Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3778 insertions, 0 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
new file mode 100644
index 000000000..367255bb4
--- /dev/null
+++ b/drivers/net/tun.c
@@ -0,0 +1,3778 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  TUN - Universal TUN/TAP device driver.
+ *  Copyright (C) 1999-2002 Maxim Krasnyansky <maxk@qualcomm.com>
+ *
+ *  $Id: tun.c,v 1.15 2002/03/01 02:44:24 maxk Exp $
+ */
+
+/*
+ *  Changes:
+ *
+ *  Mike Kershaw <dragorn@kismetwireless.net> 2005/08/14
+ *    Add TUNSETLINK ioctl to set the link encapsulation
+ *
+ *  Mark Smith <markzzzsmith@yahoo.com.au>
+ *    Use eth_random_addr() for tap MAC address.
+ *
+ *  Harald Roelle <harald.roelle@ifi.lmu.de>  2004/04/20
+ *    Fixes in packet dropping, queue length setting and queue wakeup.
+ *    Increased default tx queue length.
+ *    Added ethtool API.
+ *    Minor cleanups
+ *
+ *  Daniel Podlejski <underley@underley.eu.org>
+ *    Modifications for 2.3.99-pre5 kernel.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#define DRV_NAME	"tun"
+#define DRV_VERSION	"1.6"
+#define DRV_DESCRIPTION	"Universal TUN/TAP device driver"
+#define DRV_COPYRIGHT	"(C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>"
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/sched/signal.h>
+#include <linux/major.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/fcntl.h>
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/miscdevice.h>
+#include <linux/ethtool.h>
+#include <linux/rtnetlink.h>
+#include <linux/compat.h>
+#include <linux/if.h>
+#include <linux/if_arp.h>
+#include <linux/if_ether.h>
+#include <linux/if_tun.h>
+#include <linux/if_vlan.h>
+#include <linux/crc32.h>
+#include <linux/nsproxy.h>
+#include <linux/virtio_net.h>
+#include <linux/rcupdate.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <net/rtnetlink.h>
+#include <net/sock.h>
+#include <net/xdp.h>
+#include <net/ip_tunnels.h>
+#include <linux/seq_file.h>
+#include <linux/uio.h>
+#include <linux/skb_array.h>
+#include <linux/bpf.h>
+#include <linux/bpf_trace.h>
+#include <linux/mutex.h>
+#include <linux/ieee802154.h>
+#include <linux/if_ltalk.h>
+#include <uapi/linux/if_fddi.h>
+#include <uapi/linux/if_hippi.h>
+#include <uapi/linux/if_fc.h>
+#include <net/ax25.h>
+#include <net/rose.h>
+#include <net/6lowpan.h>
+
+#include <linux/uaccess.h>
+#include <linux/proc_fs.h>
+
+static void tun_default_link_ksettings(struct net_device *dev,
+				       struct ethtool_link_ksettings *cmd);
+
+#define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
+
+/* TUN device flags */
+
+/* IFF_ATTACH_QUEUE is never stored in device flags,
+ * overload it to mean fasync when stored there.
+ */
+#define TUN_FASYNC	IFF_ATTACH_QUEUE
+/* High bits in flags field are unused. */
+#define TUN_VNET_LE     0x80000000
+#define TUN_VNET_BE     0x40000000
+
+#define TUN_FEATURES (IFF_NO_PI | IFF_ONE_QUEUE | IFF_VNET_HDR | \
+		      IFF_MULTI_QUEUE | IFF_NAPI | IFF_NAPI_FRAGS)
+
+#define GOODCOPY_LEN 128
+
+#define FLT_EXACT_COUNT 8
+struct tap_filter {
+	unsigned int    count;    /* Number of addrs. Zero means disabled */
+	u32             mask[2];  /* Mask of the hashed addrs */
+	unsigned char	addr[FLT_EXACT_COUNT][ETH_ALEN];
+};
+
+/* MAX_TAP_QUEUES 256 is chosen to allow rx/tx queues to be equal
+ * to max number of VCPUs in guest. */
+#define MAX_TAP_QUEUES 256
+#define MAX_TAP_FLOWS  4096
+
+#define TUN_FLOW_EXPIRE (3 * HZ)
+
+/* A tun_file connects an open character device to a tuntap netdevice. It
+ * also contains all socket related structures (except sock_fprog and tap_filter)
+ * to serve as one transmit queue for tuntap device. The sock_fprog and
+ * tap_filter were kept in tun_struct since they were used for filtering for the
+ * netdevice not for a specific queue (at least I didn't see the requirement for
+ * this).
+ *
+ * RCU usage:
+ * The tun_file and tun_struct are loosely coupled, the pointer from one to the
+ * other can only be read while rcu_read_lock or rtnl_lock is held.
+ */
+struct tun_file {
+	struct sock sk;
+	struct socket socket;
+	struct tun_struct __rcu *tun;
+	struct fasync_struct *fasync;
+	/* only used for fasnyc */
+	unsigned int flags;
+	union {
+		u16 queue_index;
+		unsigned int ifindex;
+	};
+	struct napi_struct napi;
+	bool napi_enabled;
+	bool napi_frags_enabled;
+	struct mutex napi_mutex;	/* Protects access to the above napi */
+	struct list_head next;
+	struct tun_struct *detached;
+	struct ptr_ring tx_ring;
+	struct xdp_rxq_info xdp_rxq;
+};
+
+struct tun_page {
+	struct page *page;
+	int count;
+};
+
+struct tun_flow_entry {
+	struct hlist_node hash_link;
+	struct rcu_head rcu;
+	struct tun_struct *tun;
+
+	u32 rxhash;
+	u32 rps_rxhash;
+	int queue_index;
+	unsigned long updated ____cacheline_aligned_in_smp;
+};
+
+#define TUN_NUM_FLOW_ENTRIES 1024
+#define TUN_MASK_FLOW_ENTRIES (TUN_NUM_FLOW_ENTRIES - 1)
+
+struct tun_prog {
+	struct rcu_head rcu;
+	struct bpf_prog *prog;
+};
+
+/* Since the socket were moved to tun_file, to preserve the behavior of persist
+ * device, socket filter, sndbuf and vnet header size were restore when the
+ * file were attached to a persist device.
+ */
+struct tun_struct {
+	struct tun_file __rcu	*tfiles[MAX_TAP_QUEUES];
+	unsigned int            numqueues;
+	unsigned int 		flags;
+	kuid_t			owner;
+	kgid_t			group;
+
+	struct net_device	*dev;
+	netdev_features_t	set_features;
+#define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
+			  NETIF_F_TSO6)
+
+	int			align;
+	int			vnet_hdr_sz;
+	int			sndbuf;
+	struct tap_filter	txflt;
+	struct sock_fprog	fprog;
+	/* protected by rtnl lock */
+	bool			filter_attached;
+	u32			msg_enable;
+	spinlock_t lock;
+	struct hlist_head flows[TUN_NUM_FLOW_ENTRIES];
+	struct timer_list flow_gc_timer;
+	unsigned long ageing_time;
+	unsigned int numdisabled;
+	struct list_head disabled;
+	void *security;
+	u32 flow_count;
+	u32 rx_batched;
+	atomic_long_t rx_frame_errors;
+	struct bpf_prog __rcu *xdp_prog;
+	struct tun_prog __rcu *steering_prog;
+	struct tun_prog __rcu *filter_prog;
+	struct ethtool_link_ksettings link_ksettings;
+	/* init args */
+	struct file *file;
+	struct ifreq *ifr;
+};
+
+struct veth {
+	__be16 h_vlan_proto;
+	__be16 h_vlan_TCI;
+};
+
+static void tun_flow_init(struct tun_struct *tun);
+static void tun_flow_uninit(struct tun_struct *tun);
+
+static int tun_napi_receive(struct napi_struct *napi, int budget)
+{
+	struct tun_file *tfile = container_of(napi, struct tun_file, napi);
+	struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
+	struct sk_buff_head process_queue;
+	struct sk_buff *skb;
+	int received = 0;
+
+	__skb_queue_head_init(&process_queue);
+
+	spin_lock(&queue->lock);
+	skb_queue_splice_tail_init(queue, &process_queue);
+	spin_unlock(&queue->lock);
+
+	while (received < budget && (skb = __skb_dequeue(&process_queue))) {
+		napi_gro_receive(napi, skb);
+		++received;
+	}
+
+	if (!skb_queue_empty(&process_queue)) {
+		spin_lock(&queue->lock);
+		skb_queue_splice(&process_queue, queue);
+		spin_unlock(&queue->lock);
+	}
+
+	return received;
+}
+
+static int tun_napi_poll(struct napi_struct *napi, int budget)
+{
+	unsigned int received;
+
+	received = tun_napi_receive(napi, budget);
+
+	if (received < budget)
+		napi_complete_done(napi, received);
+
+	return received;
+}
+
+static void tun_napi_init(struct tun_struct *tun, struct tun_file *tfile,
+			  bool napi_en, bool napi_frags)
+{
+	tfile->napi_enabled = napi_en;
+	tfile->napi_frags_enabled = napi_en && napi_frags;
+	if (napi_en) {
+		netif_napi_add_tx(tun->dev, &tfile->napi, tun_napi_poll);
+		napi_enable(&tfile->napi);
+	}
+}
+
+static void tun_napi_enable(struct tun_file *tfile)
+{
+	if (tfile->napi_enabled)
+		napi_enable(&tfile->napi);
+}
+
+static void tun_napi_disable(struct tun_file *tfile)
+{
+	if (tfile->napi_enabled)
+		napi_disable(&tfile->napi);
+}
+
+static void tun_napi_del(struct tun_file *tfile)
+{
+	if (tfile->napi_enabled)
+		netif_napi_del(&tfile->napi);
+}
+
+static bool tun_napi_frags_enabled(const struct tun_file *tfile)
+{
+	return tfile->napi_frags_enabled;
+}
+
+#ifdef CONFIG_TUN_VNET_CROSS_LE
+static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
+{
+	return tun->flags & TUN_VNET_BE ? false :
+		virtio_legacy_is_little_endian();
+}
+
+static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+	int be = !!(tun->flags & TUN_VNET_BE);
+
+	if (put_user(be, argp))
+		return -EFAULT;
+
+	return 0;
+}
+
+static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+	int be;
+
+	if (get_user(be, argp))
+		return -EFAULT;
+
+	if (be)
+		tun->flags |= TUN_VNET_BE;
+	else
+		tun->flags &= ~TUN_VNET_BE;
+
+	return 0;
+}
+#else
+static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
+{
+	return virtio_legacy_is_little_endian();
+}
+
+static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+	return -EINVAL;
+}
+
+static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+	return -EINVAL;
+}
+#endif /* CONFIG_TUN_VNET_CROSS_LE */
+
+static inline bool tun_is_little_endian(struct tun_struct *tun)
+{
+	return tun->flags & TUN_VNET_LE ||
+		tun_legacy_is_little_endian(tun);
+}
+
+static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
+{
+	return __virtio16_to_cpu(tun_is_little_endian(tun), val);
+}
+
+static inline __virtio16 cpu_to_tun16(struct tun_struct *tun, u16 val)
+{
+	return __cpu_to_virtio16(tun_is_little_endian(tun), val);
+}
+
+static inline u32 tun_hashfn(u32 rxhash)
+{
+	return rxhash & TUN_MASK_FLOW_ENTRIES;
+}
+
+static struct tun_flow_entry *tun_flow_find(struct hlist_head *head, u32 rxhash)
+{
+	struct tun_flow_entry *e;
+
+	hlist_for_each_entry_rcu(e, head, hash_link) {
+		if (e->rxhash == rxhash)
+			return e;
+	}
+	return NULL;
+}
+
+static struct tun_flow_entry *tun_flow_create(struct tun_struct *tun,
+					      struct hlist_head *head,
+					      u32 rxhash, u16 queue_index)
+{
+	struct tun_flow_entry *e = kmalloc(sizeof(*e), GFP_ATOMIC);
+
+	if (e) {
+		netif_info(tun, tx_queued, tun->dev,
+			   "create flow: hash %u index %u\n",
+			   rxhash, queue_index);
+		e->updated = jiffies;
+		e->rxhash = rxhash;
+		e->rps_rxhash = 0;
+		e->queue_index = queue_index;
+		e->tun = tun;
+		hlist_add_head_rcu(&e->hash_link, head);
+		++tun->flow_count;
+	}
+	return e;
+}
+
+static void tun_flow_delete(struct tun_struct *tun, struct tun_flow_entry *e)
+{
+	netif_info(tun, tx_queued, tun->dev, "delete flow: hash %u index %u\n",
+		   e->rxhash, e->queue_index);
+	hlist_del_rcu(&e->hash_link);
+	kfree_rcu(e, rcu);
+	--tun->flow_count;
+}
+
+static void tun_flow_flush(struct tun_struct *tun)
+{
+	int i;
+
+	spin_lock_bh(&tun->lock);
+	for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
+		struct tun_flow_entry *e;
+		struct hlist_node *n;
+
+		hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link)
+			tun_flow_delete(tun, e);
+	}
+	spin_unlock_bh(&tun->lock);
+}
+
+static void tun_flow_delete_by_queue(struct tun_struct *tun, u16 queue_index)
+{
+	int i;
+
+	spin_lock_bh(&tun->lock);
+	for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
+		struct tun_flow_entry *e;
+		struct hlist_node *n;
+
+		hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link) {
+			if (e->queue_index == queue_index)
+				tun_flow_delete(tun, e);
+		}
+	}
+	spin_unlock_bh(&tun->lock);
+}
+
+static void tun_flow_cleanup(struct timer_list *t)
+{
+	struct tun_struct *tun = from_timer(tun, t, flow_gc_timer);
+	unsigned long delay = tun->ageing_time;
+	unsigned long next_timer = jiffies + delay;
+	unsigned long count = 0;
+	int i;
+
+	spin_lock(&tun->lock);
+	for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
+		struct tun_flow_entry *e;
+		struct hlist_node *n;
+
+		hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link) {
+			unsigned long this_timer;
+
+			this_timer = e->updated + delay;
+			if (time_before_eq(this_timer, jiffies)) {
+				tun_flow_delete(tun, e);
+				continue;
+			}
+			count++;
+			if (time_before(this_timer, next_timer))
+				next_timer = this_timer;
+		}
+	}
+
+	if (count)
+		mod_timer(&tun->flow_gc_timer, round_jiffies_up(next_timer));
+	spin_unlock(&tun->lock);
+}
+
+static void tun_flow_update(struct tun_struct *tun, u32 rxhash,
+			    struct tun_file *tfile)
+{
+	struct hlist_head *head;
+	struct tun_flow_entry *e;
+	unsigned long delay = tun->ageing_time;
+	u16 queue_index = tfile->queue_index;
+
+	head = &tun->flows[tun_hashfn(rxhash)];
+
+	rcu_read_lock();
+
+	e = tun_flow_find(head, rxhash);
+	if (likely(e)) {
+		/* TODO: keep queueing to old queue until it's empty? */
+		if (READ_ONCE(e->queue_index) != queue_index)
+			WRITE_ONCE(e->queue_index, queue_index);
+		if (e->updated != jiffies)
+			e->updated = jiffies;
+		sock_rps_record_flow_hash(e->rps_rxhash);
+	} else {
+		spin_lock_bh(&tun->lock);
+		if (!tun_flow_find(head, rxhash) &&
+		    tun->flow_count < MAX_TAP_FLOWS)
+			tun_flow_create(tun, head, rxhash, queue_index);
+
+		if (!timer_pending(&tun->flow_gc_timer))
+			mod_timer(&tun->flow_gc_timer,
+				  round_jiffies_up(jiffies + delay));
+		spin_unlock_bh(&tun->lock);
+	}
+
+	rcu_read_unlock();
+}
+
+/* Save the hash received in the stack receive path and update the
+ * flow_hash table accordingly.
