text: /*
   * 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 <net/tcp.h>
  #include <linux/udp.h>
  #include <linux/moduleparam.h>
  #include <linux/mm.h>
  #include <linux/slab.h>
  #include <net/ip.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 {
  	struct page *page;
  	unsigned offset;
  };
  
  #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;
  
  		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(skb_frag_page(frag)));
  		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 = skb_frag_size(frag);
  		tx->flags = 0;
  	}
  
  	np->tx.req_prod_pvt = prod;
  }
  
  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 frags = skb_shinfo(skb)->nr_frags;
  	unsigned int offset = offset_in_page(data);
  	unsigned int len = skb_headlen(skb);
  	unsigned long flags;
  
  	/* If skb->len is too big for wire format, drop skb and alert
  	 * user about misconfiguration.
  	 */
  	if (unlikely(skb->len > XEN_NETIF_MAX_TX_SIZE)) {
  		net_alert_ratelimited(
  			"xennet: skb->len = %u, too big for wire format\n",
  			skb->len);
  		goto drop;
  	}
  
  	frags += DIV_ROUND_UP(offset + len, 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_irqsave(&np->tx_lock, flags);
  
  	if (unlikely(!netif_carrier_ok(dev) ||
  		     (frags > 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) {
  		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_frag_page(&skb_shinfo(skb)->frags[0]))
  			__free_page(page);
  
  		/* 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;
  	unsigned int len;
  	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)->page =
  			skb_frag_page(&skb_shinfo(skb)->frags[0]);
  		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_frag_size_set(&skb_shinfo(skb)->frags[0], rx->status - len);
  			skb->data_len = rx->status - len;
  		} else {
  			__skb_fill_page_desc(skb, 0, NULL, 0, 0);
  			skb_shinfo(skb)->nr_frags = 0;
  		}
  
  		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 - len);
  		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) ?
  		XEN_NETIF_MAX_TX_SIZE - MAX_TCP_HEADER : 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);
  
  	netif_set_gso_max_size(netdev, XEN_NETIF_MAX_TX_SIZE - MAX_TCP_HEADER);
  
  	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);
  }
  
  /**
   * 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 = 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;
  }
  
  /**
   * 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_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;
  }
  
  /**
   * Callback received when the backend's state changes.
   */
  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:
  		netif_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_initial_domain())
  		return 0;
  
  	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)
  {
  	if (xen_initial_domain())
  		return;
  
  	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");
  