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 <net/xdp.h>
  26 #include <linux/virtio_net.h>
  27 #include <linux/skb_array.h>
  28
  29 #define TAP_IFFEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
  30
  31 #define TAP_VNET_LE 0x80000000
  32 #define TAP_VNET_BE 0x40000000
  33
  34 #ifdef CONFIG_TUN_VNET_CROSS_LE
  35 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  36 {
  37         return q->flags & TAP_VNET_BE ? false :
  38                 virtio_legacy_is_little_endian();
  39 }
  40
  41 static long tap_get_vnet_be(struct tap_queue *q, int __user *sp)
  42 {
  43         int s = !!(q->flags & TAP_VNET_BE);
  44
  45         if (put_user(s, sp))
  46                 return -EFAULT;
  47
  48         return 0;
  49 }
  50
  51 static long tap_set_vnet_be(struct tap_queue *q, int __user *sp)
  52 {
  53         int s;
  54
  55         if (get_user(s, sp))
  56                 return -EFAULT;
  57
  58         if (s)
  59                 q->flags |= TAP_VNET_BE;
  60         else
  61                 q->flags &= ~TAP_VNET_BE;
  62
  63         return 0;
  64 }
  65 #else
  66 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  67 {
  68         return virtio_legacy_is_little_endian();
  69 }
  70
  71 static long tap_get_vnet_be(struct tap_queue *q, int __user *argp)
  72 {
  73         return -EINVAL;
  74 }
  75
  76 static long tap_set_vnet_be(struct tap_queue *q, int __user *argp)
  77 {
  78         return -EINVAL;
  79 }
  80 #endif /* CONFIG_TUN_VNET_CROSS_LE */
  81
  82 static inline bool tap_is_little_endian(struct tap_queue *q)
  83 {
  84         return q->flags & TAP_VNET_LE ||
  85                 tap_legacy_is_little_endian(q);
  86 }
  87
  88 static inline u16 tap16_to_cpu(struct tap_queue *q, __virtio16 val)
  89 {
  90         return __virtio16_to_cpu(tap_is_little_endian(q), val);
  91 }
  92
  93 static inline __virtio16 cpu_to_tap16(struct tap_queue *q, u16 val)
  94 {
  95         return __cpu_to_virtio16(tap_is_little_endian(q), val);
  96 }
  97
  98 static struct proto tap_proto = {
  99         .name = "tap",
 100         .owner = THIS_MODULE,
 101         .obj_size = sizeof(struct tap_queue),
 102 };
 103
 104 #define TAP_NUM_DEVS (1U << MINORBITS)
 105
 106 static LIST_HEAD(major_list);
 107
 108 struct major_info {
 109         struct rcu_head rcu;
 110         dev_t major;
 111         struct idr minor_idr;
 112         spinlock_t minor_lock;
 113         const char *device_name;
 114         struct list_head next;
 115 };
 116
 117 #define GOODCOPY_LEN 128
 118
 119 static const struct proto_ops tap_socket_ops;
 120
 121 #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
 122 #define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)
 123
 124 static struct tap_dev *tap_dev_get_rcu(const struct net_device *dev)
 125 {
 126         return rcu_dereference(dev->rx_handler_data);
 127 }
 128
 129 /*
 130  * RCU usage:
 131  * The tap_queue and the macvlan_dev are loosely coupled, the
 132  * pointers from one to the other can only be read while rcu_read_lock
 133  * or rtnl is held.
 134  *
 135  * Both the file and the macvlan_dev hold a reference on the tap_queue
 136  * through sock_hold(&q->sk). When the macvlan_dev goes away first,
 137  * q->vlan becomes inaccessible. When the files gets closed,
 138  * tap_get_queue() fails.
 139  *
 140  * There may still be references to the struct sock inside of the
 141  * queue from outbound SKBs, but these never reference back to the
 142  * file or the dev. The data structure is freed through __sk_free
 143  * when both our references and any pending SKBs are gone.
 144  */
 145
 146 static int tap_enable_queue(struct tap_dev *tap, struct file *file,
 147                             struct tap_queue *q)
 148 {
 149         int err = -EINVAL;
 150
 151         ASSERT_RTNL();
 152
 153         if (q->enabled)
 154                 goto out;
 155
 156         err = 0;
 157         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 158         q->queue_index = tap->numvtaps;
 159         q->enabled = true;
 160
 161         tap->numvtaps++;
 162 out:
 163         return err;
 164 }
 165
 166 /* Requires RTNL */
 167 static int tap_set_queue(struct tap_dev *tap, struct file *file,
 168                          struct tap_queue *q)
 169 {
 170         if (tap->numqueues == MAX_TAP_QUEUES)
 171                 return -EBUSY;
 172
 173         rcu_assign_pointer(q->tap, tap);
 174         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 175         sock_hold(&q->sk);
 176
 177         q->file = file;
 178         q->queue_index = tap->numvtaps;
 179         q->enabled = true;
 180         file->private_data = q;
 181         list_add_tail(&q->next, &tap->queue_list);
 182
 183         tap->numvtaps++;
 184         tap->numqueues++;
 185
 186         return 0;
 187 }
 188
 189 static int tap_disable_queue(struct tap_queue *q)
 190 {
 191         struct tap_dev *tap;
 192         struct tap_queue *nq;
 193
 194         ASSERT_RTNL();
 195         if (!q->enabled)
 196                 return -EINVAL;
 197
 198         tap = rtnl_dereference(q->tap);
 199
 200         if (tap) {
 201                 int index = q->queue_index;
 202                 BUG_ON(index >= tap->numvtaps);
 203                 nq = rtnl_dereference(tap->taps[tap->numvtaps - 1]);
 204                 nq->queue_index = index;
 205
 206                 rcu_assign_pointer(tap->taps[index], nq);
 207                 RCU_INIT_POINTER(tap->taps[tap->numvtaps - 1], NULL);
 208                 q->enabled = false;
 209
 210                 tap->numvtaps--;
 211         }
 212
 213         return 0;
 214 }
 215
 216 /*
 217  * The file owning the queue got closed, give up both
 218  * the reference that the files holds as well as the
 219  * one from the macvlan_dev if that still exists.
