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/net_namespace.h>
  22 #include <net/rtnetlink.h>
  23 #include <net/sock.h>
  24 #include <linux/virtio_net.h>
  25 #include <linux/skb_array.h>
  26
  27 #define TAP_IFFEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
  28
  29 #define TAP_VNET_LE 0x80000000
  30 #define TAP_VNET_BE 0x40000000
  31
  32 #ifdef CONFIG_TUN_VNET_CROSS_LE
  33 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  34 {
  35         return q->flags & TAP_VNET_BE ? false :
  36                 virtio_legacy_is_little_endian();
  37 }
  38
  39 static long tap_get_vnet_be(struct tap_queue *q, int __user *sp)
  40 {
  41         int s = !!(q->flags & TAP_VNET_BE);
  42
  43         if (put_user(s, sp))
  44                 return -EFAULT;
  45
  46         return 0;
  47 }
  48
  49 static long tap_set_vnet_be(struct tap_queue *q, int __user *sp)
  50 {
  51         int s;
  52
  53         if (get_user(s, sp))
  54                 return -EFAULT;
  55
  56         if (s)
  57                 q->flags |= TAP_VNET_BE;
  58         else
  59                 q->flags &= ~TAP_VNET_BE;
  60
  61         return 0;
  62 }
  63 #else
  64 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  65 {
  66         return virtio_legacy_is_little_endian();
  67 }
  68
  69 static long tap_get_vnet_be(struct tap_queue *q, int __user *argp)
  70 {
  71         return -EINVAL;
  72 }
  73
  74 static long tap_set_vnet_be(struct tap_queue *q, int __user *argp)
  75 {
  76         return -EINVAL;
  77 }
  78 #endif /* CONFIG_TUN_VNET_CROSS_LE */
  79
  80 static inline bool tap_is_little_endian(struct tap_queue *q)
  81 {
  82         return q->flags & TAP_VNET_LE ||
  83                 tap_legacy_is_little_endian(q);
  84 }
  85
  86 static inline u16 tap16_to_cpu(struct tap_queue *q, __virtio16 val)
  87 {
  88         return __virtio16_to_cpu(tap_is_little_endian(q), val);
  89 }
  90
  91 static inline __virtio16 cpu_to_tap16(struct tap_queue *q, u16 val)
  92 {
  93         return __cpu_to_virtio16(tap_is_little_endian(q), val);
  94 }
  95
  96 static struct proto tap_proto = {
  97         .name = "tap",
  98         .owner = THIS_MODULE,
  99         .obj_size = sizeof(struct tap_queue),
 100 };
 101
 102 #define TAP_NUM_DEVS (1U << MINORBITS)
 103
 104 static LIST_HEAD(major_list);
 105
 106 struct major_info {
 107         struct rcu_head rcu;
 108         dev_t major;
 109         struct idr minor_idr;
 110         spinlock_t minor_lock;
 111         const char *device_name;
 112         struct list_head next;
 113 };
 114
 115 #define GOODCOPY_LEN 128
 116
 117 static const struct proto_ops tap_socket_ops;
 118
 119 #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
 120 #define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)
 121
 122 static struct tap_dev *tap_dev_get_rcu(const struct net_device *dev)
 123 {
 124         return rcu_dereference(dev->rx_handler_data);
 125 }
 126
 127 /*
 128  * RCU usage:
 129  * The tap_queue and the macvlan_dev are loosely coupled, the
 130  * pointers from one to the other can only be read while rcu_read_lock
 131  * or rtnl is held.
 132  *
 133  * Both the file and the macvlan_dev hold a reference on the tap_queue
 134  * through sock_hold(&q->sk). When the macvlan_dev goes away first,
 135  * q->vlan becomes inaccessible. When the files gets closed,
 136  * tap_get_queue() fails.
 137  *
 138  * There may still be references to the struct sock inside of the
 139  * queue from outbound SKBs, but these never reference back to the
 140  * file or the dev. The data structure is freed through __sk_free
 141  * when both our references and any pending SKBs are gone.
 142  */
 143
 144 static int tap_enable_queue(struct tap_dev *tap, struct file *file,
 145                             struct tap_queue *q)
 146 {
 147         int err = -EINVAL;
 148
 149         ASSERT_RTNL();
 150
 151         if (q->enabled)
 152                 goto out;
 153
 154         err = 0;
 155         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 156         q->queue_index = tap->numvtaps;
 157         q->enabled = true;
 158
 159         tap->numvtaps++;
 160 out:
 161         return err;
 162 }
 163
 164 /* Requires RTNL */
 165 static int tap_set_queue(struct tap_dev *tap, struct file *file,
 166                          struct tap_queue *q)
 167 {
 168         if (tap->numqueues == MAX_TAP_QUEUES)
 169                 return -EBUSY;
 170
 171         rcu_assign_pointer(q->tap, tap);
 172         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 173         sock_hold(&q->sk);
 174
 175         q->file = file;
 176         q->queue_index = tap->numvtaps;
 177         q->enabled = true;
 178         file->private_data = q;
 179         list_add_tail(&q->next, &tap->queue_list);
 180
 181         tap->numvtaps++;
 182         tap->numqueues++;
 183
 184         return 0;
 185 }
 186
 187 static int tap_disable_queue(struct tap_queue *q)
 188 {
 189         struct tap_dev *tap;
 190         struct tap_queue *nq;
 191
 192         ASSERT_RTNL();
 193         if (!q->enabled)
 194                 return -EINVAL;
 195
 196         tap = rtnl_dereference(q->tap);
 197
 198         if (tap) {
 199                 int index = q->queue_index;
 200                 BUG_ON(index >= tap->numvtaps);
 201                 nq = rtnl_dereference(tap->taps[tap->numvtaps - 1]);
 202                 nq->queue_index = index;
 203
 204                 rcu_assign_pointer(tap->taps[index], nq);
 205                 RCU_INIT_POINTER(tap->taps[tap->numvtaps - 1], NULL);
 206                 q->enabled = false;
 207
 208                 tap->numvtaps--;
 209         }
 210
 211         return 0;
 212 }
 213
 214 /*
 215  * The file owning the queue got closed, give up both
 216  * the reference that the files holds as well as the
 217  * one from the macvlan_dev if that still exists.
