drivers/net/tun.c - third_party/linux - Git at Google

 /*
  *  TUN - Universal TUN/TAP device driver.
  *  Copyright (C) 1999-2002 Maxim Krasnyansky <maxk@qualcomm.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  *  GNU General Public License for more details.
  *
  *  $Id: tun.c,v 1.15 2002/03/01 02:44:24 maxk Exp $
  */

 /*
  *  Changes:
  *
  *  Brian Braunstein <linuxkernel@bristyle.com> 2007/03/23
  *    Fixed hw address handling.  Now net_device.dev_addr is kept consistent
  *    with tun.dev_addr when the address is set by this module.
  *
  *  Mike Kershaw <dragorn@kismetwireless.net> 2005/08/14
  *    Add TUNSETLINK ioctl to set the link encapsulation
  *
  *  Mark Smith <markzzzsmith@yahoo.com.au>
  *   Use random_ether_addr() for tap MAC address.
  *
  *  Harald Roelle <harald.roelle@ifi.lmu.de>  2004/04/20
  *    Fixes in packet dropping, queue length setting and queue wakeup.
  *    Increased default tx queue length.
  *    Added ethtool API.
  *    Minor cleanups
  *
  *  Daniel Podlejski <underley@underley.eu.org>
  *    Modifications for 2.3.99-pre5 kernel.
  */

 #define DRV_NAME	"tun"
 #define DRV_VERSION	"1.6"
 #define DRV_DESCRIPTION	"Universal TUN/TAP device driver"
 #define DRV_COPYRIGHT	"(C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>"

 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/major.h>
 #include <linux/slab.h>
 #include <linux/poll.h>
 #include <linux/fcntl.h>
 #include <linux/init.h>
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/miscdevice.h>
 #include <linux/ethtool.h>
 #include <linux/rtnetlink.h>
 #include <linux/if.h>
 #include <linux/if_arp.h>
 #include <linux/if_ether.h>
 #include <linux/if_tun.h>
 #include <linux/crc32.h>
 #include <net/net_namespace.h>

 #include <asm/system.h>
 #include <asm/uaccess.h>

 #ifdef TUN_DEBUG
 static int debug;
 #endif

 /* Network device part of the driver */

 static LIST_HEAD(tun_dev_list);
 static const struct ethtool_ops tun_ethtool_ops;

 /* Net device open. */
 static int tun_net_open(struct net_device *dev)
 {
 	netif_start_queue(dev);
 	return 0;
 }

 /* Net device close. */
 static int tun_net_close(struct net_device *dev)
 {
 	netif_stop_queue(dev);
 	return 0;
 }

 /* Net device start xmit */
 static int tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);

 	DBG(KERN_INFO "%s: tun_net_xmit %d\n", tun->dev->name, skb->len);

 	/* Drop packet if interface is not attached */
 	if (!tun->attached)
 		goto drop;

 	/* Packet dropping */
 	if (skb_queue_len(&tun->readq) >= dev->tx_queue_len) {
 		if (!(tun->flags & TUN_ONE_QUEUE)) {
 			/* Normal queueing mode. */
 			/* Packet scheduler handles dropping of further packets. */
 			netif_stop_queue(dev);

 			/* We won't see all dropped packets individually, so overrun
 			 * error is more appropriate. */
 			dev->stats.tx_fifo_errors++;
 		} else {
 			/* Single queue mode.
 			 * Driver handles dropping of all packets itself. */
 			goto drop;
 		}
 	}

 	/* Queue packet */
 	skb_queue_tail(&tun->readq, skb);
 	dev->trans_start = jiffies;

 	/* Notify and wake up reader process */
 	if (tun->flags & TUN_FASYNC)
 		kill_fasync(&tun->fasync, SIGIO, POLL_IN);
 	wake_up_interruptible(&tun->read_wait);
 	return 0;

 drop:
 	dev->stats.tx_dropped++;
 	kfree_skb(skb);
 	return 0;
 }

 /** Add the specified Ethernet address to this multicast filter. */
 static void
 add_multi(u32* filter, const u8* addr)
 {
 	int bit_nr = ether_crc(ETH_ALEN, addr) >> 26;
 	filter[bit_nr >> 5] |= 1 << (bit_nr & 31);
 }

 /** Remove the specified Ethernet addres from this multicast filter. */
 static void
 del_multi(u32* filter, const u8* addr)
 {
 	int bit_nr = ether_crc(ETH_ALEN, addr) >> 26;
 	filter[bit_nr >> 5] &= ~(1 << (bit_nr & 31));
 }

 /** Update the list of multicast groups to which the network device belongs.
  * This list is used to filter packets being sent from the character device to
  * the network device. */
 static void
 tun_net_mclist(struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);
 	const struct dev_mc_list *mclist;
 	int i;
 	DECLARE_MAC_BUF(mac);
 	DBG(KERN_DEBUG "%s: tun_net_mclist: mc_count %d\n",
 			dev->name, dev->mc_count);
 	memset(tun->chr_filter, 0, sizeof tun->chr_filter);
 	for (i = 0, mclist = dev->mc_list; i < dev->mc_count && mclist != NULL;
 			i++, mclist = mclist->next) {
 		add_multi(tun->net_filter, mclist->dmi_addr);
 		DBG(KERN_DEBUG "%s: tun_net_mclist: %s\n",
 		    dev->name, print_mac(mac, mclist->dmi_addr));
 	}
 }

 #define MIN_MTU 68
 #define MAX_MTU 65535

 static int
 tun_net_change_mtu(struct net_device *dev, int new_mtu)
 {
 	if (new_mtu < MIN_MTU || new_mtu + dev->hard_header_len > MAX_MTU)
 		return -EINVAL;
 	dev->mtu = new_mtu;
 	return 0;
 }

 /* Initialize net device. */
 static void tun_net_init(struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);

 	switch (tun->flags & TUN_TYPE_MASK) {
 	case TUN_TUN_DEV:
 		/* Point-to-Point TUN Device */
 		dev->hard_header_len = 0;
 		dev->addr_len = 0;
 		dev->mtu = 1500;
 		dev->change_mtu = tun_net_change_mtu;

 		/* Zero header length */
 		dev->type = ARPHRD_NONE;
 		dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
 		dev->tx_queue_len = TUN_READQ_SIZE;  /* We prefer our own queue length */
 		break;

 	case TUN_TAP_DEV:
 		/* Ethernet TAP Device */
 		dev->set_multicast_list = tun_net_mclist;

 		ether_setup(dev);
 		dev->change_mtu = tun_net_change_mtu;

 		/* random address already created for us by tun_set_iff, use it */
 		memcpy(dev->dev_addr, tun->dev_addr, min(sizeof(tun->dev_addr), sizeof(dev->dev_addr)) );

 		dev->tx_queue_len = TUN_READQ_SIZE;  /* We prefer our own queue length */
 		break;
 	}
 }

 /* Character device part */

 /* Poll */
 static unsigned int tun_chr_poll(struct file *file, poll_table * wait)
 {
 	struct tun_struct *tun = file->private_data;
 	unsigned int mask = POLLOUT | POLLWRNORM;

 	if (!tun)
 		return -EBADFD;

