nl80211/cfg80211: enable DFS for IBSS mode

To use DFS in IBSS mode, userspace is required to react to radar events.
It can inform nl80211 that it is capable of doing so by adding a
NL80211_ATTR_HANDLE_DFS attribute when joining the IBSS.

This attribute is supplied to let the kernelspace know that the
userspace application can and will handle radar events, e.g. by
intiating channel switches to a valid channel. DFS channels may
only be used if this attribute is supplied and the driver supports
it. Driver support will be checked even if a channel without DFS
will be initially joined, as a DFS channel may be chosen later.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
[fix attribute name in commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 3c8be6104ba4..935dea9485da 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -1249,7 +1249,7 @@ int cfg80211_can_use_iftype_chan(struct cfg80211_registered_device *rdev,
         enum cfg80211_chan_mode chmode;
         int num_different_channels = 0;
         int total = 1;
-        bool radar_required;
+        bool radar_required = false;
         int i, j;
 
         ASSERT_RTNL();
@@ -1264,14 +1264,20 @@ int cfg80211_can_use_iftype_chan(struct cfg80211_registered_device *rdev,
         case NL80211_IFTYPE_MESH_POINT:
         case NL80211_IFTYPE_P2P_GO:
         case NL80211_IFTYPE_WDS:
-                radar_required = !!(chan &&
-                                    (chan->flags & IEEE80211_CHAN_RADAR));
+                /* if the interface could potentially choose a DFS channel,
+                 * then mark DFS as required.
+                 */
+                if (!chan) {
+                        if (chanmode != CHAN_MODE_UNDEFINED && radar_detect)
+                                radar_required = true;
+                        break;
+                }
+                radar_required = !!(chan->flags & IEEE80211_CHAN_RADAR);
                 break;
         case NL80211_IFTYPE_P2P_CLIENT:
         case NL80211_IFTYPE_STATION:
         case NL80211_IFTYPE_P2P_DEVICE:
         case NL80211_IFTYPE_MONITOR:
-                radar_required = false;
                 break;
         case NUM_NL80211_IFTYPES:
         case NL80211_IFTYPE_UNSPECIFIED: