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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * PPP async serial channel driver for Linux.
  *
  * Copyright 1999 Paul Mackerras.
  *
  * This driver provides the encapsulation and framing for sending
  * and receiving PPP frames over async serial lines.  It relies on
  * the generic PPP layer to give it frames to send and to process
  * received frames.  It implements the PPP line discipline.
  *
  * Part of the code in this driver was inspired by the old async-only
  * PPP driver, written by Michael Callahan and Al Longyear, and
  * subsequently hacked by Paul Mackerras.
  */
 
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/skbuff.h>
 #include <linux/tty.h>
 #include <linux/netdevice.h>
 #include <linux/poll.h>
 #include <linux/crc-ccitt.h>
 #include <linux/ppp_defs.h>
 #include <linux/ppp-ioctl.h>
 #include <linux/ppp_channel.h>
 #include <linux/spinlock.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/jiffies.h>
 #include <linux/slab.h>
 #include <asm/unaligned.h>
 #include <linux/uaccess.h>
 #include <asm/string.h>
 
 #define PPP_VERSION "2.4.2"
 
 #define OBUFSIZE    4096
 
 /* Structure for storing local state. */
 struct asyncppp {
     struct tty_struct *tty;
     unsigned int    flags;
     unsigned int    state;
     unsigned int    rbits;
     int     mru;
     spinlock_t  xmit_lock;
     spinlock_t  recv_lock;
     unsigned long   xmit_flags;
     u32     xaccm[8];
     u32     raccm;
     unsigned int    bytes_sent;
     unsigned int    bytes_rcvd;
 
     struct sk_buff  *tpkt;
     int     tpkt_pos;
     u16     tfcs;
     unsigned char   *optr;
     unsigned char   *olim;
     unsigned long   last_xmit;
 
     struct sk_buff  *rpkt;
     int     lcp_fcs;
     struct sk_buff_head rqueue;
 
     struct tasklet_struct tsk;
 
     refcount_t  refcnt;
     struct completion dead;
     struct ppp_channel chan;    /* interface to generic ppp layer */
     unsigned char   obuf[OBUFSIZE];
 };
 
 /* Bit numbers in xmit_flags */
 #define XMIT_WAKEUP 0
 #define XMIT_FULL   1
 #define XMIT_BUSY   2
 
 /* State bits */
 #define SC_TOSS     1
 #define SC_ESCAPE   2
 #define SC_PREV_ERROR   4
 
 /* Bits in rbits */
 #define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
 
 static int flag_time = HZ;
 module_param(flag_time, int, 0);
 MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_LDISC(N_PPP);
 
 /*
  * Prototypes.
  */
 static int ppp_async_encode(struct asyncppp *ap);
 static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
 static int ppp_async_push(struct asyncppp *ap);
 static void ppp_async_flush_output(struct asyncppp *ap);
 static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
                 const char *flags, int count);
 static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
                unsigned long arg);
 static void ppp_async_process(struct tasklet_struct *t);
 
 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
                int len, int inbound);
 
 static const struct ppp_channel_ops async_ops = {
     .start_xmit = ppp_async_send,
     .ioctl      = ppp_async_ioctl,
 };
 
 /*
  * Routines implementing the PPP line discipline.
  */
 
 /*
  * We have a potential race on dereferencing tty->disc_data,
  * because the tty layer provides no locking at all - thus one
  * cpu could be running ppp_asynctty_receive while another
  * calls ppp_asynctty_close, which zeroes tty->disc_data and
  * frees the memory that ppp_asynctty_receive is using.  The best
  * way to fix this is to use a rwlock in the tty struct, but for now
  * we use a single global rwlock for all ttys in ppp line discipline.
  *
  * FIXME: this is no longer true. The _close path for the ldisc is
  * now guaranteed to be sane.
  */
 static DEFINE_RWLOCK(disc_data_lock);
 
 static struct asyncppp *ap_get(struct tty_struct *tty)
 {
     struct asyncppp *ap;
 
     read_lock(&disc_data_lock);
     ap = tty->disc_data;
     if (ap != NULL)
         refcount_inc(&ap->refcnt);
     read_unlock(&disc_data_lock);
     return ap;
 }
 
 static void ap_put(struct asyncppp *ap)
 {
     if (refcount_dec_and_test(&ap->refcnt))
         complete(&ap->dead);
 }
 
