net: ipv4: add second dif to udp socket lookups

[linux.git] / net / core / dev.c

/*
 *      NET3    Protocol independent device support routines.
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 *      Derived from the non IP parts of dev.c 1.0.19
 *              Authors:        Ross Biro
 *                              Fred N. van Kempen, <[email protected]>
 *                              Mark Evans, <[email protected]>
 *
 *      Additional Authors:
 *              Florian la Roche <[email protected]>
 *              Alan Cox <[email protected]>
 *              David Hinds <[email protected]>
 *              Alexey Kuznetsov <[email protected]>
 *              Adam Sulmicki <[email protected]>
 *              Pekka Riikonen <[email protected]>
 *
 *      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/notifier.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/pci.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 "net-sysfs.h"

/* Instead of increasing this, you should create a hash table. */
#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 net_device *dev,
                                         struct netdev_notifier_info *info);
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);

/* 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
}

/* 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);
        hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net, dev->name));
        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);
        hlist_del_rcu(&dev->name_hlist);
        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);

#ifdef CONFIG_LOCKDEP
/*
 * register_netdevice() inits txq->_xmit_lock and sets lockdep class
 * according to dev->type
 */
static const unsigned short netdev_lock_type[] = {
         ARPHRD_NETROM, ARPHRD_ETHER, ARPHRD_EETHER, ARPHRD_AX25,
         ARPHRD_PRONET, ARPHRD_CHAOS, ARPHRD_IEEE802, ARPHRD_ARCNET,
         ARPHRD_APPLETLK, ARPHRD_DLCI, ARPHRD_ATM, ARPHRD_METRICOM,
         ARPHRD_IEEE1394, ARPHRD_EUI64, ARPHRD_INFINIBAND, ARPHRD_SLIP,
         ARPHRD_CSLIP, ARPHRD_SLIP6, ARPHRD_CSLIP6, ARPHRD_RSRVD,
         ARPHRD_ADAPT, ARPHRD_ROSE, ARPHRD_X25, ARPHRD_HWX25,
         ARPHRD_PPP, ARPHRD_CISCO, ARPHRD_LAPB, ARPHRD_DDCMP,
         ARPHRD_RAWHDLC, ARPHRD_TUNNEL, ARPHRD_TUNNEL6, ARPHRD_FRAD,
         ARPHRD_SKIP, ARPHRD_LOOPBACK, ARPHRD_LOCALTLK, ARPHRD_FDDI,
         ARPHRD_BIF, ARPHRD_SIT, ARPHRD_IPDDP, ARPHRD_IPGRE,
         ARPHRD_PIMREG, ARPHRD_HIPPI, ARPHRD_ASH, ARPHRD_ECONET,
         ARPHRD_IRDA, ARPHRD_FCPP, ARPHRD_FCAL, ARPHRD_FCPL,
         ARPHRD_FCFABRIC, ARPHRD_IEEE80211, ARPHRD_IEEE80211_PRISM,
         ARPHRD_IEEE80211_RADIOTAP, ARPHRD_PHONET, ARPHRD_PHONET_PIPE,
         ARPHRD_IEEE802154, ARPHRD_VOID, ARPHRD_NONE};

static const char *const netdev_lock_name[] = {
        "_xmit_NETROM", "_xmit_ETHER", "_xmit_EETHER", "_xmit_AX25",
        "_xmit_PRONET", "_xmit_CHAOS", "_xmit_IEEE802", "_xmit_ARCNET",
        "_xmit_APPLETLK", "_xmit_DLCI", "_xmit_ATM", "_xmit_METRICOM",
        "_xmit_IEEE1394", "_xmit_EUI64", "_xmit_INFINIBAND", "_xmit_SLIP",
        "_xmit_CSLIP", "_xmit_SLIP6", "_xmit_CSLIP6", "_xmit_RSRVD",
        "_xmit_ADAPT", "_xmit_ROSE", "_xmit_X25", "_xmit_HWX25",
        "_xmit_PPP", "_xmit_CISCO", "_xmit_LAPB", "_xmit_DDCMP",
        "_xmit_RAWHDLC", "_xmit_TUNNEL", "_xmit_TUNNEL6", "_xmit_FRAD",
        "_xmit_SKIP", "_xmit_LOOPBACK", "_xmit_LOCALTLK", "_xmit_FDDI",
        "_xmit_BIF", "_xmit_SIT", "_xmit_IPDDP", "_xmit_IPGRE",
        "_xmit_PIMREG", "_xmit_HIPPI", "_xmit_ASH", "_xmit_ECONET",
        "_xmit_IRDA", "_xmit_FCPP", "_xmit_FCAL", "_xmit_FCPL",
        "_xmit_FCFABRIC", "_xmit_IEEE80211", "_xmit_IEEE80211_PRISM",
        "_xmit_IEEE80211_RADIOTAP", "_xmit_PHONET", "_xmit_PHONET_PIPE",
        "_xmit_IEEE802154", "_xmit_VOID", "_xmit_NONE"};

static struct lock_class_key netdev_xmit_lock_key[ARRAY_SIZE(netdev_lock_type)];
static struct lock_class_key netdev_addr_lock_key[ARRAY_SIZE(netdev_lock_type)];

static inline unsigned short netdev_lock_pos(unsigned short dev_type)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(netdev_lock_type); i++)
                if (netdev_lock_type[i] == dev_type)
                        return i;
        /* the last key is used by default */
        return ARRAY_SIZE(netdev_lock_type) - 1;
}

static inline void netdev_set_xmit_lockdep_class(spinlock_t *lock,
                                                 unsigned short dev_type)
{
        int i;

        i = netdev_lock_pos(dev_type);
        lockdep_set_class_and_name(lock, &netdev_xmit_lock_key[i],
                                   netdev_lock_name[i]);
}

static inline void netdev_set_addr_lockdep_class(struct net_device *dev)
{
        int i;

        i = netdev_lock_pos(dev->type);
        lockdep_set_class_and_name(&dev->addr_list_lock,
                                   &netdev_addr_lock_key[i],
                                   netdev_lock_name[i]);
}
#else
static inline void netdev_set_xmit_lockdep_class(spinlock_t *lock,
                                                 unsigned short dev_type)
{
}
static inline void netdev_set_addr_lockdep_class(struct net_device *dev)
{
}
#endif

/*******************************************************************************
 *
 *              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 net_device *dev;
        struct hlist_head *head = dev_name_hash(net, name);

        hlist_for_each_entry(dev, head, name_hlist)
                if (!strncmp(dev->name, name, IFNAMSIZ))
                        return dev;

        return 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 net_device *dev;
        struct hlist_head *head = dev_name_hash(net, name);

        hlist_for_each_entry_rcu(dev, head, name_hlist)
                if (!strncmp(dev->name, name, IFNAMSIZ))
                        return dev;

        return 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_PREEMPT 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 (strlen(name) >= 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;

        p = strnchr(name, IFNAMSIZ-1, '%');
        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);
        }

        if (buf != name)
                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;
}

/**
 *      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)
{
        char buf[IFNAMSIZ];
        struct net *net;
        int ret;

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

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

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

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);
        if (dev->flags & IFF_UP)
                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);
        hlist_del_rcu(&dev->name_hlist);
        write_unlock_bh(&dev_base_lock);

        synchronize_rcu();

        write_lock_bh(&dev_base_lock);
        hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net, dev->name));
        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)
{
        char *new_ifalias;

        ASSERT_RTNL();

        if (len >= IFALIASZ)
                return -EINVAL;

        if (!len) {
                kfree(dev->ifalias);
                dev->ifalias = NULL;
                return 0;
        }

        new_ifalias = krealloc(dev->ifalias, len + 1, GFP_KERNEL);
        if (!new_ifalias)
                return -ENOMEM;
        dev->ifalias = new_ifalias;
        memcpy(dev->ifalias, alias, len);
        dev->ifalias[len] = 0;

        return len;
}


/**
 *      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;

                change_info.flags_changed = 0;
                call_netdevice_notifiers_info(NETDEV_CHANGE, dev,
                                              &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)
{
        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(NETDEV_PRE_UP, dev);
        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
 *
 *      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)
{
        int ret;

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

        ret = __dev_open(dev);
        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);

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

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

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_device *dev;
        struct net_device *last;
        struct net *net;
        int err;

        rtnl_lock();
        err = raw_notifier_chain_register(&netdev_chain, nb);
        if (err)
                goto unlock;
        if (dev_boot_phase)
                goto unlock;
        for_each_net(net) {
                for_each_netdev(net, dev) {
                        err = call_netdevice_notifier(nb, NETDEV_REGISTER, dev);
                        err = notifier_to_errno(err);
                        if (err)
                                goto rollback;

                        if (!(dev->flags & IFF_UP))
                                continue;

                        call_netdevice_notifier(nb, NETDEV_UP, dev);
                }
        }

unlock:
        rtnl_unlock();
        return err;

rollback:
        last = dev;
        for_each_net(net) {
                for_each_netdev(net, dev) {
                        if (dev == last)
                                goto outroll;

                        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);
                }
        }

outroll:
        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_device *dev;
        struct net *net;
        int err;

        rtnl_lock();
        err = raw_notifier_chain_unregister(&netdev_chain, nb);
        if (err)
                goto unlock;

        for_each_net(net) {
                for_each_netdev(net, 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);
                }
        }
unlock:
        rtnl_unlock();
        return err;
}
EXPORT_SYMBOL(unregister_netdevice_notifier);

/**
 *      call_netdevice_notifiers_info - call all network notifier blocks
 *      @val: value passed unmodified to notifier function
 *      @dev: net_device pointer passed unmodified to notifier function
 *      @info: notifier information data
 *
 *      Call all network notifier blocks.  Parameters and return value
 *      are as for raw_notifier_call_chain().
 */

static int call_netdevice_notifiers_info(unsigned long val,
                                         struct net_device *dev,
                                         struct netdev_notifier_info *info)
{
        ASSERT_RTNL();
        netdev_notifier_info_init(info, dev);
        return raw_notifier_call_chain(&netdev_chain, val, info);
}

/**
 *      call_netdevice_notifiers - call all network notifier blocks
 *      @val: value passed unmodified to notifier function
 *      @dev: net_device pointer passed unmodified to notifier function
 *
 *      Call all network notifier blocks.  Parameters and return value
 *      are as for raw_notifier_call_chain().
 */

int call_netdevice_notifiers(unsigned long val, struct net_device *dev)
{
        struct netdev_notifier_info info;

        return call_netdevice_notifiers_info(val, dev, &info);
}
EXPORT_SYMBOL(call_netdevice_notifiers);

#ifdef CONFIG_NET_INGRESS
static struct static_key ingress_needed __read_mostly;

void net_inc_ingress_queue(void)
{
        static_key_slow_inc(&ingress_needed);
}
EXPORT_SYMBOL_GPL(net_inc_ingress_queue);

void net_dec_ingress_queue(void)
{
        static_key_slow_dec(&ingress_needed);
}
EXPORT_SYMBOL_GPL(net_dec_ingress_queue);
#endif

#ifdef CONFIG_NET_EGRESS
static struct static_key egress_needed __read_mostly;

void net_inc_egress_queue(void)
{
        static_key_slow_inc(&egress_needed);
}
EXPORT_SYMBOL_GPL(net_inc_egress_queue);

void net_dec_egress_queue(void)
{
        static_key_slow_dec(&egress_needed);
}
EXPORT_SYMBOL_GPL(net_dec_egress_queue);
#endif

static struct static_key netstamp_needed __read_mostly;
#ifdef HAVE_JUMP_LABEL
static atomic_t netstamp_needed_deferred;
static atomic_t netstamp_wanted;
static void netstamp_clear(struct work_struct *work)
{
        int deferred = atomic_xchg(&netstamp_needed_deferred, 0);
        int wanted;

        wanted = atomic_add_return(deferred, &netstamp_wanted);
        if (wanted > 0)
                static_key_enable(&netstamp_needed);
        else
                static_key_disable(&netstamp_needed);
}
static DECLARE_WORK(netstamp_work, netstamp_clear);
#endif

void net_enable_timestamp(void)
{
#ifdef HAVE_JUMP_LABEL
        int wanted;

        while (1) {
                wanted = atomic_read(&netstamp_wanted);
                if (wanted <= 0)
                        break;
                if (atomic_cmpxchg(&netstamp_wanted, wanted, wanted + 1) == wanted)
                        return;
        }
        atomic_inc(&netstamp_needed_deferred);
        schedule_work(&netstamp_work);
#else
        static_key_slow_inc(&netstamp_needed);
#endif
}
EXPORT_SYMBOL(net_enable_timestamp);

void net_disable_timestamp(void)
{
#ifdef HAVE_JUMP_LABEL
        int wanted;

        while (1) {
                wanted = atomic_read(&netstamp_wanted);
                if (wanted <= 1)
                        break;
                if (atomic_cmpxchg(&netstamp_wanted, wanted, wanted - 1) == wanted)
                        return;
        }
        atomic_dec(&netstamp_needed_deferred);
        schedule_work(&netstamp_work);
#else
        static_key_slow_dec(&netstamp_needed);
#endif
}
EXPORT_SYMBOL(net_disable_timestamp);

static inline void net_timestamp_set(struct sk_buff *skb)
{
        skb->tstamp = 0;
        if (static_key_false(&netstamp_needed))
                __net_timestamp(skb);
}

#define net_timestamp_check(COND, SKB)                  \
        if (static_key_false(&netstamp_needed)) {               \
                if ((COND) && !(SKB)->tstamp)   \
                        __net_timestamp(SKB);           \
        }                                               \

bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb)
{
        unsigned int len;

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

        len = dev->mtu + dev->hard_header_len + VLAN_HLEN;
        if (skb->len <= len)
                return true;

        /* if TSO is enabled, we don't care about the length as the packet
         * could be forwarded without being segmented before
         */
        if (skb_is_gso(skb))
                return true;

        return false;
}
EXPORT_SYMBOL_GPL(is_skb_forwardable);

int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
{
        int ret = ____dev_forward_skb(dev, skb);

        if (likely(!ret)) {
                skb->protocol = eth_type_trans(skb, dev);
                skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(__dev_forward_skb);

/**
 * dev_forward_skb - loopback an skb to another netif
 *
 * @dev: destination network device
 * @skb: buffer to forward
 *
 * return values:
 *      NET_RX_SUCCESS  (no congestion)
 *      NET_RX_DROP     (packet was dropped, but freed)
 *
 * dev_forward_skb can be used for injecting an skb from the
 * start_xmit function of one device into the receive queue
 * of another device.
 *
 * The receiving device may be in another namespace, so
 * we have to clear all information in the skb that could
 * impact namespace isolation.
 */
int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
{
        return __dev_forward_skb(dev, skb) ?: netif_rx_internal(skb);
}
EXPORT_SYMBOL_GPL(dev_forward_skb);

static inline int deliver_skb(struct sk_buff *skb,
                              struct packet_type *pt_prev,
                              struct net_device *orig_dev)
{
        if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC)))
                return -ENOMEM;
        refcount_inc(&skb->users);
        return pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
}

static inline void deliver_ptype_list_skb(struct sk_buff *skb,
                                          struct packet_type **pt,
                                          struct net_device *orig_dev,
                                          __be16 type,
                                          struct list_head *ptype_list)
{
        struct packet_type *ptype, *pt_prev = *pt;

        list_for_each_entry_rcu(ptype, ptype_list, list) {
                if (ptype->type != type)
                        continue;
                if (pt_prev)
                        deliver_skb(skb, pt_prev, orig_dev);
                pt_prev = ptype;
        }
        *pt = pt_prev;
}

static inline bool skb_loop_sk(struct packet_type *ptype, struct sk_buff *skb)
{
        if (!ptype->af_packet_priv || !skb->sk)
                return false;

        if (ptype->id_match)
                return ptype->id_match(ptype, skb->sk);
        else if ((struct sock *)ptype->af_packet_priv == skb->sk)
                return true;

        return false;
}

/*
 *      Support routine. Sends outgoing frames to any network
 *      taps currently in use.
 */

void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
{
        struct packet_type *ptype;
        struct sk_buff *skb2 = NULL;
        struct packet_type *pt_prev = NULL;
        struct list_head *ptype_list = &ptype_all;

        rcu_read_lock();
again:
        list_for_each_entry_rcu(ptype, ptype_list, list) {
                /* Never send packets back to the socket
                 * they originated from - MvS ([email protected])
                 */
                if (skb_loop_sk(ptype, skb))
                        continue;

                if (pt_prev) {
                        deliver_skb(skb2, pt_prev, skb->dev);
                        pt_prev = ptype;
                        continue;
                }

                /* need to clone skb, done only once */
                skb2 = skb_clone(skb, GFP_ATOMIC);
                if (!skb2)
                        goto out_unlock;

                net_timestamp_set(skb2);

                /* skb->nh should be correctly
                 * set by sender, so that the second statement is
                 * just protection against buggy protocols.
                 */
                skb_reset_mac_header(skb2);

                if (skb_network_header(skb2) < skb2->data ||
                    skb_network_header(skb2) > skb_tail_pointer(skb2)) {
                        net_crit_ratelimited("protocol %04x is buggy, dev %s\n",
                                             ntohs(skb2->protocol),
                                             dev->name);
                        skb_reset_network_header(skb2);
                }

                skb2->transport_header = skb2->network_header;
                skb2->pkt_type = PACKET_OUTGOING;
                pt_prev = ptype;
        }

        if (ptype_list == &ptype_all) {
                ptype_list = &dev->ptype_all;
                goto again;
        }
out_unlock:
        if (pt_prev)
                pt_prev->func(skb2, skb->dev, pt_prev, skb->dev);
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(dev_queue_xmit_nit);

/**
 * netif_setup_tc - Handle tc mappings on real_num_tx_queues change
 * @dev: Network device
 * @txq: number of queues available
 *
 * If real_num_tx_queues is changed the tc mappings may no longer be
 * valid. To resolve this verify the tc mapping remains valid and if
 * not NULL the mapping. With no priorities mapping to this
 * offset/count pair it will no longer be used. In the worst case TC0
 * is invalid nothing can be done so disable priority mappings. If is
 * expected that drivers will fix this mapping if they can before
 * calling netif_set_real_num_tx_queues.
 */
static void netif_setup_tc(struct net_device *dev, unsigned int txq)
{
        int i;
        struct netdev_tc_txq *tc = &dev->tc_to_txq[0];

        /* If TC0 is invalidated disable TC mapping */
        if (tc->offset + tc->count > txq) {
                pr_warn("Number of in use tx queues changed invalidating tc mappings. Priority traffic classification disabled!\n");
                dev->num_tc = 0;
                return;
        }

        /* Invalidated prio to tc mappings set to TC0 */
        for (i = 1; i < TC_BITMASK + 1; i++) {
                int q = netdev_get_prio_tc_map(dev, i);

                tc = &dev->tc_to_txq[q];
                if (tc->offset + tc->count > txq) {
                        pr_warn("Number of in use tx queues changed. Priority %i to tc mapping %i is no longer valid. Setting map to 0\n",
                                i, q);
                        netdev_set_prio_tc_map(dev, i, 0);
                }
        }
}

int netdev_txq_to_tc(struct net_device *dev, unsigned int txq)
{
        if (dev->num_tc) {
                struct netdev_tc_txq *tc = &dev->tc_to_txq[0];
                int i;

                for (i = 0; i < TC_MAX_QUEUE; i++, tc++) {
                        if ((txq - tc->offset) < tc->count)
                                return i;
                }

                return -1;
        }

        return 0;
}

#ifdef CONFIG_XPS
static DEFINE_MUTEX(xps_map_mutex);
#define xmap_dereference(P)             \
        rcu_dereference_protected((P), lockdep_is_held(&xps_map_mutex))

static bool remove_xps_queue(struct xps_dev_maps *dev_maps,
                             int tci, u16 index)
{
        struct xps_map *map = NULL;
        int pos;

        if (dev_maps)
                map = xmap_dereference(dev_maps->cpu_map[tci]);
        if (!map)
                return false;

        for (pos = map->len; pos--;) {
                if (map->queues[pos] != index)
                        continue;

                if (map->len > 1) {
                        map->queues[pos] = map->queues[--map->len];
                        break;
                }

                RCU_INIT_POINTER(dev_maps->cpu_map[tci], NULL);
                kfree_rcu(map, rcu);
                return false;
        }

        return true;
}

static bool remove_xps_queue_cpu(struct net_device *dev,
                                 struct xps_dev_maps *dev_maps,
                                 int cpu, u16 offset, u16 count)
{
        int num_tc = dev->num_tc ? : 1;
        bool active = false;
        int tci;

        for (tci = cpu * num_tc; num_tc--; tci++) {
                int i, j;

                for (i = count, j = offset; i--; j++) {
                        if (!remove_xps_queue(dev_maps, cpu, j))
                                break;
                }

                active |= i < 0;
        }

        return active;
}

static void netif_reset_xps_queues(struct net_device *dev, u16 offset,
                                   u16 count)
{
        struct xps_dev_maps *dev_maps;
        int cpu, i;
        bool active = false;

        mutex_lock(&xps_map_mutex);
        dev_maps = xmap_dereference(dev->xps_maps);

        if (!dev_maps)
                goto out_no_maps;

        for_each_possible_cpu(cpu)
                active |= remove_xps_queue_cpu(dev, dev_maps, cpu,
                                               offset, count);

        if (!active) {
                RCU_INIT_POINTER(dev->xps_maps, NULL);
                kfree_rcu(dev_maps, rcu);
        }

        for (i = offset + (count - 1); count--; i--)
                netdev_queue_numa_node_write(netdev_get_tx_queue(dev, i),
                                             NUMA_NO_NODE);

out_no_maps:
        mutex_unlock(&xps_map_mutex);
}

static void netif_reset_xps_queues_gt(struct net_device *dev, u16 index)
{
        netif_reset_xps_queues(dev, index, dev->num_tx_queues - index);
}

static struct xps_map *expand_xps_map(struct xps_map *map,
                                      int cpu, u16 index)
{
        struct xps_map *new_map;
        int alloc_len = XPS_MIN_MAP_ALLOC;
        int i, pos;

        for (pos = 0; map && pos < map->len; pos++) {
                if (map->queues[pos] != index)
                        continue;
                return map;
        }

        /* Need to add queue to this CPU's existing map */
        if (map) {
                if (pos < map->alloc_len)
                        return map;

                alloc_len = map->alloc_len * 2;
        }

        /* Need to allocate new map to store queue on this CPU's map */
        new_map = kzalloc_node(XPS_MAP_SIZE(alloc_len), GFP_KERNEL,
                               cpu_to_node(cpu));
        if (!new_map)
                return NULL;

        for (i = 0; i < pos; i++)
                new_map->queues[i] = map->queues[i];
        new_map->alloc_len = alloc_len;
        new_map->len = pos;

        return new_map;
}

int netif_set_xps_queue(struct net_device *dev, const struct cpumask *mask,
                        u16 index)
{
        struct xps_dev_maps *dev_maps, *new_dev_maps = NULL;
        int i, cpu, tci, numa_node_id = -2;
        int maps_sz, num_tc = 1, tc = 0;
        struct xps_map *map, *new_map;
        bool active = false;

        if (dev->num_tc) {
                num_tc = dev->num_tc;
                tc = netdev_txq_to_tc(dev, index);
                if (tc < 0)
                        return -EINVAL;
        }

        maps_sz = XPS_DEV_MAPS_SIZE(num_tc);
        if (maps_sz < L1_CACHE_BYTES)
                maps_sz = L1_CACHE_BYTES;

        mutex_lock(&xps_map_mutex);

        dev_maps = xmap_dereference(dev->xps_maps);

        /* allocate memory for queue storage */
        for_each_cpu_and(cpu, cpu_online_mask, mask) {
                if (!new_dev_maps)
                        new_dev_maps = kzalloc(maps_sz, GFP_KERNEL);
                if (!new_dev_maps) {
                        mutex_unlock(&xps_map_mutex);
                        return -ENOMEM;
                }

                tci = cpu * num_tc + tc;
                map = dev_maps ? xmap_dereference(dev_maps->cpu_map[tci]) :
                                 NULL;

                map = expand_xps_map(map, cpu, index);
                if (!map)
                        goto error;

                RCU_INIT_POINTER(new_dev_maps->cpu_map[tci], map);
        }

        if (!new_dev_maps)
                goto out_no_new_maps;

        for_each_possible_cpu(cpu) {
                /* copy maps belonging to foreign traffic classes */
                for (i = tc, tci = cpu * num_tc; dev_maps && i--; tci++) {
                        /* fill in the new device map from the old device map */
                        map = xmap_dereference(dev_maps->cpu_map[tci]);
                        RCU_INIT_POINTER(new_dev_maps->cpu_map[tci], map);
                }

                /* We need to explicitly update tci as prevous loop
                 * could break out early if dev_maps is NULL.
                 */
                tci = cpu * num_tc + tc;

                if (cpumask_test_cpu(cpu, mask) && cpu_online(cpu)) {
                        /* add queue to CPU maps */
                        int pos = 0;

                        map = xmap_dereference(new_dev_maps->cpu_map[tci]);
                        while ((pos < map->len) && (map->queues[pos] != index))
                                pos++;

                        if (pos == map->len)
                                map->queues[map->len++] = index;
#ifdef CONFIG_NUMA
                        if (numa_node_id == -2)
                                numa_node_id = cpu_to_node(cpu);
                        else if (numa_node_id != cpu_to_node(cpu))
                                numa_node_id = -1;
#endif
                } else if (dev_maps) {
                        /* fill in the new device map from the old device map */
                        map = xmap_dereference(dev_maps->cpu_map[tci]);
                        RCU_INIT_POINTER(new_dev_maps->cpu_map[tci], map);
                }

