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 <linux/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
53 struct sk_buff *tpkt;
54 int tpkt_pos;
55 u16 tfcs;
56 unsigned char *optr;
57 unsigned char *olim;
58 unsigned long last_xmit;
59
60 struct sk_buff *rpkt;
61 int lcp_fcs;
62 struct sk_buff_head rqueue;
63
64 struct tasklet_struct tsk;
65
66 refcount_t refcnt;
67 struct completion dead;
68 struct ppp_channel chan; /* interface to generic ppp layer */
69 unsigned char obuf[OBUFSIZE];
70 };
71
72 /* Bit numbers in xmit_flags */
73 #define XMIT_WAKEUP 0
74 #define XMIT_FULL 1
75 #define XMIT_BUSY 2
76
77 /* State bits */
78 #define SC_TOSS 1
79 #define SC_ESCAPE 2
80 #define SC_PREV_ERROR 4
81
82 /* Bits in rbits */
83 #define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
84
85 static int flag_time = HZ;
86 module_param(flag_time, int, 0);
87 MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
88 MODULE_DESCRIPTION("PPP async serial channel module");
89 MODULE_LICENSE("GPL");
90 MODULE_ALIAS_LDISC(N_PPP);
91
92 /*
93 * Prototypes.
94 */
95 static int ppp_async_encode(struct asyncppp *ap);
96 static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
97 static int ppp_async_push(struct asyncppp *ap);
98 static void ppp_async_flush_output(struct asyncppp *ap);
99 static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
100 const u8 *flags, int count);
101 static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
102 unsigned long arg);
103 static void ppp_async_process(struct tasklet_struct *t);
104
105 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
106 int len, int inbound);
107
108 static const struct ppp_channel_ops async_ops = {
109 .start_xmit = ppp_async_send,
110 .ioctl = ppp_async_ioctl,
111 };
112
113 /*
114 * Routines implementing the PPP line discipline.
115 */
116
117 /*
118 * We have a potential race on dereferencing tty->disc_data,
119 * because the tty layer provides no locking at all - thus one
120 * cpu could be running ppp_asynctty_receive while another
121 * calls ppp_asynctty_close, which zeroes tty->disc_data and
122 * frees the memory that ppp_asynctty_receive is using. The best
123 * way to fix this is to use a rwlock in the tty struct, but for now
124 * we use a single global rwlock for all ttys in ppp line discipline.
125 *
126 * FIXME: this is no longer true. The _close path for the ldisc is
127 * now guaranteed to be sane.
128 */
129 static DEFINE_RWLOCK(disc_data_lock);
130
ap_get(struct tty_struct * tty)131 static struct asyncppp *ap_get(struct tty_struct *tty)
132 {
133 struct asyncppp *ap;
134
135 read_lock(&disc_data_lock);
136 ap = tty->disc_data;
137 if (ap != NULL)
138 refcount_inc(&ap->refcnt);
139 read_unlock(&disc_data_lock);
140 return ap;
141 }
142
ap_put(struct asyncppp * ap)143 static void ap_put(struct asyncppp *ap)
144 {
145 if (refcount_dec_and_test(&ap->refcnt))
146 complete(&ap->dead);
147 }
148
149 /*
150 * Called when a tty is put into PPP line discipline. Called in process
151 * context.
152 */
153 static int
ppp_asynctty_open(struct tty_struct * tty)154 ppp_asynctty_open(struct tty_struct *tty)
155 {
156 struct asyncppp *ap;
157 int err;
158 int speed;
159
160 if (tty->ops->write == NULL)
161 return -EOPNOTSUPP;
162
163 err = -ENOMEM;
164 ap = kzalloc_obj(*ap);
165 if (!ap)
166 goto out;
167
168 /* initialize the asyncppp structure */
169 ap->tty = tty;
170 ap->mru = PPP_MRU;
171 spin_lock_init(&ap->xmit_lock);
172 spin_lock_init(&ap->recv_lock);
173 ap->xaccm[0] = ~0U;
174 ap->xaccm[3] = 0x60000000U;
175 ap->raccm = ~0U;
176 ap->optr = ap->obuf;
177 ap->olim = ap->obuf;
178 ap->lcp_fcs = -1;
179
180 skb_queue_head_init(&ap->rqueue);
181 tasklet_setup(&ap->tsk, ppp_async_process);
182
183 refcount_set(&ap->refcnt, 1);
184 init_completion(&ap->dead);
185
186 ap->chan.private = ap;
187 ap->chan.ops = &async_ops;
188 ap->chan.mtu = PPP_MRU;
189 speed = tty_get_baud_rate(tty);
190 ap->chan.speed = speed;
191 err = ppp_register_channel(&ap->chan);
192 if (err)
193 goto out_free;
194
195 tty->disc_data = ap;
196 tty->receive_room = 65536;
197 return 0;
198
199 out_free:
200 kfree(ap);
201 out:
202 return err;
203 }
204
205 /*
206 * Called when the tty is put into another line discipline
207 * or it hangs up. We have to wait for any cpu currently
208 * executing in any of the other ppp_asynctty_* routines to
209 * finish before we can call ppp_unregister_channel and free
210 * the asyncppp struct. This routine must be called from
211 * process context, not interrupt or softirq context.
