Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1522 insertions, 0 deletions

diff --git a/drivers/net/slip.c b/drivers/net/slip.c
new file mode 100644
index 0000000..4ce52f5
--- /dev/null
+++ b/drivers/net/slip.c
@@ -0,0 +1,1522 @@
+/*
+ * 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.
+ *	Vitaly E. Lavrov	:	Sane behaviour on tty hangup.
+ *	Alexey Kuznetsov	:	Cleanup interfaces to tty&netdevice modules.
+ */
+
+#define SL_CHECK_TRANSMIT
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <linux/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/rtnetlink.h>
+#include <linux/if_arp.h>
+#include <linux/if_slip.h>
+#include <linux/init.h>
+#include "slip.h"
+#ifdef CONFIG_INET
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <net/slhc_vj.h>
+#endif
+
+#define SLIP_VERSION	"0.8.4-NET3.019-NEWTTY"
+
+static struct net_device **slip_devs;
+
+static int slip_maxdev = SL_NRUNIT;
+module_param(slip_maxdev, int, 0);
+MODULE_PARM_DESC(slip_maxdev, "Maximum number of slip devices");
+
+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);
+static int sl_ioctl(struct net_device *dev,struct ifreq *rq,int cmd);
+#endif
+
+/********************************
+*  Buffer administration routines:
+*	sl_alloc_bufs()
+*	sl_free_bufs()
+*	sl_realloc_bufs()
+*
+* NOTE: sl_realloc_bufs != sl_free_bufs + sl_alloc_bufs, because
+*	sl_realloc_bufs provides strong atomicity and reallocation
+*	on actively running device.
+*********************************/
+
+/* 
+   Allocate channel buffers.
+ */
+
+static int
+sl_alloc_bufs(struct slip *sl, int mtu)
+{
+	int err = -ENOBUFS;
+	unsigned long len;
+	char * rbuff = NULL;
+	char * xbuff = NULL;
+#ifdef SL_INCLUDE_CSLIP
+	char * cbuff = NULL;
+	struct slcompress *slcomp = NULL;
+#endif
+
+	/*
+	 * Allocate the SLIP frame buffers:
+	 *
+	 * rbuff	Receive buffer.
+	 * xbuff	Transmit buffer.
+	 * cbuff        Temporary compression buffer.
+	 */
+	len = 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;
+	rbuff = kmalloc(len + 4, GFP_KERNEL);
+	if (rbuff == NULL)
+		goto err_exit;
+	xbuff = kmalloc(len + 4, GFP_KERNEL);
+	if (xbuff == NULL)
+		goto err_exit;
+#ifdef SL_INCLUDE_CSLIP
+	cbuff = kmalloc(len + 4, GFP_KERNEL);
+	if (cbuff == NULL)
+		goto err_exit;
+	slcomp = slhc_init(16, 16);
+	if (slcomp == NULL)
+		goto err_exit;
+#endif
+	spin_lock_bh(&sl->lock);
+	if (sl->tty == NULL) {
+		spin_unlock_bh(&sl->lock);
+		err = -ENODEV;
+		goto err_exit;
+	}
+	sl->mtu	     = mtu;
+	sl->buffsize = len;
+	sl->rcount   = 0;
+	sl->xleft    = 0;
+	rbuff = xchg(&sl->rbuff, rbuff);
+	xbuff = xchg(&sl->xbuff, xbuff);
+#ifdef SL_INCLUDE_CSLIP
+	cbuff = xchg(&sl->cbuff, cbuff);
+	slcomp = xchg(&sl->slcomp, slcomp);
+#ifdef CONFIG_SLIP_MODE_SLIP6
+	sl->xdata    = 0;
+	sl->xbits    = 0;
+#endif
+#endif
+	spin_unlock_bh(&sl->lock);
+	err = 0;
+
+	/* Cleanup */
+err_exit:
+#ifdef SL_INCLUDE_CSLIP
+	if (cbuff)
+		kfree(cbuff);
+	if (slcomp)
+		slhc_free(slcomp);
+#endif
+	if (xbuff)
+		kfree(xbuff);
+	if (rbuff)
+		kfree(rbuff);
+	return err;
+}
+
+/* Free a SLIP channel buffers. */
+static void
+sl_free_bufs(struct slip *sl)
+{
+	void * tmp;
+
+	/* Free all SLIP frame buffers. */
+	if ((tmp = xchg(&sl->rbuff, NULL)) != NULL)
+		kfree(tmp);
+	if ((tmp = xchg(&sl->xbuff, NULL)) != NULL)
+		kfree(tmp);
+#ifdef SL_INCLUDE_CSLIP
+	if ((tmp = xchg(&sl->cbuff, NULL)) != NULL)
+		kfree(tmp);
+	if ((tmp = xchg(&sl->slcomp, NULL)) != NULL)
+		slhc_free(tmp);
+#endif
+}
+
+/* 
+   Reallocate slip channel buffers.