                /* copy maps belonging to foreign traffic classes */
                for (i = num_tc - tc, tci++; dev_maps && --i; tci++) {
                        /* fill in the new device map from the old device map */
                        map = xmap_dereference(dev_maps->cpu_map[tci]);
                        RCU_INIT_POINTER(new_dev_maps->cpu_map[tci], map);
                }
        }

        rcu_assign_pointer(dev->xps_maps, new_dev_maps);

        /* Cleanup old maps */
        if (!dev_maps)
                goto out_no_old_maps;

        for_each_possible_cpu(cpu) {
                for (i = num_tc, tci = cpu * num_tc; i--; tci++) {
                        new_map = xmap_dereference(new_dev_maps->cpu_map[tci]);
                        map = xmap_dereference(dev_maps->cpu_map[tci]);
                        if (map && map != new_map)
                                kfree_rcu(map, rcu);
                }
        }

        kfree_rcu(dev_maps, rcu);

out_no_old_maps:
        dev_maps = new_dev_maps;
        active = true;

out_no_new_maps:
        /* update Tx queue numa node */
        netdev_queue_numa_node_write(netdev_get_tx_queue(dev, index),
                                     (numa_node_id >= 0) ? numa_node_id :
                                     NUMA_NO_NODE);

        if (!dev_maps)
                goto out_no_maps;

        /* removes queue from unused CPUs */
        for_each_possible_cpu(cpu) {
                for (i = tc, tci = cpu * num_tc; i--; tci++)
                        active |= remove_xps_queue(dev_maps, tci, index);
                if (!cpumask_test_cpu(cpu, mask) || !cpu_online(cpu))
                        active |= remove_xps_queue(dev_maps, tci, index);
                for (i = num_tc - tc, tci++; --i; tci++)
                        active |= remove_xps_queue(dev_maps, tci, index);
        }

        /* free map if not active */
        if (!active) {
                RCU_INIT_POINTER(dev->xps_maps, NULL);
                kfree_rcu(dev_maps, rcu);
        }

out_no_maps:
        mutex_unlock(&xps_map_mutex);

        return 0;
error:
        /* remove any maps that we added */
        for_each_possible_cpu(cpu) {
                for (i = num_tc, tci = cpu * num_tc; i--; tci++) {
                        new_map = xmap_dereference(new_dev_maps->cpu_map[tci]);
                        map = dev_maps ?
                              xmap_dereference(dev_maps->cpu_map[tci]) :
                              NULL;
                        if (new_map && new_map != map)
                                kfree(new_map);
                }
        }

        mutex_unlock(&xps_map_mutex);

        kfree(new_dev_maps);
        return -ENOMEM;
}
EXPORT_SYMBOL(netif_set_xps_queue);

#endif
void netdev_reset_tc(struct net_device *dev)
{
#ifdef CONFIG_XPS
        netif_reset_xps_queues_gt(dev, 0);
#endif
        dev->num_tc = 0;
        memset(dev->tc_to_txq, 0, sizeof(dev->tc_to_txq));
        memset(dev->prio_tc_map, 0, sizeof(dev->prio_tc_map));
}
EXPORT_SYMBOL(netdev_reset_tc);

int netdev_set_tc_queue(struct net_device *dev, u8 tc, u16 count, u16 offset)
{
        if (tc >= dev->num_tc)
                return -EINVAL;

#ifdef CONFIG_XPS
        netif_reset_xps_queues(dev, offset, count);
#endif
        dev->tc_to_txq[tc].count = count;
        dev->tc_to_txq[tc].offset = offset;
        return 0;
}
EXPORT_SYMBOL(netdev_set_tc_queue);

int netdev_set_num_tc(struct net_device *dev, u8 num_tc)
{
        if (num_tc > TC_MAX_QUEUE)
                return -EINVAL;

#ifdef CONFIG_XPS
        netif_reset_xps_queues_gt(dev, 0);
#endif
        dev->num_tc = num_tc;
        return 0;
}
EXPORT_SYMBOL(netdev_set_num_tc);

/*
 * Routine to help set real_num_tx_queues. To avoid skbs mapped to queues
 * greater then real_num_tx_queues stale skbs on the qdisc must be flushed.
 */
int netif_set_real_num_tx_queues(struct net_device *dev, unsigned int txq)
{
        int rc;

        if (txq < 1 || txq > dev->num_tx_queues)
                return -EINVAL;

        if (dev->reg_state == NETREG_REGISTERED ||
            dev->reg_state == NETREG_UNREGISTERING) {
                ASSERT_RTNL();

                rc = netdev_queue_update_kobjects(dev, dev->real_num_tx_queues,
                                                  txq);
                if (rc)
                        return rc;

                if (dev->num_tc)
                        netif_setup_tc(dev, txq);

                if (txq < dev->real_num_tx_queues) {
                        qdisc_reset_all_tx_gt(dev, txq);
#ifdef CONFIG_XPS
                        netif_reset_xps_queues_gt(dev, txq);
#endif
                }
        }

        dev->real_num_tx_queues = txq;
        return 0;
}
EXPORT_SYMBOL(netif_set_real_num_tx_queues);

#ifdef CONFIG_SYSFS
/**
 *      netif_set_real_num_rx_queues - set actual number of RX queues used
 *      @dev: Network device
 *      @rxq: Actual number of RX queues
 *
 *      This must be called either with the rtnl_lock held or before
 *      registration of the net device.  Returns 0 on success, or a
 *      negative error code.  If called before registration, it always
 *      succeeds.
 */
int netif_set_real_num_rx_queues(struct net_device *dev, unsigned int rxq)
{
        int rc;

        if (rxq < 1 || rxq > dev->num_rx_queues)
                return -EINVAL;

        if (dev->reg_state == NETREG_REGISTERED) {
                ASSERT_RTNL();

                rc = net_rx_queue_update_kobjects(dev, dev->real_num_rx_queues,
                                                  rxq);
                if (rc)
                        return rc;
        }

        dev->real_num_rx_queues = rxq;
        return 0;
}
EXPORT_SYMBOL(netif_set_real_num_rx_queues);
#endif

/**
 * netif_get_num_default_rss_queues - default number of RSS queues
 *
 * This routine should set an upper limit on the number of RSS queues
 * used by default by multiqueue devices.
 */
int netif_get_num_default_rss_queues(void)
{
        return is_kdump_kernel() ?
                1 : min_t(int, DEFAULT_MAX_NUM_RSS_QUEUES, num_online_cpus());
}
EXPORT_SYMBOL(netif_get_num_default_rss_queues);

static void __netif_reschedule(struct Qdisc *q)
{
        struct softnet_data *sd;
        unsigned long flags;

        local_irq_save(flags);
        sd = this_cpu_ptr(&softnet_data);
        q->next_sched = NULL;
        *sd->output_queue_tailp = q;
        sd->output_queue_tailp = &q->next_sched;
        raise_softirq_irqoff(NET_TX_SOFTIRQ);
        local_irq_restore(flags);
}

void __netif_schedule(struct Qdisc *q)
{
        if (!test_and_set_bit(__QDISC_STATE_SCHED, &q->state))
                __netif_reschedule(q);
}
EXPORT_SYMBOL(__netif_schedule);

struct dev_kfree_skb_cb {
        enum skb_free_reason reason;
};

static struct dev_kfree_skb_cb *get_kfree_skb_cb(const struct sk_buff *skb)
{
        return (struct dev_kfree_skb_cb *)skb->cb;
}

void netif_schedule_queue(struct netdev_queue *txq)
{
        rcu_read_lock();
        if (!(txq->state & QUEUE_STATE_ANY_XOFF)) {
                struct Qdisc *q = rcu_dereference(txq->qdisc);

                __netif_schedule(q);
        }
        rcu_read_unlock();
}
EXPORT_SYMBOL(netif_schedule_queue);

void netif_tx_wake_queue(struct netdev_queue *dev_queue)
{
        if (test_and_clear_bit(__QUEUE_STATE_DRV_XOFF, &dev_queue->state)) {
                struct Qdisc *q;

                rcu_read_lock();
                q = rcu_dereference(dev_queue->qdisc);
                __netif_schedule(q);
                rcu_read_unlock();
        }
}
EXPORT_SYMBOL(netif_tx_wake_queue);

void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
{
        unsigned long flags;

        if (unlikely(!skb))
                return;

        if (likely(refcount_read(&skb->users) == 1)) {
                smp_rmb();
                refcount_set(&skb->users, 0);
        } else if (likely(!refcount_dec_and_test(&skb->users))) {
                return;
        }
        get_kfree_skb_cb(skb)->reason = reason;
        local_irq_save(flags);
        skb->next = __this_cpu_read(softnet_data.completion_queue);
        __this_cpu_write(softnet_data.completion_queue, skb);
        raise_softirq_irqoff(NET_TX_SOFTIRQ);
        local_irq_restore(flags);
}
EXPORT_SYMBOL(__dev_kfree_skb_irq);

void __dev_kfree_skb_any(struct sk_buff *skb, enum skb_free_reason reason)
{
        if (in_irq() || irqs_disabled())
                __dev_kfree_skb_irq(skb, reason);
        else
                dev_kfree_skb(skb);
}
EXPORT_SYMBOL(__dev_kfree_skb_any);


/**
 * netif_device_detach - mark device as removed
 * @dev: network device
 *
 * Mark device as removed from system and therefore no longer available.
 */
void netif_device_detach(struct net_device *dev)
{
        if (test_and_clear_bit(__LINK_STATE_PRESENT, &dev->state) &&
            netif_running(dev)) {
                netif_tx_stop_all_queues(dev);
        }
}
EXPORT_SYMBOL(netif_device_detach);

/**
 * netif_device_attach - mark device as attached
 * @dev: network device
 *
 * Mark device as attached from system and restart if needed.
 */
void netif_device_attach(struct net_device *dev)
{
        if (!test_and_set_bit(__LINK_STATE_PRESENT, &dev->state) &&
            netif_running(dev)) {
                netif_tx_wake_all_queues(dev);
                __netdev_watchdog_up(dev);
        }
}
EXPORT_SYMBOL(netif_device_attach);

/*
 * Returns a Tx hash based on the given packet descriptor a Tx queues' number
 * to be used as a distribution range.
 */
u16 __skb_tx_hash(const struct net_device *dev, struct sk_buff *skb,
                  unsigned int num_tx_queues)
{
        u32 hash;
        u16 qoffset = 0;
        u16 qcount = num_tx_queues;

        if (skb_rx_queue_recorded(skb)) {
                hash = skb_get_rx_queue(skb);
                while (unlikely(hash >= num_tx_queues))
                        hash -= num_tx_queues;
                return hash;
        }

        if (dev->num_tc) {
                u8 tc = netdev_get_prio_tc_map(dev, skb->priority);

                qoffset = dev->tc_to_txq[tc].offset;
                qcount = dev->tc_to_txq[tc].count;
        }

        return (u16) reciprocal_scale(skb_get_hash(skb), qcount) + qoffset;
}
EXPORT_SYMBOL(__skb_tx_hash);

static void skb_warn_bad_offload(const struct sk_buff *skb)
{
        static const netdev_features_t null_features;
        struct net_device *dev = skb->dev;
        const char *name = "";

        if (!net_ratelimit())
                return;

        if (dev) {
                if (dev->dev.parent)
                        name = dev_driver_string(dev->dev.parent);
                else
                        name = netdev_name(dev);
        }
        WARN(1, "%s: caps=(%pNF, %pNF) len=%d data_len=%d gso_size=%d "
             "gso_type=%d ip_summed=%d\n",
             name, dev ? &dev->features : &null_features,
             skb->sk ? &skb->sk->sk_route_caps : &null_features,
             skb->len, skb->data_len, skb_shinfo(skb)->gso_size,
             skb_shinfo(skb)->gso_type, skb->ip_summed);
}

/*
 * Invalidate hardware checksum when packet is to be mangled, and
 * complete checksum manually on outgoing path.
 */
int skb_checksum_help(struct sk_buff *skb)
{
        __wsum csum;
        int ret = 0, offset;

        if (skb->ip_summed == CHECKSUM_COMPLETE)
                goto out_set_summed;

        if (unlikely(skb_shinfo(skb)->gso_size)) {
                skb_warn_bad_offload(skb);
                return -EINVAL;
        }

        /* Before computing a checksum, we should make sure no frag could
         * be modified by an external entity : checksum could be wrong.
         */
        if (skb_has_shared_frag(skb)) {
                ret = __skb_linearize(skb);
                if (ret)
                        goto out;
        }

        offset = skb_checksum_start_offset(skb);
        BUG_ON(offset >= skb_headlen(skb));
        csum = skb_checksum(skb, offset, skb->len - offset, 0);

        offset += skb->csum_offset;
        BUG_ON(offset + sizeof(__sum16) > skb_headlen(skb));

        if (skb_cloned(skb) &&
            !skb_clone_writable(skb, offset + sizeof(__sum16))) {
                ret = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
                if (ret)
                        goto out;
        }

        *(__sum16 *)(skb->data + offset) = csum_fold(csum) ?: CSUM_MANGLED_0;
out_set_summed:
        skb->ip_summed = CHECKSUM_NONE;
out:
        return ret;
}
EXPORT_SYMBOL(skb_checksum_help);

int skb_crc32c_csum_help(struct sk_buff *skb)
{
        __le32 crc32c_csum;
        int ret = 0, offset, start;

        if (skb->ip_summed != CHECKSUM_PARTIAL)
                goto out;

        if (unlikely(skb_is_gso(skb)))
                goto out;

        /* Before computing a checksum, we should make sure no frag could
         * be modified by an external entity : checksum could be wrong.
         */
        if (unlikely(skb_has_shared_frag(skb))) {
                ret = __skb_linearize(skb);
                if (ret)
                        goto out;
        }
        start = skb_checksum_start_offset(skb);
        offset = start + offsetof(struct sctphdr, checksum);
        if (WARN_ON_ONCE(offset >= skb_headlen(skb))) {
                ret = -EINVAL;
                goto out;
        }
        if (skb_cloned(skb) &&
            !skb_clone_writable(skb, offset + sizeof(__le32))) {
                ret = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
                if (ret)
                        goto out;
        }
        crc32c_csum = cpu_to_le32(~__skb_checksum(skb, start,
                                                  skb->len - start, ~(__u32)0,
                                                  crc32c_csum_stub));
        *(__le32 *)(skb->data + offset) = crc32c_csum;
        skb->ip_summed = CHECKSUM_NONE;
        skb->csum_not_inet = 0;
out:
        return ret;
}

__be16 skb_network_protocol(struct sk_buff *skb, int *depth)
{
        __be16 type = skb->protocol;

        /* Tunnel gso handlers can set protocol to ethernet. */
        if (type == htons(ETH_P_TEB)) {
                struct ethhdr *eth;

                if (unlikely(!pskb_may_pull(skb, sizeof(struct ethhdr))))
                        return 0;

                eth = (struct ethhdr *)skb_mac_header(skb);
                type = eth->h_proto;
        }

        return __vlan_get_protocol(skb, type, depth);
}

/**
 *      skb_mac_gso_segment - mac layer segmentation handler.
 *      @skb: buffer to segment
 *      @features: features for the output path (see dev->features)
 */
struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
                                    netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EPROTONOSUPPORT);
        struct packet_offload *ptype;
        int vlan_depth = skb->mac_len;
        __be16 type = skb_network_protocol(skb, &vlan_depth);

        if (unlikely(!type))
                return ERR_PTR(-EINVAL);

        __skb_pull(skb, vlan_depth);

        rcu_read_lock();
        list_for_each_entry_rcu(ptype, &offload_base, list) {
                if (ptype->type == type && ptype->callbacks.gso_segment) {
                        segs = ptype->callbacks.gso_segment(skb, features);
                        break;
                }
        }
        rcu_read_unlock();

        __skb_push(skb, skb->data - skb_mac_header(skb));

        return segs;
}
EXPORT_SYMBOL(skb_mac_gso_segment);


/* openvswitch calls this on rx path, so we need a different check.
 */
static inline bool skb_needs_check(struct sk_buff *skb, bool tx_path)
{
        if (tx_path)
                return skb->ip_summed != CHECKSUM_PARTIAL &&
                       skb->ip_summed != CHECKSUM_NONE;

        return skb->ip_summed == CHECKSUM_NONE;
}

/**
 *      __skb_gso_segment - Perform segmentation on skb.
 *      @skb: buffer to segment
 *      @features: features for the output path (see dev->features)
 *      @tx_path: whether it is called in TX path
 *
 *      This function segments the given skb and returns a list of segments.
 *
 *      It may return NULL if the skb requires no segmentation.  This is
 *      only possible when GSO is used for verifying header integrity.
 *
 *      Segmentation preserves SKB_SGO_CB_OFFSET bytes of previous skb cb.
 */
struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
                                  netdev_features_t features, bool tx_path)
{
        struct sk_buff *segs;

        if (unlikely(skb_needs_check(skb, tx_path))) {
                int err;

                /* We're going to init ->check field in TCP or UDP header */
                err = skb_cow_head(skb, 0);
                if (err < 0)
                        return ERR_PTR(err);
        }

        /* Only report GSO partial support if it will enable us to
         * support segmentation on this frame without needing additional
         * work.
         */
        if (features & NETIF_F_GSO_PARTIAL) {
                netdev_features_t partial_features = NETIF_F_GSO_ROBUST;
                struct net_device *dev = skb->dev;

                partial_features |= dev->features & dev->gso_partial_features;
                if (!skb_gso_ok(skb, features | partial_features))
                        features &= ~NETIF_F_GSO_PARTIAL;
        }

        BUILD_BUG_ON(SKB_SGO_CB_OFFSET +
                     sizeof(*SKB_GSO_CB(skb)) > sizeof(skb->cb));

        SKB_GSO_CB(skb)->mac_offset = skb_headroom(skb);
        SKB_GSO_CB(skb)->encap_level = 0;

        skb_reset_mac_header(skb);
        skb_reset_mac_len(skb);

        segs = skb_mac_gso_segment(skb, features);

        if (unlikely(skb_needs_check(skb, tx_path)))
                skb_warn_bad_offload(skb);

        return segs;
}
EXPORT_SYMBOL(__skb_gso_segment);

/* Take action when hardware reception checksum errors are detected. */
#ifdef CONFIG_BUG
void netdev_rx_csum_fault(struct net_device *dev)
{
        if (net_ratelimit()) {
                pr_err("%s: hw csum failure\n", dev ? dev->name : "<unknown>");
                dump_stack();
        }
}
EXPORT_SYMBOL(netdev_rx_csum_fault);
#endif

/* Actually, we should eliminate this check as soon as we know, that:
 * 1. IOMMU is present and allows to map all the memory.
 * 2. No high memory really exists on this machine.
 */

static int illegal_highdma(struct net_device *dev, struct sk_buff *skb)
{
#ifdef CONFIG_HIGHMEM
        int i;

        if (!(dev->features & NETIF_F_HIGHDMA)) {
                for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                        skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

                        if (PageHighMem(skb_frag_page(frag)))
                                return 1;
                }
        }

        if (PCI_DMA_BUS_IS_PHYS) {
                struct device *pdev = dev->dev.parent;

                if (!pdev)
                        return 0;
                for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                        skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
                        dma_addr_t addr = page_to_phys(skb_frag_page(frag));

                        if (!pdev->dma_mask || addr + PAGE_SIZE - 1 > *pdev->dma_mask)
                                return 1;
                }
        }
#endif
        return 0;
}

/* If MPLS offload request, verify we are testing hardware MPLS features
 * instead of standard features for the netdev.
 */
#if IS_ENABLED(CONFIG_NET_MPLS_GSO)
static netdev_features_t net_mpls_features(struct sk_buff *skb,
                                           netdev_features_t features,
                                           __be16 type)
{
        if (eth_p_mpls(type))
                features &= skb->dev->mpls_features;

        return features;
}
#else
static netdev_features_t net_mpls_features(struct sk_buff *skb,
                                           netdev_features_t features,
                                           __be16 type)
{
        return features;
}
#endif

static netdev_features_t harmonize_features(struct sk_buff *skb,
        netdev_features_t features)
{
        int tmp;
        __be16 type;

        type = skb_network_protocol(skb, &tmp);
        features = net_mpls_features(skb, features, type);

        if (skb->ip_summed != CHECKSUM_NONE &&
            !can_checksum_protocol(features, type)) {
                features &= ~(NETIF_F_CSUM_MASK | NETIF_F_GSO_MASK);
        }
        if (illegal_highdma(skb->dev, skb))
                features &= ~NETIF_F_SG;

        return features;
}

netdev_features_t passthru_features_check(struct sk_buff *skb,
                                          struct net_device *dev,
                                          netdev_features_t features)
{
        return features;
}
EXPORT_SYMBOL(passthru_features_check);

static netdev_features_t dflt_features_check(const struct sk_buff *skb,
                                             struct net_device *dev,
                                             netdev_features_t features)
{
        return vlan_features_check(skb, features);
}

static netdev_features_t gso_features_check(const struct sk_buff *skb,
                                            struct net_device *dev,
                                            netdev_features_t features)
{
        u16 gso_segs = skb_shinfo(skb)->gso_segs;

        if (gso_segs > dev->gso_max_segs)
                return features & ~NETIF_F_GSO_MASK;

        /* Support for GSO partial features requires software
         * intervention before we can actually process the packets
         * so we need to strip support for any partial features now
         * and we can pull them back in after we have partially
         * segmented the frame.
         */
        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL))
                features &= ~dev->gso_partial_features;

        /* Make sure to clear the IPv4 ID mangling feature if the
         * IPv4 header has the potential to be fragmented.
         */
        if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
                struct iphdr *iph = skb->encapsulation ?
                                    inner_ip_hdr(skb) : ip_hdr(skb);

                if (!(iph->frag_off & htons(IP_DF)))
                        features &= ~NETIF_F_TSO_MANGLEID;
        }

        return features;
}

netdev_features_t netif_skb_features(struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;
        netdev_features_t features = dev->features;

        if (skb_is_gso(skb))
                features = gso_features_check(skb, dev, features);

        /* If encapsulation offload request, verify we are testing
         * hardware encapsulation features instead of standard
         * features for the netdev
         */
        if (skb->encapsulation)
                features &= dev->hw_enc_features;

        if (skb_vlan_tagged(skb))
                features = netdev_intersect_features(features,
                                                     dev->vlan_features |
                                                     NETIF_F_HW_VLAN_CTAG_TX |
                                                     NETIF_F_HW_VLAN_STAG_TX);

        if (dev->netdev_ops->ndo_features_check)
                features &= dev->netdev_ops->ndo_features_check(skb, dev,
                                                                features);
        else
                features &= dflt_features_check(skb, dev, features);

        return harmonize_features(skb, features);
}
EXPORT_SYMBOL(netif_skb_features);

static int xmit_one(struct sk_buff *skb, struct net_device *dev,
                    struct netdev_queue *txq, bool more)
{
        unsigned int len;
        int rc;

        if (!list_empty(&ptype_all) || !list_empty(&dev->ptype_all))
                dev_queue_xmit_nit(skb, dev);

        len = skb->len;
        trace_net_dev_start_xmit(skb, dev);
        rc = netdev_start_xmit(skb, dev, txq, more);
        trace_net_dev_xmit(skb, rc, dev, len);

        return rc;
}

struct sk_buff *dev_hard_start_xmit(struct sk_buff *first, struct net_device *dev,
                                    struct netdev_queue *txq, int *ret)
{
        struct sk_buff *skb = first;
        int rc = NETDEV_TX_OK;

        while (skb) {
                struct sk_buff *next = skb->next;

                skb->next = NULL;
                rc = xmit_one(skb, dev, txq, next != NULL);
                if (unlikely(!dev_xmit_complete(rc))) {
                        skb->next = next;
                        goto out;
                }

                skb = next;
                if (netif_xmit_stopped(txq) && skb) {
                        rc = NETDEV_TX_BUSY;
                        break;
                }
        }

out:
        *ret = rc;
        return skb;
}

static struct sk_buff *validate_xmit_vlan(struct sk_buff *skb,
                                          netdev_features_t features)
{
        if (skb_vlan_tag_present(skb) &&
            !vlan_hw_offload_capable(features, skb->vlan_proto))
                skb = __vlan_hwaccel_push_inside(skb);
        return skb;
}

int skb_csum_hwoffload_help(struct sk_buff *skb,
                            const netdev_features_t features)
{
        if (unlikely(skb->csum_not_inet))
                return !!(features & NETIF_F_SCTP_CRC) ? 0 :
                        skb_crc32c_csum_help(skb);

        return !!(features & NETIF_F_CSUM_MASK) ? 0 : skb_checksum_help(skb);
}
EXPORT_SYMBOL(skb_csum_hwoffload_help);

static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device *dev)
{
        netdev_features_t features;

        features = netif_skb_features(skb);
        skb = validate_xmit_vlan(skb, features);
        if (unlikely(!skb))
                goto out_null;

        if (netif_needs_gso(skb, features)) {
                struct sk_buff *segs;

                segs = skb_gso_segment(skb, features);
                if (IS_ERR(segs)) {
                        goto out_kfree_skb;
                } else if (segs) {
                        consume_skb(skb);
                        skb = segs;
                }
        } else {
                if (skb_needs_linearize(skb, features) &&
                    __skb_linearize(skb))
                        goto out_kfree_skb;

                if (validate_xmit_xfrm(skb, features))
                        goto out_kfree_skb;

                /* If packet is not checksummed and device does not
                 * support checksumming for this protocol, complete
                 * checksumming here.
                 */
                if (skb->ip_summed == CHECKSUM_PARTIAL) {
                        if (skb->encapsulation)
                                skb_set_inner_transport_header(skb,
                                                               skb_checksum_start_offset(skb));
                        else
                                skb_set_transport_header(skb,
                                                         skb_checksum_start_offset(skb));
                        if (skb_csum_hwoffload_help(skb, features))
                                goto out_kfree_skb;
                }
        }

        return skb;

out_kfree_skb:
        kfree_skb(skb);
out_null:
        atomic_long_inc(&dev->tx_dropped);
        return NULL;
}

struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *dev)
{
        struct sk_buff *next, *head = NULL, *tail;

        for (; skb != NULL; skb = next) {
                next = skb->next;
                skb->next = NULL;

