/*
   *  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:
   *

   *  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 pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #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/compat.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 <linux/nsproxy.h>

  #include <linux/virtio_net.h>

  #include <linux/rcupdate.h>

  #include <net/net_namespace.h>

  #include <net/netns/generic.h>

  #include <net/rtnetlink.h>

  #include <net/sock.h>

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

  /* Uncomment to enable debugging */
  /* #define TUN_DEBUG 1 */

  #ifdef TUN_DEBUG
  static int debug;

  #define tun_debug(level, tun, fmt, args...)			\
  do {								\
  	if (tun->debug)						\
  		netdev_printk(level, tun->dev, fmt, ##args);	\
  } while (0)
  #define DBG1(level, fmt, args...)				\
  do {								\
  	if (debug == 2)						\
  		printk(level fmt, ##args);			\
  } while (0)

  #else

  #define tun_debug(level, tun, fmt, args...)			\
  do {								\
  	if (0)							\
  		netdev_printk(level, tun->dev, fmt, ##args);	\
  } while (0)
  #define DBG1(level, fmt, args...)				\
  do {								\
  	if (0)							\
  		printk(level fmt, ##args);			\
  } while (0)

  #endif

  #define FLT_EXACT_COUNT 8
  struct tap_filter {
  	unsigned int    count;    /* Number of addrs. Zero means disabled */
  	u32             mask[2];  /* Mask of the hashed addrs */
  	unsigned char	addr[FLT_EXACT_COUNT][ETH_ALEN];
  };

  struct tun_file {

  	atomic_t count;

  	struct tun_struct *tun;

  	struct net *net;

  };

  struct tun_sock;

  struct tun_struct {

  	struct tun_file		*tfile;

  	unsigned int 		flags;

  	uid_t			owner;
  	gid_t			group;

  	struct net_device	*dev;

  	u32			set_features;
  #define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
  			  NETIF_F_TSO6|NETIF_F_UFO)

  	struct fasync_struct	*fasync;

  	struct tap_filter       txflt;

  	struct socket		socket;

  	struct socket_wq	wq;

  
  	int			vnet_hdr_sz;

  #ifdef TUN_DEBUG
  	int debug;

  #endif

  };

  struct tun_sock {
  	struct sock		sk;
  	struct tun_struct	*tun;
  };
  
  static inline struct tun_sock *tun_sk(struct sock *sk)
  {
  	return container_of(sk, struct tun_sock, sk);
  }

  static int tun_attach(struct tun_struct *tun, struct file *file)
  {

  	struct tun_file *tfile = file->private_data;

  	int err;

  
  	ASSERT_RTNL();

  	netif_tx_lock_bh(tun->dev);
  
  	err = -EINVAL;
  	if (tfile->tun)
  		goto out;
  
  	err = -EBUSY;
  	if (tun->tfile)
  		goto out;
  
  	err = 0;

  	tfile->tun = tun;
  	tun->tfile = tfile;

  	tun->socket.file = file;

  	netif_carrier_on(tun->dev);

  	dev_hold(tun->dev);

  	sock_hold(tun->socket.sk);

  	atomic_inc(&tfile->count);

  out:
  	netif_tx_unlock_bh(tun->dev);
  	return err;

  }

  static void __tun_detach(struct tun_struct *tun)
  {

  	/* Detach from net device */

  	netif_tx_lock_bh(tun->dev);

  	netif_carrier_off(tun->dev);

  	tun->tfile = NULL;

  	tun->socket.file = NULL;

  	netif_tx_unlock_bh(tun->dev);

  
  	/* Drop read queue */

  	skb_queue_purge(&tun->socket.sk->sk_receive_queue);

  
  	/* Drop the extra count on the net device */
  	dev_put(tun->dev);
  }
  
  static void tun_detach(struct tun_struct *tun)
  {
  	rtnl_lock();
  	__tun_detach(tun);
  	rtnl_unlock();

  }
  
  static struct tun_struct *__tun_get(struct tun_file *tfile)
  {

  	struct tun_struct *tun = NULL;
  
  	if (atomic_inc_not_zero(&tfile->count))
  		tun = tfile->tun;
  
  	return tun;

  }
  
  static struct tun_struct *tun_get(struct file *file)
  {
  	return __tun_get(file->private_data);
  }
  
  static void tun_put(struct tun_struct *tun)
  {

  	struct tun_file *tfile = tun->tfile;
  
  	if (atomic_dec_and_test(&tfile->count))
  		tun_detach(tfile->tun);

  }

  /* TAP filtering */

  static void addr_hash_set(u32 *mask, const u8 *addr)
  {
  	int n = ether_crc(ETH_ALEN, addr) >> 26;
  	mask[n >> 5] |= (1 << (n & 31));
  }
  
  static unsigned int addr_hash_test(const u32 *mask, const u8 *addr)
  {
  	int n = ether_crc(ETH_ALEN, addr) >> 26;
  	return mask[n >> 5] & (1 << (n & 31));
  }
  
  static int update_filter(struct tap_filter *filter, void __user *arg)
  {
  	struct { u8 u[ETH_ALEN]; } *addr;
  	struct tun_filter uf;
  	int err, alen, n, nexact;
  
  	if (copy_from_user(&uf, arg, sizeof(uf)))
  		return -EFAULT;
  
  	if (!uf.count) {
  		/* Disabled */
  		filter->count = 0;
  		return 0;
  	}
  
  	alen = ETH_ALEN * uf.count;
  	addr = kmalloc(alen, GFP_KERNEL);
  	if (!addr)
  		return -ENOMEM;
  
  	if (copy_from_user(addr, arg + sizeof(uf), alen)) {
  		err = -EFAULT;
  		goto done;
  	}
  
