/* 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/file.h>

  #include <linux/slab.h>

  #include <linux/vmalloc.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 <linux/if_vlan.h>

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

  static int experimental_zcopytx = 1;

  module_param(experimental_zcopytx, int, 0444);

  MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
  		                       " 1 -Enable; 0 - Disable");

  /* 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

  /*
   * For transmit, used buffer len is unused; we override it to track buffer
   * status internally; used for zerocopy tx only.
   */
  /* Lower device DMA failed */
  #define VHOST_DMA_FAILED_LEN	3
  /* Lower device DMA done */
  #define VHOST_DMA_DONE_LEN	2
  /* Lower device DMA in progress */
  #define VHOST_DMA_IN_PROGRESS	1
  /* Buffer unused */
  #define VHOST_DMA_CLEAR_LEN	0
  
  #define VHOST_DMA_IS_DONE(len) ((len) >= VHOST_DMA_DONE_LEN)

  enum {

  	VHOST_NET_FEATURES = VHOST_FEATURES |
  			 (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
  			 (1ULL << VIRTIO_NET_F_MRG_RXBUF),
  };
  
  enum {

  	VHOST_NET_VQ_RX = 0,
  	VHOST_NET_VQ_TX = 1,
  	VHOST_NET_VQ_MAX = 2,
  };

  struct vhost_net_ubuf_ref {

  	/* refcount follows semantics similar to kref:
  	 *  0: object is released
  	 *  1: no outstanding ubufs
  	 * >1: outstanding ubufs
  	 */
  	atomic_t refcount;

  	wait_queue_head_t wait;
  	struct vhost_virtqueue *vq;
  };

  struct vhost_net_virtqueue {
  	struct vhost_virtqueue vq;

  	/* hdr is used to store the virtio header.
  	 * Since each iovec has >= 1 byte length, we never need more than
  	 * header length entries to store the header. */
  	struct iovec hdr[sizeof(struct virtio_net_hdr_mrg_rxbuf)];
  	size_t vhost_hlen;
  	size_t sock_hlen;

  	/* vhost zerocopy support fields below: */
  	/* last used idx for outstanding DMA zerocopy buffers */
  	int upend_idx;
  	/* first used idx for DMA done zerocopy buffers */
  	int done_idx;
  	/* an array of userspace buffers info */
  	struct ubuf_info *ubuf_info;
  	/* Reference counting for outstanding ubufs.
  	 * Protected by vq mutex. Writers must also take device mutex. */

  	struct vhost_net_ubuf_ref *ubufs;

  };

  struct vhost_net {
  	struct vhost_dev dev;

  	struct vhost_net_virtqueue vqs[VHOST_NET_VQ_MAX];

  	struct vhost_poll poll[VHOST_NET_VQ_MAX];

  	/* Number of TX recently submitted.
  	 * Protected by tx vq lock. */
  	unsigned tx_packets;
  	/* Number of times zerocopy TX recently failed.
  	 * Protected by tx vq lock. */
  	unsigned tx_zcopy_err;

  	/* Flush in progress. Protected by tx vq lock. */
  	bool tx_flush;

  };

  static unsigned vhost_net_zcopy_mask __read_mostly;

  static void vhost_net_enable_zcopy(int vq)

  {

  	vhost_net_zcopy_mask |= 0x1 << vq;

  }

  static struct vhost_net_ubuf_ref *
  vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy)

  {

  	struct vhost_net_ubuf_ref *ubufs;

  	/* No zero copy backend? Nothing to count. */
  	if (!zcopy)
  		return NULL;
  	ubufs = kmalloc(sizeof(*ubufs), GFP_KERNEL);
  	if (!ubufs)
  		return ERR_PTR(-ENOMEM);

  	atomic_set(&ubufs->refcount, 1);

  	init_waitqueue_head(&ubufs->wait);
  	ubufs->vq = vq;
  	return ubufs;
  }

  static int vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs)

  {

  	int r = atomic_sub_return(1, &ubufs->refcount);
  	if (unlikely(!r))
  		wake_up(&ubufs->wait);
  	return r;

