Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1033 insertions, 0 deletions

diff --git a/drivers/net/ppp_async.c b/drivers/net/ppp_async.c
new file mode 100644
index 00000000000..33b9d79b1aa
--- /dev/null
+++ b/drivers/net/ppp_async.c
@@ -0,0 +1,1033 @@
+/*
+ * PPP async serial channel driver for Linux.
+ *
+ * Copyright 1999 Paul Mackerras.
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ *
+ * 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/if_ppp.h>
+#include <linux/ppp_channel.h>
+#include <linux/spinlock.h>
+#include <linux/init.h>
+#include <asm/uaccess.h>
+
+#define PPP_VERSION     "2.4.2"
+
+#define OBUFSIZE        256
+
+/* 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;
+
+        atomic_t        refcnt;
+        struct semaphore dead_sem;
+        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,
+                            char *flags, int count);
+static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
+                           unsigned long arg);
+static void ppp_async_process(unsigned long arg);
+
+static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
+                           int len, int inbound);
+
+static struct ppp_channel_ops async_ops = {
+        ppp_async_send,
+        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)
+                atomic_inc(&ap->refcnt);
+        read_unlock(&disc_data_lock);
+        return ap;
+}
+
+static void ap_put(struct asyncppp *ap)
+{
+        if (atomic_dec_and_test(&ap->refcnt))
+                up(&ap->dead_sem);
+}
+
+/*
+ * 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;
+
+        err = -ENOMEM;
+        ap = kmalloc(sizeof(*ap), GFP_KERNEL);
+        if (ap == 0)
+                goto out;
+
+        /* initialize the asyncppp structure */
+        memset(ap, 0, sizeof(*ap));
+        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_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
+
+        atomic_set(&ap->refcnt, 1);
+        init_MUTEX_LOCKED(&ap->dead_sem);
+
+        ap->chan.private = ap;
+        ap->chan.ops = &async_ops;
+        ap->chan.mtu = PPP_MRU;
+        err = ppp_register_channel(&ap->chan);
+        if (err)
+                goto out_free;
+
+        tty->disc_data = ap;
+
+        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 == 0)
+                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 (!atomic_dec_and_test(&ap->refcnt))
+                down(&ap->dead_sem);
+        tasklet_kill(&ap->tsk);
+
+        ppp_unregister_channel(&ap->chan);
+        if (ap->rpkt != 0)
+                kfree_skb(ap->rpkt);
+        skb_queue_purge(&ap->rqueue);
+        if (ap->tpkt != 0)
+                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 int ppp_asynctty_hangup(struct tty_struct *tty)
+{
+        ppp_asynctty_close(tty);
+        return 0;
+}
+
+/*
+ * 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 __user *buf, size_t count)
+{
+        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, struct file *file,
+                   unsigned int cmd, unsigned long arg)
+{
+        struct asyncppp *ap = ap_get(tty);
+        int err, val;
+        int __user *p = (int __user *)arg;
+
+        if (ap == 0)
+                return -ENXIO;
+        err = -EFAULT;
+        switch (cmd) {
+        case PPPIOCGCHAN:
+                err = -ENXIO;
+                if (ap == 0)
+                        break;
+                err = -EFAULT;
+                if (put_user(ppp_channel_index(&ap->chan), p))
+                        break;
+                err = 0;
+                break;
+
+        case PPPIOCGUNIT:
+                err = -ENXIO;
+                if (ap == 0)
+                        break;
+                err = -EFAULT;
+                if (put_user(ppp_unit_number(&ap->chan), p))
+                        break;
+                err = 0;
+                break;
+
+        case TCGETS:
+        case TCGETA:
+                err = n_tty_ioctl(tty, file, cmd, arg);
+                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(tty, file, cmd, arg);
+                break;
+
+        case FIONREAD:
+                val = 0;
+                if (put_user(val, p))
+                        break;
+                err = 0;
+                break;
+
+        default:
+                err = -ENOIOCTLCMD;
+        }
+
+        ap_put(ap);
+        return err;
+}
+
+/* No kernel lock - fine */
+static unsigned int
+ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
+{
+        return 0;
+}
+
+static int
+ppp_asynctty_room(struct tty_struct *tty)
+{
+        return 65535;
+}
+
+/*
+ * This can now be called from hard interrupt level as well
+ * as soft interrupt level or mainline.