+ */
+
+static int sl_realloc_bufs(struct slip *sl, int mtu)
+{
+	int err = 0;
+	struct net_device *dev = sl->dev;
+	unsigned char *xbuff, *rbuff;
+#ifdef SL_INCLUDE_CSLIP
+	unsigned char *cbuff;
+#endif
+	int len = 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
+		if (mtu >= sl->mtu) {
+			printk(KERN_WARNING "%s: unable to grow slip buffers, MTU change cancelled.\n",
+			       dev->name);
+			err = -ENOBUFS;
+		}
+		goto done;
+	}
+
+	spin_lock_bh(&sl->lock);
+
+	err = -ENODEV;
+	if (sl->tty == NULL)
+		goto done_on_bh;
+
+	xbuff    = xchg(&sl->xbuff, xbuff);
+	rbuff    = xchg(&sl->rbuff, rbuff);
+#ifdef SL_INCLUDE_CSLIP
+	cbuff    = xchg(&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, rbuff, sl->rcount);
+		} else  {
+			sl->rcount = 0;
+			sl->rx_over_errors++;
+			set_bit(SLF_ERROR, &sl->flags);
+		}
+	}
+	sl->mtu      = mtu;
+	dev->mtu      = mtu;
+	sl->buffsize = len;
+	err = 0;
+
+done_on_bh:
+	spin_unlock_bh(&sl->lock);
+
+done:
+	if (xbuff)
+		kfree(xbuff);
+	if (rbuff)
+		kfree(rbuff);
+#ifdef SL_INCLUDE_CSLIP
+	if (cbuff)
+		kfree(cbuff);
+#endif
+	return err;
+}
+
+
+/* Set the "sending" flag.  This must be atomic hence the set_bit. */
+static inline void
+sl_lock(struct slip *sl)
+{
+	netif_stop_queue(sl->dev);
+}
+
+
+/* Clear the "sending" flag.  This must be atomic, hence the ASM. */
+static inline void
+sl_unlock(struct slip *sl)
+{
+	netif_wake_queue(sl->dev);
+}
+
+/* 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(KERN_WARNING "%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(KERN_INFO "%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 */
+
+	sl->rx_bytes+=count;
+	
+	skb = dev_alloc_skb(count);
+	if (skb == NULL)  {
+		printk(KERN_WARNING "%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->dev->last_rx = jiffies;
+	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 (len > sl->mtu) {		/* Sigh, shouldn't occur BUT ... */
+		printk(KERN_WARNING "%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, sl->xbuff, count);
+#ifdef SL_CHECK_TRANSMIT
+	sl->dev->trans_start = jiffies;
+#endif
+	sl->xleft = count - actual;
+	sl->xhead = sl->xbuff + actual;
+#ifdef CONFIG_SLIP_SMART
+	/* VSV */
+	clear_bit(SLF_OUTWAIT, &sl->flags);	/* reset outfill flag */
+#endif
+}
+
+/*
+ * 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 || !netif_running(sl->dev)) {
+		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);
+		return;
+	}
+
+	actual = tty->driver->write(tty, sl->xhead, sl->xleft);
+	sl->xleft -= actual;
+	sl->xhead += actual;
+}
+
+static void sl_tx_timeout(struct net_device *dev)
+{
+	struct slip *sl = netdev_priv(dev);
+
+	spin_lock(&sl->lock);
+
+	if (netif_queue_stopped(dev)) {
+		if (!netif_running(dev))
+			goto out;
+
+		/* May be we must check transmitter timeout here ?
