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 const u8 *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(struct tasklet_struct *t);
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_setup(&ap->tsk, ppp_async_process);
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 void ppp_asynctty_hangup(struct tty_struct *tty)
251 {
252 ppp_asynctty_close(tty);
253 }
254
255 /*
256 * Read does nothing - no data is ever available this way.
257 * Pppd reads and writes packets via /dev/ppp instead.
258 */
259 static ssize_t
ppp_asynctty_read(struct tty_struct * tty,struct file * file,u8 * buf,size_t count,void ** cookie,unsigned long offset)260 ppp_asynctty_read(struct tty_struct *tty, struct file *file, u8 *buf,
261 size_t count, void **cookie, unsigned long offset)
262 {
263 return -EAGAIN;
264 }
265
266 /*
267 * Write on the tty does nothing, the packets all come in
268 * from the ppp generic stuff.
269 */
270 static ssize_t
ppp_asynctty_write(struct tty_struct * tty,struct file * file,const u8 * buf,size_t count)271 ppp_asynctty_write(struct tty_struct *tty, struct file *file, const u8 *buf,
272 size_t count)
273 {
274 return -EAGAIN;
275 }
276
277 /*
278 * Called in process context only. May be re-entered by multiple
279 * ioctl calling threads.
280 */
281
282 static int
ppp_asynctty_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)283 ppp_asynctty_ioctl(struct tty_struct *tty, 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)
290 return -ENXIO;
291 err = -EFAULT;
292 switch (cmd) {
293 case PPPIOCGCHAN:
294 err = -EFAULT;
295 if (put_user(ppp_channel_index(&ap->chan), p))
296 break;
297 err = 0;
298 break;
299
300 case PPPIOCGUNIT:
301 err = -EFAULT;
302 if (put_user(ppp_unit_number(&ap->chan), p))
303 break;
304 err = 0;
305 break;
306
307 case TCFLSH:
308 /* flush our buffers and the serial port's buffer */
309 if (arg == TCIOFLUSH || arg == TCOFLUSH)
310 ppp_async_flush_output(ap);
311 err = n_tty_ioctl_helper(tty, cmd, arg);
312 break;
313
314 case FIONREAD:
315 val = 0;
316 if (put_user(val, p))
317 break;
318 err = 0;
319 break;
320
321 default:
322 /* Try the various mode ioctls */
323 err = tty_mode_ioctl(tty, cmd, arg);
324 }
325
326 ap_put(ap);
327 return err;
328 }
329
330 /* May sleep, don't call from interrupt level or with interrupts disabled */
331 static void
ppp_asynctty_receive(struct tty_struct * tty,const u8 * buf,const u8 * cflags,size_t count)332 ppp_asynctty_receive(struct tty_struct *tty, const u8 *buf, const u8 *cflags,
333 size_t count)
334 {
335 struct asyncppp *ap = ap_get(tty);
336 unsigned long flags;
337
338 if (!ap)
339 return;
340 spin_lock_irqsave(&ap->recv_lock, flags);
341 ppp_async_input(ap, buf, cflags, count);
342 spin_unlock_irqrestore(&ap->recv_lock, flags);
343 if (!skb_queue_empty(&ap->rqueue))
344 tasklet_schedule(&ap->tsk);
345 ap_put(ap);
346 tty_unthrottle(tty);
347 }
348
349 static void
ppp_asynctty_wakeup(struct tty_struct * tty)350 ppp_asynctty_wakeup(struct tty_struct *tty)
351 {
352 struct asyncppp *ap = ap_get(tty);
353
354 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
355 if (!ap)
356 return;
357 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
358 tasklet_schedule(&ap->tsk);
359 ap_put(ap);
360 }
361
362
363 static struct tty_ldisc_ops ppp_ldisc = {
364 .owner = THIS_MODULE,
365 .num = N_PPP,
366 .name = "ppp",
367 .open = ppp_asynctty_open,
368 .close = ppp_asynctty_close,
369 .hangup = ppp_asynctty_hangup,
370 .read = ppp_asynctty_read,
371 .write = ppp_asynctty_write,
372 .ioctl = ppp_asynctty_ioctl,
373 .receive_buf = ppp_asynctty_receive,
374 .write_wakeup = ppp_asynctty_wakeup,
375 };
376
377 static int __init
ppp_async_init(void)378 ppp_async_init(void)
379 {
380 int err;
381
382 err = tty_register_ldisc(&ppp_ldisc);
383 if (err != 0)
384 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
385 err);
386 return err;
387 }
388
389 /*
390 * The following routines provide the PPP channel interface.
