[RFC PATCH 32/33] Add the Xen virtual network device driver.

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The network device frontend driver allows the kernel to access network
devices exported exported by a virtual machine containing a physical
network device driver.

Signed-off-by: Ian Pratt <[email protected]>
Signed-off-by: Christian Limpach <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
Cc: [email protected]
---

 drivers/net/Kconfig             |    2
 drivers/xen/Kconfig.net         |   14
 drivers/xen/Makefile            |    3
 drivers/xen/net_driver_util.c   |   58 +
 drivers/xen/netfront/Makefile   |    4
 drivers/xen/netfront/netfront.c | 1326 ++++++++++++++++++++++++++++++++++++++++ include/xen/net_driver_util.h   |   48 +
 7 files changed, 1455 insertions(+)

diff -r eadc12b20f35 drivers/net/Kconfig
--- a/drivers/net/Kconfig	Fri Jun 09 15:02:44 2006 -0400
+++ b/drivers/net/Kconfig	Fri Jun 09 15:03:12 2006 -0400
@@ -2325,6 +2325,8 @@ source "drivers/atm/Kconfig"
 
 source "drivers/s390/net/Kconfig"
 
+source "drivers/xen/Kconfig.net"
+
 config ISERIES_VETH
 	tristate "iSeries Virtual Ethernet driver support"
 	depends on PPC_ISERIES
diff -r eadc12b20f35 drivers/xen/Makefile
--- a/drivers/xen/Makefile	Fri Jun 09 15:02:44 2006 -0400
+++ b/drivers/xen/Makefile	Fri Jun 09 15:03:12 2006 -0400
@@ -5,3 +5,5 @@ obj-y	+= console/
 obj-y	+= console/
 obj-y	+= xenbus/
 
+obj-$(CONFIG_XEN_NETDEV_FRONTEND)	+= netfront/
+
diff -r eadc12b20f35 drivers/xen/Kconfig.net
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/drivers/xen/Kconfig.net	Fri Jun 09 15:03:12 2006 -0400
@@ -0,0 +1,14 @@
+menu "Xen network device drivers"
+        depends on NETDEVICES && XEN
+
+config XEN_NETDEV_FRONTEND
+	tristate "Network-device frontend driver"
+	depends on XEN
+	default y
+	help
+	  The network-device frontend driver allows the kernel to access
+	  network interfaces within another guest OS. Unless you are building a
+	  dedicated device-driver domain, or your master control domain
+	  (domain 0), then you almost certainly want to say Y here.
+
+endmenu
diff -r eadc12b20f35 drivers/xen/netfront/Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/drivers/xen/netfront/Makefile	Fri Jun 09 15:03:12 2006 -0400
@@ -0,0 +1,4 @@
+
+obj-$(CONFIG_XEN_NETDEV_FRONTEND)	:= xennet.o
+
+xennet-objs := netfront.o
diff -r eadc12b20f35 drivers/xen/netfront/netfront.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/drivers/xen/netfront/netfront.c	Fri Jun 09 15:03:12 2006 -0400
@@ -0,0 +1,1584 @@
+/******************************************************************************
+ * 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/config.h>
+#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 <net/sock.h>
+#include <net/pkt_sched.h>
+#include <net/arp.h>
+#include <net/route.h>
+#include <asm/io.h>
+#include <asm/uaccess.h>
+#include <xen/evtchn.h>
+#include <xen/xenbus.h>
+#include <xen/interface/io/netif.h>
+#include <xen/interface/memory.h>
+#ifdef CONFIG_XEN_BALLOON
+#include <xen/balloon.h>
+#endif
+#include <asm/page.h>
+#include <asm/uaccess.h>
+#include <xen/interface/grant_table.h>
+#include <xen/gnttab.h>
+
+#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)
+
+static inline void init_skb_shinfo(struct sk_buff *skb)
+{
+	atomic_set(&(skb_shinfo(skb)->dataref), 1);
+	skb_shinfo(skb)->nr_frags = 0;
+	skb_shinfo(skb)->frag_list = NULL;
+}
+
+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 handle;
+	unsigned int evtchn, irq;
+
+	/* 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 each
+	 * array 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+1];
+
+#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_TX_RING_SIZE + 1];
+
+	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];
+};
+
+/*
+ * Access macros for acquiring freeing slots in {tx,rx}_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;
+}
+
+#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 talk_to_backend(struct xenbus_device *, struct netfront_info *);
+static int setup_device(struct xenbus_device *, struct netfront_info *);
+static struct net_device *create_netdev(int, struct xenbus_device *);
+
+static void netfront_closing(struct xenbus_device *);
+
+static void end_access(int, void *);
+static void netif_disconnect_backend(struct netfront_info *);
+static void close_netdev(struct netfront_info *);
+static void netif_free(struct netfront_info *);
+
+static void show_device(struct netfront_info *);
+
+static void 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.  Switch to
+ * Connected state.