                /* in case skb wont be segmented, point to itself */
                skb->prev = skb;

                skb = validate_xmit_skb(skb, dev);
                if (!skb)
                        continue;

                if (!head)
                        head = skb;
                else
                        tail->next = skb;
                /* If skb was segmented, skb->prev points to
                 * the last segment. If not, it still contains skb.
                 */
                tail = skb->prev;
        }
        return head;
}
EXPORT_SYMBOL_GPL(validate_xmit_skb_list);

static void qdisc_pkt_len_init(struct sk_buff *skb)
{
        const struct skb_shared_info *shinfo = skb_shinfo(skb);

        qdisc_skb_cb(skb)->pkt_len = skb->len;

        /* To get more precise estimation of bytes sent on wire,
         * we add to pkt_len the headers size of all segments
         */
        if (shinfo->gso_size)  {
                unsigned int hdr_len;
                u16 gso_segs = shinfo->gso_segs;

                /* mac layer + network layer */
                hdr_len = skb_transport_header(skb) - skb_mac_header(skb);

                /* + transport layer */
                if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
                        hdr_len += tcp_hdrlen(skb);
                else
                        hdr_len += sizeof(struct udphdr);

                if (shinfo->gso_type & SKB_GSO_DODGY)
                        gso_segs = DIV_ROUND_UP(skb->len - hdr_len,
                                                shinfo->gso_size);

                qdisc_skb_cb(skb)->pkt_len += (gso_segs - 1) * hdr_len;
        }
}

static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
                                 struct net_device *dev,
                                 struct netdev_queue *txq)
{
        spinlock_t *root_lock = qdisc_lock(q);
        struct sk_buff *to_free = NULL;
        bool contended;
        int rc;

        qdisc_calculate_pkt_len(skb, q);
        /*
         * Heuristic to force contended enqueues to serialize on a
         * separate lock before trying to get qdisc main lock.
         * This permits qdisc->running owner to get the lock more
         * often and dequeue packets faster.
         */
        contended = qdisc_is_running(q);
        if (unlikely(contended))
                spin_lock(&q->busylock);

        spin_lock(root_lock);
        if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) {
                __qdisc_drop(skb, &to_free);
                rc = NET_XMIT_DROP;
        } else if ((q->flags & TCQ_F_CAN_BYPASS) && !qdisc_qlen(q) &&
                   qdisc_run_begin(q)) {
                /*
                 * This is a work-conserving queue; there are no old skbs
                 * waiting to be sent out; and the qdisc is not running -
                 * xmit the skb directly.
                 */

                qdisc_bstats_update(q, skb);

                if (sch_direct_xmit(skb, q, dev, txq, root_lock, true)) {
                        if (unlikely(contended)) {
                                spin_unlock(&q->busylock);
                                contended = false;
                        }
                        __qdisc_run(q);
                } else
                        qdisc_run_end(q);

                rc = NET_XMIT_SUCCESS;
        } else {
                rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;
                if (qdisc_run_begin(q)) {
                        if (unlikely(contended)) {
                                spin_unlock(&q->busylock);
                                contended = false;
                        }
                        __qdisc_run(q);
                }
        }
        spin_unlock(root_lock);
        if (unlikely(to_free))
                kfree_skb_list(to_free);
        if (unlikely(contended))
                spin_unlock(&q->busylock);
        return rc;
}

#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
static void skb_update_prio(struct sk_buff *skb)
{
        struct netprio_map *map = rcu_dereference_bh(skb->dev->priomap);

        if (!skb->priority && skb->sk && map) {
                unsigned int prioidx =
                        sock_cgroup_prioidx(&skb->sk->sk_cgrp_data);

                if (prioidx < map->priomap_len)
                        skb->priority = map->priomap[prioidx];
        }
}
#else
#define skb_update_prio(skb)
#endif

DEFINE_PER_CPU(int, xmit_recursion);
EXPORT_SYMBOL(xmit_recursion);

/**
 *      dev_loopback_xmit - loop back @skb
 *      @net: network namespace this loopback is happening in
 *      @sk:  sk needed to be a netfilter okfn
 *      @skb: buffer to transmit
 */
int dev_loopback_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        skb_reset_mac_header(skb);
        __skb_pull(skb, skb_network_offset(skb));
        skb->pkt_type = PACKET_LOOPBACK;
        skb->ip_summed = CHECKSUM_UNNECESSARY;
        WARN_ON(!skb_dst(skb));
        skb_dst_force(skb);
        netif_rx_ni(skb);
        return 0;
}
EXPORT_SYMBOL(dev_loopback_xmit);

#ifdef CONFIG_NET_EGRESS
static struct sk_buff *
sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
{
        struct tcf_proto *cl = rcu_dereference_bh(dev->egress_cl_list);
        struct tcf_result cl_res;

        if (!cl)
                return skb;

        /* qdisc_skb_cb(skb)->pkt_len was already set by the caller. */
        qdisc_bstats_cpu_update(cl->q, skb);

        switch (tcf_classify(skb, cl, &cl_res, false)) {
        case TC_ACT_OK:
        case TC_ACT_RECLASSIFY:
                skb->tc_index = TC_H_MIN(cl_res.classid);
                break;
        case TC_ACT_SHOT:
                qdisc_qstats_cpu_drop(cl->q);
                *ret = NET_XMIT_DROP;
                kfree_skb(skb);
                return NULL;
        case TC_ACT_STOLEN:
        case TC_ACT_QUEUED:
        case TC_ACT_TRAP:
                *ret = NET_XMIT_SUCCESS;
                consume_skb(skb);
                return NULL;
        case TC_ACT_REDIRECT:
                /* No need to push/pop skb's mac_header here on egress! */
                skb_do_redirect(skb);
                *ret = NET_XMIT_SUCCESS;
                return NULL;
        default:
                break;
        }

        return skb;
}
#endif /* CONFIG_NET_EGRESS */

static inline int get_xps_queue(struct net_device *dev, struct sk_buff *skb)
{
#ifdef CONFIG_XPS
        struct xps_dev_maps *dev_maps;
        struct xps_map *map;
        int queue_index = -1;

        rcu_read_lock();
        dev_maps = rcu_dereference(dev->xps_maps);
        if (dev_maps) {
                unsigned int tci = skb->sender_cpu - 1;

                if (dev->num_tc) {
                        tci *= dev->num_tc;
                        tci += netdev_get_prio_tc_map(dev, skb->priority);
                }

                map = rcu_dereference(dev_maps->cpu_map[tci]);
                if (map) {
                        if (map->len == 1)
                                queue_index = map->queues[0];
                        else
                                queue_index = map->queues[reciprocal_scale(skb_get_hash(skb),
                                                                           map->len)];
                        if (unlikely(queue_index >= dev->real_num_tx_queues))
                                queue_index = -1;
                }
        }
        rcu_read_unlock();

        return queue_index;
#else
        return -1;
#endif
}

static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb)
{
        struct sock *sk = skb->sk;
        int queue_index = sk_tx_queue_get(sk);

        if (queue_index < 0 || skb->ooo_okay ||
            queue_index >= dev->real_num_tx_queues) {
                int new_index = get_xps_queue(dev, skb);

                if (new_index < 0)
                        new_index = skb_tx_hash(dev, skb);

                if (queue_index != new_index && sk &&
                    sk_fullsock(sk) &&
                    rcu_access_pointer(sk->sk_dst_cache))
                        sk_tx_queue_set(sk, new_index);

                queue_index = new_index;
        }

        return queue_index;
}

struct netdev_queue *netdev_pick_tx(struct net_device *dev,
                                    struct sk_buff *skb,
                                    void *accel_priv)
{
        int queue_index = 0;

#ifdef CONFIG_XPS
        u32 sender_cpu = skb->sender_cpu - 1;

        if (sender_cpu >= (u32)NR_CPUS)
                skb->sender_cpu = raw_smp_processor_id() + 1;
#endif

        if (dev->real_num_tx_queues != 1) {
                const struct net_device_ops *ops = dev->netdev_ops;

                if (ops->ndo_select_queue)
                        queue_index = ops->ndo_select_queue(dev, skb, accel_priv,
                                                            __netdev_pick_tx);
                else
                        queue_index = __netdev_pick_tx(dev, skb);

                if (!accel_priv)
                        queue_index = netdev_cap_txqueue(dev, queue_index);
        }

        skb_set_queue_mapping(skb, queue_index);
        return netdev_get_tx_queue(dev, queue_index);
}

/**
 *      __dev_queue_xmit - transmit a buffer
 *      @skb: buffer to transmit
 *      @accel_priv: private data used for L2 forwarding offload
 *
 *      Queue a buffer for transmission to a network device. The caller must
 *      have set the device and priority and built the buffer before calling
 *      this function. The function can be called from an interrupt.
 *
 *      A negative errno code is returned on a failure. A success does not
 *      guarantee the frame will be transmitted as it may be dropped due
 *      to congestion or traffic shaping.
 *
 * -----------------------------------------------------------------------------------
 *      I notice this method can also return errors from the queue disciplines,
 *      including NET_XMIT_DROP, which is a positive value.  So, errors can also
 *      be positive.
 *
 *      Regardless of the return value, the skb is consumed, so it is currently
 *      difficult to retry a send to this method.  (You can bump the ref count
 *      before sending to hold a reference for retry if you are careful.)
 *
 *      When calling this method, interrupts MUST be enabled.  This is because
 *      the BH enable code must have IRQs enabled so that it will not deadlock.
 *          --BLG
 */
static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv)
{
        struct net_device *dev = skb->dev;
        struct netdev_queue *txq;
        struct Qdisc *q;
        int rc = -ENOMEM;

        skb_reset_mac_header(skb);

        if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
                __skb_tstamp_tx(skb, NULL, skb->sk, SCM_TSTAMP_SCHED);

        /* Disable soft irqs for various locks below. Also
         * stops preemption for RCU.
         */
        rcu_read_lock_bh();

        skb_update_prio(skb);

        qdisc_pkt_len_init(skb);
#ifdef CONFIG_NET_CLS_ACT
        skb->tc_at_ingress = 0;
# ifdef CONFIG_NET_EGRESS
        if (static_key_false(&egress_needed)) {
                skb = sch_handle_egress(skb, &rc, dev);
                if (!skb)
                        goto out;
        }
# endif
#endif
        /* If device/qdisc don't need skb->dst, release it right now while
         * its hot in this cpu cache.
         */
        if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
                skb_dst_drop(skb);
        else
                skb_dst_force(skb);

        txq = netdev_pick_tx(dev, skb, accel_priv);
        q = rcu_dereference_bh(txq->qdisc);

        trace_net_dev_queue(skb);
        if (q->enqueue) {
                rc = __dev_xmit_skb(skb, q, dev, txq);
                goto out;
        }

        /* The device has no queue. Common case for software devices:
         * loopback, all the sorts of tunnels...

         * Really, it is unlikely that netif_tx_lock protection is necessary
         * here.  (f.e. loopback and IP tunnels are clean ignoring statistics
         * counters.)
         * However, it is possible, that they rely on protection
         * made by us here.

         * Check this and shot the lock. It is not prone from deadlocks.
         *Either shot noqueue qdisc, it is even simpler 8)
         */
        if (dev->flags & IFF_UP) {
                int cpu = smp_processor_id(); /* ok because BHs are off */

                if (txq->xmit_lock_owner != cpu) {
                        if (unlikely(__this_cpu_read(xmit_recursion) >
                                     XMIT_RECURSION_LIMIT))
                                goto recursion_alert;

                        skb = validate_xmit_skb(skb, dev);
                        if (!skb)
                                goto out;

                        HARD_TX_LOCK(dev, txq, cpu);

                        if (!netif_xmit_stopped(txq)) {
                                __this_cpu_inc(xmit_recursion);
                                skb = dev_hard_start_xmit(skb, dev, txq, &rc);
                                __this_cpu_dec(xmit_recursion);
                                if (dev_xmit_complete(rc)) {
                                        HARD_TX_UNLOCK(dev, txq);
                                        goto out;
                                }
                        }
                        HARD_TX_UNLOCK(dev, txq);
                        net_crit_ratelimited("Virtual device %s asks to queue packet!\n",
                                             dev->name);
                } else {
                        /* Recursion is detected! It is possible,
                         * unfortunately
                         */
recursion_alert:
                        net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n",
                                             dev->name);
                }
        }

        rc = -ENETDOWN;
        rcu_read_unlock_bh();

        atomic_long_inc(&dev->tx_dropped);
        kfree_skb_list(skb);
        return rc;
out:
        rcu_read_unlock_bh();
        return rc;
}

int dev_queue_xmit(struct sk_buff *skb)
{
        return __dev_queue_xmit(skb, NULL);
}
EXPORT_SYMBOL(dev_queue_xmit);

int dev_queue_xmit_accel(struct sk_buff *skb, void *accel_priv)
{
        return __dev_queue_xmit(skb, accel_priv);
}
EXPORT_SYMBOL(dev_queue_xmit_accel);


/*************************************************************************
 *                      Receiver routines
 *************************************************************************/

int netdev_max_backlog __read_mostly = 1000;
EXPORT_SYMBOL(netdev_max_backlog);

int netdev_tstamp_prequeue __read_mostly = 1;
int netdev_budget __read_mostly = 300;
unsigned int __read_mostly netdev_budget_usecs = 2000;
int weight_p __read_mostly = 64;           /* old backlog weight */
int dev_weight_rx_bias __read_mostly = 1;  /* bias for backlog weight */
int dev_weight_tx_bias __read_mostly = 1;  /* bias for output_queue quota */
int dev_rx_weight __read_mostly = 64;
int dev_tx_weight __read_mostly = 64;

/* Called with irq disabled */
static inline void ____napi_schedule(struct softnet_data *sd,
                                     struct napi_struct *napi)
{
        list_add_tail(&napi->poll_list, &sd->poll_list);
        __raise_softirq_irqoff(NET_RX_SOFTIRQ);
}

#ifdef CONFIG_RPS

/* One global table that all flow-based protocols share. */
struct rps_sock_flow_table __rcu *rps_sock_flow_table __read_mostly;
EXPORT_SYMBOL(rps_sock_flow_table);
u32 rps_cpu_mask __read_mostly;
EXPORT_SYMBOL(rps_cpu_mask);

struct static_key rps_needed __read_mostly;
EXPORT_SYMBOL(rps_needed);
struct static_key rfs_needed __read_mostly;
EXPORT_SYMBOL(rfs_needed);

static struct rps_dev_flow *
set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
            struct rps_dev_flow *rflow, u16 next_cpu)
{
        if (next_cpu < nr_cpu_ids) {
#ifdef CONFIG_RFS_ACCEL
                struct netdev_rx_queue *rxqueue;
                struct rps_dev_flow_table *flow_table;
                struct rps_dev_flow *old_rflow;
                u32 flow_id;
                u16 rxq_index;
                int rc;

                /* Should we steer this flow to a different hardware queue? */
                if (!skb_rx_queue_recorded(skb) || !dev->rx_cpu_rmap ||
                    !(dev->features & NETIF_F_NTUPLE))
                        goto out;
                rxq_index = cpu_rmap_lookup_index(dev->rx_cpu_rmap, next_cpu);
                if (rxq_index == skb_get_rx_queue(skb))
                        goto out;

                rxqueue = dev->_rx + rxq_index;
                flow_table = rcu_dereference(rxqueue->rps_flow_table);
                if (!flow_table)
                        goto out;
                flow_id = skb_get_hash(skb) & flow_table->mask;
                rc = dev->netdev_ops->ndo_rx_flow_steer(dev, skb,
                                                        rxq_index, flow_id);
                if (rc < 0)
                        goto out;
                old_rflow = rflow;
                rflow = &flow_table->flows[flow_id];
                rflow->filter = rc;
                if (old_rflow->filter == rflow->filter)
                        old_rflow->filter = RPS_NO_FILTER;
        out:
#endif
                rflow->last_qtail =
                        per_cpu(softnet_data, next_cpu).input_queue_head;
        }

        rflow->cpu = next_cpu;
        return rflow;
}

/*
 * get_rps_cpu is called from netif_receive_skb and returns the target
 * CPU from the RPS map of the receiving queue for a given skb.
 * rcu_read_lock must be held on entry.
 */
static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
                       struct rps_dev_flow **rflowp)
{
        const struct rps_sock_flow_table *sock_flow_table;
        struct netdev_rx_queue *rxqueue = dev->_rx;
        struct rps_dev_flow_table *flow_table;
        struct rps_map *map;
        int cpu = -1;
        u32 tcpu;
        u32 hash;

        if (skb_rx_queue_recorded(skb)) {
                u16 index = skb_get_rx_queue(skb);

                if (unlikely(index >= dev->real_num_rx_queues)) {
                        WARN_ONCE(dev->real_num_rx_queues > 1,
                                  "%s received packet on queue %u, but number "
                                  "of RX queues is %u\n",
                                  dev->name, index, dev->real_num_rx_queues);
                        goto done;
                }
                rxqueue += index;
        }

        /* Avoid computing hash if RFS/RPS is not active for this rxqueue */

        flow_table = rcu_dereference(rxqueue->rps_flow_table);
        map = rcu_dereference(rxqueue->rps_map);
        if (!flow_table && !map)
                goto done;

        skb_reset_network_header(skb);
        hash = skb_get_hash(skb);
        if (!hash)
                goto done;

        sock_flow_table = rcu_dereference(rps_sock_flow_table);
        if (flow_table && sock_flow_table) {
                struct rps_dev_flow *rflow;
                u32 next_cpu;
                u32 ident;

                /* First check into global flow table if there is a match */
                ident = sock_flow_table->ents[hash & sock_flow_table->mask];
                if ((ident ^ hash) & ~rps_cpu_mask)
                        goto try_rps;

                next_cpu = ident & rps_cpu_mask;

                /* OK, now we know there is a match,
                 * we can look at the local (per receive queue) flow table
                 */
                rflow = &flow_table->flows[hash & flow_table->mask];
                tcpu = rflow->cpu;

                /*
                 * If the desired CPU (where last recvmsg was done) is
                 * different from current CPU (one in the rx-queue flow
                 * table entry), switch if one of the following holds:
                 *   - Current CPU is unset (>= nr_cpu_ids).
                 *   - Current CPU is offline.
                 *   - The current CPU's queue tail has advanced beyond the
                 *     last packet that was enqueued using this table entry.
                 *     This guarantees that all previous packets for the flow
                 *     have been dequeued, thus preserving in order delivery.
                 */
                if (unlikely(tcpu != next_cpu) &&
                    (tcpu >= nr_cpu_ids || !cpu_online(tcpu) ||
                     ((int)(per_cpu(softnet_data, tcpu).input_queue_head -
                      rflow->last_qtail)) >= 0)) {
                        tcpu = next_cpu;
                        rflow = set_rps_cpu(dev, skb, rflow, next_cpu);
                }

                if (tcpu < nr_cpu_ids && cpu_online(tcpu)) {
                        *rflowp = rflow;
                        cpu = tcpu;
                        goto done;
                }
        }

try_rps:

        if (map) {
                tcpu = map->cpus[reciprocal_scale(hash, map->len)];
                if (cpu_online(tcpu)) {
                        cpu = tcpu;
                        goto done;
                }
        }

done:
        return cpu;
}

#ifdef CONFIG_RFS_ACCEL

/**
 * rps_may_expire_flow - check whether an RFS hardware filter may be removed
 * @dev: Device on which the filter was set
 * @rxq_index: RX queue index
 * @flow_id: Flow ID passed to ndo_rx_flow_steer()
 * @filter_id: Filter ID returned by ndo_rx_flow_steer()
 *
 * Drivers that implement ndo_rx_flow_steer() should periodically call
 * this function for each installed filter and remove the filters for
 * which it returns %true.
 */
bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index,
                         u32 flow_id, u16 filter_id)
{
        struct netdev_rx_queue *rxqueue = dev->_rx + rxq_index;
        struct rps_dev_flow_table *flow_table;
        struct rps_dev_flow *rflow;
        bool expire = true;
        unsigned int cpu;

        rcu_read_lock();
        flow_table = rcu_dereference(rxqueue->rps_flow_table);
        if (flow_table && flow_id <= flow_table->mask) {
                rflow = &flow_table->flows[flow_id];
                cpu = ACCESS_ONCE(rflow->cpu);
                if (rflow->filter == filter_id && cpu < nr_cpu_ids &&
                    ((int)(per_cpu(softnet_data, cpu).input_queue_head -
                           rflow->last_qtail) <
                     (int)(10 * flow_table->mask)))
                        expire = false;
        }
        rcu_read_unlock();
        return expire;
}
EXPORT_SYMBOL(rps_may_expire_flow);

#endif /* CONFIG_RFS_ACCEL */

/* Called from hardirq (IPI) context */
static void rps_trigger_softirq(void *data)
{
        struct softnet_data *sd = data;

        ____napi_schedule(sd, &sd->backlog);
        sd->received_rps++;
}

#endif /* CONFIG_RPS */

/*
 * Check if this softnet_data structure is another cpu one
 * If yes, queue it to our IPI list and return 1
 * If no, return 0
 */
static int rps_ipi_queued(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
        struct softnet_data *mysd = this_cpu_ptr(&softnet_data);

        if (sd != mysd) {
                sd->rps_ipi_next = mysd->rps_ipi_list;
                mysd->rps_ipi_list = sd;

                __raise_softirq_irqoff(NET_RX_SOFTIRQ);
                return 1;
        }
#endif /* CONFIG_RPS */
        return 0;
}

#ifdef CONFIG_NET_FLOW_LIMIT
int netdev_flow_limit_table_len __read_mostly = (1 << 12);
#endif

static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen)
{
#ifdef CONFIG_NET_FLOW_LIMIT
        struct sd_flow_limit *fl;
        struct softnet_data *sd;
        unsigned int old_flow, new_flow;

        if (qlen < (netdev_max_backlog >> 1))
                return false;

        sd = this_cpu_ptr(&softnet_data);

        rcu_read_lock();
        fl = rcu_dereference(sd->flow_limit);
        if (fl) {
                new_flow = skb_get_hash(skb) & (fl->num_buckets - 1);
                old_flow = fl->history[fl->history_head];
                fl->history[fl->history_head] = new_flow;

                fl->history_head++;
                fl->history_head &= FLOW_LIMIT_HISTORY - 1;

                if (likely(fl->buckets[old_flow]))
                        fl->buckets[old_flow]--;

                if (++fl->buckets[new_flow] > (FLOW_LIMIT_HISTORY >> 1)) {
                        fl->count++;
                        rcu_read_unlock();
                        return true;
                }
        }
        rcu_read_unlock();
#endif
        return false;
}

/*
 * enqueue_to_backlog is called to queue an skb to a per CPU backlog
 * queue (may be a remote CPU queue).
 */
static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
                              unsigned int *qtail)
{
        struct softnet_data *sd;
        unsigned long flags;
        unsigned int qlen;

        sd = &per_cpu(softnet_data, cpu);

        local_irq_save(flags);

        rps_lock(sd);
        if (!netif_running(skb->dev))
                goto drop;
        qlen = skb_queue_len(&sd->input_pkt_queue);
        if (qlen <= netdev_max_backlog && !skb_flow_limit(skb, qlen)) {
                if (qlen) {
enqueue:
                        __skb_queue_tail(&sd->input_pkt_queue, skb);
                        input_queue_tail_incr_save(sd, qtail);
                        rps_unlock(sd);
                        local_irq_restore(flags);
                        return NET_RX_SUCCESS;
                }

                /* Schedule NAPI for backlog device
                 * We can use non atomic operation since we own the queue lock
                 */
                if (!__test_and_set_bit(NAPI_STATE_SCHED, &sd->backlog.state)) {
                        if (!rps_ipi_queued(sd))
                                ____napi_schedule(sd, &sd->backlog);
                }
                goto enqueue;
        }

drop:
        sd->dropped++;
        rps_unlock(sd);

        local_irq_restore(flags);

        atomic_long_inc(&skb->dev->rx_dropped);
        kfree_skb(skb);
        return NET_RX_DROP;
}

static u32 netif_receive_generic_xdp(struct sk_buff *skb,
                                     struct bpf_prog *xdp_prog)
{
        struct xdp_buff xdp;
        u32 act = XDP_DROP;
        void *orig_data;
        int hlen, off;
        u32 mac_len;

        /* Reinjected packets coming from act_mirred or similar should
         * not get XDP generic processing.
         */
        if (skb_cloned(skb))
                return XDP_PASS;

        if (skb_linearize(skb))
                goto do_drop;

