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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  TUN - Universal TUN/TAP device driver.
  *  Copyright (C) 1999-2002 Maxim Krasnyansky <maxk@qualcomm.com>
  *
  *  $Id: tun.c,v 1.15 2002/03/01 02:44:24 maxk Exp $
  */
 
 /*
  *  Changes:
  *
  *  Mike Kershaw <dragorn@kismetwireless.net> 2005/08/14
  *    Add TUNSETLINK ioctl to set the link encapsulation
  *
  *  Mark Smith <markzzzsmith@yahoo.com.au>
  *    Use eth_random_addr() for tap MAC address.
  *
  *  Harald Roelle <harald.roelle@ifi.lmu.de>  2004/04/20
  *    Fixes in packet dropping, queue length setting and queue wakeup.
  *    Increased default tx queue length.
  *    Added ethtool API.
  *    Minor cleanups
  *
  *  Daniel Podlejski <underley@underley.eu.org>
  *    Modifications for 2.3.99-pre5 kernel.
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #define DRV_NAME    "tun"
 #define DRV_VERSION "1.6"
 #define DRV_DESCRIPTION "Universal TUN/TAP device driver"
 #define DRV_COPYRIGHT   "(C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>"
 
 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/sched/signal.h>
 #include <linux/major.h>
 #include <linux/slab.h>
 #include <linux/poll.h>
 #include <linux/fcntl.h>
 #include <linux/init.h>
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/miscdevice.h>
 #include <linux/ethtool.h>
 #include <linux/rtnetlink.h>
 #include <linux/compat.h>
 #include <linux/if.h>
 #include <linux/if_arp.h>
 #include <linux/if_ether.h>
 #include <linux/if_tun.h>
 #include <linux/if_vlan.h>
 #include <linux/crc32.h>
 #include <linux/nsproxy.h>
 #include <linux/virtio_net.h>
 #include <linux/rcupdate.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
 #include <net/sock.h>
 #include <net/xdp.h>
 #include <net/ip_tunnels.h>
 #include <linux/seq_file.h>
 #include <linux/uio.h>
 #include <linux/skb_array.h>
 #include <linux/bpf.h>
 #include <linux/bpf_trace.h>
 #include <linux/mutex.h>
 #include <linux/ieee802154.h>
 #include <linux/if_ltalk.h>
 #include <uapi/linux/if_fddi.h>
 #include <uapi/linux/if_hippi.h>
 #include <uapi/linux/if_fc.h>
 #include <net/ax25.h>
 #include <net/rose.h>
 #include <net/6lowpan.h>
 
 #include <linux/uaccess.h>
 #include <linux/proc_fs.h>
 
 static void tun_default_link_ksettings(struct net_device *dev,
                        struct ethtool_link_ksettings *cmd);
 
 #define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
 
 /* TUN device flags */
 
 /* IFF_ATTACH_QUEUE is never stored in device flags,
  * overload it to mean fasync when stored there.
  */
 #define TUN_FASYNC  IFF_ATTACH_QUEUE
 /* High bits in flags field are unused. */
 #define TUN_VNET_LE     0x80000000
 #define TUN_VNET_BE     0x40000000
 
 #define TUN_FEATURES (IFF_NO_PI | IFF_ONE_QUEUE | IFF_VNET_HDR | \
               IFF_MULTI_QUEUE | IFF_NAPI | IFF_NAPI_FRAGS)
 
 #define GOODCOPY_LEN 128
 
 #define FLT_EXACT_COUNT 8
 struct tap_filter {
     unsigned int    count;    /* Number of addrs. Zero means disabled */
     u32             mask[2];  /* Mask of the hashed addrs */
     unsigned char   addr[FLT_EXACT_COUNT][ETH_ALEN];
 };
 
 /* MAX_TAP_QUEUES 256 is chosen to allow rx/tx queues to be equal
  * to max number of VCPUs in guest. */
 #define MAX_TAP_QUEUES 256
 #define MAX_TAP_FLOWS  4096
 
 #define TUN_FLOW_EXPIRE (3 * HZ)
 
 /* A tun_file connects an open character device to a tuntap netdevice. It
  * also contains all socket related structures (except sock_fprog and tap_filter)
  * to serve as one transmit queue for tuntap device. The sock_fprog and
  * tap_filter were kept in tun_struct since they were used for filtering for the
  * netdevice not for a specific queue (at least I didn't see the requirement for
  * this).
  *
  * RCU usage:
  * The tun_file and tun_struct are loosely coupled, the pointer from one to the
  * other can only be read while rcu_read_lock or rtnl_lock is held.
  */
 struct tun_file {
     struct sock sk;
     struct socket socket;
     struct tun_struct __rcu *tun;
     struct fasync_struct *fasync;
     /* only used for fasnyc */
     unsigned int flags;
     union {
         u16 queue_index;
         unsigned int ifindex;
     };
     struct napi_struct napi;
     bool napi_enabled;
     bool napi_frags_enabled;
     struct mutex napi_mutex;    /* Protects access to the above napi */
     struct list_head next;
     struct tun_struct *detached;
     struct ptr_ring tx_ring;
     struct xdp_rxq_info xdp_rxq;
 };
 
 struct tun_page {
     struct page *page;
     int count;
 };
 
 struct tun_flow_entry {
     struct hlist_node hash_link;
     struct rcu_head rcu;
     struct tun_struct *tun;
 
     u32 rxhash;
     u32 rps_rxhash;
     int queue_index;
     unsigned long updated ____cacheline_aligned_in_smp;
 };
 
 #define TUN_NUM_FLOW_ENTRIES 1024
 #define TUN_MASK_FLOW_ENTRIES (TUN_NUM_FLOW_ENTRIES - 1)
 
 struct tun_prog {
     struct rcu_head rcu;
     struct bpf_prog *prog;
 };
 
 /* Since the socket were moved to tun_file, to preserve the behavior of persist
  * device, socket filter, sndbuf and vnet header size were restore when the
  * file were attached to a persist device.
  */
 struct tun_struct {
     struct tun_file __rcu   *tfiles[MAX_TAP_QUEUES];
     unsigned int            numqueues;
     unsigned int        flags;
     kuid_t          owner;
     kgid_t          group;
 
     struct net_device   *dev;
     netdev_features_t   set_features;
 #define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
               NETIF_F_TSO6)
 
     int         align;
     int         vnet_hdr_sz;
     int         sndbuf;
     struct tap_filter   txflt;
     struct sock_fprog   fprog;
     /* protected by rtnl lock */
     bool            filter_attached;
     u32         msg_enable;
     spinlock_t lock;
     struct hlist_head flows[TUN_NUM_FLOW_ENTRIES];
     struct timer_list flow_gc_timer;
     unsigned long ageing_time;
     unsigned int numdisabled;
     struct list_head disabled;
     void *security;
     u32 flow_count;
     u32 rx_batched;
     atomic_long_t rx_frame_errors;
     struct bpf_prog __rcu *xdp_prog;
     struct tun_prog __rcu *steering_prog;
     struct tun_prog __rcu *filter_prog;
     struct ethtool_link_ksettings link_ksettings;
     /* init args */
     struct file *file;
     struct ifreq *ifr;
 };
 
 struct veth {
     __be16 h_vlan_proto;
     __be16 h_vlan_TCI;
 };
 
 static void tun_flow_init(struct tun_struct *tun);
 static void tun_flow_uninit(struct tun_struct *tun);
 
 static int tun_napi_receive(struct napi_struct *napi, int budget)
 {
     struct tun_file *tfile = container_of(napi, struct tun_file, napi);
     struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
     struct sk_buff_head process_queue;
     struct sk_buff *skb;
     int received = 0;
 
     __skb_queue_head_init(&process_queue);
 
     spin_lock(&queue->lock);
     skb_queue_splice_tail_init(queue, &process_queue);
     spin_unlock(&queue->lock);
 
     while (received < budget && (skb = __skb_dequeue(&process_queue))) {
         napi_gro_receive(napi, skb);
         ++received;
     }
 
     if (!skb_queue_empty(&process_queue)) {
         spin_lock(&queue->lock);
         skb_queue_splice(&process_queue, queue);
         spin_unlock(&queue->lock);
     }
 
     return received;
 }
 
 static int tun_napi_poll(struct napi_struct *napi, int budget)
 {
     unsigned int received;
 
     received = tun_napi_receive(napi, budget);
 
     if (received < budget)
         napi_complete_done(napi, received);
 
     return received;
 }
 
 static void tun_napi_init(struct tun_struct *tun, struct tun_file *tfile,
               bool napi_en, bool napi_frags)
 {
     tfile->napi_enabled = napi_en;
     tfile->napi_frags_enabled = napi_en && napi_frags;
     if (napi_en) {
         netif_napi_add_tx(tun->dev, &tfile->napi, tun_napi_poll);
         napi_enable(&tfile->napi);
     }
 }
 
 static void tun_napi_enable(struct tun_file *tfile)
 {
     if (tfile->napi_enabled)
         napi_enable(&tfile->napi);
 }
 
 static void tun_napi_disable(struct tun_file *tfile)
 {
     if (tfile->napi_enabled)
         napi_disable(&tfile->napi);
 }
 
 static void tun_napi_del(struct tun_file *tfile)
 {
     if (tfile->napi_enabled)
         netif_napi_del(&tfile->napi);
 }
 
 static bool tun_napi_frags_enabled(const struct tun_file *tfile)
 {
     return tfile->napi_frags_enabled;
 }
 
 #ifdef CONFIG_TUN_VNET_CROSS_LE
 static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
 {
     return tun->flags & TUN_VNET_BE ? false :
         virtio_legacy_is_little_endian();
 }
 
 static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
 {
     int be = !!(tun->flags & TUN_VNET_BE);
 
     if (put_user(be, argp))
         return -EFAULT;
 
     return 0;
 }
 
 static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
 {
     int be;
 
     if (get_user(be, argp))
         return -EFAULT;
 
     if (be)
         tun->flags |= TUN_VNET_BE;
     else
         tun->flags &= ~TUN_VNET_BE;
 
     return 0;
 }
 #else
 static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
 {
     return virtio_legacy_is_little_endian();
 }
 
 static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
 {
     return -EINVAL;
 }
 
 static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
 {
     return -EINVAL;
 }
 #endif /* CONFIG_TUN_VNET_CROSS_LE */
 
 static inline bool tun_is_little_endian(struct tun_struct *tun)
 {
     return tun->flags & TUN_VNET_LE ||
         tun_legacy_is_little_endian(tun);
 }
 
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
 {
     return __virtio16_to_cpu(tun_is_little_endian(tun), val);
 }
 
 static inline __virtio16 cpu_to_tun16(struct tun_struct *tun, u16 val)
 {
     return __cpu_to_virtio16(tun_is_little_endian(tun), val);
 }
 
 static inline u32 tun_hashfn(u32 rxhash)
 {
     return rxhash & TUN_MASK_FLOW_ENTRIES;
 }
 
 static struct tun_flow_entry *tun_flow_find(struct hlist_head *head, u32 rxhash)
 {
     struct tun_flow_entry *e;
 
     hlist_for_each_entry_rcu(e, head, hash_link) {
         if (e->rxhash == rxhash)
             return e;
     }
     return NULL;
 }
 
 static struct tun_flow_entry *tun_flow_create(struct tun_struct *tun,
                           struct hlist_head *head,
                           u32 rxhash, u16 queue_index)
 {
     struct tun_flow_entry *e = kmalloc(sizeof(*e), GFP_ATOMIC);
 
     if (e) {
         netif_info(tun, tx_queued, tun->dev,
                "create flow: hash %u index %u\n",
                rxhash, queue_index);
         e->updated = jiffies;
         e->rxhash = rxhash;
         e->rps_rxhash = 0;
         e->queue_index = queue_index;
         e->tun = tun;
         hlist_add_head_rcu(&e->hash_link, head);
         ++tun->flow_count;
     }
     return e;
 }
 
 static void tun_flow_delete(struct tun_struct *tun, struct tun_flow_entry *e)
 {
     netif_info(tun, tx_queued, tun->dev, "delete flow: hash %u index %u\n",
            e->rxhash, e->queue_index);
     hlist_del_rcu(&e->hash_link);
     kfree_rcu(e, rcu);
     --tun->flow_count;
 }
 
 static void tun_flow_flush(struct tun_struct *tun)
 {
     int i;
 
     spin_lock_bh(&tun->lock);
     for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
         struct tun_flow_entry *e;
         struct hlist_node *n;
 
         hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link)
             tun_flow_delete(tun, e);
     }
     spin_unlock_bh(&tun->lock);
 }
 
 static void tun_flow_delete_by_queue(struct tun_struct *tun, u16 queue_index)
 {
     int i;
 
     spin_lock_bh(&tun->lock);
     for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
         struct tun_flow_entry *e;
         struct hlist_node *n;
 
         hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link) {
             if (e->queue_index == queue_index)
                 tun_flow_delete(tun, e);
         }
     }
     spin_unlock_bh(&tun->lock);
 }
 
 static void tun_flow_cleanup(struct timer_list *t)
 {
     struct tun_struct *tun = from_timer(tun, t, flow_gc_timer);
     unsigned long delay = tun->ageing_time;
     unsigned long next_timer = jiffies + delay;
     unsigned long count = 0;
     int i;
 
     spin_lock(&tun->lock);
     for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
         struct tun_flow_entry *e;
         struct hlist_node *n;
 
         hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link) {
             unsigned long this_timer;
 
             this_timer = e->updated + delay;
             if (time_before_eq(this_timer, jiffies)) {
                 tun_flow_delete(tun, e);
                 continue;
             }
             count++;
             if (time_before(this_timer, next_timer))
                 next_timer = this_timer;
         }
     }
 
     if (count)
         mod_timer(&tun->flow_gc_timer, round_jiffies_up(next_timer));
     spin_unlock(&tun->lock);
 }
 
 static void tun_flow_update(struct tun_struct *tun, u32 rxhash,
                 struct tun_file *tfile)
 {
     struct hlist_head *head;
     struct tun_flow_entry *e;
     unsigned long delay = tun->ageing_time;
     u16 queue_index = tfile->queue_index;
 
     head = &tun->flows[tun_hashfn(rxhash)];
 
     rcu_read_lock();
 
     e = tun_flow_find(head, rxhash);
     if (likely(e)) {
         /* TODO: keep queueing to old queue until it's empty? */
         if (READ_ONCE(e->queue_index) != queue_index)
             WRITE_ONCE(e->queue_index, queue_index);
         if (e->updated != jiffies)
             e->updated = jiffies;
         sock_rps_record_flow_hash(e->rps_rxhash);
     } else {
         spin_lock_bh(&tun->lock);
         if (!tun_flow_find(head, rxhash) &&
             tun->flow_count < MAX_TAP_FLOWS)
             tun_flow_create(tun, head, rxhash, queue_index);
 
         if (!timer_pending(&tun->flow_gc_timer))
             mod_timer(&tun->flow_gc_timer,
                   round_jiffies_up(jiffies + delay));
         spin_unlock_bh(&tun->lock);
     }
 
     rcu_read_unlock();
 }
 
 /* Save the hash received in the stack receive path and update the
  * flow_hash table accordingly.
  */
 static inline void tun_flow_save_rps_rxhash(struct tun_flow_entry *e, u32 hash)
 {
     if (unlikely(e->rps_rxhash != hash))
         e->rps_rxhash = hash;
 }
 
