xref: /linux/drivers/net/tap.c (revision e5c86679d5e864947a52fb31e45a425dea3e7fa9)
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 	struct mutex minor_lock;
110 	const char *device_name;
111 	struct list_head next;
112 };
113 
114 #define GOODCOPY_LEN 128
115 
116 static const struct proto_ops tap_socket_ops;
117 
118 #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
119 #define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)
120 
121 static struct tap_dev *tap_dev_get_rcu(const struct net_device *dev)
122 {
123 	return rcu_dereference(dev->rx_handler_data);
124 }
125 
126 /*
127  * RCU usage:
128  * The tap_queue and the macvlan_dev are loosely coupled, the
129  * pointers from one to the other can only be read while rcu_read_lock
130  * or rtnl is held.
131  *
132  * Both the file and the macvlan_dev hold a reference on the tap_queue
133  * through sock_hold(&q->sk). When the macvlan_dev goes away first,
134  * q->vlan becomes inaccessible. When the files gets closed,
135  * tap_get_queue() fails.
136  *
137  * There may still be references to the struct sock inside of the
138  * queue from outbound SKBs, but these never reference back to the
139  * file or the dev. The data structure is freed through __sk_free
140  * when both our references and any pending SKBs are gone.
141  */
142 
143 static int tap_enable_queue(struct tap_dev *tap, struct file *file,
144 			    struct tap_queue *q)
145 {
146 	int err = -EINVAL;
147 
148 	ASSERT_RTNL();
149 
150 	if (q->enabled)
151 		goto out;
152 
153 	err = 0;
154 	rcu_assign_pointer(tap->taps[tap->numvtaps], q);
155 	q->queue_index = tap->numvtaps;
156 	q->enabled = true;
157 
158 	tap->numvtaps++;
159 out:
160 	return err;
161 }
162 
163 /* Requires RTNL */
164 static int tap_set_queue(struct tap_dev *tap, struct file *file,
165 			 struct tap_queue *q)
166 {
167 	if (tap->numqueues == MAX_TAP_QUEUES)
168 		return -EBUSY;
169 
170 	rcu_assign_pointer(q->tap, tap);
171 	rcu_assign_pointer(tap->taps[tap->numvtaps], q);
172 	sock_hold(&q->sk);
173 
174 	q->file = file;
175 	q->queue_index = tap->numvtaps;
176 	q->enabled = true;
177 	file->private_data = q;
178 	list_add_tail(&q->next, &tap->queue_list);
179 
180 	tap->numvtaps++;
181 	tap->numqueues++;
182 
183 	return 0;
184 }
185 
186 static int tap_disable_queue(struct tap_queue *q)
187 {
188 	struct tap_dev *tap;
189 	struct tap_queue *nq;
190 
191 	ASSERT_RTNL();
192 	if (!q->enabled)
193 		return -EINVAL;
194 
195 	tap = rtnl_dereference(q->tap);
196 
197 	if (tap) {
198 		int index = q->queue_index;
199 		BUG_ON(index >= tap->numvtaps);
200 		nq = rtnl_dereference(tap->taps[tap->numvtaps - 1]);
201 		nq->queue_index = index;
202 
203 		rcu_assign_pointer(tap->taps[index], nq);
204 		RCU_INIT_POINTER(tap->taps[tap->numvtaps - 1], NULL);
205 		q->enabled = false;
206 
207 		tap->numvtaps--;
208 	}
209 
210 	return 0;
211 }
212 
213 /*
214  * The file owning the queue got closed, give up both
215  * the reference that the files holds as well as the
216  * one from the macvlan_dev if that still exists.
217  *
218  * Using the spinlock makes sure that we don't get
219  * to the queue again after destroying it.
220  */
221 static void tap_put_queue(struct tap_queue *q)
222 {
223 	struct tap_dev *tap;
224 
225 	rtnl_lock();
226 	tap = rtnl_dereference(q->tap);
227 
228 	if (tap) {
229 		if (q->enabled)
230 			BUG_ON(tap_disable_queue(q));
231 
232 		tap->numqueues--;
233 		RCU_INIT_POINTER(q->tap, NULL);
234 		sock_put(&q->sk);
235 		list_del_init(&q->next);
236 	}
237 
238 	rtnl_unlock();
239 
240 	synchronize_rcu();
241 	sock_put(&q->sk);
242 }
243 
244 /*
245  * Select a queue based on the rxq of the device on which this packet
246  * arrived. If the incoming device is not mq, calculate a flow hash
247  * to select a queue. If all fails, find the first available queue.
