drivers/net/tap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/etherdevice.h>
   3 #include <linux/if_tap.h>
   4 #include <linux/if_vlan.h>
   5 #include <linux/interrupt.h>
   6 #include <linux/nsproxy.h>
   7 #include <linux/compat.h>
   8 #include <linux/if_tun.h>
   9 #include <linux/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/cache.h>
  12 #include <linux/sched/signal.h>
  13 #include <linux/types.h>
  14 #include <linux/slab.h>
  15 #include <linux/wait.h>
  16 #include <linux/cdev.h>
  17 #include <linux/idr.h>
  18 #include <linux/fs.h>
  19 #include <linux/uio.h>
  20
  21 #include <net/gso.h>
  22 #include <net/net_namespace.h>
  23 #include <net/rtnetlink.h>
  24 #include <net/sock.h>
  25 #include <linux/virtio_net.h>
  26 #include <linux/skb_array.h>
  27
  28 #define TAP_IFFEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
  29
  30 #define TAP_VNET_LE 0x80000000
  31 #define TAP_VNET_BE 0x40000000
  32
  33 #ifdef CONFIG_TUN_VNET_CROSS_LE
  34 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  35 {
  36         return q->flags & TAP_VNET_BE ? false :
  37                 virtio_legacy_is_little_endian();
  38 }
  39
  40 static long tap_get_vnet_be(struct tap_queue *q, int __user *sp)
  41 {
  42         int s = !!(q->flags & TAP_VNET_BE);
  43
  44         if (put_user(s, sp))
  45                 return -EFAULT;
  46
  47         return 0;
  48 }
  49
  50 static long tap_set_vnet_be(struct tap_queue *q, int __user *sp)
  51 {
  52         int s;
  53
  54         if (get_user(s, sp))
  55                 return -EFAULT;
  56
  57         if (s)
  58                 q->flags |= TAP_VNET_BE;
  59         else
  60                 q->flags &= ~TAP_VNET_BE;
  61
  62         return 0;
  63 }
  64 #else
  65 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  66 {
  67         return virtio_legacy_is_little_endian();
  68 }
  69
  70 static long tap_get_vnet_be(struct tap_queue *q, int __user *argp)
  71 {
  72         return -EINVAL;
  73 }
  74
  75 static long tap_set_vnet_be(struct tap_queue *q, int __user *argp)
  76 {
  77         return -EINVAL;
  78 }
  79 #endif /* CONFIG_TUN_VNET_CROSS_LE */
  80
  81 static inline bool tap_is_little_endian(struct tap_queue *q)
  82 {
  83         return q->flags & TAP_VNET_LE ||
  84                 tap_legacy_is_little_endian(q);
  85 }
  86
  87 static inline u16 tap16_to_cpu(struct tap_queue *q, __virtio16 val)
  88 {
  89         return __virtio16_to_cpu(tap_is_little_endian(q), val);
  90 }
  91
  92 static inline __virtio16 cpu_to_tap16(struct tap_queue *q, u16 val)
  93 {
  94         return __cpu_to_virtio16(tap_is_little_endian(q), val);
  95 }
  96
  97 static struct proto tap_proto = {
  98         .name = "tap",
  99         .owner = THIS_MODULE,
 100         .obj_size = sizeof(struct tap_queue),
 101 };
 102
 103 #define TAP_NUM_DEVS (1U << MINORBITS)
 104
 105 static LIST_HEAD(major_list);
 106
 107 struct major_info {
 108         struct rcu_head rcu;
 109         dev_t major;
 110         struct idr minor_idr;
 111         spinlock_t minor_lock;
 112         const char *device_name;
 113         struct list_head next;
 114 };
 115
 116 #define GOODCOPY_LEN 128
 117
 118 static const struct proto_ops tap_socket_ops;
 119
 120 #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
 121 #define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)
 122
 123 static struct tap_dev *tap_dev_get_rcu(const struct net_device *dev)
 124 {
 125         return rcu_dereference(dev->rx_handler_data);
 126 }
 127
 128 /*
 129  * RCU usage:
 130  * The tap_queue and the macvlan_dev are loosely coupled, the
 131  * pointers from one to the other can only be read while rcu_read_lock
 132  * or rtnl is held.
 133  *
 134  * Both the file and the macvlan_dev hold a reference on the tap_queue
 135  * through sock_hold(&q->sk). When the macvlan_dev goes away first,
 136  * q->vlan becomes inaccessible. When the files gets closed,
 137  * tap_get_queue() fails.
 138  *
 139  * There may still be references to the struct sock inside of the
 140  * queue from outbound SKBs, but these never reference back to the
 141  * file or the dev. The data structure is freed through __sk_free
 142  * when both our references and any pending SKBs are gone.
 143  */
 144
 145 static int tap_enable_queue(struct tap_dev *tap, struct file *file,
 146                             struct tap_queue *q)
 147 {
 148         int err = -EINVAL;
 149
 150         ASSERT_RTNL();
 151
 152         if (q->enabled)
 153                 goto out;
 154
 155         err = 0;
 156         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 157         q->queue_index = tap->numvtaps;
 158         q->enabled = true;
 159
 160         tap->numvtaps++;
 161 out:
 162         return err;
 163 }
 164
 165 /* Requires RTNL */
 166 static int tap_set_queue(struct tap_dev *tap, struct file *file,
 167                          struct tap_queue *q)
 168 {
 169         if (tap->numqueues == MAX_TAP_QUEUES)
 170                 return -EBUSY;
 171
 172         rcu_assign_pointer(q->tap, tap);
 173         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 174         sock_hold(&q->sk);
 175
 176         q->file = file;
 177         q->queue_index = tap->numvtaps;
 178         q->enabled = true;
 179         file->private_data = q;
 180         list_add_tail(&q->next, &tap->queue_list);
 181
 182         tap->numvtaps++;
 183         tap->numqueues++;
 184
 185         return 0;
 186 }
 187
 188 static int tap_disable_queue(struct tap_queue *q)
 189 {
 190         struct tap_dev *tap;
 191         struct tap_queue *nq;
 192
 193         ASSERT_RTNL();
 194         if (!q->enabled)
 195                 return -EINVAL;
 196
 197         tap = rtnl_dereference(q->tap);
 198
 199         if (tap) {
 200                 int index = q->queue_index;
 201                 BUG_ON(index >= tap->numvtaps);
 202                 nq = rtnl_dereference(tap->taps[tap->numvtaps - 1]);
 203                 nq->queue_index = index;
 204
 205                 rcu_assign_pointer(tap->taps[index], nq);
 206                 RCU_INIT_POINTER(tap->taps[tap->numvtaps - 1], NULL);
 207                 q->enabled = false;
 208
 209                 tap->numvtaps--;
 210         }
 211
 212         return 0;
 213 }
 214
 215 /*
 216  * The file owning the queue got closed, give up both
 217  * the reference that the files holds as well as the
 218  * one from the macvlan_dev if that still exists.
