#include <linux/etherdevice.h>
#include <linux/if_macvlan.h>
#include <linux/if_vlan.h>
#include <linux/interrupt.h>
#include <linux/nsproxy.h>
#include <linux/compat.h>
#include <linux/if_tun.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/cache.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/cdev.h>
#include <linux/idr.h>
#include <linux/fs.h>
#include <linux/uio.h>

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

/*
 * 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;
};

#define MACVTAP_FEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)

#define MACVTAP_VNET_LE 0x80000000

static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
{
        return __virtio16_to_cpu(q->flags & MACVTAP_VNET_LE, val);
}

static inline __virtio16 cpu_to_macvtap16(struct macvtap_queue *q, u16 val)
{
        return __cpu_to_virtio16(q->flags & MACVTAP_VNET_LE, val);
}

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

/*
 * Variables for dealing with macvtaps device numbers.
 */
static dev_t macvtap_major;
#define MACVTAP_NUM_DEVS (1U << MINORBITS)
static DEFINE_MUTEX(minor_lock);
static DEFINE_IDR(minor_idr);

#define GOODCOPY_LEN 128
static 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)
#define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG)

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

/*
 * RCU usage:
 * The macvtap_queue and the macvlan_dev are loosely coupled, the
 * pointers from one to the other can only be read while rcu_read_lock
 * or rtnl is held.
 *
 * Both the file and the macvlan_dev hold a reference on the macvtap_queue
 * through sock_hold(&q->sk). When the macvlan_dev goes away first,
 * q->vlan becomes inaccessible. When the files gets closed,
 * macvtap_get_queue() fails.
 *
 * There may still be references to the struct sock inside of the
 * queue from outbound SKBs, but these never reference back to the
 * file or the dev. The data structure is freed through __sk_free
 * when both our references and any pending SKBs are gone.
 */

static int macvtap_enable_queue(struct net_device *dev, struct file *file,
                                struct macvtap_queue *q)
{
        struct macvlan_dev *vlan = netdev_priv(dev);
        int err = -EINVAL;

        ASSERT_RTNL();

        if (q->enabled)
                goto out;

        err = 0;
        rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);
        q->queue_index = vlan->numvtaps;
        q->enabled = true;

        vlan->numvtaps++;
out:
        return err;
}

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

        if (vlan->numqueues == MAX_MACVTAP_QUEUES)
                return -EBUSY;

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

        q->file = file;
        q->queue_index = vlan->numvtaps;
        q->enabled = true;
        file->private_data = q;
        list_add_tail(&q->next, &vlan->queue_list);

        vlan->numvtaps++;
        vlan->numqueues++;

        return 0;
}

static int macvtap_disable_queue(struct macvtap_queue *q)
{
        struct macvlan_dev *vlan;
        struct macvtap_queue *nq;

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

        vlan = rtnl_dereference(q->vlan);

        if (vlan) {
                int index = q->queue_index;
                BUG_ON(index >= vlan->numvtaps);
                nq = rtnl_dereference(vlan->taps[vlan->numvtaps - 1]);
                nq->queue_index = index;

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

                vlan->numvtaps--;
        }

        return 0;
}

/*
 * The file owning the queue got closed, give up both
 * the reference that the files holds as well as the
 * one from the macvlan_dev if that still exists.
 *
 * Using the spinlock makes sure that we don't get
 * to the queue again after destroying it.
 */
static void macvtap_put_queue(struct macvtap_queue *q)
{
        struct macvlan_dev *vlan;

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

        if (vlan) {
                if (q->enabled)
                        BUG_ON(macvtap_disable_queue(q));

                vlan->numqueues--;
                RCU_INIT_POINTER(q->vlan, NULL);
                sock_put(&q->sk);
                list_del_init(&q->next);
        }

        rtnl_unlock();

