// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      NET3    Protocol independent device support routines.
 *
 *	Derived from the non IP parts of dev.c 1.0.19
 *              Authors:	Ross Biro
 *				Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *				Mark Evans, <evansmp@uhura.aston.ac.uk>
 *
 *	Additional Authors:
 *		Florian la Roche <rzsfl@rz.uni-sb.de>
 *		Alan Cox <gw4pts@gw4pts.ampr.org>
 *		David Hinds <dahinds@users.sourceforge.net>
 *		Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
 *		Adam Sulmicki <adam@cfar.umd.edu>
 *              Pekka Riikonen <priikone@poesidon.pspt.fi>
 *
 *	Changes:
 *              D.J. Barrow     :       Fixed bug where dev->refcnt gets set
 *                                      to 2 if register_netdev gets called
 *                                      before net_dev_init & also removed a
 *                                      few lines of code in the process.
 *		Alan Cox	:	device private ioctl copies fields back.
 *		Alan Cox	:	Transmit queue code does relevant
 *					stunts to keep the queue safe.
 *		Alan Cox	:	Fixed double lock.
 *		Alan Cox	:	Fixed promisc NULL pointer trap
 *		????????	:	Support the full private ioctl range
 *		Alan Cox	:	Moved ioctl permission check into
 *					drivers
 *		Tim Kordas	:	SIOCADDMULTI/SIOCDELMULTI
 *		Alan Cox	:	100 backlog just doesn't cut it when
 *					you start doing multicast video 8)
 *		Alan Cox	:	Rewrote net_bh and list manager.
 *              Alan Cox        :       Fix ETH_P_ALL echoback lengths.
 *		Alan Cox	:	Took out transmit every packet pass
 *					Saved a few bytes in the ioctl handler
 *		Alan Cox	:	Network driver sets packet type before
 *					calling netif_rx. Saves a function
 *					call a packet.
 *		Alan Cox	:	Hashed net_bh()
 *		Richard Kooijman:	Timestamp fixes.
 *		Alan Cox	:	Wrong field in SIOCGIFDSTADDR
 *		Alan Cox	:	Device lock protection.
 *              Alan Cox        :       Fixed nasty side effect of device close
 *					changes.
 *		Rudi Cilibrasi	:	Pass the right thing to
 *					set_mac_address()
 *		Dave Miller	:	32bit quantity for the device lock to
 *					make it work out on a Sparc.
 *		Bjorn Ekwall	:	Added KERNELD hack.
 *		Alan Cox	:	Cleaned up the backlog initialise.
 *		Craig Metz	:	SIOCGIFCONF fix if space for under
 *					1 device.
 *	    Thomas Bogendoerfer :	Return ENODEV for dev_open, if there
 *					is no device open function.
 *		Andi Kleen	:	Fix error reporting for SIOCGIFCONF
 *	    Michael Chastain	:	Fix signed/unsigned for SIOCGIFCONF
 *		Cyrus Durgin	:	Cleaned for KMOD
 *		Adam Sulmicki   :	Bug Fix : Network Device Unload
 *					A network device unload needs to purge
 *					the backlog queue.
 *	Paul Rusty Russell	:	SIOCSIFNAME
 *              Pekka Riikonen  :	Netdev boot-time settings code
 *              Andrew Morton   :       Make unregister_netdevice wait
 *                                      indefinitely on dev->refcnt
 *              J Hadi Salim    :       - Backlog queue sampling
 *				        - netif_rx() feedback
 */

#include <linux/uaccess.h>
#include <linux/bitops.h>
#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/hash.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/mutex.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/if_ether.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/skbuff.h>
#include <linux/bpf.h>
#include <linux/bpf_trace.h>
#include <net/net_namespace.h>
#include <net/sock.h>
#include <net/busy_poll.h>
#include <linux/rtnetlink.h>
#include <linux/stat.h>
#include <net/dst.h>
#include <net/dst_metadata.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netpoll.h>
#include <linux/rcupdate.h>
#include <linux/delay.h>
#include <net/iw_handler.h>
#include <asm/current.h>
#include <linux/audit.h>
#include <linux/dmaengine.h>
#include <linux/err.h>
#include <linux/ctype.h>
#include <linux/if_arp.h>
#include <linux/if_vlan.h>
#include <linux/ip.h>
#include <net/ip.h>
#include <net/mpls.h>
#include <linux/ipv6.h>
#include <linux/in.h>
#include <linux/jhash.h>
#include <linux/random.h>
#include <trace/events/napi.h>
#include <trace/events/net.h>
#include <trace/events/skb.h>
#include <linux/inetdevice.h>
#include <linux/cpu_rmap.h>
#include <linux/static_key.h>
#include <linux/hashtable.h>
#include <linux/vmalloc.h>
#include <linux/if_macvlan.h>
#include <linux/errqueue.h>
#include <linux/hrtimer.h>
#include <linux/netfilter_ingress.h>
#include <linux/crash_dump.h>
#include <linux/sctp.h>
#include <net/udp_tunnel.h>
#include <linux/net_namespace.h>
#include <linux/indirect_call_wrapper.h>
#include <net/devlink.h>

#include "net-sysfs.h"

#define MAX_GRO_SKBS 8

/* This should be increased if a protocol with a bigger head is added. */
#define GRO_MAX_HEAD (MAX_HEADER + 128)

static DEFINE_SPINLOCK(ptype_lock);
static DEFINE_SPINLOCK(offload_lock);
struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly;
struct list_head ptype_all __read_mostly;	/* Taps */
static struct list_head offload_base __read_mostly;

static int netif_rx_internal(struct sk_buff *skb);
static int call_netdevice_notifiers_info(unsigned long val,
					 struct netdev_notifier_info *info);
static int call_netdevice_notifiers_extack(unsigned long val,
					   struct net_device *dev,
					   struct netlink_ext_ack *extack);
static struct napi_struct *napi_by_id(unsigned int napi_id);

/*
 * The @dev_base_head list is protected by @dev_base_lock and the rtnl
 * semaphore.
 *
 * Pure readers hold dev_base_lock for reading, or rcu_read_lock()
 *
 * Writers must hold the rtnl semaphore while they loop through the
 * dev_base_head list, and hold dev_base_lock for writing when they do the
 * actual updates.  This allows pure readers to access the list even
 * while a writer is preparing to update it.
 *
 * To put it another way, dev_base_lock is held for writing only to
 * protect against pure readers; the rtnl semaphore provides the
 * protection against other writers.
 *
 * See, for example usages, register_netdevice() and
 * unregister_netdevice(), which must be called with the rtnl
 * semaphore held.
 */
DEFINE_RWLOCK(dev_base_lock);
EXPORT_SYMBOL(dev_base_lock);

static DEFINE_MUTEX(ifalias_mutex);