 219  *
 220  * Using the spinlock makes sure that we don't get
 221  * to the queue again after destroying it.
 222  */
 223 static void tap_put_queue(struct tap_queue *q)
 224 {
 225         struct tap_dev *tap;
 226
 227         rtnl_lock();
 228         tap = rtnl_dereference(q->tap);
 229
 230         if (tap) {
 231                 if (q->enabled)
 232                         BUG_ON(tap_disable_queue(q));
 233
 234                 tap->numqueues--;
 235                 RCU_INIT_POINTER(q->tap, NULL);
 236                 sock_put(&q->sk);
 237                 list_del_init(&q->next);
 238         }
 239
 240         rtnl_unlock();
 241
 242         synchronize_rcu();
 243         sock_put(&q->sk);
 244 }
 245
 246 /*
 247  * Select a queue based on the rxq of the device on which this packet
 248  * arrived. If the incoming device is not mq, calculate a flow hash
 249  * to select a queue. If all fails, find the first available queue.
 250  * Cache vlan->numvtaps since it can become zero during the execution
 251  * of this function.
 252  */
 253 static struct tap_queue *tap_get_queue(struct tap_dev *tap,
 254                                        struct sk_buff *skb)
 255 {
 256         struct tap_queue *queue = NULL;
 257         /* Access to taps array is protected by rcu, but access to numvtaps
 258          * isn't. Below we use it to lookup a queue, but treat it as a hint
 259          * and validate that the result isn't NULL - in case we are
 260          * racing against queue removal.
 261          */
 262         int numvtaps = READ_ONCE(tap->numvtaps);
 263         __u32 rxq;
 264
 265         if (!numvtaps)
 266                 goto out;
 267
 268         if (numvtaps == 1)
 269                 goto single;
 270
 271         /* Check if we can use flow to select a queue */
 272         rxq = skb_get_hash(skb);
 273         if (rxq) {
 274                 queue = rcu_dereference(tap->taps[rxq % numvtaps]);
 275                 goto out;
 276         }
 277
 278         if (likely(skb_rx_queue_recorded(skb))) {
 279                 rxq = skb_get_rx_queue(skb);
 280
 281                 while (unlikely(rxq >= numvtaps))
 282                         rxq -= numvtaps;
 283
 284                 queue = rcu_dereference(tap->taps[rxq]);
 285                 goto out;
 286         }
 287
 288 single:
 289         queue = rcu_dereference(tap->taps[0]);
 290 out:
 291         return queue;
 292 }
 293
 294 /*
 295  * The net_device is going away, give up the reference
 296  * that it holds on all queues and safely set the pointer
 297  * from the queues to NULL.
 298  */
 299 void tap_del_queues(struct tap_dev *tap)
 300 {
 301         struct tap_queue *q, *tmp;
 302
 303         ASSERT_RTNL();
 304         list_for_each_entry_safe(q, tmp, &tap->queue_list, next) {
 305                 list_del_init(&q->next);
 306                 RCU_INIT_POINTER(q->tap, NULL);
 307                 if (q->enabled)
 308                         tap->numvtaps--;
 309                 tap->numqueues--;
 310                 sock_put(&q->sk);
 311         }
 312         BUG_ON(tap->numvtaps);
 313         BUG_ON(tap->numqueues);
 314         /* guarantee that any future tap_set_queue will fail */
 315         tap->numvtaps = MAX_TAP_QUEUES;
 316 }
 317 EXPORT_SYMBOL_GPL(tap_del_queues);
 318
 319 rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
 320 {
 321         struct sk_buff *skb = *pskb;
 322         struct net_device *dev = skb->dev;
 323         struct tap_dev *tap;
 324         struct tap_queue *q;
 325         netdev_features_t features = TAP_FEATURES;
 326         enum skb_drop_reason drop_reason;
 327
 328         tap = tap_dev_get_rcu(dev);
 329         if (!tap)
 330                 return RX_HANDLER_PASS;
 331
 332         q = tap_get_queue(tap, skb);
 333         if (!q)
 334                 return RX_HANDLER_PASS;
 335
 336         skb_push(skb, ETH_HLEN);
 337
 338         /* Apply the forward feature mask so that we perform segmentation
 339          * according to users wishes.  This only works if VNET_HDR is
 340          * enabled.