  	/* The filter is updated without holding any locks. Which is
  	 * perfectly safe. We disable it first and in the worst
  	 * case we'll accept a few undesired packets. */
  	filter->count = 0;
  	wmb();
  
  	/* Use first set of addresses as an exact filter */
  	for (n = 0; n < uf.count && n < FLT_EXACT_COUNT; n++)
  		memcpy(filter->addr[n], addr[n].u, ETH_ALEN);
  
  	nexact = n;

  	/* Remaining multicast addresses are hashed,
  	 * unicast will leave the filter disabled. */

  	memset(filter->mask, 0, sizeof(filter->mask));

  	for (; n < uf.count; n++) {
  		if (!is_multicast_ether_addr(addr[n].u)) {
  			err = 0; /* no filter */
  			goto done;
  		}

  		addr_hash_set(filter->mask, addr[n].u);

  	}

  
  	/* For ALLMULTI just set the mask to all ones.
  	 * This overrides the mask populated above. */
  	if ((uf.flags & TUN_FLT_ALLMULTI))
  		memset(filter->mask, ~0, sizeof(filter->mask));
  
  	/* Now enable the filter */
  	wmb();
  	filter->count = nexact;
  
  	/* Return the number of exact filters */
  	err = nexact;
  
  done:
  	kfree(addr);
  	return err;
  }
  
  /* Returns: 0 - drop, !=0 - accept */
  static int run_filter(struct tap_filter *filter, const struct sk_buff *skb)
  {
  	/* Cannot use eth_hdr(skb) here because skb_mac_hdr() is incorrect
  	 * at this point. */
  	struct ethhdr *eh = (struct ethhdr *) skb->data;
  	int i;
  
  	/* Exact match */
  	for (i = 0; i < filter->count; i++)
  		if (!compare_ether_addr(eh->h_dest, filter->addr[i]))
  			return 1;
  
  	/* Inexact match (multicast only) */
  	if (is_multicast_ether_addr(eh->h_dest))
  		return addr_hash_test(filter->mask, eh->h_dest);
  
  	return 0;
  }
  
  /*
   * Checks whether the packet is accepted or not.
   * Returns: 0 - drop, !=0 - accept
   */
  static int check_filter(struct tap_filter *filter, const struct sk_buff *skb)
  {
  	if (!filter->count)
  		return 1;
  
  	return run_filter(filter, skb);
  }

  /* Network device part of the driver */

  static const struct ethtool_ops tun_ethtool_ops;

  /* Net device detach from fd. */
  static void tun_net_uninit(struct net_device *dev)
  {
  	struct tun_struct *tun = netdev_priv(dev);
  	struct tun_file *tfile = tun->tfile;
  
  	/* Inform the methods they need to stop using the dev.
  	 */
  	if (tfile) {

  		wake_up_all(&tun->wq.wait);

  		if (atomic_dec_and_test(&tfile->count))
  			__tun_detach(tun);
  	}
  }

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

  	sock_put(tun->socket.sk);

  }

  /* 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 netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)

  {
  	struct tun_struct *tun = netdev_priv(dev);

  	tun_debug(KERN_INFO, tun, "tun_net_xmit %d
  ", skb->len);

  
  	/* Drop packet if interface is not attached */

  	if (!tun->tfile)

  		goto drop;

  	/* Drop if the filter does not like it.
  	 * This is a noop if the filter is disabled.
  	 * Filter can be enabled only for the TAP devices. */
  	if (!check_filter(&tun->txflt, skb))
  		goto drop;

  	if (tun->socket.sk->sk_filter &&
  	    sk_filter(tun->socket.sk, skb))
  		goto drop;

  	if (skb_queue_len(&tun->socket.sk->sk_receive_queue) >= 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;
  		}
  	}

  	/* Orphan the skb - required as we might hang on to it
  	 * for indefinite time. */
  	skb_orphan(skb);

  	/* Enqueue packet */

  	skb_queue_tail(&tun->socket.sk->sk_receive_queue, skb);

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

  	wake_up_interruptible_poll(&tun->wq.wait, POLLIN |

  				   POLLRDNORM | POLLRDBAND);

  	return NETDEV_TX_OK;

  
  drop:

  	dev->stats.tx_dropped++;

  	kfree_skb(skb);

  	return NETDEV_TX_OK;

  }

  static void tun_net_mclist(struct net_device *dev)

  {

  	/*
  	 * This callback is supposed to deal with mc filter in
  	 * _rx_ path and has nothing to do with the _tx_ path.
  	 * In rx path we always accept everything userspace gives us.
  	 */