248  * Cache vlan->numvtaps since it can become zero during the execution
249  * of this function.
250  */
251 static struct tap_queue *tap_get_queue(struct tap_dev *tap,
252 				       struct sk_buff *skb)
253 {
254 	struct tap_queue *queue = NULL;
255 	/* Access to taps array is protected by rcu, but access to numvtaps
256 	 * isn't. Below we use it to lookup a queue, but treat it as a hint
257 	 * and validate that the result isn't NULL - in case we are
258 	 * racing against queue removal.
259 	 */
260 	int numvtaps = ACCESS_ONCE(tap->numvtaps);
261 	__u32 rxq;
262 
263 	if (!numvtaps)
264 		goto out;
265 
266 	if (numvtaps == 1)
267 		goto single;
268 
269 	/* Check if we can use flow to select a queue */
270 	rxq = skb_get_hash(skb);
271 	if (rxq) {
272 		queue = rcu_dereference(tap->taps[rxq % numvtaps]);
273 		goto out;
274 	}
275 
276 	if (likely(skb_rx_queue_recorded(skb))) {
277 		rxq = skb_get_rx_queue(skb);
278 
279 		while (unlikely(rxq >= numvtaps))
280 			rxq -= numvtaps;
281 
282 		queue = rcu_dereference(tap->taps[rxq]);
283 		goto out;
284 	}
285 
286 single:
287 	queue = rcu_dereference(tap->taps[0]);
288 out:
289 	return queue;
290 }
291 
292 /*
293  * The net_device is going away, give up the reference
294  * that it holds on all queues and safely set the pointer
295  * from the queues to NULL.
296  */
297 void tap_del_queues(struct tap_dev *tap)
298 {
299 	struct tap_queue *q, *tmp;
300 
301 	ASSERT_RTNL();
302 	list_for_each_entry_safe(q, tmp, &tap->queue_list, next) {
303 		list_del_init(&q->next);
304 		RCU_INIT_POINTER(q->tap, NULL);
305 		if (q->enabled)
306 			tap->numvtaps--;
307 		tap->numqueues--;
308 		sock_put(&q->sk);
309 	}
310 	BUG_ON(tap->numvtaps);
311 	BUG_ON(tap->numqueues);
312 	/* guarantee that any future tap_set_queue will fail */
313 	tap->numvtaps = MAX_TAP_QUEUES;
314 }
315 EXPORT_SYMBOL_GPL(tap_del_queues);
316 
317 rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
318 {
319 	struct sk_buff *skb = *pskb;
320 	struct net_device *dev = skb->dev;
321 	struct tap_dev *tap;
322 	struct tap_queue *q;
323 	netdev_features_t features = TAP_FEATURES;
324 
325 	tap = tap_dev_get_rcu(dev);
326 	if (!tap)
327 		return RX_HANDLER_PASS;
328 
329 	q = tap_get_queue(tap, skb);
330 	if (!q)
331 		return RX_HANDLER_PASS;
332 
333 	if (__skb_array_full(&q->skb_array))
334 		goto drop;
335 
336 	skb_push(skb, ETH_HLEN);
337 
338 	/* Apply the forward feature mask so that we perform segmentation
339 	 * according to users wishes.  This only works if VNET_HDR is
340 	 * enabled.
341 	 */
342 	if (q->flags & IFF_VNET_HDR)
343 		features |= tap->tap_features;
344 	if (netif_needs_gso(skb, features)) {
345 		struct sk_buff *segs = __skb_gso_segment(skb, features, false);
346 
347 		if (IS_ERR(segs))
348 			goto drop;
349 
350 		if (!segs) {
351 			if (skb_array_produce(&q->skb_array, skb))
352 				goto drop;
353 			goto wake_up;
354 		}
355 
356 		consume_skb(skb);
357 		while (segs) {
358 			struct sk_buff *nskb = segs->next;
359 
360 			segs->next = NULL;
361 			if (skb_array_produce(&q->skb_array, segs)) {
362 				kfree_skb(segs);
363 				kfree_skb_list(nskb);
364 				break;
365 			}
366 			segs = nskb;
367 		}
368 	} else {
369 		/* If we receive a partial checksum and the tap side
370 		 * doesn't support checksum offload, compute the checksum.
371 		 * Note: it doesn't matter which checksum feature to
372 		 *	  check, we either support them all or none.
