slip.c

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/*
 * 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, <[e-mail]>
 *		Fred N. van Kempen, <[e-mail]>
 *
 * 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 <[e-mail]>
 *					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 <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/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

#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 {
	struct slip	ctrl;		/* SLIP things			*/
	struct net_device	dev;		/* the device			*/
} slip_ctrl_t;
static slip_ctrl_t	**slip_ctrls = NULL;

int slip_maxdev = SL_NRUNIT;		/* Can be overridden with insmod! */
MODULE_PARM(slip_maxdev, "i");

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);
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("%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("%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 */

	sl->rx_bytes+=count;
	
	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 (len > sl->mtu) {		/* Sigh, shouldn't occur BUT ... */
		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;
#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, 0, sl->xhead, sl->xleft);
	sl->xleft -= actual;
	sl->xhead += actual;
}

static void sl_tx_timeout(struct net_device *dev)
{
	struct slip *sl = (struct slip*)(dev->priv);

	spin_lock(&sl->lock);

	if (netif_queue_stopped(dev)) {
		struct slip *sl = (struct slip*)(dev->priv);

		if (!netif_running(dev))
			goto out;

		/* 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 */
			goto out;
		}
		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);
#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 = (struct slip*)(dev->priv);