        /* The XDP program wants to see the packet starting at the MAC
         * header.
         */
        mac_len = skb->data - skb_mac_header(skb);
        hlen = skb_headlen(skb) + mac_len;
        xdp.data = skb->data - mac_len;
        xdp.data_end = xdp.data + hlen;
        xdp.data_hard_start = skb->data - skb_headroom(skb);
        orig_data = xdp.data;

        act = bpf_prog_run_xdp(xdp_prog, &xdp);

        off = xdp.data - orig_data;
        if (off > 0)
                __skb_pull(skb, off);
        else if (off < 0)
                __skb_push(skb, -off);

        switch (act) {
        case XDP_REDIRECT:
        case XDP_TX:
                __skb_push(skb, mac_len);
                /* fall through */
        case XDP_PASS:
                break;

        default:
                bpf_warn_invalid_xdp_action(act);
                /* fall through */
        case XDP_ABORTED:
                trace_xdp_exception(skb->dev, xdp_prog, act);
                /* fall through */
        case XDP_DROP:
        do_drop:
                kfree_skb(skb);
                break;
        }

        return act;
}

/* When doing generic XDP we have to bypass the qdisc layer and the
 * network taps in order to match in-driver-XDP behavior.
 */
static void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)
{
        struct net_device *dev = skb->dev;
        struct netdev_queue *txq;
        bool free_skb = true;
        int cpu, rc;

        txq = netdev_pick_tx(dev, skb, NULL);
        cpu = smp_processor_id();
        HARD_TX_LOCK(dev, txq, cpu);
        if (!netif_xmit_stopped(txq)) {
                rc = netdev_start_xmit(skb, dev, txq, 0);
                if (dev_xmit_complete(rc))
                        free_skb = false;
        }
        HARD_TX_UNLOCK(dev, txq);
        if (free_skb) {
                trace_xdp_exception(dev, xdp_prog, XDP_TX);
                kfree_skb(skb);
        }
}

static struct static_key generic_xdp_needed __read_mostly;

static int do_xdp_generic(struct sk_buff *skb)
{
        struct bpf_prog *xdp_prog = rcu_dereference(skb->dev->xdp_prog);

        if (xdp_prog) {
                u32 act = netif_receive_generic_xdp(skb, xdp_prog);
                int err;

                if (act != XDP_PASS) {
                        switch (act) {
                        case XDP_REDIRECT:
                                err = xdp_do_generic_redirect(skb->dev, skb);
                                if (err)
                                        goto out_redir;
                        /* fallthru to submit skb */
                        case XDP_TX:
                                generic_xdp_tx(skb, xdp_prog);
                                break;
                        }
                        return XDP_DROP;
                }
        }
        return XDP_PASS;
out_redir:
        trace_xdp_exception(skb->dev, xdp_prog, XDP_REDIRECT);
        kfree_skb(skb);
        return XDP_DROP;
}

static int netif_rx_internal(struct sk_buff *skb)
{
        int ret;

        net_timestamp_check(netdev_tstamp_prequeue, skb);

        trace_netif_rx(skb);

        if (static_key_false(&generic_xdp_needed)) {
                int ret = do_xdp_generic(skb);

                /* Consider XDP consuming the packet a success from
                 * the netdev point of view we do not want to count
                 * this as an error.
                 */
                if (ret != XDP_PASS)
                        return NET_RX_SUCCESS;
        }

#ifdef CONFIG_RPS
        if (static_key_false(&rps_needed)) {
                struct rps_dev_flow voidflow, *rflow = &voidflow;
                int cpu;

                preempt_disable();
                rcu_read_lock();

                cpu = get_rps_cpu(skb->dev, skb, &rflow);
                if (cpu < 0)
                        cpu = smp_processor_id();

                ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);

                rcu_read_unlock();
                preempt_enable();
        } else
#endif
        {
                unsigned int qtail;

                ret = enqueue_to_backlog(skb, get_cpu(), &qtail);
                put_cpu();
        }
        return ret;
}

/**
 *      netif_rx        -       post buffer to the network code
 *      @skb: buffer to post
 *
 *      This function receives a packet from a device driver and queues it for
 *      the upper (protocol) levels to process.  It always succeeds. The buffer
 *      may be dropped during processing for congestion control or by the
 *      protocol layers.
 *
 *      return values:
 *      NET_RX_SUCCESS  (no congestion)
 *      NET_RX_DROP     (packet was dropped)
 *
 */

int netif_rx(struct sk_buff *skb)
{
        trace_netif_rx_entry(skb);

        return netif_rx_internal(skb);
}
EXPORT_SYMBOL(netif_rx);

int netif_rx_ni(struct sk_buff *skb)
{
        int err;

        trace_netif_rx_ni_entry(skb);

        preempt_disable();
        err = netif_rx_internal(skb);
        if (local_softirq_pending())
                do_softirq();
        preempt_enable();

        return err;
}
EXPORT_SYMBOL(netif_rx_ni);

static __latent_entropy void net_tx_action(struct softirq_action *h)
{
        struct softnet_data *sd = this_cpu_ptr(&softnet_data);

        if (sd->completion_queue) {
                struct sk_buff *clist;

                local_irq_disable();
                clist = sd->completion_queue;
                sd->completion_queue = NULL;
                local_irq_enable();

                while (clist) {
                        struct sk_buff *skb = clist;

                        clist = clist->next;

                        WARN_ON(refcount_read(&skb->users));
                        if (likely(get_kfree_skb_cb(skb)->reason == SKB_REASON_CONSUMED))
                                trace_consume_skb(skb);
                        else
                                trace_kfree_skb(skb, net_tx_action);

                        if (skb->fclone != SKB_FCLONE_UNAVAILABLE)
                                __kfree_skb(skb);
                        else
                                __kfree_skb_defer(skb);
                }

                __kfree_skb_flush();
        }

        if (sd->output_queue) {
                struct Qdisc *head;

                local_irq_disable();
                head = sd->output_queue;
                sd->output_queue = NULL;
                sd->output_queue_tailp = &sd->output_queue;
                local_irq_enable();

                while (head) {
                        struct Qdisc *q = head;
                        spinlock_t *root_lock;

                        head = head->next_sched;

                        root_lock = qdisc_lock(q);
                        spin_lock(root_lock);
                        /* We need to make sure head->next_sched is read
                         * before clearing __QDISC_STATE_SCHED
                         */
                        smp_mb__before_atomic();
                        clear_bit(__QDISC_STATE_SCHED, &q->state);
                        qdisc_run(q);
                        spin_unlock(root_lock);
                }
        }
}

#if IS_ENABLED(CONFIG_BRIDGE) && IS_ENABLED(CONFIG_ATM_LANE)
/* This hook is defined here for ATM LANE */
int (*br_fdb_test_addr_hook)(struct net_device *dev,
                             unsigned char *addr) __read_mostly;
EXPORT_SYMBOL_GPL(br_fdb_test_addr_hook);
#endif

static inline struct sk_buff *
sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
                   struct net_device *orig_dev)
{
#ifdef CONFIG_NET_CLS_ACT
        struct tcf_proto *cl = rcu_dereference_bh(skb->dev->ingress_cl_list);
        struct tcf_result cl_res;

        /* If there's at least one ingress present somewhere (so
         * we get here via enabled static key), remaining devices
         * that are not configured with an ingress qdisc will bail
         * out here.
         */
        if (!cl)
                return skb;
        if (*pt_prev) {
                *ret = deliver_skb(skb, *pt_prev, orig_dev);
                *pt_prev = NULL;
        }

        qdisc_skb_cb(skb)->pkt_len = skb->len;
        skb->tc_at_ingress = 1;
        qdisc_bstats_cpu_update(cl->q, skb);

        switch (tcf_classify(skb, cl, &cl_res, false)) {
        case TC_ACT_OK:
        case TC_ACT_RECLASSIFY:
                skb->tc_index = TC_H_MIN(cl_res.classid);
                break;
        case TC_ACT_SHOT:
                qdisc_qstats_cpu_drop(cl->q);
                kfree_skb(skb);
                return NULL;
        case TC_ACT_STOLEN:
        case TC_ACT_QUEUED:
        case TC_ACT_TRAP:
                consume_skb(skb);
                return NULL;
        case TC_ACT_REDIRECT:
                /* skb_mac_header check was done by cls/act_bpf, so
                 * we can safely push the L2 header back before
                 * redirecting to another netdev
                 */
                __skb_push(skb, skb->mac_len);
                skb_do_redirect(skb);
                return NULL;
        default:
                break;
        }
#endif /* CONFIG_NET_CLS_ACT */
        return skb;
}

/**
 *      netdev_is_rx_handler_busy - check if receive handler is registered
 *      @dev: device to check
 *
 *      Check if a receive handler is already registered for a given device.
 *      Return true if there one.
 *
 *      The caller must hold the rtnl_mutex.
 */
bool netdev_is_rx_handler_busy(struct net_device *dev)
{
        ASSERT_RTNL();
        return dev && rtnl_dereference(dev->rx_handler);
}
EXPORT_SYMBOL_GPL(netdev_is_rx_handler_busy);

/**
 *      netdev_rx_handler_register - register receive handler
 *      @dev: device to register a handler for
 *      @rx_handler: receive handler to register
 *      @rx_handler_data: data pointer that is used by rx handler
 *
 *      Register a receive handler for a device. This handler will then be
 *      called from __netif_receive_skb. A negative errno code is returned
 *      on a failure.
 *
 *      The caller must hold the rtnl_mutex.
 *
 *      For a general description of rx_handler, see enum rx_handler_result.
 */
int netdev_rx_handler_register(struct net_device *dev,
                               rx_handler_func_t *rx_handler,
                               void *rx_handler_data)
{
        if (netdev_is_rx_handler_busy(dev))
                return -EBUSY;

        /* Note: rx_handler_data must be set before rx_handler */
        rcu_assign_pointer(dev->rx_handler_data, rx_handler_data);
        rcu_assign_pointer(dev->rx_handler, rx_handler);

        return 0;
}
EXPORT_SYMBOL_GPL(netdev_rx_handler_register);

/**
 *      netdev_rx_handler_unregister - unregister receive handler
 *      @dev: device to unregister a handler from
 *
 *      Unregister a receive handler from a device.
 *
 *      The caller must hold the rtnl_mutex.
 */
void netdev_rx_handler_unregister(struct net_device *dev)
{

        ASSERT_RTNL();
        RCU_INIT_POINTER(dev->rx_handler, NULL);
        /* a reader seeing a non NULL rx_handler in a rcu_read_lock()
         * section has a guarantee to see a non NULL rx_handler_data
         * as well.
         */
        synchronize_net();
        RCU_INIT_POINTER(dev->rx_handler_data, NULL);
}
EXPORT_SYMBOL_GPL(netdev_rx_handler_unregister);

/*
 * Limit the use of PFMEMALLOC reserves to those protocols that implement
 * the special handling of PFMEMALLOC skbs.
 */
static bool skb_pfmemalloc_protocol(struct sk_buff *skb)
{
        switch (skb->protocol) {
        case htons(ETH_P_ARP):
        case htons(ETH_P_IP):
        case htons(ETH_P_IPV6):
        case htons(ETH_P_8021Q):
        case htons(ETH_P_8021AD):
                return true;
        default:
                return false;
        }
}

static inline int nf_ingress(struct sk_buff *skb, struct packet_type **pt_prev,
                             int *ret, struct net_device *orig_dev)
{
#ifdef CONFIG_NETFILTER_INGRESS
        if (nf_hook_ingress_active(skb)) {
                int ingress_retval;

                if (*pt_prev) {
                        *ret = deliver_skb(skb, *pt_prev, orig_dev);
                        *pt_prev = NULL;
                }

                rcu_read_lock();
                ingress_retval = nf_hook_ingress(skb);
                rcu_read_unlock();
                return ingress_retval;
        }
#endif /* CONFIG_NETFILTER_INGRESS */
        return 0;
}

static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc)
{
        struct packet_type *ptype, *pt_prev;
        rx_handler_func_t *rx_handler;
        struct net_device *orig_dev;
        bool deliver_exact = false;
        int ret = NET_RX_DROP;
        __be16 type;

        net_timestamp_check(!netdev_tstamp_prequeue, skb);

        trace_netif_receive_skb(skb);

        orig_dev = skb->dev;

        skb_reset_network_header(skb);
        if (!skb_transport_header_was_set(skb))
                skb_reset_transport_header(skb);
        skb_reset_mac_len(skb);

        pt_prev = NULL;

another_round:
        skb->skb_iif = skb->dev->ifindex;

        __this_cpu_inc(softnet_data.processed);

        if (skb->protocol == cpu_to_be16(ETH_P_8021Q) ||
            skb->protocol == cpu_to_be16(ETH_P_8021AD)) {
                skb = skb_vlan_untag(skb);
                if (unlikely(!skb))
                        goto out;
        }

        if (skb_skip_tc_classify(skb))
                goto skip_classify;

        if (pfmemalloc)
                goto skip_taps;

        list_for_each_entry_rcu(ptype, &ptype_all, list) {
                if (pt_prev)
                        ret = deliver_skb(skb, pt_prev, orig_dev);
                pt_prev = ptype;
        }

        list_for_each_entry_rcu(ptype, &skb->dev->ptype_all, list) {
                if (pt_prev)
                        ret = deliver_skb(skb, pt_prev, orig_dev);
                pt_prev = ptype;
        }

skip_taps:
#ifdef CONFIG_NET_INGRESS
        if (static_key_false(&ingress_needed)) {
                skb = sch_handle_ingress(skb, &pt_prev, &ret, orig_dev);
                if (!skb)
                        goto out;

                if (nf_ingress(skb, &pt_prev, &ret, orig_dev) < 0)
                        goto out;
        }
#endif
        skb_reset_tc(skb);
skip_classify:
        if (pfmemalloc && !skb_pfmemalloc_protocol(skb))
                goto drop;

        if (skb_vlan_tag_present(skb)) {
                if (pt_prev) {
                        ret = deliver_skb(skb, pt_prev, orig_dev);
                        pt_prev = NULL;
                }
                if (vlan_do_receive(&skb))
                        goto another_round;
                else if (unlikely(!skb))
                        goto out;
        }

        rx_handler = rcu_dereference(skb->dev->rx_handler);
        if (rx_handler) {
                if (pt_prev) {
                        ret = deliver_skb(skb, pt_prev, orig_dev);
                        pt_prev = NULL;
                }
                switch (rx_handler(&skb)) {
                case RX_HANDLER_CONSUMED:
                        ret = NET_RX_SUCCESS;
                        goto out;
                case RX_HANDLER_ANOTHER:
                        goto another_round;
                case RX_HANDLER_EXACT:
                        deliver_exact = true;
                case RX_HANDLER_PASS:
                        break;
                default:
                        BUG();
                }
        }

        if (unlikely(skb_vlan_tag_present(skb))) {
                if (skb_vlan_tag_get_id(skb))
                        skb->pkt_type = PACKET_OTHERHOST;
                /* Note: we might in the future use prio bits
                 * and set skb->priority like in vlan_do_receive()
                 * For the time being, just ignore Priority Code Point
                 */
                skb->vlan_tci = 0;
        }

        type = skb->protocol;

        /* deliver only exact match when indicated */
        if (likely(!deliver_exact)) {
                deliver_ptype_list_skb(skb, &pt_prev, orig_dev, type,
                                       &ptype_base[ntohs(type) &
                                                   PTYPE_HASH_MASK]);
        }

        deliver_ptype_list_skb(skb, &pt_prev, orig_dev, type,
                               &orig_dev->ptype_specific);

        if (unlikely(skb->dev != orig_dev)) {
                deliver_ptype_list_skb(skb, &pt_prev, orig_dev, type,
                                       &skb->dev->ptype_specific);
        }

        if (pt_prev) {
                if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC)))
                        goto drop;
                else
                        ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
        } else {
drop:
                if (!deliver_exact)
                        atomic_long_inc(&skb->dev->rx_dropped);
                else
                        atomic_long_inc(&skb->dev->rx_nohandler);
                kfree_skb(skb);
                /* Jamal, now you will not able to escape explaining
                 * me how you were going to use this. :-)
                 */
                ret = NET_RX_DROP;
        }

out:
        return ret;
}

static int __netif_receive_skb(struct sk_buff *skb)
{
        int ret;

        if (sk_memalloc_socks() && skb_pfmemalloc(skb)) {
                unsigned int noreclaim_flag;

                /*
                 * PFMEMALLOC skbs are special, they should
                 * - be delivered to SOCK_MEMALLOC sockets only
                 * - stay away from userspace
                 * - have bounded memory usage
                 *
                 * Use PF_MEMALLOC as this saves us from propagating the allocation
                 * context down to all allocation sites.
                 */
                noreclaim_flag = memalloc_noreclaim_save();
                ret = __netif_receive_skb_core(skb, true);
                memalloc_noreclaim_restore(noreclaim_flag);
        } else
                ret = __netif_receive_skb_core(skb, false);

        return ret;
}

static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp)
{
        struct bpf_prog *old = rtnl_dereference(dev->xdp_prog);
        struct bpf_prog *new = xdp->prog;
        int ret = 0;

        switch (xdp->command) {
        case XDP_SETUP_PROG:
                rcu_assign_pointer(dev->xdp_prog, new);
                if (old)
                        bpf_prog_put(old);

                if (old && !new) {
                        static_key_slow_dec(&generic_xdp_needed);
                } else if (new && !old) {
                        static_key_slow_inc(&generic_xdp_needed);
                        dev_disable_lro(dev);
                }
                break;

        case XDP_QUERY_PROG:
                xdp->prog_attached = !!old;
                xdp->prog_id = old ? old->aux->id : 0;
                break;

        default:
                ret = -EINVAL;
                break;
        }

        return ret;
}

static int netif_receive_skb_internal(struct sk_buff *skb)
{
        int ret;

        net_timestamp_check(netdev_tstamp_prequeue, skb);

        if (skb_defer_rx_timestamp(skb))
                return NET_RX_SUCCESS;

        rcu_read_lock();

        if (static_key_false(&generic_xdp_needed)) {
                int ret = do_xdp_generic(skb);

                if (ret != XDP_PASS) {
                        rcu_read_unlock();
                        return NET_RX_DROP;
                }
        }

#ifdef CONFIG_RPS
        if (static_key_false(&rps_needed)) {
                struct rps_dev_flow voidflow, *rflow = &voidflow;
                int cpu = get_rps_cpu(skb->dev, skb, &rflow);

                if (cpu >= 0) {
                        ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
                        rcu_read_unlock();
                        return ret;
                }
        }
#endif
        ret = __netif_receive_skb(skb);
        rcu_read_unlock();
        return ret;
}

/**
 *      netif_receive_skb - process receive buffer from network
 *      @skb: buffer to process
 *
 *      netif_receive_skb() is the main receive data processing function.
 *      It always succeeds. The buffer may be dropped during processing
 *      for congestion control or by the protocol layers.
 *
 *      This function may only be called from softirq context and interrupts
 *      should be enabled.
 *
 *      Return values (usually ignored):
 *      NET_RX_SUCCESS: no congestion
 *      NET_RX_DROP: packet was dropped
 */
int netif_receive_skb(struct sk_buff *skb)
{
        trace_netif_receive_skb_entry(skb);

        return netif_receive_skb_internal(skb);
}
EXPORT_SYMBOL(netif_receive_skb);

DEFINE_PER_CPU(struct work_struct, flush_works);

/* Network device is going away, flush any packets still pending */
static void flush_backlog(struct work_struct *work)
{
        struct sk_buff *skb, *tmp;
        struct softnet_data *sd;

        local_bh_disable();
        sd = this_cpu_ptr(&softnet_data);

        local_irq_disable();
        rps_lock(sd);
        skb_queue_walk_safe(&sd->input_pkt_queue, skb, tmp) {
                if (skb->dev->reg_state == NETREG_UNREGISTERING) {
                        __skb_unlink(skb, &sd->input_pkt_queue);
                        kfree_skb(skb);
                        input_queue_head_incr(sd);
                }
        }
        rps_unlock(sd);
        local_irq_enable();

        skb_queue_walk_safe(&sd->process_queue, skb, tmp) {
                if (skb->dev->reg_state == NETREG_UNREGISTERING) {
                        __skb_unlink(skb, &sd->process_queue);
                        kfree_skb(skb);
                        input_queue_head_incr(sd);
                }
        }
        local_bh_enable();
}

static void flush_all_backlogs(void)
{
        unsigned int cpu;

        get_online_cpus();

        for_each_online_cpu(cpu)
                queue_work_on(cpu, system_highpri_wq,
                              per_cpu_ptr(&flush_works, cpu));

        for_each_online_cpu(cpu)
                flush_work(per_cpu_ptr(&flush_works, cpu));

        put_online_cpus();
}

static int napi_gro_complete(struct sk_buff *skb)
{
        struct packet_offload *ptype;
        __be16 type = skb->protocol;
        struct list_head *head = &offload_base;
        int err = -ENOENT;

        BUILD_BUG_ON(sizeof(struct napi_gro_cb) > sizeof(skb->cb));

        if (NAPI_GRO_CB(skb)->count == 1) {
                skb_shinfo(skb)->gso_size = 0;
                goto out;
        }

        rcu_read_lock();
        list_for_each_entry_rcu(ptype, head, list) {
                if (ptype->type != type || !ptype->callbacks.gro_complete)
                        continue;

                err = ptype->callbacks.gro_complete(skb, 0);
                break;
        }
        rcu_read_unlock();

        if (err) {
                WARN_ON(&ptype->list == head);
                kfree_skb(skb);
                return NET_RX_SUCCESS;
        }

out:
        return netif_receive_skb_internal(skb);
}

/* napi->gro_list contains packets ordered by age.
 * youngest packets at the head of it.
 * Complete skbs in reverse order to reduce latencies.
 */
void napi_gro_flush(struct napi_struct *napi, bool flush_old)
{
        struct sk_buff *skb, *prev = NULL;

        /* scan list and build reverse chain */
        for (skb = napi->gro_list; skb != NULL; skb = skb->next) {
                skb->prev = prev;
                prev = skb;
        }

        for (skb = prev; skb; skb = prev) {
                skb->next = NULL;

                if (flush_old && NAPI_GRO_CB(skb)->age == jiffies)
                        return;

                prev = skb->prev;
                napi_gro_complete(skb);
                napi->gro_count--;
        }

        napi->gro_list = NULL;
}
EXPORT_SYMBOL(napi_gro_flush);

static void gro_list_prepare(struct napi_struct *napi, struct sk_buff *skb)
{
        struct sk_buff *p;
        unsigned int maclen = skb->dev->hard_header_len;
        u32 hash = skb_get_hash_raw(skb);

        for (p = napi->gro_list; p; p = p->next) {
                unsigned long diffs;

                NAPI_GRO_CB(p)->flush = 0;

                if (hash != skb_get_hash_raw(p)) {
                        NAPI_GRO_CB(p)->same_flow = 0;
                        continue;
                }

                diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev;
                diffs |= p->vlan_tci ^ skb->vlan_tci;
                diffs |= skb_metadata_dst_cmp(p, skb);
                if (maclen == ETH_HLEN)
                        diffs |= compare_ether_header(skb_mac_header(p),
                                                      skb_mac_header(skb));
                else if (!diffs)
                        diffs = memcmp(skb_mac_header(p),
                                       skb_mac_header(skb),
                                       maclen);
                NAPI_GRO_CB(p)->same_flow = !diffs;
        }
}

static void skb_gro_reset_offset(struct sk_buff *skb)
{
        const struct skb_shared_info *pinfo = skb_shinfo(skb);
        const skb_frag_t *frag0 = &pinfo->frags[0];

        NAPI_GRO_CB(skb)->data_offset = 0;
        NAPI_GRO_CB(skb)->frag0 = NULL;
        NAPI_GRO_CB(skb)->frag0_len = 0;

        if (skb_mac_header(skb) == skb_tail_pointer(skb) &&
            pinfo->nr_frags &&
            !PageHighMem(skb_frag_page(frag0))) {
                NAPI_GRO_CB(skb)->frag0 = skb_frag_address(frag0);
                NAPI_GRO_CB(skb)->frag0_len = min_t(unsigned int,
                                                    skb_frag_size(frag0),
                                                    skb->end - skb->tail);
        }
}

static void gro_pull_from_frag0(struct sk_buff *skb, int grow)
{
        struct skb_shared_info *pinfo = skb_shinfo(skb);

        BUG_ON(skb->end - skb->tail < grow);

        memcpy(skb_tail_pointer(skb), NAPI_GRO_CB(skb)->frag0, grow);

        skb->data_len -= grow;
        skb->tail += grow;

        pinfo->frags[0].page_offset += grow;
        skb_frag_size_sub(&pinfo->frags[0], grow);

        if (unlikely(!skb_frag_size(&pinfo->frags[0]))) {
                skb_frag_unref(skb, 0);
                memmove(pinfo->frags, pinfo->frags + 1,
                        --pinfo->nr_frags * sizeof(pinfo->frags[0]));
        }
}

static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
{
        struct sk_buff **pp = NULL;
        struct packet_offload *ptype;
        __be16 type = skb->protocol;
        struct list_head *head = &offload_base;
        int same_flow;
        enum gro_result ret;
        int grow;

        if (netif_elide_gro(skb->dev))
                goto normal;

        gro_list_prepare(napi, skb);

        rcu_read_lock();
        list_for_each_entry_rcu(ptype, head, list) {
                if (ptype->type != type || !ptype->callbacks.gro_receive)
                        continue;

                skb_set_network_header(skb, skb_gro_offset(skb));
                skb_reset_mac_len(skb);
                NAPI_GRO_CB(skb)->same_flow = 0;
                NAPI_GRO_CB(skb)->flush = skb_is_gso(skb) || skb_has_frag_list(skb);
                NAPI_GRO_CB(skb)->free = 0;
                NAPI_GRO_CB(skb)->encap_mark = 0;
                NAPI_GRO_CB(skb)->recursion_counter = 0;
                NAPI_GRO_CB(skb)->is_fou = 0;
                NAPI_GRO_CB(skb)->is_atomic = 1;
                NAPI_GRO_CB(skb)->gro_remcsum_start = 0;

                /* Setup for GRO checksum validation */
                switch (skb->ip_summed) {
                case CHECKSUM_COMPLETE:
                        NAPI_GRO_CB(skb)->csum = skb->csum;
                        NAPI_GRO_CB(skb)->csum_valid = 1;
                        NAPI_GRO_CB(skb)->csum_cnt = 0;
                        break;
                case CHECKSUM_UNNECESSARY:
                        NAPI_GRO_CB(skb)->csum_cnt = skb->csum_level + 1;
                        NAPI_GRO_CB(skb)->csum_valid = 0;
                        break;
                default:
                        NAPI_GRO_CB(skb)->csum_cnt = 0;
                        NAPI_GRO_CB(skb)->csum_valid = 0;
                }

                pp = ptype->callbacks.gro_receive(&napi->gro_list, skb);
                break;
        }
        rcu_read_unlock();

        if (&ptype->list == head)
                goto normal;

        if (IS_ERR(pp) && PTR_ERR(pp) == -EINPROGRESS) {
                ret = GRO_CONSUMED;
                goto ok;
        }

        same_flow = NAPI_GRO_CB(skb)->same_flow;
        ret = NAPI_GRO_CB(skb)->free ? GRO_MERGED_FREE : GRO_MERGED;

        if (pp) {
                struct sk_buff *nskb = *pp;

