dev.c

			return ret;

		case SIOCGIFMEM:
			/* Get the per device memory space. We can add this but
			 * currently do not support it */
		case SIOCSIFMEM:
			/* Set the per device memory buffer space.
			 * Not applicable in our case */
		case SIOCSIFLINK:
			return -EINVAL;

		/*
		 *	Unknown or private ioctl.
		 */
		default:
			if (cmd == SIOCWANDEV ||
			    (cmd >= SIOCDEVPRIVATE &&
			     cmd <= SIOCDEVPRIVATE + 15)) {
				dev_load(net, ifr.ifr_name);
				rtnl_lock();
				ret = dev_ifsioc(net, &ifr, cmd);
				rtnl_unlock();
				if (!ret && copy_to_user(arg, &ifr,
							 sizeof(struct ifreq)))
					ret = -EFAULT;
				return ret;
			}
			/* Take care of Wireless Extensions */
			if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST)
				return wext_handle_ioctl(net, &ifr, cmd, arg);
			return -EINVAL;
	}
}


/**
 *	dev_new_index	-	allocate an ifindex
 *	@net: the applicable net namespace
 *
 *	Returns a suitable unique value for a new device interface
 *	number.  The caller must hold the rtnl semaphore or the
 *	dev_base_lock to be sure it remains unique.
 */
static int dev_new_index(struct net *net)
{
	static int ifindex;
	for (;;) {
		if (++ifindex <= 0)
			ifindex = 1;
		if (!__dev_get_by_index(net, ifindex))
			return ifindex;
	}
}

/* Delayed registration/unregisteration */
static LIST_HEAD(net_todo_list);

static void net_set_todo(struct net_device *dev)
{
	list_add_tail(&dev->todo_list, &net_todo_list);
}

static void rollback_registered(struct net_device *dev)
{
	BUG_ON(dev_boot_phase);
	ASSERT_RTNL();

	/* Some devices call without registering for initialization unwind. */
	if (dev->reg_state == NETREG_UNINITIALIZED) {
		printk(KERN_DEBUG "unregister_netdevice: device %s/%p never "
				  "was registered\n", dev->name, dev);

		WARN_ON(1);
		return;
	}

	BUG_ON(dev->reg_state != NETREG_REGISTERED);

	/* If device is running, close it first. */
	dev_close(dev);

	/* And unlink it from device chain. */
	unlist_netdevice(dev);

	dev->reg_state = NETREG_UNREGISTERING;

	synchronize_net();

	/* Shutdown queueing discipline. */
	dev_shutdown(dev);


	/* Notify protocols, that we are about to destroy
	   this device. They should clean all the things.
	*/
	call_netdevice_notifiers(NETDEV_UNREGISTER, dev);

	/*
	 *	Flush the unicast and multicast chains
	 */
	dev_addr_discard(dev);

	if (dev->netdev_ops->ndo_uninit)
		dev->netdev_ops->ndo_uninit(dev);

	/* Notifier chain MUST detach us from master device. */
	WARN_ON(dev->master);

	/* Remove entries from kobject tree */
	netdev_unregister_kobject(dev);

	synchronize_net();

	dev_put(dev);
}

static void __netdev_init_queue_locks_one(struct net_device *dev,
					  struct netdev_queue *dev_queue,
					  void *_unused)
{
	spin_lock_init(&dev_queue->_xmit_lock);
	netdev_set_xmit_lockdep_class(&dev_queue->_xmit_lock, dev->type);
	dev_queue->xmit_lock_owner = -1;
}

static void netdev_init_queue_locks(struct net_device *dev)
{
	netdev_for_each_tx_queue(dev, __netdev_init_queue_locks_one, NULL);
	__netdev_init_queue_locks_one(dev, &dev->rx_queue, NULL);
}

unsigned long netdev_fix_features(unsigned long features, const char *name)
{
	/* Fix illegal SG+CSUM combinations. */
	if ((features & NETIF_F_SG) &&
	    !(features & NETIF_F_ALL_CSUM)) {
		if (name)
			printk(KERN_NOTICE "%s: Dropping NETIF_F_SG since no "
			       "checksum feature.\n", name);
		features &= ~NETIF_F_SG;
	}

