drivers/net/tap.c

   1 #include <linux/etherdevice.h>
   2 #include <linux/if_tap.h>
   3 #include <linux/if_vlan.h>
   4 #include <linux/interrupt.h>
   5 #include <linux/nsproxy.h>
   6 #include <linux/compat.h>
   7 #include <linux/if_tun.h>
   8 #include <linux/module.h>
   9 #include <linux/skbuff.h>
  10 #include <linux/cache.h>
  11 #include <linux/sched/signal.h>
  12 #include <linux/types.h>
  13 #include <linux/slab.h>
  14 #include <linux/wait.h>
  15 #include <linux/cdev.h>
  16 #include <linux/idr.h>
  17 #include <linux/fs.h>
  18 #include <linux/uio.h>
  19
  20 #include <net/net_namespace.h>
  21 #include <net/rtnetlink.h>
  22 #include <net/sock.h>
  23 #include <linux/virtio_net.h>
  24 #include <linux/skb_array.h>
  25
  26 #define TAP_IFFEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
  27
  28 #define TAP_VNET_LE 0x80000000
  29 #define TAP_VNET_BE 0x40000000
  30
  31 #ifdef CONFIG_TUN_VNET_CROSS_LE
  32 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  33 {
  34         return q->flags & TAP_VNET_BE ? false :
  35                 virtio_legacy_is_little_endian();
  36 }
  37
  38 static long tap_get_vnet_be(struct tap_queue *q, int __user *sp)
  39 {
  40         int s = !!(q->flags & TAP_VNET_BE);
  41
  42         if (put_user(s, sp))
  43                 return -EFAULT;
  44
  45         return 0;
  46 }
  47
  48 static long tap_set_vnet_be(struct tap_queue *q, int __user *sp)
  49 {
  50         int s;
  51
  52         if (get_user(s, sp))
  53                 return -EFAULT;
  54
  55         if (s)
  56                 q->flags |= TAP_VNET_BE;
  57         else
  58                 q->flags &= ~TAP_VNET_BE;
  59
  60         return 0;
  61 }
  62 #else
  63 static inline bool tap_legacy_is_little_endian(struct tap_queue *q)
  64 {
  65         return virtio_legacy_is_little_endian();
  66 }
  67
  68 static long tap_get_vnet_be(struct tap_queue *q, int __user *argp)
  69 {
  70         return -EINVAL;
  71 }
  72
  73 static long tap_set_vnet_be(struct tap_queue *q, int __user *argp)
  74 {
  75         return -EINVAL;
  76 }
  77 #endif /* CONFIG_TUN_VNET_CROSS_LE */
  78
  79 static inline bool tap_is_little_endian(struct tap_queue *q)
  80 {
  81         return q->flags & TAP_VNET_LE ||
  82                 tap_legacy_is_little_endian(q);
  83 }
  84
  85 static inline u16 tap16_to_cpu(struct tap_queue *q, __virtio16 val)
  86 {
  87         return __virtio16_to_cpu(tap_is_little_endian(q), val);
  88 }
  89
  90 static inline __virtio16 cpu_to_tap16(struct tap_queue *q, u16 val)
  91 {
  92         return __cpu_to_virtio16(tap_is_little_endian(q), val);
  93 }
  94
  95 static struct proto tap_proto = {
  96         .name = "tap",
  97         .owner = THIS_MODULE,
  98         .obj_size = sizeof(struct tap_queue),
  99 };
 100
 101 #define TAP_NUM_DEVS (1U << MINORBITS)
 102
 103 static LIST_HEAD(major_list);
 104
 105 struct major_info {
 106         struct rcu_head rcu;
 107         dev_t major;
 108         struct idr minor_idr;
 109         spinlock_t minor_lock;
 110         const char *device_name;
 111         struct list_head next;
 112 };
 113
 114 #define GOODCOPY_LEN 128
 115
 116 static const struct proto_ops tap_socket_ops;
 117
 118 #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
 119 #define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)
 120
 121 static struct tap_dev *tap_dev_get_rcu(const struct net_device *dev)
 122 {
 123         return rcu_dereference(dev->rx_handler_data);
 124 }
 125
 126 /*
 127  * RCU usage:
 128  * The tap_queue and the macvlan_dev are loosely coupled, the
 129  * pointers from one to the other can only be read while rcu_read_lock
 130  * or rtnl is held.
 131  *
 132  * Both the file and the macvlan_dev hold a reference on the tap_queue
 133  * through sock_hold(&q->sk). When the macvlan_dev goes away first,
 134  * q->vlan becomes inaccessible. When the files gets closed,
 135  * tap_get_queue() fails.
 136  *
 137  * There may still be references to the struct sock inside of the
 138  * queue from outbound SKBs, but these never reference back to the
 139  * file or the dev. The data structure is freed through __sk_free
 140  * when both our references and any pending SKBs are gone.
