1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * PPP async serial channel driver for Linux.
4 *
5 * Copyright 1999 Paul Mackerras.
6 *
7 * This driver provides the encapsulation and framing for sending
8 * and receiving PPP frames over async serial lines. It relies on
9 * the generic PPP layer to give it frames to send and to process
10 * received frames. It implements the PPP line discipline.
11 *
12 * Part of the code in this driver was inspired by the old async-only
13 * PPP driver, written by Michael Callahan and Al Longyear, and
14 * subsequently hacked by Paul Mackerras.
15 */
16
17 #include <linux/module.h>
18 #include <linux/kernel.h>
19 #include <linux/skbuff.h>
20 #include <linux/tty.h>
21 #include <linux/netdevice.h>
22 #include <linux/poll.h>
23 #include <linux/crc-ccitt.h>
24 #include <linux/ppp_defs.h>
25 #include <linux/ppp-ioctl.h>
26 #include <linux/ppp_channel.h>
27 #include <linux/spinlock.h>
28 #include <linux/init.h>
29 #include <linux/interrupt.h>
30 #include <linux/jiffies.h>
31 #include <linux/slab.h>
32 #include <asm/unaligned.h>
33 #include <linux/uaccess.h>
34 #include <asm/string.h>
35
36 #define PPP_VERSION "2.4.2"
37
38 #define OBUFSIZE 4096
39
40 /* Structure for storing local state. */
41 struct asyncppp {
42 struct tty_struct *tty;
43 unsigned int flags;
44 unsigned int state;
45 unsigned int rbits;
46 int mru;
47 spinlock_t xmit_lock;
48 spinlock_t recv_lock;
49 unsigned long xmit_flags;
50 u32 xaccm[8];
51 u32 raccm;
52 unsigned int bytes_sent;
53 unsigned int bytes_rcvd;
54
55 struct sk_buff *tpkt;
56 int tpkt_pos;
57 u16 tfcs;
58 unsigned char *optr;
59 unsigned char *olim;
60 unsigned long last_xmit;
61
62 struct sk_buff *rpkt;
63 int lcp_fcs;
64 struct sk_buff_head rqueue;
65
66 struct tasklet_struct tsk;
67
68 refcount_t refcnt;
69 struct completion dead;
70 struct ppp_channel chan; /* interface to generic ppp layer */
71 unsigned char obuf[OBUFSIZE];
72 };
73
74 /* Bit numbers in xmit_flags */
75 #define XMIT_WAKEUP 0
76 #define XMIT_FULL 1
77 #define XMIT_BUSY 2
78
79 /* State bits */
80 #define SC_TOSS 1
81 #define SC_ESCAPE 2
82 #define SC_PREV_ERROR 4
83
84 /* Bits in rbits */
85 #define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
86
87 static int flag_time = HZ;
88 module_param(flag_time, int, 0);
89 MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
90 MODULE_LICENSE("GPL");
91 MODULE_ALIAS_LDISC(N_PPP);
92
93 /*
94 * Prototypes.
95 */
96 static int ppp_async_encode(struct asyncppp *ap);
97 static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
98 static int ppp_async_push(struct asyncppp *ap);
99 static void ppp_async_flush_output(struct asyncppp *ap);
100 static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
101 char *flags, int count);
102 static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
103 unsigned long arg);
104 static void ppp_async_process(unsigned long arg);
105
106 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
107 int len, int inbound);
108
109 static const struct ppp_channel_ops async_ops = {
110 .start_xmit = ppp_async_send,
111 .ioctl = 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 */
130 static DEFINE_RWLOCK(disc_data_lock);
131
ap_get(struct tty_struct * tty)132 static 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 refcount_inc(&ap->refcnt);
140 read_unlock(&disc_data_lock);
141 return ap;
142 }
143
ap_put(struct asyncppp * ap)144 static void ap_put(struct asyncppp *ap)
145 {
146 if (refcount_dec_and_test(&ap->refcnt))
147 complete(&ap->dead);
148 }
149
150 /*
151 * Called when a tty is put into PPP line discipline. Called in process
152 * context.