 /*
  * Called when a tty is put into PPP line discipline. Called in process
  * context.
  */
 static int
 ppp_asynctty_open(struct tty_struct *tty)
 {
     struct asyncppp *ap;
     int err;
     int speed;
 
     if (tty->ops->write == NULL)
         return -EOPNOTSUPP;
 
     err = -ENOMEM;
     ap = kzalloc(sizeof(*ap), GFP_KERNEL);
     if (!ap)
         goto out;
 
     /* initialize the asyncppp structure */
     ap->tty = tty;
     ap->mru = PPP_MRU;
     spin_lock_init(&ap->xmit_lock);
     spin_lock_init(&ap->recv_lock);
     ap->xaccm[0] = ~0U;
     ap->xaccm[3] = 0x60000000U;
     ap->raccm = ~0U;
     ap->optr = ap->obuf;
     ap->olim = ap->obuf;
     ap->lcp_fcs = -1;
 
     skb_queue_head_init(&ap->rqueue);
     tasklet_setup(&ap->tsk, ppp_async_process);
 
     refcount_set(&ap->refcnt, 1);
     init_completion(&ap->dead);
 
     ap->chan.private = ap;
     ap->chan.ops = &async_ops;
     ap->chan.mtu = PPP_MRU;
     speed = tty_get_baud_rate(tty);
     ap->chan.speed = speed;
     err = ppp_register_channel(&ap->chan);
     if (err)
         goto out_free;
 
     tty->disc_data = ap;
     tty->receive_room = 65536;
     return 0;
 
  out_free:
     kfree(ap);
  out:
     return err;
 }
 
 /*
  * Called when the tty is put into another line discipline
  * or it hangs up.  We have to wait for any cpu currently
  * executing in any of the other ppp_asynctty_* routines to
  * finish before we can call ppp_unregister_channel and free
  * the asyncppp struct.  This routine must be called from
  * process context, not interrupt or softirq context.
  */
 static void
 ppp_asynctty_close(struct tty_struct *tty)
 {
     struct asyncppp *ap;
 
     write_lock_irq(&disc_data_lock);
     ap = tty->disc_data;
     tty->disc_data = NULL;
     write_unlock_irq(&disc_data_lock);
     if (!ap)
         return;
 
     /*
      * We have now ensured that nobody can start using ap from now
      * on, but we have to wait for all existing users to finish.
      * Note that ppp_unregister_channel ensures that no calls to
      * our channel ops (i.e. ppp_async_send/ioctl) are in progress
      * by the time it returns.
      */
     if (!refcount_dec_and_test(&ap->refcnt))
         wait_for_completion(&ap->dead);
     tasklet_kill(&ap->tsk);
 
     ppp_unregister_channel(&ap->chan);
     kfree_skb(ap->rpkt);
     skb_queue_purge(&ap->rqueue);
     kfree_skb(ap->tpkt);
     kfree(ap);
 }
 
 /*
  * Called on tty hangup in process context.
  *
  * Wait for I/O to driver to complete and unregister PPP channel.
  * This is already done by the close routine, so just call that.
  */
 static void ppp_asynctty_hangup(struct tty_struct *tty)
 {
     ppp_asynctty_close(tty);
 }
 
 /*
  * Read does nothing - no data is ever available this way.
  * Pppd reads and writes packets via /dev/ppp instead.
  */
 static ssize_t
 ppp_asynctty_read(struct tty_struct *tty, struct file *file,
           unsigned char *buf, size_t count,
           void **cookie, unsigned long offset)
 {
     return -EAGAIN;
 }
 
 /*
  * Write on the tty does nothing, the packets all come in
  * from the ppp generic stuff.
  */
 static ssize_t
 ppp_asynctty_write(struct tty_struct *tty, struct file *file,
            const unsigned char *buf, size_t count)
 {
     return -EAGAIN;
 }
 
