DFS: Allow switch to DFS channel after radar detection in ETSI

This is to comply with uniform spreading requirement for ETSI domain
(section 4.7.2.7 in EN 301 893 - V1.8.1). ETSI uniform spreading
requires equal probability for the usable channels. The previous channel
selection logic after a radar detection did not fully comply with the
uniform spreading requirement for the domain by ignoring DFS channels.
Consider DFS channels also during channel selection when the current DFS
domain is ETSI.

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qti.qualcomm.com>

src/ap/dfs.c

@@ -889,6 +889,13 @@ static int hostapd_dfs_start_channel_switch(struct hostapd_iface *iface)
 	if (iface->cac_started)
 		return hostapd_dfs_start_channel_switch_cac(iface);
 
+	/*
+	 * Allow selection of DFS channel in ETSI to comply with
+	 * uniform spreading.
+	 */
+	if (iface->dfs_domain == HOSTAPD_DFS_REGION_ETSI)
+		skip_radar = 0;
+
 	/* Perform channel switch/CSA */
 	channel = dfs_get_valid_channel(iface, &secondary_channel,
 					&vht_oper_centr_freq_seg0_idx,

src/ap/hostapd.h

@@ -475,6 +475,8 @@ struct hostapd_iface {
 
 	struct dl_list sta_seen; /* struct hostapd_sta_info */
 	unsigned int num_sta_seen;
+
+	u8 dfs_domain;
 };
 
 /* hostapd.c */

src/ap/hw_features.c

@@ -93,6 +93,7 @@ int hostapd_get_hw_features(struct hostapd_iface *iface)
 	}
 
 	iface->hw_flags = flags;
+	iface->dfs_domain = dfs_domain;
 
 	hostapd_free_hw_features(iface->hw_features, iface->num_hw_features);
 	iface->hw_features = modes;