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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>
Changli Gao96545ae2011-01-06 13:37:36 +000035#include <asm/unaligned.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070036#include <asm/uaccess.h>
Philippe De Muyter6722e782005-11-08 09:40:26 -080037#include <asm/string.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038
39#define PPP_VERSION "2.4.2"
40
fangxiaozhi208f2032009-11-17 04:02:24 -080041#define OBUFSIZE 4096
Linus Torvalds1da177e2005-04-16 15:20:36 -070042
43/* Structure for storing local state. */
44struct asyncppp {
45 struct tty_struct *tty;
46 unsigned int flags;
47 unsigned int state;
48 unsigned int rbits;
49 int mru;
50 spinlock_t xmit_lock;
51 spinlock_t recv_lock;
52 unsigned long xmit_flags;
53 u32 xaccm[8];
54 u32 raccm;
55 unsigned int bytes_sent;
56 unsigned int bytes_rcvd;
57
58 struct sk_buff *tpkt;
59 int tpkt_pos;
60 u16 tfcs;
61 unsigned char *optr;
62 unsigned char *olim;
63 unsigned long last_xmit;
64
65 struct sk_buff *rpkt;
66 int lcp_fcs;
67 struct sk_buff_head rqueue;
68
69 struct tasklet_struct tsk;
70
71 atomic_t refcnt;
72 struct semaphore dead_sem;
73 struct ppp_channel chan; /* interface to generic ppp layer */
74 unsigned char obuf[OBUFSIZE];
75};
76
77/* Bit numbers in xmit_flags */
78#define XMIT_WAKEUP 0
79#define XMIT_FULL 1
80#define XMIT_BUSY 2
81
82/* State bits */
83#define SC_TOSS 1
84#define SC_ESCAPE 2
85#define SC_PREV_ERROR 4
86
87/* Bits in rbits */
88#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
89
90static int flag_time = HZ;
91module_param(flag_time, int, 0);
92MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
93MODULE_LICENSE("GPL");
94MODULE_ALIAS_LDISC(N_PPP);
95
96/*
97 * Prototypes.
98 */
99static int ppp_async_encode(struct asyncppp *ap);
100static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
101static int ppp_async_push(struct asyncppp *ap);
102static void ppp_async_flush_output(struct asyncppp *ap);
103static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
104 char *flags, int count);
105static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
106 unsigned long arg);
107static void ppp_async_process(unsigned long arg);
108
109static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
110 int len, int inbound);
111
stephen hemmingerd7100da2010-08-04 07:34:36 +0000112static const struct ppp_channel_ops async_ops = {
113 .start_xmit = ppp_async_send,
114 .ioctl = ppp_async_ioctl,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115};
116
117/*
118 * Routines implementing the PPP line discipline.
119 */
120
121/*
122 * We have a potential race on dereferencing tty->disc_data,
123 * because the tty layer provides no locking at all - thus one
124 * cpu could be running ppp_asynctty_receive while another
125 * calls ppp_asynctty_close, which zeroes tty->disc_data and
126 * frees the memory that ppp_asynctty_receive is using. The best
127 * way to fix this is to use a rwlock in the tty struct, but for now
128 * we use a single global rwlock for all ttys in ppp line discipline.
129 *
Jeff Garzik6aa20a22006-09-13 13:24:59 -0400130 * FIXME: this is no longer true. The _close path for the ldisc is
131 * now guaranteed to be sane.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132 */
133static DEFINE_RWLOCK(disc_data_lock);
134
135static struct asyncppp *ap_get(struct tty_struct *tty)
136{
137 struct asyncppp *ap;
138
139 read_lock(&disc_data_lock);
140 ap = tty->disc_data;
141 if (ap != NULL)
142 atomic_inc(&ap->refcnt);
143 read_unlock(&disc_data_lock);
144 return ap;
145}
146
147static void ap_put(struct asyncppp *ap)
148{
149 if (atomic_dec_and_test(&ap->refcnt))
150 up(&ap->dead_sem);
151}
152
153/*
154 * Called when a tty is put into PPP line discipline. Called in process
155 * context.
