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netfront.c

/******************************************************************************
 * 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/version.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/ethtool.h>
#include <linux/in.h>
#include <linux/if_ether.h>
#include <linux/io.h>
#include <linux/moduleparam.h>
#include <net/sock.h>
#include <net/pkt_sched.h>
#include <net/arp.h>
#include <net/route.h>
#include <asm/uaccess.h>
#include <xen/evtchn.h>
#include <xen/xenbus.h>
#include <xen/interface/io/netif.h>
#include <xen/interface/memory.h>
#include <xen/balloon.h>
#include <asm/page.h>
#include <asm/maddr.h>
#include <asm/uaccess.h>
#include <xen/interface/grant_table.h>
#include <xen/gnttab.h>

#ifdef HAVE_XEN_PLATFORM_COMPAT_H
#include <xen/platform-compat.h>
#endif

struct netfront_cb {
      struct page *page;
      unsigned offset;
};

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

/*
 * Mutually-exclusive module options to select receive data path:
 *  rx_copy : Packets are copied by network backend into local memory
 *  rx_flip : Page containing packet data is transferred to our ownership
 * For fully-virtualised guests there is no option - copying must be used.
 * For paravirtualised guests, flipping is the default.
 */
#ifdef CONFIG_XEN
static int MODPARM_rx_copy = 0;
module_param_named(rx_copy, MODPARM_rx_copy, bool, 0);
MODULE_PARM_DESC(rx_copy, "Copy packets from network card (rather than flip)");
static int MODPARM_rx_flip = 0;
module_param_named(rx_flip, MODPARM_rx_flip, bool, 0);
MODULE_PARM_DESC(rx_flip, "Flip packets from network card (rather than copy)");
#else
static const int MODPARM_rx_copy = 1;
static const int MODPARM_rx_flip = 0;
#endif

#define RX_COPY_THRESHOLD 256

/* If we don't have GSO, fake things up so that we never try to use it. */
#if defined(NETIF_F_GSO)
#define HAVE_GSO              1
#define HAVE_TSO              1 /* TSO is a subset of GSO */
static inline void dev_disable_gso_features(struct net_device *dev)
{
      /* Turn off all GSO bits except ROBUST. */
      dev->features &= (1 << NETIF_F_GSO_SHIFT) - 1;
      dev->features |= NETIF_F_GSO_ROBUST;
}
#elif defined(NETIF_F_TSO)
#define HAVE_TSO                       1

/* Some older kernels cannot cope with incorrect checksums,
 * particularly in netfilter. I'm not sure there is 100% correlation
 * with the presence of NETIF_F_TSO but it appears to be a good first
 * approximiation.
 */
#define HAVE_NO_CSUM_OFFLOAD           1

#define gso_size tso_size
#define gso_segs tso_segs
static inline void dev_disable_gso_features(struct net_device *dev)
{
       /* Turn off all TSO bits. */
       dev->features &= ~NETIF_F_TSO;
}
static inline int skb_is_gso(const struct sk_buff *skb)
{
        return skb_shinfo(skb)->tso_size;
}
static inline int skb_gso_ok(struct sk_buff *skb, int features)
{
        return (features & NETIF_F_TSO);
}

static inline int netif_needs_gso(struct net_device *dev, struct sk_buff *skb)
{
        return skb_is_gso(skb) &&
               (!skb_gso_ok(skb, dev->features) ||
                unlikely(skb->ip_summed != CHECKSUM_HW));
}
#else
#define netif_needs_gso(dev, skb)   0
#define dev_disable_gso_features(dev)     ((void)0)
#endif

#define GRANT_INVALID_REF     0

#define NET_TX_RING_SIZE __RING_SIZE((struct netif_tx_sring *)0, PAGE_SIZE)
#define NET_RX_RING_SIZE __RING_SIZE((struct netif_rx_sring *)0, PAGE_SIZE)

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

      struct net_device_stats stats;

      struct netif_tx_front_ring tx;
      struct netif_rx_front_ring rx;

      spinlock_t   tx_lock;
      spinlock_t   rx_lock;

      unsigned int irq;
      unsigned int copying_receiver;
      unsigned int carrier;

      /* 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;

      /*
       * {tx,rx}_skbs store outstanding skbuffs. The first entry in tx_skbs
       * is an index into a chain of free entries.
       */
      struct sk_buff *tx_skbs[NET_TX_RING_SIZE+1];
      struct sk_buff *rx_skbs[NET_RX_RING_SIZE];

#define TX_MAX_TARGET min_t(int, NET_RX_RING_SIZE, 256)
      grant_ref_t gref_tx_head;
      grant_ref_t grant_tx_ref[NET_TX_RING_SIZE + 1];
      grant_ref_t gref_rx_head;
      grant_ref_t grant_rx_ref[NET_RX_RING_SIZE];

      struct xenbus_device *xbdev;
      int tx_ring_ref;
      int rx_ring_ref;
      u8 mac[ETH_ALEN];