 220  *
 221  * Using the spinlock makes sure that we don't get
 222  * to the queue again after destroying it.
 223  */
 224 static void tap_put_queue(struct tap_queue *q)
 225 {
 226         struct tap_dev *tap;
 227
 228         rtnl_lock();
 229         tap = rtnl_dereference(q->tap);
 230
 231         if (tap) {
 232                 if (q->enabled)
 233                         BUG_ON(tap_disable_queue(q));
 234
 235                 tap->numqueues--;
 236                 RCU_INIT_POINTER(q->tap, NULL);
 237                 sock_put(&q->sk);
 238                 list_del_init(&q->next);
 239         }
 240
 241         rtnl_unlock();
 242
 243         synchronize_rcu();
 244         sock_put(&q->sk);
 245 }
 246
 247 /*
 248  * Select a queue based on the rxq of the device on which this packet
 249  * arrived. If the incoming device is not mq, calculate a flow hash
 250  * to select a queue. If all fails, find the first available queue.
 251  * Cache vlan->numvtaps since it can become zero during the execution
 252  * of this function.
 253  */
 254 static struct tap_queue *tap_get_queue(struct tap_dev *tap,
 255                                        struct sk_buff *skb)
 256 {
 257         struct tap_queue *queue = NULL;
 258         /* Access to taps array is protected by rcu, but access to numvtaps
 259          * isn't. Below we use it to lookup a queue, but treat it as a hint
 260          * and validate that the result isn't NULL - in case we are
 261          * racing against queue removal.
 262          */
 263         int numvtaps = READ_ONCE(tap->numvtaps);
 264         __u32 rxq;
 265
 266         if (!numvtaps)
 267                 goto out;
 268
 269         if (numvtaps == 1)
 270                 goto single;
 271
 272         /* Check if we can use flow to select a queue */
 273         rxq = skb_get_hash(skb);
 274         if (rxq) {
 275                 queue = rcu_dereference(tap->taps[rxq % numvtaps]);
 276                 goto out;
 277         }
 278
 279         if (likely(skb_rx_queue_recorded(skb))) {
 280                 rxq = skb_get_rx_queue(skb);
 281
 282                 while (unlikely(rxq >= numvtaps))
 283                         rxq -= numvtaps;
 284
 285                 queue = rcu_dereference(tap->taps[rxq]);
 286                 goto out;
 287         }
 288
 289 single:
 290         queue = rcu_dereference(tap->taps[0]);
 291 out:
 292         return queue;
 293 }
 294
 295 /*
 296  * The net_device is going away, give up the reference
 297  * that it holds on all queues and safely set the pointer
 298  * from the queues to NULL.
 299  */
 300 void tap_del_queues(struct tap_dev *tap)
 301 {
 302         struct tap_queue *q, *tmp;
 303
 304         ASSERT_RTNL();
 305         list_for_each_entry_safe(q, tmp, &tap->queue_list, next) {
 306                 list_del_init(&q->next);
 307                 RCU_INIT_POINTER(q->tap, NULL);
 308                 if (q->enabled)
 309                         tap->numvtaps--;
 310                 tap->numqueues--;
 311                 sock_put(&q->sk);
 312         }
 313         BUG_ON(tap->numvtaps);
 314         BUG_ON(tap->numqueues);
 315         /* guarantee that any future tap_set_queue will fail */
 316         tap->numvtaps = MAX_TAP_QUEUES;
 317 }
 318 EXPORT_SYMBOL_GPL(tap_del_queues);
 319
 320 rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
 321 {
 322         struct sk_buff *skb = *pskb;
 323         struct net_device *dev = skb->dev;
 324         struct tap_dev *tap;
 325         struct tap_queue *q;
 326         netdev_features_t features = TAP_FEATURES;
 327         enum skb_drop_reason drop_reason;
 328
 329         tap = tap_dev_get_rcu(dev);
 330         if (!tap)
 331                 return RX_HANDLER_PASS;
 332
 333         q = tap_get_queue(tap, skb);
 334         if (!q)
 335                 return RX_HANDLER_PASS;
 336
 337         skb_push(skb, ETH_HLEN);
 338
 339         /* Apply the forward feature mask so that we perform segmentation
 340          * according to users wishes.  This only works if VNET_HDR is
 341          * enabled.
 342          */
 343         if (q->flags & IFF_VNET_HDR)
 344                 features |= tap->tap_features;
 345         if (netif_needs_gso(skb, features)) {
 346                 struct sk_buff *segs = __skb_gso_segment(skb, features, false);
 347                 struct sk_buff *next;
 348
 349                 if (IS_ERR(segs)) {
 350                         drop_reason = SKB_DROP_REASON_SKB_GSO_SEG;
 351                         goto drop;
 352                 }
 353
 354                 if (!segs) {
 355                         if (ptr_ring_produce(&q->ring, skb)) {
 356                                 drop_reason = SKB_DROP_REASON_FULL_RING;
 357                                 goto drop;
 358                         }
 359                         goto wake_up;
 360                 }
 361
 362                 consume_skb(skb);
 363                 skb_list_walk_safe(segs, skb, next) {
 364                         skb_mark_not_on_list(skb);
 365                         if (ptr_ring_produce(&q->ring, skb)) {
 366                                 drop_reason = SKB_DROP_REASON_FULL_RING;
 367                                 kfree_skb_reason(skb, drop_reason);
 368                                 kfree_skb_list_reason(next, drop_reason);
 369                                 break;
 370                         }
 371                 }
 372         } else {
 373                 /* If we receive a partial checksum and the tap side
 374                  * doesn't support checksum offload, compute the checksum.