156 */
157static int
158ppp_asynctty_open(struct tty_struct *tty)
159{
160 struct asyncppp *ap;
161 int err;
Gabriele Paoloni9c705262009-03-13 16:09:12 -0700162 int speed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163
Alan Coxf34d7a52008-04-30 00:54:13 -0700164 if (tty->ops->write == NULL)
165 return -EOPNOTSUPP;
166
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167 err = -ENOMEM;
Yoann Padioleaudd00cc42007-07-19 01:49:03 -0700168 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
Joe Perchescd228d52007-11-12 18:07:31 -0800169 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 goto out;
171
172 /* initialize the asyncppp structure */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 ap->tty = tty;
174 ap->mru = PPP_MRU;
175 spin_lock_init(&ap->xmit_lock);
176 spin_lock_init(&ap->recv_lock);
177 ap->xaccm[0] = ~0U;
178 ap->xaccm[3] = 0x60000000U;
179 ap->raccm = ~0U;
180 ap->optr = ap->obuf;
181 ap->olim = ap->obuf;
182 ap->lcp_fcs = -1;
183
184 skb_queue_head_init(&ap->rqueue);
185 tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
186
187 atomic_set(&ap->refcnt, 1);
Thomas Gleixner0bce1982010-09-07 14:32:22 +0000188 sema_init(&ap->dead_sem, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189
190 ap->chan.private = ap;
191 ap->chan.ops = &async_ops;
192 ap->chan.mtu = PPP_MRU;
Gabriele Paoloni9c705262009-03-13 16:09:12 -0700193 speed = tty_get_baud_rate(tty);
194 ap->chan.speed = speed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195 err = ppp_register_channel(&ap->chan);
196 if (err)
197 goto out_free;
198
199 tty->disc_data = ap;
Alan Cox33f0f882006-01-09 20:54:13 -0800200 tty->receive_room = 65536;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 return 0;
202
203 out_free:
204 kfree(ap);
205 out:
206 return err;
207}
208
209/*
210 * Called when the tty is put into another line discipline
211 * or it hangs up. We have to wait for any cpu currently
212 * executing in any of the other ppp_asynctty_* routines to
213 * finish before we can call ppp_unregister_channel and free
214 * the asyncppp struct. This routine must be called from
215 * process context, not interrupt or softirq context.
216 */
217static void
218ppp_asynctty_close(struct tty_struct *tty)
219{
220 struct asyncppp *ap;
221
222 write_lock_irq(&disc_data_lock);
223 ap = tty->disc_data;
224 tty->disc_data = NULL;
225 write_unlock_irq(&disc_data_lock);
Joe Perchescd228d52007-11-12 18:07:31 -0800226 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227 return;
228
229 /*
230 * We have now ensured that nobody can start using ap from now
231 * on, but we have to wait for all existing users to finish.
232 * Note that ppp_unregister_channel ensures that no calls to
233 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
234 * by the time it returns.
235 */
236 if (!atomic_dec_and_test(&ap->refcnt))
237 down(&ap->dead_sem);
238 tasklet_kill(&ap->tsk);
239
240 ppp_unregister_channel(&ap->chan);
Wei Yongjun1d2f8c92009-02-25 00:16:08 +0000241 kfree_skb(ap->rpkt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 skb_queue_purge(&ap->rqueue);
Wei Yongjun1d2f8c92009-02-25 00:16:08 +0000243 kfree_skb(ap->tpkt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700244 kfree(ap);
245}
246
247/*
248 * Called on tty hangup in process context.
249 *
250 * Wait for I/O to driver to complete and unregister PPP channel.
251 * This is already done by the close routine, so just call that.
252 */
253static int ppp_asynctty_hangup(struct tty_struct *tty)
254{
255 ppp_asynctty_close(tty);
256 return 0;
257}
258
259/*
260 * Read does nothing - no data is ever available this way.
261 * Pppd reads and writes packets via /dev/ppp instead.
