drivers/net/ppp_async.c

   1 /*
   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>
  33 #include <linux/jiffies.h>
  34 #include <asm/uaccess.h>
  35 #include <asm/string.h>
  36
  37 #define PPP_VERSION     "2.4.2"
  38
  39 #define OBUFSIZE        256
  40
  41 /* Structure for storing local state. */
  42 struct asyncppp {
  43         struct tty_struct *tty;
  44         unsigned int    flags;
  45         unsigned int    state;
  46         unsigned int    rbits;
  47         int             mru;
  48         spinlock_t      xmit_lock;
  49         spinlock_t      recv_lock;
  50         unsigned long   xmit_flags;
  51         u32             xaccm[8];
  52         u32             raccm;
  53         unsigned int    bytes_sent;
  54         unsigned int    bytes_rcvd;
  55
  56         struct sk_buff  *tpkt;
  57         int             tpkt_pos;
  58         u16             tfcs;
  59         unsigned char   *optr;
  60         unsigned char   *olim;
  61         unsigned long   last_xmit;
  62
  63         struct sk_buff  *rpkt;
  64         int             lcp_fcs;
  65         struct sk_buff_head rqueue;
  66
  67         struct tasklet_struct tsk;
  68
  69         atomic_t        refcnt;
  70         struct semaphore dead_sem;
  71         struct ppp_channel chan;        /* interface to generic ppp layer */
  72         unsigned char   obuf[OBUFSIZE];
  73 };
  74
  75 /* Bit numbers in xmit_flags */
  76 #define XMIT_WAKEUP     0
  77 #define XMIT_FULL       1
  78 #define XMIT_BUSY       2
  79
  80 /* State bits */
  81 #define SC_TOSS         1
  82 #define SC_ESCAPE       2
  83 #define SC_PREV_ERROR   4
  84
  85 /* Bits in rbits */
  86 #define SC_RCV_BITS     (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
  87
  88 static int flag_time = HZ;
  89 module_param(flag_time, int, 0);
  90 MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
  91 MODULE_LICENSE("GPL");
  92 MODULE_ALIAS_LDISC(N_PPP);
  93
  94 /*
  95  * Prototypes.
  96  */
  97 static int ppp_async_encode(struct asyncppp *ap);
  98 static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
  99 static int ppp_async_push(struct asyncppp *ap);
 100 static void ppp_async_flush_output(struct asyncppp *ap);
 101 static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
 102                             char *flags, int count);
 103 static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
 104                            unsigned long arg);
 105 static void ppp_async_process(unsigned long arg);
 106
 107 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
 108                            int len, int inbound);
 109
 110 static struct ppp_channel_ops async_ops = {
 111         ppp_async_send,
 112         ppp_async_ioctl
 113 };
 114
 115 /*
 116  * Routines implementing the PPP line discipline.
 117  */
 118
 119 /*
 120  * We have a potential race on dereferencing tty->disc_data,
 121  * because the tty layer provides no locking at all - thus one
 122  * cpu could be running ppp_asynctty_receive while another
 123  * calls ppp_asynctty_close, which zeroes tty->disc_data and
 124  * frees the memory that ppp_asynctty_receive is using.  The best
 125  * way to fix this is to use a rwlock in the tty struct, but for now
 126  * we use a single global rwlock for all ttys in ppp line discipline.
 127  *
 128  * FIXME: this is no longer true. The _close path for the ldisc is
 129  * now guaranteed to be sane.
 130  */
 131 static DEFINE_RWLOCK(disc_data_lock);
 132
 133 static struct asyncppp *ap_get(struct tty_struct *tty)
 134 {
 135         struct asyncppp *ap;
 136
 137         read_lock(&disc_data_lock);
 138         ap = tty->disc_data;
 139         if (ap != NULL)
 140                 atomic_inc(&ap->refcnt);
 141         read_unlock(&disc_data_lock);
 142         return ap;
 143 }
 144
 145 static void ap_put(struct asyncppp *ap)
 146 {
 147         if (atomic_dec_and_test(&ap->refcnt))
 148                 up(&ap->dead_sem);
 149 }
 150
 151 /*
 152  * Called when a tty is put into PPP line discipline. Called in process
 153  * context.