 141  */
 142
 143 static int tap_enable_queue(struct tap_dev *tap, struct file *file,
 144                             struct tap_queue *q)
 145 {
 146         int err = -EINVAL;
 147
 148         ASSERT_RTNL();
 149
 150         if (q->enabled)
 151                 goto out;
 152
 153         err = 0;
 154         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 155         q->queue_index = tap->numvtaps;
 156         q->enabled = true;
 157
 158         tap->numvtaps++;
 159 out:
 160         return err;
 161 }
 162
 163 /* Requires RTNL */
 164 static int tap_set_queue(struct tap_dev *tap, struct file *file,
 165                          struct tap_queue *q)
 166 {
 167         if (tap->numqueues == MAX_TAP_QUEUES)
 168                 return -EBUSY;
 169
 170         rcu_assign_pointer(q->tap, tap);
 171         rcu_assign_pointer(tap->taps[tap->numvtaps], q);
 172         sock_hold(&q->sk);
 173
 174         q->file = file;
 175         q->queue_index = tap->numvtaps;
 176         q->enabled = true;
 177         file->private_data = q;
 178         list_add_tail(&q->next, &tap->queue_list);
 179
 180         tap->numvtaps++;
 181         tap->numqueues++;
 182
 183         return 0;
 184 }
 185
 186 static int tap_disable_queue(struct tap_queue *q)
 187 {
 188         struct tap_dev *tap;
 189         struct tap_queue *nq;
 190
 191         ASSERT_RTNL();
 192         if (!q->enabled)
 193                 return -EINVAL;
 194
 195         tap = rtnl_dereference(q->tap);
 196
 197         if (tap) {
 198                 int index = q->queue_index;
 199                 BUG_ON(index >= tap->numvtaps);
 200                 nq = rtnl_dereference(tap->taps[tap->numvtaps - 1]);
 201                 nq->queue_index = index;
 202
 203                 rcu_assign_pointer(tap->taps[index], nq);
 204                 RCU_INIT_POINTER(tap->taps[tap->numvtaps - 1], NULL);
 205                 q->enabled = false;
 206
 207                 tap->numvtaps--;
 208         }
 209
 210         return 0;
 211 }
 212
 213 /*
 214  * The file owning the queue got closed, give up both
 215  * the reference that the files holds as well as the
 216  * one from the macvlan_dev if that still exists.
 217  *
 218  * Using the spinlock makes sure that we don't get
 219  * to the queue again after destroying it.
 220  */
 221 static void tap_put_queue(struct tap_queue *q)
 222 {
 223         struct tap_dev *tap;
 224
 225         rtnl_lock();
 226         tap = rtnl_dereference(q->tap);
 227
 228         if (tap) {
 229                 if (q->enabled)
 230                         BUG_ON(tap_disable_queue(q));
 231
 232                 tap->numqueues--;
 233                 RCU_INIT_POINTER(q->tap, NULL);
 234                 sock_put(&q->sk);
 235                 list_del_init(&q->next);
 236         }
 237
 238         rtnl_unlock();
 239
 240         synchronize_rcu();
 241         sock_put(&q->sk);
 242 }
 243
 244 /*
 245  * Select a queue based on the rxq of the device on which this packet
 246  * arrived. If the incoming device is not mq, calculate a flow hash
 247  * to select a queue. If all fails, find the first available queue.
 248  * Cache vlan->numvtaps since it can become zero during the execution
 249  * of this function.
 250  */
 251 static struct tap_queue *tap_get_queue(struct tap_dev *tap,
 252                                        struct sk_buff *skb)
 253 {
 254         struct tap_queue *queue = NULL;
 255         /* Access to taps array is protected by rcu, but access to numvtaps
 256          * isn't. Below we use it to lookup a queue, but treat it as a hint
 257          * and validate that the result isn't NULL - in case we are
 258          * racing against queue removal.
 259          */
 260         int numvtaps = ACCESS_ONCE(tap->numvtaps);
 261         __u32 rxq;
 262
 263         if (!numvtaps)
 264                 goto out;
 265
 266         if (numvtaps == 1)
 267                 goto single;
 268
 269         /* Check if we can use flow to select a queue */
 270         rxq = skb_get_hash(skb);
 271         if (rxq) {
 272                 queue = rcu_dereference(tap->taps[rxq % numvtaps]);
 273                 goto out;
 274         }
 275
 276         if (likely(skb_rx_queue_recorded(skb))) {
 277                 rxq = skb_get_rx_queue(skb);
 278
 279                 while (unlikely(rxq >= numvtaps))
 280                         rxq -= numvtaps;
 281
 282                 queue = rcu_dereference(tap->taps[rxq]);
 283                 goto out;
 284         }
 285
 286 single:
 287         queue = rcu_dereference(tap->taps[0]);
 288 out:
 289         return queue;
 290 }
 291
 292 /*
 293  * The net_device is going away, give up the reference
 294  * that it holds on all queues and safely set the pointer
 295  * from the queues to NULL.
 296  */
 297 void tap_del_queues(struct tap_dev *tap)
 298 {
 299         struct tap_queue *q, *tmp;
 300
 301         ASSERT_RTNL();
 302         list_for_each_entry_safe(q, tmp, &tap->queue_list, next) {
 303                 list_del_init(&q->next);
 304                 RCU_INIT_POINTER(q->tap, NULL);
 305                 if (q->enabled)
 306                         tap->numvtaps--;
 307                 tap->numqueues--;
 308                 sock_put(&q->sk);
 309         }
 310         BUG_ON(tap->numvtaps);
 311         BUG_ON(tap->numqueues);
 312         /* guarantee that any future tap_set_queue will fail */
 313         tap->numvtaps = MAX_TAP_QUEUES;
 314 }
 315 EXPORT_SYMBOL_GPL(tap_del_queues);
 316
 317 rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
 318 {
 319         struct sk_buff *skb = *pskb;
 320         struct net_device *dev = skb->dev;
 321         struct tap_dev *tap;
 322         struct tap_queue *q;
 323         netdev_features_t features = TAP_FEATURES;
 324
 325         tap = tap_dev_get_rcu(dev);
 326         if (!tap)
 327                 return RX_HANDLER_PASS;
 328
 329         q = tap_get_queue(tap, skb);
 330         if (!q)
 331                 return RX_HANDLER_PASS;
 332
 333         if (__skb_array_full(&q->skb_array))
 334                 goto drop;
 335
 336         skb_push(skb, ETH_HLEN);
 337
 338         /* Apply the forward feature mask so that we perform segmentation
 339          * according to users wishes.  This only works if VNET_HDR is
 340          * enabled.