	/* TSO requires that SG is present as well. */
	if ((features & NETIF_F_TSO) && !(features & NETIF_F_SG)) {
		if (name)
			printk(KERN_NOTICE "%s: Dropping NETIF_F_TSO since no "
			       "SG feature.\n", name);
		features &= ~NETIF_F_TSO;
	}

	if (features & NETIF_F_UFO) {
		if (!(features & NETIF_F_GEN_CSUM)) {
			if (name)
				printk(KERN_ERR "%s: Dropping NETIF_F_UFO "
				       "since no NETIF_F_HW_CSUM feature.\n",
				       name);
			features &= ~NETIF_F_UFO;
		}

		if (!(features & NETIF_F_SG)) {
			if (name)
				printk(KERN_ERR "%s: Dropping NETIF_F_UFO "
				       "since no NETIF_F_SG feature.\n", name);
			features &= ~NETIF_F_UFO;
		}
	}

	return features;
}
EXPORT_SYMBOL(netdev_fix_features);

/**
 *	register_netdevice	- register a network device
 *	@dev: device to register
 *
 *	Take a completed network device structure and add it to the kernel
 *	interfaces. A %NETDEV_REGISTER message is sent to the netdev notifier
 *	chain. 0 is returned on success. A negative errno code is returned
 *	on a failure to set up the device, or if the name is a duplicate.
 *
 *	Callers must hold the rtnl semaphore. You may want
 *	register_netdev() instead of this.
 *
 *	BUGS:
 *	The locking appears insufficient to guarantee two parallel registers
 *	will not get the same name.
 */

int register_netdevice(struct net_device *dev)
{
	struct hlist_head *head;
	struct hlist_node *p;
	int ret;
	struct net *net = dev_net(dev);

	BUG_ON(dev_boot_phase);
	ASSERT_RTNL();

	might_sleep();

	/* When net_device's are persistent, this will be fatal. */
	BUG_ON(dev->reg_state != NETREG_UNINITIALIZED);
	BUG_ON(!net);

	spin_lock_init(&dev->addr_list_lock);
	netdev_set_addr_lockdep_class(dev);
	netdev_init_queue_locks(dev);

	dev->iflink = -1;

#ifdef CONFIG_COMPAT_NET_DEV_OPS
	/* Netdevice_ops API compatiability support.
	 * This is temporary until all network devices are converted.
	 */
	if (dev->netdev_ops) {
		const struct net_device_ops *ops = dev->netdev_ops;

		dev->init = ops->ndo_init;
		dev->uninit = ops->ndo_uninit;
		dev->open = ops->ndo_open;
		dev->change_rx_flags = ops->ndo_change_rx_flags;
		dev->set_rx_mode = ops->ndo_set_rx_mode;
		dev->set_multicast_list = ops->ndo_set_multicast_list;
		dev->set_mac_address = ops->ndo_set_mac_address;
		dev->validate_addr = ops->ndo_validate_addr;
		dev->do_ioctl = ops->ndo_do_ioctl;
		dev->set_config = ops->ndo_set_config;
		dev->change_mtu = ops->ndo_change_mtu;
		dev->tx_timeout = ops->ndo_tx_timeout;
		dev->get_stats = ops->ndo_get_stats;
		dev->vlan_rx_register = ops->ndo_vlan_rx_register;
		dev->vlan_rx_add_vid = ops->ndo_vlan_rx_add_vid;
		dev->vlan_rx_kill_vid = ops->ndo_vlan_rx_kill_vid;
#ifdef CONFIG_NET_POLL_CONTROLLER
		dev->poll_controller = ops->ndo_poll_controller;
#endif
	} else {
		char drivername[64];
		pr_info("%s (%s): not using net_device_ops yet\n",
			dev->name, netdev_drivername(dev, drivername, 64));

		/* This works only because net_device_ops and the
		   compatiablity structure are the same. */
		dev->netdev_ops = (void *) &(dev->init);
	}
#endif

	/* Init, if this function is available */
	if (dev->netdev_ops->ndo_init) {
		ret = dev->netdev_ops->ndo_init(dev);
		if (ret) {
			if (ret > 0)
				ret = -EIO;
			goto out;
		}
	}

	if (!dev_valid_name(dev->name)) {
		ret = -EINVAL;
		goto err_uninit;
	}

	dev->ifindex = dev_new_index(net);
	if (dev->iflink == -1)
		dev->iflink = dev->ifindex;

