net/mac80211/link.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * MLO link handling
  *
  * Copyright (C) 2022-2023 Intel Corporation
  */
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <net/mac80211.h>
 #include "ieee80211_i.h"
 #include "driver-ops.h"
 #include "key.h"
 #include "debugfs_netdev.h"

 void ieee80211_link_setup(struct ieee80211_link_data *link)
 {
 	if (link->sdata->vif.type == NL80211_IFTYPE_STATION)
 		ieee80211_mgd_setup_link(link);
 }

 void ieee80211_link_init(struct ieee80211_sub_if_data *sdata,
 			 int link_id,
 			 struct ieee80211_link_data *link,
 			 struct ieee80211_bss_conf *link_conf)
 {
 	bool deflink = link_id < 0;

 	if (link_id < 0)
 		link_id = 0;

 	rcu_assign_pointer(sdata->vif.link_conf[link_id], link_conf);
 	rcu_assign_pointer(sdata->link[link_id], link);

 	link->sdata = sdata;
 	link->link_id = link_id;
 	link->conf = link_conf;
 	link_conf->link_id = link_id;
 	link_conf->vif = &sdata->vif;

 	INIT_WORK(&link->csa_finalize_work,
 		  ieee80211_csa_finalize_work);
 	INIT_WORK(&link->color_change_finalize_work,
 		  ieee80211_color_change_finalize_work);
 	INIT_DELAYED_WORK(&link->color_collision_detect_work,
 			  ieee80211_color_collision_detection_work);
 	INIT_LIST_HEAD(&link->assigned_chanctx_list);
 	INIT_LIST_HEAD(&link->reserved_chanctx_list);
 	INIT_DELAYED_WORK(&link->dfs_cac_timer_work,
 			  ieee80211_dfs_cac_timer_work);

 	if (!deflink) {
 		switch (sdata->vif.type) {
 		case NL80211_IFTYPE_AP:
 			ether_addr_copy(link_conf->addr,
 					sdata->wdev.links[link_id].addr);
 			link_conf->bssid = link_conf->addr;
 			WARN_ON(!(sdata->wdev.valid_links & BIT(link_id)));
 			break;
 		case NL80211_IFTYPE_STATION:
 			/* station sets the bssid in ieee80211_mgd_setup_link */
 			break;
 		default:
 			WARN_ON(1);
 		}

 		ieee80211_link_debugfs_add(link);
 	}
 }

 void ieee80211_link_stop(struct ieee80211_link_data *link)
 {
 	if (link->sdata->vif.type == NL80211_IFTYPE_STATION)
 		ieee80211_mgd_stop_link(link);

 	cancel_delayed_work_sync(&link->color_collision_detect_work);
 	ieee80211_link_release_channel(link);
 }

 struct link_container {
 	struct ieee80211_link_data data;
 	struct ieee80211_bss_conf conf;
 };

 static void ieee80211_tear_down_links(struct ieee80211_sub_if_data *sdata,
 				      struct link_container **links, u16 mask)
 {
 	struct ieee80211_link_data *link;
 	LIST_HEAD(keys);
 	unsigned int link_id;

 	for (link_id = 0; link_id < IEEE80211_MLD_MAX_NUM_LINKS; link_id++) {
 		if (!(mask & BIT(link_id)))
 			continue;
 		link = &links[link_id]->data;
 		if (link_id == 0 && !link)
 			link = &sdata->deflink;
 		if (WARN_ON(!link))
 			continue;
 		ieee80211_remove_link_keys(link, &keys);
 		ieee80211_link_debugfs_remove(link);
 		ieee80211_link_stop(link);
 	}

 	synchronize_rcu();

 	ieee80211_free_key_list(sdata->local, &keys);
 }

 static void ieee80211_free_links(struct ieee80211_sub_if_data *sdata,
 				 struct link_container **links)
 {
 	unsigned int link_id;

 	for (link_id = 0; link_id < IEEE80211_MLD_MAX_NUM_LINKS; link_id++)
 		kfree(links[link_id]);
 }

 static int ieee80211_check_dup_link_addrs(struct ieee80211_sub_if_data *sdata)
 {
 	unsigned int i, j;

 	for (i = 0; i < IEEE80211_MLD_MAX_NUM_LINKS; i++) {
 		struct ieee80211_link_data *link1;

