Merge tag 'doc-4.11-images' of git://git.lwn.net/linux into drm-misc-next

Pointer for Markus's image conversion work.

We need this so we can merge all the pretty drm graphs for 4.12.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

1 files changed, 1285 insertions, 0 deletions

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
new file mode 100644
index 000000000000..4d4173d25dd0
--- /dev/null
+++ b/drivers/net/tap.c
@@ -0,0 +1,1285 @@
+#include <linux/etherdevice.h>
+#include <linux/if_tap.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/signal.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>
+
+#define TAP_IFFEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
+
+#define TAP_VNET_LE 0x80000000
+#define TAP_VNET_BE 0x40000000
+
+#ifdef CONFIG_TUN_VNET_CROSS_LE
+static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
+{
+	return q->flags & TAP_VNET_BE ? false :
+		virtio_legacy_is_little_endian();
+}
+
+static long tap_get_vnet_be(struct tap_queue *q, int __user *sp)
+{
+	int s = !!(q->flags & TAP_VNET_BE);
+
+	if (put_user(s, sp))
+		return -EFAULT;
+
+	return 0;
+}
+
+static long tap_set_vnet_be(struct tap_queue *q, int __user *sp)
+{
+	int s;
+
+	if (get_user(s, sp))
+		return -EFAULT;
+
+	if (s)
+		q->flags |= TAP_VNET_BE;
+	else
+		q->flags &= ~TAP_VNET_BE;
+
+	return 0;
+}
+#else
+static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
+{
+	return virtio_legacy_is_little_endian();
+}
+
+static long tap_get_vnet_be(struct tap_queue *q, int __user *argp)
+{
+	return -EINVAL;
+}
+
+static long tap_set_vnet_be(struct tap_queue *q, int __user *argp)
+{
+	return -EINVAL;
+}
+#endif /* CONFIG_TUN_VNET_CROSS_LE */
+
+static inline bool tap_is_little_endian(struct tap_queue *q)
+{
+	return q->flags & TAP_VNET_LE ||
+		tap_legacy_is_little_endian(q);
+}
+
+static inline u16 tap16_to_cpu(struct tap_queue *q, __virtio16 val)
+{
+	return __virtio16_to_cpu(tap_is_little_endian(q), val);
+}
+
+static inline __virtio16 cpu_to_tap16(struct tap_queue *q, u16 val)
+{
+	return __cpu_to_virtio16(tap_is_little_endian(q), val);
+}
+
+static struct proto tap_proto = {
+	.name = "tap",
+	.owner = THIS_MODULE,
+	.obj_size = sizeof(struct tap_queue),
+};
+
+#define TAP_NUM_DEVS (1U << MINORBITS)
+
+static LIST_HEAD(major_list);
+
+struct major_info {
+	struct rcu_head rcu;
+	dev_t major;
+	struct idr minor_idr;
+	struct mutex minor_lock;
+	const char *device_name;
+	struct list_head next;
+};
+
+#define GOODCOPY_LEN 128
+
+static const struct proto_ops tap_socket_ops;
+
+#define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
+#define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)
+
+static struct tap_dev *tap_dev_get_rcu(const struct net_device *dev)
+{
+	return rcu_dereference(dev->rx_handler_data);
+}
+
+/*
+ * RCU usage:
+ * The tap_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 tap_queue
+ * through sock_hold(&q->sk). When the macvlan_dev goes away first,
+ * q->vlan becomes inaccessible. When the files gets closed,
+ * tap_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 tap_enable_queue(struct tap_dev *tap, struct file *file,
+			    struct tap_queue *q)
+{
+	int err = -EINVAL;
+
+	ASSERT_RTNL();
+
+	if (q->enabled)
+		goto out;
+
+	err = 0;
+	rcu_assign_pointer(tap->taps[tap->numvtaps], q);
+	q->queue_index = tap->numvtaps;
+	q->enabled = true;
+
+	tap->numvtaps++;
+out:
+	return err;
+}
+
+/* Requires RTNL */
+static int tap_set_queue(struct tap_dev *tap, struct file *file,
+			 struct tap_queue *q)
+{
+	if (tap->numqueues == MAX_TAP_QUEUES)
+		return -EBUSY;
+
+	rcu_assign_pointer(q->tap, tap);
+	rcu_assign_pointer(tap->taps[tap->numvtaps], q);