 /* We try to identify a flow through its rxhash. The reason that
  * we do not check rxq no. is because some cards(e.g 82599), chooses
  * the rxq based on the txq where the last packet of the flow comes. As
  * the userspace application move between processors, we may get a
  * different rxq no. here.
  */
 static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb)
 {
     struct tun_flow_entry *e;
     u32 txq = 0;
     u32 numqueues = 0;
 
     numqueues = READ_ONCE(tun->numqueues);
 
     txq = __skb_get_hash_symmetric(skb);
     e = tun_flow_find(&tun->flows[tun_hashfn(txq)], txq);
     if (e) {
         tun_flow_save_rps_rxhash(e, txq);
         txq = e->queue_index;
     } else {
         /* use multiply and shift instead of expensive divide */
         txq = ((u64)txq * numqueues) >> 32;
     }
 
     return txq;
 }
 
 static u16 tun_ebpf_select_queue(struct tun_struct *tun, struct sk_buff *skb)
 {
     struct tun_prog *prog;
     u32 numqueues;
     u16 ret = 0;
 
     numqueues = READ_ONCE(tun->numqueues);
     if (!numqueues)
         return 0;
 
     prog = rcu_dereference(tun->steering_prog);
     if (prog)
         ret = bpf_prog_run_clear_cb(prog->prog, skb);
 
     return ret % numqueues;
 }
 
 static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb,
                 struct net_device *sb_dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
     u16 ret;
 
     rcu_read_lock();
     if (rcu_dereference(tun->steering_prog))
         ret = tun_ebpf_select_queue(tun, skb);
     else
         ret = tun_automq_select_queue(tun, skb);
     rcu_read_unlock();
 
     return ret;
 }
 
 static inline bool tun_not_capable(struct tun_struct *tun)
 {
     const struct cred *cred = current_cred();
     struct net *net = dev_net(tun->dev);
 
     return ((uid_valid(tun->owner) && !uid_eq(cred->euid, tun->owner)) ||
           (gid_valid(tun->group) && !in_egroup_p(tun->group))) &&
         !ns_capable(net->user_ns, CAP_NET_ADMIN);
 }
 
 static void tun_set_real_num_queues(struct tun_struct *tun)
 {
     netif_set_real_num_tx_queues(tun->dev, tun->numqueues);
     netif_set_real_num_rx_queues(tun->dev, tun->numqueues);
 }
 
 static void tun_disable_queue(struct tun_struct *tun, struct tun_file *tfile)
 {
     tfile->detached = tun;
     list_add_tail(&tfile->next, &tun->disabled);
     ++tun->numdisabled;
 }
 
 static struct tun_struct *tun_enable_queue(struct tun_file *tfile)
 {
     struct tun_struct *tun = tfile->detached;
 
     tfile->detached = NULL;
     list_del_init(&tfile->next);
     --tun->numdisabled;
     return tun;
 }
 
 void tun_ptr_free(void *ptr)
 {
     if (!ptr)
         return;
     if (tun_is_xdp_frame(ptr)) {
         struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
 
         xdp_return_frame(xdpf);
     } else {
         __skb_array_destroy_skb(ptr);
     }
 }
 EXPORT_SYMBOL_GPL(tun_ptr_free);
 
 static void tun_queue_purge(struct tun_file *tfile)
 {
     void *ptr;
 
     while ((ptr = ptr_ring_consume(&tfile->tx_ring)) != NULL)
         tun_ptr_free(ptr);
 
     skb_queue_purge(&tfile->sk.sk_write_queue);
     skb_queue_purge(&tfile->sk.sk_error_queue);
 }
 
 static void __tun_detach(struct tun_file *tfile, bool clean)
 {
     struct tun_file *ntfile;
     struct tun_struct *tun;
 
     tun = rtnl_dereference(tfile->tun);
 
     if (tun && clean) {
         if (!tfile->detached)
             tun_napi_disable(tfile);
         tun_napi_del(tfile);
     }
 
     if (tun && !tfile->detached) {
         u16 index = tfile->queue_index;
         BUG_ON(index >= tun->numqueues);
 
         rcu_assign_pointer(tun->tfiles[index],
                    tun->tfiles[tun->numqueues - 1]);
         ntfile = rtnl_dereference(tun->tfiles[index]);
         ntfile->queue_index = index;
         rcu_assign_pointer(tun->tfiles[tun->numqueues - 1],
                    NULL);
 
         --tun->numqueues;
         if (clean) {
             RCU_INIT_POINTER(tfile->tun, NULL);
             sock_put(&tfile->sk);
         } else {
             tun_disable_queue(tun, tfile);
             tun_napi_disable(tfile);
         }
 
         synchronize_net();
         tun_flow_delete_by_queue(tun, tun->numqueues + 1);
         /* Drop read queue */
         tun_queue_purge(tfile);
         tun_set_real_num_queues(tun);
     } else if (tfile->detached && clean) {
         tun = tun_enable_queue(tfile);
         sock_put(&tfile->sk);
     }
 
     if (clean) {
         if (tun && tun->numqueues == 0 && tun->numdisabled == 0) {
             netif_carrier_off(tun->dev);
 
             if (!(tun->flags & IFF_PERSIST) &&
                 tun->dev->reg_state == NETREG_REGISTERED)
                 unregister_netdevice(tun->dev);
         }
         if (tun)
             xdp_rxq_info_unreg(&tfile->xdp_rxq);
         ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
         sock_put(&tfile->sk);
     }
 }
 
 static void tun_detach(struct tun_file *tfile, bool clean)
 {
     struct tun_struct *tun;
     struct net_device *dev;
 
     rtnl_lock();
     tun = rtnl_dereference(tfile->tun);
     dev = tun ? tun->dev : NULL;
     __tun_detach(tfile, clean);
     if (dev)
         netdev_state_change(dev);
     rtnl_unlock();
 }
 
 static void tun_detach_all(struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
     struct tun_file *tfile, *tmp;
     int i, n = tun->numqueues;
 
     for (i = 0; i < n; i++) {
         tfile = rtnl_dereference(tun->tfiles[i]);
         BUG_ON(!tfile);
         tun_napi_disable(tfile);
         tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN;
         tfile->socket.sk->sk_data_ready(tfile->socket.sk);
         RCU_INIT_POINTER(tfile->tun, NULL);
         --tun->numqueues;
     }
     list_for_each_entry(tfile, &tun->disabled, next) {
         tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN;
         tfile->socket.sk->sk_data_ready(tfile->socket.sk);
         RCU_INIT_POINTER(tfile->tun, NULL);
     }
     BUG_ON(tun->numqueues != 0);
 
     synchronize_net();
     for (i = 0; i < n; i++) {
         tfile = rtnl_dereference(tun->tfiles[i]);
         tun_napi_del(tfile);
         /* Drop read queue */
         tun_queue_purge(tfile);
         xdp_rxq_info_unreg(&tfile->xdp_rxq);
         sock_put(&tfile->sk);
     }
     list_for_each_entry_safe(tfile, tmp, &tun->disabled, next) {
         tun_napi_del(tfile);
         tun_enable_queue(tfile);
         tun_queue_purge(tfile);
         xdp_rxq_info_unreg(&tfile->xdp_rxq);
         sock_put(&tfile->sk);
     }
     BUG_ON(tun->numdisabled != 0);
 
     if (tun->flags & IFF_PERSIST)
         module_put(THIS_MODULE);
 }
 
 static int tun_attach(struct tun_struct *tun, struct file *file,
               bool skip_filter, bool napi, bool napi_frags,
               bool publish_tun)
 {
     struct tun_file *tfile = file->private_data;
     struct net_device *dev = tun->dev;
     int err;
 
     err = security_tun_dev_attach(tfile->socket.sk, tun->security);
     if (err < 0)
         goto out;
 
     err = -EINVAL;
     if (rtnl_dereference(tfile->tun) && !tfile->detached)
         goto out;
 
     err = -EBUSY;
     if (!(tun->flags & IFF_MULTI_QUEUE) && tun->numqueues == 1)
         goto out;
 
     err = -E2BIG;
     if (!tfile->detached &&
         tun->numqueues + tun->numdisabled == MAX_TAP_QUEUES)
         goto out;
 
     err = 0;
 
     /* Re-attach the filter to persist device */
     if (!skip_filter && (tun->filter_attached == true)) {
         lock_sock(tfile->socket.sk);
         err = sk_attach_filter(&tun->fprog, tfile->socket.sk);
         release_sock(tfile->socket.sk);
         if (!err)
             goto out;
     }
 
     if (!tfile->detached &&
         ptr_ring_resize(&tfile->tx_ring, dev->tx_queue_len,
                 GFP_KERNEL, tun_ptr_free)) {
         err = -ENOMEM;
         goto out;
     }
 
     tfile->queue_index = tun->numqueues;
     tfile->socket.sk->sk_shutdown &= ~RCV_SHUTDOWN;
 
     if (tfile->detached) {
         /* Re-attach detached tfile, updating XDP queue_index */
         WARN_ON(!xdp_rxq_info_is_reg(&tfile->xdp_rxq));
 
         if (tfile->xdp_rxq.queue_index    != tfile->queue_index)
             tfile->xdp_rxq.queue_index = tfile->queue_index;
     } else {
         /* Setup XDP RX-queue info, for new tfile getting attached */
         err = xdp_rxq_info_reg(&tfile->xdp_rxq,
                        tun->dev, tfile->queue_index, 0);
         if (err < 0)
             goto out;
         err = xdp_rxq_info_reg_mem_model(&tfile->xdp_rxq,
                          MEM_TYPE_PAGE_SHARED, NULL);
         if (err < 0) {
             xdp_rxq_info_unreg(&tfile->xdp_rxq);
             goto out;
         }
         err = 0;
     }
 
     if (tfile->detached) {
         tun_enable_queue(tfile);
         tun_napi_enable(tfile);
     } else {
         sock_hold(&tfile->sk);
         tun_napi_init(tun, tfile, napi, napi_frags);
     }
 
     if (rtnl_dereference(tun->xdp_prog))
         sock_set_flag(&tfile->sk, SOCK_XDP);
 
     /* device is allowed to go away first, so no need to hold extra
      * refcnt.
      */
 
     /* Publish tfile->tun and tun->tfiles only after we've fully
      * initialized tfile; otherwise we risk using half-initialized
      * object.
      */
     if (publish_tun)
         rcu_assign_pointer(tfile->tun, tun);
     rcu_assign_pointer(tun->tfiles[tun->numqueues], tfile);
     tun->numqueues++;
     tun_set_real_num_queues(tun);
 out:
     return err;
 }
 
 static struct tun_struct *tun_get(struct tun_file *tfile)
 {
     struct tun_struct *tun;
 
     rcu_read_lock();
     tun = rcu_dereference(tfile->tun);
     if (tun)
         dev_hold(tun->dev);
     rcu_read_unlock();
 
     return tun;
 }
 
 static void tun_put(struct tun_struct *tun)
 {
     dev_put(tun->dev);
 }
 
 /* TAP filtering */
 static void addr_hash_set(u32 *mask, const u8 *addr)
 {
     int n = ether_crc(ETH_ALEN, addr) >> 26;
     mask[n >> 5] |= (1 << (n & 31));
 }
 
 static unsigned int addr_hash_test(const u32 *mask, const u8 *addr)
 {
     int n = ether_crc(ETH_ALEN, addr) >> 26;
     return mask[n >> 5] & (1 << (n & 31));
 }
 
 static int update_filter(struct tap_filter *filter, void __user *arg)
 {
     struct { u8 u[ETH_ALEN]; } *addr;
     struct tun_filter uf;
     int err, alen, n, nexact;
 
     if (copy_from_user(&uf, arg, sizeof(uf)))
         return -EFAULT;
 
     if (!uf.count) {
         /* Disabled */
         filter->count = 0;
         return 0;
     }
 
     alen = ETH_ALEN * uf.count;
     addr = memdup_user(arg + sizeof(uf), alen);
     if (IS_ERR(addr))
         return PTR_ERR(addr);
 
     /* The filter is updated without holding any locks. Which is
      * perfectly safe. We disable it first and in the worst
      * case we'll accept a few undesired packets. */
     filter->count = 0;
     wmb();
 
     /* Use first set of addresses as an exact filter */
     for (n = 0; n < uf.count && n < FLT_EXACT_COUNT; n++)
         memcpy(filter->addr[n], addr[n].u, ETH_ALEN);
 
     nexact = n;
 
     /* Remaining multicast addresses are hashed,
      * unicast will leave the filter disabled. */
     memset(filter->mask, 0, sizeof(filter->mask));
     for (; n < uf.count; n++) {
         if (!is_multicast_ether_addr(addr[n].u)) {
             err = 0; /* no filter */
             goto free_addr;
         }
         addr_hash_set(filter->mask, addr[n].u);
     }
 
     /* For ALLMULTI just set the mask to all ones.
      * This overrides the mask populated above. */
     if ((uf.flags & TUN_FLT_ALLMULTI))
         memset(filter->mask, ~0, sizeof(filter->mask));
 
     /* Now enable the filter */
     wmb();
     filter->count = nexact;
 
     /* Return the number of exact filters */
     err = nexact;
 free_addr:
     kfree(addr);
     return err;
 }
 