 154  */
 155 static int
 156 ppp_asynctty_open(struct tty_struct *tty)
 157 {
 158         struct asyncppp *ap;
 159         int err;
 160
 161         err = -ENOMEM;
 162         ap = kmalloc(sizeof(*ap), GFP_KERNEL);
 163         if (ap == 0)
 164                 goto out;
 165
 166         /* initialize the asyncppp structure */
 167         memset(ap, 0, sizeof(*ap));
 168         ap->tty = tty;
 169         ap->mru = PPP_MRU;
 170         spin_lock_init(&ap->xmit_lock);
 171         spin_lock_init(&ap->recv_lock);
 172         ap->xaccm[0] = ~0U;
 173         ap->xaccm[3] = 0x60000000U;
 174         ap->raccm = ~0U;
 175         ap->optr = ap->obuf;
 176         ap->olim = ap->obuf;
 177         ap->lcp_fcs = -1;
 178
 179         skb_queue_head_init(&ap->rqueue);
 180         tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
 181
 182         atomic_set(&ap->refcnt, 1);
 183         init_MUTEX_LOCKED(&ap->dead_sem);
 184
 185         ap->chan.private = ap;
 186         ap->chan.ops = &async_ops;
 187         ap->chan.mtu = PPP_MRU;
 188         err = ppp_register_channel(&ap->chan);
 189         if (err)
 190                 goto out_free;
 191
 192         tty->disc_data = ap;
 193         tty->receive_room = 65536;
 194         return 0;
 195
 196  out_free:
 197         kfree(ap);
 198  out:
 199         return err;
 200 }
 201
 202 /*
 203  * Called when the tty is put into another line discipline
 204  * or it hangs up.  We have to wait for any cpu currently
 205  * executing in any of the other ppp_asynctty_* routines to
 206  * finish before we can call ppp_unregister_channel and free
 207  * the asyncppp struct.  This routine must be called from
 208  * process context, not interrupt or softirq context.
 209  */
 210 static void
 211 ppp_asynctty_close(struct tty_struct *tty)
 212 {
 213         struct asyncppp *ap;
 214
 215         write_lock_irq(&disc_data_lock);
 216         ap = tty->disc_data;
 217         tty->disc_data = NULL;
 218         write_unlock_irq(&disc_data_lock);
 219         if (ap == 0)
 220                 return;
 221
 222         /*
 223          * We have now ensured that nobody can start using ap from now
 224          * on, but we have to wait for all existing users to finish.
 225          * Note that ppp_unregister_channel ensures that no calls to
 226          * our channel ops (i.e. ppp_async_send/ioctl) are in progress
 227          * by the time it returns.
 228          */
 229         if (!atomic_dec_and_test(&ap->refcnt))
 230                 down(&ap->dead_sem);
 231         tasklet_kill(&ap->tsk);
 232
 233         ppp_unregister_channel(&ap->chan);
 234         if (ap->rpkt != 0)
 235                 kfree_skb(ap->rpkt);
 236         skb_queue_purge(&ap->rqueue);
 237         if (ap->tpkt != 0)
 238                 kfree_skb(ap->tpkt);
 239         kfree(ap);
 240 }
 241
 242 /*
 243  * Called on tty hangup in process context.
 244  *
 245  * Wait for I/O to driver to complete and unregister PPP channel.
 246  * This is already done by the close routine, so just call that.
