/* Copyright (C) 2009 Red Hat, Inc.
   * Author: Michael S. Tsirkin <mst@redhat.com>
   *
   * This work is licensed under the terms of the GNU GPL, version 2.
   *
   * virtio-net server in host kernel.
   */
  
  #include <linux/compat.h>
  #include <linux/eventfd.h>
  #include <linux/vhost.h>
  #include <linux/virtio_net.h>

  #include <linux/miscdevice.h>
  #include <linux/module.h>

  #include <linux/moduleparam.h>

  #include <linux/mutex.h>
  #include <linux/workqueue.h>
  #include <linux/rcupdate.h>
  #include <linux/file.h>

  #include <linux/slab.h>

  
  #include <linux/net.h>
  #include <linux/if_packet.h>
  #include <linux/if_arp.h>
  #include <linux/if_tun.h>

  #include <linux/if_macvlan.h>

  
  #include <net/sock.h>
  
  #include "vhost.h"

  static int experimental_zcopytx;
  module_param(experimental_zcopytx, int, 0444);
  MODULE_PARM_DESC(experimental_zcopytx, "Enable Experimental Zero Copy TX");

  /* Max number of bytes transferred before requeueing the job.
   * Using this limit prevents one virtqueue from starving others. */
  #define VHOST_NET_WEIGHT 0x80000

  /* MAX number of TX used buffers for outstanding zerocopy */
  #define VHOST_MAX_PEND 128
  #define VHOST_GOODCOPY_LEN 256

  enum {
  	VHOST_NET_VQ_RX = 0,
  	VHOST_NET_VQ_TX = 1,
  	VHOST_NET_VQ_MAX = 2,
  };
  
  enum vhost_net_poll_state {
  	VHOST_NET_POLL_DISABLED = 0,
  	VHOST_NET_POLL_STARTED = 1,
  	VHOST_NET_POLL_STOPPED = 2,
  };
  
  struct vhost_net {
  	struct vhost_dev dev;
  	struct vhost_virtqueue vqs[VHOST_NET_VQ_MAX];
  	struct vhost_poll poll[VHOST_NET_VQ_MAX];
  	/* Tells us whether we are polling a socket for TX.
  	 * We only do this when socket buffer fills up.
  	 * Protected by tx vq lock. */
  	enum vhost_net_poll_state tx_poll_state;
  };

  static bool vhost_sock_zcopy(struct socket *sock)
  {
  	return unlikely(experimental_zcopytx) &&
  		sock_flag(sock->sk, SOCK_ZEROCOPY);
  }

  /* Pop first len bytes from iovec. Return number of segments used. */
  static int move_iovec_hdr(struct iovec *from, struct iovec *to,
  			  size_t len, int iov_count)
  {
  	int seg = 0;
  	size_t size;

  	while (len && seg < iov_count) {
  		size = min(from->iov_len, len);
  		to->iov_base = from->iov_base;
  		to->iov_len = size;
  		from->iov_len -= size;
  		from->iov_base += size;
  		len -= size;
  		++from;
  		++to;
  		++seg;
  	}
  	return seg;
  }

  /* Copy iovec entries for len bytes from iovec. */
  static void copy_iovec_hdr(const struct iovec *from, struct iovec *to,
  			   size_t len, int iovcount)
  {
  	int seg = 0;
  	size_t size;

  	while (len && seg < iovcount) {
  		size = min(from->iov_len, len);
  		to->iov_base = from->iov_base;
  		to->iov_len = size;
  		len -= size;
  		++from;
  		++to;
  		++seg;
  	}
  }

  
  /* Caller must have TX VQ lock */
  static void tx_poll_stop(struct vhost_net *net)
  {
  	if (likely(net->tx_poll_state != VHOST_NET_POLL_STARTED))
  		return;
  	vhost_poll_stop(net->poll + VHOST_NET_VQ_TX);
  	net->tx_poll_state = VHOST_NET_POLL_STOPPED;
  }
  
  /* Caller must have TX VQ lock */
  static void tx_poll_start(struct vhost_net *net, struct socket *sock)
  {
  	if (unlikely(net->tx_poll_state != VHOST_NET_POLL_STOPPED))
  		return;
  	vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);
  	net->tx_poll_state = VHOST_NET_POLL_STARTED;
  }
  