+ */
+static inline void tun_flow_save_rps_rxhash(struct tun_flow_entry *e, u32 hash)
+{
+	if (unlikely(e->rps_rxhash != hash))
+		e->rps_rxhash = hash;
+}
+
+/* We try to identify a flow through its rxhash. The reason that
+ * we do not check rxq no. is because some cards(e.g 82599), chooses
+ * the rxq based on the txq where the last packet of the flow comes. As
+ * the userspace application move between processors, we may get a
+ * different rxq no. here.
+ */
+static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb)
+{
+	struct tun_flow_entry *e;
+	u32 txq = 0;
+	u32 numqueues = 0;
+
+	numqueues = READ_ONCE(tun->numqueues);
+
+	txq = __skb_get_hash_symmetric(skb);
+	e = tun_flow_find(&tun->flows[tun_hashfn(txq)], txq);
+	if (e) {
+		tun_flow_save_rps_rxhash(e, txq);
+		txq = e->queue_index;
+	} else {
+		/* use multiply and shift instead of expensive divide */
+		txq = ((u64)txq * numqueues) >> 32;
+	}
+
+	return txq;
+}
+
+static u16 tun_ebpf_select_queue(struct tun_struct *tun, struct sk_buff *skb)
+{
+	struct tun_prog *prog;
+	u32 numqueues;
+	u16 ret = 0;
+
+	numqueues = READ_ONCE(tun->numqueues);
+	if (!numqueues)
+		return 0;
+
+	prog = rcu_dereference(tun->steering_prog);
+	if (prog)
+		ret = bpf_prog_run_clear_cb(prog->prog, skb);
+
+	return ret % numqueues;
+}
+
+static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb,
+			    struct net_device *sb_dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+	u16 ret;
+
+	rcu_read_lock();
+	if (rcu_dereference(tun->steering_prog))
+		ret = tun_ebpf_select_queue(tun, skb);
+	else
+		ret = tun_automq_select_queue(tun, skb);
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static inline bool tun_not_capable(struct tun_struct *tun)
+{
+	const struct cred *cred = current_cred();
+	struct net *net = dev_net(tun->dev);
+
+	return ((uid_valid(tun->owner) && !uid_eq(cred->euid, tun->owner)) ||
+		  (gid_valid(tun->group) && !in_egroup_p(tun->group))) &&
+		!ns_capable(net->user_ns, CAP_NET_ADMIN);
+}
+
+static void tun_set_real_num_queues(struct tun_struct *tun)
+{
+	netif_set_real_num_tx_queues(tun->dev, tun->numqueues);
+	netif_set_real_num_rx_queues(tun->dev, tun->numqueues);
+}
+
+static void tun_disable_queue(struct tun_struct *tun, struct tun_file *tfile)
+{
+	tfile->detached = tun;
+	list_add_tail(&tfile->next, &tun->disabled);
+	++tun->numdisabled;
+}
+
+static struct tun_struct *tun_enable_queue(struct tun_file *tfile)
+{
+	struct tun_struct *tun = tfile->detached;
+
+	tfile->detached = NULL;
+	list_del_init(&tfile->next);
+	--tun->numdisabled;
+	return tun;
+}
+
+void tun_ptr_free(void *ptr)
+{
+	if (!ptr)
+		return;
+	if (tun_is_xdp_frame(ptr)) {
+		struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
+
+		xdp_return_frame(xdpf);
+	} else {
+		__skb_array_destroy_skb(ptr);
+	}
+}
+EXPORT_SYMBOL_GPL(tun_ptr_free);
+
+static void tun_queue_purge(struct tun_file *tfile)
+{
+	void *ptr;
+
+	while ((ptr = ptr_ring_consume(&tfile->tx_ring)) != NULL)
+		tun_ptr_free(ptr);
+
+	skb_queue_purge(&tfile->sk.sk_write_queue);
+	skb_queue_purge(&tfile->sk.sk_error_queue);
+}
+
+static void __tun_detach(struct tun_file *tfile, bool clean)
+{
+	struct tun_file *ntfile;
+	struct tun_struct *tun;
+
+	tun = rtnl_dereference(tfile->tun);
+
+	if (tun && clean) {
+		if (!tfile->detached)
+			tun_napi_disable(tfile);
+		tun_napi_del(tfile);
+	}
+
+	if (tun && !tfile->detached) {
+		u16 index = tfile->queue_index;
+		BUG_ON(index >= tun->numqueues);
+
+		rcu_assign_pointer(tun->tfiles[index],
+				   tun->tfiles[tun->numqueues - 1]);
+		ntfile = rtnl_dereference(tun->tfiles[index]);
+		ntfile->queue_index = index;
+		rcu_assign_pointer(tun->tfiles[tun->numqueues - 1],
+				   NULL);
+
+		--tun->numqueues;
+		if (clean) {
+			RCU_INIT_POINTER(tfile->tun, NULL);
+			sock_put(&tfile->sk);
+		} else {
+			tun_disable_queue(tun, tfile);
+			tun_napi_disable(tfile);
+		}
+
+		synchronize_net();
+		tun_flow_delete_by_queue(tun, tun->numqueues + 1);
+		/* Drop read queue */
+		tun_queue_purge(tfile);
+		tun_set_real_num_queues(tun);
+	} else if (tfile->detached && clean) {
+		tun = tun_enable_queue(tfile);
+		sock_put(&tfile->sk);
+	}
+
+	if (clean) {
+		if (tun && tun->numqueues == 0 && tun->numdisabled == 0) {
+			netif_carrier_off(tun->dev);
+
+			if (!(tun->flags & IFF_PERSIST) &&
+			    tun->dev->reg_state == NETREG_REGISTERED)
+				unregister_netdevice(tun->dev);
+		}
+		if (tun)
+			xdp_rxq_info_unreg(&tfile->xdp_rxq);
+		ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
+	}
+}
+
+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();
+
+	if (clean)
+		sock_put(&tfile->sk);
+}
+
+static void tun_detach_all(struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+	struct tun_file *tfile, *tmp;
+	int i, n = tun->numqueues;
+
+	for (i = 0; i < n; i++) {
+		tfile = rtnl_dereference(tun->tfiles[i]);
+		BUG_ON(!tfile);
+		tun_napi_disable(tfile);
+		tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN;
+		tfile->socket.sk->sk_data_ready(tfile->socket.sk);
+		RCU_INIT_POINTER(tfile->tun, NULL);
+		--tun->numqueues;
+	}
+	list_for_each_entry(tfile, &tun->disabled, next) {
+		tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN;
+		tfile->socket.sk->sk_data_ready(tfile->socket.sk);
+		RCU_INIT_POINTER(tfile->tun, NULL);
+	}
+	BUG_ON(tun->numqueues != 0);
+
+	synchronize_net();
+	for (i = 0; i < n; i++) {
+		tfile = rtnl_dereference(tun->tfiles[i]);
+		tun_napi_del(tfile);
+		/* Drop read queue */
+		tun_queue_purge(tfile);
+		xdp_rxq_info_unreg(&tfile->xdp_rxq);
+		sock_put(&tfile->sk);
+	}
+	list_for_each_entry_safe(tfile, tmp, &tun->disabled, next) {
+		tun_napi_del(tfile);
+		tun_enable_queue(tfile);
+		tun_queue_purge(tfile);
+		xdp_rxq_info_unreg(&tfile->xdp_rxq);
+		sock_put(&tfile->sk);
+	}
+	BUG_ON(tun->numdisabled != 0);
+
+	if (tun->flags & IFF_PERSIST)
+		module_put(THIS_MODULE);
+}
+
+static int tun_attach(struct tun_struct *tun, struct file *file,
+		      bool skip_filter, bool napi, bool napi_frags,
+		      bool publish_tun)
+{
+	struct tun_file *tfile = file->private_data;
+	struct net_device *dev = tun->dev;
+	int err;
+
+	err = security_tun_dev_attach(tfile->socket.sk, tun->security);
+	if (err < 0)
+		goto out;
+
+	err = -EINVAL;
+	if (rtnl_dereference(tfile->tun) && !tfile->detached)
+		goto out;
+
+	err = -EBUSY;
+	if (!(tun->flags & IFF_MULTI_QUEUE) && tun->numqueues == 1)
+		goto out;
+
+	err = -E2BIG;
+	if (!tfile->detached &&
+	    tun->numqueues + tun->numdisabled == MAX_TAP_QUEUES)
+		goto out;
+
+	err = 0;
+
+	/* Re-attach the filter to persist device */
+	if (!skip_filter && (tun->filter_attached == true)) {
+		lock_sock(tfile->socket.sk);
+		err = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+		release_sock(tfile->socket.sk);
+		if (!err)
+			goto out;
+	}
+
+	if (!tfile->detached &&
+	    ptr_ring_resize(&tfile->tx_ring, dev->tx_queue_len,
+			    GFP_KERNEL, tun_ptr_free)) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	tfile->queue_index = tun->numqueues;
+	tfile->socket.sk->sk_shutdown &= ~RCV_SHUTDOWN;
+
+	if (tfile->detached) {
+		/* Re-attach detached tfile, updating XDP queue_index */
+		WARN_ON(!xdp_rxq_info_is_reg(&tfile->xdp_rxq));
+
+		if (tfile->xdp_rxq.queue_index    != tfile->queue_index)
+			tfile->xdp_rxq.queue_index = tfile->queue_index;
+	} else {
+		/* Setup XDP RX-queue info, for new tfile getting attached */
+		err = xdp_rxq_info_reg(&tfile->xdp_rxq,
+				       tun->dev, tfile->queue_index, 0);
+		if (err < 0)
+			goto out;
+		err = xdp_rxq_info_reg_mem_model(&tfile->xdp_rxq,
+						 MEM_TYPE_PAGE_SHARED, NULL);
+		if (err < 0) {
+			xdp_rxq_info_unreg(&tfile->xdp_rxq);
+			goto out;
+		}
+		err = 0;
+	}
+
+	if (tfile->detached) {
+		tun_enable_queue(tfile);
+		tun_napi_enable(tfile);
+	} else {
+		sock_hold(&tfile->sk);
+		tun_napi_init(tun, tfile, napi, napi_frags);
+	}
+
+	if (rtnl_dereference(tun->xdp_prog))
+		sock_set_flag(&tfile->sk, SOCK_XDP);
+
+	/* device is allowed to go away first, so no need to hold extra
+	 * refcnt.
+	 */
+
+	/* Publish tfile->tun and tun->tfiles only after we've fully
+	 * initialized tfile; otherwise we risk using half-initialized
+	 * object.
+	 */
+	if (publish_tun)
+		rcu_assign_pointer(tfile->tun, tun);
+	rcu_assign_pointer(tun->tfiles[tun->numqueues], tfile);
+	tun->numqueues++;
+	tun_set_real_num_queues(tun);
+out:
+	return err;
+}
+
+static struct tun_struct *tun_get(struct tun_file *tfile)
+{
+	struct tun_struct *tun;
+
+	rcu_read_lock();
+	tun = rcu_dereference(tfile->tun);
+	if (tun)
+		dev_hold(tun->dev);
+	rcu_read_unlock();
+
+	return tun;
+}
+
+static void tun_put(struct tun_struct *tun)
+{
+	dev_put(tun->dev);
+}
+
+/* TAP filtering */
+static void addr_hash_set(u32 *mask, const u8 *addr)
+{
+	int n = ether_crc(ETH_ALEN, addr) >> 26;
+	mask[n >> 5] |= (1 << (n & 31));
+}
+
+static unsigned int addr_hash_test(const u32 *mask, const u8 *addr)
+{
+	int n = ether_crc(ETH_ALEN, addr) >> 26;
+	return mask[n >> 5] & (1 << (n & 31));
+}
+
+static int update_filter(struct tap_filter *filter, void __user *arg)
+{
+	struct { u8 u[ETH_ALEN]; } *addr;
+	struct tun_filter uf;
+	int err, alen, n, nexact;
+
+	if (copy_from_user(&uf, arg, sizeof(uf)))
+		return -EFAULT;
+
+	if (!uf.count) {
+		/* Disabled */
+		filter->count = 0;
+		return 0;
+	}
+
+	alen = ETH_ALEN * uf.count;
+	addr = memdup_user(arg + sizeof(uf), alen);
+	if (IS_ERR(addr))
+		return PTR_ERR(addr);
+
+	/* The filter is updated without holding any locks. Which is
+	 * perfectly safe. We disable it first and in the worst
+	 * case we'll accept a few undesired packets. */
+	filter->count = 0;
+	wmb();
+
+	/* Use first set of addresses as an exact filter */
+	for (n = 0; n < uf.count && n < FLT_EXACT_COUNT; n++)
+		memcpy(filter->addr[n], addr[n].u, ETH_ALEN);
+
+	nexact = n;
+
+	/* Remaining multicast addresses are hashed,
+	 * unicast will leave the filter disabled. */
+	memset(filter->mask, 0, sizeof(filter->mask));
+	for (; n < uf.count; n++) {
+		if (!is_multicast_ether_addr(addr[n].u)) {
+			err = 0; /* no filter */
+			goto free_addr;
+		}
+		addr_hash_set(filter->mask, addr[n].u);
+	}
+
+	/* For ALLMULTI just set the mask to all ones.