 375                  * Note: it doesn't matter which checksum feature to
 376                  *        check, we either support them all or none.
 377                  */
 378                 if (skb->ip_summed == CHECKSUM_PARTIAL &&
 379                     !(features & NETIF_F_CSUM_MASK) &&
 380                     skb_checksum_help(skb)) {
 381                         drop_reason = SKB_DROP_REASON_SKB_CSUM;
 382                         goto drop;
 383                 }
 384                 if (ptr_ring_produce(&q->ring, skb)) {
 385                         drop_reason = SKB_DROP_REASON_FULL_RING;
 386                         goto drop;
 387                 }
 388         }
 389
 390 wake_up:
 391         wake_up_interruptible_poll(sk_sleep(&q->sk), EPOLLIN | EPOLLRDNORM | EPOLLRDBAND);
 392         return RX_HANDLER_CONSUMED;
 393
 394 drop:
 395         /* Count errors/drops only here, thus don't care about args. */
 396         if (tap->count_rx_dropped)
 397                 tap->count_rx_dropped(tap);
 398         kfree_skb_reason(skb, drop_reason);
 399         return RX_HANDLER_CONSUMED;
 400 }
 401 EXPORT_SYMBOL_GPL(tap_handle_frame);
 402
 403 static struct major_info *tap_get_major(int major)
 404 {
 405         struct major_info *tap_major;
 406
 407         list_for_each_entry_rcu(tap_major, &major_list, next) {
 408                 if (tap_major->major == major)
 409                         return tap_major;
 410         }
 411
 412         return NULL;
 413 }
 414
 415 int tap_get_minor(dev_t major, struct tap_dev *tap)
 416 {
 417         int retval = -ENOMEM;
 418         struct major_info *tap_major;
 419
 420         rcu_read_lock();
 421         tap_major = tap_get_major(MAJOR(major));
 422         if (!tap_major) {
 423                 retval = -EINVAL;
 424                 goto unlock;
 425         }
 426
 427         spin_lock(&tap_major->minor_lock);
 428         retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);
 429         if (retval >= 0) {
 430                 tap->minor = retval;
 431         } else if (retval == -ENOSPC) {
 432                 netdev_err(tap->dev, "Too many tap devices\n");
 433                 retval = -EINVAL;
 434         }
 435         spin_unlock(&tap_major->minor_lock);
 436
 437 unlock:
 438         rcu_read_unlock();
 439         return retval < 0 ? retval : 0;
 440 }
 441 EXPORT_SYMBOL_GPL(tap_get_minor);
 442
 443 void tap_free_minor(dev_t major, struct tap_dev *tap)
 444 {
 445         struct major_info *tap_major;
 446
 447         rcu_read_lock();
 448         tap_major = tap_get_major(MAJOR(major));
 449         if (!tap_major) {
 450                 goto unlock;
 451         }
 452
 453         spin_lock(&tap_major->minor_lock);
 454         if (tap->minor) {
 455                 idr_remove(&tap_major->minor_idr, tap->minor);
 456                 tap->minor = 0;
 457         }
 458         spin_unlock(&tap_major->minor_lock);
 459
 460 unlock:
 461         rcu_read_unlock();
 462 }
 463 EXPORT_SYMBOL_GPL(tap_free_minor);
 464
 465 static struct tap_dev *dev_get_by_tap_file(int major, int minor)
 466 {
 467         struct net_device *dev = NULL;
 468         struct tap_dev *tap;
 469         struct major_info *tap_major;
 470
 471         rcu_read_lock();
 472         tap_major = tap_get_major(major);
 473         if (!tap_major) {
 474                 tap = NULL;
 475                 goto unlock;
 476         }
 477
 478         spin_lock(&tap_major->minor_lock);
 479         tap = idr_find(&tap_major->minor_idr, minor);
 480         if (tap) {
 481                 dev = tap->dev;
 482                 dev_hold(dev);
 483         }
 484         spin_unlock(&tap_major->minor_lock);
 485
 486 unlock:
 487         rcu_read_unlock();
 488         return tap;
 489 }
 490
 491 static void tap_sock_write_space(struct sock *sk)
 492 {
 493         wait_queue_head_t *wqueue;
 494
 495         if (!sock_writeable(sk) ||
 496             !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
 497                 return;
 498
 499         wqueue = sk_sleep(sk);
 500         if (wqueue && waitqueue_active(wqueue))
 501                 wake_up_interruptible_poll(wqueue, EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
 502 }
 503
 504 static void tap_sock_destruct(struct sock *sk)
 505 {
 506         struct tap_queue *q = container_of(sk, struct tap_queue, sk);
 507
 508         ptr_ring_cleanup(&q->ring, __skb_array_destroy_skb);
 509 }
 510
 511 static int tap_open(struct inode *inode, struct file *file)
 512 {
 513         struct net *net = current->nsproxy->net_ns;
 514         struct tap_dev *tap;
 515         struct tap_queue *q;
 516         int err = -ENODEV;
 517
 518         rtnl_lock();
 519         tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
 520         if (!tap)
 521                 goto err;
 522
 523         err = -ENOMEM;
 524         q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
 525                                              &tap_proto, 0);
 526         if (!q)
 527                 goto err;
 528         if (ptr_ring_init(&q->ring, tap->dev->tx_queue_len, GFP_KERNEL)) {
 529                 sk_free(&q->sk);
 530                 goto err;
 531         }
 532
 533         init_waitqueue_head(&q->sock.wq.wait);
 534         q->sock.type = SOCK_RAW;
 535         q->sock.state = SS_CONNECTED;
 536         q->sock.file = file;
 537         q->sock.ops = &tap_socket_ops;
 538         sock_init_data_uid(&q->sock, &q->sk, current_fsuid());
 539         q->sk.sk_write_space = tap_sock_write_space;
 540         q->sk.sk_destruct = tap_sock_destruct;
 541         q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;
 542         q->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
 543
 544         /*
 545          * so far only KVM virtio_net uses tap, enable zero copy between
 546          * guest kernel and host kernel when lower device supports zerocopy
 547          *
 548          * The macvlan supports zerocopy iff the lower device supports zero
 549          * copy so we don't have to look at the lower device directly.