  /* Expects to be always run from workqueue - which acts as
   * read-size critical section for our kind of RCU. */
  static void handle_tx(struct vhost_net *net)
  {
  	struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX];

  	unsigned out, in, s;
  	int head;

  	struct msghdr msg = {
  		.msg_name = NULL,
  		.msg_namelen = 0,
  		.msg_control = NULL,
  		.msg_controllen = 0,
  		.msg_iov = vq->iov,
  		.msg_flags = MSG_DONTWAIT,
  	};
  	size_t len, total_len = 0;
  	int err, wmem;
  	size_t hdr_size;

  	struct socket *sock;

  	struct vhost_ubuf_ref *uninitialized_var(ubufs);
  	bool zcopy;

  	/* TODO: check that we are running from vhost_worker? */

  	sock = rcu_dereference_check(vq->private_data, 1);

  	if (!sock)
  		return;
  
  	wmem = atomic_read(&sock->sk->sk_wmem_alloc);

  	if (wmem >= sock->sk->sk_sndbuf) {
  		mutex_lock(&vq->mutex);
  		tx_poll_start(net, sock);
  		mutex_unlock(&vq->mutex);

  		return;

  	}

  	mutex_lock(&vq->mutex);

  	vhost_disable_notify(&net->dev, vq);

  	if (wmem < sock->sk->sk_sndbuf / 2)

  		tx_poll_stop(net);

  	hdr_size = vq->vhost_hlen;

  	zcopy = vhost_sock_zcopy(sock);

  
  	for (;;) {

  		/* Release DMAs done buffers first */
  		if (zcopy)
  			vhost_zerocopy_signal_used(vq);

  		head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
  					 ARRAY_SIZE(vq->iov),
  					 &out, &in,
  					 NULL, NULL);

  		/* On error, stop handling until the next kick. */

  		if (unlikely(head < 0))

  			break;

  		/* Nothing new?  Wait for eventfd to tell us they refilled. */
  		if (head == vq->num) {

  			int num_pends;

  			wmem = atomic_read(&sock->sk->sk_wmem_alloc);
  			if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {
  				tx_poll_start(net, sock);
  				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
  				break;
  			}

  			/* If more outstanding DMAs, queue the work.
  			 * Handle upend_idx wrap around
  			 */
  			num_pends = likely(vq->upend_idx >= vq->done_idx) ?
  				    (vq->upend_idx - vq->done_idx) :
  				    (vq->upend_idx + UIO_MAXIOV - vq->done_idx);
  			if (unlikely(num_pends > VHOST_MAX_PEND)) {

  				tx_poll_start(net, sock);
  				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
  				break;
  			}

  			if (unlikely(vhost_enable_notify(&net->dev, vq))) {
  				vhost_disable_notify(&net->dev, vq);

  				continue;
  			}
  			break;
  		}
  		if (in) {
  			vq_err(vq, "Unexpected descriptor format for TX: "
  			       "out %d, int %d
  ", out, in);
  			break;
  		}
  		/* Skip header. TODO: support TSO. */
  		s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
  		msg.msg_iovlen = out;
  		len = iov_length(vq->iov, out);
  		/* Sanity check */
  		if (!len) {
  			vq_err(vq, "Unexpected header len for TX: "
  			       "%zd expected %zd
  ",
  			       iov_length(vq->hdr, s), hdr_size);
  			break;
  		}

  		/* use msg_control to pass vhost zerocopy ubuf info to skb */
  		if (zcopy) {
  			vq->heads[vq->upend_idx].id = head;
  			if (len < VHOST_GOODCOPY_LEN) {
  				/* copy don't need to wait for DMA done */
  				vq->heads[vq->upend_idx].len =
  							VHOST_DMA_DONE_LEN;
  				msg.msg_control = NULL;
  				msg.msg_controllen = 0;
  				ubufs = NULL;
  			} else {
  				struct ubuf_info *ubuf = &vq->ubuf_info[head];
  
  				vq->heads[vq->upend_idx].len = len;
  				ubuf->callback = vhost_zerocopy_callback;
  				ubuf->arg = vq->ubufs;
  				ubuf->desc = vq->upend_idx;
  				msg.msg_control = ubuf;
  				msg.msg_controllen = sizeof(ubuf);
  				ubufs = vq->ubufs;
  				kref_get(&ubufs->kref);
  			}
  			vq->upend_idx = (vq->upend_idx + 1) % UIO_MAXIOV;
  		}

