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32 results

macvtap.c

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  • macvtap.c 30.77 KiB
    #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/init.h>
    #include <linux/wait.h>
    #include <linux/cdev.h>
    #include <linux/idr.h>
    #include <linux/fs.h>
    
    #include <net/net_namespace.h>
    #include <net/rtnetlink.h>
    #include <net/sock.h>
    #include <linux/virtio_net.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;
    };
    
    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 struct class *macvtap_class;
    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)
    /*
     * 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;
    }
    
    static int macvtap_set_queue(struct net_device *dev, struct file *file,
    			     struct macvtap_queue *q)
    {
    	struct macvlan_dev *vlan = netdev_priv(dev);
    	int err = -EBUSY;
    
    	rtnl_lock();
    	if (vlan->numqueues == MAX_MACVTAP_QUEUES)
    		goto out;
    
    	err = 0;
    	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++;
    
    out:
    	rtnl_unlock();
    	return err;
    }
    
    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;
    
    	/* Check if we can use flow to select a queue */
    	rxq = skb_get_rxhash(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;
    	}
    
    	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, *qlist[MAX_MACVTAP_QUEUES];
    	int i, j = 0;
    
    	ASSERT_RTNL();
    	list_for_each_entry_safe(q, tmp, &vlan->queue_list, next) {
    		list_del_init(&q->next);
    		qlist[j++] = q;
    		RCU_INIT_POINTER(q->vlan, NULL);
    		if (q->enabled)
    			vlan->numvtaps--;
    		vlan->numqueues--;
    	}
    	for (i = 0; i < vlan->numvtaps; i++)
    		RCU_INIT_POINTER(vlan->taps[i], NULL);
    	BUG_ON(vlan->numvtaps);
    	BUG_ON(vlan->numqueues);
    	/* guarantee that any future macvtap_set_queue will fail */
    	vlan->numvtaps = MAX_MACVTAP_QUEUES;
    
    	for (--j; j >= 0; j--)
    		sock_put(&qlist[j]->sk);
    }
    
    /*
     * Forward happens for data that gets sent from one macvlan
     * endpoint to another one in bridge mode. We just take
     * the skb and put it into the receive queue.
     */
    static int macvtap_forward(struct net_device *dev, struct sk_buff *skb)
    {
    	struct macvlan_dev *vlan = netdev_priv(dev);
    	struct macvtap_queue *q = macvtap_get_queue(dev, skb);
    	netdev_features_t features;
    	if (!q)
    		goto drop;
    
    	if (skb_queue_len(&q->sk.sk_receive_queue) >= dev->tx_queue_len)
    		goto drop;
    
    	skb->dev = dev;
    	/* Apply the forward feature mask so that we perform segmentation
    	 * according to users wishes.
    	 */
    	features = netif_skb_features(skb) & 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) {
    			skb_queue_tail(&q->sk.sk_receive_queue, skb);
    			goto wake_up;
    		}
    
    		kfree_skb(skb);
    		while (segs) {
    			struct sk_buff *nskb = segs->next;
    
    			segs->next = NULL;
    			skb_queue_tail(&q->sk.sk_receive_queue, segs);
    			segs = nskb;
    		}
    	} else {
    		skb_queue_tail(&q->sk.sk_receive_queue, skb);
    	}
    
    wake_up:
    	wake_up_interruptible_poll(sk_sleep(&q->sk), POLLIN | POLLRDNORM | POLLRDBAND);
    	return NET_RX_SUCCESS;
    
    drop:
    	kfree_skb(skb);
    	return NET_RX_DROP;
    }
    
    /*
     * Receive is for data from the external interface (lowerdev),
     * in case of macvtap, we can treat that the same way as
     * forward, which macvlan cannot.
     */
    static int macvtap_receive(struct sk_buff *skb)
    {
    	skb_push(skb, ETH_HLEN);
    	return macvtap_forward(skb->dev, skb);
    }
    
    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\n");
    		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);
    	INIT_LIST_HEAD(&vlan->queue_list);
    
    	/* Since macvlan supports all offloads by default, make
    	 * tap support all offloads also.
    	 */
    	vlan->tap_features = TUN_OFFLOADS;
    