      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];
};

struct netfront_rx_info {
      struct netif_rx_response rx;
      struct netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
};

/*
 * Implement our own carrier flag: the network stack's version causes delays
 * when the carrier is re-enabled (in particular, dev_activate() may not
 * immediately be called, which can cause packet loss).
 */
#define netfront_carrier_on(netif)  ((netif)->carrier = 1)
#define netfront_carrier_off(netif) ((netif)->carrier = 0)
#define netfront_carrier_ok(netif)  ((netif)->carrier)

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

static inline void add_id_to_freelist(struct sk_buff **list, unsigned short id)
{
      list[id] = list[0];
      list[0]  = (void *)(unsigned long)id;
}

static inline unsigned short get_id_from_freelist(struct sk_buff **list)
{
      unsigned int id = (unsigned int)(unsigned long)list[0];
      list[0] = list[id];
      return id;
}

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

static inline 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 inline 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;
}

#define DPRINTK(fmt, args...)                   \
      pr_debug("netfront (%s:%d) " fmt,         \
             __FUNCTION__, __LINE__, ##args)
#define IPRINTK(fmt, args...)                   \
      printk(KERN_INFO "netfront: " fmt, ##args)
#define WPRINTK(fmt, args...)                   \
      printk(KERN_WARNING "netfront: " fmt, ##args)

static int setup_device(struct xenbus_device *, struct netfront_info *);
static struct net_device *create_netdev(struct xenbus_device *);

static void end_access(int, void *);
static void netif_disconnect_backend(struct netfront_info *);

static int network_connect(struct net_device *);
static void network_tx_buf_gc(struct net_device *);
static void network_alloc_rx_buffers(struct net_device *);
static int send_fake_arp(struct net_device *);

static irqreturn_t netif_int(int irq, void *dev_id, struct pt_regs *ptregs);

#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 inline int xennet_can_sg(struct net_device *dev)
{
      return dev->features & NETIF_F_SG;
}

/**
 * Entry point to this code when a new device is created.  Allocate the basic
 * structures and the ring buffers for communication with the backend, and
 * inform the backend of the appropriate details for those.
 */
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 = create_netdev(dev);
      if (IS_ERR(netdev)) {
            err = PTR_ERR(netdev);
            xenbus_dev_fatal(dev, err, "creating netdev");
            return err;
      }

      info = netdev_priv(netdev);
      dev->dev.driver_data = info;

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

      return 0;

 fail:
      free_netdev(netdev);
      dev->dev.driver_data = NULL;
      return err;
}

static int __devexit netfront_remove(struct xenbus_device *dev)
{
      struct netfront_info *info = dev->dev.driver_data;

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

      netif_disconnect_backend(info);

      del_timer_sync(&info->rx_refill_timer);

      xennet_sysfs_delif(info->netdev);

      unregister_netdev(info->netdev);

      free_netdev(info->netdev);

      return 0;
}

/**
 * We are reconnecting to the backend, due to a suspend/resume, or a backend
 * driver restart.  We tear down our netif structure and recreate it, but
 * leave the device-layer structures intact so that this is transparent to the
 * rest of the kernel.
 */
static int netfront_resume(struct xenbus_device *dev)
{
      struct netfront_info *info = dev->dev.driver_data;

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

      netif_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;
}

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

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

      /* Create shared ring, alloc event channel. */
      err = setup_device(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",
                      irq_to_evtchn_port(info->irq));
      if (err) {
            message = "writing event-channel";
            goto abort_transaction;
      }

      err = xenbus_printf(xbt, dev->nodename, "request-rx-copy", "%u",
                      info->copying_receiver);
      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;
      }

#ifdef HAVE_NO_CSUM_OFFLOAD
      err = xenbus_printf(xbt, dev->nodename, "feature-no-csum-offload", "%d", 1);
      if (err) {
            message = "writing feature-no-csum-offload";
            goto abort_transaction;
      }
#endif

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

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

      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:
      netif_disconnect_backend(info);
 out:
      return err;
}

static int setup_device(struct xenbus_device *dev, struct netfront_info *info)
{
      struct netif_tx_sring *txs;
      struct 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;
      info->irq = 0;

      txs = (struct netif_tx_sring *)get_zeroed_page(GFP_KERNEL);
      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 netif_rx_sring *)get_zeroed_page(GFP_KERNEL);
      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;

      memcpy(netdev->dev_addr, info->mac, ETH_ALEN);

      err = bind_listening_port_to_irqhandler(
            dev->otherend_id, netif_int, SA_SAMPLE_RANDOM, netdev->name,
            netdev);
      if (err < 0)
            goto fail;
      info->irq = err;

      return 0;

 fail:
      return err;
}

/**
 * Callback received when the backend's state changes.
 */
static void backend_changed(struct xenbus_device *dev,
                      enum xenbus_state backend_state)
{
      struct netfront_info *np = dev->dev.driver_data;
      struct net_device *netdev = np->netdev;

