mac80211: enable DFS for IBSS mode

Allow changing to DFS channels if the channel is available for
beaconing and userspace controls DFS operation.

Channel switch announcement from other stations on DFS channels will
be interpreted as radar event. These channels will then be marked as
unvailable.

Signed-off-by: Simon Wunderlich <[e-mail]>
Signed-off-by: Mathias Kretschmer <[e-mail]>
Signed-off-by: Johannes Berg <[e-mail]>

net/mac80211/ibss.c

···
 	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);
···
 		}
 		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);
···
 	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;
···
 	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,
···
 		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,
···
 	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();
···
 	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;
 }
···
 
 	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 */

net/mac80211/ieee80211_i.h

···
 	bool privacy;
 
 	bool control_port;
+	bool userspace_handles_dfs;
 
 	u8 bssid[ETH_ALEN] __aligned(2);
 	u8 ssid[IEEE80211_MAX_SSID_LEN];