262 */
263static ssize_t
264ppp_asynctty_read(struct tty_struct *tty, struct file *file,
265 unsigned char __user *buf, size_t count)
266{
267 return -EAGAIN;
268}
269
270/*
271 * Write on the tty does nothing, the packets all come in
272 * from the ppp generic stuff.
273 */
274static ssize_t
275ppp_asynctty_write(struct tty_struct *tty, struct file *file,
276 const unsigned char *buf, size_t count)
277{
278 return -EAGAIN;
279}
280
281/*
282 * Called in process context only. May be re-entered by multiple
283 * ioctl calling threads.
284 */
Jeff Garzik6aa20a22006-09-13 13:24:59 -0400285
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286static int
287ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
288 unsigned int cmd, unsigned long arg)
289{
290 struct asyncppp *ap = ap_get(tty);
291 int err, val;
292 int __user *p = (int __user *)arg;
293
Joe Perchescd228d52007-11-12 18:07:31 -0800294 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700295 return -ENXIO;
296 err = -EFAULT;
297 switch (cmd) {
298 case PPPIOCGCHAN:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299 err = -EFAULT;
300 if (put_user(ppp_channel_index(&ap->chan), p))
301 break;
302 err = 0;
303 break;
304
305 case PPPIOCGUNIT:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306 err = -EFAULT;
307 if (put_user(ppp_unit_number(&ap->chan), p))
308 break;
309 err = 0;
310 break;
311
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 case TCFLSH:
313 /* flush our buffers and the serial port's buffer */
314 if (arg == TCIOFLUSH || arg == TCOFLUSH)
315 ppp_async_flush_output(ap);
Alan Coxd0127532007-11-07 01:27:34 -0800316 err = tty_perform_flush(tty, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700317 break;
318
319 case FIONREAD:
320 val = 0;
321 if (put_user(val, p))
322 break;
323 err = 0;
324 break;
325
326 default:
Alan Coxd0127532007-11-07 01:27:34 -0800327 /* Try the various mode ioctls */
328 err = tty_mode_ioctl(tty, file, cmd, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 }
330
331 ap_put(ap);
332 return err;
333}
334
335/* No kernel lock - fine */
336static unsigned int
337ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
338{
339 return 0;
340}
341
Tilman Schmidt92d326f2009-10-01 04:28:44 +0000342/* May sleep, don't call from interrupt level or with interrupts disabled */
Linus Torvalds55db4c62011-06-04 06:33:24 +0900343static void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
345 char *cflags, int count)
346{
347 struct asyncppp *ap = ap_get(tty);
348 unsigned long flags;
349
Joe Perchescd228d52007-11-12 18:07:31 -0800350 if (!ap)
Linus Torvalds55db4c62011-06-04 06:33:24 +0900351 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 spin_lock_irqsave(&ap->recv_lock, flags);
353 ppp_async_input(ap, buf, cflags, count);
354 spin_unlock_irqrestore(&ap->recv_lock, flags);
David S. Millerb03efcf2005-07-08 14:57:23 -0700355 if (!skb_queue_empty(&ap->rqueue))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356 tasklet_schedule(&ap->tsk);
357 ap_put(ap);
Linus Torvalds4a21b8c2009-07-16 09:14:23 -0700358 tty_unthrottle(tty);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359}
360
361static void
362ppp_asynctty_wakeup(struct tty_struct *tty)
363{
364 struct asyncppp *ap = ap_get(tty);
365
366 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
Joe Perchescd228d52007-11-12 18:07:31 -0800367 if (!ap)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 return;
369 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
370 tasklet_schedule(&ap->tsk);
371 ap_put(ap);
372}
373
374
Alan Coxa352def2008-07-16 21:53:12 +0100375static struct tty_ldisc_ops ppp_ldisc = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 .owner = THIS_MODULE,
377 .magic = TTY_LDISC_MAGIC,
378 .name = "ppp",
379 .open = ppp_asynctty_open,
380 .close = ppp_asynctty_close,
381 .hangup = ppp_asynctty_hangup,
382 .read = ppp_asynctty_read,
383 .write = ppp_asynctty_write,
384 .ioctl = ppp_asynctty_ioctl,
385 .poll = ppp_asynctty_poll,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 .receive_buf = ppp_asynctty_receive,
387 .write_wakeup = ppp_asynctty_wakeup,
388};
389
390static int __init
391ppp_async_init(void)
392{
393 int err;
394
395 err = tty_register_ldisc(N_PPP, &ppp_ldisc);
396 if (err != 0)
397 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
398 err);
399 return err;
400}
401
402/*
403 * The following routines provide the PPP channel interface.
