1 // SPDX-License-Identifier: GPL-2.0
2 /* drivers/net/wireless/virt_wifi.c
3  *
4  * A fake implementation of cfg80211_ops that can be tacked on to an ethernet
5  * net_device to make it appear as a wireless connection.
6  *
7  * Copyright (C) 2018 Google, Inc.
8  *
9  * Author: schuffelen@google.com
10  */
11 
12 #include <net/cfg80211.h>
13 #include <net/rtnetlink.h>
14 #include <linux/etherdevice.h>
15 #include <linux/math64.h>
16 #include <linux/module.h>
17 
18 static struct wiphy *common_wiphy;
19 
20 struct virt_wifi_wiphy_priv {
21 	struct delayed_work scan_result;
22 	struct cfg80211_scan_request *scan_request;
23 	bool being_deleted;
24 };
25 
26 static struct ieee80211_channel channel_2ghz = {
27 	.band = NL80211_BAND_2GHZ,
28 	.center_freq = 2432,
29 	.hw_value = 2432,
30 	.max_power = 20,
31 };
32 
33 static struct ieee80211_rate bitrates_2ghz[] = {
34 	{ .bitrate = 10 },
35 	{ .bitrate = 20 },
36 	{ .bitrate = 55 },
37 	{ .bitrate = 110 },
38 	{ .bitrate = 60 },
39 	{ .bitrate = 120 },
40 	{ .bitrate = 240 },
41 };
42 
43 static struct ieee80211_supported_band band_2ghz = {
44 	.channels = &channel_2ghz,
45 	.bitrates = bitrates_2ghz,
46 	.band = NL80211_BAND_2GHZ,
47 	.n_channels = 1,
48 	.n_bitrates = ARRAY_SIZE(bitrates_2ghz),
49 	.ht_cap = {
50 		.ht_supported = true,
51 		.cap = IEEE80211_HT_CAP_SUP_WIDTH_20_40 |
52 		       IEEE80211_HT_CAP_GRN_FLD |
53 		       IEEE80211_HT_CAP_SGI_20 |
54 		       IEEE80211_HT_CAP_SGI_40 |
55 		       IEEE80211_HT_CAP_DSSSCCK40,
56 		.ampdu_factor = 0x3,
57 		.ampdu_density = 0x6,
58 		.mcs = {
59 			.rx_mask = {0xff, 0xff},
60 			.tx_params = IEEE80211_HT_MCS_TX_DEFINED,
61 		},
62 	},
63 };
64 
65 static struct ieee80211_channel channel_5ghz = {
66 	.band = NL80211_BAND_5GHZ,
67 	.center_freq = 5240,
68 	.hw_value = 5240,
69 	.max_power = 20,
70 };
71 
72 static struct ieee80211_rate bitrates_5ghz[] = {
73 	{ .bitrate = 60 },
74 	{ .bitrate = 120 },
75 	{ .bitrate = 240 },
76 };
77 
78 #define RX_MCS_MAP (IEEE80211_VHT_MCS_SUPPORT_0_9 << 0 | \
79 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 2 | \
80 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 4 | \
81 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 6 | \
82 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 8 | \
83 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 10 | \
84 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 12 | \
85 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 14)
86 
87 #define TX_MCS_MAP (IEEE80211_VHT_MCS_SUPPORT_0_9 << 0 | \
88 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 2 | \
89 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 4 | \
90 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 6 | \
91 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 8 | \
92 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 10 | \
93 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 12 | \