212 */
213 static void
ppp_asynctty_close(struct tty_struct * tty)214 ppp_asynctty_close(struct tty_struct *tty)
215 {
216 struct asyncppp *ap;
217
218 write_lock_irq(&disc_data_lock);
219 ap = tty->disc_data;
220 tty->disc_data = NULL;
221 write_unlock_irq(&disc_data_lock);
222 if (!ap)
223 return;
224
225 /*
226 * We have now ensured that nobody can start using ap from now
227 * on, but we have to wait for all existing users to finish.
228 * Note that ppp_unregister_channel ensures that no calls to
229 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
230 * by the time it returns.
231 */
232 if (!refcount_dec_and_test(&ap->refcnt))
233 wait_for_completion(&ap->dead);
234 tasklet_kill(&ap->tsk);
235
236 ppp_unregister_channel(&ap->chan);
237 kfree_skb(ap->rpkt);
238 skb_queue_purge(&ap->rqueue);
239 kfree_skb(ap->tpkt);
240 kfree(ap);
241 }
242
243 /*
244 * Called on tty hangup in process context.
245 *
246 * Wait for I/O to driver to complete and unregister PPP channel.
247 * This is already done by the close routine, so just call that.
248 */
ppp_asynctty_hangup(struct tty_struct * tty)249 static void ppp_asynctty_hangup(struct tty_struct *tty)
250 {
251 ppp_asynctty_close(tty);
252 }
253
254 /*
255 * Read does nothing - no data is ever available this way.
256 * Pppd reads and writes packets via /dev/ppp instead.
257 */
258 static ssize_t
ppp_asynctty_read(struct tty_struct * tty,struct file * file,u8 * buf,size_t count,void ** cookie,unsigned long offset)259 ppp_asynctty_read(struct tty_struct *tty, struct file *file, u8 *buf,
260 size_t count, void **cookie, unsigned long offset)
261 {
262 return -EAGAIN;
263 }
264
265 /*
266 * Write on the tty does nothing, the packets all come in
267 * from the ppp generic stuff.
268 */
269 static ssize_t
ppp_asynctty_write(struct tty_struct * tty,struct file * file,const u8 * buf,size_t count)270 ppp_asynctty_write(struct tty_struct *tty, struct file *file, const u8 *buf,
271 size_t count)
272 {
273 return -EAGAIN;
274 }
275
276 /*
277 * Called in process context only. May be re-entered by multiple
278 * ioctl calling threads.