+		 *      14 Oct 1994 Dmitry Gorodchanin.
+		 */
+#ifdef SL_CHECK_TRANSMIT
+		if (time_before(jiffies, dev->trans_start + 20 * HZ))  {
+			/* 20 sec timeout not reached */
+			goto out;
+		}
+		printk(KERN_WARNING "%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);
+#endif
+	}
+
+out:
+	spin_unlock(&sl->lock);
+}
+
+
+/* Encapsulate an IP datagram and kick it into a TTY queue. */
+static int
+sl_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct slip *sl = netdev_priv(dev);
+
+	spin_lock(&sl->lock);
+	if (!netif_running(dev))  {
+		spin_unlock(&sl->lock);
+		printk(KERN_WARNING "%s: xmit call when iface is down\n", dev->name);
+		dev_kfree_skb(skb);
+		return 0;
+	}
+	if (sl->tty == NULL) {
+		spin_unlock(&sl->lock);
+		dev_kfree_skb(skb);
+		return 0;
+	}
+
+	sl_lock(sl);
+	sl->tx_bytes+=skb->len;
+	sl_encaps(sl, skb->data, skb->len);
+	spin_unlock(&sl->lock);
+
+	dev_kfree_skb(skb);
+	return 0;
+}
+
+
+/******************************************
+ *   Routines looking at netdevice side.
+ ******************************************/
+
+/* Netdevice UP -> DOWN routine */
+
+static int
+sl_close(struct net_device *dev)
+{
+	struct slip *sl = netdev_priv(dev);
+
+	spin_lock_bh(&sl->lock);
+	if (sl->tty) {
+		/* TTY discipline is running. */
+		sl->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
+	}
+	netif_stop_queue(dev);
+	sl->rcount   = 0;
+	sl->xleft    = 0;
+	spin_unlock_bh(&sl->lock);
+
+	return 0;
+}
+
+/* Netdevice DOWN -> UP routine */
+
+static int sl_open(struct net_device *dev)
+{
+	struct slip *sl = netdev_priv(dev);
+
+	if (sl->tty==NULL)
+		return -ENODEV;
+
+	sl->flags &= (1 << SLF_INUSE);
+	netif_start_queue(dev);
+	return 0;
+}
+
+/* Netdevice change MTU request */
+
+static int sl_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct slip *sl = netdev_priv(dev);
+
+	if (new_mtu < 68 || new_mtu > 65534)
+		return -EINVAL;
+
+	if (new_mtu != dev->mtu)
+		return sl_realloc_bufs(sl, new_mtu);
+	return 0;
+}
+
+/* Netdevice get statistics request */
+
+static struct net_device_stats *
+sl_get_stats(struct net_device *dev)
+{
+	static struct net_device_stats stats;
+	struct slip *sl = netdev_priv(dev);
+#ifdef SL_INCLUDE_CSLIP
+	struct slcompress *comp;
+#endif
+
+	memset(&stats, 0, sizeof(struct net_device_stats));
+
+	stats.rx_packets     = sl->rx_packets;
+	stats.tx_packets     = sl->tx_packets;
+	stats.rx_bytes	     = sl->rx_bytes;
+	stats.tx_bytes	     = sl->tx_bytes;
+	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);
+}
+
+/* Netdevice register callback */
+
+static int sl_init(struct net_device *dev)
+{
+	struct slip *sl = netdev_priv(dev);
+
+	/*
+	 *	Finish setting up the DEVICE info. 
