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                 struct sk_buff *next;
 345
 346                 if (IS_ERR(segs))
 347                         goto drop;
 348
 349                 if (!segs) {
 350                         if (ptr_ring_produce(&q->ring, skb))
 351                                 goto drop;
 352                         goto wake_up;
 353                 }
 354
 355                 consume_skb(skb);
 356                 skb_list_walk_safe(segs, skb, next) {
 357                         skb_mark_not_on_list(skb);
 358                         if (ptr_ring_produce(&q->ring, skb)) {
 359                                 kfree_skb(skb);
 360                                 kfree_skb_list(next);
 361                                 break;
 362                         }
 363                 }
 364         } else {
 365                 /* If we receive a partial checksum and the tap side
 366                  * doesn't support checksum offload, compute the checksum.
 367                  * Note: it doesn't matter which checksum feature to
 368                  *        check, we either support them all or none.
 369                  */
 370                 if (skb->ip_summed == CHECKSUM_PARTIAL &&
 371                     !(features & NETIF_F_CSUM_MASK) &&
 372                     skb_checksum_help(skb))
 373                         goto drop;
 374                 if (ptr_ring_produce(&q->ring, skb))
 375                         goto drop;
 376         }
 377
 378 wake_up:
 379         wake_up_interruptible_poll(sk_sleep(&q->sk), EPOLLIN | EPOLLRDNORM | EPOLLRDBAND);
 380         return RX_HANDLER_CONSUMED;
 381
 382 drop:
 383         /* Count errors/drops only here, thus don't care about args. */
 384         if (tap->count_rx_dropped)
 385                 tap->count_rx_dropped(tap);
 386         kfree_skb(skb);
 387         return RX_HANDLER_CONSUMED;
 388 }
 389 EXPORT_SYMBOL_GPL(tap_handle_frame);
 390
 391 static struct major_info *tap_get_major(int major)
 392 {
 393         struct major_info *tap_major;
 394
 395         list_for_each_entry_rcu(tap_major, &major_list, next) {
 396                 if (tap_major->major == major)
 397                         return tap_major;
 398         }
 399
 400         return NULL;
 401 }
 402
 403 int tap_get_minor(dev_t major, struct tap_dev *tap)
 404 {
 405         int retval = -ENOMEM;
 406         struct major_info *tap_major;
 407
 408         rcu_read_lock();
 409         tap_major = tap_get_major(MAJOR(major));
 410         if (!tap_major) {
 411                 retval = -EINVAL;
 412                 goto unlock;
 413         }
 414
 415         spin_lock(&tap_major->minor_lock);
 416         retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);
 417         if (retval >= 0) {
 418                 tap->minor = retval;
 419         } else if (retval == -ENOSPC) {
 420                 netdev_err(tap->dev, "Too many tap devices\n");
 421                 retval = -EINVAL;
 422         }
 423         spin_unlock(&tap_major->minor_lock);
 424
 425 unlock:
 426         rcu_read_unlock();
 427         return retval < 0 ? retval : 0;
 428 }
 429 EXPORT_SYMBOL_GPL(tap_get_minor);
 430
 431 void tap_free_minor(dev_t major, struct tap_dev *tap)
 432 {
 433         struct major_info *tap_major;
 434
 435         rcu_read_lock();
 436         tap_major = tap_get_major(MAJOR(major));
 437         if (!tap_major) {
 438                 goto unlock;
 439         }
 440
 441         spin_lock(&tap_major->minor_lock);
 442         if (tap->minor) {
 443                 idr_remove(&tap_major->minor_idr, tap->minor);
 444                 tap->minor = 0;
 445         }
 446         spin_unlock(&tap_major->minor_lock);
 447
 448 unlock:
 449         rcu_read_unlock();
 450 }
 451 EXPORT_SYMBOL_GPL(tap_free_minor);
 452
 453 static struct tap_dev *dev_get_by_tap_file(int major, int minor)
 454 {
 455         struct net_device *dev = NULL;
 456         struct tap_dev *tap;
 457         struct major_info *tap_major;
 458
 459         rcu_read_lock();
 460         tap_major = tap_get_major(major);
 461         if (!tap_major) {
 462                 tap = NULL;
 463                 goto unlock;
 464         }
 465
 466         spin_lock(&tap_major->minor_lock);
 467         tap = idr_find(&tap_major->minor_idr, minor);
 468         if (tap) {
 469                 dev = tap->dev;
 470                 dev_hold(dev);