404 */
405static int
406ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
407{
408 struct asyncppp *ap = chan->private;
409 void __user *argp = (void __user *)arg;
410 int __user *p = argp;
411 int err, val;
412 u32 accm[8];
413
414 err = -EFAULT;
415 switch (cmd) {
416 case PPPIOCGFLAGS:
417 val = ap->flags | ap->rbits;
418 if (put_user(val, p))
419 break;
420 err = 0;
421 break;
422 case PPPIOCSFLAGS:
423 if (get_user(val, p))
424 break;
425 ap->flags = val & ~SC_RCV_BITS;
426 spin_lock_irq(&ap->recv_lock);
427 ap->rbits = val & SC_RCV_BITS;
428 spin_unlock_irq(&ap->recv_lock);
429 err = 0;
430 break;
431
432 case PPPIOCGASYNCMAP:
433 if (put_user(ap->xaccm[0], (u32 __user *)argp))
434 break;
435 err = 0;
436 break;
437 case PPPIOCSASYNCMAP:
438 if (get_user(ap->xaccm[0], (u32 __user *)argp))
439 break;
440 err = 0;
441 break;
442
443 case PPPIOCGRASYNCMAP:
444 if (put_user(ap->raccm, (u32 __user *)argp))
445 break;
446 err = 0;
447 break;
448 case PPPIOCSRASYNCMAP:
449 if (get_user(ap->raccm, (u32 __user *)argp))
450 break;
451 err = 0;
452 break;
453
454 case PPPIOCGXASYNCMAP:
455 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
456 break;
457 err = 0;
458 break;
459 case PPPIOCSXASYNCMAP:
460 if (copy_from_user(accm, argp, sizeof(accm)))
461 break;
462 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
463 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
464 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
465 err = 0;
466 break;
467
468 case PPPIOCGMRU:
469 if (put_user(ap->mru, p))
470 break;
471 err = 0;
472 break;
473 case PPPIOCSMRU:
474 if (get_user(val, p))
475 break;
476 if (val < PPP_MRU)
477 val = PPP_MRU;
478 ap->mru = val;
479 err = 0;
480 break;
481
482 default:
483 err = -ENOTTY;
484 }
485
486 return err;
487}
488
489/*
490 * This is called at softirq level to deliver received packets
491 * to the ppp_generic code, and to tell the ppp_generic code
492 * if we can accept more output now.
493 */
494static void ppp_async_process(unsigned long arg)
495{
496 struct asyncppp *ap = (struct asyncppp *) arg;
497 struct sk_buff *skb;
498
499 /* process received packets */
500 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
501 if (skb->cb[0])
502 ppp_input_error(&ap->chan, 0);
503 ppp_input(&ap->chan, skb);
504 }
505
506 /* try to push more stuff out */
507 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
508 ppp_output_wakeup(&ap->chan);
509}
510
511/*
512 * Procedures for encapsulation and framing.
513 */
514
515/*
516 * Procedure to encode the data for async serial transmission.
517 * Does octet stuffing (escaping), puts the address/control bytes
518 * on if A/C compression is disabled, and does protocol compression.
519 * Assumes ap->tpkt != 0 on entry.
520 * Returns 1 if we finished the current frame, 0 otherwise.