    	/* Don't put anything that may fail after macvlan_common_newlink
    	 * because we can't undo what it does.
    	 */
    	return macvlan_common_newlink(src_net, dev, tb, data,
    				      macvtap_receive, macvtap_forward);
    }
    
    static void macvtap_dellink(struct net_device *dev,
    			    struct list_head *head)
    {
    	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(SOCK_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)
    {
    	skb_queue_purge(&sk->sk_receive_queue);
    }
    
    static int macvtap_open(struct inode *inode, struct file *file)
    {
    	struct net *net = current->nsproxy->net_ns;
    	struct net_device *dev = dev_get_by_macvtap_minor(iminor(inode));
    	struct macvtap_queue *q;
    	int err;
    
    	err = -ENODEV;
    	if (!dev)
    		goto out;
    
    	err = -ENOMEM;
    	q = (struct macvtap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
    					     &macvtap_proto);
    	if (!q)
    		goto out;
    
    	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 = macvtap_set_queue(dev, file, q);
    	if (err)
    		sock_put(&q->sk);
    
    out:
    	if (dev)
    		dev_put(dev);
    
    	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_queue_empty(&q->sk.sk_receive_queue))
    		mask |= POLLIN | POLLRDNORM;
    
    	if (sock_writeable(&q->sk) ||
    	    (!test_and_set_bit(SOCK_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);
    	if (!skb)
    		return NULL;
    
    	skb_reserve(skb, prepad);
    	skb_put(skb, linear);
    	skb->data_len = len - linear;
    	skb->len += len - linear;
    
    	return skb;
    }
    
    /* set skb frags from iovec, this can move to core network code for reuse */
    static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
    				  int offset, size_t count)
    {
    	int len = iov_length(from, count) - offset;
    	int copy = skb_headlen(skb);
    	int size, offset1 = 0;
    	int i = 0;
    
    	/* Skip over from offset */
    	while (count && (offset >= from->iov_len)) {
    		offset -= from->iov_len;
    		++from;
    		--count;
    	}
    
    	/* copy up to skb headlen */
    	while (count && (copy > 0)) {
    		size = min_t(unsigned int, copy, from->iov_len - offset);
    		if (copy_from_user(skb->data + offset1, from->iov_base + offset,
    				   size))
    			return -EFAULT;
    		if (copy > size) {
    			++from;
    			--count;
    			offset = 0;
    		} else
    			offset += size;
    		copy -= size;
    		offset1 += size;
    	}
    
    	if (len == offset1)
    		return 0;
    
    	while (count--) {
    		struct page *page[MAX_SKB_FRAGS];
    		int num_pages;
    		unsigned long base;
    		unsigned long truesize;
    
    		len = from->iov_len - offset;
    		if (!len) {
    			offset = 0;
    			++from;
    			continue;
    		}
    		base = (unsigned long)from->iov_base + offset;
    		size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
    		if (i + size > MAX_SKB_FRAGS)
    			return -EMSGSIZE;
    		num_pages = get_user_pages_fast(base, size, 0, &page[i]);
    		if (num_pages != size) {
    			int j;
    
    			for (j = 0; j < num_pages; j++)
    				put_page(page[i + j]);
    			return -EFAULT;
    		}
    		truesize = size * PAGE_SIZE;
    		skb->data_len += len;
    		skb->len += len;
    		skb->truesize += truesize;
    		atomic_add(truesize, &skb->sk->sk_wmem_alloc);
    		while (len) {
    			int off = base & ~PAGE_MASK;
    			int size = min_t(int, len, PAGE_SIZE - off);
    			__skb_fill_page_desc(skb, i, page[i], off, size);
    			skb_shinfo(skb)->nr_frags++;
    			/* increase sk_wmem_alloc */
    			base += size;
    			len -= size;
    			i++;
    		}
    		offset = 0;
    		++from;
    	}
    	return 0;
    }
    
    /*
     * macvtap_skb_from_vnet_hdr and macvtap_skb_to_vnet_hdr should
     * be shared with the tun/tap driver.
     */
    static int macvtap_skb_from_vnet_hdr(struct sk_buff *skb,
    				     struct virtio_net_hdr *vnet_hdr)
    {
    	unsigned short gso_type = 0;
    	if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
    		switch (vnet_hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
    		case VIRTIO_NET_HDR_GSO_TCPV4:
    			gso_type = SKB_GSO_TCPV4;
    			break;
    		case VIRTIO_NET_HDR_GSO_TCPV6:
    			gso_type = SKB_GSO_TCPV6;
    			break;
    		case VIRTIO_NET_HDR_GSO_UDP:
    			gso_type = SKB_GSO_UDP;
    			break;
    		default:
    			return -EINVAL;
    		}
    
