/*
 * slip.c	This module implements the SLIP protocol for kernel-based
 *		devices like TTY.  It interfaces between a raw TTY, and the
 *		kernel's INET protocol layers.
 *
 * Version:	@(#)slip.c	0.8.3	12/24/94
 *
 * Authors:	Laurence Culhane, <loz@holmes.demon.co.uk>
 *		Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
 *
 * Fixes:
 *		Alan Cox	: 	Sanity checks and avoid tx overruns.
 *					Has a new sl->mtu field.
 *		Alan Cox	: 	Found cause of overrun. ifconfig sl0 mtu upwards.
 *					Driver now spots this and grows/shrinks its buffers(hack!).
 *					Memory leak if you run out of memory setting up a slip driver fixed.
 *		Matt Dillon	:	Printable slip (borrowed from NET2E)
 *	Pauline Middelink	:	Slip driver fixes.
 *		Alan Cox	:	Honours the old SL_COMPRESSED flag
 *		Alan Cox	:	KISS AX.25 and AXUI IP support
 *		Michael Riepe	:	Automatic CSLIP recognition added
 *		Charles Hedrick :	CSLIP header length problem fix.
 *		Alan Cox	:	Corrected non-IP cases of the above.
 *		Alan Cox	:	Now uses hardware type as per FvK.
 *		Alan Cox	:	Default to 192.168.0.0 (RFC 1597)
 *		A.N.Kuznetsov	:	dev_tint() recursion fix.
 *	Dmitry Gorodchanin	:	SLIP memory leaks
 *      Dmitry Gorodchanin      :       Code cleanup. Reduce tty driver
 *                                      buffering from 4096 to 256 bytes.
 *                                      Improving SLIP response time.
 *                                      CONFIG_SLIP_MODE_SLIP6.
 *                                      ifconfig sl? up & down now works correctly.
 *					Modularization.
 *              Alan Cox        :       Oops - fix AX.25 buffer lengths
 *      Dmitry Gorodchanin      :       Even more cleanups. Preserve CSLIP
 *                                      statistics. Include CSLIP code only
 *                                      if it really needed.
 *		Alan Cox	:	Free slhc buffers in the right place.
 *		Alan Cox	:	Allow for digipeated IP over AX.25
 *		Matti Aarnio	:	Dynamic SLIP devices, with ideas taken
 *					from Jim Freeman's <jfree@caldera.com>
 *					dynamic PPP devices.  We do NOT kfree()
 *					device entries, just reg./unreg. them
 *					as they are needed.  We kfree() them
 *					at module cleanup.
 *					With MODULE-loading ``insmod'', user can
 *					issue parameter:   slip_maxdev=1024
 *					(Or how much he/she wants.. Default is 256)
 * *	Stanislav Voronyi	:	Slip line checking, with ideas taken
 *					from multislip BSDI driver which was written
 *					by Igor Chechik, RELCOM Corp. Only algorithms
 * 					have been ported to Linux SLIP driver.
 */

#define SL_CHECK_TRANSMIT
#include <linux/config.h>
#include <linux/module.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/bitops.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/if_slip.h>
#include "slip.h"
#ifdef CONFIG_INET
#include <linux/ip.h>
#include <linux/tcp.h>
#include <net/slhc_vj.h>
#endif

#ifdef MODULE
#define SLIP_VERSION    "0.8.4-NET3.019-NEWTTY-MODULAR"
#else
#define	SLIP_VERSION	"0.8.4-NET3.019-NEWTTY"
#endif


typedef struct slip_ctrl {
	char		if_name[8];	/* "sl0\0" .. "sl99999\0"	*/
	struct slip	ctrl;		/* SLIP things			*/
	struct device	dev;		/* the device			*/
} slip_ctrl_t;
static slip_ctrl_t	**slip_ctrls = NULL;
int slip_maxdev = SL_NRUNIT;		/* Can be overridden with insmod! */

static struct tty_ldisc	sl_ldisc;

static int slip_esc(unsigned char *p, unsigned char *d, int len);
static void slip_unesc(struct slip *sl, unsigned char c);
#ifdef CONFIG_SLIP_MODE_SLIP6
static int slip_esc6(unsigned char *p, unsigned char *d, int len);
static void slip_unesc6(struct slip *sl, unsigned char c);
#endif
#ifdef CONFIG_SLIP_SMART
static void sl_keepalive(unsigned long sls);
static void sl_outfill(unsigned long sls);
#endif

/* Find a free SLIP channel, and link in this `tty' line. */
static inline struct slip *
sl_alloc(void)
{
	slip_ctrl_t *slp;
	int i;

	if (slip_ctrls == NULL) return NULL;	/* Master array missing ! */

	for (i = 0; i < slip_maxdev; i++) {
	  slp = slip_ctrls[i];
	  /* Not allocated ? */
	  if (slp == NULL)
	    break;
	  /* Not in use ? */
	  if (!set_bit(SLF_INUSE, &slp->ctrl.flags))
	    break;
	}
	/* SLP is set.. */

	/* Sorry, too many, all slots in use */
	if (i >= slip_maxdev) return NULL;

	/* If no channels are available, allocate one */
	if (!slp &&
	    (slip_ctrls[i] = (slip_ctrl_t *)kmalloc(sizeof(slip_ctrl_t),
						    GFP_KERNEL)) != NULL) {
	  slp = slip_ctrls[i];
	  memset(slp, 0, sizeof(slip_ctrl_t));

