cfg80211: Dynamic channel bandwidth changes in AP mode

This extends NL80211_CMD_SET_CHANNEL to allow dynamic channel bandwidth
changes in AP mode (including P2P GO) during a lifetime of the BSS. This
can be used to implement, e.g., HT 20/40 MHz co-existence rules on the
2.4 GHz band.
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -2290,6 +2290,10 @@ struct cfg80211_qos_map {
  * @channel_switch: initiate channel-switch procedure (with CSA)
  *
  * @set_qos_map: Set QoS mapping information to the driver
+ *
+ * @set_ap_chanwidth: Set the AP (including P2P GO) mode channel width for the
+ *	given interface This is used e.g. for dynamic HT 20/40 MHz channel width
+ *	changes during the lifetime of the BSS.
  */
 struct cfg80211_ops {
 	int	(*suspend)(struct wiphy *wiphy, struct cfg80211_wowlan *wow);
@@ -2533,9 +2537,13 @@ struct cfg80211_ops {
 	int	(*channel_switch)(struct wiphy *wiphy,
 				  struct net_device *dev,
 				  struct cfg80211_csa_settings *params);
+
 	int     (*set_qos_map)(struct wiphy *wiphy,
 			       struct net_device *dev,
 			       struct cfg80211_qos_map *qos_map);
+
+	int	(*set_ap_chanwidth)(struct wiphy *wiphy, struct net_device *dev,
+				    struct cfg80211_chan_def *chandef);
 };
 
 /*

include/uapi/linux/nl80211.h

@@ -3929,6 +3929,9 @@ enum nl80211_ap_sme_features {
  *	interface. An active monitor interface behaves like a normal monitor
  *	interface, but gets added to the driver. It ensures that incoming
  *	unicast packets directed at the configured interface address get ACKed.
+ * @NL80211_FEATURE_AP_MODE_CHAN_WIDTH_CHANGE: This driver supports dynamic
+ *	channel bandwidth change (e.g., HT 20 <-> 40 MHz channel) during the
+ *	lifetime of a BSS.
  */
 enum nl80211_feature_flags {
 	NL80211_FEATURE_SK_TX_STATUS			= 1 << 0,
@@ -3949,6 +3952,7 @@ enum nl80211_feature_flags {
 	NL80211_FEATURE_FULL_AP_CLIENT_STATE		= 1 << 15,
 	NL80211_FEATURE_USERSPACE_MPM			= 1 << 16,
 	NL80211_FEATURE_ACTIVE_MONITOR			= 1 << 17,
+	NL80211_FEATURE_AP_MODE_CHAN_WIDTH_CHANGE	= 1 << 18,
 };
 
 /**

net/wireless/nl80211.c

@@ -1928,18 +1928,20 @@ static int nl80211_parse_chandef(struct cfg80211_registered_device *rdev,
 }
 
 static int __nl80211_set_channel(struct cfg80211_registered_device *rdev,
-				 struct wireless_dev *wdev,
+				 struct net_device *dev,
 				 struct genl_info *info)
 {
 	struct cfg80211_chan_def chandef;
 	int result;
 	enum nl80211_iftype iftype = NL80211_IFTYPE_MONITOR;
+	struct wireless_dev *wdev = NULL;
 
-	if (wdev)
-		iftype = wdev->iftype;
-
+	if (dev)
+		wdev = dev->ieee80211_ptr;
 	if (!nl80211_can_set_dev_channel(wdev))
 		return -EOPNOTSUPP;
+	if (wdev)
+		iftype = wdev->iftype;
 
 	result = nl80211_parse_chandef(rdev, info, &chandef);
 	if (result)
@@ -1948,14 +1950,27 @@ static int __nl80211_set_channel(struct cfg80211_registered_device *rdev,
 	switch (iftype) {
 	case NL80211_IFTYPE_AP:
 	case NL80211_IFTYPE_P2P_GO:
-		if (wdev->beacon_interval) {
-			result = -EBUSY;
-			break;
-		}
 		if (!cfg80211_reg_can_beacon(&rdev->wiphy, &chandef, iftype)) {
 			result = -EINVAL;
 			break;
 		}
+		if (wdev->beacon_interval) {
+			if (!dev || !rdev->ops->set_ap_chanwidth ||
+			    !(rdev->wiphy.features &
+			      NL80211_FEATURE_AP_MODE_CHAN_WIDTH_CHANGE)) {
+				result = -EBUSY;
+				break;
+			}
+
+			/* Only allow dynamic channel width changes */
+			if (chandef.chan != wdev->preset_chandef.chan) {
+				result = -EBUSY;
+				break;
+			}
+			result = rdev_set_ap_chanwidth(rdev, dev, &chandef);
+			if (result)
+				break;
+		}
 		wdev->preset_chandef = chandef;
 		result = 0;
 		break;
@@ -1977,7 +1992,7 @@ static int nl80211_set_channel(struct sk_buff *skb, struct genl_info *info)
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
 	struct net_device *netdev = info->user_ptr[1];
 
-	return __nl80211_set_channel(rdev, netdev->ieee80211_ptr, info);
+	return __nl80211_set_channel(rdev, netdev, info);
 }
 
 static int nl80211_set_wds_peer(struct sk_buff *skb, struct genl_info *info)
@@ -2099,9 +2114,10 @@ static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	if (info->attrs[NL80211_ATTR_WIPHY_FREQ]) {
-		result = __nl80211_set_channel(rdev,
-				nl80211_can_set_dev_channel(wdev) ? wdev : NULL,
-				info);
+		result = __nl80211_set_channel(
+			rdev,
+			nl80211_can_set_dev_channel(wdev) ? netdev : NULL,
+			info);
 		if (result)
 			return result;
 	}

net/wireless/rdev-ops.h

@@ -950,4 +950,17 @@ static inline int rdev_set_qos_map(struct cfg80211_registered_device *rdev,
 	return ret;
 }
 
+static inline int
+rdev_set_ap_chanwidth(struct cfg80211_registered_device *rdev,
+		      struct net_device *dev, struct cfg80211_chan_def *chandef)
+{
+	int ret;
+
+	trace_rdev_set_ap_chanwidth(&rdev->wiphy, dev, chandef);
+	ret = rdev->ops->set_ap_chanwidth(&rdev->wiphy, dev, chandef);
+	trace_rdev_return_int(&rdev->wiphy, ret);
+
+	return ret;
+}
+
 #endif /* __CFG80211_RDEV_OPS */

net/wireless/trace.h

@@ -1919,6 +1919,24 @@ TRACE_EVENT(rdev_set_qos_map,
 		  WIPHY_PR_ARG, NETDEV_PR_ARG, __entry->num_des)
 );
 
+TRACE_EVENT(rdev_set_ap_chanwidth,
+	TP_PROTO(struct wiphy *wiphy, struct net_device *netdev,
+		 struct cfg80211_chan_def *chandef),
+	TP_ARGS(wiphy, netdev, chandef),
+	TP_STRUCT__entry(
+		WIPHY_ENTRY
+		NETDEV_ENTRY
+		CHAN_DEF_ENTRY
+	),
+	TP_fast_assign(
+		WIPHY_ASSIGN;
+		NETDEV_ASSIGN;
+		CHAN_DEF_ASSIGN(chandef);
+	),
+	TP_printk(WIPHY_PR_FMT ", " NETDEV_PR_FMT ", " CHAN_DEF_PR_FMT,
+		  WIPHY_PR_ARG, NETDEV_PR_ARG, CHAN_DEF_PR_ARG)
+);
+
 /*************************************************************
  *	     cfg80211 exported functions traces		     *
  *************************************************************/