mkiss.c

linux-2.6.15.6

			count = kiss_esc(p, (unsigned char *)ax->xbuff, len);
		}
  	}
	spin_unlock_bh(&ax->buflock);

	set_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
	actual = ax->tty->driver->write(ax->tty, ax->xbuff, count);
	ax->stats.tx_packets++;
	ax->stats.tx_bytes += actual;

	ax->dev->trans_start = jiffies;
	ax->xleft = count - actual;
	ax->xhead = ax->xbuff + actual;
}

/* Encapsulate an AX.25 packet and kick it into a TTY queue. */
static int ax_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct mkiss *ax = netdev_priv(dev);

	if (!netif_running(dev))  {
		printk(KERN_ERR "mkiss: %s: xmit call when iface is down\n", dev->name);
		return 1;
	}

	if (netif_queue_stopped(dev)) {
		/*
		 * May be we must check transmitter timeout here ?
		 *      14 Oct 1994 Dmitry Gorodchanin.
		 */
		if (time_before(jiffies, dev->trans_start + 20 * HZ)) {
			/* 20 sec timeout not reached */
			return 1;
		}

		printk(KERN_ERR "mkiss: %s: transmit timed out, %s?\n", dev->name,
		       (ax->tty->driver->chars_in_buffer(ax->tty) || ax->xleft) ?
		       "bad line quality" : "driver error");

		ax->xleft = 0;
		clear_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
		netif_start_queue(dev);
	}

	/* We were not busy, so we are now... :-) */
	if (skb != NULL) {
		netif_stop_queue(dev);
		ax_encaps(dev, skb->data, skb->len);
		kfree_skb(skb);
	}

	return 0;
}

static int ax_open_dev(struct net_device *dev)
{
	struct mkiss *ax = netdev_priv(dev);

	if (ax->tty == NULL)
		return -ENODEV;

	return 0;
}

#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)

/* Return the frame type ID */
static int ax_header(struct sk_buff *skb, struct net_device *dev, unsigned short type,
	  void *daddr, void *saddr, unsigned len)
{
#ifdef CONFIG_INET
	if (type != htons(ETH_P_AX25))
		return ax25_hard_header(skb, dev, type, daddr, saddr, len);
#endif
	return 0;
}


static int ax_rebuild_header(struct sk_buff *skb)
{
#ifdef CONFIG_INET
	return ax25_rebuild_header(skb);
#else
	return 0;
#endif
}

#endif	/* CONFIG_{AX25,AX25_MODULE} */

/* Open the low-level part of the AX25 channel. Easy! */
static int ax_open(struct net_device *dev)
{
	struct mkiss *ax = netdev_priv(dev);
	unsigned long len;

	if (ax->tty == NULL)
		return -ENODEV;

	/*
	 * Allocate the frame buffers:
	 *
	 * rbuff	Receive buffer.
	 * xbuff	Transmit 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;

	if ((ax->rbuff = kmalloc(len + 4, GFP_KERNEL)) == NULL)
		goto norbuff;

	if ((ax->xbuff = kmalloc(len + 4, GFP_KERNEL)) == NULL)
		goto noxbuff;

	ax->mtu	     = dev->mtu + 73;
	ax->buffsize = len;
	ax->rcount   = 0;
	ax->xleft    = 0;

	ax->flags   &= (1 << AXF_INUSE);      /* Clear ESCAPE & ERROR flags */

	spin_lock_init(&ax->buflock);

	return 0;

noxbuff:
	kfree(ax->rbuff);

norbuff:
	return -ENOMEM;
}


/* Close the low-level part of the AX25 channel. Easy! */
static int ax_close(struct net_device *dev)
{
	struct mkiss *ax = netdev_priv(dev);

	if (ax->tty)
		clear_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);

	netif_stop_queue(dev);

	return 0;
}

static struct net_device_stats *ax_get_stats(struct net_device *dev)
{
	struct mkiss *ax = netdev_priv(dev);

	return &ax->stats;
}

static void ax_setup(struct net_device *dev)
{
	static char ax25_bcast[AX25_ADDR_LEN] =
		{'Q'<<1,'S'<<1,'T'<<1,' '<<1,' '<<1,' '<<1,'0'<<1};
	static char ax25_test[AX25_ADDR_LEN] =
		{'L'<<1,'I'<<1,'N'<<1,'U'<<1,'X'<<1,' '<<1,'1'<<1};

