drivers/net/ppp/ppp

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This source file includes following definitions.
ap_get
ap_put
ppp_asynctty_open
ppp_asynctty_close
ppp_asynctty_hangup
ppp_asynctty_read
ppp_asynctty_write
ppp_asynctty_ioctl
ppp_asynctty_poll
ppp_asynctty_receive
ppp_asynctty_wakeup
ppp_async_init
ppp_async_ioctl
ppp_async_process
ppp_async_encode
ppp_async_send
ppp_async_push
ppp_async_flush_output
scan_ordinary
process_input_packet
ppp_async_input
async_lcp_peek
ppp_async_cleanup
   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * PPP async serial channel driver for Linux.
   4  *
   5  * Copyright 1999 Paul Mackerras.
   6  *
   7  * This driver provides the encapsulation and framing for sending
   8  * and receiving PPP frames over async serial lines.  It relies on
   9  * the generic PPP layer to give it frames to send and to process
  10  * received frames.  It implements the PPP line discipline.
  11  *
  12  * Part of the code in this driver was inspired by the old async-only
  13  * PPP driver, written by Michael Callahan and Al Longyear, and
  14  * subsequently hacked by Paul Mackerras.
  15  */
  16 
  17 #include <linux/module.h>
  18 #include <linux/kernel.h>
  19 #include <linux/skbuff.h>
  20 #include <linux/tty.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/poll.h>
  23 #include <linux/crc-ccitt.h>
  24 #include <linux/ppp_defs.h>
  25 #include <linux/ppp-ioctl.h>
  26 #include <linux/ppp_channel.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/init.h>
  29 #include <linux/interrupt.h>
  30 #include <linux/jiffies.h>
  31 #include <linux/slab.h>
  32 #include <asm/unaligned.h>
  33 #include <linux/uaccess.h>
  34 #include <asm/string.h>
  35 
  36 #define PPP_VERSION     "2.4.2"
  37 
  38 #define OBUFSIZE        4096
  39 
  40 /* Structure for storing local state. */
  41 struct asyncppp {
  42         struct tty_struct *tty;
  43         unsigned int    flags;
  44         unsigned int    state;
  45         unsigned int    rbits;
  46         int             mru;
  47         spinlock_t      xmit_lock;
  48         spinlock_t      recv_lock;
  49         unsigned long   xmit_flags;
  50         u32             xaccm[8];
  51         u32             raccm;
  52         unsigned int    bytes_sent;
  53         unsigned int    bytes_rcvd;
  54 
  55         struct sk_buff  *tpkt;
  56         int             tpkt_pos;
  57         u16             tfcs;
  58         unsigned char   *optr;
  59         unsigned char   *olim;
  60         unsigned long   last_xmit;
  61 
  62         struct sk_buff  *rpkt;
  63         int             lcp_fcs;
  64         struct sk_buff_head rqueue;
  65 
  66         struct tasklet_struct tsk;
  67 
  68         refcount_t      refcnt;
  69         struct completion dead;
  70         struct ppp_channel chan;        /* interface to generic ppp layer */
  71         unsigned char   obuf[OBUFSIZE];
  72 };
  73 
  74 /* Bit numbers in xmit_flags */
  75 #define XMIT_WAKEUP     0
  76 #define XMIT_FULL       1
  77 #define XMIT_BUSY       2
  78 
  79 /* State bits */
  80 #define SC_TOSS         1
  81 #define SC_ESCAPE       2
  82 #define SC_PREV_ERROR   4
  83 
  84 /* Bits in rbits */
  85 #define SC_RCV_BITS     (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
  86 
  87 static int flag_time = HZ;
  88 module_param(flag_time, int, 0);
  89 MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
  90 MODULE_LICENSE("GPL");
  91 MODULE_ALIAS_LDISC(N_PPP);
  92 
  93 /*
  94  * Prototypes.
  95  */
  96 static int ppp_async_encode(struct asyncppp *ap);
  97 static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
  98 static int ppp_async_push(struct asyncppp *ap);
  99 static void ppp_async_flush_output(struct asyncppp *ap);
 100 static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
 101                             char *flags, int count);
 102 static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
 103                            unsigned long arg);
 104 static void ppp_async_process(unsigned long arg);
 105 
 106 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
 107                            int len, int inbound);
 108 
 109 static const struct ppp_channel_ops async_ops = {
 110         .start_xmit = ppp_async_send,
 111         .ioctl      = ppp_async_ioctl,
 112 };
 113 
 114 /*
 115  * Routines implementing the PPP line discipline.