+ */
+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;
+	unsigned int handle;
+
+	err = xenbus_scanf(XBT_NIL, dev->nodename, "handle", "%u", &handle);
+	if (err != 1) {
+		xenbus_dev_fatal(dev, err, "reading handle");
+		return err;
+	}
+
+	netdev = create_netdev(handle, 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 = talk_to_backend(dev, info);
+	if (err) {
+		xennet_sysfs_delif(info->netdev);
+		unregister_netdev(netdev);
+		free_netdev(netdev);
+		dev->dev.driver_data = NULL;
+		return err;
+	}
+
+	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 talk_to_backend(dev, info);
+}
+
+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", info->evtchn);
+	if (err) {
+		message = "writing event-channel";
+		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:
+	netif_free(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;
+
+	err = xenbus_alloc_evtchn(dev, &info->evtchn);
+	if (err)
+		goto fail;
+
+	memcpy(netdev->dev_addr, info->mac, ETH_ALEN);
+	err = bind_evtchn_to_irqhandler(info->evtchn, netif_int,
+					SA_SAMPLE_RANDOM, netdev->name, netdev);
+	if (err < 0)
+		goto fail;
+	info->irq = err;
+	return 0;
+
+ fail:
+	netif_free(info);
+	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("\n");
+
+	switch (backend_state) {
+	case XenbusStateInitialising:
+	case XenbusStateInitialised:
+	case XenbusStateConnected:
+	case XenbusStateUnknown:
+	case XenbusStateClosed:
+		break;
+
+	case XenbusStateInitWait:
+		network_connect(netdev);
+		xenbus_switch_state(dev, XenbusStateConnected);
+		(void)send_fake_arp(netdev);
+		show_device(np);
+		break;
+
+	case XenbusStateClosing:
+		netfront_closing(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 int network_open(struct net_device *dev)
+{
+	struct netfront_info *np = netdev_priv(dev);
+
+	memset(&np->stats, 0, sizeof(np->stats));
+
+	network_alloc_rx_buffers(dev);
+	np->rx.sring->rsp_event = np->rx.rsp_cons + 1;
+
+	netif_start_queue(dev);
+
+	return 0;
+}
+
+static inline int netfront_tx_slot_available(struct netfront_info *np)
+{
+	return RING_FREE_REQUESTS(&np->tx) >= MAX_SKB_FRAGS + 1;
+}
+
+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 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;
+
+	if (unlikely(!netif_carrier_ok(dev)))
+		return;
+
+	do {
+		prod = np->tx.sring->rsp_prod;
+		rmb(); /* Ensure we see responses up to 'rp'. */
+
+		for (cons = np->tx.rsp_cons; cons != prod; cons++) {
+			id  = RING_GET_RESPONSE(&np->tx, cons)->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");
+				break; /* bail immediately */
+			}
+			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;
+	int i, batch_target;
+	RING_IDX req_prod = np->rx.req_prod_pvt;
+	struct xen_memory_reservation reservation;
+	grant_ref_t ref;
+
+	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++) {
+		/*
+		 * Subtract dev_alloc_skb headroom (16 bytes) and shared info
+		 * tailroom then round down to SKB_DATA_ALIGN boundary.