 341          */
 342         if (q->flags & IFF_VNET_HDR)
 343                 features |= tap->tap_features;
 344         if (netif_needs_gso(skb, features)) {
 345                 struct sk_buff *segs = __skb_gso_segment(skb, features, false);
 346
 347                 if (IS_ERR(segs))
 348                         goto drop;
 349
 350                 if (!segs) {
 351                         if (skb_array_produce(&q->skb_array, skb))
 352                                 goto drop;
 353                         goto wake_up;
 354                 }
 355
 356                 consume_skb(skb);
 357                 while (segs) {
 358                         struct sk_buff *nskb = segs->next;
 359
 360                         segs->next = NULL;
 361                         if (skb_array_produce(&q->skb_array, segs)) {
 362                                 kfree_skb(segs);
 363                                 kfree_skb_list(nskb);
 364                                 break;
 365                         }
 366                         segs = nskb;
 367                 }
 368         } else {
 369                 /* If we receive a partial checksum and the tap side
 370                  * doesn't support checksum offload, compute the checksum.
 371                  * Note: it doesn't matter which checksum feature to
 372                  *        check, we either support them all or none.
 373                  */
 374                 if (skb->ip_summed == CHECKSUM_PARTIAL &&
 375                     !(features & NETIF_F_CSUM_MASK) &&
 376                     skb_checksum_help(skb))
 377                         goto drop;
 378                 if (skb_array_produce(&q->skb_array, skb))
 379                         goto drop;
 380         }
 381
 382 wake_up:
 383         wake_up_interruptible_poll(sk_sleep(&q->sk), POLLIN | POLLRDNORM | POLLRDBAND);
 384         return RX_HANDLER_CONSUMED;
 385
 386 drop:
 387         /* Count errors/drops only here, thus don't care about args. */
 388         if (tap->count_rx_dropped)
 389                 tap->count_rx_dropped(tap);
 390         kfree_skb(skb);
 391         return RX_HANDLER_CONSUMED;
 392 }
 393 EXPORT_SYMBOL_GPL(tap_handle_frame);
 394
 395 static struct major_info *tap_get_major(int major)
 396 {
 397         struct major_info *tap_major;
 398
 399         list_for_each_entry_rcu(tap_major, &major_list, next) {
 400                 if (tap_major->major == major)
 401                         return tap_major;
 402         }
 403
 404         return NULL;
 405 }
 406
 407 int tap_get_minor(dev_t major, struct tap_dev *tap)
 408 {
 409         int retval = -ENOMEM;
 410         struct major_info *tap_major;
 411
 412         rcu_read_lock();
 413         tap_major = tap_get_major(MAJOR(major));
 414         if (!tap_major) {
 415                 retval = -EINVAL;
 416                 goto unlock;
 417         }
 418
 419         spin_lock(&tap_major->minor_lock);
 420         retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);
 421         if (retval >= 0) {
 422                 tap->minor = retval;
 423         } else if (retval == -ENOSPC) {
 424                 netdev_err(tap->dev, "Too many tap devices\n");
 425                 retval = -EINVAL;
 426         }
 427         spin_unlock(&tap_major->minor_lock);
 428
 429 unlock:
 430         rcu_read_unlock();
 431         return retval < 0 ? retval : 0;
 432 }
 433 EXPORT_SYMBOL_GPL(tap_get_minor);
 434
 435 void tap_free_minor(dev_t major, struct tap_dev *tap)
 436 {
 437         struct major_info *tap_major;
 438
 439         rcu_read_lock();
 440         tap_major = tap_get_major(MAJOR(major));
 441         if (!tap_major) {
 442                 goto unlock;
 443         }
 444
 445         spin_lock(&tap_major->minor_lock);
 446         if (tap->minor) {
 447                 idr_remove(&tap_major->minor_idr, tap->minor);
 448                 tap->minor = 0;
 449         }
 450         spin_unlock(&tap_major->minor_lock);
 451
 452 unlock:
 453         rcu_read_unlock();
 454 }
 455 EXPORT_SYMBOL_GPL(tap_free_minor);
 456
 457 static struct tap_dev *dev_get_by_tap_file(int major, int minor)
 458 {
 459         struct net_device *dev = NULL;
 460         struct tap_dev *tap;
 461         struct major_info *tap_major;
 462
 463         rcu_read_lock();
 464         tap_major = tap_get_major(major);
 465         if (!tap_major) {
 466                 tap = NULL;
 467                 goto unlock;
 468         }
 469
 470         spin_lock(&tap_major->minor_lock);
 471         tap = idr_find(&tap_major->minor_idr, minor);
 472         if (tap) {
 473                 dev = tap->dev;
 474                 dev_hold(dev);
 475         }
 476         spin_unlock(&tap_major->minor_lock);
 477
 478 unlock:
 479         rcu_read_unlock();
 480         return tap;
 481 }
 482
 483 static void tap_sock_write_space(struct sock *sk)
 484 {
 485         wait_queue_head_t *wqueue;
 486
 487         if (!sock_writeable(sk) ||
 488             !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
 489                 return;
 490
 491         wqueue = sk_sleep(sk);
 492         if (wqueue && waitqueue_active(wqueue))
 493                 wake_up_interruptible_poll(wqueue, POLLOUT | POLLWRNORM | POLLWRBAND);
 494 }
 495
 496 static void tap_sock_destruct(struct sock *sk)
 497 {
 498         struct tap_queue *q = container_of(sk, struct tap_queue, sk);
 499
 500         skb_array_cleanup(&q->skb_array);
 501 }
 502
 503 static int tap_open(struct inode *inode, struct file *file)
 504 {
 505         struct net *net = current->nsproxy->net_ns;
 506         struct tap_dev *tap;
 507         struct tap_queue *q;
 508         int err = -ENODEV;
 509
 510         rtnl_lock();
 511         tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
 512         if (!tap)
 513                 goto err;
 514
 515         err = -ENOMEM;
