/*
 *  TUN - Universal TUN/TAP device driver.
 *  Copyright (C) 1999-2002 Maxim Krasnyansky <maxk@qualcomm.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 *
 *  $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 <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/uaccess.h>
#include <linux/proc_fs.h>

static void tun_default_link_ksettings(struct net_device *dev,
                                       struct ethtool_link_ksettings *cmd);

/* Uncomment to enable debugging */
/* #define TUN_DEBUG 1 */

#ifdef TUN_DEBUG
static int debug;

#define tun_debug(level, tun, fmt, args...)                     \
do {                                                            \
        if (tun->debug)                                         \
                netdev_printk(level, tun->dev, fmt, ##args);    \
} while (0)
#define DBG1(level, fmt, args...)                               \
do {                                                            \
        if (debug == 2)                                         \
                printk(level fmt, ##args);                      \
} while (0)
#else
#define tun_debug(level, tun, fmt, args...)                     \
do {                                                            \
        if (0)                                                  \
                netdev_printk(level, tun->dev, fmt, ##args);    \
} while (0)
#define DBG1(level, fmt, args...)                               \
do {                                                            \
        if (0)                                                  \
                printk(level fmt, ##args);                      \
} while (0)
#endif

#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)

struct tun_pcpu_stats {
        u64 rx_packets;
        u64 rx_bytes;
        u64 tx_packets;
        u64 tx_bytes;
        struct u64_stats_sync syncp;
        u32 rx_dropped;
        u32 tx_dropped;
        u32 rx_frame_errors;
};

/* 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 socket_wq wq;
        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;
#ifdef TUN_DEBUG
        int debug;
#endif
        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;
        struct tun_pcpu_stats __percpu *pcpu_stats;
        struct bpf_prog __rcu *xdp_prog;
        struct tun_prog __rcu *steering_prog;
        struct tun_prog __rcu *filter_prog;
        struct ethtool_link_ksettings link_ksettings;
};

struct veth {
        __be16 h_vlan_proto;
        __be16 h_vlan_TCI;
};

bool tun_is_xdp_frame(void *ptr)
{
        return (unsigned long)ptr & TUN_XDP_FLAG;
}
EXPORT_SYMBOL(tun_is_xdp_frame);

void *tun_xdp_to_ptr(void *ptr)
{
        return (void *)((unsigned long)ptr | TUN_XDP_FLAG);
}
EXPORT_SYMBOL(tun_xdp_to_ptr);

void *tun_ptr_to_xdp(void *ptr)
{
        return (void *)((unsigned long)ptr & ~TUN_XDP_FLAG);
}
EXPORT_SYMBOL(tun_ptr_to_xdp);

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(tun->dev, &tfile->napi, tun_napi_poll,
                               NAPI_POLL_WEIGHT);
                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) {
                tun_debug(KERN_INFO, tun, "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)
{
        tun_debug(KERN_INFO, tun, "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;

        tun_debug(KERN_INFO, tun, "tun_flow_cleanup\n");

        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 (e->queue_index != queue_index)
                        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;
        u16 ret = 0;

        prog = rcu_dereference(tun->steering_prog);
        if (prog)
                ret = bpf_prog_run_clear_cb(prog->prog, skb);

        return ret % tun->numqueues;
}

static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb,
                            struct net_device *sb_dev,
                            select_queue_fallback_t fallback)
{
        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) {
                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;

                --tun->numqueues;
                if (clean) {
                        RCU_INIT_POINTER(tfile->tun, NULL);
                        sock_put(&tfile->sk);
                } else
                        tun_disable_queue(tun, 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_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)
{
        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);
                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);
        } 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.
         */
        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;

/* 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)
{
        struct tun_struct *tun = netdev_priv(dev);
        int i;

        netif_tx_start_all_queues(dev);

        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);
        }

        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_key_false(&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);
        int txq = skb->queue_mapping;
        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 (txq >= tun->numqueues)
                goto drop;

        if (!rcu_dereference(tun->steering_prog))
                tun_automq_xmit(tun, skb);

        tun_debug(KERN_INFO, tun, "tun_net_xmit %d\n", skb->len);

        BUG_ON(!tfile);

        /* 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))
                goto drop;

        if (tfile->socket.sk->sk_filter &&
            sk_filter(tfile->socket.sk, skb))
                goto drop;

        len = run_ebpf_filter(tun, skb, len);
        if (len == 0 || pskb_trim(skb, len))
                goto drop;

        if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC)))
                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(skb);

        if (ptr_ring_produce(&tfile->tx_ring, skb))
                goto drop;

        /* 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:
        this_cpu_inc(tun->pcpu_stats->tx_dropped);
        skb_tx_error(skb);
        kfree_skb(skb);
        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)
{
        u32 rx_dropped = 0, tx_dropped = 0, rx_frame_errors = 0;
        struct tun_struct *tun = netdev_priv(dev);
        struct tun_pcpu_stats *p;
        int i;

        for_each_possible_cpu(i) {
                u64 rxpackets, rxbytes, txpackets, txbytes;
                unsigned int start;

                p = per_cpu_ptr(tun->pcpu_stats, i);
                do {
                        start = u64_stats_fetch_begin(&p->syncp);
                        rxpackets       = p->rx_packets;
                        rxbytes         = p->rx_bytes;
                        txpackets       = p->tx_packets;
                        txbytes         = p->tx_bytes;
                } while (u64_stats_fetch_retry(&p->syncp, start));

                stats->rx_packets       += rxpackets;
                stats->rx_bytes         += rxbytes;
                stats->tx_packets       += txpackets;
                stats->tx_bytes         += txbytes;

