mac80211: fix scan when operating on DFS channels in ETSI domains

In non-ETSI regulatory domains scan is blocked when operating channel
is a DFS channel. For ETSI, however, once DFS channel is marked as
available after the CAC, this channel will remain available (for some
time) even after leaving this channel.

Therefore a scan can be done without any impact on the availability
of the DFS channel as no new CAC is required after the scan.

Enable scan in mac80211 in these cases.

Signed-off-by: Aaron Komisar <aaron.komisar@tandemg.com>
Link: https://lore.kernel.org/r/1570024728-17284-1-git-send-email-aaron.komisar@tandemg.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 28 insertions, 2 deletions

diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index adf94ba1ed77..4d31d9688dc2 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -520,10 +520,33 @@ static int ieee80211_start_sw_scan(struct ieee80211_local *local,
         return 0;
 }
 
+static bool __ieee80211_can_leave_ch(struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_local *local = sdata->local;
+        struct ieee80211_sub_if_data *sdata_iter;
+
+        if (!ieee80211_is_radar_required(local))
+                return true;
+
+        if (!regulatory_pre_cac_allowed(local->hw.wiphy))
+                return false;
+
+        mutex_lock(&local->iflist_mtx);
+        list_for_each_entry(sdata_iter, &local->interfaces, list) {
+                if (sdata_iter->wdev.cac_started) {
+                        mutex_unlock(&local->iflist_mtx);
+                        return false;
+                }
+        }
+        mutex_unlock(&local->iflist_mtx);
+
+        return true;
+}
+
 static bool ieee80211_can_scan(struct ieee80211_local *local,
                                struct ieee80211_sub_if_data *sdata)
 {
-        if (ieee80211_is_radar_required(local))
+        if (!__ieee80211_can_leave_ch(sdata))
                 return false;
 
         if (!list_empty(&local->roc_list))
@@ -630,7 +653,10 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 
         lockdep_assert_held(&local->mtx);
 
-        if (local->scan_req || ieee80211_is_radar_required(local))
+        if (local->scan_req)
+                return -EBUSY;
+
+        if (!__ieee80211_can_leave_ch(sdata))
                 return -EBUSY;
 
         if (!ieee80211_can_scan(local, sdata)) {