+	sock_hold(&q->sk);
+
+	q->file = file;
+	q->queue_index = tap->numvtaps;
+	q->enabled = true;
+	file->private_data = q;
+	list_add_tail(&q->next, &tap->queue_list);
+
+	tap->numvtaps++;
+	tap->numqueues++;
+
+	return 0;
+}
+
+static int tap_disable_queue(struct tap_queue *q)
+{
+	struct tap_dev *tap;
+	struct tap_queue *nq;
+
+	ASSERT_RTNL();
+	if (!q->enabled)
+		return -EINVAL;
+
+	tap = rtnl_dereference(q->tap);
+
+	if (tap) {
+		int index = q->queue_index;
+		BUG_ON(index >= tap->numvtaps);
+		nq = rtnl_dereference(tap->taps[tap->numvtaps - 1]);
+		nq->queue_index = index;
+
+		rcu_assign_pointer(tap->taps[index], nq);
+		RCU_INIT_POINTER(tap->taps[tap->numvtaps - 1], NULL);
+		q->enabled = false;
+
+		tap->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 tap_put_queue(struct tap_queue *q)
+{
+	struct tap_dev *tap;
+
+	rtnl_lock();
+	tap = rtnl_dereference(q->tap);
+
+	if (tap) {
+		if (q->enabled)
+			BUG_ON(tap_disable_queue(q));
+
+		tap->numqueues--;
+		RCU_INIT_POINTER(q->tap, 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 tap_queue *tap_get_queue(struct tap_dev *tap,
+				       struct sk_buff *skb)
+{
+	struct tap_queue *queue = 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(tap->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) {
+		queue = rcu_dereference(tap->taps[rxq % numvtaps]);
+		goto out;
+	}
+
+	if (likely(skb_rx_queue_recorded(skb))) {
+		rxq = skb_get_rx_queue(skb);
+
+		while (unlikely(rxq >= numvtaps))
+			rxq -= numvtaps;
+
+		queue = rcu_dereference(tap->taps[rxq]);
+		goto out;
+	}
+
+single:
+	queue = rcu_dereference(tap->taps[0]);
+out:
+	return queue;
+}
+
+/*
+ * 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.
+ */
+void tap_del_queues(struct tap_dev *tap)
+{
+	struct tap_queue *q, *tmp;
+
+	ASSERT_RTNL();
+	list_for_each_entry_safe(q, tmp, &tap->queue_list, next) {
+		list_del_init(&q->next);
+		RCU_INIT_POINTER(q->tap, NULL);
+		if (q->enabled)
+			tap->numvtaps--;
+		tap->numqueues--;
+		sock_put(&q->sk);
+	}
+	BUG_ON(tap->numvtaps);
+	BUG_ON(tap->numqueues);
+	/* guarantee that any future tap_set_queue will fail */
+	tap->numvtaps = MAX_TAP_QUEUES;
+}
+EXPORT_SYMBOL_GPL(tap_del_queues);
+
+rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
+{
+	struct sk_buff *skb = *pskb;
+	struct net_device *dev = skb->dev;
+	struct tap_dev *tap;
+	struct tap_queue *q;
+	netdev_features_t features = TAP_FEATURES;
+
+	tap = tap_dev_get_rcu(dev);
+	if (!tap)
+		return RX_HANDLER_PASS;
+
+	q = tap_get_queue(tap, 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 |= tap->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. */
+	if (tap->count_rx_dropped)
+		tap->count_rx_dropped(tap);
+	kfree_skb(skb);
+	return RX_HANDLER_CONSUMED;
+}
+EXPORT_SYMBOL_GPL(tap_handle_frame);
+
+static struct major_info *tap_get_major(int major)
+{
+	struct major_info *tap_major;
+
+	list_for_each_entry_rcu(tap_major, &major_list, next) {
+		if (tap_major->major == major)
+			return tap_major;
+	}
+
+	return NULL;
+}
+
+int tap_get_minor(dev_t major, struct tap_dev *tap)
+{
+	int retval = -ENOMEM;
+	struct major_info *tap_major;
+
+	rcu_read_lock();
+	tap_major = tap_get_major(MAJOR(major));
+	if (!tap_major) {
+		retval = -EINVAL;
+		goto unlock;
+	}
+
+	mutex_lock(&tap_major->minor_lock);
+	retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_KERNEL);
+	if (retval >= 0) {
+		tap->minor = retval;
+	} else if (retval == -ENOSPC) {
+		netdev_err(tap->dev, "Too many tap devices\n");
+		retval = -EINVAL;
+	}
+	mutex_unlock(&tap_major->minor_lock);
+
+unlock:
+	rcu_read_unlock();
+	return retval < 0 ? retval : 0;
+}
+EXPORT_SYMBOL_GPL(tap_get_minor);
+