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

/*
 * Select a queue based on the rxq of the device on which this packet
 * arrived. If the incoming device is not mq, calculate a flow hash
 * to select a queue. If all fails, find the first available queue.
 * Cache vlan->numvtaps since it can become zero during the execution
 * of this function.
 */
static struct macvtap_queue *macvtap_get_queue(struct net_device *dev,
                                               struct sk_buff *skb)
{
        struct macvlan_dev *vlan = netdev_priv(dev);
        struct macvtap_queue *tap = NULL;
        /* Access to taps array is protected by rcu, but access to numvtaps
         * isn't. Below we use it to lookup a queue, but treat it as a hint
         * and validate that the result isn't NULL - in case we are
         * racing against queue removal.
         */
        int numvtaps = ACCESS_ONCE(vlan->numvtaps);
        __u32 rxq;

        if (!numvtaps)
                goto out;

        /* Check if we can use flow to select a queue */
        rxq = skb_get_hash(skb);
        if (rxq) {
                tap = rcu_dereference(vlan->taps[rxq % numvtaps]);
                goto out;
        }

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

                while (unlikely(rxq >= numvtaps))
                        rxq -= numvtaps;

                tap = rcu_dereference(vlan->taps[rxq]);
                goto out;
        }

        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);
}

static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb)
{
        struct sk_buff *skb = *pskb;
        struct net_device *dev = skb->dev;
        struct macvlan_dev *vlan;
        struct macvtap_queue *q;
        netdev_features_t features = TAP_FEATURES;

        vlan = macvtap_get_vlan_rcu(dev);
        if (!vlan)
                return RX_HANDLER_PASS;

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

        if (skb_queue_len(&q->sk.sk_receive_queue) >= dev->tx_queue_len)
                goto drop;

        skb_push(skb, ETH_HLEN);

        /* Apply the forward feature mask so that we perform segmentation
         * according to users wishes.  This only works if VNET_HDR is
         * enabled.
         */
        if (q->flags & IFF_VNET_HDR)
                features |= vlan->tap_features;
        if (netif_needs_gso(skb, features)) {
                struct sk_buff *segs = __skb_gso_segment(skb, features, false);

                if (IS_ERR(segs))
                        goto drop;

                if (!segs) {
                        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 {
                /* 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_ALL_CSUM) &&
                    skb_checksum_help(skb))
                        goto drop;
                skb_queue_tail(&q->sk.sk_receive_queue, skb);
        }

wake_up:
        wake_up_interruptible_poll(sk_sleep(&q->sk), POLLIN | POLLRDNORM | POLLRDBAND);
        return RX_HANDLER_CONSUMED;

drop:
        /* Count errors/drops only here, thus don't care about args. */
        macvlan_count_rx(vlan, 0, 0, 0);
        kfree_skb(skb);
        return RX_HANDLER_CONSUMED;
}

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

        mutex_lock(&minor_lock);
        retval = idr_alloc(&minor_idr, vlan, 1, MACVTAP_NUM_DEVS, GFP_KERNEL);
        if (retval >= 0) {
                vlan->minor = retval;
        } else if (retval == -ENOSPC) {
                printk(KERN_ERR "too many macvtap devices\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);
        int err;

        INIT_LIST_HEAD(&vlan->queue_list);

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

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

        /* Don't put anything that may fail after macvlan_common_newlink
         * because we can't undo what it does.
         */
        return macvlan_common_newlink(src_net, dev, tb, data);
}

static void macvtap_dellink(struct net_device *dev,
                            struct list_head *head)
{
        netdev_rx_handler_unregister(dev);
        macvtap_del_queues(dev);
        macvlan_dellink(dev, head);
}

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

static struct rtnl_link_ops macvtap_link_ops __read_mostly = {
        .kind           = "macvtap",
        .setup          = macvtap_setup,
        .newlink        = macvtap_newlink,
        .dellink        = macvtap_dellink,
};


static void macvtap_sock_write_space(struct sock *sk)
{
        wait_queue_head_t *wqueue;

        if (!sock_writeable(sk) ||
            !test_and_clear_bit(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;
        struct macvtap_queue *q;
        int err = -ENODEV;

