ppp_async.c

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/*
 * 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.
 *
 * ==FILEVERSION 20000227==
 */

#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/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>

#ifndef spin_trylock_bh
#define spin_trylock_bh(lock)	({ int __r; local_bh_disable();	\
				   __r = spin_trylock(lock);	\
				   if (!__r) local_bh_enable();	\
				   __r; })
#endif

#define PPP_VERSION	"2.4.1"

#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 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

/* State bits */
#define SC_TOSS		0x20000000
#define SC_ESCAPE	0x40000000

/* 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_PARM(flag_time, "i");

/*
 * 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 async_lcp_peek(struct asyncppp *ap, unsigned char *data,
			   int len, int inbound);

struct ppp_channel_ops async_ops = {
	ppp_async_send,
	ppp_async_ioctl
};

/*
 * Routines implementing the PPP line discipline.
 */

/*
 * Called when a tty is put into PPP line discipline.
 */
static int
ppp_asynctty_open(struct tty_struct *tty)
{
	struct asyncppp *ap;
	int err;

	MOD_INC_USE_COUNT;
	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;

	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:
	MOD_DEC_USE_COUNT;
	return err;
}

/*
 * Called when the tty is put into another line discipline
 * or it hangs up.
 * We assume that while we are in this routine, the tty layer
 * won't call any of the other line discipline entries for the
 * same tty.
 */
static void
ppp_asynctty_close(struct tty_struct *tty)
{
	struct asyncppp *ap = tty->disc_data;

	if (ap == 0)
		return;
	tty->disc_data = 0;
	ppp_unregister_channel(&ap->chan);
	if (ap->rpkt != 0)
		kfree_skb(ap->rpkt);
	if (ap->tpkt != 0)
		kfree_skb(ap->tpkt);
	kfree(ap);
	MOD_DEC_USE_COUNT;
}

/*
 * Read does nothing.
 */
static ssize_t
ppp_asynctty_read(struct tty_struct *tty, struct file *file,
		  unsigned char *buf, size_t count)
{
	/* For now, do the same as the old 2.3.x code useta */
	struct asyncppp *ap = tty->disc_data;

	if (ap == 0)
		return -ENXIO;
	return ppp_channel_read(&ap->chan, file, buf, count);
}

/*
 * 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)
{
	/* For now, do the same as the old 2.3.x code useta */
	struct asyncppp *ap = tty->disc_data;

	if (ap == 0)
		return -ENXIO;
	return ppp_channel_write(&ap->chan, buf, count);
}

static int
ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
		   unsigned int cmd, unsigned long arg)
{
	struct asyncppp *ap = tty->disc_data;
	int err, val;

	err = -EFAULT;
	switch (cmd) {
	case PPPIOCGCHAN:
		err = -ENXIO;
		if (ap == 0)
			break;
		err = -EFAULT;
		if (put_user(ppp_channel_index(&ap->chan), (int *) arg))
			break;
		err = 0;
		break;

	case PPPIOCGUNIT:
		err = -ENXIO;
		if (ap == 0)
			break;
		err = -EFAULT;
		if (put_user(ppp_unit_number(&ap->chan), (int *) arg))
			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, (int *) arg))
			break;
		err = 0;
		break;

/*
 * For now, do the same as the old 2.3 driver useta
 */
	case PPPIOCGFLAGS:
	case PPPIOCSFLAGS:
	case PPPIOCGASYNCMAP:
	case PPPIOCSASYNCMAP:
	case PPPIOCGRASYNCMAP:
	case PPPIOCSRASYNCMAP:
	case PPPIOCGXASYNCMAP:
	case PPPIOCSXASYNCMAP:
	case PPPIOCGMRU:
	case PPPIOCSMRU:
		err = -EPERM;
		if (!capable(CAP_NET_ADMIN))
			break;
		err = ppp_async_ioctl(&ap->chan, cmd, arg);
		break;

	case PPPIOCATTACH:
	case PPPIOCDETACH:
		err = ppp_channel_ioctl(&ap->chan, cmd, arg);
		break;

	default:
		err = -ENOIOCTLCMD;
	}

	return err;
}

/* No kernel lock - fine */
static unsigned int
ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
{
	unsigned int mask;
	struct asyncppp *ap = tty->disc_data;

	mask = POLLOUT | POLLWRNORM;
/*
 * For now, do the same as the old 2.3 driver useta
 */
	if (ap != 0)
		mask |= ppp_channel_poll(&ap->chan, file, wait);
	if (test_bit(TTY_OTHER_CLOSED, &tty->flags) || tty_hung_up_p(file))
		mask |= POLLHUP;
	return mask;
}

static int
ppp_asynctty_room(struct tty_struct *tty)
{
	return 65535;
}

static void
ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
		  char *flags, int count)
{
	struct asyncppp *ap = tty->disc_data;

	if (ap == 0)
		return;
	spin_lock_bh(&ap->recv_lock);
	ppp_async_input(ap, buf, flags, count);
	spin_unlock_bh(&ap->recv_lock);
	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 = tty->disc_data;

	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
	if (ap == 0)
		return;
	if (ppp_async_push(ap))
		ppp_output_wakeup(&ap->chan);
}


static struct tty_ldisc ppp_ldisc = {
	magic:	TTY_LDISC_MAGIC,
	name:	"ppp",
	open:	ppp_asynctty_open,
	close:	ppp_asynctty_close,
	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,
};

int
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;
	int err, val;
	u32 accm[8];

	err = -EFAULT;
	switch (cmd) {
	case PPPIOCGFLAGS:
		val = ap->flags | ap->rbits;
		if (put_user(val, (int *) arg))
			break;
		err = 0;
		break;
	case PPPIOCSFLAGS:
		if (get_user(val, (int *) arg))
			break;
		ap->flags = val & ~SC_RCV_BITS;
		spin_lock_bh(&ap->recv_lock);
		ap->rbits = val & SC_RCV_BITS;
		spin_unlock_bh(&ap->recv_lock);
		err = 0;
		break;

	case PPPIOCGASYNCMAP:
		if (put_user(ap->xaccm[0], (u32 *) arg))
			break;
		err = 0;
		break;
	case PPPIOCSASYNCMAP:
		if (get_user(ap->xaccm[0], (u32 *) arg))
			break;
		err = 0;
		break;

	case PPPIOCGRASYNCMAP:
		if (put_user(ap->raccm, (u32 *) arg))
			break;
		err = 0;
		break;
	case PPPIOCSRASYNCMAP:
		if (get_user(ap->raccm, (u32 *) arg))
			break;
		err = 0;
		break;

	case PPPIOCGXASYNCMAP:
		if (copy_to_user((void *) arg, ap->xaccm, sizeof(ap->xaccm)))
			break;
		err = 0;
		break;
	case PPPIOCSXASYNCMAP:
		if (copy_from_user(accm, (void *) arg, 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, (int *) arg))
			break;
		err = 0;
		break;
	case PPPIOCSMRU:
		if (get_user(val, (int *) arg))
			break;
		if (val < PPP_MRU)
			val = PPP_MRU;
		ap->mru = val;
		err = 0;
		break;

	default:
		err = -ENOTTY;
	}

	return err;
}

/*
 * Procedures for encapsulation and framing.
 */

u16 ppp_crc16_table[256] = {
	0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
	0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
	0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
	0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
	0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
	0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
	0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
	0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
	0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
	0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
	0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
	0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
	0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
	0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
	0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
	0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
	0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
	0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
	0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
	0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
	0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
	0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
	0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
	0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
	0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
	0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
	0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,