153 */
154 static int
ppp_asynctty_open(struct tty_struct * tty)155 ppp_asynctty_open(struct tty_struct *tty)
156 {
157 struct asyncppp *ap;
158 int err;
159 int speed;
160
161 if (tty->ops->write == NULL)
162 return -EOPNOTSUPP;
163
164 err = -ENOMEM;
165 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
166 if (!ap)
167 goto out;
168
169 /* initialize the asyncppp structure */
170 ap->tty = tty;
171 ap->mru = PPP_MRU;
172 spin_lock_init(&ap->xmit_lock);
173 spin_lock_init(&ap->recv_lock);
174 ap->xaccm[0] = ~0U;
175 ap->xaccm[3] = 0x60000000U;
176 ap->raccm = ~0U;
177 ap->optr = ap->obuf;
178 ap->olim = ap->obuf;
179 ap->lcp_fcs = -1;
180
181 skb_queue_head_init(&ap->rqueue);
182 tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
183
184 refcount_set(&ap->refcnt, 1);
185 init_completion(&ap->dead);
186
187 ap->chan.private = ap;
188 ap->chan.ops = &async_ops;
189 ap->chan.mtu = PPP_MRU;
190 speed = tty_get_baud_rate(tty);
191 ap->chan.speed = speed;
192 err = ppp_register_channel(&ap->chan);
193 if (err)
194 goto out_free;
195
196 tty->disc_data = ap;
197 tty->receive_room = 65536;
198 return 0;
199
200 out_free:
201 kfree(ap);
202 out:
203 return err;
204 }
205
206 /*
207 * Called when the tty is put into another line discipline
208 * or it hangs up. We have to wait for any cpu currently
209 * executing in any of the other ppp_asynctty_* routines to
210 * finish before we can call ppp_unregister_channel and free
211 * the asyncppp struct. This routine must be called from
212 * process context, not interrupt or softirq context.
213 */
214 static void
ppp_asynctty_close(struct tty_struct * tty)215 ppp_asynctty_close(struct tty_struct *tty)
216 {
217 struct asyncppp *ap;
218
219 write_lock_irq(&disc_data_lock);
220 ap = tty->disc_data;
221 tty->disc_data = NULL;
222 write_unlock_irq(&disc_data_lock);
223 if (!ap)
224 return;
225
226 /*
227 * We have now ensured that nobody can start using ap from now
228 * on, but we have to wait for all existing users to finish.
229 * Note that ppp_unregister_channel ensures that no calls to
230 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
231 * by the time it returns.
232 */
233 if (!refcount_dec_and_test(&ap->refcnt))
234 wait_for_completion(&ap->dead);
235 tasklet_kill(&ap->tsk);
236
237 ppp_unregister_channel(&ap->chan);
238 kfree_skb(ap->rpkt);
239 skb_queue_purge(&ap->rqueue);
240 kfree_skb(ap->tpkt);
241 kfree(ap);
242 }
243
244 /*
245 * Called on tty hangup in process context.
246 *
247 * Wait for I/O to driver to complete and unregister PPP channel.
248 * This is already done by the close routine, so just call that.
249 */
ppp_asynctty_hangup(struct tty_struct * tty)250 static int ppp_asynctty_hangup(struct tty_struct *tty)
251 {
252 ppp_asynctty_close(tty);
253 return 0;
254 }
255
256 /*
257 * Read does nothing - no data is ever available this way.
258 * Pppd reads and writes packets via /dev/ppp instead.
259 */
260 static ssize_t
ppp_asynctty_read(struct tty_struct * tty,struct file * file,unsigned char * buf,size_t count,void ** cookie,unsigned long offset)261 ppp_asynctty_read(struct tty_struct *tty, struct file *file,
262 unsigned char *buf, size_t count,
263 void **cookie, unsigned long offset)
264 {
265 return -EAGAIN;
266 }
267
268 /*
269 * Write on the tty does nothing, the packets all come in
270 * from the ppp generic stuff.