+	 */
+
+	dev->mtu		= sl->mtu;
+	dev->type		= ARPHRD_SLIP + sl->mode;
+#ifdef SL_CHECK_TRANSMIT
+	dev->tx_timeout		= sl_tx_timeout;
+	dev->watchdog_timeo	= 20*HZ;
+#endif
+	return 0;
+}
+
+
+static void sl_uninit(struct net_device *dev)
+{
+	struct slip *sl = netdev_priv(dev);
+
+	sl_free_bufs(sl);
+}
+
+static void sl_setup(struct net_device *dev)
+{
+	dev->init		= sl_init;
+	dev->uninit	  	= sl_uninit;
+	dev->open		= sl_open;
+	dev->destructor		= free_netdev;
+	dev->stop		= sl_close;
+	dev->get_stats	        = sl_get_stats;
+	dev->change_mtu		= sl_change_mtu;
+	dev->hard_start_xmit	= sl_xmit;
+#ifdef CONFIG_SLIP_SMART
+	dev->do_ioctl		= sl_ioctl;
+#endif
+	dev->hard_header_len	= 0;
+	dev->addr_len		= 0;
+	dev->tx_queue_len	= 10;
+
+	SET_MODULE_OWNER(dev);
+
+	/* New-style flags. */
+	dev->flags		= IFF_NOARP|IFF_POINTOPOINT|IFF_MULTICAST;
+}
+
+/******************************************
+  Routines looking at TTY side.
+ ******************************************/
+
+
+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. This will not
+ * be re-entered while running but other ldisc functions may be called
+ * in parallel
+ */
+ 
+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 ||
+	    !netif_running(sl->dev))
+		return;
+
+	/* Read the characters out of the buffer */
+	while (count--) {
+		if (fp && *fp++) {
+			if (!test_and_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++);
+	}
+}
+
+/************************************
+ *  slip_open helper routines.
+ ************************************/
+
+/* Collect hanged up channels */
+
+static void sl_sync(void)
+{
+	int i;
+	struct net_device *dev;
+	struct slip	  *sl;
+
+	for (i = 0; i < slip_maxdev; i++) {
+		if ((dev = slip_devs[i]) == NULL)
+			break;
+
+		sl = netdev_priv(dev);
+		if (sl->tty || sl->leased)
+			continue;
+		if (dev->flags&IFF_UP)
+			dev_close(dev);
+	}
+}
+
+
+/* Find a free SLIP channel, and link in this `tty' line. */
+static struct slip *
+sl_alloc(dev_t line)
+{
+	int i;
+	int sel = -1;
+	int score = -1;
+	struct net_device *dev = NULL;
+	struct slip       *sl;
+
+	if (slip_devs == NULL) 
+		return NULL;	/* Master array missing ! */
+
+	for (i = 0; i < slip_maxdev; i++) {
+		dev = slip_devs[i];
+		if (dev == NULL)
+			break;
+
+		sl = netdev_priv(dev);
+		if (sl->leased) {
+			if (sl->line != line)
+				continue;
+			if (sl->tty)
+				return NULL;
+
+			/* Clear ESCAPE & ERROR flags */
+			sl->flags &= (1 << SLF_INUSE);
+			return sl;
+		}
+
+		if (sl->tty)
+			continue;
+
+		if (current->pid == sl->pid) {
+			if (sl->line == line && score < 3) {
+				sel = i;
+				score = 3;
+				continue;
+			}
+			if (score < 2) {
+				sel = i;
+				score = 2;
+			}
+			continue;
+		}
+		if (sl->line == line && score < 1) {
+			sel = i;
+			score = 1;
+			continue;
+		}
+		if (score < 0) {
+			sel = i;
+			score = 0;
+		}
+	}
+
+	if (sel >= 0) {
+		i = sel;
+		dev = slip_devs[i];
+		if (score > 1) {
+			sl = netdev_priv(dev);
+			sl->flags &= (1 << SLF_INUSE);