 116  */
 117 
 118 /*
 119  * We have a potential race on dereferencing tty->disc_data,
 120  * because the tty layer provides no locking at all - thus one
 121  * cpu could be running ppp_asynctty_receive while another
 122  * calls ppp_asynctty_close, which zeroes tty->disc_data and
 123  * frees the memory that ppp_asynctty_receive is using.  The best
 124  * way to fix this is to use a rwlock in the tty struct, but for now
 125  * we use a single global rwlock for all ttys in ppp line discipline.
 126  *
 127  * FIXME: this is no longer true. The _close path for the ldisc is
 128  * now guaranteed to be sane.
 129  */
 130 static DEFINE_RWLOCK(disc_data_lock);
 131 
 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 
 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
 155 ppp_asynctty_open(struct tty_struct *tty)
 156 {
 157         struct asyncppp *ap;
 158         int err;
 159         int speed;
 160 
 161         if (tty->ops->write == NULL)
 162                 return -EOPNOTSUPP;
 163 
 164         err = -ENOMEM;
 165         ap = kzalloc(sizeof(*ap), GFP_KERNEL);
 166         if (!ap)
 167                 goto out;
 168 
 169         /* initialize the asyncppp structure */
 170         ap->tty = tty;
 171         ap->mru = PPP_MRU;
 172         spin_lock_init(&ap->xmit_lock);
 173         spin_lock_init(&ap->recv_lock);
 174         ap->xaccm[0] = ~0U;
 175         ap->xaccm[3] = 0x60000000U;
 176         ap->raccm = ~0U;
 177         ap->optr = ap->obuf;
 178         ap->olim = ap->obuf;
 179         ap->lcp_fcs = -1;
 180 
 181         skb_queue_head_init(&ap->rqueue);
 182         tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
 183 
 184         refcount_set(&ap->refcnt, 1);
 185         init_completion(&ap->dead);
 186 
 187         ap->chan.private = ap;
 188         ap->chan.ops = &async_ops;
 189         ap->chan.mtu = PPP_MRU;
 190         speed = tty_get_baud_rate(tty);
 191         ap->chan.speed = speed;
 192         err = ppp_register_channel(&ap->chan);
 193         if (err)
 194                 goto out_free;
 195 
 196         tty->disc_data = ap;
 197         tty->receive_room = 65536;
 198         return 0;
 199 
 200  out_free:
 201         kfree(ap);
 202  out:
 203         return err;
 204 }
 205 
 206 /*
 207  * Called when the tty is put into another line discipline
 208  * or it hangs up.  We have to wait for any cpu currently
 209  * executing in any of the other ppp_asynctty_* routines to
 210  * finish before we can call ppp_unregister_channel and free
 211  * the asyncppp struct.  This routine must be called from
 212  * process context, not interrupt or softirq context.
 213  */
 214 static void
 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  */
 250 static int ppp_asynctty_hangup(struct tty_struct *tty)
 251 {
 252         ppp_asynctty_close(tty);
 253         return 0;
 254 }
 255 
 256 /*
 257  * Read does nothing - no data is ever available this way.
 258  * Pppd reads and writes packets via /dev/ppp instead.
 259  */
 260 static ssize_t
 261 ppp_asynctty_read(struct tty_struct *tty, struct file *file,
 262                   unsigned char __user *buf, size_t count)
 263 {
 264         return -EAGAIN;
 265 }
 266 
 267 /*
 268  * Write on the tty does nothing, the packets all come in
 269  * from the ppp generic stuff.
 270  */
 271 static ssize_t
 272 ppp_asynctty_write(struct tty_struct *tty, struct file *file,
 273                    const unsigned char *buf, size_t count)
 274 {
 275         return -EAGAIN;
 276 }
 277 
 278 /*
 279  * Called in process context only. May be re-entered by multiple
 280  * ioctl calling threads.