+	 * This overrides the mask populated above. */
+	if ((uf.flags & TUN_FLT_ALLMULTI))
+		memset(filter->mask, ~0, sizeof(filter->mask));
+
+	/* Now enable the filter */
+	wmb();
+	filter->count = nexact;
+
+	/* Return the number of exact filters */
+	err = nexact;
+free_addr:
+	kfree(addr);
+	return err;
+}
+
+/* Returns: 0 - drop, !=0 - accept */
+static int run_filter(struct tap_filter *filter, const struct sk_buff *skb)
+{
+	/* Cannot use eth_hdr(skb) here because skb_mac_hdr() is incorrect
+	 * at this point. */
+	struct ethhdr *eh = (struct ethhdr *) skb->data;
+	int i;
+
+	/* Exact match */
+	for (i = 0; i < filter->count; i++)
+		if (ether_addr_equal(eh->h_dest, filter->addr[i]))
+			return 1;
+
+	/* Inexact match (multicast only) */
+	if (is_multicast_ether_addr(eh->h_dest))
+		return addr_hash_test(filter->mask, eh->h_dest);
+
+	return 0;
+}
+
+/*
+ * Checks whether the packet is accepted or not.
+ * Returns: 0 - drop, !=0 - accept
+ */
+static int check_filter(struct tap_filter *filter, const struct sk_buff *skb)
+{
+	if (!filter->count)
+		return 1;
+
+	return run_filter(filter, skb);
+}
+
+/* Network device part of the driver */
+
+static const struct ethtool_ops tun_ethtool_ops;
+
+static int tun_net_init(struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+	struct ifreq *ifr = tun->ifr;
+	int err;
+
+	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
+	if (!dev->tstats)
+		return -ENOMEM;
+
+	spin_lock_init(&tun->lock);
+
+	err = security_tun_dev_alloc_security(&tun->security);
+	if (err < 0) {
+		free_percpu(dev->tstats);
+		return err;
+	}
+
+	tun_flow_init(tun);
+
+	dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
+			   TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
+			   NETIF_F_HW_VLAN_STAG_TX;
+	dev->features = dev->hw_features | NETIF_F_LLTX;
+	dev->vlan_features = dev->features &
+			     ~(NETIF_F_HW_VLAN_CTAG_TX |
+			       NETIF_F_HW_VLAN_STAG_TX);
+
+	tun->flags = (tun->flags & ~TUN_FEATURES) |
+		      (ifr->ifr_flags & TUN_FEATURES);
+
+	INIT_LIST_HEAD(&tun->disabled);
+	err = tun_attach(tun, tun->file, false, ifr->ifr_flags & IFF_NAPI,
+			 ifr->ifr_flags & IFF_NAPI_FRAGS, false);
+	if (err < 0) {
+		tun_flow_uninit(tun);
+		security_tun_dev_free_security(tun->security);
+		free_percpu(dev->tstats);
+		return err;
+	}
+	return 0;
+}
+
+/* Net device detach from fd. */
+static void tun_net_uninit(struct net_device *dev)
+{
+	tun_detach_all(dev);
+}
+
+/* Net device open. */
+static int tun_net_open(struct net_device *dev)
+{
+	netif_tx_start_all_queues(dev);
+
+	return 0;
+}
+
+/* Net device close. */
+static int tun_net_close(struct net_device *dev)
+{
+	netif_tx_stop_all_queues(dev);
+	return 0;
+}
+
+/* Net device start xmit */
+static void tun_automq_xmit(struct tun_struct *tun, struct sk_buff *skb)
+{
+#ifdef CONFIG_RPS
+	if (tun->numqueues == 1 && static_branch_unlikely(&rps_needed)) {
+		/* Select queue was not called for the skbuff, so we extract the
+		 * RPS hash and save it into the flow_table here.
+		 */
+		struct tun_flow_entry *e;
+		__u32 rxhash;
+
+		rxhash = __skb_get_hash_symmetric(skb);
+		e = tun_flow_find(&tun->flows[tun_hashfn(rxhash)], rxhash);
+		if (e)
+			tun_flow_save_rps_rxhash(e, rxhash);
+	}
+#endif
+}
+
+static unsigned int run_ebpf_filter(struct tun_struct *tun,
+				    struct sk_buff *skb,
+				    int len)
+{
+	struct tun_prog *prog = rcu_dereference(tun->filter_prog);
+
+	if (prog)
+		len = bpf_prog_run_clear_cb(prog->prog, skb);
+
+	return len;
+}
+
+/* Net device start xmit */
+static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+	enum skb_drop_reason drop_reason;
+	int txq = skb->queue_mapping;
+	struct netdev_queue *queue;
+	struct tun_file *tfile;
+	int len = skb->len;
+
+	rcu_read_lock();
+	tfile = rcu_dereference(tun->tfiles[txq]);
+
+	/* Drop packet if interface is not attached */
+	if (!tfile) {
+		drop_reason = SKB_DROP_REASON_DEV_READY;
+		goto drop;
+	}
+
+	if (!rcu_dereference(tun->steering_prog))
+		tun_automq_xmit(tun, skb);
+
+	netif_info(tun, tx_queued, tun->dev, "%s %d\n", __func__, skb->len);
+
+	/* Drop if the filter does not like it.
+	 * This is a noop if the filter is disabled.
+	 * Filter can be enabled only for the TAP devices. */
+	if (!check_filter(&tun->txflt, skb)) {
+		drop_reason = SKB_DROP_REASON_TAP_TXFILTER;
+		goto drop;
+	}
+
+	if (tfile->socket.sk->sk_filter &&
+	    sk_filter(tfile->socket.sk, skb)) {
+		drop_reason = SKB_DROP_REASON_SOCKET_FILTER;
+		goto drop;
+	}
+
+	len = run_ebpf_filter(tun, skb, len);
+	if (len == 0) {
+		drop_reason = SKB_DROP_REASON_TAP_FILTER;
+		goto drop;
+	}
+
+	if (pskb_trim(skb, len)) {
+		drop_reason = SKB_DROP_REASON_NOMEM;
+		goto drop;
+	}
+
+	if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC))) {
+		drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT;
+		goto drop;
+	}
+
+	skb_tx_timestamp(skb);
+
+	/* Orphan the skb - required as we might hang on to it
+	 * for indefinite time.
+	 */
+	skb_orphan(skb);
+
+	nf_reset_ct(skb);
+
+	if (ptr_ring_produce(&tfile->tx_ring, skb)) {
+		drop_reason = SKB_DROP_REASON_FULL_RING;
+		goto drop;
+	}
+
+	/* NETIF_F_LLTX requires to do our own update of trans_start */
+	queue = netdev_get_tx_queue(dev, txq);
+	txq_trans_cond_update(queue);
+
+	/* Notify and wake up reader process */
+	if (tfile->flags & TUN_FASYNC)
+		kill_fasync(&tfile->fasync, SIGIO, POLL_IN);
+	tfile->socket.sk->sk_data_ready(tfile->socket.sk);
+
+	rcu_read_unlock();
+	return NETDEV_TX_OK;
+
+drop:
+	dev_core_stats_tx_dropped_inc(dev);
+	skb_tx_error(skb);
+	kfree_skb_reason(skb, drop_reason);
+	rcu_read_unlock();
+	return NET_XMIT_DROP;
+}
+
+static void tun_net_mclist(struct net_device *dev)
+{
+	/*
+	 * This callback is supposed to deal with mc filter in
+	 * _rx_ path and has nothing to do with the _tx_ path.
+	 * In rx path we always accept everything userspace gives us.
+	 */
+}
+
+static netdev_features_t tun_net_fix_features(struct net_device *dev,
+	netdev_features_t features)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	return (features & tun->set_features) | (features & ~TUN_USER_FEATURES);
+}
+
+static void tun_set_headroom(struct net_device *dev, int new_hr)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	if (new_hr < NET_SKB_PAD)
+		new_hr = NET_SKB_PAD;
+
+	tun->align = new_hr;
+}
+
+static void
+tun_net_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	dev_get_tstats64(dev, stats);
+
+	stats->rx_frame_errors +=
+		(unsigned long)atomic_long_read(&tun->rx_frame_errors);
+}
+
+static int tun_xdp_set(struct net_device *dev, struct bpf_prog *prog,
+		       struct netlink_ext_ack *extack)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+	struct tun_file *tfile;
+	struct bpf_prog *old_prog;
+	int i;
+
+	old_prog = rtnl_dereference(tun->xdp_prog);
+	rcu_assign_pointer(tun->xdp_prog, prog);
+	if (old_prog)
+		bpf_prog_put(old_prog);
+
+	for (i = 0; i < tun->numqueues; i++) {
+		tfile = rtnl_dereference(tun->tfiles[i]);
+		if (prog)
+			sock_set_flag(&tfile->sk, SOCK_XDP);
+		else
+			sock_reset_flag(&tfile->sk, SOCK_XDP);
+	}
+	list_for_each_entry(tfile, &tun->disabled, next) {
+		if (prog)
+			sock_set_flag(&tfile->sk, SOCK_XDP);
+		else
+			sock_reset_flag(&tfile->sk, SOCK_XDP);
+	}
+
+	return 0;
+}
+
+static int tun_xdp(struct net_device *dev, struct netdev_bpf *xdp)
+{
+	switch (xdp->command) {
+	case XDP_SETUP_PROG:
+		return tun_xdp_set(dev, xdp->prog, xdp->extack);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int tun_net_change_carrier(struct net_device *dev, bool new_carrier)
+{
+	if (new_carrier) {
+		struct tun_struct *tun = netdev_priv(dev);
+
+		if (!tun->numqueues)
+			return -EPERM;
+
+		netif_carrier_on(dev);
+	} else {
+		netif_carrier_off(dev);
+	}
+	return 0;
+}
+
+static const struct net_device_ops tun_netdev_ops = {
+	.ndo_init		= tun_net_init,
+	.ndo_uninit		= tun_net_uninit,
+	.ndo_open		= tun_net_open,
+	.ndo_stop		= tun_net_close,
+	.ndo_start_xmit		= tun_net_xmit,
+	.ndo_fix_features	= tun_net_fix_features,
+	.ndo_select_queue	= tun_select_queue,
+	.ndo_set_rx_headroom	= tun_set_headroom,
+	.ndo_get_stats64	= tun_net_get_stats64,
+	.ndo_change_carrier	= tun_net_change_carrier,
+};
+
+static void __tun_xdp_flush_tfile(struct tun_file *tfile)
+{
+	/* Notify and wake up reader process */
+	if (tfile->flags & TUN_FASYNC)
+		kill_fasync(&tfile->fasync, SIGIO, POLL_IN);
+	tfile->socket.sk->sk_data_ready(tfile->socket.sk);
+}
+
+static int tun_xdp_xmit(struct net_device *dev, int n,
+			struct xdp_frame **frames, u32 flags)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+	struct tun_file *tfile;
+	u32 numqueues;
+	int nxmit = 0;
+	int i;
+
+	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
+		return -EINVAL;
+
+	rcu_read_lock();
+
+resample:
+	numqueues = READ_ONCE(tun->numqueues);
+	if (!numqueues) {
+		rcu_read_unlock();
+		return -ENXIO; /* Caller will free/return all frames */
+	}
+
+	tfile = rcu_dereference(tun->tfiles[smp_processor_id() %
+					    numqueues]);
+	if (unlikely(!tfile))
+		goto resample;
+
+	spin_lock(&tfile->tx_ring.producer_lock);
+	for (i = 0; i < n; i++) {
+		struct xdp_frame *xdp = frames[i];
+		/* Encode the XDP flag into lowest bit for consumer to differ
+		 * XDP buffer from sk_buff.
+		 */
+		void *frame = tun_xdp_to_ptr(xdp);
+
+		if (__ptr_ring_produce(&tfile->tx_ring, frame)) {
+			dev_core_stats_tx_dropped_inc(dev);
+			break;
+		}
+		nxmit++;
+	}
+	spin_unlock(&tfile->tx_ring.producer_lock);
+
+	if (flags & XDP_XMIT_FLUSH)
+		__tun_xdp_flush_tfile(tfile);
+
+	rcu_read_unlock();
+	return nxmit;
+}
+
+static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
+{
+	struct xdp_frame *frame = xdp_convert_buff_to_frame(xdp);
+	int nxmit;
+
+	if (unlikely(!frame))
+		return -EOVERFLOW;
+
+	nxmit = tun_xdp_xmit(dev, 1, &frame, XDP_XMIT_FLUSH);
+	if (!nxmit)
+		xdp_return_frame_rx_napi(frame);
+	return nxmit;
+}
+
+static const struct net_device_ops tap_netdev_ops = {
+	.ndo_init		= tun_net_init,
+	.ndo_uninit		= tun_net_uninit,
+	.ndo_open		= tun_net_open,
+	.ndo_stop		= tun_net_close,
+	.ndo_start_xmit		= tun_net_xmit,
+	.ndo_fix_features	= tun_net_fix_features,
+	.ndo_set_rx_mode	= tun_net_mclist,
+	.ndo_set_mac_address	= eth_mac_addr,
+	.ndo_validate_addr	= eth_validate_addr,
+	.ndo_select_queue	= tun_select_queue,
+	.ndo_features_check	= passthru_features_check,
+	.ndo_set_rx_headroom	= tun_set_headroom,
+	.ndo_get_stats64	= dev_get_tstats64,
+	.ndo_bpf		= tun_xdp,
+	.ndo_xdp_xmit		= tun_xdp_xmit,
+	.ndo_change_carrier	= tun_net_change_carrier,
+};
+
+static void tun_flow_init(struct tun_struct *tun)
+{
+	int i;
+
+	for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++)
+		INIT_HLIST_HEAD(&tun->flows[i]);
+
+	tun->ageing_time = TUN_FLOW_EXPIRE;
+	timer_setup(&tun->flow_gc_timer, tun_flow_cleanup, 0);
+	mod_timer(&tun->flow_gc_timer,
+		  round_jiffies_up(jiffies + tun->ageing_time));
+}
+
+static void tun_flow_uninit(struct tun_struct *tun)
+{
+	del_timer_sync(&tun->flow_gc_timer);
+	tun_flow_flush(tun);
+}
+
+#define MIN_MTU 68
+#define MAX_MTU 65535
+
+/* Initialize net device. */
+static void tun_net_initialize(struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	switch (tun->flags & TUN_TYPE_MASK) {
+	case IFF_TUN:
+		dev->netdev_ops = &tun_netdev_ops;
+		dev->header_ops = &ip_tunnel_header_ops;
+
+		/* Point-to-Point TUN Device */
+		dev->hard_header_len = 0;
+		dev->addr_len = 0;
+		dev->mtu = 1500;
+
+		/* Zero header length */
+		dev->type = ARPHRD_NONE;
+		dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
+		break;
+
+	case IFF_TAP:
+		dev->netdev_ops = &tap_netdev_ops;
+		/* Ethernet TAP Device */
+		ether_setup(dev);
+		dev->priv_flags &= ~IFF_TX_SKB_SHARING;
+		dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+
+		eth_hw_addr_random(dev);
+
+		break;
+	}
+
+	dev->min_mtu = MIN_MTU;
+	dev->max_mtu = MAX_MTU - dev->hard_header_len;
+}
+
+static bool tun_sock_writeable(struct tun_struct *tun, struct tun_file *tfile)
+{
+	struct sock *sk = tfile->socket.sk;
+
+	return (tun->dev->flags & IFF_UP) && sock_writeable(sk);
+}
+
+/* Character device part */
+
+/* Poll */
+static __poll_t tun_chr_poll(struct file *file, poll_table *wait)
+{
+	struct tun_file *tfile = file->private_data;
+	struct tun_struct *tun = tun_get(tfile);
+	struct sock *sk;
+	__poll_t mask = 0;
+
+	if (!tun)
+		return EPOLLERR;
+
+	sk = tfile->socket.sk;
+
+	poll_wait(file, sk_sleep(sk), wait);
+
+	if (!ptr_ring_empty(&tfile->tx_ring))
+		mask |= EPOLLIN | EPOLLRDNORM;
+
+	/* Make sure SOCKWQ_ASYNC_NOSPACE is set if not writable to
+	 * guarantee EPOLLOUT to be raised by either here or
+	 * tun_sock_write_space(). Then process could get notification
+	 * after it writes to a down device and meets -EIO.