521 */
522
523#define PUT_BYTE(ap, buf, c, islcp) do { \
524 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
525 *buf++ = PPP_ESCAPE; \
Changli Gaoe6539e22011-06-14 21:58:13 +0000526 *buf++ = c ^ PPP_TRANS; \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527 } else \
528 *buf++ = c; \
529} while (0)
530
531static int
532ppp_async_encode(struct asyncppp *ap)
533{
534 int fcs, i, count, c, proto;
535 unsigned char *buf, *buflim;
536 unsigned char *data;
537 int islcp;
538
539 buf = ap->obuf;
540 ap->olim = buf;
541 ap->optr = buf;
542 i = ap->tpkt_pos;
543 data = ap->tpkt->data;
544 count = ap->tpkt->len;
545 fcs = ap->tfcs;
Changli Gao96545ae2011-01-06 13:37:36 +0000546 proto = get_unaligned_be16(data);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547
548 /*
549 * LCP packets with code values between 1 (configure-reqest)
550 * and 7 (code-reject) must be sent as though no options
551 * had been negotiated.
552 */
553 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
554
555 if (i == 0) {
556 if (islcp)
557 async_lcp_peek(ap, data, count, 0);
558
559 /*
560 * Start of a new packet - insert the leading FLAG
561 * character if necessary.
562 */
Joe Perches8e95a202009-12-03 07:58:21 +0000563 if (islcp || flag_time == 0 ||
564 time_after_eq(jiffies, ap->last_xmit + flag_time))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700565 *buf++ = PPP_FLAG;
566 ap->last_xmit = jiffies;
567 fcs = PPP_INITFCS;
568
569 /*
570 * Put in the address/control bytes if necessary
571 */
572 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
573 PUT_BYTE(ap, buf, 0xff, islcp);
574 fcs = PPP_FCS(fcs, 0xff);
575 PUT_BYTE(ap, buf, 0x03, islcp);
576 fcs = PPP_FCS(fcs, 0x03);
577 }
578 }
579
580 /*
581 * Once we put in the last byte, we need to put in the FCS
582 * and closing flag, so make sure there is at least 7 bytes
583 * of free space in the output buffer.
584 */
585 buflim = ap->obuf + OBUFSIZE - 6;
586 while (i < count && buf < buflim) {
587 c = data[i++];
588 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
589 continue; /* compress protocol field */
590 fcs = PPP_FCS(fcs, c);
591 PUT_BYTE(ap, buf, c, islcp);
592 }
593
594 if (i < count) {
595 /*
596 * Remember where we are up to in this packet.
597 */
598 ap->olim = buf;
599 ap->tpkt_pos = i;
600 ap->tfcs = fcs;
601 return 0;
602 }
603
604 /*
605 * We have finished the packet. Add the FCS and flag.
606 */
607 fcs = ~fcs;
608 c = fcs & 0xff;
609 PUT_BYTE(ap, buf, c, islcp);
610 c = (fcs >> 8) & 0xff;
611 PUT_BYTE(ap, buf, c, islcp);
612 *buf++ = PPP_FLAG;
613 ap->olim = buf;
614
615 kfree_skb(ap->tpkt);
616 ap->tpkt = NULL;
617 return 1;
618}
619
620/*
621 * Transmit-side routines.
622 */
623
624/*
625 * Send a packet to the peer over an async tty line.
626 * Returns 1 iff the packet was accepted.
627 * If the packet was not accepted, we will call ppp_output_wakeup
628 * at some later time.
629 */
630static int
631ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
632{
633 struct asyncppp *ap = chan->private;
634
635 ppp_async_push(ap);
636
637 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
638 return 0; /* already full */
639 ap->tpkt = skb;
640 ap->tpkt_pos = 0;
641
642 ppp_async_push(ap);
643 return 1;
644}
645
646/*
647 * Push as much data as possible out to the tty.
648 */
649static int
650ppp_async_push(struct asyncppp *ap)
651{
652 int avail, sent, done = 0;
653 struct tty_struct *tty = ap->tty;
654 int tty_stuffed = 0;
655
656 /*
657 * We can get called recursively here if the tty write
658 * function calls our wakeup function. This can happen
659 * for example on a pty with both the master and slave
660 * set to PPP line discipline.
