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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>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090034#include <linux/slab.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070035#include <asm/uaccess.h>
Philippe De Muyter6722e782005-11-08 09:40:26 -080036#include <asm/string.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38#define PPP_VERSION "2.4.2"
39
fangxiaozhi208f2032009-11-17 04:02:24 -080040#define OBUFSIZE 4096
Linus Torvalds1da177e2005-04-16 15:20:36 -070041
42/* Structure for storing local state. */
43struct asyncppp {
44 struct tty_struct *tty;
45 unsigned int flags;
46 unsigned int state;
47 unsigned int rbits;
48 int mru;
49 spinlock_t xmit_lock;
50 spinlock_t recv_lock;
51 unsigned long xmit_flags;
52 u32 xaccm[8];
53 u32 raccm;
54 unsigned int bytes_sent;
55 unsigned int bytes_rcvd;
56
57 struct sk_buff *tpkt;
58 int tpkt_pos;
59 u16 tfcs;
60 unsigned char *optr;
61 unsigned char *olim;
62 unsigned long last_xmit;
63
64 struct sk_buff *rpkt;
65 int lcp_fcs;
66 struct sk_buff_head rqueue;
67
68 struct tasklet_struct tsk;
69
70 atomic_t refcnt;
71 struct semaphore dead_sem;
72 struct ppp_channel chan; /* interface to generic ppp layer */
73 unsigned char obuf[OBUFSIZE];
74};
75
76/* Bit numbers in xmit_flags */
77#define XMIT_WAKEUP 0
78#define XMIT_FULL 1
79#define XMIT_BUSY 2
80
81/* State bits */
82#define SC_TOSS 1
83#define SC_ESCAPE 2
84#define SC_PREV_ERROR 4
85
86/* Bits in rbits */
87#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
88
89static int flag_time = HZ;
90module_param(flag_time, int, 0);
91MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
92MODULE_LICENSE("GPL");
93MODULE_ALIAS_LDISC(N_PPP);
94
95/*
96 * Prototypes.
97 */
98static int ppp_async_encode(struct asyncppp *ap);
99static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
100static int ppp_async_push(struct asyncppp *ap);
101static void ppp_async_flush_output(struct asyncppp *ap);
102static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
103 char *flags, int count);
104static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
105 unsigned long arg);
106static void ppp_async_process(unsigned long arg);
107
108static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
109 int len, int inbound);
110
stephen hemmingerd7100da2010-08-04 07:34:36 +0000111static const struct ppp_channel_ops async_ops = {
112 .start_xmit = ppp_async_send,
113 .ioctl = ppp_async_ioctl,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114};
115
116/*
117 * Routines implementing the PPP line discipline.
118 */
119
120/*
121 * We have a potential race on dereferencing tty->disc_data,
122 * because the tty layer provides no locking at all - thus one
123 * cpu could be running ppp_asynctty_receive while another
124 * calls ppp_asynctty_close, which zeroes tty->disc_data and
125 * frees the memory that ppp_asynctty_receive is using. The best
126 * way to fix this is to use a rwlock in the tty struct, but for now
127 * we use a single global rwlock for all ttys in ppp line discipline.
128 *
Jeff Garzik6aa20a22006-09-13 13:24:59 -0400129 * FIXME: this is no longer true. The _close path for the ldisc is
130 * now guaranteed to be sane.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131 */
132static DEFINE_RWLOCK(disc_data_lock);
133
134static struct asyncppp *ap_get(struct tty_struct *tty)
135{
136 struct asyncppp *ap;
137
138 read_lock(&disc_data_lock);
139 ap = tty->disc_data;
140 if (ap != NULL)
141 atomic_inc(&ap->refcnt);
142 read_unlock(&disc_data_lock);
143 return ap;
144}
145
146static void ap_put(struct asyncppp *ap)
147{
148 if (atomic_dec_and_test(&ap->refcnt))
149 up(&ap->dead_sem);
150}
151
152/*
153 * Called when a tty is put into PPP line discipline. Called in process
154 * context.
