/* A network driver using virtio.
 *
 * Copyright 2007 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
//#define DEBUG
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/module.h>
#include <linux/virtio.h>
#include <linux/virtio_net.h>
#include <linux/scatterlist.h>
#include <linux/if_vlan.h>

static int napi_weight = 128;
module_param(napi_weight, int, 0444);

static int csum = 1, gso = 1;
module_param(csum, bool, 0444);
module_param(gso, bool, 0444);

/* FIXME: MTU in config. */
#define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
#define GOOD_COPY_LEN   128

#define VIRTNET_SEND_COMMAND_SG_MAX    2

struct virtnet_info
{
        struct virtio_device *vdev;
        struct virtqueue *rvq, *svq, *cvq;
        struct net_device *dev;
        struct napi_struct napi;
        unsigned int status;

        /* Number of input buffers, and max we've ever had. */
        unsigned int num, max;

        /* I like... big packets and I cannot lie! */
        bool big_packets;

        /* Host will merge rx buffers for big packets (shake it! shake it!) */
        bool mergeable_rx_bufs;

        /* Receive & send queues. */
        struct sk_buff_head recv;
        struct sk_buff_head send;

        /* Work struct for refilling if we run low on memory. */
        struct delayed_work refill;

        /* Chain pages by the private ptr. */
        struct page *pages;
};

struct skb_vnet_hdr {
        union {
                struct virtio_net_hdr hdr;
                struct virtio_net_hdr_mrg_rxbuf mhdr;
        };
        unsigned int num_sg;
};

static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
{
        return (struct skb_vnet_hdr *)skb->cb;
}

static void give_a_page(struct virtnet_info *vi, struct page *page)
{
        page->private = (unsigned long)vi->pages;
        vi->pages = page;
}

static void trim_pages(struct virtnet_info *vi, struct sk_buff *skb)
{
        unsigned int i;

        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
                give_a_page(vi, skb_shinfo(skb)->frags[i].page);
        skb_shinfo(skb)->nr_frags = 0;
        skb->data_len = 0;
}

static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
{
        struct page *p = vi->pages;

        if (p)
                vi->pages = (struct page *)p->private;
        else
                p = alloc_page(gfp_mask);
        return p;
}

static void skb_xmit_done(struct virtqueue *svq)
{
        struct virtnet_info *vi = svq->vdev->priv;

        /* Suppress further interrupts. */
        svq->vq_ops->disable_cb(svq);

        /* We were probably waiting for more output buffers. */
        netif_wake_queue(vi->dev);
}

static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                        unsigned len)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
        int err;
        int i;

        if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
                pr_debug("%s: short packet %i\n", dev->name, len);
                dev->stats.rx_length_errors++;
                goto drop;
        }

        if (vi->mergeable_rx_bufs) {
                unsigned int copy;
                char *p = page_address(skb_shinfo(skb)->frags[0].page);

                if (len > PAGE_SIZE)
                        len = PAGE_SIZE;
                len -= sizeof(struct virtio_net_hdr_mrg_rxbuf);

                memcpy(&hdr->mhdr, p, sizeof(hdr->mhdr));
                p += sizeof(hdr->mhdr);

                copy = len;
                if (copy > skb_tailroom(skb))
                        copy = skb_tailroom(skb);

                memcpy(skb_put(skb, copy), p, copy);

                len -= copy;

                if (!len) {
                        give_a_page(vi, skb_shinfo(skb)->frags[0].page);
                        skb_shinfo(skb)->nr_frags--;
                } else {
                        skb_shinfo(skb)->frags[0].page_offset +=
                                sizeof(hdr->mhdr) + copy;
                        skb_shinfo(skb)->frags[0].size = len;
                        skb->data_len += len;
                        skb->len += len;
                }

                while (--hdr->mhdr.num_buffers) {
                        struct sk_buff *nskb;

                        i = skb_shinfo(skb)->nr_frags;
                        if (i >= MAX_SKB_FRAGS) {
                                pr_debug("%s: packet too long %d\n", dev->name,
                                         len);
                                dev->stats.rx_length_errors++;
                                goto drop;
                        }