 516         q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
 517                                              &tap_proto, 0);
 518         if (!q)
 519                 goto err;
 520         if (skb_array_init(&q->skb_array, tap->dev->tx_queue_len, GFP_KERNEL)) {
 521                 sk_free(&q->sk);
 522                 goto err;
 523         }
 524
 525         RCU_INIT_POINTER(q->sock.wq, &q->wq);
 526         init_waitqueue_head(&q->wq.wait);
 527         q->sock.type = SOCK_RAW;
 528         q->sock.state = SS_CONNECTED;
 529         q->sock.file = file;
 530         q->sock.ops = &tap_socket_ops;
 531         sock_init_data(&q->sock, &q->sk);
 532         q->sk.sk_write_space = tap_sock_write_space;
 533         q->sk.sk_destruct = tap_sock_destruct;
 534         q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;
 535         q->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
 536
 537         /*
 538          * so far only KVM virtio_net uses tap, enable zero copy between
 539          * guest kernel and host kernel when lower device supports zerocopy
 540          *
 541          * The macvlan supports zerocopy iff the lower device supports zero
 542          * copy so we don't have to look at the lower device directly.
 543          */
 544         if ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
 545                 sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 546
 547         err = tap_set_queue(tap, file, q);
 548         if (err) {
 549                 /* tap_sock_destruct() will take care of freeing skb_array */
 550                 goto err_put;
 551         }
 552
 553         dev_put(tap->dev);
 554
 555         rtnl_unlock();
 556         return err;
 557
 558 err_put:
 559         sock_put(&q->sk);
 560 err:
 561         if (tap)
 562                 dev_put(tap->dev);
 563
 564         rtnl_unlock();
 565         return err;
 566 }
 567
 568 static int tap_release(struct inode *inode, struct file *file)
 569 {
 570         struct tap_queue *q = file->private_data;
 571         tap_put_queue(q);
 572         return 0;
 573 }
 574
 575 static unsigned int tap_poll(struct file *file, poll_table *wait)
 576 {
 577         struct tap_queue *q = file->private_data;
 578         unsigned int mask = POLLERR;
 579
 580         if (!q)
 581                 goto out;
 582
 583         mask = 0;
 584         poll_wait(file, &q->wq.wait, wait);
 585
 586         if (!skb_array_empty(&q->skb_array))
 587                 mask |= POLLIN | POLLRDNORM;
 588
 589         if (sock_writeable(&q->sk) ||
 590             (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) &&
 591              sock_writeable(&q->sk)))
 592                 mask |= POLLOUT | POLLWRNORM;
 593
 594 out:
 595         return mask;
 596 }
 597
 598 static inline struct sk_buff *tap_alloc_skb(struct sock *sk, size_t prepad,
 599                                             size_t len, size_t linear,
 600                                                 int noblock, int *err)
 601 {
 602         struct sk_buff *skb;
 603
 604         /* Under a page?  Don't bother with paged skb. */
 605         if (prepad + len < PAGE_SIZE || !linear)
 606                 linear = len;
 607
 608         skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
 609                                    err, 0);
 610         if (!skb)
 611                 return NULL;
 612
 613         skb_reserve(skb, prepad);
 614         skb_put(skb, linear);
 615         skb->data_len = len - linear;
 616         skb->len += len - linear;
 617
 618         return skb;
 619 }
 620
 621 /* Neighbour code has some assumptions on HH_DATA_MOD alignment */
 622 #define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
 623
 624 /* Get packet from user space buffer */
 625 static ssize_t tap_get_user(struct tap_queue *q, struct msghdr *m,
 626                             struct iov_iter *from, int noblock)
 627 {
 628         int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
 629         struct sk_buff *skb;
 630         struct tap_dev *tap;
 631         unsigned long total_len = iov_iter_count(from);
 632         unsigned long len = total_len;
 633         int err;
 634         struct virtio_net_hdr vnet_hdr = { 0 };
 635         int vnet_hdr_len = 0;
 636         int copylen = 0;
 637         int depth;
 638         bool zerocopy = false;
 639         size_t linear;
 640
 641         if (q->flags & IFF_VNET_HDR) {
 642                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 643
 644                 err = -EINVAL;
 645                 if (len < vnet_hdr_len)
 646                         goto err;
 647                 len -= vnet_hdr_len;
 648
 649                 err = -EFAULT;
 650                 if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
 651                         goto err;
 652                 iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
 653                 if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
 654                      tap16_to_cpu(q, vnet_hdr.csum_start) +
 655                      tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
 656                              tap16_to_cpu(q, vnet_hdr.hdr_len))
 657                         vnet_hdr.hdr_len = cpu_to_tap16(q,
 658                                  tap16_to_cpu(q, vnet_hdr.csum_start) +
 659                                  tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
 660                 err = -EINVAL;
 661                 if (tap16_to_cpu(q, vnet_hdr.hdr_len) > len)
 662                         goto err;
 663         }
 664
 665         err = -EINVAL;
 666         if (unlikely(len < ETH_HLEN))
 667                 goto err;
 668
 669         if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
 670                 struct iov_iter i;
 671
 672                 copylen = vnet_hdr.hdr_len ?
