#include <linux/etherdevice.h>
  #include <linux/if_macvlan.h>

  #include <linux/if_vlan.h>

  #include <linux/interrupt.h>
  #include <linux/nsproxy.h>
  #include <linux/compat.h>
  #include <linux/if_tun.h>
  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/cache.h>
  #include <linux/sched.h>
  #include <linux/types.h>

  #include <linux/slab.h>

  #include <linux/wait.h>
  #include <linux/cdev.h>

  #include <linux/idr.h>

  #include <linux/fs.h>

  #include <linux/uio.h>

  
  #include <net/net_namespace.h>
  #include <net/rtnetlink.h>
  #include <net/sock.h>

  #include <linux/virtio_net.h>

  #include <linux/skb_array.h>

  
  /*
   * A macvtap queue is the central object of this driver, it connects
   * an open character device to a macvlan interface. There can be
   * multiple queues on one interface, which map back to queues
   * implemented in hardware on the underlying device.
   *
   * macvtap_proto is used to allocate queues through the sock allocation
   * mechanism.
   *

   */
  struct macvtap_queue {
  	struct sock sk;
  	struct socket sock;

  	struct socket_wq wq;

  	int vnet_hdr_sz;

  	struct macvlan_dev __rcu *vlan;

  	struct file *file;

  	unsigned int flags;

  	u16 queue_index;

  	bool enabled;
  	struct list_head next;

  	struct skb_array skb_array;

  };

  #define MACVTAP_FEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
  
  #define MACVTAP_VNET_LE 0x80000000

  #define MACVTAP_VNET_BE 0x40000000
  
  #ifdef CONFIG_TUN_VNET_CROSS_LE
  static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
  {
  	return q->flags & MACVTAP_VNET_BE ? false :
  		virtio_legacy_is_little_endian();
  }
  
  static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *sp)
  {
  	int s = !!(q->flags & MACVTAP_VNET_BE);
  
  	if (put_user(s, sp))
  		return -EFAULT;
  
  	return 0;
  }
  
  static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *sp)
  {
  	int s;
  
  	if (get_user(s, sp))
  		return -EFAULT;
  
  	if (s)
  		q->flags |= MACVTAP_VNET_BE;
  	else
  		q->flags &= ~MACVTAP_VNET_BE;
  
  	return 0;
  }
  #else
  static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
  {
  	return virtio_legacy_is_little_endian();
  }
  
  static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *argp)
  {
  	return -EINVAL;
  }
  
  static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *argp)
  {
  	return -EINVAL;
  }
  #endif /* CONFIG_TUN_VNET_CROSS_LE */

  static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
  {

  	return q->flags & MACVTAP_VNET_LE ||

  		macvtap_legacy_is_little_endian(q);

  }

  
  static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
  {

  	return __virtio16_to_cpu(macvtap_is_little_endian(q), val);

  }
  
  static inline __virtio16 cpu_to_macvtap16(struct macvtap_queue *q, u16 val)
  {

  	return __cpu_to_virtio16(macvtap_is_little_endian(q), val);

  }

  static struct proto macvtap_proto = {
  	.name = "macvtap",
  	.owner = THIS_MODULE,
  	.obj_size = sizeof (struct macvtap_queue),
  };
  
  /*

   * Variables for dealing with macvtaps device numbers.

   */

  static dev_t macvtap_major;

  #define MACVTAP_NUM_DEVS (1U << MINORBITS)
  static DEFINE_MUTEX(minor_lock);
  static DEFINE_IDR(minor_idr);

  #define GOODCOPY_LEN 128

  static const void *macvtap_net_namespace(struct device *d)
  {
  	struct net_device *dev = to_net_dev(d->parent);
  	return dev_net(dev);
  }
  
  static struct class macvtap_class = {
  	.name = "macvtap",
  	.owner = THIS_MODULE,
  	.ns_type = &net_ns_type_operations,
  	.namespace = macvtap_net_namespace,
  };

  static struct cdev macvtap_cdev;

  static const struct proto_ops macvtap_socket_ops;

  #define TUN_OFFLOADS (NETIF_F_HW_CSUM | NETIF_F_TSO_ECN | NETIF_F_TSO | \

  		      NETIF_F_TSO6 | NETIF_F_UFO)

  #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)

  #define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)

  static struct macvlan_dev *macvtap_get_vlan_rcu(const struct net_device *dev)
  {
  	return rcu_dereference(dev->rx_handler_data);
  }

  /*
   * RCU usage:

   * The macvtap_queue and the macvlan_dev are loosely coupled, the
   * pointers from one to the other can only be read while rcu_read_lock

   * or rtnl is held.

   *

   * Both the file and the macvlan_dev hold a reference on the macvtap_queue
   * through sock_hold(&q->sk). When the macvlan_dev goes away first,
   * q->vlan becomes inaccessible. When the files gets closed,
   * macvtap_get_queue() fails.

   *

   * There may still be references to the struct sock inside of the
   * queue from outbound SKBs, but these never reference back to the
   * file or the dev. The data structure is freed through __sk_free
   * when both our references and any pending SKBs are gone.