 550          */
 551         if ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
 552                 sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 553
 554         err = tap_set_queue(tap, file, q);
 555         if (err) {
 556                 /* tap_sock_destruct() will take care of freeing ptr_ring */
 557                 goto err_put;
 558         }
 559
 560         /* tap groks IOCB_NOWAIT just fine, mark it as such */
 561         file->f_mode |= FMODE_NOWAIT;
 562
 563         dev_put(tap->dev);
 564
 565         rtnl_unlock();
 566         return err;
 567
 568 err_put:
 569         sock_put(&q->sk);
 570 err:
 571         if (tap)
 572                 dev_put(tap->dev);
 573
 574         rtnl_unlock();
 575         return err;
 576 }
 577
 578 static int tap_release(struct inode *inode, struct file *file)
 579 {
 580         struct tap_queue *q = file->private_data;
 581         tap_put_queue(q);
 582         return 0;
 583 }
 584
 585 static __poll_t tap_poll(struct file *file, poll_table *wait)
 586 {
 587         struct tap_queue *q = file->private_data;
 588         __poll_t mask = EPOLLERR;
 589
 590         if (!q)
 591                 goto out;
 592
 593         mask = 0;
 594         poll_wait(file, &q->sock.wq.wait, wait);
 595
 596         if (!ptr_ring_empty(&q->ring))
 597                 mask |= EPOLLIN | EPOLLRDNORM;
 598
 599         if (sock_writeable(&q->sk) ||
 600             (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) &&
 601              sock_writeable(&q->sk)))
 602                 mask |= EPOLLOUT | EPOLLWRNORM;
 603
 604 out:
 605         return mask;
 606 }
 607
 608 static inline struct sk_buff *tap_alloc_skb(struct sock *sk, size_t prepad,
 609                                             size_t len, size_t linear,
 610                                                 int noblock, int *err)
 611 {
 612         struct sk_buff *skb;
 613
 614         /* Under a page?  Don't bother with paged skb. */
 615         if (prepad + len < PAGE_SIZE || !linear)
 616                 linear = len;
 617
 618         if (len - linear > MAX_SKB_FRAGS * (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
 619                 linear = len - MAX_SKB_FRAGS * (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER);
 620         skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
 621                                    err, PAGE_ALLOC_COSTLY_ORDER);
 622         if (!skb)
 623                 return NULL;
 624
 625         skb_reserve(skb, prepad);
 626         skb_put(skb, linear);
 627         skb->data_len = len - linear;
 628         skb->len += len - linear;
 629
 630         return skb;
 631 }
 632
 633 /* Neighbour code has some assumptions on HH_DATA_MOD alignment */
 634 #define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
 635
 636 /* Get packet from user space buffer */
 637 static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 638                             struct iov_iter *from, int noblock)
 639 {
 640         int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
 641         struct sk_buff *skb;
 642         struct tap_dev *tap;
 643         unsigned long total_len = iov_iter_count(from);
 644         unsigned long len = total_len;
 645         int err;
 646         struct virtio_net_hdr vnet_hdr = { 0 };
 647         int vnet_hdr_len = 0;
 648         int copylen = 0;
 649         int depth;
 650         bool zerocopy = false;
 651         size_t linear;
 652         enum skb_drop_reason drop_reason;
 653
 654         if (q->flags & IFF_VNET_HDR) {
 655                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 656
 657                 err = -EINVAL;
 658                 if (len < vnet_hdr_len)
 659                         goto err;
 660                 len -= vnet_hdr_len;
 661
 662                 err = -EFAULT;
 663                 if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
 664                         goto err;
 665                 iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
 666                 if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
 667                      tap16_to_cpu(q, vnet_hdr.csum_start) +
 668                      tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
 669                              tap16_to_cpu(q, vnet_hdr.hdr_len))
 670                         vnet_hdr.hdr_len = cpu_to_tap16(q,
 671                                  tap16_to_cpu(q, vnet_hdr.csum_start) +
 672                                  tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
 673                 err = -EINVAL;
 674                 if (tap16_to_cpu(q, vnet_hdr.hdr_len) > len)
 675                         goto err;
 676         }
 677
 678         err = -EINVAL;
 679         if (unlikely(len < ETH_HLEN))
 680                 goto err;
 681
 682         if (msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
 683                 struct iov_iter i;
 684
 685                 copylen = vnet_hdr.hdr_len ?