271 */
272 static ssize_t
ppp_asynctty_write(struct tty_struct * tty,struct file * file,const unsigned char * buf,size_t count)273 ppp_asynctty_write(struct tty_struct *tty, struct file *file,
274 const unsigned char *buf, size_t count)
275 {
276 return -EAGAIN;
277 }
278
279 /*
280 * Called in process context only. May be re-entered by multiple
281 * ioctl calling threads.
282 */
283
284 static int
ppp_asynctty_ioctl(struct tty_struct * tty,struct file * file,unsigned int cmd,unsigned long arg)285 ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
286 unsigned int cmd, unsigned long arg)
287 {
288 struct asyncppp *ap = ap_get(tty);
289 int err, val;
290 int __user *p = (int __user *)arg;
291
292 if (!ap)
293 return -ENXIO;
294 err = -EFAULT;
295 switch (cmd) {
296 case PPPIOCGCHAN:
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 = -EFAULT;
305 if (put_user(ppp_unit_number(&ap->chan), p))
306 break;
307 err = 0;
308 break;
309
310 case TCFLSH:
311 /* flush our buffers and the serial port's buffer */
312 if (arg == TCIOFLUSH || arg == TCOFLUSH)
313 ppp_async_flush_output(ap);
314 err = n_tty_ioctl_helper(tty, file, cmd, arg);
315 break;
316
317 case FIONREAD:
318 val = 0;
319 if (put_user(val, p))
320 break;
321 err = 0;
322 break;
323
324 default:
325 /* Try the various mode ioctls */
326 err = tty_mode_ioctl(tty, file, cmd, arg);
327 }
328
329 ap_put(ap);
330 return err;
331 }
332
333 /* No kernel lock - fine */
334 static __poll_t
ppp_asynctty_poll(struct tty_struct * tty,struct file * file,poll_table * wait)335 ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
336 {
337 return 0;
338 }
339
340 /* May sleep, don't call from interrupt level or with interrupts disabled */
341 static void
ppp_asynctty_receive(struct tty_struct * tty,const unsigned char * buf,char * cflags,int count)342 ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
343 char *cflags, int count)
344 {
345 struct asyncppp *ap = ap_get(tty);
346 unsigned long flags;
347
348 if (!ap)
349 return;
350 spin_lock_irqsave(&ap->recv_lock, flags);
351 ppp_async_input(ap, buf, cflags, count);
352 spin_unlock_irqrestore(&ap->recv_lock, flags);
353 if (!skb_queue_empty(&ap->rqueue))
354 tasklet_schedule(&ap->tsk);
355 ap_put(ap);
356 tty_unthrottle(tty);
357 }
358
359 static void
ppp_asynctty_wakeup(struct tty_struct * tty)360 ppp_asynctty_wakeup(struct tty_struct *tty)
361 {
362 struct asyncppp *ap = ap_get(tty);
363
364 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
365 if (!ap)
366 return;
367 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
368 tasklet_schedule(&ap->tsk);
369 ap_put(ap);
370 }
371
372
373 static struct tty_ldisc_ops ppp_ldisc = {
374 .owner = THIS_MODULE,
375 .magic = TTY_LDISC_MAGIC,
376 .name = "ppp",
377 .open = ppp_asynctty_open,
378 .close = ppp_asynctty_close,
379 .hangup = ppp_asynctty_hangup,
380 .read = ppp_asynctty_read,
381 .write = ppp_asynctty_write,
382 .ioctl = ppp_asynctty_ioctl,
383 .poll = ppp_asynctty_poll,
384 .receive_buf = ppp_asynctty_receive,
385 .write_wakeup = ppp_asynctty_wakeup,
386 };
387
388 static int __init
ppp_async_init(void)389 ppp_async_init(void)
390 {
391 int err;
392
393 err = tty_register_ldisc(N_PPP, &ppp_ldisc);
394 if (err != 0)
395 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
396 err);
397 return err;
398 }
399
400 /*
401 * The following routines provide the PPP channel interface.