                        nskb = vi->rvq->vq_ops->get_buf(vi->rvq, &len);
                        if (!nskb) {
                                pr_debug("%s: rx error: %d buffers missing\n",
                                         dev->name, hdr->mhdr.num_buffers);
                                dev->stats.rx_length_errors++;
                                goto drop;
                        }

                        __skb_unlink(nskb, &vi->recv);
                        vi->num--;

                        skb_shinfo(skb)->frags[i] = skb_shinfo(nskb)->frags[0];
                        skb_shinfo(nskb)->nr_frags = 0;
                        kfree_skb(nskb);

                        if (len > PAGE_SIZE)
                                len = PAGE_SIZE;

                        skb_shinfo(skb)->frags[i].size = len;
                        skb_shinfo(skb)->nr_frags++;
                        skb->data_len += len;
                        skb->len += len;
                }
        } else {
                len -= sizeof(hdr->hdr);

                if (len <= MAX_PACKET_LEN)
                        trim_pages(vi, skb);

                err = pskb_trim(skb, len);
                if (err) {
                        pr_debug("%s: pskb_trim failed %i %d\n", dev->name,
                                 len, err);
                        dev->stats.rx_dropped++;
                        goto drop;
                }
        }

        skb->truesize += skb->data_len;
        dev->stats.rx_bytes += skb->len;
        dev->stats.rx_packets++;

        if (hdr->hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
                pr_debug("Needs csum!\n");
                if (!skb_partial_csum_set(skb,
                                          hdr->hdr.csum_start,
                                          hdr->hdr.csum_offset))
                        goto frame_err;
        }

        skb->protocol = eth_type_trans(skb, dev);
        pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
                 ntohs(skb->protocol), skb->len, skb->pkt_type);

        if (hdr->hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
                pr_debug("GSO!\n");
                switch (hdr->hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
                case VIRTIO_NET_HDR_GSO_TCPV4:
                        skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
                        break;
                case VIRTIO_NET_HDR_GSO_UDP:
                        skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
                        break;
                case VIRTIO_NET_HDR_GSO_TCPV6:
                        skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
                        break;
                default:
                        if (net_ratelimit())
                                printk(KERN_WARNING "%s: bad gso type %u.\n",
                                       dev->name, hdr->hdr.gso_type);
                        goto frame_err;
                }

                if (hdr->hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN)
                        skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;

                skb_shinfo(skb)->gso_size = hdr->hdr.gso_size;
                if (skb_shinfo(skb)->gso_size == 0) {
                        if (net_ratelimit())
                                printk(KERN_WARNING "%s: zero gso size.\n",
                                       dev->name);
                        goto frame_err;
                }

                /* Header must be checked, and gso_segs computed. */
                skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
                skb_shinfo(skb)->gso_segs = 0;
        }

        netif_receive_skb(skb);
        return;

frame_err:
        dev->stats.rx_frame_errors++;
drop:
        dev_kfree_skb(skb);
}

static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp)
{
        struct sk_buff *skb;
        struct scatterlist sg[2+MAX_SKB_FRAGS];
        int num, err, i;
        bool oom = false;

        sg_init_table(sg, 2+MAX_SKB_FRAGS);
        do {
                struct skb_vnet_hdr *hdr;

                skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN + NET_IP_ALIGN);
                if (unlikely(!skb)) {
                        oom = true;
                        break;
                }

                skb_reserve(skb, NET_IP_ALIGN);
                skb_put(skb, MAX_PACKET_LEN);

                hdr = skb_vnet_hdr(skb);
                sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr));

                if (vi->big_packets) {
                        for (i = 0; i < MAX_SKB_FRAGS; i++) {
                                skb_frag_t *f = &skb_shinfo(skb)->frags[i];
                                f->page = get_a_page(vi, gfp);
                                if (!f->page)
                                        break;

                                f->page_offset = 0;
                                f->size = PAGE_SIZE;

                                skb->data_len += PAGE_SIZE;
                                skb->len += PAGE_SIZE;