 247  */
 248 static int ppp_asynctty_hangup(struct tty_struct *tty)
 249 {
 250         ppp_asynctty_close(tty);
 251         return 0;
 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
 259 ppp_asynctty_read(struct tty_struct *tty, struct file *file,
 260                   unsigned char __user *buf, size_t count)
 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
 270 ppp_asynctty_write(struct tty_struct *tty, struct file *file,
 271                    const unsigned char *buf, 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
 282 ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
 283                    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 == 0)
 290                 return -ENXIO;
 291         err = -EFAULT;
 292         switch (cmd) {
 293         case PPPIOCGCHAN:
 294                 err = -ENXIO;
 295                 if (ap == 0)
 296                         break;
 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 = -ENXIO;
 305                 if (ap == 0)
 306                         break;
 307                 err = -EFAULT;
 308                 if (put_user(ppp_unit_number(&ap->chan), p))
 309                         break;
 310                 err = 0;
 311                 break;
 312
 313         case TCGETS:
 314         case TCGETA:
 315                 err = n_tty_ioctl(tty, file, cmd, arg);
 316                 break;
 317
 318         case TCFLSH:
 319                 /* flush our buffers and the serial port's buffer */
 320                 if (arg == TCIOFLUSH || arg == TCOFLUSH)
 321                         ppp_async_flush_output(ap);
 322                 err = n_tty_ioctl(tty, file, cmd, arg);
 323                 break;
 324
 325         case FIONREAD:
 326                 val = 0;
 327                 if (put_user(val, p))
 328                         break;
 329                 err = 0;
 330                 break;
 331
 332         default:
 333                 err = -ENOIOCTLCMD;
 334         }
 335
 336         ap_put(ap);
 337         return err;
 338 }
 339
 340 /* No kernel lock - fine */
 341 static unsigned int
 342 ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
 343 {
 344         return 0;
 345 }
 346
 347 /*
 348  * This can now be called from hard interrupt level as well
 349  * as soft interrupt level or mainline.
 350  */
 351 static void
 352 ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
 353                   char *cflags, int count)
 354 {
 355         struct asyncppp *ap = ap_get(tty);
 356         unsigned long flags;
 357
 358         if (ap == 0)
 359                 return;
 360         spin_lock_irqsave(&ap->recv_lock, flags);
 361         ppp_async_input(ap, buf, cflags, count);
 362         spin_unlock_irqrestore(&ap->recv_lock, flags);
 363         if (!skb_queue_empty(&ap->rqueue))
 364                 tasklet_schedule(&ap->tsk);
 365         ap_put(ap);
 366         if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
 367             && tty->driver->unthrottle)
 368                 tty->driver->unthrottle(tty);
 369 }
 370
 371 static void
 372 ppp_asynctty_wakeup(struct tty_struct *tty)
 373 {
 374         struct asyncppp *ap = ap_get(tty);
 375
 376         clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 377         if (ap == 0)
 378                 return;
 379         set_bit(XMIT_WAKEUP, &ap->xmit_flags);
 380         tasklet_schedule(&ap->tsk);
 381         ap_put(ap);
 382 }
 383
 384
 385 static struct tty_ldisc ppp_ldisc = {
 386         .owner  = THIS_MODULE,
 387         .magic  = TTY_LDISC_MAGIC,
 388         .name   = "ppp",
 389         .open   = ppp_asynctty_open,
 390         .close  = ppp_asynctty_close,
 391         .hangup = ppp_asynctty_hangup,
 392         .read   = ppp_asynctty_read,
 393         .write  = ppp_asynctty_write,
 394         .ioctl  = ppp_asynctty_ioctl,
 395         .poll   = ppp_asynctty_poll,
 396         .receive_buf = ppp_asynctty_receive,
 397         .write_wakeup = ppp_asynctty_wakeup,
 398 };
 399
 400 static int __init
 401 ppp_async_init(void)
 402 {
 403         int err;
 404
 405         err = tty_register_ldisc(N_PPP, &ppp_ldisc);
 406         if (err != 0)
 407                 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
 408                        err);
 409         return err;
 410 }
 411
 412 /*
 413  * The following routines provide the PPP channel interface.