155 */
156static int
157ppp_asynctty_open(struct tty_struct *tty)
158{
159 struct asyncppp *ap;
160 int err;
Gabriele Paoloni9c705262009-03-13 16:09:12 -0700161 int speed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162
Alan Coxf34d7a52008-04-30 00:54:13 -0700163 if (tty->ops->write == NULL)
164 return -EOPNOTSUPP;
165
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 err = -ENOMEM;
Yoann Padioleaudd00cc42007-07-19 01:49:03 -0700167 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
Joe Perchescd228d52007-11-12 18:07:31 -0800168 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169 goto out;
170
171 /* initialize the asyncppp structure */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 ap->tty = tty;
173 ap->mru = PPP_MRU;
174 spin_lock_init(&ap->xmit_lock);
175 spin_lock_init(&ap->recv_lock);
176 ap->xaccm[0] = ~0U;
177 ap->xaccm[3] = 0x60000000U;
178 ap->raccm = ~0U;
179 ap->optr = ap->obuf;
180 ap->olim = ap->obuf;
181 ap->lcp_fcs = -1;
182
183 skb_queue_head_init(&ap->rqueue);
184 tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
185
186 atomic_set(&ap->refcnt, 1);
Thomas Gleixner0bce1982010-09-07 14:32:22 +0000187 sema_init(&ap->dead_sem, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188
189 ap->chan.private = ap;
190 ap->chan.ops = &async_ops;
191 ap->chan.mtu = PPP_MRU;
Gabriele Paoloni9c705262009-03-13 16:09:12 -0700192 speed = tty_get_baud_rate(tty);
193 ap->chan.speed = speed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 err = ppp_register_channel(&ap->chan);
195 if (err)
196 goto out_free;
197
198 tty->disc_data = ap;
Alan Cox33f0f882006-01-09 20:54:13 -0800199 tty->receive_room = 65536;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200 return 0;
201
202 out_free:
203 kfree(ap);
204 out:
205 return err;
206}
207
208/*
209 * Called when the tty is put into another line discipline
210 * or it hangs up. We have to wait for any cpu currently
211 * executing in any of the other ppp_asynctty_* routines to
212 * finish before we can call ppp_unregister_channel and free
213 * the asyncppp struct. This routine must be called from
214 * process context, not interrupt or softirq context.
215 */
216static void
217ppp_asynctty_close(struct tty_struct *tty)
218{
219 struct asyncppp *ap;
220
221 write_lock_irq(&disc_data_lock);
222 ap = tty->disc_data;
223 tty->disc_data = NULL;
224 write_unlock_irq(&disc_data_lock);
Joe Perchescd228d52007-11-12 18:07:31 -0800225 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226 return;
227
228 /*
229 * We have now ensured that nobody can start using ap from now
230 * on, but we have to wait for all existing users to finish.
231 * Note that ppp_unregister_channel ensures that no calls to
232 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
233 * by the time it returns.
234 */
235 if (!atomic_dec_and_test(&ap->refcnt))
236 down(&ap->dead_sem);
237 tasklet_kill(&ap->tsk);
238
239 ppp_unregister_channel(&ap->chan);
Wei Yongjun1d2f8c92009-02-25 00:16:08 +0000240 kfree_skb(ap->rpkt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700241 skb_queue_purge(&ap->rqueue);
Wei Yongjun1d2f8c92009-02-25 00:16:08 +0000242 kfree_skb(ap->tpkt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700243 kfree(ap);
244}
245
246/*
247 * Called on tty hangup in process context.
248 *
249 * Wait for I/O to driver to complete and unregister PPP channel.
250 * This is already done by the close routine, so just call that.
251 */
252static int ppp_asynctty_hangup(struct tty_struct *tty)
253{
254 ppp_asynctty_close(tty);
255 return 0;
256}
257
258/*
259 * Read does nothing - no data is ever available this way.
260 * Pppd reads and writes packets via /dev/ppp instead.