94 		    IEEE80211_VHT_MCS_SUPPORT_0_9 << 14)
95 
96 static struct ieee80211_supported_band band_5ghz = {
97 	.channels = &channel_5ghz,
98 	.bitrates = bitrates_5ghz,
99 	.band = NL80211_BAND_5GHZ,
100 	.n_channels = 1,
101 	.n_bitrates = ARRAY_SIZE(bitrates_5ghz),
102 	.ht_cap = {
103 		.ht_supported = true,
104 		.cap = IEEE80211_HT_CAP_SUP_WIDTH_20_40 |
105 		       IEEE80211_HT_CAP_GRN_FLD |
106 		       IEEE80211_HT_CAP_SGI_20 |
107 		       IEEE80211_HT_CAP_SGI_40 |
108 		       IEEE80211_HT_CAP_DSSSCCK40,
109 		.ampdu_factor = 0x3,
110 		.ampdu_density = 0x6,
111 		.mcs = {
112 			.rx_mask = {0xff, 0xff},
113 			.tx_params = IEEE80211_HT_MCS_TX_DEFINED,
114 		},
115 	},
116 	.vht_cap = {
117 		.vht_supported = true,
118 		.cap = IEEE80211_VHT_CAP_MAX_MPDU_LENGTH_11454 |
119 		       IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ |
120 		       IEEE80211_VHT_CAP_RXLDPC |
121 		       IEEE80211_VHT_CAP_SHORT_GI_80 |
122 		       IEEE80211_VHT_CAP_SHORT_GI_160 |
123 		       IEEE80211_VHT_CAP_TXSTBC |
124 		       IEEE80211_VHT_CAP_RXSTBC_1 |
125 		       IEEE80211_VHT_CAP_RXSTBC_2 |
126 		       IEEE80211_VHT_CAP_RXSTBC_3 |
127 		       IEEE80211_VHT_CAP_RXSTBC_4 |
128 		       IEEE80211_VHT_CAP_MAX_A_MPDU_LENGTH_EXPONENT_MASK,
129 		.vht_mcs = {
130 			.rx_mcs_map = cpu_to_le16(RX_MCS_MAP),
131 			.tx_mcs_map = cpu_to_le16(TX_MCS_MAP),
132 		}
133 	},
134 };
135 
136 /* Assigned at module init. Guaranteed locally-administered and unicast. */
137 static u8 fake_router_bssid[ETH_ALEN] __ro_after_init = {};
138 
139 static void virt_wifi_inform_bss(struct wiphy *wiphy)
140 {
141 	u64 tsf = div_u64(ktime_get_boottime_ns(), 1000);
142 	struct cfg80211_bss *informed_bss;
143 	static const struct {
144 		u8 tag;
145 		u8 len;
146 		u8 ssid[8];
147 	} __packed ssid = {
148 		.tag = WLAN_EID_SSID,
149 		.len = 8,
150 		.ssid = "VirtWifi",
151 	};
152 
153 	informed_bss = cfg80211_inform_bss(wiphy, &channel_5ghz,
154 					   CFG80211_BSS_FTYPE_PRESP,
155 					   fake_router_bssid, tsf,
156 					   WLAN_CAPABILITY_ESS, 0,
157 					   (void *)&ssid, sizeof(ssid),
158 					   DBM_TO_MBM(-50), GFP_KERNEL);
159 	cfg80211_put_bss(wiphy, informed_bss);
160 }
161 
162 /* Called with the rtnl lock held. */
163 static int virt_wifi_scan(struct wiphy *wiphy,
164 			  struct cfg80211_scan_request *request)
165 {
166 	struct virt_wifi_wiphy_priv *priv = wiphy_priv(wiphy);
167 
168 	wiphy_debug(wiphy, "scan\n");
169 
170 	if (priv->scan_request || priv->being_deleted)
171 		return -EBUSY;
172 
173 	priv->scan_request = request;
174 	schedule_delayed_work(&priv->scan_result, HZ * 2);
175 
176 	return 0;
177 }
178 
179 /* Acquires and releases the rdev BSS lock. */
180 static void virt_wifi_scan_result(struct work_struct *work)
181 {
182 	struct virt_wifi_wiphy_priv *priv =
183 		container_of(work, struct virt_wifi_wiphy_priv,
184 			     scan_result.work);