 		link1 = sdata_dereference(sdata->link[i], sdata);
 		if (!link1)
 			continue;
 		for (j = i + 1; j < IEEE80211_MLD_MAX_NUM_LINKS; j++) {
 			struct ieee80211_link_data *link2;

 			link2 = sdata_dereference(sdata->link[j], sdata);
 			if (!link2)
 				continue;

 			if (ether_addr_equal(link1->conf->addr,
 					     link2->conf->addr))
 				return -EALREADY;
 		}
 	}

 	return 0;
 }

 static void ieee80211_set_vif_links_bitmaps(struct ieee80211_sub_if_data *sdata,
 					    u16 valid_links, u16 dormant_links)
 {
 	sdata->vif.valid_links = valid_links;
 	sdata->vif.dormant_links = dormant_links;

 	if (!valid_links ||
 	    WARN((~valid_links & dormant_links) ||
 		 !(valid_links & ~dormant_links),
 		 "Invalid links: valid=0x%x, dormant=0x%x",
 		 valid_links, dormant_links)) {
 		sdata->vif.active_links = 0;
 		sdata->vif.dormant_links = 0;
 		return;
 	}

 	switch (sdata->vif.type) {
 	case NL80211_IFTYPE_AP:
 		/* in an AP all links are always active */
 		sdata->vif.active_links = valid_links;

 		/* AP links are not expected to be disabled */
 		WARN_ON(dormant_links);
 		break;
 	case NL80211_IFTYPE_STATION:
 		if (sdata->vif.active_links)
 			break;
 		sdata->vif.active_links = valid_links & ~dormant_links;
 		WARN_ON(hweight16(sdata->vif.active_links) > 1);
 		break;
 	default:
 		WARN_ON(1);
 	}
 }

 static int ieee80211_vif_update_links(struct ieee80211_sub_if_data *sdata,
 				      struct link_container **to_free,
 				      u16 new_links, u16 dormant_links)
 {
 	u16 old_links = sdata->vif.valid_links;
 	u16 old_active = sdata->vif.active_links;
 	unsigned long add = new_links & ~old_links;
 	unsigned long rem = old_links & ~new_links;
 	unsigned int link_id;
 	int ret;
 	struct link_container *links[IEEE80211_MLD_MAX_NUM_LINKS] = {}, *link;
 	struct ieee80211_bss_conf *old[IEEE80211_MLD_MAX_NUM_LINKS];
 	struct ieee80211_link_data *old_data[IEEE80211_MLD_MAX_NUM_LINKS];
 	bool use_deflink = old_links == 0; /* set for error case */

 	sdata_assert_lock(sdata);

 	memset(to_free, 0, sizeof(links));

 	if (old_links == new_links)
 		return 0;

 	/* if there were no old links, need to clear the pointers to deflink */
 	if (!old_links)
 		rem |= BIT(0);

 	/* allocate new link structures first */
 	for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
 		link = kzalloc(sizeof(*link), GFP_KERNEL);
 		if (!link) {
 			ret = -ENOMEM;
 			goto free;
 		}
 		links[link_id] = link;
 	}

 	/* keep track of the old pointers for the driver */
 	BUILD_BUG_ON(sizeof(old) != sizeof(sdata->vif.link_conf));
 	memcpy(old, sdata->vif.link_conf, sizeof(old));
 	/* and for us in error cases */
 	BUILD_BUG_ON(sizeof(old_data) != sizeof(sdata->link));
 	memcpy(old_data, sdata->link, sizeof(old_data));

 	/* grab old links to free later */
 	for_each_set_bit(link_id, &rem, IEEE80211_MLD_MAX_NUM_LINKS) {
 		if (rcu_access_pointer(sdata->link[link_id]) != &sdata->deflink) {
 			/*
 			 * we must have allocated the data through this path so
 			 * we know we can free both at the same time
 			 */
 			to_free[link_id] = container_of(rcu_access_pointer(sdata->link[link_id]),
 							typeof(*links[link_id]),
 							data);
 		}

 		RCU_INIT_POINTER(sdata->link[link_id], NULL);
 		RCU_INIT_POINTER(sdata->vif.link_conf[link_id], NULL);
 	}