                                skb_shinfo(skb)->nr_frags++;
                        }
                }

                num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
                skb_queue_head(&vi->recv, skb);

                err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb);
                if (err < 0) {
                        skb_unlink(skb, &vi->recv);
                        trim_pages(vi, skb);
                        kfree_skb(skb);
                        break;
                }
                vi->num++;
        } while (err >= num);
        if (unlikely(vi->num > vi->max))
                vi->max = vi->num;
        vi->rvq->vq_ops->kick(vi->rvq);
        return !oom;
}

/* Returns false if we couldn't fill entirely (OOM). */
static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
{
        struct sk_buff *skb;
        struct scatterlist sg[1];
        int err;
        bool oom = false;

        if (!vi->mergeable_rx_bufs)
                return try_fill_recv_maxbufs(vi, gfp);

        do {
                skb_frag_t *f;

                skb = netdev_alloc_skb(vi->dev, GOOD_COPY_LEN + NET_IP_ALIGN);
                if (unlikely(!skb)) {
                        oom = true;
                        break;
                }

                skb_reserve(skb, NET_IP_ALIGN);

                f = &skb_shinfo(skb)->frags[0];
                f->page = get_a_page(vi, gfp);
                if (!f->page) {
                        oom = true;
                        kfree_skb(skb);
                        break;
                }

                f->page_offset = 0;
                f->size = PAGE_SIZE;

                skb_shinfo(skb)->nr_frags++;

                sg_init_one(sg, page_address(f->page), PAGE_SIZE);
                skb_queue_head(&vi->recv, skb);

                err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 1, skb);
                if (err < 0) {
                        skb_unlink(skb, &vi->recv);
                        kfree_skb(skb);
                        break;
                }
                vi->num++;
        } while (err > 0);
        if (unlikely(vi->num > vi->max))
                vi->max = vi->num;
        vi->rvq->vq_ops->kick(vi->rvq);
        return !oom;
}

static void skb_recv_done(struct virtqueue *rvq)
{
        struct virtnet_info *vi = rvq->vdev->priv;
        /* Schedule NAPI, Suppress further interrupts if successful. */
        if (napi_schedule_prep(&vi->napi)) {
                rvq->vq_ops->disable_cb(rvq);
                __napi_schedule(&vi->napi);
        }
}

static void refill_work(struct work_struct *work)
{
        struct virtnet_info *vi;
        bool still_empty;

        vi = container_of(work, struct virtnet_info, refill.work);
        napi_disable(&vi->napi);
        try_fill_recv(vi, GFP_KERNEL);
        still_empty = (vi->num == 0);
        napi_enable(&vi->napi);

        /* In theory, this can happen: if we don't get any buffers in
         * we will *never* try to fill again. */
        if (still_empty)
                schedule_delayed_work(&vi->refill, HZ/2);
}

static int virtnet_poll(struct napi_struct *napi, int budget)
{
        struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
        struct sk_buff *skb = NULL;
        unsigned int len, received = 0;

again:
        while (received < budget &&
               (skb = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) {
                __skb_unlink(skb, &vi->recv);
                receive_skb(vi->dev, skb, len);
                vi->num--;
                received++;
        }

        if (vi->num < vi->max / 2) {
                if (!try_fill_recv(vi, GFP_ATOMIC))
                        schedule_delayed_work(&vi->refill, 0);
        }

        /* Out of packets? */
        if (received < budget) {
                napi_complete(napi);
                if (unlikely(!vi->rvq->vq_ops->enable_cb(vi->rvq))
                    && napi_schedule_prep(napi)) {
                        vi->rvq->vq_ops->disable_cb(vi->rvq);
                        __napi_schedule(napi);
                        goto again;
                }
        }

        return received;
}

static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
{
        struct sk_buff *skb;
        unsigned int len, tot_sgs = 0;

        while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
                pr_debug("Sent skb %p\n", skb);
                __skb_unlink(skb, &vi->send);
                vi->dev->stats.tx_bytes += skb->len;
                vi->dev->stats.tx_packets++;
                tot_sgs += skb_vnet_hdr(skb)->num_sg;
                dev_kfree_skb_any(skb);
        }
        return tot_sgs;
}

static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
{
        struct scatterlist sg[2+MAX_SKB_FRAGS];
        struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
        const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;

        sg_init_table(sg, 2+MAX_SKB_FRAGS);

        pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);