661 * We use the XMIT_BUSY bit to detect this and get out,
662 * leaving the XMIT_WAKEUP bit set to tell the other
663 * instance that it may now be able to write more now.
664 */
665 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
666 return 0;
667 spin_lock_bh(&ap->xmit_lock);
668 for (;;) {
669 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
670 tty_stuffed = 0;
671 if (!tty_stuffed && ap->optr < ap->olim) {
672 avail = ap->olim - ap->optr;
673 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
Alan Coxf34d7a52008-04-30 00:54:13 -0700674 sent = tty->ops->write(tty, ap->optr, avail);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700675 if (sent < 0)
676 goto flush; /* error, e.g. loss of CD */
677 ap->optr += sent;
678 if (sent < avail)
679 tty_stuffed = 1;
680 continue;
681 }
Joe Perchescd228d52007-11-12 18:07:31 -0800682 if (ap->optr >= ap->olim && ap->tpkt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 if (ppp_async_encode(ap)) {
684 /* finished processing ap->tpkt */
685 clear_bit(XMIT_FULL, &ap->xmit_flags);
686 done = 1;
687 }
688 continue;
689 }
690 /*
691 * We haven't made any progress this time around.
692 * Clear XMIT_BUSY to let other callers in, but
693 * after doing so we have to check if anyone set
694 * XMIT_WAKEUP since we last checked it. If they
695 * did, we should try again to set XMIT_BUSY and go
696 * around again in case XMIT_BUSY was still set when
697 * the other caller tried.
698 */
699 clear_bit(XMIT_BUSY, &ap->xmit_flags);
700 /* any more work to do? if not, exit the loop */
Joe Perches8e95a202009-12-03 07:58:21 +0000701 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
702 (!tty_stuffed && ap->tpkt)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 break;
704 /* more work to do, see if we can do it now */
705 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
706 break;
707 }
708 spin_unlock_bh(&ap->xmit_lock);
709 return done;
710
711flush:
712 clear_bit(XMIT_BUSY, &ap->xmit_flags);
Joe Perchescd228d52007-11-12 18:07:31 -0800713 if (ap->tpkt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714 kfree_skb(ap->tpkt);
715 ap->tpkt = NULL;
716 clear_bit(XMIT_FULL, &ap->xmit_flags);
717 done = 1;
718 }
719 ap->optr = ap->olim;
720 spin_unlock_bh(&ap->xmit_lock);
721 return done;
722}
723
724/*
725 * Flush output from our internal buffers.
726 * Called for the TCFLSH ioctl. Can be entered in parallel
727 * but this is covered by the xmit_lock.
728 */
729static void
730ppp_async_flush_output(struct asyncppp *ap)
731{
732 int done = 0;
733
734 spin_lock_bh(&ap->xmit_lock);
735 ap->optr = ap->olim;
736 if (ap->tpkt != NULL) {
737 kfree_skb(ap->tpkt);
738 ap->tpkt = NULL;
739 clear_bit(XMIT_FULL, &ap->xmit_flags);
740 done = 1;
741 }
742 spin_unlock_bh(&ap->xmit_lock);
743 if (done)
744 ppp_output_wakeup(&ap->chan);
745}
746
747/*
748 * Receive-side routines.