 218  *
 219  * Using the spinlock makes sure that we don't get
 220  * to the queue again after destroying it.
 221  */
 222 static void tap_put_queue(struct tap_queue *q)
 223 {
 224         struct tap_dev *tap;
 225
 226         rtnl_lock();
 227         tap = rtnl_dereference(q->tap);
 228
 229         if (tap) {
 230                 if (q->enabled)
 231                         BUG_ON(tap_disable_queue(q));
 232
 233                 tap->numqueues--;
 234                 RCU_INIT_POINTER(q->tap, NULL);
 235                 sock_put(&q->sk);
 236                 list_del_init(&q->next);
 237         }
 238
 239         rtnl_unlock();
 240
 241         synchronize_rcu();
 242         sock_put(&q->sk);
 243 }
 244
 245 /*
 246  * Select a queue based on the rxq of the device on which this packet
 247  * arrived. If the incoming device is not mq, calculate a flow hash
 248  * to select a queue. If all fails, find the first available queue.
 249  * Cache vlan->numvtaps since it can become zero during the execution
 250  * of this function.
 251  */
 252 static struct tap_queue *tap_get_queue(struct tap_dev *tap,
 253                                        struct sk_buff *skb)
 254 {
 255         struct tap_queue *queue = NULL;
 256         /* Access to taps array is protected by rcu, but access to numvtaps
 257          * isn't. Below we use it to lookup a queue, but treat it as a hint
 258          * and validate that the result isn't NULL - in case we are
 259          * racing against queue removal.
 260          */
 261         int numvtaps = READ_ONCE(tap->numvtaps);
 262         __u32 rxq;
 263
 264         if (!numvtaps)
 265                 goto out;
 266
 267         if (numvtaps == 1)
 268                 goto single;
 269
 270         /* Check if we can use flow to select a queue */
 271         rxq = skb_get_hash(skb);
 272         if (rxq) {
 273                 queue = rcu_dereference(tap->taps[rxq % numvtaps]);
 274                 goto out;
 275         }
 276
 277         if (likely(skb_rx_queue_recorded(skb))) {
 278                 rxq = skb_get_rx_queue(skb);
 279
 280                 while (unlikely(rxq >= numvtaps))
 281                         rxq -= numvtaps;
 282
 283                 queue = rcu_dereference(tap->taps[rxq]);
 284                 goto out;
 285         }
 286
 287 single:
 288         queue = rcu_dereference(tap->taps[0]);
 289 out:
 290         return queue;
 291 }
 292
 293 /*
 294  * The net_device is going away, give up the reference
 295  * that it holds on all queues and safely set the pointer
 296  * from the queues to NULL.
 297  */
 298 void tap_del_queues(struct tap_dev *tap)
 299 {
 300         struct tap_queue *q, *tmp;
 301
 302         ASSERT_RTNL();
 303         list_for_each_entry_safe(q, tmp, &tap->queue_list, next) {
 304                 list_del_init(&q->next);
 305                 RCU_INIT_POINTER(q->tap, NULL);
 306                 if (q->enabled)
 307                         tap->numvtaps--;
 308                 tap->numqueues--;
 309                 sock_put(&q->sk);
 310         }
 311         BUG_ON(tap->numvtaps);
 312         BUG_ON(tap->numqueues);
 313         /* guarantee that any future tap_set_queue will fail */
 314         tap->numvtaps = MAX_TAP_QUEUES;
 315 }
 316 EXPORT_SYMBOL_GPL(tap_del_queues);
 317
 318 rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
 319 {
 320         struct sk_buff *skb = *pskb;
 321         struct net_device *dev = skb->dev;
 322         struct tap_dev *tap;
 323         struct tap_queue *q;
 324         netdev_features_t features = TAP_FEATURES;
 325
 326         tap = tap_dev_get_rcu(dev);
 327         if (!tap)
 328                 return RX_HANDLER_PASS;
 329
 330         q = tap_get_queue(tap, skb);
 331         if (!q)
 332                 return RX_HANDLER_PASS;
 333
 334         skb_push(skb, ETH_HLEN);
 335
 336         /* Apply the forward feature mask so that we perform segmentation
 337          * according to users wishes.  This only works if VNET_HDR is
 338          * enabled.
 339          */
 340         if (q->flags & IFF_VNET_HDR)
 341                 features |= tap->tap_features;
 342         if (netif_needs_gso(skb, features)) {
 343                 struct sk_buff *segs = __skb_gso_segment(skb, features, false);
 344
 345                 if (IS_ERR(segs))
 346                         goto drop;
 347
 348                 if (!segs) {
 349                         if (ptr_ring_produce(&q->ring, skb))
 350                                 goto drop;
 351                         goto wake_up;
 352                 }
 353
 354                 consume_skb(skb);
 355                 while (segs) {
 356                         struct sk_buff *nskb = segs->next;
 357
 358                         segs->next = NULL;
 359                         if (ptr_ring_produce(&q->ring, segs)) {
 360                                 kfree_skb(segs);
 361                                 kfree_skb_list(nskb);
 362                                 break;
 363                         }
 364                         segs = nskb;
 365                 }
 366         } else {
 367                 /* If we receive a partial checksum and the tap side
 368                  * doesn't support checksum offload, compute the checksum.