        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                hdr->hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
                hdr->hdr.csum_start = skb->csum_start - skb_headroom(skb);
                hdr->hdr.csum_offset = skb->csum_offset;
        } else {
                hdr->hdr.flags = 0;
                hdr->hdr.csum_offset = hdr->hdr.csum_start = 0;
        }

        if (skb_is_gso(skb)) {
                hdr->hdr.hdr_len = skb_headlen(skb);
                hdr->hdr.gso_size = skb_shinfo(skb)->gso_size;
                if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
                        hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
                else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
                        hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
                else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
                        hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_UDP;
                else
                        BUG();
                if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_ECN)
                        hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_ECN;
        } else {
                hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;
                hdr->hdr.gso_size = hdr->hdr.hdr_len = 0;
        }

        hdr->mhdr.num_buffers = 0;

        /* Encode metadata header at front. */
        if (vi->mergeable_rx_bufs)
                sg_set_buf(sg, &hdr->mhdr, sizeof(hdr->mhdr));
        else
                sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr));

        hdr->num_sg = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
        return vi->svq->vq_ops->add_buf(vi->svq, sg, hdr->num_sg, 0, skb);
}

static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);
        int capacity;

again:
        /* Free up any pending old buffers before queueing new ones. */
        free_old_xmit_skbs(vi);

        /* Try to transmit */
        capacity = xmit_skb(vi, skb);

        /* This can happen with OOM and indirect buffers. */
        if (unlikely(capacity < 0)) {
                netif_stop_queue(dev);
                dev_warn(&dev->dev, "Unexpected full queue\n");
                if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
                        vi->svq->vq_ops->disable_cb(vi->svq);
                        netif_start_queue(dev);
                        goto again;
                }
                return NETDEV_TX_BUSY;
        }
        vi->svq->vq_ops->kick(vi->svq);

        /*
         * Put new one in send queue.  You'd expect we'd need this before
         * xmit_skb calls add_buf(), since the callback can be triggered
         * immediately after that.  But since the callback just triggers
         * another call back here, normal network xmit locking prevents the
         * race.
         */
        __skb_queue_head(&vi->send, skb);

        /* Don't wait up for transmitted skbs to be freed. */
        skb_orphan(skb);
        nf_reset(skb);

        /* Apparently nice girls don't return TX_BUSY; stop the queue
         * before it gets out of hand.  Naturally, this wastes entries. */
        if (capacity < 2+MAX_SKB_FRAGS) {
                netif_stop_queue(dev);
                if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
                        /* More just got used, free them then recheck. */
                        capacity += free_old_xmit_skbs(vi);
                        if (capacity >= 2+MAX_SKB_FRAGS) {
                                netif_start_queue(dev);
                                vi->svq->vq_ops->disable_cb(vi->svq);
                        }
                }
        }

        return NETDEV_TX_OK;
}

static int virtnet_set_mac_address(struct net_device *dev, void *p)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct virtio_device *vdev = vi->vdev;
        int ret;

        ret = eth_mac_addr(dev, p);
        if (ret)
                return ret;

        if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
                vdev->config->set(vdev, offsetof(struct virtio_net_config, mac),
                                  dev->dev_addr, dev->addr_len);

        return 0;
}

#ifdef CONFIG_NET_POLL_CONTROLLER
static void virtnet_netpoll(struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);

        napi_schedule(&vi->napi);
}
#endif

static int virtnet_open(struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);

        napi_enable(&vi->napi);

        /* If all buffers were filled by other side before we napi_enabled, we
         * won't get another interrupt, so process any outstanding packets
         * now.  virtnet_poll wants re-enable the queue, so we disable here.
         * We synchronize against interrupts via NAPI_STATE_SCHED */
        if (napi_schedule_prep(&vi->napi)) {
                vi->rvq->vq_ops->disable_cb(vi->rvq);
                __napi_schedule(&vi->napi);
        }
        return 0;
}