 471         }
 472         spin_unlock(&tap_major->minor_lock);
 473
 474 unlock:
 475         rcu_read_unlock();
 476         return tap;
 477 }
 478
 479 static void tap_sock_write_space(struct sock *sk)
 480 {
 481         wait_queue_head_t *wqueue;
 482
 483         if (!sock_writeable(sk) ||
 484             !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
 485                 return;
 486
 487         wqueue = sk_sleep(sk);
 488         if (wqueue && waitqueue_active(wqueue))
 489                 wake_up_interruptible_poll(wqueue, EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
 490 }
 491
 492 static void tap_sock_destruct(struct sock *sk)
 493 {
 494         struct tap_queue *q = container_of(sk, struct tap_queue, sk);
 495
 496         ptr_ring_cleanup(&q->ring, __skb_array_destroy_skb);
 497 }
 498
 499 static int tap_open(struct inode *inode, struct file *file)
 500 {
 501         struct net *net = current->nsproxy->net_ns;
 502         struct tap_dev *tap;
 503         struct tap_queue *q;
 504         int err = -ENODEV;
 505
 506         rtnl_lock();
 507         tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
 508         if (!tap)
 509                 goto err;
 510
 511         err = -ENOMEM;
 512         q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
 513                                              &tap_proto, 0);
 514         if (!q)
 515                 goto err;
 516         if (ptr_ring_init(&q->ring, tap->dev->tx_queue_len, GFP_KERNEL)) {
 517                 sk_free(&q->sk);
 518                 goto err;
 519         }
 520
 521         init_waitqueue_head(&q->sock.wq.wait);
 522         q->sock.type = SOCK_RAW;
 523         q->sock.state = SS_CONNECTED;
 524         q->sock.file = file;
 525         q->sock.ops = &tap_socket_ops;
 526         sock_init_data(&q->sock, &q->sk);
 527         q->sk.sk_write_space = tap_sock_write_space;
 528         q->sk.sk_destruct = tap_sock_destruct;
 529         q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;
 530         q->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
 531
 532         /*
 533          * so far only KVM virtio_net uses tap, enable zero copy between
 534          * guest kernel and host kernel when lower device supports zerocopy
 535          *
 536          * The macvlan supports zerocopy iff the lower device supports zero
 537          * copy so we don't have to look at the lower device directly.
 538          */
 539         if ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
 540                 sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 541
 542         err = tap_set_queue(tap, file, q);
 543         if (err) {
 544                 /* tap_sock_destruct() will take care of freeing ptr_ring */
 545                 goto err_put;
 546         }
 547
 548         dev_put(tap->dev);
 549
 550         rtnl_unlock();
 551         return err;
 552
 553 err_put:
 554         sock_put(&q->sk);
 555 err:
 556         if (tap)
 557                 dev_put(tap->dev);
 558
 559         rtnl_unlock();
 560         return err;
 561 }
 562
 563 static int tap_release(struct inode *inode, struct file *file)
 564 {
 565         struct tap_queue *q = file->private_data;
 566         tap_put_queue(q);
 567         return 0;
 568 }
 569
 570 static __poll_t tap_poll(struct file *file, poll_table *wait)
 571 {
 572         struct tap_queue *q = file->private_data;
 573         __poll_t mask = EPOLLERR;
 574
 575         if (!q)
 576                 goto out;
 577
 578         mask = 0;
 579         poll_wait(file, &q->sock.wq.wait, wait);
 580
 581         if (!ptr_ring_empty(&q->ring))
 582                 mask |= EPOLLIN | EPOLLRDNORM;
 583
 584         if (sock_writeable(&q->sk) ||
 585             (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) &&
 586              sock_writeable(&q->sk)))
 587                 mask |= EPOLLOUT | EPOLLWRNORM;
 588
 589 out:
 590         return mask;
 591 }
 592
 593 static inline struct sk_buff *tap_alloc_skb(struct sock *sk, size_t prepad,
 594                                             size_t len, size_t linear,
 595                                                 int noblock, int *err)
 596 {
 597         struct sk_buff *skb;
 598
 599         /* Under a page?  Don't bother with paged skb. */
 600         if (prepad + len < PAGE_SIZE || !linear)
 601                 linear = len;
 602