402 */
403 static int
ppp_async_ioctl(struct ppp_channel * chan,unsigned int cmd,unsigned long arg)404 ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
405 {
406 struct asyncppp *ap = chan->private;
407 void __user *argp = (void __user *)arg;
408 int __user *p = argp;
409 int err, val;
410 u32 accm[8];
411
412 err = -EFAULT;
413 switch (cmd) {
414 case PPPIOCGFLAGS:
415 val = ap->flags | ap->rbits;
416 if (put_user(val, p))
417 break;
418 err = 0;
419 break;
420 case PPPIOCSFLAGS:
421 if (get_user(val, p))
422 break;
423 ap->flags = val & ~SC_RCV_BITS;
424 spin_lock_irq(&ap->recv_lock);
425 ap->rbits = val & SC_RCV_BITS;
426 spin_unlock_irq(&ap->recv_lock);
427 err = 0;
428 break;
429
430 case PPPIOCGASYNCMAP:
431 if (put_user(ap->xaccm[0], (u32 __user *)argp))
432 break;
433 err = 0;
434 break;
435 case PPPIOCSASYNCMAP:
436 if (get_user(ap->xaccm[0], (u32 __user *)argp))
437 break;
438 err = 0;
439 break;
440
441 case PPPIOCGRASYNCMAP:
442 if (put_user(ap->raccm, (u32 __user *)argp))
443 break;
444 err = 0;
445 break;
446 case PPPIOCSRASYNCMAP:
447 if (get_user(ap->raccm, (u32 __user *)argp))
448 break;
449 err = 0;
450 break;
451
452 case PPPIOCGXASYNCMAP:
453 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
454 break;
455 err = 0;
456 break;
457 case PPPIOCSXASYNCMAP:
458 if (copy_from_user(accm, argp, sizeof(accm)))
459 break;
460 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
461 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
462 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
463 err = 0;
464 break;
465
466 case PPPIOCGMRU:
467 if (put_user(ap->mru, p))
468 break;
469 err = 0;
470 break;
471 case PPPIOCSMRU:
472 if (get_user(val, p))
473 break;
474 if (val < PPP_MRU)
475 val = PPP_MRU;
476 ap->mru = val;
477 err = 0;
478 break;
479
480 default:
481 err = -ENOTTY;
482 }
483
484 return err;
485 }
486
487 /*
488 * This is called at softirq level to deliver received packets
489 * to the ppp_generic code, and to tell the ppp_generic code
490 * if we can accept more output now.
491 */
ppp_async_process(unsigned long arg)492 static void ppp_async_process(unsigned long arg)
493 {
494 struct asyncppp *ap = (struct asyncppp *) arg;
495 struct sk_buff *skb;
496
497 /* process received packets */
498 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
499 if (skb->cb[0])
500 ppp_input_error(&ap->chan, 0);
501 ppp_input(&ap->chan, skb);
502 }
503
504 /* try to push more stuff out */
505 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
506 ppp_output_wakeup(&ap->chan);
507 }
508
509 /*
510 * Procedures for encapsulation and framing.
511 */
512
513 /*
514 * Procedure to encode the data for async serial transmission.
515 * Does octet stuffing (escaping), puts the address/control bytes
516 * on if A/C compression is disabled, and does protocol compression.
517 * Assumes ap->tpkt != 0 on entry.
518 * Returns 1 if we finished the current frame, 0 otherwise.