+		 */
+		skb = __dev_alloc_skb(
+			((PAGE_SIZE - sizeof(struct skb_shared_info)) &
+			 (-SKB_DATA_ALIGN(1))) - 16,
+			GFP_ATOMIC|__GFP_NOWARN);
+		if (skb == NULL) {
+			/* 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));
+			return;
+		}
+		__skb_queue_tail(&np->rx_batch, skb);
+	}
+
+	/* Is the batch large enough to be worthwhile? */
+	if (i < (np->rx_target/2))
+		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++) {
+		if ((skb = __skb_dequeue(&np->rx_batch)) == NULL)
+			break;
+
+		skb->dev = dev;
+
+		id = get_id_from_freelist(np->rx_skbs);
+
+		np->rx_skbs[id] = skb;
+
+		RING_GET_REQUEST(&np->rx, req_prod + i)->id = id;
+		ref = gnttab_claim_grant_reference(&np->gref_rx_head);
+		BUG_ON((signed short)ref < 0);
+		np->grant_rx_ref[id] = ref;
+		gnttab_grant_foreign_transfer_ref(ref,
+						  np->xbdev->otherend_id,
+						  __pa(skb->head) >> PAGE_SHIFT);
+		RING_GET_REQUEST(&np->rx, req_prod + i)->gref = ref;
+		np->rx_pfn_array[i] = virt_to_mfn(skb->head);
+
+#ifndef CONFIG_XEN_SHADOW_MODE
+		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+			/* Remove this page before passing back to Xen. */
+			set_phys_to_machine(__pa(skb->head) >> PAGE_SHIFT,
+					    INVALID_P2M_ENTRY);
+			MULTI_update_va_mapping(np->rx_mcl+i,
+						(unsigned long)skb->head,
+						__pte(0), 0);
+		}
+#endif
+	}
+
+#ifdef CONFIG_XEN_BALLOON
+	/* Tell the ballon driver what is going on. */
+	balloon_update_driver_allowance(i);
+#endif
+
+	reservation.extent_start = np->rx_pfn_array;
+	reservation.nr_extents   = i;
+	reservation.extent_order = 0;
+	reservation.address_bits = 0;
+	reservation.domid        = DOMID_SELF;
+
+#ifndef CONFIG_XEN_SHADOW_MODE
+	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
+#endif
+		if (HYPERVISOR_memory_op(XENMEM_decrease_reservation,
+					 &reservation) != i)
+			panic("Unable to reduce memory reservation\n");
+
+	/* Above is a suitable barrier to ensure backend will see requests. */
+	np->rx.req_prod_pvt = req_prod + i;
+	RING_PUSH_REQUESTS(&np->rx);
+}
+
+
+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;
+	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(!netif_carrier_ok(dev) ||
+		     (frags > 1 && !xennet_can_sg(dev)))) {
+		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 = (skb->ip_summed == CHECKSUM_HW) ? NETTXF_csum_blank : 0;
+
+	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);
+	network_tx_buf_gc(dev);
+	spin_unlock_irqrestore(&np->tx_lock, flags);
+
+	if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx) &&
+	    likely(netif_running(dev)))
+		netif_rx_schedule(dev);
+
+	return IRQ_HANDLED;
+}
+
+
+static int netif_poll(struct net_device *dev, int *pbudget)
+{
+	struct netfront_info *np = netdev_priv(dev);
+	struct sk_buff *skb, *nskb;
+	struct netif_rx_response *rx;
+	RING_IDX i, rp;
+	struct mmu_update *mmu = np->rx_mmu;
+	struct multicall_entry *mcl = np->rx_mcl;
+	int work_done, budget, more_to_do = 1;
+	struct sk_buff_head rxq;
+	unsigned long flags;
+	unsigned long mfn;