279 */
280
281 static int
ppp_asynctty_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)282 ppp_asynctty_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
283 {
284 struct asyncppp *ap = ap_get(tty);
285 int err, val;
286 int __user *p = (int __user *)arg;
287
288 if (!ap)
289 return -ENXIO;
290 err = -EFAULT;
291 switch (cmd) {
292 case PPPIOCGCHAN:
293 err = -EFAULT;
294 if (put_user(ppp_channel_index(&ap->chan), p))
295 break;
296 err = 0;
297 break;
298
299 case PPPIOCGUNIT:
300 err = -EFAULT;
301 if (put_user(ppp_unit_number(&ap->chan), p))
302 break;
303 err = 0;
304 break;
305
306 case TCFLSH:
307 /* flush our buffers and the serial port's buffer */
308 if (arg == TCIOFLUSH || arg == TCOFLUSH)
309 ppp_async_flush_output(ap);
310 err = n_tty_ioctl_helper(tty, cmd, arg);
311 break;
312
313 case FIONREAD:
314 val = 0;
315 if (put_user(val, p))
316 break;
317 err = 0;
318 break;
319
320 default:
321 /* Try the various mode ioctls */
322 err = tty_mode_ioctl(tty, cmd, arg);
323 }
324
325 ap_put(ap);
326 return err;
327 }
328
329 /* May sleep, don't call from interrupt level or with interrupts disabled */
330 static void
ppp_asynctty_receive(struct tty_struct * tty,const u8 * buf,const u8 * cflags,size_t count)331 ppp_asynctty_receive(struct tty_struct *tty, const u8 *buf, const u8 *cflags,
332 size_t count)
333 {
334 struct asyncppp *ap = ap_get(tty);
335 unsigned long flags;
336
337 if (!ap)
338 return;
339 spin_lock_irqsave(&ap->recv_lock, flags);
340 ppp_async_input(ap, buf, cflags, count);
341 spin_unlock_irqrestore(&ap->recv_lock, flags);
342 if (!skb_queue_empty(&ap->rqueue))
343 tasklet_schedule(&ap->tsk);
344 ap_put(ap);
345 tty_unthrottle(tty);
346 }
347
348 static void
ppp_asynctty_wakeup(struct tty_struct * tty)349 ppp_asynctty_wakeup(struct tty_struct *tty)
350 {
351 struct asyncppp *ap = ap_get(tty);
352
353 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
354 if (!ap)
355 return;
356 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
357 tasklet_schedule(&ap->tsk);
358 ap_put(ap);
359 }
360
361
362 static struct tty_ldisc_ops ppp_ldisc = {
363 .owner = THIS_MODULE,
364 .num = N_PPP,
365 .name = "ppp",
366 .open = ppp_asynctty_open,
367 .close = ppp_asynctty_close,
368 .hangup = ppp_asynctty_hangup,
369 .read = ppp_asynctty_read,
370 .write = ppp_asynctty_write,
371 .ioctl = ppp_asynctty_ioctl,
372 .receive_buf = ppp_asynctty_receive,
373 .write_wakeup = ppp_asynctty_wakeup,
374 };
375
376 static int __init
ppp_async_init(void)377 ppp_async_init(void)
378 {
379 int err;
380
381 err = tty_register_ldisc(&ppp_ldisc);
382 if (err != 0)
383 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
384 err);
385 return err;
386 }
387
388 /*
389 * The following routines provide the PPP channel interface.
390 */
391 static int
ppp_async_ioctl(struct ppp_channel * chan,unsigned int cmd,unsigned long arg)392 ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
393 {
394 struct asyncppp *ap = chan->private;
395 void __user *argp = (void __user *)arg;
396 int __user *p = argp;
397 int err, val;
398 u32 accm[8];
399
400 err = -EFAULT;
401 switch (cmd) {
402 case PPPIOCGFLAGS:
403 val = ap->flags | ap->rbits;
404 if (put_user(val, p))
405 break;
406 err = 0;
407 break;
408 case PPPIOCSFLAGS:
409 if (get_user(val, p))
410 break;
411 ap->flags = val & ~SC_RCV_BITS;
412 spin_lock_irq(&ap->recv_lock);
413 ap->rbits = val & SC_RCV_BITS;
414 spin_unlock_irq(&ap->recv_lock);
415 err = 0;
416 break;
417
418 case PPPIOCGASYNCMAP:
419 if (put_user(ap->xaccm[0], (u32 __user *)argp))
420 break;
421 err = 0;
422 break;
423 case PPPIOCSASYNCMAP:
424 if (get_user(ap->xaccm[0], (u32 __user *)argp))
425 break;
426 err = 0;
427 break;
428
429 case PPPIOCGRASYNCMAP:
430 if (put_user(ap->raccm, (u32 __user *)argp))
431 break;
432 err = 0;
433 break;
434 case PPPIOCSRASYNCMAP:
435 if (get_user(ap->raccm, (u32 __user *)argp))
436 break;
437 err = 0;
438 break;
439
440 case PPPIOCGXASYNCMAP:
441 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
442 break;
443 err = 0;
444 break;
445 case PPPIOCSXASYNCMAP:
446 if (copy_from_user(accm, argp, sizeof(accm)))
447 break;
448 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
449 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
450 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
451 err = 0;
452 break;
453
454 case PPPIOCGMRU:
455 if (put_user(ap->mru, p))
456 break;
457 err = 0;
458 break;
459 case PPPIOCSMRU:
460 if (get_user(val, p))
461 break;
462 if (val > U16_MAX) {
463 err = -EINVAL;
464 break;
465 }
466 if (val < PPP_MRU)
467 val = PPP_MRU;
468 ap->mru = val;
469 err = 0;
470 break;
471
472 default:
473 err = -ENOTTY;
474 }
475
476 return err;
477 }
478
479 /*
480 * This is called at softirq level to deliver received packets
481 * to the ppp_generic code, and to tell the ppp_generic code
482 * if we can accept more output now.