 	DBG(KERN_INFO "%s: tun_chr_poll\n", tun->dev->name);

 	poll_wait(file, &tun->read_wait, wait);

 	if (!skb_queue_empty(&tun->readq))
 		mask |= POLLIN | POLLRDNORM;

 	return mask;
 }

 /* Get packet from user space buffer */
 static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv, size_t count)
 {
 	struct tun_pi pi = { 0, __constant_htons(ETH_P_IP) };
 	struct sk_buff *skb;
 	size_t len = count, align = 0;

 	if (!(tun->flags & TUN_NO_PI)) {
 		if ((len -= sizeof(pi)) > count)
 			return -EINVAL;

 		if(memcpy_fromiovec((void *)&pi, iv, sizeof(pi)))
 			return -EFAULT;
 	}

 	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV)
 		align = NET_IP_ALIGN;

 	if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
 		tun->dev->stats.rx_dropped++;
 		return -ENOMEM;
 	}

 	if (align)
 		skb_reserve(skb, align);
 	if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
 		tun->dev->stats.rx_dropped++;
 		kfree_skb(skb);
 		return -EFAULT;
 	}

 	switch (tun->flags & TUN_TYPE_MASK) {
 	case TUN_TUN_DEV:
 		skb_reset_mac_header(skb);
 		skb->protocol = pi.proto;
 		skb->dev = tun->dev;
 		break;
 	case TUN_TAP_DEV:
 		skb->protocol = eth_type_trans(skb, tun->dev);
 		break;
 	};

 	if (tun->flags & TUN_NOCHECKSUM)
 		skb->ip_summed = CHECKSUM_UNNECESSARY;

 	netif_rx_ni(skb);
 	tun->dev->last_rx = jiffies;

 	tun->dev->stats.rx_packets++;
 	tun->dev->stats.rx_bytes += len;

 	return count;
 }

 static ssize_t tun_chr_aio_write(struct kiocb *iocb, const struct iovec *iv,
 			      unsigned long count, loff_t pos)
 {
 	struct tun_struct *tun = iocb->ki_filp->private_data;

 	if (!tun)
 		return -EBADFD;

 	DBG(KERN_INFO "%s: tun_chr_write %ld\n", tun->dev->name, count);

 	return tun_get_user(tun, (struct iovec *) iv, iov_length(iv, count));
 }

 /* Put packet to the user space buffer */
 static __inline__ ssize_t tun_put_user(struct tun_struct *tun,
 				       struct sk_buff *skb,
 				       struct iovec *iv, int len)
 {
 	struct tun_pi pi = { 0, skb->protocol };
 	ssize_t total = 0;

 	if (!(tun->flags & TUN_NO_PI)) {
 		if ((len -= sizeof(pi)) < 0)
 			return -EINVAL;

 		if (len < skb->len) {
 			/* Packet will be striped */
 			pi.flags |= TUN_PKT_STRIP;
 		}

 		if (memcpy_toiovec(iv, (void *) &pi, sizeof(pi)))
 			return -EFAULT;
 		total += sizeof(pi);
 	}

 	len = min_t(int, skb->len, len);

 	skb_copy_datagram_iovec(skb, 0, iv, len);
 	total += len;

 	tun->dev->stats.tx_packets++;
 	tun->dev->stats.tx_bytes += len;

 	return total;
 }

 static ssize_t tun_chr_aio_read(struct kiocb *iocb, const struct iovec *iv,
 			    unsigned long count, loff_t pos)
 {
 	struct file *file = iocb->ki_filp;
 	struct tun_struct *tun = file->private_data;
 	DECLARE_WAITQUEUE(wait, current);
 	struct sk_buff *skb;
 	ssize_t len, ret = 0;
 	DECLARE_MAC_BUF(mac);

 	if (!tun)
 		return -EBADFD;

 	DBG(KERN_INFO "%s: tun_chr_read\n", tun->dev->name);

 	len = iov_length(iv, count);
 	if (len < 0)
 		return -EINVAL;

 	add_wait_queue(&tun->read_wait, &wait);
 	while (len) {
 		const u8 ones[ ETH_ALEN] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 		u8 addr[ ETH_ALEN];
 		int bit_nr;

 		current->state = TASK_INTERRUPTIBLE;

 		/* Read frames from the queue */
 		if (!(skb=skb_dequeue(&tun->readq))) {
 			if (file->f_flags & O_NONBLOCK) {
 				ret = -EAGAIN;
 				break;
 			}
 			if (signal_pending(current)) {
 				ret = -ERESTARTSYS;
 				break;
 			}

 			/* Nothing to read, let's sleep */
 			schedule();
 			continue;
 		}
 		netif_wake_queue(tun->dev);

 		/** Decide whether to accept this packet. This code is designed to
 		 * behave identically to an Ethernet interface. Accept the packet if
 		 * - we are promiscuous.
 		 * - the packet is addressed to us.
 		 * - the packet is broadcast.
 		 * - the packet is multicast and
 		 *   - we are multicast promiscous.
 		 *   - we belong to the multicast group.
 		 */
 		skb_copy_from_linear_data(skb, addr, min_t(size_t, sizeof addr,
 								   skb->len));
 		bit_nr = ether_crc(sizeof addr, addr) >> 26;
 		if ((tun->if_flags & IFF_PROMISC) ||
 				memcmp(addr, tun->dev_addr, sizeof addr) == 0 ||
 				memcmp(addr, ones, sizeof addr) == 0 ||
 				(((addr[0] == 1 && addr[1] == 0 && addr[2] == 0x5e) ||
 				  (addr[0] == 0x33 && addr[1] == 0x33)) &&
 				 ((tun->if_flags & IFF_ALLMULTI) ||
 				  (tun->chr_filter[bit_nr >> 5] & (1 << (bit_nr & 31)))))) {
 			DBG(KERN_DEBUG "%s: tun_chr_readv: accepted: %s\n",
 					tun->dev->name, print_mac(mac, addr));
 			ret = tun_put_user(tun, skb, (struct iovec *) iv, len);
 			kfree_skb(skb);
 			break;
 		} else {
 			DBG(KERN_DEBUG "%s: tun_chr_readv: rejected: %s\n",
 					tun->dev->name, print_mac(mac, addr));
 			kfree_skb(skb);
 			continue;
 		}
 	}

 	current->state = TASK_RUNNING;
 	remove_wait_queue(&tun->read_wait, &wait);

 	return ret;
 }

 static void tun_setup(struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);

 	skb_queue_head_init(&tun->readq);
 	init_waitqueue_head(&tun->read_wait);

 	tun->owner = -1;
 	tun->group = -1;

 	dev->open = tun_net_open;
 	dev->hard_start_xmit = tun_net_xmit;
 	dev->stop = tun_net_close;
 	dev->ethtool_ops = &tun_ethtool_ops;
 	dev->destructor = free_netdev;
 }

 static struct tun_struct *tun_get_by_name(const char *name)
 {
 	struct tun_struct *tun;

