slip: Move the SLIP drivers

Move the Serial Line Internet Protocol (SLIP) drivers into
drivers/net/slip/ and make the necessary Kconfig and Makefile
changes.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Alan Cox <alan@linux.intel.com>

1 files changed, 1444 insertions, 0 deletions

diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
new file mode 100644
index 000000000000..ba08341fb92c
--- /dev/null
+++ b/drivers/net/slip/slip.c
@@ -0,0 +1,1444 @@
+/*
+ * 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/module.h>
+#include <linux/moduleparam.h>
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <linux/bitops.h>
+#include <linux/sched.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/compat.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/slab.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);
+#endif
+#ifdef CONFIG_SLIP_MODE_SLIP6
+	sl->xdata    = 0;
+	sl->xbits    = 0;
+#endif
+	spin_unlock_bh(&sl->lock);
+	err = 0;
+
+	/* Cleanup */
+err_exit:
+#ifdef SL_INCLUDE_CSLIP
+	kfree(cbuff);
+	slhc_free(slcomp);
+#endif
+	kfree(xbuff);
+	kfree(rbuff);
+	return err;
+}
+
+/* Free a SLIP channel buffers. */
+static void sl_free_bufs(struct slip *sl)
+{
+	/* Free all SLIP frame buffers. */
+	kfree(xchg(&sl->rbuff, NULL));
+	kfree(xchg(&sl->xbuff, NULL));
+#ifdef SL_INCLUDE_CSLIP
+	kfree(xchg(&sl->cbuff, NULL));
+	slhc_free(xchg(&sl->slcomp, NULL));
+#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 = kmalloc(len + 4, GFP_ATOMIC);
+	rbuff = kmalloc(len + 4, GFP_ATOMIC);
+#ifdef SL_INCLUDE_CSLIP
+	cbuff = 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;
+			dev->stats.tx_dropped++;
+		}
+	}
+	sl->xhead = sl->xbuff;
+
+	if (sl->rcount)  {
+		if (sl->rcount <= len) {
+			memcpy(sl->rbuff, rbuff, sl->rcount);
+		} else  {
+			sl->rcount = 0;
+			dev->stats.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:
+	kfree(xbuff);
+	kfree(rbuff);
+#ifdef SL_INCLUDE_CSLIP
+	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 net_device *dev = sl->dev;
+	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 = sl->rbuff[0];
+		if (c & 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", dev->name);
+				return;
+			}
+			/* make sure we've reserved enough space for uncompress
+			   to use */
+			if (count + 80 > sl->buffsize) {
+				dev->stats.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", dev->name);
+			}
+			sl->rbuff[0] &= 0x4f;
+			if (slhc_remember(sl->slcomp, sl->rbuff, count) <= 0)
+				return;
+		}
+	}
+#endif  /* SL_INCLUDE_CSLIP */
+
+	dev->stats.rx_bytes += count;
+
+	skb = dev_alloc_skb(count);
+	if (skb == NULL) {
+		printk(KERN_WARNING "%s: memory squeeze, dropping packet.\n", dev->name);
+		dev->stats.rx_dropped++;
+		return;
+	}
+	skb->dev = dev;
+	memcpy(skb_put(skb, count), sl->rbuff, count);
+	skb_reset_mac_header(skb);
+	skb->protocol = htons(ETH_P_IP);
+	netif_rx_ni(skb);
+	dev->stats.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->dev->stats.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 the ops->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.
+	 */
+	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
+	actual = sl->tty->ops->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 = 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->dev->stats.tx_packets++;
+		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+		sl_unlock(sl);
+		return;
+	}
+
+	actual = tty->ops->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(dev) + 20 * HZ))  {
+			/* 20 sec timeout not reached */
+			goto out;
+		}
+		printk(KERN_WARNING "%s: transmit timed out, %s?\n",
+			dev->name,
+			(tty_chars_in_buffer(sl->tty) || sl->xleft) ?