	/* Check for existence of name */
	head = dev_name_hash(net, dev->name);
	hlist_for_each(p, head) {
		struct net_device *d
			= hlist_entry(p, struct net_device, name_hlist);
		if (!strncmp(d->name, dev->name, IFNAMSIZ)) {
			ret = -EEXIST;
			goto err_uninit;
		}
	}

	/* Fix illegal checksum combinations */
	if ((dev->features & NETIF_F_HW_CSUM) &&
	    (dev->features & (NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM))) {
		printk(KERN_NOTICE "%s: mixed HW and IP checksum settings.\n",
		       dev->name);
		dev->features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM);
	}

	if ((dev->features & NETIF_F_NO_CSUM) &&
	    (dev->features & (NETIF_F_HW_CSUM|NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM))) {
		printk(KERN_NOTICE "%s: mixed no checksumming and other settings.\n",
		       dev->name);
		dev->features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM|NETIF_F_HW_CSUM);
	}

	dev->features = netdev_fix_features(dev->features, dev->name);

	/* Enable software GSO if SG is supported. */
	if (dev->features & NETIF_F_SG)
		dev->features |= NETIF_F_GSO;

	netdev_initialize_kobject(dev);
	ret = netdev_register_kobject(dev);
	if (ret)
		goto err_uninit;
	dev->reg_state = NETREG_REGISTERED;

	/*
	 *	Default initial state at registry is that the
	 *	device is present.
	 */

	set_bit(__LINK_STATE_PRESENT, &dev->state);

	dev_init_scheduler(dev);
	dev_hold(dev);
	list_netdevice(dev);

	/* Notify protocols, that a new device appeared. */
	ret = call_netdevice_notifiers(NETDEV_REGISTER, dev);
	ret = notifier_to_errno(ret);
	if (ret) {
		rollback_registered(dev);
		dev->reg_state = NETREG_UNREGISTERED;
	}

out:
	return ret;

err_uninit:
	if (dev->netdev_ops->ndo_uninit)
		dev->netdev_ops->ndo_uninit(dev);
	goto out;
}

/**
 *	register_netdev	- register a network device
 *	@dev: device to register
 *
 *	Take a completed network device structure and add it to the kernel
 *	interfaces. A %NETDEV_REGISTER message is sent to the netdev notifier
 *	chain. 0 is returned on success. A negative errno code is returned
 *	on a failure to set up the device, or if the name is a duplicate.
 *
 *	This is a wrapper around register_netdevice that takes the rtnl semaphore
 *	and expands the device name if you passed a format string to
 *	alloc_netdev.
 */
int register_netdev(struct net_device *dev)
{
	int err;

	rtnl_lock();

	/*
	 * If the name is a format string the caller wants us to do a
	 * name allocation.
	 */
	if (strchr(dev->name, '%')) {
		err = dev_alloc_name(dev, dev->name);
		if (err < 0)
			goto out;
	}

	err = register_netdevice(dev);
out:
	rtnl_unlock();
	return err;
}
EXPORT_SYMBOL(register_netdev);

/*
 * netdev_wait_allrefs - wait until all references are gone.
 *
 * This is called when unregistering network devices.
 *
 * Any protocol or device that holds a reference should register
 * for netdevice notification, and cleanup and put back the
 * reference if they receive an UNREGISTER event.
 * We can get stuck here if buggy protocols don't correctly
 * call dev_put.
 */
static void netdev_wait_allrefs(struct net_device *dev)
{
	unsigned long rebroadcast_time, warning_time;

	rebroadcast_time = warning_time = jiffies;
	while (atomic_read(&dev->refcnt) != 0) {
		if (time_after(jiffies, rebroadcast_time + 1 * HZ)) {
			rtnl_lock();

			/* Rebroadcast unregister notification */
			call_netdevice_notifiers(NETDEV_UNREGISTER, dev);

			if (test_bit(__LINK_STATE_LINKWATCH_PENDING,
				     &dev->state)) {
				/* We must not have linkwatch events
				 * pending on unregister. If this
				 * happens, we simply run the queue
				 * unscheduled, resulting in a noop
				 * for this device.
				 */
				linkwatch_run_queue();
			}

			__rtnl_unlock();

			rebroadcast_time = jiffies;
		}

		msleep(250);

		if (time_after(jiffies, warning_time + 10 * HZ)) {
			printk(KERN_EMERG "unregister_netdevice: "
			       "waiting for %s to become free. Usage "
			       "count = %d\n",
			       dev->name, atomic_read(&dev->refcnt));
			warning_time = jiffies;
		}
	}
}