 281  */
 282 
 283 static int
 284 ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
 285                    unsigned int cmd, unsigned long arg)
 286 {
 287         struct asyncppp *ap = ap_get(tty);
 288         int err, val;
 289         int __user *p = (int __user *)arg;
 290 
 291         if (!ap)
 292                 return -ENXIO;
 293         err = -EFAULT;
 294         switch (cmd) {
 295         case PPPIOCGCHAN:
 296                 err = -EFAULT;
 297                 if (put_user(ppp_channel_index(&ap->chan), p))
 298                         break;
 299                 err = 0;
 300                 break;
 301 
 302         case PPPIOCGUNIT:
 303                 err = -EFAULT;
 304                 if (put_user(ppp_unit_number(&ap->chan), p))
 305                         break;
 306                 err = 0;
 307                 break;
 308 
 309         case TCFLSH:
 310                 /* flush our buffers and the serial port's buffer */
 311                 if (arg == TCIOFLUSH || arg == TCOFLUSH)
 312                         ppp_async_flush_output(ap);
 313                 err = n_tty_ioctl_helper(tty, file, cmd, arg);
 314                 break;
 315 
 316         case FIONREAD:
 317                 val = 0;
 318                 if (put_user(val, p))
 319                         break;
 320                 err = 0;
 321                 break;
 322 
 323         default:
 324                 /* Try the various mode ioctls */
 325                 err = tty_mode_ioctl(tty, file, cmd, arg);
 326         }
 327 
 328         ap_put(ap);
 329         return err;
 330 }
 331 
 332 /* No kernel lock - fine */
 333 static __poll_t
 334 ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
 335 {
 336         return 0;
 337 }
 338 
 339 /* May sleep, don't call from interrupt level or with interrupts disabled */
 340 static void
 341 ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
 342                   char *cflags, int count)
 343 {
 344         struct asyncppp *ap = ap_get(tty);
 345         unsigned long flags;
 346 
 347         if (!ap)
 348                 return;
 349         spin_lock_irqsave(&ap->recv_lock, flags);
 350         ppp_async_input(ap, buf, cflags, count);
 351         spin_unlock_irqrestore(&ap->recv_lock, flags);
 352         if (!skb_queue_empty(&ap->rqueue))
 353                 tasklet_schedule(&ap->tsk);
 354         ap_put(ap);
 355         tty_unthrottle(tty);
 356 }
 357 
 358 static void
 359 ppp_asynctty_wakeup(struct tty_struct *tty)
 360 {
 361         struct asyncppp *ap = ap_get(tty);
 362 
 363         clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 364         if (!ap)
 365                 return;
 366         set_bit(XMIT_WAKEUP, &ap->xmit_flags);
 367         tasklet_schedule(&ap->tsk);
 368         ap_put(ap);
 369 }
 370 
 371 
 372 static struct tty_ldisc_ops ppp_ldisc = {
 373         .owner  = THIS_MODULE,
 374         .magic  = TTY_LDISC_MAGIC,
 375         .name   = "ppp",
 376         .open   = ppp_asynctty_open,
 377         .close  = ppp_asynctty_close,
 378         .hangup = ppp_asynctty_hangup,
 379         .read   = ppp_asynctty_read,
 380         .write  = ppp_asynctty_write,
 381         .ioctl  = ppp_asynctty_ioctl,
 382         .poll   = ppp_asynctty_poll,
 383         .receive_buf = ppp_asynctty_receive,
 384         .write_wakeup = ppp_asynctty_wakeup,
 385 };
 386 
 387 static int __init
 388 ppp_async_init(void)
 389 {
 390         int err;
 391 
 392         err = tty_register_ldisc(N_PPP, &ppp_ldisc);
 393         if (err != 0)
 394                 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
 395                        err);
 396         return err;
 397 }
 398 
 399 /*
 400  * The following routines provide the PPP channel interface.
