dev.c

			/* don't resend NETDEV_UNREGISTER_BATCH, _BATCH users
			 * should have already handle it the first time */

			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_first_entry(&list, 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_txq_stats_fold - fold tx_queues stats
 *	@dev: device to get statistics from
 *	@stats: struct net_device_stats to hold results
 */
void dev_txq_stats_fold(const struct net_device *dev,
			struct net_device_stats *stats)
{
	unsigned long tx_bytes = 0, tx_packets = 0, tx_dropped = 0;
	unsigned int i;
	struct netdev_queue *txq;

	for (i = 0; i < dev->num_tx_queues; i++) {
		txq = netdev_get_tx_queue(dev, i);
		tx_bytes   += txq->tx_bytes;
		tx_packets += txq->tx_packets;
		tx_dropped += txq->tx_dropped;
	}
	if (tx_bytes || tx_packets || tx_dropped) {
		stats->tx_bytes   = tx_bytes;
		stats->tx_packets = tx_packets;
		stats->tx_dropped = tx_dropped;
	}
}
EXPORT_SYMBOL(dev_txq_stats_fold);

/**
 *	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);

	dev_txq_stats_fold(dev, &dev->stats);
	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;
	struct net_device *p;
#ifdef CONFIG_RPS
	struct netdev_rx_queue *rx;
	int i;
#endif

	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 = ALIGN(alloc_size, NETDEV_ALIGN);
		alloc_size += sizeof_priv;
	}
	/* ensure 32-byte alignment of whole construct */
	alloc_size += NETDEV_ALIGN - 1;

	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");
		goto free_p;
	}

#ifdef CONFIG_RPS
	rx = kcalloc(queue_count, sizeof(struct netdev_rx_queue), GFP_KERNEL);
	if (!rx) {
		printk(KERN_ERR "alloc_netdev: Unable to allocate "
		       "rx queues.\n");
		goto free_tx;
	}

	atomic_set(&rx->count, queue_count);

	/*
	 * Set a pointer to first element in the array which holds the
	 * reference count.
	 */
	for (i = 0; i < queue_count; i++)
		rx[i].first = rx;
#endif

	dev = PTR_ALIGN(p, NETDEV_ALIGN);
	dev->padded = (char *)dev - (char *)p;

	if (dev_addr_init(dev))
		goto free_rx;

	dev_mc_init(dev);
	dev_uc_init(dev);

	dev_net_set(dev, &init_net);

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

#ifdef CONFIG_RPS
	dev->_rx = rx;
	dev->num_rx_queues = queue_count;
#endif

	dev->gso_max_size = GSO_MAX_SIZE;

	netdev_init_queues(dev);

	INIT_LIST_HEAD(&dev->ethtool_ntuple_list.list);
	dev->ethtool_ntuple_list.count = 0;
	INIT_LIST_HEAD(&dev->napi_list);
	INIT_LIST_HEAD(&dev->unreg_list);
	INIT_LIST_HEAD(&dev->link_watch_list);
	dev->priv_flags = IFF_XMIT_DST_RELEASE;
	setup(dev);
	strcpy(dev->name, name);
	return dev;

free_rx:
#ifdef CONFIG_RPS
	kfree(rx);
free_tx:
#endif
	kfree(tx);
free_p:
	kfree(p);
	return NULL;
}
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);

	/* Flush device addresses */
	dev_addr_flush(dev);

	/* Clear ethtool n-tuple list */
	ethtool_ntuple_flush(dev);

	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);
}
EXPORT_SYMBOL(free_netdev);

/**
 *	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();
}
EXPORT_SYMBOL(synchronize_net);

/**
 *	unregister_netdevice_queue - remove device from the kernel
 *	@dev: device
 *	@head: list
 *
 *	This function shuts down a device interface and removes it
 *	from the kernel tables.
 *	If head not NULL, device is queued to be unregistered later.
 *
 *	Callers must hold the rtnl semaphore.  You may want
 *	unregister_netdev() instead of this.
 */

void unregister_netdevice_queue(struct net_device *dev, struct list_head *head)
{
	ASSERT_RTNL();

	if (head) {
		list_move_tail(&dev->unreg_list, head);
	} else {
		rollback_registered(dev);
		/* Finish processing unregister after unlock */
		net_set_todo(dev);
	}
}
EXPORT_SYMBOL(unregister_netdevice_queue);

/**
 *	unregister_netdevice_many - unregister many devices
 *	@head: list of devices
 */
void unregister_netdevice_many(struct list_head *head)
{
	struct net_device *dev;

	if (!list_empty(head)) {
		rollback_registered_many(head);
		list_for_each_entry(dev, head, unreg_list)
			net_set_todo(dev);
	}
}
EXPORT_SYMBOL(unregister_netdevice_many);

/**
 *	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)
{
	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;
	if (__dev_get_by_name(net, dev->name)) {
		/* We get here if we can't use the current device name */
		if (!pat)
			goto out;
		if (dev_get_valid_name(net, pat, dev->name, 1))
			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);
	call_netdevice_notifiers(NETDEV_UNREGISTER_BATCH, dev);

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

	netdev_unregister_kobject(dev);

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

	/* 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);

	/*
	 *	Prevent userspace races by waiting until the network
	 *	device is fully setup before sending notifications.
	 */
	rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);