  		/* TODO: Check specific error and bomb out unless ENOBUFS? */
  		err = sock->ops->sendmsg(NULL, sock, &msg, len);
  		if (unlikely(err < 0)) {

  			if (zcopy) {
  				if (ubufs)
  					vhost_ubuf_put(ubufs);
  				vq->upend_idx = ((unsigned)vq->upend_idx - 1) %
  					UIO_MAXIOV;
  			}

  			vhost_discard_vq_desc(vq, 1);

  			tx_poll_start(net, sock);
  			break;
  		}
  		if (err != len)

  			pr_debug("Truncated TX packet: "
  				 " len %d != %zd
  ", err, len);

  		if (!zcopy)
  			vhost_add_used_and_signal(&net->dev, vq, head, 0);

  		total_len += len;
  		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
  			vhost_poll_queue(&vq->poll);
  			break;
  		}
  	}
  
  	mutex_unlock(&vq->mutex);

  }

  static int peek_head_len(struct sock *sk)
  {
  	struct sk_buff *head;
  	int len = 0;

  	unsigned long flags;

  	spin_lock_irqsave(&sk->sk_receive_queue.lock, flags);

  	head = skb_peek(&sk->sk_receive_queue);

  	if (likely(head))

  		len = head->len;

  	spin_unlock_irqrestore(&sk->sk_receive_queue.lock, flags);

  	return len;
  }
  
  /* This is a multi-buffer version of vhost_get_desc, that works if
   *	vq has read descriptors only.
   * @vq		- the relevant virtqueue
   * @datalen	- data length we'll be reading
   * @iovcount	- returned count of io vectors we fill
   * @log		- vhost log
   * @log_num	- log offset

   * @quota       - headcount quota, 1 for big buffer

   *	returns number of buffer heads allocated, negative on error
   */
  static int get_rx_bufs(struct vhost_virtqueue *vq,
  		       struct vring_used_elem *heads,
  		       int datalen,
  		       unsigned *iovcount,
  		       struct vhost_log *log,

  		       unsigned *log_num,
  		       unsigned int quota)

  {
  	unsigned int out, in;
  	int seg = 0;
  	int headcount = 0;
  	unsigned d;
  	int r, nlogs = 0;

  	while (datalen > 0 && headcount < quota) {

  		if (unlikely(seg >= UIO_MAXIOV)) {

  			r = -ENOBUFS;
  			goto err;
  		}
  		d = vhost_get_vq_desc(vq->dev, vq, vq->iov + seg,
  				      ARRAY_SIZE(vq->iov) - seg, &out,
  				      &in, log, log_num);
  		if (d == vq->num) {
  			r = 0;
  			goto err;
  		}
  		if (unlikely(out || in <= 0)) {
  			vq_err(vq, "unexpected descriptor format for RX: "
  				"out %d, in %d
  ", out, in);
  			r = -EINVAL;
  			goto err;
  		}
  		if (unlikely(log)) {
  			nlogs += *log_num;
  			log += *log_num;
  		}
  		heads[headcount].id = d;
  		heads[headcount].len = iov_length(vq->iov + seg, in);
  		datalen -= heads[headcount].len;
  		++headcount;
  		seg += in;
  	}
  	heads[headcount - 1].len += datalen;
  	*iovcount = seg;
  	if (unlikely(log))
  		*log_num = nlogs;
  	return headcount;
  err:
  	vhost_discard_vq_desc(vq, headcount);
  	return r;
  }

  /* Expects to be always run from workqueue - which acts as
   * read-size critical section for our kind of RCU. */

  static void handle_rx(struct vhost_net *net)

  {

  	struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
  	unsigned uninitialized_var(in), log;
  	struct vhost_log *vq_log;
  	struct msghdr msg = {
  		.msg_name = NULL,
  		.msg_namelen = 0,
  		.msg_control = NULL, /* FIXME: get and handle RX aux data. */
  		.msg_controllen = 0,
  		.msg_iov = vq->iov,
  		.msg_flags = MSG_DONTWAIT,
  	};

  	struct virtio_net_hdr_mrg_rxbuf hdr = {
  		.hdr.flags = 0,
  		.hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE
  	};

  	size_t total_len = 0;

  	int err, headcount, mergeable;

  	size_t vhost_hlen, sock_hlen;
  	size_t vhost_len, sock_len;