519 */
520
521 #define PUT_BYTE(ap, buf, c, islcp) do { \
522 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
523 *buf++ = PPP_ESCAPE; \
524 *buf++ = c ^ PPP_TRANS; \
525 } else \
526 *buf++ = c; \
527 } while (0)
528
529 static int
ppp_async_encode(struct asyncppp * ap)530 ppp_async_encode(struct asyncppp *ap)
531 {
532 int fcs, i, count, c, proto;
533 unsigned char *buf, *buflim;
534 unsigned char *data;
535 int islcp;
536
537 buf = ap->obuf;
538 ap->olim = buf;
539 ap->optr = buf;
540 i = ap->tpkt_pos;
541 data = ap->tpkt->data;
542 count = ap->tpkt->len;
543 fcs = ap->tfcs;
544 proto = get_unaligned_be16(data);
545
546 /*
547 * LCP packets with code values between 1 (configure-reqest)
548 * and 7 (code-reject) must be sent as though no options
549 * had been negotiated.
550 */
551 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
552
553 if (i == 0) {
554 if (islcp)
555 async_lcp_peek(ap, data, count, 0);
556
557 /*
558 * Start of a new packet - insert the leading FLAG
559 * character if necessary.
560 */
561 if (islcp || flag_time == 0 ||
562 time_after_eq(jiffies, ap->last_xmit + flag_time))
563 *buf++ = PPP_FLAG;
564 ap->last_xmit = jiffies;
565 fcs = PPP_INITFCS;
566
567 /*
568 * Put in the address/control bytes if necessary
569 */
570 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
571 PUT_BYTE(ap, buf, 0xff, islcp);
572 fcs = PPP_FCS(fcs, 0xff);
573 PUT_BYTE(ap, buf, 0x03, islcp);
574 fcs = PPP_FCS(fcs, 0x03);
575 }
576 }
577
578 /*
579 * Once we put in the last byte, we need to put in the FCS
580 * and closing flag, so make sure there is at least 7 bytes
581 * of free space in the output buffer.
582 */
583 buflim = ap->obuf + OBUFSIZE - 6;
584 while (i < count && buf < buflim) {
585 c = data[i++];
586 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
587 continue; /* compress protocol field */
588 fcs = PPP_FCS(fcs, c);
589 PUT_BYTE(ap, buf, c, islcp);
590 }
591
592 if (i < count) {
593 /*
594 * Remember where we are up to in this packet.
595 */
596 ap->olim = buf;
597 ap->tpkt_pos = i;
598 ap->tfcs = fcs;
599 return 0;
600 }
601
602 /*
603 * We have finished the packet. Add the FCS and flag.
604 */
605 fcs = ~fcs;
606 c = fcs & 0xff;
607 PUT_BYTE(ap, buf, c, islcp);
608 c = (fcs >> 8) & 0xff;
609 PUT_BYTE(ap, buf, c, islcp);
610 *buf++ = PPP_FLAG;
611 ap->olim = buf;
612
613 consume_skb(ap->tpkt);
614 ap->tpkt = NULL;
615 return 1;
616 }
617
618 /*
619 * Transmit-side routines.
620 */
621
622 /*
623 * Send a packet to the peer over an async tty line.
624 * Returns 1 iff the packet was accepted.
625 * If the packet was not accepted, we will call ppp_output_wakeup
626 * at some later time.
627 */
628 static int
ppp_async_send(struct ppp_channel * chan,struct sk_buff * skb)629 ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
630 {
631 struct asyncppp *ap = chan->private;
632
633 ppp_async_push(ap);
634
635 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
636 return 0; /* already full */
637 ap->tpkt = skb;
638 ap->tpkt_pos = 0;
639
640 ppp_async_push(ap);
641 return 1;
642 }
643
644 /*
645 * Push as much data as possible out to the tty.
646 */
647 static int
ppp_async_push(struct asyncppp * ap)648 ppp_async_push(struct asyncppp *ap)
649 {
650 int avail, sent, done = 0;
651 struct tty_struct *tty = ap->tty;
652 int tty_stuffed = 0;
653
654 /*
655 * We can get called recursively here if the tty write
656 * function calls our wakeup function. This can happen
657 * for example on a pty with both the master and slave
658 * set to PPP line discipline.