/* protects napi_hash addition/deletion and napi_gen_id */
static DEFINE_SPINLOCK(napi_hash_lock);

static unsigned int napi_gen_id = NR_CPUS;
static DEFINE_READ_MOSTLY_HASHTABLE(napi_hash, 8);

static seqcount_t devnet_rename_seq;

static inline void dev_base_seq_inc(struct net *net)
{
	while (++net->dev_base_seq == 0)
		;
}

static inline struct hlist_head *dev_name_hash(struct net *net, const char *name)
{
	unsigned int hash = full_name_hash(net, name, strnlen(name, IFNAMSIZ));

	return &net->dev_name_head[hash_32(hash, NETDEV_HASHBITS)];
}

static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex)
{
	return &net->dev_index_head[ifindex & (NETDEV_HASHENTRIES - 1)];
}

static inline void rps_lock(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
	spin_lock(&sd->input_pkt_queue.lock);
#endif
}

static inline void rps_unlock(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
	spin_unlock(&sd->input_pkt_queue.lock);
#endif
}

static struct netdev_name_node *netdev_name_node_alloc(struct net_device *dev,
						       const char *name)
{
	struct netdev_name_node *name_node;

	name_node = kmalloc(sizeof(*name_node), GFP_KERNEL);
	if (!name_node)
		return NULL;
	INIT_HLIST_NODE(&name_node->hlist);
	name_node->dev = dev;
	name_node->name = name;
	return name_node;
}

static struct netdev_name_node *
netdev_name_node_head_alloc(struct net_device *dev)
{
	struct netdev_name_node *name_node;

	name_node = netdev_name_node_alloc(dev, dev->name);
	if (!name_node)
		return NULL;
	INIT_LIST_HEAD(&name_node->list);
	return name_node;
}

static void netdev_name_node_free(struct netdev_name_node *name_node)
{
	kfree(name_node);
}

static void netdev_name_node_add(struct net *net,
				 struct netdev_name_node *name_node)
{
	hlist_add_head_rcu(&name_node->hlist,
			   dev_name_hash(net, name_node->name));
}

static void netdev_name_node_del(struct netdev_name_node *name_node)
{
	hlist_del_rcu(&name_node->hlist);
}

static struct netdev_name_node *netdev_name_node_lookup(struct net *net,
							const char *name)
{
	struct hlist_head *head = dev_name_hash(net, name);
	struct netdev_name_node *name_node;

	hlist_for_each_entry(name_node, head, hlist)
		if (!strcmp(name_node->name, name))
			return name_node;
	return NULL;
}

static struct netdev_name_node *netdev_name_node_lookup_rcu(struct net *net,
							    const char *name)
{
	struct hlist_head *head = dev_name_hash(net, name);
	struct netdev_name_node *name_node;

	hlist_for_each_entry_rcu(name_node, head, hlist)
		if (!strcmp(name_node->name, name))
			return name_node;
	return NULL;
}

int netdev_name_node_alt_create(struct net_device *dev, const char *name)
{
	struct netdev_name_node *name_node;
	struct net *net = dev_net(dev);

	name_node = netdev_name_node_lookup(net, name);
	if (name_node)
		return -EEXIST;
	name_node = netdev_name_node_alloc(dev, name);
	if (!name_node)
		return -ENOMEM;
	netdev_name_node_add(net, name_node);
	/* The node that holds dev->name acts as a head of per-device list. */
	list_add_tail(&name_node->list, &dev->name_node->list);

	return 0;
}
EXPORT_SYMBOL(netdev_name_node_alt_create);

static void __netdev_name_node_alt_destroy(struct netdev_name_node *name_node)
{
	list_del(&name_node->list);
	netdev_name_node_del(name_node);
	kfree(name_node->name);
	netdev_name_node_free(name_node);
}

int netdev_name_node_alt_destroy(struct net_device *dev, const char *name)
{
	struct netdev_name_node *name_node;
	struct net *net = dev_net(dev);

	name_node = netdev_name_node_lookup(net, name);
	if (!name_node)
		return -ENOENT;
	/* lookup might have found our primary name or a name belonging
	 * to another device.
	 */
	if (name_node == dev->name_node || name_node->dev != dev)
		return -EINVAL;

	__netdev_name_node_alt_destroy(name_node);

	return 0;
}
EXPORT_SYMBOL(netdev_name_node_alt_destroy);

static void netdev_name_node_alt_flush(struct net_device *dev)
{
	struct netdev_name_node *name_node, *tmp;

	list_for_each_entry_safe(name_node, tmp, &dev->name_node->list, list)
		__netdev_name_node_alt_destroy(name_node);
}

/* Device list insertion */
static void list_netdevice(struct net_device *dev)
{
	struct net *net = dev_net(dev);

	ASSERT_RTNL();

	write_lock_bh(&dev_base_lock);
	list_add_tail_rcu(&dev->dev_list, &net->dev_base_head);
	netdev_name_node_add(net, dev->name_node);
	hlist_add_head_rcu(&dev->index_hlist,
			   dev_index_hash(net, dev->ifindex));
	write_unlock_bh(&dev_base_lock);

	dev_base_seq_inc(net);
}

/* Device list removal
 * caller must respect a RCU grace period before freeing/reusing dev
 */
static void unlist_netdevice(struct net_device *dev)
{
	ASSERT_RTNL();

	/* Unlink dev from the device chain */
	write_lock_bh(&dev_base_lock);
	list_del_rcu(&dev->dev_list);
	netdev_name_node_del(dev->name_node);
	hlist_del_rcu(&dev->index_hlist);
	write_unlock_bh(&dev_base_lock);

	dev_base_seq_inc(dev_net(dev));
}

/*
 *	Our notifier list
 */

static RAW_NOTIFIER_HEAD(netdev_chain);

/*
 *	Device drivers call our routines to queue packets here. We empty the
 *	queue in the local softnet handler.
 */

DEFINE_PER_CPU_ALIGNED(struct softnet_data, softnet_data);
EXPORT_PER_CPU_SYMBOL(softnet_data);

/*******************************************************************************
 *
 *		Protocol management and registration routines
 *
 *******************************************************************************/


/*
 *	Add a protocol ID to the list. Now that the input handler is
 *	smarter we can dispense with all the messy stuff that used to be
 *	here.
 *
 *	BEWARE!!! Protocol handlers, mangling input packets,
 *	MUST BE last in hash buckets and checking protocol handlers
 *	MUST start from promiscuous ptype_all chain in net_bh.
 *	It is true now, do not change it.
 *	Explanation follows: if protocol handler, mangling packet, will
 *	be the first on list, it is not able to sense, that packet
 *	is cloned and should be copied-on-write, so that it will
 *	change it and subsequent readers will get broken packet.
 *							--ANK (980803)
 */

static inline struct list_head *ptype_head(const struct packet_type *pt)
{
	if (pt->type == htons(ETH_P_ALL))
		return pt->dev ? &pt->dev->ptype_all : &ptype_all;
	else
		return pt->dev ? &pt->dev->ptype_specific :
				 &ptype_base[ntohs(pt->type) & PTYPE_HASH_MASK];
}