261 */
262static ssize_t
263ppp_asynctty_read(struct tty_struct *tty, struct file *file,
264 unsigned char __user *buf, size_t count)
265{
266 return -EAGAIN;
267}
268
269/*
270 * Write on the tty does nothing, the packets all come in
271 * from the ppp generic stuff.
272 */
273static ssize_t
274ppp_asynctty_write(struct tty_struct *tty, struct file *file,
275 const unsigned char *buf, size_t count)
276{
277 return -EAGAIN;
278}
279
280/*
281 * Called in process context only. May be re-entered by multiple
282 * ioctl calling threads.
283 */
Jeff Garzik6aa20a22006-09-13 13:24:59 -0400284
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285static int
286ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
287 unsigned int cmd, unsigned long arg)
288{
289 struct asyncppp *ap = ap_get(tty);
290 int err, val;
291 int __user *p = (int __user *)arg;
292
Joe Perchescd228d52007-11-12 18:07:31 -0800293 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294 return -ENXIO;
295 err = -EFAULT;
296 switch (cmd) {
297 case PPPIOCGCHAN:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298 err = -EFAULT;
299 if (put_user(ppp_channel_index(&ap->chan), p))
300 break;
301 err = 0;
302 break;
303
304 case PPPIOCGUNIT:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305 err = -EFAULT;
306 if (put_user(ppp_unit_number(&ap->chan), p))
307 break;
308 err = 0;
309 break;
310
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 case TCFLSH:
312 /* flush our buffers and the serial port's buffer */
313 if (arg == TCIOFLUSH || arg == TCOFLUSH)
314 ppp_async_flush_output(ap);
Alan Coxd0127532007-11-07 01:27:34 -0800315 err = tty_perform_flush(tty, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316 break;
317
318 case FIONREAD:
319 val = 0;
320 if (put_user(val, p))
321 break;
322 err = 0;
323 break;
324
325 default:
Alan Coxd0127532007-11-07 01:27:34 -0800326 /* Try the various mode ioctls */
327 err = tty_mode_ioctl(tty, file, cmd, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 }
329
330 ap_put(ap);
331 return err;
332}
333
334/* No kernel lock - fine */
335static unsigned int
336ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
337{
338 return 0;
339}
340
Tilman Schmidt92d326f2009-10-01 04:28:44 +0000341/* May sleep, don't call from interrupt level or with interrupts disabled */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342static void
343ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
344 char *cflags, int count)
345{
346 struct asyncppp *ap = ap_get(tty);
347 unsigned long flags;
348
Joe Perchescd228d52007-11-12 18:07:31 -0800349 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 return;
351 spin_lock_irqsave(&ap->recv_lock, flags);
352 ppp_async_input(ap, buf, cflags, count);
353 spin_unlock_irqrestore(&ap->recv_lock, flags);
David S. Millerb03efcf2005-07-08 14:57:23 -0700354 if (!skb_queue_empty(&ap->rqueue))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700355 tasklet_schedule(&ap->tsk);
356 ap_put(ap);
Linus Torvalds4a21b8c2009-07-16 09:14:23 -0700357 tty_unthrottle(tty);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358}
359
360static void
361ppp_asynctty_wakeup(struct tty_struct *tty)
362{
363 struct asyncppp *ap = ap_get(tty);
364
365 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
Joe Perchescd228d52007-11-12 18:07:31 -0800366 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 return;
368 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
369 tasklet_schedule(&ap->tsk);
370 ap_put(ap);
371}
372
373
Alan Coxa352def2008-07-16 21:53:12 +0100374static struct tty_ldisc_ops ppp_ldisc = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 .owner = THIS_MODULE,
376 .magic = TTY_LDISC_MAGIC,
377 .name = "ppp",
378 .open = ppp_asynctty_open,
379 .close = ppp_asynctty_close,
380 .hangup = ppp_asynctty_hangup,
381 .read = ppp_asynctty_read,
382 .write = ppp_asynctty_write,
383 .ioctl = ppp_asynctty_ioctl,
384 .poll = ppp_asynctty_poll,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 .receive_buf = ppp_asynctty_receive,
386 .write_wakeup = ppp_asynctty_wakeup,
387};
388
389static int __init
390ppp_async_init(void)
391{
392 int err;
393
394 err = tty_register_ldisc(N_PPP, &ppp_ldisc);
395 if (err != 0)
396 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
397 err);
398 return err;
399}
400
401/*
402 * The following routines provide the PPP channel interface.