+				"bad line quality" : "driver error");
+		sl->xleft = 0;
+		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
+		sl_unlock(sl);
+#endif
+	}
+out:
+	spin_unlock(&sl->lock);
+}
+
+
+/* Encapsulate an IP datagram and kick it into a TTY queue. */
+static netdev_tx_t
+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 NETDEV_TX_OK;
+	}
+	if (sl->tty == NULL) {
+		spin_unlock(&sl->lock);
+		dev_kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
+
+	sl_lock(sl);
+	dev->stats.tx_bytes += skb->len;
+	sl_encaps(sl, skb->data, skb->len);
+	spin_unlock(&sl->lock);
+
+	dev_kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+
+/******************************************
+ *   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. */
+		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
+	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 rtnl_link_stats64 *
+sl_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
+{
+	struct net_device_stats *devstats = &dev->stats;
+#ifdef SL_INCLUDE_CSLIP
+	struct slip *sl = netdev_priv(dev);
+	struct slcompress *comp = sl->slcomp;
+#endif
+	stats->rx_packets     = devstats->rx_packets;
+	stats->tx_packets     = devstats->tx_packets;
+	stats->rx_bytes       = devstats->rx_bytes;
+	stats->tx_bytes       = devstats->tx_bytes;
+	stats->rx_dropped     = devstats->rx_dropped;
+	stats->tx_dropped     = devstats->tx_dropped;
+	stats->tx_errors      = devstats->tx_errors;
+	stats->rx_errors      = devstats->rx_errors;
+	stats->rx_over_errors = devstats->rx_over_errors;
+
+#ifdef SL_INCLUDE_CSLIP
+	if (comp) {
+		/* Generic compressed statistics */
+		stats->rx_compressed   = comp->sls_i_compressed;
+		stats->tx_compressed   = comp->sls_o_compressed;
+
+		/* Are we really still needs this? */
+		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
+	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->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);
+}
+
+/* Hook the destructor so we can free slip devices at the right point in time */
+static void sl_free_netdev(struct net_device *dev)
+{
+	int i = dev->base_addr;
+	free_netdev(dev);
+	slip_devs[i] = NULL;
+}
+
+static const struct net_device_ops sl_netdev_ops = {
+	.ndo_init		= sl_init,
+	.ndo_uninit	  	= sl_uninit,
+	.ndo_open		= sl_open,
+	.ndo_stop		= sl_close,
+	.ndo_start_xmit		= sl_xmit,
+	.ndo_get_stats64        = sl_get_stats64,
+	.ndo_change_mtu		= sl_change_mtu,
+	.ndo_tx_timeout		= sl_tx_timeout,
+#ifdef CONFIG_SLIP_SMART
+	.ndo_do_ioctl		= sl_ioctl,
+#endif
+};
+
+
+static void sl_setup(struct net_device *dev)
+{
+	dev->netdev_ops		= &sl_netdev_ops;
+	dev->destructor		= sl_free_netdev;
+
+	dev->hard_header_len	= 0;
+	dev->addr_len		= 0;
+	dev->tx_queue_len	= 10;
+
+	/* New-style flags. */
+	dev->flags		= IFF_NOARP|IFF_POINTOPOINT|IFF_MULTICAST;
+}
+
+/******************************************
+  Routines looking at TTY side.
+ ******************************************/
+
+
+/*
+ * 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 = 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->dev->stats.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++) {
+		dev = slip_devs[i];
+		if (dev == 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;
+	char name[IFNAMSIZ];
+	struct net_device *dev = NULL;
+	struct slip       *sl;
+
+	for (i = 0; i < slip_maxdev; i++) {
+		dev = slip_devs[i];
+		if (dev == NULL)
+			break;
+	}
+	/* Sorry, too many, all slots in use */
+	if (i >= slip_maxdev)
+		return NULL;
+
+	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
+	/* initialize timer_list struct */
+	init_timer(&sl->keepalive_timer);
+	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;
+
+	if (tty->ops->write == NULL)
+		return -EOPNOTSUPP;
+
+	/* 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 = 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;
+	sl = sl_alloc(tty_devnum(tty));
+	if (sl == NULL)
+		goto err_exit;
+
+	sl->tty = tty;
+	tty->disc_data = sl;
+	sl->pid = current->pid;
+
+	if (!test_bit(SLF_INUSE, &sl->flags)) {
+		/* Perform the low-level SLIP initialization. */
+		err = sl_alloc_bufs(sl, SL_MTU);
+		if (err)
+			goto err_free_chan;
+
+		set_bit(SLF_INUSE, &sl->flags);
+
+		err = register_netdevice(sl->dev);
+		if (err)
+			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();
+	tty->receive_room = 65536;	/* We don't flow control */
+
+	/* TTY layer expects 0 on success */
+	return 0;
+
+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;
+}
+
+/*
+ * Close down a SLIP channel.