  }

  static void vhost_net_ubuf_put_and_wait(struct vhost_net_ubuf_ref *ubufs)

  {

  	vhost_net_ubuf_put(ubufs);
  	wait_event(ubufs->wait, !atomic_read(&ubufs->refcount));

  }
  
  static void vhost_net_ubuf_put_wait_and_free(struct vhost_net_ubuf_ref *ubufs)
  {
  	vhost_net_ubuf_put_and_wait(ubufs);

  	kfree(ubufs);
  }

  static void vhost_net_clear_ubuf_info(struct vhost_net *n)
  {

  	int i;

  	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
  		kfree(n->vqs[i].ubuf_info);
  		n->vqs[i].ubuf_info = NULL;

  	}
  }

  static int vhost_net_set_ubuf_info(struct vhost_net *n)

  {
  	bool zcopy;
  	int i;

  	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {

  		zcopy = vhost_net_zcopy_mask & (0x1 << i);

  		if (!zcopy)
  			continue;
  		n->vqs[i].ubuf_info = kmalloc(sizeof(*n->vqs[i].ubuf_info) *
  					      UIO_MAXIOV, GFP_KERNEL);
  		if  (!n->vqs[i].ubuf_info)
  			goto err;
  	}
  	return 0;
  
  err:

  	vhost_net_clear_ubuf_info(n);

  	return -ENOMEM;
  }

  static void vhost_net_vq_reset(struct vhost_net *n)

  {
  	int i;

  	vhost_net_clear_ubuf_info(n);

  	for (i = 0; i < VHOST_NET_VQ_MAX; i++) {
  		n->vqs[i].done_idx = 0;
  		n->vqs[i].upend_idx = 0;
  		n->vqs[i].ubufs = NULL;

  		n->vqs[i].vhost_hlen = 0;
  		n->vqs[i].sock_hlen = 0;

  	}
  
  }

  static void vhost_net_tx_packet(struct vhost_net *net)
  {
  	++net->tx_packets;
  	if (net->tx_packets < 1024)
  		return;
  	net->tx_packets = 0;
  	net->tx_zcopy_err = 0;
  }
  
  static void vhost_net_tx_err(struct vhost_net *net)
  {
  	++net->tx_zcopy_err;
  }
  
  static bool vhost_net_tx_select_zcopy(struct vhost_net *net)
  {

  	/* TX flush waits for outstanding DMAs to be done.
  	 * Don't start new DMAs.
  	 */
  	return !net->tx_flush &&
  		net->tx_packets / 64 >= net->tx_zcopy_err;

  }

  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;
  	}
  }

  /* In case of DMA done not in order in lower device driver for some reason.
   * upend_idx is used to track end of used idx, done_idx is used to track head
   * of used idx. Once lower device DMA done contiguously, we will signal KVM
   * guest used idx.
   */

  static void vhost_zerocopy_signal_used(struct vhost_net *net,
  				       struct vhost_virtqueue *vq)

  {

  	struct vhost_net_virtqueue *nvq =
  		container_of(vq, struct vhost_net_virtqueue, vq);

  	int i, add;

  	int j = 0;

  	for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) {

  		if (vq->heads[i].len == VHOST_DMA_FAILED_LEN)
  			vhost_net_tx_err(net);

  		if (VHOST_DMA_IS_DONE(vq->heads[i].len)) {
  			vq->heads[i].len = VHOST_DMA_CLEAR_LEN;

  			++j;
  		} else
  			break;
  	}

  	while (j) {
  		add = min(UIO_MAXIOV - nvq->done_idx, j);
  		vhost_add_used_and_signal_n(vq->dev, vq,
  					    &vq->heads[nvq->done_idx], add);
  		nvq->done_idx = (nvq->done_idx + add) % UIO_MAXIOV;
  		j -= add;
  	}

  }

  static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)

  {

  	struct vhost_net_ubuf_ref *ubufs = ubuf->ctx;

  	struct vhost_virtqueue *vq = ubufs->vq;

  	int cnt;

  	rcu_read_lock_bh();

  	/* set len to mark this desc buffers done DMA */
  	vq->heads[ubuf->desc].len = success ?
  		VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;

  	cnt = vhost_net_ubuf_put(ubufs);

  	/*
  	 * Trigger polling thread if guest stopped submitting new buffers:

  	 * in this case, the refcount after decrement will eventually reach 1.