391 */
392 static int
ppp_async_ioctl(struct ppp_channel * chan,unsigned int cmd,unsigned long arg)393 ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
394 {
395 struct asyncppp *ap = chan->private;
396 void __user *argp = (void __user *)arg;
397 int __user *p = argp;
398 int err, val;
399 u32 accm[8];
400
401 err = -EFAULT;
402 switch (cmd) {
403 case PPPIOCGFLAGS:
404 val = ap->flags | ap->rbits;
405 if (put_user(val, p))
406 break;
407 err = 0;
408 break;
409 case PPPIOCSFLAGS:
410 if (get_user(val, p))
411 break;
412 ap->flags = val & ~SC_RCV_BITS;
413 spin_lock_irq(&ap->recv_lock);
414 ap->rbits = val & SC_RCV_BITS;
415 spin_unlock_irq(&ap->recv_lock);
416 err = 0;
417 break;
418
419 case PPPIOCGASYNCMAP:
420 if (put_user(ap->xaccm[0], (u32 __user *)argp))
421 break;
422 err = 0;
423 break;
424 case PPPIOCSASYNCMAP:
425 if (get_user(ap->xaccm[0], (u32 __user *)argp))
426 break;
427 err = 0;
428 break;
429
430 case PPPIOCGRASYNCMAP:
431 if (put_user(ap->raccm, (u32 __user *)argp))
432 break;
433 err = 0;
434 break;
435 case PPPIOCSRASYNCMAP:
436 if (get_user(ap->raccm, (u32 __user *)argp))
437 break;
438 err = 0;
439 break;
440
441 case PPPIOCGXASYNCMAP:
442 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
443 break;
444 err = 0;
445 break;
446 case PPPIOCSXASYNCMAP:
447 if (copy_from_user(accm, argp, sizeof(accm)))
448 break;
449 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
450 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
451 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
452 err = 0;
453 break;
454
455 case PPPIOCGMRU:
456 if (put_user(ap->mru, p))
457 break;
458 err = 0;
459 break;
460 case PPPIOCSMRU:
461 if (get_user(val, p))
462 break;
463 if (val < PPP_MRU)
464 val = PPP_MRU;
465 ap->mru = val;
466 err = 0;
467 break;
468
469 default:
470 err = -ENOTTY;
471 }
472
473 return err;
474 }
475
476 /*
477 * This is called at softirq level to deliver received packets
478 * to the ppp_generic code, and to tell the ppp_generic code
479 * if we can accept more output now.
480 */
ppp_async_process(struct tasklet_struct * t)481 static void ppp_async_process(struct tasklet_struct *t)
482 {
483 struct asyncppp *ap = from_tasklet(ap, t, tsk);
484 struct sk_buff *skb;
485
486 /* process received packets */
487 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
488 if (skb->cb[0])
489 ppp_input_error(&ap->chan, 0);
490 ppp_input(&ap->chan, skb);
491 }
492
493 /* try to push more stuff out */
494 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
495 ppp_output_wakeup(&ap->chan);
496 }
497
498 /*
499 * Procedures for encapsulation and framing.
500 */
501
502 /*
503 * Procedure to encode the data for async serial transmission.
504 * Does octet stuffing (escaping), puts the address/control bytes
505 * on if A/C compression is disabled, and does protocol compression.
506 * Assumes ap->tpkt != 0 on entry.
507 * Returns 1 if we finished the current frame, 0 otherwise.