	  /* Initialize channel control data */
	  set_bit(SLF_INUSE, &slp->ctrl.flags);
	  slp->ctrl.tty         = NULL;
	  sprintf(slp->if_name, "sl%d", i);
	  slp->dev.name         = slp->if_name;
	  slp->dev.base_addr    = i;
	  slp->dev.priv         = (void*)&(slp->ctrl);
	  slp->dev.next         = NULL;
	  slp->dev.init         = slip_init;
/* printk(KERN_INFO "slip: kmalloc()ed SLIP control node for line %s\n",
   slp->if_name); */
	}
	if (slp != NULL) {

	  /* register device so that it can be ifconfig'ed       */
	  /* slip_init() will be called as a side-effect         */
	  /* SIDE-EFFECT WARNING: slip_init() CLEARS slp->ctrl ! */

	  if (register_netdev(&(slp->dev)) == 0) {
	    /* (Re-)Set the INUSE bit.   Very Important! */
	    set_bit(SLF_INUSE, &slp->ctrl.flags);
	    slp->ctrl.dev = &(slp->dev);
	    slp->dev.priv = (void*)&(slp->ctrl);

/* printk(KERN_INFO "slip: linked in netdev %s for active use\n",
   slp->if_name); */

	    return (&(slp->ctrl));

	  } else {
	    clear_bit(SLF_INUSE,&(slp->ctrl.flags));
	    printk("sl_alloc() - register_netdev() failure.\n");
	  }
	}

	return NULL;
}


/* Free a SLIP channel. */
static inline void
sl_free(struct slip *sl)
{
	/* Free all SLIP frame buffers. */
	if (sl->rbuff)  {
		kfree(sl->rbuff);
	}
	sl->rbuff = NULL;
	if (sl->xbuff)  {
		kfree(sl->xbuff);
	}
	sl->xbuff = NULL;
#ifdef SL_INCLUDE_CSLIP
	/* Save CSLIP statistics */
	if (sl->slcomp)  {
		sl->rx_compressed += sl->slcomp->sls_i_compressed;
		sl->rx_dropped    += sl->slcomp->sls_i_tossed;
		sl->tx_compressed += sl->slcomp->sls_o_compressed;
		sl->tx_misses     += sl->slcomp->sls_o_misses;
	}
	if (sl->cbuff)  {
		kfree(sl->cbuff);
	}
	sl->cbuff = NULL;
	if(sl->slcomp)
		slhc_free(sl->slcomp);
	sl->slcomp = NULL;
#endif

	if (!clear_bit(SLF_INUSE, &sl->flags)) {
		printk("%s: sl_free for already free unit.\n", sl->dev->name);
	}
}

/* MTU has been changed by the IP layer. Unfortunately we are not told
   about this, but we spot it ourselves and fix things up. We could be
   in an upcall from the tty driver, or in an ip packet queue. */

static void sl_changedmtu(struct slip *sl)
{
	struct device *dev = sl->dev;
	unsigned char *xbuff, *rbuff, *oxbuff, *orbuff;
#ifdef SL_INCLUDE_CSLIP
	unsigned char *cbuff, *ocbuff;
#endif
	int len;
	unsigned long flags;

	len = dev->mtu * 2;
/*
 * allow for arrival of larger UDP packets, even if we say not to
 * also fixes a bug in which SunOS sends 512-byte packets even with
 * an MSS of 128
 */
	if (len < 576 * 2)  {
		len = 576 * 2;
	}

	xbuff = (unsigned char *) kmalloc (len + 4, GFP_ATOMIC);
	rbuff = (unsigned char *) kmalloc (len + 4, GFP_ATOMIC);
#ifdef SL_INCLUDE_CSLIP
	cbuff = (unsigned char *) kmalloc (len + 4, GFP_ATOMIC);
#endif

#ifdef SL_INCLUDE_CSLIP
	if (xbuff == NULL || rbuff == NULL || cbuff == NULL)  {
#else
	if (xbuff == NULL || rbuff == NULL)  {
#endif
		printk("%s: unable to grow slip buffers, MTU change cancelled.\n",
		       sl->dev->name);
		dev->mtu = sl->mtu;
		if (xbuff != NULL)  {
			kfree(xbuff);
		}
		if (rbuff != NULL)  {
			kfree(rbuff);
		}
#ifdef SL_INCLUDE_CSLIP
		if (cbuff != NULL)  {
			kfree(cbuff);
		}
#endif
		return;
	}

	save_flags(flags); cli();

	oxbuff    = sl->xbuff;
	sl->xbuff = xbuff;
	orbuff    = sl->rbuff;
	sl->rbuff = rbuff;
#ifdef SL_INCLUDE_CSLIP
	ocbuff    = sl->cbuff;
	sl->cbuff = cbuff;
#endif
	if (sl->xleft)  {
		if (sl->xleft <= len)  {
			memcpy(sl->xbuff, sl->xhead, sl->xleft);
		} else  {
			sl->xleft = 0;
			sl->tx_dropped++;
		}
	}
	sl->xhead = sl->xbuff;

	if (sl->rcount)  {
		if (sl->rcount <= len) {
			memcpy(sl->rbuff, orbuff, sl->rcount);
		} else  {
			sl->rcount = 0;
			sl->rx_over_errors++;
			set_bit(SLF_ERROR, &sl->flags);
		}
	}
	sl->mtu      = dev->mtu;
	
	sl->buffsize = len;

	restore_flags(flags);

	if (oxbuff != NULL)   {
		kfree(oxbuff);
	}
	if (orbuff != NULL)    {
		kfree(orbuff);
	}
#ifdef SL_INCLUDE_CSLIP
	if (ocbuff != NULL)  {
		kfree(ocbuff);
	}
#endif
}