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

        rtnl_unlock();
        return err;
}

static int macvtap_release(struct inode *inode, struct file *file)
{
        struct macvtap_queue *q = file->private_data;
        macvtap_put_queue(q);
        return 0;
}

static unsigned int macvtap_poll(struct file *file, poll_table * wait)
{
        struct macvtap_queue *q = file->private_data;
        unsigned int mask = POLLERR;

        if (!q)
                goto out;

        mask = 0;
        poll_wait(file, &q->wq.wait, wait);

        if (!skb_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, 0);
        if (!skb)
                return NULL;

        skb_reserve(skb, prepad);
        skb_put(skb, linear);
        skb->data_len = len - linear;
        skb->len += len - linear;

        return skb;
}

/*
 * 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 macvtap_queue *q,
                                     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, macvtap16_to_cpu(q, vnet_hdr->csum_start),
                                          macvtap16_to_cpu(q, vnet_hdr->csum_offset)))
                        return -EINVAL;
        }

        if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
                skb_shinfo(skb)->gso_size = macvtap16_to_cpu(q, 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 void macvtap_skb_to_vnet_hdr(struct macvtap_queue *q,
                                    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 = cpu_to_macvtap16(q, skb_headlen(skb));
                vnet_hdr->gso_size = cpu_to_macvtap16(q, 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;
                if (skb_vlan_tag_present(skb))
                        vnet_hdr->csum_start = cpu_to_macvtap16(q,
                                skb_checksum_start_offset(skb) + VLAN_HLEN);
                else
                        vnet_hdr->csum_start = cpu_to_macvtap16(q,
                                skb_checksum_start_offset(skb));
                vnet_hdr->csum_offset = cpu_to_macvtap16(q, skb->csum_offset);
        } else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
                vnet_hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
        } /* else everything is zero */
}

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

/* Get packet from user space buffer */
static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
                                struct iov_iter *from, int noblock)
{
        int good_linear = SKB_MAX_HEAD(MACVTAP_RESERVE);
        struct sk_buff *skb;
        struct macvlan_dev *vlan;
        unsigned long total_len = iov_iter_count(from);
        unsigned long len = total_len;
        int err;
        struct virtio_net_hdr vnet_hdr = { 0 };
        int vnet_hdr_len = 0;
        int copylen = 0;
        bool zerocopy = false;
        size_t linear;
        ssize_t n;

        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 = -EFAULT;
                n = copy_from_iter(&vnet_hdr, sizeof(vnet_hdr), from);
                if (n != sizeof(vnet_hdr))
                        goto err;
                iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
                if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
                     macvtap16_to_cpu(q, vnet_hdr.csum_start) +
                     macvtap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
                             macvtap16_to_cpu(q, vnet_hdr.hdr_len))
                        vnet_hdr.hdr_len = cpu_to_macvtap16(q,
                                 macvtap16_to_cpu(q, vnet_hdr.csum_start) +
                                 macvtap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
                err = -EINVAL;
                if (macvtap16_to_cpu(q, vnet_hdr.hdr_len) > len)
                        goto err;
        }

        err = -EINVAL;
        if (unlikely(len < ETH_HLEN))
                goto err;

        if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
                struct iov_iter i;

                copylen = vnet_hdr.hdr_len ?
                        macvtap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
                if (copylen > good_linear)
                        copylen = good_linear;
                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;
                if (macvtap16_to_cpu(q, vnet_hdr.hdr_len) > good_linear)
                        linear = good_linear;
                else
                        linear = macvtap16_to_cpu(q, vnet_hdr.hdr_len);
        }

        skb = macvtap_alloc_skb(&q->sk, MACVTAP_RESERVE, copylen,
                                linear, noblock, &err);
        if (!skb)
                goto err;

        if (zerocopy)
                err = zerocopy_sg_from_iter(skb, from);
        else {
                err = skb_copy_datagram_from_iter(skb, 0, from, len);
                if (!err && 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(q, 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) {
                skb->dev = vlan->dev;
                dev_queue_xmit(skb);
        } else {
                kfree_skb(skb);
        }
        rcu_read_unlock();

        return total_len;

err_kfree:
        kfree_skb(skb);

err:
        rcu_read_lock();
        vlan = rcu_dereference(q->vlan);
        if (vlan)
                this_cpu_inc(vlan->pcpu_stats->tx_dropped);
        rcu_read_unlock();

        return err;
}

static ssize_t macvtap_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct file *file = iocb->ki_filp;
        struct macvtap_queue *q = file->private_data;