 603         skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
 604                                    err, 0);
 605         if (!skb)
 606                 return NULL;
 607
 608         skb_reserve(skb, prepad);
 609         skb_put(skb, linear);
 610         skb->data_len = len - linear;
 611         skb->len += len - linear;
 612
 613         return skb;
 614 }
 615
 616 /* Neighbour code has some assumptions on HH_DATA_MOD alignment */
 617 #define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
 618
 619 /* Get packet from user space buffer */
 620 static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 621                             struct iov_iter *from, int noblock)
 622 {
 623         int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
 624         struct sk_buff *skb;
 625         struct tap_dev *tap;
 626         unsigned long total_len = iov_iter_count(from);
 627         unsigned long len = total_len;
 628         int err;
 629         struct virtio_net_hdr vnet_hdr = { 0 };
 630         int vnet_hdr_len = 0;
 631         int copylen = 0;
 632         int depth;
 633         bool zerocopy = false;
 634         size_t linear;
 635
 636         if (q->flags & IFF_VNET_HDR) {
 637                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 638
 639                 err = -EINVAL;
 640                 if (len < vnet_hdr_len)
 641                         goto err;
 642                 len -= vnet_hdr_len;
 643
 644                 err = -EFAULT;
 645                 if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
 646                         goto err;
 647                 iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
 648                 if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
 649                      tap16_to_cpu(q, vnet_hdr.csum_start) +
 650                      tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
 651                              tap16_to_cpu(q, vnet_hdr.hdr_len))
 652                         vnet_hdr.hdr_len = cpu_to_tap16(q,
 653                                  tap16_to_cpu(q, vnet_hdr.csum_start) +
 654                                  tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
 655                 err = -EINVAL;
 656                 if (tap16_to_cpu(q, vnet_hdr.hdr_len) > len)
 657                         goto err;
 658         }
 659
 660         err = -EINVAL;
 661         if (unlikely(len < ETH_HLEN))
 662                 goto err;
 663
 664         if (msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
 665                 struct iov_iter i;
 666
 667                 copylen = vnet_hdr.hdr_len ?
 668                         tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
 669                 if (copylen > good_linear)
 670                         copylen = good_linear;
 671                 else if (copylen < ETH_HLEN)
 672                         copylen = ETH_HLEN;
 673                 linear = copylen;
 674                 i = *from;
 675                 iov_iter_advance(&i, copylen);
 676                 if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
 677                         zerocopy = true;
 678         }
 679
 680         if (!zerocopy) {
 681                 copylen = len;
 682                 linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
 683                 if (linear > good_linear)
 684                         linear = good_linear;
 685                 else if (linear < ETH_HLEN)
 686                         linear = ETH_HLEN;
 687         }
 688
 689         skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,
 690                             linear, noblock, &err);
 691         if (!skb)
 692                 goto err;
 693
 694         if (zerocopy)
 695                 err = zerocopy_sg_from_iter(skb, from);
 696         else
 697                 err = skb_copy_datagram_from_iter(skb, 0, from, len);
 698
 699         if (err)
 700                 goto err_kfree;
 701
 702         skb_set_network_header(skb, ETH_HLEN);
 703         skb_reset_mac_header(skb);
 704         skb->protocol = eth_hdr(skb)->h_proto;
 705
 706         if (vnet_hdr_len) {
 707                 err = virtio_net_hdr_to_skb(skb, &vnet_hdr,
 708                                             tap_is_little_endian(q));
 709                 if (err)
 710                         goto err_kfree;
 711         }
 712
 713         skb_probe_transport_header(skb);