+			return sl;
+		}
+	}
+
+	/* Sorry, too many, all slots in use */
+	if (i >= slip_maxdev)
+		return NULL;
+
+	if (dev) {
+		sl = netdev_priv(dev);
+		if (test_bit(SLF_INUSE, &sl->flags)) {
+			unregister_netdevice(dev);
+			dev = NULL;
+			slip_devs[i] = NULL;
+		}
+	}
+	
+	if (!dev) {
+		char name[IFNAMSIZ];
+		sprintf(name, "sl%d", i);
+
+		dev = alloc_netdev(sizeof(*sl), name, sl_setup);
+		if (!dev)
+			return NULL;
+		dev->base_addr  = i;
+	}
+
+	sl = netdev_priv(dev);
+
+	/* Initialize channel control data */
+	sl->magic       = SLIP_MAGIC;
+	sl->dev	      	= dev;
+	spin_lock_init(&sl->lock);
+	sl->mode        = SL_MODE_DEFAULT;
+#ifdef CONFIG_SLIP_SMART
+	init_timer(&sl->keepalive_timer);	/* initialize timer_list struct */
+	sl->keepalive_timer.data=(unsigned long)sl;
+	sl->keepalive_timer.function=sl_keepalive;
+	init_timer(&sl->outfill_timer);
+	sl->outfill_timer.data=(unsigned long)sl;
+	sl->outfill_timer.function=sl_outfill;
+#endif
+	slip_devs[i] = dev;
+				   
+	return sl;
+}
+
+/*
+ * 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...
+ *
+ * Called in process context serialized from other ldisc calls.
+ */
+
+static int slip_open(struct tty_struct *tty)
+{
+	struct slip *sl;
+	int err;
+
+	if(!capable(CAP_NET_ADMIN))
+		return -EPERM;
+		
+	/* RTnetlink lock is misused here to serialize concurrent
+	   opens of slip channels. There are better ways, but it is
+	   the simplest one.
+	 */
+	rtnl_lock();
+
+	/* Collect hanged up channels. */
+	sl_sync();
+
+	sl = (struct slip *) tty->disc_data;
+
+	err = -EEXIST;
+	/* First make sure we're not already connected. */
+	if (sl && sl->magic == SLIP_MAGIC)
+		goto err_exit;
+
+	/* OK.  Find a free SLIP channel to use. */
+	err = -ENFILE;
+	if ((sl = sl_alloc(tty_devnum(tty))) == NULL)
+		goto err_exit;
+
+	sl->tty = tty;
+	tty->disc_data = sl;
+	sl->line = tty_devnum(tty);
+	sl->pid = current->pid;
+	
+	/* FIXME: already done before we were called - seems this can go */
+	if (tty->driver->flush_buffer)
+		tty->driver->flush_buffer(tty);
+		
+	if (!test_bit(SLF_INUSE, &sl->flags)) {
+		/* Perform the low-level SLIP initialization. */
+		if ((err = sl_alloc_bufs(sl, SL_MTU)) != 0)
+			goto err_free_chan;
+
+		set_bit(SLF_INUSE, &sl->flags);
+
+		if ((err = register_netdevice(sl->dev)))
+			goto err_free_bufs;
+	}
+
+#ifdef CONFIG_SLIP_SMART
+	if (sl->keepalive) {
+		sl->keepalive_timer.expires=jiffies+sl->keepalive*HZ;
+		add_timer (&sl->keepalive_timer);
+	}
+	if (sl->outfill) {
+		sl->outfill_timer.expires=jiffies+sl->outfill*HZ;
+		add_timer (&sl->outfill_timer);
+	}
+#endif
+
+	/* Done.  We have linked the TTY line to a channel. */
+	rtnl_unlock();
+	return sl->dev->base_addr;
+
+err_free_bufs:
+	sl_free_bufs(sl);
+
+err_free_chan:
+	sl->tty = NULL;
+	tty->disc_data = NULL;
+	clear_bit(SLF_INUSE, &sl->flags);
+
+err_exit:
+	rtnl_unlock();
+
+	/* Count references from TTY module */
+	return err;
+}
+
+/*
+
+  FIXME: 1,2 are fixed 3 was never true anyway.