/* Set the "sending" flag.  This must be atomic, hence the ASM. */
static inline void
sl_lock(struct slip *sl)
{
	if (set_bit(0, (void *) &sl->dev->tbusy))  {
		printk("%s: trying to lock already locked device!\n", sl->dev->name);
        }
}


/* Clear the "sending" flag.  This must be atomic, hence the ASM. */
static inline void
sl_unlock(struct slip *sl)
{
	if (!clear_bit(0, (void *)&sl->dev->tbusy))  {
		printk("%s: trying to unlock already unlocked device!\n", sl->dev->name);
        }
}

/* Send one completely decapsulated IP datagram to the IP layer. */
static void
sl_bump(struct slip *sl)
{
	struct sk_buff *skb;
	int count;

	count = sl->rcount;
#ifdef SL_INCLUDE_CSLIP
	if (sl->mode & (SL_MODE_ADAPTIVE | SL_MODE_CSLIP)) {
		unsigned char c;
		if ((c = sl->rbuff[0]) & SL_TYPE_COMPRESSED_TCP) {
			/* ignore compressed packets when CSLIP is off */
			if (!(sl->mode & SL_MODE_CSLIP)) {
				printk("%s: compressed packet ignored\n", sl->dev->name);
				return;
			}
			/* make sure we've reserved enough space for uncompress to use */
			if (count + 80 > sl->buffsize) {
				sl->rx_over_errors++;
				return;
			}
			count = slhc_uncompress(sl->slcomp, sl->rbuff, count);
			if (count <= 0) {
				return;
			}
		} else if (c >= SL_TYPE_UNCOMPRESSED_TCP) {
			if (!(sl->mode & SL_MODE_CSLIP)) {
				/* turn on header compression */
				sl->mode |= SL_MODE_CSLIP;
				sl->mode &= ~SL_MODE_ADAPTIVE;
				printk("%s: header compression turned on\n", sl->dev->name);
			}
			sl->rbuff[0] &= 0x4f;
			if (slhc_remember(sl->slcomp, sl->rbuff, count) <= 0) {
				return;
			}
		}
	}
#endif  /* SL_INCLUDE_CSLIP */

	skb = dev_alloc_skb(count);
	if (skb == NULL)  {
		printk("%s: memory squeeze, dropping packet.\n", sl->dev->name);
		sl->rx_dropped++;
		return;
	}
	skb->dev = sl->dev;
	memcpy(skb_put(skb,count), sl->rbuff, count);
	skb->mac.raw=skb->data;
	skb->protocol=htons(ETH_P_IP);
	netif_rx(skb);
	sl->rx_packets++;
}

/* Encapsulate one IP datagram and stuff into a TTY queue. */
static void
sl_encaps(struct slip *sl, unsigned char *icp, int len)
{
	unsigned char *p;
	int actual, count;


	if (sl->mtu != sl->dev->mtu) {	/* Someone has been ifconfigging */

		sl_changedmtu(sl);
	}

	if (len > sl->mtu) {		/* Sigh, shouldn't occur BUT ... */
		len = sl->mtu;
		printk ("%s: truncating oversized transmit packet!\n", sl->dev->name);
		sl->tx_dropped++;
		sl_unlock(sl);
		return;
	}

	p = icp;
#ifdef SL_INCLUDE_CSLIP
	if (sl->mode & SL_MODE_CSLIP)  {
		len = slhc_compress(sl->slcomp, p, len, sl->cbuff, &p, 1);
	}
#endif
#ifdef CONFIG_SLIP_MODE_SLIP6
	if(sl->mode & SL_MODE_SLIP6)
		count = slip_esc6(p, (unsigned char *) sl->xbuff, len);
	else
#endif
		count = slip_esc(p, (unsigned char *) sl->xbuff, len);

	/* Order of next two lines is *very* important.
	 * When we are sending a little amount of data,
	 * the transfer may be completed inside driver.write()
	 * routine, because it's running with interrupts enabled.
	 * In this case we *never* got WRITE_WAKEUP event,
	 * if we did not request it before write operation.
	 *       14 Oct 1994  Dmitry Gorodchanin.
	 */
	sl->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
	actual = sl->tty->driver.write(sl->tty, 0, sl->xbuff, count);
#ifdef SL_CHECK_TRANSMIT
	sl->dev->trans_start = jiffies;
#endif
	sl->xleft = count - actual;
	sl->xhead = sl->xbuff + actual;
	/* VSV */
	clear_bit(SLF_OUTWAIT, &sl->flags);	/* reset outfill flag */
}

/*
 * Called by the driver when there's room for more data.  If we have
 * more packets to send, we send them here.
 */
static void slip_write_wakeup(struct tty_struct *tty)
{
	int actual;
	struct slip *sl = (struct slip *) tty->disc_data;