 341          */
 342         if (q->flags & IFF_VNET_HDR)
 343                 features |= tap->tap_features;
 344         if (netif_needs_gso(skb, features)) {
 345                 struct sk_buff *segs = __skb_gso_segment(skb, features, false);
 346                 struct sk_buff *next;
 347
 348                 if (IS_ERR(segs)) {
 349                         drop_reason = SKB_DROP_REASON_SKB_GSO_SEG;
 350                         goto drop;
 351                 }
 352
 353                 if (!segs) {
 354                         if (ptr_ring_produce(&q->ring, skb)) {
 355                                 drop_reason = SKB_DROP_REASON_FULL_RING;
 356                                 goto drop;
 357                         }
 358                         goto wake_up;
 359                 }
 360
 361                 consume_skb(skb);
 362                 skb_list_walk_safe(segs, skb, next) {
 363                         skb_mark_not_on_list(skb);
 364                         if (ptr_ring_produce(&q->ring, skb)) {
 365                                 drop_reason = SKB_DROP_REASON_FULL_RING;
 366                                 kfree_skb_reason(skb, drop_reason);
 367                                 kfree_skb_list_reason(next, drop_reason);
 368                                 break;
 369                         }
 370                 }
 371         } else {
 372                 /* If we receive a partial checksum and the tap side
 373                  * doesn't support checksum offload, compute the checksum.
 374                  * Note: it doesn't matter which checksum feature to
 375                  *        check, we either support them all or none.
 376                  */
 377                 if (skb->ip_summed == CHECKSUM_PARTIAL &&
 378                     !(features & NETIF_F_CSUM_MASK) &&
 379                     skb_checksum_help(skb)) {
 380                         drop_reason = SKB_DROP_REASON_SKB_CSUM;
 381                         goto drop;
 382                 }
 383                 if (ptr_ring_produce(&q->ring, skb)) {
 384                         drop_reason = SKB_DROP_REASON_FULL_RING;
 385                         goto drop;
 386                 }
 387         }
 388
 389 wake_up:
 390         wake_up_interruptible_poll(sk_sleep(&q->sk), EPOLLIN | EPOLLRDNORM | EPOLLRDBAND);
 391         return RX_HANDLER_CONSUMED;
 392
 393 drop:
 394         /* Count errors/drops only here, thus don't care about args. */
 395         if (tap->count_rx_dropped)
 396                 tap->count_rx_dropped(tap);
 397         kfree_skb_reason(skb, drop_reason);
 398         return RX_HANDLER_CONSUMED;
 399 }
 400 EXPORT_SYMBOL_GPL(tap_handle_frame);
 401
 402 static struct major_info *tap_get_major(int major)
 403 {
 404         struct major_info *tap_major;
 405
 406         list_for_each_entry_rcu(tap_major, &major_list, next) {
 407                 if (tap_major->major == major)
 408                         return tap_major;
 409         }
 410
 411         return NULL;
 412 }
 413
 414 int tap_get_minor(dev_t major, struct tap_dev *tap)
 415 {
 416         int retval = -ENOMEM;
 417         struct major_info *tap_major;
 418
 419         rcu_read_lock();
 420         tap_major = tap_get_major(MAJOR(major));
 421         if (!tap_major) {
 422                 retval = -EINVAL;
 423                 goto unlock;
 424         }
 425
 426         spin_lock(&tap_major->minor_lock);
 427         retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);
 428         if (retval >= 0) {
 429                 tap->minor = retval;
 430         } else if (retval == -ENOSPC) {
 431                 netdev_err(tap->dev, "Too many tap devices\n");
 432                 retval = -EINVAL;
 433         }
 434         spin_unlock(&tap_major->minor_lock);
 435
 436 unlock:
 437         rcu_read_unlock();
 438         return retval < 0 ? retval : 0;
 439 }
 440 EXPORT_SYMBOL_GPL(tap_get_minor);
 441
 442 void tap_free_minor(dev_t major, struct tap_dev *tap)
 443 {
 444         struct major_info *tap_major;
 445
 446         rcu_read_lock();
 447         tap_major = tap_get_major(MAJOR(major));
 448         if (!tap_major) {
 449                 goto unlock;
 450         }
 451
 452         spin_lock(&tap_major->minor_lock);
 453         if (tap->minor) {
 454                 idr_remove(&tap_major->minor_idr, tap->minor);
 455                 tap->minor = 0;
 456         }
 457         spin_unlock(&tap_major->minor_lock);
 458
 459 unlock:
 460         rcu_read_unlock();
 461 }
 462 EXPORT_SYMBOL_GPL(tap_free_minor);
 463
 464 static struct tap_dev *dev_get_by_tap_file(int major, int minor)
 465 {
 466         struct net_device *dev = NULL;
 467         struct tap_dev *tap;
 468         struct major_info *tap_major;
 469
 470         rcu_read_lock();
 471         tap_major = tap_get_major(major);
 472         if (!tap_major) {
 473                 tap = NULL;
 474                 goto unlock;
 475         }
 476
 477         spin_lock(&tap_major->minor_lock);
 478         tap = idr_find(&tap_major->minor_idr, minor);
 479         if (tap) {
 480                 dev = tap->dev;
 481                 dev_hold(dev);
 482         }
 483         spin_unlock(&tap_major->minor_lock);
 484
 485 unlock:
 486         rcu_read_unlock();
 487         return tap;
 488 }
 489
 490 static void tap_sock_write_space(struct sock *sk)
 491 {
 492         wait_queue_head_t *wqueue;
 493
 494         if (!sock_writeable(sk) ||
 495             !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
 496                 return;
 497
 498         wqueue = sk_sleep(sk);
 499         if (wqueue && waitqueue_active(wqueue))
 500                 wake_up_interruptible_poll(wqueue, EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
 501 }
 502
 503 static void tap_sock_destruct(struct sock *sk)
 504 {
 505         struct tap_queue *q = container_of(sk, struct tap_queue, sk);
 506
 507         ptr_ring_cleanup(&q->ring, __skb_array_destroy_skb);
 508 }
 509
 510 static int tap_open(struct inode *inode, struct file *file)
 511 {
 512         struct net *net = current->nsproxy->net_ns;
 513         struct tap_dev *tap;
 514         struct tap_queue *q;
 515         int err = -ENODEV;
 516
 517         rtnl_lock();
 518         tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
 519         if (!tap)
 520                 goto err;
 521
 522         err = -ENOMEM;
 523         q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
 524                                              &tap_proto, 0);
 525         if (!q)
 526                 goto err;
 527         if (ptr_ring_init(&q->ring, tap->dev->tx_queue_len, GFP_KERNEL)) {
 528                 sk_free(&q->sk);
 529                 goto err;
 530         }
 531
 532         init_waitqueue_head(&q->sock.wq.wait);
 533         q->sock.type = SOCK_RAW;
 534         q->sock.state = SS_CONNECTED;
 535         q->sock.file = file;
 536         q->sock.ops = &tap_socket_ops;
 537         sock_init_data_uid(&q->sock, &q->sk, inode->i_uid);
 538         q->sk.sk_write_space = tap_sock_write_space;
 539         q->sk.sk_destruct = tap_sock_destruct;
 540         q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;
 541         q->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
 542
 543         /*
 544          * so far only KVM virtio_net uses tap, enable zero copy between
 545          * guest kernel and host kernel when lower device supports zerocopy
 546          *
 547          * The macvlan supports zerocopy iff the lower device supports zero
 548          * copy so we don't have to look at the lower device directly.