  }

  #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;
  }

  static u32 tun_net_fix_features(struct net_device *dev, u32 features)
  {
  	struct tun_struct *tun = netdev_priv(dev);
  
  	return (features & tun->set_features) | (features & ~TUN_USER_FEATURES);
  }

  #ifdef CONFIG_NET_POLL_CONTROLLER
  static void tun_poll_controller(struct net_device *dev)
  {
  	/*
  	 * Tun only receives frames when:
  	 * 1) the char device endpoint gets data from user space
  	 * 2) the tun socket gets a sendmsg call from user space
  	 * Since both of those are syncronous operations, we are guaranteed
  	 * never to have pending data when we poll for it
  	 * so theres nothing to do here but return.
  	 * We need this though so netpoll recognizes us as an interface that
  	 * supports polling, which enables bridge devices in virt setups to
  	 * still use netconsole
  	 */
  	return;
  }
  #endif

  static const struct net_device_ops tun_netdev_ops = {

  	.ndo_uninit		= tun_net_uninit,

  	.ndo_open		= tun_net_open,
  	.ndo_stop		= tun_net_close,

  	.ndo_start_xmit		= tun_net_xmit,

  	.ndo_change_mtu		= tun_net_change_mtu,

  	.ndo_fix_features	= tun_net_fix_features,

  #ifdef CONFIG_NET_POLL_CONTROLLER
  	.ndo_poll_controller	= tun_poll_controller,
  #endif

  };
  
  static const struct net_device_ops tap_netdev_ops = {

  	.ndo_uninit		= tun_net_uninit,

  	.ndo_open		= tun_net_open,
  	.ndo_stop		= tun_net_close,

  	.ndo_start_xmit		= tun_net_xmit,

  	.ndo_change_mtu		= tun_net_change_mtu,

  	.ndo_fix_features	= tun_net_fix_features,

  	.ndo_set_multicast_list	= tun_net_mclist,
  	.ndo_set_mac_address	= eth_mac_addr,
  	.ndo_validate_addr	= eth_validate_addr,

  #ifdef CONFIG_NET_POLL_CONTROLLER
  	.ndo_poll_controller	= tun_poll_controller,
  #endif

  };

  /* 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:

  		dev->netdev_ops = &tun_netdev_ops;

  		/* Point-to-Point TUN Device */
  		dev->hard_header_len = 0;
  		dev->addr_len = 0;
  		dev->mtu = 1500;
  
  		/* 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:

  		dev->netdev_ops = &tap_netdev_ops;

  		/* Ethernet TAP Device */

  		ether_setup(dev);

  		dev->priv_flags &= ~IFF_TX_SKB_SHARING;

  		random_ether_addr(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_file *tfile = file->private_data;
  	struct tun_struct *tun = __tun_get(tfile);

  	struct sock *sk;

  	unsigned int mask = 0;

  
  	if (!tun)

  		return POLLERR;

  	sk = tun->socket.sk;

  	tun_debug(KERN_INFO, tun, "tun_chr_poll
  ");

  	poll_wait(file, &tun->wq.wait, wait);

  	if (!skb_queue_empty(&sk->sk_receive_queue))

  		mask |= POLLIN | POLLRDNORM;

  	if (sock_writeable(sk) ||
  	    (!test_and_set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags) &&
  	     sock_writeable(sk)))
  		mask |= POLLOUT | POLLWRNORM;

  	if (tun->dev->reg_state != NETREG_REGISTERED)
  		mask = POLLERR;

  	tun_put(tun);

  	return mask;
  }

  /* prepad is the amount to reserve at front.  len is length after that.
   * linear is a hint as to how much to copy (usually headers). */

  static struct sk_buff *tun_alloc_skb(struct tun_struct *tun,
  				     size_t prepad, size_t len,
  				     size_t linear, int noblock)

  {

  	struct sock *sk = tun->socket.sk;

  	struct sk_buff *skb;

  	int err;

  	sock_update_classid(sk);

  	/* Under a page?  Don't bother with paged skb. */

  	if (prepad + len < PAGE_SIZE || !linear)

  		linear = len;

  	skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
  				   &err);

  	if (!skb)

  		return ERR_PTR(err);

  
  	skb_reserve(skb, prepad);
  	skb_put(skb, linear);

  	skb->data_len = len - linear;
  	skb->len += len - linear;

  
  	return skb;
  }

  /* Get packet from user space buffer */

  static ssize_t tun_get_user(struct tun_struct *tun,
  			    const struct iovec *iv, size_t count,
  			    int noblock)

  {

  	struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };

  	struct sk_buff *skb;

  	size_t len = count, align = NET_SKB_PAD;

  	struct virtio_net_hdr gso = { 0 };

  	int offset = 0;

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

  		if (memcpy_fromiovecend((void *)&pi, iv, 0, sizeof(pi)))

  			return -EFAULT;

  		offset += sizeof(pi);

  	}

  	if (tun->flags & TUN_VNET_HDR) {

  		if ((len -= tun->vnet_hdr_sz) > count)

  			return -EINVAL;

  		if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso)))

  			return -EFAULT;

  		if ((gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
  		    gso.csum_start + gso.csum_offset + 2 > gso.hdr_len)
  			gso.hdr_len = gso.csum_start + gso.csum_offset + 2;

  		if (gso.hdr_len > len)
  			return -EINVAL;

  		offset += tun->vnet_hdr_sz;

  	}

  	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {

  		align += NET_IP_ALIGN;

  		if (unlikely(len < ETH_HLEN ||
  			     (gso.hdr_len && gso.hdr_len < ETH_HLEN)))

  			return -EINVAL;
  	}

  	skb = tun_alloc_skb(tun, align, len, gso.hdr_len, noblock);
  	if (IS_ERR(skb)) {
  		if (PTR_ERR(skb) != -EAGAIN)
  			tun->dev->stats.rx_dropped++;
  		return PTR_ERR(skb);

  	}

  	if (skb_copy_datagram_from_iovec(skb, 0, iv, offset, len)) {

  		tun->dev->stats.rx_dropped++;

  		kfree_skb(skb);

  		return -EFAULT;

