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 = READ_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         skb_push(skb, ETH_HLEN);
 334
 335         /* Apply the forward feature mask so that we perform segmentation
 336          * according to users wishes.  This only works if VNET_HDR is
 337          * enabled.
 338          */
 339         if (q->flags & IFF_VNET_HDR)
 340                 features |= tap->tap_features;
 341         if (netif_needs_gso(skb, features)) {
 342                 struct sk_buff *segs = __skb_gso_segment(skb, features, false);
 343
 344                 if (IS_ERR(segs))
 345                         goto drop;
 346
 347                 if (!segs) {
 348                         if (ptr_ring_produce(&q->ring, skb))
 349                                 goto drop;
 350                         goto wake_up;
 351                 }
 352
 353                 consume_skb(skb);
 354                 while (segs) {
 355                         struct sk_buff *nskb = segs->next;
 356
 357                         segs->next = NULL;
 358                         if (ptr_ring_produce(&q->ring, segs)) {
 359                                 kfree_skb(segs);
 360                                 kfree_skb_list(nskb);
 361                                 break;
 362                         }
 363                         segs = nskb;
 364                 }
 365         } else {
 366                 /* If we receive a partial checksum and the tap side
 367                  * doesn't support checksum offload, compute the checksum.
 368                  * Note: it doesn't matter which checksum feature to
 369                  *        check, we either support them all or none.
 370                  */
 371                 if (skb->ip_summed == CHECKSUM_PARTIAL &&
 372                     !(features & NETIF_F_CSUM_MASK) &&
 373                     skb_checksum_help(skb))
 374                         goto drop;
 375                 if (ptr_ring_produce(&q->ring, skb))
 376                         goto drop;
 377         }
 378
 379 wake_up:
 380         wake_up_interruptible_poll(sk_sleep(&q->sk), EPOLLIN | EPOLLRDNORM | EPOLLRDBAND);
 381         return RX_HANDLER_CONSUMED;
 382
 383 drop:
 384         /* Count errors/drops only here, thus don't care about args. */
 385         if (tap->count_rx_dropped)
 386                 tap->count_rx_dropped(tap);
 387         kfree_skb(skb);
 388         return RX_HANDLER_CONSUMED;
 389 }
 390 EXPORT_SYMBOL_GPL(tap_handle_frame);
 391
 392 static struct major_info *tap_get_major(int major)
 393 {
 394         struct major_info *tap_major;
 395
 396         list_for_each_entry_rcu(tap_major, &major_list, next) {
 397                 if (tap_major->major == major)
 398                         return tap_major;
 399         }
 400
 401         return NULL;
 402 }
 403
 404 int tap_get_minor(dev_t major, struct tap_dev *tap)
 405 {
 406         int retval = -ENOMEM;
 407         struct major_info *tap_major;
 408
 409         rcu_read_lock();
 410         tap_major = tap_get_major(MAJOR(major));
 411         if (!tap_major) {
 412                 retval = -EINVAL;
 413                 goto unlock;
 414         }
 415
 416         spin_lock(&tap_major->minor_lock);
 417         retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);
 418         if (retval >= 0) {
 419                 tap->minor = retval;
 420         } else if (retval == -ENOSPC) {
 421                 netdev_err(tap->dev, "Too many tap devices\n");
 422                 retval = -EINVAL;
 423         }
 424         spin_unlock(&tap_major->minor_lock);
 425
 426 unlock:
 427         rcu_read_unlock();
 428         return retval < 0 ? retval : 0;
 429 }
 430 EXPORT_SYMBOL_GPL(tap_get_minor);
 431
 432 void tap_free_minor(dev_t major, struct tap_dev *tap)
 433 {
 434         struct major_info *tap_major;
 435
 436         rcu_read_lock();
 437         tap_major = tap_get_major(MAJOR(major));
 438         if (!tap_major) {
 439                 goto unlock;
 440         }
 441
 442         spin_lock(&tap_major->minor_lock);
 443         if (tap->minor) {
 444                 idr_remove(&tap_major->minor_idr, tap->minor);
 445                 tap->minor = 0;
 446         }
 447         spin_unlock(&tap_major->minor_lock);
 448
 449 unlock:
 450         rcu_read_unlock();
 451 }
 452 EXPORT_SYMBOL_GPL(tap_free_minor);
 453
 454 static struct tap_dev *dev_get_by_tap_file(int major, int minor)
 455 {
 456         struct net_device *dev = NULL;
 457         struct tap_dev *tap;
 458         struct major_info *tap_major;
 459
 460         rcu_read_lock();
 461         tap_major = tap_get_major(major);
 462         if (!tap_major) {
 463                 tap = NULL;
 464                 goto unlock;