483 */
ppp_async_process(struct tasklet_struct * t)484 static void ppp_async_process(struct tasklet_struct *t)
485 {
486 struct asyncppp *ap = from_tasklet(ap, t, tsk);
487 struct sk_buff *skb;
488
489 /* process received packets */
490 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
491 if (skb->cb[0])
492 ppp_input_error(&ap->chan);
493 ppp_input(&ap->chan, skb);
494 }
495
496 /* try to push more stuff out */
497 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
498 ppp_output_wakeup(&ap->chan);
499 }
500
501 /*
502 * Procedures for encapsulation and framing.
503 */
504
505 /*
506 * Procedure to encode the data for async serial transmission.
507 * Does octet stuffing (escaping), puts the address/control bytes
508 * on if A/C compression is disabled, and does protocol compression.
509 * Assumes ap->tpkt != 0 on entry.
510 * Returns 1 if we finished the current frame, 0 otherwise.
511 */
512
513 #define PUT_BYTE(ap, buf, c, islcp) do { \
514 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
515 *buf++ = PPP_ESCAPE; \
516 *buf++ = c ^ PPP_TRANS; \
517 } else \
518 *buf++ = c; \
519 } while (0)
520
521 static int
ppp_async_encode(struct asyncppp * ap)522 ppp_async_encode(struct asyncppp *ap)
523 {
524 int fcs, i, count, c, proto;
525 unsigned char *buf, *buflim;
526 unsigned char *data;
527 int islcp;
528
529 buf = ap->obuf;
530 ap->olim = buf;
531 ap->optr = buf;
532 i = ap->tpkt_pos;
533 data = ap->tpkt->data;
534 count = ap->tpkt->len;
535 fcs = ap->tfcs;
536 proto = get_unaligned_be16(data);
537
538 /*
539 * LCP packets with code values between 1 (configure-request)
540 * and 7 (code-reject) must be sent as though no options
541 * had been negotiated.
542 */
543 islcp = proto == PPP_LCP && count >= 3 && 1 <= data[2] && data[2] <= 7;
544
545 if (i == 0) {
546 if (islcp)
547 async_lcp_peek(ap, data, count, 0);
548
549 /*
550 * Start of a new packet - insert the leading FLAG
551 * character if necessary.
552 */
553 if (islcp || flag_time == 0 ||
554 time_after_eq(jiffies, ap->last_xmit + flag_time))
555 *buf++ = PPP_FLAG;
556 ap->last_xmit = jiffies;
557 fcs = PPP_INITFCS;
558
559 /*
560 * Put in the address/control bytes if necessary
561 */
562 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
563 PUT_BYTE(ap, buf, 0xff, islcp);
564 fcs = PPP_FCS(fcs, 0xff);
565 PUT_BYTE(ap, buf, 0x03, islcp);
566 fcs = PPP_FCS(fcs, 0x03);
567 }
568 }
569
570 /*
571 * Once we put in the last byte, we need to put in the FCS
572 * and closing flag, so make sure there is at least 7 bytes
573 * of free space in the output buffer.
574 */
575 buflim = ap->obuf + OBUFSIZE - 6;
576 while (i < count && buf < buflim) {
577 c = data[i++];
578 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
579 continue; /* compress protocol field */
580 fcs = PPP_FCS(fcs, c);
581 PUT_BYTE(ap, buf, c, islcp);
582 }
583
584 if (i < count) {
585 /*
586 * Remember where we are up to in this packet.
587 */
588 ap->olim = buf;
589 ap->tpkt_pos = i;
590 ap->tfcs = fcs;
591 return 0;
592 }
593
594 /*
595 * We have finished the packet. Add the FCS and flag.
