wifi: mac80211: implement link switching

Implement an API function and debugfs file to switch
active links.

Change-Id: I92385ba882ec984a9a2ad18293173436657e82aa
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -7128,4 +7128,32 @@ static inline bool ieee80211_is_tx_data(struct sk_buff *skb)
 	       ieee80211_is_data(hdr->frame_control);
 }
 
+/**
+ * ieee80211_set_active_links - set active links in client mode
+ * @vif: interface to set active links on
+ * @active_links: the new active links bitmap
+ *
+ * This changes the active links on an interface. The interface
+ * must be in client mode (in AP mode, all links are always active),
+ * and @active_links must be a subset of the vif's valid_links.
+ *
+ * If a link is switched off and another is switched on at the same
+ * time (e.g. active_links going from 0x1 to 0x10) then you will get
+ * a sequence of calls like
+ *  - change_vif_links(0x11)
+ *  - unassign_vif_chanctx(link_id=0)
+ *  - change_sta_links(0x11) for each affected STA (the AP)
+ *    (TDLS connections on now inactive links should be torn down)
+ *  - remove group keys on the old link (link_id 0)
+ *  - add new group keys (GTK/IGTK/BIGTK) on the new link (link_id 4)
+ *  - change_sta_links(0x10) for each affected STA (the AP)
+ *  - assign_vif_chanctx(link_id=4)
+ *  - change_vif_links(0x10)
+ *
+ * Note: This function acquires some mac80211 locks and must not
+ *	 be called with any driver locks held that could cause a
+ *	 lock dependency inversion. Best call it without locks.
+ */
+int ieee80211_set_active_links(struct ieee80211_vif *vif, u16 active_links);
+
 #endif /* MAC80211_H */

net/mac80211/debugfs_netdev.c

@@ -570,6 +570,30 @@ static ssize_t ieee80211_if_parse_tsf(
 }
 IEEE80211_IF_FILE_RW(tsf);
 
+static ssize_t ieee80211_if_fmt_valid_links(const struct ieee80211_sub_if_data *sdata,
+					    char *buf, int buflen)
+{
+	return snprintf(buf, buflen, "0x%x\n", sdata->vif.valid_links);
+}
+IEEE80211_IF_FILE_R(valid_links);
+
+static ssize_t ieee80211_if_fmt_active_links(const struct ieee80211_sub_if_data *sdata,
+					     char *buf, int buflen)
+{
+	return snprintf(buf, buflen, "0x%x\n", sdata->vif.active_links);
+}
+
+static ssize_t ieee80211_if_parse_active_links(struct ieee80211_sub_if_data *sdata,
+					       const char *buf, int buflen)
+{
+	u16 active_links;
+
+	if (kstrtou16(buf, 0, &active_links))
+		return -EINVAL;
+
+	return ieee80211_set_active_links(&sdata->vif, active_links) ?: buflen;
+}
+IEEE80211_IF_FILE_RW(active_links);
 
 #ifdef CONFIG_MAC80211_MESH
 IEEE80211_IF_FILE(estab_plinks, u.mesh.estab_plinks, ATOMIC);
@@ -670,6 +694,8 @@ static void add_sta_files(struct ieee80211_sub_if_data *sdata)
 	DEBUGFS_ADD_MODE(uapsd_queues, 0600);
 	DEBUGFS_ADD_MODE(uapsd_max_sp_len, 0600);
 	DEBUGFS_ADD_MODE(tdls_wider_bw, 0600);
+	DEBUGFS_ADD_MODE(valid_links, 0200);
+	DEBUGFS_ADD_MODE(active_links, 0600);
 }
 
 static void add_ap_files(struct ieee80211_sub_if_data *sdata)

net/mac80211/key.c

@@ -1445,3 +1445,37 @@ void ieee80211_key_replay(struct ieee80211_key_conf *keyconf)
 	}
 }
 EXPORT_SYMBOL_GPL(ieee80211_key_replay);
+
+int ieee80211_key_switch_links(struct ieee80211_sub_if_data *sdata,
+			       unsigned long del_links_mask,
+			       unsigned long add_links_mask)
+{
+	struct ieee80211_key *key;
+	int ret;
+
+	list_for_each_entry(key, &sdata->key_list, list) {
+		if (key->conf.link_id < 0 ||
+		    !(del_links_mask & BIT(key->conf.link_id)))
+			continue;
+
+		/* shouldn't happen for per-link keys */
+		WARN_ON(key->sta);
+
+		ieee80211_key_disable_hw_accel(key);
+	}
+
+	list_for_each_entry(key, &sdata->key_list, list) {
+		if (key->conf.link_id < 0 ||
+		    !(add_links_mask & BIT(key->conf.link_id)))
+			continue;
+
+		/* shouldn't happen for per-link keys */
+		WARN_ON(key->sta);
+
+		ret = ieee80211_key_enable_hw_accel(key);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}

net/mac80211/key.h

@@ -165,6 +165,9 @@ void ieee80211_free_keys(struct ieee80211_sub_if_data *sdata,
 void ieee80211_free_sta_keys(struct ieee80211_local *local,
 			     struct sta_info *sta);
 void ieee80211_reenable_keys(struct ieee80211_sub_if_data *sdata);
+int ieee80211_key_switch_links(struct ieee80211_sub_if_data *sdata,
+			       unsigned long del_links_mask,
+			       unsigned long add_links_mask);
 
 #define key_mtx_dereference(local, ref) \
 	rcu_dereference_protected(ref, lockdep_is_held(&((local)->key_mtx)))

net/mac80211/link.c

@@ -9,6 +9,7 @@
 #include <net/mac80211.h>
 #include "ieee80211_i.h"
 #include "driver-ops.h"
+#include "key.h"
 
 void ieee80211_link_setup(struct ieee80211_link_data *link)
 {
@@ -300,3 +301,147 @@ void ieee80211_vif_clear_links(struct ieee80211_sub_if_data *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 (sdata->vif.type != NL80211_IFTYPE_STATION)
+		return -EINVAL;
+
+	/* cannot activate links that don't exist */
+	if (active_links & ~sdata->vif.valid_links)
+		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;
+		ret = drv_change_sta_links(local, sdata, &sta->sta,
+					   old_active,
+					   old_active | active_links);
+		WARN_ON(ret); // FIXME //
+	}
+
+	ret = ieee80211_key_switch_links(sdata, rem, add);
+	WARN_ON(ret); // FIXME //
+
+	list_for_each_entry(sta, &local->sta_list, list) {
+		if (sdata != sta->sdata)
+			continue;
+		ret = drv_change_sta_links(local, sdata, &sta->sta,
+					   old_active | active_links,
+					   active_links);
+		WARN_ON(ret); // FIXME //
+	}
+
+	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(ret); // FIXME //
+
+		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 |
+						  BSS_CHANGED_EHT_PUNCTURING);
+		ieee80211_mgd_set_link_qos_params(link);
+	}
+
+	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(ret); // FIXME //
+	}
+
+	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_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);
+	sdata_unlock(sdata);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ieee80211_set_active_links);