 465         }
 466
 467         spin_lock(&tap_major->minor_lock);
 468         tap = idr_find(&tap_major->minor_idr, minor);
 469         if (tap) {
 470                 dev = tap->dev;
 471                 dev_hold(dev);
 472         }
 473         spin_unlock(&tap_major->minor_lock);
 474
 475 unlock:
 476         rcu_read_unlock();
 477         return tap;
 478 }
 479
 480 static void tap_sock_write_space(struct sock *sk)
 481 {
 482         wait_queue_head_t *wqueue;
 483
 484         if (!sock_writeable(sk) ||
 485             !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
 486                 return;
 487
 488         wqueue = sk_sleep(sk);
 489         if (wqueue && waitqueue_active(wqueue))
 490                 wake_up_interruptible_poll(wqueue, EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
 491 }
 492
 493 static void tap_sock_destruct(struct sock *sk)
 494 {
 495         struct tap_queue *q = container_of(sk, struct tap_queue, sk);
 496
 497         ptr_ring_cleanup(&q->ring, __skb_array_destroy_skb);
 498 }
 499
 500 static int tap_open(struct inode *inode, struct file *file)
 501 {
 502         struct net *net = current->nsproxy->net_ns;
 503         struct tap_dev *tap;
 504         struct tap_queue *q;
 505         int err = -ENODEV;
 506
 507         rtnl_lock();
 508         tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
 509         if (!tap)
 510                 goto err;
 511
 512         err = -ENOMEM;
 513         q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
 514                                              &tap_proto, 0);
 515         if (!q)
 516                 goto err;
 517         if (ptr_ring_init(&q->ring, tap->dev->tx_queue_len, GFP_KERNEL)) {
 518                 sk_free(&q->sk);
 519                 goto err;
 520         }
 521
 522         RCU_INIT_POINTER(q->sock.wq, &q->wq);
 523         init_waitqueue_head(&q->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->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, struct msghdr *m,
 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 (m && m->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, ETH_HLEN);
 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 = m->msg_control;
 728                 skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
 729                 skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 730         } else if (m && m->msg_control) {
 731                 struct ubuf_info *uarg = m->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                 if (skb)
 834                         kfree_skb(skb);
 835                 return 0;
 836         }
 837
 838         if (skb)
 839                 goto put;
 840
 841         while (1) {
 842                 if (!noblock)
 843                         prepare_to_wait(sk_sleep(&q->sk), &wait,
 844                                         TASK_INTERRUPTIBLE);
 845
 846                 /* Read frames from the queue */
 847                 skb = ptr_ring_consume(&q->ring);
 848                 if (skb)
 849                         break;
 850                 if (noblock) {
 851                         ret = -EAGAIN;
 852                         break;
 853                 }
 854                 if (signal_pending(current)) {
 855                         ret = -ERESTARTSYS;
 856                         break;
 857                 }
 858                 /* Nothing to read, let's sleep */
 859                 schedule();
 860         }
 861         if (!noblock)
 862                 finish_wait(sk_sleep(&q->sk), &wait);
 863
 864 put:
 865         if (skb) {
 866                 ret = tap_put_user(q, skb, to);
 867                 if (unlikely(ret < 0))
 868                         kfree_skb(skb);
 869                 else
 870                         consume_skb(skb);
 871         }
 872         return ret;
 873 }
 874
 875 static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
 876 {
 877         struct file *file = iocb->ki_filp;
 878         struct tap_queue *q = file->private_data;
 879         ssize_t len = iov_iter_count(to), ret;
 880
 881         ret = tap_do_read(q, to, file->f_flags & O_NONBLOCK, NULL);
 882         ret = min_t(ssize_t, ret, len);
 883         if (ret > 0)
 884                 iocb->ki_pos = ret;
 885         return ret;
 886 }
 887
 888 static struct tap_dev *tap_get_tap_dev(struct tap_queue *q)
 889 {
 890         struct tap_dev *tap;
 891
 892         ASSERT_RTNL();
 893         tap = rtnl_dereference(q->tap);
 894         if (tap)
 895                 dev_hold(tap->dev);
 896
 897         return tap;
 898 }
 899
 900 static void tap_put_tap_dev(struct tap_dev *tap)
 901 {
 902         dev_put(tap->dev);
 903 }
 904
 905 static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