 549          */
 550         if ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
 551                 sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 552
 553         err = tap_set_queue(tap, file, q);
 554         if (err) {
 555                 /* tap_sock_destruct() will take care of freeing ptr_ring */
 556                 goto err_put;
 557         }
 558
 559         /* tap groks IOCB_NOWAIT just fine, mark it as such */
 560         file->f_mode |= FMODE_NOWAIT;
 561
 562         dev_put(tap->dev);
 563
 564         rtnl_unlock();
 565         return err;
 566
 567 err_put:
 568         sock_put(&q->sk);
 569 err:
 570         if (tap)
 571                 dev_put(tap->dev);
 572
 573         rtnl_unlock();
 574         return err;
 575 }
 576
 577 static int tap_release(struct inode *inode, struct file *file)
 578 {
 579         struct tap_queue *q = file->private_data;
 580         tap_put_queue(q);
 581         return 0;
 582 }
 583
 584 static __poll_t tap_poll(struct file *file, poll_table *wait)
 585 {
 586         struct tap_queue *q = file->private_data;
 587         __poll_t mask = EPOLLERR;
 588
 589         if (!q)
 590                 goto out;
 591
 592         mask = 0;
 593         poll_wait(file, &q->sock.wq.wait, wait);
 594
 595         if (!ptr_ring_empty(&q->ring))
 596                 mask |= EPOLLIN | EPOLLRDNORM;
 597
 598         if (sock_writeable(&q->sk) ||
 599             (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) &&
 600              sock_writeable(&q->sk)))
 601                 mask |= EPOLLOUT | EPOLLWRNORM;
 602
 603 out:
 604         return mask;
 605 }
 606
 607 static inline struct sk_buff *tap_alloc_skb(struct sock *sk, size_t prepad,
 608                                             size_t len, size_t linear,
 609                                                 int noblock, int *err)
 610 {
 611         struct sk_buff *skb;
 612
 613         /* Under a page?  Don't bother with paged skb. */
 614         if (prepad + len < PAGE_SIZE || !linear)
 615                 linear = len;
 616
 617         if (len - linear > MAX_SKB_FRAGS * (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
 618                 linear = len - MAX_SKB_FRAGS * (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER);
 619         skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
 620                                    err, PAGE_ALLOC_COSTLY_ORDER);
 621         if (!skb)
 622                 return NULL;
 623
 624         skb_reserve(skb, prepad);
 625         skb_put(skb, linear);
 626         skb->data_len = len - linear;
 627         skb->len += len - linear;
 628
 629         return skb;
 630 }
 631
 632 /* Neighbour code has some assumptions on HH_DATA_MOD alignment */
 633 #define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
 634
 635 /* Get packet from user space buffer */
 636 static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 637                             struct iov_iter *from, int noblock)
 638 {
 639         int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
 640         struct sk_buff *skb;
 641         struct tap_dev *tap;
 642         unsigned long total_len = iov_iter_count(from);
 643         unsigned long len = total_len;
 644         int err;
 645         struct virtio_net_hdr vnet_hdr = { 0 };
 646         int vnet_hdr_len = 0;
 647         int copylen = 0;
 648         int depth;
 649         bool zerocopy = false;
 650         size_t linear;
 651         enum skb_drop_reason drop_reason;
 652
 653         if (q->flags & IFF_VNET_HDR) {
 654                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 655
 656                 err = -EINVAL;
 657                 if (len < vnet_hdr_len)
 658                         goto err;
 659                 len -= vnet_hdr_len;
 660
 661                 err = -EFAULT;
 662                 if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
 663                         goto err;
 664                 iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
 665                 if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
 666                      tap16_to_cpu(q, vnet_hdr.csum_start) +
 667                      tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
 668                              tap16_to_cpu(q, vnet_hdr.hdr_len))
 669                         vnet_hdr.hdr_len = cpu_to_tap16(q,
 670                                  tap16_to_cpu(q, vnet_hdr.csum_start) +
 671                                  tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
 672                 err = -EINVAL;
 673                 if (tap16_to_cpu(q, vnet_hdr.hdr_len) > len)
 674                         goto err;
 675         }
 676
 677         err = -EINVAL;
 678         if (unlikely(len < ETH_HLEN))
 679                 goto err;
 680
 681         if (msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
 682                 struct iov_iter i;
 683
 684                 copylen = vnet_hdr.hdr_len ?