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

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;
}


/**
 *	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 | NETIF_F_UFO;
	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)
		for (i = 0; i < NETDEV_HASHENTRIES; i++)
			INIT_HLIST_HEAD(&hash[i]);

	return hash;
}

/* Initialize per network namespace state */
static int __net_init netdev_init(struct net *net)
{
	INIT_LIST_HEAD(&net->dev_base_head);

	net->dev_name_head = netdev_create_hash();
	if (net->dev_name_head == NULL)
		goto err_name;

	net->dev_index_head = netdev_create_hash();
	if (net->dev_index_head == NULL)
		goto err_idx;

	return 0;

err_idx:
	kfree(net->dev_name_head);
err_name:
	return -ENOMEM;
}

/**
 *	netdev_drivername - network driver for the device
 *	@dev: network device
 *	@buffer: buffer for resulting name
 *	@len: size of buffer
 *
 *	Determine network driver for device.
 */
char *netdev_drivername(const struct net_device *dev, char *buffer, int len)
{
	const struct device_driver *driver;
	const struct device *parent;

	if (len <= 0 || !buffer)
		return buffer;
	buffer[0] = 0;

	parent = dev->dev.parent;

	if (!parent)
		return buffer;

	driver = parent->driver;
	if (driver && driver->name)
		strlcpy(buffer, driver->name, len);
	return buffer;
}

static void __net_exit netdev_exit(struct net *net)
{
	kfree(net->dev_name_head);
	kfree(net->dev_index_head);
}

static struct pernet_operations __net_initdata netdev_net_ops = {
	.init = netdev_init,
	.exit = netdev_exit,
};

static void __net_exit default_device_exit(struct net *net)
{
	struct net_device *dev, *aux;
	/*
	 * Push all migratable network devices back to the
	 * initial network namespace
	 */
	rtnl_lock();
	for_each_netdev_safe(net, dev, aux) {
		int err;
		char fb_name[IFNAMSIZ];

		/* Ignore unmoveable devices (i.e. loopback) */
		if (dev->features & NETIF_F_NETNS_LOCAL)
			continue;

		/* Leave virtual devices for the generic cleanup */
		if (dev->rtnl_link_ops)
			continue;

		/* Push remaing network devices to init_net */
		snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex);
		err = dev_change_net_namespace(dev, &init_net, fb_name);
		if (err) {
			printk(KERN_EMERG "%s: failed to move %s to init_net: %d\n",
				__func__, dev->name, err);
			BUG();
		}
	}
	rtnl_unlock();
}

static void __net_exit default_device_exit_batch(struct list_head *net_list)
{
	/* At exit all network devices most be removed from a network
	 * namespace.  Do this in the reverse order of registeration.
	 * Do this across as many network namespaces as possible to
	 * improve batching efficiency.
	 */
	struct net_device *dev;
	struct net *net;
	LIST_HEAD(dev_kill_list);

	rtnl_lock();
	list_for_each_entry(net, net_list, exit_list) {
		for_each_netdev_reverse(net, dev) {
			if (dev->rtnl_link_ops)
				dev->rtnl_link_ops->dellink(dev, &dev_kill_list);
			else
				unregister_netdevice_queue(dev, &dev_kill_list);
		}
	}
	unregister_netdevice_many(&dev_kill_list);
	rtnl_unlock();
}

static struct pernet_operations __net_initdata default_device_ops = {
	.exit = default_device_exit,
	.exit_batch = default_device_exit_batch,
};

/*
 *	Initialize the DEV module. At boot time this walks the device list and
 *	unhooks any devices that fail to initialise (normally hardware not
 *	present) and leaves us with a valid list of present and active devices.
 *
 */

/*
 *       This is called single threaded during boot, so no need
 *       to take the rtnl semaphore.
 */
static int __init net_dev_init(void)
{
	int i, rc = -ENOMEM;

	BUG_ON(!dev_boot_phase);

	if (dev_proc_init())
		goto out;

	if (netdev_kobject_init())
		goto out;

	INIT_LIST_HEAD(&ptype_all);
	for (i = 0; i < PTYPE_HASH_SIZE; i++)
		INIT_LIST_HEAD(&ptype_base[i]);

	if (register_pernet_subsys(&netdev_net_ops))
		goto out;

	/*
	 *	Initialise the packet receive queues.
	 */

	for_each_possible_cpu(i) {
		struct softnet_data *queue;

		queue = &per_cpu(softnet_data, i);
		skb_queue_head_init(&queue->input_pkt_queue);
		queue->completion_queue = NULL;
		INIT_LIST_HEAD(&queue->poll_list);

#ifdef CONFIG_RPS
		queue->csd.func = trigger_softirq;
		queue->csd.info = queue;
		queue->csd.flags = 0;
#endif

		queue->backlog.poll = process_backlog;
		queue->backlog.weight = weight_p;
		queue->backlog.gro_list = NULL;
		queue->backlog.gro_count = 0;
	}

	dev_boot_phase = 0;

	/* The loopback device is special if any other network devices
	 * is present in a network namespace the loopback device must
	 * be present. Since we now dynamically allocate and free the
	 * loopback device ensure this invariant is maintained by
	 * keeping the loopback device as the first device on the
	 * list of network devices.  Ensuring the loopback devices
	 * is the first device that appears and the last network device
	 * that disappears.
	 */
	if (register_pernet_device(&loopback_net_ops))
		goto out;

	if (register_pernet_device(&default_device_ops))
		goto out;

	open_softirq(NET_TX_SOFTIRQ, net_tx_action);
	open_softirq(NET_RX_SOFTIRQ, net_rx_action);

	hotcpu_notifier(dev_cpu_callback, 0);
	dst_init();
	dev_mcast_init();
	rc = 0;
out:
	return rc;
}

subsys_initcall(net_dev_init);

static int __init initialize_hashrnd(void)
{
	get_random_bytes(&hashrnd, sizeof(hashrnd));
	return 0;
}

late_initcall_sync(initialize_hashrnd);