403 */
404static int
405ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
406{
407 struct asyncppp *ap = chan->private;
408 void __user *argp = (void __user *)arg;
409 int __user *p = argp;
410 int err, val;
411 u32 accm[8];
412
413 err = -EFAULT;
414 switch (cmd) {
415 case PPPIOCGFLAGS:
416 val = ap->flags | ap->rbits;
417 if (put_user(val, p))
418 break;
419 err = 0;
420 break;
421 case PPPIOCSFLAGS:
422 if (get_user(val, p))
423 break;
424 ap->flags = val & ~SC_RCV_BITS;
425 spin_lock_irq(&ap->recv_lock);
426 ap->rbits = val & SC_RCV_BITS;
427 spin_unlock_irq(&ap->recv_lock);
428 err = 0;
429 break;
430
431 case PPPIOCGASYNCMAP:
432 if (put_user(ap->xaccm[0], (u32 __user *)argp))
433 break;
434 err = 0;
435 break;
436 case PPPIOCSASYNCMAP:
437 if (get_user(ap->xaccm[0], (u32 __user *)argp))
438 break;
439 err = 0;
440 break;
441
442 case PPPIOCGRASYNCMAP:
443 if (put_user(ap->raccm, (u32 __user *)argp))
444 break;
445 err = 0;
446 break;
447 case PPPIOCSRASYNCMAP:
448 if (get_user(ap->raccm, (u32 __user *)argp))
449 break;
450 err = 0;
451 break;
452
453 case PPPIOCGXASYNCMAP:
454 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
455 break;
456 err = 0;
457 break;
458 case PPPIOCSXASYNCMAP:
459 if (copy_from_user(accm, argp, sizeof(accm)))
460 break;
461 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
462 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
463 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
464 err = 0;
465 break;
466
467 case PPPIOCGMRU:
468 if (put_user(ap->mru, p))
469 break;
470 err = 0;
471 break;
472 case PPPIOCSMRU:
473 if (get_user(val, p))
474 break;
475 if (val < PPP_MRU)
476 val = PPP_MRU;
477 ap->mru = val;
478 err = 0;
479 break;
480
481 default:
482 err = -ENOTTY;
483 }
484
485 return err;
486}
487
488/*
489 * This is called at softirq level to deliver received packets
490 * to the ppp_generic code, and to tell the ppp_generic code
491 * if we can accept more output now.
492 */
493static void ppp_async_process(unsigned long arg)
494{
495 struct asyncppp *ap = (struct asyncppp *) arg;
496 struct sk_buff *skb;
497
498 /* process received packets */
499 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
500 if (skb->cb[0])
501 ppp_input_error(&ap->chan, 0);
502 ppp_input(&ap->chan, skb);
503 }
504
505 /* try to push more stuff out */
506 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
507 ppp_output_wakeup(&ap->chan);
508}
509
510/*
511 * Procedures for encapsulation and framing.
512 */
513
514/*
515 * Procedure to encode the data for async serial transmission.
516 * Does octet stuffing (escaping), puts the address/control bytes
517 * on if A/C compression is disabled, and does protocol compression.
518 * Assumes ap->tpkt != 0 on entry.
519 * Returns 1 if we finished the current frame, 0 otherwise.