+void tap_free_minor(dev_t major, struct tap_dev *tap)
+{
+	struct major_info *tap_major;
+
+	rcu_read_lock();
+	tap_major = tap_get_major(MAJOR(major));
+	if (!tap_major) {
+		goto unlock;
+	}
+
+	mutex_lock(&tap_major->minor_lock);
+	if (tap->minor) {
+		idr_remove(&tap_major->minor_idr, tap->minor);
+		tap->minor = 0;
+	}
+	mutex_unlock(&tap_major->minor_lock);
+
+unlock:
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(tap_free_minor);
+
+static struct tap_dev *dev_get_by_tap_file(int major, int minor)
+{
+	struct net_device *dev = NULL;
+	struct tap_dev *tap;
+	struct major_info *tap_major;
+
+	rcu_read_lock();
+	tap_major = tap_get_major(major);
+	if (!tap_major) {
+		tap = NULL;
+		goto unlock;
+	}
+
+	mutex_lock(&tap_major->minor_lock);
+	tap = idr_find(&tap_major->minor_idr, minor);
+	if (tap) {
+		dev = tap->dev;
+		dev_hold(dev);
+	}
+	mutex_unlock(&tap_major->minor_lock);
+
+unlock:
+	rcu_read_unlock();
+	return tap;
+}
+
+static void tap_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 tap_sock_destruct(struct sock *sk)
+{
+	struct tap_queue *q = container_of(sk, struct tap_queue, sk);
+
+	skb_array_cleanup(&q->skb_array);
+}
+
+static int tap_open(struct inode *inode, struct file *file)
+{
+	struct net *net = current->nsproxy->net_ns;
+	struct tap_dev *tap;
+	struct tap_queue *q;
+	int err = -ENODEV;
+
+	rtnl_lock();
+	tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
+	if (!tap)
+		goto err;
+
+	err = -ENOMEM;
+	q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
+					     &tap_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 = &tap_socket_ops;
+	sock_init_data(&q->sock, &q->sk);
+	q->sk.sk_write_space = tap_sock_write_space;
+	q->sk.sk_destruct = tap_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 tap, 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 ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
+		sock_set_flag(&q->sk, SOCK_ZEROCOPY);
+
+	err = -ENOMEM;
+	if (skb_array_init(&q->skb_array, tap->dev->tx_queue_len, GFP_KERNEL))
+		goto err_array;
+
+	err = tap_set_queue(tap, file, q);
+	if (err)
+		goto err_queue;
+
+	dev_put(tap->dev);
+
+	rtnl_unlock();
+	return err;
+
+err_queue:
+	skb_array_cleanup(&q->skb_array);
+err_array:
+	sock_put(&q->sk);
+err:
+	if (tap)
+		dev_put(tap->dev);
+
+	rtnl_unlock();
+	return err;
+}
+
+static int tap_release(struct inode *inode, struct file *file)
+{
+	struct tap_queue *q = file->private_data;
+	tap_put_queue(q);
+	return 0;
+}
+
+static unsigned int tap_poll(struct file *file, poll_table *wait)
+{
+	struct tap_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 *tap_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 TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
+
+/* Get packet from user space buffer */
+static ssize_t tap_get_user(struct tap_queue *q, struct msghdr *m,
+			    struct iov_iter *from, int noblock)
+{
+	int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
+	struct sk_buff *skb;
+	struct tap_dev *tap;
+	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;
+
+	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;
+		if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
+			goto err;
+		iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
+		if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
+		     tap16_to_cpu(q, vnet_hdr.csum_start) +
+		     tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
+			     tap16_to_cpu(q, vnet_hdr.hdr_len))
+			vnet_hdr.hdr_len = cpu_to_tap16(q,
+				 tap16_to_cpu(q, vnet_hdr.csum_start) +
+				 tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
+		err = -EINVAL;
+		if (tap16_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 ?