 369                  * Note: it doesn't matter which checksum feature to
 370                  *        check, we either support them all or none.
 371                  */
 372                 if (skb->ip_summed == CHECKSUM_PARTIAL &&
 373                     !(features & NETIF_F_CSUM_MASK) &&
 374                     skb_checksum_help(skb))
 375                         goto drop;
 376                 if (ptr_ring_produce(&q->ring, skb))
 377                         goto drop;
 378         }
 379
 380 wake_up:
 381         wake_up_interruptible_poll(sk_sleep(&q->sk), EPOLLIN | EPOLLRDNORM | EPOLLRDBAND);
 382         return RX_HANDLER_CONSUMED;
 383
 384 drop:
 385         /* Count errors/drops only here, thus don't care about args. */
 386         if (tap->count_rx_dropped)
 387                 tap->count_rx_dropped(tap);
 388         kfree_skb(skb);
 389         return RX_HANDLER_CONSUMED;
 390 }
 391 EXPORT_SYMBOL_GPL(tap_handle_frame);
 392
 393 static struct major_info *tap_get_major(int major)
 394 {
 395         struct major_info *tap_major;
 396
 397         list_for_each_entry_rcu(tap_major, &major_list, next) {
 398                 if (tap_major->major == major)
 399                         return tap_major;
 400         }
 401
 402         return NULL;
 403 }
 404
 405 int tap_get_minor(dev_t major, struct tap_dev *tap)
 406 {
 407         int retval = -ENOMEM;
 408         struct major_info *tap_major;
 409
 410         rcu_read_lock();
 411         tap_major = tap_get_major(MAJOR(major));
 412         if (!tap_major) {
 413                 retval = -EINVAL;
 414                 goto unlock;
 415         }
 416
 417         spin_lock(&tap_major->minor_lock);
 418         retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);
 419         if (retval >= 0) {
 420                 tap->minor = retval;
 421         } else if (retval == -ENOSPC) {
 422                 netdev_err(tap->dev, "Too many tap devices\n");
 423                 retval = -EINVAL;
 424         }
 425         spin_unlock(&tap_major->minor_lock);
 426
 427 unlock:
 428         rcu_read_unlock();
 429         return retval < 0 ? retval : 0;
 430 }
 431 EXPORT_SYMBOL_GPL(tap_get_minor);
 432
 433 void tap_free_minor(dev_t major, struct tap_dev *tap)
 434 {
 435         struct major_info *tap_major;
 436
 437         rcu_read_lock();
 438         tap_major = tap_get_major(MAJOR(major));
 439         if (!tap_major) {
 440                 goto unlock;
 441         }
 442
 443         spin_lock(&tap_major->minor_lock);
 444         if (tap->minor) {
 445                 idr_remove(&tap_major->minor_idr, tap->minor);
 446                 tap->minor = 0;
 447         }
 448         spin_unlock(&tap_major->minor_lock);
 449
 450 unlock:
 451         rcu_read_unlock();
 452 }
 453 EXPORT_SYMBOL_GPL(tap_free_minor);
 454
 455 static struct tap_dev *dev_get_by_tap_file(int major, int minor)
 456 {
 457         struct net_device *dev = NULL;
 458         struct tap_dev *tap;
 459         struct major_info *tap_major;
 460
 461         rcu_read_lock();
 462         tap_major = tap_get_major(major);
 463         if (!tap_major) {
 464                 tap = NULL;
 465                 goto unlock;
 466         }
 467
 468         spin_lock(&tap_major->minor_lock);
 469         tap = idr_find(&tap_major->minor_idr, minor);
 470         if (tap) {
 471                 dev = tap->dev;
 472                 dev_hold(dev);
 473         }
 474         spin_unlock(&tap_major->minor_lock);
 475
 476 unlock:
 477         rcu_read_unlock();
 478         return tap;
 479 }
 480
 481 static void tap_sock_write_space(struct sock *sk)
 482 {
 483         wait_queue_head_t *wqueue;
 484
 485         if (!sock_writeable(sk) ||
 486             !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
 487                 return;
 488
 489         wqueue = sk_sleep(sk);
 490         if (wqueue && waitqueue_active(wqueue))
 491                 wake_up_interruptible_poll(wqueue, EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
 492 }
 493
 494 static void tap_sock_destruct(struct sock *sk)
 495 {
 496         struct tap_queue *q = container_of(sk, struct tap_queue, sk);
 497
 498         ptr_ring_cleanup(&q->ring, __skb_array_destroy_skb);
 499 }
 500
 501 static int tap_open(struct inode *inode, struct file *file)
 502 {
 503         struct net *net = current->nsproxy->net_ns;
 504         struct tap_dev *tap;
 505         struct tap_queue *q;
 506         int err = -ENODEV;
 507
 508         rtnl_lock();
 509         tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
 510         if (!tap)
 511                 goto err;
 512
 513         err = -ENOMEM;
 514         q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
 515                                              &tap_proto, 0);
 516         if (!q)
 517                 goto err;
 518         if (ptr_ring_init(&q->ring, tap->dev->tx_queue_len, GFP_KERNEL)) {
 519                 sk_free(&q->sk);
 520                 goto err;
 521         }
 522
 523         init_waitqueue_head(&q->sock.wq.wait);
 524         q->sock.type = SOCK_RAW;
 525         q->sock.state = SS_CONNECTED;
 526         q->sock.file = file;
 527         q->sock.ops = &tap_socket_ops;
 528         sock_init_data(&q->sock, &q->sk);
 529         q->sk.sk_write_space = tap_sock_write_space;
 530         q->sk.sk_destruct = tap_sock_destruct;
 531         q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;
 532         q->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
 533
 534         /*
 535          * so far only KVM virtio_net uses tap, enable zero copy between
 536          * guest kernel and host kernel when lower device supports zerocopy
 537          *
 538          * The macvlan supports zerocopy iff the lower device supports zero
 539          * copy so we don't have to look at the lower device directly.