520 */
521
522#define PUT_BYTE(ap, buf, c, islcp) do { \
523 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
524 *buf++ = PPP_ESCAPE; \
525 *buf++ = c ^ 0x20; \
526 } else \
527 *buf++ = c; \
528} while (0)
529
530static int
531ppp_async_encode(struct asyncppp *ap)
532{
533 int fcs, i, count, c, proto;
534 unsigned char *buf, *buflim;
535 unsigned char *data;
536 int islcp;
537
538 buf = ap->obuf;
539 ap->olim = buf;
540 ap->optr = buf;
541 i = ap->tpkt_pos;
542 data = ap->tpkt->data;
543 count = ap->tpkt->len;
544 fcs = ap->tfcs;
545 proto = (data[0] << 8) + data[1];
546
547 /*
548 * LCP packets with code values between 1 (configure-reqest)
549 * and 7 (code-reject) must be sent as though no options
550 * had been negotiated.
551 */
552 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
553
554 if (i == 0) {
555 if (islcp)
556 async_lcp_peek(ap, data, count, 0);
557
558 /*
559 * Start of a new packet - insert the leading FLAG
560 * character if necessary.
561 */
Joe Perches8e95a202009-12-03 07:58:21 +0000562 if (islcp || flag_time == 0 ||
563 time_after_eq(jiffies, ap->last_xmit + flag_time))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564 *buf++ = PPP_FLAG;
565 ap->last_xmit = jiffies;
566 fcs = PPP_INITFCS;
567
568 /*
569 * Put in the address/control bytes if necessary
570 */
571 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
572 PUT_BYTE(ap, buf, 0xff, islcp);
573 fcs = PPP_FCS(fcs, 0xff);
574 PUT_BYTE(ap, buf, 0x03, islcp);
575 fcs = PPP_FCS(fcs, 0x03);
576 }
577 }
578
579 /*
580 * Once we put in the last byte, we need to put in the FCS
581 * and closing flag, so make sure there is at least 7 bytes
582 * of free space in the output buffer.
583 */
584 buflim = ap->obuf + OBUFSIZE - 6;
585 while (i < count && buf < buflim) {
586 c = data[i++];
587 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
588 continue; /* compress protocol field */
589 fcs = PPP_FCS(fcs, c);
590 PUT_BYTE(ap, buf, c, islcp);
591 }
592
593 if (i < count) {
594 /*
595 * Remember where we are up to in this packet.
596 */
597 ap->olim = buf;
598 ap->tpkt_pos = i;
599 ap->tfcs = fcs;
600 return 0;
601 }
602
603 /*
604 * We have finished the packet. Add the FCS and flag.
605 */
606 fcs = ~fcs;
607 c = fcs & 0xff;
608 PUT_BYTE(ap, buf, c, islcp);
609 c = (fcs >> 8) & 0xff;
610 PUT_BYTE(ap, buf, c, islcp);
611 *buf++ = PPP_FLAG;
612 ap->olim = buf;
613
614 kfree_skb(ap->tpkt);
615 ap->tpkt = NULL;
616 return 1;
617}
618
619/*
620 * Transmit-side routines.
621 */
622
623/*
624 * Send a packet to the peer over an async tty line.
625 * Returns 1 iff the packet was accepted.
626 * If the packet was not accepted, we will call ppp_output_wakeup
627 * at some later time.
628 */
629static int
630ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
631{
632 struct asyncppp *ap = chan->private;
633
634 ppp_async_push(ap);
635
636 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
637 return 0; /* already full */
638 ap->tpkt = skb;
639 ap->tpkt_pos = 0;
640
641 ppp_async_push(ap);
642 return 1;
643}
644
645/*
646 * Push as much data as possible out to the tty.
647 */
648static int
649ppp_async_push(struct asyncppp *ap)
650{
651 int avail, sent, done = 0;
652 struct tty_struct *tty = ap->tty;
653 int tty_stuffed = 0;
654
655 /*
656 * We can get called recursively here if the tty write
657 * function calls our wakeup function. This can happen
658 * for example on a pty with both the master and slave
659 * set to PPP line discipline.
660 * We use the XMIT_BUSY bit to detect this and get out,
661 * leaving the XMIT_WAKEUP bit set to tell the other
662 * instance that it may now be able to write more now.
