mac80211: add channel switch command and beacon callbacks

The count field in CSA must be decremented with each beacon
transmitted. This patch implements the functionality for drivers
using ieee80211_beacon_get(). Other drivers must call back manually
after reaching count == 0.

This patch also contains the handling and finish worker for the channel
switch command, and mac80211/chanctx code to allow to change a channel
definition of an active channel context.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
[small cleanups, catch identical chandef]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -152,11 +152,14 @@ struct ieee80211_low_level_stats {
  * @IEEE80211_CHANCTX_CHANGE_WIDTH: The channel width changed
  * @IEEE80211_CHANCTX_CHANGE_RX_CHAINS: The number of RX chains changed
  * @IEEE80211_CHANCTX_CHANGE_RADAR: radar detection flag changed
+ * @IEEE80211_CHANCTX_CHANGE_CHANNEL: switched to another operating channel,
+ *	this is used only with channel switching with CSA
  */
 enum ieee80211_chanctx_change {
 	IEEE80211_CHANCTX_CHANGE_WIDTH		= BIT(0),
 	IEEE80211_CHANCTX_CHANGE_RX_CHAINS	= BIT(1),
 	IEEE80211_CHANCTX_CHANGE_RADAR		= BIT(2),
+	IEEE80211_CHANCTX_CHANGE_CHANNEL	= BIT(3),
 };
 
 /**
@@ -1084,6 +1087,7 @@ enum ieee80211_vif_flags {
  * @addr: address of this interface
  * @p2p: indicates whether this AP or STA interface is a p2p
  *	interface, i.e. a GO or p2p-sta respectively
+ * @csa_active: marks whether a channel switch is going on
  * @driver_flags: flags/capabilities the driver has for this interface,
  *	these need to be set (or cleared) when the interface is added
  *	or, if supported by the driver, the interface type is changed
@@ -1106,6 +1110,7 @@ struct ieee80211_vif {
 	struct ieee80211_bss_conf bss_conf;
 	u8 addr[ETH_ALEN];
 	bool p2p;
+	bool csa_active;
 
 	u8 cab_queue;
 	u8 hw_queue[IEEE80211_NUM_ACS];
@@ -2637,6 +2642,16 @@ enum ieee80211_roc_type {
  * @ipv6_addr_change: IPv6 address assignment on the given interface changed.
  *	Currently, this is only called for managed or P2P client interfaces.
  *	This callback is optional; it must not sleep.
+ *
+ * @channel_switch_beacon: Starts a channel switch to a new channel.
+ *	Beacons are modified to include CSA or ECSA IEs before calling this
+ *	function. The corresponding count fields in these IEs must be
+ *	decremented, and when they reach zero the driver must call
+ *	ieee80211_csa_finish(). Drivers which use ieee80211_beacon_get()
+ *	get the csa counter decremented by mac80211, but must check if it is
+ *	zero using ieee80211_csa_is_complete() after the beacon has been
+ *	transmitted and then call ieee80211_csa_finish().
+ *
  */
 struct ieee80211_ops {
 	void (*tx)(struct ieee80211_hw *hw,
@@ -2824,6 +2839,9 @@ struct ieee80211_ops {
 				 struct ieee80211_vif *vif,
 				 struct inet6_dev *idev);
 #endif
+	void (*channel_switch_beacon)(struct ieee80211_hw *hw,
+				      struct ieee80211_vif *vif,
+				      struct cfg80211_chan_def *chandef);
 };
 
 /**
@@ -3318,6 +3336,25 @@ static inline struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
 	return ieee80211_beacon_get_tim(hw, vif, NULL, NULL);
 }
 