/**
 *	dev_add_pack - add packet handler
 *	@pt: packet type declaration
 *
 *	Add a protocol handler to the networking stack. The passed &packet_type
 *	is linked into kernel lists and may not be freed until it has been
 *	removed from the kernel lists.
 *
 *	This call does not sleep therefore it can not
 *	guarantee all CPU's that are in middle of receiving packets
 *	will see the new packet type (until the next received packet).
 */

void dev_add_pack(struct packet_type *pt)
{
	struct list_head *head = ptype_head(pt);

	spin_lock(&ptype_lock);
	list_add_rcu(&pt->list, head);
	spin_unlock(&ptype_lock);
}
EXPORT_SYMBOL(dev_add_pack);

/**
 *	__dev_remove_pack	 - remove packet handler
 *	@pt: packet type declaration
 *
 *	Remove a protocol handler that was previously added to the kernel
 *	protocol handlers by dev_add_pack(). The passed &packet_type is removed
 *	from the kernel lists and can be freed or reused once this function
 *	returns.
 *
 *      The packet type might still be in use by receivers
 *	and must not be freed until after all the CPU's have gone
 *	through a quiescent state.
 */
void __dev_remove_pack(struct packet_type *pt)
{
	struct list_head *head = ptype_head(pt);
	struct packet_type *pt1;

	spin_lock(&ptype_lock);

	list_for_each_entry(pt1, head, list) {
		if (pt == pt1) {
			list_del_rcu(&pt->list);
			goto out;
		}
	}

	pr_warn("dev_remove_pack: %p not found\n", pt);
out:
	spin_unlock(&ptype_lock);
}
EXPORT_SYMBOL(__dev_remove_pack);

/**
 *	dev_remove_pack	 - remove packet handler
 *	@pt: packet type declaration
 *
 *	Remove a protocol handler that was previously added to the kernel
 *	protocol handlers by dev_add_pack(). The passed &packet_type is removed
 *	from the kernel lists and can be freed or reused once this function
 *	returns.
 *
 *	This call sleeps to guarantee that no CPU is looking at the packet
 *	type after return.
 */
void dev_remove_pack(struct packet_type *pt)
{
	__dev_remove_pack(pt);

	synchronize_net();
}
EXPORT_SYMBOL(dev_remove_pack);


/**
 *	dev_add_offload - register offload handlers
 *	@po: protocol offload declaration
 *
 *	Add protocol offload handlers to the networking stack. The passed
 *	&proto_offload is linked into kernel lists and may not be freed until
 *	it has been removed from the kernel lists.
 *
 *	This call does not sleep therefore it can not
 *	guarantee all CPU's that are in middle of receiving packets
 *	will see the new offload handlers (until the next received packet).
 */
void dev_add_offload(struct packet_offload *po)
{
	struct packet_offload *elem;

	spin_lock(&offload_lock);
	list_for_each_entry(elem, &offload_base, list) {
		if (po->priority < elem->priority)
			break;
	}
	list_add_rcu(&po->list, elem->list.prev);
	spin_unlock(&offload_lock);
}
EXPORT_SYMBOL(dev_add_offload);

/**
 *	__dev_remove_offload	 - remove offload handler
 *	@po: packet offload declaration
 *
 *	Remove a protocol offload handler that was previously added to the
 *	kernel offload handlers by dev_add_offload(). The passed &offload_type
 *	is removed from the kernel lists and can be freed or reused once this
 *	function returns.
 *
 *      The packet type might still be in use by receivers
 *	and must not be freed until after all the CPU's have gone
 *	through a quiescent state.
 */
static void __dev_remove_offload(struct packet_offload *po)
{
	struct list_head *head = &offload_base;
	struct packet_offload *po1;

	spin_lock(&offload_lock);

	list_for_each_entry(po1, head, list) {
		if (po == po1) {
			list_del_rcu(&po->list);
			goto out;
		}
	}

	pr_warn("dev_remove_offload: %p not found\n", po);
out:
	spin_unlock(&offload_lock);
}

/**
 *	dev_remove_offload	 - remove packet offload handler
 *	@po: packet offload declaration
 *
 *	Remove a packet offload handler that was previously added to the kernel
 *	offload handlers by dev_add_offload(). The passed &offload_type is
 *	removed from the kernel lists and can be freed or reused once this
 *	function returns.
 *
 *	This call sleeps to guarantee that no CPU is looking at the packet
 *	type after return.
 */
void dev_remove_offload(struct packet_offload *po)
{
	__dev_remove_offload(po);

	synchronize_net();
}
EXPORT_SYMBOL(dev_remove_offload);

/******************************************************************************
 *
 *		      Device Boot-time Settings Routines
 *
 ******************************************************************************/

/* Boot time configuration table */
static struct netdev_boot_setup dev_boot_setup[NETDEV_BOOT_SETUP_MAX];

/**
 *	netdev_boot_setup_add	- add new setup entry
 *	@name: name of the device
 *	@map: configured settings for the device
 *
 *	Adds new setup entry to the dev_boot_setup list.  The function
 *	returns 0 on error and 1 on success.  This is a generic routine to
 *	all netdevices.
 */
static int netdev_boot_setup_add(char *name, struct ifmap *map)
{
	struct netdev_boot_setup *s;
	int i;

	s = dev_boot_setup;
	for (i = 0; i < NETDEV_BOOT_SETUP_MAX; i++) {
		if (s[i].name[0] == '\0' || s[i].name[0] == ' ') {
			memset(s[i].name, 0, sizeof(s[i].name));
			strlcpy(s[i].name, name, IFNAMSIZ);
			memcpy(&s[i].map, map, sizeof(s[i].map));
			break;
		}
	}

	return i >= NETDEV_BOOT_SETUP_MAX ? 0 : 1;
}

/**
 * netdev_boot_setup_check	- check boot time settings
 * @dev: the netdevice
 *
 * Check boot time settings for the device.
 * The found settings are set for the device to be used
 * later in the device probing.
 * Returns 0 if no settings found, 1 if they are.
 */
int netdev_boot_setup_check(struct net_device *dev)
{
	struct netdev_boot_setup *s = dev_boot_setup;
	int i;

	for (i = 0; i < NETDEV_BOOT_SETUP_MAX; i++) {
		if (s[i].name[0] != '\0' && s[i].name[0] != ' ' &&
		    !strcmp(dev->name, s[i].name)) {
			dev->irq = s[i].map.irq;
			dev->base_addr = s[i].map.base_addr;
			dev->mem_start = s[i].map.mem_start;
			dev->mem_end = s[i].map.mem_end;
			return 1;
		}
	}
	return 0;
}
EXPORT_SYMBOL(netdev_boot_setup_check);


/**
 * netdev_boot_base	- get address from boot time settings
 * @prefix: prefix for network device
 * @unit: id for network device
 *
 * Check boot time settings for the base address of device.
 * The found settings are set for the device to be used
 * later in the device probing.
 * Returns 0 if no settings found.
 */
unsigned long netdev_boot_base(const char *prefix, int unit)
{
	const struct netdev_boot_setup *s = dev_boot_setup;
	char name[IFNAMSIZ];
	int i;

	sprintf(name, "%s%d", prefix, unit);

	/*
	 * If device already registered then return base of 1
	 * to indicate not to probe for this interface
	 */
	if (__dev_get_by_name(&init_net, name))
		return 1;

	for (i = 0; i < NETDEV_BOOT_SETUP_MAX; i++)
		if (!strcmp(name, s[i].name))
			return s[i].map.base_addr;
	return 0;
}