659 * We use the XMIT_BUSY bit to detect this and get out,
660 * leaving the XMIT_WAKEUP bit set to tell the other
661 * instance that it may now be able to write more now.
662 */
663 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
664 return 0;
665 spin_lock_bh(&ap->xmit_lock);
666 for (;;) {
667 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
668 tty_stuffed = 0;
669 if (!tty_stuffed && ap->optr < ap->olim) {
670 avail = ap->olim - ap->optr;
671 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
672 sent = tty->ops->write(tty, ap->optr, avail);
673 if (sent < 0)
674 goto flush; /* error, e.g. loss of CD */
675 ap->optr += sent;
676 if (sent < avail)
677 tty_stuffed = 1;
678 continue;
679 }
680 if (ap->optr >= ap->olim && ap->tpkt) {
681 if (ppp_async_encode(ap)) {
682 /* finished processing ap->tpkt */
683 clear_bit(XMIT_FULL, &ap->xmit_flags);
684 done = 1;
685 }
686 continue;
687 }
688 /*
689 * We haven't made any progress this time around.
690 * Clear XMIT_BUSY to let other callers in, but
691 * after doing so we have to check if anyone set
692 * XMIT_WAKEUP since we last checked it. If they
693 * did, we should try again to set XMIT_BUSY and go
694 * around again in case XMIT_BUSY was still set when
695 * the other caller tried.
696 */
697 clear_bit(XMIT_BUSY, &ap->xmit_flags);
698 /* any more work to do? if not, exit the loop */
699 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
700 (!tty_stuffed && ap->tpkt)))
701 break;
702 /* more work to do, see if we can do it now */
703 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
704 break;
705 }
706 spin_unlock_bh(&ap->xmit_lock);
707 return done;
708
709 flush:
710 clear_bit(XMIT_BUSY, &ap->xmit_flags);
711 if (ap->tpkt) {
712 kfree_skb(ap->tpkt);
713 ap->tpkt = NULL;
714 clear_bit(XMIT_FULL, &ap->xmit_flags);
715 done = 1;
716 }
717 ap->optr = ap->olim;
718 spin_unlock_bh(&ap->xmit_lock);
719 return done;
720 }
721
722 /*
723 * Flush output from our internal buffers.
724 * Called for the TCFLSH ioctl. Can be entered in parallel
725 * but this is covered by the xmit_lock.
726 */
727 static void
ppp_async_flush_output(struct asyncppp * ap)728 ppp_async_flush_output(struct asyncppp *ap)
729 {
730 int done = 0;
731
732 spin_lock_bh(&ap->xmit_lock);
733 ap->optr = ap->olim;
734 if (ap->tpkt != NULL) {
735 kfree_skb(ap->tpkt);
736 ap->tpkt = NULL;
737 clear_bit(XMIT_FULL, &ap->xmit_flags);
738 done = 1;
739 }
740 spin_unlock_bh(&ap->xmit_lock);
741 if (done)
742 ppp_output_wakeup(&ap->chan);
743 }
744
745 /*
746 * Receive-side routines.