+  
+   Let me to blame a bit.
+   1. TTY module calls this funstion on soft interrupt.
+   2. TTY module calls this function WITH MASKED INTERRUPTS!
+   3. TTY module does not notify us about line discipline
+      shutdown,
+
+   Seems, now it is clean. The solution is to consider netdevice and
+   line discipline sides as two independent threads.
+
+   By-product (not desired): sl? does not feel hangups and remains open.
+   It is supposed, that user level program (dip, diald, slattach...)
+   will catch SIGHUP and make the rest of work. 
+
+   I see no way to make more with current tty code. --ANK
+ */
+
+/*
+ * Close down a SLIP channel.
+ * This means flushing out any pending queues, and then returning. This
+ * call is serialized against other ldisc functions.
+ */
+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 || sl->tty != tty)
+		return;
+
+	tty->disc_data = NULL;
+	sl->tty = NULL;
+	if (!sl->leased)
+		sl->line = 0;
+
+	/* VSV = very important to remove timers */
+#ifdef CONFIG_SLIP_SMART
+	del_timer_sync(&sl->keepalive_timer);
+	del_timer_sync(&sl->outfill_timer);
+#endif
+
+	/* Count references from TTY module */
+}
+
+ /************************************************************************
+  *			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:
+#ifdef CONFIG_SLIP_SMART
+		/* drop keeptest bit = VSV */
+		if (test_bit(SLF_KEEPTEST, &sl->flags))
+			clear_bit(SLF_KEEPTEST, &sl->flags);
+#endif
+
+		if (!test_and_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 (test_and_clear_bit(SLF_ESCAPE, &sl->flags))  {
+			s = ESC;
+		}
+		break;
+	 case ESC_END:
+		if (test_and_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) {
+#ifdef CONFIG_SLIP_SMART
+		/* drop keeptest bit = VSV */
+		if (test_bit(SLF_KEEPTEST, &sl->flags))
+			clear_bit(SLF_KEEPTEST, &sl->flags);
+#endif
+
+		if (!test_and_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, struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct slip *sl = (struct slip *) tty->disc_data;
+	unsigned int tmp;
+	int __user *p = (int __user *)arg;
+
+	/* First make sure we're connected. */
+	if (!sl || sl->magic != SLIP_MAGIC) {
+		return -EINVAL;
+	}
+
+	switch(cmd) {
+	 case SIOCGIFNAME:
+		tmp = strlen(sl->dev->name) + 1;
+		if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
+			return -EFAULT;
+		return 0;
+
+	case SIOCGIFENCAP:
+		if (put_user(sl->mode, p))
+			return -EFAULT;
+		return 0;
+
+	case SIOCSIFENCAP:
+		if (get_user(tmp, p))
+			return -EFAULT;
+#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 (get_user(tmp, p))
+			return -EFAULT;
+                if (tmp > 255) /* max for unchar */
+			return -EINVAL;
+
+		spin_lock_bh(&sl->lock);
+		if (!sl->tty) {
+			spin_unlock_bh(&sl->lock);
+			return -ENODEV;
+		}