    		if (vnet_hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
    			gso_type |= SKB_GSO_TCP_ECN;
    
    		if (vnet_hdr->gso_size == 0)
    			return -EINVAL;
    	}
    
    	if (vnet_hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
    		if (!skb_partial_csum_set(skb, vnet_hdr->csum_start,
    					  vnet_hdr->csum_offset))
    			return -EINVAL;
    	}
    
    	if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
    		skb_shinfo(skb)->gso_size = vnet_hdr->gso_size;
    		skb_shinfo(skb)->gso_type = gso_type;
    
    		/* Header must be checked, and gso_segs computed. */
    		skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
    		skb_shinfo(skb)->gso_segs = 0;
    	}
    	return 0;
    }
    
    static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
    				   struct virtio_net_hdr *vnet_hdr)
    {
    	memset(vnet_hdr, 0, sizeof(*vnet_hdr));
    
    	if (skb_is_gso(skb)) {
    		struct skb_shared_info *sinfo = skb_shinfo(skb);
    
    		/* This is a hint as to how much should be linear. */
    		vnet_hdr->hdr_len = skb_headlen(skb);
    		vnet_hdr->gso_size = sinfo->gso_size;
    		if (sinfo->gso_type & SKB_GSO_TCPV4)
    			vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
    		else if (sinfo->gso_type & SKB_GSO_TCPV6)
    			vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
    		else if (sinfo->gso_type & SKB_GSO_UDP)
    			vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
    		else
    			BUG();
    		if (sinfo->gso_type & SKB_GSO_TCP_ECN)
    			vnet_hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
    	} else
    		vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
    
    	if (skb->ip_summed == CHECKSUM_PARTIAL) {
    		vnet_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
    		vnet_hdr->csum_start = skb_checksum_start_offset(skb);
    		vnet_hdr->csum_offset = skb->csum_offset;
    	} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
    		vnet_hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
    	} /* else everything is zero */
    
    	return 0;
    }
    
    /* Get packet from user space buffer */
    static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
    				const struct iovec *iv, unsigned long total_len,
    				size_t count, int noblock)
    {
    	struct sk_buff *skb;
    	struct macvlan_dev *vlan;
    	unsigned long len = total_len;
    	int err;
    	struct virtio_net_hdr vnet_hdr = { 0 };
    	int vnet_hdr_len = 0;
    	int copylen = 0;
    	bool zerocopy = false;
    	size_t linear;
    
    	if (q->flags & IFF_VNET_HDR) {
    		vnet_hdr_len = q->vnet_hdr_sz;
    
    		err = -EINVAL;
    		if (len < vnet_hdr_len)
    			goto err;
    		len -= vnet_hdr_len;
    
    		err = memcpy_fromiovecend((void *)&vnet_hdr, iv, 0,
    					   sizeof(vnet_hdr));
    		if (err < 0)
    			goto err;
    		if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
    		     vnet_hdr.csum_start + vnet_hdr.csum_offset + 2 >
    							vnet_hdr.hdr_len)
    			vnet_hdr.hdr_len = vnet_hdr.csum_start +
    						vnet_hdr.csum_offset + 2;
    		err = -EINVAL;
    		if (vnet_hdr.hdr_len > len)
    			goto err;
    	}
    
    	err = -EINVAL;
    	if (unlikely(len < ETH_HLEN))
    		goto err;
    
    	err = -EMSGSIZE;
    	if (unlikely(count > UIO_MAXIOV))
    		goto err;
    
    	if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
    		copylen = vnet_hdr.hdr_len ? vnet_hdr.hdr_len : GOODCOPY_LEN;
    		linear = copylen;
    		if (iov_pages(iv, vnet_hdr_len + copylen, count)
    		    <= MAX_SKB_FRAGS)
    			zerocopy = true;
    	}
    
    	if (!zerocopy) {
    		copylen = len;
    		linear = vnet_hdr.hdr_len;
    	}
    
    	skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, copylen,
    				linear, noblock, &err);
    	if (!skb)
    		goto err;
    
    	if (zerocopy)
    		err = zerocopy_sg_from_iovec(skb, iv, vnet_hdr_len, count);
    	else {
    		err = skb_copy_datagram_from_iovec(skb, 0, iv, vnet_hdr_len,
    						   len);
    		if (!err && m && m->msg_control) {
    			struct ubuf_info *uarg = m->msg_control;
    			uarg->callback(uarg, false);
    		}
    	}
    