      DPRINTK("%s\n", xenbus_strstate(backend_state));

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

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

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

/** Send a packet on a net device to encourage switches to learn the
 * MAC. We send a fake ARP request.
 *
 * @param dev device
 * @return 0 on success, error code otherwise
 */
static int send_fake_arp(struct net_device *dev)
{
      struct sk_buff *skb;
      u32             src_ip, dst_ip;

      dst_ip = INADDR_BROADCAST;
      src_ip = inet_select_addr(dev, dst_ip, RT_SCOPE_LINK);

      /* No IP? Then nothing to do. */
      if (src_ip == 0)
            return 0;

      skb = arp_create(ARPOP_REPLY, ETH_P_ARP,
                   dst_ip, dev, src_ip,
                   /*dst_hw*/ NULL, /*src_hw*/ NULL,
                   /*target_hw*/ dev->dev_addr);
      if (skb == NULL)
            return -ENOMEM;

      return dev_queue_xmit(skb);
}

static inline 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 inline void network_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 int network_open(struct net_device *dev)
{
      struct netfront_info *np = netdev_priv(dev);

      memset(&np->stats, 0, sizeof(np->stats));

      spin_lock_bh(&np->rx_lock);
      if (netfront_carrier_ok(np)) {
            network_alloc_rx_buffers(dev);
            np->rx.sring->rsp_event = np->rx.rsp_cons + 1;
            if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
                  netif_rx_schedule(dev);
      }
      spin_unlock_bh(&np->rx_lock);

      network_maybe_wake_tx(dev);

      return 0;
}

static void network_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(!netfront_carrier_ok(np));

      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 netif_tx_response *txrsp;

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

                  id  = txrsp->id;
                  skb = np->tx_skbs[id];
                  if (unlikely(gnttab_query_foreign_access(
                        np->grant_tx_ref[id]) != 0)) {
                        printk(KERN_ALERT "network_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_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();
      } while ((cons == prod) && (prod != np->tx.sring->rsp_prod));

      network_maybe_wake_tx(dev);
}

static void rx_refill_timeout(unsigned long data)
{
      struct net_device *dev = (struct net_device *)data;
      netif_rx_schedule(dev);
}

static void network_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;
      struct xen_memory_reservation reservation;
      grant_ref_t ref;
      unsigned long pfn;
      void *vaddr;
      int nr_flips;
      netif_rx_request_t *req;

      if (unlikely(!netfront_carrier_ok(np)))
            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++) {
            /*
             * Allocate an skb and a page. Do not use __dev_alloc_skb as
             * that will allocate page-sized buffers which is not
             * necessary here.
             * 16 bytes added as necessary headroom for netif_receive_skb.
             */
            skb = alloc_skb(RX_COPY_THRESHOLD + 16 + NET_IP_ALIGN,
                        GFP_ATOMIC | __GFP_NOWARN);
            if (unlikely(!skb))
                  goto no_skb;

            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_reserve(skb, 16 + NET_IP_ALIGN); /* mimic dev_alloc_skb() */
            skb_shinfo(skb)->frags[0].page = page;
            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 (nr_flips = i = 0; ; i++) {
            if ((skb = __skb_dequeue(&np->rx_batch)) == 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_shinfo(skb)->frags[0].page);
            vaddr = page_address(skb_shinfo(skb)->frags[0].page);

            req = RING_GET_REQUEST(&np->rx, req_prod + i);
            if (!np->copying_receiver) {
                  gnttab_grant_foreign_transfer_ref(ref,
                                            np->xbdev->otherend_id,
                                            pfn);
                  np->rx_pfn_array[nr_flips] = pfn_to_mfn(pfn);
                  if (!xen_feature(XENFEAT_auto_translated_physmap)) {
                        /* Remove this page before passing
                         * back to Xen. */
                        set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
                        MULTI_update_va_mapping(np->rx_mcl+i,
                                          (unsigned long)vaddr,
                                          __pte(0), 0);
                  }
                  nr_flips++;
            } else {
                  gnttab_grant_foreign_access_ref(ref,
                                          np->xbdev->otherend_id,
                                          pfn_to_mfn(pfn),
                                          0);
            }