   */

  static int macvtap_enable_queue(struct net_device *dev, struct file *file,

  				struct macvtap_queue *q)
  {
  	struct macvlan_dev *vlan = netdev_priv(dev);

  	int err = -EINVAL;

  	ASSERT_RTNL();

  
  	if (q->enabled)
  		goto out;
  
  	err = 0;
  	rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);
  	q->queue_index = vlan->numvtaps;
  	q->enabled = true;
  
  	vlan->numvtaps++;
  out:

  	return err;
  }

  /* Requires RTNL */

  static int macvtap_set_queue(struct net_device *dev, struct file *file,
  			     struct macvtap_queue *q)
  {
  	struct macvlan_dev *vlan = netdev_priv(dev);

  	if (vlan->numqueues == MAX_MACVTAP_QUEUES)

  		return -EBUSY;

  	rcu_assign_pointer(q->vlan, vlan);

  	rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);

  	sock_hold(&q->sk);

  
  	q->file = file;

  	q->queue_index = vlan->numvtaps;

  	q->enabled = true;

  	file->private_data = q;

  	list_add_tail(&q->next, &vlan->queue_list);

  	vlan->numvtaps++;

  	vlan->numqueues++;

  	return 0;

  }

  static int macvtap_disable_queue(struct macvtap_queue *q)

  {
  	struct macvlan_dev *vlan;
  	struct macvtap_queue *nq;

  	ASSERT_RTNL();

  	if (!q->enabled)
  		return -EINVAL;

  	vlan = rtnl_dereference(q->vlan);

  	if (vlan) {
  		int index = q->queue_index;
  		BUG_ON(index >= vlan->numvtaps);

  		nq = rtnl_dereference(vlan->taps[vlan->numvtaps - 1]);

  		nq->queue_index = index;
  
  		rcu_assign_pointer(vlan->taps[index], nq);
  		RCU_INIT_POINTER(vlan->taps[vlan->numvtaps - 1], NULL);
  		q->enabled = false;
  
  		vlan->numvtaps--;
  	}
  
  	return 0;
  }

  /*

   * The file owning the queue got closed, give up both
   * the reference that the files holds as well as the
   * one from the macvlan_dev if that still exists.

   *
   * Using the spinlock makes sure that we don't get
   * to the queue again after destroying it.

   */

  static void macvtap_put_queue(struct macvtap_queue *q)

  {

  	struct macvlan_dev *vlan;

  	rtnl_lock();
  	vlan = rtnl_dereference(q->vlan);

  	if (vlan) {

  		if (q->enabled)

  			BUG_ON(macvtap_disable_queue(q));

  		vlan->numqueues--;

  		RCU_INIT_POINTER(q->vlan, NULL);

  		sock_put(&q->sk);

  		list_del_init(&q->next);

  	}

  	rtnl_unlock();

  
  	synchronize_rcu();
  	sock_put(&q->sk);
  }
  
  /*

   * Select a queue based on the rxq of the device on which this packet
   * arrived. If the incoming device is not mq, calculate a flow hash
   * to select a queue. If all fails, find the first available queue.
   * Cache vlan->numvtaps since it can become zero during the execution
   * of this function.

   */
  static struct macvtap_queue *macvtap_get_queue(struct net_device *dev,
  					       struct sk_buff *skb)
  {
  	struct macvlan_dev *vlan = netdev_priv(dev);

  	struct macvtap_queue *tap = NULL;

  	/* Access to taps array is protected by rcu, but access to numvtaps
  	 * isn't. Below we use it to lookup a queue, but treat it as a hint
  	 * and validate that the result isn't NULL - in case we are
  	 * racing against queue removal.
  	 */

  	int numvtaps = ACCESS_ONCE(vlan->numvtaps);

  	__u32 rxq;
  
  	if (!numvtaps)
  		goto out;

  	if (numvtaps == 1)
  		goto single;

  	/* Check if we can use flow to select a queue */

  	rxq = skb_get_hash(skb);

  	if (rxq) {
  		tap = rcu_dereference(vlan->taps[rxq % numvtaps]);

  		goto out;

  	}

  	if (likely(skb_rx_queue_recorded(skb))) {
  		rxq = skb_get_rx_queue(skb);

  		while (unlikely(rxq >= numvtaps))
  			rxq -= numvtaps;
  
  		tap = rcu_dereference(vlan->taps[rxq]);

  		goto out;

  	}

  single:

  	tap = rcu_dereference(vlan->taps[0]);

  out:
  	return tap;

  }

  /*
   * The net_device is going away, give up the reference

   * that it holds on all queues and safely set the pointer
   * from the queues to NULL.

   */

  static void macvtap_del_queues(struct net_device *dev)
  {
  	struct macvlan_dev *vlan = netdev_priv(dev);

  	struct macvtap_queue *q, *tmp;

  	ASSERT_RTNL();

  	list_for_each_entry_safe(q, tmp, &vlan->queue_list, next) {
  		list_del_init(&q->next);

  		RCU_INIT_POINTER(q->vlan, NULL);

  		if (q->enabled)
  			vlan->numvtaps--;
  		vlan->numqueues--;

  		sock_put(&q->sk);

  	}

  	BUG_ON(vlan->numvtaps);
  	BUG_ON(vlan->numqueues);

  	/* guarantee that any future macvtap_set_queue will fail */
  	vlan->numvtaps = MAX_MACVTAP_QUEUES;

  }

  static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb)

  {

  	struct sk_buff *skb = *pskb;
  	struct net_device *dev = skb->dev;
  	struct macvlan_dev *vlan;
  	struct macvtap_queue *q;

  	netdev_features_t features = TAP_FEATURES;

  	vlan = macvtap_get_vlan_rcu(dev);
  	if (!vlan)
  		return RX_HANDLER_PASS;
  
  	q = macvtap_get_queue(dev, skb);

  	if (!q)

  		return RX_HANDLER_PASS;

  	if (__skb_array_full(&q->skb_array))

  		goto drop;

  	skb_push(skb, ETH_HLEN);

  	/* Apply the forward feature mask so that we perform segmentation

  	 * according to users wishes.  This only works if VNET_HDR is
  	 * enabled.