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

/* Put packet to the user space buffer */
static ssize_t macvtap_put_user(struct macvtap_queue *q,
                                const struct sk_buff *skb,
                                struct iov_iter *iter)
{
        int ret;
        int vnet_hdr_len = 0;
        int vlan_offset = 0;
        int total;

        if (q->flags & IFF_VNET_HDR) {
                struct virtio_net_hdr vnet_hdr;
                vnet_hdr_len = q->vnet_hdr_sz;
                if (iov_iter_count(iter) < vnet_hdr_len)
                        return -EINVAL;

                macvtap_skb_to_vnet_hdr(q, skb, &vnet_hdr);

                if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
                    sizeof(vnet_hdr))
                        return -EFAULT;

                iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));
        }
        total = vnet_hdr_len;
        total += skb->len;

        if (skb_vlan_tag_present(skb)) {
                struct {
                        __be16 h_vlan_proto;
                        __be16 h_vlan_TCI;
                } veth;
                veth.h_vlan_proto = skb->vlan_proto;
                veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));

                vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
                total += VLAN_HLEN;

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

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

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

done:
        return ret ? ret : total;
}

static ssize_t macvtap_do_read(struct macvtap_queue *q,
                               struct iov_iter *to,
                               int noblock)
{
        DEFINE_WAIT(wait);
        struct sk_buff *skb;
        ssize_t ret = 0;

        if (!iov_iter_count(to))
                return 0;

        while (1) {
                if (!noblock)
                        prepare_to_wait(sk_sleep(&q->sk), &wait,
                                        TASK_INTERRUPTIBLE);

                /* Read frames from the queue */
                skb = skb_dequeue(&q->sk.sk_receive_queue);
                if (skb)
                        break;
                if (noblock) {
                        ret = -EAGAIN;
                        break;
                }
                if (signal_pending(current)) {
                        ret = -ERESTARTSYS;
                        break;
                }
                /* Nothing to read, let's sleep */
                schedule();
        }
        if (skb) {
                ret = macvtap_put_user(q, skb, to);
                if (unlikely(ret < 0))
                        kfree_skb(skb);
                else
                        consume_skb(skb);
        }
        if (!noblock)
                finish_wait(sk_sleep(&q->sk), &wait);
        return ret;
}

static ssize_t macvtap_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *file = iocb->ki_filp;
        struct macvtap_queue *q = file->private_data;
        ssize_t len = iov_iter_count(to), ret;

        ret = macvtap_do_read(q, to, file->f_flags & O_NONBLOCK);
        ret = min_t(ssize_t, ret, len);
        if (ret > 0)
                iocb->ki_pos = ret;
        return ret;
}

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

        ASSERT_RTNL();
        vlan = rtnl_dereference(q->vlan);
        if (vlan)
                dev_hold(vlan->dev);

        return vlan;
}

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

static int macvtap_ioctl_set_queue(struct file *file, unsigned int flags)
{
        struct macvtap_queue *q = file->private_data;
        struct macvlan_dev *vlan;
        int ret;

        vlan = macvtap_get_vlan(q);
        if (!vlan)
                return -EINVAL;

        if (flags & IFF_ATTACH_QUEUE)
                ret = macvtap_enable_queue(vlan->dev, file, q);
        else if (flags & IFF_DETACH_QUEUE)
                ret = macvtap_disable_queue(q);
        else
                ret = -EINVAL;

        macvtap_put_vlan(vlan);
        return ret;
}

static int set_offload(struct macvtap_queue *q, unsigned long arg)
{
        struct macvlan_dev *vlan;
        netdev_features_t features;
        netdev_features_t feature_mask = 0;

        vlan = rtnl_dereference(q->vlan);
        if (!vlan)
                return -ENOLINK;