 	/* link them into data structures */
 	for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
 		WARN_ON(!use_deflink &&
 			rcu_access_pointer(sdata->link[link_id]) == &sdata->deflink);

 		link = links[link_id];
 		ieee80211_link_init(sdata, link_id, &link->data, &link->conf);
 		ieee80211_link_setup(&link->data);
 	}

 	if (new_links == 0)
 		ieee80211_link_init(sdata, -1, &sdata->deflink,
 				    &sdata->vif.bss_conf);

 	ret = ieee80211_check_dup_link_addrs(sdata);
 	if (!ret) {
 		/* for keys we will not be able to undo this */
 		ieee80211_tear_down_links(sdata, to_free, rem);

 		ieee80211_set_vif_links_bitmaps(sdata, new_links, dormant_links);

 		/* tell the driver */
 		ret = drv_change_vif_links(sdata->local, sdata,
 					   old_links & old_active,
 					   new_links & sdata->vif.active_links,
 					   old);
 	}

 	if (ret) {
 		/* restore config */
 		memcpy(sdata->link, old_data, sizeof(old_data));
 		memcpy(sdata->vif.link_conf, old, sizeof(old));
 		ieee80211_set_vif_links_bitmaps(sdata, old_links, dormant_links);
 		/* and free (only) the newly allocated links */
 		memset(to_free, 0, sizeof(links));
 		goto free;
 	}

 	/* use deflink/bss_conf again if and only if there are no more links */
 	use_deflink = new_links == 0;

 	goto deinit;
 free:
 	/* if we failed during allocation, only free all */
 	for (link_id = 0; link_id < IEEE80211_MLD_MAX_NUM_LINKS; link_id++) {
 		kfree(links[link_id]);
 		links[link_id] = NULL;
 	}
 deinit:
 	if (use_deflink)
 		ieee80211_link_init(sdata, -1, &sdata->deflink,
 				    &sdata->vif.bss_conf);
 	return ret;
 }

 int ieee80211_vif_set_links(struct ieee80211_sub_if_data *sdata,
 			    u16 new_links, u16 dormant_links)
 {
 	struct link_container *links[IEEE80211_MLD_MAX_NUM_LINKS];
 	int ret;

 	ret = ieee80211_vif_update_links(sdata, links, new_links,
 					 dormant_links);
 	ieee80211_free_links(sdata, links);

 	return ret;
 }

 void ieee80211_vif_clear_links(struct ieee80211_sub_if_data *sdata)
 {
 	struct link_container *links[IEEE80211_MLD_MAX_NUM_LINKS];

 	/*
 	 * The locking here is different because when we free links
 	 * in the station case we need to be able to cancel_work_sync()
 	 * something that also takes the lock.
 	 */

 	sdata_lock(sdata);
 	ieee80211_vif_update_links(sdata, links, 0, 0);
 	sdata_unlock(sdata);

 	ieee80211_free_links(sdata, links);
 }

 static int _ieee80211_set_active_links(struct ieee80211_sub_if_data *sdata,
 				       u16 active_links)
 {
 	struct ieee80211_bss_conf *link_confs[IEEE80211_MLD_MAX_NUM_LINKS];
 	struct ieee80211_local *local = sdata->local;
 	u16 old_active = sdata->vif.active_links;
 	unsigned long rem = old_active & ~active_links;
 	unsigned long add = active_links & ~old_active;
 	struct sta_info *sta;
 	unsigned int link_id;
 	int ret, i;

 	if (!ieee80211_sdata_running(sdata))
 		return -ENETDOWN;

 	if (sdata->vif.type != NL80211_IFTYPE_STATION)
 		return -EINVAL;

 	if (active_links & ~ieee80211_vif_usable_links(&sdata->vif))
 		return -EINVAL;

 	/* nothing to do */
 	if (old_active == active_links)
 		return 0;

 	for (i = 0; i < IEEE80211_MLD_MAX_NUM_LINKS; i++)
 		link_confs[i] = sdata_dereference(sdata->vif.link_conf[i],
 						  sdata);

 	if (add) {
 		sdata->vif.active_links |= active_links;
 		ret = drv_change_vif_links(local, sdata,
 					   old_active,
 					   sdata->vif.active_links,
 					   link_confs);
 		if (ret) {
 			sdata->vif.active_links = old_active;
 			return ret;
 		}
 	}

 	for_each_set_bit(link_id, &rem, IEEE80211_MLD_MAX_NUM_LINKS) {
 		struct ieee80211_link_data *link;

 		link = sdata_dereference(sdata->link[link_id], sdata);

