[RFC] mac80211: upgrade passive scan to active scan on DFS channels after beacon rx

[Felix Fietkau <nbd@xxxxxxxx>]

In client mode, we can't connect to hidden SSID APs or SSIDs not advertised
in beacons on DFS channels, since we're forced to passive scan. Fix this by
sending out a probe request immediately after the first beacon, if active
scan was requested by the user.

Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
---
 net/mac80211/ieee80211_i.h |  5 +++++
 net/mac80211/scan.c        | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 330ea62231fa..958e3e114d0f 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1128,6 +1128,9 @@ struct tpt_led_trigger {
  *	a scan complete for an aborted scan.
  * @SCAN_HW_CANCELLED: Set for our scan work function when the scan is being
  *	cancelled.
+ * @SCAN_BEACON_WAIT: Set whenever we're passive scanning because of radar/no-IR
+ *	and could send a probe request after receiving a beacon.
+ * @SCAN_BEACON_DONE: Beacon received, we can now send a probe request
  */
 enum {
 	SCAN_SW_SCANNING,
@@ -1136,6 +1139,8 @@ enum {
 	SCAN_COMPLETED,
 	SCAN_ABORTED,
 	SCAN_HW_CANCELLED,
+	SCAN_BEACON_WAIT,
+	SCAN_BEACON_DONE,
 };
 
 /**
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 5e6b275afc9e..b698756887eb 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -281,6 +281,16 @@ void ieee80211_scan_rx(struct ieee80211_local *local, struct sk_buff *skb)
 	if (likely(!sdata1 && !sdata2))
 		return;
 
+	if (test_and_clear_bit(SCAN_BEACON_WAIT, &local->scanning)) {
+		/*
+		 * we were passive scanning because of radar/no-IR, but
+		 * the beacon/proberesp rx gives us an opportunity to upgrade
+		 * to active scan
+		 */
+		 set_bit(SCAN_BEACON_DONE, &local->scanning);
+		 ieee80211_queue_delayed_work(&local->hw, &local->scan_work, 0);
+	}
+
 	if (ieee80211_is_probe_resp(mgmt->frame_control)) {
 		struct cfg80211_scan_request *scan_req;
 		struct cfg80211_sched_scan_request *sched_scan_req;
@@ -787,6 +797,8 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 						IEEE80211_CHAN_RADAR)) ||
 		    !req->n_ssids) {
 			next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
+			if (req->n_ssids)
+				set_bit(SCAN_BEACON_WAIT, &local->scanning);
 		} else {
 			ieee80211_scan_state_send_probe(local, &next_delay);
 			next_delay = IEEE80211_CHANNEL_TIME;
@@ -998,6 +1010,8 @@ static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
 	    !scan_req->n_ssids) {
 		*next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
 		local->next_scan_state = SCAN_DECISION;
+		if (scan_req->n_ssids)
+			set_bit(SCAN_BEACON_WAIT, &local->scanning);
 		return;
 	}
 
@@ -1090,6 +1104,8 @@ void ieee80211_scan_work(struct work_struct *work)
 			goto out;
 	}
 
+	clear_bit(SCAN_BEACON_WAIT, &local->scanning);
+
 	/*
 	 * as long as no delay is required advance immediately
 	 * without scheduling a new work
@@ -1100,6 +1116,10 @@ void ieee80211_scan_work(struct work_struct *work)
 			goto out_complete;
 		}
 
+		if (test_and_clear_bit(SCAN_BEACON_DONE, &local->scanning) &&
+		    local->next_scan_state == SCAN_DECISION)
+			local->next_scan_state = SCAN_SEND_PROBE;
+
 		switch (local->next_scan_state) {
 		case SCAN_DECISION:
 			/* if no more bands/channels left, complete scan */
-- 
2.32.0 (Apple Git-132)