+/**
+ * ieee80211_csa_finish - notify mac80211 about channel switch
+ * @vif: &struct ieee80211_vif pointer from the add_interface callback.
+ *
+ * After a channel switch announcement was scheduled and the counter in this
+ * announcement hit zero, this function must be called by the driver to
+ * notify mac80211 that the channel can be changed.
+ */
+void ieee80211_csa_finish(struct ieee80211_vif *vif);
+
+/**
+ * ieee80211_csa_is_complete - find out if counters reached zero
+ * @vif: &struct ieee80211_vif pointer from the add_interface callback.
+ *
+ * This function returns whether the channel switch counters reached zero.
+ */
+bool ieee80211_csa_is_complete(struct ieee80211_vif *vif);
+
+
 /**
  * ieee80211_proberesp_get - retrieve a Probe Response template
  * @hw: pointer obtained from ieee80211_alloc_hw().

net/mac80211/cfg.c

@@ -860,8 +860,8 @@ static int ieee80211_set_probe_resp(struct ieee80211_sub_if_data *sdata,
 	return 0;
 }
 
-static int ieee80211_assign_beacon(struct ieee80211_sub_if_data *sdata,
-				   struct cfg80211_beacon_data *params)
+int ieee80211_assign_beacon(struct ieee80211_sub_if_data *sdata,
+			    struct cfg80211_beacon_data *params)
 {
 	struct beacon_data *new, *old;
 	int new_head_len, new_tail_len;
@@ -1024,6 +1024,12 @@ static int ieee80211_change_beacon(struct wiphy *wiphy, struct net_device *dev,
 
 	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
+	/* don't allow changing the beacon while CSA is in place - offset
+	 * of channel switch counter may change
+	 */
+	if (sdata->vif.csa_active)
+		return -EBUSY;
+
 	old = rtnl_dereference(sdata->u.ap.beacon);
 	if (!old)
 		return -ENOENT;
@@ -1048,6 +1054,10 @@ static int ieee80211_stop_ap(struct wiphy *wiphy, struct net_device *dev)
 		return -ENOENT;
 	old_probe_resp = rtnl_dereference(sdata->u.ap.probe_resp);
 
+	/* abort any running channel switch */
+	sdata->vif.csa_active = false;
+	cancel_work_sync(&sdata->csa_finalize_work);
+
 	/* turn off carrier for this interface and dependent VLANs */
 	list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
 		netif_carrier_off(vlan->dev);
@@ -2775,6 +2785,178 @@ static int ieee80211_start_radar_detection(struct wiphy *wiphy,
 	return 0;
 }
 