 		/* FIXME: kill TDLS connections on the link */

 		ieee80211_link_release_channel(link);
 	}

 	list_for_each_entry(sta, &local->sta_list, list) {
 		if (sdata != sta->sdata)
 			continue;

 		/* this is very temporary, but do it anyway */
 		__ieee80211_sta_recalc_aggregates(sta,
 						  old_active | active_links);

 		ret = drv_change_sta_links(local, sdata, &sta->sta,
 					   old_active,
 					   old_active | active_links);
 		WARN_ON_ONCE(ret);
 	}

 	ret = ieee80211_key_switch_links(sdata, rem, add);
 	WARN_ON_ONCE(ret);

 	list_for_each_entry(sta, &local->sta_list, list) {
 		if (sdata != sta->sdata)
 			continue;

 		__ieee80211_sta_recalc_aggregates(sta, active_links);

 		ret = drv_change_sta_links(local, sdata, &sta->sta,
 					   old_active | active_links,
 					   active_links);
 		WARN_ON_ONCE(ret);

 		/*
 		 * Do it again, just in case - the driver might very
 		 * well have called ieee80211_sta_recalc_aggregates()
 		 * from there when filling in the new links, which
 		 * would set it wrong since the vif's active links are
 		 * not switched yet...
 		 */
 		__ieee80211_sta_recalc_aggregates(sta, active_links);
 	}

 	for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
 		struct ieee80211_link_data *link;

 		link = sdata_dereference(sdata->link[link_id], sdata);

 		ret = ieee80211_link_use_channel(link, &link->conf->chandef,
 						 IEEE80211_CHANCTX_SHARED);
 		WARN_ON_ONCE(ret);

 		ieee80211_mgd_set_link_qos_params(link);
 		ieee80211_link_info_change_notify(sdata, link,
 						  BSS_CHANGED_ERP_CTS_PROT |
 						  BSS_CHANGED_ERP_PREAMBLE |
 						  BSS_CHANGED_ERP_SLOT |
 						  BSS_CHANGED_HT |
 						  BSS_CHANGED_BASIC_RATES |
 						  BSS_CHANGED_BSSID |
 						  BSS_CHANGED_CQM |
 						  BSS_CHANGED_QOS |
 						  BSS_CHANGED_TXPOWER |
 						  BSS_CHANGED_BANDWIDTH |
 						  BSS_CHANGED_TWT |
 						  BSS_CHANGED_HE_OBSS_PD |
 						  BSS_CHANGED_HE_BSS_COLOR);
 	}

 	old_active = sdata->vif.active_links;
 	sdata->vif.active_links = active_links;

 	if (rem) {
 		ret = drv_change_vif_links(local, sdata, old_active,
 					   active_links, link_confs);
 		WARN_ON_ONCE(ret);
 	}

 	return 0;
 }

 int __ieee80211_set_active_links(struct ieee80211_vif *vif, u16 active_links)
 {
 	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
 	struct ieee80211_local *local = sdata->local;
 	u16 old_active;
 	int ret;

 	sdata_assert_lock(sdata);
 	mutex_lock(&local->sta_mtx);
 	mutex_lock(&local->mtx);
 	mutex_lock(&local->key_mtx);
 	old_active = sdata->vif.active_links;
 	if (old_active & active_links) {
 		/*
 		 * if there's at least one link that stays active across
 		 * the change then switch to it (to those) first, and
 		 * then enable the additional links
 		 */
 		ret = _ieee80211_set_active_links(sdata,
 						  old_active & active_links);
 		if (!ret)
 			ret = _ieee80211_set_active_links(sdata, active_links);
 	} else {
 		/* otherwise switch directly */
 		ret = _ieee80211_set_active_links(sdata, active_links);
 	}
 	mutex_unlock(&local->key_mtx);
 	mutex_unlock(&local->mtx);
 	mutex_unlock(&local->sta_mtx);

 	return ret;
 }

 int ieee80211_set_active_links(struct ieee80211_vif *vif, u16 active_links)
 {
 	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
 	int ret;

 	sdata_lock(sdata);
 	ret = __ieee80211_set_active_links(vif, active_links);
 	sdata_unlock(sdata);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(ieee80211_set_active_links);

 void ieee80211_set_active_links_async(struct ieee80211_vif *vif,
 				      u16 active_links)
 {
 	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);

 	if (!ieee80211_sdata_running(sdata))
 		return;

 	if (sdata->vif.type != NL80211_IFTYPE_STATION)
 		return;

 	if (active_links & ~ieee80211_vif_usable_links(&sdata->vif))
 		return;