747 */
748
749 /* see how many ordinary chars there are at the start of buf */
750 static inline int
scan_ordinary(struct asyncppp * ap,const unsigned char * buf,int count)751 scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
752 {
753 int i, c;
754
755 for (i = 0; i < count; ++i) {
756 c = buf[i];
757 if (c == PPP_ESCAPE || c == PPP_FLAG ||
758 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
759 break;
760 }
761 return i;
762 }
763
764 /* called when a flag is seen - do end-of-packet processing */
765 static void
process_input_packet(struct asyncppp * ap)766 process_input_packet(struct asyncppp *ap)
767 {
768 struct sk_buff *skb;
769 unsigned char *p;
770 unsigned int len, fcs;
771
772 skb = ap->rpkt;
773 if (ap->state & (SC_TOSS | SC_ESCAPE))
774 goto err;
775
776 if (skb == NULL)
777 return; /* 0-length packet */
778
779 /* check the FCS */
780 p = skb->data;
781 len = skb->len;
782 if (len < 3)
783 goto err; /* too short */
784 fcs = PPP_INITFCS;
785 for (; len > 0; --len)
786 fcs = PPP_FCS(fcs, *p++);
787 if (fcs != PPP_GOODFCS)
788 goto err; /* bad FCS */
789 skb_trim(skb, skb->len - 2);
790
791 /* check for address/control and protocol compression */
792 p = skb->data;
793 if (p[0] == PPP_ALLSTATIONS) {
794 /* chop off address/control */
795 if (p[1] != PPP_UI || skb->len < 3)
796 goto err;
797 p = skb_pull(skb, 2);
798 }
799
800 /* If protocol field is not compressed, it can be LCP packet */
801 if (!(p[0] & 0x01)) {
802 unsigned int proto;
803
804 if (skb->len < 2)
805 goto err;
806 proto = (p[0] << 8) + p[1];
807 if (proto == PPP_LCP)
808 async_lcp_peek(ap, p, skb->len, 1);
809 }
810
811 /* queue the frame to be processed */
812 skb->cb[0] = ap->state;
813 skb_queue_tail(&ap->rqueue, skb);
814 ap->rpkt = NULL;
815 ap->state = 0;
816 return;
817
818 err:
819 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
820 ap->state = SC_PREV_ERROR;
821 if (skb) {
822 /* make skb appear as freshly allocated */
823 skb_trim(skb, 0);
824 skb_reserve(skb, - skb_headroom(skb));
825 }
826 }
827
828 /* Called when the tty driver has data for us. Runs parallel with the
829 other ldisc functions but will not be re-entered */
830
831 static void
ppp_async_input(struct asyncppp * ap,const unsigned char * buf,char * flags,int count)832 ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
833 char *flags, int count)
834 {
835 struct sk_buff *skb;
836 int c, i, j, n, s, f;
837 unsigned char *sp;
838
839 /* update bits used for 8-bit cleanness detection */
840 if (~ap->rbits & SC_RCV_BITS) {
841 s = 0;
842 for (i = 0; i < count; ++i) {
843 c = buf[i];
844 if (flags && flags[i] != 0)
845 continue;
846 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
847 c = ((c >> 4) ^ c) & 0xf;
848 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
849 }
850 ap->rbits |= s;
851 }
852
853 while (count > 0) {
854 /* scan through and see how many chars we can do in bulk */
855 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
856 n = 1;
857 else
858 n = scan_ordinary(ap, buf, count);
859
860 f = 0;
861 if (flags && (ap->state & SC_TOSS) == 0) {
862 /* check the flags to see if any char had an error */
863 for (j = 0; j < n; ++j)
864 if ((f = flags[j]) != 0)
865 break;
866 }
867 if (f != 0) {
868 /* start tossing */
869 ap->state |= SC_TOSS;
870
871 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
872 /* stuff the chars in the skb */
873 skb = ap->rpkt;
874 if (!skb) {
875 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
876 if (!skb)
877 goto nomem;
878 ap->rpkt = skb;
879 }
880 if (skb->len == 0) {
881 /* Try to get the payload 4-byte aligned.
882 * This should match the
883 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
884 * process_input_packet, but we do not have
885 * enough chars here to test buf[1] and buf[2].