/*
 * Saves at boot time configured settings for any netdevice.
 */
int __init netdev_boot_setup(char *str)
{
	int ints[5];
	struct ifmap map;

	str = get_options(str, ARRAY_SIZE(ints), ints);
	if (!str || !*str)
		return 0;

	/* Save settings */
	memset(&map, 0, sizeof(map));
	if (ints[0] > 0)
		map.irq = ints[1];
	if (ints[0] > 1)
		map.base_addr = ints[2];
	if (ints[0] > 2)
		map.mem_start = ints[3];
	if (ints[0] > 3)
		map.mem_end = ints[4];

	/* Add new entry to the list */
	return netdev_boot_setup_add(str, &map);
}

__setup("netdev=", netdev_boot_setup);

/*******************************************************************************
 *
 *			    Device Interface Subroutines
 *
 *******************************************************************************/

/**
 *	dev_get_iflink	- get 'iflink' value of a interface
 *	@dev: targeted interface
 *
 *	Indicates the ifindex the interface is linked to.
 *	Physical interfaces have the same 'ifindex' and 'iflink' values.
 */

int dev_get_iflink(const struct net_device *dev)
{
	if (dev->netdev_ops && dev->netdev_ops->ndo_get_iflink)
		return dev->netdev_ops->ndo_get_iflink(dev);

	return dev->ifindex;
}
EXPORT_SYMBOL(dev_get_iflink);

/**
 *	dev_fill_metadata_dst - Retrieve tunnel egress information.
 *	@dev: targeted interface
 *	@skb: The packet.
 *
 *	For better visibility of tunnel traffic OVS needs to retrieve
 *	egress tunnel information for a packet. Following API allows
 *	user to get this info.
 */
int dev_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)
{
	struct ip_tunnel_info *info;

	if (!dev->netdev_ops  || !dev->netdev_ops->ndo_fill_metadata_dst)
		return -EINVAL;

	info = skb_tunnel_info_unclone(skb);
	if (!info)
		return -ENOMEM;
	if (unlikely(!(info->mode & IP_TUNNEL_INFO_TX)))
		return -EINVAL;

	return dev->netdev_ops->ndo_fill_metadata_dst(dev, skb);
}
EXPORT_SYMBOL_GPL(dev_fill_metadata_dst);

/**
 *	__dev_get_by_name	- find a device by its name
 *	@net: the applicable net namespace
 *	@name: name to find
 *
 *	Find an interface by name. Must be called under RTNL semaphore
 *	or @dev_base_lock. If the name is found a pointer to the device
 *	is returned. If the name is not found then %NULL is returned. The
 *	reference counters are not incremented so the caller must be
 *	careful with locks.
 */

struct net_device *__dev_get_by_name(struct net *net, const char *name)
{
	struct netdev_name_node *node_name;

	node_name = netdev_name_node_lookup(net, name);
	return node_name ? node_name->dev : NULL;
}
EXPORT_SYMBOL(__dev_get_by_name);

/**
 * dev_get_by_name_rcu	- find a device by its name
 * @net: the applicable net namespace
 * @name: name to find
 *
 * Find an interface by name.
 * If the name is found a pointer to the device is returned.
 * If the name is not found then %NULL is returned.
 * The reference counters are not incremented so the caller must be
 * careful with locks. The caller must hold RCU lock.
 */

struct net_device *dev_get_by_name_rcu(struct net *net, const char *name)
{
	struct netdev_name_node *node_name;

	node_name = netdev_name_node_lookup_rcu(net, name);
	return node_name ? node_name->dev : NULL;
}
EXPORT_SYMBOL(dev_get_by_name_rcu);

/**
 *	dev_get_by_name		- find a device by its name
 *	@net: the applicable net namespace
 *	@name: name to find
 *
 *	Find an interface by name. This can be called from any
 *	context and does its own locking. The returned handle has
 *	the usage count incremented and the caller must use dev_put() to
 *	release it when it is no longer needed. %NULL is returned if no
 *	matching device is found.
 */

struct net_device *dev_get_by_name(struct net *net, const char *name)
{
	struct net_device *dev;

	rcu_read_lock();
	dev = dev_get_by_name_rcu(net, name);
	if (dev)
		dev_hold(dev);
	rcu_read_unlock();
	return dev;
}
EXPORT_SYMBOL(dev_get_by_name);

/**
 *	__dev_get_by_index - find a device by its ifindex
 *	@net: the applicable net namespace
 *	@ifindex: index of device
 *
 *	Search for an interface by index. Returns %NULL if the device
 *	is not found or a pointer to the device. The device has not
 *	had its reference counter increased so the caller must be careful
 *	about locking. The caller must hold either the RTNL semaphore
 *	or @dev_base_lock.
 */

struct net_device *__dev_get_by_index(struct net *net, int ifindex)
{
	struct net_device *dev;
	struct hlist_head *head = dev_index_hash(net, ifindex);

	hlist_for_each_entry(dev, head, index_hlist)
		if (dev->ifindex == ifindex)
			return dev;

	return NULL;
}
EXPORT_SYMBOL(__dev_get_by_index);

/**
 *	dev_get_by_index_rcu - find a device by its ifindex
 *	@net: the applicable net namespace
 *	@ifindex: index of device
 *
 *	Search for an interface by index. Returns %NULL if the device
 *	is not found or a pointer to the device. The device has not
 *	had its reference counter increased so the caller must be careful
 *	about locking. The caller must hold RCU lock.
 */

struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex)
{
	struct net_device *dev;
	struct hlist_head *head = dev_index_hash(net, ifindex);

	hlist_for_each_entry_rcu(dev, head, index_hlist)
		if (dev->ifindex == ifindex)
			return dev;

	return NULL;
}
EXPORT_SYMBOL(dev_get_by_index_rcu);


/**
 *	dev_get_by_index - find a device by its ifindex
 *	@net: the applicable net namespace
 *	@ifindex: index of device
 *
 *	Search for an interface by index. Returns NULL if the device
 *	is not found or a pointer to the device. The device returned has
 *	had a reference added and the pointer is safe until the user calls
 *	dev_put to indicate they have finished with it.
 */

struct net_device *dev_get_by_index(struct net *net, int ifindex)
{
	struct net_device *dev;

	rcu_read_lock();
	dev = dev_get_by_index_rcu(net, ifindex);
	if (dev)
		dev_hold(dev);
	rcu_read_unlock();
	return dev;
}
EXPORT_SYMBOL(dev_get_by_index);

/**
 *	dev_get_by_napi_id - find a device by napi_id
 *	@napi_id: ID of the NAPI struct
 *
 *	Search for an interface by NAPI ID. Returns %NULL if the device
 *	is not found or a pointer to the device. The device has not had
 *	its reference counter increased so the caller must be careful
 *	about locking. The caller must hold RCU lock.
 */

struct net_device *dev_get_by_napi_id(unsigned int napi_id)
{
	struct napi_struct *napi;

