xen-netfront.c

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/*
 * Virtual network driver for conversing with remote driver backends.
 *
 * Copyright (c) 2002-2005, K A Fraser
 * Copyright (c) 2005, XenSource Ltd
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/ethtool.h>
#include <linux/if_ether.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/moduleparam.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <net/ip.h>

#include <asm/xen/page.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/page.h>
#include <xen/platform_pci.h>
#include <xen/grant_table.h>

#include <xen/interface/io/netif.h>
#include <xen/interface/memory.h>
#include <xen/interface/grant_table.h>

static const struct ethtool_ops xennet_ethtool_ops;

struct netfront_cb {
    int pull_to;
};

#define NETFRONT_SKB_CB(skb)    ((struct netfront_cb *)((skb)->cb))

#define RX_COPY_THRESHOLD 256

#define GRANT_INVALID_REF   0

#define NET_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
#define NET_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)
#define TX_MAX_TARGET min_t(int, NET_TX_RING_SIZE, 256)

struct netfront_stats {
    u64         rx_packets;
    u64         tx_packets;
    u64         rx_bytes;
    u64         tx_bytes;
    struct u64_stats_sync   syncp;
};

struct netfront_info {
    struct list_head list;
    struct net_device *netdev;

    struct napi_struct napi;

    unsigned int evtchn;
    struct xenbus_device *xbdev;

    spinlock_t   tx_lock;
    struct xen_netif_tx_front_ring tx;
    int tx_ring_ref;

    /*
     * {tx,rx}_skbs store outstanding skbuffs. Free tx_skb entries
     * are linked from tx_skb_freelist through skb_entry.link.
     *
     *  NB. Freelist index entries are always going to be less than
     *  PAGE_OFFSET, whereas pointers to skbs will always be equal or
     *  greater than PAGE_OFFSET: we use this property to distinguish
     *  them.
     */
    union skb_entry {
        struct sk_buff *skb;
        unsigned long link;
    } tx_skbs[NET_TX_RING_SIZE];
    grant_ref_t gref_tx_head;
    grant_ref_t grant_tx_ref[NET_TX_RING_SIZE];
    unsigned tx_skb_freelist;

    spinlock_t   rx_lock ____cacheline_aligned_in_smp;
    struct xen_netif_rx_front_ring rx;
    int rx_ring_ref;

    /* Receive-ring batched refills. */
#define RX_MIN_TARGET 8
#define RX_DFL_MIN_TARGET 64
#define RX_MAX_TARGET min_t(int, NET_RX_RING_SIZE, 256)
    unsigned rx_min_target, rx_max_target, rx_target;
    struct sk_buff_head rx_batch;

    struct timer_list rx_refill_timer;

    struct sk_buff *rx_skbs[NET_RX_RING_SIZE];
    grant_ref_t gref_rx_head;
    grant_ref_t grant_rx_ref[NET_RX_RING_SIZE];

    unsigned long rx_pfn_array[NET_RX_RING_SIZE];
    struct multicall_entry rx_mcl[NET_RX_RING_SIZE+1];
    struct mmu_update rx_mmu[NET_RX_RING_SIZE];

    /* Statistics */
    struct netfront_stats __percpu *stats;

    unsigned long rx_gso_checksum_fixup;
};

struct netfront_rx_info {
    struct xen_netif_rx_response rx;
    struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
};

static void skb_entry_set_link(union skb_entry *list, unsigned short id)
{
    list->link = id;
}

static int skb_entry_is_link(const union skb_entry *list)
{
    BUILD_BUG_ON(sizeof(list->skb) != sizeof(list->link));
    return (unsigned long)list->skb < PAGE_OFFSET;
}

/*
 * Access macros for acquiring freeing slots in tx_skbs[].
 */

static void add_id_to_freelist(unsigned *head, union skb_entry *list,
                   unsigned short id)
{
    skb_entry_set_link(&list[id], *head);
    *head = id;
}

static unsigned short get_id_from_freelist(unsigned *head,
                       union skb_entry *list)
{
    unsigned int id = *head;
    *head = list[id].link;
    return id;
}

static int xennet_rxidx(RING_IDX idx)
{
    return idx & (NET_RX_RING_SIZE - 1);
}

static struct sk_buff *xennet_get_rx_skb(struct netfront_info *np,
                     RING_IDX ri)
{
    int i = xennet_rxidx(ri);
    struct sk_buff *skb = np->rx_skbs[i];
    np->rx_skbs[i] = NULL;
    return skb;
}

static grant_ref_t xennet_get_rx_ref(struct netfront_info *np,
                        RING_IDX ri)
{
    int i = xennet_rxidx(ri);
    grant_ref_t ref = np->grant_rx_ref[i];
    np->grant_rx_ref[i] = GRANT_INVALID_REF;
    return ref;
}

#ifdef CONFIG_SYSFS
static int xennet_sysfs_addif(struct net_device *netdev);
static void xennet_sysfs_delif(struct net_device *netdev);
#else /* !CONFIG_SYSFS */
#define xennet_sysfs_addif(dev) (0)
#define xennet_sysfs_delif(dev) do { } while (0)
#endif

static bool xennet_can_sg(struct net_device *dev)
{
    return dev->features & NETIF_F_SG;
}


static void rx_refill_timeout(unsigned long data)
{
    struct net_device *dev = (struct net_device *)data;
    struct netfront_info *np = netdev_priv(dev);
    napi_schedule(&np->napi);
}

static int netfront_tx_slot_available(struct netfront_info *np)
{
    return (np->tx.req_prod_pvt - np->tx.rsp_cons) <
        (TX_MAX_TARGET - MAX_SKB_FRAGS - 2);
}

static void xennet_maybe_wake_tx(struct net_device *dev)
{
    struct netfront_info *np = netdev_priv(dev);

    if (unlikely(netif_queue_stopped(dev)) &&
        netfront_tx_slot_available(np) &&
        likely(netif_running(dev)))
        netif_wake_queue(dev);
}

static void xennet_alloc_rx_buffers(struct net_device *dev)
{
    unsigned short id;
    struct netfront_info *np = netdev_priv(dev);
    struct sk_buff *skb;
    struct page *page;
    int i, batch_target, notify;
    RING_IDX req_prod = np->rx.req_prod_pvt;
    grant_ref_t ref;
    unsigned long pfn;
    void *vaddr;
    struct xen_netif_rx_request *req;

    if (unlikely(!netif_carrier_ok(dev)))
        return;

    /*
     * Allocate skbuffs greedily, even though we batch updates to the
     * receive ring. This creates a less bursty demand on the memory
     * allocator, so should reduce the chance of failed allocation requests
     * both for ourself and for other kernel subsystems.
     */
    batch_target = np->rx_target - (req_prod - np->rx.rsp_cons);
    for (i = skb_queue_len(&np->rx_batch); i < batch_target; i++) {
        skb = __netdev_alloc_skb(dev, RX_COPY_THRESHOLD + NET_IP_ALIGN,
                     GFP_ATOMIC | __GFP_NOWARN);
        if (unlikely(!skb))
            goto no_skb;

        /* Align ip header to a 16 bytes boundary */
        skb_reserve(skb, NET_IP_ALIGN);

        page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
        if (!page) {
            kfree_skb(skb);
no_skb:
            /* Any skbuffs queued for refill? Force them out. */
            if (i != 0)
                goto refill;
            /* Could not allocate any skbuffs. Try again later. */
            mod_timer(&np->rx_refill_timer,
                  jiffies + (HZ/10));
            break;
        }

        __skb_fill_page_desc(skb, 0, page, 0, 0);
        skb_shinfo(skb)->nr_frags = 1;
        __skb_queue_tail(&np->rx_batch, skb);
    }