 540          */
 541         if ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
 542                 sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 543
 544         err = tap_set_queue(tap, file, q);
 545         if (err) {
 546                 /* tap_sock_destruct() will take care of freeing ptr_ring */
 547                 goto err_put;
 548         }
 549
 550         dev_put(tap->dev);
 551
 552         rtnl_unlock();
 553         return err;
 554
 555 err_put:
 556         sock_put(&q->sk);
 557 err:
 558         if (tap)
 559                 dev_put(tap->dev);
 560
 561         rtnl_unlock();
 562         return err;
 563 }
 564
 565 static int tap_release(struct inode *inode, struct file *file)
 566 {
 567         struct tap_queue *q = file->private_data;
 568         tap_put_queue(q);
 569         return 0;
 570 }
 571
 572 static __poll_t tap_poll(struct file *file, poll_table *wait)
 573 {
 574         struct tap_queue *q = file->private_data;
 575         __poll_t mask = EPOLLERR;
 576
 577         if (!q)
 578                 goto out;
 579
 580         mask = 0;
 581         poll_wait(file, &q->sock.wq.wait, wait);
 582
 583         if (!ptr_ring_empty(&q->ring))
 584                 mask |= EPOLLIN | EPOLLRDNORM;
 585
 586         if (sock_writeable(&q->sk) ||
 587             (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) &&
 588              sock_writeable(&q->sk)))
 589                 mask |= EPOLLOUT | EPOLLWRNORM;
 590
 591 out:
 592         return mask;
 593 }
 594
 595 static inline struct sk_buff *tap_alloc_skb(struct sock *sk, size_t prepad,
 596                                             size_t len, size_t linear,
 597                                                 int noblock, int *err)
 598 {
 599         struct sk_buff *skb;
 600
 601         /* Under a page?  Don't bother with paged skb. */
 602         if (prepad + len < PAGE_SIZE || !linear)
 603                 linear = len;
 604
 605         skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
 606                                    err, 0);
 607         if (!skb)
 608                 return NULL;
 609
 610         skb_reserve(skb, prepad);
 611         skb_put(skb, linear);
 612         skb->data_len = len - linear;
 613         skb->len += len - linear;
 614
 615         return skb;
 616 }
 617
 618 /* Neighbour code has some assumptions on HH_DATA_MOD alignment */
 619 #define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
 620
 621 /* Get packet from user space buffer */
 622 static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 623                             struct iov_iter *from, int noblock)
 624 {
 625         int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
 626         struct sk_buff *skb;
 627         struct tap_dev *tap;
 628         unsigned long total_len = iov_iter_count(from);
 629         unsigned long len = total_len;
 630         int err;
 631         struct virtio_net_hdr vnet_hdr = { 0 };
 632         int vnet_hdr_len = 0;
 633         int copylen = 0;
 634         int depth;
 635         bool zerocopy = false;
 636         size_t linear;
 637
 638         if (q->flags & IFF_VNET_HDR) {
 639                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 640
 641                 err = -EINVAL;
 642                 if (len < vnet_hdr_len)
 643                         goto err;
 644                 len -= vnet_hdr_len;
 645
 646                 err = -EFAULT;
 647                 if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
 648                         goto err;
 649                 iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
 650                 if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
 651                      tap16_to_cpu(q, vnet_hdr.csum_start) +
 652                      tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
 653                              tap16_to_cpu(q, vnet_hdr.hdr_len))
 654                         vnet_hdr.hdr_len = cpu_to_tap16(q,
 655                                  tap16_to_cpu(q, vnet_hdr.csum_start) +
 656                                  tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
 657                 err = -EINVAL;
 658                 if (tap16_to_cpu(q, vnet_hdr.hdr_len) > len)
 659                         goto err;
 660         }
 661
 662         err = -EINVAL;
 663         if (unlikely(len < ETH_HLEN))
 664                 goto err;
 665
 666         if (msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
 667                 struct iov_iter i;
 668
 669                 copylen = vnet_hdr.hdr_len ?