                /* u32 counters */
                rx_dropped      += p->rx_dropped;
                rx_frame_errors += p->rx_frame_errors;
                tx_dropped      += p->tx_dropped;
        }
        stats->rx_dropped  = rx_dropped;
        stats->rx_frame_errors = rx_frame_errors;
        stats->tx_dropped = tx_dropped;
}

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 u32 tun_xdp_query(struct net_device *dev)
{
        struct tun_struct *tun = netdev_priv(dev);
        const struct bpf_prog *xdp_prog;

        xdp_prog = rtnl_dereference(tun->xdp_prog);
        if (xdp_prog)
                return xdp_prog->aux->id;

        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);
        case XDP_QUERY_PROG:
                xdp->prog_id = tun_xdp_query(dev);
                return 0;
        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_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 drops = 0;
        int cnt = n;
        int i;

        if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
                return -EINVAL;

        rcu_read_lock();

        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]);

        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)) {
                        this_cpu_inc(tun->pcpu_stats->tx_dropped);
                        xdp_return_frame_rx_napi(xdp);
                        drops++;
                }
        }
        spin_unlock(&tfile->tx_ring.producer_lock);

        if (flags & XDP_XMIT_FLUSH)
                __tun_xdp_flush_tfile(tfile);

        rcu_read_unlock();
        return cnt - drops;
}

static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
{
        struct xdp_frame *frame = convert_to_xdp_frame(xdp);

        if (unlikely(!frame))
                return -EOVERFLOW;

        return tun_xdp_xmit(dev, 1, &frame, XDP_XMIT_FLUSH);
}

static const struct net_device_ops tap_netdev_ops = {
        .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        = tun_net_get_stats64,
        .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_init(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;

                /* 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;

        tun_debug(KERN_INFO, tun, "tun_chr_poll\n");

        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(-ENOMEM);

        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 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);

        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(act);
                /* fall through */
        case XDP_ABORTED:
                trace_xdp_exception(tun->dev, xdp_prog, act);
                /* fall through */
        case XDP_DROP:
                this_cpu_inc(tun->pcpu_stats->rx_dropped);
                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(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.data_hard_start = buf;
                xdp.data = buf + pad;
                xdp_set_data_meta_invalid(&xdp);
                xdp.data_end = xdp.data + len;
                xdp.rxq = &tfile->xdp_rxq;

                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)
                        goto err_xdp;
                if (err == XDP_REDIRECT)
                        xdp_do_flush_map();
                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(alloc_frag, buf, buflen, len, pad);

err_xdp:
        put_page(alloc_frag->page);
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 };
        struct tun_pcpu_stats *stats;
        int good_linear;
        int copylen;
        bool zerocopy = false;
        int err;
        u32 rxhash = 0;
        int skb_xdp = 1;
        bool frags = tun_napi_frags_enabled(tfile);

        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)) {
                        this_cpu_inc(tun->pcpu_stats->rx_dropped);
                        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)
                                this_cpu_inc(tun->pcpu_stats->rx_dropped);
                        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:
                        this_cpu_inc(tun->pcpu_stats->rx_dropped);
                        kfree_skb(skb);
                        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))) {
                this_cpu_inc(tun->pcpu_stats->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:
                                this_cpu_inc(tun->pcpu_stats->rx_dropped);
                                kfree_skb(skb);
                                return -EINVAL;
                        }
                }

                skb_reset_mac_header(skb);
                skb->protocol = pi.proto;
                skb->dev = tun->dev;
                break;
        case IFF_TAP:
                if (!frags)
                        skb->protocol = eth_type_trans(skb, tun->dev);
                break;
        }

        /* copy skb_ubuf_info for callback when skb has no error */
        if (zerocopy) {
                skb_shinfo(skb)->destructor_arg = msg_control;
                skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
                skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
        } else if (msg_control) {
                struct ubuf_info *uarg = msg_control;
                uarg->callback(uarg, false);
        }

        skb_reset_network_header(skb);
        skb_probe_transport_header(skb);

        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();
                                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();
                goto drop;
        }

        if (frags) {
                /* Exercise flow dissector code path. */
                u32 headlen = eth_get_headlen(skb->data, skb_headlen(skb));

                if (unlikely(headlen > skb_headlen(skb))) {
                        this_cpu_inc(tun->pcpu_stats->rx_dropped);
                        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_ni(skb);

        }
        rcu_read_unlock();

        stats = get_cpu_ptr(tun->pcpu_stats);
        u64_stats_update_begin(&stats->syncp);
        stats->rx_packets++;
        stats->rx_bytes += len;
        u64_stats_update_end(&stats->syncp);
        put_cpu_ptr(stats);