596 */
597 fcs = ~fcs;
598 c = fcs & 0xff;
599 PUT_BYTE(ap, buf, c, islcp);
600 c = (fcs >> 8) & 0xff;
601 PUT_BYTE(ap, buf, c, islcp);
602 *buf++ = PPP_FLAG;
603 ap->olim = buf;
604
605 consume_skb(ap->tpkt);
606 ap->tpkt = NULL;
607 return 1;
608 }
609
610 /*
611 * Transmit-side routines.
612 */
613
614 /*
615 * Send a packet to the peer over an async tty line.
616 * Returns 1 iff the packet was accepted.
617 * If the packet was not accepted, we will call ppp_output_wakeup
618 * at some later time.
619 */
620 static int
ppp_async_send(struct ppp_channel * chan,struct sk_buff * skb)621 ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
622 {
623 struct asyncppp *ap = chan->private;
624
625 ppp_async_push(ap);
626
627 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
628 return 0; /* already full */
629 ap->tpkt = skb;
630 ap->tpkt_pos = 0;
631
632 ppp_async_push(ap);
633 return 1;
634 }
635
636 /*
637 * Push as much data as possible out to the tty.
638 */
639 static int
ppp_async_push(struct asyncppp * ap)640 ppp_async_push(struct asyncppp *ap)
641 {
642 int avail, sent, done = 0;
643 struct tty_struct *tty = ap->tty;
644 int tty_stuffed = 0;
645
646 /*
647 * We can get called recursively here if the tty write
648 * function calls our wakeup function. This can happen
649 * for example on a pty with both the master and slave
650 * set to PPP line discipline.
651 * We use the XMIT_BUSY bit to detect this and get out,
652 * leaving the XMIT_WAKEUP bit set to tell the other
653 * instance that it may now be able to write more now.
654 */
655 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
656 return 0;
657 spin_lock_bh(&ap->xmit_lock);
658 for (;;) {
659 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
660 tty_stuffed = 0;
661 if (!tty_stuffed && ap->optr < ap->olim) {
662 avail = ap->olim - ap->optr;
663 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
664 sent = tty->ops->write(tty, ap->optr, avail);
665 if (sent < 0)
666 goto flush; /* error, e.g. loss of CD */
667 ap->optr += sent;
668 if (sent < avail)
669 tty_stuffed = 1;
670 continue;
671 }
672 if (ap->optr >= ap->olim && ap->tpkt) {
673 if (ppp_async_encode(ap)) {
674 /* finished processing ap->tpkt */
675 clear_bit(XMIT_FULL, &ap->xmit_flags);
676 done = 1;
677 }
678 continue;
679 }
680 /*
681 * We haven't made any progress this time around.
682 * Clear XMIT_BUSY to let other callers in, but
683 * after doing so we have to check if anyone set
684 * XMIT_WAKEUP since we last checked it. If they
685 * did, we should try again to set XMIT_BUSY and go
686 * around again in case XMIT_BUSY was still set when
687 * the other caller tried.
688 */
689 clear_bit(XMIT_BUSY, &ap->xmit_flags);
690 /* any more work to do? if not, exit the loop */
691 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
692 (!tty_stuffed && ap->tpkt)))
693 break;
694 /* more work to do, see if we can do it now */
695 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
696 break;
697 }
698 spin_unlock_bh(&ap->xmit_lock);
699 return done;
700
701 flush:
702 clear_bit(XMIT_BUSY, &ap->xmit_flags);
703 if (ap->tpkt) {
704 kfree_skb(ap->tpkt);
705 ap->tpkt = NULL;
706 clear_bit(XMIT_FULL, &ap->xmit_flags);
707 done = 1;
708 }
709 ap->optr = ap->olim;
710 spin_unlock_bh(&ap->xmit_lock);
711 return done;
712 }
713
714 /*
715 * Flush output from our internal buffers.
716 * Called for the TCFLSH ioctl. Can be entered in parallel
717 * but this is covered by the xmit_lock.
718 */
719 static void
ppp_async_flush_output(struct asyncppp * ap)720 ppp_async_flush_output(struct asyncppp *ap)
721 {
722 int done = 0;
723
724 spin_lock_bh(&ap->xmit_lock);
725 ap->optr = ap->olim;
726 if (ap->tpkt != NULL) {
727 kfree_skb(ap->tpkt);
728 ap->tpkt = NULL;
729 clear_bit(XMIT_FULL, &ap->xmit_flags);
730 done = 1;
731 }
732 spin_unlock_bh(&ap->xmit_lock);
733 if (done)
734 ppp_output_wakeup(&ap->chan);
735 }
736
737 /*
738 * Receive-side routines.