663 */
664 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
665 return 0;
666 spin_lock_bh(&ap->xmit_lock);
667 for (;;) {
668 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
669 tty_stuffed = 0;
670 if (!tty_stuffed && ap->optr < ap->olim) {
671 avail = ap->olim - ap->optr;
672 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
Alan Coxf34d7a52008-04-30 00:54:13 -0700673 sent = tty->ops->write(tty, ap->optr, avail);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 if (sent < 0)
675 goto flush; /* error, e.g. loss of CD */
676 ap->optr += sent;
677 if (sent < avail)
678 tty_stuffed = 1;
679 continue;
680 }
Joe Perchescd228d52007-11-12 18:07:31 -0800681 if (ap->optr >= ap->olim && ap->tpkt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700682 if (ppp_async_encode(ap)) {
683 /* finished processing ap->tpkt */
684 clear_bit(XMIT_FULL, &ap->xmit_flags);
685 done = 1;
686 }
687 continue;
688 }
689 /*
690 * We haven't made any progress this time around.
691 * Clear XMIT_BUSY to let other callers in, but
692 * after doing so we have to check if anyone set
693 * XMIT_WAKEUP since we last checked it. If they
694 * did, we should try again to set XMIT_BUSY and go
695 * around again in case XMIT_BUSY was still set when
696 * the other caller tried.
697 */
698 clear_bit(XMIT_BUSY, &ap->xmit_flags);
699 /* any more work to do? if not, exit the loop */
Joe Perches8e95a202009-12-03 07:58:21 +0000700 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
701 (!tty_stuffed && ap->tpkt)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700702 break;
703 /* more work to do, see if we can do it now */
704 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
705 break;
706 }
707 spin_unlock_bh(&ap->xmit_lock);
708 return done;
709
710flush:
711 clear_bit(XMIT_BUSY, &ap->xmit_flags);
Joe Perchescd228d52007-11-12 18:07:31 -0800712 if (ap->tpkt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713 kfree_skb(ap->tpkt);
714 ap->tpkt = NULL;
715 clear_bit(XMIT_FULL, &ap->xmit_flags);
716 done = 1;
717 }
718 ap->optr = ap->olim;
719 spin_unlock_bh(&ap->xmit_lock);
720 return done;
721}
722
723/*
724 * Flush output from our internal buffers.
725 * Called for the TCFLSH ioctl. Can be entered in parallel
726 * but this is covered by the xmit_lock.
727 */
728static void
729ppp_async_flush_output(struct asyncppp *ap)
730{
731 int done = 0;
732
733 spin_lock_bh(&ap->xmit_lock);
734 ap->optr = ap->olim;
735 if (ap->tpkt != NULL) {
736 kfree_skb(ap->tpkt);
737 ap->tpkt = NULL;
738 clear_bit(XMIT_FULL, &ap->xmit_flags);
739 done = 1;
740 }
741 spin_unlock_bh(&ap->xmit_lock);
742 if (done)
743 ppp_output_wakeup(&ap->chan);
744}
745
746/*
747 * Receive-side routines.