 673                         tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
 674                 if (copylen > good_linear)
 675                         copylen = good_linear;
 676                 else if (copylen < ETH_HLEN)
 677                         copylen = ETH_HLEN;
 678                 linear = copylen;
 679                 i = *from;
 680                 iov_iter_advance(&i, copylen);
 681                 if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
 682                         zerocopy = true;
 683         }
 684
 685         if (!zerocopy) {
 686                 copylen = len;
 687                 linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
 688                 if (linear > good_linear)
 689                         linear = good_linear;
 690                 else if (linear < ETH_HLEN)
 691                         linear = ETH_HLEN;
 692         }
 693
 694         skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,
 695                             linear, noblock, &err);
 696         if (!skb)
 697                 goto err;
 698
 699         if (zerocopy)
 700                 err = zerocopy_sg_from_iter(skb, from);
 701         else
 702                 err = skb_copy_datagram_from_iter(skb, 0, from, len);
 703
 704         if (err)
 705                 goto err_kfree;
 706
 707         skb_set_network_header(skb, ETH_HLEN);
 708         skb_reset_mac_header(skb);
 709         skb->protocol = eth_hdr(skb)->h_proto;
 710
 711         if (vnet_hdr_len) {
 712                 err = virtio_net_hdr_to_skb(skb, &vnet_hdr,
 713                                             tap_is_little_endian(q));
 714                 if (err)
 715                         goto err_kfree;
 716         }
 717
 718         skb_probe_transport_header(skb, ETH_HLEN);
 719
 720         /* Move network header to the right position for VLAN tagged packets */
 721         if ((skb->protocol == htons(ETH_P_8021Q) ||
 722              skb->protocol == htons(ETH_P_8021AD)) &&
 723             __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
 724                 skb_set_network_header(skb, depth);
 725
 726         rcu_read_lock();
 727         tap = rcu_dereference(q->tap);
 728         /* copy skb_ubuf_info for callback when skb has no error */
 729         if (zerocopy) {
 730                 skb_shinfo(skb)->destructor_arg = m->msg_control;
 731                 skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
 732                 skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 733         } else if (m && m->msg_control) {
 734                 struct ubuf_info *uarg = m->msg_control;
 735                 uarg->callback(uarg, false);
 736         }
 737
 738         if (tap) {
 739                 skb->dev = tap->dev;
 740                 dev_queue_xmit(skb);
 741         } else {
 742                 kfree_skb(skb);
 743         }
 744         rcu_read_unlock();
 745
 746         return total_len;
 747
 748 err_kfree:
 749         kfree_skb(skb);
 750
 751 err:
 752         rcu_read_lock();
 753         tap = rcu_dereference(q->tap);
 754         if (tap && tap->count_tx_dropped)
 755                 tap->count_tx_dropped(tap);
 756         rcu_read_unlock();
 757
 758         return err;
 759 }
 760
 761 static ssize_t tap_write_iter(struct kiocb *iocb, struct iov_iter *from)
 762 {
 763         struct file *file = iocb->ki_filp;
 764         struct tap_queue *q = file->private_data;
 765
 766         return tap_get_user(q, NULL, from, file->f_flags & O_NONBLOCK);
 767 }
 768
 769 /* Put packet to the user space buffer */
 770 static ssize_t tap_put_user(struct tap_queue *q,
 771                             const struct sk_buff *skb,
 772                             struct iov_iter *iter)
 773 {
 774         int ret;
 775         int vnet_hdr_len = 0;
 776         int vlan_offset = 0;
 777         int total;
 778
 779         if (q->flags & IFF_VNET_HDR) {
 780                 int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0;
 781                 struct virtio_net_hdr vnet_hdr;
 782
 783                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 784                 if (iov_iter_count(iter) < vnet_hdr_len)
 785                         return -EINVAL;
 786
 787                 if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
 788                                             tap_is_little_endian(q), true,
 789                                             vlan_hlen))
 790                         BUG();
 791
 792                 if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
 793                     sizeof(vnet_hdr))
 794                         return -EFAULT;
 795
 796                 iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));
 797         }
 798         total = vnet_hdr_len;
 799         total += skb->len;
 800
 801         if (skb_vlan_tag_present(skb)) {
 802                 struct {
 803                         __be16 h_vlan_proto;
 804                         __be16 h_vlan_TCI;
 805                 } veth;
 806                 veth.h_vlan_proto = skb->vlan_proto;
 807                 veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
 808
 809                 vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
 810                 total += VLAN_HLEN;
 811