185 	struct wiphy *wiphy = priv_to_wiphy(priv);
186 	struct cfg80211_scan_info scan_info = { .aborted = false };
187 
188 	virt_wifi_inform_bss(wiphy);
189 
190 	/* Schedules work which acquires and releases the rtnl lock. */
191 	cfg80211_scan_done(priv->scan_request, &scan_info);
192 	priv->scan_request = NULL;
193 }
194 
195 /* May acquire and release the rdev BSS lock. */
196 static void virt_wifi_cancel_scan(struct wiphy *wiphy)
197 {
198 	struct virt_wifi_wiphy_priv *priv = wiphy_priv(wiphy);
199 
200 	cancel_delayed_work_sync(&priv->scan_result);
201 	/* Clean up dangling callbacks if necessary. */
202 	if (priv->scan_request) {
203 		struct cfg80211_scan_info scan_info = { .aborted = true };
204 		/* Schedules work which acquires and releases the rtnl lock. */
205 		cfg80211_scan_done(priv->scan_request, &scan_info);
206 		priv->scan_request = NULL;
207 	}
208 }
209 
210 struct virt_wifi_netdev_priv {
211 	struct delayed_work connect;
212 	struct net_device *lowerdev;
213 	struct net_device *upperdev;
214 	u32 tx_packets;
215 	u32 tx_failed;
216 	u8 connect_requested_bss[ETH_ALEN];
217 	bool is_up;
218 	bool is_connected;
219 	bool being_deleted;
220 };
221 
222 /* Called with the rtnl lock held. */
223 static int virt_wifi_connect(struct wiphy *wiphy, struct net_device *netdev,
224 			     struct cfg80211_connect_params *sme)
225 {
226 	struct virt_wifi_netdev_priv *priv = netdev_priv(netdev);
227 	bool could_schedule;
228 
229 	if (priv->being_deleted || !priv->is_up)
230 		return -EBUSY;
231 
232 	could_schedule = schedule_delayed_work(&priv->connect, HZ * 2);
233 	if (!could_schedule)
234 		return -EBUSY;
235 
236 	if (sme->bssid) {
237 		ether_addr_copy(priv->connect_requested_bss, sme->bssid);
238 	} else {
239 		virt_wifi_inform_bss(wiphy);
240 		eth_zero_addr(priv->connect_requested_bss);
241 	}
242 
243 	wiphy_debug(wiphy, "connect\n");
244 
245 	return 0;
246 }
247 
248 /* Acquires and releases the rdev event lock. */
249 static void virt_wifi_connect_complete(struct work_struct *work)
250 {
251 	struct virt_wifi_netdev_priv *priv =
252 		container_of(work, struct virt_wifi_netdev_priv, connect.work);
253 	u8 *requested_bss = priv->connect_requested_bss;
254 	bool right_addr = ether_addr_equal(requested_bss, fake_router_bssid);
255 	u16 status = WLAN_STATUS_SUCCESS;
256 
257 	if (is_zero_ether_addr(requested_bss))
258 		requested_bss = NULL;
259 
260 	if (!priv->is_up || (requested_bss && !right_addr))
261 		status = WLAN_STATUS_UNSPECIFIED_FAILURE;
262 	else
263 		priv->is_connected = true;
264 
265 	/* Schedules an event that acquires the rtnl lock. */
266 	cfg80211_connect_result(priv->upperdev, requested_bss, NULL, 0, NULL, 0,
267 				status, GFP_KERNEL);
268 	netif_carrier_on(priv->upperdev);
269 }
270 
271 /* May acquire and release the rdev event lock. */
272 static void virt_wifi_cancel_connect(struct net_device *netdev)