 906 {
 907         struct tap_queue *q = file->private_data;
 908         struct tap_dev *tap;
 909         int ret;
 910
 911         tap = tap_get_tap_dev(q);
 912         if (!tap)
 913                 return -EINVAL;
 914
 915         if (flags & IFF_ATTACH_QUEUE)
 916                 ret = tap_enable_queue(tap, file, q);
 917         else if (flags & IFF_DETACH_QUEUE)
 918                 ret = tap_disable_queue(q);
 919         else
 920                 ret = -EINVAL;
 921
 922         tap_put_tap_dev(tap);
 923         return ret;
 924 }
 925
 926 static int set_offload(struct tap_queue *q, unsigned long arg)
 927 {
 928         struct tap_dev *tap;
 929         netdev_features_t features;
 930         netdev_features_t feature_mask = 0;
 931
 932         tap = rtnl_dereference(q->tap);
 933         if (!tap)
 934                 return -ENOLINK;
 935
 936         features = tap->dev->features;
 937
 938         if (arg & TUN_F_CSUM) {
 939                 feature_mask = NETIF_F_HW_CSUM;
 940
 941                 if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
 942                         if (arg & TUN_F_TSO_ECN)
 943                                 feature_mask |= NETIF_F_TSO_ECN;
 944                         if (arg & TUN_F_TSO4)
 945                                 feature_mask |= NETIF_F_TSO;
 946                         if (arg & TUN_F_TSO6)
 947                                 feature_mask |= NETIF_F_TSO6;
 948                 }
 949         }
 950
 951         /* tun/tap driver inverts the usage for TSO offloads, where
 952          * setting the TSO bit means that the userspace wants to
 953          * accept TSO frames and turning it off means that user space
 954          * does not support TSO.
 955          * For tap, we have to invert it to mean the same thing.
 956          * When user space turns off TSO, we turn off GSO/LRO so that
 957          * user-space will not receive TSO frames.
 958          */
 959         if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6))
 960                 features |= RX_OFFLOADS;
 961         else
 962                 features &= ~RX_OFFLOADS;
 963
 964         /* tap_features are the same as features on tun/tap and
 965          * reflect user expectations.
 966          */
 967         tap->tap_features = feature_mask;
 968         if (tap->update_features)
 969                 tap->update_features(tap, features);
 970
 971         return 0;
 972 }
 973
 974 /*
 975  * provide compatibility with generic tun/tap interface
 976  */
 977 static long tap_ioctl(struct file *file, unsigned int cmd,
 978                       unsigned long arg)
 979 {
 980         struct tap_queue *q = file->private_data;
 981         struct tap_dev *tap;
 982         void __user *argp = (void __user *)arg;
 983         struct ifreq __user *ifr = argp;
 984         unsigned int __user *up = argp;
 985         unsigned short u;
 986         int __user *sp = argp;
 987         struct sockaddr sa;
 988         int s;
 989         int ret;
 990
 991         switch (cmd) {
 992         case TUNSETIFF:
 993                 /* ignore the name, just look at flags */
 994                 if (get_user(u, &ifr->ifr_flags))
 995                         return -EFAULT;
 996
 997                 ret = 0;
 998                 if ((u & ~TAP_IFFEATURES) != (IFF_NO_PI | IFF_TAP))
 999                         ret = -EINVAL;
1000                 else
1001                         q->flags = (q->flags & ~TAP_IFFEATURES) | u;
1002
1003                 return ret;
1004
1005         case TUNGETIFF:
1006                 rtnl_lock();
1007                 tap = tap_get_tap_dev(q);
1008                 if (!tap) {
1009                         rtnl_unlock();
1010                         return -ENOLINK;
1011                 }
1012
1013                 ret = 0;
1014                 u = q->flags;
1015                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1016                     put_user(u, &ifr->ifr_flags))
1017                         ret = -EFAULT;
1018                 tap_put_tap_dev(tap);
1019                 rtnl_unlock();
1020                 return ret;
1021
1022         case TUNSETQUEUE:
1023                 if (get_user(u, &ifr->ifr_flags))
1024                         return -EFAULT;
1025                 rtnl_lock();
1026                 ret = tap_ioctl_set_queue(file, u);
1027                 rtnl_unlock();
1028                 return ret;
1029
1030         case TUNGETFEATURES:
1031                 if (put_user(IFF_TAP | IFF_NO_PI | TAP_IFFEATURES, up))
1032                         return -EFAULT;
1033                 return 0;
1034
1035         case TUNSETSNDBUF:
1036                 if (get_user(s, sp))