    	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 = macvtap_skb_from_vnet_hdr(skb, &vnet_hdr);
    		if (err)
    			goto err_kfree;
    	}
    
    	skb_probe_transport_header(skb, ETH_HLEN);
    
    	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;
    	}
    	if (vlan)
    		macvlan_start_xmit(skb, vlan->dev);
    	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)
    		vlan->dev->stats.tx_dropped++;
    	rcu_read_unlock();
    
    	return err;
    }
    
    static ssize_t macvtap_aio_write(struct kiocb *iocb, const struct iovec *iv,
    				 unsigned long count, loff_t pos)
    {
    	struct file *file = iocb->ki_filp;
    	ssize_t result = -ENOLINK;
    	struct macvtap_queue *q = file->private_data;
    
    	result = macvtap_get_user(q, NULL, iv, iov_length(iv, count), count,
    				  file->f_flags & O_NONBLOCK);
    	return result;
    }
    
    /* Put packet to the user space buffer */
    static ssize_t macvtap_put_user(struct macvtap_queue *q,
    				const struct sk_buff *skb,
    				const struct iovec *iv, int len)
    {
    	struct macvlan_dev *vlan;
    	int ret;
    	int vnet_hdr_len = 0;
    	int vlan_offset = 0;
    	int copied;
    
    	if (q->flags & IFF_VNET_HDR) {
    		struct virtio_net_hdr vnet_hdr;
    		vnet_hdr_len = q->vnet_hdr_sz;
    		if ((len -= vnet_hdr_len) < 0)
    			return -EINVAL;
    
    		ret = macvtap_skb_to_vnet_hdr(skb, &vnet_hdr);
    		if (ret)
    			return ret;
    
    		if (memcpy_toiovecend(iv, (void *)&vnet_hdr, 0, sizeof(vnet_hdr)))
    			return -EFAULT;
    	}
    	copied = vnet_hdr_len;
    
    	if (!vlan_tx_tag_present(skb))
    		len = min_t(int, skb->len, len);
    	else {
    		int copy;
    		struct {
    			__be16 h_vlan_proto;
    			__be16 h_vlan_TCI;
    		} veth;
    		veth.h_vlan_proto = skb->vlan_proto;
    		veth.h_vlan_TCI = htons(vlan_tx_tag_get(skb));
    
    		vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
    		len = min_t(int, skb->len + VLAN_HLEN, len);
    
    		copy = min_t(int, vlan_offset, len);
    		ret = skb_copy_datagram_const_iovec(skb, 0, iv, copied, copy);
    		len -= copy;
    		copied += copy;
    		if (ret || !len)
    			goto done;
    
    		copy = min_t(int, sizeof(veth), len);
    		ret = memcpy_toiovecend(iv, (void *)&veth, copied, copy);
    		len -= copy;
    		copied += copy;
    		if (ret || !len)
    			goto done;
    	}
    
    	ret = skb_copy_datagram_const_iovec(skb, vlan_offset, iv, copied, len);
    	copied += len;
    
    done:
    	rcu_read_lock();
    	vlan = rcu_dereference(q->vlan);
    	if (vlan)
    		macvlan_count_rx(vlan, copied - vnet_hdr_len, ret == 0, 0);
    	rcu_read_unlock();
    
    	return ret ? ret : copied;
    }
    
    static ssize_t macvtap_do_read(struct macvtap_queue *q, struct kiocb *iocb,
    			       const struct iovec *iv, unsigned long len,
    			       int noblock)
    {
    	DEFINE_WAIT(wait);
    	struct sk_buff *skb;
    	ssize_t ret = 0;
    
    	while (len) {
    		if (!noblock)
    			prepare_to_wait(sk_sleep(&q->sk), &wait,
    					TASK_INTERRUPTIBLE);
    