	WARN_ON_ONCE(!rcu_read_lock_held());

	if (napi_id < MIN_NAPI_ID)
		return NULL;

	napi = napi_by_id(napi_id);

	return napi ? napi->dev : NULL;
}
EXPORT_SYMBOL(dev_get_by_napi_id);

/**
 *	netdev_get_name - get a netdevice name, knowing its ifindex.
 *	@net: network namespace
 *	@name: a pointer to the buffer where the name will be stored.
 *	@ifindex: the ifindex of the interface to get the name from.
 *
 *	The use of raw_seqcount_begin() and cond_resched() before
 *	retrying is required as we want to give the writers a chance
 *	to complete when CONFIG_PREEMPTION is not set.
 */
int netdev_get_name(struct net *net, char *name, int ifindex)
{
	struct net_device *dev;
	unsigned int seq;

retry:
	seq = raw_seqcount_begin(&devnet_rename_seq);
	rcu_read_lock();
	dev = dev_get_by_index_rcu(net, ifindex);
	if (!dev) {
		rcu_read_unlock();
		return -ENODEV;
	}

	strcpy(name, dev->name);
	rcu_read_unlock();
	if (read_seqcount_retry(&devnet_rename_seq, seq)) {
		cond_resched();
		goto retry;
	}

	return 0;
}

/**
 *	dev_getbyhwaddr_rcu - find a device by its hardware address
 *	@net: the applicable net namespace
 *	@type: media type of device
 *	@ha: hardware address
 *
 *	Search for an interface by MAC address. Returns NULL if the device
 *	is not found or a pointer to the device.
 *	The caller must hold RCU or RTNL.
 *	The returned device has not had its ref count increased
 *	and the caller must therefore be careful about locking
 *
 */

struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
				       const char *ha)
{
	struct net_device *dev;

	for_each_netdev_rcu(net, dev)
		if (dev->type == type &&
		    !memcmp(dev->dev_addr, ha, dev->addr_len))
			return dev;

	return NULL;
}
EXPORT_SYMBOL(dev_getbyhwaddr_rcu);

struct net_device *__dev_getfirstbyhwtype(struct net *net, unsigned short type)
{
	struct net_device *dev;

	ASSERT_RTNL();
	for_each_netdev(net, dev)
		if (dev->type == type)
			return dev;

	return NULL;
}
EXPORT_SYMBOL(__dev_getfirstbyhwtype);

struct net_device *dev_getfirstbyhwtype(struct net *net, unsigned short type)
{
	struct net_device *dev, *ret = NULL;

	rcu_read_lock();
	for_each_netdev_rcu(net, dev)
		if (dev->type == type) {
			dev_hold(dev);
			ret = dev;
			break;
		}
	rcu_read_unlock();
	return ret;
}
EXPORT_SYMBOL(dev_getfirstbyhwtype);

/**
 *	__dev_get_by_flags - find any device with given flags
 *	@net: the applicable net namespace
 *	@if_flags: IFF_* values
 *	@mask: bitmask of bits in if_flags to check
 *
 *	Search for any interface with the given flags. Returns NULL if a device
 *	is not found or a pointer to the device. Must be called inside
 *	rtnl_lock(), and result refcount is unchanged.
 */

struct net_device *__dev_get_by_flags(struct net *net, unsigned short if_flags,
				      unsigned short mask)
{
	struct net_device *dev, *ret;

	ASSERT_RTNL();

	ret = NULL;
	for_each_netdev(net, dev) {
		if (((dev->flags ^ if_flags) & mask) == 0) {
			ret = dev;
			break;
		}
	}
	return ret;
}
EXPORT_SYMBOL(__dev_get_by_flags);

/**
 *	dev_valid_name - check if name is okay for network device
 *	@name: name string
 *
 *	Network device names need to be valid file names to
 *	to allow sysfs to work.  We also disallow any kind of
 *	whitespace.
 */
bool dev_valid_name(const char *name)
{
	if (*name == '\0')
		return false;
	if (strnlen(name, IFNAMSIZ) == IFNAMSIZ)
		return false;
	if (!strcmp(name, ".") || !strcmp(name, ".."))
		return false;

	while (*name) {
		if (*name == '/' || *name == ':' || isspace(*name))
			return false;
		name++;
	}
	return true;
}
EXPORT_SYMBOL(dev_valid_name);

/**
 *	__dev_alloc_name - allocate a name for a device
 *	@net: network namespace to allocate the device name in
 *	@name: name format string
 *	@buf:  scratch buffer and result name string
 *
 *	Passed a format string - eg "lt%d" it will try and find a suitable
 *	id. It scans list of devices to build up a free map, then chooses
 *	the first empty slot. The caller must hold the dev_base or rtnl lock
 *	while allocating the name and adding the device in order to avoid
 *	duplicates.
 *	Limited to bits_per_byte * page size devices (ie 32K on most platforms).
 *	Returns the number of the unit assigned or a negative errno code.
 */

static int __dev_alloc_name(struct net *net, const char *name, char *buf)
{
	int i = 0;
	const char *p;
	const int max_netdevices = 8*PAGE_SIZE;
	unsigned long *inuse;
	struct net_device *d;

	if (!dev_valid_name(name))
		return -EINVAL;

	p = strchr(name, '%');
	if (p) {
		/*
		 * Verify the string as this thing may have come from
		 * the user.  There must be either one "%d" and no other "%"
		 * characters.
		 */
		if (p[1] != 'd' || strchr(p + 2, '%'))
			return -EINVAL;

		/* Use one page as a bit array of possible slots */
		inuse = (unsigned long *) get_zeroed_page(GFP_ATOMIC);
		if (!inuse)
			return -ENOMEM;

		for_each_netdev(net, d) {
			if (!sscanf(d->name, name, &i))
				continue;
			if (i < 0 || i >= max_netdevices)
				continue;

			/*  avoid cases where sscanf is not exact inverse of printf */
			snprintf(buf, IFNAMSIZ, name, i);
			if (!strncmp(buf, d->name, IFNAMSIZ))
				set_bit(i, inuse);
		}

		i = find_first_zero_bit(inuse, max_netdevices);
		free_page((unsigned long) inuse);
	}

	snprintf(buf, IFNAMSIZ, name, i);
	if (!__dev_get_by_name(net, buf))
		return i;

	/* It is possible to run out of possible slots
	 * when the name is long and there isn't enough space left
	 * for the digits, or if all bits are used.
	 */
	return -ENFILE;
}

static int dev_alloc_name_ns(struct net *net,
			     struct net_device *dev,
			     const char *name)
{
	char buf[IFNAMSIZ];
	int ret;

	BUG_ON(!net);
	ret = __dev_alloc_name(net, name, buf);
	if (ret >= 0)
		strlcpy(dev->name, buf, IFNAMSIZ);
	return ret;
}