  	 * We also trigger polling periodically after each 16 packets
  	 * (the value 16 here is more or less arbitrary, it's tuned to trigger
  	 * less than 10% of times).
  	 */

  	if (cnt <= 1 || !(cnt % 16))

  		vhost_poll_queue(&vq->poll);

  
  	rcu_read_unlock_bh();

  }

  /* 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_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];

  	struct vhost_virtqueue *vq = &nvq->vq;

  	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;

  	size_t hdr_size;

  	struct socket *sock;

  	struct vhost_net_ubuf_ref *uninitialized_var(ubufs);

  	bool zcopy, zcopy_used;

  	mutex_lock(&vq->mutex);
  	sock = vq->private_data;

  	if (!sock)

  		goto out;

  	vhost_disable_notify(&net->dev, vq);

  	hdr_size = nvq->vhost_hlen;

  	zcopy = nvq->ubufs;

  
  	for (;;) {

  		/* Release DMAs done buffers first */
  		if (zcopy)

  			vhost_zerocopy_signal_used(net, vq);

  		/* If more outstanding DMAs, queue the work.
  		 * Handle upend_idx wrap around
  		 */
  		if (unlikely((nvq->upend_idx + vq->num - VHOST_MAX_PEND)
  			      % UIO_MAXIOV == nvq->done_idx))
  			break;

  		head = vhost_get_vq_desc(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) {

  			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, nvq->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(nvq->hdr, s), hdr_size);

  			break;
  		}

  
  		zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
  				   && (nvq->upend_idx + 1) % UIO_MAXIOV !=
  				      nvq->done_idx
  				   && vhost_net_tx_select_zcopy(net);

  		/* use msg_control to pass vhost zerocopy ubuf info to skb */

  		if (zcopy_used) {

  			struct ubuf_info *ubuf;
  			ubuf = nvq->ubuf_info + nvq->upend_idx;

  			vq->heads[nvq->upend_idx].id = head;

  			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
  			ubuf->callback = vhost_zerocopy_callback;
  			ubuf->ctx = nvq->ubufs;
  			ubuf->desc = nvq->upend_idx;
  			msg.msg_control = ubuf;
  			msg.msg_controllen = sizeof(ubuf);
  			ubufs = nvq->ubufs;

  			atomic_inc(&ubufs->refcount);

  			nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;

  		} else {

  			msg.msg_control = NULL;

  			ubufs = NULL;
  		}

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

  			if (zcopy_used) {

  				vhost_net_ubuf_put(ubufs);

  				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
  					% UIO_MAXIOV;

  			}

  			vhost_discard_vq_desc(vq, 1);

  			break;
  		}
  		if (err != len)

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

  		if (!zcopy_used)

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

  		else

  			vhost_zerocopy_signal_used(net, vq);

  		total_len += len;

  		vhost_net_tx_packet(net);

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

  out:

  	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;

  		if (vlan_tx_tag_present(head))
  			len += VLAN_HLEN;
  	}

  	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;
  		}

  		r = vhost_get_vq_desc(vq, vq->iov + seg,

  				      ARRAY_SIZE(vq->iov) - seg, &out,
  				      &in, log, log_num);

  		if (unlikely(r < 0))
  			goto err;
  
  		d = r;

  		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;

  
  	/* Detect overrun */
  	if (unlikely(datalen > 0)) {
  		r = UIO_MAXIOV + 1;
  		goto err;
  	}

  	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_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_RX];
  	struct vhost_virtqueue *vq = &nvq->vq;

  	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, mergeable;
  	s16 headcount;

  	size_t vhost_hlen, sock_hlen;
  	size_t vhost_len, sock_len;

  	struct socket *sock;

  	mutex_lock(&vq->mutex);

  	sock = vq->private_data;
  	if (!sock)
  		goto out;

  	vhost_disable_notify(&net->dev, vq);

  	vhost_hlen = nvq->vhost_hlen;
  	sock_hlen = nvq->sock_hlen;

  	vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?