+	grant_ref_t ref;
+
+	spin_lock(&np->rx_lock);
+
+	if (unlikely(!netif_carrier_ok(dev))) {
+		spin_unlock(&np->rx_lock);
+		return 0;
+	}
+
+	skb_queue_head_init(&rxq);
+
+	if ((budget = *pbudget) > dev->quota)
+		budget = dev->quota;
+	rp = np->rx.sring->rsp_prod;
+	rmb(); /* Ensure we see queued responses up to 'rp'. */
+
+	for (i = np->rx.rsp_cons, work_done = 0;
+	     (i != rp) && (work_done < budget);
+	     i++, work_done++) {
+		rx = RING_GET_RESPONSE(&np->rx, i);
+
+		/*
+                 * 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 = np->grant_rx_ref[rx->id]) == GRANT_INVALID_REF) {
+			WPRINTK("Bad rx response id %d.\n", rx->id);
+			work_done--;
+			continue;
+		}
+
+		/* Memory pressure, insufficient buffer headroom, ... */
+		if ((mfn = gnttab_end_foreign_transfer_ref(ref)) == 0) {
+			if (net_ratelimit())
+				WPRINTK("Unfulfilled rx req (id=%d, st=%d).\n",
+					rx->id, rx->status);
+			RING_GET_REQUEST(&np->rx, np->rx.req_prod_pvt)->id =
+				rx->id;
+			RING_GET_REQUEST(&np->rx, np->rx.req_prod_pvt)->gref =
+				ref;
+			np->rx.req_prod_pvt++;
+			RING_PUSH_REQUESTS(&np->rx);
+			work_done--;
+			continue;
+		}
+
+		gnttab_release_grant_reference(&np->gref_rx_head, ref);
+		np->grant_rx_ref[rx->id] = GRANT_INVALID_REF;
+
+		skb = np->rx_skbs[rx->id];
+		add_id_to_freelist(np->rx_skbs, rx->id);
+
+		/* NB. We handle skb overflow later. */
+		skb->data = skb->head + rx->offset;
+		skb->len  = rx->status;
+		skb->tail = skb->data + skb->len;
+
+		if (rx->flags & NETRXF_data_validated)
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+		np->stats.rx_packets++;
+		np->stats.rx_bytes += rx->status;
+
+#ifndef CONFIG_XEN_SHADOW_MODE
+		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+			/* Remap the page. */
+			MULTI_update_va_mapping(mcl, (unsigned long)skb->head,
+						pfn_pte_ma(mfn, PAGE_KERNEL),
+						0);
+			mcl++;
+			mmu->ptr = ((maddr_t)mfn << PAGE_SHIFT)
+				| MMU_MACHPHYS_UPDATE;
+			mmu->val = __pa(skb->head) >> PAGE_SHIFT;
+			mmu++;
+
+			set_phys_to_machine(__pa(skb->head) >> PAGE_SHIFT,
+					    mfn);
+		}
+#endif
+
+		__skb_queue_tail(&rxq, skb);
+	}
+
+#ifdef CONFIG_XEN_BALLOON
+	/* Some pages are no longer absent... */
+	balloon_update_driver_allowance(-work_done);
+#endif
+
+	/* Do all the remapping work, and M2P updates, in one big hypercall. */
+	if (likely((mcl - np->rx_mcl) != 0)) {
+		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++;
+		(void)HYPERVISOR_multicall(np->rx_mcl, mcl - np->rx_mcl);
+	}
+
+	while ((skb = __skb_dequeue(&rxq)) != NULL) {
+		if (skb->len > (dev->mtu + ETH_HLEN + 4)) {
+			if (net_ratelimit())
+				printk(KERN_INFO "Received packet too big for "
+				       "MTU (%d > %d)\n",
+				       skb->len - ETH_HLEN - 4, dev->mtu);
+			skb->len  = 0;
+			skb->tail = skb->data;
+			init_skb_shinfo(skb);
+			dev_kfree_skb(skb);
+			continue;
+		}
+
+		/*
+		 * Enough room in skbuff for the data we were passed? Also,
+		 * Linux expects at least 16 bytes headroom in each rx buffer.