    		/* Read frames from the queue */
    		skb = skb_dequeue(&q->sk.sk_receive_queue);
    		if (!skb) {
    			if (noblock) {
    				ret = -EAGAIN;
    				break;
    			}
    			if (signal_pending(current)) {
    				ret = -ERESTARTSYS;
    				break;
    			}
    			/* Nothing to read, let's sleep */
    			schedule();
    			continue;
    		}
    		ret = macvtap_put_user(q, skb, iv, len);
    		kfree_skb(skb);
    		break;
    	}
    
    	if (!noblock)
    		finish_wait(sk_sleep(&q->sk), &wait);
    	return ret;
    }
    
    static ssize_t macvtap_aio_read(struct kiocb *iocb, const struct iovec *iv,
    				unsigned long count, loff_t pos)
    {
    	struct file *file = iocb->ki_filp;
    	struct macvtap_queue *q = file->private_data;
    	ssize_t len, ret = 0;
    
    	len = iov_length(iv, count);
    	if (len < 0) {
    		ret = -EINVAL;
    		goto out;
    	}
    
    	ret = macvtap_do_read(q, iocb, iv, len, file->f_flags & O_NONBLOCK);
    	ret = min_t(ssize_t, ret, len); /* XXX copied from tun.c. Why? */
    out:
    	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 = vlan->dev->features &
    			    (feature_mask | ~TUN_OFFLOADS);
    	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 int u;
    	int __user *sp = argp;
    	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 & ~(IFF_VNET_HDR | IFF_MULTI_QUEUE)) !=
    		    (IFF_NO_PI | IFF_TAP))
    			ret = -EINVAL;
    		else
    			q->flags = u;
    
    		return ret;
    
    	case TUNGETIFF:
    		rtnl_lock();
    		vlan = macvtap_get_vlan(q);
    		if (!vlan) {
    			rtnl_unlock();
    			return -ENOLINK;
    		}
    
    		ret = 0;
    		if (copy_to_user(&ifr->ifr_name, vlan->dev->name, IFNAMSIZ) ||
    		    put_user(q->flags, &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 | IFF_VNET_HDR |
    			     IFF_MULTI_QUEUE, up))
    			return -EFAULT;
    		return 0;
    
    	case TUNSETSNDBUF:
    		if (get_user(u, up))
    			return -EFAULT;
    
    		q->sk.sk_sndbuf = u;
    		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 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;
    
    		/* TODO: only accept frames with the features that
    			 got enabled for forwarded frames */
    		if (!(q->flags & IFF_VNET_HDR))
    			return  -EINVAL;
    		rtnl_lock();
    		ret = set_offload(q, arg);
    		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,
    	.aio_read	= macvtap_aio_read,
    	.aio_write	= macvtap_aio_write,
    	.poll		= macvtap_poll,
    	.llseek		= no_llseek,
    	.unlocked_ioctl	= macvtap_ioctl,
    #ifdef CONFIG_COMPAT
    	.compat_ioctl	= macvtap_compat_ioctl,
    #endif
    };
    
    static int macvtap_sendmsg(struct kiocb *iocb, 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_iov, total_len, m->msg_iovlen,
    			    m->msg_flags & MSG_DONTWAIT);
    }
    
    static int macvtap_recvmsg(struct kiocb *iocb, 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, iocb, m->msg_iov, total_len,
    			  flags & MSG_DONTWAIT);
    	if (ret > total_len) {
    		m->msg_flags |= MSG_TRUNC;
    		ret = flags & MSG_TRUNC ? ret : total_len;
    	}
    	return ret;
    }
    
    /* Ops structure to mimic raw sockets with tun */
    static const struct proto_ops macvtap_socket_ops = {
    	.sendmsg = macvtap_sendmsg,
    	.recvmsg = macvtap_recvmsg,
    };
    
    /* 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_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;
    
    	if (dev->rtnl_link_ops != &macvtap_link_ops)
    		return NOTIFY_DONE;
    
    	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%d", dev->ifindex);
    		if (IS_ERR(classdev)) {
    			macvtap_free_minor(vlan);
    			return notifier_from_errno(PTR_ERR(classdev));
    		}
    		break;
    	case NETDEV_UNREGISTER:
    		devt = MKDEV(MAJOR(macvtap_major), vlan->minor);
    		device_destroy(macvtap_class, devt);
    		macvtap_free_minor(vlan);
    		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;
    
    	macvtap_class = class_create(THIS_MODULE, "macvtap");
    	if (IS_ERR(macvtap_class)) {
    		err = PTR_ERR(macvtap_class);
    		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);
    }
    module_exit(macvtap_exit);
    
    MODULE_ALIAS_RTNL_LINK("macvtap");
    MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
    MODULE_LICENSE("GPL");