508 */
509
510 #define PUT_BYTE(ap, buf, c, islcp) do { \
511 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
512 *buf++ = PPP_ESCAPE; \
513 *buf++ = c ^ PPP_TRANS; \
514 } else \
515 *buf++ = c; \
516 } while (0)
517
518 static int
ppp_async_encode(struct asyncppp * ap)519 ppp_async_encode(struct asyncppp *ap)
520 {
521 int fcs, i, count, c, proto;
522 unsigned char *buf, *buflim;
523 unsigned char *data;
524 int islcp;
525
526 buf = ap->obuf;
527 ap->olim = buf;
528 ap->optr = buf;
529 i = ap->tpkt_pos;
530 data = ap->tpkt->data;
531 count = ap->tpkt->len;
532 fcs = ap->tfcs;
533 proto = get_unaligned_be16(data);
534
535 /*
536 * LCP packets with code values between 1 (configure-reqest)
537 * and 7 (code-reject) must be sent as though no options
538 * had been negotiated.
539 */
540 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
541
542 if (i == 0) {
543 if (islcp)
544 async_lcp_peek(ap, data, count, 0);
545
546 /*
547 * Start of a new packet - insert the leading FLAG
548 * character if necessary.
549 */
550 if (islcp || flag_time == 0 ||
551 time_after_eq(jiffies, ap->last_xmit + flag_time))
552 *buf++ = PPP_FLAG;
553 ap->last_xmit = jiffies;
554 fcs = PPP_INITFCS;
555
556 /*
557 * Put in the address/control bytes if necessary
558 */
559 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
560 PUT_BYTE(ap, buf, 0xff, islcp);
561 fcs = PPP_FCS(fcs, 0xff);
562 PUT_BYTE(ap, buf, 0x03, islcp);
563 fcs = PPP_FCS(fcs, 0x03);
564 }
565 }
566
567 /*
568 * Once we put in the last byte, we need to put in the FCS
569 * and closing flag, so make sure there is at least 7 bytes
570 * of free space in the output buffer.
571 */
572 buflim = ap->obuf + OBUFSIZE - 6;
573 while (i < count && buf < buflim) {
574 c = data[i++];
575 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
576 continue; /* compress protocol field */
577 fcs = PPP_FCS(fcs, c);
578 PUT_BYTE(ap, buf, c, islcp);
579 }
580
581 if (i < count) {
582 /*
583 * Remember where we are up to in this packet.
584 */
585 ap->olim = buf;
586 ap->tpkt_pos = i;
587 ap->tfcs = fcs;
588 return 0;
589 }
590
591 /*
592 * We have finished the packet. Add the FCS and flag.
593 */
594 fcs = ~fcs;
595 c = fcs & 0xff;
596 PUT_BYTE(ap, buf, c, islcp);
597 c = (fcs >> 8) & 0xff;
598 PUT_BYTE(ap, buf, c, islcp);
599 *buf++ = PPP_FLAG;
600 ap->olim = buf;
601
602 consume_skb(ap->tpkt);
603 ap->tpkt = NULL;
604 return 1;
605 }
606
607 /*
608 * Transmit-side routines.
609 */
610
611 /*
612 * Send a packet to the peer over an async tty line.
613 * Returns 1 iff the packet was accepted.
614 * If the packet was not accepted, we will call ppp_output_wakeup
615 * at some later time.
616 */
617 static int
ppp_async_send(struct ppp_channel * chan,struct sk_buff * skb)618 ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
619 {
620 struct asyncppp *ap = chan->private;
621
622 ppp_async_push(ap);
623
624 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
625 return 0; /* already full */
626 ap->tpkt = skb;
627 ap->tpkt_pos = 0;
628
629 ppp_async_push(ap);
630 return 1;
631 }
632
633 /*
634 * Push as much data as possible out to the tty.