 714
 715         /* Move network header to the right position for VLAN tagged packets */
 716         if ((skb->protocol == htons(ETH_P_8021Q) ||
 717              skb->protocol == htons(ETH_P_8021AD)) &&
 718             __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
 719                 skb_set_network_header(skb, depth);
 720
 721         rcu_read_lock();
 722         tap = rcu_dereference(q->tap);
 723         /* copy skb_ubuf_info for callback when skb has no error */
 724         if (zerocopy) {
 725                 skb_shinfo(skb)->destructor_arg = msg_control;
 726                 skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
 727                 skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 728         } else if (msg_control) {
 729                 struct ubuf_info *uarg = msg_control;
 730                 uarg->callback(uarg, false);
 731         }
 732
 733         if (tap) {
 734                 skb->dev = tap->dev;
 735                 dev_queue_xmit(skb);
 736         } else {
 737                 kfree_skb(skb);
 738         }
 739         rcu_read_unlock();
 740
 741         return total_len;
 742
 743 err_kfree:
 744         kfree_skb(skb);
 745
 746 err:
 747         rcu_read_lock();
 748         tap = rcu_dereference(q->tap);
 749         if (tap && tap->count_tx_dropped)
 750                 tap->count_tx_dropped(tap);
 751         rcu_read_unlock();
 752
 753         return err;
 754 }
 755
 756 static ssize_t tap_write_iter(struct kiocb *iocb, struct iov_iter *from)
 757 {
 758         struct file *file = iocb->ki_filp;
 759         struct tap_queue *q = file->private_data;
 760
 761         return tap_get_user(q, NULL, from, file->f_flags & O_NONBLOCK);
 762 }
 763
 764 /* Put packet to the user space buffer */
 765 static ssize_t tap_put_user(struct tap_queue *q,
 766                             const struct sk_buff *skb,
 767                             struct iov_iter *iter)
 768 {
 769         int ret;
 770         int vnet_hdr_len = 0;
 771         int vlan_offset = 0;
 772         int total;
 773
 774         if (q->flags & IFF_VNET_HDR) {
 775                 int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0;
 776                 struct virtio_net_hdr vnet_hdr;
 777
 778                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
 779                 if (iov_iter_count(iter) < vnet_hdr_len)
 780                         return -EINVAL;
 781
 782                 if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
 783                                             tap_is_little_endian(q), true,
 784                                             vlan_hlen))
 785                         BUG();
 786
 787                 if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
 788                     sizeof(vnet_hdr))
 789                         return -EFAULT;
 790
 791                 iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));
 792         }
 793         total = vnet_hdr_len;
 794         total += skb->len;
 795
 796         if (skb_vlan_tag_present(skb)) {
 797                 struct {
 798                         __be16 h_vlan_proto;
 799                         __be16 h_vlan_TCI;
 800                 } veth;
 801                 veth.h_vlan_proto = skb->vlan_proto;
 802                 veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
 803
 804                 vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
 805                 total += VLAN_HLEN;
 806
 807                 ret = skb_copy_datagram_iter(skb, 0, iter, vlan_offset);
 808                 if (ret || !iov_iter_count(iter))
 809                         goto done;
 810
 811                 ret = copy_to_iter(&veth, sizeof(veth), iter);
 812                 if (ret != sizeof(veth) || !iov_iter_count(iter))
 813                         goto done;
 814         }
 815
 816         ret = skb_copy_datagram_iter(skb, vlan_offset, iter,
 817                                      skb->len - vlan_offset);
 818
 819 done:
 820         return ret ? ret : total;
 821 }
 822
 823 static ssize_t tap_do_read(struct tap_queue *q,
 824                            struct iov_iter *to,
 825                            int noblock, struct sk_buff *skb)
 826 {
 827         DEFINE_WAIT(wait);
 828         ssize_t ret = 0;
 829
 830         if (!iov_iter_count(to)) {
 831                 kfree_skb(skb);
