--- /dev/null
+/*
+ * 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/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 <asm/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;
+
+ 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 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)
+ 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;
+ 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_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
+
+ atomic_set(&ap->refcnt, 1);
+ sema_init(&ap->dead_sem, 0);
+
+ 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 (!atomic_dec_and_test(&ap->refcnt))
+ down(&ap->dead_sem);
+ 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 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)
+ 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, file, 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, file, cmd, arg);
+ }
+
+ 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;
+}
+
+/* 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,
+ 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,
+ .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_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 ^ 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, 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) {
+ /* chop off address/control */
+ if (p[1] != PPP_UI || 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) {
+ /* 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,
+ 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(skb, n);
+ memcpy(sp, 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)
+{
+ if (tty_unregister_ldisc(N_PPP) != 0)
+ printk(KERN_ERR "failed to unregister PPP line discipline\n");
+}
+
+module_init(ppp_async_init);
+module_exit(ppp_async_cleanup);
Code Review / kvmfornfv.git / blobdiff