    /* Is the batch large enough to be worthwhile? */
    if (i < (np->rx_target/2)) {
        if (req_prod > np->rx.sring->req_prod)
            goto push;
        return;
    }

    /* Adjust our fill target if we risked running out of buffers. */
    if (((req_prod - np->rx.sring->rsp_prod) < (np->rx_target / 4)) &&
        ((np->rx_target *= 2) > np->rx_max_target))
        np->rx_target = np->rx_max_target;

 refill:
    for (i = 0; ; i++) {
        skb = __skb_dequeue(&np->rx_batch);
        if (skb == NULL)
            break;

        skb->dev = dev;

        id = xennet_rxidx(req_prod + i);

        BUG_ON(np->rx_skbs[id]);
        np->rx_skbs[id] = skb;

        ref = gnttab_claim_grant_reference(&np->gref_rx_head);
        BUG_ON((signed short)ref < 0);
        np->grant_rx_ref[id] = ref;

        pfn = page_to_pfn(skb_frag_page(&skb_shinfo(skb)->frags[0]));
        vaddr = page_address(skb_frag_page(&skb_shinfo(skb)->frags[0]));

        req = RING_GET_REQUEST(&np->rx, req_prod + i);
        gnttab_grant_foreign_access_ref(ref,
                        np->xbdev->otherend_id,
                        pfn_to_mfn(pfn),
                        0);

        req->id = id;
        req->gref = ref;
    }

    wmb();      /* barrier so backend seens requests */

    /* Above is a suitable barrier to ensure backend will see requests. */
    np->rx.req_prod_pvt = req_prod + i;
 push:
    RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->rx, notify);
    if (notify)
        notify_remote_via_irq(np->netdev->irq);
}

static int xennet_open(struct net_device *dev)
{
    struct netfront_info *np = netdev_priv(dev);

    napi_enable(&np->napi);

    spin_lock_bh(&np->rx_lock);
    if (netif_carrier_ok(dev)) {
        xennet_alloc_rx_buffers(dev);
        np->rx.sring->rsp_event = np->rx.rsp_cons + 1;
        if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
            napi_schedule(&np->napi);
    }
    spin_unlock_bh(&np->rx_lock);

    netif_start_queue(dev);

    return 0;
}

static void xennet_tx_buf_gc(struct net_device *dev)
{
    RING_IDX cons, prod;
    unsigned short id;
    struct netfront_info *np = netdev_priv(dev);
    struct sk_buff *skb;

    BUG_ON(!netif_carrier_ok(dev));

    do {
        prod = np->tx.sring->rsp_prod;
        rmb(); /* Ensure we see responses up to 'rp'. */

        for (cons = np->tx.rsp_cons; cons != prod; cons++) {
            struct xen_netif_tx_response *txrsp;

            txrsp = RING_GET_RESPONSE(&np->tx, cons);
            if (txrsp->status == XEN_NETIF_RSP_NULL)
                continue;

            id  = txrsp->id;
            skb = np->tx_skbs[id].skb;
            if (unlikely(gnttab_query_foreign_access(
                np->grant_tx_ref[id]) != 0)) {
                printk(KERN_ALERT "xennet_tx_buf_gc: warning "
                       "-- grant still in use by backend "
                       "domain.\n");
                BUG();
            }
            gnttab_end_foreign_access_ref(
                np->grant_tx_ref[id], GNTMAP_readonly);
            gnttab_release_grant_reference(
                &np->gref_tx_head, np->grant_tx_ref[id]);
            np->grant_tx_ref[id] = GRANT_INVALID_REF;
            add_id_to_freelist(&np->tx_skb_freelist, np->tx_skbs, id);
            dev_kfree_skb_irq(skb);
        }

        np->tx.rsp_cons = prod;

        /*
         * Set a new event, then check for race with update of tx_cons.
         * Note that it is essential to schedule a callback, no matter
         * how few buffers are pending. Even if there is space in the
         * transmit ring, higher layers may be blocked because too much
         * data is outstanding: in such cases notification from Xen is
         * likely to be the only kick that we'll get.
         */
        np->tx.sring->rsp_event =
            prod + ((np->tx.sring->req_prod - prod) >> 1) + 1;
        mb();       /* update shared area */
    } while ((cons == prod) && (prod != np->tx.sring->rsp_prod));

    xennet_maybe_wake_tx(dev);
}

static void xennet_make_frags(struct sk_buff *skb, struct net_device *dev,
                  struct xen_netif_tx_request *tx)
{
    struct netfront_info *np = netdev_priv(dev);
    char *data = skb->data;
    unsigned long mfn;
    RING_IDX prod = np->tx.req_prod_pvt;
    int frags = skb_shinfo(skb)->nr_frags;
    unsigned int offset = offset_in_page(data);
    unsigned int len = skb_headlen(skb);
    unsigned int id;
    grant_ref_t ref;
    int i;

    /* While the header overlaps a page boundary (including being
       larger than a page), split it it into page-sized chunks. */
    while (len > PAGE_SIZE - offset) {
        tx->size = PAGE_SIZE - offset;
        tx->flags |= XEN_NETTXF_more_data;
        len -= tx->size;
        data += tx->size;
        offset = 0;

        id = get_id_from_freelist(&np->tx_skb_freelist, np->tx_skbs);
        np->tx_skbs[id].skb = skb_get(skb);
        tx = RING_GET_REQUEST(&np->tx, prod++);
        tx->id = id;
        ref = gnttab_claim_grant_reference(&np->gref_tx_head);
        BUG_ON((signed short)ref < 0);

        mfn = virt_to_mfn(data);
        gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
                        mfn, GNTMAP_readonly);

        tx->gref = np->grant_tx_ref[id] = ref;
        tx->offset = offset;
        tx->size = len;
        tx->flags = 0;
    }

    /* Grant backend access to each skb fragment page. */
    for (i = 0; i < frags; i++) {
        skb_frag_t *frag = skb_shinfo(skb)->frags + i;
        struct page *page = skb_frag_page(frag);

        len = skb_frag_size(frag);
        offset = frag->page_offset;

        /* Data must not cross a page boundary. */
        BUG_ON(len + offset > PAGE_SIZE<<compound_order(page));

        /* Skip unused frames from start of page */
        page += offset >> PAGE_SHIFT;
        offset &= ~PAGE_MASK;

        while (len > 0) {
            unsigned long bytes;

            BUG_ON(offset >= PAGE_SIZE);

            bytes = PAGE_SIZE - offset;
            if (bytes > len)
                bytes = len;

            tx->flags |= XEN_NETTXF_more_data;

            id = get_id_from_freelist(&np->tx_skb_freelist,
                          np->tx_skbs);
            np->tx_skbs[id].skb = skb_get(skb);
            tx = RING_GET_REQUEST(&np->tx, prod++);
            tx->id = id;
            ref = gnttab_claim_grant_reference(&np->gref_tx_head);
            BUG_ON((signed short)ref < 0);

            mfn = pfn_to_mfn(page_to_pfn(page));
            gnttab_grant_foreign_access_ref(ref,
                            np->xbdev->otherend_id,
                            mfn, GNTMAP_readonly);

            tx->gref = np->grant_tx_ref[id] = ref;
            tx->offset = offset;
            tx->size = bytes;
            tx->flags = 0;

            offset += bytes;
            len -= bytes;

            /* Next frame */
            if (offset == PAGE_SIZE && len) {
                BUG_ON(!PageCompound(page));
                page++;
                offset = 0;
            }
        }
    }

    np->tx.req_prod_pvt = prod;
}

/*
 * Count how many ring slots are required to send the frags of this
 * skb. Each frag might be a compound page.
 */
static int xennet_count_skb_frag_slots(struct sk_buff *skb)
{
    int i, frags = skb_shinfo(skb)->nr_frags;
    int pages = 0;

    for (i = 0; i < frags; i++) {
        skb_frag_t *frag = skb_shinfo(skb)->frags + i;
        unsigned long size = skb_frag_size(frag);
        unsigned long offset = frag->page_offset;