 832                 return 0;
 833         }
 834
 835         if (skb)
 836                 goto put;
 837
 838         while (1) {
 839                 if (!noblock)
 840                         prepare_to_wait(sk_sleep(&q->sk), &wait,
 841                                         TASK_INTERRUPTIBLE);
 842
 843                 /* Read frames from the queue */
 844                 skb = ptr_ring_consume(&q->ring);
 845                 if (skb)
 846                         break;
 847                 if (noblock) {
 848                         ret = -EAGAIN;
 849                         break;
 850                 }
 851                 if (signal_pending(current)) {
 852                         ret = -ERESTARTSYS;
 853                         break;
 854                 }
 855                 /* Nothing to read, let's sleep */
 856                 schedule();
 857         }
 858         if (!noblock)
 859                 finish_wait(sk_sleep(&q->sk), &wait);
 860
 861 put:
 862         if (skb) {
 863                 ret = tap_put_user(q, skb, to);
 864                 if (unlikely(ret < 0))
 865                         kfree_skb(skb);
 866                 else
 867                         consume_skb(skb);
 868         }
 869         return ret;
 870 }
 871
 872 static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
 873 {
 874         struct file *file = iocb->ki_filp;
 875         struct tap_queue *q = file->private_data;
 876         ssize_t len = iov_iter_count(to), ret;
 877
 878         ret = tap_do_read(q, to, file->f_flags & O_NONBLOCK, NULL);
 879         ret = min_t(ssize_t, ret, len);
 880         if (ret > 0)
 881                 iocb->ki_pos = ret;
 882         return ret;
 883 }
 884
 885 static struct tap_dev *tap_get_tap_dev(struct tap_queue *q)
 886 {
 887         struct tap_dev *tap;
 888
 889         ASSERT_RTNL();
 890         tap = rtnl_dereference(q->tap);
 891         if (tap)
 892                 dev_hold(tap->dev);
 893
 894         return tap;
 895 }
 896
 897 static void tap_put_tap_dev(struct tap_dev *tap)
 898 {
 899         dev_put(tap->dev);
 900 }
 901
 902 static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
 903 {
 904         struct tap_queue *q = file->private_data;
 905         struct tap_dev *tap;
 906         int ret;
 907
 908         tap = tap_get_tap_dev(q);
 909         if (!tap)
 910                 return -EINVAL;
 911
 912         if (flags & IFF_ATTACH_QUEUE)
 913                 ret = tap_enable_queue(tap, file, q);
 914         else if (flags & IFF_DETACH_QUEUE)
 915                 ret = tap_disable_queue(q);
 916         else
 917                 ret = -EINVAL;
 918
 919         tap_put_tap_dev(tap);
 920         return ret;
 921 }
 922
 923 static int set_offload(struct tap_queue *q, unsigned long arg)
 924 {
 925         struct tap_dev *tap;
 926         netdev_features_t features;
 927         netdev_features_t feature_mask = 0;
 928
 929         tap = rtnl_dereference(q->tap);
 930         if (!tap)
 931                 return -ENOLINK;
 932
 933         features = tap->dev->features;
 934
 935         if (arg & TUN_F_CSUM) {
 936                 feature_mask = NETIF_F_HW_CSUM;
 937
 938                 if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
 939                         if (arg & TUN_F_TSO_ECN)
 940                                 feature_mask |= NETIF_F_TSO_ECN;
 941                         if (arg & TUN_F_TSO4)
 942                                 feature_mask |= NETIF_F_TSO;
 943                         if (arg & TUN_F_TSO6)
 944                                 feature_mask |= NETIF_F_TSO6;
 945                 }
 946         }
 947
 948         /* tun/tap driver inverts the usage for TSO offloads, where
 949          * setting the TSO bit means that the userspace wants to
 950          * accept TSO frames and turning it off means that user space
 951          * does not support TSO.
 952          * For tap, we have to invert it to mean the same thing.
 953          * When user space turns off TSO, we turn off GSO/LRO so that
 954          * user-space will not receive TSO frames.
 955          */
 956         if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6))
 957                 features |= RX_OFFLOADS;
 958         else
 959                 features &= ~RX_OFFLOADS;
 960
 961         /* tap_features are the same as features on tun/tap and
 962          * reflect user expectations.
