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>

1 files changed, 28 insertions, 12 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index ca75f60041d2..0f1b18f209d6 100644
--- a/net/wireless/nl80211.c
+++ b/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;
         }