748 */
749
750/* see how many ordinary chars there are at the start of buf */
751static inline int
752scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
753{
754 int i, c;
755
756 for (i = 0; i < count; ++i) {
757 c = buf[i];
Joe Perches8e95a202009-12-03 07:58:21 +0000758 if (c == PPP_ESCAPE || c == PPP_FLAG ||
759 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760 break;
761 }
762 return i;
763}
764
765/* called when a flag is seen - do end-of-packet processing */
766static void
767process_input_packet(struct asyncppp *ap)
768{
769 struct sk_buff *skb;
770 unsigned char *p;
771 unsigned int len, fcs, proto;
772
773 skb = ap->rpkt;
774 if (ap->state & (SC_TOSS | SC_ESCAPE))
775 goto err;
776
777 if (skb == NULL)
778 return; /* 0-length packet */
779
780 /* check the FCS */
781 p = skb->data;
782 len = skb->len;
783 if (len < 3)
784 goto err; /* too short */
785 fcs = PPP_INITFCS;
786 for (; len > 0; --len)
787 fcs = PPP_FCS(fcs, *p++);
788 if (fcs != PPP_GOODFCS)
789 goto err; /* bad FCS */
790 skb_trim(skb, skb->len - 2);
791
792 /* check for address/control and protocol compression */
793 p = skb->data;
Paul Mackerras7c5050e2007-04-19 13:05:52 -0700794 if (p[0] == PPP_ALLSTATIONS) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700795 /* chop off address/control */
Paul Mackerras7c5050e2007-04-19 13:05:52 -0700796 if (p[1] != PPP_UI || skb->len < 3)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 goto err;
798 p = skb_pull(skb, 2);
799 }
800 proto = p[0];
801 if (proto & 1) {
802 /* protocol is compressed */
803 skb_push(skb, 1)[0] = 0;
804 } else {
805 if (skb->len < 2)
806 goto err;
807 proto = (proto << 8) + p[1];
808 if (proto == PPP_LCP)
809 async_lcp_peek(ap, p, skb->len, 1);
810 }
811
812 /* queue the frame to be processed */
813 skb->cb[0] = ap->state;
814 skb_queue_tail(&ap->rqueue, skb);
815 ap->rpkt = NULL;
816 ap->state = 0;
817 return;
818
819 err:
820 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
821 ap->state = SC_PREV_ERROR;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800822 if (skb) {
823 /* make skb appear as freshly allocated */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824 skb_trim(skb, 0);
Philippe De Muyter6722e782005-11-08 09:40:26 -0800825 skb_reserve(skb, - skb_headroom(skb));
826 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700827}
828
829/* Called when the tty driver has data for us. Runs parallel with the
830 other ldisc functions but will not be re-entered */
831
832static void
833ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
834 char *flags, int count)
835{
836 struct sk_buff *skb;
837 int c, i, j, n, s, f;
838 unsigned char *sp;
839
840 /* update bits used for 8-bit cleanness detection */
841 if (~ap->rbits & SC_RCV_BITS) {
842 s = 0;
843 for (i = 0; i < count; ++i) {
844 c = buf[i];
Joe Perchescd228d52007-11-12 18:07:31 -0800845 if (flags && flags[i] != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 continue;
847 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
848 c = ((c >> 4) ^ c) & 0xf;
849 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
850 }
851 ap->rbits |= s;
852 }
853
854 while (count > 0) {
855 /* scan through and see how many chars we can do in bulk */
856 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
857 n = 1;
858 else
859 n = scan_ordinary(ap, buf, count);
860
861 f = 0;
Joe Perchescd228d52007-11-12 18:07:31 -0800862 if (flags && (ap->state & SC_TOSS) == 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700863 /* check the flags to see if any char had an error */
864 for (j = 0; j < n; ++j)
865 if ((f = flags[j]) != 0)
866 break;
867 }
868 if (f != 0) {
869 /* start tossing */
870 ap->state |= SC_TOSS;
871
872 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
873 /* stuff the chars in the skb */
874 skb = ap->rpkt;
Joe Perchescd228d52007-11-12 18:07:31 -0800875 if (!skb) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
Joe Perchescd228d52007-11-12 18:07:31 -0800877 if (!skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 goto nomem;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800879 ap->rpkt = skb;
880 }
881 if (skb->len == 0) {
882 /* Try to get the payload 4-byte aligned.
883 * This should match the
884 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
885 * process_input_packet, but we do not have
886 * enough chars here to test buf[1] and buf[2].
