wifi: cfg80211: reg: Support P2P operation on DFS channels

FCC-594280 D01 Section B.3 allows peer-to-peer and ad hoc devices to
operate on DFS channels while they operate under the control of a
concurrent DFS master. For example, it is possible to have a P2P GO on a
DFS channel as long as BSS connection is active on the same channel.
Allow such operation by adding additional regulatory flags to indicate
DFS concurrent channels and capable devices. Add the required
relaxations in DFS regulatory checks.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Reviewed-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20231220133549.bdfb8a9c7c54.I973563562969a27fea8ec5685b96a3a47afe142f@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

3 files changed, 92 insertions, 7 deletions

diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index dfb4893421d7..ceb9174c5c3d 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -515,9 +515,83 @@ static u32 cfg80211_get_end_freq(u32 center_freq,
 	return end_freq;
 }
 
+static bool
+cfg80211_dfs_permissive_check_wdev(struct cfg80211_registered_device *rdev,
+				   enum nl80211_iftype iftype,
+				   struct wireless_dev *wdev,
+				   struct ieee80211_channel *chan)
+{
+	unsigned int link_id;
+
+	for_each_valid_link(wdev, link_id) {
+		struct ieee80211_channel *other_chan = NULL;
+		struct cfg80211_chan_def chandef = {};
+		int ret;
+
+		/* In order to avoid daisy chaining only allow BSS STA */
+		if (wdev->iftype != NL80211_IFTYPE_STATION ||
+		    !wdev->links[link_id].client.current_bss)
+			continue;
+
+		other_chan =
+			wdev->links[link_id].client.current_bss->pub.channel;
+
+		if (!other_chan)
+			continue;
+
+		if (chan == other_chan)
+			return true;
+
+		/* continue if we can't get the channel */
+		ret = rdev_get_channel(rdev, wdev, link_id, &chandef);
+		if (ret)
+			continue;
+
+		if (cfg80211_is_sub_chan(&chandef, chan, false))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Check if P2P GO is allowed to operate on a DFS channel
+ */
+static bool cfg80211_dfs_permissive_chan(struct wiphy *wiphy,
+					 enum nl80211_iftype iftype,
+					 struct ieee80211_channel *chan)
+{
+	struct wireless_dev *wdev;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+
+	lockdep_assert_held(&rdev->wiphy.mtx);
+
+	if (!wiphy_ext_feature_isset(&rdev->wiphy,
+				     NL80211_EXT_FEATURE_DFS_CONCURRENT) ||
+	    !(chan->flags & IEEE80211_CHAN_DFS_CONCURRENT))
+		return false;
+
+	/* only valid for P2P GO */
+	if (iftype != NL80211_IFTYPE_P2P_GO)
+		return false;
+
+	/*
+	 * Allow only if there's a concurrent BSS
+	 */
+	list_for_each_entry(wdev, &rdev->wiphy.wdev_list, list) {
+		bool ret = cfg80211_dfs_permissive_check_wdev(rdev, iftype,
+							      wdev, chan);
+		if (ret)
+			return ret;
+	}
+
+	return false;
+}
+
 static int cfg80211_get_chans_dfs_required(struct wiphy *wiphy,
 					    u32 center_freq,
-					    u32 bandwidth)
+					    u32 bandwidth,
+					    enum nl80211_iftype iftype)
 {
 	struct ieee80211_channel *c;
 	u32 freq, start_freq, end_freq;
@@ -530,9 +604,11 @@ static int cfg80211_get_chans_dfs_required(struct wiphy *wiphy,
 		if (!c)
 			return -EINVAL;
 
-		if (c->flags & IEEE80211_CHAN_RADAR)
+		if (c->flags & IEEE80211_CHAN_RADAR &&
+		    !cfg80211_dfs_permissive_chan(wiphy, iftype, c))
 			return 1;
 	}
+
 	return 0;
 }
 
@@ -558,7 +634,7 @@ int cfg80211_chandef_dfs_required(struct wiphy *wiphy,
 
 		ret = cfg80211_get_chans_dfs_required(wiphy,
 					ieee80211_chandef_to_khz(chandef),
-					width);
+					width, iftype);
 		if (ret < 0)
 			return ret;
 		else if (ret > 0)
@@ -569,7 +645,7 @@ int cfg80211_chandef_dfs_required(struct wiphy *wiphy,
 
 		ret = cfg80211_get_chans_dfs_required(wiphy,
 					MHZ_TO_KHZ(chandef->center_freq2),
-					width);
+					width, iftype);
 		if (ret < 0)
 			return ret;
 		else if (ret > 0)
@@ -1337,15 +1413,19 @@ static bool _cfg80211_reg_can_beacon(struct wiphy *wiphy,
 				     bool check_no_ir)
 {
 	bool res;
-	u32 prohibited_flags = IEEE80211_CHAN_DISABLED |
-			       IEEE80211_CHAN_RADAR;
+	u32 prohibited_flags = IEEE80211_CHAN_DISABLED;
+	int dfs_required;
 
 	trace_cfg80211_reg_can_beacon(wiphy, chandef, iftype, check_no_ir);
 
 	if (check_no_ir)
 		prohibited_flags |= IEEE80211_CHAN_NO_IR;
 
-	if (cfg80211_chandef_dfs_required(wiphy, chandef, iftype) > 0 &&
+	dfs_required = cfg80211_chandef_dfs_required(wiphy, chandef, iftype);
+	if (dfs_required != 0)
+		prohibited_flags |= IEEE80211_CHAN_RADAR;
+
+	if (dfs_required > 0 &&
 	    cfg80211_chandef_dfs_available(wiphy, chandef)) {
 		/* We can skip IEEE80211_CHAN_NO_IR if chandef dfs available */
 		prohibited_flags = IEEE80211_CHAN_DISABLED;
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 8b45fb420f4c..bd65c3ccc5e7 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -1201,6 +1201,9 @@ static int nl80211_msg_put_channel(struct sk_buff *msg, struct wiphy *wiphy,
 		if ((chan->flags & IEEE80211_CHAN_NO_EHT) &&
 		    nla_put_flag(msg, NL80211_FREQUENCY_ATTR_NO_EHT))
 			goto nla_put_failure;
+		if ((chan->flags & IEEE80211_CHAN_DFS_CONCURRENT) &&
+		    nla_put_flag(msg, NL80211_FREQUENCY_ATTR_DFS_CONCURRENT))
+			goto nla_put_failure;
 	}
 
 	if (nla_put_u32(msg, NL80211_FREQUENCY_ATTR_MAX_TX_POWER,
diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index 2ef4f6cc7a32..9a61b3322fd2 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -1593,6 +1593,8 @@ static u32 map_regdom_flags(u32 rd_flags)
 		channel_flags |= IEEE80211_CHAN_NO_320MHZ;
 	if (rd_flags & NL80211_RRF_NO_EHT)
 		channel_flags |= IEEE80211_CHAN_NO_EHT;
+	if (rd_flags & NL80211_RRF_DFS_CONCURRENT)
+		channel_flags |= IEEE80211_CHAN_DFS_CONCURRENT;
 	if (rd_flags & NL80211_RRF_PSD)
 		channel_flags |= IEEE80211_CHAN_PSD;
 	return channel_flags;