+static struct cfg80211_beacon_data *
+cfg80211_beacon_dup(struct cfg80211_beacon_data *beacon)
+{
+	struct cfg80211_beacon_data *new_beacon;
+	u8 *pos;
+	int len;
+
+	len = beacon->head_len + beacon->tail_len + beacon->beacon_ies_len +
+	      beacon->proberesp_ies_len + beacon->assocresp_ies_len +
+	      beacon->probe_resp_len;
+
+	new_beacon = kzalloc(sizeof(*new_beacon) + len, GFP_KERNEL);
+	if (!new_beacon)
+		return NULL;
+
+	pos = (u8 *)(new_beacon + 1);
+	if (beacon->head_len) {
+		new_beacon->head_len = beacon->head_len;
+		new_beacon->head = pos;
+		memcpy(pos, beacon->head, beacon->head_len);
+		pos += beacon->head_len;
+	}
+	if (beacon->tail_len) {
+		new_beacon->tail_len = beacon->tail_len;
+		new_beacon->tail = pos;
+		memcpy(pos, beacon->tail, beacon->tail_len);
+		pos += beacon->tail_len;
+	}
+	if (beacon->beacon_ies_len) {
+		new_beacon->beacon_ies_len = beacon->beacon_ies_len;
+		new_beacon->beacon_ies = pos;
+		memcpy(pos, beacon->beacon_ies, beacon->beacon_ies_len);
+		pos += beacon->beacon_ies_len;
+	}
+	if (beacon->proberesp_ies_len) {
+		new_beacon->proberesp_ies_len = beacon->proberesp_ies_len;
+		new_beacon->proberesp_ies = pos;
+		memcpy(pos, beacon->proberesp_ies, beacon->proberesp_ies_len);
+		pos += beacon->proberesp_ies_len;
+	}
+	if (beacon->assocresp_ies_len) {
+		new_beacon->assocresp_ies_len = beacon->assocresp_ies_len;
+		new_beacon->assocresp_ies = pos;
+		memcpy(pos, beacon->assocresp_ies, beacon->assocresp_ies_len);
+		pos += beacon->assocresp_ies_len;
+	}
+	if (beacon->probe_resp_len) {
+		new_beacon->probe_resp_len = beacon->probe_resp_len;
+		beacon->probe_resp = pos;
+		memcpy(pos, beacon->probe_resp, beacon->probe_resp_len);
+		pos += beacon->probe_resp_len;
+	}
+
+	return new_beacon;
+}
+
+void ieee80211_csa_finalize_work(struct work_struct *work)
+{
+	struct ieee80211_sub_if_data *sdata =
+		container_of(work, struct ieee80211_sub_if_data,
+			     csa_finalize_work);
+	struct ieee80211_local *local = sdata->local;
+	int err, changed;
+
+	if (!ieee80211_sdata_running(sdata))
+		return;
+
+	if (WARN_ON(sdata->vif.type != NL80211_IFTYPE_AP))
+		return;
+
+	sdata->radar_required = sdata->csa_radar_required;
+	err = ieee80211_vif_change_channel(sdata, &local->csa_chandef,
+					   &changed);
+	if (WARN_ON(err < 0))
+		return;
+
+	err = ieee80211_assign_beacon(sdata, sdata->u.ap.next_beacon);
+	if (err < 0)
+		return;
+
+	changed |= err;
+	kfree(sdata->u.ap.next_beacon);
+	sdata->u.ap.next_beacon = NULL;
+	sdata->vif.csa_active = false;
+
+	ieee80211_wake_queues_by_reason(&sdata->local->hw,
+					IEEE80211_MAX_QUEUE_MAP,
+					IEEE80211_QUEUE_STOP_REASON_CSA);
+
+	ieee80211_bss_info_change_notify(sdata, changed);
+
+	cfg80211_ch_switch_notify(sdata->dev, &local->csa_chandef);
+}
+
+static int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev,
+				    struct cfg80211_csa_settings *params)
+{
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_chanctx_conf *chanctx_conf;
+	struct ieee80211_chanctx *chanctx;
+	int err, num_chanctx;
+
+	if (!list_empty(&local->roc_list) || local->scanning)
+		return -EBUSY;
+
+	if (sdata->wdev.cac_started)
+		return -EBUSY;
+
+	if (cfg80211_chandef_identical(&params->chandef,
+				       &sdata->vif.bss_conf.chandef))
+		return -EINVAL;
+
+	rcu_read_lock();
+	chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
+	if (!chanctx_conf) {
+		rcu_read_unlock();
+		return -EBUSY;
+	}
+
+	/* don't handle for multi-VIF cases */
+	chanctx = container_of(chanctx_conf, struct ieee80211_chanctx, conf);
+	if (chanctx->refcount > 1) {
+		rcu_read_unlock();
+		return -EBUSY;
+	}
+	num_chanctx = 0;
+	list_for_each_entry_rcu(chanctx, &local->chanctx_list, list)
+		num_chanctx++;
+	rcu_read_unlock();
+
+	if (num_chanctx > 1)
+		return -EBUSY;
+
+	/* don't allow another channel switch if one is already active. */
+	if (sdata->vif.csa_active)
+		return -EBUSY;
+
+	/* only handle AP for now. */
+	switch (sdata->vif.type) {
+	case NL80211_IFTYPE_AP:
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	sdata->u.ap.next_beacon = cfg80211_beacon_dup(&params->beacon_after);
+	if (!sdata->u.ap.next_beacon)
+		return -ENOMEM;
+
+	sdata->csa_counter_offset_beacon = params->counter_offset_beacon;
+	sdata->csa_counter_offset_presp = params->counter_offset_presp;
+	sdata->csa_radar_required = params->radar_required;
+
+	if (params->block_tx)
+		ieee80211_stop_queues_by_reason(&local->hw,
+				IEEE80211_MAX_QUEUE_MAP,
+				IEEE80211_QUEUE_STOP_REASON_CSA);
+
+	err = ieee80211_assign_beacon(sdata, &params->beacon_csa);
+	if (err < 0)
+		return err;
+
+	local->csa_chandef = params->chandef;
+	sdata->vif.csa_active = true;
+
+	ieee80211_bss_info_change_notify(sdata, err);
+	drv_channel_switch_beacon(sdata, &params->chandef);
+
+	return 0;
+}
+
 static int ieee80211_mgmt_tx(struct wiphy *wiphy, struct wireless_dev *wdev,
 			     struct ieee80211_channel *chan, bool offchan,
 			     unsigned int wait, const u8 *buf, size_t len,
@@ -3492,4 +3674,5 @@ struct cfg80211_ops mac80211_config_ops = {
 	.get_et_strings = ieee80211_get_et_strings,
 	.get_channel = ieee80211_cfg_get_channel,
 	.start_radar_detection = ieee80211_start_radar_detection,
+	.channel_switch = ieee80211_channel_switch,
 };