 /* Returns: 0 - drop, !=0 - accept */
 static int run_filter(struct tap_filter *filter, const struct sk_buff *skb)
 {
     /* Cannot use eth_hdr(skb) here because skb_mac_hdr() is incorrect
      * at this point. */
     struct ethhdr *eh = (struct ethhdr *) skb->data;
     int i;
 
     /* Exact match */
     for (i = 0; i < filter->count; i++)
         if (ether_addr_equal(eh->h_dest, filter->addr[i]))
             return 1;
 
     /* Inexact match (multicast only) */
     if (is_multicast_ether_addr(eh->h_dest))
         return addr_hash_test(filter->mask, eh->h_dest);
 
     return 0;
 }
 
 /*
  * Checks whether the packet is accepted or not.
  * Returns: 0 - drop, !=0 - accept
  */
 static int check_filter(struct tap_filter *filter, const struct sk_buff *skb)
 {
     if (!filter->count)
         return 1;
 
     return run_filter(filter, skb);
 }
 
 /* Network device part of the driver */
 
 static const struct ethtool_ops tun_ethtool_ops;
 
 static int tun_net_init(struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
     struct ifreq *ifr = tun->ifr;
     int err;
 
     dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
     if (!dev->tstats)
         return -ENOMEM;
 
     spin_lock_init(&tun->lock);
 
     err = security_tun_dev_alloc_security(&tun->security);
     if (err < 0) {
         free_percpu(dev->tstats);
         return err;
     }
 
     tun_flow_init(tun);
 
     dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
                TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
                NETIF_F_HW_VLAN_STAG_TX;
     dev->features = dev->hw_features | NETIF_F_LLTX;
     dev->vlan_features = dev->features &
                  ~(NETIF_F_HW_VLAN_CTAG_TX |
                    NETIF_F_HW_VLAN_STAG_TX);
 
     tun->flags = (tun->flags & ~TUN_FEATURES) |
               (ifr->ifr_flags & TUN_FEATURES);
 
     INIT_LIST_HEAD(&tun->disabled);
     err = tun_attach(tun, tun->file, false, ifr->ifr_flags & IFF_NAPI,
              ifr->ifr_flags & IFF_NAPI_FRAGS, false);
     if (err < 0) {
         tun_flow_uninit(tun);
         security_tun_dev_free_security(tun->security);
         free_percpu(dev->tstats);
         return err;
     }
     return 0;
 }
 
 /* Net device detach from fd. */
 static void tun_net_uninit(struct net_device *dev)
 {
     tun_detach_all(dev);
 }
 
 /* Net device open. */
 static int tun_net_open(struct net_device *dev)
 {
     netif_tx_start_all_queues(dev);
 
     return 0;
 }
 
 /* Net device close. */
 static int tun_net_close(struct net_device *dev)
 {
     netif_tx_stop_all_queues(dev);
     return 0;
 }
 
 /* Net device start xmit */
 static void tun_automq_xmit(struct tun_struct *tun, struct sk_buff *skb)
 {
 #ifdef CONFIG_RPS
     if (tun->numqueues == 1 && static_branch_unlikely(&rps_needed)) {
         /* Select queue was not called for the skbuff, so we extract the
          * RPS hash and save it into the flow_table here.
          */
         struct tun_flow_entry *e;
         __u32 rxhash;
 
         rxhash = __skb_get_hash_symmetric(skb);
         e = tun_flow_find(&tun->flows[tun_hashfn(rxhash)], rxhash);
         if (e)
             tun_flow_save_rps_rxhash(e, rxhash);
     }
 #endif
 }
 
 static unsigned int run_ebpf_filter(struct tun_struct *tun,
                     struct sk_buff *skb,
                     int len)
 {
     struct tun_prog *prog = rcu_dereference(tun->filter_prog);
 
     if (prog)
         len = bpf_prog_run_clear_cb(prog->prog, skb);
 
     return len;
 }
 
 /* Net device start xmit */
 static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
     enum skb_drop_reason drop_reason;
     int txq = skb->queue_mapping;
     struct netdev_queue *queue;
     struct tun_file *tfile;
     int len = skb->len;
 
     rcu_read_lock();
     tfile = rcu_dereference(tun->tfiles[txq]);
 
     /* Drop packet if interface is not attached */
     if (!tfile) {
         drop_reason = SKB_DROP_REASON_DEV_READY;
         goto drop;
     }
 
     if (!rcu_dereference(tun->steering_prog))
         tun_automq_xmit(tun, skb);
 
     netif_info(tun, tx_queued, tun->dev, "%s %d\n", __func__, skb->len);
 
     /* Drop if the filter does not like it.
      * This is a noop if the filter is disabled.
      * Filter can be enabled only for the TAP devices. */
     if (!check_filter(&tun->txflt, skb)) {
         drop_reason = SKB_DROP_REASON_TAP_TXFILTER;
         goto drop;
     }
 
     if (tfile->socket.sk->sk_filter &&
         sk_filter(tfile->socket.sk, skb)) {
         drop_reason = SKB_DROP_REASON_SOCKET_FILTER;
         goto drop;
     }
 
     len = run_ebpf_filter(tun, skb, len);
     if (len == 0) {
         drop_reason = SKB_DROP_REASON_TAP_FILTER;
         goto drop;
     }
 
     if (pskb_trim(skb, len)) {
         drop_reason = SKB_DROP_REASON_NOMEM;
         goto drop;
     }
 
     if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC))) {
         drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT;
         goto drop;
     }
 
     skb_tx_timestamp(skb);
 
     /* Orphan the skb - required as we might hang on to it
      * for indefinite time.
      */
     skb_orphan(skb);
 
     nf_reset_ct(skb);
 
     if (ptr_ring_produce(&tfile->tx_ring, skb)) {
         drop_reason = SKB_DROP_REASON_FULL_RING;
         goto drop;
     }
 
     /* NETIF_F_LLTX requires to do our own update of trans_start */
     queue = netdev_get_tx_queue(dev, txq);
     txq_trans_cond_update(queue);
 
     /* Notify and wake up reader process */
     if (tfile->flags & TUN_FASYNC)
         kill_fasync(&tfile->fasync, SIGIO, POLL_IN);
     tfile->socket.sk->sk_data_ready(tfile->socket.sk);
 
     rcu_read_unlock();
     return NETDEV_TX_OK;
 
 drop:
     dev_core_stats_tx_dropped_inc(dev);
     skb_tx_error(skb);
     kfree_skb_reason(skb, drop_reason);
     rcu_read_unlock();
     return NET_XMIT_DROP;
 }
 
 static void tun_net_mclist(struct net_device *dev)
 {
     /*
      * This callback is supposed to deal with mc filter in
      * _rx_ path and has nothing to do with the _tx_ path.
      * In rx path we always accept everything userspace gives us.
      */
 }
 
 static netdev_features_t tun_net_fix_features(struct net_device *dev,
     netdev_features_t features)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     return (features & tun->set_features) | (features & ~TUN_USER_FEATURES);
 }
 
 static void tun_set_headroom(struct net_device *dev, int new_hr)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     if (new_hr < NET_SKB_PAD)
         new_hr = NET_SKB_PAD;
 
     tun->align = new_hr;
 }
 
 static void
 tun_net_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     dev_get_tstats64(dev, stats);
 
     stats->rx_frame_errors +=
         (unsigned long)atomic_long_read(&tun->rx_frame_errors);
 }
 
 static int tun_xdp_set(struct net_device *dev, struct bpf_prog *prog,
                struct netlink_ext_ack *extack)
 {
     struct tun_struct *tun = netdev_priv(dev);
     struct tun_file *tfile;
     struct bpf_prog *old_prog;
     int i;
 
     old_prog = rtnl_dereference(tun->xdp_prog);
     rcu_assign_pointer(tun->xdp_prog, prog);
     if (old_prog)
         bpf_prog_put(old_prog);
 
     for (i = 0; i < tun->numqueues; i++) {
         tfile = rtnl_dereference(tun->tfiles[i]);
         if (prog)
             sock_set_flag(&tfile->sk, SOCK_XDP);
         else
             sock_reset_flag(&tfile->sk, SOCK_XDP);
     }
     list_for_each_entry(tfile, &tun->disabled, next) {
         if (prog)
             sock_set_flag(&tfile->sk, SOCK_XDP);
         else
             sock_reset_flag(&tfile->sk, SOCK_XDP);
     }
 
     return 0;
 }
 
 static int tun_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 {
     switch (xdp->command) {
     case XDP_SETUP_PROG:
         return tun_xdp_set(dev, xdp->prog, xdp->extack);
     default:
         return -EINVAL;
     }
 }
 
 static int tun_net_change_carrier(struct net_device *dev, bool new_carrier)
 {
     if (new_carrier) {
         struct tun_struct *tun = netdev_priv(dev);
 
         if (!tun->numqueues)
             return -EPERM;
 
         netif_carrier_on(dev);
     } else {
         netif_carrier_off(dev);
     }
     return 0;
 }
 
 static const struct net_device_ops tun_netdev_ops = {
     .ndo_init       = tun_net_init,
     .ndo_uninit     = tun_net_uninit,
     .ndo_open       = tun_net_open,
     .ndo_stop       = tun_net_close,
     .ndo_start_xmit     = tun_net_xmit,
     .ndo_fix_features   = tun_net_fix_features,
     .ndo_select_queue   = tun_select_queue,
     .ndo_set_rx_headroom    = tun_set_headroom,
     .ndo_get_stats64    = tun_net_get_stats64,
     .ndo_change_carrier = tun_net_change_carrier,
 };
 
 static void __tun_xdp_flush_tfile(struct tun_file *tfile)
 {
     /* Notify and wake up reader process */
     if (tfile->flags & TUN_FASYNC)
         kill_fasync(&tfile->fasync, SIGIO, POLL_IN);
     tfile->socket.sk->sk_data_ready(tfile->socket.sk);
 }
 
 static int tun_xdp_xmit(struct net_device *dev, int n,
             struct xdp_frame **frames, u32 flags)
 {
     struct tun_struct *tun = netdev_priv(dev);
     struct tun_file *tfile;
     u32 numqueues;
     int nxmit = 0;
     int i;
 
     if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
         return -EINVAL;
 
     rcu_read_lock();
 
 resample:
     numqueues = READ_ONCE(tun->numqueues);
     if (!numqueues) {
         rcu_read_unlock();
         return -ENXIO; /* Caller will free/return all frames */
     }
 
     tfile = rcu_dereference(tun->tfiles[smp_processor_id() %
                         numqueues]);
     if (unlikely(!tfile))
         goto resample;
 
     spin_lock(&tfile->tx_ring.producer_lock);
     for (i = 0; i < n; i++) {
         struct xdp_frame *xdp = frames[i];
         /* Encode the XDP flag into lowest bit for consumer to differ
          * XDP buffer from sk_buff.
          */
         void *frame = tun_xdp_to_ptr(xdp);
 
         if (__ptr_ring_produce(&tfile->tx_ring, frame)) {
             dev_core_stats_tx_dropped_inc(dev);
             break;
         }
         nxmit++;
     }
     spin_unlock(&tfile->tx_ring.producer_lock);
 
     if (flags & XDP_XMIT_FLUSH)
         __tun_xdp_flush_tfile(tfile);
 
     rcu_read_unlock();
     return nxmit;
 }
 
 static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
 {
     struct xdp_frame *frame = xdp_convert_buff_to_frame(xdp);
     int nxmit;
 
     if (unlikely(!frame))
         return -EOVERFLOW;
 
     nxmit = tun_xdp_xmit(dev, 1, &frame, XDP_XMIT_FLUSH);
     if (!nxmit)
         xdp_return_frame_rx_napi(frame);
     return nxmit;
 }
 
 static const struct net_device_ops tap_netdev_ops = {
     .ndo_init       = tun_net_init,
     .ndo_uninit     = tun_net_uninit,
     .ndo_open       = tun_net_open,
     .ndo_stop       = tun_net_close,
     .ndo_start_xmit     = tun_net_xmit,
     .ndo_fix_features   = tun_net_fix_features,
     .ndo_set_rx_mode    = tun_net_mclist,
     .ndo_set_mac_address    = eth_mac_addr,
     .ndo_validate_addr  = eth_validate_addr,
     .ndo_select_queue   = tun_select_queue,
     .ndo_features_check = passthru_features_check,
     .ndo_set_rx_headroom    = tun_set_headroom,
     .ndo_get_stats64    = dev_get_tstats64,
     .ndo_bpf        = tun_xdp,
     .ndo_xdp_xmit       = tun_xdp_xmit,
     .ndo_change_carrier = tun_net_change_carrier,
 };
 
 static void tun_flow_init(struct tun_struct *tun)
 {
     int i;
 
     for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++)
         INIT_HLIST_HEAD(&tun->flows[i]);
 
     tun->ageing_time = TUN_FLOW_EXPIRE;
     timer_setup(&tun->flow_gc_timer, tun_flow_cleanup, 0);
     mod_timer(&tun->flow_gc_timer,
           round_jiffies_up(jiffies + tun->ageing_time));
 }
 
 static void tun_flow_uninit(struct tun_struct *tun)
 {
     del_timer_sync(&tun->flow_gc_timer);
     tun_flow_flush(tun);
 }
 
 #define MIN_MTU 68
 #define MAX_MTU 65535
 
 /* Initialize net device. */
 static void tun_net_initialize(struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     switch (tun->flags & TUN_TYPE_MASK) {
     case IFF_TUN:
         dev->netdev_ops = &tun_netdev_ops;
         dev->header_ops = &ip_tunnel_header_ops;
 
         /* Point-to-Point TUN Device */
         dev->hard_header_len = 0;
         dev->addr_len = 0;
         dev->mtu = 1500;
 