 401  */
 402 static int
 403 ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
 404 {
 405         struct asyncppp *ap = chan->private;
 406         void __user *argp = (void __user *)arg;
 407         int __user *p = argp;
 408         int err, val;
 409         u32 accm[8];
 410 
 411         err = -EFAULT;
 412         switch (cmd) {
 413         case PPPIOCGFLAGS:
 414                 val = ap->flags | ap->rbits;
 415                 if (put_user(val, p))
 416                         break;
 417                 err = 0;
 418                 break;
 419         case PPPIOCSFLAGS:
 420                 if (get_user(val, p))
 421                         break;
 422                 ap->flags = val & ~SC_RCV_BITS;
 423                 spin_lock_irq(&ap->recv_lock);
 424                 ap->rbits = val & SC_RCV_BITS;
 425                 spin_unlock_irq(&ap->recv_lock);
 426                 err = 0;
 427                 break;
 428 
 429         case PPPIOCGASYNCMAP:
 430                 if (put_user(ap->xaccm[0], (u32 __user *)argp))
 431                         break;
 432                 err = 0;
 433                 break;
 434         case PPPIOCSASYNCMAP:
 435                 if (get_user(ap->xaccm[0], (u32 __user *)argp))
 436                         break;
 437                 err = 0;
 438                 break;
 439 
 440         case PPPIOCGRASYNCMAP:
 441                 if (put_user(ap->raccm, (u32 __user *)argp))
 442                         break;
 443                 err = 0;
 444                 break;
 445         case PPPIOCSRASYNCMAP:
 446                 if (get_user(ap->raccm, (u32 __user *)argp))
 447                         break;
 448                 err = 0;
 449                 break;
 450 
 451         case PPPIOCGXASYNCMAP:
 452                 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
 453                         break;
 454                 err = 0;
 455                 break;
 456         case PPPIOCSXASYNCMAP:
 457                 if (copy_from_user(accm, argp, sizeof(accm)))
 458                         break;
 459                 accm[2] &= ~0x40000000U;        /* can't escape 0x5e */
 460                 accm[3] |= 0x60000000U;         /* must escape 0x7d, 0x7e */
 461                 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
 462                 err = 0;
 463                 break;
 464 
 465         case PPPIOCGMRU:
 466                 if (put_user(ap->mru, p))
 467                         break;
 468                 err = 0;
 469                 break;
 470         case PPPIOCSMRU:
 471                 if (get_user(val, p))
 472                         break;
 473                 if (val < PPP_MRU)
 474                         val = PPP_MRU;
 475                 ap->mru = val;
 476                 err = 0;
 477                 break;
 478 
 479         default:
 480                 err = -ENOTTY;
 481         }
 482 
 483         return err;
 484 }
 485 
 486 /*
 487  * This is called at softirq level to deliver received packets
 488  * to the ppp_generic code, and to tell the ppp_generic code
 489  * if we can accept more output now.
 490  */
 491 static void ppp_async_process(unsigned long arg)
 492 {
 493         struct asyncppp *ap = (struct asyncppp *) arg;
 494         struct sk_buff *skb;
 495 
 496         /* process received packets */
 497         while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
 498                 if (skb->cb[0])
 499                         ppp_input_error(&ap->chan, 0);
 500                 ppp_input(&ap->chan, skb);
 501         }
 502 
 503         /* try to push more stuff out */
 504         if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
 505                 ppp_output_wakeup(&ap->chan);
 506 }
 507 
 508 /*
 509  * Procedures for encapsulation and framing.
 510  */
 511 
 512 /*
 513  * Procedure to encode the data for async serial transmission.
 514  * Does octet stuffing (escaping), puts the address/control bytes
 515  * on if A/C compression is disabled, and does protocol compression.
 516  * Assumes ap->tpkt != 0 on entry.
 517  * Returns 1 if we finished the current frame, 0 otherwise.
 518  */
 519 
 520 #define PUT_BYTE(ap, buf, c, islcp)     do {            \
 521         if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
 522                 *buf++ = PPP_ESCAPE;                    \
 523                 *buf++ = c ^ PPP_TRANS;                 \
 524         } else                                          \
 525                 *buf++ = c;                             \
 526 } while (0)
 527 
 528 static int
 529 ppp_async_encode(struct asyncppp *ap)
 530 {
 531         int fcs, i, count, c, proto;
 532         unsigned char *buf, *buflim;
 533         unsigned char *data;
 534         int islcp;
 535 
 536         buf = ap->obuf;
 537         ap->olim = buf;
 538         ap->optr = buf;
 539         i = ap->tpkt_pos;
 540         data = ap->tpkt->data;
 541         count = ap->tpkt->len;
 542         fcs = ap->tfcs;
 543         proto = get_unaligned_be16(data);
 544 
 545         /*
 546          * LCP packets with code values between 1 (configure-reqest)
 547          * and 7 (code-reject) must be sent as though no options
 548          * had been negotiated.