 414  */
 415 static int
 416 ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
 417 {
 418         struct asyncppp *ap = chan->private;
 419         void __user *argp = (void __user *)arg;
 420         int __user *p = argp;
 421         int err, val;
 422         u32 accm[8];
 423
 424         err = -EFAULT;
 425         switch (cmd) {
 426         case PPPIOCGFLAGS:
 427                 val = ap->flags | ap->rbits;
 428                 if (put_user(val, p))
 429                         break;
 430                 err = 0;
 431                 break;
 432         case PPPIOCSFLAGS:
 433                 if (get_user(val, p))
 434                         break;
 435                 ap->flags = val & ~SC_RCV_BITS;
 436                 spin_lock_irq(&ap->recv_lock);
 437                 ap->rbits = val & SC_RCV_BITS;
 438                 spin_unlock_irq(&ap->recv_lock);
 439                 err = 0;
 440                 break;
 441
 442         case PPPIOCGASYNCMAP:
 443                 if (put_user(ap->xaccm[0], (u32 __user *)argp))
 444                         break;
 445                 err = 0;
 446                 break;
 447         case PPPIOCSASYNCMAP:
 448                 if (get_user(ap->xaccm[0], (u32 __user *)argp))
 449                         break;
 450                 err = 0;
 451                 break;
 452
 453         case PPPIOCGRASYNCMAP:
 454                 if (put_user(ap->raccm, (u32 __user *)argp))
 455                         break;
 456                 err = 0;
 457                 break;
 458         case PPPIOCSRASYNCMAP:
 459                 if (get_user(ap->raccm, (u32 __user *)argp))
 460                         break;
 461                 err = 0;
 462                 break;
 463
 464         case PPPIOCGXASYNCMAP:
 465                 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
 466                         break;
 467                 err = 0;
 468                 break;
 469         case PPPIOCSXASYNCMAP:
 470                 if (copy_from_user(accm, argp, sizeof(accm)))
 471                         break;
 472                 accm[2] &= ~0x40000000U;        /* can't escape 0x5e */
 473                 accm[3] |= 0x60000000U;         /* must escape 0x7d, 0x7e */
 474                 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
 475                 err = 0;
 476                 break;
 477
 478         case PPPIOCGMRU:
 479                 if (put_user(ap->mru, p))
 480                         break;
 481                 err = 0;
 482                 break;
 483         case PPPIOCSMRU:
 484                 if (get_user(val, p))
 485                         break;
 486                 if (val < PPP_MRU)
 487                         val = PPP_MRU;
 488                 ap->mru = val;
 489                 err = 0;
 490                 break;
 491
 492         default:
 493                 err = -ENOTTY;
 494         }
 495
 496         return err;
 497 }
 498
 499 /*
 500  * This is called at softirq level to deliver received packets
 501  * to the ppp_generic code, and to tell the ppp_generic code
 502  * if we can accept more output now.
 503  */
 504 static void ppp_async_process(unsigned long arg)
 505 {
 506         struct asyncppp *ap = (struct asyncppp *) arg;
 507         struct sk_buff *skb;
 508
 509         /* process received packets */
 510         while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
 511                 if (skb->cb[0])
 512                         ppp_input_error(&ap->chan, 0);
 513                 ppp_input(&ap->chan, skb);
 514         }
 515
 516         /* try to push more stuff out */
 517         if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
 518                 ppp_output_wakeup(&ap->chan);
 519 }
 520
 521 /*
 522  * Procedures for encapsulation and framing.
 523  */
 524
 525 /*
 526  * Procedure to encode the data for async serial transmission.
 527  * Does octet stuffing (escaping), puts the address/control bytes
 528  * on if A/C compression is disabled, and does protocol compression.
 529  * Assumes ap->tpkt != 0 on entry.
 530  * Returns 1 if we finished the current frame, 0 otherwise.
 531  */
 532
 533 #define PUT_BYTE(ap, buf, c, islcp)     do {            \
 534         if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
 535                 *buf++ = PPP_ESCAPE;                    \
 536                 *buf++ = c ^ 0x20;                      \
 537         } else                                          \
 538                 *buf++ = c;                             \
 539 } while (0)
 540
 541 static int
 542 ppp_async_encode(struct asyncppp *ap)
 543 {
 544         int fcs, i, count, c, proto;
 545         unsigned char *buf, *buflim;
 546         unsigned char *data;
 547         int islcp;
 548
 549         buf = ap->obuf;
 550         ap->olim = buf;
 551         ap->optr = buf;
 552         i = ap->tpkt_pos;
 553         data = ap->tpkt->data;
 554         count = ap->tpkt->len;
 555         fcs = ap->tfcs;
 556         proto = (data[0] << 8) + data[1];
 557
 558         /*
 559          * LCP packets with code values between 1 (configure-reqest)
 560          * and 7 (code-reject) must be sent as though no options
 561          * had been negotiated.