         /* Zero header length */
         dev->type = ARPHRD_NONE;
         dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
         break;
 
     case IFF_TAP:
         dev->netdev_ops = &tap_netdev_ops;
         /* Ethernet TAP Device */
         ether_setup(dev);
         dev->priv_flags &= ~IFF_TX_SKB_SHARING;
         dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 
         eth_hw_addr_random(dev);
 
         break;
     }
 
     dev->min_mtu = MIN_MTU;
     dev->max_mtu = MAX_MTU - dev->hard_header_len;
 }
 
 static bool tun_sock_writeable(struct tun_struct *tun, struct tun_file *tfile)
 {
     struct sock *sk = tfile->socket.sk;
 
     return (tun->dev->flags & IFF_UP) && sock_writeable(sk);
 }
 
 /* Character device part */
 
 /* Poll */
 static __poll_t tun_chr_poll(struct file *file, poll_table *wait)
 {
     struct tun_file *tfile = file->private_data;
     struct tun_struct *tun = tun_get(tfile);
     struct sock *sk;
     __poll_t mask = 0;
 
     if (!tun)
         return EPOLLERR;
 
     sk = tfile->socket.sk;
 
     poll_wait(file, sk_sleep(sk), wait);
 
     if (!ptr_ring_empty(&tfile->tx_ring))
         mask |= EPOLLIN | EPOLLRDNORM;
 
     /* Make sure SOCKWQ_ASYNC_NOSPACE is set if not writable to
      * guarantee EPOLLOUT to be raised by either here or
      * tun_sock_write_space(). Then process could get notification
      * after it writes to a down device and meets -EIO.
      */
     if (tun_sock_writeable(tun, tfile) ||
         (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags) &&
          tun_sock_writeable(tun, tfile)))
         mask |= EPOLLOUT | EPOLLWRNORM;
 
     if (tun->dev->reg_state != NETREG_REGISTERED)
         mask = EPOLLERR;
 
     tun_put(tun);
     return mask;
 }
 
 static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile,
                         size_t len,
                         const struct iov_iter *it)
 {
     struct sk_buff *skb;
     size_t linear;
     int err;
     int i;
 
     if (it->nr_segs > MAX_SKB_FRAGS + 1)
         return ERR_PTR(-EMSGSIZE);
 
     local_bh_disable();
     skb = napi_get_frags(&tfile->napi);
     local_bh_enable();
     if (!skb)
         return ERR_PTR(-ENOMEM);
 
     linear = iov_iter_single_seg_count(it);
     err = __skb_grow(skb, linear);
     if (err)
         goto free;
 
     skb->len = len;
     skb->data_len = len - linear;
     skb->truesize += skb->data_len;
 
     for (i = 1; i < it->nr_segs; i++) {
         size_t fragsz = it->iov[i].iov_len;
         struct page *page;
         void *frag;
 
         if (fragsz == 0 || fragsz > PAGE_SIZE) {
             err = -EINVAL;
             goto free;
         }
         frag = netdev_alloc_frag(fragsz);
         if (!frag) {
             err = -ENOMEM;
             goto free;
         }
         page = virt_to_head_page(frag);
         skb_fill_page_desc(skb, i - 1, page,
                    frag - page_address(page), fragsz);
     }
 
     return skb;
 free:
     /* frees skb and all frags allocated with napi_alloc_frag() */
     napi_free_frags(&tfile->napi);
     return ERR_PTR(err);
 }
 
 /* prepad is the amount to reserve at front.  len is length after that.
  * linear is a hint as to how much to copy (usually headers). */
 static struct sk_buff *tun_alloc_skb(struct tun_file *tfile,
                      size_t prepad, size_t len,
                      size_t linear, int noblock)
 {
     struct sock *sk = tfile->socket.sk;
     struct sk_buff *skb;
     int err;
 
     /* Under a page?  Don't bother with paged skb. */
     if (prepad + len < PAGE_SIZE || !linear)
         linear = len;
 
     skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
                    &err, 0);
     if (!skb)
         return ERR_PTR(err);
 
     skb_reserve(skb, prepad);
     skb_put(skb, linear);
     skb->data_len = len - linear;
     skb->len += len - linear;
 
     return skb;
 }
 
 static void tun_rx_batched(struct tun_struct *tun, struct tun_file *tfile,
                struct sk_buff *skb, int more)
 {
     struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
     struct sk_buff_head process_queue;
     u32 rx_batched = tun->rx_batched;
     bool rcv = false;
 
     if (!rx_batched || (!more && skb_queue_empty(queue))) {
         local_bh_disable();
         skb_record_rx_queue(skb, tfile->queue_index);
         netif_receive_skb(skb);
         local_bh_enable();
         return;
     }
 
     spin_lock(&queue->lock);
     if (!more || skb_queue_len(queue) == rx_batched) {
         __skb_queue_head_init(&process_queue);
         skb_queue_splice_tail_init(queue, &process_queue);
         rcv = true;
     } else {
         __skb_queue_tail(queue, skb);
     }
     spin_unlock(&queue->lock);
 
     if (rcv) {
         struct sk_buff *nskb;
 
         local_bh_disable();
         while ((nskb = __skb_dequeue(&process_queue))) {
             skb_record_rx_queue(nskb, tfile->queue_index);
             netif_receive_skb(nskb);
         }
         skb_record_rx_queue(skb, tfile->queue_index);
         netif_receive_skb(skb);
         local_bh_enable();
     }
 }
 
 static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
                   int len, int noblock, bool zerocopy)
 {
     if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
         return false;
 
     if (tfile->socket.sk->sk_sndbuf != INT_MAX)
         return false;
 
     if (!noblock)
         return false;
 
     if (zerocopy)
         return false;
 
     if (SKB_DATA_ALIGN(len + TUN_RX_PAD) +
         SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PAGE_SIZE)
         return false;
 
     return true;
 }
 
 static struct sk_buff *__tun_build_skb(struct tun_file *tfile,
                        struct page_frag *alloc_frag, char *buf,
                        int buflen, int len, int pad)
 {
     struct sk_buff *skb = build_skb(buf, buflen);
 
     if (!skb)
         return ERR_PTR(-ENOMEM);
 
     skb_reserve(skb, pad);
     skb_put(skb, len);
     skb_set_owner_w(skb, tfile->socket.sk);
 
     get_page(alloc_frag->page);
     alloc_frag->offset += buflen;
 
     return skb;
 }
 
 static int tun_xdp_act(struct tun_struct *tun, struct bpf_prog *xdp_prog,
                struct xdp_buff *xdp, u32 act)
 {
     int err;
 
     switch (act) {
     case XDP_REDIRECT:
         err = xdp_do_redirect(tun->dev, xdp, xdp_prog);
         if (err)
             return err;
         break;
     case XDP_TX:
         err = tun_xdp_tx(tun->dev, xdp);
         if (err < 0)
             return err;
         break;
     case XDP_PASS:
         break;
     default:
         bpf_warn_invalid_xdp_action(tun->dev, xdp_prog, act);
         fallthrough;
     case XDP_ABORTED:
         trace_xdp_exception(tun->dev, xdp_prog, act);
         fallthrough;
     case XDP_DROP:
         dev_core_stats_rx_dropped_inc(tun->dev);
         break;
     }
 
     return act;
 }
 
 static struct sk_buff *tun_build_skb(struct tun_struct *tun,
                      struct tun_file *tfile,
                      struct iov_iter *from,
                      struct virtio_net_hdr *hdr,
                      int len, int *skb_xdp)
 {
     struct page_frag *alloc_frag = &current->task_frag;
     struct bpf_prog *xdp_prog;
     int buflen = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
     char *buf;
     size_t copied;
     int pad = TUN_RX_PAD;
     int err = 0;
 
     rcu_read_lock();
     xdp_prog = rcu_dereference(tun->xdp_prog);
     if (xdp_prog)
         pad += XDP_PACKET_HEADROOM;
     buflen += SKB_DATA_ALIGN(len + pad);
     rcu_read_unlock();
 
     alloc_frag->offset = ALIGN((u64)alloc_frag->offset, SMP_CACHE_BYTES);
     if (unlikely(!skb_page_frag_refill(buflen, alloc_frag, GFP_KERNEL)))
         return ERR_PTR(-ENOMEM);
 
     buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
     copied = copy_page_from_iter(alloc_frag->page,
                      alloc_frag->offset + pad,
                      len, from);
     if (copied != len)
         return ERR_PTR(-EFAULT);
 
     /* There's a small window that XDP may be set after the check
      * of xdp_prog above, this should be rare and for simplicity
      * we do XDP on skb in case the headroom is not enough.
      */
     if (hdr->gso_type || !xdp_prog) {
         *skb_xdp = 1;
         return __tun_build_skb(tfile, alloc_frag, buf, buflen, len,
                        pad);
     }
 
     *skb_xdp = 0;
 
     local_bh_disable();
     rcu_read_lock();
     xdp_prog = rcu_dereference(tun->xdp_prog);
     if (xdp_prog) {
         struct xdp_buff xdp;
         u32 act;
 
         xdp_init_buff(&xdp, buflen, &tfile->xdp_rxq);
         xdp_prepare_buff(&xdp, buf, pad, len, false);
 
         act = bpf_prog_run_xdp(xdp_prog, &xdp);
         if (act == XDP_REDIRECT || act == XDP_TX) {
             get_page(alloc_frag->page);
             alloc_frag->offset += buflen;
         }
         err = tun_xdp_act(tun, xdp_prog, &xdp, act);
         if (err < 0) {
             if (act == XDP_REDIRECT || act == XDP_TX)
                 put_page(alloc_frag->page);
             goto out;
         }
 
         if (err == XDP_REDIRECT)
             xdp_do_flush();
         if (err != XDP_PASS)
             goto out;
 
         pad = xdp.data - xdp.data_hard_start;
         len = xdp.data_end - xdp.data;
     }
     rcu_read_unlock();
     local_bh_enable();
 
     return __tun_build_skb(tfile, alloc_frag, buf, buflen, len, pad);
 
 out:
     rcu_read_unlock();
     local_bh_enable();
     return NULL;
 }
 
 /* Get packet from user space buffer */
 static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                 void *msg_control, struct iov_iter *from,
                 int noblock, bool more)
 {
     struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
     struct sk_buff *skb;
     size_t total_len = iov_iter_count(from);
     size_t len = total_len, align = tun->align, linear;
     struct virtio_net_hdr gso = { 0 };
     int good_linear;
     int copylen;
     bool zerocopy = false;
     int err;
     u32 rxhash = 0;
     int skb_xdp = 1;
     bool frags = tun_napi_frags_enabled(tfile);
     enum skb_drop_reason drop_reason;
 
     if (!(tun->flags & IFF_NO_PI)) {
         if (len < sizeof(pi))
             return -EINVAL;
         len -= sizeof(pi);
 
         if (!copy_from_iter_full(&pi, sizeof(pi), from))
             return -EFAULT;
     }
 
     if (tun->flags & IFF_VNET_HDR) {
         int vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
 
         if (len < vnet_hdr_sz)
             return -EINVAL;
         len -= vnet_hdr_sz;
 
         if (!copy_from_iter_full(&gso, sizeof(gso), from))
             return -EFAULT;
 
         if ((gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
             tun16_to_cpu(tun, gso.csum_start) + tun16_to_cpu(tun, gso.csum_offset) + 2 > tun16_to_cpu(tun, gso.hdr_len))
             gso.hdr_len = cpu_to_tun16(tun, tun16_to_cpu(tun, gso.csum_start) + tun16_to_cpu(tun, gso.csum_offset) + 2);
 
         if (tun16_to_cpu(tun, gso.hdr_len) > len)
             return -EINVAL;
         iov_iter_advance(from, vnet_hdr_sz - sizeof(gso));
     }
 
     if ((tun->flags & TUN_TYPE_MASK) == IFF_TAP) {
         align += NET_IP_ALIGN;
         if (unlikely(len < ETH_HLEN ||
                  (gso.hdr_len && tun16_to_cpu(tun, gso.hdr_len) < ETH_HLEN)))
             return -EINVAL;
     }
 
     good_linear = SKB_MAX_HEAD(align);
 
     if (msg_control) {
         struct iov_iter i = *from;
 
         /* There are 256 bytes to be copied in skb, so there is
          * enough room for skb expand head in case it is used.
          * The rest of the buffer is mapped from userspace.
          */
         copylen = gso.hdr_len ? tun16_to_cpu(tun, gso.hdr_len) : GOODCOPY_LEN;
         if (copylen > good_linear)
             copylen = good_linear;
         linear = copylen;
         iov_iter_advance(&i, copylen);
         if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
             zerocopy = true;
     }
 
     if (!frags && tun_can_build_skb(tun, tfile, len, noblock, zerocopy)) {
         /* For the packet that is not easy to be processed
          * (e.g gso or jumbo packet), we will do it at after
          * skb was created with generic XDP routine.
          */
         skb = tun_build_skb(tun, tfile, from, &gso, len, &skb_xdp);
         if (IS_ERR(skb)) {
             dev_core_stats_rx_dropped_inc(tun->dev);
             return PTR_ERR(skb);
         }
         if (!skb)
             return total_len;
     } else {
         if (!zerocopy) {
             copylen = len;
             if (tun16_to_cpu(tun, gso.hdr_len) > good_linear)
                 linear = good_linear;
             else
                 linear = tun16_to_cpu(tun, gso.hdr_len);
         }
 
         if (frags) {
             mutex_lock(&tfile->napi_mutex);
             skb = tun_napi_alloc_frags(tfile, copylen, from);
             /* tun_napi_alloc_frags() enforces a layout for the skb.
              * If zerocopy is enabled, then this layout will be
              * overwritten by zerocopy_sg_from_iter().
              */
             zerocopy = false;
         } else {
             skb = tun_alloc_skb(tfile, align, copylen, linear,
                         noblock);
         }
 
         if (IS_ERR(skb)) {
             if (PTR_ERR(skb) != -EAGAIN)
                 dev_core_stats_rx_dropped_inc(tun->dev);
             if (frags)
                 mutex_unlock(&tfile->napi_mutex);
             return PTR_ERR(skb);
         }
 
         if (zerocopy)
             err = zerocopy_sg_from_iter(skb, from);
         else
             err = skb_copy_datagram_from_iter(skb, 0, from, len);
 
         if (err) {
             err = -EFAULT;
             drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT;
 drop:
             dev_core_stats_rx_dropped_inc(tun->dev);
             kfree_skb_reason(skb, drop_reason);
             if (frags) {
                 tfile->napi.skb = NULL;
                 mutex_unlock(&tfile->napi_mutex);
             }
 
             return err;
         }
     }
 
     if (virtio_net_hdr_to_skb(skb, &gso, tun_is_little_endian(tun))) {
         atomic_long_inc(&tun->rx_frame_errors);
         kfree_skb(skb);
         if (frags) {
             tfile->napi.skb = NULL;
             mutex_unlock(&tfile->napi_mutex);
         }
 
         return -EINVAL;
     }
 
     switch (tun->flags & TUN_TYPE_MASK) {
     case IFF_TUN:
         if (tun->flags & IFF_NO_PI) {
             u8 ip_version = skb->len ? (skb->data[0] >> 4) : 0;
 
             switch (ip_version) {
             case 4:
                 pi.proto = htons(ETH_P_IP);
                 break;
             case 6:
                 pi.proto = htons(ETH_P_IPV6);
                 break;
             default:
                 dev_core_stats_rx_dropped_inc(tun->dev);
                 kfree_skb(skb);
                 return -EINVAL;
             }
         }
 
         skb_reset_mac_header(skb);
         skb->protocol = pi.proto;
         skb->dev = tun->dev;
         break;
     case IFF_TAP:
         if (frags && !pskb_may_pull(skb, ETH_HLEN)) {
             err = -ENOMEM;
             drop_reason = SKB_DROP_REASON_HDR_TRUNC;
             goto drop;
         }
         skb->protocol = eth_type_trans(skb, tun->dev);
         break;
     }
 