 670                         tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
 671                 if (copylen > good_linear)
 672                         copylen = good_linear;
 673                 else if (copylen < ETH_HLEN)
 674                         copylen = ETH_HLEN;
 675                 linear = copylen;
 676                 i = *from;
 677                 iov_iter_advance(&i, copylen);
 678                 if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
 679                         zerocopy = true;
 680         }
 681
 682         if (!zerocopy) {
 683                 copylen = len;
 684                 linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
 685                 if (linear > good_linear)
 686                         linear = good_linear;
 687                 else if (linear < ETH_HLEN)
 688                         linear = ETH_HLEN;
 689         }
 690
 691         skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,
 692                             linear, noblock, &err);
 693         if (!skb)
 694                 goto err;
 695
 696         if (zerocopy)
 697                 err = zerocopy_sg_from_iter(skb, from);
 698         else
 699                 err = skb_copy_datagram_from_iter(skb, 0, from, len);
 700
 701         if (err)
 702                 goto err_kfree;
 703
 704         skb_set_network_header(skb, ETH_HLEN);
 705         skb_reset_mac_header(skb);
 706         skb->protocol = eth_hdr(skb)->h_proto;
 707
 708         if (vnet_hdr_len) {
 709                 err = virtio_net_hdr_to_skb(skb, &vnet_hdr,
 710                                             tap_is_little_endian(q));
 711                 if (err)
 712                         goto err_kfree;
 713         }
 714
 715         skb_probe_transport_header(skb);
 716
 717         /* Move network header to the right position for VLAN tagged packets */
 718         if ((skb->protocol == htons(ETH_P_8021Q) ||
 719              skb->protocol == htons(ETH_P_8021AD)) &&
 720             __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
 721                 skb_set_network_header(skb, depth);
 722
 723         rcu_read_lock();
 724         tap = rcu_dereference(q->tap);
 725         /* copy skb_ubuf_info for callback when skb has no error */
 726         if (zerocopy) {
 727                 skb_shinfo(skb)->destructor_arg = msg_control;
 728                 skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
 729                 skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 730         } else if (msg_control) {
 731                 struct ubuf_info *uarg = msg_control;
 732                 uarg->callback(uarg, false);
 733         }
 734
 735         if (tap) {
 736                 skb->dev = tap->dev;
 737                 dev_queue_xmit(skb);
 738         } else {
 739                 kfree_skb(skb);
 740         }
 741         rcu_read_unlock();
 742
 743         return total_len;
 744
 745 err_kfree:
 746         kfree_skb(skb);
 747
 748 err:
 749         rcu_read_lock();
 750         tap = rcu_dereference(q->tap);
 751         if (tap && tap->count_tx_dropped)
 752                 tap->count_tx_dropped(tap);
 753         rcu_read_unlock();
 754
 755         return err;
 756 }
 757
 758 static ssize_t tap_write_iter(struct kiocb *iocb, struct iov_iter *from)
 759 {
 760         struct file *file = iocb->ki_filp;
 761         struct tap_queue *q = file->private_data;
 762
 763         return tap_get_user(q, NULL, from, file->f_flags & O_NONBLOCK);
 764 }
 765
 766 /* Put packet to the user space buffer */
 767 static ssize_t tap_put_user(struct tap_queue *q,
 768                             const struct sk_buff *skb,
 769                             struct iov_iter *iter)
 770 {
 771         int ret;
 772         int vnet_hdr_len = 0;
 773         int vlan_offset = 0;
 774         int total;
 775
 776         if (q->flags & IFF_VNET_HDR) {
 777                 int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0;
 778                 struct virtio_net_hdr vnet_hdr;
 779
 780                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 781                 if (iov_iter_count(iter) < vnet_hdr_len)
 782                         return -EINVAL;
 783
 784                 if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
 785                                             tap_is_little_endian(q), true,
 786                                             vlan_hlen))
 787                         BUG();
 788
 789                 if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
 790                     sizeof(vnet_hdr))
 791                         return -EFAULT;
 792
 793                 iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));
 794         }
 795         total = vnet_hdr_len;
 796         total += skb->len;
 797
 798         if (skb_vlan_tag_present(skb)) {
 799                 struct {
 800                         __be16 h_vlan_proto;
 801                         __be16 h_vlan_TCI;
 802                 } veth;
 803                 veth.h_vlan_proto = skb->vlan_proto;
 804                 veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
 805
 806                 vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
 807                 total += VLAN_HLEN;
 808
 809                 ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
 810                 if (ret || !iov_iter_count(iter))
 811                         goto done;
 812
 813                 ret = copy_to_iter(&veth, sizeof(veth), iter);
 814                 if (ret != sizeof(veth) || !iov_iter_count(iter))
 815                         goto done;
 816         }
 817
 818         ret = skb_copy_datagram_iter(skb, vlan_offset, iter,
 819                                      skb->len - vlan_offset);
 820
 821 done:
 822         return ret ? ret : total;
 823 }
 824
 825 static ssize_t tap_do_read(struct tap_queue *q,
 826                            struct iov_iter *to,
 827                            int noblock, struct sk_buff *skb)
 828 {
 829         DEFINE_WAIT(wait);
 830         ssize_t ret = 0;
 831
 832         if (!iov_iter_count(to)) {
 833                 kfree_skb(skb);
 834                 return 0;
 835         }
 836
 837         if (skb)
 838                 goto put;
 839