 549          */
 550         islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
 551 
 552         if (i == 0) {
 553                 if (islcp)
 554                         async_lcp_peek(ap, data, count, 0);
 555 
 556                 /*
 557                  * Start of a new packet - insert the leading FLAG
 558                  * character if necessary.
 559                  */
 560                 if (islcp || flag_time == 0 ||
 561                     time_after_eq(jiffies, ap->last_xmit + flag_time))
 562                         *buf++ = PPP_FLAG;
 563                 ap->last_xmit = jiffies;
 564                 fcs = PPP_INITFCS;
 565 
 566                 /*
 567                  * Put in the address/control bytes if necessary
 568                  */
 569                 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
 570                         PUT_BYTE(ap, buf, 0xff, islcp);
 571                         fcs = PPP_FCS(fcs, 0xff);
 572                         PUT_BYTE(ap, buf, 0x03, islcp);
 573                         fcs = PPP_FCS(fcs, 0x03);
 574                 }
 575         }
 576 
 577         /*
 578          * Once we put in the last byte, we need to put in the FCS
 579          * and closing flag, so make sure there is at least 7 bytes
 580          * of free space in the output buffer.
 581          */
 582         buflim = ap->obuf + OBUFSIZE - 6;
 583         while (i < count && buf < buflim) {
 584                 c = data[i++];
 585                 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
 586                         continue;       /* compress protocol field */
 587                 fcs = PPP_FCS(fcs, c);
 588                 PUT_BYTE(ap, buf, c, islcp);
 589         }
 590 
 591         if (i < count) {
 592                 /*
 593                  * Remember where we are up to in this packet.
 594                  */
 595                 ap->olim = buf;
 596                 ap->tpkt_pos = i;
 597                 ap->tfcs = fcs;
 598                 return 0;
 599         }
 600 
 601         /*
 602          * We have finished the packet.  Add the FCS and flag.
 603          */
 604         fcs = ~fcs;
 605         c = fcs & 0xff;
 606         PUT_BYTE(ap, buf, c, islcp);
 607         c = (fcs >> 8) & 0xff;
 608         PUT_BYTE(ap, buf, c, islcp);
 609         *buf++ = PPP_FLAG;
 610         ap->olim = buf;
 611 
 612         consume_skb(ap->tpkt);
 613         ap->tpkt = NULL;
 614         return 1;
 615 }
 616 
 617 /*
 618  * Transmit-side routines.
 619  */
 620 
 621 /*
 622  * Send a packet to the peer over an async tty line.
 623  * Returns 1 iff the packet was accepted.
 624  * If the packet was not accepted, we will call ppp_output_wakeup
 625  * at some later time.
 626  */
 627 static int
 628 ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
 629 {
 630         struct asyncppp *ap = chan->private;
 631 
 632         ppp_async_push(ap);
 633 
 634         if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
 635                 return 0;       /* already full */
 636         ap->tpkt = skb;
 637         ap->tpkt_pos = 0;
 638 
 639         ppp_async_push(ap);
 640         return 1;
 641 }
 642 
 643 /*
 644  * Push as much data as possible out to the tty.
 645  */
 646 static int
 647 ppp_async_push(struct asyncppp *ap)
 648 {
 649         int avail, sent, done = 0;
 650         struct tty_struct *tty = ap->tty;
 651         int tty_stuffed = 0;
 652 
 653         /*
 654          * We can get called recursively here if the tty write
 655          * function calls our wakeup function.  This can happen
 656          * for example on a pty with both the master and slave
 657          * set to PPP line discipline.
 658          * We use the XMIT_BUSY bit to detect this and get out,
 659          * leaving the XMIT_WAKEUP bit set to tell the other
 660          * instance that it may now be able to write more now.