        /* Skip unused frames from start of page */
        offset &= ~PAGE_MASK;

        pages += PFN_UP(offset + size);
    }

    return pages;
}

static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
    unsigned short id;
    struct netfront_info *np = netdev_priv(dev);
    struct netfront_stats *stats = this_cpu_ptr(np->stats);
    struct xen_netif_tx_request *tx;
    struct xen_netif_extra_info *extra;
    char *data = skb->data;
    RING_IDX i;
    grant_ref_t ref;
    unsigned long mfn;
    int notify;
    int slots;
    unsigned int offset = offset_in_page(data);
    unsigned int len = skb_headlen(skb);
    unsigned long flags;

    slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +
        xennet_count_skb_frag_slots(skb);
    if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
        net_alert_ratelimited(
            "xennet: skb rides the rocket: %d slots\n", slots);
        goto drop;
    }

    spin_lock_irqsave(&np->tx_lock, flags);

    if (unlikely(!netif_carrier_ok(dev) ||
             (slots > 1 && !xennet_can_sg(dev)) ||
             netif_needs_gso(skb, netif_skb_features(skb)))) {
        spin_unlock_irqrestore(&np->tx_lock, flags);
        goto drop;
    }

    i = np->tx.req_prod_pvt;

    id = get_id_from_freelist(&np->tx_skb_freelist, np->tx_skbs);
    np->tx_skbs[id].skb = skb;

    tx = RING_GET_REQUEST(&np->tx, i);

    tx->id   = id;
    ref = gnttab_claim_grant_reference(&np->gref_tx_head);
    BUG_ON((signed short)ref < 0);
    mfn = virt_to_mfn(data);
    gnttab_grant_foreign_access_ref(
        ref, np->xbdev->otherend_id, mfn, GNTMAP_readonly);
    tx->gref = np->grant_tx_ref[id] = ref;
    tx->offset = offset;
    tx->size = len;
    extra = NULL;

    tx->flags = 0;
    if (skb->ip_summed == CHECKSUM_PARTIAL)
        /* local packet? */
        tx->flags |= XEN_NETTXF_csum_blank | XEN_NETTXF_data_validated;
    else if (skb->ip_summed == CHECKSUM_UNNECESSARY)
        /* remote but checksummed. */
        tx->flags |= XEN_NETTXF_data_validated;

    if (skb_shinfo(skb)->gso_size) {
        struct xen_netif_extra_info *gso;

        gso = (struct xen_netif_extra_info *)
            RING_GET_REQUEST(&np->tx, ++i);

        if (extra)
            extra->flags |= XEN_NETIF_EXTRA_FLAG_MORE;
        else
            tx->flags |= XEN_NETTXF_extra_info;

        gso->u.gso.size = skb_shinfo(skb)->gso_size;
        gso->u.gso.type = XEN_NETIF_GSO_TYPE_TCPV4;
        gso->u.gso.pad = 0;
        gso->u.gso.features = 0;

        gso->type = XEN_NETIF_EXTRA_TYPE_GSO;
        gso->flags = 0;
        extra = gso;
    }

    np->tx.req_prod_pvt = i + 1;

    xennet_make_frags(skb, dev, tx);
    tx->size = skb->len;

    RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->tx, notify);
    if (notify)
        notify_remote_via_irq(np->netdev->irq);

    u64_stats_update_begin(&stats->syncp);
    stats->tx_bytes += skb->len;
    stats->tx_packets++;
    u64_stats_update_end(&stats->syncp);

    /* Note: It is not safe to access skb after xennet_tx_buf_gc()! */
    xennet_tx_buf_gc(dev);

    if (!netfront_tx_slot_available(np))
        netif_stop_queue(dev);

    spin_unlock_irqrestore(&np->tx_lock, flags);

    return NETDEV_TX_OK;

 drop:
    dev->stats.tx_dropped++;
    dev_kfree_skb(skb);
    return NETDEV_TX_OK;
}

static int xennet_close(struct net_device *dev)
{
    struct netfront_info *np = netdev_priv(dev);
    netif_stop_queue(np->netdev);
    napi_disable(&np->napi);
    return 0;
}

static void xennet_move_rx_slot(struct netfront_info *np, struct sk_buff *skb,
                grant_ref_t ref)
{
    int new = xennet_rxidx(np->rx.req_prod_pvt);

    BUG_ON(np->rx_skbs[new]);
    np->rx_skbs[new] = skb;
    np->grant_rx_ref[new] = ref;
    RING_GET_REQUEST(&np->rx, np->rx.req_prod_pvt)->id = new;
    RING_GET_REQUEST(&np->rx, np->rx.req_prod_pvt)->gref = ref;
    np->rx.req_prod_pvt++;
}

static int xennet_get_extras(struct netfront_info *np,
                 struct xen_netif_extra_info *extras,
                 RING_IDX rp)

{
    struct xen_netif_extra_info *extra;
    struct device *dev = &np->netdev->dev;
    RING_IDX cons = np->rx.rsp_cons;
    int err = 0;

    do {
        struct sk_buff *skb;
        grant_ref_t ref;

        if (unlikely(cons + 1 == rp)) {
            if (net_ratelimit())
                dev_warn(dev, "Missing extra info\n");
            err = -EBADR;
            break;
        }

        extra = (struct xen_netif_extra_info *)
            RING_GET_RESPONSE(&np->rx, ++cons);

        if (unlikely(!extra->type ||
                 extra->type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
            if (net_ratelimit())
                dev_warn(dev, "Invalid extra type: %d\n",
                    extra->type);
            err = -EINVAL;
        } else {
            memcpy(&extras[extra->type - 1], extra,
                   sizeof(*extra));
        }

        skb = xennet_get_rx_skb(np, cons);
        ref = xennet_get_rx_ref(np, cons);
        xennet_move_rx_slot(np, skb, ref);
    } while (extra->flags & XEN_NETIF_EXTRA_FLAG_MORE);

    np->rx.rsp_cons = cons;
    return err;
}

static int xennet_get_responses(struct netfront_info *np,
                struct netfront_rx_info *rinfo, RING_IDX rp,
                struct sk_buff_head *list)
{
    struct xen_netif_rx_response *rx = &rinfo->rx;
    struct xen_netif_extra_info *extras = rinfo->extras;
    struct device *dev = &np->netdev->dev;
    RING_IDX cons = np->rx.rsp_cons;
    struct sk_buff *skb = xennet_get_rx_skb(np, cons);
    grant_ref_t ref = xennet_get_rx_ref(np, cons);
    int max = MAX_SKB_FRAGS + (rx->status <= RX_COPY_THRESHOLD);
    int frags = 1;
    int err = 0;
    unsigned long ret;

    if (rx->flags & XEN_NETRXF_extra_info) {
        err = xennet_get_extras(np, extras, rp);
        cons = np->rx.rsp_cons;
    }

    for (;;) {
        if (unlikely(rx->status < 0 ||
                 rx->offset + rx->status > PAGE_SIZE)) {
            if (net_ratelimit())
                dev_warn(dev, "rx->offset: %x, size: %u\n",
                     rx->offset, rx->status);
            xennet_move_rx_slot(np, skb, ref);
            err = -EINVAL;
            goto next;
        }