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

      if ( nr_flips != 0 ) {
            /* Tell the ballon driver what is going on. */
            balloon_update_driver_allowance(i);

            set_xen_guest_handle(reservation.extent_start,
                             np->rx_pfn_array);
            reservation.nr_extents   = nr_flips;
            reservation.extent_order = 0;
            reservation.address_bits = 0;
            reservation.domid        = DOMID_SELF;

            if (!xen_feature(XENFEAT_auto_translated_physmap)) {
                  /* After all PTEs have been zapped, flush the TLB. */
                  np->rx_mcl[i-1].args[MULTI_UVMFLAGS_INDEX] =
                        UVMF_TLB_FLUSH|UVMF_ALL;

                  /* Give away a batch of pages. */
                  np->rx_mcl[i].op = __HYPERVISOR_memory_op;
                  np->rx_mcl[i].args[0] = XENMEM_decrease_reservation;
                  np->rx_mcl[i].args[1] = (unsigned long)&reservation;

                  /* Zap PTEs and give away pages in one big
                   * multicall. */
                  (void)HYPERVISOR_multicall(np->rx_mcl, i+1);

                  /* Check return status of HYPERVISOR_memory_op(). */
                  if (unlikely(np->rx_mcl[i].result != i))
                        panic("Unable to reduce memory reservation\n");
            } else {
                  if (HYPERVISOR_memory_op(XENMEM_decrease_reservation,
                                     &reservation) != i)
                        panic("Unable to reduce memory reservation\n");
            }
      } else {
            wmb();
      }

      /* 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->irq);
}

static void xennet_make_frags(struct sk_buff *skb, struct net_device *dev,
                        struct 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 (len > PAGE_SIZE - offset) {
            tx->size = PAGE_SIZE - offset;
            tx->flags |= NETTXF_more_data;
            len -= tx->size;
            data += tx->size;
            offset = 0;

            id = get_id_from_freelist(np->tx_skbs);
            np->tx_skbs[id] = 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;
      }

      for (i = 0; i < frags; i++) {
            skb_frag_t *frag = skb_shinfo(skb)->frags + i;

            tx->flags |= NETTXF_more_data;

            id = get_id_from_freelist(np->tx_skbs);
            np->tx_skbs[id] = 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(frag->page));
            gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
                                    mfn, GNTMAP_readonly);

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

      np->tx.req_prod_pvt = prod;
}

static int network_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
      unsigned short id;
      struct netfront_info *np = netdev_priv(dev);
      struct netif_tx_request *tx;
      struct netif_extra_info *extra;
      char *data = skb->data;
      RING_IDX i;
      grant_ref_t ref;
      unsigned long mfn;
      int notify;
      int frags = skb_shinfo(skb)->nr_frags;
      unsigned int offset = offset_in_page(data);
      unsigned int len = skb_headlen(skb);

      frags += (offset + len + PAGE_SIZE - 1) / PAGE_SIZE;
      if (unlikely(frags > MAX_SKB_FRAGS + 1)) {
            printk(KERN_ALERT "xennet: skb rides the rocket: %d frags\n",
                   frags);
            dump_stack();
            goto drop;
      }

      spin_lock_irq(&np->tx_lock);

      if (unlikely(!netfront_carrier_ok(np) ||
                 (frags > 1 && !xennet_can_sg(dev)) ||
                 netif_needs_gso(dev, skb))) {
            spin_unlock_irq(&np->tx_lock);
            goto drop;
      }

      i = np->tx.req_prod_pvt;

      id = get_id_from_freelist(np->tx_skbs);
      np->tx_skbs[id] = 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;

      tx->flags = 0;
      extra = NULL;

      if (skb->ip_summed == CHECKSUM_HW) /* local packet? */
            tx->flags |= NETTXF_csum_blank | NETTXF_data_validated;
#ifdef CONFIG_XEN
      if (skb->proto_data_valid) /* remote but checksummed? */
            tx->flags |= NETTXF_data_validated;
#endif

#ifdef HAVE_TSO
      if (skb_shinfo(skb)->gso_size) {
            struct netif_extra_info *gso = (struct netif_extra_info *)
                  RING_GET_REQUEST(&np->tx, ++i);

            if (extra)
                  extra->flags |= XEN_NETIF_EXTRA_FLAG_MORE;
            else
                  tx->flags |= 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;
      }
#endif

      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->irq);

      network_tx_buf_gc(dev);

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

      spin_unlock_irq(&np->tx_lock);

      np->stats.tx_bytes += skb->len;
      np->stats.tx_packets++;

      return 0;

 drop:
      np->stats.tx_dropped++;
      dev_kfree_skb(skb);
      return 0;
}

static irqreturn_t netif_int(int irq, void *dev_id, struct pt_regs *ptregs)
{
      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(netfront_carrier_ok(np))) {
            network_tx_buf_gc(dev);
            /* Under tx_lock: protects access to rx shared-ring indexes. */
            if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
                  netif_rx_schedule(dev);
      }

      spin_unlock_irqrestore(&np->tx_lock, flags);

      return IRQ_HANDLED;
}

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++;
}

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

{
      struct netif_extra_info *extra;
      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())
                        WPRINTK("Missing extra info\n");
                  err = -EBADR;
                  break;
            }