  	 */

  	if (q->flags & IFF_VNET_HDR)
  		features |= vlan->tap_features;

  	if (netif_needs_gso(skb, features)) {

  		struct sk_buff *segs = __skb_gso_segment(skb, features, false);
  
  		if (IS_ERR(segs))
  			goto drop;
  
  		if (!segs) {

  			if (skb_array_produce(&q->skb_array, skb))
  				goto drop;

  			goto wake_up;
  		}

  		consume_skb(skb);

  		while (segs) {
  			struct sk_buff *nskb = segs->next;
  
  			segs->next = NULL;

  			if (skb_array_produce(&q->skb_array, segs)) {
  				kfree_skb(segs);
  				kfree_skb_list(nskb);
  				break;
  			}

  			segs = nskb;
  		}
  	} else {

  		/* If we receive a partial checksum and the tap side
  		 * doesn't support checksum offload, compute the checksum.
  		 * Note: it doesn't matter which checksum feature to
  		 *        check, we either support them all or none.
  		 */
  		if (skb->ip_summed == CHECKSUM_PARTIAL &&

  		    !(features & NETIF_F_CSUM_MASK) &&

  		    skb_checksum_help(skb))
  			goto drop;

  		if (skb_array_produce(&q->skb_array, skb))
  			goto drop;

  	}
  
  wake_up:

  	wake_up_interruptible_poll(sk_sleep(&q->sk), POLLIN | POLLRDNORM | POLLRDBAND);

  	return RX_HANDLER_CONSUMED;

  
  drop:

  	/* Count errors/drops only here, thus don't care about args. */
  	macvlan_count_rx(vlan, 0, 0, 0);

  	kfree_skb(skb);

  	return RX_HANDLER_CONSUMED;

  }

  static int macvtap_get_minor(struct macvlan_dev *vlan)
  {
  	int retval = -ENOMEM;

  
  	mutex_lock(&minor_lock);

  	retval = idr_alloc(&minor_idr, vlan, 1, MACVTAP_NUM_DEVS, GFP_KERNEL);
  	if (retval >= 0) {
  		vlan->minor = retval;
  	} else if (retval == -ENOSPC) {

  		printk(KERN_ERR "too many macvtap devices
  ");
  		retval = -EINVAL;

  	}

  	mutex_unlock(&minor_lock);

  	return retval < 0 ? retval : 0;

  }
  
  static void macvtap_free_minor(struct macvlan_dev *vlan)
  {
  	mutex_lock(&minor_lock);
  	if (vlan->minor) {
  		idr_remove(&minor_idr, vlan->minor);
  		vlan->minor = 0;
  	}
  	mutex_unlock(&minor_lock);
  }
  
  static struct net_device *dev_get_by_macvtap_minor(int minor)
  {
  	struct net_device *dev = NULL;
  	struct macvlan_dev *vlan;
  
  	mutex_lock(&minor_lock);
  	vlan = idr_find(&minor_idr, minor);
  	if (vlan) {
  		dev = vlan->dev;
  		dev_hold(dev);
  	}
  	mutex_unlock(&minor_lock);
  	return dev;
  }

  static int macvtap_newlink(struct net *src_net,
  			   struct net_device *dev,
  			   struct nlattr *tb[],
  			   struct nlattr *data[])
  {

  	struct macvlan_dev *vlan = netdev_priv(dev);

  	int err;

  	INIT_LIST_HEAD(&vlan->queue_list);

  	/* Since macvlan supports all offloads by default, make
  	 * tap support all offloads also.
  	 */
  	vlan->tap_features = TUN_OFFLOADS;

  	err = netdev_rx_handler_register(dev, macvtap_handle_frame, vlan);
  	if (err)
  		return err;

  	/* Don't put anything that may fail after macvlan_common_newlink
  	 * because we can't undo what it does.
  	 */

  	err = macvlan_common_newlink(src_net, dev, tb, data);
  	if (err) {
  		netdev_rx_handler_unregister(dev);
  		return err;
  	}
  
  	return 0;

  }
  
  static void macvtap_dellink(struct net_device *dev,
  			    struct list_head *head)
  {

  	netdev_rx_handler_unregister(dev);

  	macvtap_del_queues(dev);
  	macvlan_dellink(dev, head);
  }

  static void macvtap_setup(struct net_device *dev)
  {
  	macvlan_common_setup(dev);
  	dev->tx_queue_len = TUN_READQ_SIZE;
  }

  static struct rtnl_link_ops macvtap_link_ops __read_mostly = {
  	.kind		= "macvtap",

