DFS: Add new hostapd_is_dfs_overlap() helper

Add a new hostapd_is_dfs_overlap() helper function to DFS module. This
function tells whether the selected frequency range overlaps with DFS
channels in the current hostapd configuration. Selected frequency reange
is specified by its center frequency and bandwidth.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>

src/ap/dfs.c

@@ -1290,3 +1290,56 @@ int hostapd_handle_dfs_offload(struct hostapd_iface *iface)
 		   __func__, iface->freq);
 	return 2;
 }
+
+
+int hostapd_is_dfs_overlap(struct hostapd_iface *iface, enum chan_width width,
+			   int center_freq)
+{
+	struct hostapd_channel_data *chan;
+	struct hostapd_hw_modes *mode = iface->current_mode;
+	int half_width;
+	int res = 0;
+	int i;
+
+	if (!iface->conf->ieee80211h || !mode ||
+	    mode->mode != HOSTAPD_MODE_IEEE80211A)
+		return 0;
+
+	switch (width) {
+	case CHAN_WIDTH_20_NOHT:
+	case CHAN_WIDTH_20:
+		half_width = 10;
+		break;
+	case CHAN_WIDTH_40:
+		half_width = 20;
+		break;
+	case CHAN_WIDTH_80:
+	case CHAN_WIDTH_80P80:
+		half_width = 40;
+		break;
+	case CHAN_WIDTH_160:
+		half_width = 80;
+		break;
+	default:
+		wpa_printf(MSG_WARNING, "DFS chanwidth %d not supported",
+			   width);
+		return 0;
+	}
+
+	for (i = 0; i < mode->num_channels; i++) {
+		chan = &mode->channels[i];
+
+		if (!(chan->flag & HOSTAPD_CHAN_RADAR))
+			continue;
+
+		if (center_freq - chan->freq < half_width &&
+		    chan->freq - center_freq < half_width)
+			res++;
+	}
+
+	wpa_printf(MSG_DEBUG, "DFS: (%d, %d): in range: %s",
+		   center_freq - half_width, center_freq + half_width,
+		   res ? "yes" : "no");
+
+	return res;
+}

src/ap/dfs.h

@@ -30,5 +30,7 @@ int hostapd_dfs_start_cac(struct hostapd_iface *iface, int freq,
 			  int ht_enabled, int chan_offset, int chan_width,
 			  int cf1, int cf2);
 int hostapd_handle_dfs_offload(struct hostapd_iface *iface);
+int hostapd_is_dfs_overlap(struct hostapd_iface *iface, enum chan_width width,
+			   int center_freq);
 
 #endif /* DFS_H */