/* The sequence is:
 *
 *	rtnl_lock();
 *	...
 *	register_netdevice(x1);
 *	register_netdevice(x2);
 *	...
 *	unregister_netdevice(y1);
 *	unregister_netdevice(y2);
 *      ...
 *	rtnl_unlock();
 *	free_netdev(y1);
 *	free_netdev(y2);
 *
 * We are invoked by rtnl_unlock().
 * This allows us to deal with problems:
 * 1) We can delete sysfs objects which invoke hotplug
 *    without deadlocking with linkwatch via keventd.
 * 2) Since we run with the RTNL semaphore not held, we can sleep
 *    safely in order to wait for the netdev refcnt to drop to zero.
 *
 * We must not return until all unregister events added during
 * the interval the lock was held have been completed.
 */
void netdev_run_todo(void)
{
	struct list_head list;

	/* Snapshot list, allow later requests */
	list_replace_init(&net_todo_list, &list);

	__rtnl_unlock();

	while (!list_empty(&list)) {
		struct net_device *dev
			= list_entry(list.next, struct net_device, todo_list);
		list_del(&dev->todo_list);

		if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
			printk(KERN_ERR "network todo '%s' but state %d\n",
			       dev->name, dev->reg_state);
			dump_stack();
			continue;
		}

		dev->reg_state = NETREG_UNREGISTERED;

		on_each_cpu(flush_backlog, dev, 1);

		netdev_wait_allrefs(dev);

		/* paranoia */
		BUG_ON(atomic_read(&dev->refcnt));
		WARN_ON(dev->ip_ptr);
		WARN_ON(dev->ip6_ptr);
		WARN_ON(dev->dn_ptr);

		if (dev->destructor)
			dev->destructor(dev);

		/* Free network device */
		kobject_put(&dev->dev.kobj);
	}
}

/**
 *	dev_get_stats	- get network device statistics
 *	@dev: device to get statistics from
 *
 *	Get network statistics from device. The device driver may provide
 *	its own method by setting dev->netdev_ops->get_stats; otherwise
 *	the internal statistics structure is used.
 */
const struct net_device_stats *dev_get_stats(struct net_device *dev)
 {
	const struct net_device_ops *ops = dev->netdev_ops;

	if (ops->ndo_get_stats)
		return ops->ndo_get_stats(dev);
	else
		return &dev->stats;
}
EXPORT_SYMBOL(dev_get_stats);

static void netdev_init_one_queue(struct net_device *dev,
				  struct netdev_queue *queue,
				  void *_unused)
{
	queue->dev = dev;
}

static void netdev_init_queues(struct net_device *dev)
{
	netdev_init_one_queue(dev, &dev->rx_queue, NULL);
	netdev_for_each_tx_queue(dev, netdev_init_one_queue, NULL);
	spin_lock_init(&dev->tx_global_lock);
}

/**
 *	alloc_netdev_mq - allocate network device
 *	@sizeof_priv:	size of private data to allocate space for
 *	@name:		device name format string
 *	@setup:		callback to initialize device
 *	@queue_count:	the number of subqueues to allocate
 *
 *	Allocates a struct net_device with private data area for driver use
 *	and performs basic initialization.  Also allocates subquue structs
 *	for each queue on the device at the end of the netdevice.
 */
struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
		void (*setup)(struct net_device *), unsigned int queue_count)
{
	struct netdev_queue *tx;
	struct net_device *dev;
	size_t alloc_size;
	void *p;

	BUG_ON(strlen(name) >= sizeof(dev->name));

	alloc_size = sizeof(struct net_device);
	if (sizeof_priv) {
		/* ensure 32-byte alignment of private area */
		alloc_size = (alloc_size + NETDEV_ALIGN_CONST) & ~NETDEV_ALIGN_CONST;
		alloc_size += sizeof_priv;
	}
	/* ensure 32-byte alignment of whole construct */
	alloc_size += NETDEV_ALIGN_CONST;

	p = kzalloc(alloc_size, GFP_KERNEL);
	if (!p) {
		printk(KERN_ERR "alloc_netdev: Unable to allocate device.\n");
		return NULL;
	}

	tx = kcalloc(queue_count, sizeof(struct netdev_queue), GFP_KERNEL);
	if (!tx) {
		printk(KERN_ERR "alloc_netdev: Unable to allocate "
		       "tx qdiscs.\n");
		kfree(p);
		return NULL;
	}

	dev = (struct net_device *)
		(((long)p + NETDEV_ALIGN_CONST) & ~NETDEV_ALIGN_CONST);
	dev->padded = (char *)dev - (char *)p;
	dev_net_set(dev, &init_net);

	dev->_tx = tx;
	dev->num_tx_queues = queue_count;
	dev->real_num_tx_queues = queue_count;

	dev->gso_max_size = GSO_MAX_SIZE;

	netdev_init_queues(dev);