  	.setup		= macvtap_setup,

  	.newlink	= macvtap_newlink,
  	.dellink	= macvtap_dellink,
  };
  
  
  static void macvtap_sock_write_space(struct sock *sk)
  {

  	wait_queue_head_t *wqueue;

  	if (!sock_writeable(sk) ||

  	    !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))

  		return;

  	wqueue = sk_sleep(sk);
  	if (wqueue && waitqueue_active(wqueue))
  		wake_up_interruptible_poll(wqueue, POLLOUT | POLLWRNORM | POLLWRBAND);

  }

  static void macvtap_sock_destruct(struct sock *sk)
  {

  	struct macvtap_queue *q = container_of(sk, struct macvtap_queue, sk);

  	skb_array_cleanup(&q->skb_array);

  }

  static int macvtap_open(struct inode *inode, struct file *file)
  {
  	struct net *net = current->nsproxy->net_ns;

  	struct net_device *dev;

  	struct macvtap_queue *q;

  	int err = -ENODEV;

  	rtnl_lock();
  	dev = dev_get_by_macvtap_minor(iminor(inode));

  	if (!dev)

  		goto err;

  	err = -ENOMEM;
  	q = (struct macvtap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,

  					     &macvtap_proto, 0);

  	if (!q)

  		goto err;

  	RCU_INIT_POINTER(q->sock.wq, &q->wq);

  	init_waitqueue_head(&q->wq.wait);

  	q->sock.type = SOCK_RAW;
  	q->sock.state = SS_CONNECTED;

  	q->sock.file = file;
  	q->sock.ops = &macvtap_socket_ops;

  	sock_init_data(&q->sock, &q->sk);

  	q->sk.sk_write_space = macvtap_sock_write_space;

  	q->sk.sk_destruct = macvtap_sock_destruct;

  	q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;

  	q->vnet_hdr_sz = sizeof(struct virtio_net_hdr);

  	/*
  	 * so far only KVM virtio_net uses macvtap, enable zero copy between
  	 * guest kernel and host kernel when lower device supports zerocopy

  	 *
  	 * The macvlan supports zerocopy iff the lower device supports zero
  	 * copy so we don't have to look at the lower device directly.

  	 */

  	if ((dev->features & NETIF_F_HIGHDMA) && (dev->features & NETIF_F_SG))
  		sock_set_flag(&q->sk, SOCK_ZEROCOPY);

  	err = -ENOMEM;
  	if (skb_array_init(&q->skb_array, dev->tx_queue_len, GFP_KERNEL))
  		goto err_array;

  	err = macvtap_set_queue(dev, file, q);
  	if (err)

  		goto err_queue;

  	dev_put(dev);
  
  	rtnl_unlock();
  	return err;
  
  err_queue:
  	skb_array_cleanup(&q->skb_array);
  err_array:
  	sock_put(&q->sk);
  err:

  	if (dev)
  		dev_put(dev);

  	rtnl_unlock();

  	return err;
  }
  
  static int macvtap_release(struct inode *inode, struct file *file)
  {

  	struct macvtap_queue *q = file->private_data;
  	macvtap_put_queue(q);

  	return 0;
  }
  
  static unsigned int macvtap_poll(struct file *file, poll_table * wait)
  {

  	struct macvtap_queue *q = file->private_data;

  	unsigned int mask = POLLERR;
  
  	if (!q)
  		goto out;
  
  	mask = 0;

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

  	if (!skb_array_empty(&q->skb_array))

  		mask |= POLLIN | POLLRDNORM;
  
  	if (sock_writeable(&q->sk) ||

  	    (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) &&

  	     sock_writeable(&q->sk)))
  		mask |= POLLOUT | POLLWRNORM;
  
  out:

  	return mask;
  }

  static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad,
  						size_t len, size_t linear,
  						int noblock, int *err)
  {
  	struct sk_buff *skb;
  
  	/* 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, 0);

  	if (!skb)
  		return NULL;
  
  	skb_reserve(skb, prepad);
  	skb_put(skb, linear);
  	skb->data_len = len - linear;
  	skb->len += len - linear;
  
  	return skb;
  }

  /* Neighbour code has some assumptions on HH_DATA_MOD alignment */
  #define MACVTAP_RESERVE HH_DATA_OFF(ETH_HLEN)

  /* Get packet from user space buffer */

  static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,

  				struct iov_iter *from, int noblock)

  {

  	int good_linear = SKB_MAX_HEAD(MACVTAP_RESERVE);

  	struct sk_buff *skb;

  	struct macvlan_dev *vlan;

  	unsigned long total_len = iov_iter_count(from);

  	unsigned long len = total_len;

  	int err;

  	struct virtio_net_hdr vnet_hdr = { 0 };
  	int vnet_hdr_len = 0;

  	int copylen = 0;

  	int depth;

  	bool zerocopy = false;

  	size_t linear;

  	ssize_t n;

  
  	if (q->flags & IFF_VNET_HDR) {

  		vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);

  
  		err = -EINVAL;

  		if (len < vnet_hdr_len)

  			goto err;

  		len -= vnet_hdr_len;

  		err = -EFAULT;
  		n = copy_from_iter(&vnet_hdr, sizeof(vnet_hdr), from);
  		if (n != sizeof(vnet_hdr))

  			goto err;

  		iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));

  		if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&

  		     macvtap16_to_cpu(q, vnet_hdr.csum_start) +
  		     macvtap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
  			     macvtap16_to_cpu(q, vnet_hdr.hdr_len))
  			vnet_hdr.hdr_len = cpu_to_macvtap16(q,
  				 macvtap16_to_cpu(q, vnet_hdr.csum_start) +
  				 macvtap16_to_cpu(q, vnet_hdr.csum_offset) + 2);