 	ASSERT_RTNL();
 	list_for_each_entry(tun, &tun_dev_list, list) {
 		if (!strncmp(tun->dev->name, name, IFNAMSIZ))
 		    return tun;
 	}

 	return NULL;
 }

 static int tun_set_iff(struct file *file, struct ifreq *ifr)
 {
 	struct tun_struct *tun;
 	struct net_device *dev;
 	int err;

 	tun = tun_get_by_name(ifr->ifr_name);
 	if (tun) {
 		if (tun->attached)
 			return -EBUSY;

 		/* Check permissions */
 		if (((tun->owner != -1 &&
 		      current->euid != tun->owner) ||
 		     (tun->group != -1 &&
 		      current->egid != tun->group)) &&
 		     !capable(CAP_NET_ADMIN))
 			return -EPERM;
 	}
 	else if (__dev_get_by_name(&init_net, ifr->ifr_name))
 		return -EINVAL;
 	else {
 		char *name;
 		unsigned long flags = 0;

 		err = -EINVAL;

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

 		/* Set dev type */
 		if (ifr->ifr_flags & IFF_TUN) {
 			/* TUN device */
 			flags |= TUN_TUN_DEV;
 			name = "tun%d";
 		} else if (ifr->ifr_flags & IFF_TAP) {
 			/* TAP device */
 			flags |= TUN_TAP_DEV;
 			name = "tap%d";
 		} else
 			goto failed;

 		if (*ifr->ifr_name)
 			name = ifr->ifr_name;

 		dev = alloc_netdev(sizeof(struct tun_struct), name,
 				   tun_setup);
 		if (!dev)
 			return -ENOMEM;

 		tun = netdev_priv(dev);
 		tun->dev = dev;
 		tun->flags = flags;
 		/* Be promiscuous by default to maintain previous behaviour. */
 		tun->if_flags = IFF_PROMISC;
 		/* Generate random Ethernet address. */
 		*(__be16 *)tun->dev_addr = htons(0x00FF);
 		get_random_bytes(tun->dev_addr + sizeof(u16), 4);
 		memset(tun->chr_filter, 0, sizeof tun->chr_filter);

 		tun_net_init(dev);

 		if (strchr(dev->name, '%')) {
 			err = dev_alloc_name(dev, dev->name);
 			if (err < 0)
 				goto err_free_dev;
 		}

 		err = register_netdevice(tun->dev);
 		if (err < 0)
 			goto err_free_dev;

 		list_add(&tun->list, &tun_dev_list);
 	}

 	DBG(KERN_INFO "%s: tun_set_iff\n", tun->dev->name);

 	if (ifr->ifr_flags & IFF_NO_PI)
 		tun->flags |= TUN_NO_PI;
 	else
 		tun->flags &= ~TUN_NO_PI;

 	if (ifr->ifr_flags & IFF_ONE_QUEUE)
 		tun->flags |= TUN_ONE_QUEUE;
 	else
 		tun->flags &= ~TUN_ONE_QUEUE;

 	file->private_data = tun;
 	tun->attached = 1;

 	strcpy(ifr->ifr_name, tun->dev->name);
 	return 0;

  err_free_dev:
 	free_netdev(dev);
  failed:
 	return err;
 }

 static int tun_chr_ioctl(struct inode *inode, struct file *file,
 			 unsigned int cmd, unsigned long arg)
 {
 	struct tun_struct *tun = file->private_data;
 	void __user* argp = (void __user*)arg;
 	struct ifreq ifr;
 	DECLARE_MAC_BUF(mac);

 	if (cmd == TUNSETIFF || _IOC_TYPE(cmd) == 0x89)
 		if (copy_from_user(&ifr, argp, sizeof ifr))
 			return -EFAULT;

 	if (cmd == TUNSETIFF && !tun) {
 		int err;

 		ifr.ifr_name[IFNAMSIZ-1] = '\0';

 		rtnl_lock();
 		err = tun_set_iff(file, &ifr);
 		rtnl_unlock();

 		if (err)
 			return err;

 		if (copy_to_user(argp, &ifr, sizeof(ifr)))
 			return -EFAULT;
 		return 0;
 	}

 	if (!tun)
 		return -EBADFD;

 	DBG(KERN_INFO "%s: tun_chr_ioctl cmd %d\n", tun->dev->name, cmd);

 	switch (cmd) {
 	case TUNSETNOCSUM:
 		/* Disable/Enable checksum */
 		if (arg)
 			tun->flags |= TUN_NOCHECKSUM;
 		else
 			tun->flags &= ~TUN_NOCHECKSUM;

 		DBG(KERN_INFO "%s: checksum %s\n",
 		    tun->dev->name, arg ? "disabled" : "enabled");
 		break;

 	case TUNSETPERSIST:
 		/* Disable/Enable persist mode */
 		if (arg)
 			tun->flags |= TUN_PERSIST;
 		else
 			tun->flags &= ~TUN_PERSIST;

 		DBG(KERN_INFO "%s: persist %s\n",
 		    tun->dev->name, arg ? "enabled" : "disabled");
 		break;

 	case TUNSETOWNER:
 		/* Set owner of the device */
 		tun->owner = (uid_t) arg;

 		DBG(KERN_INFO "%s: owner set to %d\n", tun->dev->name, tun->owner);
 		break;

 	case TUNSETGROUP:
 		/* Set group of the device */
 		tun->group= (gid_t) arg;

 		DBG(KERN_INFO "%s: group set to %d\n", tun->dev->name, tun->group);
 		break;

 	case TUNSETLINK:
 		/* Only allow setting the type when the interface is down */
 		if (tun->dev->flags & IFF_UP) {
 			DBG(KERN_INFO "%s: Linktype set failed because interface is up\n",
 				tun->dev->name);
 			return -EBUSY;
 		} else {
 			tun->dev->type = (int) arg;
 			DBG(KERN_INFO "%s: linktype set to %d\n", tun->dev->name, tun->dev->type);
 		}
 		break;

 #ifdef TUN_DEBUG
 	case TUNSETDEBUG:
 		tun->debug = arg;
 		break;
 #endif

 	case SIOCGIFFLAGS:
 		ifr.ifr_flags = tun->if_flags;
 		if (copy_to_user( argp, &ifr, sizeof ifr))
 			return -EFAULT;
 		return 0;

 	case SIOCSIFFLAGS:
 		/** Set the character device's interface flags. Currently only
 		 * IFF_PROMISC and IFF_ALLMULTI are used. */
 		tun->if_flags = ifr.ifr_flags;
 		DBG(KERN_INFO "%s: interface flags 0x%lx\n",
 				tun->dev->name, tun->if_flags);
 		return 0;

 	case SIOCGIFHWADDR:
 		/* Note: the actual net device's address may be different */
 		memcpy(ifr.ifr_hwaddr.sa_data, tun->dev_addr,
 				min(sizeof ifr.ifr_hwaddr.sa_data, sizeof tun->dev_addr));
 		if (copy_to_user( argp, &ifr, sizeof ifr))
 			return -EFAULT;
 		return 0;

 	case SIOCSIFHWADDR:
 	{
 		/* try to set the actual net device's hw address */
 		int ret;

 		rtnl_lock();
 		ret = dev_set_mac_address(tun->dev, &ifr.ifr_hwaddr);
 		rtnl_unlock();