 685                         tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
 686                 if (copylen > good_linear)
 687                         copylen = good_linear;
 688                 else if (copylen < ETH_HLEN)
 689                         copylen = ETH_HLEN;
 690                 linear = copylen;
 691                 i = *from;
 692                 iov_iter_advance(&i, copylen);
 693                 if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
 694                         zerocopy = true;
 695         }
 696
 697         if (!zerocopy) {
 698                 copylen = len;
 699                 linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
 700                 if (linear > good_linear)
 701                         linear = good_linear;
 702                 else if (linear < ETH_HLEN)
 703                         linear = ETH_HLEN;
 704         }
 705
 706         skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,
 707                             linear, noblock, &err);
 708         if (!skb)
 709                 goto err;
 710
 711         if (zerocopy)
 712                 err = zerocopy_sg_from_iter(skb, from);
 713         else
 714                 err = skb_copy_datagram_from_iter(skb, 0, from, len);
 715
 716         if (err) {
 717                 drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT;
 718                 goto err_kfree;
 719         }
 720
 721         skb_set_network_header(skb, ETH_HLEN);
 722         skb_reset_mac_header(skb);
 723         skb->protocol = eth_hdr(skb)->h_proto;
 724
 725         rcu_read_lock();
 726         tap = rcu_dereference(q->tap);
 727         if (!tap) {
 728                 kfree_skb(skb);
 729                 rcu_read_unlock();
 730                 return total_len;
 731         }
 732         skb->dev = tap->dev;
 733
 734         if (vnet_hdr_len) {
 735                 err = virtio_net_hdr_to_skb(skb, &vnet_hdr,
 736                                             tap_is_little_endian(q));
 737                 if (err) {
 738                         rcu_read_unlock();
 739                         drop_reason = SKB_DROP_REASON_DEV_HDR;
 740                         goto err_kfree;
 741                 }
 742         }
 743
 744         skb_probe_transport_header(skb);
 745
 746         /* Move network header to the right position for VLAN tagged packets */
 747         if (eth_type_vlan(skb->protocol) &&
 748             vlan_get_protocol_and_depth(skb, skb->protocol, &depth) != 0)
 749                 skb_set_network_header(skb, depth);
 750
 751         /* copy skb_ubuf_info for callback when skb has no error */
 752         if (zerocopy) {
 753                 skb_zcopy_init(skb, msg_control);
 754         } else if (msg_control) {
 755                 struct ubuf_info *uarg = msg_control;
 756                 uarg->callback(NULL, uarg, false);
 757         }
 758
 759         dev_queue_xmit(skb);
 760         rcu_read_unlock();
 761         return total_len;
 762
 763 err_kfree:
 764         kfree_skb_reason(skb, drop_reason);
 765
 766 err:
 767         rcu_read_lock();
 768         tap = rcu_dereference(q->tap);
 769         if (tap && tap->count_tx_dropped)
 770                 tap->count_tx_dropped(tap);
 771         rcu_read_unlock();
 772
 773         return err;
 774 }
 775
 776 static ssize_t tap_write_iter(struct kiocb *iocb, struct iov_iter *from)
 777 {
 778         struct file *file = iocb->ki_filp;
 779         struct tap_queue *q = file->private_data;
 780         int noblock = 0;
 781
 782         if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
 783                 noblock = 1;
 784
 785         return tap_get_user(q, NULL, from, noblock);
 786 }
 787
 788 /* Put packet to the user space buffer */
 789 static ssize_t tap_put_user(struct tap_queue *q,
 790                             const struct sk_buff *skb,
 791                             struct iov_iter *iter)
 792 {
 793         int ret;
 794         int vnet_hdr_len = 0;
 795         int vlan_offset = 0;
 796         int total;
 797
 798         if (q->flags & IFF_VNET_HDR) {
 799                 int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0;
 800                 struct virtio_net_hdr vnet_hdr;
 801
 802                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 803                 if (iov_iter_count(iter) < vnet_hdr_len)
 804                         return -EINVAL;
 805
 806                 if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
 807                                             tap_is_little_endian(q), true,
 808                                             vlan_hlen))
 809                         BUG();
 810
 811                 if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
 812                     sizeof(vnet_hdr))
 813                         return -EFAULT;
 814
 815                 iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));
 816         }
 817         total = vnet_hdr_len;
 818         total += skb->len;
 819
 820         if (skb_vlan_tag_present(skb)) {
 821                 struct {
 822                         __be16 h_vlan_proto;
 823                         __be16 h_vlan_TCI;
 824                 } veth;
 825                 veth.h_vlan_proto = skb->vlan_proto;
 826                 veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
 827
 828                 vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
 829                 total += VLAN_HLEN;
 830
 831                 ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
 832                 if (ret || !iov_iter_count(iter))
 833                         goto done;
 834
 835                 ret = copy_to_iter(&veth, sizeof(veth), iter);
 836                 if (ret != sizeof(veth) || !iov_iter_count(iter))
 837                         goto done;
 838         }
 839
 840         ret = skb_copy_datagram_iter(skb, vlan_offset, iter,
 841                                      skb->len - vlan_offset);
 842
 843 done:
 844         return ret ? ret : total;
 845 }
 846
 847 static ssize_t tap_do_read(struct tap_queue *q,
 848                            struct iov_iter *to,
 849                            int noblock, struct sk_buff *skb)
 850 {
 851         DEFINE_WAIT(wait);
 852         ssize_t ret = 0;
 853
 854         if (!iov_iter_count(to)) {
 855                 kfree_skb(skb);