 963          */
 964         tap->tap_features = feature_mask;
 965         if (tap->update_features)
 966                 tap->update_features(tap, features);
 967
 968         return 0;
 969 }
 970
 971 /*
 972  * provide compatibility with generic tun/tap interface
 973  */
 974 static long tap_ioctl(struct file *file, unsigned int cmd,
 975                       unsigned long arg)
 976 {
 977         struct tap_queue *q = file->private_data;
 978         struct tap_dev *tap;
 979         void __user *argp = (void __user *)arg;
 980         struct ifreq __user *ifr = argp;
 981         unsigned int __user *up = argp;
 982         unsigned short u;
 983         int __user *sp = argp;
 984         struct sockaddr sa;
 985         int s;
 986         int ret;
 987
 988         switch (cmd) {
 989         case TUNSETIFF:
 990                 /* ignore the name, just look at flags */
 991                 if (get_user(u, &ifr->ifr_flags))
 992                         return -EFAULT;
 993
 994                 ret = 0;
 995                 if ((u & ~TAP_IFFEATURES) != (IFF_NO_PI | IFF_TAP))
 996                         ret = -EINVAL;
 997                 else
 998                         q->flags = (q->flags & ~TAP_IFFEATURES) | u;
 999
1000                 return ret;
1001
1002         case TUNGETIFF:
1003                 rtnl_lock();
1004                 tap = tap_get_tap_dev(q);
1005                 if (!tap) {
1006                         rtnl_unlock();
1007                         return -ENOLINK;
1008                 }
1009
1010                 ret = 0;
1011                 u = q->flags;
1012                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1013                     put_user(u, &ifr->ifr_flags))
1014                         ret = -EFAULT;
1015                 tap_put_tap_dev(tap);
1016                 rtnl_unlock();
1017                 return ret;
1018
1019         case TUNSETQUEUE:
1020                 if (get_user(u, &ifr->ifr_flags))
1021                         return -EFAULT;
1022                 rtnl_lock();
1023                 ret = tap_ioctl_set_queue(file, u);
1024                 rtnl_unlock();
1025                 return ret;
1026
1027         case TUNGETFEATURES:
1028                 if (put_user(IFF_TAP | IFF_NO_PI | TAP_IFFEATURES, up))
1029                         return -EFAULT;
1030                 return 0;
1031
1032         case TUNSETSNDBUF:
1033                 if (get_user(s, sp))
1034                         return -EFAULT;
1035                 if (s <= 0)
1036                         return -EINVAL;
1037
1038                 q->sk.sk_sndbuf = s;
1039                 return 0;
1040
1041         case TUNGETVNETHDRSZ:
1042                 s = q->vnet_hdr_sz;
1043                 if (put_user(s, sp))
1044                         return -EFAULT;
1045                 return 0;
1046
1047         case TUNSETVNETHDRSZ:
1048                 if (get_user(s, sp))
1049                         return -EFAULT;
1050                 if (s < (int)sizeof(struct virtio_net_hdr))
1051                         return -EINVAL;
1052
1053                 q->vnet_hdr_sz = s;
1054                 return 0;
1055
1056         case TUNGETVNETLE:
1057                 s = !!(q->flags & TAP_VNET_LE);
1058                 if (put_user(s, sp))
1059                         return -EFAULT;
1060                 return 0;
1061
1062         case TUNSETVNETLE:
1063                 if (get_user(s, sp))
1064                         return -EFAULT;
1065                 if (s)
1066                         q->flags |= TAP_VNET_LE;
1067                 else
1068                         q->flags &= ~TAP_VNET_LE;
1069                 return 0;
1070
1071         case TUNGETVNETBE:
1072                 return tap_get_vnet_be(q, sp);
1073
1074         case TUNSETVNETBE:
1075                 return tap_set_vnet_be(q, sp);
1076
1077         case TUNSETOFFLOAD:
1078                 /* let the user check for future flags */
1079                 if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
1080                             TUN_F_TSO_ECN | TUN_F_UFO))
1081                         return -EINVAL;
1082
1083                 rtnl_lock();
1084                 ret = set_offload(q, arg);
1085                 rtnl_unlock();
1086                 return ret;
1087
1088         case SIOCGIFHWADDR:
1089                 rtnl_lock();
1090                 tap = tap_get_tap_dev(q);
1091                 if (!tap) {
1092                         rtnl_unlock();
1093                         return -ENOLINK;
1094                 }
1095                 ret = 0;
1096                 u = tap->dev->type;
1097                 if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1098                     copy_to_user(&ifr->ifr_hwaddr.sa_data, tap->dev->dev_addr, ETH_ALEN) ||
