cfg80211: Enable GO operation on additional channels

Allow GO operation on a channel marked with IEEE80211_CHAN_GO_CONCURRENT
iff there is an active station interface that is associated to
an AP operating on the same channel in the 2 GHz band or the same UNII band
(in the 5 GHz band). This relaxation is not allowed if the channel is
marked with IEEE80211_CHAN_RADAR.

Note that this is a permissive approach to the FCC definitions,
that require a clear assessment that the device operating the AP is
an authorized master, i.e., with radar detection and DFS capabilities.

It is assumed that such restrictions are enforced by user space.
Furthermore, it is assumed, that if the conditions that allowed for
the operation of the GO on such a channel change, i.e., the station
interface disconnected from the AP, it is the responsibility of user
space to evacuate the GO from the channel.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 73 insertions, 3 deletions

diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index 9c9501a35fb5..50202af7fba3 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -661,15 +661,85 @@ bool cfg80211_chandef_usable(struct wiphy *wiphy,
 }
 EXPORT_SYMBOL(cfg80211_chandef_usable);
 
+/*
+ * For GO only, check if the channel can be used under permissive conditions
+ * mandated by the some regulatory bodies, i.e., the channel is marked with
+ * IEEE80211_CHAN_GO_CONCURRENT and there is an additional station interface
+ * associated to an AP on the same channel or on the same UNII band
+ * (assuming that the AP is an authorized master).
+ */
+static bool cfg80211_go_permissive_chan(struct cfg80211_registered_device *rdev,
+					struct ieee80211_channel *chan)
+{
+	struct wireless_dev *wdev_iter;
+	struct wiphy *wiphy = wiphy_idx_to_wiphy(rdev->wiphy_idx);
+
+	ASSERT_RTNL();
+
+	if (!config_enabled(CONFIG_CFG80211_REG_RELAX_NO_IR) ||
+	    !(wiphy->regulatory_flags & REGULATORY_ENABLE_RELAX_NO_IR) ||
+	    !(chan->flags & IEEE80211_CHAN_GO_CONCURRENT))
+		return false;
+
+	/*
+	 * Generally, it is possible to rely on another device/driver to allow
+	 * the GO concurrent relaxation, however, since the device can further
+	 * enforce the relaxation (by doing a similar verifications as this),
+	 * and thus fail the GO instantiation, consider only the interfaces of
+	 * the current registered device.
+	 */
+	list_for_each_entry(wdev_iter, &rdev->wdev_list, list) {
+		struct ieee80211_channel *other_chan = NULL;
+		int r1, r2;
+
+		if (wdev_iter->iftype != NL80211_IFTYPE_STATION ||
+		    !netif_running(wdev_iter->netdev))
+			continue;
+
+		wdev_lock(wdev_iter);
+		if (wdev_iter->current_bss)
+			other_chan = wdev_iter->current_bss->pub.channel;
+		wdev_unlock(wdev_iter);
+
+		if (!other_chan)
+			continue;
+
+		if (chan == other_chan)
+			return true;
+
+		if (chan->band != IEEE80211_BAND_5GHZ)
+			continue;
+
+		r1 = cfg80211_get_unii(chan->center_freq);
+		r2 = cfg80211_get_unii(other_chan->center_freq);
+
+		if (r1 != -EINVAL && r1 == r2)
+			return true;
+	}
+
+	return false;
+}
+
 bool cfg80211_reg_can_beacon(struct wiphy *wiphy,
-			     struct cfg80211_chan_def *chandef)
+			     struct cfg80211_chan_def *chandef,
+			     enum nl80211_iftype iftype)
 {
+	struct cfg80211_registered_device *rdev = wiphy_to_dev(wiphy);
 	bool res;
 	u32 prohibited_flags = IEEE80211_CHAN_DISABLED |
-			       IEEE80211_CHAN_NO_IR |
 			       IEEE80211_CHAN_RADAR;
 
-	trace_cfg80211_reg_can_beacon(wiphy, chandef);
+	trace_cfg80211_reg_can_beacon(wiphy, chandef, iftype);
+
+	/*
+	 * Under certain conditions suggested by the some regulatory bodies
+	 * a GO can operate on channels marked with IEEE80211_NO_IR
+	 * so set this flag only if such relaxations are not enabled and
+	 * the conditions are not met.
+	 */
+	if (iftype != NL80211_IFTYPE_P2P_GO ||
+	    !cfg80211_go_permissive_chan(rdev, chandef->chan))
+		prohibited_flags |= IEEE80211_CHAN_NO_IR;
 
 	if (cfg80211_chandef_dfs_required(wiphy, chandef) > 0 &&
 	    cfg80211_chandef_dfs_available(wiphy, chandef)) {