  	/* TODO: check that we are running from vhost_worker? */
  	struct socket *sock = rcu_dereference_check(vq->private_data, 1);

  	if (!sock)

  		return;

  	mutex_lock(&vq->mutex);

  	vhost_disable_notify(&net->dev, vq);

  	vhost_hlen = vq->vhost_hlen;
  	sock_hlen = vq->sock_hlen;
  
  	vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
  		vq->log : NULL;

  	mergeable = vhost_has_feature(&net->dev, VIRTIO_NET_F_MRG_RXBUF);

  
  	while ((sock_len = peek_head_len(sock->sk))) {
  		sock_len += sock_hlen;
  		vhost_len = sock_len + vhost_hlen;
  		headcount = get_rx_bufs(vq, vq->heads, vhost_len,

  					&in, vq_log, &log,
  					likely(mergeable) ? UIO_MAXIOV : 1);

  		/* On error, stop handling until the next kick. */
  		if (unlikely(headcount < 0))
  			break;
  		/* OK, now we need to know about added descriptors. */
  		if (!headcount) {

  			if (unlikely(vhost_enable_notify(&net->dev, vq))) {

  				/* They have slipped one in as we were
  				 * doing that: check again. */

  				vhost_disable_notify(&net->dev, vq);

  				continue;
  			}
  			/* Nothing new?  Wait for eventfd to tell us
  			 * they refilled. */
  			break;
  		}
  		/* We don't need to be notified again. */
  		if (unlikely((vhost_hlen)))
  			/* Skip header. TODO: support TSO. */
  			move_iovec_hdr(vq->iov, vq->hdr, vhost_hlen, in);
  		else
  			/* Copy the header for use in VIRTIO_NET_F_MRG_RXBUF:

  			 * needed because recvmsg can modify msg_iov. */

  			copy_iovec_hdr(vq->iov, vq->hdr, sock_hlen, in);
  		msg.msg_iovlen = in;
  		err = sock->ops->recvmsg(NULL, sock, &msg,
  					 sock_len, MSG_DONTWAIT | MSG_TRUNC);
  		/* Userspace might have consumed the packet meanwhile:
  		 * it's not supposed to do this usually, but might be hard
  		 * to prevent. Discard data we got (if any) and keep going. */
  		if (unlikely(err != sock_len)) {
  			pr_debug("Discarded rx packet: "
  				 " len %d, expected %zd
  ", err, sock_len);
  			vhost_discard_vq_desc(vq, headcount);
  			continue;
  		}
  		if (unlikely(vhost_hlen) &&
  		    memcpy_toiovecend(vq->hdr, (unsigned char *)&hdr, 0,
  				      vhost_hlen)) {
  			vq_err(vq, "Unable to write vnet_hdr at addr %p
  ",
  			       vq->iov->iov_base);
  			break;
  		}
  		/* TODO: Should check and handle checksum. */

  		if (likely(mergeable) &&

  		    memcpy_toiovecend(vq->hdr, (unsigned char *)&headcount,
  				      offsetof(typeof(hdr), num_buffers),
  				      sizeof hdr.num_buffers)) {
  			vq_err(vq, "Failed num_buffers write");
  			vhost_discard_vq_desc(vq, headcount);
  			break;
  		}
  		vhost_add_used_and_signal_n(&net->dev, vq, vq->heads,
  					    headcount);
  		if (unlikely(vq_log))
  			vhost_log_write(vq, vq_log, log, vhost_len);
  		total_len += vhost_len;
  		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
  			vhost_poll_queue(&vq->poll);
  			break;
  		}
  	}
  
  	mutex_unlock(&vq->mutex);

  }

  static void handle_tx_kick(struct vhost_work *work)

  {

  	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
  						  poll.work);
  	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);

  	handle_tx(net);
  }

  static void handle_rx_kick(struct vhost_work *work)

  {

  	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
  						  poll.work);
  	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);

  	handle_rx(net);
  }

  static void handle_tx_net(struct vhost_work *work)