739 */
740
741 /* see how many ordinary chars there are at the start of buf */
742 static inline int
scan_ordinary(struct asyncppp * ap,const unsigned char * buf,int count)743 scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
744 {
745 int i, c;
746
747 for (i = 0; i < count; ++i) {
748 c = buf[i];
749 if (c == PPP_ESCAPE || c == PPP_FLAG ||
750 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
751 break;
752 }
753 return i;
754 }
755
756 /* called when a flag is seen - do end-of-packet processing */
757 static void
process_input_packet(struct asyncppp * ap)758 process_input_packet(struct asyncppp *ap)
759 {
760 struct sk_buff *skb;
761 unsigned char *p;
762 unsigned int len, fcs;
763
764 skb = ap->rpkt;
765 if (ap->state & (SC_TOSS | SC_ESCAPE))
766 goto err;
767
768 if (skb == NULL)
769 return; /* 0-length packet */
770
771 /* check the FCS */
772 p = skb->data;
773 len = skb->len;
774 if (len < 3)
775 goto err; /* too short */
776 fcs = PPP_INITFCS;
777 for (; len > 0; --len)
778 fcs = PPP_FCS(fcs, *p++);
779 if (fcs != PPP_GOODFCS)
780 goto err; /* bad FCS */
781 skb_trim(skb, skb->len - 2);
782
783 /* check for address/control and protocol compression */
784 p = skb->data;
785 if (p[0] == PPP_ALLSTATIONS) {
786 /* chop off address/control */
787 if (p[1] != PPP_UI || skb->len < 3)
788 goto err;
789 p = skb_pull(skb, 2);
790 }
791
792 /* If protocol field is not compressed, it can be LCP packet */
793 if (!(p[0] & 0x01)) {
794 unsigned int proto;
795
796 if (skb->len < 2)
797 goto err;
798 proto = (p[0] << 8) + p[1];
799 if (proto == PPP_LCP)
800 async_lcp_peek(ap, p, skb->len, 1);
801 }
802
803 /* queue the frame to be processed */
804 skb->cb[0] = ap->state;
805 skb_queue_tail(&ap->rqueue, skb);
806 ap->rpkt = NULL;
807 ap->state = 0;
808 return;
809
810 err:
811 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
812 ap->state = SC_PREV_ERROR;
813 if (skb) {
814 /* make skb appear as freshly allocated */
815 skb_trim(skb, 0);
816 skb_reserve(skb, - skb_headroom(skb));
817 }
818 }
819
820 /* Called when the tty driver has data for us. Runs parallel with the
821 other ldisc functions but will not be re-entered */
822
823 static void
ppp_async_input(struct asyncppp * ap,const u8 * buf,const u8 * flags,int count)824 ppp_async_input(struct asyncppp *ap, const u8 *buf, const u8 *flags, int count)
825 {
826 struct sk_buff *skb;
827 int c, i, j, n, s, f;
828 unsigned char *sp;
829
830 /* update bits used for 8-bit cleanness detection */
831 if (~ap->rbits & SC_RCV_BITS) {
832 s = 0;
833 for (i = 0; i < count; ++i) {
834 c = buf[i];
835 if (flags && flags[i] != 0)
836 continue;
837 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
838 c = ((c >> 4) ^ c) & 0xf;
839 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
840 }
841 ap->rbits |= s;
842 }
843
844 while (count > 0) {
845 /* scan through and see how many chars we can do in bulk */
846 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
847 n = 1;
848 else
849 n = scan_ordinary(ap, buf, count);
850
851 f = 0;
852 if (flags && (ap->state & SC_TOSS) == 0) {
853 /* check the flags to see if any char had an error */
854 for (j = 0; j < n; ++j)
855 if ((f = flags[j]) != 0)
856 break;
857 }
858 if (f != 0) {
859 /* start tossing */
860 ap->state |= SC_TOSS;
861
862 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
863 /* stuff the chars in the skb */
864 skb = ap->rpkt;
865 if (!skb) {
866 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
867 if (!skb)
868 goto nomem;
869 ap->rpkt = skb;
870 }
871 if (skb->len == 0) {
872 /* Try to get the payload 4-byte aligned.
873 * This should match the
874 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
875 * process_input_packet, but we do not have
876 * enough chars here to test buf[1] and buf[2].