 856                 return 0;
 857         }
 858
 859         if (skb)
 860                 goto put;
 861
 862         while (1) {
 863                 if (!noblock)
 864                         prepare_to_wait(sk_sleep(&q->sk), &wait,
 865                                         TASK_INTERRUPTIBLE);
 866
 867                 /* Read frames from the queue */
 868                 skb = ptr_ring_consume(&q->ring);
 869                 if (skb)
 870                         break;
 871                 if (noblock) {
 872                         ret = -EAGAIN;
 873                         break;
 874                 }
 875                 if (signal_pending(current)) {
 876                         ret = -ERESTARTSYS;
 877                         break;
 878                 }
 879                 /* Nothing to read, let's sleep */
 880                 schedule();
 881         }
 882         if (!noblock)
 883                 finish_wait(sk_sleep(&q->sk), &wait);
 884
 885 put:
 886         if (skb) {
 887                 ret = tap_put_user(q, skb, to);
 888                 if (unlikely(ret < 0))
 889                         kfree_skb(skb);
 890                 else
 891                         consume_skb(skb);
 892         }
 893         return ret;
 894 }
 895
 896 static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
 897 {
 898         struct file *file = iocb->ki_filp;
 899         struct tap_queue *q = file->private_data;
 900         ssize_t len = iov_iter_count(to), ret;
 901         int noblock = 0;
 902
 903         if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
 904                 noblock = 1;
 905
 906         ret = tap_do_read(q, to, noblock, NULL);
 907         ret = min_t(ssize_t, ret, len);
 908         if (ret > 0)
 909                 iocb->ki_pos = ret;
 910         return ret;
 911 }
 912
 913 static struct tap_dev *tap_get_tap_dev(struct tap_queue *q)
 914 {
 915         struct tap_dev *tap;
 916
 917         ASSERT_RTNL();
 918         tap = rtnl_dereference(q->tap);
 919         if (tap)
 920                 dev_hold(tap->dev);
 921
 922         return tap;
 923 }
 924
 925 static void tap_put_tap_dev(struct tap_dev *tap)
 926 {
 927         dev_put(tap->dev);
 928 }
 929
 930 static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
 931 {
 932         struct tap_queue *q = file->private_data;
 933         struct tap_dev *tap;
 934         int ret;
 935
 936         tap = tap_get_tap_dev(q);
 937         if (!tap)
 938                 return -EINVAL;
 939
 940         if (flags & IFF_ATTACH_QUEUE)
 941                 ret = tap_enable_queue(tap, file, q);
 942         else if (flags & IFF_DETACH_QUEUE)
 943                 ret = tap_disable_queue(q);
 944         else
 945                 ret = -EINVAL;
 946
 947         tap_put_tap_dev(tap);
 948         return ret;
 949 }
 950
 951 static int set_offload(struct tap_queue *q, unsigned long arg)
 952 {
 953         struct tap_dev *tap;
 954         netdev_features_t features;
 955         netdev_features_t feature_mask = 0;
 956
 957         tap = rtnl_dereference(q->tap);
 958         if (!tap)
 959                 return -ENOLINK;
 960
 961         features = tap->dev->features;
 962
 963         if (arg & TUN_F_CSUM) {
 964                 feature_mask = NETIF_F_HW_CSUM;
 965
 966                 if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
 967                         if (arg & TUN_F_TSO_ECN)
 968                                 feature_mask |= NETIF_F_TSO_ECN;
 969                         if (arg & TUN_F_TSO4)
 970                                 feature_mask |= NETIF_F_TSO;
 971                         if (arg & TUN_F_TSO6)
 972                                 feature_mask |= NETIF_F_TSO6;
 973                 }
 974
 975                 /* TODO: for now USO4 and USO6 should work simultaneously */
 976                 if ((arg & (TUN_F_USO4 | TUN_F_USO6)) == (TUN_F_USO4 | TUN_F_USO6))
 977                         features |= NETIF_F_GSO_UDP_L4;
 978         }
 979
 980         /* tun/tap driver inverts the usage for TSO offloads, where
 981          * setting the TSO bit means that the userspace wants to
 982          * accept TSO frames and turning it off means that user space
 983          * does not support TSO.
 984          * For tap, we have to invert it to mean the same thing.
 985          * When user space turns off TSO, we turn off GSO/LRO so that
 986          * user-space will not receive TSO frames.
 987          */
 988         if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6) ||
 989             (feature_mask & (TUN_F_USO4 | TUN_F_USO6)) == (TUN_F_USO4 | TUN_F_USO6))
 990                 features |= RX_OFFLOADS;
 991         else
 992                 features &= ~RX_OFFLOADS;
 993
 994         /* tap_features are the same as features on tun/tap and
 995          * reflect user expectations.
 996          */
 997         tap->tap_features = feature_mask;
 998         if (tap->update_features)
 999                 tap->update_features(tap, features);
1000
1001         return 0;
1002 }
1003
1004 /*
1005  * provide compatibility with generic tun/tap interface
1006  */
1007 static long tap_ioctl(struct file *file, unsigned int cmd,
1008                       unsigned long arg)
1009 {
1010         struct tap_queue *q = file->private_data;
1011         struct tap_dev *tap;
1012         void __user *argp = (void __user *)arg;
1013         struct ifreq __user *ifr = argp;
1014         unsigned int __user *up = argp;
1015         unsigned short u;
1016         int __user *sp = argp;
1017         struct sockaddr sa;
1018         int s;
1019         int ret;
1020
1021         switch (cmd) {
1022         case TUNSETIFF:
1023                 /* ignore the name, just look at flags */
1024                 if (get_user(u, &ifr->ifr_flags))
1025                         return -EFAULT;
1026
1027                 ret = 0;
1028                 if ((u & ~TAP_IFFEATURES) != (IFF_NO_PI | IFF_TAP))
1029                         ret = -EINVAL;
1030                 else
1031                         q->flags = (q->flags & ~TAP_IFFEATURES) | u;
1032
1033                 return ret;
1034
1035         case TUNGETIFF:
1036                 rtnl_lock();
1037                 tap = tap_get_tap_dev(q);
1038                 if (!tap) {
1039                         rtnl_unlock();
1040                         return -ENOLINK;