  		vq->log : NULL;

  	mergeable = vhost_has_feature(vq, 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;

  		/* On overrun, truncate and discard */
  		if (unlikely(headcount > UIO_MAXIOV)) {
  			msg.msg_iovlen = 1;
  			err = sock->ops->recvmsg(NULL, sock, &msg,
  						 1, MSG_DONTWAIT | MSG_TRUNC);
  			pr_debug("Discarded rx packet: len %zd
  ", sock_len);
  			continue;
  		}

  		/* 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, nvq->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, nvq->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(nvq->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(nvq->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;
  		}
  	}

  out:

  	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;

  	struct vhost_dev *dev;

  	struct vhost_virtqueue **vqs;

  	int i;

  	n = kmalloc(sizeof *n, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
  	if (!n) {
  		n = vmalloc(sizeof *n);
  		if (!n)
  			return -ENOMEM;
  	}

  	vqs = kmalloc(VHOST_NET_VQ_MAX * sizeof(*vqs), GFP_KERNEL);
  	if (!vqs) {

  		kvfree(n);

  		return -ENOMEM;
  	}

  
  	dev = &n->dev;

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

  	for (i = 0; i < VHOST_NET_VQ_MAX; i++) {
  		n->vqs[i].ubufs = NULL;
  		n->vqs[i].ubuf_info = NULL;
  		n->vqs[i].upend_idx = 0;
  		n->vqs[i].done_idx = 0;

  		n->vqs[i].vhost_hlen = 0;
  		n->vqs[i].sock_hlen = 0;

  	}

  	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);

  	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);

  
  	f->private_data = n;
  
  	return 0;
  }
  
  static void vhost_net_disable_vq(struct vhost_net *n,
  				 struct vhost_virtqueue *vq)
  {

  	struct vhost_net_virtqueue *nvq =
  		container_of(vq, struct vhost_net_virtqueue, vq);
  	struct vhost_poll *poll = n->poll + (nvq - n->vqs);

  	if (!vq->private_data)
  		return;

  	vhost_poll_stop(poll);

  }

  static int vhost_net_enable_vq(struct vhost_net *n,

  				struct vhost_virtqueue *vq)
  {

  	struct vhost_net_virtqueue *nvq =
  		container_of(vq, struct vhost_net_virtqueue, vq);
  	struct vhost_poll *poll = n->poll + (nvq - n->vqs);

  	struct socket *sock;

  	sock = vq->private_data;

  	if (!sock)

  		return 0;

  	return vhost_poll_start(poll, 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 = vq->private_data;

  	vhost_net_disable_vq(n, vq);

  	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].vq);
  	*rx_sock = vhost_net_stop_vq(n, &n->vqs[VHOST_NET_VQ_RX].vq);

  }
  
  static void vhost_net_flush_vq(struct vhost_net *n, int index)
  {
  	vhost_poll_flush(n->poll + index);

  	vhost_poll_flush(&n->vqs[index].vq.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);

  	if (n->vqs[VHOST_NET_VQ_TX].ubufs) {

  		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);

  		n->tx_flush = true;

  		mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);

  		/* Wait for all lower device DMAs done. */

  		vhost_net_ubuf_put_and_wait(n->vqs[VHOST_NET_VQ_TX].ubufs);

  		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);

  		n->tx_flush = false;

  		atomic_set(&n->vqs[VHOST_NET_VQ_TX].ubufs->refcount, 1);

  		mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);

  	}

  }
  
  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_stop(&n->dev);

  	vhost_dev_cleanup(&n->dev, false);

  	vhost_net_vq_reset(n);

  	if (tx_sock)

  		sockfd_put(tx_sock);

  	if (rx_sock)

  		sockfd_put(rx_sock);

  	/* Make sure no callbacks are outstanding */
  	synchronize_rcu_bh();

  	/* We do an extra flush before freeing memory,
  	 * since jobs can re-queue themselves. */
  	vhost_net_flush(n);

  	kfree(n->dev.vqs);

  	kvfree(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:

  	sockfd_put(sock);