373 		 */
374 		if (skb->ip_summed == CHECKSUM_PARTIAL &&
375 		    !(features & NETIF_F_CSUM_MASK) &&
376 		    skb_checksum_help(skb))
377 			goto drop;
378 		if (skb_array_produce(&q->skb_array, skb))
379 			goto drop;
380 	}
381 
382 wake_up:
383 	wake_up_interruptible_poll(sk_sleep(&q->sk), POLLIN | POLLRDNORM | POLLRDBAND);
384 	return RX_HANDLER_CONSUMED;
385 
386 drop:
387 	/* Count errors/drops only here, thus don't care about args. */
388 	if (tap->count_rx_dropped)
389 		tap->count_rx_dropped(tap);
390 	kfree_skb(skb);
391 	return RX_HANDLER_CONSUMED;
392 }
393 EXPORT_SYMBOL_GPL(tap_handle_frame);
394 
395 static struct major_info *tap_get_major(int major)
396 {
397 	struct major_info *tap_major;
398 
399 	list_for_each_entry_rcu(tap_major, &major_list, next) {
400 		if (tap_major->major == major)
401 			return tap_major;
402 	}
403 
404 	return NULL;
405 }
406 
407 int tap_get_minor(dev_t major, struct tap_dev *tap)
408 {
409 	int retval = -ENOMEM;
410 	struct major_info *tap_major;
411 
412 	rcu_read_lock();
413 	tap_major = tap_get_major(MAJOR(major));
414 	if (!tap_major) {
415 		retval = -EINVAL;
416 		goto unlock;
417 	}
418 
419 	mutex_lock(&tap_major->minor_lock);
420 	retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_KERNEL);
421 	if (retval >= 0) {
422 		tap->minor = retval;
423 	} else if (retval == -ENOSPC) {
424 		netdev_err(tap->dev, "Too many tap devices\n");
425 		retval = -EINVAL;
426 	}
427 	mutex_unlock(&tap_major->minor_lock);
428 
429 unlock:
430 	rcu_read_unlock();
431 	return retval < 0 ? retval : 0;
432 }
433 EXPORT_SYMBOL_GPL(tap_get_minor);
434 
435 void tap_free_minor(dev_t major, struct tap_dev *tap)
436 {
437 	struct major_info *tap_major;
438 
439 	rcu_read_lock();
440 	tap_major = tap_get_major(MAJOR(major));
441 	if (!tap_major) {
442 		goto unlock;
443 	}
444 
445 	mutex_lock(&tap_major->minor_lock);
446 	if (tap->minor) {
447 		idr_remove(&tap_major->minor_idr, tap->minor);
448 		tap->minor = 0;
449 	}
450 	mutex_unlock(&tap_major->minor_lock);
451 
452 unlock:
453 	rcu_read_unlock();
454 }
455 EXPORT_SYMBOL_GPL(tap_free_minor);
456 
457 static struct tap_dev *dev_get_by_tap_file(int major, int minor)
458 {
459 	struct net_device *dev = NULL;
460 	struct tap_dev *tap;
461 	struct major_info *tap_major;
462 
463 	rcu_read_lock();
464 	tap_major = tap_get_major(major);
465 	if (!tap_major) {
466 		tap = NULL;
467 		goto unlock;
468 	}
469 
470 	mutex_lock(&tap_major->minor_lock);
471 	tap = idr_find(&tap_major->minor_idr, minor);
472 	if (tap) {
473 		dev = tap->dev;
474 		dev_hold(dev);
475 	}
476 	mutex_unlock(&tap_major->minor_lock);
477 
478 unlock:
479 	rcu_read_unlock();
480 	return tap;
481 }
482 
483 static void tap_sock_write_space(struct sock *sk)
484 {
485 	wait_queue_head_t *wqueue;
486 
487 	if (!sock_writeable(sk) ||
488 	    !test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags))
489 		return;
490 
491 	wqueue = sk_sleep(sk);
492 	if (wqueue && waitqueue_active(wqueue))
493 		wake_up_interruptible_poll(wqueue, POLLOUT | POLLWRNORM | POLLWRBAND);
494 }
495 
496 static void tap_sock_destruct(struct sock *sk)
497 {
498 	struct tap_queue *q = container_of(sk, struct tap_queue, sk);
499 
500 	skb_array_cleanup(&q->skb_array);
501 }
502 
503 static int tap_open(struct inode *inode, struct file *file)
504 {
505 	struct net *net = current->nsproxy->net_ns;
506 	struct tap_dev *tap;
507 	struct tap_queue *q;
508 	int err = -ENODEV;
509 
510 	rtnl_lock();
511 	tap = dev_get_by_tap_file(imajor(inode), iminor(inode));
512 	if (!tap)
513 		goto err;
514 
515 	err = -ENOMEM;
516 	q = (struct tap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
517 					     &tap_proto, 0);
518 	if (!q)
519 		goto err;
520 
521 	RCU_INIT_POINTER(q->sock.wq, &q->wq);
522 	init_waitqueue_head(&q->wq.wait);
523 	q->sock.type = SOCK_RAW;
524 	q->sock.state = SS_CONNECTED;
525 	q->sock.file = file;
526 	q->sock.ops = &tap_socket_ops;
527 	sock_init_data(&q->sock, &q->sk);
528 	q->sk.sk_write_space = tap_sock_write_space;
529 	q->sk.sk_destruct = tap_sock_destruct;
530 	q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;
531 	q->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
532 
533 	/*
534 	 * so far only KVM virtio_net uses tap, enable zero copy between
535 	 * guest kernel and host kernel when lower device supports zerocopy
536 	 *
537 	 * The macvlan supports zerocopy iff the lower device supports zero
538 	 * copy so we don't have to look at the lower device directly.