	/* First make sure we're connected. */
	if (!sl || sl->magic != SLIP_MAGIC || !sl->dev->start) {
		return;
	}
	if (sl->xleft <= 0)  {
		/* Now serial buffer is almost free & we can start
		 * transmission of another packet */
		sl->tx_packets++;
		tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
		sl_unlock(sl);
		mark_bh(NET_BH);
		return;
	}

	actual = tty->driver.write(tty, 0, sl->xhead, sl->xleft);
	sl->xleft -= actual;
	sl->xhead += actual;
}

/* Encapsulate an IP datagram and kick it into a TTY queue. */
static int
sl_xmit(struct sk_buff *skb, struct device *dev)
{
	struct slip *sl = (struct slip*)(dev->priv);

	if (!dev->start)  {
		printk("%s: xmit call when iface is down\n", dev->name);
		return 1;
	}
	/*
	 * If we are busy already- too bad.  We ought to be able
	 * to queue things at this point, to allow for a little
	 * frame buffer.  Oh well...
	 * -----------------------------------------------------
	 * I hate queues in SLIP driver. May be it's efficient,
	 * but for me latency is more important. ;)
	 * So, no queues !
	 *        14 Oct 1994  Dmitry Gorodchanin.
	 */
	if (dev->tbusy) {
		/* May be we must check transmitter timeout here ?
		 *      14 Oct 1994 Dmitry Gorodchanin.
		 */
#ifdef SL_CHECK_TRANSMIT
		if (jiffies - dev->trans_start  < 20 * HZ)  {
			/* 20 sec timeout not reached */
			return 1;
		}
		printk("%s: transmit timed out, %s?\n", dev->name,
		       (sl->tty->driver.chars_in_buffer(sl->tty) || sl->xleft) ?
		       "bad line quality" : "driver error");
		sl->xleft = 0;
		sl->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
		sl_unlock(sl);
#else
		return 1;
#endif
	}

	/* We were not busy, so we are now... :-) */
	if (skb != NULL) {
		sl_lock(sl);
		sl_encaps(sl, skb->data, skb->len);
		dev_kfree_skb(skb, FREE_WRITE);
	}
	return 0;
}


/* Return the frame type ID.  This is normally IP but maybe be AX.25. */

/* Fill in the MAC-level header. Not used by SLIP. */
static int
sl_header(struct sk_buff *skb, struct device *dev, unsigned short type,
	  void *daddr, void *saddr, unsigned len)
{
	return 0;
}


/* Rebuild the MAC-level header.  Not used by SLIP. */
static int
sl_rebuild_header(void *buff, struct device *dev, unsigned long raddr,
		  struct sk_buff *skb)
{
	return 0;
}


/* Open the low-level part of the SLIP channel. Easy! */
static int
sl_open(struct device *dev)
{
	struct slip *sl = (struct slip*)(dev->priv);
	unsigned long len;

	if (sl->tty == NULL) {
		return -ENODEV;
	}

	/*
	 * Allocate the SLIP frame buffers:
	 *
	 * rbuff	Receive buffer.
	 * xbuff	Transmit buffer.
	 * cbuff        Temporary compression buffer.
	 */
	len = dev->mtu * 2;
	/*
	 * allow for arrival of larger UDP packets, even if we say not to
	 * also fixes a bug in which SunOS sends 512-byte packets even with
	 * an MSS of 128
	 */
	if (len < 576 * 2)  {
		len = 576 * 2;
	}
	sl->rbuff = (unsigned char *) kmalloc(len + 4, GFP_KERNEL);
	if (sl->rbuff == NULL)   {
		goto norbuff;
	}
	sl->xbuff = (unsigned char *) kmalloc(len + 4, GFP_KERNEL);
	if (sl->xbuff == NULL)   {
		goto noxbuff;
	}
#ifdef SL_INCLUDE_CSLIP
	sl->cbuff = (unsigned char *) kmalloc(len + 4, GFP_KERNEL);
	if (sl->cbuff == NULL)   {
		goto nocbuff;
	}
	sl->slcomp = slhc_init(16, 16);
	if (sl->slcomp == NULL)  {
		goto noslcomp;
	}
#endif
	sl->mtu	     = dev->mtu;
	sl->buffsize = len;
	sl->rcount   = 0;
	sl->xleft    = 0;
#ifdef CONFIG_SLIP_MODE_SLIP6
	sl->xdata    = 0;
	sl->xbits    = 0;
#endif
	sl->flags   &= (1 << SLF_INUSE);      /* Clear ESCAPE & ERROR flags */
#ifdef CONFIG_SLIP_SMART	
	sl->keepalive=0;		/* no keepalive by default = VSV */
	init_timer(&sl->keepalive_timer);	/* initialize timer_list struct */
	sl->keepalive_timer.data=(unsigned long)sl;
	sl->keepalive_timer.function=sl_keepalive;	
	sl->outfill=0;			/* & outfill too */
	init_timer(&sl->outfill_timer);
	sl->outfill_timer.data=(unsigned long)sl;
	sl->outfill_timer.function=sl_outfill;
#endif
	/* Needed because address '0' is special */
	if (dev->pa_addr == 0)  {
		dev->pa_addr=ntohl(0xC0A80001);
	}
	dev->tbusy  = 0;
/*	dev->flags |= IFF_UP; */
	dev->start  = 1;

	return 0;