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

            if (unlikely(!extra->type ||
                       extra->type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
                  if (net_ratelimit())
                        WPRINTK("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,
                        int *pages_flipped_p)
{
      int pages_flipped = *pages_flipped_p;
      struct mmu_update *mmu;
      struct multicall_entry *mcl;
      struct netif_rx_response *rx = &rinfo->rx;
      struct netif_extra_info *extras = rinfo->extras;
      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 & NETRXF_extra_info) {
            err = xennet_get_extras(np, extras, rp);
            cons = np->rx.rsp_cons;
      }

      for (;;) {
            unsigned long mfn;

            if (unlikely(rx->status < 0 ||
                       rx->offset + rx->status > PAGE_SIZE)) {
                  if (net_ratelimit())
                        WPRINTK("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())
                        WPRINTK("Bad rx response id %d.\n", rx->id);
                  err = -EINVAL;
                  goto next;
            }

            if (!np->copying_receiver) {
                  /* Memory pressure, insufficient buffer
                   * headroom, ... */
                  if (!(mfn = gnttab_end_foreign_transfer_ref(ref))) {
                        if (net_ratelimit())
                              WPRINTK("Unfulfilled rx req "
                                    "(id=%d, st=%d).\n",
                                    rx->id, rx->status);
                        xennet_move_rx_slot(np, skb, ref);
                        err = -ENOMEM;
                        goto next;
                  }

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

                        mcl = np->rx_mcl + pages_flipped;
                        mmu = np->rx_mmu + pages_flipped;

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

                        set_phys_to_machine(pfn, mfn);
                  }
                  pages_flipped++;
            } else {
                  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 & NETRXF_more_data))
                  break;

            if (cons + frags == rp) {
                  if (net_ratelimit())
                        WPRINTK("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())
                  WPRINTK("Too many frags\n");
            err = -E2BIG;
      }

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

      *pages_flipped_p = pages_flipped;

      return err;
}

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;
      skb_frag_t *frag = shinfo->frags + nr_frags;
      struct sk_buff *nskb;

      while ((nskb = __skb_dequeue(list))) {
            struct netif_rx_response *rx =
                  RING_GET_RESPONSE(&np->rx, ++cons);

            frag->page = skb_shinfo(nskb)->frags[0].page;
            frag->page_offset = rx->offset;
            frag->size = rx->status;

            skb->data_len += rx->status;

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

            frag++;
            nr_frags++;
      }

      shinfo->nr_frags = nr_frags;
      return cons;
}

static int xennet_set_skb_gso(struct sk_buff *skb,
                        struct netif_extra_info *gso)
{
      if (!gso->u.gso.size) {
            if (net_ratelimit())
                  WPRINTK("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())
                  WPRINTK("Bad GSO type %d.\n", gso->u.gso.type);
            return -EINVAL;
      }

#ifdef HAVE_TSO
      skb_shinfo(skb)->gso_size = gso->u.gso.size;
#ifdef HAVE_GSO
      skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;

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

      return 0;
#else
      if (net_ratelimit())
            WPRINTK("GSO unsupported by this kernel.\n");
      return -EINVAL;
#endif
}

static int netif_poll(struct net_device *dev, int *pbudget)
{
      struct netfront_info *np = netdev_priv(dev);
      struct sk_buff *skb;
      struct netfront_rx_info rinfo;
      struct netif_rx_response *rx = &rinfo.rx;
      struct netif_extra_info *extras = rinfo.extras;
      RING_IDX i, rp;
      struct multicall_entry *mcl;
      int work_done, budget, more_to_do = 1;
      struct sk_buff_head rxq;
      struct sk_buff_head errq;
      struct sk_buff_head tmpq;
      unsigned long flags;
      unsigned int len;
      int pages_flipped = 0;
      int err;

      spin_lock(&np->rx_lock); /* no need for spin_lock_bh() in ->poll() */

      if (unlikely(!netfront_carrier_ok(np))) {
            spin_unlock(&np->rx_lock);
            return 0;
      }

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

      if ((budget = *pbudget) > dev->quota)
            budget = dev->quota;
      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,
                                 &pages_flipped);

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

            skb = __skb_dequeue(&tmpq);

            if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
                  struct 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)->page = skb_shinfo(skb)->frags[0].page;
            NETFRONT_SKB_CB(skb)->offset = rx->offset;

            len = rx->status;
            if (len > RX_COPY_THRESHOLD)
                  len = RX_COPY_THRESHOLD;
            skb_put(skb, len);

            if (rx->status > len) {
                  skb_shinfo(skb)->frags[0].page_offset =
                        rx->offset + len;
                  skb_shinfo(skb)->frags[0].size = rx->status - len;
                  skb->data_len = rx->status - len;
            } else {
                  skb_shinfo(skb)->frags[0].page = NULL;
                  skb_shinfo(skb)->nr_frags = 0;
            }