749 */
750
751/* see how many ordinary chars there are at the start of buf */
752static inline int
753scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
754{
755 int i, c;
756
757 for (i = 0; i < count; ++i) {
758 c = buf[i];
Joe Perches8e95a202009-12-03 07:58:21 +0000759 if (c == PPP_ESCAPE || c == PPP_FLAG ||
760 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 break;
762 }
763 return i;
764}
765
766/* called when a flag is seen - do end-of-packet processing */
767static void
768process_input_packet(struct asyncppp *ap)
769{
770 struct sk_buff *skb;
771 unsigned char *p;
772 unsigned int len, fcs, proto;
773
774 skb = ap->rpkt;
775 if (ap->state & (SC_TOSS | SC_ESCAPE))
776 goto err;
777
778 if (skb == NULL)
779 return; /* 0-length packet */
780
781 /* check the FCS */
782 p = skb->data;
783 len = skb->len;
784 if (len < 3)
785 goto err; /* too short */
786 fcs = PPP_INITFCS;
787 for (; len > 0; --len)
788 fcs = PPP_FCS(fcs, *p++);
789 if (fcs != PPP_GOODFCS)
790 goto err; /* bad FCS */
791 skb_trim(skb, skb->len - 2);
792
793 /* check for address/control and protocol compression */
794 p = skb->data;
Paul Mackerras7c5050e2007-04-19 13:05:52 -0700795 if (p[0] == PPP_ALLSTATIONS) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700796 /* chop off address/control */
Paul Mackerras7c5050e2007-04-19 13:05:52 -0700797 if (p[1] != PPP_UI || skb->len < 3)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 goto err;
799 p = skb_pull(skb, 2);
800 }
801 proto = p[0];
802 if (proto & 1) {
803 /* protocol is compressed */
804 skb_push(skb, 1)[0] = 0;
805 } else {
806 if (skb->len < 2)
807 goto err;
808 proto = (proto << 8) + p[1];
809 if (proto == PPP_LCP)
810 async_lcp_peek(ap, p, skb->len, 1);
811 }
812
813 /* queue the frame to be processed */
814 skb->cb[0] = ap->state;
815 skb_queue_tail(&ap->rqueue, skb);
816 ap->rpkt = NULL;
817 ap->state = 0;
818 return;
819
820 err:
821 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
822 ap->state = SC_PREV_ERROR;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800823 if (skb) {
824 /* make skb appear as freshly allocated */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825 skb_trim(skb, 0);
Philippe De Muyter6722e782005-11-08 09:40:26 -0800826 skb_reserve(skb, - skb_headroom(skb));
827 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700828}
829
830/* Called when the tty driver has data for us. Runs parallel with the
831 other ldisc functions but will not be re-entered */
832
833static void
834ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
835 char *flags, int count)
836{
837 struct sk_buff *skb;
838 int c, i, j, n, s, f;
839 unsigned char *sp;
840
841 /* update bits used for 8-bit cleanness detection */
842 if (~ap->rbits & SC_RCV_BITS) {
843 s = 0;
844 for (i = 0; i < count; ++i) {
845 c = buf[i];
Joe Perchescd228d52007-11-12 18:07:31 -0800846 if (flags && flags[i] != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700847 continue;
848 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
849 c = ((c >> 4) ^ c) & 0xf;
850 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
851 }
852 ap->rbits |= s;
853 }
854
855 while (count > 0) {
856 /* scan through and see how many chars we can do in bulk */
857 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
858 n = 1;
859 else
860 n = scan_ordinary(ap, buf, count);
861
862 f = 0;
Joe Perchescd228d52007-11-12 18:07:31 -0800863 if (flags && (ap->state & SC_TOSS) == 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 /* check the flags to see if any char had an error */
865 for (j = 0; j < n; ++j)
866 if ((f = flags[j]) != 0)
867 break;
868 }
869 if (f != 0) {
870 /* start tossing */
871 ap->state |= SC_TOSS;
872
873 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
874 /* stuff the chars in the skb */
875 skb = ap->rpkt;
Joe Perchescd228d52007-11-12 18:07:31 -0800876 if (!skb) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700877 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
Joe Perchescd228d52007-11-12 18:07:31 -0800878 if (!skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 goto nomem;
Philippe De Muyter6722e782005-11-08 09:40:26 -0800880 ap->rpkt = skb;
881 }
882 if (skb->len == 0) {
883 /* Try to get the payload 4-byte aligned.
884 * This should match the
885 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
886 * process_input_packet, but we do not have
887 * enough chars here to test buf[1] and buf[2].