 812                 ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
 813                 if (ret || !iov_iter_count(iter))
 814                         goto done;
 815
 816                 ret = copy_to_iter(&veth, sizeof(veth), iter);
 817                 if (ret != sizeof(veth) || !iov_iter_count(iter))
 818                         goto done;
 819         }
 820
 821         ret = skb_copy_datagram_iter(skb, vlan_offset, iter,
 822                                      skb->len - vlan_offset);
 823
 824 done:
 825         return ret ? ret : total;
 826 }
 827
 828 static ssize_t tap_do_read(struct tap_queue *q,
 829                            struct iov_iter *to,
 830                            int noblock, struct sk_buff *skb)
 831 {
 832         DEFINE_WAIT(wait);
 833         ssize_t ret = 0;
 834
 835         if (!iov_iter_count(to)) {
 836                 if (skb)
 837                         kfree_skb(skb);
 838                 return 0;
 839         }
 840
 841         if (skb)
 842                 goto put;
 843
 844         while (1) {
 845                 if (!noblock)
 846                         prepare_to_wait(sk_sleep(&q->sk), &wait,
 847                                         TASK_INTERRUPTIBLE);
 848
 849                 /* Read frames from the queue */
 850                 skb = skb_array_consume(&q->skb_array);
 851                 if (skb)
 852                         break;
 853                 if (noblock) {
 854                         ret = -EAGAIN;
 855                         break;
 856                 }
 857                 if (signal_pending(current)) {
 858                         ret = -ERESTARTSYS;
 859                         break;
 860                 }
 861                 /* Nothing to read, let's sleep */
 862                 schedule();
 863         }
 864         if (!noblock)
 865                 finish_wait(sk_sleep(&q->sk), &wait);
 866
 867 put:
 868         if (skb) {
 869                 ret = tap_put_user(q, skb, to);
 870                 if (unlikely(ret < 0))
 871                         kfree_skb(skb);
 872                 else
 873                         consume_skb(skb);
 874         }
 875         return ret;
 876 }
 877
 878 static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
 879 {
 880         struct file *file = iocb->ki_filp;
 881         struct tap_queue *q = file->private_data;
 882         ssize_t len = iov_iter_count(to), ret;
 883
 884         ret = tap_do_read(q, to, file->f_flags & O_NONBLOCK, NULL);
 885         ret = min_t(ssize_t, ret, len);
 886         if (ret > 0)
 887                 iocb->ki_pos = ret;
 888         return ret;
 889 }
 890
 891 static struct tap_dev *tap_get_tap_dev(struct tap_queue *q)
 892 {
 893         struct tap_dev *tap;
 894
 895         ASSERT_RTNL();
 896         tap = rtnl_dereference(q->tap);
 897         if (tap)
 898                 dev_hold(tap->dev);
 899
 900         return tap;
 901 }
 902
 903 static void tap_put_tap_dev(struct tap_dev *tap)
 904 {
 905         dev_put(tap->dev);
 906 }
 907
 908 static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
 909 {
 910         struct tap_queue *q = file->private_data;
 911         struct tap_dev *tap;
 912         int ret;
 913
 914         tap = tap_get_tap_dev(q);
 915         if (!tap)
 916                 return -EINVAL;
 917
 918         if (flags & IFF_ATTACH_QUEUE)
 919                 ret = tap_enable_queue(tap, file, q);
 920         else if (flags & IFF_DETACH_QUEUE)
 921                 ret = tap_disable_queue(q);
 922         else
 923                 ret = -EINVAL;
 924
 925         tap_put_tap_dev(tap);
 926         return ret;
 927 }
 928
 929 static int set_offload(struct tap_queue *q, unsigned long arg)
 930 {
 931         struct tap_dev *tap;
 932         netdev_features_t features;
 933         netdev_features_t feature_mask = 0;
 934
 935         tap = rtnl_dereference(q->tap);
 936         if (!tap)
 937                 return -ENOLINK;
 938
 939         features = tap->dev->features;
 940
 941         if (arg & TUN_F_CSUM) {
 942                 feature_mask = NETIF_F_HW_CSUM;
 943
 944                 if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
 945                         if (arg & TUN_F_TSO_ECN)
 946                                 feature_mask |= NETIF_F_TSO_ECN;
 947                         if (arg & TUN_F_TSO4)
 948                                 feature_mask |= NETIF_F_TSO;
 949                         if (arg & TUN_F_TSO6)
 950                                 feature_mask |= NETIF_F_TSO6;
 951                 }
 952         }
 953
 954         /* tun/tap driver inverts the usage for TSO offloads, where
 955          * setting the TSO bit means that the userspace wants to
 956          * accept TSO frames and turning it off means that user space
 957          * does not support TSO.
 958          * For tap, we have to invert it to mean the same thing.
 959          * When user space turns off TSO, we turn off GSO/LRO so that
 960          * user-space will not receive TSO frames.
 961          */
 962         if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6))
 963                 features |= RX_OFFLOADS;
 964         else
 965                 features &= ~RX_OFFLOADS;
 966
 967         /* tap_features are the same as features on tun/tap and
 968          * reflect user expectations.