/**
 *	dev_alloc_name - allocate a name for a device
 *	@dev: device
 *	@name: name format string
 *
 *	Passed a format string - eg "lt%d" it will try and find a suitable
 *	id. It scans list of devices to build up a free map, then chooses
 *	the first empty slot. The caller must hold the dev_base or rtnl lock
 *	while allocating the name and adding the device in order to avoid
 *	duplicates.
 *	Limited to bits_per_byte * page size devices (ie 32K on most platforms).
 *	Returns the number of the unit assigned or a negative errno code.
 */

int dev_alloc_name(struct net_device *dev, const char *name)
{
	return dev_alloc_name_ns(dev_net(dev), dev, name);
}
EXPORT_SYMBOL(dev_alloc_name);

static int dev_get_valid_name(struct net *net, struct net_device *dev,
			      const char *name)
{
	BUG_ON(!net);

	if (!dev_valid_name(name))
		return -EINVAL;

	if (strchr(name, '%'))
		return dev_alloc_name_ns(net, dev, name);
	else if (__dev_get_by_name(net, name))
		return -EEXIST;
	else if (dev->name != name)
		strlcpy(dev->name, name, IFNAMSIZ);

	return 0;
}

/**
 *	dev_change_name - change name of a device
 *	@dev: device
 *	@newname: name (or format string) must be at least IFNAMSIZ
 *
 *	Change name of a device, can pass format strings "eth%d".
 *	for wildcarding.
 */
int dev_change_name(struct net_device *dev, const char *newname)
{
	unsigned char old_assign_type;
	char oldname[IFNAMSIZ];
	int err = 0;
	int ret;
	struct net *net;

	ASSERT_RTNL();
	BUG_ON(!dev_net(dev));

	net = dev_net(dev);

	/* Some auto-enslaved devices e.g. failover slaves are
	 * special, as userspace might rename the device after
	 * the interface had been brought up and running since
	 * the point kernel initiated auto-enslavement. Allow
	 * live name change even when these slave devices are
	 * up and running.
	 *
	 * Typically, users of these auto-enslaving devices
	 * don't actually care about slave name change, as
	 * they are supposed to operate on master interface
	 * directly.
	 */
	if (dev->flags & IFF_UP &&
	    likely(!(dev->priv_flags & IFF_LIVE_RENAME_OK)))
		return -EBUSY;

	write_seqcount_begin(&devnet_rename_seq);

	if (strncmp(newname, dev->name, IFNAMSIZ) == 0) {
		write_seqcount_end(&devnet_rename_seq);
		return 0;
	}

	memcpy(oldname, dev->name, IFNAMSIZ);

	err = dev_get_valid_name(net, dev, newname);
	if (err < 0) {
		write_seqcount_end(&devnet_rename_seq);
		return err;
	}

	if (oldname[0] && !strchr(oldname, '%'))
		netdev_info(dev, "renamed from %s\n", oldname);

	old_assign_type = dev->name_assign_type;
	dev->name_assign_type = NET_NAME_RENAMED;

rollback:
	ret = device_rename(&dev->dev, dev->name);
	if (ret) {
		memcpy(dev->name, oldname, IFNAMSIZ);
		dev->name_assign_type = old_assign_type;
		write_seqcount_end(&devnet_rename_seq);
		return ret;
	}

	write_seqcount_end(&devnet_rename_seq);

	netdev_adjacent_rename_links(dev, oldname);

	write_lock_bh(&dev_base_lock);
	netdev_name_node_del(dev->name_node);
	write_unlock_bh(&dev_base_lock);

	synchronize_rcu();

	write_lock_bh(&dev_base_lock);
	netdev_name_node_add(net, dev->name_node);
	write_unlock_bh(&dev_base_lock);

	ret = call_netdevice_notifiers(NETDEV_CHANGENAME, dev);
	ret = notifier_to_errno(ret);

	if (ret) {
		/* err >= 0 after dev_alloc_name() or stores the first errno */
		if (err >= 0) {
			err = ret;
			write_seqcount_begin(&devnet_rename_seq);
			memcpy(dev->name, oldname, IFNAMSIZ);
			memcpy(oldname, newname, IFNAMSIZ);
			dev->name_assign_type = old_assign_type;
			old_assign_type = NET_NAME_RENAMED;
			goto rollback;
		} else {
			pr_err("%s: name change rollback failed: %d\n",
			       dev->name, ret);
		}
	}

	return err;
}

/**
 *	dev_set_alias - change ifalias of a device
 *	@dev: device
 *	@alias: name up to IFALIASZ
 *	@len: limit of bytes to copy from info
 *
 *	Set ifalias for a device,
 */
int dev_set_alias(struct net_device *dev, const char *alias, size_t len)
{
	struct dev_ifalias *new_alias = NULL;

	if (len >= IFALIASZ)
		return -EINVAL;

	if (len) {
		new_alias = kmalloc(sizeof(*new_alias) + len + 1, GFP_KERNEL);
		if (!new_alias)
			return -ENOMEM;

		memcpy(new_alias->ifalias, alias, len);
		new_alias->ifalias[len] = 0;
	}

	mutex_lock(&ifalias_mutex);
	new_alias = rcu_replace_pointer(dev->ifalias, new_alias,
					mutex_is_locked(&ifalias_mutex));
	mutex_unlock(&ifalias_mutex);

	if (new_alias)
		kfree_rcu(new_alias, rcuhead);

	return len;
}
EXPORT_SYMBOL(dev_set_alias);

/**
 *	dev_get_alias - get ifalias of a device
 *	@dev: device
 *	@name: buffer to store name of ifalias
 *	@len: size of buffer
 *
 *	get ifalias for a device.  Caller must make sure dev cannot go
 *	away,  e.g. rcu read lock or own a reference count to device.
 */
int dev_get_alias(const struct net_device *dev, char *name, size_t len)
{
	const struct dev_ifalias *alias;
	int ret = 0;

	rcu_read_lock();
	alias = rcu_dereference(dev->ifalias);
	if (alias)
		ret = snprintf(name, len, "%s", alias->ifalias);
	rcu_read_unlock();

	return ret;
}

/**
 *	netdev_features_change - device changes features
 *	@dev: device to cause notification
 *
 *	Called to indicate a device has changed features.
 */
void netdev_features_change(struct net_device *dev)
{
	call_netdevice_notifiers(NETDEV_FEAT_CHANGE, dev);
}
EXPORT_SYMBOL(netdev_features_change);

/**
 *	netdev_state_change - device changes state
 *	@dev: device to cause notification
 *
 *	Called to indicate a device has changed state. This function calls
 *	the notifier chains for netdev_chain and sends a NEWLINK message
 *	to the routing socket.
 */
void netdev_state_change(struct net_device *dev)
{
	if (dev->flags & IFF_UP) {
		struct netdev_notifier_change_info change_info = {
			.info.dev = dev,
		};

		call_netdevice_notifiers_info(NETDEV_CHANGE,
					      &change_info.info);
		rtmsg_ifinfo(RTM_NEWLINK, dev, 0, GFP_KERNEL);
	}
}
EXPORT_SYMBOL(netdev_state_change);

