current frame, 0 otherwise.
531 */
532
533#define PUT_BYTE(ap, buf, c, islcp) do { \
534 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
535 *buf++ = PPP_ESCAPE; \
536 *buf++ = c ^ 0x20; \
537 } else \
538 *buf++ = c; \
539} while (0)
540
541static int
542ppp_async_encode(struct asyncppp *ap)
543{
544 int fcs, i, count, c, proto;
545 unsigned char *buf, *buflim;
546 unsigned char *data;
547 int islcp;
548
549 buf = ap->obuf;
550 ap->olim = buf;
551 ap->optr = buf;
552 i = ap->tpkt_pos;
553 data = ap->tpkt->data;
554 count = ap->tpkt->len;
555 fcs = ap->tfcs;
556 proto = (data[0] << 8) + data[1];
557
558 /*
559 * LCP packets with code values between 1 (configure-reqest)
560 * and 7 (code-reject) must be sent as though no options
561 * had been negotiated.
562 */
563 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
564
565 if (i == 0) {
566 if (islcp)
567 async_lcp_peek(ap, data, count, 0);
568
569 /*
570 * Start of a new packet - insert the leading FLAG
571 * character if necessary.
572 */
573 if (islcp || flag_time == 0
Marcelo Feitoza Parisiff5688a2006-01-09 18:37:15 -0800574 || time_after_eq(jiffies, ap->last_xmit + flag_time))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700575 *buf++ = PPP_FLAG;
576 ap->last_xmit = jiffies;
577 fcs = PPP_INITFCS;
578
579 /*
580 * Put in the address/control bytes if necessary
581 */
582 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
583 PUT_BYTE(ap, buf, 0xff, islcp);
584 fcs = PPP_FCS(fcs, 0xff);
585 PUT_BYTE(ap, buf, 0x03, islcp);
586 fcs = PPP_FCS(fcs, 0x03);
587 }
588 }
589
590 /*
591 * Once we put in the last byte, we need to put in the FCS
592 * and closing flag, so make sure there is at least 7 bytes
593 * of free space in the output buffer.
594 */
595 buflim = ap->obuf + OBUFSIZE - 6;
596 while (i < count && buf < buflim) {
597 c = data[i++];
598 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
599 continue; /* compress protocol field */
600 fcs = PPP_FCS(fcs, c);
601 PUT_BYTE(ap, buf, c, islcp);
602 }
603
604 if (i < count) {
605 /*
606 * Remember where we are up to in this packet.
607 */
608 ap->olim = buf;
609 ap->tpkt_pos = i;
610 ap->tfcs = fcs;
611 return 0;
612 }
613
614 /*
615 * We have finished the packet. Add the FCS and flag.
616 */
617 fcs = ~fcs;
618 c = fcs & 0xff;
619 PUT_BYTE(ap, buf, c, islcp);
620 c = (fcs >> 8) & 0xff;
621 PUT_BYTE(ap, buf, c, islcp);
622 *buf++ = PPP_FLAG;
623 ap->olim = buf;
624
625 kfree_skb(ap->tpkt);
626 ap->tpkt = NULL;
627 return 1;
628}
629
630/*
631 * Transmit-side routines.
632 */
633
634/*
635 * Send a packet to the peer over an async tty line.
636 * Returns 1 iff the packet was accepted.
637 * If the packet was not accepted, we will call ppp_output_wakeup
638 * at some later time.
639 */
640static int
641ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
642{
643 struct asyncppp *ap = chan->private;
644
645 ppp_async_push(ap);
646
647 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
648 return 0; /* already full */
649 ap->tpkt = skb;
650 ap->tpkt_pos = 0;
651
652 ppp_async_push(ap);
653 return 1;
654}
655
656/*
657 * Push as much data as possible out to the tty.
658 */
659static int
660ppp_async_push(struct asyncppp *ap)
661{
662 int avail, sent, done = 0;
663 struct tty_struct *tty = ap->tty;
664 int tty_stuffed = 0;
665
666 /*
667 * We can get called recursively here if the tty write
668 * function calls our wakeup function. This can happen
669 * for example on a pty with both the master and slave
670 * set to PPP line discipline.