  		err = -EINVAL;

  		if (macvtap16_to_cpu(q, vnet_hdr.hdr_len) > len)

  			goto err;
  	}

  	err = -EINVAL;

  	if (unlikely(len < ETH_HLEN))

  		goto err;

  	if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {

  		struct iov_iter i;

  		copylen = vnet_hdr.hdr_len ?
  			macvtap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;

  		if (copylen > good_linear)
  			copylen = good_linear;

  		else if (copylen < ETH_HLEN)
  			copylen = ETH_HLEN;

  		linear = copylen;

  		i = *from;
  		iov_iter_advance(&i, copylen);
  		if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)

  			zerocopy = true;
  	}
  
  	if (!zerocopy) {

  		copylen = len;

  		linear = macvtap16_to_cpu(q, vnet_hdr.hdr_len);
  		if (linear > good_linear)

  			linear = good_linear;

  		else if (linear < ETH_HLEN)
  			linear = ETH_HLEN;

  	}

  	skb = macvtap_alloc_skb(&q->sk, MACVTAP_RESERVE, copylen,

  				linear, noblock, &err);

  	if (!skb)
  		goto err;

  	if (zerocopy)

  		err = zerocopy_sg_from_iter(skb, from);

  	else

  		err = skb_copy_datagram_from_iter(skb, 0, from, len);

  	if (err)

  		goto err_kfree;

  
  	skb_set_network_header(skb, ETH_HLEN);

  	skb_reset_mac_header(skb);
  	skb->protocol = eth_hdr(skb)->h_proto;
  
  	if (vnet_hdr_len) {

  		err = virtio_net_hdr_to_skb(skb, &vnet_hdr,
  					    macvtap_is_little_endian(q));

  		if (err)
  			goto err_kfree;
  	}

  	skb_probe_transport_header(skb, ETH_HLEN);

  	/* Move network header to the right position for VLAN tagged packets */
  	if ((skb->protocol == htons(ETH_P_8021Q) ||
  	     skb->protocol == htons(ETH_P_8021AD)) &&
  	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
  		skb_set_network_header(skb, depth);

  	rcu_read_lock();
  	vlan = rcu_dereference(q->vlan);

  	/* copy skb_ubuf_info for callback when skb has no error */

  	if (zerocopy) {

  		skb_shinfo(skb)->destructor_arg = m->msg_control;

  		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;

  		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;

  	} else if (m && m->msg_control) {
  		struct ubuf_info *uarg = m->msg_control;
  		uarg->callback(uarg, false);

  	}

  	if (vlan) {

  		skb->dev = vlan->dev;
  		dev_queue_xmit(skb);

  	} else {

  		kfree_skb(skb);

  	}

  	rcu_read_unlock();

  	return total_len;

  err_kfree:
  	kfree_skb(skb);

  err:

  	rcu_read_lock();
  	vlan = rcu_dereference(q->vlan);

  	if (vlan)

  		this_cpu_inc(vlan->pcpu_stats->tx_dropped);

  	rcu_read_unlock();

  	return err;

  }

  static ssize_t macvtap_write_iter(struct kiocb *iocb, struct iov_iter *from)

  {
  	struct file *file = iocb->ki_filp;

  	struct macvtap_queue *q = file->private_data;

  	return macvtap_get_user(q, NULL, from, file->f_flags & O_NONBLOCK);

  }
  
  /* Put packet to the user space buffer */
  static ssize_t macvtap_put_user(struct macvtap_queue *q,
  				const struct sk_buff *skb,

  				struct iov_iter *iter)

  {

  	int ret;

  	int vnet_hdr_len = 0;

  	int vlan_offset = 0;

  	int total;

  
  	if (q->flags & IFF_VNET_HDR) {
  		struct virtio_net_hdr vnet_hdr;

  		vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);

  		if (iov_iter_count(iter) < vnet_hdr_len)

  			return -EINVAL;

  		ret = virtio_net_hdr_from_skb(skb, &vnet_hdr,

  					      macvtap_is_little_endian(q), true);

  		if (ret)
  			BUG();

  		if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
  		    sizeof(vnet_hdr))

  			return -EFAULT;

  
  		iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));

  	}

  	total = vnet_hdr_len;

  	total += skb->len;

  	if (skb_vlan_tag_present(skb)) {

  		struct {
  			__be16 h_vlan_proto;
  			__be16 h_vlan_TCI;
  		} veth;

  		veth.h_vlan_proto = skb->vlan_proto;

  		veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));

  
  		vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);

  		total += VLAN_HLEN;

  		ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
  		if (ret || !iov_iter_count(iter))

  			goto done;

  		ret = copy_to_iter(&veth, sizeof(veth), iter);
  		if (ret != sizeof(veth) || !iov_iter_count(iter))

  			goto done;
  	}

  	ret = skb_copy_datagram_iter(skb, vlan_offset, iter,
  				     skb->len - vlan_offset);

  done:

  	return ret ? ret : total;

  }

  static ssize_t macvtap_do_read(struct macvtap_queue *q,

  			       struct iov_iter *to,

  			       int noblock)