                *pp = nskb->next;
                nskb->next = NULL;
                napi_gro_complete(nskb);
                napi->gro_count--;
        }

        if (same_flow)
                goto ok;

        if (NAPI_GRO_CB(skb)->flush)
                goto normal;

        if (unlikely(napi->gro_count >= MAX_GRO_SKBS)) {
                struct sk_buff *nskb = napi->gro_list;

                /* locate the end of the list to select the 'oldest' flow */
                while (nskb->next) {
                        pp = &nskb->next;
                        nskb = *pp;
                }
                *pp = NULL;
                nskb->next = NULL;
                napi_gro_complete(nskb);
        } else {
                napi->gro_count++;
        }
        NAPI_GRO_CB(skb)->count = 1;
        NAPI_GRO_CB(skb)->age = jiffies;
        NAPI_GRO_CB(skb)->last = skb;
        skb_shinfo(skb)->gso_size = skb_gro_len(skb);
        skb->next = napi->gro_list;
        napi->gro_list = skb;
        ret = GRO_HELD;

pull:
        grow = skb_gro_offset(skb) - skb_headlen(skb);
        if (grow > 0)
                gro_pull_from_frag0(skb, grow);
ok:
        return ret;

normal:
        ret = GRO_NORMAL;
        goto pull;
}

struct packet_offload *gro_find_receive_by_type(__be16 type)
{
        struct list_head *offload_head = &offload_base;
        struct packet_offload *ptype;

        list_for_each_entry_rcu(ptype, offload_head, list) {
                if (ptype->type != type || !ptype->callbacks.gro_receive)
                        continue;
                return ptype;
        }
        return NULL;
}
EXPORT_SYMBOL(gro_find_receive_by_type);

struct packet_offload *gro_find_complete_by_type(__be16 type)
{
        struct list_head *offload_head = &offload_base;
        struct packet_offload *ptype;

        list_for_each_entry_rcu(ptype, offload_head, list) {
                if (ptype->type != type || !ptype->callbacks.gro_complete)
                        continue;
                return ptype;
        }
        return NULL;
}
EXPORT_SYMBOL(gro_find_complete_by_type);

static void napi_skb_free_stolen_head(struct sk_buff *skb)
{
        skb_dst_drop(skb);
        secpath_reset(skb);
        kmem_cache_free(skbuff_head_cache, skb);
}

static gro_result_t napi_skb_finish(gro_result_t ret, struct sk_buff *skb)
{
        switch (ret) {
        case GRO_NORMAL:
                if (netif_receive_skb_internal(skb))
                        ret = GRO_DROP;
                break;

        case GRO_DROP:
                kfree_skb(skb);
                break;

        case GRO_MERGED_FREE:
                if (NAPI_GRO_CB(skb)->free == NAPI_GRO_FREE_STOLEN_HEAD)
                        napi_skb_free_stolen_head(skb);
                else
                        __kfree_skb(skb);
                break;

        case GRO_HELD:
        case GRO_MERGED:
        case GRO_CONSUMED:
                break;
        }

        return ret;
}

gro_result_t napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
{
        skb_mark_napi_id(skb, napi);
        trace_napi_gro_receive_entry(skb);

        skb_gro_reset_offset(skb);

        return napi_skb_finish(dev_gro_receive(napi, skb), skb);
}
EXPORT_SYMBOL(napi_gro_receive);

static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
{
        if (unlikely(skb->pfmemalloc)) {
                consume_skb(skb);
                return;
        }
        __skb_pull(skb, skb_headlen(skb));
        /* restore the reserve we had after netdev_alloc_skb_ip_align() */
        skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN - skb_headroom(skb));
        skb->vlan_tci = 0;
        skb->dev = napi->dev;
        skb->skb_iif = 0;
        skb->encapsulation = 0;
        skb_shinfo(skb)->gso_type = 0;
        skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
        secpath_reset(skb);

        napi->skb = skb;
}

struct sk_buff *napi_get_frags(struct napi_struct *napi)
{
        struct sk_buff *skb = napi->skb;

        if (!skb) {
                skb = napi_alloc_skb(napi, GRO_MAX_HEAD);
                if (skb) {
                        napi->skb = skb;
                        skb_mark_napi_id(skb, napi);
                }
        }
        return skb;
}
EXPORT_SYMBOL(napi_get_frags);

static gro_result_t napi_frags_finish(struct napi_struct *napi,
                                      struct sk_buff *skb,
                                      gro_result_t ret)
{
        switch (ret) {
        case GRO_NORMAL:
        case GRO_HELD:
                __skb_push(skb, ETH_HLEN);
                skb->protocol = eth_type_trans(skb, skb->dev);
                if (ret == GRO_NORMAL && netif_receive_skb_internal(skb))
                        ret = GRO_DROP;
                break;

        case GRO_DROP:
                napi_reuse_skb(napi, skb);
                break;

        case GRO_MERGED_FREE:
                if (NAPI_GRO_CB(skb)->free == NAPI_GRO_FREE_STOLEN_HEAD)
                        napi_skb_free_stolen_head(skb);
                else
                        napi_reuse_skb(napi, skb);
                break;

        case GRO_MERGED:
        case GRO_CONSUMED:
                break;
        }

        return ret;
}

/* Upper GRO stack assumes network header starts at gro_offset=0
 * Drivers could call both napi_gro_frags() and napi_gro_receive()
 * We copy ethernet header into skb->data to have a common layout.
 */
static struct sk_buff *napi_frags_skb(struct napi_struct *napi)
{
        struct sk_buff *skb = napi->skb;
        const struct ethhdr *eth;
        unsigned int hlen = sizeof(*eth);

        napi->skb = NULL;

        skb_reset_mac_header(skb);
        skb_gro_reset_offset(skb);

        eth = skb_gro_header_fast(skb, 0);
        if (unlikely(skb_gro_header_hard(skb, hlen))) {
                eth = skb_gro_header_slow(skb, hlen, 0);
                if (unlikely(!eth)) {
                        net_warn_ratelimited("%s: dropping impossible skb from %s\n",
                                             __func__, napi->dev->name);
                        napi_reuse_skb(napi, skb);
                        return NULL;
                }
        } else {
                gro_pull_from_frag0(skb, hlen);
                NAPI_GRO_CB(skb)->frag0 += hlen;
                NAPI_GRO_CB(skb)->frag0_len -= hlen;
        }
        __skb_pull(skb, hlen);

        /*
         * This works because the only protocols we care about don't require
         * special handling.
         * We'll fix it up properly in napi_frags_finish()
         */
        skb->protocol = eth->h_proto;

        return skb;
}

gro_result_t napi_gro_frags(struct napi_struct *napi)
{
        struct sk_buff *skb = napi_frags_skb(napi);

        if (!skb)
                return GRO_DROP;

        trace_napi_gro_frags_entry(skb);

        return napi_frags_finish(napi, skb, dev_gro_receive(napi, skb));
}
EXPORT_SYMBOL(napi_gro_frags);

/* Compute the checksum from gro_offset and return the folded value
 * after adding in any pseudo checksum.
 */
__sum16 __skb_gro_checksum_complete(struct sk_buff *skb)
{
        __wsum wsum;
        __sum16 sum;

        wsum = skb_checksum(skb, skb_gro_offset(skb), skb_gro_len(skb), 0);

        /* NAPI_GRO_CB(skb)->csum holds pseudo checksum */
        sum = csum_fold(csum_add(NAPI_GRO_CB(skb)->csum, wsum));
        if (likely(!sum)) {
                if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
                    !skb->csum_complete_sw)
                        netdev_rx_csum_fault(skb->dev);
        }

        NAPI_GRO_CB(skb)->csum = wsum;
        NAPI_GRO_CB(skb)->csum_valid = 1;

        return sum;
}
EXPORT_SYMBOL(__skb_gro_checksum_complete);

static void net_rps_send_ipi(struct softnet_data *remsd)
{
#ifdef CONFIG_RPS
        while (remsd) {
                struct softnet_data *next = remsd->rps_ipi_next;

                if (cpu_online(remsd->cpu))
                        smp_call_function_single_async(remsd->cpu, &remsd->csd);
                remsd = next;
        }
#endif
}

/*
 * net_rps_action_and_irq_enable sends any pending IPI's for rps.
 * Note: called with local irq disabled, but exits with local irq enabled.
 */
static void net_rps_action_and_irq_enable(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
        struct softnet_data *remsd = sd->rps_ipi_list;

        if (remsd) {
                sd->rps_ipi_list = NULL;

                local_irq_enable();

                /* Send pending IPI's to kick RPS processing on remote cpus. */
                net_rps_send_ipi(remsd);
        } else
#endif
                local_irq_enable();
}

static bool sd_has_rps_ipi_waiting(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
        return sd->rps_ipi_list != NULL;
#else
        return false;
#endif
}

static int process_backlog(struct napi_struct *napi, int quota)
{
        struct softnet_data *sd = container_of(napi, struct softnet_data, backlog);
        bool again = true;
        int work = 0;

        /* Check if we have pending ipi, its better to send them now,
         * not waiting net_rx_action() end.
         */
        if (sd_has_rps_ipi_waiting(sd)) {
                local_irq_disable();
                net_rps_action_and_irq_enable(sd);
        }

        napi->weight = dev_rx_weight;
        while (again) {
                struct sk_buff *skb;

                while ((skb = __skb_dequeue(&sd->process_queue))) {
                        rcu_read_lock();
                        __netif_receive_skb(skb);
                        rcu_read_unlock();
                        input_queue_head_incr(sd);
                        if (++work >= quota)
                                return work;

                }

                local_irq_disable();
                rps_lock(sd);
                if (skb_queue_empty(&sd->input_pkt_queue)) {
                        /*
                         * Inline a custom version of __napi_complete().
                         * only current cpu owns and manipulates this napi,
                         * and NAPI_STATE_SCHED is the only possible flag set
                         * on backlog.
                         * We can use a plain write instead of clear_bit(),
                         * and we dont need an smp_mb() memory barrier.
                         */
                        napi->state = 0;
                        again = false;
                } else {
                        skb_queue_splice_tail_init(&sd->input_pkt_queue,
                                                   &sd->process_queue);
                }
                rps_unlock(sd);
                local_irq_enable();
        }

        return work;
}

/**
 * __napi_schedule - schedule for receive
 * @n: entry to schedule
 *
 * The entry's receive function will be scheduled to run.
 * Consider using __napi_schedule_irqoff() if hard irqs are masked.
 */
void __napi_schedule(struct napi_struct *n)
{
        unsigned long flags;

        local_irq_save(flags);
        ____napi_schedule(this_cpu_ptr(&softnet_data), n);
        local_irq_restore(flags);
}
EXPORT_SYMBOL(__napi_schedule);

/**
 *      napi_schedule_prep - check if napi can be scheduled
 *      @n: napi context
 *
 * Test if NAPI routine is already running, and if not mark
 * it as running.  This is used as a condition variable
 * insure only one NAPI poll instance runs.  We also make
 * sure there is no pending NAPI disable.
 */
bool napi_schedule_prep(struct napi_struct *n)
{
        unsigned long val, new;

        do {
                val = READ_ONCE(n->state);
                if (unlikely(val & NAPIF_STATE_DISABLE))
                        return false;
                new = val | NAPIF_STATE_SCHED;

                /* Sets STATE_MISSED bit if STATE_SCHED was already set
                 * This was suggested by Alexander Duyck, as compiler
                 * emits better code than :
                 * if (val & NAPIF_STATE_SCHED)
                 *     new |= NAPIF_STATE_MISSED;
                 */
                new |= (val & NAPIF_STATE_SCHED) / NAPIF_STATE_SCHED *
                                                   NAPIF_STATE_MISSED;
        } while (cmpxchg(&n->state, val, new) != val);

        return !(val & NAPIF_STATE_SCHED);
}
EXPORT_SYMBOL(napi_schedule_prep);

/**
 * __napi_schedule_irqoff - schedule for receive
 * @n: entry to schedule
 *
 * Variant of __napi_schedule() assuming hard irqs are masked
 */
void __napi_schedule_irqoff(struct napi_struct *n)
{
        ____napi_schedule(this_cpu_ptr(&softnet_data), n);
}
EXPORT_SYMBOL(__napi_schedule_irqoff);

bool napi_complete_done(struct napi_struct *n, int work_done)
{
        unsigned long flags, val, new;

        /*
         * 1) Don't let napi dequeue from the cpu poll list
         *    just in case its running on a different cpu.
         * 2) If we are busy polling, do nothing here, we have
         *    the guarantee we will be called later.
         */
        if (unlikely(n->state & (NAPIF_STATE_NPSVC |
                                 NAPIF_STATE_IN_BUSY_POLL)))
                return false;

        if (n->gro_list) {
                unsigned long timeout = 0;

                if (work_done)
                        timeout = n->dev->gro_flush_timeout;

                if (timeout)
                        hrtimer_start(&n->timer, ns_to_ktime(timeout),
                                      HRTIMER_MODE_REL_PINNED);
                else
                        napi_gro_flush(n, false);
        }
        if (unlikely(!list_empty(&n->poll_list))) {
                /* If n->poll_list is not empty, we need to mask irqs */
                local_irq_save(flags);
                list_del_init(&n->poll_list);
                local_irq_restore(flags);
        }

        do {
                val = READ_ONCE(n->state);

                WARN_ON_ONCE(!(val & NAPIF_STATE_SCHED));

                new = val & ~(NAPIF_STATE_MISSED | NAPIF_STATE_SCHED);

                /* If STATE_MISSED was set, leave STATE_SCHED set,
                 * because we will call napi->poll() one more time.
                 * This C code was suggested by Alexander Duyck to help gcc.
                 */
                new |= (val & NAPIF_STATE_MISSED) / NAPIF_STATE_MISSED *
                                                    NAPIF_STATE_SCHED;
        } while (cmpxchg(&n->state, val, new) != val);

        if (unlikely(val & NAPIF_STATE_MISSED)) {
                __napi_schedule(n);
                return false;
        }

        return true;
}
EXPORT_SYMBOL(napi_complete_done);

/* must be called under rcu_read_lock(), as we dont take a reference */
static struct napi_struct *napi_by_id(unsigned int napi_id)
{
        unsigned int hash = napi_id % HASH_SIZE(napi_hash);
        struct napi_struct *napi;

        hlist_for_each_entry_rcu(napi, &napi_hash[hash], napi_hash_node)
                if (napi->napi_id == napi_id)
                        return napi;

        return NULL;
}

#if defined(CONFIG_NET_RX_BUSY_POLL)

#define BUSY_POLL_BUDGET 8

static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock)
{
        int rc;

        /* Busy polling means there is a high chance device driver hard irq
         * could not grab NAPI_STATE_SCHED, and that NAPI_STATE_MISSED was
         * set in napi_schedule_prep().
         * Since we are about to call napi->poll() once more, we can safely
         * clear NAPI_STATE_MISSED.
         *
         * Note: x86 could use a single "lock and ..." instruction
         * to perform these two clear_bit()
         */
        clear_bit(NAPI_STATE_MISSED, &napi->state);
        clear_bit(NAPI_STATE_IN_BUSY_POLL, &napi->state);

        local_bh_disable();

        /* All we really want here is to re-enable device interrupts.
         * Ideally, a new ndo_busy_poll_stop() could avoid another round.
         */
        rc = napi->poll(napi, BUSY_POLL_BUDGET);
        netpoll_poll_unlock(have_poll_lock);
        if (rc == BUSY_POLL_BUDGET)
                __napi_schedule(napi);
        local_bh_enable();
}

void napi_busy_loop(unsigned int napi_id,
                    bool (*loop_end)(void *, unsigned long),
                    void *loop_end_arg)
{
        unsigned long start_time = loop_end ? busy_loop_current_time() : 0;
        int (*napi_poll)(struct napi_struct *napi, int budget);
        void *have_poll_lock = NULL;
        struct napi_struct *napi;

restart:
        napi_poll = NULL;

        rcu_read_lock();

        napi = napi_by_id(napi_id);
        if (!napi)
                goto out;

        preempt_disable();
        for (;;) {
                int work = 0;

                local_bh_disable();
                if (!napi_poll) {
                        unsigned long val = READ_ONCE(napi->state);

                        /* If multiple threads are competing for this napi,
                         * we avoid dirtying napi->state as much as we can.
                         */
                        if (val & (NAPIF_STATE_DISABLE | NAPIF_STATE_SCHED |
                                   NAPIF_STATE_IN_BUSY_POLL))
                                goto count;
                        if (cmpxchg(&napi->state, val,
                                    val | NAPIF_STATE_IN_BUSY_POLL |
                                          NAPIF_STATE_SCHED) != val)
                                goto count;
                        have_poll_lock = netpoll_poll_lock(napi);
                        napi_poll = napi->poll;
                }
                work = napi_poll(napi, BUSY_POLL_BUDGET);
                trace_napi_poll(napi, work, BUSY_POLL_BUDGET);
count:
                if (work > 0)
                        __NET_ADD_STATS(dev_net(napi->dev),
                                        LINUX_MIB_BUSYPOLLRXPACKETS, work);
                local_bh_enable();

                if (!loop_end || loop_end(loop_end_arg, start_time))
                        break;

                if (unlikely(need_resched())) {
                        if (napi_poll)
                                busy_poll_stop(napi, have_poll_lock);
                        preempt_enable();
                        rcu_read_unlock();
                        cond_resched();
                        if (loop_end(loop_end_arg, start_time))
                                return;
                        goto restart;
                }
                cpu_relax();
        }
        if (napi_poll)
                busy_poll_stop(napi, have_poll_lock);
        preempt_enable();
out:
        rcu_read_unlock();
}
EXPORT_SYMBOL(napi_busy_loop);

#endif /* CONFIG_NET_RX_BUSY_POLL */

static void napi_hash_add(struct napi_struct *napi)
{
        if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state) ||
            test_and_set_bit(NAPI_STATE_HASHED, &napi->state))
                return;

        spin_lock(&napi_hash_lock);

        /* 0..NR_CPUS range is reserved for sender_cpu use */
        do {
                if (unlikely(++napi_gen_id < MIN_NAPI_ID))
                        napi_gen_id = MIN_NAPI_ID;
        } while (napi_by_id(napi_gen_id));
        napi->napi_id = napi_gen_id;

        hlist_add_head_rcu(&napi->napi_hash_node,
                           &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);

        spin_unlock(&napi_hash_lock);
}

/* Warning : caller is responsible to make sure rcu grace period
 * is respected before freeing memory containing @napi
 */
bool napi_hash_del(struct napi_struct *napi)
{
        bool rcu_sync_needed = false;

        spin_lock(&napi_hash_lock);

        if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state)) {
                rcu_sync_needed = true;
                hlist_del_rcu(&napi->napi_hash_node);
        }
        spin_unlock(&napi_hash_lock);
        return rcu_sync_needed;
}
EXPORT_SYMBOL_GPL(napi_hash_del);

static enum hrtimer_restart napi_watchdog(struct hrtimer *timer)
{
        struct napi_struct *napi;

        napi = container_of(timer, struct napi_struct, timer);

        /* Note : we use a relaxed variant of napi_schedule_prep() not setting
         * NAPI_STATE_MISSED, since we do not react to a device IRQ.
         */
        if (napi->gro_list && !napi_disable_pending(napi) &&
            !test_and_set_bit(NAPI_STATE_SCHED, &napi->state))
                __napi_schedule_irqoff(napi);

        return HRTIMER_NORESTART;
}

void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
                    int (*poll)(struct napi_struct *, int), int weight)
{
        INIT_LIST_HEAD(&napi->poll_list);
        hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
        napi->timer.function = napi_watchdog;
        napi->gro_count = 0;
        napi->gro_list = NULL;
        napi->skb = NULL;
        napi->poll = poll;
        if (weight > NAPI_POLL_WEIGHT)
                pr_err_once("netif_napi_add() called with weight %d on device %s\n",
                            weight, dev->name);
        napi->weight = weight;
        list_add(&napi->dev_list, &dev->napi_list);
        napi->dev = dev;
#ifdef CONFIG_NETPOLL
        napi->poll_owner = -1;
#endif
        set_bit(NAPI_STATE_SCHED, &napi->state);
        napi_hash_add(napi);
}
EXPORT_SYMBOL(netif_napi_add);

void napi_disable(struct napi_struct *n)
{
        might_sleep();
        set_bit(NAPI_STATE_DISABLE, &n->state);

        while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
                msleep(1);
        while (test_and_set_bit(NAPI_STATE_NPSVC, &n->state))
                msleep(1);

        hrtimer_cancel(&n->timer);

        clear_bit(NAPI_STATE_DISABLE, &n->state);
}
EXPORT_SYMBOL(napi_disable);

/* Must be called in process context */
void netif_napi_del(struct napi_struct *napi)
{
        might_sleep();
        if (napi_hash_del(napi))
                synchronize_net();
        list_del_init(&napi->dev_list);
        napi_free_frags(napi);

        kfree_skb_list(napi->gro_list);
        napi->gro_list = NULL;
        napi->gro_count = 0;
}
EXPORT_SYMBOL(netif_napi_del);

static int napi_poll(struct napi_struct *n, struct list_head *repoll)
{
        void *have;
        int work, weight;

        list_del_init(&n->poll_list);

        have = netpoll_poll_lock(n);

        weight = n->weight;

        /* This NAPI_STATE_SCHED test is for avoiding a race
         * with netpoll's poll_napi().  Only the entity which
         * obtains the lock and sees NAPI_STATE_SCHED set will
         * actually make the ->poll() call.  Therefore we avoid
         * accidentally calling ->poll() when NAPI is not scheduled.
         */
        work = 0;
        if (test_bit(NAPI_STATE_SCHED, &n->state)) {
                work = n->poll(n, weight);
                trace_napi_poll(n, work, weight);
        }

        WARN_ON_ONCE(work > weight);

        if (likely(work < weight))
                goto out_unlock;

        /* Drivers must not modify the NAPI state if they
         * consume the entire weight.  In such cases this code
         * still "owns" the NAPI instance and therefore can
         * move the instance around on the list at-will.
         */
        if (unlikely(napi_disable_pending(n))) {
                napi_complete(n);
                goto out_unlock;
        }

        if (n->gro_list) {
                /* flush too old packets
                 * If HZ < 1000, flush all packets.
                 */
                napi_gro_flush(n, HZ >= 1000);
        }

        /* Some drivers may have called napi_schedule
         * prior to exhausting their budget.
         */
        if (unlikely(!list_empty(&n->poll_list))) {
                pr_warn_once("%s: Budget exhausted after napi rescheduled\n",
                             n->dev ? n->dev->name : "backlog");
                goto out_unlock;
        }

        list_add_tail(&n->poll_list, repoll);

out_unlock:
        netpoll_poll_unlock(have);

        return work;
}

static __latent_entropy void net_rx_action(struct softirq_action *h)
{
        struct softnet_data *sd = this_cpu_ptr(&softnet_data);
        unsigned long time_limit = jiffies +
                usecs_to_jiffies(netdev_budget_usecs);
        int budget = netdev_budget;
        LIST_HEAD(list);
        LIST_HEAD(repoll);

        local_irq_disable();
        list_splice_init(&sd->poll_list, &list);
        local_irq_enable();

        for (;;) {
                struct napi_struct *n;

                if (list_empty(&list)) {
                        if (!sd_has_rps_ipi_waiting(sd) && list_empty(&repoll))
                                goto out;
                        break;
                }

                n = list_first_entry(&list, struct napi_struct, poll_list);
                budget -= napi_poll(n, &repoll);

                /* If softirq window is exhausted then punt.
                 * Allow this to run for 2 jiffies since which will allow
                 * an average latency of 1.5/HZ.
                 */
                if (unlikely(budget <= 0 ||
                             time_after_eq(jiffies, time_limit))) {
                        sd->time_squeeze++;
                        break;
                }
        }

        local_irq_disable();

        list_splice_tail_init(&sd->poll_list, &list);
        list_splice_tail(&repoll, &list);
        list_splice(&list, &sd->poll_list);
        if (!list_empty(&sd->poll_list))
                __raise_softirq_irqoff(NET_RX_SOFTIRQ);

        net_rps_action_and_irq_enable(sd);
out:
        __kfree_skb_flush();
}

struct netdev_adjacent {
        struct net_device *dev;

        /* upper master flag, there can only be one master device per list */
        bool master;

        /* counter for the number of times this device was added to us */
        u16 ref_nr;

        /* private field for the users */
        void *private;

        struct list_head list;
        struct rcu_head rcu;
};

static struct netdev_adjacent *__netdev_find_adj(struct net_device *adj_dev,
                                                 struct list_head *adj_list)
{
        struct netdev_adjacent *adj;

        list_for_each_entry(adj, adj_list, list) {
                if (adj->dev == adj_dev)
                        return adj;
        }
        return NULL;
}

static int __netdev_has_upper_dev(struct net_device *upper_dev, void *data)
{
        struct net_device *dev = data;

        return upper_dev == dev;
}

/**
 * netdev_has_upper_dev - Check if device is linked to an upper device
 * @dev: device
 * @upper_dev: upper device to check
 *
 * Find out if a device is linked to specified upper device and return true
 * in case it is. Note that this checks only immediate upper device,
 * not through a complete stack of devices. The caller must hold the RTNL lock.
 */
bool netdev_has_upper_dev(struct net_device *dev,
                          struct net_device *upper_dev)
{
        ASSERT_RTNL();

        return netdev_walk_all_upper_dev_rcu(dev, __netdev_has_upper_dev,
                                             upper_dev);
}
EXPORT_SYMBOL(netdev_has_upper_dev);