 		if (ret == 0) {
 			/** Set the character device's hardware address. This is used when
 			 * filtering packets being sent from the network device to the character
 			 * device. */
 			memcpy(tun->dev_addr, ifr.ifr_hwaddr.sa_data,
 					min(sizeof ifr.ifr_hwaddr.sa_data, sizeof tun->dev_addr));
 			DBG(KERN_DEBUG "%s: set hardware address: %x:%x:%x:%x:%x:%x\n",
 					tun->dev->name,
 					tun->dev_addr[0], tun->dev_addr[1], tun->dev_addr[2],
 					tun->dev_addr[3], tun->dev_addr[4], tun->dev_addr[5]);
 		}

 		return  ret;
 	}

 	case SIOCADDMULTI:
 		/** Add the specified group to the character device's multicast filter
 		 * list. */
 		add_multi(tun->chr_filter, ifr.ifr_hwaddr.sa_data);
 		DBG(KERN_DEBUG "%s: add multi: %s\n",
 		    tun->dev->name, print_mac(mac, ifr.ifr_hwaddr.sa_data));
 		return 0;

 	case SIOCDELMULTI:
 		/** Remove the specified group from the character device's multicast
 		 * filter list. */
 		del_multi(tun->chr_filter, ifr.ifr_hwaddr.sa_data);
 		DBG(KERN_DEBUG "%s: del multi: %s\n",
 		    tun->dev->name, print_mac(mac, ifr.ifr_hwaddr.sa_data));
 		return 0;

 	default:
 		return -EINVAL;
 	};

 	return 0;
 }

 static int tun_chr_fasync(int fd, struct file *file, int on)
 {
 	struct tun_struct *tun = file->private_data;
 	int ret;

 	if (!tun)
 		return -EBADFD;

 	DBG(KERN_INFO "%s: tun_chr_fasync %d\n", tun->dev->name, on);

 	if ((ret = fasync_helper(fd, file, on, &tun->fasync)) < 0)
 		return ret;

 	if (on) {
 		ret = __f_setown(file, task_pid(current), PIDTYPE_PID, 0);
 		if (ret)
 			return ret;
 		tun->flags |= TUN_FASYNC;
 	} else
 		tun->flags &= ~TUN_FASYNC;

 	return 0;
 }

 static int tun_chr_open(struct inode *inode, struct file * file)
 {
 	DBG1(KERN_INFO "tunX: tun_chr_open\n");
 	file->private_data = NULL;
 	return 0;
 }

 static int tun_chr_close(struct inode *inode, struct file *file)
 {
 	struct tun_struct *tun = file->private_data;

 	if (!tun)
 		return 0;

 	DBG(KERN_INFO "%s: tun_chr_close\n", tun->dev->name);

 	tun_chr_fasync(-1, file, 0);

 	rtnl_lock();

 	/* Detach from net device */
 	file->private_data = NULL;
 	tun->attached = 0;

 	/* Drop read queue */
 	skb_queue_purge(&tun->readq);

 	if (!(tun->flags & TUN_PERSIST)) {
 		list_del(&tun->list);
 		unregister_netdevice(tun->dev);
 	}

 	rtnl_unlock();

 	return 0;
 }

 static const struct file_operations tun_fops = {
 	.owner	= THIS_MODULE,
 	.llseek = no_llseek,
 	.read  = do_sync_read,
 	.aio_read  = tun_chr_aio_read,
 	.write = do_sync_write,
 	.aio_write = tun_chr_aio_write,
 	.poll	= tun_chr_poll,
 	.ioctl	= tun_chr_ioctl,
 	.open	= tun_chr_open,
 	.release = tun_chr_close,
 	.fasync = tun_chr_fasync
 };

 static struct miscdevice tun_miscdev = {
 	.minor = TUN_MINOR,
 	.name = "tun",
 	.fops = &tun_fops,
 };

 /* ethtool interface */

 static int tun_get_settings(struct net_device *dev, struct ethtool_cmd *cmd)
 {
 	cmd->supported		= 0;
 	cmd->advertising	= 0;
 	cmd->speed		= SPEED_10;
 	cmd->duplex		= DUPLEX_FULL;
 	cmd->port		= PORT_TP;
 	cmd->phy_address	= 0;
 	cmd->transceiver	= XCVR_INTERNAL;
 	cmd->autoneg		= AUTONEG_DISABLE;
 	cmd->maxtxpkt		= 0;
 	cmd->maxrxpkt		= 0;
 	return 0;
 }

 static void tun_get_drvinfo(struct net_device *dev, struct ethtool_drvinfo *info)
 {
 	struct tun_struct *tun = netdev_priv(dev);

 	strcpy(info->driver, DRV_NAME);
 	strcpy(info->version, DRV_VERSION);
 	strcpy(info->fw_version, "N/A");

 	switch (tun->flags & TUN_TYPE_MASK) {
 	case TUN_TUN_DEV:
 		strcpy(info->bus_info, "tun");
 		break;
 	case TUN_TAP_DEV:
 		strcpy(info->bus_info, "tap");
 		break;
 	}
 }

 static u32 tun_get_msglevel(struct net_device *dev)
 {
 #ifdef TUN_DEBUG
 	struct tun_struct *tun = netdev_priv(dev);
 	return tun->debug;
 #else
 	return -EOPNOTSUPP;
 #endif
 }

 static void tun_set_msglevel(struct net_device *dev, u32 value)
 {
 #ifdef TUN_DEBUG
 	struct tun_struct *tun = netdev_priv(dev);
 	tun->debug = value;
 #endif
 }

 static u32 tun_get_link(struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);
 	return tun->attached;
 }

 static u32 tun_get_rx_csum(struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);
 	return (tun->flags & TUN_NOCHECKSUM) == 0;
 }

 static int tun_set_rx_csum(struct net_device *dev, u32 data)
 {
 	struct tun_struct *tun = netdev_priv(dev);
 	if (data)
 		tun->flags &= ~TUN_NOCHECKSUM;
 	else
 		tun->flags |= TUN_NOCHECKSUM;
 	return 0;
 }

 static const struct ethtool_ops tun_ethtool_ops = {
 	.get_settings	= tun_get_settings,
 	.get_drvinfo	= tun_get_drvinfo,
 	.get_msglevel	= tun_get_msglevel,
 	.set_msglevel	= tun_set_msglevel,
 	.get_link	= tun_get_link,
 	.get_rx_csum	= tun_get_rx_csum,
 	.set_rx_csum	= tun_set_rx_csum
 };

 static int __init tun_init(void)
 {
 	int ret = 0;

 	printk(KERN_INFO "tun: %s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
 	printk(KERN_INFO "tun: %s\n", DRV_COPYRIGHT);

 	ret = misc_register(&tun_miscdev);
 	if (ret)
 		printk(KERN_ERR "tun: Can't register misc device %d\n", TUN_MINOR);
 	return ret;
 }

 static void tun_cleanup(void)
 {
 	struct tun_struct *tun, *nxt;

 	misc_deregister(&tun_miscdev);

 	rtnl_lock();
 	list_for_each_entry_safe(tun, nxt, &tun_dev_list, list) {
 		DBG(KERN_INFO "%s cleaned up\n", tun->dev->name);
 		unregister_netdevice(tun->dev);
 	}
 	rtnl_unlock();