 686                         tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
 687                 if (copylen > good_linear)
 688                         copylen = good_linear;
 689                 else if (copylen < ETH_HLEN)
 690                         copylen = ETH_HLEN;
 691                 linear = copylen;
 692                 i = *from;
 693                 iov_iter_advance(&i, copylen);
 694                 if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
 695                         zerocopy = true;
 696         }
 697
 698         if (!zerocopy) {
 699                 copylen = len;
 700                 linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
 701                 if (linear > good_linear)
 702                         linear = good_linear;
 703                 else if (linear < ETH_HLEN)
 704                         linear = ETH_HLEN;
 705         }
 706
 707         skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,
 708                             linear, noblock, &err);
 709         if (!skb)
 710                 goto err;
 711
 712         if (zerocopy)
 713                 err = zerocopy_sg_from_iter(skb, from);
 714         else
 715                 err = skb_copy_datagram_from_iter(skb, 0, from, len);
 716
 717         if (err) {
 718                 drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT;
 719                 goto err_kfree;
 720         }
 721
 722         skb_set_network_header(skb, ETH_HLEN);
 723         skb_reset_mac_header(skb);
 724         skb->protocol = eth_hdr(skb)->h_proto;
 725
 726         rcu_read_lock();
 727         tap = rcu_dereference(q->tap);
 728         if (!tap) {
 729                 kfree_skb(skb);
 730                 rcu_read_unlock();
 731                 return total_len;
 732         }
 733         skb->dev = tap->dev;
 734
 735         if (vnet_hdr_len) {
 736                 err = virtio_net_hdr_to_skb(skb, &vnet_hdr,
 737                                             tap_is_little_endian(q));
 738                 if (err) {
 739                         rcu_read_unlock();
 740                         drop_reason = SKB_DROP_REASON_DEV_HDR;
 741                         goto err_kfree;
 742                 }
 743         }
 744
 745         skb_probe_transport_header(skb);
 746
 747         /* Move network header to the right position for VLAN tagged packets */
 748         if (eth_type_vlan(skb->protocol) &&
 749             vlan_get_protocol_and_depth(skb, skb->protocol, &depth) != 0)
 750                 skb_set_network_header(skb, depth);
 751
 752         /* copy skb_ubuf_info for callback when skb has no error */
 753         if (zerocopy) {
 754                 skb_zcopy_init(skb, msg_control);
 755         } else if (msg_control) {
 756                 struct ubuf_info *uarg = msg_control;
 757                 uarg->callback(NULL, uarg, false);
 758         }
 759
 760         dev_queue_xmit(skb);
 761         rcu_read_unlock();
 762         return total_len;
 763
 764 err_kfree:
 765         kfree_skb_reason(skb, drop_reason);
 766
 767 err:
 768         rcu_read_lock();
 769         tap = rcu_dereference(q->tap);
 770         if (tap && tap->count_tx_dropped)
 771                 tap->count_tx_dropped(tap);
 772         rcu_read_unlock();
 773
 774         return err;
 775 }
 776
 777 static ssize_t tap_write_iter(struct kiocb *iocb, struct iov_iter *from)
 778 {
 779         struct file *file = iocb->ki_filp;
 780         struct tap_queue *q = file->private_data;
 781         int noblock = 0;
 782
 783         if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
 784                 noblock = 1;
 785
 786         return tap_get_user(q, NULL, from, noblock);
 787 }
 788
 789 /* Put packet to the user space buffer */
 790 static ssize_t tap_put_user(struct tap_queue *q,
 791                             const struct sk_buff *skb,
 792                             struct iov_iter *iter)
 793 {
 794         int ret;
 795         int vnet_hdr_len = 0;
 796         int vlan_offset = 0;
 797         int total;
 798
 799         if (q->flags & IFF_VNET_HDR) {
 800                 int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0;
 801                 struct virtio_net_hdr vnet_hdr;
 802
 803                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 804                 if (iov_iter_count(iter) < vnet_hdr_len)
 805                         return -EINVAL;
 806
 807                 if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
 808                                             tap_is_little_endian(q), true,
 809                                             vlan_hlen))
 810                         BUG();
 811
 812                 if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
 813                     sizeof(vnet_hdr))
 814                         return -EFAULT;
 815
 816                 iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));
 817         }
 818         total = vnet_hdr_len;
 819         total += skb->len;
 820
 821         if (skb_vlan_tag_present(skb)) {
 822                 struct {
 823                         __be16 h_vlan_proto;
 824                         __be16 h_vlan_TCI;
 825                 } veth;
 826                 veth.h_vlan_proto = skb->vlan_proto;
 827                 veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
 828
 829                 vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
 830                 total += VLAN_HLEN;
 831
 832                 ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
 833                 if (ret || !iov_iter_count(iter))
 834                         goto done;
 835
 836                 ret = copy_to_iter(&veth, sizeof(veth), iter);
 837                 if (ret != sizeof(veth) || !iov_iter_count(iter))
 838                         goto done;
 839         }
 840
 841         ret = skb_copy_datagram_iter(skb, vlan_offset, iter,
 842                                      skb->len - vlan_offset);
 843
 844 done:
 845         return ret ? ret : total;
 846 }
 847
 848 static ssize_t tap_do_read(struct tap_queue *q,
 849                            struct iov_iter *to,
 850                            int noblock, struct sk_buff *skb)
 851 {
 852         DEFINE_WAIT(wait);
 853         ssize_t ret = 0;
 854
 855         if (!iov_iter_count(to)) {
 856                 kfree_skb(skb);
 857                 return 0;