887 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888 if (buf[0] != PPP_ALLSTATIONS)
889 skb_reserve(skb, 2 + (buf[0] & 1));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 }
891 if (n > skb_tailroom(skb)) {
892 /* packet overflowed MRU */
893 ap->state |= SC_TOSS;
894 } else {
895 sp = skb_put(skb, n);
896 memcpy(sp, buf, n);
897 if (ap->state & SC_ESCAPE) {
898 sp[0] ^= 0x20;
899 ap->state &= ~SC_ESCAPE;
900 }
901 }
902 }
903
904 if (n >= count)
905 break;
906
907 c = buf[n];
908 if (flags != NULL && flags[n] != 0) {
909 ap->state |= SC_TOSS;
910 } else if (c == PPP_FLAG) {
911 process_input_packet(ap);
912 } else if (c == PPP_ESCAPE) {
913 ap->state |= SC_ESCAPE;
914 } else if (I_IXON(ap->tty)) {
915 if (c == START_CHAR(ap->tty))
916 start_tty(ap->tty);
917 else if (c == STOP_CHAR(ap->tty))
918 stop_tty(ap->tty);
919 }
920 /* otherwise it's a char in the recv ACCM */
921 ++n;
922
923 buf += n;
Joe Perchescd228d52007-11-12 18:07:31 -0800924 if (flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700925 flags += n;
926 count -= n;
927 }
928 return;
929
930 nomem:
931 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
932 ap->state |= SC_TOSS;
933}
934
935/*
936 * We look at LCP frames going past so that we can notice
937 * and react to the LCP configure-ack from the peer.
938 * In the situation where the peer has been sent a configure-ack
939 * already, LCP is up once it has sent its configure-ack
940 * so the immediately following packet can be sent with the
941 * configured LCP options. This allows us to process the following
942 * packet correctly without pppd needing to respond quickly.
943 *
944 * We only respond to the received configure-ack if we have just
945 * sent a configure-request, and the configure-ack contains the
946 * same data (this is checked using a 16-bit crc of the data).
947 */
948#define CONFREQ 1 /* LCP code field values */
949#define CONFACK 2
950#define LCP_MRU 1 /* LCP option numbers */
951#define LCP_ASYNCMAP 2
952
953static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
954 int len, int inbound)
955{
956 int dlen, fcs, i, code;
957 u32 val;
958
959 data += 2; /* skip protocol bytes */
960 len -= 2;
961 if (len < 4) /* 4 = code, ID, length */
962 return;
963 code = data[0];
964 if (code != CONFACK && code != CONFREQ)
965 return;
966 dlen = (data[2] << 8) + data[3];
967 if (len < dlen)
968 return; /* packet got truncated or length is bogus */
969
970 if (code == (inbound? CONFACK: CONFREQ)) {
971 /*
972 * sent confreq or received confack:
973 * calculate the crc of the data from the ID field on.
974 */
975 fcs = PPP_INITFCS;
976 for (i = 1; i < dlen; ++i)
977 fcs = PPP_FCS(fcs, data[i]);
978
979 if (!inbound) {
980 /* outbound confreq - remember the crc for later */
981 ap->lcp_fcs = fcs;
982 return;
983 }
984
985 /* received confack, check the crc */
986 fcs ^= ap->lcp_fcs;
987 ap->lcp_fcs = -1;
988 if (fcs != 0)
989 return;
990 } else if (inbound)
991 return; /* not interested in received confreq */
992
993 /* process the options in the confack */
994 data += 4;
995 dlen -= 4;
996 /* data[0] is code, data[1] is length */
997 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
998 switch (data[0]) {
999 case LCP_MRU:
1000 val = (data[2] << 8) + data[3];
1001 if (inbound)
1002 ap->mru = val;
1003 else
1004 ap->chan.mtu = val;
1005 break;
1006 case LCP_ASYNCMAP:
1007 val = (data[2] << 24) + (data[3] << 16)
1008 + (data[4] << 8) + data[5];
1009 if (inbound)
1010 ap->raccm = val;
1011 else
1012 ap->xaccm[0] = val;
1013 break;
1014 }
1015 dlen -= data[1];
1016 data += data[1];
1017 }
1018}
1019
1020static void __exit ppp_async_cleanup(void)
1021{
Alexey Dobriyan64ccd712005-06-23 00:10:33 -07001022 if (tty_unregister_ldisc(N_PPP) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1024}
1025
1026module_init(ppp_async_init);
1027module_exit(ppp_async_cleanup);