 }

 module_init(tun_init);
 module_exit(tun_cleanup);
 MODULE_DESCRIPTION(DRV_DESCRIPTION);
 MODULE_AUTHOR(DRV_COPYRIGHT);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_MISCDEV(TUN_MINOR);
	/*
	* TUN - Universal TUN/TAP device driver.
	* Copyright (C) 1999-2002 Maxim Krasnyansky <maxk@qualcomm.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* $Id: tun.c,v 1.15 2002/03/01 02:44:24 maxk Exp $
	*/

	/*
	* Changes:
	*
	* Brian Braunstein <linuxkernel@bristyle.com> 2007/03/23
	* Fixed hw address handling. Now net_device.dev_addr is kept consistent
	* with tun.dev_addr when the address is set by this module.
	*
	* Mike Kershaw <dragorn@kismetwireless.net> 2005/08/14
	* Add TUNSETLINK ioctl to set the link encapsulation
	*
	* Mark Smith <markzzzsmith@yahoo.com.au>
	* Use random_ether_addr() for tap MAC address.
	*
	* Harald Roelle <harald.roelle@ifi.lmu.de> 2004/04/20
	* Fixes in packet dropping, queue length setting and queue wakeup.
	* Increased default tx queue length.
	* Added ethtool API.
	* Minor cleanups
	*
	* Daniel Podlejski <underley@underley.eu.org>
	* Modifications for 2.3.99-pre5 kernel.
	*/

	#define DRV_NAME "tun"
	#define DRV_VERSION "1.6"
	#define DRV_DESCRIPTION "Universal TUN/TAP device driver"
	#define DRV_COPYRIGHT "(C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>"

	#include <linux/module.h>
	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/major.h>
	#include <linux/slab.h>
	#include <linux/poll.h>
	#include <linux/fcntl.h>
	#include <linux/init.h>
	#include <linux/skbuff.h>
	#include <linux/netdevice.h>
	#include <linux/etherdevice.h>
	#include <linux/miscdevice.h>
	#include <linux/ethtool.h>
	#include <linux/rtnetlink.h>
	#include <linux/if.h>
	#include <linux/if_arp.h>
	#include <linux/if_ether.h>
	#include <linux/if_tun.h>
	#include <linux/crc32.h>
	#include <net/net_namespace.h>

	#include <asm/system.h>
	#include <asm/uaccess.h>

	#ifdef TUN_DEBUG
	static int debug;
	#endif

	/* Network device part of the driver */

	static LIST_HEAD(tun_dev_list);
	static const struct ethtool_ops tun_ethtool_ops;

	/* Net device open. */
	static int tun_net_open(struct net_device *dev)
	{
	netif_start_queue(dev);
	return 0;
	}

	/* Net device close. */
	static int tun_net_close(struct net_device *dev)
	{
	netif_stop_queue(dev);
	return 0;
	}

	/* Net device start xmit */
	static int tun_net_xmit(struct sk_buff skb, struct net_device dev)
	{
	struct tun_struct *tun = netdev_priv(dev);

	DBG(KERN_INFO "%s: tun_net_xmit %d\n", tun->dev->name, skb->len);

	/* Drop packet if interface is not attached */
	if (!tun->attached)
	goto drop;

	/* Packet dropping */
	if (skb_queue_len(&tun->readq) >= dev->tx_queue_len) {
	if (!(tun->flags & TUN_ONE_QUEUE)) {
	/* Normal queueing mode. */
	/* Packet scheduler handles dropping of further packets. */
	netif_stop_queue(dev);

	/* We won't see all dropped packets individually, so overrun
	* error is more appropriate. */
	dev->stats.tx_fifo_errors++;
	} else {
	/* Single queue mode.
	* Driver handles dropping of all packets itself. */
	goto drop;
	}
	}

	/* Queue packet */
	skb_queue_tail(&tun->readq, skb);
	dev->trans_start = jiffies;

	/* Notify and wake up reader process */
	if (tun->flags & TUN_FASYNC)
	kill_fasync(&tun->fasync, SIGIO, POLL_IN);
	wake_up_interruptible(&tun->read_wait);
	return 0;

	drop:
	dev->stats.tx_dropped++;
	kfree_skb(skb);
	return 0;
	}

	/** Add the specified Ethernet address to this multicast filter. */
	static void
	add_multi(u32* filter, const u8* addr)
	{
	int bit_nr = ether_crc(ETH_ALEN, addr) >> 26;
	filter[bit_nr >> 5] \|= 1 << (bit_nr & 31);
	}

	/** Remove the specified Ethernet addres from this multicast filter. */
	static void
	del_multi(u32* filter, const u8* addr)
	{
	int bit_nr = ether_crc(ETH_ALEN, addr) >> 26;
	filter[bit_nr >> 5] &= ~(1 << (bit_nr & 31));
	}

	/** Update the list of multicast groups to which the network device belongs.
	* This list is used to filter packets being sent from the character device to
	* the network device. */
	static void
	tun_net_mclist(struct net_device *dev)
	{
	struct tun_struct *tun = netdev_priv(dev);
	const struct dev_mc_list *mclist;
	int i;
	DECLARE_MAC_BUF(mac);
	DBG(KERN_DEBUG "%s: tun_net_mclist: mc_count %d\n",
	dev->name, dev->mc_count);
	memset(tun->chr_filter, 0, sizeof tun->chr_filter);
	for (i = 0, mclist = dev->mc_list; i < dev->mc_count && mclist != NULL;
	i++, mclist = mclist->next) {
	add_multi(tun->net_filter, mclist->dmi_addr);
	DBG(KERN_DEBUG "%s: tun_net_mclist: %s\n",
	dev->name, print_mac(mac, mclist->dmi_addr));
	}
	}

	#define MIN_MTU 68
	#define MAX_MTU 65535

	static int
	tun_net_change_mtu(struct net_device *dev, int new_mtu)
	{
	if (new_mtu < MIN_MTU \|\| new_mtu + dev->hard_header_len > MAX_MTU)
	return -EINVAL;
	dev->mtu = new_mtu;
	return 0;
	}

	/* Initialize net device. */
	static void tun_net_init(struct net_device *dev)
	{
	struct tun_struct *tun = netdev_priv(dev);

	switch (tun->flags & TUN_TYPE_MASK) {
	case TUN_TUN_DEV:
	/* Point-to-Point TUN Device */
	dev->hard_header_len = 0;
	dev->addr_len = 0;
	dev->mtu = 1500;
	dev->change_mtu = tun_net_change_mtu;

	/* Zero header length */
	dev->type = ARPHRD_NONE;
	dev->flags = IFF_POINTOPOINT \| IFF_NOARP \| IFF_MULTICAST;
	dev->tx_queue_len = TUN_READQ_SIZE; /* We prefer our own queue length */
	break;

	case TUN_TAP_DEV:
	/* Ethernet TAP Device */
	dev->set_multicast_list = tun_net_mclist;

	ether_setup(dev);
	dev->change_mtu = tun_net_change_mtu;