635 */
636 static int
ppp_async_push(struct asyncppp * ap)637 ppp_async_push(struct asyncppp *ap)
638 {
639 int avail, sent, done = 0;
640 struct tty_struct *tty = ap->tty;
641 int tty_stuffed = 0;
642
643 /*
644 * We can get called recursively here if the tty write
645 * function calls our wakeup function. This can happen
646 * for example on a pty with both the master and slave
647 * set to PPP line discipline.
648 * We use the XMIT_BUSY bit to detect this and get out,
649 * leaving the XMIT_WAKEUP bit set to tell the other
650 * instance that it may now be able to write more now.
651 */
652 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
653 return 0;
654 spin_lock_bh(&ap->xmit_lock);
655 for (;;) {
656 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
657 tty_stuffed = 0;
658 if (!tty_stuffed && ap->optr < ap->olim) {
659 avail = ap->olim - ap->optr;
660 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
661 sent = tty->ops->write(tty, ap->optr, avail);
662 if (sent < 0)
663 goto flush; /* error, e.g. loss of CD */
664 ap->optr += sent;
665 if (sent < avail)
666 tty_stuffed = 1;
667 continue;
668 }
669 if (ap->optr >= ap->olim && ap->tpkt) {
670 if (ppp_async_encode(ap)) {
671 /* finished processing ap->tpkt */
672 clear_bit(XMIT_FULL, &ap->xmit_flags);
673 done = 1;
674 }
675 continue;
676 }
677 /*
678 * We haven't made any progress this time around.
679 * Clear XMIT_BUSY to let other callers in, but
680 * after doing so we have to check if anyone set
681 * XMIT_WAKEUP since we last checked it. If they
682 * did, we should try again to set XMIT_BUSY and go
683 * around again in case XMIT_BUSY was still set when
684 * the other caller tried.
685 */
686 clear_bit(XMIT_BUSY, &ap->xmit_flags);
687 /* any more work to do? if not, exit the loop */
688 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
689 (!tty_stuffed && ap->tpkt)))
690 break;
691 /* more work to do, see if we can do it now */
692 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
693 break;
694 }
695 spin_unlock_bh(&ap->xmit_lock);
696 return done;
697
698 flush:
699 clear_bit(XMIT_BUSY, &ap->xmit_flags);
700 if (ap->tpkt) {
701 kfree_skb(ap->tpkt);
702 ap->tpkt = NULL;
703 clear_bit(XMIT_FULL, &ap->xmit_flags);
704 done = 1;
705 }
706 ap->optr = ap->olim;
707 spin_unlock_bh(&ap->xmit_lock);
708 return done;
709 }
710
711 /*
712 * Flush output from our internal buffers.
713 * Called for the TCFLSH ioctl. Can be entered in parallel
714 * but this is covered by the xmit_lock.
715 */
716 static void
ppp_async_flush_output(struct asyncppp * ap)717 ppp_async_flush_output(struct asyncppp *ap)
718 {
719 int done = 0;
720
721 spin_lock_bh(&ap->xmit_lock);
722 ap->optr = ap->olim;
723 if (ap->tpkt != NULL) {
724 kfree_skb(ap->tpkt);
725 ap->tpkt = NULL;
726 clear_bit(XMIT_FULL, &ap->xmit_flags);
727 done = 1;
728 }
729 spin_unlock_bh(&ap->xmit_lock);
730 if (done)
731 ppp_output_wakeup(&ap->chan);
732 }
733
734 /*
735 * Receive-side routines.