+	 */
+	if (tun_sock_writeable(tun, tfile) ||
+	    (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags) &&
+	     tun_sock_writeable(tun, tfile)))
+		mask |= EPOLLOUT | EPOLLWRNORM;
+
+	if (tun->dev->reg_state != NETREG_REGISTERED)
+		mask = EPOLLERR;
+
+	tun_put(tun);
+	return mask;
+}
+
+static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile,
+					    size_t len,
+					    const struct iov_iter *it)
+{
+	struct sk_buff *skb;
+	size_t linear;
+	int err;
+	int i;
+
+	if (it->nr_segs > MAX_SKB_FRAGS + 1 ||
+	    len > (ETH_MAX_MTU - NET_SKB_PAD - NET_IP_ALIGN))
+		return ERR_PTR(-EMSGSIZE);
+
+	local_bh_disable();
+	skb = napi_get_frags(&tfile->napi);
+	local_bh_enable();
+	if (!skb)
+		return ERR_PTR(-ENOMEM);
+
+	linear = iov_iter_single_seg_count(it);
+	err = __skb_grow(skb, linear);
+	if (err)
+		goto free;
+
+	skb->len = len;
+	skb->data_len = len - linear;
+	skb->truesize += skb->data_len;
+
+	for (i = 1; i < it->nr_segs; i++) {
+		size_t fragsz = it->iov[i].iov_len;
+		struct page *page;
+		void *frag;
+
+		if (fragsz == 0 || fragsz > PAGE_SIZE) {
+			err = -EINVAL;
+			goto free;
+		}
+		frag = netdev_alloc_frag(fragsz);
+		if (!frag) {
+			err = -ENOMEM;
+			goto free;
+		}
+		page = virt_to_head_page(frag);
+		skb_fill_page_desc(skb, i - 1, page,
+				   frag - page_address(page), fragsz);
+	}
+
+	return skb;
+free:
+	/* frees skb and all frags allocated with napi_alloc_frag() */
+	napi_free_frags(&tfile->napi);
+	return ERR_PTR(err);
+}
+
+/* prepad is the amount to reserve at front.  len is length after that.
+ * linear is a hint as to how much to copy (usually headers). */
+static struct sk_buff *tun_alloc_skb(struct tun_file *tfile,
+				     size_t prepad, size_t len,
+				     size_t linear, int noblock)
+{
+	struct sock *sk = tfile->socket.sk;
+	struct sk_buff *skb;
+	int err;
+
+	/* Under a page?  Don't bother with paged skb. */
+	if (prepad + len < PAGE_SIZE || !linear)
+		linear = len;
+
+	skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
+				   &err, 0);
+	if (!skb)
+		return ERR_PTR(err);
+
+	skb_reserve(skb, prepad);
+	skb_put(skb, linear);
+	skb->data_len = len - linear;
+	skb->len += len - linear;
+
+	return skb;
+}
+
+static void tun_rx_batched(struct tun_struct *tun, struct tun_file *tfile,
+			   struct sk_buff *skb, int more)
+{
+	struct sk_buff_head *queue = &tfile->sk.sk_write_queue;
+	struct sk_buff_head process_queue;
+	u32 rx_batched = tun->rx_batched;
+	bool rcv = false;
+
+	if (!rx_batched || (!more && skb_queue_empty(queue))) {
+		local_bh_disable();
+		skb_record_rx_queue(skb, tfile->queue_index);
+		netif_receive_skb(skb);
+		local_bh_enable();
+		return;
+	}
+
+	spin_lock(&queue->lock);
+	if (!more || skb_queue_len(queue) == rx_batched) {
+		__skb_queue_head_init(&process_queue);
+		skb_queue_splice_tail_init(queue, &process_queue);
+		rcv = true;
+	} else {
+		__skb_queue_tail(queue, skb);
+	}
+	spin_unlock(&queue->lock);
+
+	if (rcv) {
+		struct sk_buff *nskb;
+
+		local_bh_disable();
+		while ((nskb = __skb_dequeue(&process_queue))) {
+			skb_record_rx_queue(nskb, tfile->queue_index);
+			netif_receive_skb(nskb);
+		}
+		skb_record_rx_queue(skb, tfile->queue_index);
+		netif_receive_skb(skb);
+		local_bh_enable();
+	}
+}
+
+static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
+			      int len, int noblock, bool zerocopy)
+{
+	if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
+		return false;
+
+	if (tfile->socket.sk->sk_sndbuf != INT_MAX)
+		return false;
+
+	if (!noblock)
+		return false;
+
+	if (zerocopy)
+		return false;
+
+	if (SKB_DATA_ALIGN(len + TUN_RX_PAD + XDP_PACKET_HEADROOM) +
+	    SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PAGE_SIZE)
+		return false;
+
+	return true;
+}
+
+static struct sk_buff *__tun_build_skb(struct tun_file *tfile,
+				       struct page_frag *alloc_frag, char *buf,
+				       int buflen, int len, int pad)
+{
+	struct sk_buff *skb = build_skb(buf, buflen);
+
+	if (!skb)
+		return ERR_PTR(-ENOMEM);
+
+	skb_reserve(skb, pad);
+	skb_put(skb, len);
+	skb_set_owner_w(skb, tfile->socket.sk);
+
+	get_page(alloc_frag->page);
+	alloc_frag->offset += buflen;
+
+	return skb;
+}
+
+static int tun_xdp_act(struct tun_struct *tun, struct bpf_prog *xdp_prog,
+		       struct xdp_buff *xdp, u32 act)
+{
+	int err;
+
+	switch (act) {
+	case XDP_REDIRECT:
+		err = xdp_do_redirect(tun->dev, xdp, xdp_prog);
+		if (err) {
+			dev_core_stats_rx_dropped_inc(tun->dev);
+			return err;
+		}
+		dev_sw_netstats_rx_add(tun->dev, xdp->data_end - xdp->data);
+		break;
+	case XDP_TX:
+		err = tun_xdp_tx(tun->dev, xdp);
+		if (err < 0) {
+			dev_core_stats_rx_dropped_inc(tun->dev);
+			return err;
+		}
+		dev_sw_netstats_rx_add(tun->dev, xdp->data_end - xdp->data);
+		break;
+	case XDP_PASS:
+		break;
+	default:
+		bpf_warn_invalid_xdp_action(tun->dev, xdp_prog, act);
+		fallthrough;
+	case XDP_ABORTED:
+		trace_xdp_exception(tun->dev, xdp_prog, act);
+		fallthrough;
+	case XDP_DROP:
+		dev_core_stats_rx_dropped_inc(tun->dev);
+		break;
+	}
+
+	return act;
+}
+
+static struct sk_buff *tun_build_skb(struct tun_struct *tun,
+				     struct tun_file *tfile,
+				     struct iov_iter *from,
+				     struct virtio_net_hdr *hdr,
+				     int len, int *skb_xdp)
+{
+	struct page_frag *alloc_frag = &current->task_frag;
+	struct bpf_prog *xdp_prog;
+	int buflen = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	char *buf;
+	size_t copied;
+	int pad = TUN_RX_PAD;
+	int err = 0;
+
+	rcu_read_lock();
+	xdp_prog = rcu_dereference(tun->xdp_prog);
+	if (xdp_prog)
+		pad += XDP_PACKET_HEADROOM;
+	buflen += SKB_DATA_ALIGN(len + pad);
+	rcu_read_unlock();
+
+	alloc_frag->offset = ALIGN((u64)alloc_frag->offset, SMP_CACHE_BYTES);
+	if (unlikely(!skb_page_frag_refill(buflen, alloc_frag, GFP_KERNEL)))
+		return ERR_PTR(-ENOMEM);
+
+	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
+	copied = copy_page_from_iter(alloc_frag->page,
+				     alloc_frag->offset + pad,
+				     len, from);
+	if (copied != len)
+		return ERR_PTR(-EFAULT);
+
+	/* There's a small window that XDP may be set after the check
+	 * of xdp_prog above, this should be rare and for simplicity
+	 * we do XDP on skb in case the headroom is not enough.
+	 */
+	if (hdr->gso_type || !xdp_prog) {
+		*skb_xdp = 1;
+		return __tun_build_skb(tfile, alloc_frag, buf, buflen, len,
+				       pad);
+	}
+
+	*skb_xdp = 0;
+
+	local_bh_disable();
+	rcu_read_lock();
+	xdp_prog = rcu_dereference(tun->xdp_prog);
+	if (xdp_prog) {
+		struct xdp_buff xdp;
+		u32 act;
+
+		xdp_init_buff(&xdp, buflen, &tfile->xdp_rxq);
+		xdp_prepare_buff(&xdp, buf, pad, len, false);
+
+		act = bpf_prog_run_xdp(xdp_prog, &xdp);
+		if (act == XDP_REDIRECT || act == XDP_TX) {
+			get_page(alloc_frag->page);
+			alloc_frag->offset += buflen;
+		}
+		err = tun_xdp_act(tun, xdp_prog, &xdp, act);
+		if (err < 0) {
+			if (act == XDP_REDIRECT || act == XDP_TX)
+				put_page(alloc_frag->page);
+			goto out;
+		}
+
+		if (err == XDP_REDIRECT)
+			xdp_do_flush();
+		if (err != XDP_PASS)
+			goto out;
+
+		pad = xdp.data - xdp.data_hard_start;
+		len = xdp.data_end - xdp.data;
+	}
+	rcu_read_unlock();
+	local_bh_enable();
+
+	return __tun_build_skb(tfile, alloc_frag, buf, buflen, len, pad);
+
+out:
+	rcu_read_unlock();
+	local_bh_enable();
+	return NULL;
+}
+
+/* Get packet from user space buffer */
+static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
+			    void *msg_control, struct iov_iter *from,
+			    int noblock, bool more)
+{
+	struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
+	struct sk_buff *skb;
+	size_t total_len = iov_iter_count(from);
+	size_t len = total_len, align = tun->align, linear;
+	struct virtio_net_hdr gso = { 0 };
+	int good_linear;
+	int copylen;
+	bool zerocopy = false;
+	int err;
+	u32 rxhash = 0;
+	int skb_xdp = 1;
+	bool frags = tun_napi_frags_enabled(tfile);
+	enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
+
+	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);
+		err = PTR_ERR_OR_ZERO(skb);
+		if (err)
+			goto drop;
+		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);
+		}
+
+		err = PTR_ERR_OR_ZERO(skb);
+		if (err)
+			goto drop;
+
+		if (zerocopy)
+			err = zerocopy_sg_from_iter(skb, from);
+		else
+			err = skb_copy_datagram_from_iter(skb, 0, from, len);
+
+		if (err) {
+			err = -EFAULT;
+			drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT;
+			goto drop;
+		}
+	}
+
+	if (virtio_net_hdr_to_skb(skb, &gso, tun_is_little_endian(tun))) {
+		atomic_long_inc(&tun->rx_frame_errors);
+		err = -EINVAL;
+		goto free_skb;
+	}
+
+	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:
+				err = -EINVAL;
+				goto drop;
+			}
+		}
+
+		skb_reset_mac_header(skb);
+		skb->protocol = pi.proto;
+		skb->dev = tun->dev;
+		break;
+	case IFF_TAP:
+		if (frags && !pskb_may_pull(skb, ETH_HLEN)) {
+			err = -ENOMEM;
+			drop_reason = SKB_DROP_REASON_HDR_TRUNC;
+			goto drop;
+		}
+		skb->protocol = eth_type_trans(skb, tun->dev);
+		break;
+	}
+
+	/* copy skb_ubuf_info for callback when skb has no error */
+	if (zerocopy) {
+		skb_zcopy_init(skb, msg_control);
+	} else if (msg_control) {
+		struct ubuf_info *uarg = msg_control;
+		uarg->callback(NULL, uarg, false);
+	}
+
+	skb_reset_network_header(skb);
+	skb_probe_transport_header(skb);
+	skb_record_rx_queue(skb, tfile->queue_index);
+
+	if (skb_xdp) {
+		struct bpf_prog *xdp_prog;
+		int ret;
+
+		local_bh_disable();
+		rcu_read_lock();
+		xdp_prog = rcu_dereference(tun->xdp_prog);
+		if (xdp_prog) {
+			ret = do_xdp_generic(xdp_prog, skb);
+			if (ret != XDP_PASS) {
+				rcu_read_unlock();
+				local_bh_enable();
+				goto unlock_frags;
+			}
+		}
+		rcu_read_unlock();
+		local_bh_enable();
+	}
+
+	/* Compute the costly rx hash only if needed for flow updates.