 840         while (1) {
 841                 if (!noblock)
 842                         prepare_to_wait(sk_sleep(&q->sk), &wait,
 843                                         TASK_INTERRUPTIBLE);
 844
 845                 /* Read frames from the queue */
 846                 skb = ptr_ring_consume(&q->ring);
 847                 if (skb)
 848                         break;
 849                 if (noblock) {
 850                         ret = -EAGAIN;
 851                         break;
 852                 }
 853                 if (signal_pending(current)) {
 854                         ret = -ERESTARTSYS;
 855                         break;
 856                 }
 857                 /* Nothing to read, let's sleep */
 858                 schedule();
 859         }
 860         if (!noblock)
 861                 finish_wait(sk_sleep(&q->sk), &wait);
 862
 863 put:
 864         if (skb) {
 865                 ret = tap_put_user(q, skb, to);
 866                 if (unlikely(ret < 0))
 867                         kfree_skb(skb);
 868                 else
 869                         consume_skb(skb);
 870         }
 871         return ret;
 872 }
 873
 874 static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
 875 {
 876         struct file *file = iocb->ki_filp;
 877         struct tap_queue *q = file->private_data;
 878         ssize_t len = iov_iter_count(to), ret;
 879
 880         ret = tap_do_read(q, to, file->f_flags & O_NONBLOCK, NULL);
 881         ret = min_t(ssize_t, ret, len);
 882         if (ret > 0)
 883                 iocb->ki_pos = ret;
 884         return ret;
 885 }
 886
 887 static struct tap_dev *tap_get_tap_dev(struct tap_queue *q)
 888 {
 889         struct tap_dev *tap;
 890
 891         ASSERT_RTNL();
 892         tap = rtnl_dereference(q->tap);
 893         if (tap)
 894                 dev_hold(tap->dev);
 895
 896         return tap;
 897 }
 898
 899 static void tap_put_tap_dev(struct tap_dev *tap)
 900 {
 901         dev_put(tap->dev);
 902 }
 903
 904 static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
 905 {
 906         struct tap_queue *q = file->private_data;
 907         struct tap_dev *tap;
 908         int ret;
 909
 910         tap = tap_get_tap_dev(q);
 911         if (!tap)
 912                 return -EINVAL;
 913
 914         if (flags & IFF_ATTACH_QUEUE)
 915                 ret = tap_enable_queue(tap, file, q);
 916         else if (flags & IFF_DETACH_QUEUE)
 917                 ret = tap_disable_queue(q);
 918         else
 919                 ret = -EINVAL;
 920
 921         tap_put_tap_dev(tap);
 922         return ret;
 923 }
 924
 925 static int set_offload(struct tap_queue *q, unsigned long arg)
 926 {
 927         struct tap_dev *tap;
 928         netdev_features_t features;
 929         netdev_features_t feature_mask = 0;
 930
 931         tap = rtnl_dereference(q->tap);
 932         if (!tap)
 933                 return -ENOLINK;
 934
 935         features = tap->dev->features;
 936
 937         if (arg & TUN_F_CSUM) {
 938                 feature_mask = NETIF_F_HW_CSUM;
 939
 940                 if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
 941                         if (arg & TUN_F_TSO_ECN)
 942                                 feature_mask |= NETIF_F_TSO_ECN;
 943                         if (arg & TUN_F_TSO4)
 944                                 feature_mask |= NETIF_F_TSO;
 945                         if (arg & TUN_F_TSO6)
 946                                 feature_mask |= NETIF_F_TSO6;
 947                 }
 948         }
 949
 950         /* tun/tap driver inverts the usage for TSO offloads, where
 951          * setting the TSO bit means that the userspace wants to
 952          * accept TSO frames and turning it off means that user space
 953          * does not support TSO.
 954          * For tap, we have to invert it to mean the same thing.
 955          * When user space turns off TSO, we turn off GSO/LRO so that
 956          * user-space will not receive TSO frames.
 957          */
 958         if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6))
 959                 features |= RX_OFFLOADS;
 960         else
 961                 features &= ~RX_OFFLOADS;
 962
 963         /* tap_features are the same as features on tun/tap and
 964          * reflect user expectations.
 965          */
 966         tap->tap_features = feature_mask;
 967         if (tap->update_features)
 968                 tap->update_features(tap, features);
 969
 970         return 0;
 971 }
 972
 973 /*
 974  * provide compatibility with generic tun/tap interface
 975  */
 976 static long tap_ioctl(struct file *file, unsigned int cmd,
 977                       unsigned long arg)
 978 {
 979         struct tap_queue *q = file->private_data;
 980         struct tap_dev *tap;
 981         void __user *argp = (void __user *)arg;
 982         struct ifreq __user *ifr = argp;
 983         unsigned int __user *up = argp;
 984         unsigned short u;
 985         int __user *sp = argp;
 986         struct sockaddr sa;
 987         int s;
 988         int ret;
 989
 990         switch (cmd) {
 991         case TUNSETIFF:
 992                 /* ignore the name, just look at flags */
 993                 if (get_user(u, &ifr->ifr_flags))
 994                         return -EFAULT;
 995
 996                 ret = 0;
 997                 if ((u & ~TAP_IFFEATURES) != (IFF_NO_PI | IFF_TAP))
 998                         ret = -EINVAL;
 999                 else
1000                         q->flags = (q->flags & ~TAP_IFFEATURES) | u;
1001
1002                 return ret;
1003
1004         case TUNGETIFF:
1005                 rtnl_lock();
1006                 tap = tap_get_tap_dev(q);
1007                 if (!tap) {
1008                         rtnl_unlock();
1009                         return -ENOLINK;
1010                 }
1011
1012                 ret = 0;
1013                 u = q->flags;
1014                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1015                     put_user(u, &ifr->ifr_flags))
1016                         ret = -EFAULT;
1017                 tap_put_tap_dev(tap);
1018                 rtnl_unlock();
1019                 return ret;
1020
1021         case TUNSETQUEUE:
1022                 if (get_user(u, &ifr->ifr_flags))