539 	 */
540 	if ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
541 		sock_set_flag(&q->sk, SOCK_ZEROCOPY);
542 
543 	err = -ENOMEM;
544 	if (skb_array_init(&q->skb_array, tap->dev->tx_queue_len, GFP_KERNEL))
545 		goto err_array;
546 
547 	err = tap_set_queue(tap, file, q);
548 	if (err)
549 		goto err_queue;
550 
551 	dev_put(tap->dev);
552 
553 	rtnl_unlock();
554 	return err;
555 
556 err_queue:
557 	skb_array_cleanup(&q->skb_array);
558 err_array:
559 	sock_put(&q->sk);
560 err:
561 	if (tap)
562 		dev_put(tap->dev);
563 
564 	rtnl_unlock();
565 	return err;
566 }
567 
568 static int tap_release(struct inode *inode, struct file *file)
569 {
570 	struct tap_queue *q = file->private_data;
571 	tap_put_queue(q);
572 	return 0;
573 }
574 
575 static unsigned int tap_poll(struct file *file, poll_table *wait)
576 {
577 	struct tap_queue *q = file->private_data;
578 	unsigned int mask = POLLERR;
579 
580 	if (!q)
581 		goto out;
582 
583 	mask = 0;
584 	poll_wait(file, &q->wq.wait, wait);
585 
586 	if (!skb_array_empty(&q->skb_array))
587 		mask |= POLLIN | POLLRDNORM;
588 
589 	if (sock_writeable(&q->sk) ||
590 	    (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &q->sock.flags) &&
591 	     sock_writeable(&q->sk)))
592 		mask |= POLLOUT | POLLWRNORM;
593 
594 out:
595 	return mask;
596 }
597 
598 static inline struct sk_buff *tap_alloc_skb(struct sock *sk, size_t prepad,
599 					    size_t len, size_t linear,
600 						int noblock, int *err)
601 {
602 	struct sk_buff *skb;
603 
604 	/* Under a page?  Don't bother with paged skb. */
605 	if (prepad + len < PAGE_SIZE || !linear)
606 		linear = len;
607 
608 	skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
609 				   err, 0);
610 	if (!skb)
611 		return NULL;
612 
613 	skb_reserve(skb, prepad);
614 	skb_put(skb, linear);
615 	skb->data_len = len - linear;
616 	skb->len += len - linear;
617 
618 	return skb;
619 }
620 
621 /* Neighbour code has some assumptions on HH_DATA_MOD alignment */
622 #define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
623 
624 /* Get packet from user space buffer */
625 static ssize_t tap_get_user(struct tap_queue *q, struct msghdr *m,
626 			    struct iov_iter *from, int noblock)
627 {
628 	int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
629 	struct sk_buff *skb;
630 	struct tap_dev *tap;
631 	unsigned long total_len = iov_iter_count(from);
632 	unsigned long len = total_len;
633 	int err;
634 	struct virtio_net_hdr vnet_hdr = { 0 };
635 	int vnet_hdr_len = 0;
636 	int copylen = 0;
637 	int depth;
638 	bool zerocopy = false;
639 	size_t linear;
640 
641 	if (q->flags & IFF_VNET_HDR) {
642 		vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
643 
644 		err = -EINVAL;
645 		if (len < vnet_hdr_len)
646 			goto err;
647 		len -= vnet_hdr_len;
648 
649 		err = -EFAULT;
650 		if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
651 			goto err;
652 		iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
653 		if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
654 		     tap16_to_cpu(q, vnet_hdr.csum_start) +
655 		     tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
656 			     tap16_to_cpu(q, vnet_hdr.hdr_len))
657 			vnet_hdr.hdr_len = cpu_to_tap16(q,
658 				 tap16_to_cpu(q, vnet_hdr.csum_start) +
659 				 tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
660 		err = -EINVAL;
661 		if (tap16_to_cpu(q, vnet_hdr.hdr_len) > len)
662 			goto err;
663 	}
664 
665 	err = -EINVAL;
666 	if (unlikely(len < ETH_HLEN))
667 		goto err;
668 
669 	if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
670 		struct iov_iter i;
671 
672 		copylen = vnet_hdr.hdr_len ?