+	 * We may get a very small possibility of OOO during switching, not
+	 * worth to optimize.
+	 */
+	if (!rcu_access_pointer(tun->steering_prog) && tun->numqueues > 1 &&
+	    !tfile->detached)
+		rxhash = __skb_get_hash_symmetric(skb);
+
+	rcu_read_lock();
+	if (unlikely(!(tun->dev->flags & IFF_UP))) {
+		err = -EIO;
+		rcu_read_unlock();
+		drop_reason = SKB_DROP_REASON_DEV_READY;
+		goto drop;
+	}
+
+	if (frags) {
+		u32 headlen;
+
+		/* Exercise flow dissector code path. */
+		skb_push(skb, ETH_HLEN);
+		headlen = eth_get_headlen(tun->dev, skb->data,
+					  skb_headlen(skb));
+
+		if (unlikely(headlen > skb_headlen(skb))) {
+			WARN_ON_ONCE(1);
+			err = -ENOMEM;
+			dev_core_stats_rx_dropped_inc(tun->dev);
+napi_busy:
+			napi_free_frags(&tfile->napi);
+			rcu_read_unlock();
+			mutex_unlock(&tfile->napi_mutex);
+			return err;
+		}
+
+		if (likely(napi_schedule_prep(&tfile->napi))) {
+			local_bh_disable();
+			napi_gro_frags(&tfile->napi);
+			napi_complete(&tfile->napi);
+			local_bh_enable();
+		} else {
+			err = -EBUSY;
+			goto napi_busy;
+		}
+		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);
+
+		if (unlikely(tfile->detached)) {
+			spin_unlock_bh(&queue->lock);
+			rcu_read_unlock();
+			err = -EBUSY;
+			goto free_skb;
+		}
+
+		__skb_queue_tail(queue, skb);
+		queue_len = skb_queue_len(queue);
+		spin_unlock(&queue->lock);
+
+		if (!more || queue_len > NAPI_POLL_WEIGHT)
+			napi_schedule(&tfile->napi);
+
+		local_bh_enable();
+	} else if (!IS_ENABLED(CONFIG_4KSTACKS)) {
+		tun_rx_batched(tun, tfile, skb, more);
+	} else {
+		netif_rx(skb);
+	}
+	rcu_read_unlock();
+
+	preempt_disable();
+	dev_sw_netstats_rx_add(tun->dev, len);
+	preempt_enable();
+
+	if (rxhash)
+		tun_flow_update(tun, rxhash, tfile);
+
+	return total_len;
+
+drop:
+	if (err != -EAGAIN)
+		dev_core_stats_rx_dropped_inc(tun->dev);
+
+free_skb:
+	if (!IS_ERR_OR_NULL(skb))
+		kfree_skb_reason(skb, drop_reason);
+
+unlock_frags:
+	if (frags) {
+		tfile->napi.skb = NULL;
+		mutex_unlock(&tfile->napi_mutex);
+	}
+
+	return err ?: total_len;
+}
+
+static ssize_t tun_chr_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct tun_file *tfile = file->private_data;
+	struct tun_struct *tun = tun_get(tfile);
+	ssize_t result;
+	int noblock = 0;
+
+	if (!tun)
+		return -EBADFD;
+
+	if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
+		noblock = 1;
+
+	result = tun_get_user(tun, tfile, NULL, from, noblock, false);
+
+	tun_put(tun);
+	return result;
+}
+
+static ssize_t tun_put_user_xdp(struct tun_struct *tun,
+				struct tun_file *tfile,
+				struct xdp_frame *xdp_frame,
+				struct iov_iter *iter)
+{
+	int vnet_hdr_sz = 0;
+	size_t size = xdp_frame->len;
+	size_t ret;
+
+	if (tun->flags & IFF_VNET_HDR) {
+		struct virtio_net_hdr gso = { 0 };
+
+		vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
+		if (unlikely(iov_iter_count(iter) < vnet_hdr_sz))
+			return -EINVAL;
+		if (unlikely(copy_to_iter(&gso, sizeof(gso), iter) !=
+			     sizeof(gso)))
+			return -EFAULT;
+		iov_iter_advance(iter, vnet_hdr_sz - sizeof(gso));
+	}
+
+	ret = copy_to_iter(xdp_frame->data, size, iter) + vnet_hdr_sz;
+
+	preempt_disable();
+	dev_sw_netstats_tx_add(tun->dev, 1, ret);
+	preempt_enable();
+
+	return ret;
+}
+
+/* Put packet to the user space buffer */
+static ssize_t tun_put_user(struct tun_struct *tun,
+			    struct tun_file *tfile,
+			    struct sk_buff *skb,
+			    struct iov_iter *iter)
+{
+	struct tun_pi pi = { 0, skb->protocol };
+	ssize_t total;
+	int vlan_offset = 0;
+	int vlan_hlen = 0;
+	int vnet_hdr_sz = 0;
+
+	if (skb_vlan_tag_present(skb))
+		vlan_hlen = VLAN_HLEN;
+
+	if (tun->flags & IFF_VNET_HDR)
+		vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
+
+	total = skb->len + vlan_hlen + vnet_hdr_sz;
+
+	if (!(tun->flags & IFF_NO_PI)) {
+		if (iov_iter_count(iter) < sizeof(pi))
+			return -EINVAL;
+
+		total += sizeof(pi);
+		if (iov_iter_count(iter) < total) {
+			/* Packet will be striped */
+			pi.flags |= TUN_PKT_STRIP;
+		}
+
+		if (copy_to_iter(&pi, sizeof(pi), iter) != sizeof(pi))
+			return -EFAULT;
+	}
+
+	if (vnet_hdr_sz) {
+		struct virtio_net_hdr gso;
+
+		if (iov_iter_count(iter) < vnet_hdr_sz)
+			return -EINVAL;
+
+		if (virtio_net_hdr_from_skb(skb, &gso,
+					    tun_is_little_endian(tun), true,
+					    vlan_hlen)) {
+			struct skb_shared_info *sinfo = skb_shinfo(skb);
+			pr_err("unexpected GSO type: "
+			       "0x%x, gso_size %d, hdr_len %d\n",
+			       sinfo->gso_type, tun16_to_cpu(tun, gso.gso_size),
+			       tun16_to_cpu(tun, gso.hdr_len));
+			print_hex_dump(KERN_ERR, "tun: ",
+				       DUMP_PREFIX_NONE,
+				       16, 1, skb->head,
+				       min((int)tun16_to_cpu(tun, gso.hdr_len), 64), true);
+			WARN_ON_ONCE(1);
+			return -EINVAL;
+		}
+
+		if (copy_to_iter(&gso, sizeof(gso), iter) != sizeof(gso))
+			return -EFAULT;
+
+		iov_iter_advance(iter, vnet_hdr_sz - sizeof(gso));
+	}
+
+	if (vlan_hlen) {
+		int ret;
+		struct veth veth;
+
+		veth.h_vlan_proto = skb->vlan_proto;
+		veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
+
+		vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
+
+		ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
+		if (ret || !iov_iter_count(iter))
+			goto done;
+
+		ret = copy_to_iter(&veth, sizeof(veth), iter);
+		if (ret != sizeof(veth) || !iov_iter_count(iter))
+			goto done;
+	}
+
+	skb_copy_datagram_iter(skb, vlan_offset, iter, skb->len - vlan_offset);
+
+done:
+	/* caller is in process context, */
+	preempt_disable();
+	dev_sw_netstats_tx_add(tun->dev, 1, skb->len + vlan_hlen);
+	preempt_enable();
+
+	return total;
+}
+
+static void *tun_ring_recv(struct tun_file *tfile, int noblock, int *err)
+{
+	DECLARE_WAITQUEUE(wait, current);
+	void *ptr = NULL;
+	int error = 0;
+
+	ptr = ptr_ring_consume(&tfile->tx_ring);
+	if (ptr)
+		goto out;
+	if (noblock) {
+		error = -EAGAIN;
+		goto out;
+	}
+
+	add_wait_queue(&tfile->socket.wq.wait, &wait);
+
+	while (1) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		ptr = ptr_ring_consume(&tfile->tx_ring);
+		if (ptr)
+			break;
+		if (signal_pending(current)) {
+			error = -ERESTARTSYS;
+			break;
+		}
+		if (tfile->socket.sk->sk_shutdown & RCV_SHUTDOWN) {
+			error = -EFAULT;
+			break;
+		}
+
+		schedule();
+	}
+
+	__set_current_state(TASK_RUNNING);
+	remove_wait_queue(&tfile->socket.wq.wait, &wait);
+
+out:
+	*err = error;
+	return ptr;
+}
+
+static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
+			   struct iov_iter *to,
+			   int noblock, void *ptr)
+{
+	ssize_t ret;
+	int err;
+
+	if (!iov_iter_count(to)) {
+		tun_ptr_free(ptr);
+		return 0;
+	}
+
+	if (!ptr) {
+		/* Read frames from ring */
+		ptr = tun_ring_recv(tfile, noblock, &err);
+		if (!ptr)
+			return err;
+	}
+
+	if (tun_is_xdp_frame(ptr)) {
+		struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
+
+		ret = tun_put_user_xdp(tun, tfile, xdpf, to);
+		xdp_return_frame(xdpf);
+	} else {
+		struct sk_buff *skb = ptr;
+
+		ret = tun_put_user(tun, tfile, skb, to);
+		if (unlikely(ret < 0))
+			kfree_skb(skb);
+		else
+			consume_skb(skb);
+	}
+
+	return ret;
+}
+
+static ssize_t tun_chr_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct tun_file *tfile = file->private_data;
+	struct tun_struct *tun = tun_get(tfile);
+	ssize_t len = iov_iter_count(to), ret;
+	int noblock = 0;
+
+	if (!tun)
+		return -EBADFD;
+
+	if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
+		noblock = 1;
+
+	ret = tun_do_read(tun, tfile, to, noblock, NULL);
+	ret = min_t(ssize_t, ret, len);
+	if (ret > 0)
+		iocb->ki_pos = ret;
+	tun_put(tun);
+	return ret;
+}
+
+static void tun_prog_free(struct rcu_head *rcu)
+{
+	struct tun_prog *prog = container_of(rcu, struct tun_prog, rcu);
+
+	bpf_prog_destroy(prog->prog);
+	kfree(prog);
+}
+
+static int __tun_set_ebpf(struct tun_struct *tun,
+			  struct tun_prog __rcu **prog_p,
+			  struct bpf_prog *prog)
+{
+	struct tun_prog *old, *new = NULL;
+
+	if (prog) {
+		new = kmalloc(sizeof(*new), GFP_KERNEL);
+		if (!new)
+			return -ENOMEM;
+		new->prog = prog;
+	}
+
+	spin_lock_bh(&tun->lock);
+	old = rcu_dereference_protected(*prog_p,
+					lockdep_is_held(&tun->lock));
+	rcu_assign_pointer(*prog_p, new);
+	spin_unlock_bh(&tun->lock);
+
+	if (old)
+		call_rcu(&old->rcu, tun_prog_free);
+
+	return 0;
+}
+
+static void tun_free_netdev(struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	BUG_ON(!(list_empty(&tun->disabled)));
+
+	free_percpu(dev->tstats);
+	tun_flow_uninit(tun);
+	security_tun_dev_free_security(tun->security);
+	__tun_set_ebpf(tun, &tun->steering_prog, NULL);
+	__tun_set_ebpf(tun, &tun->filter_prog, NULL);
+}
+
+static void tun_setup(struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	tun->owner = INVALID_UID;
+	tun->group = INVALID_GID;
+	tun_default_link_ksettings(dev, &tun->link_ksettings);
+
+	dev->ethtool_ops = &tun_ethtool_ops;
+	dev->needs_free_netdev = true;
+	dev->priv_destructor = tun_free_netdev;
+	/* We prefer our own queue length */
+	dev->tx_queue_len = TUN_READQ_SIZE;
+}
+
+/* Trivial set of netlink ops to allow deleting tun or tap
+ * device with netlink.