  {

  	DEFINE_WAIT(wait);

  	struct sk_buff *skb;

  	ssize_t ret = 0;

  	if (!iov_iter_count(to))
  		return 0;
  
  	while (1) {

  		if (!noblock)
  			prepare_to_wait(sk_sleep(&q->sk), &wait,
  					TASK_INTERRUPTIBLE);

  
  		/* Read frames from the queue */

  		skb = skb_array_consume(&q->skb_array);

  		if (skb)
  			break;
  		if (noblock) {
  			ret = -EAGAIN;
  			break;

  		}

  		if (signal_pending(current)) {
  			ret = -ERESTARTSYS;
  			break;
  		}
  		/* Nothing to read, let's sleep */
  		schedule();
  	}

  	if (!noblock)
  		finish_wait(sk_sleep(&q->sk), &wait);

  	if (skb) {
  		ret = macvtap_put_user(q, skb, to);

  		if (unlikely(ret < 0))
  			kfree_skb(skb);
  		else
  			consume_skb(skb);

  	}

  	return ret;
  }

  static ssize_t macvtap_read_iter(struct kiocb *iocb, struct iov_iter *to)

  {
  	struct file *file = iocb->ki_filp;
  	struct macvtap_queue *q = file->private_data;

  	ssize_t len = iov_iter_count(to), ret;

  	ret = macvtap_do_read(q, to, file->f_flags & O_NONBLOCK);

  	ret = min_t(ssize_t, ret, len);

  	if (ret > 0)
  		iocb->ki_pos = ret;

  	return ret;
  }

  static struct macvlan_dev *macvtap_get_vlan(struct macvtap_queue *q)
  {
  	struct macvlan_dev *vlan;

  	ASSERT_RTNL();
  	vlan = rtnl_dereference(q->vlan);

  	if (vlan)
  		dev_hold(vlan->dev);

  
  	return vlan;
  }
  
  static void macvtap_put_vlan(struct macvlan_dev *vlan)
  {
  	dev_put(vlan->dev);
  }

  static int macvtap_ioctl_set_queue(struct file *file, unsigned int flags)
  {
  	struct macvtap_queue *q = file->private_data;
  	struct macvlan_dev *vlan;
  	int ret;
  
  	vlan = macvtap_get_vlan(q);
  	if (!vlan)
  		return -EINVAL;
  
  	if (flags & IFF_ATTACH_QUEUE)
  		ret = macvtap_enable_queue(vlan->dev, file, q);
  	else if (flags & IFF_DETACH_QUEUE)
  		ret = macvtap_disable_queue(q);

  	else
  		ret = -EINVAL;

  
  	macvtap_put_vlan(vlan);
  	return ret;
  }

  static int set_offload(struct macvtap_queue *q, unsigned long arg)
  {
  	struct macvlan_dev *vlan;
  	netdev_features_t features;
  	netdev_features_t feature_mask = 0;
  
  	vlan = rtnl_dereference(q->vlan);
  	if (!vlan)
  		return -ENOLINK;
  
  	features = vlan->dev->features;
  
  	if (arg & TUN_F_CSUM) {
  		feature_mask = NETIF_F_HW_CSUM;
  
  		if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
  			if (arg & TUN_F_TSO_ECN)
  				feature_mask |= NETIF_F_TSO_ECN;
  			if (arg & TUN_F_TSO4)
  				feature_mask |= NETIF_F_TSO;
  			if (arg & TUN_F_TSO6)
  				feature_mask |= NETIF_F_TSO6;
  		}

  
  		if (arg & TUN_F_UFO)
  			feature_mask |= NETIF_F_UFO;

  	}
  
  	/* tun/tap driver inverts the usage for TSO offloads, where
  	 * setting the TSO bit means that the userspace wants to
  	 * accept TSO frames and turning it off means that user space
  	 * does not support TSO.
  	 * For macvtap, we have to invert it to mean the same thing.
  	 * When user space turns off TSO, we turn off GSO/LRO so that
  	 * user-space will not receive TSO frames.
  	 */

  	if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_UFO))

  		features |= RX_OFFLOADS;
  	else
  		features &= ~RX_OFFLOADS;
  
  	/* tap_features are the same as features on tun/tap and
  	 * reflect user expectations.
  	 */

  	vlan->tap_features = feature_mask;

  	vlan->set_features = features;
  	netdev_update_features(vlan->dev);
  
  	return 0;
  }

  /*
   * provide compatibility with generic tun/tap interface
   */
  static long macvtap_ioctl(struct file *file, unsigned int cmd,
  			  unsigned long arg)
  {

  	struct macvtap_queue *q = file->private_data;
  	struct macvlan_dev *vlan;

  	void __user *argp = (void __user *)arg;
  	struct ifreq __user *ifr = argp;
  	unsigned int __user *up = argp;

  	unsigned short u;

  	int __user *sp = argp;

  	struct sockaddr sa;

  	int s;

  	int ret;

  
  	switch (cmd) {
  	case TUNSETIFF:
  		/* ignore the name, just look at flags */
  		if (get_user(u, &ifr->ifr_flags))
  			return -EFAULT;

  
  		ret = 0;

  		if ((u & ~MACVTAP_FEATURES) != (IFF_NO_PI | IFF_TAP))

  			ret = -EINVAL;
  		else

  			q->flags = (q->flags & ~MACVTAP_FEATURES) | u;

  
  		return ret;

  
  	case TUNGETIFF:

  		rtnl_lock();

  		vlan = macvtap_get_vlan(q);

  		if (!vlan) {
  			rtnl_unlock();

  			return -ENOLINK;