     /* copy skb_ubuf_info for callback when skb has no error */
     if (zerocopy) {
         skb_zcopy_init(skb, msg_control);
     } else if (msg_control) {
         struct ubuf_info *uarg = msg_control;
         uarg->callback(NULL, uarg, false);
     }
 
     skb_reset_network_header(skb);
     skb_probe_transport_header(skb);
     skb_record_rx_queue(skb, tfile->queue_index);
 
     if (skb_xdp) {
         struct bpf_prog *xdp_prog;
         int ret;
 
         local_bh_disable();
         rcu_read_lock();
         xdp_prog = rcu_dereference(tun->xdp_prog);
         if (xdp_prog) {
             ret = do_xdp_generic(xdp_prog, skb);
             if (ret != XDP_PASS) {
                 rcu_read_unlock();
                 local_bh_enable();
                 if (frags) {
                     tfile->napi.skb = NULL;
                     mutex_unlock(&tfile->napi_mutex);
                 }
                 return total_len;
             }
         }
         rcu_read_unlock();
         local_bh_enable();
     }
 
     /* Compute the costly rx hash only if needed for flow updates.
      * We may get a very small possibility of OOO during switching, not
      * worth to optimize.
      */
     if (!rcu_access_pointer(tun->steering_prog) && tun->numqueues > 1 &&
         !tfile->detached)
         rxhash = __skb_get_hash_symmetric(skb);
 
     rcu_read_lock();
     if (unlikely(!(tun->dev->flags & IFF_UP))) {
         err = -EIO;
         rcu_read_unlock();
         drop_reason = SKB_DROP_REASON_DEV_READY;
         goto drop;
     }
 
     if (frags) {
         u32 headlen;
 
         /* Exercise flow dissector code path. */
         skb_push(skb, ETH_HLEN);
         headlen = eth_get_headlen(tun->dev, skb->data,
                       skb_headlen(skb));
 
         if (unlikely(headlen > skb_headlen(skb))) {
             dev_core_stats_rx_dropped_inc(tun->dev);
             napi_free_frags(&tfile->napi);
             rcu_read_unlock();
             mutex_unlock(&tfile->napi_mutex);
             WARN_ON(1);
             return -ENOMEM;
         }
 
         local_bh_disable();
         napi_gro_frags(&tfile->napi);
         local_bh_enable();
         mutex_unlock(&tfile->napi_mutex);
     } else if (tfile->napi_enabled) {
         struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
         int queue_len;
 
         spin_lock_bh(&queue->lock);
         __skb_queue_tail(queue, skb);
         queue_len = skb_queue_len(queue);
         spin_unlock(&queue->lock);
 
         if (!more || queue_len > NAPI_POLL_WEIGHT)
             napi_schedule(&tfile->napi);
 
         local_bh_enable();
     } else if (!IS_ENABLED(CONFIG_4KSTACKS)) {
         tun_rx_batched(tun, tfile, skb, more);
     } else {
         netif_rx(skb);
     }
     rcu_read_unlock();
 
     preempt_disable();
     dev_sw_netstats_rx_add(tun->dev, len);
     preempt_enable();
 
     if (rxhash)
         tun_flow_update(tun, rxhash, tfile);
 
     return total_len;
 }
 
 static ssize_t tun_chr_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
     struct file *file = iocb->ki_filp;
     struct tun_file *tfile = file->private_data;
     struct tun_struct *tun = tun_get(tfile);
     ssize_t result;
     int noblock = 0;
 
     if (!tun)
         return -EBADFD;
 
     if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
         noblock = 1;
 
     result = tun_get_user(tun, tfile, NULL, from, noblock, false);
 
     tun_put(tun);
     return result;
 }
 
 static ssize_t tun_put_user_xdp(struct tun_struct *tun,
                 struct tun_file *tfile,
                 struct xdp_frame *xdp_frame,
                 struct iov_iter *iter)
 {
     int vnet_hdr_sz = 0;
     size_t size = xdp_frame->len;
     size_t ret;
 
     if (tun->flags & IFF_VNET_HDR) {
         struct virtio_net_hdr gso = { 0 };
 
         vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
         if (unlikely(iov_iter_count(iter) < vnet_hdr_sz))
             return -EINVAL;
         if (unlikely(copy_to_iter(&gso, sizeof(gso), iter) !=
                  sizeof(gso)))
             return -EFAULT;
         iov_iter_advance(iter, vnet_hdr_sz - sizeof(gso));
     }
 
     ret = copy_to_iter(xdp_frame->data, size, iter) + vnet_hdr_sz;
 
     preempt_disable();
     dev_sw_netstats_tx_add(tun->dev, 1, ret);
     preempt_enable();
 
     return ret;
 }
 
 /* Put packet to the user space buffer */
 static ssize_t tun_put_user(struct tun_struct *tun,
                 struct tun_file *tfile,
                 struct sk_buff *skb,
                 struct iov_iter *iter)
 {
     struct tun_pi pi = { 0, skb->protocol };
     ssize_t total;
     int vlan_offset = 0;
     int vlan_hlen = 0;
     int vnet_hdr_sz = 0;
 
     if (skb_vlan_tag_present(skb))
         vlan_hlen = VLAN_HLEN;
 
     if (tun->flags & IFF_VNET_HDR)
         vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
 
     total = skb->len + vlan_hlen + vnet_hdr_sz;
 
     if (!(tun->flags & IFF_NO_PI)) {
         if (iov_iter_count(iter) < sizeof(pi))
             return -EINVAL;
 
         total += sizeof(pi);
         if (iov_iter_count(iter) < total) {
             /* Packet will be striped */
             pi.flags |= TUN_PKT_STRIP;
         }
 
         if (copy_to_iter(&pi, sizeof(pi), iter) != sizeof(pi))
             return -EFAULT;
     }
 
     if (vnet_hdr_sz) {
         struct virtio_net_hdr gso;
 
         if (iov_iter_count(iter) < vnet_hdr_sz)
             return -EINVAL;
 
         if (virtio_net_hdr_from_skb(skb, &gso,
                         tun_is_little_endian(tun), true,
                         vlan_hlen)) {
             struct skb_shared_info *sinfo = skb_shinfo(skb);
             pr_err("unexpected GSO type: "
                    "0x%x, gso_size %d, hdr_len %d\n",
                    sinfo->gso_type, tun16_to_cpu(tun, gso.gso_size),
                    tun16_to_cpu(tun, gso.hdr_len));
             print_hex_dump(KERN_ERR, "tun: ",
                        DUMP_PREFIX_NONE,
                        16, 1, skb->head,
                        min((int)tun16_to_cpu(tun, gso.hdr_len), 64), true);
             WARN_ON_ONCE(1);
             return -EINVAL;
         }
 
         if (copy_to_iter(&gso, sizeof(gso), iter) != sizeof(gso))
             return -EFAULT;
 
         iov_iter_advance(iter, vnet_hdr_sz - sizeof(gso));
     }
 
     if (vlan_hlen) {
         int ret;
         struct veth veth;
 
         veth.h_vlan_proto = skb->vlan_proto;
         veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
 
         vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
 
         ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
         if (ret || !iov_iter_count(iter))
             goto done;
 
         ret = copy_to_iter(&veth, sizeof(veth), iter);
         if (ret != sizeof(veth) || !iov_iter_count(iter))
             goto done;
     }
 
     skb_copy_datagram_iter(skb, vlan_offset, iter, skb->len - vlan_offset);
 
 done:
     /* caller is in process context, */
     preempt_disable();
     dev_sw_netstats_tx_add(tun->dev, 1, skb->len + vlan_hlen);
     preempt_enable();
 
     return total;
 }
 
 static void *tun_ring_recv(struct tun_file *tfile, int noblock, int *err)
 {
     DECLARE_WAITQUEUE(wait, current);
     void *ptr = NULL;
     int error = 0;
 
     ptr = ptr_ring_consume(&tfile->tx_ring);
     if (ptr)
         goto out;
     if (noblock) {
         error = -EAGAIN;
         goto out;
     }
 
     add_wait_queue(&tfile->socket.wq.wait, &wait);
 
     while (1) {
         set_current_state(TASK_INTERRUPTIBLE);
         ptr = ptr_ring_consume(&tfile->tx_ring);
         if (ptr)
             break;
         if (signal_pending(current)) {
             error = -ERESTARTSYS;
             break;
         }
         if (tfile->socket.sk->sk_shutdown & RCV_SHUTDOWN) {
             error = -EFAULT;
             break;
         }
 
         schedule();
     }
 
     __set_current_state(TASK_RUNNING);
     remove_wait_queue(&tfile->socket.wq.wait, &wait);
 
 out:
     *err = error;
     return ptr;
 }
 
 static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
                struct iov_iter *to,
                int noblock, void *ptr)
 {
     ssize_t ret;
     int err;
 
     if (!iov_iter_count(to)) {
         tun_ptr_free(ptr);
         return 0;
     }
 
     if (!ptr) {
         /* Read frames from ring */
         ptr = tun_ring_recv(tfile, noblock, &err);
         if (!ptr)
             return err;
     }
 
     if (tun_is_xdp_frame(ptr)) {
         struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
 
         ret = tun_put_user_xdp(tun, tfile, xdpf, to);
         xdp_return_frame(xdpf);
     } else {
         struct sk_buff *skb = ptr;
 
         ret = tun_put_user(tun, tfile, skb, to);
         if (unlikely(ret < 0))
             kfree_skb(skb);
         else
             consume_skb(skb);
     }
 
     return ret;
 }
 
 static ssize_t tun_chr_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
     struct file *file = iocb->ki_filp;
     struct tun_file *tfile = file->private_data;
     struct tun_struct *tun = tun_get(tfile);
     ssize_t len = iov_iter_count(to), ret;
     int noblock = 0;
 
     if (!tun)
         return -EBADFD;
 
     if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
         noblock = 1;
 
     ret = tun_do_read(tun, tfile, to, noblock, NULL);
     ret = min_t(ssize_t, ret, len);
     if (ret > 0)
         iocb->ki_pos = ret;
     tun_put(tun);
     return ret;
 }
 
 static void tun_prog_free(struct rcu_head *rcu)
 {
     struct tun_prog *prog = container_of(rcu, struct tun_prog, rcu);
 
     bpf_prog_destroy(prog->prog);
     kfree(prog);
 }
 
 static int __tun_set_ebpf(struct tun_struct *tun,
               struct tun_prog __rcu **prog_p,
               struct bpf_prog *prog)
 {
     struct tun_prog *old, *new = NULL;
 
     if (prog) {
         new = kmalloc(sizeof(*new), GFP_KERNEL);
         if (!new)
             return -ENOMEM;
         new->prog = prog;
     }
 
     spin_lock_bh(&tun->lock);
     old = rcu_dereference_protected(*prog_p,
                     lockdep_is_held(&tun->lock));
     rcu_assign_pointer(*prog_p, new);
     spin_unlock_bh(&tun->lock);
 
     if (old)
         call_rcu(&old->rcu, tun_prog_free);
 
     return 0;
 }
 
 static void tun_free_netdev(struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     BUG_ON(!(list_empty(&tun->disabled)));
 
     free_percpu(dev->tstats);
     tun_flow_uninit(tun);
     security_tun_dev_free_security(tun->security);
     __tun_set_ebpf(tun, &tun->steering_prog, NULL);
     __tun_set_ebpf(tun, &tun->filter_prog, NULL);
 }
 
 static void tun_setup(struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     tun->owner = INVALID_UID;
     tun->group = INVALID_GID;
     tun_default_link_ksettings(dev, &tun->link_ksettings);
 
     dev->ethtool_ops = &tun_ethtool_ops;
     dev->needs_free_netdev = true;
     dev->priv_destructor = tun_free_netdev;
     /* We prefer our own queue length */
     dev->tx_queue_len = TUN_READQ_SIZE;
 }
 