+ */
+static int tun_validate(struct nlattr *tb[], struct nlattr *data[],
+			struct netlink_ext_ack *extack)
+{
+	NL_SET_ERR_MSG(extack,
+		       "tun/tap creation via rtnetlink is not supported.");
+	return -EOPNOTSUPP;
+}
+
+static size_t tun_get_size(const struct net_device *dev)
+{
+	BUILD_BUG_ON(sizeof(u32) != sizeof(uid_t));
+	BUILD_BUG_ON(sizeof(u32) != sizeof(gid_t));
+
+	return nla_total_size(sizeof(uid_t)) + /* OWNER */
+	       nla_total_size(sizeof(gid_t)) + /* GROUP */
+	       nla_total_size(sizeof(u8)) + /* TYPE */
+	       nla_total_size(sizeof(u8)) + /* PI */
+	       nla_total_size(sizeof(u8)) + /* VNET_HDR */
+	       nla_total_size(sizeof(u8)) + /* PERSIST */
+	       nla_total_size(sizeof(u8)) + /* MULTI_QUEUE */
+	       nla_total_size(sizeof(u32)) + /* NUM_QUEUES */
+	       nla_total_size(sizeof(u32)) + /* NUM_DISABLED_QUEUES */
+	       0;
+}
+
+static int tun_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	if (nla_put_u8(skb, IFLA_TUN_TYPE, tun->flags & TUN_TYPE_MASK))
+		goto nla_put_failure;
+	if (uid_valid(tun->owner) &&
+	    nla_put_u32(skb, IFLA_TUN_OWNER,
+			from_kuid_munged(current_user_ns(), tun->owner)))
+		goto nla_put_failure;
+	if (gid_valid(tun->group) &&
+	    nla_put_u32(skb, IFLA_TUN_GROUP,
+			from_kgid_munged(current_user_ns(), tun->group)))
+		goto nla_put_failure;
+	if (nla_put_u8(skb, IFLA_TUN_PI, !(tun->flags & IFF_NO_PI)))
+		goto nla_put_failure;
+	if (nla_put_u8(skb, IFLA_TUN_VNET_HDR, !!(tun->flags & IFF_VNET_HDR)))
+		goto nla_put_failure;
+	if (nla_put_u8(skb, IFLA_TUN_PERSIST, !!(tun->flags & IFF_PERSIST)))
+		goto nla_put_failure;
+	if (nla_put_u8(skb, IFLA_TUN_MULTI_QUEUE,
+		       !!(tun->flags & IFF_MULTI_QUEUE)))
+		goto nla_put_failure;
+	if (tun->flags & IFF_MULTI_QUEUE) {
+		if (nla_put_u32(skb, IFLA_TUN_NUM_QUEUES, tun->numqueues))
+			goto nla_put_failure;
+		if (nla_put_u32(skb, IFLA_TUN_NUM_DISABLED_QUEUES,
+				tun->numdisabled))
+			goto nla_put_failure;
+	}
+
+	return 0;
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
+static struct rtnl_link_ops tun_link_ops __read_mostly = {
+	.kind		= DRV_NAME,
+	.priv_size	= sizeof(struct tun_struct),
+	.setup		= tun_setup,
+	.validate	= tun_validate,
+	.get_size       = tun_get_size,
+	.fill_info      = tun_fill_info,
+};
+
+static void tun_sock_write_space(struct sock *sk)
+{
+	struct tun_file *tfile;
+	wait_queue_head_t *wqueue;
+
+	if (!sock_writeable(sk))
+		return;
+
+	if (!test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
+		return;
+
+	wqueue = sk_sleep(sk);
+	if (wqueue && waitqueue_active(wqueue))
+		wake_up_interruptible_sync_poll(wqueue, EPOLLOUT |
+						EPOLLWRNORM | EPOLLWRBAND);
+
+	tfile = container_of(sk, struct tun_file, sk);
+	kill_fasync(&tfile->fasync, SIGIO, POLL_OUT);
+}
+
+static void tun_put_page(struct tun_page *tpage)
+{
+	if (tpage->page)
+		__page_frag_cache_drain(tpage->page, tpage->count);
+}
+
+static int tun_xdp_one(struct tun_struct *tun,
+		       struct tun_file *tfile,
+		       struct xdp_buff *xdp, int *flush,
+		       struct tun_page *tpage)
+{
+	unsigned int datasize = xdp->data_end - xdp->data;
+	struct tun_xdp_hdr *hdr = xdp->data_hard_start;
+	struct virtio_net_hdr *gso = &hdr->gso;
+	struct bpf_prog *xdp_prog;
+	struct sk_buff *skb = NULL;
+	struct sk_buff_head *queue;
+	u32 rxhash = 0, act;
+	int buflen = hdr->buflen;
+	int ret = 0;
+	bool skb_xdp = false;
+	struct page *page;
+
+	xdp_prog = rcu_dereference(tun->xdp_prog);
+	if (xdp_prog) {
+		if (gso->gso_type) {
+			skb_xdp = true;
+			goto build;
+		}
+
+		xdp_init_buff(xdp, buflen, &tfile->xdp_rxq);
+		xdp_set_data_meta_invalid(xdp);
+
+		act = bpf_prog_run_xdp(xdp_prog, xdp);
+		ret = tun_xdp_act(tun, xdp_prog, xdp, act);
+		if (ret < 0) {
+			put_page(virt_to_head_page(xdp->data));
+			return ret;
+		}
+
+		switch (ret) {
+		case XDP_REDIRECT:
+			*flush = true;
+			fallthrough;
+		case XDP_TX:
+			return 0;
+		case XDP_PASS:
+			break;
+		default:
+			page = virt_to_head_page(xdp->data);
+			if (tpage->page == page) {
+				++tpage->count;
+			} else {
+				tun_put_page(tpage);
+				tpage->page = page;
+				tpage->count = 1;
+			}
+			return 0;
+		}
+	}
+
+build:
+	skb = build_skb(xdp->data_hard_start, buflen);
+	if (!skb) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	skb_reserve(skb, xdp->data - xdp->data_hard_start);
+	skb_put(skb, xdp->data_end - xdp->data);
+
+	if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
+		atomic_long_inc(&tun->rx_frame_errors);
+		kfree_skb(skb);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	skb->protocol = eth_type_trans(skb, tun->dev);
+	skb_reset_network_header(skb);
+	skb_probe_transport_header(skb);
+	skb_record_rx_queue(skb, tfile->queue_index);
+
+	if (skb_xdp) {
+		ret = do_xdp_generic(xdp_prog, skb);
+		if (ret != XDP_PASS) {
+			ret = 0;
+			goto out;
+		}
+	}
+
+	if (!rcu_dereference(tun->steering_prog) && tun->numqueues > 1 &&
+	    !tfile->detached)
+		rxhash = __skb_get_hash_symmetric(skb);
+
+	if (tfile->napi_enabled) {
+		queue = &tfile->sk.sk_write_queue;
+		spin_lock(&queue->lock);
+
+		if (unlikely(tfile->detached)) {
+			spin_unlock(&queue->lock);
+			kfree_skb(skb);
+			return -EBUSY;
+		}
+
+		__skb_queue_tail(queue, skb);
+		spin_unlock(&queue->lock);
+		ret = 1;
+	} else {
+		netif_receive_skb(skb);
+		ret = 0;
+	}
+
+	/* No need to disable preemption here since this function is
+	 * always called with bh disabled
+	 */
+	dev_sw_netstats_rx_add(tun->dev, datasize);
+
+	if (rxhash)
+		tun_flow_update(tun, rxhash, tfile);
+
+out:
+	return ret;
+}
+
+static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
+{
+	int ret, i;
+	struct tun_file *tfile = container_of(sock, struct tun_file, socket);
+	struct tun_struct *tun = tun_get(tfile);
+	struct tun_msg_ctl *ctl = m->msg_control;
+	struct xdp_buff *xdp;
+
+	if (!tun)
+		return -EBADFD;
+
+	if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
+	    ctl && ctl->type == TUN_MSG_PTR) {
+		struct tun_page tpage;
+		int n = ctl->num;
+		int flush = 0, queued = 0;
+
+		memset(&tpage, 0, sizeof(tpage));
+
+		local_bh_disable();
+		rcu_read_lock();
+
+		for (i = 0; i < n; i++) {
+			xdp = &((struct xdp_buff *)ctl->ptr)[i];
+			ret = tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
+			if (ret > 0)
+				queued += ret;
+		}
+
+		if (flush)
+			xdp_do_flush();
+
+		if (tfile->napi_enabled && queued > 0)
+			napi_schedule(&tfile->napi);
+
+		rcu_read_unlock();
+		local_bh_enable();
+
+		tun_put_page(&tpage);
+
+		ret = total_len;
+		goto out;
+	}
+
+	ret = tun_get_user(tun, tfile, ctl ? ctl->ptr : NULL, &m->msg_iter,
+			   m->msg_flags & MSG_DONTWAIT,
+			   m->msg_flags & MSG_MORE);
+out:
+	tun_put(tun);
+	return ret;
+}
+
+static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
+		       int flags)
+{
+	struct tun_file *tfile = container_of(sock, struct tun_file, socket);
+	struct tun_struct *tun = tun_get(tfile);
+	void *ptr = m->msg_control;
+	int ret;
+
+	if (!tun) {
+		ret = -EBADFD;
+		goto out_free;
+	}
+
+	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC|MSG_ERRQUEUE)) {
+		ret = -EINVAL;
+		goto out_put_tun;
+	}
+	if (flags & MSG_ERRQUEUE) {
+		ret = sock_recv_errqueue(sock->sk, m, total_len,
+					 SOL_PACKET, TUN_TX_TIMESTAMP);
+		goto out;
+	}
+	ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT, ptr);
+	if (ret > (ssize_t)total_len) {
+		m->msg_flags |= MSG_TRUNC;
+		ret = flags & MSG_TRUNC ? ret : total_len;
+	}
+out:
+	tun_put(tun);
+	return ret;
+
+out_put_tun:
+	tun_put(tun);
+out_free:
+	tun_ptr_free(ptr);
+	return ret;
+}
+
+static int tun_ptr_peek_len(void *ptr)
+{
+	if (likely(ptr)) {
+		if (tun_is_xdp_frame(ptr)) {
+			struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
+
+			return xdpf->len;
+		}
+		return __skb_array_len_with_tag(ptr);
+	} else {
+		return 0;
+	}
+}
+
+static int tun_peek_len(struct socket *sock)
+{
+	struct tun_file *tfile = container_of(sock, struct tun_file, socket);
+	struct tun_struct *tun;
+	int ret = 0;
+
+	tun = tun_get(tfile);
+	if (!tun)
+		return 0;
+
+	ret = PTR_RING_PEEK_CALL(&tfile->tx_ring, tun_ptr_peek_len);
+	tun_put(tun);
+
+	return ret;
+}
+
+/* Ops structure to mimic raw sockets with tun */
+static const struct proto_ops tun_socket_ops = {
+	.peek_len = tun_peek_len,
+	.sendmsg = tun_sendmsg,
+	.recvmsg = tun_recvmsg,
+};
+
+static struct proto tun_proto = {
+	.name		= "tun",
+	.owner		= THIS_MODULE,
+	.obj_size	= sizeof(struct tun_file),
+};
+
+static int tun_flags(struct tun_struct *tun)
+{
+	return tun->flags & (TUN_FEATURES | IFF_PERSIST | IFF_TUN | IFF_TAP);
+}
+
+static ssize_t tun_flags_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
+	return sysfs_emit(buf, "0x%x\n", tun_flags(tun));
+}
+
+static ssize_t owner_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
+	return uid_valid(tun->owner)?
+		sysfs_emit(buf, "%u\n",
+			   from_kuid_munged(current_user_ns(), tun->owner)) :
+		sysfs_emit(buf, "-1\n");
+}
+
+static ssize_t group_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
+	return gid_valid(tun->group) ?
+		sysfs_emit(buf, "%u\n",
+			   from_kgid_munged(current_user_ns(), tun->group)) :
+		sysfs_emit(buf, "-1\n");
+}
+
+static DEVICE_ATTR_RO(tun_flags);
+static DEVICE_ATTR_RO(owner);
+static DEVICE_ATTR_RO(group);
+
+static struct attribute *tun_dev_attrs[] = {
+	&dev_attr_tun_flags.attr,
+	&dev_attr_owner.attr,
+	&dev_attr_group.attr,
+	NULL
+};
+
+static const struct attribute_group tun_attr_group = {
+	.attrs = tun_dev_attrs
+};
+
+static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
+{
+	struct tun_struct *tun;
+	struct tun_file *tfile = file->private_data;
+	struct net_device *dev;
+	int err;
+
+	if (tfile->detached)
+		return -EINVAL;
+
+	if ((ifr->ifr_flags & IFF_NAPI_FRAGS)) {
+		if (!capable(CAP_NET_ADMIN))
+			return -EPERM;
+
+		if (!(ifr->ifr_flags & IFF_NAPI) ||
+		    (ifr->ifr_flags & TUN_TYPE_MASK) != IFF_TAP)
+			return -EINVAL;
+	}
+
+	dev = __dev_get_by_name(net, ifr->ifr_name);
+	if (dev) {
+		if (ifr->ifr_flags & IFF_TUN_EXCL)
+			return -EBUSY;
+		if ((ifr->ifr_flags & IFF_TUN) && dev->netdev_ops == &tun_netdev_ops)
+			tun = netdev_priv(dev);
+		else if ((ifr->ifr_flags & IFF_TAP) && dev->netdev_ops == &tap_netdev_ops)
+			tun = netdev_priv(dev);
+		else
+			return -EINVAL;
+
+		if (!!(ifr->ifr_flags & IFF_MULTI_QUEUE) !=
+		    !!(tun->flags & IFF_MULTI_QUEUE))
+			return -EINVAL;
+
+		if (tun_not_capable(tun))
+			return -EPERM;
+		err = security_tun_dev_open(tun->security);
+		if (err < 0)
+			return err;
+
+		err = tun_attach(tun, file, ifr->ifr_flags & IFF_NOFILTER,
+				 ifr->ifr_flags & IFF_NAPI,
+				 ifr->ifr_flags & IFF_NAPI_FRAGS, true);
+		if (err < 0)
+			return err;
+
+		if (tun->flags & IFF_MULTI_QUEUE &&
+		    (tun->numqueues + tun->numdisabled > 1)) {
+			/* One or more queue has already been attached, no need
+			 * to initialize the device again.
+			 */
+			netdev_state_change(dev);
+			return 0;
+		}
+
+		tun->flags = (tun->flags & ~TUN_FEATURES) |
+			      (ifr->ifr_flags & TUN_FEATURES);
+
+		netdev_state_change(dev);
+	} else {
+		char *name;
+		unsigned long flags = 0;
+		int queues = ifr->ifr_flags & IFF_MULTI_QUEUE ?
+			     MAX_TAP_QUEUES : 1;
+
+		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+			return -EPERM;
+		err = security_tun_dev_create();
+		if (err < 0)
+			return err;
+
+		/* Set dev type */
+		if (ifr->ifr_flags & IFF_TUN) {
+			/* TUN device */
+			flags |= IFF_TUN;
+			name = "tun%d";
+		} else if (ifr->ifr_flags & IFF_TAP) {
+			/* TAP device */
+			flags |= IFF_TAP;
+			name = "tap%d";
+		} else
+			return -EINVAL;
+
+		if (*ifr->ifr_name)
+			name = ifr->ifr_name;
+
+		dev = alloc_netdev_mqs(sizeof(struct tun_struct), name,
+				       NET_NAME_UNKNOWN, tun_setup, queues,
+				       queues);
+
+		if (!dev)
+			return -ENOMEM;
+
+		dev_net_set(dev, net);
+		dev->rtnl_link_ops = &tun_link_ops;
+		dev->ifindex = tfile->ifindex;
+		dev->sysfs_groups[0] = &tun_attr_group;
+
+		tun = netdev_priv(dev);
+		tun->dev = dev;
+		tun->flags = flags;
+		tun->txflt.count = 0;
+		tun->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
+
+		tun->align = NET_SKB_PAD;
+		tun->filter_attached = false;
+		tun->sndbuf = tfile->socket.sk->sk_sndbuf;
+		tun->rx_batched = 0;
+		RCU_INIT_POINTER(tun->steering_prog, NULL);
+
+		tun->ifr = ifr;
+		tun->file = file;
+
+		tun_net_initialize(dev);
+
+		err = register_netdevice(tun->dev);
+		if (err < 0) {
+			free_netdev(dev);
+			return err;
+		}
+		/* free_netdev() won't check refcnt, to avoid race
+		 * with dev_put() we need publish tun after registration.