/**
 * netdev_has_upper_dev_all - Check if device is linked to an upper device
 * @dev: device
 * @upper_dev: upper device to check
 *
 * Find out if a device is linked to specified upper device and return true
 * in case it is. Note that this checks the entire upper device chain.
 * The caller must hold rcu lock.
 */

bool netdev_has_upper_dev_all_rcu(struct net_device *dev,
                                  struct net_device *upper_dev)
{
        return !!netdev_walk_all_upper_dev_rcu(dev, __netdev_has_upper_dev,
                                               upper_dev);
}
EXPORT_SYMBOL(netdev_has_upper_dev_all_rcu);

/**
 * netdev_has_any_upper_dev - Check if device is linked to some device
 * @dev: device
 *
 * Find out if a device is linked to an upper device and return true in case
 * it is. The caller must hold the RTNL lock.
 */
static bool netdev_has_any_upper_dev(struct net_device *dev)
{
        ASSERT_RTNL();

        return !list_empty(&dev->adj_list.upper);
}

/**
 * netdev_master_upper_dev_get - Get master upper device
 * @dev: device
 *
 * Find a master upper device and return pointer to it or NULL in case
 * it's not there. The caller must hold the RTNL lock.
 */
struct net_device *netdev_master_upper_dev_get(struct net_device *dev)
{
        struct netdev_adjacent *upper;

        ASSERT_RTNL();

        if (list_empty(&dev->adj_list.upper))
                return NULL;

        upper = list_first_entry(&dev->adj_list.upper,
                                 struct netdev_adjacent, list);
        if (likely(upper->master))
                return upper->dev;
        return NULL;
}
EXPORT_SYMBOL(netdev_master_upper_dev_get);

/**
 * netdev_has_any_lower_dev - Check if device is linked to some device
 * @dev: device
 *
 * Find out if a device is linked to a lower device and return true in case
 * it is. The caller must hold the RTNL lock.
 */
static bool netdev_has_any_lower_dev(struct net_device *dev)
{
        ASSERT_RTNL();

        return !list_empty(&dev->adj_list.lower);
}

void *netdev_adjacent_get_private(struct list_head *adj_list)
{
        struct netdev_adjacent *adj;

        adj = list_entry(adj_list, struct netdev_adjacent, list);

        return adj->private;
}
EXPORT_SYMBOL(netdev_adjacent_get_private);

/**
 * netdev_upper_get_next_dev_rcu - Get the next dev from upper list
 * @dev: device
 * @iter: list_head ** of the current position
 *
 * Gets the next device from the dev's upper list, starting from iter
 * position. The caller must hold RCU read lock.
 */
struct net_device *netdev_upper_get_next_dev_rcu(struct net_device *dev,
                                                 struct list_head **iter)
{
        struct netdev_adjacent *upper;

        WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_rtnl_is_held());

        upper = list_entry_rcu((*iter)->next, struct netdev_adjacent, list);

        if (&upper->list == &dev->adj_list.upper)
                return NULL;

        *iter = &upper->list;

        return upper->dev;
}
EXPORT_SYMBOL(netdev_upper_get_next_dev_rcu);

static struct net_device *netdev_next_upper_dev_rcu(struct net_device *dev,
                                                    struct list_head **iter)
{
        struct netdev_adjacent *upper;

        WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_rtnl_is_held());

        upper = list_entry_rcu((*iter)->next, struct netdev_adjacent, list);

        if (&upper->list == &dev->adj_list.upper)
                return NULL;

        *iter = &upper->list;

        return upper->dev;
}

int netdev_walk_all_upper_dev_rcu(struct net_device *dev,
                                  int (*fn)(struct net_device *dev,
                                            void *data),
                                  void *data)
{
        struct net_device *udev;
        struct list_head *iter;
        int ret;

        for (iter = &dev->adj_list.upper,
             udev = netdev_next_upper_dev_rcu(dev, &iter);
             udev;
             udev = netdev_next_upper_dev_rcu(dev, &iter)) {
                /* first is the upper device itself */
                ret = fn(udev, data);
                if (ret)
                        return ret;

                /* then look at all of its upper devices */
                ret = netdev_walk_all_upper_dev_rcu(udev, fn, data);
                if (ret)
                        return ret;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(netdev_walk_all_upper_dev_rcu);

/**
 * netdev_lower_get_next_private - Get the next ->private from the
 *                                 lower neighbour list
 * @dev: device
 * @iter: list_head ** of the current position
 *
 * Gets the next netdev_adjacent->private from the dev's lower neighbour
 * list, starting from iter position. The caller must hold either hold the
 * RTNL lock or its own locking that guarantees that the neighbour lower
 * list will remain unchanged.
 */
void *netdev_lower_get_next_private(struct net_device *dev,
                                    struct list_head **iter)
{
        struct netdev_adjacent *lower;

        lower = list_entry(*iter, struct netdev_adjacent, list);

        if (&lower->list == &dev->adj_list.lower)
                return NULL;

        *iter = lower->list.next;

        return lower->private;
}
EXPORT_SYMBOL(netdev_lower_get_next_private);

/**
 * netdev_lower_get_next_private_rcu - Get the next ->private from the
 *                                     lower neighbour list, RCU
 *                                     variant
 * @dev: device
 * @iter: list_head ** of the current position
 *
 * Gets the next netdev_adjacent->private from the dev's lower neighbour
 * list, starting from iter position. The caller must hold RCU read lock.
 */
void *netdev_lower_get_next_private_rcu(struct net_device *dev,
                                        struct list_head **iter)
{
        struct netdev_adjacent *lower;

        WARN_ON_ONCE(!rcu_read_lock_held());

        lower = list_entry_rcu((*iter)->next, struct netdev_adjacent, list);

        if (&lower->list == &dev->adj_list.lower)
                return NULL;

        *iter = &lower->list;

        return lower->private;
}
EXPORT_SYMBOL(netdev_lower_get_next_private_rcu);

/**
 * netdev_lower_get_next - Get the next device from the lower neighbour
 *                         list
 * @dev: device
 * @iter: list_head ** of the current position
 *
 * Gets the next netdev_adjacent from the dev's lower neighbour
 * list, starting from iter position. The caller must hold RTNL lock or
 * its own locking that guarantees that the neighbour lower
 * list will remain unchanged.
 */
void *netdev_lower_get_next(struct net_device *dev, struct list_head **iter)
{
        struct netdev_adjacent *lower;

        lower = list_entry(*iter, struct netdev_adjacent, list);

        if (&lower->list == &dev->adj_list.lower)
                return NULL;

        *iter = lower->list.next;

        return lower->dev;
}
EXPORT_SYMBOL(netdev_lower_get_next);

static struct net_device *netdev_next_lower_dev(struct net_device *dev,
                                                struct list_head **iter)
{
        struct netdev_adjacent *lower;

        lower = list_entry((*iter)->next, struct netdev_adjacent, list);

        if (&lower->list == &dev->adj_list.lower)
                return NULL;

        *iter = &lower->list;

        return lower->dev;
}

int netdev_walk_all_lower_dev(struct net_device *dev,
                              int (*fn)(struct net_device *dev,
                                        void *data),
                              void *data)
{
        struct net_device *ldev;
        struct list_head *iter;
        int ret;

        for (iter = &dev->adj_list.lower,
             ldev = netdev_next_lower_dev(dev, &iter);
             ldev;
             ldev = netdev_next_lower_dev(dev, &iter)) {
                /* first is the lower device itself */
                ret = fn(ldev, data);
                if (ret)
                        return ret;

                /* then look at all of its lower devices */
                ret = netdev_walk_all_lower_dev(ldev, fn, data);
                if (ret)
                        return ret;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(netdev_walk_all_lower_dev);

static struct net_device *netdev_next_lower_dev_rcu(struct net_device *dev,
                                                    struct list_head **iter)
{
        struct netdev_adjacent *lower;

        lower = list_entry_rcu((*iter)->next, struct netdev_adjacent, list);
        if (&lower->list == &dev->adj_list.lower)
                return NULL;

        *iter = &lower->list;

        return lower->dev;
}

int netdev_walk_all_lower_dev_rcu(struct net_device *dev,
                                  int (*fn)(struct net_device *dev,
                                            void *data),
                                  void *data)
{
        struct net_device *ldev;
        struct list_head *iter;
        int ret;

        for (iter = &dev->adj_list.lower,
             ldev = netdev_next_lower_dev_rcu(dev, &iter);
             ldev;
             ldev = netdev_next_lower_dev_rcu(dev, &iter)) {
                /* first is the lower device itself */
                ret = fn(ldev, data);
                if (ret)
                        return ret;

                /* then look at all of its lower devices */
                ret = netdev_walk_all_lower_dev_rcu(ldev, fn, data);
                if (ret)
                        return ret;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(netdev_walk_all_lower_dev_rcu);

/**
 * netdev_lower_get_first_private_rcu - Get the first ->private from the
 *                                     lower neighbour list, RCU
 *                                     variant
 * @dev: device
 *
 * Gets the first netdev_adjacent->private from the dev's lower neighbour
 * list. The caller must hold RCU read lock.
 */
void *netdev_lower_get_first_private_rcu(struct net_device *dev)
{
        struct netdev_adjacent *lower;

        lower = list_first_or_null_rcu(&dev->adj_list.lower,
                        struct netdev_adjacent, list);
        if (lower)
                return lower->private;
        return NULL;
}
EXPORT_SYMBOL(netdev_lower_get_first_private_rcu);

/**
 * netdev_master_upper_dev_get_rcu - Get master upper device
 * @dev: device
 *
 * Find a master upper device and return pointer to it or NULL in case
 * it's not there. The caller must hold the RCU read lock.
 */
struct net_device *netdev_master_upper_dev_get_rcu(struct net_device *dev)
{
        struct netdev_adjacent *upper;

        upper = list_first_or_null_rcu(&dev->adj_list.upper,
                                       struct netdev_adjacent, list);
        if (upper && likely(upper->master))
                return upper->dev;
        return NULL;
}
EXPORT_SYMBOL(netdev_master_upper_dev_get_rcu);

static int netdev_adjacent_sysfs_add(struct net_device *dev,
                              struct net_device *adj_dev,
                              struct list_head *dev_list)
{
        char linkname[IFNAMSIZ+7];

        sprintf(linkname, dev_list == &dev->adj_list.upper ?
                "upper_%s" : "lower_%s", adj_dev->name);
        return sysfs_create_link(&(dev->dev.kobj), &(adj_dev->dev.kobj),
                                 linkname);
}
static void netdev_adjacent_sysfs_del(struct net_device *dev,
                               char *name,
                               struct list_head *dev_list)
{
        char linkname[IFNAMSIZ+7];

        sprintf(linkname, dev_list == &dev->adj_list.upper ?
                "upper_%s" : "lower_%s", name);
        sysfs_remove_link(&(dev->dev.kobj), linkname);
}

static inline bool netdev_adjacent_is_neigh_list(struct net_device *dev,
                                                 struct net_device *adj_dev,
                                                 struct list_head *dev_list)
{
        return (dev_list == &dev->adj_list.upper ||
                dev_list == &dev->adj_list.lower) &&
                net_eq(dev_net(dev), dev_net(adj_dev));
}

static int __netdev_adjacent_dev_insert(struct net_device *dev,
                                        struct net_device *adj_dev,
                                        struct list_head *dev_list,
                                        void *private, bool master)
{
        struct netdev_adjacent *adj;
        int ret;

        adj = __netdev_find_adj(adj_dev, dev_list);

        if (adj) {
                adj->ref_nr += 1;
                pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d\n",
                         dev->name, adj_dev->name, adj->ref_nr);

                return 0;
        }

        adj = kmalloc(sizeof(*adj), GFP_KERNEL);
        if (!adj)
                return -ENOMEM;

        adj->dev = adj_dev;
        adj->master = master;
        adj->ref_nr = 1;
        adj->private = private;
        dev_hold(adj_dev);

        pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d; dev_hold on %s\n",
                 dev->name, adj_dev->name, adj->ref_nr, adj_dev->name);

        if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list)) {
                ret = netdev_adjacent_sysfs_add(dev, adj_dev, dev_list);
                if (ret)
                        goto free_adj;
        }

        /* Ensure that master link is always the first item in list. */
        if (master) {
                ret = sysfs_create_link(&(dev->dev.kobj),
                                        &(adj_dev->dev.kobj), "master");
                if (ret)
                        goto remove_symlinks;

                list_add_rcu(&adj->list, dev_list);
        } else {
                list_add_tail_rcu(&adj->list, dev_list);
        }

        return 0;

remove_symlinks:
        if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list))
                netdev_adjacent_sysfs_del(dev, adj_dev->name, dev_list);
free_adj:
        kfree(adj);
        dev_put(adj_dev);

        return ret;
}

static void __netdev_adjacent_dev_remove(struct net_device *dev,
                                         struct net_device *adj_dev,
                                         u16 ref_nr,
                                         struct list_head *dev_list)
{
        struct netdev_adjacent *adj;

        pr_debug("Remove adjacency: dev %s adj_dev %s ref_nr %d\n",
                 dev->name, adj_dev->name, ref_nr);

        adj = __netdev_find_adj(adj_dev, dev_list);

        if (!adj) {
                pr_err("Adjacency does not exist for device %s from %s\n",
                       dev->name, adj_dev->name);
                WARN_ON(1);
                return;
        }

        if (adj->ref_nr > ref_nr) {
                pr_debug("adjacency: %s to %s ref_nr - %d = %d\n",
                         dev->name, adj_dev->name, ref_nr,
                         adj->ref_nr - ref_nr);
                adj->ref_nr -= ref_nr;
                return;
        }

        if (adj->master)
                sysfs_remove_link(&(dev->dev.kobj), "master");

        if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list))
                netdev_adjacent_sysfs_del(dev, adj_dev->name, dev_list);

        list_del_rcu(&adj->list);
        pr_debug("adjacency: dev_put for %s, because link removed from %s to %s\n",
                 adj_dev->name, dev->name, adj_dev->name);
        dev_put(adj_dev);
        kfree_rcu(adj, rcu);
}

static int __netdev_adjacent_dev_link_lists(struct net_device *dev,
                                            struct net_device *upper_dev,
                                            struct list_head *up_list,
                                            struct list_head *down_list,
                                            void *private, bool master)
{
        int ret;

        ret = __netdev_adjacent_dev_insert(dev, upper_dev, up_list,
                                           private, master);
        if (ret)
                return ret;

        ret = __netdev_adjacent_dev_insert(upper_dev, dev, down_list,
                                           private, false);
        if (ret) {
                __netdev_adjacent_dev_remove(dev, upper_dev, 1, up_list);
                return ret;
        }

        return 0;
}

static void __netdev_adjacent_dev_unlink_lists(struct net_device *dev,
                                               struct net_device *upper_dev,
                                               u16 ref_nr,
                                               struct list_head *up_list,
                                               struct list_head *down_list)
{
        __netdev_adjacent_dev_remove(dev, upper_dev, ref_nr, up_list);
        __netdev_adjacent_dev_remove(upper_dev, dev, ref_nr, down_list);
}

static int __netdev_adjacent_dev_link_neighbour(struct net_device *dev,
                                                struct net_device *upper_dev,
                                                void *private, bool master)
{
        return __netdev_adjacent_dev_link_lists(dev, upper_dev,
                                                &dev->adj_list.upper,
                                                &upper_dev->adj_list.lower,
                                                private, master);
}

static void __netdev_adjacent_dev_unlink_neighbour(struct net_device *dev,
                                                   struct net_device *upper_dev)
{
        __netdev_adjacent_dev_unlink_lists(dev, upper_dev, 1,
                                           &dev->adj_list.upper,
                                           &upper_dev->adj_list.lower);
}

static int __netdev_upper_dev_link(struct net_device *dev,
                                   struct net_device *upper_dev, bool master,
                                   void *upper_priv, void *upper_info)
{
        struct netdev_notifier_changeupper_info changeupper_info;
        int ret = 0;

        ASSERT_RTNL();

        if (dev == upper_dev)
                return -EBUSY;

        /* To prevent loops, check if dev is not upper device to upper_dev. */
        if (netdev_has_upper_dev(upper_dev, dev))
                return -EBUSY;

        if (netdev_has_upper_dev(dev, upper_dev))
                return -EEXIST;

        if (master && netdev_master_upper_dev_get(dev))
                return -EBUSY;

        changeupper_info.upper_dev = upper_dev;
        changeupper_info.master = master;
        changeupper_info.linking = true;
        changeupper_info.upper_info = upper_info;

        ret = call_netdevice_notifiers_info(NETDEV_PRECHANGEUPPER, dev,
                                            &changeupper_info.info);
        ret = notifier_to_errno(ret);
        if (ret)
                return ret;

        ret = __netdev_adjacent_dev_link_neighbour(dev, upper_dev, upper_priv,
                                                   master);
        if (ret)
                return ret;

        ret = call_netdevice_notifiers_info(NETDEV_CHANGEUPPER, dev,
                                            &changeupper_info.info);
        ret = notifier_to_errno(ret);
        if (ret)
                goto rollback;

        return 0;

rollback:
        __netdev_adjacent_dev_unlink_neighbour(dev, upper_dev);

        return ret;
}

/**
 * netdev_upper_dev_link - Add a link to the upper device
 * @dev: device
 * @upper_dev: new upper device
 *
 * Adds a link to device which is upper to this one. The caller must hold
 * the RTNL lock. On a failure a negative errno code is returned.
 * On success the reference counts are adjusted and the function
 * returns zero.
 */
int netdev_upper_dev_link(struct net_device *dev,
                          struct net_device *upper_dev)
{
        return __netdev_upper_dev_link(dev, upper_dev, false, NULL, NULL);
}
EXPORT_SYMBOL(netdev_upper_dev_link);

/**
 * netdev_master_upper_dev_link - Add a master link to the upper device
 * @dev: device
 * @upper_dev: new upper device
 * @upper_priv: upper device private
 * @upper_info: upper info to be passed down via notifier
 *
 * Adds a link to device which is upper to this one. In this case, only
 * one master upper device can be linked, although other non-master devices
 * might be linked as well. The caller must hold the RTNL lock.
 * On a failure a negative errno code is returned. On success the reference
 * counts are adjusted and the function returns zero.
 */
int netdev_master_upper_dev_link(struct net_device *dev,
                                 struct net_device *upper_dev,
                                 void *upper_priv, void *upper_info)
{
        return __netdev_upper_dev_link(dev, upper_dev, true,
                                       upper_priv, upper_info);
}
EXPORT_SYMBOL(netdev_master_upper_dev_link);

/**
 * netdev_upper_dev_unlink - Removes a link to upper device
 * @dev: device
 * @upper_dev: new upper device
 *
 * Removes a link to device which is upper to this one. The caller must hold
 * the RTNL lock.
 */
void netdev_upper_dev_unlink(struct net_device *dev,
                             struct net_device *upper_dev)
{
        struct netdev_notifier_changeupper_info changeupper_info;

        ASSERT_RTNL();

        changeupper_info.upper_dev = upper_dev;
        changeupper_info.master = netdev_master_upper_dev_get(dev) == upper_dev;
        changeupper_info.linking = false;

        call_netdevice_notifiers_info(NETDEV_PRECHANGEUPPER, dev,
                                      &changeupper_info.info);

        __netdev_adjacent_dev_unlink_neighbour(dev, upper_dev);

        call_netdevice_notifiers_info(NETDEV_CHANGEUPPER, dev,
                                      &changeupper_info.info);
}
EXPORT_SYMBOL(netdev_upper_dev_unlink);

/**
 * netdev_bonding_info_change - Dispatch event about slave change
 * @dev: device
 * @bonding_info: info to dispatch
 *
 * Send NETDEV_BONDING_INFO to netdev notifiers with info.
 * The caller must hold the RTNL lock.
 */
void netdev_bonding_info_change(struct net_device *dev,
                                struct netdev_bonding_info *bonding_info)
{
        struct netdev_notifier_bonding_info     info;

        memcpy(&info.bonding_info, bonding_info,
               sizeof(struct netdev_bonding_info));
        call_netdevice_notifiers_info(NETDEV_BONDING_INFO, dev,
                                      &info.info);
}
EXPORT_SYMBOL(netdev_bonding_info_change);

static void netdev_adjacent_add_links(struct net_device *dev)
{
        struct netdev_adjacent *iter;

        struct net *net = dev_net(dev);

        list_for_each_entry(iter, &dev->adj_list.upper, list) {
                if (!net_eq(net, dev_net(iter->dev)))
                        continue;
                netdev_adjacent_sysfs_add(iter->dev, dev,
                                          &iter->dev->adj_list.lower);
                netdev_adjacent_sysfs_add(dev, iter->dev,
                                          &dev->adj_list.upper);
        }

        list_for_each_entry(iter, &dev->adj_list.lower, list) {
                if (!net_eq(net, dev_net(iter->dev)))
                        continue;
                netdev_adjacent_sysfs_add(iter->dev, dev,
                                          &iter->dev->adj_list.upper);
                netdev_adjacent_sysfs_add(dev, iter->dev,
                                          &dev->adj_list.lower);
        }
}

static void netdev_adjacent_del_links(struct net_device *dev)
{
        struct netdev_adjacent *iter;

        struct net *net = dev_net(dev);

        list_for_each_entry(iter, &dev->adj_list.upper, list) {
                if (!net_eq(net, dev_net(iter->dev)))
                        continue;
                netdev_adjacent_sysfs_del(iter->dev, dev->name,
                                          &iter->dev->adj_list.lower);
                netdev_adjacent_sysfs_del(dev, iter->dev->name,
                                          &dev->adj_list.upper);
        }

        list_for_each_entry(iter, &dev->adj_list.lower, list) {
                if (!net_eq(net, dev_net(iter->dev)))
                        continue;
                netdev_adjacent_sysfs_del(iter->dev, dev->name,
                                          &iter->dev->adj_list.upper);
                netdev_adjacent_sysfs_del(dev, iter->dev->name,
                                          &dev->adj_list.lower);
        }
}

void netdev_adjacent_rename_links(struct net_device *dev, char *oldname)
{
        struct netdev_adjacent *iter;

        struct net *net = dev_net(dev);

        list_for_each_entry(iter, &dev->adj_list.upper, list) {
                if (!net_eq(net, dev_net(iter->dev)))
                        continue;
                netdev_adjacent_sysfs_del(iter->dev, oldname,
                                          &iter->dev->adj_list.lower);
                netdev_adjacent_sysfs_add(iter->dev, dev,
                                          &iter->dev->adj_list.lower);
        }

        list_for_each_entry(iter, &dev->adj_list.lower, list) {
                if (!net_eq(net, dev_net(iter->dev)))
                        continue;
                netdev_adjacent_sysfs_del(iter->dev, oldname,
                                          &iter->dev->adj_list.upper);
                netdev_adjacent_sysfs_add(iter->dev, dev,
                                          &iter->dev->adj_list.upper);
        }
}

void *netdev_lower_dev_get_private(struct net_device *dev,
                                   struct net_device *lower_dev)
{
        struct netdev_adjacent *lower;

        if (!lower_dev)
                return NULL;
        lower = __netdev_find_adj(lower_dev, &dev->adj_list.lower);
        if (!lower)
                return NULL;

        return lower->private;
}
EXPORT_SYMBOL(netdev_lower_dev_get_private);


int dev_get_nest_level(struct net_device *dev)
{
        struct net_device *lower = NULL;
        struct list_head *iter;
        int max_nest = -1;
        int nest;

        ASSERT_RTNL();

        netdev_for_each_lower_dev(dev, lower, iter) {
                nest = dev_get_nest_level(lower);
                if (max_nest < nest)
                        max_nest = nest;
        }

        return max_nest + 1;
}
EXPORT_SYMBOL(dev_get_nest_level);

/**
 * netdev_lower_change - Dispatch event about lower device state change
 * @lower_dev: device
 * @lower_state_info: state to dispatch
 *
 * Send NETDEV_CHANGELOWERSTATE to netdev notifiers with info.
 * The caller must hold the RTNL lock.
 */
void netdev_lower_state_changed(struct net_device *lower_dev,
                                void *lower_state_info)
{
        struct netdev_notifier_changelowerstate_info changelowerstate_info;

        ASSERT_RTNL();
        changelowerstate_info.lower_state_info = lower_state_info;
        call_netdevice_notifiers_info(NETDEV_CHANGELOWERSTATE, lower_dev,
                                      &changelowerstate_info.info);
}
EXPORT_SYMBOL(netdev_lower_state_changed);

static void dev_change_rx_flags(struct net_device *dev, int flags)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        if (ops->ndo_change_rx_flags)
                ops->ndo_change_rx_flags(dev, flags);
}

static int __dev_set_promiscuity(struct net_device *dev, int inc, bool notify)
{
        unsigned int old_flags = dev->flags;
        kuid_t uid;
        kgid_t gid;

        ASSERT_RTNL();

        dev->flags |= IFF_PROMISC;
        dev->promiscuity += inc;
        if (dev->promiscuity == 0) {
                /*
                 * Avoid overflow.
                 * If inc causes overflow, untouch promisc and return error.
                 */
                if (inc < 0)
                        dev->flags &= ~IFF_PROMISC;
                else {
                        dev->promiscuity -= inc;
                        pr_warn("%s: promiscuity touches roof, set promiscuity failed. promiscuity feature of device might be broken.\n",
                                dev->name);
                        return -EOVERFLOW;
                }
        }
        if (dev->flags != old_flags) {
                pr_info("device %s %s promiscuous mode\n",
                        dev->name,
                        dev->flags & IFF_PROMISC ? "entered" : "left");
                if (audit_enabled) {
                        current_uid_gid(&uid, &gid);
                        audit_log(current->audit_context, GFP_ATOMIC,
                                AUDIT_ANOM_PROMISCUOUS,
                                "dev=%s prom=%d old_prom=%d auid=%u uid=%u gid=%u ses=%u",
                                dev->name, (dev->flags & IFF_PROMISC),
                                (old_flags & IFF_PROMISC),
                                from_kuid(&init_user_ns, audit_get_loginuid(current)),
                                from_kuid(&init_user_ns, uid),
                                from_kgid(&init_user_ns, gid),
                                audit_get_sessionid(current));
                }

                dev_change_rx_flags(dev, IFF_PROMISC);
        }
        if (notify)
                __dev_notify_flags(dev, old_flags, IFF_PROMISC);
        return 0;
}