  		}

  		ret = 0;

  		u = q->flags;

  		if (copy_to_user(&ifr->ifr_name, vlan->dev->name, IFNAMSIZ) ||

  		    put_user(u, &ifr->ifr_flags))

  			ret = -EFAULT;

  		macvtap_put_vlan(vlan);

  		rtnl_unlock();

  		return ret;

  	case TUNSETQUEUE:
  		if (get_user(u, &ifr->ifr_flags))
  			return -EFAULT;

  		rtnl_lock();
  		ret = macvtap_ioctl_set_queue(file, u);
  		rtnl_unlock();

  		return ret;

  	case TUNGETFEATURES:

  		if (put_user(IFF_TAP | IFF_NO_PI | MACVTAP_FEATURES, up))

  			return -EFAULT;
  		return 0;
  
  	case TUNSETSNDBUF:

  		if (get_user(s, sp))

  			return -EFAULT;

  		q->sk.sk_sndbuf = s;

  		return 0;

  	case TUNGETVNETHDRSZ:
  		s = q->vnet_hdr_sz;
  		if (put_user(s, sp))
  			return -EFAULT;
  		return 0;
  
  	case TUNSETVNETHDRSZ:
  		if (get_user(s, sp))
  			return -EFAULT;
  		if (s < (int)sizeof(struct virtio_net_hdr))
  			return -EINVAL;
  
  		q->vnet_hdr_sz = s;
  		return 0;

  	case TUNGETVNETLE:
  		s = !!(q->flags & MACVTAP_VNET_LE);
  		if (put_user(s, sp))
  			return -EFAULT;
  		return 0;
  
  	case TUNSETVNETLE:
  		if (get_user(s, sp))
  			return -EFAULT;
  		if (s)
  			q->flags |= MACVTAP_VNET_LE;
  		else
  			q->flags &= ~MACVTAP_VNET_LE;
  		return 0;

  	case TUNGETVNETBE:
  		return macvtap_get_vnet_be(q, sp);
  
  	case TUNSETVNETBE:
  		return macvtap_set_vnet_be(q, sp);

  	case TUNSETOFFLOAD:
  		/* let the user check for future flags */
  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |

  			    TUN_F_TSO_ECN | TUN_F_UFO))

  			return -EINVAL;

  		rtnl_lock();
  		ret = set_offload(q, arg);
  		rtnl_unlock();
  		return ret;

  	case SIOCGIFHWADDR:
  		rtnl_lock();
  		vlan = macvtap_get_vlan(q);
  		if (!vlan) {
  			rtnl_unlock();
  			return -ENOLINK;
  		}
  		ret = 0;
  		u = vlan->dev->type;
  		if (copy_to_user(&ifr->ifr_name, vlan->dev->name, IFNAMSIZ) ||
  		    copy_to_user(&ifr->ifr_hwaddr.sa_data, vlan->dev->dev_addr, ETH_ALEN) ||
  		    put_user(u, &ifr->ifr_hwaddr.sa_family))
  			ret = -EFAULT;
  		macvtap_put_vlan(vlan);
  		rtnl_unlock();
  		return ret;
  
  	case SIOCSIFHWADDR:

  		if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
  			return -EFAULT;

  		rtnl_lock();
  		vlan = macvtap_get_vlan(q);
  		if (!vlan) {
  			rtnl_unlock();
  			return -ENOLINK;
  		}

  		ret = dev_set_mac_address(vlan->dev, &sa);

  		macvtap_put_vlan(vlan);
  		rtnl_unlock();
  		return ret;

  	default:
  		return -EINVAL;
  	}
  }
  
  #ifdef CONFIG_COMPAT
  static long macvtap_compat_ioctl(struct file *file, unsigned int cmd,
  				 unsigned long arg)
  {
  	return macvtap_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
  }
  #endif
  
  static const struct file_operations macvtap_fops = {
  	.owner		= THIS_MODULE,
  	.open		= macvtap_open,
  	.release	= macvtap_release,

  	.read_iter	= macvtap_read_iter,

  	.write_iter	= macvtap_write_iter,

  	.poll		= macvtap_poll,
  	.llseek		= no_llseek,
  	.unlocked_ioctl	= macvtap_ioctl,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl	= macvtap_compat_ioctl,
  #endif
  };

  static int macvtap_sendmsg(struct socket *sock, struct msghdr *m,
  			   size_t total_len)

  {
  	struct macvtap_queue *q = container_of(sock, struct macvtap_queue, sock);

  	return macvtap_get_user(q, m, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);

  }

  static int macvtap_recvmsg(struct socket *sock, struct msghdr *m,
  			   size_t total_len, int flags)

  {
  	struct macvtap_queue *q = container_of(sock, struct macvtap_queue, sock);
  	int ret;
  	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
  		return -EINVAL;

  	ret = macvtap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT);

  	if (ret > total_len) {
  		m->msg_flags |= MSG_TRUNC;
  		ret = flags & MSG_TRUNC ? ret : total_len;
  	}

  	return ret;
  }

  static int macvtap_peek_len(struct socket *sock)
  {
  	struct macvtap_queue *q = container_of(sock, struct macvtap_queue,
  					       sock);
  	return skb_array_peek_len(&q->skb_array);
  }