 	/* nothing to do */
 	if (sdata->vif.active_links == active_links)
 		return;

 	sdata->desired_active_links = active_links;
 	schedule_work(&sdata->activate_links_work);
 }
 EXPORT_SYMBOL_GPL(ieee80211_set_active_links_async);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* MLO link handling
	*
	* Copyright (C) 2022-2023 Intel Corporation
	*/
	#include <linux/slab.h>
	#include <linux/kernel.h>
	#include <net/mac80211.h>
	#include "ieee80211_i.h"
	#include "driver-ops.h"
	#include "key.h"
	#include "debugfs_netdev.h"

	void ieee80211_link_setup(struct ieee80211_link_data *link)
	{
	if (link->sdata->vif.type == NL80211_IFTYPE_STATION)
	ieee80211_mgd_setup_link(link);
	}

	void ieee80211_link_init(struct ieee80211_sub_if_data *sdata,
	int link_id,
	struct ieee80211_link_data *link,
	struct ieee80211_bss_conf *link_conf)
	{
	bool deflink = link_id < 0;

	if (link_id < 0)
	link_id = 0;

	rcu_assign_pointer(sdata->vif.link_conf[link_id], link_conf);
	rcu_assign_pointer(sdata->link[link_id], link);

	link->sdata = sdata;
	link->link_id = link_id;
	link->conf = link_conf;
	link_conf->link_id = link_id;
	link_conf->vif = &sdata->vif;

	INIT_WORK(&link->csa_finalize_work,
	ieee80211_csa_finalize_work);
	INIT_WORK(&link->color_change_finalize_work,
	ieee80211_color_change_finalize_work);
	INIT_DELAYED_WORK(&link->color_collision_detect_work,
	ieee80211_color_collision_detection_work);
	INIT_LIST_HEAD(&link->assigned_chanctx_list);
	INIT_LIST_HEAD(&link->reserved_chanctx_list);
	INIT_DELAYED_WORK(&link->dfs_cac_timer_work,
	ieee80211_dfs_cac_timer_work);

	if (!deflink) {
	switch (sdata->vif.type) {
	case NL80211_IFTYPE_AP:
	ether_addr_copy(link_conf->addr,
	sdata->wdev.links[link_id].addr);
	link_conf->bssid = link_conf->addr;
	WARN_ON(!(sdata->wdev.valid_links & BIT(link_id)));
	break;
	case NL80211_IFTYPE_STATION:
	/* station sets the bssid in ieee80211_mgd_setup_link */
	break;
	default:
	WARN_ON(1);
	}

	ieee80211_link_debugfs_add(link);
	}
	}

	void ieee80211_link_stop(struct ieee80211_link_data *link)
	{
	if (link->sdata->vif.type == NL80211_IFTYPE_STATION)
	ieee80211_mgd_stop_link(link);

	cancel_delayed_work_sync(&link->color_collision_detect_work);
	ieee80211_link_release_channel(link);
	}

	struct link_container {
	struct ieee80211_link_data data;
	struct ieee80211_bss_conf conf;
	};

	static void ieee80211_tear_down_links(struct ieee80211_sub_if_data *sdata,
	struct link_container **links, u16 mask)
	{
	struct ieee80211_link_data *link;
	LIST_HEAD(keys);
	unsigned int link_id;

	for (link_id = 0; link_id < IEEE80211_MLD_MAX_NUM_LINKS; link_id++) {
	if (!(mask & BIT(link_id)))
	continue;
	link = &links[link_id]->data;
	if (link_id == 0 && !link)
	link = &sdata->deflink;
	if (WARN_ON(!link))
	continue;
	ieee80211_remove_link_keys(link, &keys);
	ieee80211_link_debugfs_remove(link);
	ieee80211_link_stop(link);
	}

	synchronize_rcu();

	ieee80211_free_key_list(sdata->local, &keys);
	}

	static void ieee80211_free_links(struct ieee80211_sub_if_data *sdata,
	struct link_container **links)
	{
	unsigned int link_id;

	for (link_id = 0; link_id < IEEE80211_MLD_MAX_NUM_LINKS; link_id++)
	kfree(links[link_id]);
	}