  	}

  	if (gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
  		if (!skb_partial_csum_set(skb, gso.csum_start,
  					  gso.csum_offset)) {
  			tun->dev->stats.rx_frame_errors++;
  			kfree_skb(skb);
  			return -EINVAL;
  		}

  	}

  	switch (tun->flags & TUN_TYPE_MASK) {
  	case TUN_TUN_DEV:

  		if (tun->flags & TUN_NO_PI) {
  			switch (skb->data[0] & 0xf0) {
  			case 0x40:
  				pi.proto = htons(ETH_P_IP);
  				break;
  			case 0x60:
  				pi.proto = htons(ETH_P_IPV6);
  				break;
  			default:
  				tun->dev->stats.rx_dropped++;
  				kfree_skb(skb);
  				return -EINVAL;
  			}
  		}

  		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 (gso.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
  		pr_debug("GSO!
  ");
  		switch (gso.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
  		case VIRTIO_NET_HDR_GSO_TCPV4:
  			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
  			break;
  		case VIRTIO_NET_HDR_GSO_TCPV6:
  			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
  			break;

  		case VIRTIO_NET_HDR_GSO_UDP:
  			skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
  			break;

  		default:
  			tun->dev->stats.rx_frame_errors++;
  			kfree_skb(skb);
  			return -EINVAL;
  		}
  
  		if (gso.gso_type & VIRTIO_NET_HDR_GSO_ECN)
  			skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
  
  		skb_shinfo(skb)->gso_size = gso.gso_size;
  		if (skb_shinfo(skb)->gso_size == 0) {
  			tun->dev->stats.rx_frame_errors++;
  			kfree_skb(skb);
  			return -EINVAL;
  		}
  
  		/* Header must be checked, and gso_segs computed. */
  		skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
  		skb_shinfo(skb)->gso_segs = 0;
  	}

  	netif_rx_ni(skb);

  	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 file *file = iocb->ki_filp;

  	struct tun_struct *tun = tun_get(file);

  	ssize_t result;

  
  	if (!tun)
  		return -EBADFD;

  	tun_debug(KERN_INFO, tun, "tun_chr_write %ld
  ", count);

  	result = tun_get_user(tun, iv, iov_length(iv, count),

  			      file->f_flags & O_NONBLOCK);

  
  	tun_put(tun);
  	return result;

  }

  /* Put packet to the user space buffer */

  static ssize_t tun_put_user(struct tun_struct *tun,
  			    struct sk_buff *skb,
  			    const 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_toiovecend(iv, (void *) &pi, 0, sizeof(pi)))

  			return -EFAULT;
  		total += sizeof(pi);

  	}

  	if (tun->flags & TUN_VNET_HDR) {
  		struct virtio_net_hdr gso = { 0 }; /* no info leak */

  		if ((len -= tun->vnet_hdr_sz) < 0)

  			return -EINVAL;
  
  		if (skb_is_gso(skb)) {
  			struct skb_shared_info *sinfo = skb_shinfo(skb);
  
  			/* This is a hint as to how much should be linear. */
  			gso.hdr_len = skb_headlen(skb);
  			gso.gso_size = sinfo->gso_size;
  			if (sinfo->gso_type & SKB_GSO_TCPV4)
  				gso.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
  			else if (sinfo->gso_type & SKB_GSO_TCPV6)
  				gso.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;

  			else if (sinfo->gso_type & SKB_GSO_UDP)
  				gso.gso_type = VIRTIO_NET_HDR_GSO_UDP;

  			else {

  				pr_err("unexpected GSO type: "

  				       "0x%x, gso_size %d, hdr_len %d
  ",
  				       sinfo->gso_type, gso.gso_size,
  				       gso.hdr_len);
  				print_hex_dump(KERN_ERR, "tun: ",
  					       DUMP_PREFIX_NONE,
  					       16, 1, skb->head,
  					       min((int)gso.hdr_len, 64), true);
  				WARN_ON_ONCE(1);
  				return -EINVAL;
  			}

  			if (sinfo->gso_type & SKB_GSO_TCP_ECN)
  				gso.gso_type |= VIRTIO_NET_HDR_GSO_ECN;
  		} else
  			gso.gso_type = VIRTIO_NET_HDR_GSO_NONE;
  
  		if (skb->ip_summed == CHECKSUM_PARTIAL) {
  			gso.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;

  			gso.csum_start = skb_checksum_start_offset(skb);

  			gso.csum_offset = skb->csum_offset;

  		} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
  			gso.flags = VIRTIO_NET_HDR_F_DATA_VALID;

  		} /* else everything is zero */

  		if (unlikely(memcpy_toiovecend(iv, (void *)&gso, total,
  					       sizeof(gso))))

  			return -EFAULT;

  		total += tun->vnet_hdr_sz;

  	}

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

  	skb_copy_datagram_const_iovec(skb, 0, iv, total, len);

  	total += skb->len;

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

  
  	return total;
  }

  static ssize_t tun_do_read(struct tun_struct *tun,
  			   struct kiocb *iocb, const struct iovec *iv,
  			   ssize_t len, int noblock)

  {

  	DECLARE_WAITQUEUE(wait, current);
  	struct sk_buff *skb;

  	ssize_t ret = 0;

  	tun_debug(KERN_INFO, tun, "tun_chr_read
  ");

  	if (unlikely(!noblock))
  		add_wait_queue(&tun->wq.wait, &wait);

  	while (len) {

  		current->state = TASK_INTERRUPTIBLE;
  