 /* Trivial set of netlink ops to allow deleting tun or tap
  * device with netlink.
  */
 static int tun_validate(struct nlattr *tb[], struct nlattr *data[],
             struct netlink_ext_ack *extack)
 {
     NL_SET_ERR_MSG(extack,
                "tun/tap creation via rtnetlink is not supported.");
     return -EOPNOTSUPP;
 }
 
 static size_t tun_get_size(const struct net_device *dev)
 {
     BUILD_BUG_ON(sizeof(u32) != sizeof(uid_t));
     BUILD_BUG_ON(sizeof(u32) != sizeof(gid_t));
 
     return nla_total_size(sizeof(uid_t)) + /* OWNER */
            nla_total_size(sizeof(gid_t)) + /* GROUP */
            nla_total_size(sizeof(u8)) + /* TYPE */
            nla_total_size(sizeof(u8)) + /* PI */
            nla_total_size(sizeof(u8)) + /* VNET_HDR */
            nla_total_size(sizeof(u8)) + /* PERSIST */
            nla_total_size(sizeof(u8)) + /* MULTI_QUEUE */
            nla_total_size(sizeof(u32)) + /* NUM_QUEUES */
            nla_total_size(sizeof(u32)) + /* NUM_DISABLED_QUEUES */
            0;
 }
 
 static int tun_fill_info(struct sk_buff *skb, const struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     if (nla_put_u8(skb, IFLA_TUN_TYPE, tun->flags & TUN_TYPE_MASK))
         goto nla_put_failure;
     if (uid_valid(tun->owner) &&
         nla_put_u32(skb, IFLA_TUN_OWNER,
             from_kuid_munged(current_user_ns(), tun->owner)))
         goto nla_put_failure;
     if (gid_valid(tun->group) &&
         nla_put_u32(skb, IFLA_TUN_GROUP,
             from_kgid_munged(current_user_ns(), tun->group)))
         goto nla_put_failure;
     if (nla_put_u8(skb, IFLA_TUN_PI, !(tun->flags & IFF_NO_PI)))
         goto nla_put_failure;
     if (nla_put_u8(skb, IFLA_TUN_VNET_HDR, !!(tun->flags & IFF_VNET_HDR)))
         goto nla_put_failure;
     if (nla_put_u8(skb, IFLA_TUN_PERSIST, !!(tun->flags & IFF_PERSIST)))
         goto nla_put_failure;
     if (nla_put_u8(skb, IFLA_TUN_MULTI_QUEUE,
                !!(tun->flags & IFF_MULTI_QUEUE)))
         goto nla_put_failure;
     if (tun->flags & IFF_MULTI_QUEUE) {
         if (nla_put_u32(skb, IFLA_TUN_NUM_QUEUES, tun->numqueues))
             goto nla_put_failure;
         if (nla_put_u32(skb, IFLA_TUN_NUM_DISABLED_QUEUES,
                 tun->numdisabled))
             goto nla_put_failure;
     }
 
     return 0;
 
 nla_put_failure:
     return -EMSGSIZE;
 }
 
 static struct rtnl_link_ops tun_link_ops __read_mostly = {
     .kind       = DRV_NAME,
     .priv_size  = sizeof(struct tun_struct),
     .setup      = tun_setup,
     .validate   = tun_validate,
     .get_size       = tun_get_size,
     .fill_info      = tun_fill_info,
 };
 
 static void tun_sock_write_space(struct sock *sk)
 {
     struct tun_file *tfile;
     wait_queue_head_t *wqueue;
 
     if (!sock_writeable(sk))
         return;
 
     if (!test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
         return;
 
     wqueue = sk_sleep(sk);
     if (wqueue && waitqueue_active(wqueue))
         wake_up_interruptible_sync_poll(wqueue, EPOLLOUT |
                         EPOLLWRNORM | EPOLLWRBAND);
 
     tfile = container_of(sk, struct tun_file, sk);
     kill_fasync(&tfile->fasync, SIGIO, POLL_OUT);
 }
 
 static void tun_put_page(struct tun_page *tpage)
 {
     if (tpage->page)
         __page_frag_cache_drain(tpage->page, tpage->count);
 }
 
 static int tun_xdp_one(struct tun_struct *tun,
                struct tun_file *tfile,
                struct xdp_buff *xdp, int *flush,
                struct tun_page *tpage)
 {
     unsigned int datasize = xdp->data_end - xdp->data;
     struct tun_xdp_hdr *hdr = xdp->data_hard_start;
     struct virtio_net_hdr *gso = &hdr->gso;
     struct bpf_prog *xdp_prog;
     struct sk_buff *skb = NULL;
     struct sk_buff_head *queue;
     u32 rxhash = 0, act;
     int buflen = hdr->buflen;
     int ret = 0;
     bool skb_xdp = false;
     struct page *page;
 
     xdp_prog = rcu_dereference(tun->xdp_prog);
     if (xdp_prog) {
         if (gso->gso_type) {
             skb_xdp = true;
             goto build;
         }
 
         xdp_init_buff(xdp, buflen, &tfile->xdp_rxq);
         xdp_set_data_meta_invalid(xdp);
 
         act = bpf_prog_run_xdp(xdp_prog, xdp);
         ret = tun_xdp_act(tun, xdp_prog, xdp, act);
         if (ret < 0) {
             put_page(virt_to_head_page(xdp->data));
             return ret;
         }
 
         switch (ret) {
         case XDP_REDIRECT:
             *flush = true;
             fallthrough;
         case XDP_TX:
             return 0;
         case XDP_PASS:
             break;
         default:
             page = virt_to_head_page(xdp->data);
             if (tpage->page == page) {
                 ++tpage->count;
             } else {
                 tun_put_page(tpage);
                 tpage->page = page;
                 tpage->count = 1;
             }
             return 0;
         }
     }
 
 build:
     skb = build_skb(xdp->data_hard_start, buflen);
     if (!skb) {
         ret = -ENOMEM;
         goto out;
     }
 
     skb_reserve(skb, xdp->data - xdp->data_hard_start);
     skb_put(skb, xdp->data_end - xdp->data);
 
     if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
         atomic_long_inc(&tun->rx_frame_errors);
         kfree_skb(skb);
         ret = -EINVAL;
         goto out;
     }
 
     skb->protocol = eth_type_trans(skb, tun->dev);
     skb_reset_network_header(skb);
     skb_probe_transport_header(skb);
     skb_record_rx_queue(skb, tfile->queue_index);
 
     if (skb_xdp) {
         ret = do_xdp_generic(xdp_prog, skb);
         if (ret != XDP_PASS) {
             ret = 0;
             goto out;
         }
     }
 
     if (!rcu_dereference(tun->steering_prog) && tun->numqueues > 1 &&
         !tfile->detached)
         rxhash = __skb_get_hash_symmetric(skb);
 
     if (tfile->napi_enabled) {
         queue = &tfile->sk.sk_write_queue;
         spin_lock(&queue->lock);
         __skb_queue_tail(queue, skb);
         spin_unlock(&queue->lock);
         ret = 1;
     } else {
         netif_receive_skb(skb);
         ret = 0;
     }
 
     /* No need to disable preemption here since this function is
      * always called with bh disabled
      */
     dev_sw_netstats_rx_add(tun->dev, datasize);
 
     if (rxhash)
         tun_flow_update(tun, rxhash, tfile);
 
 out:
     return ret;
 }
 
 static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 {
     int ret, i;
     struct tun_file *tfile = container_of(sock, struct tun_file, socket);
     struct tun_struct *tun = tun_get(tfile);
     struct tun_msg_ctl *ctl = m->msg_control;
     struct xdp_buff *xdp;
 
     if (!tun)
         return -EBADFD;
 
     if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
         ctl && ctl->type == TUN_MSG_PTR) {
         struct tun_page tpage;
         int n = ctl->num;
         int flush = 0, queued = 0;
 
         memset(&tpage, 0, sizeof(tpage));
 
         local_bh_disable();
         rcu_read_lock();
 
         for (i = 0; i < n; i++) {
             xdp = &((struct xdp_buff *)ctl->ptr)[i];
             ret = tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
             if (ret > 0)
                 queued += ret;
         }
 
         if (flush)
             xdp_do_flush();
 
         if (tfile->napi_enabled && queued > 0)
             napi_schedule(&tfile->napi);
 
         rcu_read_unlock();
         local_bh_enable();
 
         tun_put_page(&tpage);
 
         ret = total_len;
         goto out;
     }
 
     ret = tun_get_user(tun, tfile, ctl ? ctl->ptr : NULL, &m->msg_iter,
                m->msg_flags & MSG_DONTWAIT,
                m->msg_flags & MSG_MORE);
 out:
     tun_put(tun);
     return ret;
 }
 
 static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
                int flags)
 {
     struct tun_file *tfile = container_of(sock, struct tun_file, socket);
     struct tun_struct *tun = tun_get(tfile);
     void *ptr = m->msg_control;
     int ret;
 
     if (!tun) {
         ret = -EBADFD;
         goto out_free;
     }
 
     if (flags & ~(MSG_DONTWAIT|MSG_TRUNC|MSG_ERRQUEUE)) {
         ret = -EINVAL;
         goto out_put_tun;
     }
     if (flags & MSG_ERRQUEUE) {
         ret = sock_recv_errqueue(sock->sk, m, total_len,
                      SOL_PACKET, TUN_TX_TIMESTAMP);
         goto out;
     }
     ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT, ptr);
     if (ret > (ssize_t)total_len) {
         m->msg_flags |= MSG_TRUNC;
         ret = flags & MSG_TRUNC ? ret : total_len;
     }
 out:
     tun_put(tun);
     return ret;
 
 out_put_tun:
     tun_put(tun);
 out_free:
     tun_ptr_free(ptr);
     return ret;
 }
 
 static int tun_ptr_peek_len(void *ptr)
 {
     if (likely(ptr)) {
         if (tun_is_xdp_frame(ptr)) {
             struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
 
             return xdpf->len;
         }
         return __skb_array_len_with_tag(ptr);
     } else {
         return 0;
     }
 }
 
 static int tun_peek_len(struct socket *sock)
 {
     struct tun_file *tfile = container_of(sock, struct tun_file, socket);
     struct tun_struct *tun;
     int ret = 0;
 
     tun = tun_get(tfile);
     if (!tun)
         return 0;
 
     ret = PTR_RING_PEEK_CALL(&tfile->tx_ring, tun_ptr_peek_len);
     tun_put(tun);
 
     return ret;
 }
 
 /* Ops structure to mimic raw sockets with tun */
 static const struct proto_ops tun_socket_ops = {
     .peek_len = tun_peek_len,
     .sendmsg = tun_sendmsg,
     .recvmsg = tun_recvmsg,
 };
 
 static struct proto tun_proto = {
     .name       = "tun",
     .owner      = THIS_MODULE,
     .obj_size   = sizeof(struct tun_file),
 };
 
 static int tun_flags(struct tun_struct *tun)
 {
     return tun->flags & (TUN_FEATURES | IFF_PERSIST | IFF_TUN | IFF_TAP);
 }
 
 static ssize_t tun_flags_show(struct device *dev, struct device_attribute *attr,
                   char *buf)
 {
     struct tun_struct *tun = netdev_priv(to_net_dev(dev));
     return sprintf(buf, "0x%x\n", tun_flags(tun));
 }
 
 static ssize_t owner_show(struct device *dev, struct device_attribute *attr,
               char *buf)
 {
     struct tun_struct *tun = netdev_priv(to_net_dev(dev));
     return uid_valid(tun->owner)?
         sprintf(buf, "%u\n",
             from_kuid_munged(current_user_ns(), tun->owner)):
         sprintf(buf, "-1\n");
 }
 
 static ssize_t group_show(struct device *dev, struct device_attribute *attr,
               char *buf)
 {
     struct tun_struct *tun = netdev_priv(to_net_dev(dev));
     return gid_valid(tun->group) ?
         sprintf(buf, "%u\n",
             from_kgid_munged(current_user_ns(), tun->group)):
         sprintf(buf, "-1\n");
 }
 
 static DEVICE_ATTR_RO(tun_flags);
 static DEVICE_ATTR_RO(owner);
 static DEVICE_ATTR_RO(group);
 
 static struct attribute *tun_dev_attrs[] = {
     &dev_attr_tun_flags.attr,
     &dev_attr_owner.attr,
     &dev_attr_group.attr,
     NULL
 };
 
 static const struct attribute_group tun_attr_group = {
     .attrs = tun_dev_attrs
 };
 
 static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 {
     struct tun_struct *tun;
     struct tun_file *tfile = file->private_data;
     struct net_device *dev;
     int err;
 
     if (tfile->detached)
         return -EINVAL;
 
     if ((ifr->ifr_flags & IFF_NAPI_FRAGS)) {
         if (!capable(CAP_NET_ADMIN))
             return -EPERM;
 
         if (!(ifr->ifr_flags & IFF_NAPI) ||
             (ifr->ifr_flags & TUN_TYPE_MASK) != IFF_TAP)
             return -EINVAL;
     }
 
     dev = __dev_get_by_name(net, ifr->ifr_name);
     if (dev) {
         if (ifr->ifr_flags & IFF_TUN_EXCL)
             return -EBUSY;
         if ((ifr->ifr_flags & IFF_TUN) && dev->netdev_ops == &tun_netdev_ops)
             tun = netdev_priv(dev);
         else if ((ifr->ifr_flags & IFF_TAP) && dev->netdev_ops == &tap_netdev_ops)
             tun = netdev_priv(dev);
         else
             return -EINVAL;
 
         if (!!(ifr->ifr_flags & IFF_MULTI_QUEUE) !=
             !!(tun->flags & IFF_MULTI_QUEUE))
             return -EINVAL;
 
         if (tun_not_capable(tun))
             return -EPERM;
         err = security_tun_dev_open(tun->security);
         if (err < 0)
             return err;
 
         err = tun_attach(tun, file, ifr->ifr_flags & IFF_NOFILTER,
                  ifr->ifr_flags & IFF_NAPI,
                  ifr->ifr_flags & IFF_NAPI_FRAGS, true);
         if (err < 0)
             return err;
 
         if (tun->flags & IFF_MULTI_QUEUE &&
             (tun->numqueues + tun->numdisabled > 1)) {
             /* One or more queue has already been attached, no need
              * to initialize the device again.
              */
             netdev_state_change(dev);
             return 0;
         }
 
         tun->flags = (tun->flags & ~TUN_FEATURES) |
                   (ifr->ifr_flags & TUN_FEATURES);
 
         netdev_state_change(dev);
     } else {
         char *name;
         unsigned long flags = 0;
         int queues = ifr->ifr_flags & IFF_MULTI_QUEUE ?
                  MAX_TAP_QUEUES : 1;
 
         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
             return -EPERM;
         err = security_tun_dev_create();
         if (err < 0)
             return err;
 