/*
 * Send command via the control virtqueue and check status.  Commands
 * supported by the hypervisor, as indicated by feature bits, should
 * never fail unless improperly formated.
 */
static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
                                 struct scatterlist *data, int out, int in)
{
        struct scatterlist *s, sg[VIRTNET_SEND_COMMAND_SG_MAX + 2];
        struct virtio_net_ctrl_hdr ctrl;
        virtio_net_ctrl_ack status = ~0;
        unsigned int tmp;
        int i;

        /* Caller should know better */
        BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ||
                (out + in > VIRTNET_SEND_COMMAND_SG_MAX));

        out++; /* Add header */
        in++; /* Add return status */

        ctrl.class = class;
        ctrl.cmd = cmd;

        sg_init_table(sg, out + in);

        sg_set_buf(&sg[0], &ctrl, sizeof(ctrl));
        for_each_sg(data, s, out + in - 2, i)
                sg_set_buf(&sg[i + 1], sg_virt(s), s->length);
        sg_set_buf(&sg[out + in - 1], &status, sizeof(status));

        BUG_ON(vi->cvq->vq_ops->add_buf(vi->cvq, sg, out, in, vi) < 0);

        vi->cvq->vq_ops->kick(vi->cvq);

        /*
         * Spin for a response, the kick causes an ioport write, trapping
         * into the hypervisor, so the request should be handled immediately.
         */
        while (!vi->cvq->vq_ops->get_buf(vi->cvq, &tmp))
                cpu_relax();

        return status == VIRTIO_NET_OK;
}

static int virtnet_close(struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);

        napi_disable(&vi->napi);

        return 0;
}

static int virtnet_set_tx_csum(struct net_device *dev, u32 data)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct virtio_device *vdev = vi->vdev;

        if (data && !virtio_has_feature(vdev, VIRTIO_NET_F_CSUM))
                return -ENOSYS;

        return ethtool_op_set_tx_hw_csum(dev, data);
}

static void virtnet_set_rx_mode(struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct scatterlist sg[2];
        u8 promisc, allmulti;
        struct virtio_net_ctrl_mac *mac_data;
        struct dev_addr_list *addr;
        struct netdev_hw_addr *ha;
        void *buf;
        int i;

        /* We can't dynamicaly set ndo_set_rx_mode, so return gracefully */
        if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
                return;

        promisc = ((dev->flags & IFF_PROMISC) != 0);
        allmulti = ((dev->flags & IFF_ALLMULTI) != 0);

        sg_init_one(sg, &promisc, sizeof(promisc));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
                                  VIRTIO_NET_CTRL_RX_PROMISC,
                                  sg, 1, 0))
                dev_warn(&dev->dev, "Failed to %sable promisc mode.\n",
                         promisc ? "en" : "dis");

        sg_init_one(sg, &allmulti, sizeof(allmulti));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
                                  VIRTIO_NET_CTRL_RX_ALLMULTI,
                                  sg, 1, 0))
                dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
                         allmulti ? "en" : "dis");

        /* MAC filter - use one buffer for both lists */
        mac_data = buf = kzalloc(((dev->uc.count + dev->mc_count) * ETH_ALEN) +
                                 (2 * sizeof(mac_data->entries)), GFP_ATOMIC);
        if (!buf) {
                dev_warn(&dev->dev, "No memory for MAC address buffer\n");
                return;
        }

        sg_init_table(sg, 2);

        /* Store the unicast list and count in the front of the buffer */
        mac_data->entries = dev->uc.count;
        i = 0;
        list_for_each_entry(ha, &dev->uc.list, list)
                memcpy(&mac_data->macs[i++][0], ha->addr, ETH_ALEN);

        sg_set_buf(&sg[0], mac_data,
                   sizeof(mac_data->entries) + (dev->uc.count * ETH_ALEN));