	INIT_LIST_HEAD(&dev->napi_list);
	setup(dev);
	strcpy(dev->name, name);
	return dev;
}
EXPORT_SYMBOL(alloc_netdev_mq);

/**
 *	free_netdev - free network device
 *	@dev: device
 *
 *	This function does the last stage of destroying an allocated device
 * 	interface. The reference to the device object is released.
 *	If this is the last reference then it will be freed.
 */
void free_netdev(struct net_device *dev)
{
	struct napi_struct *p, *n;

	release_net(dev_net(dev));

	kfree(dev->_tx);

	list_for_each_entry_safe(p, n, &dev->napi_list, dev_list)
		netif_napi_del(p);

	/*  Compatibility with error handling in drivers */
	if (dev->reg_state == NETREG_UNINITIALIZED) {
		kfree((char *)dev - dev->padded);
		return;
	}

	BUG_ON(dev->reg_state != NETREG_UNREGISTERED);
	dev->reg_state = NETREG_RELEASED;

	/* will free via device release */
	put_device(&dev->dev);
}

/**
 *	synchronize_net -  Synchronize with packet receive processing
 *
 *	Wait for packets currently being received to be done.
 *	Does not block later packets from starting.
 */
void synchronize_net(void)
{
	might_sleep();
	synchronize_rcu();
}

/**
 *	unregister_netdevice - remove device from the kernel
 *	@dev: device
 *
 *	This function shuts down a device interface and removes it
 *	from the kernel tables.
 *
 *	Callers must hold the rtnl semaphore.  You may want
 *	unregister_netdev() instead of this.
 */

void unregister_netdevice(struct net_device *dev)
{
	ASSERT_RTNL();

	rollback_registered(dev);
	/* Finish processing unregister after unlock */
	net_set_todo(dev);
}

/**
 *	unregister_netdev - remove device from the kernel
 *	@dev: device
 *
 *	This function shuts down a device interface and removes it
 *	from the kernel tables.
 *
 *	This is just a wrapper for unregister_netdevice that takes
 *	the rtnl semaphore.  In general you want to use this and not
 *	unregister_netdevice.
 */
void unregister_netdev(struct net_device *dev)
{
	rtnl_lock();
	unregister_netdevice(dev);
	rtnl_unlock();
}

EXPORT_SYMBOL(unregister_netdev);

/**
 *	dev_change_net_namespace - move device to different nethost namespace
 *	@dev: device
 *	@net: network namespace
 *	@pat: If not NULL name pattern to try if the current device name
 *	      is already taken in the destination network namespace.
 *
 *	This function shuts down a device interface and moves it
 *	to a new network namespace. On success 0 is returned, on
 *	a failure a netagive errno code is returned.
 *
 *	Callers must hold the rtnl semaphore.
 */

int dev_change_net_namespace(struct net_device *dev, struct net *net, const char *pat)
{
	char buf[IFNAMSIZ];
	const char *destname;
	int err;

	ASSERT_RTNL();

	/* Don't allow namespace local devices to be moved. */
	err = -EINVAL;
	if (dev->features & NETIF_F_NETNS_LOCAL)
		goto out;

#ifdef CONFIG_SYSFS
	/* Don't allow real devices to be moved when sysfs
	 * is enabled.
	 */
	err = -EINVAL;
	if (dev->dev.parent)
		goto out;
#endif

	/* Ensure the device has been registrered */
	err = -EINVAL;
	if (dev->reg_state != NETREG_REGISTERED)
		goto out;

	/* Get out if there is nothing todo */
	err = 0;
	if (net_eq(dev_net(dev), net))
		goto out;