 661          */
 662         if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
 663                 return 0;
 664         spin_lock_bh(&ap->xmit_lock);
 665         for (;;) {
 666                 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
 667                         tty_stuffed = 0;
 668                 if (!tty_stuffed && ap->optr < ap->olim) {
 669                         avail = ap->olim - ap->optr;
 670                         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 671                         sent = tty->ops->write(tty, ap->optr, avail);
 672                         if (sent < 0)
 673                                 goto flush;     /* error, e.g. loss of CD */
 674                         ap->optr += sent;
 675                         if (sent < avail)
 676                                 tty_stuffed = 1;
 677                         continue;
 678                 }
 679                 if (ap->optr >= ap->olim && ap->tpkt) {
 680                         if (ppp_async_encode(ap)) {
 681                                 /* finished processing ap->tpkt */
 682                                 clear_bit(XMIT_FULL, &ap->xmit_flags);
 683                                 done = 1;
 684                         }
 685                         continue;
 686                 }
 687                 /*
 688                  * We haven't made any progress this time around.
 689                  * Clear XMIT_BUSY to let other callers in, but
 690                  * after doing so we have to check if anyone set
 691                  * XMIT_WAKEUP since we last checked it.  If they
 692                  * did, we should try again to set XMIT_BUSY and go
 693                  * around again in case XMIT_BUSY was still set when
 694                  * the other caller tried.
 695                  */
 696                 clear_bit(XMIT_BUSY, &ap->xmit_flags);
 697                 /* any more work to do? if not, exit the loop */
 698                 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
 699                       (!tty_stuffed && ap->tpkt)))
 700                         break;
 701                 /* more work to do, see if we can do it now */
 702                 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
 703                         break;
 704         }
 705         spin_unlock_bh(&ap->xmit_lock);
 706         return done;
 707 
 708 flush:
 709         clear_bit(XMIT_BUSY, &ap->xmit_flags);
 710         if (ap->tpkt) {
 711                 kfree_skb(ap->tpkt);
 712                 ap->tpkt = NULL;
 713                 clear_bit(XMIT_FULL, &ap->xmit_flags);
 714                 done = 1;
 715         }
 716         ap->optr = ap->olim;
 717         spin_unlock_bh(&ap->xmit_lock);
 718         return done;
 719 }
 720 
 721 /*
 722  * Flush output from our internal buffers.
 723  * Called for the TCFLSH ioctl. Can be entered in parallel
 724  * but this is covered by the xmit_lock.
 725  */
 726 static void
 727 ppp_async_flush_output(struct asyncppp *ap)
 728 {
 729         int done = 0;
 730 
 731         spin_lock_bh(&ap->xmit_lock);
 732         ap->optr = ap->olim;
 733         if (ap->tpkt != NULL) {
 734                 kfree_skb(ap->tpkt);
 735                 ap->tpkt = NULL;
 736                 clear_bit(XMIT_FULL, &ap->xmit_flags);
 737                 done = 1;
 738         }
 739         spin_unlock_bh(&ap->xmit_lock);
 740         if (done)
 741                 ppp_output_wakeup(&ap->chan);
 742 }
 743 
 744 /*
 745  * Receive-side routines.
