Force OFDM/HT/VHT to be disabled on channel 14

The regulatory rules in Japan do not allow OFDM to be used on channel
14. While this was to some extend assumed to be enforced by drivers
(many of which apparently don't), it is safer to make hostapd enforce
this by disabling any OFDM-related functionality. This tries to avoid
backwards compatibility issues by downgrading the mode rather than
rejecting the invalid configuration.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/ap/hw_features.c

@@ -943,6 +943,15 @@ int hostapd_select_hw_mode(struct hostapd_iface *iface)
 	if (iface->num_hw_features < 1)
 		return -1;
 
+	if ((iface->conf->hw_mode == HOSTAPD_MODE_IEEE80211G ||
+	     iface->conf->ieee80211n || iface->conf->ieee80211ac) &&
+	    iface->conf->channel == 14) {
+		wpa_printf(MSG_INFO, "Disable OFDM/HT/VHT on channel 14");
+		iface->conf->hw_mode = HOSTAPD_MODE_IEEE80211B;
+		iface->conf->ieee80211n = 0;
+		iface->conf->ieee80211ac = 0;
+	}
+
 	iface->current_mode = NULL;
 	for (i = 0; i < iface->num_hw_features; i++) {
 		struct hostapd_hw_modes *mode = &iface->hw_features[i];