1037                         return -EFAULT;
1038                 if (s <= 0)
1039                         return -EINVAL;
1040
1041                 q->sk.sk_sndbuf = s;
1042                 return 0;
1043
1044         case TUNGETVNETHDRSZ:
1045                 s = q->vnet_hdr_sz;
1046                 if (put_user(s, sp))
1047                         return -EFAULT;
1048                 return 0;
1049
1050         case TUNSETVNETHDRSZ:
1051                 if (get_user(s, sp))
1052                         return -EFAULT;
1053                 if (s < (int)sizeof(struct virtio_net_hdr))
1054                         return -EINVAL;
1055
1056                 q->vnet_hdr_sz = s;
1057                 return 0;
1058
1059         case TUNGETVNETLE:
1060                 s = !!(q->flags & TAP_VNET_LE);
1061                 if (put_user(s, sp))
1062                         return -EFAULT;
1063                 return 0;
1064
1065         case TUNSETVNETLE:
1066                 if (get_user(s, sp))
1067                         return -EFAULT;
1068                 if (s)
1069                         q->flags |= TAP_VNET_LE;
1070                 else
1071                         q->flags &= ~TAP_VNET_LE;
1072                 return 0;
1073
1074         case TUNGETVNETBE:
1075                 return tap_get_vnet_be(q, sp);
1076
1077         case TUNSETVNETBE:
1078                 return tap_set_vnet_be(q, sp);
1079
1080         case TUNSETOFFLOAD:
1081                 /* let the user check for future flags */
1082                 if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
1083                             TUN_F_TSO_ECN | TUN_F_UFO))
1084                         return -EINVAL;
1085
1086                 rtnl_lock();
1087                 ret = set_offload(q, arg);
1088                 rtnl_unlock();
1089                 return ret;
1090
1091         case SIOCGIFHWADDR:
1092                 rtnl_lock();
1093                 tap = tap_get_tap_dev(q);
1094                 if (!tap) {
1095                         rtnl_unlock();
1096                         return -ENOLINK;
1097                 }
1098                 ret = 0;
1099                 u = tap->dev->type;
1100                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1101                     copy_to_user(&ifr->ifr_hwaddr.sa_data, tap->dev->dev_addr, ETH_ALEN) ||
1102                     put_user(u, &ifr->ifr_hwaddr.sa_family))
1103                         ret = -EFAULT;
1104                 tap_put_tap_dev(tap);
1105                 rtnl_unlock();
1106                 return ret;
1107
1108         case SIOCSIFHWADDR:
1109                 if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
1110                         return -EFAULT;
1111                 rtnl_lock();
1112                 tap = tap_get_tap_dev(q);
1113                 if (!tap) {
1114                         rtnl_unlock();
1115                         return -ENOLINK;
1116                 }
1117                 ret = dev_set_mac_address(tap->dev, &sa);
1118                 tap_put_tap_dev(tap);
1119                 rtnl_unlock();
1120                 return ret;
1121
1122         default:
1123                 return -EINVAL;
1124         }
1125 }
1126
1127 #ifdef CONFIG_COMPAT
1128 static long tap_compat_ioctl(struct file *file, unsigned int cmd,
1129                              unsigned long arg)
1130 {
1131         return tap_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
1132 }
1133 #endif
1134
1135 static const struct file_operations tap_fops = {
1136         .owner          = THIS_MODULE,
1137         .open           = tap_open,
1138         .release        = tap_release,
1139         .read_iter      = tap_read_iter,
1140         .write_iter     = tap_write_iter,
1141         .poll           = tap_poll,
1142         .llseek         = no_llseek,
1143         .unlocked_ioctl = tap_ioctl,
1144 #ifdef CONFIG_COMPAT
1145         .compat_ioctl   = tap_compat_ioctl,
1146 #endif
1147 };
1148
1149 static int tap_sendmsg(struct socket *sock, struct msghdr *m,
1150                        size_t total_len)
1151 {
1152         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1153         return tap_get_user(q, m, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);
1154 }
1155
1156 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
1157                        size_t total_len, int flags)
1158 {
1159         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1160         struct sk_buff *skb = m->msg_control;
1161         int ret;
1162         if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
1163                 if (skb)
1164                         kfree_skb(skb);
1165                 return -EINVAL;
1166         }
1167         ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT, skb);