         /* Set dev type */
         if (ifr->ifr_flags & IFF_TUN) {
             /* TUN device */
             flags |= IFF_TUN;
             name = "tun%d";
         } else if (ifr->ifr_flags & IFF_TAP) {
             /* TAP device */
             flags |= IFF_TAP;
             name = "tap%d";
         } else
             return -EINVAL;
 
         if (*ifr->ifr_name)
             name = ifr->ifr_name;
 
         dev = alloc_netdev_mqs(sizeof(struct tun_struct), name,
                        NET_NAME_UNKNOWN, tun_setup, queues,
                        queues);
 
         if (!dev)
             return -ENOMEM;
 
         dev_net_set(dev, net);
         dev->rtnl_link_ops = &tun_link_ops;
         dev->ifindex = tfile->ifindex;
         dev->sysfs_groups[0] = &tun_attr_group;
 
         tun = netdev_priv(dev);
         tun->dev = dev;
         tun->flags = flags;
         tun->txflt.count = 0;
         tun->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
 
         tun->align = NET_SKB_PAD;
         tun->filter_attached = false;
         tun->sndbuf = tfile->socket.sk->sk_sndbuf;
         tun->rx_batched = 0;
         RCU_INIT_POINTER(tun->steering_prog, NULL);
 
         tun->ifr = ifr;
         tun->file = file;
 
         tun_net_initialize(dev);
 
         err = register_netdevice(tun->dev);
         if (err < 0) {
             free_netdev(dev);
             return err;
         }
         /* free_netdev() won't check refcnt, to avoid race
          * with dev_put() we need publish tun after registration.
          */
         rcu_assign_pointer(tfile->tun, tun);
     }
 
     if (ifr->ifr_flags & IFF_NO_CARRIER)
         netif_carrier_off(tun->dev);
     else
         netif_carrier_on(tun->dev);
 
     /* Make sure persistent devices do not get stuck in
      * xoff state.
      */
     if (netif_running(tun->dev))
         netif_tx_wake_all_queues(tun->dev);
 
     strcpy(ifr->ifr_name, tun->dev->name);
     return 0;
 }
 
 static void tun_get_iff(struct tun_struct *tun, struct ifreq *ifr)
 {
     strcpy(ifr->ifr_name, tun->dev->name);
 
     ifr->ifr_flags = tun_flags(tun);
 
 }
 
 /* This is like a cut-down ethtool ops, except done via tun fd so no
  * privs required. */
 static int set_offload(struct tun_struct *tun, unsigned long arg)
 {
     netdev_features_t features = 0;
 
     if (arg & TUN_F_CSUM) {
         features |= NETIF_F_HW_CSUM;
         arg &= ~TUN_F_CSUM;
 
         if (arg & (TUN_F_TSO4|TUN_F_TSO6)) {
             if (arg & TUN_F_TSO_ECN) {
                 features |= NETIF_F_TSO_ECN;
                 arg &= ~TUN_F_TSO_ECN;
             }
             if (arg & TUN_F_TSO4)
                 features |= NETIF_F_TSO;
             if (arg & TUN_F_TSO6)
                 features |= NETIF_F_TSO6;
             arg &= ~(TUN_F_TSO4|TUN_F_TSO6);
         }
 
         arg &= ~TUN_F_UFO;
     }
 
     /* This gives the user a way to test for new features in future by
      * trying to set them. */
     if (arg)
         return -EINVAL;
 
     tun->set_features = features;
     tun->dev->wanted_features &= ~TUN_USER_FEATURES;
     tun->dev->wanted_features |= features;
     netdev_update_features(tun->dev);
 
     return 0;
 }
 
 static void tun_detach_filter(struct tun_struct *tun, int n)
 {
     int i;
     struct tun_file *tfile;
 
     for (i = 0; i < n; i++) {
         tfile = rtnl_dereference(tun->tfiles[i]);
         lock_sock(tfile->socket.sk);
         sk_detach_filter(tfile->socket.sk);
         release_sock(tfile->socket.sk);
     }
 
     tun->filter_attached = false;
 }
 
 static int tun_attach_filter(struct tun_struct *tun)
 {
     int i, ret = 0;
     struct tun_file *tfile;
 
     for (i = 0; i < tun->numqueues; i++) {
         tfile = rtnl_dereference(tun->tfiles[i]);
         lock_sock(tfile->socket.sk);
         ret = sk_attach_filter(&tun->fprog, tfile->socket.sk);
         release_sock(tfile->socket.sk);
         if (ret) {
             tun_detach_filter(tun, i);
             return ret;
         }
     }
 
     tun->filter_attached = true;
     return ret;
 }
 
 static void tun_set_sndbuf(struct tun_struct *tun)
 {
     struct tun_file *tfile;
     int i;
 
     for (i = 0; i < tun->numqueues; i++) {
         tfile = rtnl_dereference(tun->tfiles[i]);
         tfile->socket.sk->sk_sndbuf = tun->sndbuf;
     }
 }
 
 static int tun_set_queue(struct file *file, struct ifreq *ifr)
 {
     struct tun_file *tfile = file->private_data;
     struct tun_struct *tun;
     int ret = 0;
 
     rtnl_lock();
 
     if (ifr->ifr_flags & IFF_ATTACH_QUEUE) {
         tun = tfile->detached;
         if (!tun) {
             ret = -EINVAL;
             goto unlock;
         }
         ret = security_tun_dev_attach_queue(tun->security);
         if (ret < 0)
             goto unlock;
         ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI,
                  tun->flags & IFF_NAPI_FRAGS, true);
     } else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
         tun = rtnl_dereference(tfile->tun);
         if (!tun || !(tun->flags & IFF_MULTI_QUEUE) || tfile->detached)
             ret = -EINVAL;
         else
             __tun_detach(tfile, false);
     } else
         ret = -EINVAL;
 
     if (ret >= 0)
         netdev_state_change(tun->dev);
 
 unlock:
     rtnl_unlock();
     return ret;
 }
 
 static int tun_set_ebpf(struct tun_struct *tun, struct tun_prog __rcu **prog_p,
             void __user *data)
 {
     struct bpf_prog *prog;
     int fd;
 
     if (copy_from_user(&fd, data, sizeof(fd)))
         return -EFAULT;
 
     if (fd == -1) {
         prog = NULL;
     } else {
         prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
         if (IS_ERR(prog))
             return PTR_ERR(prog);
     }
 
     return __tun_set_ebpf(tun, prog_p, prog);
 }
 
 /* Return correct value for tun->dev->addr_len based on tun->dev->type. */
 static unsigned char tun_get_addr_len(unsigned short type)
 {
     switch (type) {
     case ARPHRD_IP6GRE:
     case ARPHRD_TUNNEL6:
         return sizeof(struct in6_addr);
     case ARPHRD_IPGRE:
     case ARPHRD_TUNNEL:
     case ARPHRD_SIT:
         return 4;
     case ARPHRD_ETHER:
         return ETH_ALEN;
     case ARPHRD_IEEE802154:
     case ARPHRD_IEEE802154_MONITOR:
         return IEEE802154_EXTENDED_ADDR_LEN;
     case ARPHRD_PHONET_PIPE:
     case ARPHRD_PPP:
     case ARPHRD_NONE:
         return 0;
     case ARPHRD_6LOWPAN:
         return EUI64_ADDR_LEN;
     case ARPHRD_FDDI:
         return FDDI_K_ALEN;
     case ARPHRD_HIPPI:
         return HIPPI_ALEN;
     case ARPHRD_IEEE802:
         return FC_ALEN;
     case ARPHRD_ROSE:
         return ROSE_ADDR_LEN;
     case ARPHRD_NETROM:
         return AX25_ADDR_LEN;
     case ARPHRD_LOCALTLK:
         return LTALK_ALEN;
     default:
         return 0;
     }
 }
 
 static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
                 unsigned long arg, int ifreq_len)
 {
     struct tun_file *tfile = file->private_data;
     struct net *net = sock_net(&tfile->sk);
     struct tun_struct *tun;
     void __user* argp = (void __user*)arg;
     unsigned int ifindex, carrier;
     struct ifreq ifr;
     kuid_t owner;
     kgid_t group;
     int sndbuf;
     int vnet_hdr_sz;
     int le;
     int ret;
     bool do_notify = false;
 
     if (cmd == TUNSETIFF || cmd == TUNSETQUEUE ||
         (_IOC_TYPE(cmd) == SOCK_IOC_TYPE && cmd != SIOCGSKNS)) {
         if (copy_from_user(&ifr, argp, ifreq_len))
             return -EFAULT;
     } else {
         memset(&ifr, 0, sizeof(ifr));
     }
     if (cmd == TUNGETFEATURES) {
         /* Currently this just means: "what IFF flags are valid?".
          * This is needed because we never checked for invalid flags on
          * TUNSETIFF.
          */
         return put_user(IFF_TUN | IFF_TAP | IFF_NO_CARRIER |
                 TUN_FEATURES, (unsigned int __user*)argp);
     } else if (cmd == TUNSETQUEUE) {
         return tun_set_queue(file, &ifr);
     } else if (cmd == SIOCGSKNS) {
         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
             return -EPERM;
         return open_related_ns(&net->ns, get_net_ns);
     }
 
     rtnl_lock();
 
     tun = tun_get(tfile);
     if (cmd == TUNSETIFF) {
         ret = -EEXIST;
         if (tun)
             goto unlock;
 
         ifr.ifr_name[IFNAMSIZ-1] = '\0';
 
         ret = tun_set_iff(net, file, &ifr);
 
         if (ret)
             goto unlock;
 
         if (copy_to_user(argp, &ifr, ifreq_len))
             ret = -EFAULT;
         goto unlock;
     }
     if (cmd == TUNSETIFINDEX) {
         ret = -EPERM;
         if (tun)
             goto unlock;
 
         ret = -EFAULT;
         if (copy_from_user(&ifindex, argp, sizeof(ifindex)))
             goto unlock;
 
         ret = 0;
         tfile->ifindex = ifindex;
         goto unlock;
     }
 
     ret = -EBADFD;
     if (!tun)
         goto unlock;
 
     netif_info(tun, drv, tun->dev, "tun_chr_ioctl cmd %u\n", cmd);
 
     net = dev_net(tun->dev);
     ret = 0;
     switch (cmd) {
     case TUNGETIFF:
         tun_get_iff(tun, &ifr);
 
         if (tfile->detached)
             ifr.ifr_flags |= IFF_DETACH_QUEUE;
         if (!tfile->socket.sk->sk_filter)
             ifr.ifr_flags |= IFF_NOFILTER;
 
         if (copy_to_user(argp, &ifr, ifreq_len))
             ret = -EFAULT;
         break;
 
     case TUNSETNOCSUM:
         /* Disable/Enable checksum */
 
         /* [unimplemented] */
         netif_info(tun, drv, tun->dev, "ignored: set checksum %s\n",
                arg ? "disabled" : "enabled");
         break;
 
     case TUNSETPERSIST:
         /* Disable/Enable persist mode. Keep an extra reference to the
          * module to prevent the module being unprobed.
          */
         if (arg && !(tun->flags & IFF_PERSIST)) {
             tun->flags |= IFF_PERSIST;
             __module_get(THIS_MODULE);
             do_notify = true;
         }
         if (!arg && (tun->flags & IFF_PERSIST)) {
             tun->flags &= ~IFF_PERSIST;
             module_put(THIS_MODULE);
             do_notify = true;
         }
 
         netif_info(tun, drv, tun->dev, "persist %s\n",
                arg ? "enabled" : "disabled");
         break;
 
     case TUNSETOWNER:
         /* Set owner of the device */
         owner = make_kuid(current_user_ns(), arg);
         if (!uid_valid(owner)) {
             ret = -EINVAL;
             break;
         }
         tun->owner = owner;
         do_notify = true;
         netif_info(tun, drv, tun->dev, "owner set to %u\n",
                from_kuid(&init_user_ns, tun->owner));
         break;
 
     case TUNSETGROUP:
         /* Set group of the device */
         group = make_kgid(current_user_ns(), arg);
         if (!gid_valid(group)) {
             ret = -EINVAL;
             break;
         }
         tun->group = group;
         do_notify = true;
         netif_info(tun, drv, tun->dev, "group set to %u\n",
                from_kgid(&init_user_ns, tun->group));
         break;
 
     case TUNSETLINK:
         /* Only allow setting the type when the interface is down */
         if (tun->dev->flags & IFF_UP) {
             netif_info(tun, drv, tun->dev,
                    "Linktype set failed because interface is up\n");
             ret = -EBUSY;
         } else {
             ret = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE,
                                tun->dev);
             ret = notifier_to_errno(ret);
             if (ret) {
                 netif_info(tun, drv, tun->dev,
                        "Refused to change device type\n");
                 break;
             }
             tun->dev->type = (int) arg;
             tun->dev->addr_len = tun_get_addr_len(tun->dev->type);
             netif_info(tun, drv, tun->dev, "linktype set to %d\n",
                    tun->dev->type);
             call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE,
                          tun->dev);
         }
         break;
 
     case TUNSETDEBUG:
         tun->msg_enable = (u32)arg;
         break;
 
     case TUNSETOFFLOAD:
         ret = set_offload(tun, arg);
         break;
 
     case TUNSETTXFILTER:
         /* Can be set only for TAPs */
         ret = -EINVAL;
         if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
             break;
         ret = update_filter(&tun->txflt, (void __user *)arg);
         break;
 
     case SIOCGIFHWADDR:
         /* Get hw address */
         dev_get_mac_address(&ifr.ifr_hwaddr, net, tun->dev->name);
         if (copy_to_user(argp, &ifr, ifreq_len))
             ret = -EFAULT;
         break;
 
     case SIOCSIFHWADDR:
         /* Set hw address */
         ret = dev_set_mac_address_user(tun->dev, &ifr.ifr_hwaddr, NULL);
         break;
 
     case TUNGETSNDBUF:
         sndbuf = tfile->socket.sk->sk_sndbuf;
         if (copy_to_user(argp, &sndbuf, sizeof(sndbuf)))
             ret = -EFAULT;
         break;
 
     case TUNSETSNDBUF:
         if (copy_from_user(&sndbuf, argp, sizeof(sndbuf))) {
             ret = -EFAULT;
             break;
         }
         if (sndbuf <= 0) {
             ret = -EINVAL;
             break;
         }
 
         tun->sndbuf = sndbuf;
         tun_set_sndbuf(tun);
         break;
 
     case TUNGETVNETHDRSZ:
         vnet_hdr_sz = tun->vnet_hdr_sz;
         if (copy_to_user(argp, &vnet_hdr_sz, sizeof(vnet_hdr_sz)))
             ret = -EFAULT;
         break;
 
     case TUNSETVNETHDRSZ:
         if (copy_from_user(&vnet_hdr_sz, argp, sizeof(vnet_hdr_sz))) {
             ret = -EFAULT;
             break;
         }
         if (vnet_hdr_sz < (int)sizeof(struct virtio_net_hdr)) {
             ret = -EINVAL;
             break;
         }
 