 /*
  * Called in process context only. May be re-entered by multiple
  * ioctl calling threads.
  */
 
 static int
 ppp_asynctty_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 {
     struct asyncppp *ap = ap_get(tty);
     int err, val;
     int __user *p = (int __user *)arg;
 
     if (!ap)
         return -ENXIO;
     err = -EFAULT;
     switch (cmd) {
     case PPPIOCGCHAN:
         err = -EFAULT;
         if (put_user(ppp_channel_index(&ap->chan), p))
             break;
         err = 0;
         break;
 
     case PPPIOCGUNIT:
         err = -EFAULT;
         if (put_user(ppp_unit_number(&ap->chan), p))
             break;
         err = 0;
         break;
 
     case TCFLSH:
         /* flush our buffers and the serial port's buffer */
         if (arg == TCIOFLUSH || arg == TCOFLUSH)
             ppp_async_flush_output(ap);
         err = n_tty_ioctl_helper(tty, cmd, arg);
         break;
 
     case FIONREAD:
         val = 0;
         if (put_user(val, p))
             break;
         err = 0;
         break;
 
     default:
         /* Try the various mode ioctls */
         err = tty_mode_ioctl(tty, cmd, arg);
     }
 
     ap_put(ap);
     return err;
 }
 
 /* No kernel lock - fine */
 static __poll_t
 ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
 {
     return 0;
 }
 
 /* May sleep, don't call from interrupt level or with interrupts disabled */
 static void
 ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
           const char *cflags, int count)
 {
     struct asyncppp *ap = ap_get(tty);
     unsigned long flags;
 
     if (!ap)
         return;
     spin_lock_irqsave(&ap->recv_lock, flags);
     ppp_async_input(ap, buf, cflags, count);
     spin_unlock_irqrestore(&ap->recv_lock, flags);
     if (!skb_queue_empty(&ap->rqueue))
         tasklet_schedule(&ap->tsk);
     ap_put(ap);
     tty_unthrottle(tty);
 }
 
 static void
 ppp_asynctty_wakeup(struct tty_struct *tty)
 {
     struct asyncppp *ap = ap_get(tty);
 
     clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
     if (!ap)
         return;
     set_bit(XMIT_WAKEUP, &ap->xmit_flags);
     tasklet_schedule(&ap->tsk);
     ap_put(ap);
 }
 
 
 static struct tty_ldisc_ops ppp_ldisc = {
     .owner  = THIS_MODULE,
     .num    = N_PPP,
     .name   = "ppp",
     .open   = ppp_asynctty_open,
     .close  = ppp_asynctty_close,
     .hangup = ppp_asynctty_hangup,
     .read   = ppp_asynctty_read,
     .write  = ppp_asynctty_write,
     .ioctl  = ppp_asynctty_ioctl,
     .poll   = ppp_asynctty_poll,
     .receive_buf = ppp_asynctty_receive,
     .write_wakeup = ppp_asynctty_wakeup,
 };
 
 static int __init
 ppp_async_init(void)
 {
     int err;
 
     err = tty_register_ldisc(&ppp_ldisc);
     if (err != 0)
         printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
                err);
     return err;
 }
 
 /*
  * The following routines provide the PPP channel interface.
  */
 static int
 ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
 {
     struct asyncppp *ap = chan->private;
     void __user *argp = (void __user *)arg;
     int __user *p = argp;
     int err, val;
     u32 accm[8];
 
     err = -EFAULT;
     switch (cmd) {
     case PPPIOCGFLAGS:
         val = ap->flags | ap->rbits;
         if (put_user(val, p))
             break;
         err = 0;
         break;
     case PPPIOCSFLAGS:
         if (get_user(val, p))
             break;
         ap->flags = val & ~SC_RCV_BITS;
         spin_lock_irq(&ap->recv_lock);
         ap->rbits = val & SC_RCV_BITS;
         spin_unlock_irq(&ap->recv_lock);
         err = 0;
         break;
 
     case PPPIOCGASYNCMAP:
         if (put_user(ap->xaccm[0], (u32 __user *)argp))
             break;
         err = 0;
         break;
     case PPPIOCSASYNCMAP:
         if (get_user(ap->xaccm[0], (u32 __user *)argp))
             break;
         err = 0;
         break;
 