  {

  	struct vhost_net *net = container_of(work, struct vhost_net,
  					     poll[VHOST_NET_VQ_TX].work);

  	handle_tx(net);
  }

  static void handle_rx_net(struct vhost_work *work)

  {

  	struct vhost_net *net = container_of(work, struct vhost_net,
  					     poll[VHOST_NET_VQ_RX].work);

  	handle_rx(net);
  }
  
  static int vhost_net_open(struct inode *inode, struct file *f)
  {
  	struct vhost_net *n = kmalloc(sizeof *n, GFP_KERNEL);

  	struct vhost_dev *dev;

  	int r;

  	if (!n)
  		return -ENOMEM;

  
  	dev = &n->dev;

  	n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick;
  	n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick;

  	r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX);

  	if (r < 0) {
  		kfree(n);
  		return r;
  	}

  	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);
  	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);

  	n->tx_poll_state = VHOST_NET_POLL_DISABLED;
  
  	f->private_data = n;
  
  	return 0;
  }
  
  static void vhost_net_disable_vq(struct vhost_net *n,
  				 struct vhost_virtqueue *vq)
  {
  	if (!vq->private_data)
  		return;
  	if (vq == n->vqs + VHOST_NET_VQ_TX) {
  		tx_poll_stop(n);
  		n->tx_poll_state = VHOST_NET_POLL_DISABLED;
  	} else
  		vhost_poll_stop(n->poll + VHOST_NET_VQ_RX);
  }
  
  static void vhost_net_enable_vq(struct vhost_net *n,
  				struct vhost_virtqueue *vq)
  {

  	struct socket *sock;
  
  	sock = rcu_dereference_protected(vq->private_data,
  					 lockdep_is_held(&vq->mutex));

  	if (!sock)
  		return;
  	if (vq == n->vqs + VHOST_NET_VQ_TX) {
  		n->tx_poll_state = VHOST_NET_POLL_STOPPED;
  		tx_poll_start(n, sock);
  	} else
  		vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);
  }
  
  static struct socket *vhost_net_stop_vq(struct vhost_net *n,
  					struct vhost_virtqueue *vq)
  {
  	struct socket *sock;
  
  	mutex_lock(&vq->mutex);

  	sock = rcu_dereference_protected(vq->private_data,
  					 lockdep_is_held(&vq->mutex));

  	vhost_net_disable_vq(n, vq);
  	rcu_assign_pointer(vq->private_data, NULL);
  	mutex_unlock(&vq->mutex);
  	return sock;
  }
  
  static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
  			   struct socket **rx_sock)
  {
  	*tx_sock = vhost_net_stop_vq(n, n->vqs + VHOST_NET_VQ_TX);
  	*rx_sock = vhost_net_stop_vq(n, n->vqs + VHOST_NET_VQ_RX);
  }
  
  static void vhost_net_flush_vq(struct vhost_net *n, int index)
  {
  	vhost_poll_flush(n->poll + index);
  	vhost_poll_flush(&n->dev.vqs[index].poll);
  }
  
  static void vhost_net_flush(struct vhost_net *n)
  {
  	vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
  	vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
  }
  
  static int vhost_net_release(struct inode *inode, struct file *f)
  {
  	struct vhost_net *n = f->private_data;
  	struct socket *tx_sock;
  	struct socket *rx_sock;
  
  	vhost_net_stop(n, &tx_sock, &rx_sock);
  	vhost_net_flush(n);
  	vhost_dev_cleanup(&n->dev);
  	if (tx_sock)
  		fput(tx_sock->file);
  	if (rx_sock)
  		fput(rx_sock->file);
  	/* We do an extra flush before freeing memory,
  	 * since jobs can re-queue themselves. */
  	vhost_net_flush(n);
  	kfree(n);
  	return 0;
  }
  
  static struct socket *get_raw_socket(int fd)
  {
  	struct {
  		struct sockaddr_ll sa;
  		char  buf[MAX_ADDR_LEN];
  	} uaddr;
  	int uaddr_len = sizeof uaddr, r;
  	struct socket *sock = sockfd_lookup(fd, &r);

  	if (!sock)
  		return ERR_PTR(-ENOTSOCK);
  