673 			tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
674 		if (copylen > good_linear)
675 			copylen = good_linear;
676 		else if (copylen < ETH_HLEN)
677 			copylen = ETH_HLEN;
678 		linear = copylen;
679 		i = *from;
680 		iov_iter_advance(&i, copylen);
681 		if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
682 			zerocopy = true;
683 	}
684 
685 	if (!zerocopy) {
686 		copylen = len;
687 		linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
688 		if (linear > good_linear)
689 			linear = good_linear;
690 		else if (linear < ETH_HLEN)
691 			linear = ETH_HLEN;
692 	}
693 
694 	skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,
695 			    linear, noblock, &err);
696 	if (!skb)
697 		goto err;
698 
699 	if (zerocopy)
700 		err = zerocopy_sg_from_iter(skb, from);
701 	else
702 		err = skb_copy_datagram_from_iter(skb, 0, from, len);
703 
704 	if (err)
705 		goto err_kfree;
706 
707 	skb_set_network_header(skb, ETH_HLEN);
708 	skb_reset_mac_header(skb);
709 	skb->protocol = eth_hdr(skb)->h_proto;
710 
711 	if (vnet_hdr_len) {
712 		err = virtio_net_hdr_to_skb(skb, &vnet_hdr,
713 					    tap_is_little_endian(q));
714 		if (err)
715 			goto err_kfree;
716 	}
717 
718 	skb_probe_transport_header(skb, ETH_HLEN);
719 
720 	/* Move network header to the right position for VLAN tagged packets */
721 	if ((skb->protocol == htons(ETH_P_8021Q) ||
722 	     skb->protocol == htons(ETH_P_8021AD)) &&
723 	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
724 		skb_set_network_header(skb, depth);
725 
726 	rcu_read_lock();
727 	tap = rcu_dereference(q->tap);
728 	/* copy skb_ubuf_info for callback when skb has no error */
729 	if (zerocopy) {
730 		skb_shinfo(skb)->destructor_arg = m->msg_control;
731 		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
732 		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
733 	} else if (m && m->msg_control) {
734 		struct ubuf_info *uarg = m->msg_control;
735 		uarg->callback(uarg, false);
736 	}
737 
738 	if (tap) {
739 		skb->dev = tap->dev;
740 		dev_queue_xmit(skb);
741 	} else {
742 		kfree_skb(skb);
743 	}
744 	rcu_read_unlock();
745 
746 	return total_len;
747 
748 err_kfree:
749 	kfree_skb(skb);
750 
751 err:
752 	rcu_read_lock();
753 	tap = rcu_dereference(q->tap);
754 	if (tap && tap->count_tx_dropped)
755 		tap->count_tx_dropped(tap);
756 	rcu_read_unlock();
757 
758 	return err;
759 }
760 
761 static ssize_t tap_write_iter(struct kiocb *iocb, struct iov_iter *from)
762 {
763 	struct file *file = iocb->ki_filp;
764 	struct tap_queue *q = file->private_data;
765 
766 	return tap_get_user(q, NULL, from, file->f_flags & O_NONBLOCK);
767 }
768 
769 /* Put packet to the user space buffer */
770 static ssize_t tap_put_user(struct tap_queue *q,
771 			    const struct sk_buff *skb,
772 			    struct iov_iter *iter)
773 {
774 	int ret;
775 	int vnet_hdr_len = 0;
776 	int vlan_offset = 0;
777 	int total;
778 
779 	if (q->flags & IFF_VNET_HDR) {
780 		struct virtio_net_hdr vnet_hdr;
781 		vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
782 		if (iov_iter_count(iter) < vnet_hdr_len)
783 			return -EINVAL;
784 
785 		if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
786 					    tap_is_little_endian(q), true))
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)