273 {
274 	struct virt_wifi_netdev_priv *priv = netdev_priv(netdev);
275 
276 	/* If there is work pending, clean up dangling callbacks. */
277 	if (cancel_delayed_work_sync(&priv->connect)) {
278 		/* Schedules an event that acquires the rtnl lock. */
279 		cfg80211_connect_result(priv->upperdev,
280 					priv->connect_requested_bss, NULL, 0,
281 					NULL, 0,
282 					WLAN_STATUS_UNSPECIFIED_FAILURE,
283 					GFP_KERNEL);
284 	}
285 }
286 
287 /* Called with the rtnl lock held. Acquires the rdev event lock. */
288 static int virt_wifi_disconnect(struct wiphy *wiphy, struct net_device *netdev,
289 				u16 reason_code)
290 {
291 	struct virt_wifi_netdev_priv *priv = netdev_priv(netdev);
292 
293 	if (priv->being_deleted)
294 		return -EBUSY;
295 
296 	wiphy_debug(wiphy, "disconnect\n");
297 	virt_wifi_cancel_connect(netdev);
298 
299 	cfg80211_disconnected(netdev, reason_code, NULL, 0, true, GFP_KERNEL);
300 	priv->is_connected = false;
301 	netif_carrier_off(netdev);
302 
303 	return 0;
304 }
305 
306 /* Called with the rtnl lock held. */
307 static int virt_wifi_get_station(struct wiphy *wiphy, struct net_device *dev,
308 				 const u8 *mac, struct station_info *sinfo)
309 {
310 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
311 
312 	wiphy_debug(wiphy, "get_station\n");
313 
314 	if (!priv->is_connected || !ether_addr_equal(mac, fake_router_bssid))
315 		return -ENOENT;
316 
317 	sinfo->filled = BIT_ULL(NL80211_STA_INFO_TX_PACKETS) |
318 		BIT_ULL(NL80211_STA_INFO_TX_FAILED) |
319 		BIT_ULL(NL80211_STA_INFO_SIGNAL) |
320 		BIT_ULL(NL80211_STA_INFO_TX_BITRATE);
321 	sinfo->tx_packets = priv->tx_packets;
322 	sinfo->tx_failed = priv->tx_failed;
323 	/* For CFG80211_SIGNAL_TYPE_MBM, value is expressed in _dBm_ */
324 	sinfo->signal = -50;
325 	sinfo->txrate = (struct rate_info) {
326 		.legacy = 10, /* units are 100kbit/s */
327 	};
328 	return 0;
329 }
330 
331 /* Called with the rtnl lock held. */
332 static int virt_wifi_dump_station(struct wiphy *wiphy, struct net_device *dev,
333 				  int idx, u8 *mac, struct station_info *sinfo)
334 {
335 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
336 
337 	wiphy_debug(wiphy, "dump_station\n");
338 
339 	if (idx != 0 || !priv->is_connected)
340 		return -ENOENT;
341 
342 	ether_addr_copy(mac, fake_router_bssid);
343 	return virt_wifi_get_station(wiphy, dev, fake_router_bssid, sinfo);
344 }
345 
346 static const struct cfg80211_ops virt_wifi_cfg80211_ops = {
347 	.scan = virt_wifi_scan,
348 
349 	.connect = virt_wifi_connect,
350 	.disconnect = virt_wifi_disconnect,
351 
352 	.get_station = virt_wifi_get_station,
353 	.dump_station = virt_wifi_dump_station,
354 };
355 
356 /* Acquires and releases the rtnl lock. */
357 static struct wiphy *virt_wifi_make_wiphy(void)
358 {
359 	struct wiphy *wiphy;
360 	struct virt_wifi_wiphy_priv *priv;
361 	int err;
362 