 858         }
 859
 860         if (skb)
 861                 goto put;
 862
 863         while (1) {
 864                 if (!noblock)
 865                         prepare_to_wait(sk_sleep(&q->sk), &wait,
 866                                         TASK_INTERRUPTIBLE);
 867
 868                 /* Read frames from the queue */
 869                 skb = ptr_ring_consume(&q->ring);
 870                 if (skb)
 871                         break;
 872                 if (noblock) {
 873                         ret = -EAGAIN;
 874                         break;
 875                 }
 876                 if (signal_pending(current)) {
 877                         ret = -ERESTARTSYS;
 878                         break;
 879                 }
 880                 /* Nothing to read, let's sleep */
 881                 schedule();
 882         }
 883         if (!noblock)
 884                 finish_wait(sk_sleep(&q->sk), &wait);
 885
 886 put:
 887         if (skb) {
 888                 ret = tap_put_user(q, skb, to);
 889                 if (unlikely(ret < 0))
 890                         kfree_skb(skb);
 891                 else
 892                         consume_skb(skb);
 893         }
 894         return ret;
 895 }
 896
 897 static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
 898 {
 899         struct file *file = iocb->ki_filp;
 900         struct tap_queue *q = file->private_data;
 901         ssize_t len = iov_iter_count(to), ret;
 902         int noblock = 0;
 903
 904         if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
 905                 noblock = 1;
 906
 907         ret = tap_do_read(q, to, noblock, NULL);
 908         ret = min_t(ssize_t, ret, len);
 909         if (ret > 0)
 910                 iocb->ki_pos = ret;
 911         return ret;
 912 }
 913
 914 static struct tap_dev *tap_get_tap_dev(struct tap_queue *q)
 915 {
 916         struct tap_dev *tap;
 917
 918         ASSERT_RTNL();
 919         tap = rtnl_dereference(q->tap);
 920         if (tap)
 921                 dev_hold(tap->dev);
 922
 923         return tap;
 924 }
 925
 926 static void tap_put_tap_dev(struct tap_dev *tap)
 927 {
 928         dev_put(tap->dev);
 929 }
 930
 931 static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
 932 {
 933         struct tap_queue *q = file->private_data;
 934         struct tap_dev *tap;
 935         int ret;
 936
 937         tap = tap_get_tap_dev(q);
 938         if (!tap)
 939                 return -EINVAL;
 940
 941         if (flags & IFF_ATTACH_QUEUE)
 942                 ret = tap_enable_queue(tap, file, q);
 943         else if (flags & IFF_DETACH_QUEUE)
 944                 ret = tap_disable_queue(q);
 945         else
 946                 ret = -EINVAL;
 947
 948         tap_put_tap_dev(tap);
 949         return ret;
 950 }
 951
 952 static int set_offload(struct tap_queue *q, unsigned long arg)
 953 {
 954         struct tap_dev *tap;
 955         netdev_features_t features;
 956         netdev_features_t feature_mask = 0;
 957
 958         tap = rtnl_dereference(q->tap);
 959         if (!tap)
 960                 return -ENOLINK;
 961
 962         features = tap->dev->features;
 963
 964         if (arg & TUN_F_CSUM) {
 965                 feature_mask = NETIF_F_HW_CSUM;
 966
 967                 if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
 968                         if (arg & TUN_F_TSO_ECN)
 969                                 feature_mask |= NETIF_F_TSO_ECN;
 970                         if (arg & TUN_F_TSO4)
 971                                 feature_mask |= NETIF_F_TSO;
 972                         if (arg & TUN_F_TSO6)
 973                                 feature_mask |= NETIF_F_TSO6;
 974                 }
 975
 976                 /* TODO: for now USO4 and USO6 should work simultaneously */
 977                 if ((arg & (TUN_F_USO4 | TUN_F_USO6)) == (TUN_F_USO4 | TUN_F_USO6))
 978                         features |= NETIF_F_GSO_UDP_L4;
 979         }
 980
 981         /* tun/tap driver inverts the usage for TSO offloads, where
 982          * setting the TSO bit means that the userspace wants to
 983          * accept TSO frames and turning it off means that user space
 984          * does not support TSO.
 985          * For tap, we have to invert it to mean the same thing.
 986          * When user space turns off TSO, we turn off GSO/LRO so that
 987          * user-space will not receive TSO frames.
 988          */
 989         if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6) ||
 990             (feature_mask & (TUN_F_USO4 | TUN_F_USO6)) == (TUN_F_USO4 | TUN_F_USO6))
 991                 features |= RX_OFFLOADS;
 992         else
 993                 features &= ~RX_OFFLOADS;
 994
 995         /* tap_features are the same as features on tun/tap and
 996          * reflect user expectations.
 997          */
 998         tap->tap_features = feature_mask;
 999         if (tap->update_features)
1000                 tap->update_features(tap, features);
1001
1002         return 0;
1003 }
1004
1005 /*
1006  * provide compatibility with generic tun/tap interface
1007  */
1008 static long tap_ioctl(struct file *file, unsigned int cmd,
1009                       unsigned long arg)
1010 {
1011         struct tap_queue *q = file->private_data;
1012         struct tap_dev *tap;
1013         void __user *argp = (void __user *)arg;
1014         struct ifreq __user *ifr = argp;
1015         unsigned int __user *up = argp;
1016         unsigned short u;
1017         int __user *sp = argp;
1018         struct sockaddr sa;
1019         int s;
1020         int ret;
1021
1022         switch (cmd) {
1023         case TUNSETIFF:
1024                 /* ignore the name, just look at flags */
1025                 if (get_user(u, &ifr->ifr_flags))
1026                         return -EFAULT;
1027
1028                 ret = 0;
1029                 if ((u & ~TAP_IFFEATURES) != (IFF_NO_PI | IFF_TAP))
1030                         ret = -EINVAL;
1031                 else
1032                         q->flags = (q->flags & ~TAP_IFFEATURES) | u;
1033
1034                 return ret;
1035
1036         case TUNGETIFF:
1037                 rtnl_lock();
1038                 tap = tap_get_tap_dev(q);
1039                 if (!tap) {
1040                         rtnl_unlock();
1041                         return -ENOLINK;
1042                 }
1043