  		/* Read frames from the queue */

  		if (!(skb=skb_dequeue(&tun->socket.sk->sk_receive_queue))) {

  			if (noblock) {

  				ret = -EAGAIN;
  				break;
  			}
  			if (signal_pending(current)) {
  				ret = -ERESTARTSYS;
  				break;
  			}

  			if (tun->dev->reg_state != NETREG_REGISTERED) {
  				ret = -EIO;
  				break;
  			}

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

  		ret = tun_put_user(tun, skb, iv, len);

  		kfree_skb(skb);
  		break;

  	}
  
  	current->state = TASK_RUNNING;

  	if (unlikely(!noblock))
  		remove_wait_queue(&tun->wq.wait, &wait);

  	return ret;
  }
  
  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_file *tfile = file->private_data;
  	struct tun_struct *tun = __tun_get(tfile);
  	ssize_t len, ret;
  
  	if (!tun)
  		return -EBADFD;
  	len = iov_length(iv, count);
  	if (len < 0) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	ret = tun_do_read(tun, iocb, iv, len, file->f_flags & O_NONBLOCK);
  	ret = min_t(ssize_t, ret, len);

  out:
  	tun_put(tun);

  	return ret;
  }

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

  	tun->owner = -1;

  	tun->group = -1;

  	dev->ethtool_ops = &tun_ethtool_ops;

  	dev->destructor = tun_free_netdev;

  }

  /* Trivial set of netlink ops to allow deleting tun or tap
   * device with netlink.
   */
  static int tun_validate(struct nlattr *tb[], struct nlattr *data[])
  {
  	return -EINVAL;
  }
  
  static struct rtnl_link_ops tun_link_ops __read_mostly = {
  	.kind		= DRV_NAME,
  	.priv_size	= sizeof(struct tun_struct),
  	.setup		= tun_setup,
  	.validate	= tun_validate,
  };

  static void tun_sock_write_space(struct sock *sk)
  {
  	struct tun_struct *tun;

  	wait_queue_head_t *wqueue;

  
  	if (!sock_writeable(sk))
  		return;

  	if (!test_and_clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags))
  		return;

  	wqueue = sk_sleep(sk);
  	if (wqueue && waitqueue_active(wqueue))
  		wake_up_interruptible_sync_poll(wqueue, POLLOUT |

  						POLLWRNORM | POLLWRBAND);

  	tun = tun_sk(sk)->tun;

  	kill_fasync(&tun->fasync, SIGIO, POLL_OUT);
  }
  
  static void tun_sock_destruct(struct sock *sk)
  {

  	free_netdev(tun_sk(sk)->tun->dev);

  }

  static int tun_sendmsg(struct kiocb *iocb, struct socket *sock,
  		       struct msghdr *m, size_t total_len)
  {
  	struct tun_struct *tun = container_of(sock, struct tun_struct, socket);
  	return tun_get_user(tun, m->msg_iov, total_len,
  			    m->msg_flags & MSG_DONTWAIT);
  }
  
  static int tun_recvmsg(struct kiocb *iocb, struct socket *sock,
  		       struct msghdr *m, size_t total_len,
  		       int flags)
  {
  	struct tun_struct *tun = container_of(sock, struct tun_struct, socket);
  	int ret;
  	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
  		return -EINVAL;
  	ret = tun_do_read(tun, iocb, m->msg_iov, total_len,
  			  flags & MSG_DONTWAIT);
  	if (ret > total_len) {
  		m->msg_flags |= MSG_TRUNC;
  		ret = flags & MSG_TRUNC ? ret : total_len;
  	}
  	return ret;
  }
  
  /* Ops structure to mimic raw sockets with tun */
  static const struct proto_ops tun_socket_ops = {
  	.sendmsg = tun_sendmsg,
  	.recvmsg = tun_recvmsg,
  };

  static struct proto tun_proto = {
  	.name		= "tun",
  	.owner		= THIS_MODULE,
  	.obj_size	= sizeof(struct tun_sock),
  };

  static int tun_flags(struct tun_struct *tun)
  {
  	int flags = 0;
  
  	if (tun->flags & TUN_TUN_DEV)
  		flags |= IFF_TUN;
  	else
  		flags |= IFF_TAP;
  
  	if (tun->flags & TUN_NO_PI)
  		flags |= IFF_NO_PI;
  
  	if (tun->flags & TUN_ONE_QUEUE)
  		flags |= IFF_ONE_QUEUE;
  
  	if (tun->flags & TUN_VNET_HDR)
  		flags |= IFF_VNET_HDR;
  
  	return flags;
  }
  
  static ssize_t tun_show_flags(struct device *dev, struct device_attribute *attr,
  			      char *buf)
  {
  	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
  	return sprintf(buf, "0x%x
  ", tun_flags(tun));
  }
  
  static ssize_t tun_show_owner(struct device *dev, struct device_attribute *attr,
  			      char *buf)
  {
  	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
  	return sprintf(buf, "%d
  ", tun->owner);
  }
  
  static ssize_t tun_show_group(struct device *dev, struct device_attribute *attr,
  			      char *buf)
  {
  	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
  	return sprintf(buf, "%d
  ", tun->group);
  }
  
  static DEVICE_ATTR(tun_flags, 0444, tun_show_flags, NULL);
  static DEVICE_ATTR(owner, 0444, tun_show_owner, NULL);
  static DEVICE_ATTR(group, 0444, tun_show_group, NULL);

  static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)