     case PPPIOCGRASYNCMAP:
         if (put_user(ap->raccm, (u32 __user *)argp))
             break;
         err = 0;
         break;
     case PPPIOCSRASYNCMAP:
         if (get_user(ap->raccm, (u32 __user *)argp))
             break;
         err = 0;
         break;
 
     case PPPIOCGXASYNCMAP:
         if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
             break;
         err = 0;
         break;
     case PPPIOCSXASYNCMAP:
         if (copy_from_user(accm, argp, sizeof(accm)))
             break;
         accm[2] &= ~0x40000000U;    /* can't escape 0x5e */
         accm[3] |= 0x60000000U;     /* must escape 0x7d, 0x7e */
         memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
         err = 0;
         break;
 
     case PPPIOCGMRU:
         if (put_user(ap->mru, p))
             break;
         err = 0;
         break;
     case PPPIOCSMRU:
         if (get_user(val, p))
             break;
         if (val < PPP_MRU)
             val = PPP_MRU;
         ap->mru = val;
         err = 0;
         break;
 
     default:
         err = -ENOTTY;
     }
 
     return err;
 }
 
 /*
  * This is called at softirq level to deliver received packets
  * to the ppp_generic code, and to tell the ppp_generic code
  * if we can accept more output now.
  */
 static void ppp_async_process(struct tasklet_struct *t)
 {
     struct asyncppp *ap = from_tasklet(ap, t, tsk);
     struct sk_buff *skb;
 
     /* process received packets */
     while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
         if (skb->cb[0])
             ppp_input_error(&ap->chan, 0);
         ppp_input(&ap->chan, skb);
     }
 
     /* try to push more stuff out */
     if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
         ppp_output_wakeup(&ap->chan);
 }
 
 /*
  * Procedures for encapsulation and framing.
  */
 
 /*
  * Procedure to encode the data for async serial transmission.
  * Does octet stuffing (escaping), puts the address/control bytes
  * on if A/C compression is disabled, and does protocol compression.
  * Assumes ap->tpkt != 0 on entry.
  * Returns 1 if we finished the current frame, 0 otherwise.
  */
 
 #define PUT_BYTE(ap, buf, c, islcp) do {        \
     if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
         *buf++ = PPP_ESCAPE;            \
         *buf++ = c ^ PPP_TRANS;         \
     } else                      \
         *buf++ = c;             \
 } while (0)
 
 static int
 ppp_async_encode(struct asyncppp *ap)
 {
     int fcs, i, count, c, proto;
     unsigned char *buf, *buflim;
     unsigned char *data;
     int islcp;
 
     buf = ap->obuf;
     ap->olim = buf;
     ap->optr = buf;
     i = ap->tpkt_pos;
     data = ap->tpkt->data;
     count = ap->tpkt->len;
     fcs = ap->tfcs;
     proto = get_unaligned_be16(data);
 
     /*
      * LCP packets with code values between 1 (configure-reqest)
      * and 7 (code-reject) must be sent as though no options
      * had been negotiated.
      */
     islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
 
     if (i == 0) {
         if (islcp)
             async_lcp_peek(ap, data, count, 0);
 
         /*
          * Start of a new packet - insert the leading FLAG
          * character if necessary.
          */
         if (islcp || flag_time == 0 ||
             time_after_eq(jiffies, ap->last_xmit + flag_time))
             *buf++ = PPP_FLAG;
         ap->last_xmit = jiffies;
         fcs = PPP_INITFCS;
 
         /*
          * Put in the address/control bytes if necessary
          */
         if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
             PUT_BYTE(ap, buf, 0xff, islcp);
             fcs = PPP_FCS(fcs, 0xff);
             PUT_BYTE(ap, buf, 0x03, islcp);
             fcs = PPP_FCS(fcs, 0x03);
         }
     }
 
     /*
      * Once we put in the last byte, we need to put in the FCS
      * and closing flag, so make sure there is at least 7 bytes
      * of free space in the output buffer.
      */
     buflim = ap->obuf + OBUFSIZE - 6;
     while (i < count && buf < buflim) {
         c = data[i++];
         if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
             continue;   /* compress protocol field */
         fcs = PPP_FCS(fcs, c);
         PUT_BYTE(ap, buf, c, islcp);
     }
 
     if (i < count) {
         /*
          * Remember where we are up to in this packet.
          */
         ap->olim = buf;
         ap->tpkt_pos = i;
         ap->tfcs = fcs;
         return 0;
     }
 