671 * We use the XMIT_BUSY bit to detect this and get out,
672 * leaving the XMIT_WAKEUP bit set to tell the other
673 * instance that it may now be able to write more now.
674 */
675 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
676 return 0;
677 spin_lock_bh(&ap->xmit_lock);
678 for (;;) {
679 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
680 tty_stuffed = 0;
681 if (!tty_stuffed && ap->optr < ap->olim) {
682 avail = ap->olim - ap->optr;
683 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
684 sent = tty->driver->write(tty, ap->optr, avail);
685 if (sent < 0)
686 goto flush; /* error, e.g. loss of CD */
687 ap->optr += sent;
688 if (sent < avail)
689 tty_stuffed = 1;
690 continue;
691 }
692 if (ap->optr >= ap->olim && ap->tpkt != 0) {
693 if (ppp_async_encode(ap)) {
694 /* finished processing ap->tpkt */
695 clear_bit(XMIT_FULL, &ap->xmit_flags);
696 done = 1;
697 }
698 continue;
699 }
700 /*
701 * We haven't made any progress this time around.
702 * Clear XMIT_BUSY to let other callers in, but
703 * after doing so we have to check if anyone set
704 * XMIT_WAKEUP since we last checked it. If they
705 * did, we should try again to set XMIT_BUSY and go
706 * around again in case XMIT_BUSY was still set when
707 * the other caller tried.
708 */
709 clear_bit(XMIT_BUSY, &ap->xmit_flags);
710 /* any more work to do? if not, exit the loop */
711 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags)
712 || (!tty_stuffed && ap->tpkt != 0)))
713 break;
714 /* more work to do, see if we can do it now */
715 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
716 break;
717 }
718 spin_unlock_bh(&ap->xmit_lock);
719 return done;
720
721flush:
722 clear_bit(XMIT_BUSY, &ap->xmit_flags);
723 if (ap->tpkt != 0) {
724 kfree_skb(ap->tpkt);
725 ap->tpkt = NULL;
726 clear_bit(XMIT_FULL, &ap->xmit_flags);
727 done = 1;
728 }
729 ap->optr = ap->olim;
730 spin_unlock_bh(&ap->xmit_lock);
731 return done;
732}
733
734/*
735 * Flush output from our internal buffers.
736 * Called for the TCFLSH ioctl. Can be entered in parallel
737 * but this is covered by the xmit_lock.
738 */
739static void
740ppp_async_flush_output(struct asyncppp *ap)
741{
742 int done = 0;
743
744 spin_lock_bh(&ap->xmit_lock);
745 ap->optr = ap->olim;
746 if (ap->tpkt != NULL) {
747 kfree_skb(ap->tpkt);
748 ap->tpkt = NULL;
749 clear_bit(XMIT_FULL, &ap->xmit_flags);
750 done = 1;
751 }
752 spin_unlock_bh(&ap->xmit_lock);
753 if (done)
754 ppp_output_wakeup(&ap->chan);
755}
756
757/*
758 * Receive-side routines.