        /*
         * This definitely indicates a bug, either in this driver or in
         * the backend driver. In future this should flag the bad
         * situation to the system controller to reboot the backed.
         */
        if (ref == GRANT_INVALID_REF) {
            if (net_ratelimit())
                dev_warn(dev, "Bad rx response id %d.\n",
                     rx->id);
            err = -EINVAL;
            goto next;
        }

        ret = gnttab_end_foreign_access_ref(ref, 0);
        BUG_ON(!ret);

        gnttab_release_grant_reference(&np->gref_rx_head, ref);

        __skb_queue_tail(list, skb);

next:
        if (!(rx->flags & XEN_NETRXF_more_data))
            break;

        if (cons + frags == rp) {
            if (net_ratelimit())
                dev_warn(dev, "Need more frags\n");
            err = -ENOENT;
            break;
        }

        rx = RING_GET_RESPONSE(&np->rx, cons + frags);
        skb = xennet_get_rx_skb(np, cons + frags);
        ref = xennet_get_rx_ref(np, cons + frags);
        frags++;
    }

    if (unlikely(frags > max)) {
        if (net_ratelimit())
            dev_warn(dev, "Too many frags\n");
        err = -E2BIG;
    }

    if (unlikely(err))
        np->rx.rsp_cons = cons + frags;

    return err;
}

static int xennet_set_skb_gso(struct sk_buff *skb,
                  struct xen_netif_extra_info *gso)
{
    if (!gso->u.gso.size) {
        if (net_ratelimit())
            printk(KERN_WARNING "GSO size must not be zero.\n");
        return -EINVAL;
    }

    /* Currently only TCPv4 S.O. is supported. */
    if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4) {
        if (net_ratelimit())
            printk(KERN_WARNING "Bad GSO type %d.\n", gso->u.gso.type);
        return -EINVAL;
    }

    skb_shinfo(skb)->gso_size = gso->u.gso.size;
    skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;

    /* 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 RING_IDX xennet_fill_frags(struct netfront_info *np,
                  struct sk_buff *skb,
                  struct sk_buff_head *list)
{
    struct skb_shared_info *shinfo = skb_shinfo(skb);
    int nr_frags = shinfo->nr_frags;
    RING_IDX cons = np->rx.rsp_cons;
    struct sk_buff *nskb;

    while ((nskb = __skb_dequeue(list))) {
        struct xen_netif_rx_response *rx =
            RING_GET_RESPONSE(&np->rx, ++cons);
        skb_frag_t *nfrag = &skb_shinfo(nskb)->frags[0];

        __skb_fill_page_desc(skb, nr_frags,
                     skb_frag_page(nfrag),
                     rx->offset, rx->status);

        skb->data_len += rx->status;

        skb_shinfo(nskb)->nr_frags = 0;
        kfree_skb(nskb);

        nr_frags++;
    }

    shinfo->nr_frags = nr_frags;
    return cons;
}

static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
{
    struct iphdr *iph;
    unsigned char *th;
    int err = -EPROTO;
    int recalculate_partial_csum = 0;

    /*
     * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
     * peers can fail to set NETRXF_csum_blank when sending a GSO
     * frame. In this case force the SKB to CHECKSUM_PARTIAL and
     * recalculate the partial checksum.
     */
    if (skb->ip_summed != CHECKSUM_PARTIAL && skb_is_gso(skb)) {
        struct netfront_info *np = netdev_priv(dev);
        np->rx_gso_checksum_fixup++;
        skb->ip_summed = CHECKSUM_PARTIAL;
        recalculate_partial_csum = 1;
    }

    /* A non-CHECKSUM_PARTIAL SKB does not require setup. */
    if (skb->ip_summed != CHECKSUM_PARTIAL)
        return 0;

    if (skb->protocol != htons(ETH_P_IP))
        goto out;

    iph = (void *)skb->data;
    th = skb->data + 4 * iph->ihl;
    if (th >= skb_tail_pointer(skb))
        goto out;

    skb->csum_start = th - skb->head;
    switch (iph->protocol) {
    case IPPROTO_TCP:
        skb->csum_offset = offsetof(struct tcphdr, check);

        if (recalculate_partial_csum) {
            struct tcphdr *tcph = (struct tcphdr *)th;
            tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
                             skb->len - iph->ihl*4,
                             IPPROTO_TCP, 0);
        }
        break;
    case IPPROTO_UDP:
        skb->csum_offset = offsetof(struct udphdr, check);

        if (recalculate_partial_csum) {
            struct udphdr *udph = (struct udphdr *)th;
            udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
                             skb->len - iph->ihl*4,
                             IPPROTO_UDP, 0);
        }
        break;
    default:
        if (net_ratelimit())
            printk(KERN_ERR "Attempting to checksum a non-"
                   "TCP/UDP packet, dropping a protocol"
                   " %d packet", iph->protocol);
        goto out;
    }

    if ((th + skb->csum_offset + 2) > skb_tail_pointer(skb))
        goto out;

    err = 0;

out:
    return err;
}

static int handle_incoming_queue(struct net_device *dev,
                 struct sk_buff_head *rxq)
{
    struct netfront_info *np = netdev_priv(dev);
    struct netfront_stats *stats = this_cpu_ptr(np->stats);
    int packets_dropped = 0;
    struct sk_buff *skb;

    while ((skb = __skb_dequeue(rxq)) != NULL) {
        int pull_to = NETFRONT_SKB_CB(skb)->pull_to;

        __pskb_pull_tail(skb, pull_to - skb_headlen(skb));

        /* Ethernet work: Delayed to here as it peeks the header. */
        skb->protocol = eth_type_trans(skb, dev);

        if (checksum_setup(dev, skb)) {
            kfree_skb(skb);
            packets_dropped++;
            dev->stats.rx_errors++;
            continue;
        }

        u64_stats_update_begin(&stats->syncp);
        stats->rx_packets++;
        stats->rx_bytes += skb->len;
        u64_stats_update_end(&stats->syncp);

        /* Pass it up. */
        netif_receive_skb(skb);
    }

    return packets_dropped;
}

static int xennet_poll(struct napi_struct *napi, int budget)
{
    struct netfront_info *np = container_of(napi, struct netfront_info, napi);
    struct net_device *dev = np->netdev;
    struct sk_buff *skb;
    struct netfront_rx_info rinfo;
    struct xen_netif_rx_response *rx = &rinfo.rx;
    struct xen_netif_extra_info *extras = rinfo.extras;
    RING_IDX i, rp;
    int work_done;
    struct sk_buff_head rxq;
    struct sk_buff_head errq;
    struct sk_buff_head tmpq;
    unsigned long flags;
    int err;

    spin_lock(&np->rx_lock);

    skb_queue_head_init(&rxq);
    skb_queue_head_init(&errq);
    skb_queue_head_init(&tmpq);

    rp = np->rx.sring->rsp_prod;
    rmb(); /* Ensure we see queued responses up to 'rp'. */

    i = np->rx.rsp_cons;
    work_done = 0;
    while ((i != rp) && (work_done < budget)) {
        memcpy(rx, RING_GET_RESPONSE(&np->rx, i), sizeof(*rx));
        memset(extras, 0, sizeof(rinfo.extras));

        err = xennet_get_responses(np, &rinfo, rp, &tmpq);

        if (unlikely(err)) {
err:
            while ((skb = __skb_dequeue(&tmpq)))
                __skb_queue_tail(&errq, skb);
            dev->stats.rx_errors++;
            i = np->rx.rsp_cons;
            continue;
        }

        skb = __skb_dequeue(&tmpq);

        if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
            struct xen_netif_extra_info *gso;
            gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];

            if (unlikely(xennet_set_skb_gso(skb, gso))) {
                __skb_queue_head(&tmpq, skb);
                np->rx.rsp_cons += skb_queue_len(&tmpq);
                goto err;
            }
        }