  {

  	struct sock *sk;

  	struct tun_struct *tun;
  	struct net_device *dev;
  	int err;

  	dev = __dev_get_by_name(net, ifr->ifr_name);
  	if (dev) {

  		const struct cred *cred = current_cred();

  		if (ifr->ifr_flags & IFF_TUN_EXCL)
  			return -EBUSY;

  		if ((ifr->ifr_flags & IFF_TUN) && dev->netdev_ops == &tun_netdev_ops)
  			tun = netdev_priv(dev);
  		else if ((ifr->ifr_flags & IFF_TAP) && dev->netdev_ops == &tap_netdev_ops)
  			tun = netdev_priv(dev);
  		else
  			return -EINVAL;

  		if (((tun->owner != -1 && cred->euid != tun->owner) ||
  		     (tun->group != -1 && !in_egroup_p(tun->group))) &&
  		    !capable(CAP_NET_ADMIN))
  			return -EPERM;

  		err = security_tun_dev_attach(tun->socket.sk);

  		if (err < 0)
  			return err;

  		err = tun_attach(tun, file);
  		if (err < 0)
  			return err;

  	}

  	else {
  		char *name;
  		unsigned long flags = 0;

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

  		err = security_tun_dev_create();
  		if (err < 0)
  			return err;

  		/* 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

  			return -EINVAL;

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

  		dev_net_set(dev, net);

  		dev->rtnl_link_ops = &tun_link_ops;

  		tun = netdev_priv(dev);
  		tun->dev = dev;
  		tun->flags = flags;

  		tun->txflt.count = 0;

  		tun->vnet_hdr_sz = sizeof(struct virtio_net_hdr);

  		err = -ENOMEM;
  		sk = sk_alloc(net, AF_UNSPEC, GFP_KERNEL, &tun_proto);
  		if (!sk)
  			goto err_free_dev;

  		tun->socket.wq = &tun->wq;
  		init_waitqueue_head(&tun->wq.wait);

  		tun->socket.ops = &tun_socket_ops;

  		sock_init_data(&tun->socket, sk);
  		sk->sk_write_space = tun_sock_write_space;

  		sk->sk_sndbuf = INT_MAX;

  		tun_sk(sk)->tun = tun;

  		security_tun_dev_post_create(sk);

  		tun_net_init(dev);

  		dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
  			TUN_USER_FEATURES;
  		dev->features = dev->hw_features;

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

  			goto err_free_sk;

  		if (device_create_file(&tun->dev->dev, &dev_attr_tun_flags) ||
  		    device_create_file(&tun->dev->dev, &dev_attr_owner) ||
  		    device_create_file(&tun->dev->dev, &dev_attr_group))

  			pr_err("Failed to create tun sysfs files
  ");

  		sk->sk_destruct = tun_sock_destruct;

  
  		err = tun_attach(tun, file);
  		if (err < 0)

  			goto failed;

  	}

  	tun_debug(KERN_INFO, tun, "tun_set_iff
  ");

  
  	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;

  	if (ifr->ifr_flags & IFF_VNET_HDR)
  		tun->flags |= TUN_VNET_HDR;
  	else
  		tun->flags &= ~TUN_VNET_HDR;

  	/* Make sure persistent devices do not get stuck in
  	 * xoff state.
  	 */
  	if (netif_running(tun->dev))
  		netif_wake_queue(tun->dev);

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

   err_free_sk:
  	sock_put(sk);

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

  static int tun_get_iff(struct net *net, struct tun_struct *tun,
  		       struct ifreq *ifr)

  {

  	tun_debug(KERN_INFO, tun, "tun_get_iff
  ");

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

  	ifr->ifr_flags = tun_flags(tun);

  
  	return 0;
  }

  /* This is like a cut-down ethtool ops, except done via tun fd so no
   * privs required. */

  static int set_offload(struct tun_struct *tun, unsigned long arg)

  {

  	u32 features = 0;

  
  	if (arg & TUN_F_CSUM) {

  		features |= NETIF_F_HW_CSUM;

  		arg &= ~TUN_F_CSUM;
  
  		if (arg & (TUN_F_TSO4|TUN_F_TSO6)) {
  			if (arg & TUN_F_TSO_ECN) {
  				features |= NETIF_F_TSO_ECN;
  				arg &= ~TUN_F_TSO_ECN;
  			}
  			if (arg & TUN_F_TSO4)
  				features |= NETIF_F_TSO;
  			if (arg & TUN_F_TSO6)
  				features |= NETIF_F_TSO6;
  			arg &= ~(TUN_F_TSO4|TUN_F_TSO6);
  		}

  
  		if (arg & TUN_F_UFO) {
  			features |= NETIF_F_UFO;
  			arg &= ~TUN_F_UFO;
  		}

  	}
  
  	/* This gives the user a way to test for new features in future by
  	 * trying to set them. */
  	if (arg)
  		return -EINVAL;

  	tun->set_features = features;
  	netdev_update_features(tun->dev);

  
  	return 0;
  }

  static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
  			    unsigned long arg, int ifreq_len)