	static int ieee80211_check_dup_link_addrs(struct ieee80211_sub_if_data *sdata)
	{
	unsigned int i, j;

	for (i = 0; i < IEEE80211_MLD_MAX_NUM_LINKS; i++) {
	struct ieee80211_link_data *link1;

	link1 = sdata_dereference(sdata->link[i], sdata);
	if (!link1)
	continue;
	for (j = i + 1; j < IEEE80211_MLD_MAX_NUM_LINKS; j++) {
	struct ieee80211_link_data *link2;

	link2 = sdata_dereference(sdata->link[j], sdata);
	if (!link2)
	continue;

	if (ether_addr_equal(link1->conf->addr,
	link2->conf->addr))
	return -EALREADY;
	}
	}

	return 0;
	}

	static void ieee80211_set_vif_links_bitmaps(struct ieee80211_sub_if_data *sdata,
	u16 valid_links, u16 dormant_links)
	{
	sdata->vif.valid_links = valid_links;
	sdata->vif.dormant_links = dormant_links;

	if (!valid_links \|\|
	WARN((~valid_links & dormant_links) \|\|
	!(valid_links & ~dormant_links),
	"Invalid links: valid=0x%x, dormant=0x%x",
	valid_links, dormant_links)) {
	sdata->vif.active_links = 0;
	sdata->vif.dormant_links = 0;
	return;
	}

	switch (sdata->vif.type) {
	case NL80211_IFTYPE_AP:
	/* in an AP all links are always active */
	sdata->vif.active_links = valid_links;

	/* AP links are not expected to be disabled */
	WARN_ON(dormant_links);
	break;
	case NL80211_IFTYPE_STATION:
	if (sdata->vif.active_links)
	break;
	sdata->vif.active_links = valid_links & ~dormant_links;
	WARN_ON(hweight16(sdata->vif.active_links) > 1);
	break;
	default:
	WARN_ON(1);
	}
	}

	static int ieee80211_vif_update_links(struct ieee80211_sub_if_data *sdata,
	struct link_container **to_free,
	u16 new_links, u16 dormant_links)
	{
	u16 old_links = sdata->vif.valid_links;
	u16 old_active = sdata->vif.active_links;
	unsigned long add = new_links & ~old_links;
	unsigned long rem = old_links & ~new_links;
	unsigned int link_id;
	int ret;
	struct link_container links[IEEE80211_MLD_MAX_NUM_LINKS] = {}, link;
	struct ieee80211_bss_conf *old[IEEE80211_MLD_MAX_NUM_LINKS];
	struct ieee80211_link_data *old_data[IEEE80211_MLD_MAX_NUM_LINKS];
	bool use_deflink = old_links == 0; /* set for error case */

	sdata_assert_lock(sdata);

	memset(to_free, 0, sizeof(links));

	if (old_links == new_links)
	return 0;

	/* if there were no old links, need to clear the pointers to deflink */
	if (!old_links)
	rem \|= BIT(0);

	/* allocate new link structures first */
	for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
	link = kzalloc(sizeof(*link), GFP_KERNEL);
	if (!link) {
	ret = -ENOMEM;
	goto free;
	}
	links[link_id] = link;
	}

	/* keep track of the old pointers for the driver */
	BUILD_BUG_ON(sizeof(old) != sizeof(sdata->vif.link_conf));
	memcpy(old, sdata->vif.link_conf, sizeof(old));
	/* and for us in error cases */
	BUILD_BUG_ON(sizeof(old_data) != sizeof(sdata->link));
	memcpy(old_data, sdata->link, sizeof(old_data));

	/* grab old links to free later */
	for_each_set_bit(link_id, &rem, IEEE80211_MLD_MAX_NUM_LINKS) {
	if (rcu_access_pointer(sdata->link[link_id]) != &sdata->deflink) {
	/*
	* we must have allocated the data through this path so
	* we know we can free both at the same time
	*/
	to_free[link_id] = container_of(rcu_access_pointer(sdata->link[link_id]),
	typeof(*links[link_id]),
	data);
	}

	RCU_INIT_POINTER(sdata->link[link_id], NULL);
	RCU_INIT_POINTER(sdata->vif.link_conf[link_id], NULL);
	}