        NETFRONT_SKB_CB(skb)->pull_to = rx->status;
        if (NETFRONT_SKB_CB(skb)->pull_to > RX_COPY_THRESHOLD)
            NETFRONT_SKB_CB(skb)->pull_to = RX_COPY_THRESHOLD;

        skb_shinfo(skb)->frags[0].page_offset = rx->offset;
        skb_frag_size_set(&skb_shinfo(skb)->frags[0], rx->status);
        skb->data_len = rx->status;

        i = xennet_fill_frags(np, skb, &tmpq);

        /*
         * Truesize approximates the size of true data plus
         * any supervisor overheads. Adding hypervisor
         * overheads has been shown to significantly reduce
         * achievable bandwidth with the default receive
         * buffer size. It is therefore not wise to account
         * for it here.
         *
         * After alloc_skb(RX_COPY_THRESHOLD), truesize is set
         * to RX_COPY_THRESHOLD + the supervisor
         * overheads. Here, we add the size of the data pulled
         * in xennet_fill_frags().
         *
         * We also adjust for any unused space in the main
         * data area by subtracting (RX_COPY_THRESHOLD -
         * len). This is especially important with drivers
         * which split incoming packets into header and data,
         * using only 66 bytes of the main data area (see the
         * e1000 driver for example.)  On such systems,
         * without this last adjustement, our achievable
         * receive throughout using the standard receive
         * buffer size was cut by 25%(!!!).
         */
        skb->truesize += skb->data_len - RX_COPY_THRESHOLD;
        skb->len += skb->data_len;

        if (rx->flags & XEN_NETRXF_csum_blank)
            skb->ip_summed = CHECKSUM_PARTIAL;
        else if (rx->flags & XEN_NETRXF_data_validated)
            skb->ip_summed = CHECKSUM_UNNECESSARY;

        __skb_queue_tail(&rxq, skb);

        np->rx.rsp_cons = ++i;
        work_done++;
    }

    __skb_queue_purge(&errq);

    work_done -= handle_incoming_queue(dev, &rxq);

    /* If we get a callback with very few responses, reduce fill target. */
    /* NB. Note exponential increase, linear decrease. */
    if (((np->rx.req_prod_pvt - np->rx.sring->rsp_prod) >
         ((3*np->rx_target) / 4)) &&
        (--np->rx_target < np->rx_min_target))
        np->rx_target = np->rx_min_target;

    xennet_alloc_rx_buffers(dev);

    if (work_done < budget) {
        int more_to_do = 0;

        local_irq_save(flags);

        RING_FINAL_CHECK_FOR_RESPONSES(&np->rx, more_to_do);
        if (!more_to_do)
            __napi_complete(napi);

        local_irq_restore(flags);
    }

    spin_unlock(&np->rx_lock);

    return work_done;
}

static int xennet_change_mtu(struct net_device *dev, int mtu)
{
    int max = xennet_can_sg(dev) ? 65535 - ETH_HLEN : ETH_DATA_LEN;

    if (mtu > max)
        return -EINVAL;
    dev->mtu = mtu;
    return 0;
}

static struct rtnl_link_stats64 *xennet_get_stats64(struct net_device *dev,
                            struct rtnl_link_stats64 *tot)
{
    struct netfront_info *np = netdev_priv(dev);
    int cpu;

    for_each_possible_cpu(cpu) {
        struct netfront_stats *stats = per_cpu_ptr(np->stats, cpu);
        u64 rx_packets, rx_bytes, tx_packets, tx_bytes;
        unsigned int start;

        do {
            start = u64_stats_fetch_begin_bh(&stats->syncp);

            rx_packets = stats->rx_packets;
            tx_packets = stats->tx_packets;
            rx_bytes = stats->rx_bytes;
            tx_bytes = stats->tx_bytes;
        } while (u64_stats_fetch_retry_bh(&stats->syncp, start));

        tot->rx_packets += rx_packets;
        tot->tx_packets += tx_packets;
        tot->rx_bytes   += rx_bytes;
        tot->tx_bytes   += tx_bytes;
    }

    tot->rx_errors  = dev->stats.rx_errors;
    tot->tx_dropped = dev->stats.tx_dropped;

    return tot;
}

static void xennet_release_tx_bufs(struct netfront_info *np)
{
    struct sk_buff *skb;
    int i;

    for (i = 0; i < NET_TX_RING_SIZE; i++) {
        /* Skip over entries which are actually freelist references */
        if (skb_entry_is_link(&np->tx_skbs[i]))
            continue;

        skb = np->tx_skbs[i].skb;
        gnttab_end_foreign_access_ref(np->grant_tx_ref[i],
                          GNTMAP_readonly);
        gnttab_release_grant_reference(&np->gref_tx_head,
                           np->grant_tx_ref[i]);
        np->grant_tx_ref[i] = GRANT_INVALID_REF;
        add_id_to_freelist(&np->tx_skb_freelist, np->tx_skbs, i);
        dev_kfree_skb_irq(skb);
    }
}

static void xennet_release_rx_bufs(struct netfront_info *np)
{
    struct mmu_update      *mmu = np->rx_mmu;
    struct multicall_entry *mcl = np->rx_mcl;
    struct sk_buff_head free_list;
    struct sk_buff *skb;
    unsigned long mfn;
    int xfer = 0, noxfer = 0, unused = 0;
    int id, ref;

    dev_warn(&np->netdev->dev, "%s: fix me for copying receiver.\n",
             __func__);
    return;

    skb_queue_head_init(&free_list);

    spin_lock_bh(&np->rx_lock);

    for (id = 0; id < NET_RX_RING_SIZE; id++) {
        ref = np->grant_rx_ref[id];
        if (ref == GRANT_INVALID_REF) {
            unused++;
            continue;
        }

        skb = np->rx_skbs[id];
        mfn = gnttab_end_foreign_transfer_ref(ref);
        gnttab_release_grant_reference(&np->gref_rx_head, ref);
        np->grant_rx_ref[id] = GRANT_INVALID_REF;

        if (0 == mfn) {
            skb_shinfo(skb)->nr_frags = 0;
            dev_kfree_skb(skb);
            noxfer++;
            continue;
        }

        if (!xen_feature(XENFEAT_auto_translated_physmap)) {
            /* Remap the page. */
            const struct page *page =
                skb_frag_page(&skb_shinfo(skb)->frags[0]);
            unsigned long pfn = page_to_pfn(page);
            void *vaddr = page_address(page);

            MULTI_update_va_mapping(mcl, (unsigned long)vaddr,
                        mfn_pte(mfn, PAGE_KERNEL),
                        0);
            mcl++;
            mmu->ptr = ((u64)mfn << PAGE_SHIFT)
                | MMU_MACHPHYS_UPDATE;
            mmu->val = pfn;
            mmu++;

            set_phys_to_machine(pfn, mfn);
        }
        __skb_queue_tail(&free_list, skb);
        xfer++;
    }

    dev_info(&np->netdev->dev, "%s: %d xfer, %d noxfer, %d unused\n",
         __func__, xfer, noxfer, unused);

    if (xfer) {
        if (!xen_feature(XENFEAT_auto_translated_physmap)) {
            /* Do all the remapping work and M2P updates. */
            MULTI_mmu_update(mcl, np->rx_mmu, mmu - np->rx_mmu,
                     NULL, DOMID_SELF);
            mcl++;
            HYPERVISOR_multicall(np->rx_mcl, mcl - np->rx_mcl);
        }
    }