1041                 }
1042
1043                 ret = 0;
1044                 u = q->flags;
1045                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1046                     put_user(u, &ifr->ifr_flags))
1047                         ret = -EFAULT;
1048                 tap_put_tap_dev(tap);
1049                 rtnl_unlock();
1050                 return ret;
1051
1052         case TUNSETQUEUE:
1053                 if (get_user(u, &ifr->ifr_flags))
1054                         return -EFAULT;
1055                 rtnl_lock();
1056                 ret = tap_ioctl_set_queue(file, u);
1057                 rtnl_unlock();
1058                 return ret;
1059
1060         case TUNGETFEATURES:
1061                 if (put_user(IFF_TAP | IFF_NO_PI | TAP_IFFEATURES, up))
1062                         return -EFAULT;
1063                 return 0;
1064
1065         case TUNSETSNDBUF:
1066                 if (get_user(s, sp))
1067                         return -EFAULT;
1068                 if (s <= 0)
1069                         return -EINVAL;
1070
1071                 q->sk.sk_sndbuf = s;
1072                 return 0;
1073
1074         case TUNGETVNETHDRSZ:
1075                 s = q->vnet_hdr_sz;
1076                 if (put_user(s, sp))
1077                         return -EFAULT;
1078                 return 0;
1079
1080         case TUNSETVNETHDRSZ:
1081                 if (get_user(s, sp))
1082                         return -EFAULT;
1083                 if (s < (int)sizeof(struct virtio_net_hdr))
1084                         return -EINVAL;
1085
1086                 q->vnet_hdr_sz = s;
1087                 return 0;
1088
1089         case TUNGETVNETLE:
1090                 s = !!(q->flags & TAP_VNET_LE);
1091                 if (put_user(s, sp))
1092                         return -EFAULT;
1093                 return 0;
1094
1095         case TUNSETVNETLE:
1096                 if (get_user(s, sp))
1097                         return -EFAULT;
1098                 if (s)
1099                         q->flags |= TAP_VNET_LE;
1100                 else
1101                         q->flags &= ~TAP_VNET_LE;
1102                 return 0;
1103
1104         case TUNGETVNETBE:
1105                 return tap_get_vnet_be(q, sp);
1106
1107         case TUNSETVNETBE:
1108                 return tap_set_vnet_be(q, sp);
1109
1110         case TUNSETOFFLOAD:
1111                 /* let the user check for future flags */
1112                 if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
1113                             TUN_F_TSO_ECN | TUN_F_UFO |
1114                             TUN_F_USO4 | TUN_F_USO6))
1115                         return -EINVAL;
1116
1117                 rtnl_lock();
1118                 ret = set_offload(q, arg);
1119                 rtnl_unlock();
1120                 return ret;
1121
1122         case SIOCGIFHWADDR:
1123                 rtnl_lock();
1124                 tap = tap_get_tap_dev(q);
1125                 if (!tap) {
1126                         rtnl_unlock();
1127                         return -ENOLINK;
1128                 }
1129                 ret = 0;
1130                 dev_get_mac_address(&sa, dev_net(tap->dev), tap->dev->name);
1131                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1132                     copy_to_user(&ifr->ifr_hwaddr, &sa, sizeof(sa)))
1133                         ret = -EFAULT;
1134                 tap_put_tap_dev(tap);
1135                 rtnl_unlock();
1136                 return ret;
1137
1138         case SIOCSIFHWADDR:
1139                 if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
1140                         return -EFAULT;
1141                 rtnl_lock();
1142                 tap = tap_get_tap_dev(q);
1143                 if (!tap) {
1144                         rtnl_unlock();
1145                         return -ENOLINK;
1146                 }
1147                 ret = dev_set_mac_address_user(tap->dev, &sa, NULL);
1148                 tap_put_tap_dev(tap);
1149                 rtnl_unlock();
1150                 return ret;
1151
1152         default:
1153                 return -EINVAL;
1154         }
1155 }
1156
1157 static const struct file_operations tap_fops = {
1158         .owner          = THIS_MODULE,
1159         .open           = tap_open,
1160         .release        = tap_release,
1161         .read_iter      = tap_read_iter,
1162         .write_iter     = tap_write_iter,
1163         .poll           = tap_poll,
1164         .llseek         = no_llseek,
1165         .unlocked_ioctl = tap_ioctl,
1166         .compat_ioctl   = compat_ptr_ioctl,
1167 };
1168
1169 static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
1170 {
1171         struct tun_xdp_hdr *hdr = xdp->data_hard_start;
1172         struct virtio_net_hdr *gso = &hdr->gso;
1173         int buflen = hdr->buflen;
1174         int vnet_hdr_len = 0;
1175         struct tap_dev *tap;
1176         struct sk_buff *skb;
1177         int err, depth;
1178
1179         if (q->flags & IFF_VNET_HDR)
1180                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
1181
1182         skb = build_skb(xdp->data_hard_start, buflen);
1183         if (!skb) {
1184                 err = -ENOMEM;
1185                 goto err;
1186         }
1187
1188         skb_reserve(skb, xdp->data - xdp->data_hard_start);
1189         skb_put(skb, xdp->data_end - xdp->data);
1190
1191         skb_set_network_header(skb, ETH_HLEN);
1192         skb_reset_mac_header(skb);
1193         skb->protocol = eth_hdr(skb)->h_proto;
1194
1195         if (vnet_hdr_len) {
1196                 err = virtio_net_hdr_to_skb(skb, gso, tap_is_little_endian(q));
1197                 if (err)
1198                         goto err_kfree;
1199         }
1200
1201         /* Move network header to the right position for VLAN tagged packets */
1202         if (eth_type_vlan(skb->protocol) &&
1203             vlan_get_protocol_and_depth(skb, skb->protocol, &depth) != 0)
1204                 skb_set_network_header(skb, depth);
1205
1206         rcu_read_lock();
1207         tap = rcu_dereference(q->tap);
1208         if (tap) {
1209                 skb->dev = tap->dev;
1210                 skb_probe_transport_header(skb);
1211                 dev_queue_xmit(skb);
1212         } else {
1213                 kfree_skb(skb);
1214         }
1215         rcu_read_unlock();