 562          */
 563         islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
 564
 565         if (i == 0) {
 566                 if (islcp)
 567                         async_lcp_peek(ap, data, count, 0);
 568
 569                 /*
 570                  * Start of a new packet - insert the leading FLAG
 571                  * character if necessary.
 572                  */
 573                 if (islcp || flag_time == 0
 574                     || time_after_eq(jiffies, ap->last_xmit + flag_time))
 575                         *buf++ = PPP_FLAG;
 576                 ap->last_xmit = jiffies;
 577                 fcs = PPP_INITFCS;
 578
 579                 /*
 580                  * Put in the address/control bytes if necessary
 581                  */
 582                 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
 583                         PUT_BYTE(ap, buf, 0xff, islcp);
 584                         fcs = PPP_FCS(fcs, 0xff);
 585                         PUT_BYTE(ap, buf, 0x03, islcp);
 586                         fcs = PPP_FCS(fcs, 0x03);
 587                 }
 588         }
 589
 590         /*
 591          * Once we put in the last byte, we need to put in the FCS
 592          * and closing flag, so make sure there is at least 7 bytes
 593          * of free space in the output buffer.
 594          */
 595         buflim = ap->obuf + OBUFSIZE - 6;
 596         while (i < count && buf < buflim) {
 597                 c = data[i++];
 598                 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
 599                         continue;       /* compress protocol field */
 600                 fcs = PPP_FCS(fcs, c);
 601                 PUT_BYTE(ap, buf, c, islcp);
 602         }
 603
 604         if (i < count) {
 605                 /*
 606                  * Remember where we are up to in this packet.
 607                  */
 608                 ap->olim = buf;
 609                 ap->tpkt_pos = i;
 610                 ap->tfcs = fcs;
 611                 return 0;
 612         }
 613
 614         /*
 615          * We have finished the packet.  Add the FCS and flag.
 616          */
 617         fcs = ~fcs;
 618         c = fcs & 0xff;
 619         PUT_BYTE(ap, buf, c, islcp);
 620         c = (fcs >> 8) & 0xff;
 621         PUT_BYTE(ap, buf, c, islcp);
 622         *buf++ = PPP_FLAG;
 623         ap->olim = buf;
 624
 625         kfree_skb(ap->tpkt);
 626         ap->tpkt = NULL;
 627         return 1;
 628 }
 629
 630 /*
 631  * Transmit-side routines.
 632  */
 633
 634 /*
 635  * Send a packet to the peer over an async tty line.
 636  * Returns 1 iff the packet was accepted.
 637  * If the packet was not accepted, we will call ppp_output_wakeup
 638  * at some later time.
 639  */
 640 static int
 641 ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
 642 {
 643         struct asyncppp *ap = chan->private;
 644
 645         ppp_async_push(ap);
 646
 647         if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
 648                 return 0;       /* already full */
 649         ap->tpkt = skb;
 650         ap->tpkt_pos = 0;
 651
 652         ppp_async_push(ap);
 653         return 1;
 654 }
 655
 656 /*
 657  * Push as much data as possible out to the tty.
 658  */
 659 static int
 660 ppp_async_push(struct asyncppp *ap)
 661 {
 662         int avail, sent, done = 0;
 663         struct tty_struct *tty = ap->tty;
 664         int tty_stuffed = 0;
 665
 666         /*
 667          * We can get called recursively here if the tty write
 668          * function calls our wakeup function.  This can happen
 669          * for example on a pty with both the master and slave
 670          * set to PPP line discipline.
 671          * We use the XMIT_BUSY bit to detect this and get out,
 672          * leaving the XMIT_WAKEUP bit set to tell the other
 673          * instance that it may now be able to write more now.