    __skb_queue_purge(&free_list);

    spin_unlock_bh(&np->rx_lock);
}

static void xennet_uninit(struct net_device *dev)
{
    struct netfront_info *np = netdev_priv(dev);
    xennet_release_tx_bufs(np);
    xennet_release_rx_bufs(np);
    gnttab_free_grant_references(np->gref_tx_head);
    gnttab_free_grant_references(np->gref_rx_head);
}

static netdev_features_t xennet_fix_features(struct net_device *dev,
    netdev_features_t features)
{
    struct netfront_info *np = netdev_priv(dev);
    int val;

    if (features & NETIF_F_SG) {
        if (xenbus_scanf(XBT_NIL, np->xbdev->otherend, "feature-sg",
                 "%d", &val) < 0)
            val = 0;

        if (!val)
            features &= ~NETIF_F_SG;
    }

    if (features & NETIF_F_TSO) {
        if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
                 "feature-gso-tcpv4", "%d", &val) < 0)
            val = 0;

        if (!val)
            features &= ~NETIF_F_TSO;
    }

    return features;
}

static int xennet_set_features(struct net_device *dev,
    netdev_features_t features)
{
    if (!(features & NETIF_F_SG) && dev->mtu > ETH_DATA_LEN) {
        netdev_info(dev, "Reducing MTU because no SG offload");
        dev->mtu = ETH_DATA_LEN;
    }

    return 0;
}

static irqreturn_t xennet_interrupt(int irq, void *dev_id)
{
    struct net_device *dev = dev_id;
    struct netfront_info *np = netdev_priv(dev);
    unsigned long flags;

    spin_lock_irqsave(&np->tx_lock, flags);

    if (likely(netif_carrier_ok(dev))) {
        xennet_tx_buf_gc(dev);
        /* Under tx_lock: protects access to rx shared-ring indexes. */
        if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
            napi_schedule(&np->napi);
    }

    spin_unlock_irqrestore(&np->tx_lock, flags);

    return IRQ_HANDLED;
}

#ifdef CONFIG_NET_POLL_CONTROLLER
static void xennet_poll_controller(struct net_device *dev)
{
    xennet_interrupt(0, dev);
}
#endif

static const struct net_device_ops xennet_netdev_ops = {
    .ndo_open            = xennet_open,
    .ndo_uninit          = xennet_uninit,
    .ndo_stop            = xennet_close,
    .ndo_start_xmit      = xennet_start_xmit,
    .ndo_change_mtu      = xennet_change_mtu,
    .ndo_get_stats64     = xennet_get_stats64,
    .ndo_set_mac_address = eth_mac_addr,
    .ndo_validate_addr   = eth_validate_addr,
    .ndo_fix_features    = xennet_fix_features,
    .ndo_set_features    = xennet_set_features,
#ifdef CONFIG_NET_POLL_CONTROLLER
    .ndo_poll_controller = xennet_poll_controller,
#endif
};

static struct net_device * __devinit xennet_create_dev(struct xenbus_device *dev)
{
    int i, err;
    struct net_device *netdev;
    struct netfront_info *np;

    netdev = alloc_etherdev(sizeof(struct netfront_info));
    if (!netdev)
        return ERR_PTR(-ENOMEM);

    np                   = netdev_priv(netdev);
    np->xbdev            = dev;

    spin_lock_init(&np->tx_lock);
    spin_lock_init(&np->rx_lock);

    skb_queue_head_init(&np->rx_batch);
    np->rx_target     = RX_DFL_MIN_TARGET;
    np->rx_min_target = RX_DFL_MIN_TARGET;
    np->rx_max_target = RX_MAX_TARGET;

    init_timer(&np->rx_refill_timer);
    np->rx_refill_timer.data = (unsigned long)netdev;
    np->rx_refill_timer.function = rx_refill_timeout;

    err = -ENOMEM;
    np->stats = alloc_percpu(struct netfront_stats);
    if (np->stats == NULL)
        goto exit;

    /* Initialise tx_skbs as a free chain containing every entry. */
    np->tx_skb_freelist = 0;
    for (i = 0; i < NET_TX_RING_SIZE; i++) {
        skb_entry_set_link(&np->tx_skbs[i], i+1);
        np->grant_tx_ref[i] = GRANT_INVALID_REF;
    }

    /* Clear out rx_skbs */
    for (i = 0; i < NET_RX_RING_SIZE; i++) {
        np->rx_skbs[i] = NULL;
        np->grant_rx_ref[i] = GRANT_INVALID_REF;
    }

    /* A grant for every tx ring slot */
    if (gnttab_alloc_grant_references(TX_MAX_TARGET,
                      &np->gref_tx_head) < 0) {
        printk(KERN_ALERT "#### netfront can't alloc tx grant refs\n");
        err = -ENOMEM;
        goto exit_free_stats;
    }
    /* A grant for every rx ring slot */
    if (gnttab_alloc_grant_references(RX_MAX_TARGET,
                      &np->gref_rx_head) < 0) {
        printk(KERN_ALERT "#### netfront can't alloc rx grant refs\n");
        err = -ENOMEM;
        goto exit_free_tx;
    }

    netdev->netdev_ops  = &xennet_netdev_ops;

    netif_napi_add(netdev, &np->napi, xennet_poll, 64);
    netdev->features        = NETIF_F_IP_CSUM | NETIF_F_RXCSUM |
                  NETIF_F_GSO_ROBUST;
    netdev->hw_features = NETIF_F_IP_CSUM | NETIF_F_SG | NETIF_F_TSO;

    /*
         * Assume that all hw features are available for now. This set
         * will be adjusted by the call to netdev_update_features() in
         * xennet_connect() which is the earliest point where we can
         * negotiate with the backend regarding supported features.
         */
    netdev->features |= netdev->hw_features;

    SET_ETHTOOL_OPS(netdev, &xennet_ethtool_ops);
    SET_NETDEV_DEV(netdev, &dev->dev);

    np->netdev = netdev;

    netif_carrier_off(netdev);

    return netdev;

 exit_free_tx:
    gnttab_free_grant_references(np->gref_tx_head);
 exit_free_stats:
    free_percpu(np->stats);
 exit:
    free_netdev(netdev);
    return ERR_PTR(err);
}

static int __devinit netfront_probe(struct xenbus_device *dev,
                    const struct xenbus_device_id *id)
{
    int err;
    struct net_device *netdev;
    struct netfront_info *info;

    netdev = xennet_create_dev(dev);
    if (IS_ERR(netdev)) {
        err = PTR_ERR(netdev);
        xenbus_dev_fatal(dev, err, "creating netdev");
        return err;
    }

    info = netdev_priv(netdev);
    dev_set_drvdata(&dev->dev, info);

    err = register_netdev(info->netdev);
    if (err) {
        printk(KERN_WARNING "%s: register_netdev err=%d\n",
               __func__, err);
        goto fail;
    }

    err = xennet_sysfs_addif(info->netdev);
    if (err) {
        unregister_netdev(info->netdev);
        printk(KERN_WARNING "%s: add sysfs failed err=%d\n",
               __func__, err);
        goto fail;
    }

    return 0;

 fail:
    free_netdev(netdev);
    dev_set_drvdata(&dev->dev, NULL);
    return err;
}

static void xennet_end_access(int ref, void *page)
{
    /* This frees the page as a side-effect */
    if (ref != GRANT_INVALID_REF)
        gnttab_end_foreign_access(ref, 0, (unsigned long)page);
}

static void xennet_disconnect_backend(struct netfront_info *info)
{
    /* Stop old i/f to prevent errors whilst we rebuild the state. */
    spin_lock_bh(&info->rx_lock);
    spin_lock_irq(&info->tx_lock);
    netif_carrier_off(info->netdev);
    spin_unlock_irq(&info->tx_lock);
    spin_unlock_bh(&info->rx_lock);

    if (info->netdev->irq)
        unbind_from_irqhandler(info->netdev->irq, info->netdev);
    info->evtchn = info->netdev->irq = 0;