	/* Cleanup */
#ifdef SL_INCLUDE_CSLIP
noslcomp:
	kfree(sl->cbuff);
nocbuff:
#endif
	kfree(sl->xbuff);
noxbuff:
	kfree(sl->rbuff);
norbuff:
	return -ENOMEM;
}


/* Close the low-level part of the SLIP channel. Easy! */
static int
sl_close(struct device *dev)
{
	struct slip *sl = (struct slip*)(dev->priv);

	if (sl->tty == NULL) {
		return -EBUSY;
	}
	sl->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
	dev->tbusy = 1;
	dev->start = 0;
	
/*	dev->flags &= ~IFF_UP; */

	return 0;
}

static int
slip_receive_room(struct tty_struct *tty)
{
	return 65536;  /* We can handle an infinite amount of data. :-) */
}

/*
 * Handle the 'receiver data ready' interrupt.
 * This function is called by the 'tty_io' module in the kernel when
 * a block of SLIP data has been received, which can now be decapsulated
 * and sent on to some IP layer for further processing.
 */
static void
slip_receive_buf(struct tty_struct *tty, const unsigned char *cp, char *fp, int count)
{
	struct slip *sl = (struct slip *) tty->disc_data;

	if (!sl || sl->magic != SLIP_MAGIC || !sl->dev->start)
		return;

	/*
	 * Argh! mtu change time! - costs us the packet part received
	 * at the change
	 */
	if (sl->mtu != sl->dev->mtu)  {

		sl_changedmtu(sl);
	}

	/* Read the characters out of the buffer */
	while (count--) {
		if (fp && *fp++) {
			if (!set_bit(SLF_ERROR, &sl->flags))  {
				sl->rx_errors++;
			}
			cp++;
			continue;
		}
#ifdef CONFIG_SLIP_MODE_SLIP6
		if (sl->mode & SL_MODE_SLIP6)
			slip_unesc6(sl, *cp++);
		else
#endif
			slip_unesc(sl, *cp++);
	}
}

/*
 * Open the high-level part of the SLIP channel.
 * This function is called by the TTY module when the
 * SLIP line discipline is called for.  Because we are
 * sure the tty line exists, we only have to link it to
 * a free SLIP channel...
 */
static int
slip_open(struct tty_struct *tty)
{
	struct slip *sl = (struct slip *) tty->disc_data;
	int err;

	/* First make sure we're not already connected. */
	if (sl && sl->magic == SLIP_MAGIC) {
		return -EEXIST;
	}

	/* OK.  Find a free SLIP channel to use. */
	if ((sl = sl_alloc()) == NULL) {
		return -ENFILE;
	}

	sl->tty = tty;
	tty->disc_data = sl;
	if (tty->driver.flush_buffer)  {
		tty->driver.flush_buffer(tty);
	}
	if (tty->ldisc.flush_buffer)  {
		tty->ldisc.flush_buffer(tty);
	}

	/* Restore default settings */
	sl->mode      = SL_MODE_DEFAULT;
	sl->dev->type = ARPHRD_SLIP + sl->mode;
	/* Perform the low-level SLIP initialization. */
	if ((err = sl_open(sl->dev)))  {
		return err;
	}
	
	MOD_INC_USE_COUNT;

	/* Done.  We have linked the TTY line to a channel. */
	return sl->dev->base_addr;
}


/*
 * Close down a SLIP channel.
 * This means flushing out any pending queues, and then restoring the
 * TTY line discipline to what it was before it got hooked to SLIP
 * (which usually is TTY again).
 */
static void
slip_close(struct tty_struct *tty)
{
	struct slip *sl = (struct slip *) tty->disc_data;

	/* First make sure we're connected. */
	if (!sl || sl->magic != SLIP_MAGIC) {
		return;
	}

	(void) dev_close(sl->dev);
	
	tty->disc_data = 0;
	sl->tty = NULL;
	/* VSV = very important to remove timers */
#ifdef CONFIG_SLIP_SMART
	if (sl->keepalive)
		(void)del_timer (&sl->keepalive_timer);
	if (sl->outfill)
		(void)del_timer (&sl->outfill_timer);
#endif
	sl_free(sl);
	unregister_netdev(sl->dev);
	MOD_DEC_USE_COUNT;
}


static struct enet_statistics *
sl_get_stats(struct device *dev)
{
	static struct enet_statistics stats;
	struct slip *sl = (struct slip*)(dev->priv);
#ifdef SL_INCLUDE_CSLIP
	struct slcompress *comp;
#endif

	memset(&stats, 0, sizeof(struct enet_statistics));

	stats.rx_packets     = sl->rx_packets;
	stats.tx_packets     = sl->tx_packets;
	stats.rx_dropped     = sl->rx_dropped;
	stats.tx_dropped     = sl->tx_dropped;
	stats.tx_errors      = sl->tx_errors;
	stats.rx_errors      = sl->rx_errors;
	stats.rx_over_errors = sl->rx_over_errors;
#ifdef SL_INCLUDE_CSLIP
	stats.rx_fifo_errors = sl->rx_compressed;
	stats.tx_fifo_errors = sl->tx_compressed;
	stats.collisions     = sl->tx_misses;
	comp = sl->slcomp;
	if (comp) {
		stats.rx_fifo_errors += comp->sls_i_compressed;
		stats.rx_dropped     += comp->sls_i_tossed;
		stats.tx_fifo_errors += comp->sls_o_compressed;
		stats.collisions     += comp->sls_o_misses;
	}
#endif /* CONFIG_INET */
	return (&stats);
}