 674          */
 675         if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
 676                 return 0;
 677         spin_lock_bh(&ap->xmit_lock);
 678         for (;;) {
 679                 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
 680                         tty_stuffed = 0;
 681                 if (!tty_stuffed && ap->optr < ap->olim) {
 682                         avail = ap->olim - ap->optr;
 683                         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 684                         sent = tty->driver->write(tty, ap->optr, avail);
 685                         if (sent < 0)
 686                                 goto flush;     /* error, e.g. loss of CD */
 687                         ap->optr += sent;
 688                         if (sent < avail)
 689                                 tty_stuffed = 1;
 690                         continue;
 691                 }
 692                 if (ap->optr >= ap->olim && ap->tpkt != 0) {
 693                         if (ppp_async_encode(ap)) {
 694                                 /* finished processing ap->tpkt */
 695                                 clear_bit(XMIT_FULL, &ap->xmit_flags);
 696                                 done = 1;
 697                         }
 698                         continue;
 699                 }
 700                 /*
 701                  * We haven't made any progress this time around.
 702                  * Clear XMIT_BUSY to let other callers in, but
 703                  * after doing so we have to check if anyone set
 704                  * XMIT_WAKEUP since we last checked it.  If they
 705                  * did, we should try again to set XMIT_BUSY and go
 706                  * around again in case XMIT_BUSY was still set when
 707                  * the other caller tried.
 708                  */
 709                 clear_bit(XMIT_BUSY, &ap->xmit_flags);
 710                 /* any more work to do? if not, exit the loop */
 711                 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags)
 712                       || (!tty_stuffed && ap->tpkt != 0)))
 713                         break;
 714                 /* more work to do, see if we can do it now */
 715                 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
 716                         break;
 717         }
 718         spin_unlock_bh(&ap->xmit_lock);
 719         return done;
 720
 721 flush:
 722         clear_bit(XMIT_BUSY, &ap->xmit_flags);
 723         if (ap->tpkt != 0) {
 724                 kfree_skb(ap->tpkt);
 725                 ap->tpkt = NULL;
 726                 clear_bit(XMIT_FULL, &ap->xmit_flags);
 727                 done = 1;
 728         }
 729         ap->optr = ap->olim;
 730         spin_unlock_bh(&ap->xmit_lock);
 731         return done;
 732 }
 733
 734 /*
 735  * Flush output from our internal buffers.
 736  * Called for the TCFLSH ioctl. Can be entered in parallel
 737  * but this is covered by the xmit_lock.
 738  */
 739 static void
 740 ppp_async_flush_output(struct asyncppp *ap)
 741 {
 742         int done = 0;
 743
 744         spin_lock_bh(&ap->xmit_lock);
 745         ap->optr = ap->olim;
 746         if (ap->tpkt != NULL) {
 747                 kfree_skb(ap->tpkt);
 748                 ap->tpkt = NULL;
 749                 clear_bit(XMIT_FULL, &ap->xmit_flags);
 750                 done = 1;
 751         }
 752         spin_unlock_bh(&ap->xmit_lock);
 753         if (done)
 754                 ppp_output_wakeup(&ap->chan);
 755 }
 756
 757 /*
 758  * Receive-side routines.
 759  */
 760
 761 /* see how many ordinary chars there are at the start of buf */
 762 static inline int
 763 scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
 764 {
 765         int i, c;
 766
 767         for (i = 0; i < count; ++i) {
 768                 c = buf[i];
 769                 if (c == PPP_ESCAPE || c == PPP_FLAG
 770                     || (c < 0x20 && (ap->raccm & (1 << c)) != 0))
 771                         break;
 772         }
 773         return i;
 774 }
 775
 776 /* called when a flag is seen - do end-of-packet processing */
 777 static void
 778 process_input_packet(struct asyncppp *ap)
 779 {
 780         struct sk_buff *skb;
 781         unsigned char *p;
 782         unsigned int len, fcs, proto;
 783
 784         skb = ap->rpkt;
 785         if (ap->state & (SC_TOSS | SC_ESCAPE))
 786                 goto err;
 787
 788         if (skb == NULL)
 789                 return;         /* 0-length packet */
 790