	/* random address already created for us by tun_set_iff, use it */
	memcpy(dev->dev_addr, tun->dev_addr, min(sizeof(tun->dev_addr), sizeof(dev->dev_addr)) );

	dev->tx_queue_len = TUN_READQ_SIZE; /* We prefer our own queue length */
	break;
	}
	}

	/* Character device part */

	/* Poll */
	static unsigned int tun_chr_poll(struct file file, poll_table wait)
	{
	struct tun_struct *tun = file->private_data;
	unsigned int mask = POLLOUT \| POLLWRNORM;

	if (!tun)
	return -EBADFD;

	DBG(KERN_INFO "%s: tun_chr_poll\n", tun->dev->name);

	poll_wait(file, &tun->read_wait, wait);

	if (!skb_queue_empty(&tun->readq))
	mask \|= POLLIN \| POLLRDNORM;

	return mask;
	}

	/* Get packet from user space buffer */
	static __inline__ ssize_t tun_get_user(struct tun_struct tun, struct iovec iv, size_t count)
	{
	struct tun_pi pi = { 0, __constant_htons(ETH_P_IP) };
	struct sk_buff *skb;
	size_t len = count, align = 0;

	if (!(tun->flags & TUN_NO_PI)) {
	if ((len -= sizeof(pi)) > count)
	return -EINVAL;

	if(memcpy_fromiovec((void *)&pi, iv, sizeof(pi)))
	return -EFAULT;
	}

	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV)
	align = NET_IP_ALIGN;

	if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
	tun->dev->stats.rx_dropped++;
	return -ENOMEM;
	}

	if (align)
	skb_reserve(skb, align);
	if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
	tun->dev->stats.rx_dropped++;
	kfree_skb(skb);
	return -EFAULT;
	}

	switch (tun->flags & TUN_TYPE_MASK) {
	case TUN_TUN_DEV:
	skb_reset_mac_header(skb);
	skb->protocol = pi.proto;
	skb->dev = tun->dev;
	break;
	case TUN_TAP_DEV:
	skb->protocol = eth_type_trans(skb, tun->dev);
	break;
	};

	if (tun->flags & TUN_NOCHECKSUM)
	skb->ip_summed = CHECKSUM_UNNECESSARY;

	netif_rx_ni(skb);
	tun->dev->last_rx = jiffies;

	tun->dev->stats.rx_packets++;
	tun->dev->stats.rx_bytes += len;

	return count;
	}

	static ssize_t tun_chr_aio_write(struct kiocb iocb, const struct iovec iv,
	unsigned long count, loff_t pos)
	{
	struct tun_struct *tun = iocb->ki_filp->private_data;

	if (!tun)
	return -EBADFD;

	DBG(KERN_INFO "%s: tun_chr_write %ld\n", tun->dev->name, count);

	return tun_get_user(tun, (struct iovec *) iv, iov_length(iv, count));
	}

	/* Put packet to the user space buffer */
	static __inline__ ssize_t tun_put_user(struct tun_struct *tun,
	struct sk_buff *skb,
	struct iovec *iv, int len)
	{
	struct tun_pi pi = { 0, skb->protocol };
	ssize_t total = 0;

	if (!(tun->flags & TUN_NO_PI)) {
	if ((len -= sizeof(pi)) < 0)
	return -EINVAL;

	if (len < skb->len) {
	/* Packet will be striped */
	pi.flags \|= TUN_PKT_STRIP;
	}

	if (memcpy_toiovec(iv, (void *) &pi, sizeof(pi)))
	return -EFAULT;
	total += sizeof(pi);
	}

	len = min_t(int, skb->len, len);

	skb_copy_datagram_iovec(skb, 0, iv, len);
	total += len;

	tun->dev->stats.tx_packets++;
	tun->dev->stats.tx_bytes += len;

	return total;
	}

	static ssize_t tun_chr_aio_read(struct kiocb iocb, const struct iovec iv,
	unsigned long count, loff_t pos)
	{
	struct file *file = iocb->ki_filp;
	struct tun_struct *tun = file->private_data;
	DECLARE_WAITQUEUE(wait, current);
	struct sk_buff *skb;
	ssize_t len, ret = 0;
	DECLARE_MAC_BUF(mac);

	if (!tun)
	return -EBADFD;

	DBG(KERN_INFO "%s: tun_chr_read\n", tun->dev->name);

	len = iov_length(iv, count);
	if (len < 0)
	return -EINVAL;

	add_wait_queue(&tun->read_wait, &wait);
	while (len) {
	const u8 ones[ ETH_ALEN] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
	u8 addr[ ETH_ALEN];
	int bit_nr;

	current->state = TASK_INTERRUPTIBLE;

	/* Read frames from the queue */
	if (!(skb=skb_dequeue(&tun->readq))) {
	if (file->f_flags & O_NONBLOCK) {
	ret = -EAGAIN;
	break;
	}
	if (signal_pending(current)) {
	ret = -ERESTARTSYS;
	break;
	}

	/* Nothing to read, let's sleep */
	schedule();
	continue;
	}
	netif_wake_queue(tun->dev);

	/** Decide whether to accept this packet. This code is designed to
	* behave identically to an Ethernet interface. Accept the packet if
	* - we are promiscuous.
	* - the packet is addressed to us.
	* - the packet is broadcast.
	* - the packet is multicast and
	* - we are multicast promiscous.
	* - we belong to the multicast group.
	*/
	skb_copy_from_linear_data(skb, addr, min_t(size_t, sizeof addr,
	skb->len));
	bit_nr = ether_crc(sizeof addr, addr) >> 26;
	if ((tun->if_flags & IFF_PROMISC) \|\|
	memcmp(addr, tun->dev_addr, sizeof addr) == 0 \|\|
	memcmp(addr, ones, sizeof addr) == 0 \|\|
	(((addr[0] == 1 && addr[1] == 0 && addr[2] == 0x5e) \|\|
	(addr[0] == 0x33 && addr[1] == 0x33)) &&
	((tun->if_flags & IFF_ALLMULTI) \|\|
	(tun->chr_filter[bit_nr >> 5] & (1 << (bit_nr & 31)))))) {
	DBG(KERN_DEBUG "%s: tun_chr_readv: accepted: %s\n",
	tun->dev->name, print_mac(mac, addr));
	ret = tun_put_user(tun, skb, (struct iovec *) iv, len);
	kfree_skb(skb);
	break;
	} else {
	DBG(KERN_DEBUG "%s: tun_chr_readv: rejected: %s\n",
	tun->dev->name, print_mac(mac, addr));
	kfree_skb(skb);
	continue;
	}
	}

	current->state = TASK_RUNNING;
	remove_wait_queue(&tun->read_wait, &wait);

	return ret;
	}

	static void tun_setup(struct net_device *dev)
	{
	struct tun_struct *tun = netdev_priv(dev);

	skb_queue_head_init(&tun->readq);
	init_waitqueue_head(&tun->read_wait);

	tun->owner = -1;
	tun->group = -1;

	dev->open = tun_net_open;
	dev->hard_start_xmit = tun_net_xmit;
	dev->stop = tun_net_close;
	dev->ethtool_ops = &tun_ethtool_ops;
	dev->destructor = free_netdev;
	}

	static struct tun_struct tun_get_by_name(const char name)
	{
	struct tun_struct *tun;