+		 */
+		rcu_assign_pointer(tfile->tun, tun);
+	}
+
+	if (ifr->ifr_flags & IFF_NO_CARRIER)
+		netif_carrier_off(tun->dev);
+	else
+		netif_carrier_on(tun->dev);
+
+	/* Make sure persistent devices do not get stuck in
+	 * xoff state.
+	 */
+	if (netif_running(tun->dev))
+		netif_tx_wake_all_queues(tun->dev);
+
+	strcpy(ifr->ifr_name, tun->dev->name);
+	return 0;
+}
+
+static void tun_get_iff(struct tun_struct *tun, struct ifreq *ifr)
+{
+	strcpy(ifr->ifr_name, tun->dev->name);
+
+	ifr->ifr_flags = tun_flags(tun);
+
+}
+
+/* This is like a cut-down ethtool ops, except done via tun fd so no
+ * privs required. */
+static int set_offload(struct tun_struct *tun, unsigned long arg)
+{
+	netdev_features_t features = 0;
+
+	if (arg & TUN_F_CSUM) {
+		features |= NETIF_F_HW_CSUM;
+		arg &= ~TUN_F_CSUM;
+
+		if (arg & (TUN_F_TSO4|TUN_F_TSO6)) {
+			if (arg & TUN_F_TSO_ECN) {
+				features |= NETIF_F_TSO_ECN;
+				arg &= ~TUN_F_TSO_ECN;
+			}
+			if (arg & TUN_F_TSO4)
+				features |= NETIF_F_TSO;
+			if (arg & TUN_F_TSO6)
+				features |= NETIF_F_TSO6;
+			arg &= ~(TUN_F_TSO4|TUN_F_TSO6);
+		}
+
+		arg &= ~TUN_F_UFO;
+	}
+
+	/* This gives the user a way to test for new features in future by
+	 * trying to set them. */
+	if (arg)
+		return -EINVAL;
+
+	tun->set_features = features;
+	tun->dev->wanted_features &= ~TUN_USER_FEATURES;
+	tun->dev->wanted_features |= features;
+	netdev_update_features(tun->dev);
+
+	return 0;
+}
+
+static void tun_detach_filter(struct tun_struct *tun, int n)
+{
+	int i;
+	struct tun_file *tfile;
+
+	for (i = 0; i < n; i++) {
+		tfile = rtnl_dereference(tun->tfiles[i]);
+		lock_sock(tfile->socket.sk);
+		sk_detach_filter(tfile->socket.sk);
+		release_sock(tfile->socket.sk);
+	}
+
+	tun->filter_attached = false;
+}
+
+static int tun_attach_filter(struct tun_struct *tun)
+{
+	int i, ret = 0;
+	struct tun_file *tfile;
+
+	for (i = 0; i < tun->numqueues; i++) {
+		tfile = rtnl_dereference(tun->tfiles[i]);
+		lock_sock(tfile->socket.sk);
+		ret = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+		release_sock(tfile->socket.sk);
+		if (ret) {
+			tun_detach_filter(tun, i);
+			return ret;
+		}
+	}
+
+	tun->filter_attached = true;
+	return ret;
+}
+
+static void tun_set_sndbuf(struct tun_struct *tun)
+{
+	struct tun_file *tfile;
+	int i;
+
+	for (i = 0; i < tun->numqueues; i++) {
+		tfile = rtnl_dereference(tun->tfiles[i]);
+		tfile->socket.sk->sk_sndbuf = tun->sndbuf;
+	}
+}
+
+static int tun_set_queue(struct file *file, struct ifreq *ifr)
+{
+	struct tun_file *tfile = file->private_data;
+	struct tun_struct *tun;
+	int ret = 0;
+
+	rtnl_lock();
+
+	if (ifr->ifr_flags & IFF_ATTACH_QUEUE) {
+		tun = tfile->detached;
+		if (!tun) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+		ret = security_tun_dev_attach_queue(tun->security);
+		if (ret < 0)
+			goto unlock;
+		ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI,
+				 tun->flags & IFF_NAPI_FRAGS, true);
+	} else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
+		tun = rtnl_dereference(tfile->tun);
+		if (!tun || !(tun->flags & IFF_MULTI_QUEUE) || tfile->detached)
+			ret = -EINVAL;
+		else
+			__tun_detach(tfile, false);
+	} else
+		ret = -EINVAL;
+
+	if (ret >= 0)
+		netdev_state_change(tun->dev);
+
+unlock:
+	rtnl_unlock();
+	return ret;
+}
+
+static int tun_set_ebpf(struct tun_struct *tun, struct tun_prog __rcu **prog_p,
+			void __user *data)
+{
+	struct bpf_prog *prog;
+	int fd;
+
+	if (copy_from_user(&fd, data, sizeof(fd)))
+		return -EFAULT;
+
+	if (fd == -1) {
+		prog = NULL;
+	} else {
+		prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
+		if (IS_ERR(prog))
+			return PTR_ERR(prog);
+	}
+
+	return __tun_set_ebpf(tun, prog_p, prog);
+}
+
+/* Return correct value for tun->dev->addr_len based on tun->dev->type. */
+static unsigned char tun_get_addr_len(unsigned short type)
+{
+	switch (type) {
+	case ARPHRD_IP6GRE:
+	case ARPHRD_TUNNEL6:
+		return sizeof(struct in6_addr);
+	case ARPHRD_IPGRE:
+	case ARPHRD_TUNNEL:
+	case ARPHRD_SIT:
+		return 4;
+	case ARPHRD_ETHER:
+		return ETH_ALEN;
+	case ARPHRD_IEEE802154:
+	case ARPHRD_IEEE802154_MONITOR:
+		return IEEE802154_EXTENDED_ADDR_LEN;
+	case ARPHRD_PHONET_PIPE:
+	case ARPHRD_PPP:
+	case ARPHRD_NONE:
+		return 0;
+	case ARPHRD_6LOWPAN:
+		return EUI64_ADDR_LEN;
+	case ARPHRD_FDDI:
+		return FDDI_K_ALEN;
+	case ARPHRD_HIPPI:
+		return HIPPI_ALEN;
+	case ARPHRD_IEEE802:
+		return FC_ALEN;
+	case ARPHRD_ROSE:
+		return ROSE_ADDR_LEN;
+	case ARPHRD_NETROM:
+		return AX25_ADDR_LEN;
+	case ARPHRD_LOCALTLK:
+		return LTALK_ALEN;
+	default:
+		return 0;
+	}
+}
+
+static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg, int ifreq_len)
+{
+	struct tun_file *tfile = file->private_data;
+	struct net *net = sock_net(&tfile->sk);
+	struct tun_struct *tun;
+	void __user* argp = (void __user*)arg;
+	unsigned int carrier;
+	struct ifreq ifr;
+	kuid_t owner;
+	kgid_t group;
+	int ifindex;
+	int sndbuf;
+	int vnet_hdr_sz;
+	int le;
+	int ret;
+	bool do_notify = false;
+
+	if (cmd == TUNSETIFF || cmd == TUNSETQUEUE ||
+	    (_IOC_TYPE(cmd) == SOCK_IOC_TYPE && cmd != SIOCGSKNS)) {
+		if (copy_from_user(&ifr, argp, ifreq_len))
+			return -EFAULT;
+	} else {
+		memset(&ifr, 0, sizeof(ifr));
+	}
+	if (cmd == TUNGETFEATURES) {
+		/* Currently this just means: "what IFF flags are valid?".
+		 * This is needed because we never checked for invalid flags on
+		 * TUNSETIFF.
+		 */
+		return put_user(IFF_TUN | IFF_TAP | IFF_NO_CARRIER |
+				TUN_FEATURES, (unsigned int __user*)argp);
+	} else if (cmd == TUNSETQUEUE) {
+		return tun_set_queue(file, &ifr);
+	} else if (cmd == SIOCGSKNS) {
+		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+			return -EPERM;
+		return open_related_ns(&net->ns, get_net_ns);
+	}
+
+	rtnl_lock();
+
+	tun = tun_get(tfile);
+	if (cmd == TUNSETIFF) {
+		ret = -EEXIST;
+		if (tun)
+			goto unlock;
+
+		ifr.ifr_name[IFNAMSIZ-1] = '\0';
+
+		ret = tun_set_iff(net, file, &ifr);
+
+		if (ret)
+			goto unlock;
+
+		if (copy_to_user(argp, &ifr, ifreq_len))
+			ret = -EFAULT;
+		goto unlock;
+	}
+	if (cmd == TUNSETIFINDEX) {
+		ret = -EPERM;
+		if (tun)
+			goto unlock;
+
+		ret = -EFAULT;
+		if (copy_from_user(&ifindex, argp, sizeof(ifindex)))
+			goto unlock;
+		ret = -EINVAL;
+		if (ifindex < 0)
+			goto unlock;
+		ret = 0;
+		tfile->ifindex = ifindex;
+		goto unlock;
+	}
+
+	ret = -EBADFD;
+	if (!tun)
+		goto unlock;
+
+	netif_info(tun, drv, tun->dev, "tun_chr_ioctl cmd %u\n", cmd);
+
+	net = dev_net(tun->dev);
+	ret = 0;
+	switch (cmd) {
+	case TUNGETIFF:
+		tun_get_iff(tun, &ifr);
+
+		if (tfile->detached)
+			ifr.ifr_flags |= IFF_DETACH_QUEUE;
+		if (!tfile->socket.sk->sk_filter)
+			ifr.ifr_flags |= IFF_NOFILTER;
+
+		if (copy_to_user(argp, &ifr, ifreq_len))
+			ret = -EFAULT;
+		break;
+
+	case TUNSETNOCSUM:
+		/* Disable/Enable checksum */
+
+		/* [unimplemented] */
+		netif_info(tun, drv, tun->dev, "ignored: set checksum %s\n",
+			   arg ? "disabled" : "enabled");
+		break;
+
+	case TUNSETPERSIST:
+		/* Disable/Enable persist mode. Keep an extra reference to the
+		 * module to prevent the module being unprobed.
+		 */
+		if (arg && !(tun->flags & IFF_PERSIST)) {
+			tun->flags |= IFF_PERSIST;
+			__module_get(THIS_MODULE);
+			do_notify = true;
+		}
+		if (!arg && (tun->flags & IFF_PERSIST)) {
+			tun->flags &= ~IFF_PERSIST;
+			module_put(THIS_MODULE);
+			do_notify = true;
+		}
+
+		netif_info(tun, drv, tun->dev, "persist %s\n",
+			   arg ? "enabled" : "disabled");
+		break;
+
+	case TUNSETOWNER:
+		/* Set owner of the device */
+		owner = make_kuid(current_user_ns(), arg);
+		if (!uid_valid(owner)) {
+			ret = -EINVAL;
+			break;
+		}
+		tun->owner = owner;
+		do_notify = true;
+		netif_info(tun, drv, tun->dev, "owner set to %u\n",
+			   from_kuid(&init_user_ns, tun->owner));
+		break;
+
+	case TUNSETGROUP:
+		/* Set group of the device */
+		group = make_kgid(current_user_ns(), arg);
+		if (!gid_valid(group)) {
+			ret = -EINVAL;
+			break;
+		}
+		tun->group = group;
+		do_notify = true;
+		netif_info(tun, drv, tun->dev, "group set to %u\n",
+			   from_kgid(&init_user_ns, tun->group));
+		break;
+
+	case TUNSETLINK:
+		/* Only allow setting the type when the interface is down */
+		if (tun->dev->flags & IFF_UP) {
+			netif_info(tun, drv, tun->dev,
+				   "Linktype set failed because interface is up\n");
+			ret = -EBUSY;
+		} else {
+			ret = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE,
+						       tun->dev);
+			ret = notifier_to_errno(ret);
+			if (ret) {
+				netif_info(tun, drv, tun->dev,
+					   "Refused to change device type\n");
+				break;
+			}
+			tun->dev->type = (int) arg;
+			tun->dev->addr_len = tun_get_addr_len(tun->dev->type);
+			netif_info(tun, drv, tun->dev, "linktype set to %d\n",
+				   tun->dev->type);
+			call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE,
+						 tun->dev);
+		}
+		break;
+
+	case TUNSETDEBUG:
+		tun->msg_enable = (u32)arg;
+		break;
+
+	case TUNSETOFFLOAD:
+		ret = set_offload(tun, arg);
+		break;
+
+	case TUNSETTXFILTER:
+		/* Can be set only for TAPs */
+		ret = -EINVAL;
+		if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
+			break;
+		ret = update_filter(&tun->txflt, (void __user *)arg);
+		break;
+
+	case SIOCGIFHWADDR:
+		/* Get hw address */
+		dev_get_mac_address(&ifr.ifr_hwaddr, net, tun->dev->name);
+		if (copy_to_user(argp, &ifr, ifreq_len))
+			ret = -EFAULT;
+		break;
+
+	case SIOCSIFHWADDR:
+		/* Set hw address */
+		ret = dev_set_mac_address_user(tun->dev, &ifr.ifr_hwaddr, NULL);
+		break;
+
+	case TUNGETSNDBUF:
+		sndbuf = tfile->socket.sk->sk_sndbuf;
+		if (copy_to_user(argp, &sndbuf, sizeof(sndbuf)))
+			ret = -EFAULT;
+		break;
+
+	case TUNSETSNDBUF:
+		if (copy_from_user(&sndbuf, argp, sizeof(sndbuf))) {
+			ret = -EFAULT;
+			break;
+		}
+		if (sndbuf <= 0) {
+			ret = -EINVAL;
+			break;
+		}
+
+		tun->sndbuf = sndbuf;
+		tun_set_sndbuf(tun);
+		break;
+
+	case TUNGETVNETHDRSZ:
+		vnet_hdr_sz = tun->vnet_hdr_sz;
+		if (copy_to_user(argp, &vnet_hdr_sz, sizeof(vnet_hdr_sz)))
+			ret = -EFAULT;
+		break;
+
+	case TUNSETVNETHDRSZ:
+		if (copy_from_user(&vnet_hdr_sz, argp, sizeof(vnet_hdr_sz))) {
+			ret = -EFAULT;
+			break;
+		}
+		if (vnet_hdr_sz < (int)sizeof(struct virtio_net_hdr)) {
+			ret = -EINVAL;
+			break;
+		}
+
+		tun->vnet_hdr_sz = vnet_hdr_sz;
+		break;
+
+	case TUNGETVNETLE:
+		le = !!(tun->flags & TUN_VNET_LE);
+		if (put_user(le, (int __user *)argp))
+			ret = -EFAULT;
+		break;
+
+	case TUNSETVNETLE:
+		if (get_user(le, (int __user *)argp)) {
+			ret = -EFAULT;
+			break;
+		}
+		if (le)
+			tun->flags |= TUN_VNET_LE;
+		else
+			tun->flags &= ~TUN_VNET_LE;
+		break;
+
+	case TUNGETVNETBE:
+		ret = tun_get_vnet_be(tun, argp);
+		break;
+
+	case TUNSETVNETBE:
+		ret = tun_set_vnet_be(tun, argp);
+		break;
+
+	case TUNATTACHFILTER:
+		/* Can be set only for TAPs */
+		ret = -EINVAL;
+		if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
+			break;
+		ret = -EFAULT;
+		if (copy_from_user(&tun->fprog, argp, sizeof(tun->fprog)))
+			break;
+
+		ret = tun_attach_filter(tun);
+		break;
+
+	case TUNDETACHFILTER:
+		/* Can be set only for TAPs */
+		ret = -EINVAL;
+		if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
+			break;
+		ret = 0;
+		tun_detach_filter(tun, tun->numqueues);
+		break;
+
+	case TUNGETFILTER:
+		ret = -EINVAL;
+		if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP)
+			break;
+		ret = -EFAULT;
+		if (copy_to_user(argp, &tun->fprog, sizeof(tun->fprog)))
+			break;
+		ret = 0;
+		break;
+
+	case TUNSETSTEERINGEBPF:
+		ret = tun_set_ebpf(tun, &tun->steering_prog, argp);
+		break;
+
+	case TUNSETFILTEREBPF:
+		ret = tun_set_ebpf(tun, &tun->filter_prog, argp);
+		break;
+
+	case TUNSETCARRIER:
+		ret = -EFAULT;
+		if (copy_from_user(&carrier, argp, sizeof(carrier)))
+			goto unlock;
+
+		ret = tun_net_change_carrier(tun->dev, (bool)carrier);
+		break;
+
+	case TUNGETDEVNETNS:
+		ret = -EPERM;
+		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+			goto unlock;
+		ret = open_related_ns(&net->ns, get_net_ns);
+		break;
+
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	if (do_notify)
+		netdev_state_change(tun->dev);
+
+unlock:
+	rtnl_unlock();
+	if (tun)
+		tun_put(tun);
+	return ret;
+}
+
+static long tun_chr_ioctl(struct file *file,
+			  unsigned int cmd, unsigned long arg)
+{
+	return __tun_chr_ioctl(file, cmd, arg, sizeof (struct ifreq));
+}
+
+#ifdef CONFIG_COMPAT
+static long tun_chr_compat_ioctl(struct file *file,
+			 unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case TUNSETIFF:
+	case TUNGETIFF:
+	case TUNSETTXFILTER:
+	case TUNGETSNDBUF:
+	case TUNSETSNDBUF:
+	case SIOCGIFHWADDR:
+	case SIOCSIFHWADDR:
+		arg = (unsigned long)compat_ptr(arg);
+		break;
+	default:
+		arg = (compat_ulong_t)arg;
+		break;
+	}
+
+	/*
+	 * compat_ifreq is shorter than ifreq, so we must not access beyond
+	 * the end of that structure. All fields that are used in this
+	 * driver are compatible though, we don't need to convert the
+	 * contents.