/**
 *      dev_set_promiscuity     - update promiscuity count on a device
 *      @dev: device
 *      @inc: modifier
 *
 *      Add or remove promiscuity from a device. While the count in the device
 *      remains above zero the interface remains promiscuous. Once it hits zero
 *      the device reverts back to normal filtering operation. A negative inc
 *      value is used to drop promiscuity on the device.
 *      Return 0 if successful or a negative errno code on error.
 */
int dev_set_promiscuity(struct net_device *dev, int inc)
{
        unsigned int old_flags = dev->flags;
        int err;

        err = __dev_set_promiscuity(dev, inc, true);
        if (err < 0)
                return err;
        if (dev->flags != old_flags)
                dev_set_rx_mode(dev);
        return err;
}
EXPORT_SYMBOL(dev_set_promiscuity);

static int __dev_set_allmulti(struct net_device *dev, int inc, bool notify)
{
        unsigned int old_flags = dev->flags, old_gflags = dev->gflags;

        ASSERT_RTNL();

        dev->flags |= IFF_ALLMULTI;
        dev->allmulti += inc;
        if (dev->allmulti == 0) {
                /*
                 * Avoid overflow.
                 * If inc causes overflow, untouch allmulti and return error.
                 */
                if (inc < 0)
                        dev->flags &= ~IFF_ALLMULTI;
                else {
                        dev->allmulti -= inc;
                        pr_warn("%s: allmulti touches roof, set allmulti failed. allmulti feature of device might be broken.\n",
                                dev->name);
                        return -EOVERFLOW;
                }
        }
        if (dev->flags ^ old_flags) {
                dev_change_rx_flags(dev, IFF_ALLMULTI);
                dev_set_rx_mode(dev);
                if (notify)
                        __dev_notify_flags(dev, old_flags,
                                           dev->gflags ^ old_gflags);
        }
        return 0;
}

/**
 *      dev_set_allmulti        - update allmulti count on a device
 *      @dev: device
 *      @inc: modifier
 *
 *      Add or remove reception of all multicast frames to a device. While the
 *      count in the device remains above zero the interface remains listening
 *      to all interfaces. Once it hits zero the device reverts back to normal
 *      filtering operation. A negative @inc value is used to drop the counter
 *      when releasing a resource needing all multicasts.
 *      Return 0 if successful or a negative errno code on error.
 */

int dev_set_allmulti(struct net_device *dev, int inc)
{
        return __dev_set_allmulti(dev, inc, true);
}
EXPORT_SYMBOL(dev_set_allmulti);

/*
 *      Upload unicast and multicast address lists to device and
 *      configure RX filtering. When the device doesn't support unicast
 *      filtering it is put in promiscuous mode while unicast addresses
 *      are present.
 */
void __dev_set_rx_mode(struct net_device *dev)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        /* dev_open will call this function so the list will stay sane. */
        if (!(dev->flags&IFF_UP))
                return;

        if (!netif_device_present(dev))
                return;

        if (!(dev->priv_flags & IFF_UNICAST_FLT)) {
                /* Unicast addresses changes may only happen under the rtnl,
                 * therefore calling __dev_set_promiscuity here is safe.
                 */
                if (!netdev_uc_empty(dev) && !dev->uc_promisc) {
                        __dev_set_promiscuity(dev, 1, false);
                        dev->uc_promisc = true;
                } else if (netdev_uc_empty(dev) && dev->uc_promisc) {
                        __dev_set_promiscuity(dev, -1, false);
                        dev->uc_promisc = false;
                }
        }

        if (ops->ndo_set_rx_mode)
                ops->ndo_set_rx_mode(dev);
}

void dev_set_rx_mode(struct net_device *dev)
{
        netif_addr_lock_bh(dev);
        __dev_set_rx_mode(dev);
        netif_addr_unlock_bh(dev);
}

/**
 *      dev_get_flags - get flags reported to userspace
 *      @dev: device
 *
 *      Get the combination of flag bits exported through APIs to userspace.
 */
unsigned int dev_get_flags(const struct net_device *dev)
{
        unsigned int flags;

        flags = (dev->flags & ~(IFF_PROMISC |
                                IFF_ALLMULTI |
                                IFF_RUNNING |
                                IFF_LOWER_UP |
                                IFF_DORMANT)) |
                (dev->gflags & (IFF_PROMISC |
                                IFF_ALLMULTI));

        if (netif_running(dev)) {
                if (netif_oper_up(dev))
                        flags |= IFF_RUNNING;
                if (netif_carrier_ok(dev))
                        flags |= IFF_LOWER_UP;
                if (netif_dormant(dev))
                        flags |= IFF_DORMANT;
        }

        return flags;
}
EXPORT_SYMBOL(dev_get_flags);

int __dev_change_flags(struct net_device *dev, unsigned int flags)
{
        unsigned int old_flags = dev->flags;
        int ret;

        ASSERT_RTNL();

        /*
         *      Set the flags on our device.
         */

        dev->flags = (flags & (IFF_DEBUG | IFF_NOTRAILERS | IFF_NOARP |
                               IFF_DYNAMIC | IFF_MULTICAST | IFF_PORTSEL |
                               IFF_AUTOMEDIA)) |
                     (dev->flags & (IFF_UP | IFF_VOLATILE | IFF_PROMISC |
                                    IFF_ALLMULTI));

        /*
         *      Load in the correct multicast list now the flags have changed.
         */

        if ((old_flags ^ flags) & IFF_MULTICAST)
                dev_change_rx_flags(dev, IFF_MULTICAST);

        dev_set_rx_mode(dev);

        /*
         *      Have we downed the interface. We handle IFF_UP ourselves
         *      according to user attempts to set it, rather than blindly
         *      setting it.
         */

        ret = 0;
        if ((old_flags ^ flags) & IFF_UP) {
                if (old_flags & IFF_UP)
                        __dev_close(dev);
                else
                        ret = __dev_open(dev);
        }

        if ((flags ^ dev->gflags) & IFF_PROMISC) {
                int inc = (flags & IFF_PROMISC) ? 1 : -1;
                unsigned int old_flags = dev->flags;

                dev->gflags ^= IFF_PROMISC;

                if (__dev_set_promiscuity(dev, inc, false) >= 0)
                        if (dev->flags != old_flags)
                                dev_set_rx_mode(dev);
        }

        /* NOTE: order of synchronization of IFF_PROMISC and IFF_ALLMULTI
         * is important. Some (broken) drivers set IFF_PROMISC, when
         * IFF_ALLMULTI is requested not asking us and not reporting.
         */
        if ((flags ^ dev->gflags) & IFF_ALLMULTI) {
                int inc = (flags & IFF_ALLMULTI) ? 1 : -1;

                dev->gflags ^= IFF_ALLMULTI;
                __dev_set_allmulti(dev, inc, false);
        }

        return ret;
}

void __dev_notify_flags(struct net_device *dev, unsigned int old_flags,
                        unsigned int gchanges)
{
        unsigned int changes = dev->flags ^ old_flags;

        if (gchanges)
                rtmsg_ifinfo(RTM_NEWLINK, dev, gchanges, GFP_ATOMIC);

        if (changes & IFF_UP) {
                if (dev->flags & IFF_UP)
                        call_netdevice_notifiers(NETDEV_UP, dev);
                else
                        call_netdevice_notifiers(NETDEV_DOWN, dev);
        }

        if (dev->flags & IFF_UP &&
            (changes & ~(IFF_UP | IFF_PROMISC | IFF_ALLMULTI | IFF_VOLATILE))) {
                struct netdev_notifier_change_info change_info;

                change_info.flags_changed = changes;
                call_netdevice_notifiers_info(NETDEV_CHANGE, dev,
                                              &change_info.info);
        }
}

/**
 *      dev_change_flags - change device settings
 *      @dev: device
 *      @flags: device state flags
 *
 *      Change settings on device based state flags. The flags are
 *      in the userspace exported format.
 */
int dev_change_flags(struct net_device *dev, unsigned int flags)
{
        int ret;
        unsigned int changes, old_flags = dev->flags, old_gflags = dev->gflags;

        ret = __dev_change_flags(dev, flags);
        if (ret < 0)
                return ret;

        changes = (old_flags ^ dev->flags) | (old_gflags ^ dev->gflags);
        __dev_notify_flags(dev, old_flags, changes);
        return ret;
}
EXPORT_SYMBOL(dev_change_flags);

int __dev_set_mtu(struct net_device *dev, int new_mtu)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        if (ops->ndo_change_mtu)
                return ops->ndo_change_mtu(dev, new_mtu);

        dev->mtu = new_mtu;
        return 0;
}
EXPORT_SYMBOL(__dev_set_mtu);

/**
 *      dev_set_mtu - Change maximum transfer unit
 *      @dev: device
 *      @new_mtu: new transfer unit
 *
 *      Change the maximum transfer size of the network device.
 */
int dev_set_mtu(struct net_device *dev, int new_mtu)
{
        int err, orig_mtu;

        if (new_mtu == dev->mtu)
                return 0;

        /* MTU must be positive, and in range */
        if (new_mtu < 0 || new_mtu < dev->min_mtu) {
                net_err_ratelimited("%s: Invalid MTU %d requested, hw min %d\n",
                                    dev->name, new_mtu, dev->min_mtu);
                return -EINVAL;
        }

        if (dev->max_mtu > 0 && new_mtu > dev->max_mtu) {
                net_err_ratelimited("%s: Invalid MTU %d requested, hw max %d\n",
                                    dev->name, new_mtu, dev->max_mtu);
                return -EINVAL;
        }

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

        err = call_netdevice_notifiers(NETDEV_PRECHANGEMTU, dev);
        err = notifier_to_errno(err);
        if (err)
                return err;

        orig_mtu = dev->mtu;
        err = __dev_set_mtu(dev, new_mtu);

        if (!err) {
                err = call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
                err = notifier_to_errno(err);
                if (err) {
                        /* setting mtu back and notifying everyone again,
                         * so that they have a chance to revert changes.
                         */
                        __dev_set_mtu(dev, orig_mtu);
                        call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
                }
        }
        return err;
}
EXPORT_SYMBOL(dev_set_mtu);

/**
 *      dev_set_group - Change group this device belongs to
 *      @dev: device
 *      @new_group: group this device should belong to
 */
void dev_set_group(struct net_device *dev, int new_group)
{
        dev->group = new_group;
}
EXPORT_SYMBOL(dev_set_group);

/**
 *      dev_set_mac_address - Change Media Access Control Address
 *      @dev: device
 *      @sa: new address
 *
 *      Change the hardware (MAC) address of the device
 */
int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa)
{
        const struct net_device_ops *ops = dev->netdev_ops;
        int err;

        if (!ops->ndo_set_mac_address)
                return -EOPNOTSUPP;
        if (sa->sa_family != dev->type)
                return -EINVAL;
        if (!netif_device_present(dev))
                return -ENODEV;
        err = ops->ndo_set_mac_address(dev, sa);
        if (err)
                return err;
        dev->addr_assign_type = NET_ADDR_SET;
        call_netdevice_notifiers(NETDEV_CHANGEADDR, dev);
        add_device_randomness(dev->dev_addr, dev->addr_len);
        return 0;
}
EXPORT_SYMBOL(dev_set_mac_address);

/**
 *      dev_change_carrier - Change device carrier
 *      @dev: device
 *      @new_carrier: new value
 *
 *      Change device carrier
 */
int dev_change_carrier(struct net_device *dev, bool new_carrier)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        if (!ops->ndo_change_carrier)
                return -EOPNOTSUPP;
        if (!netif_device_present(dev))
                return -ENODEV;
        return ops->ndo_change_carrier(dev, new_carrier);
}
EXPORT_SYMBOL(dev_change_carrier);

/**
 *      dev_get_phys_port_id - Get device physical port ID
 *      @dev: device
 *      @ppid: port ID
 *
 *      Get device physical port ID
 */
int dev_get_phys_port_id(struct net_device *dev,
                         struct netdev_phys_item_id *ppid)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        if (!ops->ndo_get_phys_port_id)
                return -EOPNOTSUPP;
        return ops->ndo_get_phys_port_id(dev, ppid);
}
EXPORT_SYMBOL(dev_get_phys_port_id);

/**
 *      dev_get_phys_port_name - Get device physical port name
 *      @dev: device
 *      @name: port name
 *      @len: limit of bytes to copy to name
 *
 *      Get device physical port name
 */
int dev_get_phys_port_name(struct net_device *dev,
                           char *name, size_t len)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        if (!ops->ndo_get_phys_port_name)
                return -EOPNOTSUPP;
        return ops->ndo_get_phys_port_name(dev, name, len);
}
EXPORT_SYMBOL(dev_get_phys_port_name);

/**
 *      dev_change_proto_down - update protocol port state information
 *      @dev: device
 *      @proto_down: new value
 *
 *      This info can be used by switch drivers to set the phys state of the
 *      port.
 */
int dev_change_proto_down(struct net_device *dev, bool proto_down)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        if (!ops->ndo_change_proto_down)
                return -EOPNOTSUPP;
        if (!netif_device_present(dev))
                return -ENODEV;
        return ops->ndo_change_proto_down(dev, proto_down);
}
EXPORT_SYMBOL(dev_change_proto_down);

u8 __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op, u32 *prog_id)
{
        struct netdev_xdp xdp;

        memset(&xdp, 0, sizeof(xdp));
        xdp.command = XDP_QUERY_PROG;

        /* Query must always succeed. */
        WARN_ON(xdp_op(dev, &xdp) < 0);
        if (prog_id)
                *prog_id = xdp.prog_id;

        return xdp.prog_attached;
}

static int dev_xdp_install(struct net_device *dev, xdp_op_t xdp_op,
                           struct netlink_ext_ack *extack, u32 flags,
                           struct bpf_prog *prog)
{
        struct netdev_xdp xdp;

        memset(&xdp, 0, sizeof(xdp));
        if (flags & XDP_FLAGS_HW_MODE)
                xdp.command = XDP_SETUP_PROG_HW;
        else
                xdp.command = XDP_SETUP_PROG;
        xdp.extack = extack;
        xdp.flags = flags;
        xdp.prog = prog;

        return xdp_op(dev, &xdp);
}

/**
 *      dev_change_xdp_fd - set or clear a bpf program for a device rx path
 *      @dev: device
 *      @extack: netlink extended ack
 *      @fd: new program fd or negative value to clear
 *      @flags: xdp-related flags
 *
 *      Set or clear a bpf program for a device
 */
int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
                      int fd, u32 flags)
{
        const struct net_device_ops *ops = dev->netdev_ops;
        struct bpf_prog *prog = NULL;
        xdp_op_t xdp_op, xdp_chk;
        int err;

        ASSERT_RTNL();

        xdp_op = xdp_chk = ops->ndo_xdp;
        if (!xdp_op && (flags & (XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE)))
                return -EOPNOTSUPP;
        if (!xdp_op || (flags & XDP_FLAGS_SKB_MODE))
                xdp_op = generic_xdp_install;
        if (xdp_op == xdp_chk)
                xdp_chk = generic_xdp_install;

        if (fd >= 0) {
                if (xdp_chk && __dev_xdp_attached(dev, xdp_chk, NULL))
                        return -EEXIST;
                if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) &&
                    __dev_xdp_attached(dev, xdp_op, NULL))
                        return -EBUSY;

                prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_XDP);
                if (IS_ERR(prog))
                        return PTR_ERR(prog);
        }

        err = dev_xdp_install(dev, xdp_op, extack, flags, prog);
        if (err < 0 && prog)
                bpf_prog_put(prog);

        return err;
}

/**
 *      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)
{
        int ifindex = net->ifindex;

        for (;;) {
                if (++ifindex <= 0)
                        ifindex = 1;
                if (!__dev_get_by_index(net, ifindex))
                        return net->ifindex = ifindex;
        }
}

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

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

static void rollback_registered_many(struct list_head *head)
{
        struct net_device *dev, *tmp;
        LIST_HEAD(close_head);

        BUG_ON(dev_boot_phase);
        ASSERT_RTNL();

        list_for_each_entry_safe(dev, tmp, head, unreg_list) {
                /* Some devices call without registering
                 * for initialization unwind. Remove those
                 * devices and proceed with the remaining.
                 */
                if (dev->reg_state == NETREG_UNINITIALIZED) {
                        pr_debug("unregister_netdevice: device %s/%p never was registered\n",
                                 dev->name, dev);

                        WARN_ON(1);
                        list_del(&dev->unreg_list);
                        continue;
                }
                dev->dismantle = true;
                BUG_ON(dev->reg_state != NETREG_REGISTERED);
        }

        /* If device is running, close it first. */
        list_for_each_entry(dev, head, unreg_list)
                list_add_tail(&dev->close_list, &close_head);
        dev_close_many(&close_head, true);

        list_for_each_entry(dev, head, unreg_list) {
                /* And unlink it from device chain. */
                unlist_netdevice(dev);

                dev->reg_state = NETREG_UNREGISTERING;
        }
        flush_all_backlogs();

        synchronize_net();

        list_for_each_entry(dev, head, unreg_list) {
                struct sk_buff *skb = NULL;

                /* 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);

                if (!dev->rtnl_link_ops ||
                    dev->rtnl_link_state == RTNL_LINK_INITIALIZED)
                        skb = rtmsg_ifinfo_build_skb(RTM_DELLINK, dev, ~0U, 0,
                                                     GFP_KERNEL);

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

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

                if (skb)
                        rtmsg_ifinfo_send(skb, dev, GFP_KERNEL);

                /* Notifier chain MUST detach us all upper devices. */
                WARN_ON(netdev_has_any_upper_dev(dev));
                WARN_ON(netdev_has_any_lower_dev(dev));

                /* Remove entries from kobject tree */
                netdev_unregister_kobject(dev);
#ifdef CONFIG_XPS
                /* Remove XPS queueing entries */
                netif_reset_xps_queues_gt(dev, 0);
#endif
        }

        synchronize_net();

        list_for_each_entry(dev, head, unreg_list)
                dev_put(dev);
}

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

        list_add(&dev->unreg_list, &single);
        rollback_registered_many(&single);
        list_del(&single);
}

static netdev_features_t netdev_sync_upper_features(struct net_device *lower,
        struct net_device *upper, netdev_features_t features)
{
        netdev_features_t upper_disables = NETIF_F_UPPER_DISABLES;
        netdev_features_t feature;
        int feature_bit;

        for_each_netdev_feature(&upper_disables, feature_bit) {
                feature = __NETIF_F_BIT(feature_bit);
                if (!(upper->wanted_features & feature)
                    && (features & feature)) {
                        netdev_dbg(lower, "Dropping feature %pNF, upper dev %s has it off.\n",
                                   &feature, upper->name);
                        features &= ~feature;
                }
        }

        return features;
}

static void netdev_sync_lower_features(struct net_device *upper,
        struct net_device *lower, netdev_features_t features)
{
        netdev_features_t upper_disables = NETIF_F_UPPER_DISABLES;
        netdev_features_t feature;
        int feature_bit;

        for_each_netdev_feature(&upper_disables, feature_bit) {
                feature = __NETIF_F_BIT(feature_bit);
                if (!(features & feature) && (lower->features & feature)) {
                        netdev_dbg(upper, "Disabling feature %pNF on lower dev %s.\n",
                                   &feature, lower->name);
                        lower->wanted_features &= ~feature;
                        netdev_update_features(lower);

                        if (unlikely(lower->features & feature))
                                netdev_WARN(upper, "failed to disable %pNF on %s!\n",
                                            &feature, lower->name);
                }
        }
}

static netdev_features_t netdev_fix_features(struct net_device *dev,
        netdev_features_t features)
{
        /* Fix illegal checksum combinations */
        if ((features & NETIF_F_HW_CSUM) &&
            (features & (NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM))) {
                netdev_warn(dev, "mixed HW and IP checksum settings.\n");
                features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM);
        }

        /* TSO requires that SG is present as well. */
        if ((features & NETIF_F_ALL_TSO) && !(features & NETIF_F_SG)) {
                netdev_dbg(dev, "Dropping TSO features since no SG feature.\n");
                features &= ~NETIF_F_ALL_TSO;
        }

        if ((features & NETIF_F_TSO) && !(features & NETIF_F_HW_CSUM) &&
                                        !(features & NETIF_F_IP_CSUM)) {
                netdev_dbg(dev, "Dropping TSO features since no CSUM feature.\n");
                features &= ~NETIF_F_TSO;
                features &= ~NETIF_F_TSO_ECN;
        }

        if ((features & NETIF_F_TSO6) && !(features & NETIF_F_HW_CSUM) &&
                                         !(features & NETIF_F_IPV6_CSUM)) {
                netdev_dbg(dev, "Dropping TSO6 features since no CSUM feature.\n");
                features &= ~NETIF_F_TSO6;
        }

        /* TSO with IPv4 ID mangling requires IPv4 TSO be enabled */
        if ((features & NETIF_F_TSO_MANGLEID) && !(features & NETIF_F_TSO))
                features &= ~NETIF_F_TSO_MANGLEID;

        /* TSO ECN requires that TSO is present as well. */
        if ((features & NETIF_F_ALL_TSO) == NETIF_F_TSO_ECN)
                features &= ~NETIF_F_TSO_ECN;

        /* Software GSO depends on SG. */
        if ((features & NETIF_F_GSO) && !(features & NETIF_F_SG)) {
                netdev_dbg(dev, "Dropping NETIF_F_GSO since no SG feature.\n");
                features &= ~NETIF_F_GSO;
        }

        /* GSO partial features require GSO partial be set */
        if ((features & dev->gso_partial_features) &&
            !(features & NETIF_F_GSO_PARTIAL)) {
                netdev_dbg(dev,
                           "Dropping partially supported GSO features since no GSO partial.\n");
                features &= ~dev->gso_partial_features;
        }

        return features;
}

int __netdev_update_features(struct net_device *dev)
{
        struct net_device *upper, *lower;
        netdev_features_t features;
        struct list_head *iter;
        int err = -1;

        ASSERT_RTNL();

        features = netdev_get_wanted_features(dev);

        if (dev->netdev_ops->ndo_fix_features)
                features = dev->netdev_ops->ndo_fix_features(dev, features);

        /* driver might be less strict about feature dependencies */
        features = netdev_fix_features(dev, features);

        /* some features can't be enabled if they're off an an upper device */
        netdev_for_each_upper_dev_rcu(dev, upper, iter)
                features = netdev_sync_upper_features(dev, upper, features);

        if (dev->features == features)
                goto sync_lower;

        netdev_dbg(dev, "Features changed: %pNF -> %pNF\n",
                &dev->features, &features);

        if (dev->netdev_ops->ndo_set_features)
                err = dev->netdev_ops->ndo_set_features(dev, features);
        else
                err = 0;

        if (unlikely(err < 0)) {
                netdev_err(dev,
                        "set_features() failed (%d); wanted %pNF, left %pNF\n",
                        err, &features, &dev->features);
                /* return non-0 since some features might have changed and
                 * it's better to fire a spurious notification than miss it
                 */
                return -1;
        }

sync_lower:
        /* some features must be disabled on lower devices when disabled
         * on an upper device (think: bonding master or bridge)
         */
        netdev_for_each_lower_dev(dev, lower, iter)
                netdev_sync_lower_features(dev, lower, features);

        if (!err) {
                netdev_features_t diff = features ^ dev->features;

                if (diff & NETIF_F_RX_UDP_TUNNEL_PORT) {
                        /* udp_tunnel_{get,drop}_rx_info both need
                         * NETIF_F_RX_UDP_TUNNEL_PORT enabled on the
                         * device, or they won't do anything.
                         * Thus we need to update dev->features
                         * *before* calling udp_tunnel_get_rx_info,
                         * but *after* calling udp_tunnel_drop_rx_info.
                         */
                        if (features & NETIF_F_RX_UDP_TUNNEL_PORT) {
                                dev->features = features;
                                udp_tunnel_get_rx_info(dev);
                        } else {
                                udp_tunnel_drop_rx_info(dev);
                        }
                }

                dev->features = features;
        }

        return err < 0 ? 0 : 1;
}

/**
 *      netdev_update_features - recalculate device features
 *      @dev: the device to check
 *
 *      Recalculate dev->features set and send notifications if it
 *      has changed. Should be called after driver or hardware dependent
 *      conditions might have changed that influence the features.
 */
void netdev_update_features(struct net_device *dev)
{
        if (__netdev_update_features(dev))
                netdev_features_change(dev);
}
EXPORT_SYMBOL(netdev_update_features);

/**
 *      netdev_change_features - recalculate device features
 *      @dev: the device to check
 *
 *      Recalculate dev->features set and send notifications even
 *      if they have not changed. Should be called instead of
 *      netdev_update_features() if also dev->vlan_features might
 *      have changed to allow the changes to be propagated to stacked
 *      VLAN devices.
 */
void netdev_change_features(struct net_device *dev)
{
        __netdev_update_features(dev);
        netdev_features_change(dev);
}
EXPORT_SYMBOL(netdev_change_features);