363 	wiphy = wiphy_new(&virt_wifi_cfg80211_ops, sizeof(*priv));
364 
365 	if (!wiphy)
366 		return NULL;
367 
368 	wiphy->max_scan_ssids = 4;
369 	wiphy->max_scan_ie_len = 1000;
370 	wiphy->signal_type = CFG80211_SIGNAL_TYPE_MBM;
371 
372 	wiphy->bands[NL80211_BAND_2GHZ] = &band_2ghz;
373 	wiphy->bands[NL80211_BAND_5GHZ] = &band_5ghz;
374 	wiphy->bands[NL80211_BAND_60GHZ] = NULL;
375 
376 	wiphy->interface_modes = BIT(NL80211_IFTYPE_STATION);
377 
378 	priv = wiphy_priv(wiphy);
379 	priv->being_deleted = false;
380 	priv->scan_request = NULL;
381 	INIT_DELAYED_WORK(&priv->scan_result, virt_wifi_scan_result);
382 
383 	err = wiphy_register(wiphy);
384 	if (err < 0) {
385 		wiphy_free(wiphy);
386 		return NULL;
387 	}
388 
389 	return wiphy;
390 }
391 
392 /* Acquires and releases the rtnl lock. */
393 static void virt_wifi_destroy_wiphy(struct wiphy *wiphy)
394 {
395 	struct virt_wifi_wiphy_priv *priv;
396 
397 	WARN(!wiphy, "%s called with null wiphy", __func__);
398 	if (!wiphy)
399 		return;
400 
401 	priv = wiphy_priv(wiphy);
402 	priv->being_deleted = true;
403 	virt_wifi_cancel_scan(wiphy);
404 
405 	if (wiphy->registered)
406 		wiphy_unregister(wiphy);
407 	wiphy_free(wiphy);
408 }
409 
410 /* Enters and exits a RCU-bh critical section. */
411 static netdev_tx_t virt_wifi_start_xmit(struct sk_buff *skb,
412 					struct net_device *dev)
413 {
414 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
415 
416 	priv->tx_packets++;
417 	if (!priv->is_connected) {
418 		priv->tx_failed++;
419 		return NET_XMIT_DROP;
420 	}
421 
422 	skb->dev = priv->lowerdev;
423 	return dev_queue_xmit(skb);
424 }
425 
426 /* Called with rtnl lock held. */
427 static int virt_wifi_net_device_open(struct net_device *dev)
428 {
429 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
430 
431 	priv->is_up = true;
432 	return 0;
433 }
434 
435 /* Called with rtnl lock held. */
436 static int virt_wifi_net_device_stop(struct net_device *dev)
437 {
438 	struct virt_wifi_netdev_priv *n_priv = netdev_priv(dev);
439 
440 	n_priv->is_up = false;
441 
442 	if (!dev->ieee80211_ptr)
443 		return 0;
444 
445 	virt_wifi_cancel_scan(dev->ieee80211_ptr->wiphy);
446 	virt_wifi_cancel_connect(dev);
447 	netif_carrier_off(dev);
448 
449 	return 0;
450 }
451 
452 static int virt_wifi_net_device_get_iflink(const struct net_device *dev)
453 {
454 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
455 
456 	return priv->lowerdev->ifindex;
457 }
458 
459 static const struct net_device_ops virt_wifi_ops = {
460 	.ndo_start_xmit = virt_wifi_start_xmit,
461 	.ndo_open	= virt_wifi_net_device_open,
462 	.ndo_stop	= virt_wifi_net_device_stop,
463 	.ndo_get_iflink = virt_wifi_net_device_get_iflink,
464 };
465 
466 /* Invoked as part of rtnl lock release. */
467 static void virt_wifi_net_device_destructor(struct net_device *dev)
468 {
469 	/* Delayed past dellink to allow nl80211 to react to the device being
470 	 * deleted.