	/* link them into data structures */
	for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
	WARN_ON(!use_deflink &&
	rcu_access_pointer(sdata->link[link_id]) == &sdata->deflink);

	link = links[link_id];
	ieee80211_link_init(sdata, link_id, &link->data, &link->conf);
	ieee80211_link_setup(&link->data);
	}

	if (new_links == 0)
	ieee80211_link_init(sdata, -1, &sdata->deflink,
	&sdata->vif.bss_conf);

	ret = ieee80211_check_dup_link_addrs(sdata);
	if (!ret) {
	/* for keys we will not be able to undo this */
	ieee80211_tear_down_links(sdata, to_free, rem);

	ieee80211_set_vif_links_bitmaps(sdata, new_links, dormant_links);

	/* tell the driver */
	ret = drv_change_vif_links(sdata->local, sdata,
	old_links & old_active,
	new_links & sdata->vif.active_links,
	old);
	}

	if (ret) {
	/* restore config */
	memcpy(sdata->link, old_data, sizeof(old_data));
	memcpy(sdata->vif.link_conf, old, sizeof(old));
	ieee80211_set_vif_links_bitmaps(sdata, old_links, dormant_links);
	/* and free (only) the newly allocated links */
	memset(to_free, 0, sizeof(links));
	goto free;
	}

	/* use deflink/bss_conf again if and only if there are no more links */
	use_deflink = new_links == 0;

	goto deinit;
	free:
	/* if we failed during allocation, only free all */
	for (link_id = 0; link_id < IEEE80211_MLD_MAX_NUM_LINKS; link_id++) {
	kfree(links[link_id]);
	links[link_id] = NULL;
	}
	deinit:
	if (use_deflink)
	ieee80211_link_init(sdata, -1, &sdata->deflink,
	&sdata->vif.bss_conf);
	return ret;
	}

	int ieee80211_vif_set_links(struct ieee80211_sub_if_data *sdata,
	u16 new_links, u16 dormant_links)
	{
	struct link_container *links[IEEE80211_MLD_MAX_NUM_LINKS];
	int ret;

	ret = ieee80211_vif_update_links(sdata, links, new_links,
	dormant_links);
	ieee80211_free_links(sdata, links);

	return ret;
	}

	void ieee80211_vif_clear_links(struct ieee80211_sub_if_data *sdata)
	{
	struct link_container *links[IEEE80211_MLD_MAX_NUM_LINKS];

	/*
	* The locking here is different because when we free links
	* in the station case we need to be able to cancel_work_sync()
	* something that also takes the lock.
	*/

	sdata_lock(sdata);
	ieee80211_vif_update_links(sdata, links, 0, 0);
	sdata_unlock(sdata);

	ieee80211_free_links(sdata, links);
	}

	static int _ieee80211_set_active_links(struct ieee80211_sub_if_data *sdata,
	u16 active_links)
	{
	struct ieee80211_bss_conf *link_confs[IEEE80211_MLD_MAX_NUM_LINKS];
	struct ieee80211_local *local = sdata->local;
	u16 old_active = sdata->vif.active_links;
	unsigned long rem = old_active & ~active_links;
	unsigned long add = active_links & ~old_active;
	struct sta_info *sta;
	unsigned int link_id;
	int ret, i;

	if (!ieee80211_sdata_running(sdata))
	return -ENETDOWN;

	if (sdata->vif.type != NL80211_IFTYPE_STATION)
	return -EINVAL;

	if (active_links & ~ieee80211_vif_usable_links(&sdata->vif))
	return -EINVAL;

	/* nothing to do */
	if (old_active == active_links)
	return 0;

	for (i = 0; i < IEEE80211_MLD_MAX_NUM_LINKS; i++)
	link_confs[i] = sdata_dereference(sdata->vif.link_conf[i],
	sdata);

	if (add) {
	sdata->vif.active_links \|= active_links;
	ret = drv_change_vif_links(local, sdata,
	old_active,
	sdata->vif.active_links,
	link_confs);
	if (ret) {
	sdata->vif.active_links = old_active;
	return ret;
	}
	}

	for_each_set_bit(link_id, &rem, IEEE80211_MLD_MAX_NUM_LINKS) {
	struct ieee80211_link_data *link;

	link = sdata_dereference(sdata->link[link_id], sdata);

	/* FIXME: kill TDLS connections on the link */

	ieee80211_link_release_channel(link);
	}

	list_for_each_entry(sta, &local->sta_list, list) {
	if (sdata != sta->sdata)
	continue;