  /* Ops structure to mimic raw sockets with tun */
  static const struct proto_ops macvtap_socket_ops = {
  	.sendmsg = macvtap_sendmsg,
  	.recvmsg = macvtap_recvmsg,

  	.peek_len = macvtap_peek_len,

  };
  
  /* 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 *macvtap_get_socket(struct file *file)
  {
  	struct macvtap_queue *q;
  	if (file->f_op != &macvtap_fops)
  		return ERR_PTR(-EINVAL);
  	q = file->private_data;
  	if (!q)
  		return ERR_PTR(-EBADFD);
  	return &q->sock;
  }
  EXPORT_SYMBOL_GPL(macvtap_get_socket);

  static int macvtap_queue_resize(struct macvlan_dev *vlan)
  {
  	struct net_device *dev = vlan->dev;
  	struct macvtap_queue *q;
  	struct skb_array **arrays;
  	int n = vlan->numqueues;
  	int ret, i = 0;
  
  	arrays = kmalloc(sizeof *arrays * n, GFP_KERNEL);
  	if (!arrays)
  		return -ENOMEM;
  
  	list_for_each_entry(q, &vlan->queue_list, next)
  		arrays[i++] = &q->skb_array;
  
  	ret = skb_array_resize_multiple(arrays, n,
  					dev->tx_queue_len, GFP_KERNEL);
  
  	kfree(arrays);
  	return ret;
  }

  static int macvtap_device_event(struct notifier_block *unused,
  				unsigned long event, void *ptr)
  {

  	struct net_device *dev = netdev_notifier_info_to_dev(ptr);

  	struct macvlan_dev *vlan;

  	struct device *classdev;
  	dev_t devt;

  	int err;

  	char tap_name[IFNAMSIZ];

  
  	if (dev->rtnl_link_ops != &macvtap_link_ops)
  		return NOTIFY_DONE;

  	snprintf(tap_name, IFNAMSIZ, "tap%d", dev->ifindex);

  	vlan = netdev_priv(dev);

  
  	switch (event) {
  	case NETDEV_REGISTER:
  		/* Create the device node here after the network device has
  		 * been registered but before register_netdevice has
  		 * finished running.
  		 */

  		err = macvtap_get_minor(vlan);
  		if (err)
  			return notifier_from_errno(err);
  
  		devt = MKDEV(MAJOR(macvtap_major), vlan->minor);

  		classdev = device_create(&macvtap_class, &dev->dev, devt,
  					 dev, tap_name);

  		if (IS_ERR(classdev)) {
  			macvtap_free_minor(vlan);

  			return notifier_from_errno(PTR_ERR(classdev));

  		}

  		err = sysfs_create_link(&dev->dev.kobj, &classdev->kobj,
  					tap_name);
  		if (err)
  			return notifier_from_errno(err);

  		break;
  	case NETDEV_UNREGISTER:

  		/* vlan->minor == 0 if NETDEV_REGISTER above failed */
  		if (vlan->minor == 0)
  			break;

  		sysfs_remove_link(&dev->dev.kobj, tap_name);

  		devt = MKDEV(MAJOR(macvtap_major), vlan->minor);

  		device_destroy(&macvtap_class, devt);

  		macvtap_free_minor(vlan);

  		break;

  	case NETDEV_CHANGE_TX_QUEUE_LEN:
  		if (macvtap_queue_resize(vlan))
  			return NOTIFY_BAD;
  		break;

  	}
  
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block macvtap_notifier_block __read_mostly = {
  	.notifier_call	= macvtap_device_event,
  };

  static int macvtap_init(void)
  {
  	int err;
  
  	err = alloc_chrdev_region(&macvtap_major, 0,
  				MACVTAP_NUM_DEVS, "macvtap");
  	if (err)
  		goto out1;
  
  	cdev_init(&macvtap_cdev, &macvtap_fops);
  	err = cdev_add(&macvtap_cdev, macvtap_major, MACVTAP_NUM_DEVS);
  	if (err)
  		goto out2;

  	err = class_register(&macvtap_class);
  	if (err)

  		goto out3;

  	err = register_netdevice_notifier(&macvtap_notifier_block);

  	if (err)
  		goto out4;

  	err = macvlan_link_register(&macvtap_link_ops);
  	if (err)
  		goto out5;

  	return 0;

  out5:
  	unregister_netdevice_notifier(&macvtap_notifier_block);

  out4:

  	class_unregister(&macvtap_class);

  out3:
  	cdev_del(&macvtap_cdev);
  out2:
  	unregister_chrdev_region(macvtap_major, MACVTAP_NUM_DEVS);
  out1:
  	return err;
  }
  module_init(macvtap_init);
  
  static void macvtap_exit(void)
  {
  	rtnl_link_unregister(&macvtap_link_ops);

  	unregister_netdevice_notifier(&macvtap_notifier_block);

  	class_unregister(&macvtap_class);

  	cdev_del(&macvtap_cdev);
  	unregister_chrdev_region(macvtap_major, MACVTAP_NUM_DEVS);

  	idr_destroy(&minor_idr);

  }
  module_exit(macvtap_exit);
  
  MODULE_ALIAS_RTNL_LINK("macvtap");
  MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
  MODULE_LICENSE("GPL");