471 	 */
472 	kfree(dev->ieee80211_ptr);
473 	dev->ieee80211_ptr = NULL;
474 }
475 
476 /* No lock interaction. */
477 static void virt_wifi_setup(struct net_device *dev)
478 {
479 	ether_setup(dev);
480 	dev->netdev_ops = &virt_wifi_ops;
481 	dev->needs_free_netdev  = true;
482 }
483 
484 /* Called in a RCU read critical section from netif_receive_skb */
485 static rx_handler_result_t virt_wifi_rx_handler(struct sk_buff **pskb)
486 {
487 	struct sk_buff *skb = *pskb;
488 	struct virt_wifi_netdev_priv *priv =
489 		rcu_dereference(skb->dev->rx_handler_data);
490 
491 	if (!priv->is_connected)
492 		return RX_HANDLER_PASS;
493 
494 	/* GFP_ATOMIC because this is a packet interrupt handler. */
495 	skb = skb_share_check(skb, GFP_ATOMIC);
496 	if (!skb) {
497 		dev_err(&priv->upperdev->dev, "can't skb_share_check\n");
498 		return RX_HANDLER_CONSUMED;
499 	}
500 
501 	*pskb = skb;
502 	skb->dev = priv->upperdev;
503 	skb->pkt_type = PACKET_HOST;
504 	return RX_HANDLER_ANOTHER;
505 }
506 
507 /* Called with rtnl lock held. */
508 static int virt_wifi_newlink(struct net *src_net, struct net_device *dev,
509 			     struct nlattr *tb[], struct nlattr *data[],
510 			     struct netlink_ext_ack *extack)
511 {
512 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
513 	int err;
514 
515 	if (!tb[IFLA_LINK])
516 		return -EINVAL;
517 
518 	netif_carrier_off(dev);
519 
520 	priv->upperdev = dev;
521 	priv->lowerdev = __dev_get_by_index(src_net,
522 					    nla_get_u32(tb[IFLA_LINK]));
523 
524 	if (!priv->lowerdev)
525 		return -ENODEV;
526 	if (!tb[IFLA_MTU])
527 		dev->mtu = priv->lowerdev->mtu;
528 	else if (dev->mtu > priv->lowerdev->mtu)
529 		return -EINVAL;
530 
531 	err = netdev_rx_handler_register(priv->lowerdev, virt_wifi_rx_handler,
532 					 priv);
533 	if (err) {
534 		dev_err(&priv->lowerdev->dev,
535 			"can't netdev_rx_handler_register: %d\n", err);
536 		return err;
537 	}
538 
539 	eth_hw_addr_inherit(dev, priv->lowerdev);
540 	netif_stacked_transfer_operstate(priv->lowerdev, dev);
541 
542 	SET_NETDEV_DEV(dev, &priv->lowerdev->dev);
543 	dev->ieee80211_ptr = kzalloc(sizeof(*dev->ieee80211_ptr), GFP_KERNEL);
544 
545 	if (!dev->ieee80211_ptr) {
546 		err = -ENOMEM;
547 		goto remove_handler;
548 	}
549 
550 	dev->ieee80211_ptr->iftype = NL80211_IFTYPE_STATION;
551 	dev->ieee80211_ptr->wiphy = common_wiphy;
552 
553 	err = register_netdevice(dev);
554 	if (err) {
555 		dev_err(&priv->lowerdev->dev, "can't register_netdevice: %d\n",
556 			err);
557 		goto free_wireless_dev;
558 	}
559 
560 	err = netdev_upper_dev_link(priv->lowerdev, dev, extack);
561 	if (err) {
562 		dev_err(&priv->lowerdev->dev, "can't netdev_upper_dev_link: %d\n",
563 			err);
564 		goto unregister_netdev;
565 	}
566 
567 	dev->priv_destructor = virt_wifi_net_device_destructor;
568 	priv->being_deleted = false;
569 	priv->is_connected = false;
570 	priv->is_up = false;
571 	INIT_DELAYED_WORK(&priv->connect, virt_wifi_connect_complete);
572 	__module_get(THIS_MODULE);
573 
574 	return 0;
575 unregister_netdev:
576 	unregister_netdevice(dev);
577 free_wireless_dev:
578 	kfree(dev->ieee80211_ptr);
579 	dev->ieee80211_ptr = NULL;
580 remove_handler:
581 	netdev_rx_handler_unregister(priv->lowerdev);
582 
583 	return err;
584 }
