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85509c0007
linux/drivers/net/ppp_async.c
Alan Cox 33f0f88f1c [PATCH] TTY layer buffering revamp 
The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.

This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.

When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.

For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).

Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.

The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.

I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.

Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real.  That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.

Description:

tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification].  It
does now also return the number of chars inserted

There are also

tty_buffer_request_room(tty, len)

which asks for a buffer block of the length requested and returns the space
found.  This improves efficiency with hardware that knows how much to
transfer.

and tty_insert_flip_string_flags(tty, str, flags, len)

to insert a string of characters and flags

For a smart interface the usual code is

    len = tty_request_buffer_room(tty, amount_hardware_says);
    tty_insert_flip_string(tty, buffer_from_card, len);

More description!

At the moment tty buffers are attached directly to the tty.  This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)

I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers.  This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.

So far so good.  Lots of drivers reference tty->flip.*.  Several of them also
call directly and unsafely into function pointers it provides.  This will all
break.  Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.

At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say

 int tty_buffer_request_room(tty, size)

Try and ensure at least size bytes are available, returns actual room (may be
zero).  At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative.  (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space.  The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.

 int tty_insert_flip_char(tty, ch, flag)

As before insert a character if there is room.  Now returns 1 for success, 0
for failure.

 int tty_insert_flip_string(tty, str, len)

Insert a block of non error characters.  Returns the number inserted.

 int tty_prepare_flip_string(tty, strptr, len)

Adjust the buffer to allow len characters to be added.  Returns a buffer
pointer in strptr and the length available.  This allows for hardware that
needs to use functions like insl or mencpy_fromio.

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 08:01:59 -08:00

1038 lines
24 KiB
C
Raw Blame History

/*
* 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>
#include <asm/string.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;
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 == 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;
}
/*
* 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_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) {
/* 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 != 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;
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] ^= 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);
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