736 */
737
738 /* see how many ordinary chars there are at the start of buf */
739 static inline int
scan_ordinary(struct asyncppp * ap,const unsigned char * buf,int count)740 scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
741 {
742 int i, c;
743
744 for (i = 0; i < count; ++i) {
745 c = buf[i];
746 if (c == PPP_ESCAPE || c == PPP_FLAG ||
747 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
748 break;
749 }
750 return i;
751 }
752
753 /* called when a flag is seen - do end-of-packet processing */
754 static void
process_input_packet(struct asyncppp * ap)755 process_input_packet(struct asyncppp *ap)
756 {
757 struct sk_buff *skb;
758 unsigned char *p;
759 unsigned int len, fcs;
760
761 skb = ap->rpkt;
762 if (ap->state & (SC_TOSS | SC_ESCAPE))
763 goto err;
764
765 if (skb == NULL)
766 return; /* 0-length packet */
767
768 /* check the FCS */
769 p = skb->data;
770 len = skb->len;
771 if (len < 3)
772 goto err; /* too short */
773 fcs = PPP_INITFCS;
774 for (; len > 0; --len)
775 fcs = PPP_FCS(fcs, *p++);
776 if (fcs != PPP_GOODFCS)
777 goto err; /* bad FCS */
778 skb_trim(skb, skb->len - 2);
779
780 /* check for address/control and protocol compression */
781 p = skb->data;
782 if (p[0] == PPP_ALLSTATIONS) {
783 /* chop off address/control */
784 if (p[1] != PPP_UI || skb->len < 3)
785 goto err;
786 p = skb_pull(skb, 2);
787 }
788
789 /* If protocol field is not compressed, it can be LCP packet */
790 if (!(p[0] & 0x01)) {
791 unsigned int proto;
792
793 if (skb->len < 2)
794 goto err;
795 proto = (p[0] << 8) + p[1];
796 if (proto == PPP_LCP)
797 async_lcp_peek(ap, p, skb->len, 1);
798 }
799
800 /* queue the frame to be processed */
801 skb->cb[0] = ap->state;
802 skb_queue_tail(&ap->rqueue, skb);
803 ap->rpkt = NULL;
804 ap->state = 0;
805 return;
806
807 err:
808 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
809 ap->state = SC_PREV_ERROR;
810 if (skb) {
811 /* make skb appear as freshly allocated */
812 skb_trim(skb, 0);
813 skb_reserve(skb, - skb_headroom(skb));
814 }
815 }
816
817 /* Called when the tty driver has data for us. Runs parallel with the
818 other ldisc functions but will not be re-entered */
819
820 static void
ppp_async_input(struct asyncppp * ap,const u8 * buf,const u8 * flags,int count)821 ppp_async_input(struct asyncppp *ap, const u8 *buf, const u8 *flags, int count)
822 {
823 struct sk_buff *skb;
824 int c, i, j, n, s, f;
825 unsigned char *sp;
826
827 /* update bits used for 8-bit cleanness detection */
828 if (~ap->rbits & SC_RCV_BITS) {
829 s = 0;
830 for (i = 0; i < count; ++i) {
831 c = buf[i];
832 if (flags && flags[i] != 0)
833 continue;
834 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
835 c = ((c >> 4) ^ c) & 0xf;
836 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
837 }
838 ap->rbits |= s;
839 }
840
841 while (count > 0) {
842 /* scan through and see how many chars we can do in bulk */
843 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
844 n = 1;
845 else
846 n = scan_ordinary(ap, buf, count);
847
848 f = 0;
849 if (flags && (ap->state & SC_TOSS) == 0) {
850 /* check the flags to see if any char had an error */
851 for (j = 0; j < n; ++j)
852 if ((f = flags[j]) != 0)
853 break;
854 }
855 if (f != 0) {
856 /* start tossing */
857 ap->state |= SC_TOSS;
858
859 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
860 /* stuff the chars in the skb */
861 skb = ap->rpkt;
862 if (!skb) {
863 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
864 if (!skb)
865 goto nomem;
866 ap->rpkt = skb;
867 }
868 if (skb->len == 0) {
869 /* Try to get the payload 4-byte aligned.
870 * This should match the
871 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
872 * process_input_packet, but we do not have
873 * enough chars here to test buf[1] and buf[2].