 /************************************************************************
  *			STANDARD SLIP ENCAPSULATION		  	 *
  ************************************************************************/

int
slip_esc(unsigned char *s, unsigned char *d, int len)
{
	unsigned char *ptr = d;
	unsigned char c;

	/*
	 * Send an initial END character to flush out any
	 * data that may have accumulated in the receiver
	 * due to line noise.
	 */

	*ptr++ = END;

	/*
	 * For each byte in the packet, send the appropriate
	 * character sequence, according to the SLIP protocol.
	 */

	while (len-- > 0) {
		switch(c = *s++) {
		 case END:
			*ptr++ = ESC;
			*ptr++ = ESC_END;
			break;
		 case ESC:
			*ptr++ = ESC;
			*ptr++ = ESC_ESC;
			break;
		 default:
			*ptr++ = c;
			break;
		}
	}
	*ptr++ = END;
	return (ptr - d);
}

static void
slip_unesc(struct slip *sl, unsigned char s)
{

	switch(s) {
	 case END:
		/* drop keeptest bit = VSV */
		if (test_bit(SLF_KEEPTEST, &sl->flags))
			clear_bit(SLF_KEEPTEST, &sl->flags);

		if (!clear_bit(SLF_ERROR, &sl->flags) && (sl->rcount > 2))  {
			sl_bump(sl);
		}
		clear_bit(SLF_ESCAPE, &sl->flags);
		sl->rcount = 0;
		return;

	 case ESC:
		set_bit(SLF_ESCAPE, &sl->flags);
		return;
	 case ESC_ESC:
		if (clear_bit(SLF_ESCAPE, &sl->flags))  {
			s = ESC;
		}
		break;
	 case ESC_END:
		if (clear_bit(SLF_ESCAPE, &sl->flags))  {
			s = END;
		}
		break;
	}
	if (!test_bit(SLF_ERROR, &sl->flags))  {
		if (sl->rcount < sl->buffsize)  {
			sl->rbuff[sl->rcount++] = s;
			return;
		}
		sl->rx_over_errors++;
		set_bit(SLF_ERROR, &sl->flags);
	}
}


#ifdef CONFIG_SLIP_MODE_SLIP6
/************************************************************************
 *			 6 BIT SLIP ENCAPSULATION			*
 ************************************************************************/

int
slip_esc6(unsigned char *s, unsigned char *d, int len)
{
	unsigned char *ptr = d;
	unsigned char c;
	int i;
	unsigned short v = 0;
	short bits = 0;

	/*
	 * Send an initial END character to flush out any
	 * data that may have accumulated in the receiver
	 * due to line noise.
	 */

	*ptr++ = 0x70;

	/*
	 * Encode the packet into printable ascii characters
	 */

	for (i = 0; i < len; ++i) {
		v = (v << 8) | s[i];
		bits += 8;
		while (bits >= 6) {
			bits -= 6;
			c = 0x30 + ((v >> bits) & 0x3F);
			*ptr++ = c;
		}
	}
	if (bits) {
		c = 0x30 + ((v << (6 - bits)) & 0x3F);
		*ptr++ = c;
	}
	*ptr++ = 0x70;
	return ptr - d;
}

void
slip_unesc6(struct slip *sl, unsigned char s)
{
	unsigned char c;

	if (s == 0x70) {
		/* drop keeptest bit = VSV */
		if (test_bit(SLF_KEEPTEST, &sl->flags))
			clear_bit(SLF_KEEPTEST, &sl->flags);

		if (!clear_bit(SLF_ERROR, &sl->flags) && (sl->rcount > 2))  {
			sl_bump(sl);
		}
		sl->rcount = 0;
		sl->xbits = 0;
		sl->xdata = 0;
 	} else if (s >= 0x30 && s < 0x70) {
		sl->xdata = (sl->xdata << 6) | ((s - 0x30) & 0x3F);
		sl->xbits += 6;
		if (sl->xbits >= 8) {
			sl->xbits -= 8;
			c = (unsigned char)(sl->xdata >> sl->xbits);
			if (!test_bit(SLF_ERROR, &sl->flags))  {
				if (sl->rcount < sl->buffsize)  {
					sl->rbuff[sl->rcount++] = c;
					return;
				}
				sl->rx_over_errors++;
				set_bit(SLF_ERROR, &sl->flags);
			}
		}
 	}
}
#endif /* CONFIG_SLIP_MODE_SLIP6 */

/* Perform I/O control on an active SLIP channel. */
static int
slip_ioctl(struct tty_struct *tty, void *file, int cmd, void *arg)
{
	struct slip *sl = (struct slip *) tty->disc_data;
	int err;
	unsigned int tmp;