/**
 *      netif_stacked_transfer_operstate -      transfer operstate
 *      @rootdev: the root or lower level device to transfer state from
 *      @dev: the device to transfer operstate to
 *
 *      Transfer operational state from root to device. This is normally
 *      called when a stacking relationship exists between the root
 *      device and the device(a leaf device).
 */
void netif_stacked_transfer_operstate(const struct net_device *rootdev,
                                        struct net_device *dev)
{
        if (rootdev->operstate == IF_OPER_DORMANT)
                netif_dormant_on(dev);
        else
                netif_dormant_off(dev);

        if (netif_carrier_ok(rootdev))
                netif_carrier_on(dev);
        else
                netif_carrier_off(dev);
}
EXPORT_SYMBOL(netif_stacked_transfer_operstate);

#ifdef CONFIG_SYSFS
static int netif_alloc_rx_queues(struct net_device *dev)
{
        unsigned int i, count = dev->num_rx_queues;
        struct netdev_rx_queue *rx;
        size_t sz = count * sizeof(*rx);

        BUG_ON(count < 1);

        rx = kvzalloc(sz, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
        if (!rx)
                return -ENOMEM;

        dev->_rx = rx;

        for (i = 0; i < count; i++)
                rx[i].dev = dev;
        return 0;
}
#endif

static void netdev_init_one_queue(struct net_device *dev,
                                  struct netdev_queue *queue, void *_unused)
{
        /* Initialize queue lock */
        spin_lock_init(&queue->_xmit_lock);
        netdev_set_xmit_lockdep_class(&queue->_xmit_lock, dev->type);
        queue->xmit_lock_owner = -1;
        netdev_queue_numa_node_write(queue, NUMA_NO_NODE);
        queue->dev = dev;
#ifdef CONFIG_BQL
        dql_init(&queue->dql, HZ);
#endif
}

static void netif_free_tx_queues(struct net_device *dev)
{
        kvfree(dev->_tx);
}

static int netif_alloc_netdev_queues(struct net_device *dev)
{
        unsigned int count = dev->num_tx_queues;
        struct netdev_queue *tx;
        size_t sz = count * sizeof(*tx);

        if (count < 1 || count > 0xffff)
                return -EINVAL;

        tx = kvzalloc(sz, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
        if (!tx)
                return -ENOMEM;

        dev->_tx = tx;

        netdev_for_each_tx_queue(dev, netdev_init_one_queue, NULL);
        spin_lock_init(&dev->tx_global_lock);

        return 0;
}

void netif_tx_stop_all_queues(struct net_device *dev)
{
        unsigned int i;

        for (i = 0; i < dev->num_tx_queues; i++) {
                struct netdev_queue *txq = netdev_get_tx_queue(dev, i);

                netif_tx_stop_queue(txq);
        }
}
EXPORT_SYMBOL(netif_tx_stop_all_queues);

/**
 *      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)
{
        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);

        ret = dev_get_valid_name(net, dev, dev->name);
        if (ret < 0)
                goto out;

        /* 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->hw_features | dev->features) &
             NETIF_F_HW_VLAN_CTAG_FILTER) &&
            (!dev->netdev_ops->ndo_vlan_rx_add_vid ||
             !dev->netdev_ops->ndo_vlan_rx_kill_vid)) {
                netdev_WARN(dev, "Buggy VLAN acceleration in driver!\n");
                ret = -EINVAL;
                goto err_uninit;
        }

        ret = -EBUSY;
        if (!dev->ifindex)
                dev->ifindex = dev_new_index(net);
        else if (__dev_get_by_index(net, dev->ifindex))
                goto err_uninit;

        /* Transfer changeable features to wanted_features and enable
         * software offloads (GSO and GRO).
         */
        dev->hw_features |= NETIF_F_SOFT_FEATURES;
        dev->features |= NETIF_F_SOFT_FEATURES;

        if (dev->netdev_ops->ndo_udp_tunnel_add) {
                dev->features |= NETIF_F_RX_UDP_TUNNEL_PORT;
                dev->hw_features |= NETIF_F_RX_UDP_TUNNEL_PORT;
        }

        dev->wanted_features = dev->features & dev->hw_features;

        if (!(dev->flags & IFF_LOOPBACK))
                dev->hw_features |= NETIF_F_NOCACHE_COPY;

        /* If IPv4 TCP segmentation offload is supported we should also
         * allow the device to enable segmenting the frame with the option
         * of ignoring a static IP ID value.  This doesn't enable the
         * feature itself but allows the user to enable it later.
         */
        if (dev->hw_features & NETIF_F_TSO)
                dev->hw_features |= NETIF_F_TSO_MANGLEID;
        if (dev->vlan_features & NETIF_F_TSO)
                dev->vlan_features |= NETIF_F_TSO_MANGLEID;
        if (dev->mpls_features & NETIF_F_TSO)
                dev->mpls_features |= NETIF_F_TSO_MANGLEID;
        if (dev->hw_enc_features & NETIF_F_TSO)
                dev->hw_enc_features |= NETIF_F_TSO_MANGLEID;

        /* Make NETIF_F_HIGHDMA inheritable to VLAN devices.
         */
        dev->vlan_features |= NETIF_F_HIGHDMA;

        /* Make NETIF_F_SG inheritable to tunnel devices.
         */
        dev->hw_enc_features |= NETIF_F_SG | NETIF_F_GSO_PARTIAL;

        /* Make NETIF_F_SG inheritable to MPLS.
         */
        dev->mpls_features |= NETIF_F_SG;

        ret = call_netdevice_notifiers(NETDEV_POST_INIT, dev);
        ret = notifier_to_errno(ret);
        if (ret)
                goto err_uninit;

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

        __netdev_update_features(dev);

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

        set_bit(__LINK_STATE_PRESENT, &dev->state);

        linkwatch_init_dev(dev);

        dev_init_scheduler(dev);
        dev_hold(dev);
        list_netdevice(dev);
        add_device_randomness(dev->dev_addr, dev->addr_len);

        /* If the device has permanent device address, driver should
         * set dev_addr and also addr_assign_type should be set to
         * NET_ADDR_PERM (default value).
         */
        if (dev->addr_assign_type == NET_ADDR_PERM)
                memcpy(dev->perm_addr, dev->dev_addr, dev->addr_len);

        /* 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;
        }
        /*
         *      Prevent userspace races by waiting until the network
         *      device is fully setup before sending notifications.
         */
        if (!dev->rtnl_link_ops ||
            dev->rtnl_link_state == RTNL_LINK_INITIALIZED)
                rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U, GFP_KERNEL);

out:
        return ret;

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

/**
 *      init_dummy_netdev       - init a dummy network device for NAPI
 *      @dev: device to init
 *
 *      This takes a network device structure and initialize the minimum
 *      amount of fields so it can be used to schedule NAPI polls without
 *      registering a full blown interface. This is to be used by drivers
 *      that need to tie several hardware interfaces to a single NAPI
 *      poll scheduler due to HW limitations.
 */
int init_dummy_netdev(struct net_device *dev)
{
        /* Clear everything. Note we don't initialize spinlocks
         * are they aren't supposed to be taken by any of the
         * NAPI code and this dummy netdev is supposed to be
         * only ever used for NAPI polls
         */
        memset(dev, 0, sizeof(struct net_device));

        /* make sure we BUG if trying to hit standard
         * register/unregister code path
         */
        dev->reg_state = NETREG_DUMMY;

        /* NAPI wants this */
        INIT_LIST_HEAD(&dev->napi_list);

        /* a dummy interface is started by default */
        set_bit(__LINK_STATE_PRESENT, &dev->state);
        set_bit(__LINK_STATE_START, &dev->state);

        /* Note : We dont allocate pcpu_refcnt for dummy devices,
         * because users of this 'device' dont need to change
         * its refcount.
         */

        return 0;
}
EXPORT_SYMBOL_GPL(init_dummy_netdev);


/**
 *      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();
        err = register_netdevice(dev);
        rtnl_unlock();
        return err;
}
EXPORT_SYMBOL(register_netdev);

int netdev_refcnt_read(const struct net_device *dev)
{
        int i, refcnt = 0;

        for_each_possible_cpu(i)
                refcnt += *per_cpu_ptr(dev->pcpu_refcnt, i);
        return refcnt;
}
EXPORT_SYMBOL(netdev_refcnt_read);

/**
 * netdev_wait_allrefs - wait until all references are gone.
 * @dev: target net_device
 *
 * 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;
        int refcnt;

        linkwatch_forget_dev(dev);

        rebroadcast_time = warning_time = jiffies;
        refcnt = netdev_refcnt_read(dev);

        while (refcnt != 0) {
                if (time_after(jiffies, rebroadcast_time + 1 * HZ)) {
                        rtnl_lock();

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

                        __rtnl_unlock();
                        rcu_barrier();
                        rtnl_lock();

                        call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, 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);

                refcnt = netdev_refcnt_read(dev);

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


        /* Wait for rcu callbacks to finish before next phase */
        if (!list_empty(&list))
                rcu_barrier();

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

                rtnl_lock();
                call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
                __rtnl_unlock();

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

                dev->reg_state = NETREG_UNREGISTERED;

                netdev_wait_allrefs(dev);

                /* paranoia */
                BUG_ON(netdev_refcnt_read(dev));
                BUG_ON(!list_empty(&dev->ptype_all));
                BUG_ON(!list_empty(&dev->ptype_specific));
                WARN_ON(rcu_access_pointer(dev->ip_ptr));
                WARN_ON(rcu_access_pointer(dev->ip6_ptr));
                WARN_ON(dev->dn_ptr);

                if (dev->priv_destructor)
                        dev->priv_destructor(dev);
                if (dev->needs_free_netdev)
                        free_netdev(dev);

                /* Report a network device has been unregistered */
                rtnl_lock();
                dev_net(dev)->dev_unreg_count--;
                __rtnl_unlock();
                wake_up(&netdev_unregistering_wq);

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

/* Convert net_device_stats to rtnl_link_stats64. rtnl_link_stats64 has
 * all the same fields in the same order as net_device_stats, with only
 * the type differing, but rtnl_link_stats64 may have additional fields
 * at the end for newer counters.
 */
void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
                             const struct net_device_stats *netdev_stats)
{
#if BITS_PER_LONG == 64
        BUILD_BUG_ON(sizeof(*stats64) < sizeof(*netdev_stats));
        memcpy(stats64, netdev_stats, sizeof(*netdev_stats));
        /* zero out counters that only exist in rtnl_link_stats64 */
        memset((char *)stats64 + sizeof(*netdev_stats), 0,
               sizeof(*stats64) - sizeof(*netdev_stats));
#else
        size_t i, n = sizeof(*netdev_stats) / sizeof(unsigned long);
        const unsigned long *src = (const unsigned long *)netdev_stats;
        u64 *dst = (u64 *)stats64;

        BUILD_BUG_ON(n > sizeof(*stats64) / sizeof(u64));
        for (i = 0; i < n; i++)
                dst[i] = src[i];
        /* zero out counters that only exist in rtnl_link_stats64 */
        memset((char *)stats64 + n * sizeof(u64), 0,
               sizeof(*stats64) - n * sizeof(u64));
#endif
}
EXPORT_SYMBOL(netdev_stats_to_stats64);

/**
 *      dev_get_stats   - get network device statistics
 *      @dev: device to get statistics from
 *      @storage: place to store stats
 *
 *      Get network statistics from device. Return @storage.
 *      The device driver may provide its own method by setting
 *      dev->netdev_ops->get_stats64 or dev->netdev_ops->get_stats;
 *      otherwise the internal statistics structure is used.
 */
struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
                                        struct rtnl_link_stats64 *storage)
{
        const struct net_device_ops *ops = dev->netdev_ops;

        if (ops->ndo_get_stats64) {
                memset(storage, 0, sizeof(*storage));
                ops->ndo_get_stats64(dev, storage);
        } else if (ops->ndo_get_stats) {
                netdev_stats_to_stats64(storage, ops->ndo_get_stats(dev));
        } else {
                netdev_stats_to_stats64(storage, &dev->stats);
        }
        storage->rx_dropped += (unsigned long)atomic_long_read(&dev->rx_dropped);
        storage->tx_dropped += (unsigned long)atomic_long_read(&dev->tx_dropped);
        storage->rx_nohandler += (unsigned long)atomic_long_read(&dev->rx_nohandler);
        return storage;
}
EXPORT_SYMBOL(dev_get_stats);

struct netdev_queue *dev_ingress_queue_create(struct net_device *dev)
{
        struct netdev_queue *queue = dev_ingress_queue(dev);

#ifdef CONFIG_NET_CLS_ACT
        if (queue)
                return queue;
        queue = kzalloc(sizeof(*queue), GFP_KERNEL);
        if (!queue)
                return NULL;
        netdev_init_one_queue(dev, queue, NULL);
        RCU_INIT_POINTER(queue->qdisc, &noop_qdisc);
        queue->qdisc_sleeping = &noop_qdisc;
        rcu_assign_pointer(dev->ingress_queue, queue);
#endif
        return queue;
}

static const struct ethtool_ops default_ethtool_ops;

void netdev_set_default_ethtool_ops(struct net_device *dev,
                                    const struct ethtool_ops *ops)
{
        if (dev->ethtool_ops == &default_ethtool_ops)
                dev->ethtool_ops = ops;
}
EXPORT_SYMBOL_GPL(netdev_set_default_ethtool_ops);

void netdev_freemem(struct net_device *dev)
{
        char *addr = (char *)dev - dev->padded;

        kvfree(addr);
}

/**
 * alloc_netdev_mqs - allocate network device
 * @sizeof_priv: size of private data to allocate space for
 * @name: device name format string
 * @name_assign_type: origin of device name
 * @setup: callback to initialize device
 * @txqs: the number of TX subqueues to allocate
 * @rxqs: the number of RX subqueues to allocate
 *
 * Allocates a struct net_device with private data area for driver use
 * and performs basic initialization.  Also allocates subqueue structs
 * for each queue on the device.
 */
struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
                unsigned char name_assign_type,
                void (*setup)(struct net_device *),
                unsigned int txqs, unsigned int rxqs)
{
        struct net_device *dev;
        size_t alloc_size;
        struct net_device *p;

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

        if (txqs < 1) {
                pr_err("alloc_netdev: Unable to allocate device with zero queues\n");
                return NULL;
        }

#ifdef CONFIG_SYSFS
        if (rxqs < 1) {
                pr_err("alloc_netdev: Unable to allocate device with zero RX queues\n");
                return NULL;
        }
#endif

        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 = kvzalloc(alloc_size, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
        if (!p)
                return NULL;

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

        dev->pcpu_refcnt = alloc_percpu(int);
        if (!dev->pcpu_refcnt)
                goto free_dev;

        if (dev_addr_init(dev))
                goto free_pcpu;

        dev_mc_init(dev);
        dev_uc_init(dev);

        dev_net_set(dev, &init_net);

        dev->gso_max_size = GSO_MAX_SIZE;
        dev->gso_max_segs = GSO_MAX_SEGS;

        INIT_LIST_HEAD(&dev->napi_list);
        INIT_LIST_HEAD(&dev->unreg_list);
        INIT_LIST_HEAD(&dev->close_list);
        INIT_LIST_HEAD(&dev->link_watch_list);
        INIT_LIST_HEAD(&dev->adj_list.upper);
        INIT_LIST_HEAD(&dev->adj_list.lower);
        INIT_LIST_HEAD(&dev->ptype_all);
        INIT_LIST_HEAD(&dev->ptype_specific);
#ifdef CONFIG_NET_SCHED
        hash_init(dev->qdisc_hash);
#endif
        dev->priv_flags = IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM;
        setup(dev);

        if (!dev->tx_queue_len) {
                dev->priv_flags |= IFF_NO_QUEUE;
                dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
        }

        dev->num_tx_queues = txqs;
        dev->real_num_tx_queues = txqs;
        if (netif_alloc_netdev_queues(dev))
                goto free_all;

#ifdef CONFIG_SYSFS
        dev->num_rx_queues = rxqs;
        dev->real_num_rx_queues = rxqs;
        if (netif_alloc_rx_queues(dev))
                goto free_all;
#endif

        strcpy(dev->name, name);
        dev->name_assign_type = name_assign_type;
        dev->group = INIT_NETDEV_GROUP;
        if (!dev->ethtool_ops)
                dev->ethtool_ops = &default_ethtool_ops;

        nf_hook_ingress_init(dev);

        return dev;

free_all:
        free_netdev(dev);
        return NULL;

free_pcpu:
        free_percpu(dev->pcpu_refcnt);
free_dev:
        netdev_freemem(dev);
        return NULL;
}
EXPORT_SYMBOL(alloc_netdev_mqs);

/**
 * 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.Must be called in process
 * context.
 */
void free_netdev(struct net_device *dev)
{
        struct napi_struct *p, *n;
        struct bpf_prog *prog;

        might_sleep();
        netif_free_tx_queues(dev);
#ifdef CONFIG_SYSFS
        kvfree(dev->_rx);
#endif

        kfree(rcu_dereference_protected(dev->ingress_queue, 1));

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

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

        free_percpu(dev->pcpu_refcnt);
        dev->pcpu_refcnt = NULL;

        prog = rcu_dereference_protected(dev->xdp_prog, 1);
        if (prog) {
                bpf_prog_put(prog);
                static_key_slow_dec(&generic_xdp_needed);
        }

        /*  Compatibility with error handling in drivers */
        if (dev->reg_state == NETREG_UNINITIALIZED) {
                netdev_freemem(dev);
                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();
        if (rtnl_is_locked())
                synchronize_rcu_expedited();
        else
                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
 *
 *  Note: As most callers use a stack allocated list_head,
 *  we force a list_del() to make sure stack wont be corrupted later.
 */
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);
                list_del(head);
        }
}
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;

        /* Ensure the device has been registrered */
        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, dev, pat) < 0)
                        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.
         *
         * Note that dev->reg_state stays at NETREG_REGISTERED.
         * This is wanted because this way 8021q and macvlan know
         * the device is just moving and can keep their slaves up.
         */
        call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
        rcu_barrier();
        call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
        rtmsg_ifinfo(RTM_DELLINK, dev, ~0U, GFP_KERNEL);

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

        /* Send a netdev-removed uevent to the old namespace */
        kobject_uevent(&dev->dev.kobj, KOBJ_REMOVE);
        netdev_adjacent_del_links(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))
                dev->ifindex = dev_new_index(net);

        /* Send a netdev-add uevent to the new namespace */
        kobject_uevent(&dev->dev.kobj, KOBJ_ADD);
        netdev_adjacent_add_links(dev);

        /* Fixup kobjects */
        err = device_rename(&dev->dev, dev->name);
        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, GFP_KERNEL);

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

static int dev_cpu_dead(unsigned int oldcpu)
{
        struct sk_buff **list_skb;
        struct sk_buff *skb;
        unsigned int cpu;
        struct softnet_data *sd, *oldsd, *remsd = NULL;

        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;

        /* Append output queue from offline CPU. */
        if (oldsd->output_queue) {
                *sd->output_queue_tailp = oldsd->output_queue;
                sd->output_queue_tailp = oldsd->output_queue_tailp;
                oldsd->output_queue = NULL;
                oldsd->output_queue_tailp = &oldsd->output_queue;
        }
        /* Append NAPI poll list from offline CPU, with one exception :
         * process_backlog() must be called by cpu owning percpu backlog.
         * We properly handle process_queue & input_pkt_queue later.
         */
        while (!list_empty(&oldsd->poll_list)) {
                struct napi_struct *napi = list_first_entry(&oldsd->poll_list,
                                                            struct napi_struct,
                                                            poll_list);

                list_del_init(&napi->poll_list);
                if (napi->poll == process_backlog)
                        napi->state = 0;
                else
                        ____napi_schedule(sd, napi);
        }

        raise_softirq_irqoff(NET_TX_SOFTIRQ);
        local_irq_enable();

#ifdef CONFIG_RPS
        remsd = oldsd->rps_ipi_list;
        oldsd->rps_ipi_list = NULL;
#endif
        /* send out pending IPI's on offline CPU */
        net_rps_send_ipi(remsd);

        /* Process offline CPU's input_pkt_queue */
        while ((skb = __skb_dequeue(&oldsd->process_queue))) {
                netif_rx_ni(skb);
                input_queue_head_incr(oldsd);
        }
        while ((skb = skb_dequeue(&oldsd->input_pkt_queue))) {
                netif_rx_ni(skb);
                input_queue_head_incr(oldsd);
        }

        return 0;
}

/**
 *      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.
 */
netdev_features_t netdev_increment_features(netdev_features_t all,
        netdev_features_t one, netdev_features_t mask)
{
        if (mask & NETIF_F_HW_CSUM)
                mask |= NETIF_F_CSUM_MASK;
        mask |= NETIF_F_VLAN_CHALLENGED;

        all |= one & (NETIF_F_ONE_FOR_ALL | NETIF_F_CSUM_MASK) & mask;
        all &= one | ~NETIF_F_ALL_FOR_ALL;

        /* If one device supports hw checksumming, set for all. */
        if (all & NETIF_F_HW_CSUM)
                all &= ~(NETIF_F_CSUM_MASK & ~NETIF_F_HW_CSUM);

        return all;
}
EXPORT_SYMBOL(netdev_increment_features);

static struct hlist_head * __net_init 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)
{
        if (net != &init_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
 *
 *      Determine network driver for device.
 */
const char *netdev_drivername(const struct net_device *dev)
{
        const struct device_driver *driver;
        const struct device *parent;
        const char *empty = "";

        parent = dev->dev.parent;
        if (!parent)
                return empty;

        driver = parent->driver;
        if (driver && driver->name)
                return driver->name;
        return empty;
}

static void __netdev_printk(const char *level, const struct net_device *dev,
                            struct va_format *vaf)
{
        if (dev && dev->dev.parent) {
                dev_printk_emit(level[1] - '0',
                                dev->dev.parent,
                                "%s %s %s%s: %pV",
                                dev_driver_string(dev->dev.parent),
                                dev_name(dev->dev.parent),
                                netdev_name(dev), netdev_reg_state(dev),
                                vaf);
        } else if (dev) {
                printk("%s%s%s: %pV",
                       level, netdev_name(dev), netdev_reg_state(dev), vaf);
        } else {
                printk("%s(NULL net_device): %pV", level, vaf);
        }
}

void netdev_printk(const char *level, const struct net_device *dev,
                   const char *format, ...)
{
        struct va_format vaf;
        va_list args;

        va_start(args, format);

        vaf.fmt = format;
        vaf.va = &args;

        __netdev_printk(level, dev, &vaf);

        va_end(args);
}
EXPORT_SYMBOL(netdev_printk);

#define define_netdev_printk_level(func, level)                 \
void func(const struct net_device *dev, const char *fmt, ...)   \
{                                                               \
        struct va_format vaf;                                   \
        va_list args;                                           \
                                                                \
        va_start(args, fmt);                                    \
                                                                \
        vaf.fmt = fmt;                                          \
        vaf.va = &args;                                         \
                                                                \
        __netdev_printk(level, dev, &vaf);                      \
                                                                \
        va_end(args);                                           \
}                                                               \
EXPORT_SYMBOL(func);

define_netdev_printk_level(netdev_emerg, KERN_EMERG);
define_netdev_printk_level(netdev_alert, KERN_ALERT);
define_netdev_printk_level(netdev_crit, KERN_CRIT);
define_netdev_printk_level(netdev_err, KERN_ERR);
define_netdev_printk_level(netdev_warn, KERN_WARNING);
define_netdev_printk_level(netdev_notice, KERN_NOTICE);
define_netdev_printk_level(netdev_info, KERN_INFO);

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 remaining 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) {
                        pr_emerg("%s: failed to move %s to init_net: %d\n",
                                 __func__, dev->name, err);
                        BUG();
                }
        }
        rtnl_unlock();
}

static void __net_exit rtnl_lock_unregistering(struct list_head *net_list)
{
        /* Return with the rtnl_lock held when there are no network
         * devices unregistering in any network namespace in net_list.
         */
        struct net *net;
        bool unregistering;
        DEFINE_WAIT_FUNC(wait, woken_wake_function);

        add_wait_queue(&netdev_unregistering_wq, &wait);
        for (;;) {
                unregistering = false;
                rtnl_lock();
                list_for_each_entry(net, net_list, exit_list) {
                        if (net->dev_unreg_count > 0) {
                                unregistering = true;
                                break;
                        }
                }
                if (!unregistering)
                        break;
                __rtnl_unlock();

                wait_woken(&wait, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
        }
        remove_wait_queue(&netdev_unregistering_wq, &wait);
}

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 registration.
         * 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);

        /* To prevent network device cleanup code from dereferencing
         * loopback devices or network devices that have been freed
         * wait here for all pending unregistrations to complete,
         * before unregistring the loopback device and allowing the
         * network namespace be freed.
         *
         * The netdev todo list containing all network devices
         * unregistrations that happen in default_device_exit_batch
         * will run in the rtnl_unlock() at the end of
         * default_device_exit_batch.
         */
        rtnl_lock_unregistering(net_list);
        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->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]);

        INIT_LIST_HEAD(&offload_base);

        if (register_pernet_subsys(&netdev_net_ops))
                goto out;

        /*
         *      Initialise the packet receive queues.
         */

        for_each_possible_cpu(i) {
                struct work_struct *flush = per_cpu_ptr(&flush_works, i);
                struct softnet_data *sd = &per_cpu(softnet_data, i);

                INIT_WORK(flush, flush_backlog);

                skb_queue_head_init(&sd->input_pkt_queue);
                skb_queue_head_init(&sd->process_queue);
                INIT_LIST_HEAD(&sd->poll_list);
                sd->output_queue_tailp = &sd->output_queue;
#ifdef CONFIG_RPS
                sd->csd.func = rps_trigger_softirq;
                sd->csd.info = sd;
                sd->cpu = i;
#endif

                sd->backlog.poll = process_backlog;
                sd->backlog.weight = weight_p;
        }

        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);

        rc = cpuhp_setup_state_nocalls(CPUHP_NET_DEV_DEAD, "net/dev:dead",
                                       NULL, dev_cpu_dead);
        WARN_ON(rc < 0);
        rc = 0;
out:
        return rc;
}

subsys_initcall(net_dev_init);