        features = vlan->dev->features;

        if (arg & TUN_F_CSUM) {
                feature_mask = NETIF_F_HW_CSUM;

                if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
                        if (arg & TUN_F_TSO_ECN)
                                feature_mask |= NETIF_F_TSO_ECN;
                        if (arg & TUN_F_TSO4)
                                feature_mask |= NETIF_F_TSO;
                        if (arg & TUN_F_TSO6)
                                feature_mask |= NETIF_F_TSO6;
                }

                if (arg & TUN_F_UFO)
                        feature_mask |= NETIF_F_UFO;
        }

        /* tun/tap driver inverts the usage for TSO offloads, where
         * setting the TSO bit means that the userspace wants to
         * accept TSO frames and turning it off means that user space
         * does not support TSO.
         * For macvtap, we have to invert it to mean the same thing.
         * When user space turns off TSO, we turn off GSO/LRO so that
         * user-space will not receive TSO frames.
         */
        if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_UFO))
                features |= RX_OFFLOADS;
        else
                features &= ~RX_OFFLOADS;

        /* tap_features are the same as features on tun/tap and
         * reflect user expectations.
         */
        vlan->tap_features = feature_mask;
        vlan->set_features = features;
        netdev_update_features(vlan->dev);

        return 0;
}

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

{
        struct macvtap_queue *q = file->private_data;
        struct macvlan_dev *vlan;
        void __user *argp = (void __user *)arg;
        struct ifreq __user *ifr = argp;
        unsigned int __user *up = argp;
        unsigned short u;
        int __user *sp = argp;
        int s;
        int ret;

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

                ret = 0;
                if ((u & ~MACVTAP_FEATURES) != (IFF_NO_PI | IFF_TAP))
                        ret = -EINVAL;
                else
                        q->flags = (q->flags & ~MACVTAP_FEATURES) | u;

                return ret;

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

                ret = 0;
                u = q->flags;
                if (copy_to_user(&ifr->ifr_name, vlan->dev->name, IFNAMSIZ) ||
                    put_user(u, &ifr->ifr_flags))
                        ret = -EFAULT;
                macvtap_put_vlan(vlan);
                rtnl_unlock();
                return ret;

        case TUNSETQUEUE:
                if (get_user(u, &ifr->ifr_flags))
                        return -EFAULT;
                rtnl_lock();
                ret = macvtap_ioctl_set_queue(file, u);
                rtnl_unlock();
                return ret;

        case TUNGETFEATURES:
                if (put_user(IFF_TAP | IFF_NO_PI | MACVTAP_FEATURES, up))
                        return -EFAULT;
                return 0;

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

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

        case 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;

        default:
                return -EINVAL;
        }
}

#ifdef CONFIG_COMPAT
static long macvtap_compat_ioctl(struct file *file, unsigned int cmd,
                                 unsigned long arg)
{
        return macvtap_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static const struct file_operations macvtap_fops = {
        .owner          = THIS_MODULE,
        .open           = macvtap_open,
        .release        = macvtap_release,
        .read_iter      = macvtap_read_iter,
        .write_iter     = macvtap_write_iter,
        .poll           = macvtap_poll,
        .llseek         = no_llseek,
        .unlocked_ioctl = macvtap_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = macvtap_compat_ioctl,
#endif
};

static int macvtap_sendmsg(struct socket *sock, struct msghdr *m,
                           size_t total_len)
{
        struct macvtap_queue *q = container_of(sock, struct macvtap_queue, sock);
        return macvtap_get_user(q, m, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);
}

static int macvtap_recvmsg(struct socket *sock, struct msghdr *m,
                           size_t total_len, int flags)
{
        struct macvtap_queue *q = container_of(sock, struct macvtap_queue, sock);
        int ret;
        if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
                return -EINVAL;
        ret = macvtap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT);
        if (ret > total_len) {
                m->msg_flags |= MSG_TRUNC;
                ret = flags & MSG_TRUNC ? ret : total_len;
        }
        return ret;
}

/* 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");