        /* multicast list and count fill the end */
        mac_data = (void *)&mac_data->macs[dev->uc.count][0];

        mac_data->entries = dev->mc_count;
        addr = dev->mc_list;
        for (i = 0; i < dev->mc_count; i++, addr = addr->next)
                memcpy(&mac_data->macs[i][0], addr->da_addr, ETH_ALEN);

        sg_set_buf(&sg[1], mac_data,
                   sizeof(mac_data->entries) + (dev->mc_count * ETH_ALEN));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
                                  VIRTIO_NET_CTRL_MAC_TABLE_SET,
                                  sg, 2, 0))
                dev_warn(&dev->dev, "Failed to set MAC fitler table.\n");

        kfree(buf);
}

static void virtnet_vlan_rx_add_vid(struct net_device *dev, u16 vid)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct scatterlist sg;

        sg_init_one(&sg, &vid, sizeof(vid));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
                                  VIRTIO_NET_CTRL_VLAN_ADD, &sg, 1, 0))
                dev_warn(&dev->dev, "Failed to add VLAN ID %d.\n", vid);
}

static void virtnet_vlan_rx_kill_vid(struct net_device *dev, u16 vid)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct scatterlist sg;

        sg_init_one(&sg, &vid, sizeof(vid));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
                                  VIRTIO_NET_CTRL_VLAN_DEL, &sg, 1, 0))
                dev_warn(&dev->dev, "Failed to kill VLAN ID %d.\n", vid);
}

static const struct ethtool_ops virtnet_ethtool_ops = {
        .set_tx_csum = virtnet_set_tx_csum,
        .set_sg = ethtool_op_set_sg,
        .set_tso = ethtool_op_set_tso,
        .set_ufo = ethtool_op_set_ufo,
        .get_link = ethtool_op_get_link,
};

#define MIN_MTU 68
#define MAX_MTU 65535

static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
{
        if (new_mtu < MIN_MTU || new_mtu > MAX_MTU)
                return -EINVAL;
        dev->mtu = new_mtu;
        return 0;
}

static const struct net_device_ops virtnet_netdev = {
        .ndo_open            = virtnet_open,
        .ndo_stop            = virtnet_close,
        .ndo_start_xmit      = start_xmit,
        .ndo_validate_addr   = eth_validate_addr,
        .ndo_set_mac_address = virtnet_set_mac_address,
        .ndo_set_rx_mode     = virtnet_set_rx_mode,
        .ndo_change_mtu      = virtnet_change_mtu,
        .ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
        .ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
#ifdef CONFIG_NET_POLL_CONTROLLER
        .ndo_poll_controller = virtnet_netpoll,
#endif
};

static void virtnet_update_status(struct virtnet_info *vi)
{
        u16 v;

        if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS))
                return;

        vi->vdev->config->get(vi->vdev,
                              offsetof(struct virtio_net_config, status),
                              &v, sizeof(v));

        /* Ignore unknown (future) status bits */
        v &= VIRTIO_NET_S_LINK_UP;

        if (vi->status == v)
                return;

        vi->status = v;

        if (vi->status & VIRTIO_NET_S_LINK_UP) {
                netif_carrier_on(vi->dev);
                netif_wake_queue(vi->dev);
        } else {
                netif_carrier_off(vi->dev);
                netif_stop_queue(vi->dev);
        }
}

static void virtnet_config_changed(struct virtio_device *vdev)
{
        struct virtnet_info *vi = vdev->priv;

        virtnet_update_status(vi);
}

static int virtnet_probe(struct virtio_device *vdev)
{
        int err;
        struct net_device *dev;
        struct virtnet_info *vi;
        struct virtqueue *vqs[3];
        vq_callback_t *callbacks[] = { skb_recv_done, skb_xmit_done, NULL};
        const char *names[] = { "input", "output", "control" };
        int nvqs;

        /* Allocate ourselves a network device with room for our info */
        dev = alloc_etherdev(sizeof(struct virtnet_info));
        if (!dev)
                return -ENOMEM;

        /* Set up network device as normal. */
        dev->netdev_ops = &virtnet_netdev;
        dev->features = NETIF_F_HIGHDMA;
        SET_ETHTOOL_OPS(dev, &virtnet_ethtool_ops);
        SET_NETDEV_DEV(dev, &vdev->dev);

        /* Do we support "hardware" checksums? */
        if (csum && virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
                /* This opens up the world of extra features. */
                dev->features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
                if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_GSO)) {
                        dev->features |= NETIF_F_TSO | NETIF_F_UFO
                                | NETIF_F_TSO_ECN | NETIF_F_TSO6;
                }
                /* Individual feature bits: what can host handle? */
                if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO4))
                        dev->features |= NETIF_F_TSO;
                if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO6))
                        dev->features |= NETIF_F_TSO6;
                if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_ECN))
                        dev->features |= NETIF_F_TSO_ECN;
                if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_UFO))
                        dev->features |= NETIF_F_UFO;
        }