  	/* Parameter checking */
  	if (sock->sk->sk_type != SOCK_RAW) {
  		r = -ESOCKTNOSUPPORT;
  		goto err;
  	}
  
  	r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa,
  			       &uaddr_len, 0);
  	if (r)
  		goto err;
  
  	if (uaddr.sa.sll_family != AF_PACKET) {
  		r = -EPFNOSUPPORT;
  		goto err;
  	}
  	return sock;
  err:
  	fput(sock->file);
  	return ERR_PTR(r);
  }

  static struct socket *get_tap_socket(int fd)

  {
  	struct file *file = fget(fd);
  	struct socket *sock;

  	if (!file)
  		return ERR_PTR(-EBADF);
  	sock = tun_get_socket(file);

  	if (!IS_ERR(sock))
  		return sock;
  	sock = macvtap_get_socket(file);

  	if (IS_ERR(sock))
  		fput(file);
  	return sock;
  }
  
  static struct socket *get_socket(int fd)
  {
  	struct socket *sock;

  	/* special case to disable backend */
  	if (fd == -1)
  		return NULL;
  	sock = get_raw_socket(fd);
  	if (!IS_ERR(sock))
  		return sock;

  	sock = get_tap_socket(fd);

  	if (!IS_ERR(sock))
  		return sock;
  	return ERR_PTR(-ENOTSOCK);
  }
  
  static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
  {
  	struct socket *sock, *oldsock;
  	struct vhost_virtqueue *vq;

  	struct vhost_ubuf_ref *ubufs, *oldubufs = NULL;

  	int r;
  
  	mutex_lock(&n->dev.mutex);
  	r = vhost_dev_check_owner(&n->dev);
  	if (r)
  		goto err;
  
  	if (index >= VHOST_NET_VQ_MAX) {
  		r = -ENOBUFS;
  		goto err;
  	}
  	vq = n->vqs + index;
  	mutex_lock(&vq->mutex);
  
  	/* Verify that ring has been setup correctly. */
  	if (!vhost_vq_access_ok(vq)) {
  		r = -EFAULT;

  		goto err_vq;

  	}
  	sock = get_socket(fd);
  	if (IS_ERR(sock)) {
  		r = PTR_ERR(sock);

  		goto err_vq;

  	}
  
  	/* start polling new socket */

  	oldsock = rcu_dereference_protected(vq->private_data,
  					    lockdep_is_held(&vq->mutex));

  	if (sock != oldsock) {

  		ubufs = vhost_ubuf_alloc(vq, sock && vhost_sock_zcopy(sock));
  		if (IS_ERR(ubufs)) {
  			r = PTR_ERR(ubufs);
  			goto err_ubufs;
  		}
  		oldubufs = vq->ubufs;
  		vq->ubufs = ubufs;

  		vhost_net_disable_vq(n, vq);
  		rcu_assign_pointer(vq->private_data, sock);
  		vhost_net_enable_vq(n, vq);

  
  		r = vhost_init_used(vq);
  		if (r)
  			goto err_vq;

  	}

  	mutex_unlock(&vq->mutex);

  	if (oldubufs) {

  		vhost_ubuf_put_and_wait(oldubufs);

  		mutex_lock(&vq->mutex);
  		vhost_zerocopy_signal_used(vq);
  		mutex_unlock(&vq->mutex);
  	}

  	if (oldsock) {
  		vhost_net_flush_vq(n, index);
  		fput(oldsock->file);
  	}

  	mutex_unlock(&n->dev.mutex);
  	return 0;

  err_ubufs:
  	fput(sock->file);

  err_vq:
  	mutex_unlock(&vq->mutex);

  err:
  	mutex_unlock(&n->dev.mutex);
  	return r;
  }
  
  static long vhost_net_reset_owner(struct vhost_net *n)
  {
  	struct socket *tx_sock = NULL;
  	struct socket *rx_sock = NULL;
  	long err;

  	mutex_lock(&n->dev.mutex);
  	err = vhost_dev_check_owner(&n->dev);
  	if (err)
  		goto done;
  	vhost_net_stop(n, &tx_sock, &rx_sock);
  	vhost_net_flush(n);
  	err = vhost_dev_reset_owner(&n->dev);
  done:
  	mutex_unlock(&n->dev.mutex);
  	if (tx_sock)
  		fput(tx_sock->file);
  	if (rx_sock)
  		fput(rx_sock->file);
  	return err;
  }
  