/**
 * netdev_notify_peers - notify network peers about existence of @dev
 * @dev: network device
 *
 * Generate traffic such that interested network peers are aware of
 * @dev, such as by generating a gratuitous ARP. This may be used when
 * a device wants to inform the rest of the network about some sort of
 * reconfiguration such as a failover event or virtual machine
 * migration.
 */
void netdev_notify_peers(struct net_device *dev)
{
	rtnl_lock();
	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, dev);
	call_netdevice_notifiers(NETDEV_RESEND_IGMP, dev);
	rtnl_unlock();
}
EXPORT_SYMBOL(netdev_notify_peers);

static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack)
{
	const struct net_device_ops *ops = dev->netdev_ops;
	int ret;

	ASSERT_RTNL();

	if (!netif_device_present(dev))
		return -ENODEV;

	/* Block netpoll from trying to do any rx path servicing.
	 * If we don't do this there is a chance ndo_poll_controller
	 * or ndo_poll may be running while we open the device
	 */
	netpoll_poll_disable(dev);

	ret = call_netdevice_notifiers_extack(NETDEV_PRE_UP, dev, extack);
	ret = notifier_to_errno(ret);
	if (ret)
		return ret;

	set_bit(__LINK_STATE_START, &dev->state);

	if (ops->ndo_validate_addr)
		ret = ops->ndo_validate_addr(dev);

	if (!ret && ops->ndo_open)
		ret = ops->ndo_open(dev);

	netpoll_poll_enable(dev);

	if (ret)
		clear_bit(__LINK_STATE_START, &dev->state);
	else {
		dev->flags |= IFF_UP;
		dev_set_rx_mode(dev);
		dev_activate(dev);
		add_device_randomness(dev->dev_addr, dev->addr_len);
	}

	return ret;
}

/**
 *	dev_open	- prepare an interface for use.
 *	@dev: device to open
 *	@extack: netlink extended ack
 *
 *	Takes a device from down to up state. The device's private open
 *	function is invoked and then the multicast lists are loaded. Finally
 *	the device is moved into the up state and a %NETDEV_UP message is
 *	sent to the netdev notifier chain.
 *
 *	Calling this function on an active interface is a nop. On a failure
 *	a negative errno code is returned.
 */
int dev_open(struct net_device *dev, struct netlink_ext_ack *extack)
{
	int ret;

	if (dev->flags & IFF_UP)
		return 0;

	ret = __dev_open(dev, extack);
	if (ret < 0)
		return ret;

	rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING, GFP_KERNEL);
	call_netdevice_notifiers(NETDEV_UP, dev);

	return ret;
}
EXPORT_SYMBOL(dev_open);

static void __dev_close_many(struct list_head *head)
{
	struct net_device *dev;

	ASSERT_RTNL();
	might_sleep();

	list_for_each_entry(dev, head, close_list) {
		/* Temporarily disable netpoll until the interface is down */
		netpoll_poll_disable(dev);

		call_netdevice_notifiers(NETDEV_GOING_DOWN, dev);

		clear_bit(__LINK_STATE_START, &dev->state);

		/* Synchronize to scheduled poll. We cannot touch poll list, it
		 * can be even on different cpu. So just clear netif_running().
		 *
		 * dev->stop() will invoke napi_disable() on all of it's
		 * napi_struct instances on this device.
		 */
		smp_mb__after_atomic(); /* Commit netif_running(). */
	}

	dev_deactivate_many(head);

	list_for_each_entry(dev, head, close_list) {
		const struct net_device_ops *ops = dev->netdev_ops;

		/*
		 *	Call the device specific close. This cannot fail.
		 *	Only if device is UP
		 *
		 *	We allow it to be called even after a DETACH hot-plug
		 *	event.
		 */
		if (ops->ndo_stop)
			ops->ndo_stop(dev);

		dev->flags &= ~IFF_UP;
		netpoll_poll_enable(dev);
	}
}

static void __dev_close(struct net_device *dev)
{
	LIST_HEAD(single);

	list_add(&dev->close_list, &single);
	__dev_close_many(&single);
	list_del(&single);
}

void dev_close_many(struct list_head *head, bool unlink)
{
	struct net_device *dev, *tmp;

	/* Remove the devices that don't need to be closed */
	list_for_each_entry_safe(dev, tmp, head, close_list)
		if (!(dev->flags & IFF_UP))
			list_del_init(&dev->close_list);

	__dev_close_many(head);

	list_for_each_entry_safe(dev, tmp, head, close_list) {
		rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING, GFP_KERNEL);
		call_netdevice_notifiers(NETDEV_DOWN, dev);
		if (unlink)
			list_del_init(&dev->close_list);
	}
}
EXPORT_SYMBOL(dev_close_many);

/**
 *	dev_close - shutdown an interface.
 *	@dev: device to shutdown
 *
 *	This function moves an active device into down state. A
 *	%NETDEV_GOING_DOWN is sent to the netdev notifier chain. The device
 *	is then deactivated and finally a %NETDEV_DOWN is sent to the notifier
 *	chain.
 */
void dev_close(struct net_device *dev)
{
	if (dev->flags & IFF_UP) {
		LIST_HEAD(single);

		list_add(&dev->close_list, &single);
		dev_close_many(&single, true);
		list_del(&single);
	}
}
EXPORT_SYMBOL(dev_close);


/**
 *	dev_disable_lro - disable Large Receive Offload on a device
 *	@dev: device
 *
 *	Disable Large Receive Offload (LRO) on a net device.  Must be
 *	called under RTNL.  This is needed if received packets may be
 *	forwarded to another interface.
 */
void dev_disable_lro(struct net_device *dev)
{
	struct net_device *lower_dev;
	struct list_head *iter;

	dev->wanted_features &= ~NETIF_F_LRO;
	netdev_update_features(dev);

	if (unlikely(dev->features & NETIF_F_LRO))
		netdev_WARN(dev, "failed to disable LRO!\n");

	netdev_for_each_lower_dev(dev, lower_dev, iter)
		dev_disable_lro(lower_dev);
}
EXPORT_SYMBOL(dev_disable_lro);

/**
 *	dev_disable_gro_hw - disable HW Generic Receive Offload on a device
 *	@dev: device
 *
 *	Disable HW Generic Receive Offload (GRO_HW) on a net device.  Must be
 *	called under RTNL.  This is needed if Generic XDP is installed on
 *	the device.
 */
static void dev_disable_gro_hw(struct net_device *dev)
{
	dev->wanted_features &= ~NETIF_F_GRO_HW;
	netdev_update_features(dev);

	if (unlikely(dev->features & NETIF_F_GRO_HW))
		netdev_WARN(dev, "failed to disable GRO_HW!\n");
}

