/*
* 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_empty(&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_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);