        /* Configuration may specify what MAC to use.  Otherwise random. */
        if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
                vdev->config->get(vdev,
                                  offsetof(struct virtio_net_config, mac),
                                  dev->dev_addr, dev->addr_len);
        } else
                random_ether_addr(dev->dev_addr);

        /* Set up our device-specific information */
        vi = netdev_priv(dev);
        netif_napi_add(dev, &vi->napi, virtnet_poll, napi_weight);
        vi->dev = dev;
        vi->vdev = vdev;
        vdev->priv = vi;
        vi->pages = NULL;
        INIT_DELAYED_WORK(&vi->refill, refill_work);

        /* If we can receive ANY GSO packets, we must allocate large ones. */
        if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4)
            || virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6)
            || virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_ECN))
                vi->big_packets = true;

        if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
                vi->mergeable_rx_bufs = true;

        /* We expect two virtqueues, receive then send,
         * and optionally control. */
        nvqs = virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ? 3 : 2;

        err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
        if (err)
                goto free;

        vi->rvq = vqs[0];
        vi->svq = vqs[1];

        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)) {
                vi->cvq = vqs[2];

                if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
                        dev->features |= NETIF_F_HW_VLAN_FILTER;
        }

        /* Initialize our empty receive and send queues. */
        skb_queue_head_init(&vi->recv);
        skb_queue_head_init(&vi->send);

        err = register_netdev(dev);
        if (err) {
                pr_debug("virtio_net: registering device failed\n");
                goto free_vqs;
        }

        /* Last of all, set up some receive buffers. */
        try_fill_recv(vi, GFP_KERNEL);

        /* If we didn't even get one input buffer, we're useless. */
        if (vi->num == 0) {
                err = -ENOMEM;
                goto unregister;
        }

        vi->status = VIRTIO_NET_S_LINK_UP;
        virtnet_update_status(vi);
        netif_carrier_on(dev);

        pr_debug("virtnet: registered device %s\n", dev->name);
        return 0;

unregister:
        unregister_netdev(dev);
        cancel_delayed_work_sync(&vi->refill);
free_vqs:
        vdev->config->del_vqs(vdev);
free:
        free_netdev(dev);
        return err;
}

static void __devexit virtnet_remove(struct virtio_device *vdev)
{
        struct virtnet_info *vi = vdev->priv;
        struct sk_buff *skb;

        /* Stop all the virtqueues. */
        vdev->config->reset(vdev);

        /* Free our skbs in send and recv queues, if any. */
        while ((skb = __skb_dequeue(&vi->recv)) != NULL) {
                kfree_skb(skb);
                vi->num--;
        }
        __skb_queue_purge(&vi->send);

        BUG_ON(vi->num != 0);

        unregister_netdev(vi->dev);
        cancel_delayed_work_sync(&vi->refill);

        vdev->config->del_vqs(vi->vdev);

        while (vi->pages)
                __free_pages(get_a_page(vi, GFP_KERNEL), 0);

        free_netdev(vi->dev);
}

static struct virtio_device_id id_table[] = {
        { VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
        { 0 },
};

static unsigned int features[] = {
        VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM,
        VIRTIO_NET_F_GSO, VIRTIO_NET_F_MAC,
        VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
        VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
        VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO,
        VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
        VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
};

static struct virtio_driver virtio_net_driver = {
        .feature_table = features,
        .feature_table_size = ARRAY_SIZE(features),
        .driver.name =  KBUILD_MODNAME,
        .driver.owner = THIS_MODULE,
        .id_table =     id_table,
        .probe =        virtnet_probe,
        .remove =       __devexit_p(virtnet_remove),
        .config_changed = virtnet_config_changed,
};

static int __init init(void)
{
        return register_virtio_driver(&virtio_net_driver);
}

static void __exit fini(void)
{
        unregister_virtio_driver(&virtio_net_driver);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio network driver");
MODULE_LICENSE("GPL");