	/* First make sure we're connected. */
	if (!sl || sl->magic != SLIP_MAGIC) {
		return -EINVAL;
	}

	switch(cmd) {
	 case SIOCGIFNAME:
		err = verify_area(VERIFY_WRITE, arg, strlen(sl->dev->name) + 1);
		if (err)  {
			return err;
		}
		copy_to_user(arg, sl->dev->name, strlen(sl->dev->name) + 1);
		return 0;

	case SIOCGIFENCAP:
		err = verify_area(VERIFY_WRITE, arg, sizeof(int));
		if (err)  {
			return err;
		}
		put_user(sl->mode, (int *)arg);
		return 0;

	case SIOCSIFENCAP:
		err = verify_area(VERIFY_READ, arg, sizeof(int));
		if (err)  {
			return err;
		}
		get_user(tmp,(int *)arg);
#ifndef SL_INCLUDE_CSLIP
		if (tmp & (SL_MODE_CSLIP|SL_MODE_ADAPTIVE))  {
			return -EINVAL;
		}
#else
		if ((tmp & (SL_MODE_ADAPTIVE | SL_MODE_CSLIP)) ==
		    (SL_MODE_ADAPTIVE | SL_MODE_CSLIP))  {
			/* return -EINVAL; */
			tmp &= ~SL_MODE_ADAPTIVE;
		}
#endif
#ifndef CONFIG_SLIP_MODE_SLIP6
		if (tmp & SL_MODE_SLIP6)  {
			return -EINVAL;
		}
#endif
		sl->mode = tmp;
		sl->dev->type = ARPHRD_SLIP+sl->mode;
		return 0;

	 case SIOCSIFHWADDR:
		return -EINVAL;

#ifdef CONFIG_SLIP_SMART
	/* VSV changes start here */
        case SIOCSKEEPALIVE:
                if (sl->keepalive)
                        (void)del_timer (&sl->keepalive_timer);
		err = verify_area(VERIFY_READ, arg, sizeof(int));
		if (err)  {
			return -err;
		}
		get_user(tmp,(int *)arg);
                if (tmp > 255) /* max for unchar */
			return -EINVAL; 
		if ((sl->keepalive = (unchar) tmp) != 0) {
			sl->keepalive_timer.expires=jiffies+sl->keepalive*HZ;
			add_timer(&sl->keepalive_timer);
			set_bit(SLF_KEEPTEST, &sl->flags);
                }
		return 0;

        case SIOCGKEEPALIVE:
		err = verify_area(VERIFY_WRITE, arg, sizeof(int));
		if (err)  {
			return -err;
		}
		put_user(sl->keepalive, (int *)arg);
		return 0;

        case SIOCSOUTFILL:
                if (sl->outfill)
                         (void)del_timer (&sl->outfill_timer);
		err = verify_area(VERIFY_READ, arg, sizeof(int));
		if (err)  {
			return -err;
		}
		get_user(tmp,(int *)arg);
                if (tmp > 255) /* max for unchar */
			return -EINVAL;
                if ((sl->outfill = (unchar) tmp) != 0){
			sl->outfill_timer.expires=jiffies+sl->outfill*HZ;
			add_timer(&sl->outfill_timer);
			set_bit(SLF_OUTWAIT, &sl->flags);
		}
                return 0;

        case SIOCGOUTFILL:
		err = verify_area(VERIFY_WRITE, arg, sizeof(int));
		if (err)  {
			return -err;
		}
		put_user(sl->outfill, (int *)arg);
		return 0;
	/* VSV changes end */
#endif	

	/* Allow stty to read, but not set, the serial port */
	case TCGETS:
	case TCGETA:
		return n_tty_ioctl(tty, (struct file *) file, cmd, (unsigned long) arg);

	default:
		return -ENOIOCTLCMD;
	}
}

static int sl_open_dev(struct device *dev)
{
	struct slip *sl = (struct slip*)(dev->priv);
	if(sl->tty==NULL)
		return -ENODEV;
	return 0;
}

/* Initialize SLIP control device -- register SLIP line discipline */
#ifdef MODULE
static int slip_init_ctrl_dev(void)
#else	/* !MODULE */
int slip_init_ctrl_dev(struct device *dummy)
#endif	/* !MODULE */
{
	int status;

	if (slip_maxdev < 4) slip_maxdev = 4; /* Sanity */

	printk(KERN_INFO "SLIP: version %s (dynamic channels, max=%d)"
#ifdef CONFIG_SLIP_MODE_SLIP6
	       " (6 bit encapsulation enabled)"
#endif
	       ".\n",
	       SLIP_VERSION, slip_maxdev );
#if defined(SL_INCLUDE_CSLIP) && !defined(MODULE)
	printk("CSLIP: code copyright 1989 Regents of the University of California.\n");
#endif
#ifdef CONFIG_SLIP_SMART
	printk(KERN_INFO "SLIP linefill/keepalive option.\n");
#endif	

	slip_ctrls = (slip_ctrl_t **) kmalloc(sizeof(void*)*slip_maxdev, GFP_KERNEL);
	if (slip_ctrls == NULL) 
	{
		printk("SLIP: Can't allocate slip_ctrls[] array!  Uaargh! (-> No SLIP available)\n");
		return -ENOMEM;
	}
	
	/* Clear the pointer array, we allocate devices when we need them */
	memset(slip_ctrls, 0, sizeof(void*)*slip_maxdev); /* Pointers */