  {

  	struct tun_file *tfile = file->private_data;

  	struct tun_struct *tun;

  	void __user* argp = (void __user*)arg;

  	struct sock_fprog fprog;

  	struct ifreq ifr;

  	int sndbuf;

  	int vnet_hdr_sz;

  	int ret;

  
  	if (cmd == TUNSETIFF || _IOC_TYPE(cmd) == 0x89)

  		if (copy_from_user(&ifr, argp, ifreq_len))

  			return -EFAULT;

  	if (cmd == TUNGETFEATURES) {
  		/* Currently this just means: "what IFF flags are valid?".
  		 * This is needed because we never checked for invalid flags on
  		 * TUNSETIFF. */
  		return put_user(IFF_TUN | IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE |
  				IFF_VNET_HDR,
  				(unsigned int __user*)argp);
  	}

  	rtnl_lock();

  	tun = __tun_get(tfile);

  	if (cmd == TUNSETIFF && !tun) {

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

  		ret = tun_set_iff(tfile->net, file, &ifr);

  		if (ret)
  			goto unlock;

  		if (copy_to_user(argp, &ifr, ifreq_len))

  			ret = -EFAULT;
  		goto unlock;

  	}

  	ret = -EBADFD;

  	if (!tun)

  		goto unlock;

  	tun_debug(KERN_INFO, tun, "tun_chr_ioctl cmd %d
  ", cmd);

  	ret = 0;

  	switch (cmd) {

  	case TUNGETIFF:

  		ret = tun_get_iff(current->nsproxy->net_ns, tun, &ifr);

  		if (ret)

  			break;

  		if (copy_to_user(argp, &ifr, ifreq_len))

  			ret = -EFAULT;

  		break;

  	case TUNSETNOCSUM:
  		/* Disable/Enable checksum */

  		/* [unimplemented] */
  		tun_debug(KERN_INFO, tun, "ignored: set checksum %s
  ",

  			  arg ? "disabled" : "enabled");

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

  		tun_debug(KERN_INFO, tun, "persist %s
  ",
  			  arg ? "enabled" : "disabled");

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

  		tun_debug(KERN_INFO, tun, "owner set to %d
  ", tun->owner);

  		break;

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

  		tun_debug(KERN_INFO, tun, "group set to %d
  ", tun->group);

  		break;

  	case TUNSETLINK:
  		/* Only allow setting the type when the interface is down */
  		if (tun->dev->flags & IFF_UP) {

  			tun_debug(KERN_INFO, tun,
  				  "Linktype set failed because interface is up
  ");

  			ret = -EBUSY;

  		} else {
  			tun->dev->type = (int) arg;

  			tun_debug(KERN_INFO, tun, "linktype set to %d
  ",
  				  tun->dev->type);

  			ret = 0;

  		}

  		break;

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

  	case TUNSETOFFLOAD:

  		ret = set_offload(tun, arg);

  		break;

  	case TUNSETTXFILTER:
  		/* Can be set only for TAPs */

  		ret = -EINVAL;

  		if ((tun->flags & TUN_TYPE_MASK) != TUN_TAP_DEV)

  			break;

  		ret = update_filter(&tun->txflt, (void __user *)arg);

  		break;

  
  	case SIOCGIFHWADDR:

  		/* Get hw address */

  		memcpy(ifr.ifr_hwaddr.sa_data, tun->dev->dev_addr, ETH_ALEN);
  		ifr.ifr_hwaddr.sa_family = tun->dev->type;

  		if (copy_to_user(argp, &ifr, ifreq_len))

  			ret = -EFAULT;
  		break;

  
  	case SIOCSIFHWADDR:

  		/* Set hw address */

  		tun_debug(KERN_DEBUG, tun, "set hw address: %pM
  ",
  			  ifr.ifr_hwaddr.sa_data);

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

  		break;

  
  	case TUNGETSNDBUF:

  		sndbuf = tun->socket.sk->sk_sndbuf;

  		if (copy_to_user(argp, &sndbuf, sizeof(sndbuf)))
  			ret = -EFAULT;
  		break;
  
  	case TUNSETSNDBUF:
  		if (copy_from_user(&sndbuf, argp, sizeof(sndbuf))) {
  			ret = -EFAULT;
  			break;
  		}

  		tun->socket.sk->sk_sndbuf = sndbuf;

  		break;

  	case TUNGETVNETHDRSZ:
  		vnet_hdr_sz = tun->vnet_hdr_sz;
  		if (copy_to_user(argp, &vnet_hdr_sz, sizeof(vnet_hdr_sz)))
  			ret = -EFAULT;
  		break;
  
  	case TUNSETVNETHDRSZ:
  		if (copy_from_user(&vnet_hdr_sz, argp, sizeof(vnet_hdr_sz))) {
  			ret = -EFAULT;
  			break;
  		}
  		if (vnet_hdr_sz < (int)sizeof(struct virtio_net_hdr)) {
  			ret = -EINVAL;
  			break;
  		}
  
  		tun->vnet_hdr_sz = vnet_hdr_sz;
  		break;

  	case TUNATTACHFILTER:
  		/* Can be set only for TAPs */
  		ret = -EINVAL;
  		if ((tun->flags & TUN_TYPE_MASK) != TUN_TAP_DEV)
  			break;
  		ret = -EFAULT;
  		if (copy_from_user(&fprog, argp, sizeof(fprog)))
  			break;
  
  		ret = sk_attach_filter(&fprog, tun->socket.sk);
  		break;
  
  	case TUNDETACHFILTER:
  		/* Can be set only for TAPs */
  		ret = -EINVAL;
  		if ((tun->flags & TUN_TYPE_MASK) != TUN_TAP_DEV)
  			break;
  		ret = sk_detach_filter(tun->socket.sk);
  		break;

  	default:

  		ret = -EINVAL;
  		break;