1099                     put_user(u, &ifr->ifr_hwaddr.sa_family))
1100                         ret = -EFAULT;
1101                 tap_put_tap_dev(tap);
1102                 rtnl_unlock();
1103                 return ret;
1104
1105         case SIOCSIFHWADDR:
1106                 if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
1107                         return -EFAULT;
1108                 rtnl_lock();
1109                 tap = tap_get_tap_dev(q);
1110                 if (!tap) {
1111                         rtnl_unlock();
1112                         return -ENOLINK;
1113                 }
1114                 ret = dev_set_mac_address(tap->dev, &sa, NULL);
1115                 tap_put_tap_dev(tap);
1116                 rtnl_unlock();
1117                 return ret;
1118
1119         default:
1120                 return -EINVAL;
1121         }
1122 }
1123
1124 static const struct file_operations tap_fops = {
1125         .owner          = THIS_MODULE,
1126         .open           = tap_open,
1127         .release        = tap_release,
1128         .read_iter      = tap_read_iter,
1129         .write_iter     = tap_write_iter,
1130         .poll           = tap_poll,
1131         .llseek         = no_llseek,
1132         .unlocked_ioctl = tap_ioctl,
1133         .compat_ioctl   = compat_ptr_ioctl,
1134 };
1135
1136 static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
1137 {
1138         struct tun_xdp_hdr *hdr = xdp->data_hard_start;
1139         struct virtio_net_hdr *gso = &hdr->gso;
1140         int buflen = hdr->buflen;
1141         int vnet_hdr_len = 0;
1142         struct tap_dev *tap;
1143         struct sk_buff *skb;
1144         int err, depth;
1145
1146         if (q->flags & IFF_VNET_HDR)
1147                 vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
1148
1149         skb = build_skb(xdp->data_hard_start, buflen);
1150         if (!skb) {
1151                 err = -ENOMEM;
1152                 goto err;
1153         }
1154
1155         skb_reserve(skb, xdp->data - xdp->data_hard_start);
1156         skb_put(skb, xdp->data_end - xdp->data);
1157
1158         skb_set_network_header(skb, ETH_HLEN);
1159         skb_reset_mac_header(skb);
1160         skb->protocol = eth_hdr(skb)->h_proto;
1161
1162         if (vnet_hdr_len) {
1163                 err = virtio_net_hdr_to_skb(skb, gso, tap_is_little_endian(q));
1164                 if (err)
1165                         goto err_kfree;
1166         }
1167
1168         /* Move network header to the right position for VLAN tagged packets */
1169         if ((skb->protocol == htons(ETH_P_8021Q) ||
1170              skb->protocol == htons(ETH_P_8021AD)) &&
1171             __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
1172                 skb_set_network_header(skb, depth);
1173
1174         rcu_read_lock();
1175         tap = rcu_dereference(q->tap);
1176         if (tap) {
1177                 skb->dev = tap->dev;
1178                 skb_probe_transport_header(skb);
1179                 dev_queue_xmit(skb);
1180         } else {
1181                 kfree_skb(skb);
1182         }
1183         rcu_read_unlock();
1184
1185         return 0;
1186
1187 err_kfree:
1188         kfree_skb(skb);
1189 err:
1190         rcu_read_lock();
1191         tap = rcu_dereference(q->tap);
1192         if (tap && tap->count_tx_dropped)
1193                 tap->count_tx_dropped(tap);
1194         rcu_read_unlock();
1195         return err;
1196 }
1197
1198 static int tap_sendmsg(struct socket *sock, struct msghdr *m,
1199                        size_t total_len)
1200 {
1201         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1202         struct tun_msg_ctl *ctl = m->msg_control;
1203         struct xdp_buff *xdp;
1204         int i;
1205
1206         if (ctl && (ctl->type == TUN_MSG_PTR)) {
1207                 for (i = 0; i < ctl->num; i++) {
1208                         xdp = &((struct xdp_buff *)ctl->ptr)[i];
1209                         tap_get_user_xdp(q, xdp);
1210                 }
1211                 return 0;
1212         }
1213
1214         return tap_get_user(q, ctl ? ctl->ptr : NULL, &m->msg_iter,
1215                             m->msg_flags & MSG_DONTWAIT);
1216 }
1217
1218 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
1219                        size_t total_len, int flags)
1220 {
1221         struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1222         struct sk_buff *skb = m->msg_control;
1223         int ret;
1224         if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
1225                 kfree_skb(skb);
1226                 return -EINVAL;
1227         }
1228         ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT, skb);