const char *netdev_cmd_to_name(enum netdev_cmd cmd)
{
#define N(val) 						\
	case NETDEV_##val:				\
		return "NETDEV_" __stringify(val);
	switch (cmd) {
	N(UP) N(DOWN) N(REBOOT) N(CHANGE) N(REGISTER) N(UNREGISTER)
	N(CHANGEMTU) N(CHANGEADDR) N(GOING_DOWN) N(CHANGENAME) N(FEAT_CHANGE)
	N(BONDING_FAILOVER) N(PRE_UP) N(PRE_TYPE_CHANGE) N(POST_TYPE_CHANGE)
	N(POST_INIT) N(RELEASE) N(NOTIFY_PEERS) N(JOIN) N(CHANGEUPPER)
	N(RESEND_IGMP) N(PRECHANGEMTU) N(CHANGEINFODATA) N(BONDING_INFO)
	N(PRECHANGEUPPER) N(CHANGELOWERSTATE) N(UDP_TUNNEL_PUSH_INFO)
	N(UDP_TUNNEL_DROP_INFO) N(CHANGE_TX_QUEUE_LEN)
	N(CVLAN_FILTER_PUSH_INFO) N(CVLAN_FILTER_DROP_INFO)
	N(SVLAN_FILTER_PUSH_INFO) N(SVLAN_FILTER_DROP_INFO)
	N(PRE_CHANGEADDR)
	}
#undef N
	return "UNKNOWN_NETDEV_EVENT";
}
EXPORT_SYMBOL_GPL(netdev_cmd_to_name);

static int call_netdevice_notifier(struct notifier_block *nb, unsigned long val,
				   struct net_device *dev)
{
	struct netdev_notifier_info info = {
		.dev = dev,
	};

	return nb->notifier_call(nb, val, &info);
}

static int call_netdevice_register_notifiers(struct notifier_block *nb,
					     struct net_device *dev)
{
	int err;

	err = call_netdevice_notifier(nb, NETDEV_REGISTER, dev);
	err = notifier_to_errno(err);
	if (err)
		return err;

	if (!(dev->flags & IFF_UP))
		return 0;

	call_netdevice_notifier(nb, NETDEV_UP, dev);
	return 0;
}

static void call_netdevice_unregister_notifiers(struct notifier_block *nb,
						struct net_device *dev)
{
	if (dev->flags & IFF_UP) {
		call_netdevice_notifier(nb, NETDEV_GOING_DOWN,
					dev);
		call_netdevice_notifier(nb, NETDEV_DOWN, dev);
	}
	call_netdevice_notifier(nb, NETDEV_UNREGISTER, dev);
}

static int call_netdevice_register_net_notifiers(struct notifier_block *nb,
						 struct net *net)
{
	struct net_device *dev;
	int err;

	for_each_netdev(net, dev) {
		err = call_netdevice_register_notifiers(nb, dev);
		if (err)
			goto rollback;
	}
	return 0;

rollback:
	for_each_netdev_continue_reverse(net, dev)
		call_netdevice_unregister_notifiers(nb, dev);
	return err;
}

static void call_netdevice_unregister_net_notifiers(struct notifier_block *nb,
						    struct net *net)
{
	struct net_device *dev;

	for_each_netdev(net, dev)
		call_netdevice_unregister_notifiers(nb, dev);
}

static int dev_boot_phase = 1;

/**
 * register_netdevice_notifier - register a network notifier block
 * @nb: notifier
 *
 * Register a notifier to be called when network device events occur.
 * The notifier passed is linked into the kernel structures and must
 * not be reused until it has been unregistered. A negative errno code
 * is returned on a failure.
 *
 * When registered all registration and up events are replayed
 * to the new notifier to allow device to have a race free
 * view of the network device list.
 */

int register_netdevice_notifier(struct notifier_block *nb)
{
	struct net *net;
	int err;

	/* Close race with setup_net() and cleanup_net() */
	down_write(&pernet_ops_rwsem);
	rtnl_lock();
	err = raw_notifier_chain_register(&netdev_chain, nb);
	if (err)
		goto unlock;
	if (dev_boot_phase)
		goto unlock;
	for_each_net(net) {
		err = call_netdevice_register_net_notifiers(nb, net);
		if (err)
			goto rollback;
	}

unlock:
	rtnl_unlock();
	up_write(&pernet_ops_rwsem);
	return err;

rollback:
	for_each_net_continue_reverse(net)
		call_netdevice_unregister_net_notifiers(nb, net);

	raw_notifier_chain_unregister(&netdev_chain, nb);
	goto unlock;
}
EXPORT_SYMBOL(register_netdevice_notifier);

/**
 * unregister_netdevice_notifier - unregister a network notifier block
 * @nb: notifier
 *
 * Unregister a notifier previously registered by
 * register_netdevice_notifier(). The notifier is unlinked into the
 * kernel structures and may then be reused. A negative errno code
 * is returned on a failure.
 *
 * After unregistering unregister and down device events are synthesized
 * for all devices on the device list to the removed notifier to remove
 * the need for special case cleanup code.
 */

int unregister_netdevice_notifier(struct notifier_block *nb)
{
	struct net *net;
	int err;

	/* Close race with setup_net() and cleanup_net() */
	down_write(&pernet_ops_rwsem);
	rtnl_lock();
	err = raw_notifier_chain_unregister(&netdev_chain, nb);
	if (err)
		goto unlock;

	for_each_net(net)
		call_netdevice_unregister_net_notifiers(nb, net);

unlock:
	rtnl_unlock();
	up_write(&pernet_ops_rwsem);
	return err;
}
EXPORT_SYMBOL(unregister_netdevice_notifier);

static int __register_netdevice_notifier_net(struct net *net,
					     struct notifier_block *nb,
					     bool ignore_call_fail)
{
	int err;

	err = raw_notifier_chain_register(&net->netdev_chain, nb);
	if (err)
		return err;
	if (dev_boot_phase)
		return 0;

	err = call_netdevice_register_net_notifiers(nb, net);
	if (err && !ignore_call_fail)
		goto chain_unregister;

	return 0;

chain_unregister:
	raw_notifier_chain_unregister(&net->netdev_chain, nb);
	return err;
}

static int __unregister_netdevice_notifier_net(struct net *net,
					       struct notifier_block *nb)
{
	int err;

	err = raw_notifier_chain_unregister(&net->netdev_chain, nb);
	if (err)
		return err;

	call_netdevice_unregister_net_notifiers(nb, net);
	return 0;
}

/**
 * register_netdevice_notifier_net - register a per-netns network notifier block
 * @net: network namespace
 * @nb: notifier
 *
 * Register a notifier to be called when network device events occur.
 * The notifier passed is linked into the kernel structures and must
 * not be reused until it has been unregistered. A negative errno code
 * is returned on a failure.
 *
 * When registered all registration and up events are replayed
 * to the new notifier to allow device to have a race free
 * view of the network device list.
 */

int register_netdevice_notifier_net(struct net *net, struct notifier_block *nb)
{
	int err;

	rtnl_lock();
	err = __register_netdevice_notifier_net(net, nb, false);
	rtnl_unlock();
	return err;
}
EXPORT_SYMBOL(register_netdevice_notifier_net);

/**
 * unregister_netdevice_notifier_net - unregister a per-netns
 *                                     network notifier block
 * @net: network namespace
 * @nb: notifier
 *
 * Unregister a notifier previously registered by
 * register_netdevice_notifier(). The notifier is unlinked into the
 * kernel structures and may then be reused. A negative errno code
 * is returned on a failure.
 *
 * After unregistering unregister and down device events are synthesized
 * for all devices on the device list to the removed notifier to remove
 * the need for special case cleanup code.
 */

int unregister_netdevice_notifier…