net/mac80211/chan.c

@@ -410,6 +410,64 @@ int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
 	return ret;
 }
 
+int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
+				 const struct cfg80211_chan_def *chandef,
+				 u32 *changed)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_chanctx_conf *conf;
+	struct ieee80211_chanctx *ctx;
+	int ret;
+	u32 chanctx_changed = 0;
+
+	/* should never be called if not performing a channel switch. */
+	if (WARN_ON(!sdata->vif.csa_active))
+		return -EINVAL;
+
+	if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, chandef,
+				     IEEE80211_CHAN_DISABLED))
+		return -EINVAL;
+
+	mutex_lock(&local->chanctx_mtx);
+	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+					 lockdep_is_held(&local->chanctx_mtx));
+	if (!conf) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ctx = container_of(conf, struct ieee80211_chanctx, conf);
+	if (ctx->refcount != 1) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (sdata->vif.bss_conf.chandef.width != chandef->width) {
+		chanctx_changed = IEEE80211_CHANCTX_CHANGE_WIDTH;
+		*changed |= BSS_CHANGED_BANDWIDTH;
+	}
+
+	sdata->vif.bss_conf.chandef = *chandef;
+	ctx->conf.def = *chandef;
+
+	chanctx_changed |= IEEE80211_CHANCTX_CHANGE_CHANNEL;
+	drv_change_chanctx(local, ctx, chanctx_changed);
+
+	if (!local->use_chanctx) {
+		local->_oper_chandef = *chandef;
+		ieee80211_hw_config(local, 0);
+	}
+
+	ieee80211_recalc_chanctx_chantype(local, ctx);
+	ieee80211_recalc_smps_chanctx(local, ctx);
+	ieee80211_recalc_radar_chanctx(local, ctx);
+
+	ret = 0;
+ out:
+	mutex_unlock(&local->chanctx_mtx);
+	return ret;
+}
+
 int ieee80211_vif_change_bandwidth(struct ieee80211_sub_if_data *sdata,
 				   const struct cfg80211_chan_def *chandef,
 				   u32 *changed)

net/mac80211/driver-ops.h

@@ -1072,4 +1072,17 @@ static inline void drv_ipv6_addr_change(struct ieee80211_local *local,
 }
 #endif
 
+static inline void
+drv_channel_switch_beacon(struct ieee80211_sub_if_data *sdata,
+			  struct cfg80211_chan_def *chandef)
+{
+	struct ieee80211_local *local = sdata->local;
+
+	if (local->ops->channel_switch_beacon) {
+		trace_drv_channel_switch_beacon(local, sdata, chandef);
+		local->ops->channel_switch_beacon(&local->hw, &sdata->vif,
+						  chandef);
+	}
+}
+
 #endif /* __MAC80211_DRIVER_OPS */