    /* End access and free the pages */
    xennet_end_access(info->tx_ring_ref, info->tx.sring);
    xennet_end_access(info->rx_ring_ref, info->rx.sring);

    info->tx_ring_ref = GRANT_INVALID_REF;
    info->rx_ring_ref = GRANT_INVALID_REF;
    info->tx.sring = NULL;
    info->rx.sring = NULL;
}

static int netfront_resume(struct xenbus_device *dev)
{
    struct netfront_info *info = dev_get_drvdata(&dev->dev);

    dev_dbg(&dev->dev, "%s\n", dev->nodename);

    xennet_disconnect_backend(info);
    return 0;
}

static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
{
    char *s, *e, *macstr;
    int i;

    macstr = s = xenbus_read(XBT_NIL, dev->nodename, "mac", NULL);
    if (IS_ERR(macstr))
        return PTR_ERR(macstr);

    for (i = 0; i < ETH_ALEN; i++) {
        mac[i] = simple_strtoul(s, &e, 16);
        if ((s == e) || (*e != ((i == ETH_ALEN-1) ? '\0' : ':'))) {
            kfree(macstr);
            return -ENOENT;
        }
        s = e+1;
    }

    kfree(macstr);
    return 0;
}

static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
{
    struct xen_netif_tx_sring *txs;
    struct xen_netif_rx_sring *rxs;
    int err;
    struct net_device *netdev = info->netdev;

    info->tx_ring_ref = GRANT_INVALID_REF;
    info->rx_ring_ref = GRANT_INVALID_REF;
    info->rx.sring = NULL;
    info->tx.sring = NULL;
    netdev->irq = 0;

    err = xen_net_read_mac(dev, netdev->dev_addr);
    if (err) {
        xenbus_dev_fatal(dev, err, "parsing %s/mac", dev->nodename);
        goto fail;
    }

    txs = (struct xen_netif_tx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
    if (!txs) {
        err = -ENOMEM;
        xenbus_dev_fatal(dev, err, "allocating tx ring page");
        goto fail;
    }
    SHARED_RING_INIT(txs);
    FRONT_RING_INIT(&info->tx, txs, PAGE_SIZE);

    err = xenbus_grant_ring(dev, virt_to_mfn(txs));
    if (err < 0) {
        free_page((unsigned long)txs);
        goto fail;
    }

    info->tx_ring_ref = err;
    rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
    if (!rxs) {
        err = -ENOMEM;
        xenbus_dev_fatal(dev, err, "allocating rx ring page");
        goto fail;
    }
    SHARED_RING_INIT(rxs);
    FRONT_RING_INIT(&info->rx, rxs, PAGE_SIZE);

    err = xenbus_grant_ring(dev, virt_to_mfn(rxs));
    if (err < 0) {
        free_page((unsigned long)rxs);
        goto fail;
    }
    info->rx_ring_ref = err;

    err = xenbus_alloc_evtchn(dev, &info->evtchn);
    if (err)
        goto fail;

    err = bind_evtchn_to_irqhandler(info->evtchn, xennet_interrupt,
                    0, netdev->name, netdev);
    if (err < 0)
        goto fail;
    netdev->irq = err;
    return 0;

 fail:
    return err;
}

/* Common code used when first setting up, and when resuming. */
static int talk_to_netback(struct xenbus_device *dev,
               struct netfront_info *info)
{
    const char *message;
    struct xenbus_transaction xbt;
    int err;

    /* Create shared ring, alloc event channel. */
    err = setup_netfront(dev, info);
    if (err)
        goto out;

again:
    err = xenbus_transaction_start(&xbt);
    if (err) {
        xenbus_dev_fatal(dev, err, "starting transaction");
        goto destroy_ring;
    }

    err = xenbus_printf(xbt, dev->nodename, "tx-ring-ref", "%u",
                info->tx_ring_ref);
    if (err) {
        message = "writing tx ring-ref";
        goto abort_transaction;
    }
    err = xenbus_printf(xbt, dev->nodename, "rx-ring-ref", "%u",
                info->rx_ring_ref);
    if (err) {
        message = "writing rx ring-ref";
        goto abort_transaction;
    }
    err = xenbus_printf(xbt, dev->nodename,
                "event-channel", "%u", info->evtchn);
    if (err) {
        message = "writing event-channel";
        goto abort_transaction;
    }

    err = xenbus_printf(xbt, dev->nodename, "request-rx-copy", "%u",
                1);
    if (err) {
        message = "writing request-rx-copy";
        goto abort_transaction;
    }

    err = xenbus_printf(xbt, dev->nodename, "feature-rx-notify", "%d", 1);
    if (err) {
        message = "writing feature-rx-notify";
        goto abort_transaction;
    }

    err = xenbus_printf(xbt, dev->nodename, "feature-sg", "%d", 1);
    if (err) {
        message = "writing feature-sg";
        goto abort_transaction;
    }

    err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv4", "%d", 1);
    if (err) {
        message = "writing feature-gso-tcpv4";
        goto abort_transaction;
    }

    err = xenbus_transaction_end(xbt, 0);
    if (err) {
        if (err == -EAGAIN)
            goto again;
        xenbus_dev_fatal(dev, err, "completing transaction");
        goto destroy_ring;
    }

    return 0;

 abort_transaction:
    xenbus_transaction_end(xbt, 1);
    xenbus_dev_fatal(dev, err, "%s", message);
 destroy_ring:
    xennet_disconnect_backend(info);
 out:
    return err;
}

static int xennet_connect(struct net_device *dev)
{
    struct netfront_info *np = netdev_priv(dev);
    int i, requeue_idx, err;
    struct sk_buff *skb;
    grant_ref_t ref;
    struct xen_netif_rx_request *req;
    unsigned int feature_rx_copy;

    err = xenbus_scanf(XBT_NIL, np->xbdev->otherend,
               "feature-rx-copy", "%u", &feature_rx_copy);
    if (err != 1)
        feature_rx_copy = 0;

    if (!feature_rx_copy) {
        dev_info(&dev->dev,
             "backend does not support copying receive path\n");
        return -ENODEV;
    }

    err = talk_to_netback(np->xbdev, np);
    if (err)
        return err;

    rtnl_lock();
    netdev_update_features(dev);
    rtnl_unlock();

    spin_lock_bh(&np->rx_lock);
    spin_lock_irq(&np->tx_lock);

    /* Step 1: Discard all pending TX packet fragments. */
    xennet_release_tx_bufs(np);

    /* Step 2: Rebuild the RX buffer freelist and the RX ring itself. */
    for (requeue_idx = 0, i = 0; i < NET_RX_RING_SIZE; i++) {
        skb_frag_t *frag;
        const struct page *page;
        if (!np->rx_skbs[i])
            continue;

        skb = np->rx_skbs[requeue_idx] = xennet_get_rx_skb(np, i);
        ref = np->grant_rx_ref[requeue_idx] = xennet_get_rx_ref(np, i);
        req = RING_GET_REQUEST(&np->rx, requeue_idx);

        frag = &skb_shinfo(skb)->frags[0];
        page = skb_frag_page(frag);
        gnttab_grant_foreign_access_ref(
            ref, np->xbdev->otherend_id,
            pfn_to_mfn(page_to_pfn(page)),
            0);
        req->gref = ref;
        req->id   = requeue_idx;

        requeue_idx++;
    }

    np->rx.req_prod_pvt = requeue_idx;