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

            /*
             * Truesize must 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 - len);
            skb->len += skb->data_len;

            /*
             * Old backends do not assert data_validated but we
             * can infer it from csum_blank so test both flags.
             */
            if (rx->flags & (NETRXF_data_validated|NETRXF_csum_blank))
                  skb->ip_summed = CHECKSUM_UNNECESSARY;
            else
                  skb->ip_summed = CHECKSUM_NONE;
#ifdef CONFIG_XEN
            skb->proto_data_valid = (skb->ip_summed != CHECKSUM_NONE);
            skb->proto_csum_blank = !!(rx->flags & NETRXF_csum_blank);
#endif
            np->stats.rx_packets++;
            np->stats.rx_bytes += skb->len;

            __skb_queue_tail(&rxq, skb);

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

      if (pages_flipped) {
            /* Some pages are no longer absent... */
            balloon_update_driver_allowance(-pages_flipped);

            /* Do all the remapping work and M2P updates. */
            if (!xen_feature(XENFEAT_auto_translated_physmap)) {
                  mcl = np->rx_mcl + pages_flipped;
                  mcl->op = __HYPERVISOR_mmu_update;
                  mcl->args[0] = (unsigned long)np->rx_mmu;
                  mcl->args[1] = pages_flipped;
                  mcl->args[2] = 0;
                  mcl->args[3] = DOMID_SELF;
                  (void)HYPERVISOR_multicall(np->rx_mcl,
                                       pages_flipped + 1);
            }
      }

      while ((skb = __skb_dequeue(&errq)))
            kfree_skb(skb);

      while ((skb = __skb_dequeue(&rxq)) != NULL) {
            struct page *page = NETFRONT_SKB_CB(skb)->page;
            void *vaddr = page_address(page);
            unsigned offset = NETFRONT_SKB_CB(skb)->offset;

            memcpy(skb->data, vaddr + offset, skb_headlen(skb));

            if (page != skb_shinfo(skb)->frags[0].page)
                  __free_page(page);

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

            /* Pass it up. */
            netif_receive_skb(skb);
            dev->last_rx = jiffies;
      }

      /* 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;

      network_alloc_rx_buffers(dev);

      *pbudget   -= work_done;
      dev->quota -= work_done;

      if (work_done < budget) {
            local_irq_save(flags);

            RING_FINAL_CHECK_FOR_RESPONSES(&np->rx, more_to_do);
            if (!more_to_do)
                  __netif_rx_complete(dev);

            local_irq_restore(flags);
      }

      spin_unlock(&np->rx_lock);

      return more_to_do;
}

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

      for (i = 1; i <= NET_TX_RING_SIZE; i++) {
            if ((unsigned long)np->tx_skbs[i] < PAGE_OFFSET)
                  continue;

            skb = np->tx_skbs[i];
            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_skbs, i);
            dev_kfree_skb_irq(skb);
      }
}

static void netif_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, rc;

      if (np->copying_receiver) {
            WPRINTK("%s: fix me for copying receiver.\n", __FUNCTION__);
            return;
      }

      skb_queue_head_init(&free_list);

      spin_lock_bh(&np->rx_lock);

      for (id = 0; id < NET_RX_RING_SIZE; id++) {
            if ((ref = np->grant_rx_ref[id]) == 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;
            add_id_to_freelist(np->rx_skbs, id);

            if (0 == mfn) {
                  struct page *page = skb_shinfo(skb)->frags[0].page;
                  balloon_release_driver_page(page);
                  skb_shinfo(skb)->nr_frags = 0;
                  dev_kfree_skb(skb);
                  noxfer++;
                  continue;
            }

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

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

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

      IPRINTK("%s: %d xfer, %d noxfer, %d unused\n",
            __FUNCTION__, xfer, noxfer, unused);

      if (xfer) {
            /* Some pages are no longer absent... */
            balloon_update_driver_allowance(-xfer);

            if (!xen_feature(XENFEAT_auto_translated_physmap)) {
                  /* Do all the remapping work and M2P updates. */
                  mcl->op = __HYPERVISOR_mmu_update;
                  mcl->args[0] = (unsigned long)np->rx_mmu;
                  mcl->args[1] = mmu - np->rx_mmu;
                  mcl->args[2] = 0;
                  mcl->args[3] = DOMID_SELF;
                  mcl++;
                  rc = HYPERVISOR_multicall_check(
                        np->rx_mcl, mcl - np->rx_mcl, NULL);
                  BUG_ON(rc);
            }
      }

      while ((skb = __skb_dequeue(&free_list)) != NULL)
            dev_kfree_skb(skb);

      spin_unlock_bh(&np->rx_lock);
}

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


static struct net_device_stats *network_get_stats(struct net_device *dev)
{
      struct netfront_info *np = netdev_priv(dev);
      return &np->stats;
}