1023                         return -EFAULT;
1024                 rtnl_lock();
1025                 ret = tap_ioctl_set_queue(file, u);
1026                 rtnl_unlock();
1027                 return ret;
1028
1029         case TUNGETFEATURES:
1030                 if (put_user(IFF_TAP | IFF_NO_PI | TAP_IFFEATURES, up))
1031                         return -EFAULT;
1032                 return 0;
1033
1034         case TUNSETSNDBUF:
1035                 if (get_user(s, sp))
1036                         return -EFAULT;
1037                 if (s <= 0)
1038                         return -EINVAL;
1039
1040                 q->sk.sk_sndbuf = s;
1041                 return 0;
1042
1043         case TUNGETVNETHDRSZ:
1044                 s = q->vnet_hdr_sz;
1045                 if (put_user(s, sp))
1046                         return -EFAULT;
1047                 return 0;
1048
1049         case TUNSETVNETHDRSZ:
1050                 if (get_user(s, sp))
1051                         return -EFAULT;
1052                 if (s < (int)sizeof(struct virtio_net_hdr))
1053                         return -EINVAL;
1054
1055                 q->vnet_hdr_sz = s;
1056                 return 0;
1057
1058         case TUNGETVNETLE:
1059                 s = !!(q->flags & TAP_VNET_LE);
1060                 if (put_user(s, sp))
1061                         return -EFAULT;
1062                 return 0;
1063
1064         case TUNSETVNETLE:
1065                 if (get_user(s, sp))
1066                         return -EFAULT;
1067                 if (s)
1068                         q->flags |= TAP_VNET_LE;
1069                 else
1070                         q->flags &= ~TAP_VNET_LE;
1071                 return 0;
1072
1073         case TUNGETVNETBE:
1074                 return tap_get_vnet_be(q, sp);
1075
1076         case TUNSETVNETBE:
1077                 return tap_set_vnet_be(q, sp);
1078
1079         case TUNSETOFFLOAD:
1080                 /* let the user check for future flags */
1081                 if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
1082                             TUN_F_TSO_ECN | TUN_F_UFO))
1083                         return -EINVAL;
1084
1085                 rtnl_lock();
1086                 ret = set_offload(q, arg);
1087                 rtnl_unlock();
1088                 return ret;
1089
1090         case SIOCGIFHWADDR:
1091                 rtnl_lock();
1092                 tap = tap_get_tap_dev(q);
1093                 if (!tap) {
1094                         rtnl_unlock();
1095                         return -ENOLINK;
1096                 }
1097                 ret = 0;
1098                 u = tap->dev->type;
1099                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1100                     copy_to_user(&ifr->ifr_hwaddr.sa_data, tap->dev->dev_addr, ETH_ALEN) ||
1101                     put_user(u, &ifr->ifr_hwaddr.sa_family))
1102                         ret = -EFAULT;
1103                 tap_put_tap_dev(tap);
1104                 rtnl_unlock();
1105                 return ret;
1106
1107         case SIOCSIFHWADDR:
1108                 if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
1109                         return -EFAULT;
1110                 rtnl_lock();
1111                 tap = tap_get_tap_dev(q);
1112                 if (!tap) {
1113                         rtnl_unlock();
1114                         return -ENOLINK;
1115                 }
1116                 ret = dev_set_mac_address(tap->dev, &sa, NULL);
1117                 tap_put_tap_dev(tap);
1118                 rtnl_unlock();
1119                 return ret;
1120
1121         default:
1122                 return -EINVAL;
1123         }
1124 }
1125
1126 #ifdef CONFIG_COMPAT
1127 static long tap_compat_ioctl(struct file *file, unsigned int cmd,
1128                              unsigned long arg)
1129 {
1130         return tap_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
1131 }
1132 #endif
1133
1134 static const struct file_operations tap_fops = {
1135         .owner          = THIS_MODULE,
1136         .open           = tap_open,
1137         .release        = tap_release,
1138         .read_iter      = tap_read_iter,
1139         .write_iter     = tap_write_iter,
1140         .poll           = tap_poll,
1141         .llseek         = no_llseek,
1142         .unlocked_ioctl = tap_ioctl,
1143 #ifdef CONFIG_COMPAT
1144         .compat_ioctl   = tap_compat_ioctl,
1145 #endif
1146 };
1147
1148 static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
1149 {
1150         struct tun_xdp_hdr *hdr = xdp->data_hard_start;
1151         struct virtio_net_hdr *gso = &hdr->gso;
1152         int buflen = hdr->buflen;
1153         int vnet_hdr_len = 0;
1154         struct tap_dev *tap;
1155         struct sk_buff *skb;
1156         int err, depth;
1157
1158         if (q->flags & IFF_VNET_HDR)
1159                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
1160
1161         skb = build_skb(xdp->data_hard_start, buflen);
1162         if (!skb) {
1163                 err = -ENOMEM;
1164                 goto err;
1165         }
1166
1167         skb_reserve(skb, xdp->data - xdp->data_hard_start);
1168         skb_put(skb, xdp->data_end - xdp->data);
1169
1170         skb_set_network_header(skb, ETH_HLEN);
1171         skb_reset_mac_header(skb);
1172         skb->protocol = eth_hdr(skb)->h_proto;
1173
1174         if (vnet_hdr_len) {
1175                 err = virtio_net_hdr_to_skb(skb, gso, tap_is_little_endian(q));
1176                 if (err)
1177                         goto err_kfree;
1178         }
1179
1180         /* Move network header to the right position for VLAN tagged packets */
1181         if ((skb->protocol == htons(ETH_P_8021Q) ||
1182              skb->protocol == htons(ETH_P_8021AD)) &&
1183             __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
1184                 skb_set_network_header(skb, depth);
1185
1186         rcu_read_lock();
1187         tap = rcu_dereference(q->tap);
1188         if (tap) {
1189                 skb->dev = tap->dev;
1190                 skb_probe_transport_header(skb);
1191                 dev_queue_xmit(skb);
1192         } else {
1193                 kfree_skb(skb);
1194         }
1195         rcu_read_unlock();
1196
1197         return 0;