	/* this is very temporary, but do it anyway */
	__ieee80211_sta_recalc_aggregates(sta,
	old_active \| active_links);

	ret = drv_change_sta_links(local, sdata, &sta->sta,
	old_active,
	old_active \| active_links);
	WARN_ON_ONCE(ret);
	}

	ret = ieee80211_key_switch_links(sdata, rem, add);
	WARN_ON_ONCE(ret);

	list_for_each_entry(sta, &local->sta_list, list) {
	if (sdata != sta->sdata)
	continue;

	__ieee80211_sta_recalc_aggregates(sta, active_links);

	ret = drv_change_sta_links(local, sdata, &sta->sta,
	old_active \| active_links,
	active_links);
	WARN_ON_ONCE(ret);

	/*
	* Do it again, just in case - the driver might very
	* well have called ieee80211_sta_recalc_aggregates()
	* from there when filling in the new links, which
	* would set it wrong since the vif's active links are
	* not switched yet...
	*/
	__ieee80211_sta_recalc_aggregates(sta, active_links);
	}

	for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
	struct ieee80211_link_data *link;

	link = sdata_dereference(sdata->link[link_id], sdata);

	ret = ieee80211_link_use_channel(link, &link->conf->chandef,
	IEEE80211_CHANCTX_SHARED);
	WARN_ON_ONCE(ret);

	ieee80211_mgd_set_link_qos_params(link);
	ieee80211_link_info_change_notify(sdata, link,
	BSS_CHANGED_ERP_CTS_PROT \|
	BSS_CHANGED_ERP_PREAMBLE \|
	BSS_CHANGED_ERP_SLOT \|
	BSS_CHANGED_HT \|
	BSS_CHANGED_BASIC_RATES \|
	BSS_CHANGED_BSSID \|
	BSS_CHANGED_CQM \|
	BSS_CHANGED_QOS \|
	BSS_CHANGED_TXPOWER \|
	BSS_CHANGED_BANDWIDTH \|
	BSS_CHANGED_TWT \|
	BSS_CHANGED_HE_OBSS_PD \|
	BSS_CHANGED_HE_BSS_COLOR);
	}

	old_active = sdata->vif.active_links;
	sdata->vif.active_links = active_links;

	if (rem) {
	ret = drv_change_vif_links(local, sdata, old_active,
	active_links, link_confs);
	WARN_ON_ONCE(ret);
	}

	return 0;
	}

	int __ieee80211_set_active_links(struct ieee80211_vif *vif, u16 active_links)
	{
	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
	struct ieee80211_local *local = sdata->local;
	u16 old_active;
	int ret;

	sdata_assert_lock(sdata);
	mutex_lock(&local->sta_mtx);
	mutex_lock(&local->mtx);
	mutex_lock(&local->key_mtx);
	old_active = sdata->vif.active_links;
	if (old_active & active_links) {
	/*
	* if there's at least one link that stays active across
	* the change then switch to it (to those) first, and
	* then enable the additional links
	*/
	ret = _ieee80211_set_active_links(sdata,
	old_active & active_links);
	if (!ret)
	ret = _ieee80211_set_active_links(sdata, active_links);
	} else {
	/* otherwise switch directly */
	ret = _ieee80211_set_active_links(sdata, active_links);
	}
	mutex_unlock(&local->key_mtx);
	mutex_unlock(&local->mtx);
	mutex_unlock(&local->sta_mtx);

	return ret;
	}

	int ieee80211_set_active_links(struct ieee80211_vif *vif, u16 active_links)
	{
	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
	int ret;

	sdata_lock(sdata);
	ret = __ieee80211_set_active_links(vif, active_links);
	sdata_unlock(sdata);

	return ret;
	}
	EXPORT_SYMBOL_GPL(ieee80211_set_active_links);

	void ieee80211_set_active_links_async(struct ieee80211_vif *vif,
	u16 active_links)
	{
	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);

	if (!ieee80211_sdata_running(sdata))
	return;

	if (sdata->vif.type != NL80211_IFTYPE_STATION)
	return;

	if (active_links & ~ieee80211_vif_usable_links(&sdata->vif))
	return;

	/* nothing to do */
	if (sdata->vif.active_links == active_links)
	return;

	sdata->desired_active_links = active_links;
	schedule_work(&sdata->activate_links_work);
	}
	EXPORT_SYMBOL_GPL(ieee80211_set_active_links_async);