  	}

  unlock:
  	rtnl_unlock();
  	if (tun)
  		tun_put(tun);

  	return ret;

  }

  static long tun_chr_ioctl(struct file *file,
  			  unsigned int cmd, unsigned long arg)
  {
  	return __tun_chr_ioctl(file, cmd, arg, sizeof (struct ifreq));
  }
  
  #ifdef CONFIG_COMPAT
  static long tun_chr_compat_ioctl(struct file *file,
  			 unsigned int cmd, unsigned long arg)
  {
  	switch (cmd) {
  	case TUNSETIFF:
  	case TUNGETIFF:
  	case TUNSETTXFILTER:
  	case TUNGETSNDBUF:
  	case TUNSETSNDBUF:
  	case SIOCGIFHWADDR:
  	case SIOCSIFHWADDR:
  		arg = (unsigned long)compat_ptr(arg);
  		break;
  	default:
  		arg = (compat_ulong_t)arg;
  		break;
  	}
  
  	/*
  	 * compat_ifreq is shorter than ifreq, so we must not access beyond
  	 * the end of that structure. All fields that are used in this
  	 * driver are compatible though, we don't need to convert the
  	 * contents.
  	 */
  	return __tun_chr_ioctl(file, cmd, arg, sizeof(struct compat_ifreq));
  }
  #endif /* CONFIG_COMPAT */

  static int tun_chr_fasync(int fd, struct file *file, int on)
  {

  	struct tun_struct *tun = tun_get(file);

  	int ret;
  
  	if (!tun)
  		return -EBADFD;

  	tun_debug(KERN_INFO, tun, "tun_chr_fasync %d
  ", on);

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

  		goto out;

  	if (on) {

  		ret = __f_setown(file, task_pid(current), PIDTYPE_PID, 0);

  		if (ret)

  			goto out;

  		tun->flags |= TUN_FASYNC;

  	} else

  		tun->flags &= ~TUN_FASYNC;

  	ret = 0;
  out:

  	tun_put(tun);

  	return ret;

  }
  
  static int tun_chr_open(struct inode *inode, struct file * file)
  {

  	struct tun_file *tfile;

  	DBG1(KERN_INFO, "tunX: tun_chr_open
  ");

  
  	tfile = kmalloc(sizeof(*tfile), GFP_KERNEL);
  	if (!tfile)
  		return -ENOMEM;

  	atomic_set(&tfile->count, 0);

  	tfile->tun = NULL;

  	tfile->net = get_net(current->nsproxy->net_ns);

  	file->private_data = tfile;

  	return 0;
  }
  
  static int tun_chr_close(struct inode *inode, struct file *file)
  {

  	struct tun_file *tfile = file->private_data;

  	struct tun_struct *tun;

  	tun = __tun_get(tfile);

  	if (tun) {

  		struct net_device *dev = tun->dev;

  		tun_debug(KERN_INFO, tun, "tun_chr_close
  ");

  		__tun_detach(tun);

  		/* If desirable, unregister the netdevice. */

  		if (!(tun->flags & TUN_PERSIST)) {
  			rtnl_lock();
  			if (dev->reg_state == NETREG_REGISTERED)
  				unregister_netdevice(dev);
  			rtnl_unlock();
  		}

  	}

  	tun = tfile->tun;
  	if (tun)

  		sock_put(tun->socket.sk);

  	put_net(tfile->net);

  	kfree(tfile);

  
  	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,

  	.unlocked_ioctl	= tun_chr_ioctl,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl = tun_chr_compat_ioctl,
  #endif

  	.open	= tun_chr_open,
  	.release = tun_chr_close,

  	.fasync = tun_chr_fasync

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

  	.nodename = "net/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;

  	ethtool_cmd_speed_set(cmd, 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 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	= ethtool_op_get_link,

  };

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

  	pr_info("%s, %s
  ", DRV_DESCRIPTION, DRV_VERSION);
  	pr_info("%s
  ", DRV_COPYRIGHT);

  	ret = rtnl_link_register(&tun_link_ops);

  	if (ret) {

  		pr_err("Can't register link_ops
  ");

  		goto err_linkops;

  	}

  	ret = misc_register(&tun_miscdev);

  	if (ret) {

  		pr_err("Can't register misc device %d
  ", TUN_MINOR);

  		goto err_misc;
  	}

  	return  0;

  err_misc:

  	rtnl_link_unregister(&tun_link_ops);
  err_linkops:

  	return ret;
  }
  
  static void tun_cleanup(void)
  {

  	misc_deregister(&tun_miscdev);

  	rtnl_link_unregister(&tun_link_ops);

  }

  /* Get an underlying socket object from tun file.  Returns error unless file is
   * attached to a device.  The returned object works like a packet socket, it
   * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
   * holding a reference to the file for as long as the socket is in use. */
  struct socket *tun_get_socket(struct file *file)
  {
  	struct tun_struct *tun;
  	if (file->f_op != &tun_fops)
  		return ERR_PTR(-EINVAL);
  	tun = tun_get(file);
  	if (!tun)
  		return ERR_PTR(-EBADFD);
  	tun_put(tun);
  	return &tun->socket;
  }
  EXPORT_SYMBOL_GPL(tun_get_socket);

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

  MODULE_ALIAS("devname:net/tun");