	/* Finish setting up the DEVICE info. */
	dev->mtu             = AX_MTU;
	dev->hard_start_xmit = ax_xmit;
	dev->open            = ax_open_dev;
	dev->stop            = ax_close;
	dev->get_stats	     = ax_get_stats;
	dev->set_mac_address = ax_set_mac_address;
	dev->hard_header_len = 0;
	dev->addr_len        = 0;
	dev->type            = ARPHRD_AX25;
	dev->tx_queue_len    = 10;
	dev->hard_header     = ax_header;
	dev->rebuild_header  = ax_rebuild_header;

	memcpy(dev->broadcast, ax25_bcast, AX25_ADDR_LEN);
	memcpy(dev->dev_addr,  ax25_test,  AX25_ADDR_LEN);

	dev->flags      = IFF_BROADCAST | IFF_MULTICAST;
}

/*
 * We have a potential race on dereferencing tty->disc_data, because the tty
 * layer provides no locking at all - thus one cpu could be running
 * sixpack_receive_buf while another calls sixpack_close, which zeroes
 * tty->disc_data and frees the memory that sixpack_receive_buf is using.  The
 * best way to fix this is to use a rwlock in the tty struct, but for now we
 * use a single global rwlock for all ttys in ppp line discipline.
 */
static DEFINE_RWLOCK(disc_data_lock);

static struct mkiss *mkiss_get(struct tty_struct *tty)
{
	struct mkiss *ax;

	read_lock(&disc_data_lock);
	ax = tty->disc_data;
	if (ax)
		atomic_inc(&ax->refcnt);
	read_unlock(&disc_data_lock);

	return ax;
}

static void mkiss_put(struct mkiss *ax)
{
	if (atomic_dec_and_test(&ax->refcnt))
		up(&ax->dead_sem);
}

static int crc_force = 0;	/* Can be overridden with insmod */

static int mkiss_open(struct tty_struct *tty)
{
	struct net_device *dev;
	struct mkiss *ax;
	int err;

	if (!capable(CAP_NET_ADMIN))
		return -EPERM;

	dev = alloc_netdev(sizeof(struct mkiss), "ax%d", ax_setup);
	if (!dev) {
		err = -ENOMEM;
		goto out;
	}

	ax = netdev_priv(dev);
	ax->dev = dev;

	spin_lock_init(&ax->buflock);
	atomic_set(&ax->refcnt, 1);
	init_MUTEX_LOCKED(&ax->dead_sem);

	ax->tty = tty;
	tty->disc_data = ax;

	if (tty->driver->flush_buffer)
		tty->driver->flush_buffer(tty);

	/* Restore default settings */
	dev->type = ARPHRD_AX25;

	/* Perform the low-level AX25 initialization. */
	if ((err = ax_open(ax->dev))) {
		goto out_free_netdev;
	}

	if (register_netdev(dev))
		goto out_free_buffers;

	/* after register_netdev() - because else printk smashes the kernel */
	switch (crc_force) {
	case 3:
		ax->crcmode  = CRC_MODE_SMACK;
		printk(KERN_INFO "mkiss: %s: crc mode smack forced.\n",
		       ax->dev->name);
		break;
	case 2:
		ax->crcmode  = CRC_MODE_FLEX;
		printk(KERN_INFO "mkiss: %s: crc mode flexnet forced.\n",
		       ax->dev->name);
		break;
	case 1:
		ax->crcmode  = CRC_MODE_NONE;
		printk(KERN_INFO "mkiss: %s: crc mode disabled.\n",
		       ax->dev->name);
		break;
	case 0:
		/* fall through */
	default:
		crc_force = 0;
		printk(KERN_INFO "mkiss: %s: crc mode is auto.\n",
		       ax->dev->name);
		ax->crcmode  = CRC_MODE_SMACK_TEST;
	}
	ax->crcauto = (crc_force ? 0 : 1);

	netif_start_queue(dev);

	/* Done.  We have linked the TTY line to a channel. */
	return 0;

out_free_buffers:
	kfree(ax->rbuff);
	kfree(ax->xbuff);

out_free_netdev:
	free_netdev(dev);

out:
	return err;
}

static void mkiss_close(struct tty_struct *tty)
{
	struct mkiss *ax;

	write_lock(&disc_data_lock);
	ax = tty->disc_data;
	tty->disc_data = NULL;
	write_unlock(&disc_data_lock);

	if (ax == 0)
		return;

	/*
	 * We have now ensured that nobody can start using ap from now on, but
	 * we have to wait for all existing users to finish.
	 */
	if (!atomic_dec_and_test(&ax->refcnt))
		down(&ax->dead_sem);

	unregister_netdev(ax->dev);

	/* Free all AX25 frame buffers. */
	kfree(ax->rbuff);
	kfree(ax->xbuff);

	ax->tty = NULL;
}

/* Perform I/O control on an active ax25 channel. */
static int mkiss_ioctl(struct tty_struct *tty, struct file *file,
	unsigned int cmd, unsigned long arg)
{
	struct mkiss *ax = mkiss_get(tty);
	struct net_device *dev = ax->dev;
	unsigned int tmp, err;