828 {
829 	DEFINE_WAIT(wait);
830 	struct sk_buff *skb;
831 	ssize_t ret = 0;
832 
833 	if (!iov_iter_count(to))
834 		return 0;
835 
836 	while (1) {
837 		if (!noblock)
838 			prepare_to_wait(sk_sleep(&q->sk), &wait,
839 					TASK_INTERRUPTIBLE);
840 
841 		/* Read frames from the queue */
842 		skb = skb_array_consume(&q->skb_array);
843 		if (skb)
844 			break;
845 		if (noblock) {
846 			ret = -EAGAIN;
847 			break;
848 		}
849 		if (signal_pending(current)) {
850 			ret = -ERESTARTSYS;
851 			break;
852 		}
853 		/* Nothing to read, let's sleep */
854 		schedule();
855 	}
856 	if (!noblock)
857 		finish_wait(sk_sleep(&q->sk), &wait);
858 
859 	if (skb) {
860 		ret = tap_put_user(q, skb, to);
861 		if (unlikely(ret < 0))
862 			kfree_skb(skb);
863 		else
864 			consume_skb(skb);
865 	}
866 	return ret;
867 }
868 
869 static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
870 {
871 	struct file *file = iocb->ki_filp;
872 	struct tap_queue *q = file->private_data;
873 	ssize_t len = iov_iter_count(to), ret;
874 
875 	ret = tap_do_read(q, to, file->f_flags & O_NONBLOCK);
876 	ret = min_t(ssize_t, ret, len);
877 	if (ret > 0)
878 		iocb->ki_pos = ret;
879 	return ret;
880 }
881 
882 static struct tap_dev *tap_get_tap_dev(struct tap_queue *q)
883 {
884 	struct tap_dev *tap;
885 
886 	ASSERT_RTNL();
887 	tap = rtnl_dereference(q->tap);
888 	if (tap)
889 		dev_hold(tap->dev);
890 
891 	return tap;
892 }
893 
894 static void tap_put_tap_dev(struct tap_dev *tap)
895 {
896 	dev_put(tap->dev);
897 }
898 
899 static int tap_ioctl_set_queue(struct file *file, unsigned int flags)
900 {
901 	struct tap_queue *q = file->private_data;
902 	struct tap_dev *tap;
903 	int ret;
904 
905 	tap = tap_get_tap_dev(q);
906 	if (!tap)
907 		return -EINVAL;
908 
909 	if (flags & IFF_ATTACH_QUEUE)
910 		ret = tap_enable_queue(tap, file, q);
911 	else if (flags & IFF_DETACH_QUEUE)
912 		ret = tap_disable_queue(q);
913 	else
914 		ret = -EINVAL;
915 
916 	tap_put_tap_dev(tap);
917 	return ret;
918 }
919 
920 static int set_offload(struct tap_queue *q, unsigned long arg)
921 {
922 	struct tap_dev *tap;
923 	netdev_features_t features;
924 	netdev_features_t feature_mask = 0;
925 
926 	tap = rtnl_dereference(q->tap);
927 	if (!tap)
928 		return -ENOLINK;
929 
930 	features = tap->dev->features;
931 
932 	if (arg & TUN_F_CSUM) {
933 		feature_mask = NETIF_F_HW_CSUM;
934 
935 		if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
936 			if (arg & TUN_F_TSO_ECN)
937 				feature_mask |= NETIF_F_TSO_ECN;
938 			if (arg & TUN_F_TSO4)
939 				feature_mask |= NETIF_F_TSO;
940 			if (arg & TUN_F_TSO6)
941 				feature_mask |= NETIF_F_TSO6;
942 		}
943 
944 		if (arg & TUN_F_UFO)
945 			feature_mask |= NETIF_F_UFO;
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 | NETIF_F_UFO))
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 
1036 		q->sk.sk_sndbuf = s;
1037 		return 0;
1038 
1039 	case TUNGETVNETHDRSZ:
1040 		s = q->vnet_hdr_sz;
1041 		if (put_user(s, sp))
1042 			return -EFAULT;
1043 		return 0;
1044 
1045 	case TUNSETVNETHDRSZ:
1046 		if (get_user(s, sp))
1047 			return -EFAULT;
1048 		if (s < (int)sizeof(struct virtio_net_hdr))
1049 			return -EINVAL;
1050 
1051 		q->vnet_hdr_sz = s;
1052 		return 0;
1053 
1054 	case TUNGETVNETLE:
1055 		s = !!(q->flags & TAP_VNET_LE);
1056 		if (put_user(s, sp))
1057 			return -EFAULT;
1058 		return 0;
1059 
1060 	case TUNSETVNETLE:
1061 		if (get_user(s, sp))
1062 			return -EFAULT;
1063 		if (s)
1064 			q->flags |= TAP_VNET_LE;
1065 		else
1066 			q->flags &= ~TAP_VNET_LE;
1067 		return 0;
1068 
1069 	case TUNGETVNETBE:
1070 		return tap_get_vnet_be(q, sp);
1071 
1072 	case TUNSETVNETBE:
1073 		return tap_set_vnet_be(q, sp);
1074 
1075 	case TUNSETOFFLOAD:
1076 		/* let the user check for future flags */
1077 		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
1078 			    TUN_F_TSO_ECN | TUN_F_UFO))
1079 			return -EINVAL;
1080 
1081 		rtnl_lock();
1082 		ret = set_offload(q, arg);
1083 		rtnl_unlock();
1084 		return ret;
1085 
1086 	case SIOCGIFHWADDR:
1087 		rtnl_lock();
1088 		tap = tap_get_tap_dev(q);
1089 		if (!tap) {
1090 			rtnl_unlock();
1091 			return -ENOLINK;
1092 		}
1093 		ret = 0;
1094 		u = tap->dev->type;
1095 		if (copy_to_user(&ifr->ifr_name, tap->dev->name, IFNAMSIZ) ||
1096 		    copy_to_user(&ifr->ifr_hwaddr.sa_data, tap->dev->dev_addr, ETH_ALEN) ||
1097 		    put_user(u, &ifr->ifr_hwaddr.sa_family))
1098 			ret = -EFAULT;
1099 		tap_put_tap_dev(tap);
1100 		rtnl_unlock();
1101 		return ret;
1102 
1103 	case SIOCSIFHWADDR:
1104 		if (copy_from_user(&sa, &ifr->ifr_hwaddr, sizeof(sa)))
1105 			return -EFAULT;
1106 		rtnl_lock();
1107 		tap = tap_get_tap_dev(q);
1108 		if (!tap) {
1109 			rtnl_unlock();
1110 			return -ENOLINK;
1111 		}
1112 		ret = dev_set_mac_address(tap->dev, &sa);
1113 		tap_put_tap_dev(tap);
1114 		rtnl_unlock();
1115 		return ret;
1116 
1117 	default:
1118 		return -EINVAL;
1119 	}
1120 }
1121 
1122 #ifdef CONFIG_COMPAT
1123 static long tap_compat_ioctl(struct file *file, unsigned int cmd,
1124 			     unsigned long arg)
1125 {
1126 	return tap_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
1127 }
1128 #endif
1129 
1130 const struct file_operations tap_fops = {
1131 	.owner		= THIS_MODULE,
1132 	.open		= tap_open,
1133 	.release	= tap_release,
1134 	.read_iter	= tap_read_iter,
1135 	.write_iter	= tap_write_iter,
1136 	.poll		= tap_poll,
1137 	.llseek		= no_llseek,
1138 	.unlocked_ioctl	= tap_ioctl,
1139 #ifdef CONFIG_COMPAT
1140 	.compat_ioctl	= tap_compat_ioctl,
1141 #endif
1142 };
1143 
1144 static int tap_sendmsg(struct socket *sock, struct msghdr *m,
1145 		       size_t total_len)
1146 {
1147 	struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1148 	return tap_get_user(q, m, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);
1149 }
1150 
1151 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
1152 		       size_t total_len, int flags)
1153 {
1154 	struct tap_queue *q = container_of(sock, struct tap_queue, sock);
1155 	int ret;
1156 	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
1157 		return -EINVAL;
1158 	ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT);
1159 	if (ret > total_len) {
1160 		m->msg_flags |= MSG_TRUNC;
1161 		ret = flags & MSG_TRUNC ? ret : total_len;
1162 	}
1163 	return ret;
1164 }
1165 
1166 static int tap_peek_len(struct socket *sock)
1167 {
1168 	struct tap_queue *q = container_of(sock, struct tap_queue,
1169 					       sock);
1170 	return skb_array_peek_len(&q->skb_array);
1171 }
1172 