     /*
      * We have finished the packet.  Add the FCS and flag.
      */
     fcs = ~fcs;
     c = fcs & 0xff;
     PUT_BYTE(ap, buf, c, islcp);
     c = (fcs >> 8) & 0xff;
     PUT_BYTE(ap, buf, c, islcp);
     *buf++ = PPP_FLAG;
     ap->olim = buf;
 
     consume_skb(ap->tpkt);
     ap->tpkt = NULL;
     return 1;
 }
 
 /*
  * Transmit-side routines.
  */
 
 /*
  * Send a packet to the peer over an async tty line.
  * Returns 1 iff the packet was accepted.
  * If the packet was not accepted, we will call ppp_output_wakeup
  * at some later time.
  */
 static int
 ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
 {
     struct asyncppp *ap = chan->private;
 
     ppp_async_push(ap);
 
     if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
         return 0;   /* already full */
     ap->tpkt = skb;
     ap->tpkt_pos = 0;
 
     ppp_async_push(ap);
     return 1;
 }
 
 /*
  * Push as much data as possible out to the tty.
  */
 static int
 ppp_async_push(struct asyncppp *ap)
 {
     int avail, sent, done = 0;
     struct tty_struct *tty = ap->tty;
     int tty_stuffed = 0;
 
     /*
      * We can get called recursively here if the tty write
      * function calls our wakeup function.  This can happen
      * for example on a pty with both the master and slave
      * set to PPP line discipline.
      * We use the XMIT_BUSY bit to detect this and get out,
      * leaving the XMIT_WAKEUP bit set to tell the other
      * instance that it may now be able to write more now.
      */
     if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
         return 0;
     spin_lock_bh(&ap->xmit_lock);
     for (;;) {
         if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
             tty_stuffed = 0;
         if (!tty_stuffed && ap->optr < ap->olim) {
             avail = ap->olim - ap->optr;
             set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
             sent = tty->ops->write(tty, ap->optr, avail);
             if (sent < 0)
                 goto flush; /* error, e.g. loss of CD */
             ap->optr += sent;
             if (sent < avail)
                 tty_stuffed = 1;
             continue;
         }
         if (ap->optr >= ap->olim && ap->tpkt) {
             if (ppp_async_encode(ap)) {
                 /* finished processing ap->tpkt */
                 clear_bit(XMIT_FULL, &ap->xmit_flags);
                 done = 1;
             }
             continue;
         }
         /*
          * We haven't made any progress this time around.
          * Clear XMIT_BUSY to let other callers in, but
          * after doing so we have to check if anyone set
          * XMIT_WAKEUP since we last checked it.  If they
          * did, we should try again to set XMIT_BUSY and go
          * around again in case XMIT_BUSY was still set when
          * the other caller tried.
          */
         clear_bit(XMIT_BUSY, &ap->xmit_flags);
         /* any more work to do? if not, exit the loop */
         if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
               (!tty_stuffed && ap->tpkt)))
             break;
         /* more work to do, see if we can do it now */
         if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
             break;
     }
     spin_unlock_bh(&ap->xmit_lock);
     return done;
 
 flush:
     clear_bit(XMIT_BUSY, &ap->xmit_flags);
     if (ap->tpkt) {
         kfree_skb(ap->tpkt);
         ap->tpkt = NULL;
         clear_bit(XMIT_FULL, &ap->xmit_flags);
         done = 1;
     }
     ap->optr = ap->olim;
     spin_unlock_bh(&ap->xmit_lock);
     return done;
 }
 