	/* First make sure we're connected. */
	if (ax == NULL)
		return -ENXIO;

	switch (cmd) {
 	case SIOCGIFNAME:
		err = copy_to_user((void __user *) arg, ax->dev->name,
		                   strlen(ax->dev->name) + 1) ? -EFAULT : 0;
		break;

	case SIOCGIFENCAP:
		err = put_user(4, (int __user *) arg);
		break;

	case SIOCSIFENCAP:
		if (get_user(tmp, (int __user *) arg)) {
			err = -EFAULT;
			break;
		}

		ax->mode = tmp;
		dev->addr_len        = AX25_ADDR_LEN;
		dev->hard_header_len = AX25_KISS_HEADER_LEN +
		                       AX25_MAX_HEADER_LEN + 3;
		dev->type            = ARPHRD_AX25;

		err = 0;
		break;

	case SIOCSIFHWADDR: {
		char addr[AX25_ADDR_LEN];

		if (copy_from_user(&addr,
		                   (void __user *) arg, AX25_ADDR_LEN)) {
			err = -EFAULT;
			break;
		}

		spin_lock_irq(&dev->xmit_lock);
		memcpy(dev->dev_addr, addr, AX25_ADDR_LEN);
		spin_unlock_irq(&dev->xmit_lock);

		err = 0;
		break;
	}
	default:
		err = -ENOIOCTLCMD;
	}

	mkiss_put(ax);

	return err;
}

/*
 * Handle the 'receiver data ready' interrupt.
 * This function is called by the 'tty_io' module in the kernel when
 * a block of data has been received, which can now be decapsulated
 * and sent on to the AX.25 layer for further processing.
 */
static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
	char *fp, int count)
{
	struct mkiss *ax = mkiss_get(tty);

	if (!ax)
		return;

	/*
	 * Argh! mtu change time! - costs us the packet part received
	 * at the change
	 */
	if (ax->mtu != ax->dev->mtu + 73)
		ax_changedmtu(ax);

	/* Read the characters out of the buffer */
	while (count--) {
		if (fp != NULL && *fp++) {
			if (!test_and_set_bit(AXF_ERROR, &ax->flags))
				ax->stats.rx_errors++;
			cp++;
			continue;
		}

		kiss_unesc(ax, *cp++);
	}

	mkiss_put(ax);
	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
	    && tty->driver->unthrottle)
		tty->driver->unthrottle(tty);
}

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

/*
 * Called by the driver when there's room for more data.  If we have
 * more packets to send, we send them here.
 */
static void mkiss_write_wakeup(struct tty_struct *tty)
{
	struct mkiss *ax = mkiss_get(tty);
	int actual;

	if (!ax)
		return;

	if (ax->xleft <= 0)  {
		/* Now serial buffer is almost free & we can start
		 * transmission of another packet
		 */
		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

		netif_wake_queue(ax->dev);
		goto out;
	}

	actual = tty->driver->write(tty, ax->xhead, ax->xleft);
	ax->xleft -= actual;
	ax->xhead += actual;

out:
	mkiss_put(ax);
}

static struct tty_ldisc ax_ldisc = {
	.owner		= THIS_MODULE,
	.magic		= TTY_LDISC_MAGIC,
	.name		= "mkiss",
	.open		= mkiss_open,
	.close		= mkiss_close,
	.ioctl		= mkiss_ioctl,
	.receive_buf	= mkiss_receive_buf,
	.receive_room	= mkiss_receive_room,
	.write_wakeup	= mkiss_write_wakeup
};

static char banner[] __initdata = KERN_INFO \
	"mkiss: AX.25 Multikiss, Hans Albas PE1AYX\n";
static char msg_regfail[] __initdata = KERN_ERR \
	"mkiss: can't register line discipline (err = %d)\n";

static int __init mkiss_init_driver(void)
{
	int status;

	printk(banner);

	if ((status = tty_register_ldisc(N_AX25, &ax_ldisc)) != 0)
		printk(msg_regfail);

	return status;
}

static const char msg_unregfail[] __exitdata = KERN_ERR \
	"mkiss: can't unregister line discipline (err = %d)\n";

static void __exit mkiss_exit_driver(void)
{
	int ret;

	if ((ret = tty_unregister_ldisc(N_AX25)))
		printk(msg_unregfail, ret);
}

MODULE_AUTHOR("Ralf Baechle DL5RB <[e-mail]>");
MODULE_DESCRIPTION("KISS driver for AX.25 over TTYs");
MODULE_PARM(crc_force, "i");
MODULE_PARM_DESC(crc_force, "crc [0 = auto | 1 = none | 2 = flexnet | 3 = smack]");
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_AX25);

module_init(mkiss_init_driver);
module_exit(mkiss_exit_driver);