888 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889 if (buf[0] != PPP_ALLSTATIONS)
890 skb_reserve(skb, 2 + (buf[0] & 1));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700891 }
892 if (n > skb_tailroom(skb)) {
893 /* packet overflowed MRU */
894 ap->state |= SC_TOSS;
895 } else {
896 sp = skb_put(skb, n);
897 memcpy(sp, buf, n);
898 if (ap->state & SC_ESCAPE) {
Changli Gaoe6539e22011-06-14 21:58:13 +0000899 sp[0] ^= PPP_TRANS;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700900 ap->state &= ~SC_ESCAPE;
901 }
902 }
903 }
904
905 if (n >= count)
906 break;
907
908 c = buf[n];
909 if (flags != NULL && flags[n] != 0) {
910 ap->state |= SC_TOSS;
911 } else if (c == PPP_FLAG) {
912 process_input_packet(ap);
913 } else if (c == PPP_ESCAPE) {
914 ap->state |= SC_ESCAPE;
915 } else if (I_IXON(ap->tty)) {
916 if (c == START_CHAR(ap->tty))
917 start_tty(ap->tty);
918 else if (c == STOP_CHAR(ap->tty))
919 stop_tty(ap->tty);
920 }
921 /* otherwise it's a char in the recv ACCM */
922 ++n;
923
924 buf += n;
Joe Perchescd228d52007-11-12 18:07:31 -0800925 if (flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700926 flags += n;
927 count -= n;
928 }
929 return;
930
931 nomem:
932 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
933 ap->state |= SC_TOSS;
934}
935
936/*
937 * We look at LCP frames going past so that we can notice
938 * and react to the LCP configure-ack from the peer.
939 * In the situation where the peer has been sent a configure-ack
940 * already, LCP is up once it has sent its configure-ack
941 * so the immediately following packet can be sent with the
942 * configured LCP options. This allows us to process the following
943 * packet correctly without pppd needing to respond quickly.
944 *
945 * We only respond to the received configure-ack if we have just
946 * sent a configure-request, and the configure-ack contains the
947 * same data (this is checked using a 16-bit crc of the data).
948 */
949#define CONFREQ 1 /* LCP code field values */
950#define CONFACK 2
951#define LCP_MRU 1 /* LCP option numbers */
952#define LCP_ASYNCMAP 2
953
954static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
955 int len, int inbound)
956{
957 int dlen, fcs, i, code;
958 u32 val;
959
960 data += 2; /* skip protocol bytes */
961 len -= 2;
962 if (len < 4) /* 4 = code, ID, length */
963 return;
964 code = data[0];
965 if (code != CONFACK && code != CONFREQ)
966 return;
Changli Gao96545ae2011-01-06 13:37:36 +0000967 dlen = get_unaligned_be16(data + 2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968 if (len < dlen)
969 return; /* packet got truncated or length is bogus */
970
971 if (code == (inbound? CONFACK: CONFREQ)) {
972 /*
973 * sent confreq or received confack:
974 * calculate the crc of the data from the ID field on.
975 */
976 fcs = PPP_INITFCS;
977 for (i = 1; i < dlen; ++i)
978 fcs = PPP_FCS(fcs, data[i]);
979
980 if (!inbound) {
981 /* outbound confreq - remember the crc for later */
982 ap->lcp_fcs = fcs;
983 return;
984 }
985
986 /* received confack, check the crc */
987 fcs ^= ap->lcp_fcs;
988 ap->lcp_fcs = -1;
989 if (fcs != 0)
990 return;
991 } else if (inbound)
992 return; /* not interested in received confreq */
993
994 /* process the options in the confack */
995 data += 4;
996 dlen -= 4;
997 /* data[0] is code, data[1] is length */
998 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
999 switch (data[0]) {
1000 case LCP_MRU:
Changli Gao96545ae2011-01-06 13:37:36 +00001001 val = get_unaligned_be16(data + 2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002 if (inbound)
1003 ap->mru = val;
1004 else
1005 ap->chan.mtu = val;
1006 break;
1007 case LCP_ASYNCMAP:
Changli Gao96545ae2011-01-06 13:37:36 +00001008 val = get_unaligned_be32(data + 2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009 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);