  	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_net_virtqueue *nvq;

  	struct vhost_net_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].vq;

  	nvq = &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 = vq->private_data;

  	if (sock != oldsock) {

  		ubufs = vhost_net_ubuf_alloc(vq,
  					     sock && vhost_sock_zcopy(sock));

  		if (IS_ERR(ubufs)) {
  			r = PTR_ERR(ubufs);
  			goto err_ubufs;
  		}

  		vhost_net_disable_vq(n, vq);

  		vq->private_data = sock;

  		r = vhost_init_used(vq);
  		if (r)

  			goto err_used;

  		r = vhost_net_enable_vq(n, vq);
  		if (r)
  			goto err_used;

  		oldubufs = nvq->ubufs;
  		nvq->ubufs = ubufs;

  
  		n->tx_packets = 0;
  		n->tx_zcopy_err = 0;

  		n->tx_flush = false;

  	}

  	mutex_unlock(&vq->mutex);

  	if (oldubufs) {

  		vhost_net_ubuf_put_wait_and_free(oldubufs);

  		mutex_lock(&vq->mutex);

  		vhost_zerocopy_signal_used(n, vq);

  		mutex_unlock(&vq->mutex);
  	}

  	if (oldsock) {
  		vhost_net_flush_vq(n, index);

  		sockfd_put(oldsock);

  	}

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

  err_used:

  	vq->private_data = oldsock;

  	vhost_net_enable_vq(n, vq);
  	if (ubufs)

  		vhost_net_ubuf_put_wait_and_free(ubufs);

  err_ubufs:

  	sockfd_put(sock);

  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;

  	struct vhost_memory *memory;

  	mutex_lock(&n->dev.mutex);
  	err = vhost_dev_check_owner(&n->dev);
  	if (err)
  		goto done;

  	memory = vhost_dev_reset_owner_prepare();
  	if (!memory) {
  		err = -ENOMEM;
  		goto done;
  	}

  	vhost_net_stop(n, &tx_sock, &rx_sock);
  	vhost_net_flush(n);

  	vhost_dev_reset_owner(&n->dev, memory);

  	vhost_net_vq_reset(n);

  done:
  	mutex_unlock(&n->dev.mutex);
  	if (tx_sock)

  		sockfd_put(tx_sock);

  	if (rx_sock)

  		sockfd_put(rx_sock);

  	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;
  	}

  	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {

  		mutex_lock(&n->vqs[i].vq.mutex);

  		n->vqs[i].vq.acked_features = features;

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

  		mutex_unlock(&n->vqs[i].vq.mutex);

  	}

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

  static long vhost_net_set_owner(struct vhost_net *n)
  {
  	int r;
  
  	mutex_lock(&n->dev.mutex);

  	if (vhost_dev_has_owner(&n->dev)) {
  		r = -EBUSY;
  		goto out;
  	}

  	r = vhost_net_set_ubuf_info(n);
  	if (r)
  		goto out;
  	r = vhost_dev_set_owner(&n->dev);
  	if (r)
  		vhost_net_clear_ubuf_info(n);
  	vhost_net_flush(n);
  out:
  	mutex_unlock(&n->dev.mutex);
  	return r;
  }

  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_NET_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_NET_FEATURES)

  			return -EOPNOTSUPP;
  		return vhost_net_set_features(n, features);
  	case VHOST_RESET_OWNER:
  		return vhost_net_reset_owner(n);

  	case VHOST_SET_OWNER:
  		return vhost_net_set_owner(n);

  	default:
  		mutex_lock(&n->dev.mutex);

  		r = vhost_dev_ioctl(&n->dev, ioctl, argp);
  		if (r == -ENOIOCTLCMD)
  			r = vhost_vring_ioctl(&n->dev, ioctl, argp);
  		else
  			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 = {

  	.minor = VHOST_NET_MINOR,
  	.name = "vhost-net",
  	.fops = &vhost_net_fops,

  };

  static int vhost_net_init(void)

  {

  	if (experimental_zcopytx)

  		vhost_net_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");

  MODULE_ALIAS_MISCDEV(VHOST_NET_MINOR);
  MODULE_ALIAS("devname:vhost-net");