 791         /* check the FCS */
 792         p = skb->data;
 793         len = skb->len;
 794         if (len < 3)
 795                 goto err;       /* too short */
 796         fcs = PPP_INITFCS;
 797         for (; len > 0; --len)
 798                 fcs = PPP_FCS(fcs, *p++);
 799         if (fcs != PPP_GOODFCS)
 800                 goto err;       /* bad FCS */
 801         skb_trim(skb, skb->len - 2);
 802
 803         /* check for address/control and protocol compression */
 804         p = skb->data;
 805         if (p[0] == PPP_ALLSTATIONS) {
 806                 /* chop off address/control */
 807                 if (p[1] != PPP_UI || skb->len < 3)
 808                         goto err;
 809                 p = skb_pull(skb, 2);
 810         }
 811         proto = p[0];
 812         if (proto & 1) {
 813                 /* protocol is compressed */
 814                 skb_push(skb, 1)[0] = 0;
 815         } else {
 816                 if (skb->len < 2)
 817                         goto err;
 818                 proto = (proto << 8) + p[1];
 819                 if (proto == PPP_LCP)
 820                         async_lcp_peek(ap, p, skb->len, 1);
 821         }
 822
 823         /* queue the frame to be processed */
 824         skb->cb[0] = ap->state;
 825         skb_queue_tail(&ap->rqueue, skb);
 826         ap->rpkt = NULL;
 827         ap->state = 0;
 828         return;
 829
 830  err:
 831         /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
 832         ap->state = SC_PREV_ERROR;
 833         if (skb) {
 834                 /* make skb appear as freshly allocated */
 835                 skb_trim(skb, 0);
 836                 skb_reserve(skb, - skb_headroom(skb));
 837         }
 838 }
 839
 840 /* Called when the tty driver has data for us. Runs parallel with the
 841    other ldisc functions but will not be re-entered */
 842
 843 static void
 844 ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
 845                 char *flags, int count)
 846 {
 847         struct sk_buff *skb;
 848         int c, i, j, n, s, f;
 849         unsigned char *sp;
 850
 851         /* update bits used for 8-bit cleanness detection */
 852         if (~ap->rbits & SC_RCV_BITS) {
 853                 s = 0;
 854                 for (i = 0; i < count; ++i) {
 855                         c = buf[i];
 856                         if (flags != 0 && flags[i] != 0)
 857                                 continue;
 858                         s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
 859                         c = ((c >> 4) ^ c) & 0xf;
 860                         s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
 861                 }
 862                 ap->rbits |= s;
 863         }
 864
 865         while (count > 0) {
 866                 /* scan through and see how many chars we can do in bulk */
 867                 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
 868                         n = 1;
 869                 else
 870                         n = scan_ordinary(ap, buf, count);
 871
 872                 f = 0;
 873                 if (flags != 0 && (ap->state & SC_TOSS) == 0) {
 874                         /* check the flags to see if any char had an error */
 875                         for (j = 0; j < n; ++j)
 876                                 if ((f = flags[j]) != 0)
 877                                         break;
 878                 }
 879                 if (f != 0) {
 880                         /* start tossing */
 881                         ap->state |= SC_TOSS;
 882
 883                 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
 884                         /* stuff the chars in the skb */
 885                         skb = ap->rpkt;
 886                         if (skb == 0) {
 887                                 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
 888                                 if (skb == 0)
 889                                         goto nomem;
 890                                 ap->rpkt = skb;
 891                         }
 892                         if (skb->len == 0) {
 893                                 /* Try to get the payload 4-byte aligned.
 894                                  * This should match the
 895                                  * PPP_ALLSTATIONS/PPP_UI/compressed tests in
 896                                  * process_input_packet, but we do not have
 897                                  * enough chars here to test buf[1] and buf[2].