874 */
875 if (buf[0] != PPP_ALLSTATIONS)
876 skb_reserve(skb, 2 + (buf[0] & 1));
877 }
878 if (n > skb_tailroom(skb)) {
879 /* packet overflowed MRU */
880 ap->state |= SC_TOSS;
881 } else {
882 sp = skb_put_data(skb, buf, n);
883 if (ap->state & SC_ESCAPE) {
884 sp[0] ^= PPP_TRANS;
885 ap->state &= ~SC_ESCAPE;
886 }
887 }
888 }
889
890 if (n >= count)
891 break;
892
893 c = buf[n];
894 if (flags != NULL && flags[n] != 0) {
895 ap->state |= SC_TOSS;
896 } else if (c == PPP_FLAG) {
897 process_input_packet(ap);
898 } else if (c == PPP_ESCAPE) {
899 ap->state |= SC_ESCAPE;
900 } else if (I_IXON(ap->tty)) {
901 if (c == START_CHAR(ap->tty))
902 start_tty(ap->tty);
903 else if (c == STOP_CHAR(ap->tty))
904 stop_tty(ap->tty);
905 }
906 /* otherwise it's a char in the recv ACCM */
907 ++n;
908
909 buf += n;
910 if (flags)
911 flags += n;
912 count -= n;
913 }
914 return;
915
916 nomem:
917 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
918 ap->state |= SC_TOSS;
919 }
920
921 /*
922 * We look at LCP frames going past so that we can notice
923 * and react to the LCP configure-ack from the peer.
924 * In the situation where the peer has been sent a configure-ack
925 * already, LCP is up once it has sent its configure-ack
926 * so the immediately following packet can be sent with the
927 * configured LCP options. This allows us to process the following
928 * packet correctly without pppd needing to respond quickly.
929 *
930 * We only respond to the received configure-ack if we have just
931 * sent a configure-request, and the configure-ack contains the
932 * same data (this is checked using a 16-bit crc of the data).
933 */
934 #define CONFREQ 1 /* LCP code field values */
935 #define CONFACK 2
936 #define LCP_MRU 1 /* LCP option numbers */
937 #define LCP_ASYNCMAP 2
938
async_lcp_peek(struct asyncppp * ap,unsigned char * data,int len,int inbound)939 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
940 int len, int inbound)
941 {
942 int dlen, fcs, i, code;
943 u32 val;
944
945 data += 2; /* skip protocol bytes */
946 len -= 2;
947 if (len < 4) /* 4 = code, ID, length */
948 return;
949 code = data[0];
950 if (code != CONFACK && code != CONFREQ)
951 return;
952 dlen = get_unaligned_be16(data + 2);
953 if (len < dlen)
954 return; /* packet got truncated or length is bogus */
955
956 if (code == (inbound? CONFACK: CONFREQ)) {
957 /*
958 * sent confreq or received confack:
959 * calculate the crc of the data from the ID field on.
960 */
961 fcs = PPP_INITFCS;
962 for (i = 1; i < dlen; ++i)
963 fcs = PPP_FCS(fcs, data[i]);
964
965 if (!inbound) {
966 /* outbound confreq - remember the crc for later */
967 ap->lcp_fcs = fcs;
968 return;
969 }
970
971 /* received confack, check the crc */
972 fcs ^= ap->lcp_fcs;
973 ap->lcp_fcs = -1;
974 if (fcs != 0)
975 return;
976 } else if (inbound)
977 return; /* not interested in received confreq */
978
979 /* process the options in the confack */
980 data += 4;
981 dlen -= 4;
982 /* data[0] is code, data[1] is length */
983 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
984 switch (data[0]) {
985 case LCP_MRU:
986 val = get_unaligned_be16(data + 2);
987 if (inbound)
988 ap->mru = val;
989 else
990 ap->chan.mtu = val;
991 break;
992 case LCP_ASYNCMAP:
993 val = get_unaligned_be32(data + 2);
994 if (inbound)
995 ap->raccm = val;
996 else
997 ap->xaccm[0] = val;
998 break;
999 }
1000 dlen -= data[1];
1001 data += data[1];
1002 }
1003 }
1004
ppp_async_cleanup(void)1005 static void __exit ppp_async_cleanup(void)
1006 {
1007 tty_unregister_ldisc(&ppp_ldisc);
1008 }
1009
1010 module_init(ppp_async_init);
1011 module_exit(ppp_async_cleanup);
1012