+ */
+static void
+ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
+                  char *cflags, int count)
+{
+        struct asyncppp *ap = ap_get(tty);
+        unsigned long flags;
+
+        if (ap == 0)
+                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_len(&ap->rqueue))
+                tasklet_schedule(&ap->tsk);
+        ap_put(ap);
+        if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
+            && tty->driver->unthrottle)
+                tty->driver->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 == 0)
+                return;
+        set_bit(XMIT_WAKEUP, &ap->xmit_flags);
+        tasklet_schedule(&ap->tsk);
+        ap_put(ap);
+}
+
+
+static struct tty_ldisc ppp_ldisc = {
+        .owner  = THIS_MODULE,
+        .magic  = TTY_LDISC_MAGIC,
+        .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_room = ppp_asynctty_room,
+        .receive_buf = ppp_asynctty_receive,
+        .write_wakeup = ppp_asynctty_wakeup,
+};
+
+static int __init
+ppp_async_init(void)
+{
+        int err;
+
+        err = tty_register_ldisc(N_PPP, &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(unsigned long arg)
+{
+        struct asyncppp *ap = (struct asyncppp *) arg;
+        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 ^ 0x20;                      \
+        } 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 = (data[0] << 8) + data[1];
+
+        /*
+         * 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
+                    || 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;
+
+        kfree_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->driver->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 != 0) {
+                        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 != 0)))
+                        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 != 0) {
+                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, proto;
+
+        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 && p[1] == PPP_UI) {
+                /* chop off address/control */
+                if (skb->len < 3)
+                        goto err;
+                p = skb_pull(skb, 2);
+        }
+        proto = p[0];
+        if (proto & 1) {
+                /* protocol is compressed */
+                skb_push(skb, 1)[0] = 0;
+        } else {
+                if (skb->len < 2)
+                        goto err;
+                proto = (proto << 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)
+                skb_trim(skb, 0);
+}
+
+/* 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,
+                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 != 0 && 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 != 0 && (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 == 0) {
+                                skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
+                                if (skb == 0)
+                                        goto nomem;
+                                /* Try to get the payload 4-byte aligned */
+                                if (buf[0] != PPP_ALLSTATIONS)
+                                        skb_reserve(skb, 2 + (buf[0] & 1));
+                                ap->rpkt = skb;
+                        }
+                        if (n > skb_tailroom(skb)) {
+                                /* packet overflowed MRU */
+                                ap->state |= SC_TOSS;
+                        } else {
+                                sp = skb_put(skb, n);
+                                memcpy(sp, buf, n);
+                                if (ap->state & SC_ESCAPE) {
+                                        sp[0] ^= 0x20;
+                                        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 != 0)
+                        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 = (data[2] << 8) + data[3];
+        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 = (data[2] << 8) + data[3];
+                        if (inbound)
+                                ap->mru = val;
+                        else
+                                ap->chan.mtu = val;
+                        break;
+                case LCP_ASYNCMAP:
+                        val = (data[2] << 24) + (data[3] << 16)
+                                + (data[4] << 8) + data[5];
+                        if (inbound)
+                                ap->raccm = val;
+                        else
+                                ap->xaccm[0] = val;
+                        break;
+                }
+                dlen -= data[1];
+                data += data[1];
+        }
+}
+
+static void __exit ppp_async_cleanup(void)
+{
+        if (tty_register_ldisc(N_PPP, NULL) != 0)
+                printk(KERN_ERR "failed to unregister PPP line discipline\n");
+}
+
+module_init(ppp_async_init);
+module_exit(ppp_async_cleanup);