1229         if (ret > total_len) {
1230                 m->msg_flags |= MSG_TRUNC;
1231                 ret = flags & MSG_TRUNC ? ret : total_len;
1232         }
1233         return ret;
1234 }
1235
1236 static int tap_peek_len(struct socket *sock)
1237 {
1238         struct tap_queue *q = container_of(sock, struct tap_queue,
1239                                                sock);
1240         return PTR_RING_PEEK_CALL(&q->ring, __skb_array_len_with_tag);
1241 }
1242
1243 /* Ops structure to mimic raw sockets with tun */
1244 static const struct proto_ops tap_socket_ops = {
1245         .sendmsg = tap_sendmsg,
1246         .recvmsg = tap_recvmsg,
1247         .peek_len = tap_peek_len,
1248 };
1249
1250 /* Get an underlying socket object from tun file.  Returns error unless file is
1251  * attached to a device.  The returned object works like a packet socket, it
1252  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
1253  * holding a reference to the file for as long as the socket is in use. */
1254 struct socket *tap_get_socket(struct file *file)
1255 {
1256         struct tap_queue *q;
1257         if (file->f_op != &tap_fops)
1258                 return ERR_PTR(-EINVAL);
1259         q = file->private_data;
1260         if (!q)
1261                 return ERR_PTR(-EBADFD);
1262         return &q->sock;
1263 }
1264 EXPORT_SYMBOL_GPL(tap_get_socket);
1265
1266 struct ptr_ring *tap_get_ptr_ring(struct file *file)
1267 {
1268         struct tap_queue *q;
1269
1270         if (file->f_op != &tap_fops)
1271                 return ERR_PTR(-EINVAL);
1272         q = file->private_data;
1273         if (!q)
1274                 return ERR_PTR(-EBADFD);
1275         return &q->ring;
1276 }
1277 EXPORT_SYMBOL_GPL(tap_get_ptr_ring);
1278
1279 int tap_queue_resize(struct tap_dev *tap)
1280 {
1281         struct net_device *dev = tap->dev;
1282         struct tap_queue *q;
1283         struct ptr_ring **rings;
1284         int n = tap->numqueues;
1285         int ret, i = 0;
1286
1287         rings = kmalloc_array(n, sizeof(*rings), GFP_KERNEL);
1288         if (!rings)
1289                 return -ENOMEM;
1290
1291         list_for_each_entry(q, &tap->queue_list, next)
1292                 rings[i++] = &q->ring;
1293
1294         ret = ptr_ring_resize_multiple(rings, n,
1295                                        dev->tx_queue_len, GFP_KERNEL,
1296                                        __skb_array_destroy_skb);
1297
1298         kfree(rings);
1299         return ret;
1300 }
1301 EXPORT_SYMBOL_GPL(tap_queue_resize);
1302
1303 static int tap_list_add(dev_t major, const char *device_name)
1304 {
1305         struct major_info *tap_major;
1306
1307         tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
1308         if (!tap_major)
1309                 return -ENOMEM;
1310
1311         tap_major->major = MAJOR(major);
1312
1313         idr_init(&tap_major->minor_idr);
1314         spin_lock_init(&tap_major->minor_lock);
1315
1316         tap_major->device_name = device_name;
1317
1318         list_add_tail_rcu(&tap_major->next, &major_list);
1319         return 0;
1320 }
1321
1322 int tap_create_cdev(struct cdev *tap_cdev, dev_t *tap_major,
1323                     const char *device_name, struct module *module)
1324 {
1325         int err;
1326
1327         err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
1328         if (err)
1329                 goto out1;
1330
1331         cdev_init(tap_cdev, &tap_fops);
1332         tap_cdev->owner = module;
1333         err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
1334         if (err)
1335                 goto out2;
1336
1337         err =  tap_list_add(*tap_major, device_name);
1338         if (err)
1339                 goto out3;
1340
1341         return 0;
1342
1343 out3:
1344         cdev_del(tap_cdev);
1345 out2:
1346         unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
1347 out1:
1348         return err;
1349 }
1350 EXPORT_SYMBOL_GPL(tap_create_cdev);
1351
1352 void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
1353 {
1354         struct major_info *tap_major, *tmp;
1355
1356         cdev_del(tap_cdev);
1357         unregister_chrdev_region(major, TAP_NUM_DEVS);
1358         list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
1359                 if (tap_major->major == MAJOR(major)) {
1360                         idr_destroy(&tap_major->minor_idr);
1361                         list_del_rcu(&tap_major->next);
1362                         kfree_rcu(tap_major, rcu);
1363                 }
1364         }
1365 }
1366 EXPORT_SYMBOL_GPL(tap_destroy_cdev);
1367
1368 MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
1369 MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
1370 MODULE_LICENSE("GPL");