759 */
760
761/* see how many ordinary chars there are at the start of buf */
762static inline int
763scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
764{
765 int i, c;
766
767 for (i = 0; i < count; ++i) {
768 c = buf[i];
769 if (c == PPP_ESCAPE || c == PPP_FLAG
770 || (c < 0x20 && (ap->raccm & (1 << c)) != 0))
771 break;
772 }
773 return i;
774}
775
776/* called when a flag is seen - do end-of-packet processing */
777static void
778process_input_packet(struct asyncppp *ap)
779{
780 struct sk_buff *skb;
781 unsigned char *p;
782 unsigned int len, fcs, proto;
783
784 skb = ap->rpkt;
785 if (ap->state & (SC_TOSS | SC_ESCAPE))
786 goto err;
787
788 if (skb == NULL)
789 return; /* 0-length packet */
790
791 /* check the FCS */
792 p = skb->data;
793 len = skb->len;
794 if (len < 3)
795 goto err; /* too short */
796 fcs = PPP_INITFCS;
797 for (; len > 0; --len)
798 fcs = PPP_FCS(fcs, *p++);
799 if (fcs != PPP_GOODFCS)
800 goto err; /* bad FCS */
801 skb_trim(skb, skb->len - 2);
802
803 /* check for address/control and protocol compression */
804 p = skb->data;
Paul Mackerras7c5050e2007-04-19 13:05:52 -0700805 if (p[0] == PPP_ALLSTATIONS) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806 /* chop off address/control */
Paul Mackerras7c5050e2007-04-19 13:05:52 -0700807 if (p[1] != PPP_UI || skb->len < 3)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700808 goto err;
809 p = skb_pull(skb, 2);
810 }
811 proto = p[0];
812 if (proto & 1) {
813 /* protocol is compressed */
814 skb_push(skb, 1)[0] = 0;
815 } else {
816 if (skb->len < 2)
817 goto err;
818 proto = (proto << 8) + p[1];
819 if (proto == PPP_LCP)
820 async_lcp_peek(ap, p, skb->len, 1);
821 }
822
823 /* queue the frame to be processed */
824 skb->cb[0] = ap->state;
825 skb_queue_tail(&ap->rqueue, skb);
826 ap->rpkt = NULL;
827 ap->state = 0;
828 return;
829
830 err:
831 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
832 ap->state = SC_PREV_ERROR;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800833 if (skb) {
834 /* make skb appear as freshly allocated */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835 skb_trim(skb, 0);
Philippe De Muyter6722e782005-11-08 09:40:26 -0800836 skb_reserve(skb, - skb_headroom(skb));
837 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700838}
839
840/* Called when the tty driver has data for us. Runs parallel with the
841 other ldisc functions but will not be re-entered */
842
843static void
844ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
845 char *flags, int count)
846{
847 struct sk_buff *skb;
848 int c, i, j, n, s, f;
849 unsigned char *sp;
850
851 /* update bits used for 8-bit cleanness detection */
852 if (~ap->rbits & SC_RCV_BITS) {
853 s = 0;
854 for (i = 0; i < count; ++i) {
855 c = buf[i];
856 if (flags != 0 && flags[i] != 0)
857 continue;
858 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
859 c = ((c >> 4) ^ c) & 0xf;
860 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
861 }
862 ap->rbits |= s;
863 }
864
865 while (count > 0) {
866 /* scan through and see how many chars we can do in bulk */
867 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
868 n = 1;
869 else
870 n = scan_ordinary(ap, buf, count);
871
872 f = 0;
873 if (flags != 0 && (ap->state & SC_TOSS) == 0) {
874 /* check the flags to see if any char had an error */
875 for (j = 0; j < n; ++j)
876 if ((f = flags[j]) != 0)
877 break;
878 }
879 if (f != 0) {
880 /* start tossing */
881 ap->state |= SC_TOSS;
882
883 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
884 /* stuff the chars in the skb */
885 skb = ap->rpkt;
886 if (skb == 0) {
887 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
888 if (skb == 0)
889 goto nomem;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800890 ap->rpkt = skb;
891 }
892 if (skb->len == 0) {
893 /* Try to get the payload 4-byte aligned.
894 * This should match the
895 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
896 * process_input_packet, but we do not have
897 * enough chars here to test buf[1] and buf[2].