 969          */
 970         tap->tap_features = feature_mask;
 971         if (tap->update_features)
 972                 tap->update_features(tap, features);
 973
 974         return 0;
 975 }
 976
 977 /*
 978  * provide compatibility with generic tun/tap interface
 979  */
 980 static long tap_ioctl(struct file *file, unsigned int cmd,
 981                       unsigned long arg)
 982 {
 983         struct tap_queue *q = file->private_data;
 984         struct tap_dev *tap;
 985         void __user *argp = (void __user *)arg;
 986         struct ifreq __user *ifr = argp;
 987         unsigned int __user *up = argp;
 988         unsigned short u;
 989         int __user *sp = argp;
 990         struct sockaddr sa;
 991         int s;
 992         int ret;
 993
 994         switch (cmd) {
 995         case TUNSETIFF:
 996                 /* ignore the name, just look at flags */
 997                 if (get_user(u, &ifr->ifr_flags))
 998                         return -EFAULT;
 999
1000                 ret = 0;
1001                 if ((u & ~TAP_IFFEATURES) != (IFF_NO_PI | IFF_TAP))
1002                         ret = -EINVAL;
1003                 else
1004                         q->flags = (q->flags & ~TAP_IFFEATURES) | u;
1005
1006                 return ret;
1007
1008         case TUNGETIFF:
1009                 rtnl_lock();
1010                 tap = tap_get_tap_dev(q);
1011                 if (!tap) {
1012                         rtnl_unlock();
1013                         return -ENOLINK;
1014                 }
1015
1016                 ret = 0;
1017                 u = q->flags;
1018                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1019                     put_user(u, &ifr->ifr_flags))
1020                         ret = -EFAULT;
1021                 tap_put_tap_dev(tap);
1022                 rtnl_unlock();
1023                 return ret;
1024
1025         case TUNSETQUEUE:
1026                 if (get_user(u, &ifr->ifr_flags))
1027                         return -EFAULT;
1028                 rtnl_lock();
1029                 ret = tap_ioctl_set_queue(file, u);
1030                 rtnl_unlock();
1031                 return ret;
1032
1033         case TUNGETFEATURES:
1034                 if (put_user(IFF_TAP | IFF_NO_PI | TAP_IFFEATURES, up))
1035                         return -EFAULT;
1036                 return 0;
1037
1038         case TUNSETSNDBUF:
1039                 if (get_user(s, sp))
1040                         return -EFAULT;
1041                 if (s <= 0)
1042                         return -EINVAL;
1043
1044                 q->sk.sk_sndbuf = s;
1045                 return 0;
1046
1047         case TUNGETVNETHDRSZ:
1048                 s = q->vnet_hdr_sz;
1049                 if (put_user(s, sp))
1050                         return -EFAULT;
1051                 return 0;
1052
1053         case TUNSETVNETHDRSZ:
1054                 if (get_user(s, sp))
1055                         return -EFAULT;
1056                 if (s < (int)sizeof(struct virtio_net_hdr))
1057                         return -EINVAL;
1058
1059                 q->vnet_hdr_sz = s;
1060                 return 0;
1061
1062         case TUNGETVNETLE:
1063                 s = !!(q->flags & TAP_VNET_LE);
1064                 if (put_user(s, sp))
1065                         return -EFAULT;
1066                 return 0;
1067
1068         case TUNSETVNETLE:
1069                 if (get_user(s, sp))
1070                         return -EFAULT;
1071                 if (s)
1072                         q->flags |= TAP_VNET_LE;
1073                 else
1074                         q->flags &= ~TAP_VNET_LE;
1075                 return 0;
1076
1077         case TUNGETVNETBE:
1078                 return tap_get_vnet_be(q, sp);
1079
1080         case TUNSETVNETBE:
1081                 return tap_set_vnet_be(q, sp);
1082
1083         case TUNSETOFFLOAD:
1084                 /* let the user check for future flags */
1085                 if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
1086                             TUN_F_TSO_ECN | TUN_F_UFO))
1087                         return -EINVAL;
1088
1089                 rtnl_lock();
1090                 ret = set_offload(q, arg);
1091                 rtnl_unlock();
1092                 return ret;
1093
1094         case SIOCGIFHWADDR:
1095                 rtnl_lock();
1096                 tap = tap_get_tap_dev(q);
1097                 if (!tap) {
1098                         rtnl_unlock();
1099                         return -ENOLINK;
1100                 }
1101                 ret = 0;
1102                 u = tap->dev->type;
1103                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1104                     copy_to_user(&ifr->ifr_hwaddr.sa_data, tap->dev->dev_addr, ETH_ALEN) ||
1105                     put_user(u, &ifr->ifr_hwaddr.sa_family))
1106                         ret = -EFAULT;
1107                 tap_put_tap_dev(tap);
1108                 rtnl_unlock();
1109                 return ret;
1110
1111         case SIOCSIFHWADDR:
1112                 if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
1113                         return -EFAULT;
1114                 rtnl_lock();
1115                 tap = tap_get_tap_dev(q);
1116                 if (!tap) {
1117                         rtnl_unlock();
1118                         return -ENOLINK;
1119                 }
1120                 ret = dev_set_mac_address(tap->dev, &sa);
1121                 tap_put_tap_dev(tap);
1122                 rtnl_unlock();
1123                 return ret;
1124
1125         default:
1126                 return -EINVAL;
1127         }
1128 }
1129
1130 #ifdef CONFIG_COMPAT
1131 static long tap_compat_ioctl(struct file *file, unsigned int cmd,
1132                              unsigned long arg)
1133 {
1134         return tap_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
1135 }
1136 #endif
1137
1138 static const struct file_operations tap_fops = {