1173 /* Ops structure to mimic raw sockets with tun */
1174 static const struct proto_ops tap_socket_ops = {
1175 	.sendmsg = tap_sendmsg,
1176 	.recvmsg = tap_recvmsg,
1177 	.peek_len = tap_peek_len,
1178 };
1179 
1180 /* Get an underlying socket object from tun file.  Returns error unless file is
1181  * attached to a device.  The returned object works like a packet socket, it
1182  * can be used for sock_sendmsg/sock_recvmsg.  The caller is responsible for
1183  * holding a reference to the file for as long as the socket is in use. */
1184 struct socket *tap_get_socket(struct file *file)
1185 {
1186 	struct tap_queue *q;
1187 	if (file->f_op != &tap_fops)
1188 		return ERR_PTR(-EINVAL);
1189 	q = file->private_data;
1190 	if (!q)
1191 		return ERR_PTR(-EBADFD);
1192 	return &q->sock;
1193 }
1194 EXPORT_SYMBOL_GPL(tap_get_socket);
1195 
1196 int tap_queue_resize(struct tap_dev *tap)
1197 {
1198 	struct net_device *dev = tap->dev;
1199 	struct tap_queue *q;
1200 	struct skb_array **arrays;
1201 	int n = tap->numqueues;
1202 	int ret, i = 0;
1203 
1204 	arrays = kmalloc(sizeof *arrays * n, GFP_KERNEL);
1205 	if (!arrays)
1206 		return -ENOMEM;
1207 
1208 	list_for_each_entry(q, &tap->queue_list, next)
1209 		arrays[i++] = &q->skb_array;
1210 
1211 	ret = skb_array_resize_multiple(arrays, n,
1212 					dev->tx_queue_len, GFP_KERNEL);
1213 
1214 	kfree(arrays);
1215 	return ret;
1216 }
1217 EXPORT_SYMBOL_GPL(tap_queue_resize);
1218 
1219 static int tap_list_add(dev_t major, const char *device_name)
1220 {
1221 	struct major_info *tap_major;
1222 
1223 	tap_major = kzalloc(sizeof(*tap_major), GFP_ATOMIC);
1224 	if (!tap_major)
1225 		return -ENOMEM;
1226 
1227 	tap_major->major = MAJOR(major);
1228 
1229 	idr_init(&tap_major->minor_idr);
1230 	mutex_init(&tap_major->minor_lock);
1231 
1232 	tap_major->device_name = device_name;
1233 
1234 	list_add_tail_rcu(&tap_major->next, &major_list);
1235 	return 0;
1236 }
1237 
1238 int tap_create_cdev(struct cdev *tap_cdev,
1239 		    dev_t *tap_major, const char *device_name)
1240 {
1241 	int err;
1242 
1243 	err = alloc_chrdev_region(tap_major, 0, TAP_NUM_DEVS, device_name);
1244 	if (err)
1245 		goto out1;
1246 
1247 	cdev_init(tap_cdev, &tap_fops);
1248 	err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS);
1249 	if (err)
1250 		goto out2;
1251 
1252 	err =  tap_list_add(*tap_major, device_name);
1253 	if (err)
1254 		goto out3;
1255 
1256 	return 0;
1257 
1258 out3:
1259 	cdev_del(tap_cdev);
1260 out2:
1261 	unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);
1262 out1:
1263 	return err;
1264 }
1265 EXPORT_SYMBOL_GPL(tap_create_cdev);
1266 
1267 void tap_destroy_cdev(dev_t major, struct cdev *tap_cdev)
1268 {
1269 	struct major_info *tap_major, *tmp;
1270 
1271 	cdev_del(tap_cdev);
1272 	unregister_chrdev_region(major, TAP_NUM_DEVS);
1273 	list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
1274 		if (tap_major->major == MAJOR(major)) {
1275 			idr_destroy(&tap_major->minor_idr);
1276 			list_del_rcu(&tap_major->next);
1277 			kfree_rcu(tap_major, rcu);
1278 		}
1279 	}
1280 }
1281 EXPORT_SYMBOL_GPL(tap_destroy_cdev);
1282 
1283 MODULE_AUTHOR("Arnd Bergmann <arnd@arndb.de>");
1284 MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
1285 MODULE_LICENSE("GPL");
1286