 898                                  */
 899                                 if (buf[0] != PPP_ALLSTATIONS)
 900                                         skb_reserve(skb, 2 + (buf[0] & 1));
 901                         }
 902                         if (n > skb_tailroom(skb)) {
 903                                 /* packet overflowed MRU */
 904                                 ap->state |= SC_TOSS;
 905                         } else {
 906                                 sp = skb_put(skb, n);
 907                                 memcpy(sp, buf, n);
 908                                 if (ap->state & SC_ESCAPE) {
 909                                         sp[0] ^= 0x20;
 910                                         ap->state &= ~SC_ESCAPE;
 911                                 }
 912                         }
 913                 }
 914
 915                 if (n >= count)
 916                         break;
 917
 918                 c = buf[n];
 919                 if (flags != NULL && flags[n] != 0) {
 920                         ap->state |= SC_TOSS;
 921                 } else if (c == PPP_FLAG) {
 922                         process_input_packet(ap);
 923                 } else if (c == PPP_ESCAPE) {
 924                         ap->state |= SC_ESCAPE;
 925                 } else if (I_IXON(ap->tty)) {
 926                         if (c == START_CHAR(ap->tty))
 927                                 start_tty(ap->tty);
 928                         else if (c == STOP_CHAR(ap->tty))
 929                                 stop_tty(ap->tty);
 930                 }
 931                 /* otherwise it's a char in the recv ACCM */
 932                 ++n;
 933
 934                 buf += n;
 935                 if (flags != 0)
 936                         flags += n;
 937                 count -= n;
 938         }
 939         return;
 940
 941  nomem:
 942         printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
 943         ap->state |= SC_TOSS;
 944 }
 945
 946 /*
 947  * We look at LCP frames going past so that we can notice
 948  * and react to the LCP configure-ack from the peer.
 949  * In the situation where the peer has been sent a configure-ack
 950  * already, LCP is up once it has sent its configure-ack
 951  * so the immediately following packet can be sent with the
 952  * configured LCP options.  This allows us to process the following
 953  * packet correctly without pppd needing to respond quickly.
 954  *
 955  * We only respond to the received configure-ack if we have just
 956  * sent a configure-request, and the configure-ack contains the
 957  * same data (this is checked using a 16-bit crc of the data).
 958  */
 959 #define CONFREQ         1       /* LCP code field values */
 960 #define CONFACK         2
 961 #define LCP_MRU         1       /* LCP option numbers */
 962 #define LCP_ASYNCMAP    2
 963
 964 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
 965                            int len, int inbound)
 966 {
 967         int dlen, fcs, i, code;
 968         u32 val;
 969
 970         data += 2;              /* skip protocol bytes */
 971         len -= 2;
 972         if (len < 4)            /* 4 = code, ID, length */
 973                 return;
 974         code = data[0];
 975         if (code != CONFACK && code != CONFREQ)
 976                 return;
 977         dlen = (data[2] << 8) + data[3];
 978         if (len < dlen)
 979                 return;         /* packet got truncated or length is bogus */
 980
 981         if (code == (inbound? CONFACK: CONFREQ)) {
 982                 /*
 983                  * sent confreq or received confack:
 984                  * calculate the crc of the data from the ID field on.
 985                  */
 986                 fcs = PPP_INITFCS;
 987                 for (i = 1; i < dlen; ++i)
 988                         fcs = PPP_FCS(fcs, data[i]);
 989
 990                 if (!inbound) {
 991                         /* outbound confreq - remember the crc for later */
 992                         ap->lcp_fcs = fcs;
 993                         return;
 994                 }
 995
 996                 /* received confack, check the crc */
 997                 fcs ^= ap->lcp_fcs;
 998                 ap->lcp_fcs = -1;
 999                 if (fcs != 0)
1000                         return;
1001         } else if (inbound)
1002                 return; /* not interested in received confreq */
1003
1004         /* process the options in the confack */
1005         data += 4;
1006         dlen -= 4;
1007         /* data[0] is code, data[1] is length */
1008         while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
1009                 switch (data[0]) {
1010                 case LCP_MRU:
1011                         val = (data[2] << 8) + data[3];
1012                         if (inbound)
1013                                 ap->mru = val;
1014                         else
1015                                 ap->chan.mtu = val;
1016                         break;
1017                 case LCP_ASYNCMAP:
1018                         val = (data[2] << 24) + (data[3] << 16)
1019                                 + (data[4] << 8) + data[5];
1020                         if (inbound)
1021                                 ap->raccm = val;
1022                         else
1023                                 ap->xaccm[0] = val;
1024                         break;
1025                 }
1026                 dlen -= data[1];
1027                 data += data[1];
1028         }
1029 }
1030
1031 static void __exit ppp_async_cleanup(void)
1032 {
1033         if (tty_unregister_ldisc(N_PPP) != 0)
1034                 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1035 }
1036
1037 module_init(ppp_async_init);
1038 module_exit(ppp_async_cleanup);