 /*
  * Flush output from our internal buffers.
  * Called for the TCFLSH ioctl. Can be entered in parallel
  * but this is covered by the xmit_lock.
  */
 static void
 ppp_async_flush_output(struct asyncppp *ap)
 {
     int done = 0;
 
     spin_lock_bh(&ap->xmit_lock);
     ap->optr = ap->olim;
     if (ap->tpkt != NULL) {
         kfree_skb(ap->tpkt);
         ap->tpkt = NULL;
         clear_bit(XMIT_FULL, &ap->xmit_flags);
         done = 1;
     }
     spin_unlock_bh(&ap->xmit_lock);
     if (done)
         ppp_output_wakeup(&ap->chan);
 }
 
 /*
  * Receive-side routines.
  */
 
 /* see how many ordinary chars there are at the start of buf */
 static inline int
 scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
 {
     int i, c;
 
     for (i = 0; i < count; ++i) {
         c = buf[i];
         if (c == PPP_ESCAPE || c == PPP_FLAG ||
             (c < 0x20 && (ap->raccm & (1 << c)) != 0))
             break;
     }
     return i;
 }
 
 /* called when a flag is seen - do end-of-packet processing */
 static void
 process_input_packet(struct asyncppp *ap)
 {
     struct sk_buff *skb;
     unsigned char *p;
     unsigned int len, fcs;
 
     skb = ap->rpkt;
     if (ap->state & (SC_TOSS | SC_ESCAPE))
         goto err;
 
     if (skb == NULL)
         return;     /* 0-length packet */
 
     /* check the FCS */
     p = skb->data;
     len = skb->len;
     if (len < 3)
         goto err;   /* too short */
     fcs = PPP_INITFCS;
     for (; len > 0; --len)
         fcs = PPP_FCS(fcs, *p++);
     if (fcs != PPP_GOODFCS)
         goto err;   /* bad FCS */
     skb_trim(skb, skb->len - 2);
 
     /* check for address/control and protocol compression */
     p = skb->data;
     if (p[0] == PPP_ALLSTATIONS) {
         /* chop off address/control */
         if (p[1] != PPP_UI || skb->len < 3)
             goto err;
         p = skb_pull(skb, 2);
     }
 
     /* If protocol field is not compressed, it can be LCP packet */
     if (!(p[0] & 0x01)) {
         unsigned int proto;
 
         if (skb->len < 2)
             goto err;
         proto = (p[0] << 8) + p[1];
         if (proto == PPP_LCP)
             async_lcp_peek(ap, p, skb->len, 1);
     }
 
     /* queue the frame to be processed */
     skb->cb[0] = ap->state;
     skb_queue_tail(&ap->rqueue, skb);
     ap->rpkt = NULL;
     ap->state = 0;
     return;
 
  err:
     /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
     ap->state = SC_PREV_ERROR;
     if (skb) {
         /* make skb appear as freshly allocated */
         skb_trim(skb, 0);
         skb_reserve(skb, - skb_headroom(skb));
     }
 }
 
 /* Called when the tty driver has data for us. Runs parallel with the
    other ldisc functions but will not be re-entered */
 
 static void
 ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
         const char *flags, int count)
 {
     struct sk_buff *skb;
     int c, i, j, n, s, f;
     unsigned char *sp;
 
     /* update bits used for 8-bit cleanness detection */
     if (~ap->rbits & SC_RCV_BITS) {
         s = 0;
         for (i = 0; i < count; ++i) {
             c = buf[i];
             if (flags && flags[i] != 0)
                 continue;
             s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
             c = ((c >> 4) ^ c) & 0xf;
             s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
         }
         ap->rbits |= s;
     }
 
     while (count > 0) {
         /* scan through and see how many chars we can do in bulk */
         if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
             n = 1;
         else
             n = scan_ordinary(ap, buf, count);
 
         f = 0;
         if (flags && (ap->state & SC_TOSS) == 0) {
             /* check the flags to see if any char had an error */
             for (j = 0; j < n; ++j)
                 if ((f = flags[j]) != 0)
                     break;
         }
         if (f != 0) {
             /* start tossing */
             ap->state |= SC_TOSS;
 
         } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
             /* stuff the chars in the skb */
             skb = ap->rpkt;
             if (!skb) {
                 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
                 if (!skb)
                     goto nomem;
                 ap->rpkt = skb;
             }
             if (skb->len == 0) {
                 /* Try to get the payload 4-byte aligned.
                  * This should match the
                  * PPP_ALLSTATIONS/PPP_UI/compressed tests in
                  * process_input_packet, but we do not have
                  * enough chars here to test buf[1] and buf[2].
                  */
                 if (buf[0] != PPP_ALLSTATIONS)
                     skb_reserve(skb, 2 + (buf[0] & 1));
             }
             if (n > skb_tailroom(skb)) {
                 /* packet overflowed MRU */
                 ap->state |= SC_TOSS;
             } else {
                 sp = skb_put_data(skb, buf, n);
                 if (ap->state & SC_ESCAPE) {
                     sp[0] ^= PPP_TRANS;
                     ap->state &= ~SC_ESCAPE;
                 }
             }
         }
 
         if (n >= count)
             break;
 
         c = buf[n];
         if (flags != NULL && flags[n] != 0) {
             ap->state |= SC_TOSS;
         } else if (c == PPP_FLAG) {
             process_input_packet(ap);
         } else if (c == PPP_ESCAPE) {
             ap->state |= SC_ESCAPE;
         } else if (I_IXON(ap->tty)) {
             if (c == START_CHAR(ap->tty))
                 start_tty(ap->tty);
             else if (c == STOP_CHAR(ap->tty))
                 stop_tty(ap->tty);
         }
         /* otherwise it's a char in the recv ACCM */
         ++n;
 
         buf += n;
         if (flags)
             flags += n;
         count -= n;
     }
     return;
 
  nomem:
     printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
     ap->state |= SC_TOSS;
 }
 
 /*
  * We look at LCP frames going past so that we can notice
  * and react to the LCP configure-ack from the peer.
  * In the situation where the peer has been sent a configure-ack
  * already, LCP is up once it has sent its configure-ack
  * so the immediately following packet can be sent with the
  * configured LCP options.  This allows us to process the following
  * packet correctly without pppd needing to respond quickly.
  *
  * We only respond to the received configure-ack if we have just
  * sent a configure-request, and the configure-ack contains the
  * same data (this is checked using a 16-bit crc of the data).
  */
 #define CONFREQ     1   /* LCP code field values */
 #define CONFACK     2
 #define LCP_MRU     1   /* LCP option numbers */
 #define LCP_ASYNCMAP    2
 
 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
                int len, int inbound)
 {
     int dlen, fcs, i, code;
     u32 val;
 
     data += 2;      /* skip protocol bytes */
     len -= 2;
     if (len < 4)        /* 4 = code, ID, length */
         return;
     code = data[0];
     if (code != CONFACK && code != CONFREQ)
         return;
     dlen = get_unaligned_be16(data + 2);
     if (len < dlen)
         return;     /* packet got truncated or length is bogus */
 
     if (code == (inbound? CONFACK: CONFREQ)) {
         /*
          * sent confreq or received confack:
          * calculate the crc of the data from the ID field on.
          */
         fcs = PPP_INITFCS;
         for (i = 1; i < dlen; ++i)
             fcs = PPP_FCS(fcs, data[i]);
 
         if (!inbound) {
             /* outbound confreq - remember the crc for later */
             ap->lcp_fcs = fcs;
             return;
         }
 
         /* received confack, check the crc */
         fcs ^= ap->lcp_fcs;
         ap->lcp_fcs = -1;
         if (fcs != 0)
             return;
     } else if (inbound)
         return; /* not interested in received confreq */
 
     /* process the options in the confack */
     data += 4;
     dlen -= 4;
     /* data[0] is code, data[1] is length */
     while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
         switch (data[0]) {
         case LCP_MRU:
             val = get_unaligned_be16(data + 2);
             if (inbound)
                 ap->mru = val;
             else
                 ap->chan.mtu = val;
             break;
         case LCP_ASYNCMAP:
             val = get_unaligned_be32(data + 2);
             if (inbound)
                 ap->raccm = val;
             else
                 ap->xaccm[0] = val;
             break;
         }
         dlen -= data[1];
         data += data[1];
     }
 }
 
 static void __exit ppp_async_cleanup(void)
 {
     tty_unregister_ldisc(&ppp_ldisc);
 }
 
 module_init(ppp_async_init);
 module_exit(ppp_async_cleanup);

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