1139         .owner          = THIS_MODULE,
1140         .open           = tap_open,
1141         .release        = tap_release,
1142         .read_iter      = tap_read_iter,
1143         .write_iter     = tap_write_iter,
1144         .poll           = tap_poll,
1145         .llseek         = no_llseek,
1146         .unlocked_ioctl = tap_ioctl,
1147 #ifdef CONFIG_COMPAT
1148         .compat_ioctl   = tap_compat_ioctl,
1149 #endif
1150 };
1151
1152 static int tap_sendmsg(struct socket *sock, struct msghdr *m,
1153                        size_t total_len)
1154 {
1155         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1156         return tap_get_user(q, m, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);
1157 }
1158
1159 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
1160                        size_t total_len, int flags)
1161 {
1162         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1163         struct sk_buff *skb = m->msg_control;
1164         int ret;
1165         if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
1166                 if (skb)
1167                         kfree_skb(skb);
1168                 return -EINVAL;
1169         }
1170         ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT, skb);
1171         if (ret > total_len) {
1172                 m->msg_flags |= MSG_TRUNC;
1173                 ret = flags & MSG_TRUNC ? ret : total_len;
1174         }
1175         return ret;
1176 }
1177
1178 static int tap_peek_len(struct socket *sock)
1179 {
1180         struct tap_queue *q = container_of(sock, struct tap_queue,
1181                                                sock);
1182         return skb_array_peek_len(&q->skb_array);
1183 }
1184
1185 /* Ops structure to mimic raw sockets with tun */
1186 static const struct proto_ops tap_socket_ops = {
1187         .sendmsg = tap_sendmsg,
1188         .recvmsg = tap_recvmsg,
1189         .peek_len = tap_peek_len,
1190 };
1191
1192 /* Get an underlying socket object from tun file.  Returns error unless file is
1193  * attached to a device.  The returned object works like a packet socket, it
1194  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
1195  * holding a reference to the file for as long as the socket is in use. */
1196 struct socket *tap_get_socket(struct file *file)
1197 {
1198         struct tap_queue *q;
1199         if (file->f_op != &tap_fops)
1200                 return ERR_PTR(-EINVAL);
1201         q = file->private_data;
1202         if (!q)
1203                 return ERR_PTR(-EBADFD);
1204         return &q->sock;
1205 }
1206 EXPORT_SYMBOL_GPL(tap_get_socket);
1207
1208 struct skb_array *tap_get_skb_array(struct file *file)
1209 {
1210         struct tap_queue *q;
1211
1212         if (file->f_op != &tap_fops)
1213                 return ERR_PTR(-EINVAL);
1214         q = file->private_data;
1215         if (!q)
1216                 return ERR_PTR(-EBADFD);
1217         return &q->skb_array;
1218 }
1219 EXPORT_SYMBOL_GPL(tap_get_skb_array);
1220
1221 int tap_queue_resize(struct tap_dev *tap)
1222 {
1223         struct net_device *dev = tap->dev;
1224         struct tap_queue *q;
1225         struct skb_array **arrays;
1226         int n = tap->numqueues;
1227         int ret, i = 0;
1228
1229         arrays = kmalloc_array(n, sizeof(*arrays), GFP_KERNEL);
1230         if (!arrays)
1231                 return -ENOMEM;
1232
1233         list_for_each_entry(q, &tap->queue_list, next)
1234                 arrays[i++] = &q->skb_array;
1235
1236         ret = skb_array_resize_multiple(arrays, n,
1237                                         dev->tx_queue_len, GFP_KERNEL);
1238
1239         kfree(arrays);
1240         return ret;
1241 }
1242 EXPORT_SYMBOL_GPL(tap_queue_resize);
1243
1244 static int tap_list_add(dev_t major, const char *device_name)
1245 {
1246         struct major_info *tap_major;
1247
1248         tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
1249         if (!tap_major)
1250                 return -ENOMEM;
1251
1252         tap_major->major = MAJOR(major);
1253
1254         idr_init(&tap_major->minor_idr);
1255         spin_lock_init(&tap_major->minor_lock);
1256
1257         tap_major->device_name = device_name;
1258
1259         list_add_tail_rcu(&tap_major->next, &major_list);
1260         return 0;
1261 }
1262
1263 int tap_create_cdev(struct cdev *tap_cdev, dev_t *tap_major,
1264                     const char *device_name, struct module *module)
1265 {
1266         int err;
1267
1268         err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
1269         if (err)
1270                 goto out1;
1271
1272         cdev_init(tap_cdev, &tap_fops);
1273         tap_cdev->owner = module;
1274         err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
1275         if (err)
1276                 goto out2;
1277
1278         err =  tap_list_add(*tap_major, device_name);
1279         if (err)
1280                 goto out3;
1281
1282         return 0;
1283
1284 out3:
1285         cdev_del(tap_cdev);
1286 out2:
1287         unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
1288 out1:
1289         return err;
1290 }
1291 EXPORT_SYMBOL_GPL(tap_create_cdev);
1292
1293 void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
1294 {
1295         struct major_info *tap_major, *tmp;
1296
1297         cdev_del(tap_cdev);
1298         unregister_chrdev_region(major, TAP_NUM_DEVS);
1299         list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
1300                 if (tap_major->major == MAJOR(major)) {
1301                         idr_destroy(&tap_major->minor_idr);
1302                         list_del_rcu(&tap_major->next);
1303                         kfree_rcu(tap_major, rcu);
1304                 }
1305         }
1306 }
1307 EXPORT_SYMBOL_GPL(tap_destroy_cdev);
1308
1309 MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
1310 MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
1311 MODULE_LICENSE("GPL");