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 int xennet_set_sg(struct net_device *dev, u32 data)
{
      if (data) {
            struct netfront_info *np = netdev_priv(dev);
            int val;

            if (xenbus_scanf(XBT_NIL, np->xbdev->otherend, "feature-sg",
                         "%d", &val) < 0)
                  val = 0;
            if (!val)
                  return -ENOSYS;
      } else if (dev->mtu > ETH_DATA_LEN)
            dev->mtu = ETH_DATA_LEN;

      return ethtool_op_set_sg(dev, data);
}

static int xennet_set_tso(struct net_device *dev, u32 data)
{
#ifdef HAVE_TSO
      if (data) {
            struct netfront_info *np = netdev_priv(dev);
            int val;

            if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
                         "feature-gso-tcpv4", "%d", &val) < 0)
                  val = 0;
            if (!val)
                  return -ENOSYS;
      }

      return ethtool_op_set_tso(dev, data);
#else
      return -ENOSYS;
#endif
}

static void xennet_set_features(struct net_device *dev)
{
      dev_disable_gso_features(dev);
      xennet_set_sg(dev, 0);

      /* We need checksum offload to enable scatter/gather and TSO. */
      if (!(dev->features & NETIF_F_IP_CSUM))
            return;

      if (xennet_set_sg(dev, 1))
            return;

      /* Before 2.6.9 TSO seems to be unreliable so do not enable it
       * on older kernels.
       */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,9)
      xennet_set_tso(dev, 1);
#endif

}

static int network_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;
      netif_rx_request_t *req;
      unsigned int feature_rx_copy, feature_rx_flip;

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

      /*
       * Copy packets on receive path if:
       *  (a) This was requested by user, and the backend supports it; or
       *  (b) Flipping was requested, but this is unsupported by the backend.
       */
      np->copying_receiver = ((MODPARM_rx_copy && feature_rx_copy) ||
                        (MODPARM_rx_flip && !feature_rx_flip));

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

      xennet_set_features(dev);

      IPRINTK("device %s has %sing receive path.\n",
            dev->name, np->copying_receiver ? "copy" : "flipp");

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

      /*
       * Recovery procedure:
       *  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.
       */

      /* Step 1: Discard all pending TX packet fragments. */
      netif_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++) {
            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);

            if (!np->copying_receiver) {
                  gnttab_grant_foreign_transfer_ref(
                        ref, np->xbdev->otherend_id,
                        page_to_pfn(skb_shinfo(skb)->frags->page));
            } else {
                  gnttab_grant_foreign_access_ref(
                        ref, np->xbdev->otherend_id,
                        pfn_to_mfn(page_to_pfn(skb_shinfo(skb)->
                                           frags->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.
       */
      netfront_carrier_on(np);
      notify_remote_via_irq(np->irq);
      network_tx_buf_gc(dev);
      network_alloc_rx_buffers(dev);

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

      return 0;
}

static void netif_uninit(struct net_device *dev)
{
      struct netfront_info *np = netdev_priv(dev);
      netif_release_tx_bufs(np);
      netif_release_rx_bufs(np);
      gnttab_free_grant_references(np->gref_tx_head);
      gnttab_free_grant_references(np->gref_rx_head);
}

static struct ethtool_ops network_ethtool_ops =
{
      .get_tx_csum = ethtool_op_get_tx_csum,
      .set_tx_csum = ethtool_op_set_tx_csum,
      .get_sg = ethtool_op_get_sg,
      .set_sg = xennet_set_sg,
      .get_tso = ethtool_op_get_tso,
      .set_tso = xennet_set_tso,
      .get_link = ethtool_op_get_link,
};

#ifdef CONFIG_SYSFS
static ssize_t show_rxbuf_min(struct class_device *cd, char *buf)
{
      struct net_device *netdev = container_of(cd, struct net_device,
                                     class_dev);
      struct netfront_info *info = netdev_priv(netdev);

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

static ssize_t store_rxbuf_min(struct class_device *cd,
                         const char *buf, size_t len)
{
      struct net_device *netdev = container_of(cd, struct net_device,
                                     class_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;

      network_alloc_rx_buffers(netdev);

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

static ssize_t show_rxbuf_max(struct class_device *cd, char *buf)
{
      struct net_device *netdev = container_of(cd, struct net_device,
                                     class_dev);
      struct netfront_info *info = netdev_priv(netdev);