585 
586 /* Called with rtnl lock held. */
587 static void virt_wifi_dellink(struct net_device *dev,
588 			      struct list_head *head)
589 {
590 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
591 
592 	if (dev->ieee80211_ptr)
593 		virt_wifi_cancel_scan(dev->ieee80211_ptr->wiphy);
594 
595 	priv->being_deleted = true;
596 	virt_wifi_cancel_connect(dev);
597 	netif_carrier_off(dev);
598 
599 	netdev_rx_handler_unregister(priv->lowerdev);
600 	netdev_upper_dev_unlink(priv->lowerdev, dev);
601 
602 	unregister_netdevice_queue(dev, head);
603 	module_put(THIS_MODULE);
604 
605 	/* Deleting the wiphy is handled in the module destructor. */
606 }
607 
608 static struct rtnl_link_ops virt_wifi_link_ops = {
609 	.kind		= "virt_wifi",
610 	.setup		= virt_wifi_setup,
611 	.newlink	= virt_wifi_newlink,
612 	.dellink	= virt_wifi_dellink,
613 	.priv_size	= sizeof(struct virt_wifi_netdev_priv),
614 };
615 
616 static bool netif_is_virt_wifi_dev(const struct net_device *dev)
617 {
618 	return rcu_access_pointer(dev->rx_handler) == virt_wifi_rx_handler;
619 }
620 
621 static int virt_wifi_event(struct notifier_block *this, unsigned long event,
622 			   void *ptr)
623 {
624 	struct net_device *lower_dev = netdev_notifier_info_to_dev(ptr);
625 	struct virt_wifi_netdev_priv *priv;
626 	struct net_device *upper_dev;
627 	LIST_HEAD(list_kill);
628 
629 	if (!netif_is_virt_wifi_dev(lower_dev))
630 		return NOTIFY_DONE;
631 
632 	switch (event) {
633 	case NETDEV_UNREGISTER:
634 		priv = rtnl_dereference(lower_dev->rx_handler_data);
635 		if (!priv)
636 			return NOTIFY_DONE;
637 
638 		upper_dev = priv->upperdev;
639 
640 		upper_dev->rtnl_link_ops->dellink(upper_dev, &list_kill);
641 		unregister_netdevice_many(&list_kill);
642 		break;
643 	}
644 
645 	return NOTIFY_DONE;
646 }
647 
648 static struct notifier_block virt_wifi_notifier = {
649 	.notifier_call = virt_wifi_event,
650 };
651 
652 /* Acquires and releases the rtnl lock. */
653 static int __init virt_wifi_init_module(void)
654 {
655 	int err;
656 
657 	/* Guaranteed to be locally-administered and not multicast. */
658 	eth_random_addr(fake_router_bssid);
659 
660 	err = register_netdevice_notifier(&virt_wifi_notifier);
661 	if (err)
662 		return err;
663 
664 	err = -ENOMEM;
665 	common_wiphy = virt_wifi_make_wiphy();
666 	if (!common_wiphy)
667 		goto notifier;
668 
669 	err = rtnl_link_register(&virt_wifi_link_ops);
670 	if (err)
671 		goto destroy_wiphy;
672 
673 	return 0;
674 
675 destroy_wiphy:
676 	virt_wifi_destroy_wiphy(common_wiphy);
677 notifier:
678 	unregister_netdevice_notifier(&virt_wifi_notifier);
679 	return err;
680 }
681 
682 /* Acquires and releases the rtnl lock. */
683 static void __exit virt_wifi_cleanup_module(void)
684 {
685 	/* Will delete any devices that depend on the wiphy. */
686 	rtnl_link_unregister(&virt_wifi_link_ops);
687 	virt_wifi_destroy_wiphy(common_wiphy);
688 	unregister_netdevice_notifier(&virt_wifi_notifier);
689 }
690 
691 module_init(virt_wifi_init_module);
692 module_exit(virt_wifi_cleanup_module);
693 
694 MODULE_LICENSE("GPL v2");
695 MODULE_AUTHOR("Cody Schuffelen <schuffelen@google.com>");
696 MODULE_DESCRIPTION("Driver for a wireless wrapper of ethernet devices");
697 MODULE_ALIAS_RTNL_LINK("virt_wifi");
698