  static int vhost_net_set_features(struct vhost_net *n, u64 features)
  {

  	size_t vhost_hlen, sock_hlen, hdr_len;

  	int i;

  
  	hdr_len = (features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ?
  			sizeof(struct virtio_net_hdr_mrg_rxbuf) :
  			sizeof(struct virtio_net_hdr);
  	if (features & (1 << VHOST_NET_F_VIRTIO_NET_HDR)) {
  		/* vhost provides vnet_hdr */
  		vhost_hlen = hdr_len;
  		sock_hlen = 0;
  	} else {
  		/* socket provides vnet_hdr */
  		vhost_hlen = 0;
  		sock_hlen = hdr_len;
  	}

  	mutex_lock(&n->dev.mutex);
  	if ((features & (1 << VHOST_F_LOG_ALL)) &&
  	    !vhost_log_access_ok(&n->dev)) {
  		mutex_unlock(&n->dev.mutex);
  		return -EFAULT;
  	}
  	n->dev.acked_features = features;
  	smp_wmb();
  	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
  		mutex_lock(&n->vqs[i].mutex);

  		n->vqs[i].vhost_hlen = vhost_hlen;
  		n->vqs[i].sock_hlen = sock_hlen;

  		mutex_unlock(&n->vqs[i].mutex);
  	}
  	vhost_net_flush(n);
  	mutex_unlock(&n->dev.mutex);
  	return 0;
  }
  
  static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
  			    unsigned long arg)
  {
  	struct vhost_net *n = f->private_data;
  	void __user *argp = (void __user *)arg;
  	u64 __user *featurep = argp;
  	struct vhost_vring_file backend;
  	u64 features;
  	int r;

  	switch (ioctl) {
  	case VHOST_NET_SET_BACKEND:

  		if (copy_from_user(&backend, argp, sizeof backend))
  			return -EFAULT;

  		return vhost_net_set_backend(n, backend.index, backend.fd);
  	case VHOST_GET_FEATURES:
  		features = VHOST_FEATURES;

  		if (copy_to_user(featurep, &features, sizeof features))
  			return -EFAULT;
  		return 0;

  	case VHOST_SET_FEATURES:

  		if (copy_from_user(&features, featurep, sizeof features))
  			return -EFAULT;

  		if (features & ~VHOST_FEATURES)
  			return -EOPNOTSUPP;
  		return vhost_net_set_features(n, features);
  	case VHOST_RESET_OWNER:
  		return vhost_net_reset_owner(n);
  	default:
  		mutex_lock(&n->dev.mutex);
  		r = vhost_dev_ioctl(&n->dev, ioctl, arg);
  		vhost_net_flush(n);
  		mutex_unlock(&n->dev.mutex);
  		return r;
  	}
  }
  
  #ifdef CONFIG_COMPAT
  static long vhost_net_compat_ioctl(struct file *f, unsigned int ioctl,
  				   unsigned long arg)
  {
  	return vhost_net_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
  }
  #endif

  static const struct file_operations vhost_net_fops = {

  	.owner          = THIS_MODULE,
  	.release        = vhost_net_release,
  	.unlocked_ioctl = vhost_net_ioctl,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl   = vhost_net_compat_ioctl,
  #endif
  	.open           = vhost_net_open,

  	.llseek		= noop_llseek,

  };
  
  static struct miscdevice vhost_net_misc = {

  	MISC_DYNAMIC_MINOR,

  	"vhost-net",
  	&vhost_net_fops,
  };

  static int vhost_net_init(void)

  {

  	if (experimental_zcopytx)
  		vhost_enable_zcopy(VHOST_NET_VQ_TX);

  	return misc_register(&vhost_net_misc);

  }
  module_init(vhost_net_init);

  static void vhost_net_exit(void)

  {
  	misc_deregister(&vhost_net_misc);

  }
  module_exit(vhost_net_exit);
  
  MODULE_VERSION("0.0.1");
  MODULE_LICENSE("GPL v2");
  MODULE_AUTHOR("Michael S. Tsirkin");
  MODULE_DESCRIPTION("Host kernel accelerator for virtio net");