+		 */
+		if (unlikely(skb->tail > skb->end) ||
+		    unlikely((skb->data - skb->head) < 16)) {
+			if (net_ratelimit()) {
+				if (skb->tail > skb->end)
+					printk(KERN_INFO "Received packet "
+					       "is %zd bytes beyond tail.\n",
+					       skb->tail - skb->end);
+				else
+					printk(KERN_INFO "Received packet "
+					       "is %zd bytes before head.\n",
+					       16 - (skb->data - skb->head));
+			}
+
+			nskb = __dev_alloc_skb(skb->len + 2,
+					       GFP_ATOMIC|__GFP_NOWARN);
+			if (nskb != NULL) {
+				skb_reserve(nskb, 2);
+				skb_put(nskb, skb->len);
+				memcpy(nskb->data, skb->data, skb->len);
+				nskb->dev = skb->dev;
+				nskb->ip_summed = skb->ip_summed;
+			}
+
+			/* Reinitialise and then destroy the old skbuff. */
+			skb->len  = 0;
+			skb->tail = skb->data;
+			init_skb_shinfo(skb);
+			dev_kfree_skb(skb);
+
+			/* Switch old for new, if we copied the buffer. */
+			if ((skb = nskb) == NULL)
+				continue;
+		}
+
+		/* Set the shinfo area, which is hidden behind the data. */
+		init_skb_shinfo(skb);
+		/* 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;
+	}
+
+	np->rx.rsp_cons = i;
+
+	/* 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 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 void xennet_set_features(struct net_device *dev)
+{
+	xennet_set_sg(dev, 1);
+}
+
+static void network_connect(struct net_device *dev)
+{
+	struct netfront_info *np;
+	int i, requeue_idx;
+	struct netif_tx_request *tx;
+	struct sk_buff *skb;
+
+	xennet_set_features(dev);
+
+	np = netdev_priv(dev);
+	spin_lock_irq(&np->tx_lock);
+	spin_lock(&np->rx_lock);
+
+	/* Recovery procedure: */
+
+	/*
+	 * Step 1: Rebuild the RX and TX ring contents.
+	 * NB. We could just free the queued TX packets now but we hope
+	 * that sending them out might do some good.  We have to rebuild
+	 * the RX ring because some of our pages are currently flipped out
+	 * so we can't just free the RX skbs.
+	 * NB2. 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.
+	 */
+
+	/*
+	 * Rebuild the TX buffer freelist and the TX ring itself.
+	 * NB. This reorders packets.  We could keep more private state
+	 * to avoid this but maybe it doesn't matter so much given the
+	 * interface has been down.
+	 */
+	for (requeue_idx = 0, i = 1; i <= NET_TX_RING_SIZE; i++) {
+		if ((unsigned long)np->tx_skbs[i] < PAGE_OFFSET)
+			continue;
+
+		skb = np->tx_skbs[i];
+
+		tx = RING_GET_REQUEST(&np->tx, requeue_idx);
+		requeue_idx++;
+
+		tx->id = i;
+		gnttab_grant_foreign_access_ref(
+			np->grant_tx_ref[i], np->xbdev->otherend_id,
+			virt_to_mfn(np->tx_skbs[i]->data),
+			GNTMAP_readonly);
+		tx->gref = np->grant_tx_ref[i];
+		tx->offset = (unsigned long)skb->data & ~PAGE_MASK;
+		tx->size = skb->len;
+		tx->flags = (skb->ip_summed == CHECKSUM_HW) ?
+			NETTXF_csum_blank : 0;
+
+		np->stats.tx_bytes += skb->len;
+		np->stats.tx_packets++;
+	}
+
+	np->tx.req_prod_pvt = requeue_idx;
+	RING_PUSH_REQUESTS(&np->tx);
+
+	/* Rebuild the RX buffer freelist and the RX ring itself. */
+	for (requeue_idx = 0, i = 1; i <= NET_RX_RING_SIZE; i++) {
+		if ((unsigned long)np->rx_skbs[i] < PAGE_OFFSET)
+			continue;
+		gnttab_grant_foreign_transfer_ref(
+			np->grant_rx_ref[i], np->xbdev->otherend_id,
+			__pa(np->rx_skbs[i]->data) >> PAGE_SHIFT);
+		RING_GET_REQUEST(&np->rx, requeue_idx)->gref =
+			np->grant_rx_ref[i];
+		RING_GET_REQUEST(&np->rx, requeue_idx)->id = i;
+		requeue_idx++;
+	}
+
+	np->rx.req_prod_pvt = requeue_idx;
+	RING_PUSH_REQUESTS(&np->rx);
+
+	/*
+	 * Step 2: 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(dev);
+	notify_remote_via_irq(np->irq);
+	network_tx_buf_gc(dev);
+
+	spin_unlock(&np->rx_lock);
+	spin_unlock_irq(&np->tx_lock);
+}
+
+static void show_device(struct netfront_info *np)
+{
+#ifdef DEBUG
+	if (np) {
+		IPRINTK("<vif handle=%u %s(%s) evtchn=%u tx=%p rx=%p>\n",
+			np->handle,
+			netif_carrier_ok(np->netdev) ? "on" : "off",
+			netif_running(np->netdev) ? "open" : "closed",
+			np->evtchn,
+			np->tx,
+			np->rx);
+	} else
+		IPRINTK("<vif NULL>\n");
+#endif
+}
+
+static void netif_uninit(struct net_device *dev)
+{
+	struct netfront_info *np = netdev_priv(dev);
+	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,
+};
+
+/*
+ * 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)
+{
+}
+
+/** Create a network device.