+		if ((sl->keepalive = (unchar) tmp) != 0) {
+			mod_timer(&sl->keepalive_timer, jiffies+sl->keepalive*HZ);
+			set_bit(SLF_KEEPTEST, &sl->flags);
+                } else {
+                        del_timer (&sl->keepalive_timer);
+		}
+		spin_unlock_bh(&sl->lock);
+		return 0;
+
+        case SIOCGKEEPALIVE:
+		if (put_user(sl->keepalive, p))
+			return -EFAULT;
+		return 0;
+
+        case SIOCSOUTFILL:
+		if (get_user(tmp, p))
+			return -EFAULT;
+                if (tmp > 255) /* max for unchar */
+			return -EINVAL;
+		spin_lock_bh(&sl->lock);
+		if (!sl->tty) {
+			spin_unlock_bh(&sl->lock);
+			return -ENODEV;
+		}
+                if ((sl->outfill = (unchar) tmp) != 0){
+			mod_timer(&sl->outfill_timer, jiffies+sl->outfill*HZ);
+			set_bit(SLF_OUTWAIT, &sl->flags);
+		} else {
+                        del_timer (&sl->outfill_timer);
+		}
+		spin_unlock_bh(&sl->lock);
+                return 0;
+
+        case SIOCGOUTFILL:
+		if (put_user(sl->outfill, p))
+			return -EFAULT;
+		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, file, cmd, arg);
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
+/* VSV changes start here */
+#ifdef CONFIG_SLIP_SMART
+/* function do_ioctl called from net/core/dev.c
+   to allow get/set outfill/keepalive parameter
+   by ifconfig                                 */
+
+static int sl_ioctl(struct net_device *dev,struct ifreq *rq,int cmd)
+{
+	struct slip *sl = netdev_priv(dev);
+	unsigned long *p = (unsigned long *)&rq->ifr_ifru;
+
+	if (sl == NULL)		/* Allocation failed ?? */
+		return -ENODEV;
+
+	spin_lock_bh(&sl->lock);
+
+	if (!sl->tty) {
+		spin_unlock_bh(&sl->lock);
+		return -ENODEV;
+	}
+
+	switch(cmd){
+        case SIOCSKEEPALIVE:
+		/* max for unchar */
+                if ((unsigned)*p > 255) {
+			spin_unlock_bh(&sl->lock);
+			return -EINVAL;
+		}
+		sl->keepalive = (unchar) *p;
+		if (sl->keepalive != 0) {
+			sl->keepalive_timer.expires=jiffies+sl->keepalive*HZ;
+			mod_timer(&sl->keepalive_timer, jiffies+sl->keepalive*HZ);
+			set_bit(SLF_KEEPTEST, &sl->flags);
+                } else {
+                        del_timer(&sl->keepalive_timer);
+		}
+		break;
+
+        case SIOCGKEEPALIVE:
+		*p = sl->keepalive;
+		break;
+
+        case SIOCSOUTFILL:
+                if ((unsigned)*p > 255) { /* max for unchar */
+			spin_unlock_bh(&sl->lock);
+			return -EINVAL;
+		}
+                if ((sl->outfill = (unchar)*p) != 0){
+			mod_timer(&sl->outfill_timer, jiffies+sl->outfill*HZ);
+			set_bit(SLF_OUTWAIT, &sl->flags);
+		} else {
+                        del_timer (&sl->outfill_timer);
+		}
+                break;
+
+        case SIOCGOUTFILL:
+		*p = sl->outfill;
+		break;
+
+        case SIOCSLEASE:
+		/* Resolve race condition, when ioctl'ing hanged up 
+		   and opened by another process device.