+			tap16_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 = tap16_to_cpu(q, vnet_hdr.hdr_len);
+		if (linear > good_linear)
+			linear = good_linear;
+		else if (linear < ETH_HLEN)
+			linear = ETH_HLEN;
+	}
+
+	skb = tap_alloc_skb(&q->sk, TAP_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,
+					    tap_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();
+	tap = rcu_dereference(q->tap);
+	/* 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 (tap) {
+		skb->dev = tap->dev;
+		dev_queue_xmit(skb);
+	} else {
+		kfree_skb(skb);
+	}
+	rcu_read_unlock();
+
+	return total_len;
+
+err_kfree:
+	kfree_skb(skb);
+
+err:
+	rcu_read_lock();
+	tap = rcu_dereference(q->tap);
+	if (tap && tap->count_tx_dropped)
+		tap->count_tx_dropped(tap);
+	rcu_read_unlock();
+
+	return err;
+}
+
+static ssize_t tap_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct tap_queue *q = file->private_data;
+
+	return tap_get_user(q, NULL, from, file->f_flags & O_NONBLOCK);
+}
+
+/* Put packet to the user space buffer */
+static ssize_t tap_put_user(struct tap_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;
+
+		if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
+					    tap_is_little_endian(q), true))
+			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 tap_do_read(struct tap_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 = tap_put_user(q, skb, to);
+		if (unlikely(ret < 0))
+			kfree_skb(skb);
+		else
+			consume_skb(skb);
+	}
+	return ret;
+}
+
+static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct tap_queue *q = file->private_data;
+	ssize_t len = iov_iter_count(to), ret;
+
+	ret = tap_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 tap_dev *tap_get_tap_dev(struct tap_queue *q)
+{
+	struct tap_dev *tap;
+
+	ASSERT_RTNL();
+	tap = rtnl_dereference(q->tap);
+	if (tap)
+		dev_hold(tap->dev);
+
+	return tap;
+}
+
+static void tap_put_tap_dev(struct tap_dev *tap)
+{
+	dev_put(tap->dev);
+}
+
+static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
+{
+	struct tap_queue *q = file->private_data;
+	struct tap_dev *tap;
+	int ret;
+
+	tap = tap_get_tap_dev(q);
+	if (!tap)
+		return -EINVAL;
+
+	if (flags & IFF_ATTACH_QUEUE)
+		ret = tap_enable_queue(tap, file, q);
+	else if (flags & IFF_DETACH_QUEUE)
+		ret = tap_disable_queue(q);
+	else
+		ret = -EINVAL;
+
+	tap_put_tap_dev(tap);
+	return ret;
+}
+
+static int set_offload(struct tap_queue *q, unsigned long arg)
+{
+	struct tap_dev *tap;
+	netdev_features_t features;
+	netdev_features_t feature_mask = 0;
+
+	tap = rtnl_dereference(q->tap);
+	if (!tap)
+		return -ENOLINK;
+
+	features = tap->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 tap, 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.
+	 */
+	tap->tap_features = feature_mask;
+	if (tap->update_features)
+		tap->update_features(tap, features);
+
+	return 0;
+}
+
+/*
+ * provide compatibility with generic tun/tap interface
+ */
+static long tap_ioctl(struct file *file, unsigned int cmd,
+		      unsigned long arg)
+{
+	struct tap_queue *q = file->private_data;
+	struct tap_dev *tap;
+	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 & ~TAP_IFFEATURES) != (IFF_NO_PI | IFF_TAP))
+			ret = -EINVAL;
+		else
+			q->flags = (q->flags & ~TAP_IFFEATURES) | u;
+
+		return ret;
+
+	case TUNGETIFF:
+		rtnl_lock();
+		tap = tap_get_tap_dev(q);
+		if (!tap) {
+			rtnl_unlock();
+			return -ENOLINK;
+		}
+
+		ret = 0;
+		u = q->flags;
+		if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
+		    put_user(u, &ifr->ifr_flags))
+			ret = -EFAULT;
+		tap_put_tap_dev(tap);
+		rtnl_unlock();
+		return ret;
+
+	case TUNSETQUEUE:
+		if (get_user(u, &ifr->ifr_flags))
+			return -EFAULT;
+		rtnl_lock();
+		ret = tap_ioctl_set_queue(file, u);
+		rtnl_unlock();
+		return ret;
+
+	case TUNGETFEATURES:
+		if (put_user(IFF_TAP | IFF_NO_PI | TAP_IFFEATURES, 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 & TAP_VNET_LE);
+		if (put_user(s, sp))
+			return -EFAULT;
+		return 0;
+
+	case TUNSETVNETLE:
+		if (get_user(s, sp))
+			return -EFAULT;
+		if (s)
+			q->flags |= TAP_VNET_LE;
+		else
+			q->flags &= ~TAP_VNET_LE;
+		return 0;
+
+	case TUNGETVNETBE:
+		return tap_get_vnet_be(q, sp);
+
+	case TUNSETVNETBE:
+		return tap_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();
+		tap = tap_get_tap_dev(q);
+		if (!tap) {
+			rtnl_unlock();