	ASSERT_RTNL();
	list_for_each_entry(tun, &tun_dev_list, list) {
	if (!strncmp(tun->dev->name, name, IFNAMSIZ))
	return tun;
	}

	return NULL;
	}

	static int tun_set_iff(struct file file, struct ifreq ifr)
	{
	struct tun_struct *tun;
	struct net_device *dev;
	int err;

	tun = tun_get_by_name(ifr->ifr_name);
	if (tun) {
	if (tun->attached)
	return -EBUSY;

	/* Check permissions */
	if (((tun->owner != -1 &&
	current->euid != tun->owner) \|\|
	(tun->group != -1 &&
	current->egid != tun->group)) &&
	!capable(CAP_NET_ADMIN))
	return -EPERM;
	}
	else if (__dev_get_by_name(&init_net, ifr->ifr_name))
	return -EINVAL;
	else {
	char *name;
	unsigned long flags = 0;

	err = -EINVAL;

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

	/* Set dev type */
	if (ifr->ifr_flags & IFF_TUN) {
	/* TUN device */
	flags \|= TUN_TUN_DEV;
	name = "tun%d";
	} else if (ifr->ifr_flags & IFF_TAP) {
	/* TAP device */
	flags \|= TUN_TAP_DEV;
	name = "tap%d";
	} else
	goto failed;

	if (*ifr->ifr_name)
	name = ifr->ifr_name;

	dev = alloc_netdev(sizeof(struct tun_struct), name,
	tun_setup);
	if (!dev)
	return -ENOMEM;

	tun = netdev_priv(dev);
	tun->dev = dev;
	tun->flags = flags;
	/* Be promiscuous by default to maintain previous behaviour. */
	tun->if_flags = IFF_PROMISC;
	/* Generate random Ethernet address. */
	(__be16 )tun->dev_addr = htons(0x00FF);
	get_random_bytes(tun->dev_addr + sizeof(u16), 4);
	memset(tun->chr_filter, 0, sizeof tun->chr_filter);

	tun_net_init(dev);

	if (strchr(dev->name, '%')) {
	err = dev_alloc_name(dev, dev->name);
	if (err < 0)
	goto err_free_dev;
	}

	err = register_netdevice(tun->dev);
	if (err < 0)
	goto err_free_dev;

	list_add(&tun->list, &tun_dev_list);
	}

	DBG(KERN_INFO "%s: tun_set_iff\n", tun->dev->name);

	if (ifr->ifr_flags & IFF_NO_PI)
	tun->flags \|= TUN_NO_PI;
	else
	tun->flags &= ~TUN_NO_PI;

	if (ifr->ifr_flags & IFF_ONE_QUEUE)
	tun->flags \|= TUN_ONE_QUEUE;
	else
	tun->flags &= ~TUN_ONE_QUEUE;

	file->private_data = tun;
	tun->attached = 1;

	strcpy(ifr->ifr_name, tun->dev->name);
	return 0;

	err_free_dev:
	free_netdev(dev);
	failed:
	return err;
	}

	static int tun_chr_ioctl(struct inode inode, struct file file,
	unsigned int cmd, unsigned long arg)
	{
	struct tun_struct *tun = file->private_data;
	void __user* argp = (void __user*)arg;
	struct ifreq ifr;
	DECLARE_MAC_BUF(mac);

	if (cmd == TUNSETIFF \|\| _IOC_TYPE(cmd) == 0x89)
	if (copy_from_user(&ifr, argp, sizeof ifr))
	return -EFAULT;

	if (cmd == TUNSETIFF && !tun) {
	int err;

	ifr.ifr_name[IFNAMSIZ-1] = '\0';

	rtnl_lock();
	err = tun_set_iff(file, &ifr);
	rtnl_unlock();

	if (err)
	return err;

	if (copy_to_user(argp, &ifr, sizeof(ifr)))
	return -EFAULT;
	return 0;
	}

	if (!tun)
	return -EBADFD;

	DBG(KERN_INFO "%s: tun_chr_ioctl cmd %d\n", tun->dev->name, cmd);

	switch (cmd) {
	case TUNSETNOCSUM:
	/* Disable/Enable checksum */
	if (arg)
	tun->flags \|= TUN_NOCHECKSUM;
	else
	tun->flags &= ~TUN_NOCHECKSUM;

	DBG(KERN_INFO "%s: checksum %s\n",
	tun->dev->name, arg ? "disabled" : "enabled");
	break;

	case TUNSETPERSIST:
	/* Disable/Enable persist mode */
	if (arg)
	tun->flags \|= TUN_PERSIST;
	else
	tun->flags &= ~TUN_PERSIST;

	DBG(KERN_INFO "%s: persist %s\n",
	tun->dev->name, arg ? "enabled" : "disabled");
	break;

	case TUNSETOWNER:
	/* Set owner of the device */
	tun->owner = (uid_t) arg;

	DBG(KERN_INFO "%s: owner set to %d\n", tun->dev->name, tun->owner);
	break;

	case TUNSETGROUP:
	/* Set group of the device */
	tun->group= (gid_t) arg;

	DBG(KERN_INFO "%s: group set to %d\n", tun->dev->name, tun->group);
	break;

	case TUNSETLINK:
	/* Only allow setting the type when the interface is down */
	if (tun->dev->flags & IFF_UP) {
	DBG(KERN_INFO "%s: Linktype set failed because interface is up\n",
	tun->dev->name);
	return -EBUSY;
	} else {
	tun->dev->type = (int) arg;
	DBG(KERN_INFO "%s: linktype set to %d\n", tun->dev->name, tun->dev->type);
	}
	break;

	#ifdef TUN_DEBUG
	case TUNSETDEBUG:
	tun->debug = arg;
	break;
	#endif

	case SIOCGIFFLAGS:
	ifr.ifr_flags = tun->if_flags;
	if (copy_to_user( argp, &ifr, sizeof ifr))
	return -EFAULT;
	return 0;

	case SIOCSIFFLAGS:
	/** Set the character device's interface flags. Currently only
	* IFF_PROMISC and IFF_ALLMULTI are used. */
	tun->if_flags = ifr.ifr_flags;
	DBG(KERN_INFO "%s: interface flags 0x%lx\n",
	tun->dev->name, tun->if_flags);
	return 0;

	case SIOCGIFHWADDR:
	/* Note: the actual net device's address may be different */
	memcpy(ifr.ifr_hwaddr.sa_data, tun->dev_addr,
	min(sizeof ifr.ifr_hwaddr.sa_data, sizeof tun->dev_addr));
	if (copy_to_user( argp, &ifr, sizeof ifr))
	return -EFAULT;
	return 0;

	case SIOCSIFHWADDR:
	{
	/* try to set the actual net device's hw address */
	int ret;

	rtnl_lock();
	ret = dev_set_mac_address(tun->dev, &ifr.ifr_hwaddr);
	rtnl_unlock();