898 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899 if (buf[0] != PPP_ALLSTATIONS)
900 skb_reserve(skb, 2 + (buf[0] & 1));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 }
902 if (n > skb_tailroom(skb)) {
903 /* packet overflowed MRU */
904 ap->state |= SC_TOSS;
905 } else {
906 sp = skb_put(skb, n);
907 memcpy(sp, buf, n);
908 if (ap->state & SC_ESCAPE) {
909 sp[0] ^= 0x20;
910 ap->state &= ~SC_ESCAPE;
911 }
912 }
913 }
914
915 if (n >= count)
916 break;
917
918 c = buf[n];
919 if (flags != NULL && flags[n] != 0) {
920 ap->state |= SC_TOSS;
921 } else if (c == PPP_FLAG) {
922 process_input_packet(ap);
923 } else if (c == PPP_ESCAPE) {
924 ap->state |= SC_ESCAPE;
925 } else if (I_IXON(ap->tty)) {
926 if (c == START_CHAR(ap->tty))
927 start_tty(ap->tty);
928 else if (c == STOP_CHAR(ap->tty))
929 stop_tty(ap->tty);
930 }
931 /* otherwise it's a char in the recv ACCM */
932 ++n;
933
934 buf += n;
935 if (flags != 0)
936 flags += n;
937 count -= n;
938 }
939 return;
940
941 nomem:
942 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
943 ap->state |= SC_TOSS;
944}
945
946/*
947 * We look at LCP frames going past so that we can notice
948 * and react to the LCP configure-ack from the peer.
949 * In the situation where the peer has been sent a configure-ack
950 * already, LCP is up once it has sent its configure-ack
951 * so the immediately following packet can be sent with the
952 * configured LCP options. This allows us to process the following
953 * packet correctly without pppd needing to respond quickly.
954 *
955 * We only respond to the received configure-ack if we have just
956 * sent a configure-request, and the configure-ack contains the
957 * same data (this is checked using a 16-bit crc of the data).
958 */
959#define CONFREQ 1 /* LCP code field values */
960#define CONFACK 2
961#define LCP_MRU 1 /* LCP option numbers */
962#define LCP_ASYNCMAP 2
963
964static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
965 int len, int inbound)
966{
967 int dlen, fcs, i, code;
968 u32 val;
969
970 data += 2; /* skip protocol bytes */
971 len -= 2;
972 if (len < 4) /* 4 = code, ID, length */
973 return;
974 code = data[0];
975 if (code != CONFACK && code != CONFREQ)
976 return;
977 dlen = (data[2] << 8) + data[3];
978 if (len < dlen)
979 return; /* packet got truncated or length is bogus */
980
981 if (code == (inbound? CONFACK: CONFREQ)) {
982 /*
983 * sent confreq or received confack:
984 * calculate the crc of the data from the ID field on.
985 */
986 fcs = PPP_INITFCS;
987 for (i = 1; i < dlen; ++i)
988 fcs = PPP_FCS(fcs, data[i]);
989
990 if (!inbound) {
991 /* outbound confreq - remember the crc for later */
992 ap->lcp_fcs = fcs;
993 return;
994 }
995
996 /* received confack, check the crc */
997 fcs ^= ap->lcp_fcs;
998 ap->lcp_fcs = -1;
999 if (fcs != 0)
1000 return;
1001 } else if (inbound)
1002 return; /* not interested in received confreq */
1003
1004 /* process the options in the confack */
1005 data += 4;
1006 dlen -= 4;
1007 /* data[0] is code, data[1] is length */
1008 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
1009 switch (data[0]) {
1010 case LCP_MRU:
1011 val = (data[2] << 8) + data[3];
1012 if (inbound)
1013 ap->mru = val;
1014 else
1015 ap->chan.mtu = val;
1016 break;
1017 case LCP_ASYNCMAP:
1018 val = (data[2] << 24) + (data[3] << 16)
1019 + (data[4] << 8) + data[5];
1020 if (inbound)
1021 ap->raccm = val;
1022 else
1023 ap->xaccm[0] = val;
1024 break;
1025 }
1026 dlen -= data[1];
1027 data += data[1];
1028 }
1029}
1030
1031static void __exit ppp_async_cleanup(void)
1032{
Alexey Dobriyan64ccd712005-06-23 00:10:33 -07001033 if (tty_unregister_ldisc(N_PPP) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001034 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1035}
1036
1037module_init(ppp_async_init);
1038module_exit(ppp_async_cleanup);