1168         if (ret > total_len) {
1169                 m->msg_flags |= MSG_TRUNC;
1170                 ret = flags & MSG_TRUNC ? ret : total_len;
1171         }
1172         return ret;
1173 }
1174
1175 static int tap_peek_len(struct socket *sock)
1176 {
1177         struct tap_queue *q = container_of(sock, struct tap_queue,
1178                                                sock);
1179         return PTR_RING_PEEK_CALL(&q->ring, __skb_array_len_with_tag);
1180 }
1181
1182 /* Ops structure to mimic raw sockets with tun */
1183 static const struct proto_ops tap_socket_ops = {
1184         .sendmsg = tap_sendmsg,
1185         .recvmsg = tap_recvmsg,
1186         .peek_len = tap_peek_len,
1187 };
1188
1189 /* Get an underlying socket object from tun file.  Returns error unless file is
1190  * attached to a device.  The returned object works like a packet socket, it
1191  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
1192  * holding a reference to the file for as long as the socket is in use. */
1193 struct socket *tap_get_socket(struct file *file)
1194 {
1195         struct tap_queue *q;
1196         if (file->f_op != &tap_fops)
1197                 return ERR_PTR(-EINVAL);
1198         q = file->private_data;
1199         if (!q)
1200                 return ERR_PTR(-EBADFD);
1201         return &q->sock;
1202 }
1203 EXPORT_SYMBOL_GPL(tap_get_socket);
1204
1205 struct ptr_ring *tap_get_ptr_ring(struct file *file)
1206 {
1207         struct tap_queue *q;
1208
1209         if (file->f_op != &tap_fops)
1210                 return ERR_PTR(-EINVAL);
1211         q = file->private_data;
1212         if (!q)
1213                 return ERR_PTR(-EBADFD);
1214         return &q->ring;
1215 }
1216 EXPORT_SYMBOL_GPL(tap_get_ptr_ring);
1217
1218 int tap_queue_resize(struct tap_dev *tap)
1219 {
1220         struct net_device *dev = tap->dev;
1221         struct tap_queue *q;
1222         struct ptr_ring **rings;
1223         int n = tap->numqueues;
1224         int ret, i = 0;
1225
1226         rings = kmalloc_array(n, sizeof(*rings), GFP_KERNEL);
1227         if (!rings)
1228                 return -ENOMEM;
1229
1230         list_for_each_entry(q, &tap->queue_list, next)
1231                 rings[i++] = &q->ring;
1232
1233         ret = ptr_ring_resize_multiple(rings, n,
1234                                        dev->tx_queue_len, GFP_KERNEL,
1235                                        __skb_array_destroy_skb);
1236
1237         kfree(rings);
1238         return ret;
1239 }
1240 EXPORT_SYMBOL_GPL(tap_queue_resize);
1241
1242 static int tap_list_add(dev_t major, const char *device_name)
1243 {
1244         struct major_info *tap_major;
1245
1246         tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
1247         if (!tap_major)
1248                 return -ENOMEM;
1249
1250         tap_major->major = MAJOR(major);
1251
1252         idr_init(&tap_major->minor_idr);
1253         spin_lock_init(&tap_major->minor_lock);
1254
1255         tap_major->device_name = device_name;
1256
1257         list_add_tail_rcu(&tap_major->next, &major_list);
1258         return 0;
1259 }
1260
1261 int tap_create_cdev(struct cdev *tap_cdev, dev_t *tap_major,
1262                     const char *device_name, struct module *module)
1263 {
1264         int err;
1265
1266         err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
1267         if (err)
1268                 goto out1;
1269
1270         cdev_init(tap_cdev, &tap_fops);
1271         tap_cdev->owner = module;
1272         err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
1273         if (err)
1274                 goto out2;
1275
1276         err =  tap_list_add(*tap_major, device_name);
1277         if (err)
1278                 goto out3;
1279
1280         return 0;
1281
1282 out3:
1283         cdev_del(tap_cdev);
1284 out2:
1285         unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
1286 out1:
1287         return err;
1288 }
1289 EXPORT_SYMBOL_GPL(tap_create_cdev);
1290
1291 void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
1292 {
1293         struct major_info *tap_major, *tmp;
1294
1295         cdev_del(tap_cdev);
1296         unregister_chrdev_region(major, TAP_NUM_DEVS);
1297         list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
1298                 if (tap_major->major == MAJOR(major)) {
1299                         idr_destroy(&tap_major->minor_idr);
1300                         list_del_rcu(&tap_major->next);
1301                         kfree_rcu(tap_major, rcu);
1302                 }
1303         }
1304 }
1305 EXPORT_SYMBOL_GPL(tap_destroy_cdev);
1306
1307 MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
1308 MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
1309 MODULE_LICENSE("GPL");