         tun->vnet_hdr_sz = vnet_hdr_sz;
         break;
 
     case TUNGETVNETLE:
         le = !!(tun->flags & TUN_VNET_LE);
         if (put_user(le, (int __user *)argp))
             ret = -EFAULT;
         break;
 
     case TUNSETVNETLE:
         if (get_user(le, (int __user *)argp)) {
             ret = -EFAULT;
             break;
         }
         if (le)
             tun->flags |= TUN_VNET_LE;
         else
             tun->flags &= ~TUN_VNET_LE;
         break;
 
     case TUNGETVNETBE:
         ret = tun_get_vnet_be(tun, argp);
         break;
 
     case TUNSETVNETBE:
         ret = tun_set_vnet_be(tun, argp);
         break;
 
     case TUNATTACHFILTER:
         /* Can be set only for TAPs */
         ret = -EINVAL;
         if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
             break;
         ret = -EFAULT;
         if (copy_from_user(&tun->fprog, argp, sizeof(tun->fprog)))
             break;
 
         ret = tun_attach_filter(tun);
         break;
 
     case TUNDETACHFILTER:
         /* Can be set only for TAPs */
         ret = -EINVAL;
         if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
             break;
         ret = 0;
         tun_detach_filter(tun, tun->numqueues);
         break;
 
     case TUNGETFILTER:
         ret = -EINVAL;
         if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
             break;
         ret = -EFAULT;
         if (copy_to_user(argp, &tun->fprog, sizeof(tun->fprog)))
             break;
         ret = 0;
         break;
 
     case TUNSETSTEERINGEBPF:
         ret = tun_set_ebpf(tun, &tun->steering_prog, argp);
         break;
 
     case TUNSETFILTEREBPF:
         ret = tun_set_ebpf(tun, &tun->filter_prog, argp);
         break;
 
     case TUNSETCARRIER:
         ret = -EFAULT;
         if (copy_from_user(&carrier, argp, sizeof(carrier)))
             goto unlock;
 
         ret = tun_net_change_carrier(tun->dev, (bool)carrier);
         break;
 
     case TUNGETDEVNETNS:
         ret = -EPERM;
         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
             goto unlock;
         ret = open_related_ns(&net->ns, get_net_ns);
         break;
 
     default:
         ret = -EINVAL;
         break;
     }
 
     if (do_notify)
         netdev_state_change(tun->dev);
 
 unlock:
     rtnl_unlock();
     if (tun)
         tun_put(tun);
     return ret;
 }
 
 static long tun_chr_ioctl(struct file *file,
               unsigned int cmd, unsigned long arg)
 {
     return __tun_chr_ioctl(file, cmd, arg, sizeof (struct ifreq));
 }
 
 #ifdef CONFIG_COMPAT
 static long tun_chr_compat_ioctl(struct file *file,
              unsigned int cmd, unsigned long arg)
 {
     switch (cmd) {
     case TUNSETIFF:
     case TUNGETIFF:
     case TUNSETTXFILTER:
     case TUNGETSNDBUF:
     case TUNSETSNDBUF:
     case SIOCGIFHWADDR:
     case SIOCSIFHWADDR:
         arg = (unsigned long)compat_ptr(arg);
         break;
     default:
         arg = (compat_ulong_t)arg;
         break;
     }
 
     /*
      * compat_ifreq is shorter than ifreq, so we must not access beyond
      * the end of that structure. All fields that are used in this
      * driver are compatible though, we don't need to convert the
      * contents.
      */
     return __tun_chr_ioctl(file, cmd, arg, sizeof(struct compat_ifreq));
 }
 #endif /* CONFIG_COMPAT */
 
 static int tun_chr_fasync(int fd, struct file *file, int on)
 {
     struct tun_file *tfile = file->private_data;
     int ret;
 
     if ((ret = fasync_helper(fd, file, on, &tfile->fasync)) < 0)
         goto out;
 
     if (on) {
         __f_setown(file, task_pid(current), PIDTYPE_TGID, 0);
         tfile->flags |= TUN_FASYNC;
     } else
         tfile->flags &= ~TUN_FASYNC;
     ret = 0;
 out:
     return ret;
 }
 
 static int tun_chr_open(struct inode *inode, struct file * file)
 {
     struct net *net = current->nsproxy->net_ns;
     struct tun_file *tfile;
 
     tfile = (struct tun_file *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
                         &tun_proto, 0);
     if (!tfile)
         return -ENOMEM;
     if (ptr_ring_init(&tfile->tx_ring, 0, GFP_KERNEL)) {
         sk_free(&tfile->sk);
         return -ENOMEM;
     }
 
     mutex_init(&tfile->napi_mutex);
     RCU_INIT_POINTER(tfile->tun, NULL);
     tfile->flags = 0;
     tfile->ifindex = 0;
 
     init_waitqueue_head(&tfile->socket.wq.wait);
 
     tfile->socket.file = file;
     tfile->socket.ops = &tun_socket_ops;
 
     sock_init_data(&tfile->socket, &tfile->sk);
 
     tfile->sk.sk_write_space = tun_sock_write_space;
     tfile->sk.sk_sndbuf = INT_MAX;
 
     file->private_data = tfile;
     INIT_LIST_HEAD(&tfile->next);
 
     sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
 
     return 0;
 }
 
 static int tun_chr_close(struct inode *inode, struct file *file)
 {
     struct tun_file *tfile = file->private_data;
 
     tun_detach(tfile, true);
 
     return 0;
 }
 
 #ifdef CONFIG_PROC_FS
 static void tun_chr_show_fdinfo(struct seq_file *m, struct file *file)
 {
     struct tun_file *tfile = file->private_data;
     struct tun_struct *tun;
     struct ifreq ifr;
 
     memset(&ifr, 0, sizeof(ifr));
 
     rtnl_lock();
     tun = tun_get(tfile);
     if (tun)
         tun_get_iff(tun, &ifr);
     rtnl_unlock();
 
     if (tun)
         tun_put(tun);
 
     seq_printf(m, "iff:\t%s\n", ifr.ifr_name);
 }
 #endif
 
 static const struct file_operations tun_fops = {
     .owner  = THIS_MODULE,
     .llseek = no_llseek,
     .read_iter  = tun_chr_read_iter,
     .write_iter = tun_chr_write_iter,
     .poll   = tun_chr_poll,
     .unlocked_ioctl = tun_chr_ioctl,
 #ifdef CONFIG_COMPAT
     .compat_ioctl = tun_chr_compat_ioctl,
 #endif
     .open   = tun_chr_open,
     .release = tun_chr_close,
     .fasync = tun_chr_fasync,
 #ifdef CONFIG_PROC_FS
     .show_fdinfo = tun_chr_show_fdinfo,
 #endif
 };
 
 static struct miscdevice tun_miscdev = {
     .minor = TUN_MINOR,
     .name = "tun",
     .nodename = "net/tun",
     .fops = &tun_fops,
 };
 
 /* ethtool interface */
 
 static void tun_default_link_ksettings(struct net_device *dev,
                        struct ethtool_link_ksettings *cmd)
 {
     ethtool_link_ksettings_zero_link_mode(cmd, supported);
     ethtool_link_ksettings_zero_link_mode(cmd, advertising);
     cmd->base.speed     = SPEED_10;
     cmd->base.duplex    = DUPLEX_FULL;
     cmd->base.port      = PORT_TP;
     cmd->base.phy_address   = 0;
     cmd->base.autoneg   = AUTONEG_DISABLE;
 }
 
 static int tun_get_link_ksettings(struct net_device *dev,
                   struct ethtool_link_ksettings *cmd)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     memcpy(cmd, &tun->link_ksettings, sizeof(*cmd));
     return 0;
 }
 
 static int tun_set_link_ksettings(struct net_device *dev,
                   const struct ethtool_link_ksettings *cmd)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     memcpy(&tun->link_ksettings, cmd, sizeof(*cmd));
     return 0;
 }
 
 static void tun_get_drvinfo(struct net_device *dev, struct ethtool_drvinfo *info)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
     strlcpy(info->version, DRV_VERSION, sizeof(info->version));
 
     switch (tun->flags & TUN_TYPE_MASK) {
     case IFF_TUN:
         strlcpy(info->bus_info, "tun", sizeof(info->bus_info));
         break;
     case IFF_TAP:
         strlcpy(info->bus_info, "tap", sizeof(info->bus_info));
         break;
     }
 }
 
 static u32 tun_get_msglevel(struct net_device *dev)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     return tun->msg_enable;
 }
 
 static void tun_set_msglevel(struct net_device *dev, u32 value)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     tun->msg_enable = value;
 }
 
 static int tun_get_coalesce(struct net_device *dev,
                 struct ethtool_coalesce *ec,
                 struct kernel_ethtool_coalesce *kernel_coal,
                 struct netlink_ext_ack *extack)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     ec->rx_max_coalesced_frames = tun->rx_batched;
 
     return 0;
 }
 
 static int tun_set_coalesce(struct net_device *dev,
                 struct ethtool_coalesce *ec,
                 struct kernel_ethtool_coalesce *kernel_coal,
                 struct netlink_ext_ack *extack)
 {
     struct tun_struct *tun = netdev_priv(dev);
 
     if (ec->rx_max_coalesced_frames > NAPI_POLL_WEIGHT)
         tun->rx_batched = NAPI_POLL_WEIGHT;
     else
         tun->rx_batched = ec->rx_max_coalesced_frames;
 
     return 0;
 }
 
 static const struct ethtool_ops tun_ethtool_ops = {
     .supported_coalesce_params = ETHTOOL_COALESCE_RX_MAX_FRAMES,
     .get_drvinfo    = tun_get_drvinfo,
     .get_msglevel   = tun_get_msglevel,
     .set_msglevel   = tun_set_msglevel,
     .get_link   = ethtool_op_get_link,
     .get_ts_info    = ethtool_op_get_ts_info,
     .get_coalesce   = tun_get_coalesce,
     .set_coalesce   = tun_set_coalesce,
     .get_link_ksettings = tun_get_link_ksettings,
     .set_link_ksettings = tun_set_link_ksettings,
 };
 
 static int tun_queue_resize(struct tun_struct *tun)
 {
     struct net_device *dev = tun->dev;
     struct tun_file *tfile;
     struct ptr_ring **rings;
     int n = tun->numqueues + tun->numdisabled;
     int ret, i;
 
     rings = kmalloc_array(n, sizeof(*rings), GFP_KERNEL);
     if (!rings)
         return -ENOMEM;
 
     for (i = 0; i < tun->numqueues; i++) {
         tfile = rtnl_dereference(tun->tfiles[i]);
         rings[i] = &tfile->tx_ring;
     }
     list_for_each_entry(tfile, &tun->disabled, next)
         rings[i++] = &tfile->tx_ring;
 
     ret = ptr_ring_resize_multiple(rings, n,
                        dev->tx_queue_len, GFP_KERNEL,
                        tun_ptr_free);
 
     kfree(rings);
     return ret;
 }
 
 static int tun_device_event(struct notifier_block *unused,
                 unsigned long event, void *ptr)
 {
     struct net_device *dev = netdev_notifier_info_to_dev(ptr);
     struct tun_struct *tun = netdev_priv(dev);
     int i;
 
     if (dev->rtnl_link_ops != &tun_link_ops)
         return NOTIFY_DONE;
 
     switch (event) {
     case NETDEV_CHANGE_TX_QUEUE_LEN:
         if (tun_queue_resize(tun))
             return NOTIFY_BAD;
         break;
     case NETDEV_UP:
         for (i = 0; i < tun->numqueues; i++) {
             struct tun_file *tfile;
 
             tfile = rtnl_dereference(tun->tfiles[i]);
             tfile->socket.sk->sk_write_space(tfile->socket.sk);
         }
         break;
     default:
         break;
     }
 
     return NOTIFY_DONE;
 }
 
 static struct notifier_block tun_notifier_block __read_mostly = {
     .notifier_call  = tun_device_event,
 };
 
 static int __init tun_init(void)
 {
     int ret = 0;
 
     pr_info("%s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
 
     ret = rtnl_link_register(&tun_link_ops);
     if (ret) {
         pr_err("Can't register link_ops\n");
         goto err_linkops;
     }
 
     ret = misc_register(&tun_miscdev);
     if (ret) {
         pr_err("Can't register misc device %d\n", TUN_MINOR);
         goto err_misc;
     }
 
     ret = register_netdevice_notifier(&tun_notifier_block);
     if (ret) {
         pr_err("Can't register netdevice notifier\n");
         goto err_notifier;
     }
 
     return  0;
 
 err_notifier:
     misc_deregister(&tun_miscdev);
 err_misc:
     rtnl_link_unregister(&tun_link_ops);
 err_linkops:
     return ret;
 }
 
 static void tun_cleanup(void)
 {
     misc_deregister(&tun_miscdev);
     rtnl_link_unregister(&tun_link_ops);
     unregister_netdevice_notifier(&tun_notifier_block);
 }
 
 /* Get an underlying socket object from tun file.  Returns error unless file is
  * attached to a device.  The returned object works like a packet socket, it
  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
  * holding a reference to the file for as long as the socket is in use. */
 struct socket *tun_get_socket(struct file *file)
 {
     struct tun_file *tfile;
     if (file->f_op != &tun_fops)
         return ERR_PTR(-EINVAL);
     tfile = file->private_data;
     if (!tfile)
         return ERR_PTR(-EBADFD);
     return &tfile->socket;
 }
 EXPORT_SYMBOL_GPL(tun_get_socket);
 
 struct ptr_ring *tun_get_tx_ring(struct file *file)
 {
     struct tun_file *tfile;
 
     if (file->f_op != &tun_fops)
         return ERR_PTR(-EINVAL);
     tfile = file->private_data;
     if (!tfile)
         return ERR_PTR(-EBADFD);
     return &tfile->tx_ring;
 }
 EXPORT_SYMBOL_GPL(tun_get_tx_ring);
 
 module_init(tun_init);
 module_exit(tun_cleanup);
 MODULE_DESCRIPTION(DRV_DESCRIPTION);
 MODULE_AUTHOR(DRV_COPYRIGHT);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_MISCDEV(TUN_MINOR);
 MODULE_ALIAS("devname:net/tun");