886 */
887 if (buf[0] != PPP_ALLSTATIONS)
888 skb_reserve(skb, 2 + (buf[0] & 1));
889 }
890 if (n > skb_tailroom(skb)) {
891 /* packet overflowed MRU */
892 ap->state |= SC_TOSS;
893 } else {
894 sp = skb_put_data(skb, buf, n);
895 if (ap->state & SC_ESCAPE) {
896 sp[0] ^= PPP_TRANS;
897 ap->state &= ~SC_ESCAPE;
898 }
899 }
900 }
901
902 if (n >= count)
903 break;
904
905 c = buf[n];
906 if (flags != NULL && flags[n] != 0) {
907 ap->state |= SC_TOSS;
908 } else if (c == PPP_FLAG) {
909 process_input_packet(ap);
910 } else if (c == PPP_ESCAPE) {
911 ap->state |= SC_ESCAPE;
912 } else if (I_IXON(ap->tty)) {
913 if (c == START_CHAR(ap->tty))
914 start_tty(ap->tty);
915 else if (c == STOP_CHAR(ap->tty))
916 stop_tty(ap->tty);
917 }
918 /* otherwise it's a char in the recv ACCM */
919 ++n;
920
921 buf += n;
922 if (flags)
923 flags += n;
924 count -= n;
925 }
926 return;
927
928 nomem:
929 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
930 ap->state |= SC_TOSS;
931 }
932
933 /*
934 * We look at LCP frames going past so that we can notice
935 * and react to the LCP configure-ack from the peer.
936 * In the situation where the peer has been sent a configure-ack
937 * already, LCP is up once it has sent its configure-ack
938 * so the immediately following packet can be sent with the
939 * configured LCP options. This allows us to process the following
940 * packet correctly without pppd needing to respond quickly.
941 *
942 * We only respond to the received configure-ack if we have just
943 * sent a configure-request, and the configure-ack contains the
944 * same data (this is checked using a 16-bit crc of the data).
945 */
946 #define CONFREQ 1 /* LCP code field values */
947 #define CONFACK 2
948 #define LCP_MRU 1 /* LCP option numbers */
949 #define LCP_ASYNCMAP 2
950
async_lcp_peek(struct asyncppp * ap,unsigned char * data,int len,int inbound)951 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
952 int len, int inbound)
953 {
954 int dlen, fcs, i, code;
955 u32 val;
956
957 data += 2; /* skip protocol bytes */
958 len -= 2;
959 if (len < 4) /* 4 = code, ID, length */
960 return;
961 code = data[0];
962 if (code != CONFACK && code != CONFREQ)
963 return;
964 dlen = get_unaligned_be16(data + 2);
965 if (len < dlen)
966 return; /* packet got truncated or length is bogus */
967
968 if (code == (inbound? CONFACK: CONFREQ)) {
969 /*
970 * sent confreq or received confack:
971 * calculate the crc of the data from the ID field on.
972 */
973 fcs = PPP_INITFCS;
974 for (i = 1; i < dlen; ++i)
975 fcs = PPP_FCS(fcs, data[i]);
976
977 if (!inbound) {
978 /* outbound confreq - remember the crc for later */
979 ap->lcp_fcs = fcs;
980 return;
981 }
982
983 /* received confack, check the crc */
984 fcs ^= ap->lcp_fcs;
985 ap->lcp_fcs = -1;
986 if (fcs != 0)
987 return;
988 } else if (inbound)
989 return; /* not interested in received confreq */
990
991 /* process the options in the confack */
992 data += 4;
993 dlen -= 4;
994 /* data[0] is code, data[1] is length */
995 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
996 switch (data[0]) {
997 case LCP_MRU:
998 val = get_unaligned_be16(data + 2);
999 if (inbound)
1000 ap->mru = val;
1001 else
1002 ap->chan.mtu = val;
1003 break;
1004 case LCP_ASYNCMAP:
1005 val = get_unaligned_be32(data + 2);
1006 if (inbound)
1007 ap->raccm = val;
1008 else
1009 ap->xaccm[0] = val;
1010 break;
1011 }
1012 dlen -= data[1];
1013 data += data[1];
1014 }
1015 }
1016
ppp_async_cleanup(void)1017 static void __exit ppp_async_cleanup(void)
1018 {
1019 if (tty_unregister_ldisc(N_PPP) != 0)
1020 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1021 }
1022
1023 module_init(ppp_async_init);
1024 module_exit(ppp_async_cleanup);
1025