	if (ret == 0) {
	/** Set the character device's hardware address. This is used when
	* filtering packets being sent from the network device to the character
	* device. */
	memcpy(tun->dev_addr, ifr.ifr_hwaddr.sa_data,
	min(sizeof ifr.ifr_hwaddr.sa_data, sizeof tun->dev_addr));
	DBG(KERN_DEBUG "%s: set hardware address: %x:%x:%x:%x:%x:%x\n",
	tun->dev->name,
	tun->dev_addr[0], tun->dev_addr[1], tun->dev_addr[2],
	tun->dev_addr[3], tun->dev_addr[4], tun->dev_addr[5]);
	}

	return ret;
	}

	case SIOCADDMULTI:
	/** Add the specified group to the character device's multicast filter
	* list. */
	add_multi(tun->chr_filter, ifr.ifr_hwaddr.sa_data);
	DBG(KERN_DEBUG "%s: add multi: %s\n",
	tun->dev->name, print_mac(mac, ifr.ifr_hwaddr.sa_data));
	return 0;

	case SIOCDELMULTI:
	/** Remove the specified group from the character device's multicast
	* filter list. */
	del_multi(tun->chr_filter, ifr.ifr_hwaddr.sa_data);
	DBG(KERN_DEBUG "%s: del multi: %s\n",
	tun->dev->name, print_mac(mac, ifr.ifr_hwaddr.sa_data));
	return 0;

	default:
	return -EINVAL;
	};

	return 0;
	}

	static int tun_chr_fasync(int fd, struct file *file, int on)
	{
	struct tun_struct *tun = file->private_data;
	int ret;

	if (!tun)
	return -EBADFD;

	DBG(KERN_INFO "%s: tun_chr_fasync %d\n", tun->dev->name, on);

	if ((ret = fasync_helper(fd, file, on, &tun->fasync)) < 0)
	return ret;

	if (on) {
	ret = __f_setown(file, task_pid(current), PIDTYPE_PID, 0);
	if (ret)
	return ret;
	tun->flags \|= TUN_FASYNC;
	} else
	tun->flags &= ~TUN_FASYNC;

	return 0;
	}

	static int tun_chr_open(struct inode inode, struct file file)
	{
	DBG1(KERN_INFO "tunX: tun_chr_open\n");
	file->private_data = NULL;
	return 0;
	}

	static int tun_chr_close(struct inode inode, struct file file)
	{
	struct tun_struct *tun = file->private_data;

	if (!tun)
	return 0;

	DBG(KERN_INFO "%s: tun_chr_close\n", tun->dev->name);

	tun_chr_fasync(-1, file, 0);

	rtnl_lock();

	/* Detach from net device */
	file->private_data = NULL;
	tun->attached = 0;

	/* Drop read queue */
	skb_queue_purge(&tun->readq);

	if (!(tun->flags & TUN_PERSIST)) {
	list_del(&tun->list);
	unregister_netdevice(tun->dev);
	}

	rtnl_unlock();

	return 0;
	}

	static const struct file_operations tun_fops = {
	.owner = THIS_MODULE,
	.llseek = no_llseek,
	.read = do_sync_read,
	.aio_read = tun_chr_aio_read,
	.write = do_sync_write,
	.aio_write = tun_chr_aio_write,
	.poll = tun_chr_poll,
	.ioctl = tun_chr_ioctl,
	.open = tun_chr_open,
	.release = tun_chr_close,
	.fasync = tun_chr_fasync
	};

	static struct miscdevice tun_miscdev = {
	.minor = TUN_MINOR,
	.name = "tun",
	.fops = &tun_fops,
	};

	/* ethtool interface */

	static int tun_get_settings(struct net_device dev, struct ethtool_cmd cmd)
	{
	cmd->supported = 0;
	cmd->advertising = 0;
	cmd->speed = SPEED_10;
	cmd->duplex = DUPLEX_FULL;
	cmd->port = PORT_TP;
	cmd->phy_address = 0;
	cmd->transceiver = XCVR_INTERNAL;
	cmd->autoneg = AUTONEG_DISABLE;
	cmd->maxtxpkt = 0;
	cmd->maxrxpkt = 0;
	return 0;
	}

	static void tun_get_drvinfo(struct net_device dev, struct ethtool_drvinfo info)
	{
	struct tun_struct *tun = netdev_priv(dev);

	strcpy(info->driver, DRV_NAME);
	strcpy(info->version, DRV_VERSION);
	strcpy(info->fw_version, "N/A");

	switch (tun->flags & TUN_TYPE_MASK) {
	case TUN_TUN_DEV:
	strcpy(info->bus_info, "tun");
	break;
	case TUN_TAP_DEV:
	strcpy(info->bus_info, "tap");
	break;
	}
	}

	static u32 tun_get_msglevel(struct net_device *dev)
	{
	#ifdef TUN_DEBUG
	struct tun_struct *tun = netdev_priv(dev);
	return tun->debug;
	#else
	return -EOPNOTSUPP;
	#endif
	}

	static void tun_set_msglevel(struct net_device *dev, u32 value)
	{
	#ifdef TUN_DEBUG
	struct tun_struct *tun = netdev_priv(dev);
	tun->debug = value;
	#endif
	}

	static u32 tun_get_link(struct net_device *dev)
	{
	struct tun_struct *tun = netdev_priv(dev);
	return tun->attached;
	}

	static u32 tun_get_rx_csum(struct net_device *dev)
	{
	struct tun_struct *tun = netdev_priv(dev);
	return (tun->flags & TUN_NOCHECKSUM) == 0;
	}

	static int tun_set_rx_csum(struct net_device *dev, u32 data)
	{
	struct tun_struct *tun = netdev_priv(dev);
	if (data)
	tun->flags &= ~TUN_NOCHECKSUM;
	else
	tun->flags \|= TUN_NOCHECKSUM;
	return 0;
	}

	static const struct ethtool_ops tun_ethtool_ops = {
	.get_settings = tun_get_settings,
	.get_drvinfo = tun_get_drvinfo,
	.get_msglevel = tun_get_msglevel,
	.set_msglevel = tun_set_msglevel,
	.get_link = tun_get_link,
	.get_rx_csum = tun_get_rx_csum,
	.set_rx_csum = tun_set_rx_csum
	};

	static int __init tun_init(void)
	{
	int ret = 0;

	printk(KERN_INFO "tun: %s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
	printk(KERN_INFO "tun: %s\n", DRV_COPYRIGHT);

	ret = misc_register(&tun_miscdev);
	if (ret)
	printk(KERN_ERR "tun: Can't register misc device %d\n", TUN_MINOR);
	return ret;
	}

	static void tun_cleanup(void)
	{
	struct tun_struct tun, nxt;

	misc_deregister(&tun_miscdev);

	rtnl_lock();
	list_for_each_entry_safe(tun, nxt, &tun_dev_list, list) {
	DBG(KERN_INFO "%s cleaned up\n", tun->dev->name);
	unregister_netdevice(tun->dev);
	}
	rtnl_unlock();

	}

	module_init(tun_init);
	module_exit(tun_cleanup);
	MODULE_DESCRIPTION(DRV_DESCRIPTION);
	MODULE_AUTHOR(DRV_COPYRIGHT);
	MODULE_LICENSE("GPL");
	MODULE_ALIAS_MISCDEV(TUN_MINOR);