 746  */
 747 
 748 /* see how many ordinary chars there are at the start of buf */
 749 static inline int
 750 scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
 751 {
 752         int i, c;
 753 
 754         for (i = 0; i < count; ++i) {
 755                 c = buf[i];
 756                 if (c == PPP_ESCAPE || c == PPP_FLAG ||
 757                     (c < 0x20 && (ap->raccm & (1 << c)) != 0))
 758                         break;
 759         }
 760         return i;
 761 }
 762 
 763 /* called when a flag is seen - do end-of-packet processing */
 764 static void
 765 process_input_packet(struct asyncppp *ap)
 766 {
 767         struct sk_buff *skb;
 768         unsigned char *p;
 769         unsigned int len, fcs;
 770 
 771         skb = ap->rpkt;
 772         if (ap->state & (SC_TOSS | SC_ESCAPE))
 773                 goto err;
 774 
 775         if (skb == NULL)
 776                 return;         /* 0-length packet */
 777 
 778         /* check the FCS */
 779         p = skb->data;
 780         len = skb->len;
 781         if (len < 3)
 782                 goto err;       /* too short */
 783         fcs = PPP_INITFCS;
 784         for (; len > 0; --len)
 785                 fcs = PPP_FCS(fcs, *p++);
 786         if (fcs != PPP_GOODFCS)
 787                 goto err;       /* bad FCS */
 788         skb_trim(skb, skb->len - 2);
 789 
 790         /* check for address/control and protocol compression */
 791         p = skb->data;
 792         if (p[0] == PPP_ALLSTATIONS) {
 793                 /* chop off address/control */
 794                 if (p[1] != PPP_UI || skb->len < 3)
 795                         goto err;
 796                 p = skb_pull(skb, 2);
 797         }
 798 
 799         /* If protocol field is not compressed, it can be LCP packet */
 800         if (!(p[0] & 0x01)) {
 801                 unsigned int proto;
 802 
 803                 if (skb->len < 2)
 804                         goto err;
 805                 proto = (p[0] << 8) + p[1];
 806                 if (proto == PPP_LCP)
 807                         async_lcp_peek(ap, p, skb->len, 1);
 808         }
 809 
 810         /* queue the frame to be processed */
 811         skb->cb[0] = ap->state;
 812         skb_queue_tail(&ap->rqueue, skb);
 813         ap->rpkt = NULL;
 814         ap->state = 0;
 815         return;
 816 
 817  err:
 818         /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
 819         ap->state = SC_PREV_ERROR;
 820         if (skb) {
 821                 /* make skb appear as freshly allocated */
 822                 skb_trim(skb, 0);
 823                 skb_reserve(skb, - skb_headroom(skb));
 824         }
 825 }
 826 
 827 /* Called when the tty driver has data for us. Runs parallel with the
 828    other ldisc functions but will not be re-entered */
 829 
 830 static void
 831 ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
 832                 char *flags, int count)
 833 {
 834         struct sk_buff *skb;
 835         int c, i, j, n, s, f;
 836         unsigned char *sp;
 837 
 838         /* update bits used for 8-bit cleanness detection */
 839         if (~ap->rbits & SC_RCV_BITS) {
 840                 s = 0;
 841                 for (i = 0; i < count; ++i) {
 842                         c = buf[i];
 843                         if (flags && flags[i] != 0)
 844                                 continue;
 845                         s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
 846                         c = ((c >> 4) ^ c) & 0xf;
 847                         s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
 848                 }
 849                 ap->rbits |= s;
 850         }
 851 
 852         while (count > 0) {
 853                 /* scan through and see how many chars we can do in bulk */
 854                 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
 855                         n = 1;
 856                 else
 857                         n = scan_ordinary(ap, buf, count);
 858 
 859                 f = 0;
 860                 if (flags && (ap->state & SC_TOSS) == 0) {
 861                         /* check the flags to see if any char had an error */
 862                         for (j = 0; j < n; ++j)
 863                                 if ((f = flags[j]) != 0)
 864                                         break;
 865                 }
 866                 if (f != 0) {
 867                         /* start tossing */
 868                         ap->state |= SC_TOSS;
 869 
 870                 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
 871                         /* stuff the chars in the skb */
 872                         skb = ap->rpkt;
 873                         if (!skb) {
 874                                 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
 875                                 if (!skb)
 876                                         goto nomem;
 877                                 ap->rpkt = skb;
 878                         }
 879                         if (skb->len == 0) {
 880                                 /* Try to get the payload 4-byte aligned.
 881                                  * This should match the
 882                                  * PPP_ALLSTATIONS/PPP_UI/compressed tests in
 883                                  * process_input_packet, but we do not have
 884                                  * enough chars here to test buf[1] and buf[2].
