cfg80211: DFS check chandef usable before CAC

Check chandef we get in CAC request is usable for CAC.
All channels have to be DFS channels. Allow DFS_USABLE
and DFS_AVAILABLE channels mix. At least one channel
has to be DFS_USABLE (require CAC).
Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Reviewed-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/chan.c

@@ -351,6 +351,80 @@ int cfg80211_chandef_dfs_required(struct wiphy *wiphy,
 }
 EXPORT_SYMBOL(cfg80211_chandef_dfs_required);
 
+static int cfg80211_get_chans_dfs_usable(struct wiphy *wiphy,
+					 u32 center_freq,
+					 u32 bandwidth)
+{
+	struct ieee80211_channel *c;
+	u32 freq, start_freq, end_freq;
+	int count = 0;
+
+	start_freq = cfg80211_get_start_freq(center_freq, bandwidth);
+	end_freq = cfg80211_get_end_freq(center_freq, bandwidth);
+
+	/*
+	 * Check entire range of channels for the bandwidth.
+	 * Check all channels are DFS channels (DFS_USABLE or
+	 * DFS_AVAILABLE). Return number of usable channels
+	 * (require CAC). Allow DFS and non-DFS channel mix.
+	 */
+	for (freq = start_freq; freq <= end_freq; freq += 20) {
+		c = ieee80211_get_channel(wiphy, freq);
+		if (!c)
+			return -EINVAL;
+
+		if (c->flags & IEEE80211_CHAN_DISABLED)
+			return -EINVAL;
+
+		if (c->flags & IEEE80211_CHAN_RADAR) {
+			if (c->dfs_state == NL80211_DFS_UNAVAILABLE)
+				return -EINVAL;
+
+			if (c->dfs_state == NL80211_DFS_USABLE)
+				count++;
+		}
+	}
+
+	return count;
+}
+
+bool cfg80211_chandef_dfs_usable(struct wiphy *wiphy,
+				 const struct cfg80211_chan_def *chandef)
+{
+	int width;
+	int r1, r2 = 0;
+
+	if (WARN_ON(!cfg80211_chandef_valid(chandef)))
+		return false;
+
+	width = cfg80211_chandef_get_width(chandef);
+	if (width < 0)
+		return false;
+
+	r1 = cfg80211_get_chans_dfs_usable(wiphy, chandef->center_freq1,
+					  width);
+
+	if (r1 < 0)
+		return false;
+
+	switch (chandef->width) {
+	case NL80211_CHAN_WIDTH_80P80:
+		WARN_ON(!chandef->center_freq2);
+		r2 = cfg80211_get_chans_dfs_usable(wiphy,
+						   chandef->center_freq2,
+						   width);
+		if (r2 < 0)
+			return false;
+		break;
+	default:
+		WARN_ON(chandef->center_freq2);
+		break;
+	}
+
+	return (r1 + r2 > 0);
+}
+
+
 static bool cfg80211_secondary_chans_ok(struct wiphy *wiphy,
 					u32 center_freq, u32 bandwidth,
 					u32 prohibited_flags)

net/wireless/core.h

@@ -382,6 +382,19 @@ int cfg80211_can_use_iftype_chan(struct cfg80211_registered_device *rdev,
 				 enum cfg80211_chan_mode chanmode,
 				 u8 radar_detect);
 
+/**
+ * cfg80211_chandef_dfs_usable - checks if chandef is DFS usable
+ * @wiphy: the wiphy to validate against
+ * @chandef: the channel definition to check
+ *
+ * Checks if chandef is usable and we can/need start CAC on such channel.
+ *
+ * Return: Return true if all channels available and at least
+ *	   one channel require CAC (NL80211_DFS_USABLE)
+ */
+bool cfg80211_chandef_dfs_usable(struct wiphy *wiphy,
+				 const struct cfg80211_chan_def *chandef);
+
 void cfg80211_set_dfs_state(struct wiphy *wiphy,
 			    const struct cfg80211_chan_def *chandef,
 			    enum nl80211_dfs_state dfs_state);

net/wireless/nl80211.c

@@ -5651,7 +5651,7 @@ static int nl80211_start_radar_detection(struct sk_buff *skb,
 	if (err == 0)
 		return -EINVAL;
 
-	if (chandef.chan->dfs_state != NL80211_DFS_USABLE)
+	if (!cfg80211_chandef_dfs_usable(wdev->wiphy, &chandef))
 		return -EINVAL;
 
 	if (!rdev->ops->start_radar_detection)