1216
1217         return 0;
1218
1219 err_kfree:
1220         kfree_skb(skb);
1221 err:
1222         rcu_read_lock();
1223         tap = rcu_dereference(q->tap);
1224         if (tap && tap->count_tx_dropped)
1225                 tap->count_tx_dropped(tap);
1226         rcu_read_unlock();
1227         return err;
1228 }
1229
1230 static int tap_sendmsg(struct socket *sock, struct msghdr *m,
1231                        size_t total_len)
1232 {
1233         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1234         struct tun_msg_ctl *ctl = m->msg_control;
1235         struct xdp_buff *xdp;
1236         int i;
1237
1238         if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
1239             ctl && ctl->type == TUN_MSG_PTR) {
1240                 for (i = 0; i < ctl->num; i++) {
1241                         xdp = &((struct xdp_buff *)ctl->ptr)[i];
1242                         tap_get_user_xdp(q, xdp);
1243                 }
1244                 return 0;
1245         }
1246
1247         return tap_get_user(q, ctl ? ctl->ptr : NULL, &m->msg_iter,
1248                             m->msg_flags & MSG_DONTWAIT);
1249 }
1250
1251 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
1252                        size_t total_len, int flags)
1253 {
1254         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1255         struct sk_buff *skb = m->msg_control;
1256         int ret;
1257         if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
1258                 kfree_skb(skb);
1259                 return -EINVAL;
1260         }
1261         ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT, skb);
1262         if (ret > total_len) {
1263                 m->msg_flags |= MSG_TRUNC;
1264                 ret = flags & MSG_TRUNC ? ret : total_len;
1265         }
1266         return ret;
1267 }
1268
1269 static int tap_peek_len(struct socket *sock)
1270 {
1271         struct tap_queue *q = container_of(sock, struct tap_queue,
1272                                                sock);
1273         return PTR_RING_PEEK_CALL(&q->ring, __skb_array_len_with_tag);
1274 }
1275
1276 /* Ops structure to mimic raw sockets with tun */
1277 static const struct proto_ops tap_socket_ops = {
1278         .sendmsg = tap_sendmsg,
1279         .recvmsg = tap_recvmsg,
1280         .peek_len = tap_peek_len,
1281 };
1282
1283 /* Get an underlying socket object from tun file.  Returns error unless file is
1284  * attached to a device.  The returned object works like a packet socket, it
1285  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
1286  * holding a reference to the file for as long as the socket is in use. */
1287 struct socket *tap_get_socket(struct file *file)
1288 {
1289         struct tap_queue *q;
1290         if (file->f_op != &tap_fops)
1291                 return ERR_PTR(-EINVAL);
1292         q = file->private_data;
1293         if (!q)
1294                 return ERR_PTR(-EBADFD);
1295         return &q->sock;
1296 }
1297 EXPORT_SYMBOL_GPL(tap_get_socket);
1298
1299 struct ptr_ring *tap_get_ptr_ring(struct file *file)
1300 {
1301         struct tap_queue *q;
1302
1303         if (file->f_op != &tap_fops)
1304                 return ERR_PTR(-EINVAL);
1305         q = file->private_data;
1306         if (!q)
1307                 return ERR_PTR(-EBADFD);
1308         return &q->ring;
1309 }
1310 EXPORT_SYMBOL_GPL(tap_get_ptr_ring);
1311
1312 int tap_queue_resize(struct tap_dev *tap)
1313 {
1314         struct net_device *dev = tap->dev;
1315         struct tap_queue *q;
1316         struct ptr_ring **rings;
1317         int n = tap->numqueues;
1318         int ret, i = 0;
1319
1320         rings = kmalloc_array(n, sizeof(*rings), GFP_KERNEL);
1321         if (!rings)
1322                 return -ENOMEM;
1323
1324         list_for_each_entry(q, &tap->queue_list, next)
1325                 rings[i++] = &q->ring;
1326
1327         ret = ptr_ring_resize_multiple(rings, n,
1328                                        dev->tx_queue_len, GFP_KERNEL,
1329                                        __skb_array_destroy_skb);
1330
1331         kfree(rings);
1332         return ret;
1333 }
1334 EXPORT_SYMBOL_GPL(tap_queue_resize);
1335
1336 static int tap_list_add(dev_t major, const char *device_name)
1337 {
1338         struct major_info *tap_major;
1339
1340         tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
1341         if (!tap_major)
1342                 return -ENOMEM;
1343
1344         tap_major->major = MAJOR(major);
1345
1346         idr_init(&tap_major->minor_idr);
1347         spin_lock_init(&tap_major->minor_lock);
1348
1349         tap_major->device_name = device_name;
1350
1351         list_add_tail_rcu(&tap_major->next, &major_list);
1352         return 0;
1353 }
1354
1355 int tap_create_cdev(struct cdev *tap_cdev, dev_t *tap_major,
1356                     const char *device_name, struct module *module)
1357 {
1358         int err;
1359
1360         err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
1361         if (err)
1362                 goto out1;
1363
1364         cdev_init(tap_cdev, &tap_fops);
1365         tap_cdev->owner = module;
1366         err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
1367         if (err)
1368                 goto out2;
1369
1370         err =  tap_list_add(*tap_major, device_name);
1371         if (err)
1372                 goto out3;
1373
1374         return 0;
1375
1376 out3:
1377         cdev_del(tap_cdev);
1378 out2:
1379         unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
1380 out1:
1381         return err;
1382 }
1383 EXPORT_SYMBOL_GPL(tap_create_cdev);
1384
1385 void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
1386 {
1387         struct major_info *tap_major, *tmp;
1388
1389         cdev_del(tap_cdev);
1390         unregister_chrdev_region(major, TAP_NUM_DEVS);
1391         list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
1392                 if (tap_major->major == MAJOR(major)) {
1393                         idr_destroy(&tap_major->minor_idr);
1394                         list_del_rcu(&tap_major->next);
1395                         kfree_rcu(tap_major, rcu);
1396                 }
1397         }
1398 }
1399 EXPORT_SYMBOL_GPL(tap_destroy_cdev);
1400
1401 MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
1402 MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
1403 MODULE_LICENSE("GPL");