        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;

        if (!tun)
                return -EBADFD;

        result = tun_get_user(tun, tfile, NULL, from,
                              file->f_flags & O_NONBLOCK, 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;
        struct tun_pcpu_stats *stats;
        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;

        stats = get_cpu_ptr(tun->pcpu_stats);
        u64_stats_update_begin(&stats->syncp);
        stats->tx_packets++;
        stats->tx_bytes += ret;
        u64_stats_update_end(&stats->syncp);
        put_cpu_ptr(tun->pcpu_stats);

        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 };
        struct tun_pcpu_stats *stats;
        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, */
        stats = get_cpu_ptr(tun->pcpu_stats);
        u64_stats_update_begin(&stats->syncp);
        stats->tx_packets++;
        stats->tx_bytes += skb->len + vlan_hlen;
        u64_stats_update_end(&stats->syncp);
        put_cpu_ptr(tun->pcpu_stats);

        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->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->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;

        tun_debug(KERN_INFO, tun, "tun_do_read\n");

        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;

        if (!tun)
                return -EBADFD;
        ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK, 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(tun->pcpu_stats);
        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 tun_pcpu_stats *stats;
        struct bpf_prog *xdp_prog;
        struct sk_buff *skb = NULL;
        u32 rxhash = 0, act;
        int buflen = hdr->buflen;
        int err = 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_set_data_meta_invalid(xdp);
                xdp->rxq = &tfile->xdp_rxq;

                act = bpf_prog_run_xdp(xdp_prog, xdp);
                err = tun_xdp_act(tun, xdp_prog, xdp, act);
                if (err < 0) {
                        put_page(virt_to_head_page(xdp->data));
                        return err;
                }

                switch (err) {
                case XDP_REDIRECT:
                        *flush = true;
                        /* fall through */
                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) {
                err = -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))) {
                this_cpu_inc(tun->pcpu_stats->rx_frame_errors);
                kfree_skb(skb);
                err = -EINVAL;
                goto out;
        }

        skb->protocol = eth_type_trans(skb, tun->dev);
        skb_reset_network_header(skb);
        skb_probe_transport_header(skb);

        if (skb_xdp) {
                err = do_xdp_generic(xdp_prog, skb);
                if (err != XDP_PASS)
                        goto out;
        }

        if (!rcu_dereference(tun->steering_prog) && tun->numqueues > 1 &&
            !tfile->detached)
                rxhash = __skb_get_hash_symmetric(skb);

        skb_record_rx_queue(skb, tfile->queue_index);
        netif_receive_skb(skb);

        /* No need for get_cpu_ptr() here since this function is
         * always called with bh disabled
         */
        stats = this_cpu_ptr(tun->pcpu_stats);
        u64_stats_update_begin(&stats->syncp);
        stats->rx_packets++;
        stats->rx_bytes += datasize;
        u64_stats_update_end(&stats->syncp);

        if (rxhash)
                tun_flow_update(tun, rxhash, tfile);

out:
        return err;
}

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 (ctl && (ctl->type == TUN_MSG_PTR)) {
                struct tun_page tpage;
                int n = ctl->num;
                int flush = 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];
                        tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
                }

                if (flush)
                        xdp_do_flush_map();

                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_show_flags(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 tun_show_owner(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 tun_show_group(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(tun_flags, 0444, tun_show_flags, NULL);
static DEVICE_ATTR(owner, 0444, tun_show_owner, NULL);
static DEVICE_ATTR(group, 0444, tun_show_group, NULL);

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);
                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;
                err = dev_get_valid_name(net, dev, name);
                if (err < 0)
                        goto err_free_dev;

                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->pcpu_stats = netdev_alloc_pcpu_stats(struct tun_pcpu_stats);
                if (!tun->pcpu_stats) {
                        err = -ENOMEM;
                        goto err_free_dev;
                }

                spin_lock_init(&tun->lock);

                err = security_tun_dev_alloc_security(&tun->security);
                if (err < 0)
                        goto err_free_stat;

                tun_net_init(dev);
                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, file, false, ifr->ifr_flags & IFF_NAPI,
                                 ifr->ifr_flags & IFF_NAPI_FRAGS);
                if (err < 0)
                        goto err_free_flow;

                err = register_netdevice(tun->dev);
                if (err < 0)
                        goto err_detach;
        }

        netif_carrier_on(tun->dev);

        tun_debug(KERN_INFO, tun, "tun_set_iff\n");

        /* 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;

err_detach:
        tun_detach_all(dev);
        /* register_netdevice() already called tun_free_netdev() */
        goto err_free_dev;

err_free_flow:
        tun_flow_uninit(tun);
        security_tun_dev_free_security(tun->security);
err_free_stat:
        free_percpu(tun->pcpu_stats);
err_free_dev:
        free_netdev(dev);
        return err;
}

static void tun_get_iff(struct net *net, struct tun_struct *tun,
                       struct ifreq *ifr)
{
        tun_debug(KERN_INFO, tun, "tun_get_iff\n");

        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);
        } 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);