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

static ssize_t store_rxbuf_max(struct class_device *cd,
                         const char *buf, size_t len)
{
      struct net_device *netdev = container_of(cd, struct net_device,
                                     class_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;

      network_alloc_rx_buffers(netdev);

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

static ssize_t show_rxbuf_cur(struct class_device *cd, char *buf)
{
      struct net_device *netdev = container_of(cd, struct net_device,
                                     class_dev);
      struct netfront_info *info = netdev_priv(netdev);

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

static const struct class_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 error = 0;

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

 fail:
      while (--i >= 0)
            class_device_remove_file(&netdev->class_dev,
                               &xennet_attrs[i]);
      return error;
}

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

      for (i = 0; i < ARRAY_SIZE(xennet_attrs); i++) {
            class_device_remove_file(&netdev->class_dev,
                               &xennet_attrs[i]);
      }
}

#endif /* CONFIG_SYSFS */


/*
 * Nothing to do here. Virtual interface is point-to-point and the
 * physical interface is probably promiscuous anyway.
 */
static void network_set_multicast_list(struct net_device *dev)
{
}

static struct net_device * __devinit create_netdev(struct xenbus_device *dev)
{
      int i, err = 0;
      struct net_device *netdev = NULL;
      struct netfront_info *np = NULL;

      netdev = alloc_etherdev(sizeof(struct netfront_info));
      if (!netdev) {
            printk(KERN_WARNING "%s> alloc_etherdev failed.\n",
                   __FUNCTION__);
            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;

      /* Initialise {tx,rx}_skbs as a free chain containing every entry. */
      for (i = 0; i <= NET_TX_RING_SIZE; i++) {
            np->tx_skbs[i] = (void *)((unsigned long) i+1);
            np->grant_tx_ref[i] = GRANT_INVALID_REF;
      }

      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;
      }
      /* 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->open            = network_open;
      netdev->hard_start_xmit = network_start_xmit;
      netdev->stop            = network_close;
      netdev->get_stats       = network_get_stats;
      netdev->poll            = netif_poll;
      netdev->set_multicast_list = network_set_multicast_list;
      netdev->uninit          = netif_uninit;
      netdev->change_mtu      = xennet_change_mtu;
      netdev->weight          = 64;
      netdev->features        = NETIF_F_IP_CSUM;

      SET_ETHTOOL_OPS(netdev, &network_ethtool_ops);
      SET_MODULE_OWNER(netdev);
      SET_NETDEV_DEV(netdev, &dev->dev);

      np->netdev = netdev;

      netfront_carrier_off(np);

      return netdev;

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

/*
 * We use this notifier to send out a fake ARP reply to reset switches and
 * router ARP caches when an IP interface is brought up on a VIF.
 */
static int
inetdev_notify(struct notifier_block *this, unsigned long event, void *ptr)
{
      struct in_ifaddr  *ifa = (struct in_ifaddr *)ptr;
      struct net_device *dev = ifa->ifa_dev->dev;

      /* UP event and is it one of our devices? */
      if (event == NETDEV_UP && dev->open == network_open)
            (void)send_fake_arp(dev);

      return NOTIFY_DONE;
}


static void netif_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);
      netfront_carrier_off(info);
      spin_unlock_irq(&info->tx_lock);
      spin_unlock_bh(&info->rx_lock);

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

      end_access(info->tx_ring_ref, info->tx.sring);
      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 void end_access(int ref, void *page)
{
      if (ref != GRANT_INVALID_REF)
            gnttab_end_foreign_access(ref, 0, (unsigned long)page);
}


/* ** Driver registration ** */


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


static struct xenbus_driver netfront = {
      .name = "vif",
      .owner = THIS_MODULE,
      .ids = netfront_ids,
      .probe = netfront_probe,
      .remove = __devexit_p(netfront_remove),
      .resume = netfront_resume,
      .otherend_changed = backend_changed,
};


static struct notifier_block notifier_inetdev = {
      .notifier_call  = inetdev_notify,
      .next           = NULL,
      .priority       = 0
};

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

#ifdef CONFIG_XEN
      if (MODPARM_rx_flip && MODPARM_rx_copy) {
            WPRINTK("Cannot specify both rx_copy and rx_flip.\n");
            return -EINVAL;
      }

      if (!MODPARM_rx_flip && !MODPARM_rx_copy)
            MODPARM_rx_flip = 1; /* Default is to flip. */
#endif

      if (is_initial_xendomain())
            return 0;

      IPRINTK("Initialising virtual ethernet driver.\n");

      (void)register_inetaddr_notifier(&notifier_inetdev);

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


static void __exit netif_exit(void)
{
      if (is_initial_xendomain())
            return;

      unregister_inetaddr_notifier(&notifier_inetdev);

      return xenbus_unregister_driver(&netfront);
}
module_exit(netif_exit);

MODULE_LICENSE("Dual BSD/GPL");

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