877 */
878 if (buf[0] != PPP_ALLSTATIONS)
879 skb_reserve(skb, 2 + (buf[0] & 1));
880 }
881 if (n > skb_tailroom(skb)) {
882 /* packet overflowed MRU */
883 ap->state |= SC_TOSS;
884 } else {
885 sp = skb_put_data(skb, buf, n);
886 if (ap->state & SC_ESCAPE) {
887 sp[0] ^= PPP_TRANS;
888 ap->state &= ~SC_ESCAPE;
889 }
890 }
891 }
892
893 if (n >= count)
894 break;
895
896 c = buf[n];
897 if (flags != NULL && flags[n] != 0) {
898 ap->state |= SC_TOSS;
899 } else if (c == PPP_FLAG) {
900 process_input_packet(ap);
901 } else if (c == PPP_ESCAPE) {
902 ap->state |= SC_ESCAPE;
903 } else if (I_IXON(ap->tty)) {
904 if (c == START_CHAR(ap->tty))
905 start_tty(ap->tty);
906 else if (c == STOP_CHAR(ap->tty))
907 stop_tty(ap->tty);
908 }
909 /* otherwise it's a char in the recv ACCM */
910 ++n;
911
912 buf += n;
913 if (flags)
914 flags += n;
915 count -= n;
916 }
917 return;
918
919 nomem:
920 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
921 ap->state |= SC_TOSS;
922 }
923
924 /*
925 * We look at LCP frames going past so that we can notice
926 * and react to the LCP configure-ack from the peer.
927 * In the situation where the peer has been sent a configure-ack
928 * already, LCP is up once it has sent its configure-ack
929 * so the immediately following packet can be sent with the
930 * configured LCP options. This allows us to process the following
931 * packet correctly without pppd needing to respond quickly.
932 *
933 * We only respond to the received configure-ack if we have just
934 * sent a configure-request, and the configure-ack contains the
935 * same data (this is checked using a 16-bit crc of the data).
936 */
937 #define CONFREQ 1 /* LCP code field values */
938 #define CONFACK 2
939 #define LCP_MRU 1 /* LCP option numbers */
940 #define LCP_ASYNCMAP 2
941
async_lcp_peek(struct asyncppp * ap,unsigned char * data,int len,int inbound)942 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
943 int len, int inbound)
944 {
945 int dlen, fcs, i, code;
946 u32 val;
947
948 data += 2; /* skip protocol bytes */
949 len -= 2;
950 if (len < 4) /* 4 = code, ID, length */
951 return;
952 code = data[0];
953 if (code != CONFACK && code != CONFREQ)
954 return;
955 dlen = get_unaligned_be16(data + 2);
956 if (len < dlen)
957 return; /* packet got truncated or length is bogus */
958
959 if (code == (inbound? CONFACK: CONFREQ)) {
960 /*
961 * sent confreq or received confack:
962 * calculate the crc of the data from the ID field on.
963 */
964 fcs = PPP_INITFCS;
965 for (i = 1; i < dlen; ++i)
966 fcs = PPP_FCS(fcs, data[i]);
967
968 if (!inbound) {
969 /* outbound confreq - remember the crc for later */
970 ap->lcp_fcs = fcs;
971 return;
972 }
973
974 /* received confack, check the crc */
975 fcs ^= ap->lcp_fcs;
976 ap->lcp_fcs = -1;
977 if (fcs != 0)
978 return;
979 } else if (inbound)
980 return; /* not interested in received confreq */
981
982 /* process the options in the confack */
983 data += 4;
984 dlen -= 4;
985 /* data[0] is code, data[1] is length */
986 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
987 switch (data[0]) {
988 case LCP_MRU:
989 val = get_unaligned_be16(data + 2);
990 if (inbound)
991 ap->mru = val;
992 else
993 ap->chan.mtu = val;
994 break;
995 case LCP_ASYNCMAP:
996 val = get_unaligned_be32(data + 2);
997 if (inbound)
998 ap->raccm = val;
999 else
1000 ap->xaccm[0] = val;
1001 break;
1002 }
1003 dlen -= data[1];
1004 data += data[1];
1005 }
1006 }
1007
ppp_async_cleanup(void)1008 static void __exit ppp_async_cleanup(void)
1009 {
1010 tty_unregister_ldisc(&ppp_ldisc);
1011 }
1012
1013 module_init(ppp_async_init);
1014 module_exit(ppp_async_cleanup);
1015