 885                                  */
 886                                 if (buf[0] != PPP_ALLSTATIONS)
 887                                         skb_reserve(skb, 2 + (buf[0] & 1));
 888                         }
 889                         if (n > skb_tailroom(skb)) {
 890                                 /* packet overflowed MRU */
 891                                 ap->state |= SC_TOSS;
 892                         } else {
 893                                 sp = skb_put_data(skb, buf, n);
 894                                 if (ap->state & SC_ESCAPE) {
 895                                         sp[0] ^= PPP_TRANS;
 896                                         ap->state &= ~SC_ESCAPE;
 897                                 }
 898                         }
 899                 }
 900 
 901                 if (n >= count)
 902                         break;
 903 
 904                 c = buf[n];
 905                 if (flags != NULL && flags[n] != 0) {
 906                         ap->state |= SC_TOSS;
 907                 } else if (c == PPP_FLAG) {
 908                         process_input_packet(ap);
 909                 } else if (c == PPP_ESCAPE) {
 910                         ap->state |= SC_ESCAPE;
 911                 } else if (I_IXON(ap->tty)) {
 912                         if (c == START_CHAR(ap->tty))
 913                                 start_tty(ap->tty);
 914                         else if (c == STOP_CHAR(ap->tty))
 915                                 stop_tty(ap->tty);
 916                 }
 917                 /* otherwise it's a char in the recv ACCM */
 918                 ++n;
 919 
 920                 buf += n;
 921                 if (flags)
 922                         flags += n;
 923                 count -= n;
 924         }
 925         return;
 926 
 927  nomem:
 928         printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
 929         ap->state |= SC_TOSS;
 930 }
 931 
 932 /*
 933  * We look at LCP frames going past so that we can notice
 934  * and react to the LCP configure-ack from the peer.
 935  * In the situation where the peer has been sent a configure-ack
 936  * already, LCP is up once it has sent its configure-ack
 937  * so the immediately following packet can be sent with the
 938  * configured LCP options.  This allows us to process the following
 939  * packet correctly without pppd needing to respond quickly.
 940  *
 941  * We only respond to the received configure-ack if we have just
 942  * sent a configure-request, and the configure-ack contains the
 943  * same data (this is checked using a 16-bit crc of the data).
 944  */
 945 #define CONFREQ         1       /* LCP code field values */
 946 #define CONFACK         2
 947 #define LCP_MRU         1       /* LCP option numbers */
 948 #define LCP_ASYNCMAP    2
 949 
 950 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
 951                            int len, int inbound)
 952 {
 953         int dlen, fcs, i, code;
 954         u32 val;
 955 
 956         data += 2;              /* skip protocol bytes */
 957         len -= 2;
 958         if (len < 4)            /* 4 = code, ID, length */
 959                 return;
 960         code = data[0];
 961         if (code != CONFACK && code != CONFREQ)
 962                 return;
 963         dlen = get_unaligned_be16(data + 2);
 964         if (len < dlen)
 965                 return;         /* packet got truncated or length is bogus */
 966 
 967         if (code == (inbound? CONFACK: CONFREQ)) {
 968                 /*
 969                  * sent confreq or received confack:
 970                  * calculate the crc of the data from the ID field on.
 971                  */
 972                 fcs = PPP_INITFCS;
 973                 for (i = 1; i < dlen; ++i)
 974                         fcs = PPP_FCS(fcs, data[i]);
 975 
 976                 if (!inbound) {
 977                         /* outbound confreq - remember the crc for later */
 978                         ap->lcp_fcs = fcs;
 979                         return;
 980                 }
 981 
 982                 /* received confack, check the crc */
 983                 fcs ^= ap->lcp_fcs;
 984                 ap->lcp_fcs = -1;
 985                 if (fcs != 0)
 986                         return;
 987         } else if (inbound)
 988                 return; /* not interested in received confreq */
 989 
 990         /* process the options in the confack */
 991         data += 4;
 992         dlen -= 4;
 993         /* data[0] is code, data[1] is length */
 994         while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
 995                 switch (data[0]) {
 996                 case LCP_MRU:
 997                         val = get_unaligned_be16(data + 2);
 998                         if (inbound)
 999                                 ap->mru = val;
1000                         else
1001                                 ap->chan.mtu = val;
1002                         break;
1003                 case LCP_ASYNCMAP:
1004                         val = get_unaligned_be32(data + 2);
1005                         if (inbound)
1006                                 ap->raccm = val;
1007                         else
1008                                 ap->xaccm[0] = val;
1009                         break;
1010                 }
1011                 dlen -= data[1];
1012                 data += data[1];
1013         }
1014 }
1015 
1016 static void __exit ppp_async_cleanup(void)
1017 {
1018         if (tty_unregister_ldisc(N_PPP) != 0)
1019                 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1020 }
1021 
1022 module_init(ppp_async_init);
1023 module_exit(ppp_async_cleanup);
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/net/ppp/ppp_async.c

DEFINITIONS