+ * This means flushing out any pending queues, and then returning. This
+ * call is serialized against other ldisc functions.
+ *
+ * We also use this method fo a hangup event
+ */
+
+static void slip_close(struct tty_struct *tty)
+{
+	struct slip *sl = 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;
+
+	/* VSV = very important to remove timers */
+#ifdef CONFIG_SLIP_SMART
+	del_timer_sync(&sl->keepalive_timer);
+	del_timer_sync(&sl->outfill_timer);
+#endif
+	/* Flush network side */
+	unregister_netdev(sl->dev);
+	/* This will complete via sl_free_netdev */
+}
+
+static int slip_hangup(struct tty_struct *tty)
+{
+	slip_close(tty);
+	return 0;
+}
+ /************************************************************************
+  *			STANDARD SLIP ENCAPSULATION		  	 *
+  ************************************************************************/
+
+static 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->dev->stats.rx_over_errors++;
+		set_bit(SLF_ERROR, &sl->flags);
+	}
+}
+
+
+#ifdef CONFIG_SLIP_MODE_SLIP6
+/************************************************************************
+ *			 6 BIT SLIP ENCAPSULATION			*
+ ************************************************************************/
+
+static 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;
+}
+
+static 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->dev->stats.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 = 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;
+		}
+		sl->keepalive = (u8)tmp;
+		if (sl->keepalive != 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;
+		}
+		sl->outfill = (u8)tmp;
+		if (sl->outfill != 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
+	default:
+		return tty_mode_ioctl(tty, file, cmd, arg);
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static long slip_compat_ioctl(struct tty_struct *tty, struct file *file,
+					unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case SIOCGIFNAME:
+	case SIOCGIFENCAP:
+	case SIOCSIFENCAP:
+	case SIOCSIFHWADDR:
+	case SIOCSKEEPALIVE:
+	case SIOCGKEEPALIVE:
+	case SIOCSOUTFILL:
+	case SIOCGOUTFILL:
+		return slip_ioctl(tty, file, cmd,
+				  (unsigned long)compat_ptr(arg));
+	}
+
+	return -ENOIOCTLCMD;
+}
+#endif
+
+/* 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 = (u8)*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;
+		}
+		sl->outfill = (u8)*p;
+		if (sl->outfill != 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_ops sl_ldisc = {
+	.owner 		= THIS_MODULE,
+	.magic 		= TTY_LDISC_MAGIC,
+	.name 		= "slip",
+	.open 		= slip_open,
+	.close	 	= slip_close,
+	.hangup	 	= slip_hangup,
+	.ioctl		= slip_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= slip_compat_ioctl,
+#endif
+	.receive_buf	= slip_receive_buf,
+	.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 = kzalloc(sizeof(struct net_device *)*slip_maxdev,
+								GFP_KERNEL);
+	if (!slip_devs) {
+		printk(KERN_ERR "SLIP: Can't allocate slip devices array.\n");
+		return -ENOMEM;
+	}
+
+	/* Fill in our line protocol discipline, and register it */
+	status = tty_register_ldisc(N_SLIP, &sl_ldisc);
+	if (status != 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)
+			msleep_interruptible(100);
+
+		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));
+
+	/* FIXME: hangup is async so we should wait when doing this second
+	   phase */
+
+	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;
+
+	i = tty_unregister_ldisc(N_SLIP);
+	if (i != 0)
+		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->ops->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);
+			/* this must hangup tty & close slip */
+			tty_hangup(sl->tty);
+			/* 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);