1044                 ret = 0;
1045                 u = q->flags;
1046                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1047                     put_user(u, &ifr->ifr_flags))
1048                         ret = -EFAULT;
1049                 tap_put_tap_dev(tap);
1050                 rtnl_unlock();
1051                 return ret;
1052
1053         case TUNSETQUEUE:
1054                 if (get_user(u, &ifr->ifr_flags))
1055                         return -EFAULT;
1056                 rtnl_lock();
1057                 ret = tap_ioctl_set_queue(file, u);
1058                 rtnl_unlock();
1059                 return ret;
1060
1061         case TUNGETFEATURES:
1062                 if (put_user(IFF_TAP | IFF_NO_PI | TAP_IFFEATURES, up))
1063                         return -EFAULT;
1064                 return 0;
1065
1066         case TUNSETSNDBUF:
1067                 if (get_user(s, sp))
1068                         return -EFAULT;
1069                 if (s <= 0)
1070                         return -EINVAL;
1071
1072                 q->sk.sk_sndbuf = s;
1073                 return 0;
1074
1075         case TUNGETVNETHDRSZ:
1076                 s = q->vnet_hdr_sz;
1077                 if (put_user(s, sp))
1078                         return -EFAULT;
1079                 return 0;
1080
1081         case TUNSETVNETHDRSZ:
1082                 if (get_user(s, sp))
1083                         return -EFAULT;
1084                 if (s < (int)sizeof(struct virtio_net_hdr))
1085                         return -EINVAL;
1086
1087                 q->vnet_hdr_sz = s;
1088                 return 0;
1089
1090         case TUNGETVNETLE:
1091                 s = !!(q->flags & TAP_VNET_LE);
1092                 if (put_user(s, sp))
1093                         return -EFAULT;
1094                 return 0;
1095
1096         case TUNSETVNETLE:
1097                 if (get_user(s, sp))
1098                         return -EFAULT;
1099                 if (s)
1100                         q->flags |= TAP_VNET_LE;
1101                 else
1102                         q->flags &= ~TAP_VNET_LE;
1103                 return 0;
1104
1105         case TUNGETVNETBE:
1106                 return tap_get_vnet_be(q, sp);
1107
1108         case TUNSETVNETBE:
1109                 return tap_set_vnet_be(q, sp);
1110
1111         case TUNSETOFFLOAD:
1112                 /* let the user check for future flags */
1113                 if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
1114                             TUN_F_TSO_ECN | TUN_F_UFO |
1115                             TUN_F_USO4 | TUN_F_USO6))
1116                         return -EINVAL;
1117
1118                 rtnl_lock();
1119                 ret = set_offload(q, arg);
1120                 rtnl_unlock();
1121                 return ret;
1122
1123         case SIOCGIFHWADDR:
1124                 rtnl_lock();
1125                 tap = tap_get_tap_dev(q);
1126                 if (!tap) {
1127                         rtnl_unlock();
1128                         return -ENOLINK;
1129                 }
1130                 ret = 0;
1131                 dev_get_mac_address(&sa, dev_net(tap->dev), tap->dev->name);
1132                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1133                     copy_to_user(&ifr->ifr_hwaddr, &sa, sizeof(sa)))
1134                         ret = -EFAULT;
1135                 tap_put_tap_dev(tap);
1136                 rtnl_unlock();
1137                 return ret;
1138
1139         case SIOCSIFHWADDR:
1140                 if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
1141                         return -EFAULT;
1142                 rtnl_lock();
1143                 tap = tap_get_tap_dev(q);
1144                 if (!tap) {
1145                         rtnl_unlock();
1146                         return -ENOLINK;
1147                 }
1148                 ret = dev_set_mac_address_user(tap->dev, &sa, NULL);
1149                 tap_put_tap_dev(tap);
1150                 rtnl_unlock();
1151                 return ret;
1152
1153         default:
1154                 return -EINVAL;
1155         }
1156 }
1157
1158 static const struct file_operations tap_fops = {
1159         .owner          = THIS_MODULE,
1160         .open           = tap_open,
1161         .release        = tap_release,
1162         .read_iter      = tap_read_iter,
1163         .write_iter     = tap_write_iter,
1164         .poll           = tap_poll,
1165         .llseek         = no_llseek,
1166         .unlocked_ioctl = tap_ioctl,
1167         .compat_ioctl   = compat_ptr_ioctl,
1168 };
1169
1170 static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
1171 {
1172         struct tun_xdp_hdr *hdr = xdp->data_hard_start;
1173         struct virtio_net_hdr *gso = &hdr->gso;
1174         int buflen = hdr->buflen;
1175         int vnet_hdr_len = 0;
1176         struct tap_dev *tap;
1177         struct sk_buff *skb;
1178         int err, depth;
1179
1180         if (q->flags & IFF_VNET_HDR)
1181                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
1182
1183         skb = build_skb(xdp->data_hard_start, buflen);
1184         if (!skb) {
1185                 err = -ENOMEM;
1186                 goto err;
1187         }
1188
1189         skb_reserve(skb, xdp->data - xdp->data_hard_start);
1190         skb_put(skb, xdp->data_end - xdp->data);
1191
1192         skb_set_network_header(skb, ETH_HLEN);
1193         skb_reset_mac_header(skb);
1194         skb->protocol = eth_hdr(skb)->h_proto;
1195
1196         if (vnet_hdr_len) {
1197                 err = virtio_net_hdr_to_skb(skb, gso, tap_is_little_endian(q));
1198                 if (err)
1199                         goto err_kfree;
1200         }
1201
1202         /* Move network header to the right position for VLAN tagged packets */
1203         if (eth_type_vlan(skb->protocol) &&
1204             vlan_get_protocol_and_depth(skb, skb->protocol, &depth) != 0)
1205                 skb_set_network_header(skb, depth);
1206
1207         rcu_read_lock();
1208         tap = rcu_dereference(q->tap);
1209         if (tap) {
1210                 skb->dev = tap->dev;
1211                 skb_probe_transport_header(skb);
1212                 dev_queue_xmit(skb);
1213         } else {
1214                 kfree_skb(skb);
1215         }
1216         rcu_read_unlock();
1217
1218         return 0;
1219
1220 err_kfree:
1221         kfree_skb(skb);
1222 err:
1223         rcu_read_lock();
1224         tap = rcu_dereference(q->tap);
1225         if (tap && tap->count_tx_dropped)
1226                 tap->count_tx_dropped(tap);
1227         rcu_read_unlock();
1228         return err;
1229 }
1230
1231 static int tap_sendmsg(struct socket *sock, struct msghdr *m,
1232                        size_t total_len)
1233 {
1234         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1235         struct tun_msg_ctl *ctl = m->msg_control;
1236         struct xdp_buff *xdp;
1237         int i;
1238
1239         if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
1240             ctl && ctl->type == TUN_MSG_PTR) {
1241                 for (i = 0; i < ctl->num; i++) {
1242                         xdp = &((struct xdp_buff *)ctl->ptr)[i];
1243                         tap_get_user_xdp(q, xdp);
1244                 }
1245                 return 0;
1246         }
1247
1248         return tap_get_user(q, ctl ? ctl->ptr : NULL, &m->msg_iter,
1249                             m->msg_flags & MSG_DONTWAIT);
1250 }
1251
1252 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
1253                        size_t total_len, int flags)
1254 {
1255         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1256         struct sk_buff *skb = m->msg_control;
1257         int ret;
1258         if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
1259                 kfree_skb(skb);
1260                 return -EINVAL;
1261         }
1262         ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT, skb);
1263         if (ret > total_len) {
1264                 m->msg_flags |= MSG_TRUNC;
1265                 ret = flags & MSG_TRUNC ? ret : total_len;
1266         }
1267         return ret;
1268 }
1269
1270 static int tap_peek_len(struct socket *sock)
1271 {
1272         struct tap_queue *q = container_of(sock, struct tap_queue,
1273                                                sock);
1274         return PTR_RING_PEEK_CALL(&q->ring, __skb_array_len_with_tag);
1275 }
1276
1277 /* Ops structure to mimic raw sockets with tun */
1278 static const struct proto_ops tap_socket_ops = {
1279         .sendmsg = tap_sendmsg,
1280         .recvmsg = tap_recvmsg,
1281         .peek_len = tap_peek_len,
1282 };
1283
1284 /* Get an underlying socket object from tun file.  Returns error unless file is
1285  * attached to a device.  The returned object works like a packet socket, it
1286  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
1287  * holding a reference to the file for as long as the socket is in use. */
1288 struct socket *tap_get_socket(struct file *file)
1289 {
1290         struct tap_queue *q;
1291         if (file->f_op != &tap_fops)
1292                 return ERR_PTR(-EINVAL);
1293         q = file->private_data;
1294         if (!q)
1295                 return ERR_PTR(-EBADFD);
1296         return &q->sock;
1297 }
1298 EXPORT_SYMBOL_GPL(tap_get_socket);
1299
1300 struct ptr_ring *tap_get_ptr_ring(struct file *file)
1301 {
1302         struct tap_queue *q;
1303
1304         if (file->f_op != &tap_fops)
1305                 return ERR_PTR(-EINVAL);
1306         q = file->private_data;
1307         if (!q)
1308                 return ERR_PTR(-EBADFD);
1309         return &q->ring;
1310 }
1311 EXPORT_SYMBOL_GPL(tap_get_ptr_ring);
1312
1313 int tap_queue_resize(struct tap_dev *tap)
1314 {
1315         struct net_device *dev = tap->dev;
1316         struct tap_queue *q;
1317         struct ptr_ring **rings;
1318         int n = tap->numqueues;
1319         int ret, i = 0;
1320
1321         rings = kmalloc_array(n, sizeof(*rings), GFP_KERNEL);
1322         if (!rings)
1323                 return -ENOMEM;
1324
1325         list_for_each_entry(q, &tap->queue_list, next)
1326                 rings[i++] = &q->ring;
1327
1328         ret = ptr_ring_resize_multiple(rings, n,
1329                                        dev->tx_queue_len, GFP_KERNEL,
1330                                        __skb_array_destroy_skb);
1331
1332         kfree(rings);
1333         return ret;
1334 }
1335 EXPORT_SYMBOL_GPL(tap_queue_resize);
1336
1337 static int tap_list_add(dev_t major, const char *device_name)
1338 {
1339         struct major_info *tap_major;
1340
1341         tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
1342         if (!tap_major)
1343                 return -ENOMEM;
1344
1345         tap_major->major = MAJOR(major);
1346
1347         idr_init(&tap_major->minor_idr);
1348         spin_lock_init(&tap_major->minor_lock);
1349
1350         tap_major->device_name = device_name;
1351
1352         list_add_tail_rcu(&tap_major->next, &major_list);
1353         return 0;
1354 }
1355
1356 int tap_create_cdev(struct cdev *tap_cdev, dev_t *tap_major,
1357                     const char *device_name, struct module *module)
1358 {
1359         int err;
1360
1361         err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
1362         if (err)
1363                 goto out1;
1364
1365         cdev_init(tap_cdev, &tap_fops);
1366         tap_cdev->owner = module;
1367         err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
1368         if (err)
1369                 goto out2;
1370
1371         err =  tap_list_add(*tap_major, device_name);
1372         if (err)
1373                 goto out3;
1374
1375         return 0;
1376
1377 out3:
1378         cdev_del(tap_cdev);
1379 out2:
1380         unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
1381 out1:
1382         return err;
1383 }
1384 EXPORT_SYMBOL_GPL(tap_create_cdev);
1385
1386 void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
1387 {
1388         struct major_info *tap_major, *tmp;
1389
1390         cdev_del(tap_cdev);
1391         unregister_chrdev_region(major, TAP_NUM_DEVS);
1392         list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
1393                 if (tap_major->major == MAJOR(major)) {
1394                         idr_destroy(&tap_major->minor_idr);
1395                         list_del_rcu(&tap_major->next);
1396                         kfree_rcu(tap_major, rcu);
1397                 }
1398         }
1399 }
1400 EXPORT_SYMBOL_GPL(tap_destroy_cdev);
1401
1402 MODULE_DESCRIPTION("Common library for drivers implementing the TAP interface");
1403 MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
1404 MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
1405 MODULE_LICENSE("GPL");