	/* Fill in our line protocol discipline, and register it */
	memset(&sl_ldisc, 0, sizeof(sl_ldisc));
	sl_ldisc.magic  = TTY_LDISC_MAGIC;
	sl_ldisc.flags  = 0;
	sl_ldisc.open   = slip_open;
	sl_ldisc.close  = slip_close;
	sl_ldisc.read   = NULL;
	sl_ldisc.write  = NULL;
	sl_ldisc.ioctl  = (int (*)(struct tty_struct *, struct file *,
				   unsigned int, unsigned long)) slip_ioctl;
	sl_ldisc.select = NULL;
	sl_ldisc.receive_buf = slip_receive_buf;
	sl_ldisc.receive_room = slip_receive_room;
	sl_ldisc.write_wakeup = slip_write_wakeup;
	if ((status = tty_register_ldisc(N_SLIP, &sl_ldisc)) != 0)  {
		printk("SLIP: can't register line discipline (err = %d)\n", status);
	}


#ifdef MODULE
	return status;
#else
	/* Return "not found", so that dev_init() will unlink
	 * the placeholder device entry for us.
	 */
	return ENODEV;
#endif
      }


/* Initialize the SLIP driver.  Called by DDI. */
int
slip_init(struct device *dev)
{
	struct slip *sl = (struct slip*)(dev->priv);
	int i;

	if (sl == NULL)		/* Allocation failed ?? */
	  return -ENODEV;

	/* Set up the "SLIP Control Block". (And clear statistics) */
	
	memset(sl, 0, sizeof (struct slip));
	sl->magic  = SLIP_MAGIC;
	sl->dev	   = dev;
	
	/* Finish setting up the DEVICE info. */
	dev->mtu		= SL_MTU;
	dev->hard_start_xmit	= sl_xmit;
	dev->open		= sl_open_dev;
	dev->stop		= sl_close;
	dev->hard_header	= sl_header;
	dev->get_stats	        = sl_get_stats;
	dev->hard_header_len	= 0;
	dev->addr_len		= 0;
	dev->type		= ARPHRD_SLIP + SL_MODE_DEFAULT;
	dev->tx_queue_len	= 10;
	dev->rebuild_header	= sl_rebuild_header;

	for (i = 0; i < DEV_NUMBUFFS; i++)  {
		skb_queue_head_init(&dev->buffs[i]);
	}

	/* New-style flags. */
	dev->flags		= 0;
	dev->family		= AF_INET;
	dev->pa_addr		= 0;
	dev->pa_brdaddr	        = 0;
	dev->pa_mask		= 0;
	dev->pa_alen		= 4;

	return 0;
}
#ifdef MODULE

int
init_module(void)
{
	return slip_init_ctrl_dev();
}

void
cleanup_module(void)
{
	int i;

	if (slip_ctrls != NULL) 
	{
		for (i = 0; i < slip_maxdev; i++)  
		{
			if (slip_ctrls[i])
			{
				/*
				 * VSV = if dev->start==0, then device
				 * unregistered while close proc.
				 */ 
				if (slip_ctrls[i]->dev.start)
					unregister_netdev(&(slip_ctrls[i]->dev));

				kfree(slip_ctrls[i]);
				slip_ctrls[i] = NULL;
			}
		}
		kfree(slip_ctrls);
		slip_ctrls = NULL;
	}
	if ((i = tty_register_ldisc(N_SLIP, NULL)))  
	{
		printk("SLIP: can't unregister line discipline (err = %d)\n", i);
	}
}
#endif /* MODULE */

#ifdef CONFIG_SLIP_SMART
/*
 * This is start of the code for multislip style line checking
 * added by Stanislav Voronyi. All changes before marked VSV
 */
 
static void sl_outfill(unsigned long sls)
{
	struct slip *sl=(struct slip *)sls;

	if(sls==0L)
		return;

	if(sl->outfill)
	{
		if( test_bit(SLF_OUTWAIT, &sl->flags) )
		{
			/* no packets were transmitted, do outfill */
#ifdef CONFIG_SLIP_MODE_SLIP6
			unsigned char s = (sl->mode & SL_MODE_SLIP6)?0x70:END;
#else
			unsigned char s = END;
#endif
			/* put END into tty queue. Is it right ??? */
			if (!test_bit(0, (void *) &sl->dev->tbusy))
			{ 
				/* if device busy no outfill */
				sl->tty->driver.write(sl->tty, 0, &s, 1);
			}
		}
		else
			set_bit(SLF_OUTWAIT, &sl->flags);
		(void)del_timer(&sl->outfill_timer);
		sl->outfill_timer.expires=jiffies+sl->outfill*HZ;
		add_timer(&sl->outfill_timer);
	}
	else
		del_timer(&sl->outfill_timer);
}

static void sl_keepalive(unsigned long sls)
{
	struct slip *sl=(struct slip *)sls;

	if(sl == NULL)
		return;

	if( sl->keepalive)
	{
		if(test_bit(SLF_KEEPTEST, &sl->flags))
		{
			/* keepalive still high :(, we must hangup */
			(void)del_timer(&sl->keepalive_timer);
			if( sl->outfill ) /* outfill timer must be deleted too */
				(void)del_timer(&sl->outfill_timer);
			printk("%s: no packets received during keepalive timeout, hangup.\n", sl->dev->name);
			tty_hangup(sl->tty); /* this must hangup tty & close slip */
			/* I think we need not something else */
			return;
		}
		else
			set_bit(SLF_KEEPTEST, &sl->flags);
		(void)del_timer(&sl->keepalive_timer);
		 sl->keepalive_timer.expires=jiffies+sl->keepalive*HZ;
		add_timer(&sl->keepalive_timer);
	}
	else
		(void)del_timer(&sl->keepalive_timer);
}

#endif