	/* Pick the destination device name, and ensure
	 * we can use it in the destination network namespace.
	 */
	err = -EEXIST;
	destname = dev->name;
	if (__dev_get_by_name(net, destname)) {
		/* We get here if we can't use the current device name */
		if (!pat)
			goto out;
		if (!dev_valid_name(pat))
			goto out;
		if (strchr(pat, '%')) {
			if (__dev_alloc_name(net, pat, buf) < 0)
				goto out;
			destname = buf;
		} else
			destname = pat;
		if (__dev_get_by_name(net, destname))
			goto out;
	}

	/*
	 * And now a mini version of register_netdevice unregister_netdevice.
	 */

	/* If device is running close it first. */
	dev_close(dev);

	/* And unlink it from device chain */
	err = -ENODEV;
	unlist_netdevice(dev);

	synchronize_net();

	/* Shutdown queueing discipline. */
	dev_shutdown(dev);

	/* Notify protocols, that we are about to destroy
	   this device. They should clean all the things.
	*/
	call_netdevice_notifiers(NETDEV_UNREGISTER, dev);

	/*
	 *	Flush the unicast and multicast chains
	 */
	dev_addr_discard(dev);

	netdev_unregister_kobject(dev);

	/* Actually switch the network namespace */
	dev_net_set(dev, net);

	/* Assign the new device name */
	if (destname != dev->name)
		strcpy(dev->name, destname);

	/* If there is an ifindex conflict assign a new one */
	if (__dev_get_by_index(net, dev->ifindex)) {
		int iflink = (dev->iflink == dev->ifindex);
		dev->ifindex = dev_new_index(net);
		if (iflink)
			dev->iflink = dev->ifindex;
	}

	/* Fixup kobjects */
	err = netdev_register_kobject(dev);
	WARN_ON(err);

	/* Add the device back in the hashes */
	list_netdevice(dev);

	/* Notify protocols, that a new device appeared. */
	call_netdevice_notifiers(NETDEV_REGISTER, dev);

	synchronize_net();
	err = 0;
out:
	return err;
}

static int dev_cpu_callback(struct notifier_block *nfb,
			    unsigned long action,
			    void *ocpu)
{
	struct sk_buff **list_skb;
	struct Qdisc **list_net;
	struct sk_buff *skb;
	unsigned int cpu, oldcpu = (unsigned long)ocpu;
	struct softnet_data *sd, *oldsd;

	if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
		return NOTIFY_OK;

	local_irq_disable();
	cpu = smp_processor_id();
	sd = &per_cpu(softnet_data, cpu);
	oldsd = &per_cpu(softnet_data, oldcpu);

	/* Find end of our completion_queue. */
	list_skb = &sd->completion_queue;
	while (*list_skb)
		list_skb = &(*list_skb)->next;
	/* Append completion queue from offline CPU. */
	*list_skb = oldsd->completion_queue;
	oldsd->completion_queue = NULL;

	/* Find end of our output_queue. */
	list_net = &sd->output_queue;
	while (*list_net)
		list_net = &(*list_net)->next_sched;
	/* Append output queue from offline CPU. */
	*list_net = oldsd->output_queue;
	oldsd->output_queue = NULL;

	raise_softirq_irqoff(NET_TX_SOFTIRQ);
	local_irq_enable();

	/* Process offline CPU's input_pkt_queue */
	while ((skb = __skb_dequeue(&oldsd->input_pkt_queue)))
		netif_rx(skb);

	return NOTIFY_OK;
}

#ifdef CONFIG_NET_DMA
/**
 * net_dma_rebalance - try to maintain one DMA channel per CPU
 * @net_dma: DMA client and associated data (lock, channels, channel_mask)
 *
 * This is called when the number of channels allocated to the net_dma client
 * changes.  The net_dma client tries to have one DMA channel per CPU.
 */

static void net_dma_rebalance(struct net_dma *net_dma)
{
	unsigned int cpu, i, n, chan_idx;
	struct dma_chan *chan;

	if (cpus_empty(net_dma->channel_mask)) {
		for_each_online_cpu(cpu)
			rcu_assign_pointer(per_cpu(softnet_data, cpu).net_dma, NULL);
		return;
	}

	i = 0;
	cpu = first_cpu(cpu_online_map);

	for_each_cpu_mask_nr(chan_idx, net_dma->channel_mask) {
		chan = net_dma->channels[chan_idx];

		n = ((num_online_cpus() / cpus_weight(net_dma->channel_mask))
		   + (i < (num_online_cpus() %
			cpus_weight(net_dma->channel_mask)) ? 1 : 0));

		while(n) {
			per_cpu(softnet_data, cpu).net_dma = chan;
			cpu = next_cpu(cpu, cpu_online_map);
			n--;
		}
		i++;
	}
}