+ * @param handle device handle
+ * @param val return parameter for created device
+ * @return 0 on success, error code otherwise
+ */
+static struct net_device * __devinit create_netdev(int handle,
+						   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->handle        = handle;
+	np->xbdev         = dev;
+
+	netif_carrier_off(netdev);
+
+	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] = (void *)((unsigned long) i+1);
+		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);
+
+	err = register_netdev(netdev);
+	if (err) {
+		printk(KERN_WARNING "%s> register_netdev err=%d\n",
+		       __FUNCTION__, err);
+		goto exit_free_rx;
+	}
+
+	err = xennet_sysfs_addif(netdev);
+	if (err) {
+		/* This can be non-fatal: it only means no tuning parameters */
+		printk(KERN_WARNING "%s> add sysfs failed err=%d\n",
+		       __FUNCTION__, err);
+	}
+
+	np->netdev = netdev;
+
+	return netdev;
+
+ exit_free_rx:
+	gnttab_free_grant_references(np->gref_rx_head);
+ exit_free_tx:
+	gnttab_free_grant_references(np->gref_tx_head);
+ exit:
+	free_netdev(netdev);
+	return ERR_PTR(err);
+}
+
+#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(&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(&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(&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(&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 */
+
+
+/*
+ * 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;
+}
+
+
+/* ** Close down ** */
+
+
+/**
+ * Handle the change of state of the backend to Closing.  We must delete our
+ * device-layer structures now, to ensure that writes are flushed through to
+ * the backend.  Once is this done, we can switch to Closed in
+ * acknowledgement.
+ */
+static void netfront_closing(struct xenbus_device *dev)
+{
+	struct netfront_info *info = dev->dev.driver_data;
+
+	DPRINTK("netfront_closing: %s removed\n", dev->nodename);
+
+	close_netdev(info);
+
+	xenbus_switch_state(dev, XenbusStateClosed);
+}
+
+
+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);
+	free_netdev(info->netdev);
+
+	return 0;
+}
+
+
+static void close_netdev(struct netfront_info *info)
+{
+	del_timer_sync(&info->rx_refill_timer);
+
+	xennet_sysfs_delif(info->netdev);
+	unregister_netdev(info->netdev);
+}
+
+
+static void netif_disconnect_backend(struct netfront_info *info)
+{
+	/* Stop old i/f to prevent errors whilst we rebuild the state. */
+	spin_lock_irq(&info->tx_lock);
+	spin_lock(&info->rx_lock);
+	netif_carrier_off(info->netdev);
+	spin_unlock(&info->rx_lock);
+	spin_unlock_irq(&info->tx_lock);
+
+	if (info->irq)
+		unbind_from_irqhandler(info->irq, info->netdev);
+	info->evtchn = 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 netif_free(struct netfront_info *info)
+{
+	close_netdev(info);
+	netif_disconnect_backend(info);
+	free_netdev(info->netdev);
+}
+
+
+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,
+};
+
+static int __init netif_init(void)
+{
+	if (xen_start_info->flags & SIF_INITDOMAIN)
+		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)
+{
+	unregister_inetaddr_notifier(&notifier_inetdev);
+
+	return xenbus_unregister_driver(&netfront);
+}
+module_exit(netif_exit);
+
+MODULE_LICENSE("Dual BSD/GPL");

--
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