+	 */
+	return __tun_chr_ioctl(file, cmd, arg, sizeof(struct compat_ifreq));
+}
+#endif /* CONFIG_COMPAT */
+
+static int tun_chr_fasync(int fd, struct file *file, int on)
+{
+	struct tun_file *tfile = file->private_data;
+	int ret;
+
+	if ((ret = fasync_helper(fd, file, on, &tfile->fasync)) < 0)
+		goto out;
+
+	if (on) {
+		__f_setown(file, task_pid(current), PIDTYPE_TGID, 0);
+		tfile->flags |= TUN_FASYNC;
+	} else
+		tfile->flags &= ~TUN_FASYNC;
+	ret = 0;
+out:
+	return ret;
+}
+
+static int tun_chr_open(struct inode *inode, struct file * file)
+{
+	struct net *net = current->nsproxy->net_ns;
+	struct tun_file *tfile;
+
+	tfile = (struct tun_file *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
+					    &tun_proto, 0);
+	if (!tfile)
+		return -ENOMEM;
+	if (ptr_ring_init(&tfile->tx_ring, 0, GFP_KERNEL)) {
+		sk_free(&tfile->sk);
+		return -ENOMEM;
+	}
+
+	mutex_init(&tfile->napi_mutex);
+	RCU_INIT_POINTER(tfile->tun, NULL);
+	tfile->flags = 0;
+	tfile->ifindex = 0;
+
+	init_waitqueue_head(&tfile->socket.wq.wait);
+
+	tfile->socket.file = file;
+	tfile->socket.ops = &tun_socket_ops;
+
+	sock_init_data_uid(&tfile->socket, &tfile->sk, current_fsuid());
+
+	tfile->sk.sk_write_space = tun_sock_write_space;
+	tfile->sk.sk_sndbuf = INT_MAX;
+
+	file->private_data = tfile;
+	INIT_LIST_HEAD(&tfile->next);
+
+	sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
+
+	return 0;
+}
+
+static int tun_chr_close(struct inode *inode, struct file *file)
+{
+	struct tun_file *tfile = file->private_data;
+
+	tun_detach(tfile, true);
+
+	return 0;
+}
+
+#ifdef CONFIG_PROC_FS
+static void tun_chr_show_fdinfo(struct seq_file *m, struct file *file)
+{
+	struct tun_file *tfile = file->private_data;
+	struct tun_struct *tun;
+	struct ifreq ifr;
+
+	memset(&ifr, 0, sizeof(ifr));
+
+	rtnl_lock();
+	tun = tun_get(tfile);
+	if (tun)
+		tun_get_iff(tun, &ifr);
+	rtnl_unlock();
+
+	if (tun)
+		tun_put(tun);
+
+	seq_printf(m, "iff:\t%s\n", ifr.ifr_name);
+}
+#endif
+
+static const struct file_operations tun_fops = {
+	.owner	= THIS_MODULE,
+	.llseek = no_llseek,
+	.read_iter  = tun_chr_read_iter,
+	.write_iter = tun_chr_write_iter,
+	.poll	= tun_chr_poll,
+	.unlocked_ioctl	= tun_chr_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = tun_chr_compat_ioctl,
+#endif
+	.open	= tun_chr_open,
+	.release = tun_chr_close,
+	.fasync = tun_chr_fasync,
+#ifdef CONFIG_PROC_FS
+	.show_fdinfo = tun_chr_show_fdinfo,
+#endif
+};
+
+static struct miscdevice tun_miscdev = {
+	.minor = TUN_MINOR,
+	.name = "tun",
+	.nodename = "net/tun",
+	.fops = &tun_fops,
+};
+
+/* ethtool interface */
+
+static void tun_default_link_ksettings(struct net_device *dev,
+				       struct ethtool_link_ksettings *cmd)
+{
+	ethtool_link_ksettings_zero_link_mode(cmd, supported);
+	ethtool_link_ksettings_zero_link_mode(cmd, advertising);
+	cmd->base.speed		= SPEED_10;
+	cmd->base.duplex	= DUPLEX_FULL;
+	cmd->base.port		= PORT_TP;
+	cmd->base.phy_address	= 0;
+	cmd->base.autoneg	= AUTONEG_DISABLE;
+}
+
+static int tun_get_link_ksettings(struct net_device *dev,
+				  struct ethtool_link_ksettings *cmd)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	memcpy(cmd, &tun->link_ksettings, sizeof(*cmd));
+	return 0;
+}
+
+static int tun_set_link_ksettings(struct net_device *dev,
+				  const struct ethtool_link_ksettings *cmd)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	memcpy(&tun->link_ksettings, cmd, sizeof(*cmd));
+	return 0;
+}
+
+static void tun_get_drvinfo(struct net_device *dev, struct ethtool_drvinfo *info)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	strscpy(info->driver, DRV_NAME, sizeof(info->driver));
+	strscpy(info->version, DRV_VERSION, sizeof(info->version));
+
+	switch (tun->flags & TUN_TYPE_MASK) {
+	case IFF_TUN:
+		strscpy(info->bus_info, "tun", sizeof(info->bus_info));
+		break;
+	case IFF_TAP:
+		strscpy(info->bus_info, "tap", sizeof(info->bus_info));
+		break;
+	}
+}
+
+static u32 tun_get_msglevel(struct net_device *dev)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	return tun->msg_enable;
+}
+
+static void tun_set_msglevel(struct net_device *dev, u32 value)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	tun->msg_enable = value;
+}
+
+static int tun_get_coalesce(struct net_device *dev,
+			    struct ethtool_coalesce *ec,
+			    struct kernel_ethtool_coalesce *kernel_coal,
+			    struct netlink_ext_ack *extack)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	ec->rx_max_coalesced_frames = tun->rx_batched;
+
+	return 0;
+}
+
+static int tun_set_coalesce(struct net_device *dev,
+			    struct ethtool_coalesce *ec,
+			    struct kernel_ethtool_coalesce *kernel_coal,
+			    struct netlink_ext_ack *extack)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	if (ec->rx_max_coalesced_frames > NAPI_POLL_WEIGHT)
+		tun->rx_batched = NAPI_POLL_WEIGHT;
+	else
+		tun->rx_batched = ec->rx_max_coalesced_frames;
+
+	return 0;
+}
+
+static const struct ethtool_ops tun_ethtool_ops = {
+	.supported_coalesce_params = ETHTOOL_COALESCE_RX_MAX_FRAMES,
+	.get_drvinfo	= tun_get_drvinfo,
+	.get_msglevel	= tun_get_msglevel,
+	.set_msglevel	= tun_set_msglevel,
+	.get_link	= ethtool_op_get_link,
+	.get_ts_info	= ethtool_op_get_ts_info,
+	.get_coalesce   = tun_get_coalesce,
+	.set_coalesce   = tun_set_coalesce,
+	.get_link_ksettings = tun_get_link_ksettings,
+	.set_link_ksettings = tun_set_link_ksettings,
+};
+
+static int tun_queue_resize(struct tun_struct *tun)
+{
+	struct net_device *dev = tun->dev;
+	struct tun_file *tfile;
+	struct ptr_ring **rings;
+	int n = tun->numqueues + tun->numdisabled;
+	int ret, i;
+
+	rings = kmalloc_array(n, sizeof(*rings), GFP_KERNEL);
+	if (!rings)
+		return -ENOMEM;
+
+	for (i = 0; i < tun->numqueues; i++) {
+		tfile = rtnl_dereference(tun->tfiles[i]);
+		rings[i] = &tfile->tx_ring;
+	}
+	list_for_each_entry(tfile, &tun->disabled, next)
+		rings[i++] = &tfile->tx_ring;
+
+	ret = ptr_ring_resize_multiple(rings, n,
+				       dev->tx_queue_len, GFP_KERNEL,
+				       tun_ptr_free);
+
+	kfree(rings);
+	return ret;
+}
+
+static int tun_device_event(struct notifier_block *unused,
+			    unsigned long event, void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct tun_struct *tun = netdev_priv(dev);
+	int i;
+
+	if (dev->rtnl_link_ops != &tun_link_ops)
+		return NOTIFY_DONE;
+
+	switch (event) {
+	case NETDEV_CHANGE_TX_QUEUE_LEN:
+		if (tun_queue_resize(tun))
+			return NOTIFY_BAD;
+		break;
+	case NETDEV_UP:
+		for (i = 0; i < tun->numqueues; i++) {
+			struct tun_file *tfile;
+
+			tfile = rtnl_dereference(tun->tfiles[i]);
+			tfile->socket.sk->sk_write_space(tfile->socket.sk);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block tun_notifier_block __read_mostly = {
+	.notifier_call	= tun_device_event,
+};
+
+static int __init tun_init(void)
+{
+	int ret = 0;
+
+	pr_info("%s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
+
+	ret = rtnl_link_register(&tun_link_ops);
+	if (ret) {
+		pr_err("Can't register link_ops\n");
+		goto err_linkops;
+	}
+
+	ret = misc_register(&tun_miscdev);
+	if (ret) {
+		pr_err("Can't register misc device %d\n", TUN_MINOR);
+		goto err_misc;
+	}
+
+	ret = register_netdevice_notifier(&tun_notifier_block);
+	if (ret) {
+		pr_err("Can't register netdevice notifier\n");
+		goto err_notifier;
+	}
+
+	return  0;
+
+err_notifier:
+	misc_deregister(&tun_miscdev);
+err_misc:
+	rtnl_link_unregister(&tun_link_ops);
+err_linkops:
+	return ret;
+}
+
+static void tun_cleanup(void)
+{
+	misc_deregister(&tun_miscdev);
+	rtnl_link_unregister(&tun_link_ops);
+	unregister_netdevice_notifier(&tun_notifier_block);
+}
+
+/* Get an underlying socket object from tun file.  Returns error unless file is
+ * attached to a device.  The returned object works like a packet socket, it
+ * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
+ * holding a reference to the file for as long as the socket is in use. */
+struct socket *tun_get_socket(struct file *file)
+{
+	struct tun_file *tfile;
+	if (file->f_op != &tun_fops)
+		return ERR_PTR(-EINVAL);
+	tfile = file->private_data;
+	if (!tfile)
+		return ERR_PTR(-EBADFD);
+	return &tfile->socket;
+}
+EXPORT_SYMBOL_GPL(tun_get_socket);
+
+struct ptr_ring *tun_get_tx_ring(struct file *file)
+{
+	struct tun_file *tfile;
+
+	if (file->f_op != &tun_fops)
+		return ERR_PTR(-EINVAL);
+	tfile = file->private_data;
+	if (!tfile)
+		return ERR_PTR(-EBADFD);
+	return &tfile->tx_ring;
+}
+EXPORT_SYMBOL_GPL(tun_get_tx_ring);
+
+module_init(tun_init);
+module_exit(tun_cleanup);
+MODULE_DESCRIPTION(DRV_DESCRIPTION);
+MODULE_AUTHOR(DRV_COPYRIGHT);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_MISCDEV(TUN_MINOR);
+MODULE_ALIAS("devname:net/tun");