/**
 * netdev_dma_event - event callback for the net_dma_client
 * @client: should always be net_dma_client
 * @chan: DMA channel for the event
 * @state: DMA state to be handled
 */
static enum dma_state_client
netdev_dma_event(struct dma_client *client, struct dma_chan *chan,
	enum dma_state state)
{
	int i, found = 0, pos = -1;
	struct net_dma *net_dma =
		container_of(client, struct net_dma, client);
	enum dma_state_client ack = DMA_DUP; /* default: take no action */

	spin_lock(&net_dma->lock);
	switch (state) {
	case DMA_RESOURCE_AVAILABLE:
		for (i = 0; i < nr_cpu_ids; i++)
			if (net_dma->channels[i] == chan) {
				found = 1;
				break;
			} else if (net_dma->channels[i] == NULL && pos < 0)
				pos = i;

		if (!found && pos >= 0) {
			ack = DMA_ACK;
			net_dma->channels[pos] = chan;
			cpu_set(pos, net_dma->channel_mask);
			net_dma_rebalance(net_dma);
		}
		break;
	case DMA_RESOURCE_REMOVED:
		for (i = 0; i < nr_cpu_ids; i++)
			if (net_dma->channels[i] == chan) {
				found = 1;
				pos = i;
				break;
			}

		if (found) {
			ack = DMA_ACK;
			cpu_clear(pos, net_dma->channel_mask);
			net_dma->channels[i] = NULL;
			net_dma_rebalance(net_dma);
		}
		break;
	default:
		break;
	}
	spin_unlock(&net_dma->lock);

	return ack;
}

/**
 * netdev_dma_register - register the networking subsystem as a DMA client
 */
static int __init netdev_dma_register(void)
{
	net_dma.channels = kzalloc(nr_cpu_ids * sizeof(struct net_dma),
								GFP_KERNEL);
	if (unlikely(!net_dma.channels)) {
		printk(KERN_NOTICE
				"netdev_dma: no memory for net_dma.channels\n");
		return -ENOMEM;
	}
	spin_lock_init(&net_dma.lock);
	dma_cap_set(DMA_MEMCPY, net_dma.client.cap_mask);
	dma_async_client_register(&net_dma.client);
	dma_async_client_chan_request(&net_dma.client);
	return 0;
}

#else
static int __init netdev_dma_register(void) { return -ENODEV; }
#endif /* CONFIG_NET_DMA */

/**
 *	netdev_increment_features - increment feature set by one
 *	@all: current feature set
 *	@one: new feature set
 *	@mask: mask feature set
 *
 *	Computes a new feature set after adding a device with feature set
 *	@one to the master device with current feature set @all.  Will not
 *	enable anything that is off in @mask. Returns the new feature set.
 */
unsigned long netdev_increment_features(unsigned long all, unsigned long one,
					unsigned long mask)
{
	/* If device needs checksumming, downgrade to it. */
        if (all & NETIF_F_NO_CSUM && !(one & NETIF_F_NO_CSUM))
		all ^= NETIF_F_NO_CSUM | (one & NETIF_F_ALL_CSUM);
	else if (mask & NETIF_F_ALL_CSUM) {
		/* If one device supports v4/v6 checksumming, set for all. */
		if (one & (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM) &&
		    !(all & NETIF_F_GEN_CSUM)) {
			all &= ~NETIF_F_ALL_CSUM;
			all |= one & (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM);
		}

		/* If one device supports hw checksumming, set for all. */
		if (one & NETIF_F_GEN_CSUM && !(all & NETIF_F_GEN_CSUM)) {
			all &= ~NETIF_F_ALL_CSUM;
			all |= NETIF_F_HW_CSUM;
		}
	}

	one |= NETIF_F_ALL_CSUM;

	one |= all & NETIF_F_ONE_FOR_ALL;
	all &= one | NETIF_F_LLTX | NETIF_F_GSO;
	all |= one & mask & NETIF_F_ONE_FOR_ALL;

	return all;
}
EXPORT_SYMBOL(netdev_increment_features);

static struct hlist_head *netdev_create_hash(void)
{
	int i;
	struct hlist_head *hash;

	hash = kmalloc(sizeof(*hash) * NETDEV_HASHENTRIES, GFP_KERNEL);
	if (hash != NULL)