    /*
     * Step 3: All public and private state should now be sane.  Get
     * ready to start sending and receiving packets and give the driver
     * domain a kick because we've probably just requeued some
     * packets.
     */
    netif_carrier_on(np->netdev);
    notify_remote_via_irq(np->netdev->irq);
    xennet_tx_buf_gc(dev);
    xennet_alloc_rx_buffers(dev);

    spin_unlock_irq(&np->tx_lock);
    spin_unlock_bh(&np->rx_lock);

    return 0;
}

static void netback_changed(struct xenbus_device *dev,
                enum xenbus_state backend_state)
{
    struct netfront_info *np = dev_get_drvdata(&dev->dev);
    struct net_device *netdev = np->netdev;

    dev_dbg(&dev->dev, "%s\n", xenbus_strstate(backend_state));

    switch (backend_state) {
    case XenbusStateInitialising:
    case XenbusStateInitialised:
    case XenbusStateReconfiguring:
    case XenbusStateReconfigured:
    case XenbusStateUnknown:
    case XenbusStateClosed:
        break;

    case XenbusStateInitWait:
        if (dev->state != XenbusStateInitialising)
            break;
        if (xennet_connect(netdev) != 0)
            break;
        xenbus_switch_state(dev, XenbusStateConnected);
        break;

    case XenbusStateConnected:
        netdev_notify_peers(netdev);
        break;

    case XenbusStateClosing:
        xenbus_frontend_closed(dev);
        break;
    }
}

static const struct xennet_stat {
    char name[ETH_GSTRING_LEN];
    u16 offset;
} xennet_stats[] = {
    {
        "rx_gso_checksum_fixup",
        offsetof(struct netfront_info, rx_gso_checksum_fixup)
    },
};

static int xennet_get_sset_count(struct net_device *dev, int string_set)
{
    switch (string_set) {
    case ETH_SS_STATS:
        return ARRAY_SIZE(xennet_stats);
    default:
        return -EINVAL;
    }
}

static void xennet_get_ethtool_stats(struct net_device *dev,
                     struct ethtool_stats *stats, u64 * data)
{
    void *np = netdev_priv(dev);
    int i;

    for (i = 0; i < ARRAY_SIZE(xennet_stats); i++)
        data[i] = *(unsigned long *)(np + xennet_stats[i].offset);
}

static void xennet_get_strings(struct net_device *dev, u32 stringset, u8 * data)
{
    int i;

    switch (stringset) {
    case ETH_SS_STATS:
        for (i = 0; i < ARRAY_SIZE(xennet_stats); i++)
            memcpy(data + i * ETH_GSTRING_LEN,
                   xennet_stats[i].name, ETH_GSTRING_LEN);
        break;
    }
}

static const struct ethtool_ops xennet_ethtool_ops =
{
    .get_link = ethtool_op_get_link,

    .get_sset_count = xennet_get_sset_count,
    .get_ethtool_stats = xennet_get_ethtool_stats,
    .get_strings = xennet_get_strings,
};

#ifdef CONFIG_SYSFS
static ssize_t show_rxbuf_min(struct device *dev,
                  struct device_attribute *attr, char *buf)
{
    struct net_device *netdev = to_net_dev(dev);
    struct netfront_info *info = netdev_priv(netdev);

    return sprintf(buf, "%u\n", info->rx_min_target);
}

static ssize_t store_rxbuf_min(struct device *dev,
                   struct device_attribute *attr,
                   const char *buf, size_t len)
{
    struct net_device *netdev = to_net_dev(dev);
    struct netfront_info *np = netdev_priv(netdev);
    char *endp;
    unsigned long target;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    target = simple_strtoul(buf, &endp, 0);
    if (endp == buf)
        return -EBADMSG;

    if (target < RX_MIN_TARGET)
        target = RX_MIN_TARGET;
    if (target > RX_MAX_TARGET)
        target = RX_MAX_TARGET;

    spin_lock_bh(&np->rx_lock);
    if (target > np->rx_max_target)
        np->rx_max_target = target;
    np->rx_min_target = target;
    if (target > np->rx_target)
        np->rx_target = target;

    xennet_alloc_rx_buffers(netdev);

    spin_unlock_bh(&np->rx_lock);
    return len;
}

static ssize_t show_rxbuf_max(struct device *dev,
                  struct device_attribute *attr, char *buf)
{
    struct net_device *netdev = to_net_dev(dev);
    struct netfront_info *info = netdev_priv(netdev);

    return sprintf(buf, "%u\n", info->rx_max_target);
}

static ssize_t store_rxbuf_max(struct device *dev,
                   struct device_attribute *attr,
                   const char *buf, size_t len)
{
    struct net_device *netdev = to_net_dev(dev);
    struct netfront_info *np = netdev_priv(netdev);
    char *endp;
    unsigned long target;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    target = simple_strtoul(buf, &endp, 0);
    if (endp == buf)
        return -EBADMSG;

    if (target < RX_MIN_TARGET)
        target = RX_MIN_TARGET;
    if (target > RX_MAX_TARGET)
        target = RX_MAX_TARGET;

    spin_lock_bh(&np->rx_lock);
    if (target < np->rx_min_target)
        np->rx_min_target = target;
    np->rx_max_target = target;
    if (target < np->rx_target)
        np->rx_target = target;

    xennet_alloc_rx_buffers(netdev);

    spin_unlock_bh(&np->rx_lock);
    return len;
}

static ssize_t show_rxbuf_cur(struct device *dev,
                  struct device_attribute *attr, char *buf)
{
    struct net_device *netdev = to_net_dev(dev);
    struct netfront_info *info = netdev_priv(netdev);

    return sprintf(buf, "%u\n", info->rx_target);
}

static struct device_attribute xennet_attrs[] = {
    __ATTR(rxbuf_min, S_IRUGO|S_IWUSR, show_rxbuf_min, store_rxbuf_min),
    __ATTR(rxbuf_max, S_IRUGO|S_IWUSR, show_rxbuf_max, store_rxbuf_max),
    __ATTR(rxbuf_cur, S_IRUGO, show_rxbuf_cur, NULL),
};

static int xennet_sysfs_addif(struct net_device *netdev)
{
    int i;
    int err;

    for (i = 0; i < ARRAY_SIZE(xennet_attrs); i++) {
        err = device_create_file(&netdev->dev,
                       &xennet_attrs[i]);
        if (err)
            goto fail;
    }
    return 0;

 fail:
    while (--i >= 0)
        device_remove_file(&netdev->dev, &xennet_attrs[i]);
    return err;
}

static void xennet_sysfs_delif(struct net_device *netdev)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(xennet_attrs); i++)
        device_remove_file(&netdev->dev, &xennet_attrs[i]);
}

#endif /* CONFIG_SYSFS */

static const struct xenbus_device_id netfront_ids[] = {
    { "vif" },
    { "" }
};


static int __devexit xennet_remove(struct xenbus_device *dev)
{
    struct netfront_info *info = dev_get_drvdata(&dev->dev);

    dev_dbg(&dev->dev, "%s\n", dev->nodename);

    xennet_disconnect_backend(info);

    xennet_sysfs_delif(info->netdev);

    unregister_netdev(info->netdev);

    del_timer_sync(&info->rx_refill_timer);

    free_percpu(info->stats);

    free_netdev(info->netdev);

    return 0;
}

static DEFINE_XENBUS_DRIVER(netfront, ,
    .probe = netfront_probe,
    .remove = __devexit_p(xennet_remove),
    .resume = netfront_resume,
    .otherend_changed = netback_changed,
);

static int __init netif_init(void)
{
    if (!xen_domain())
        return -ENODEV;

    if (xen_hvm_domain() && !xen_platform_pci_unplug)
        return -ENODEV;

    printk(KERN_INFO "Initialising Xen virtual ethernet driver.\n");

    return xenbus_register_frontend(&netfront_driver);
}
module_init(netif_init);


static void __exit netif_exit(void)
{
    xenbus_unregister_driver(&netfront_driver);
}
module_exit(netif_exit);

MODULE_DESCRIPTION("Xen virtual network device frontend");
MODULE_LICENSE("GPL");
MODULE_ALIAS("xen:vif");
MODULE_ALIAS("xennet");