diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 21a0b8835cb3..275bbb2c1a5a 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -229,6 +229,7 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 	struct beacon_data *presp;
 	enum nl80211_bss_scan_width scan_width;
 	bool have_higher_than_11mbit;
+	bool radar_required = false;
 	int err;
 
 	sdata_assert_lock(sdata);
@@ -273,6 +274,23 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 		}
 		chandef.width = NL80211_CHAN_WIDTH_20;
 		chandef.center_freq1 = chan->center_freq;
+		/* check again for downgraded chandef */
+		if (!cfg80211_reg_can_beacon(local->hw.wiphy, &chandef)) {
+			sdata_info(sdata,
+				   "Failed to join IBSS, beacons forbidden\n");
+			return;
+		}
+	}
+
+	err = cfg80211_chandef_dfs_required(sdata->local->hw.wiphy,
+					    &chandef);
+	if (err > 0) {
+		if (!ifibss->userspace_handles_dfs) {
+			sdata_info(sdata,
+				   "Failed to join IBSS, DFS channel without control program\n");
+			return;
+		}
+		radar_required = true;
 	}
 
 	ieee80211_vif_release_channel(sdata);
@@ -297,6 +315,7 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 	rcu_assign_pointer(ifibss->presp, presp);
 	mgmt = (void *)presp->head;
 
+	sdata->radar_required = radar_required;
 	sdata->vif.bss_conf.enable_beacon = true;
 	sdata->vif.bss_conf.beacon_int = beacon_int;
 	sdata->vif.bss_conf.basic_rates = basic_rates;
@@ -796,6 +815,21 @@ static void ieee80211_csa_connection_drop_work(struct work_struct *work)
 	ieee80211_queue_work(&sdata->local->hw, &sdata->work);
 }
 
+static void ieee80211_ibss_csa_mark_radar(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_if_ibss *ifibss = &sdata->u.ibss;
+	int err;
+
+	/* if the current channel is a DFS channel, mark the channel as
+	 * unavailable.
+	 */
+	err = cfg80211_chandef_dfs_required(sdata->local->hw.wiphy,
+					    &ifibss->chandef);
+	if (err > 0)
+		cfg80211_radar_event(sdata->local->hw.wiphy, &ifibss->chandef,
+				     GFP_ATOMIC);
+}
+
 static bool
 ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 				  struct ieee802_11_elems *elems,
@@ -880,8 +914,7 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 		goto disconnect;
 	}
 
-	if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, &params.chandef,
-				     IEEE80211_CHAN_DISABLED)) {
+	if (!cfg80211_reg_can_beacon(sdata->local->hw.wiphy, &params.chandef)) {
 		sdata_info(sdata,
 			   "IBSS %pM switches to unsupported channel (%d MHz, width:%d, CF1/2: %d/%d MHz), disconnecting\n",
 			   ifibss->bssid,
@@ -897,10 +930,11 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 	if (err < 0)
 		goto disconnect;
 	if (err) {
-		params.radar_required = true;
+		/* IBSS-DFS only allowed with a control program */
+		if (!ifibss->userspace_handles_dfs)
+			goto disconnect;
 
-		/* TODO: IBSS-DFS not (yet) supported, disconnect. */
-		goto disconnect;
+		params.radar_required = true;
 	}
 
 	rcu_read_lock();
@@ -947,12 +981,16 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 	ieee80211_bss_info_change_notify(sdata, err);
 	drv_channel_switch_beacon(sdata, &params.chandef);
 
+	ieee80211_ibss_csa_mark_radar(sdata);
+
 	return true;
 disconnect:
 	ibss_dbg(sdata, "Can't handle channel switch, disconnect\n");
 	ieee80211_queue_work(&sdata->local->hw,
 			     &ifibss->csa_connection_drop_work);
 
+	ieee80211_ibss_csa_mark_radar(sdata);
+
 	return true;
 }
 
@@ -1688,6 +1726,7 @@ int ieee80211_ibss_join(struct ieee80211_sub_if_data *sdata,
 
 	sdata->u.ibss.privacy = params->privacy;
 	sdata->u.ibss.control_port = params->control_port;
+	sdata->u.ibss.userspace_handles_dfs = params->userspace_handles_dfs;
 	sdata->u.ibss.basic_rates = params->basic_rates;
 
 	/* fix basic_rates if channel does not support these rates */
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 8340d4939f1b..ff3c310142b5 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -501,6 +501,7 @@ struct ieee80211_if_ibss {
 	bool privacy;
 
 	bool control_port;
+	bool userspace_handles_dfs;
 
 	u8 bssid[ETH_ALEN] __aligned(2);
 	u8 ssid[IEEE80211_MAX_SSID_LEN];