1198
1199 err_kfree:
1200         kfree_skb(skb);
1201 err:
1202         rcu_read_lock();
1203         tap = rcu_dereference(q->tap);
1204         if (tap && tap->count_tx_dropped)
1205                 tap->count_tx_dropped(tap);
1206         rcu_read_unlock();
1207         return err;
1208 }
1209
1210 static int tap_sendmsg(struct socket *sock, struct msghdr *m,
1211                        size_t total_len)
1212 {
1213         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1214         struct tun_msg_ctl *ctl = m->msg_control;
1215         struct xdp_buff *xdp;
1216         int i;
1217
1218         if (ctl && (ctl->type == TUN_MSG_PTR)) {
1219                 for (i = 0; i < ctl->num; i++) {
1220                         xdp = &((struct xdp_buff *)ctl->ptr)[i];
1221                         tap_get_user_xdp(q, xdp);
1222                 }
1223                 return 0;
1224         }
1225
1226         return tap_get_user(q, ctl ? ctl->ptr : NULL, &m->msg_iter,
1227                             m->msg_flags & MSG_DONTWAIT);
1228 }
1229
1230 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
1231                        size_t total_len, int flags)
1232 {
1233         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1234         struct sk_buff *skb = m->msg_control;
1235         int ret;
1236         if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
1237                 kfree_skb(skb);
1238                 return -EINVAL;
1239         }
1240         ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT, skb);
1241         if (ret > total_len) {
1242                 m->msg_flags |= MSG_TRUNC;
1243                 ret = flags & MSG_TRUNC ? ret : total_len;
1244         }
1245         return ret;
1246 }
1247
1248 static int tap_peek_len(struct socket *sock)
1249 {
1250         struct tap_queue *q = container_of(sock, struct tap_queue,
1251                                                sock);
1252         return PTR_RING_PEEK_CALL(&q->ring, __skb_array_len_with_tag);
1253 }
1254
1255 /* Ops structure to mimic raw sockets with tun */
1256 static const struct proto_ops tap_socket_ops = {
1257         .sendmsg = tap_sendmsg,
1258         .recvmsg = tap_recvmsg,
1259         .peek_len = tap_peek_len,
1260 };
1261
1262 /* Get an underlying socket object from tun file.  Returns error unless file is
1263  * attached to a device.  The returned object works like a packet socket, it
1264  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
1265  * holding a reference to the file for as long as the socket is in use. */
1266 struct socket *tap_get_socket(struct file *file)
1267 {
1268         struct tap_queue *q;
1269         if (file->f_op != &tap_fops)
1270                 return ERR_PTR(-EINVAL);
1271         q = file->private_data;
1272         if (!q)
1273                 return ERR_PTR(-EBADFD);
1274         return &q->sock;
1275 }
1276 EXPORT_SYMBOL_GPL(tap_get_socket);
1277
1278 struct ptr_ring *tap_get_ptr_ring(struct file *file)
1279 {
1280         struct tap_queue *q;
1281
1282         if (file->f_op != &tap_fops)
1283                 return ERR_PTR(-EINVAL);
1284         q = file->private_data;
1285         if (!q)
1286                 return ERR_PTR(-EBADFD);
1287         return &q->ring;
1288 }
1289 EXPORT_SYMBOL_GPL(tap_get_ptr_ring);
1290
1291 int tap_queue_resize(struct tap_dev *tap)
1292 {
1293         struct net_device *dev = tap->dev;
1294         struct tap_queue *q;
1295         struct ptr_ring **rings;
1296         int n = tap->numqueues;
1297         int ret, i = 0;
1298
1299         rings = kmalloc_array(n, sizeof(*rings), GFP_KERNEL);
1300         if (!rings)
1301                 return -ENOMEM;
1302
1303         list_for_each_entry(q, &tap->queue_list, next)
1304                 rings[i++] = &q->ring;
1305
1306         ret = ptr_ring_resize_multiple(rings, n,
1307                                        dev->tx_queue_len, GFP_KERNEL,
1308                                        __skb_array_destroy_skb);
1309
1310         kfree(rings);
1311         return ret;
1312 }
1313 EXPORT_SYMBOL_GPL(tap_queue_resize);
1314
1315 static int tap_list_add(dev_t major, const char *device_name)
1316 {
1317         struct major_info *tap_major;
1318
1319         tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
1320         if (!tap_major)
1321                 return -ENOMEM;
1322
1323         tap_major->major = MAJOR(major);
1324
1325         idr_init(&tap_major->minor_idr);
1326         spin_lock_init(&tap_major->minor_lock);
1327
1328         tap_major->device_name = device_name;
1329
1330         list_add_tail_rcu(&tap_major->next, &major_list);
1331         return 0;
1332 }
1333
1334 int tap_create_cdev(struct cdev *tap_cdev, dev_t *tap_major,
1335                     const char *device_name, struct module *module)
1336 {
1337         int err;
1338
1339         err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
1340         if (err)
1341                 goto out1;
1342
1343         cdev_init(tap_cdev, &tap_fops);
1344         tap_cdev->owner = module;
1345         err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
1346         if (err)
1347                 goto out2;
1348
1349         err =  tap_list_add(*tap_major, device_name);
1350         if (err)
1351                 goto out3;
1352
1353         return 0;
1354
1355 out3:
1356         cdev_del(tap_cdev);
1357 out2:
1358         unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
1359 out1:
1360         return err;
1361 }
1362 EXPORT_SYMBOL_GPL(tap_create_cdev);
1363
1364 void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
1365 {
1366         struct major_info *tap_major, *tmp;
1367
1368         cdev_del(tap_cdev);
1369         unregister_chrdev_region(major, TAP_NUM_DEVS);
1370         list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
1371                 if (tap_major->major == MAJOR(major)) {
1372                         idr_destroy(&tap_major->minor_idr);
1373                         list_del_rcu(&tap_major->next);
1374                         kfree_rcu(tap_major, rcu);
1375                 }
1376         }
1377 }
1378 EXPORT_SYMBOL_GPL(tap_destroy_cdev);
1379
1380 MODULE_AUTHOR("Arnd Bergmann <[email protected]>");
1381 MODULE_AUTHOR("Sainath Grandhi <[email protected]>");
1382 MODULE_LICENSE("GPL");