+		 */
+		if (sl->tty != current->signal->tty && sl->pid != current->pid) {
+			spin_unlock_bh(&sl->lock);
+			return -EPERM;
+		}
+		sl->leased = 0;
+                if (*p)
+			sl->leased = 1;
+                break;
+
+        case SIOCGLEASE:
+		*p = sl->leased;
+	};
+	spin_unlock_bh(&sl->lock);
+	return 0;
+}
+#endif
+/* VSV changes end */
+
+static struct tty_ldisc	sl_ldisc = {
+	.owner 		= THIS_MODULE,
+	.magic 		= TTY_LDISC_MAGIC,
+	.name 		= "slip",
+	.open 		= slip_open,
+	.close	 	= slip_close,
+	.ioctl		= slip_ioctl,
+	.receive_buf	= slip_receive_buf,
+	.receive_room	= slip_receive_room,
+	.write_wakeup	= slip_write_wakeup,
+};
+
+static int __init slip_init(void)
+{
+	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)
+	printk(KERN_INFO "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_devs = kmalloc(sizeof(struct net_device *)*slip_maxdev, GFP_KERNEL);
+	if (!slip_devs) {
+		printk(KERN_ERR "SLIP: Can't allocate slip devices array!  Uaargh! (-> No SLIP available)\n");
+		return -ENOMEM;
+	}
+
+	/* Clear the pointer array, we allocate devices when we need them */
+	memset(slip_devs, 0, sizeof(struct net_device *)*slip_maxdev); 
+
+	/* Fill in our line protocol discipline, and register it */
+	if ((status = tty_register_ldisc(N_SLIP, &sl_ldisc)) != 0)  {
+		printk(KERN_ERR "SLIP: can't register line discipline (err = %d)\n", status);
+		kfree(slip_devs);
+	}
+	return status;
+}
+
+static void __exit slip_exit(void)
+{
+	int i;
+	struct net_device *dev;
+	struct slip *sl;
+	unsigned long timeout = jiffies + HZ;
+	int busy = 0;
+
+	if (slip_devs == NULL) 
+		return;
+
+	/* First of all: check for active disciplines and hangup them.
+	 */
+	do {
+		if (busy) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			schedule_timeout(HZ / 10);
+		}
+
+		busy = 0;
+		for (i = 0; i < slip_maxdev; i++) {
+			dev = slip_devs[i];
+			if (!dev)
+				continue;
+			sl = netdev_priv(dev);
+			spin_lock_bh(&sl->lock);
+			if (sl->tty) {
+				busy++;
+				tty_hangup(sl->tty);
+			}
+			spin_unlock_bh(&sl->lock);
+		}
+	} while (busy && time_before(jiffies, timeout));
+
+
+	for (i = 0; i < slip_maxdev; i++) {
+		dev = slip_devs[i];
+		if (!dev)
+			continue;
+		slip_devs[i] = NULL;
+
+		sl = netdev_priv(dev);
+		if (sl->tty) {
+			printk(KERN_ERR "%s: tty discipline still running\n",
+			       dev->name);
+			/* Intentionally leak the control block. */
+			dev->destructor = NULL;
+		} 
+
+		unregister_netdev(dev);
+	}
+
+	kfree(slip_devs);
+	slip_devs = NULL;
+
+	if ((i = tty_register_ldisc(N_SLIP, NULL)))
+	{
+		printk(KERN_ERR "SLIP: can't unregister line discipline (err = %d)\n", i);
+	}
+}
+
+module_init(slip_init);
+module_exit(slip_exit);
+
+#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;
+
+	spin_lock(&sl->lock);
+
+	if (sl->tty == NULL)
+		goto out;
+
+	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 (!netif_queue_stopped(sl->dev))
+			{
+				/* if device busy no outfill */
+				sl->tty->driver->write(sl->tty, &s, 1);
+			}
+		}
+		else
+			set_bit(SLF_OUTWAIT, &sl->flags);
+
+		mod_timer(&sl->outfill_timer, jiffies+sl->outfill*HZ);
+	}
+out:
+	spin_unlock(&sl->lock);
+}
+
+static void sl_keepalive(unsigned long sls)
+{
+	struct slip *sl=(struct slip *)sls;
+
+	spin_lock(&sl->lock);
+
+	if (sl->tty == NULL)
+		goto out;
+
+	if( sl->keepalive)
+	{
+		if(test_bit(SLF_KEEPTEST, &sl->flags))
+		{
+			/* keepalive still high :(, we must hangup */
+			if( sl->outfill ) /* outfill timer must be deleted too */
+				(void)del_timer(&sl->outfill_timer);
+			printk(KERN_DEBUG "%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 */
+			goto out;
+		}
+		else
+			set_bit(SLF_KEEPTEST, &sl->flags);
+
+		mod_timer(&sl->keepalive_timer, jiffies+sl->keepalive*HZ);
+	}
+
+out:
+	spin_unlock(&sl->lock);
+}
+
+#endif
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_LDISC(N_SLIP);