+			return -ENOLINK;
+		}
+		ret = 0;
+		u = tap->dev->type;
+		if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
+		    copy_to_user(&ifr->ifr_hwaddr.sa_data, tap->dev->dev_addr, ETH_ALEN) ||
+		    put_user(u, &ifr->ifr_hwaddr.sa_family))
+			ret = -EFAULT;
+		tap_put_tap_dev(tap);
+		rtnl_unlock();
+		return ret;
+
+	case SIOCSIFHWADDR:
+		if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
+			return -EFAULT;
+		rtnl_lock();
+		tap = tap_get_tap_dev(q);
+		if (!tap) {
+			rtnl_unlock();
+			return -ENOLINK;
+		}
+		ret = dev_set_mac_address(tap->dev, &sa);
+		tap_put_tap_dev(tap);
+		rtnl_unlock();
+		return ret;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static long tap_compat_ioctl(struct file *file, unsigned int cmd,
+			     unsigned long arg)
+{
+	return tap_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+const struct file_operations tap_fops = {
+	.owner		= THIS_MODULE,
+	.open		= tap_open,
+	.release	= tap_release,
+	.read_iter	= tap_read_iter,
+	.write_iter	= tap_write_iter,
+	.poll		= tap_poll,
+	.llseek		= no_llseek,
+	.unlocked_ioctl	= tap_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= tap_compat_ioctl,
+#endif
+};
+
+static int tap_sendmsg(struct socket *sock, struct msghdr *m,
+		       size_t total_len)
+{
+	struct tap_queue *q = container_of(sock, struct tap_queue, sock);
+	return tap_get_user(q, m, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);
+}
+
+static int tap_recvmsg(struct socket *sock, struct msghdr *m,
+		       size_t total_len, int flags)
+{
+	struct tap_queue *q = container_of(sock, struct tap_queue, sock);
+	int ret;
+	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
+		return -EINVAL;
+	ret = tap_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 tap_peek_len(struct socket *sock)
+{
+	struct tap_queue *q = container_of(sock, struct tap_queue,
+					       sock);
+	return skb_array_peek_len(&q->skb_array);
+}
+
+/* Ops structure to mimic raw sockets with tun */
+static const struct proto_ops tap_socket_ops = {
+	.sendmsg = tap_sendmsg,
+	.recvmsg = tap_recvmsg,
+	.peek_len = tap_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 *tap_get_socket(struct file *file)
+{
+	struct tap_queue *q;
+	if (file->f_op != &tap_fops)
+		return ERR_PTR(-EINVAL);
+	q = file->private_data;
+	if (!q)
+		return ERR_PTR(-EBADFD);
+	return &q->sock;
+}
+EXPORT_SYMBOL_GPL(tap_get_socket);
+
+int tap_queue_resize(struct tap_dev *tap)
+{
+	struct net_device *dev = tap->dev;
+	struct tap_queue *q;
+	struct skb_array **arrays;
+	int n = tap->numqueues;
+	int ret, i = 0;
+
+	arrays = kmalloc(sizeof *arrays * n, GFP_KERNEL);
+	if (!arrays)
+		return -ENOMEM;
+
+	list_for_each_entry(q, &tap->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;
+}
+EXPORT_SYMBOL_GPL(tap_queue_resize);
+
+static int tap_list_add(dev_t major, const char *device_name)
+{
+	struct major_info *tap_major;
+
+	tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
+	if (!tap_major)
+		return -ENOMEM;
+
+	tap_major->major = MAJOR(major);
+
+	idr_init(&tap_major->minor_idr);
+	mutex_init(&tap_major->minor_lock);
+
+	tap_major->device_name = device_name;
+
+	list_add_tail_rcu(&tap_major->next, &major_list);
+	return 0;
+}
+
+int tap_create_cdev(struct cdev *tap_cdev,
+		    dev_t *tap_major, const char *device_name)
+{
+	int err;
+
+	err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
+	if (err)
+		goto out1;
+
+	cdev_init(tap_cdev, &tap_fops);
+	err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
+	if (err)
+		goto out2;
+
+	err =  tap_list_add(*tap_major, device_name);
+	if (err)
+		goto out3;
+
+	return 0;
+
+out3:
+	cdev_del(tap_cdev);
+out2:
+	unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
+out1:
+	return err;
+}
+EXPORT_SYMBOL_GPL(tap_create_cdev);
+
+void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
+{
+	struct major_info *tap_major, *tmp;
+
+	cdev_del(tap_cdev);
+	unregister_chrdev_region(major, TAP_NUM_DEVS);
+	list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
+		if (tap_major->major == MAJOR(major)) {
+			idr_destroy(&tap_major->minor_idr);
+			list_del_rcu(&tap_major->next);
+			kfree_rcu(tap_major, rcu);
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(tap_destroy_cdev);
+
+MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
+MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
+MODULE_LICENSE("GPL");