mac80211: BSS info: check channel first

When we receive information about a BSS we check at some point
whether or not we think we're allowed to use the channel it is
on, but we do that fairly late. I don't think we should do it
that late, so do it earlier to avoid doing IBSS/mesh stuff on
that channel and then getting confused because it's disabled.
Signed-off-by: NJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/mlme.c

@@ -2602,7 +2602,15 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 	DECLARE_MAC_BUF(mac);
 	DECLARE_MAC_BUF(mac2);
 
-	beacon_timestamp = le64_to_cpu(mgmt->u.beacon.timestamp);
+	if (elems->ds_params && elems->ds_params_len == 1)
+		freq = ieee80211_channel_to_frequency(elems->ds_params[0]);
+	else
+		freq = rx_status->freq;
+
+	channel = ieee80211_get_channel(local->hw.wiphy, freq);
+
+	if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
+		return;
 
 	if (ieee80211_vif_is_mesh(&sdata->vif) && elems->mesh_id &&
 	    elems->mesh_config && mesh_matches_local(elems, sdata)) {
@@ -2645,16 +2653,6 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 		rcu_read_unlock();
 	}
 
-	if (elems->ds_params && elems->ds_params_len == 1)
-		freq = ieee80211_channel_to_frequency(elems->ds_params[0]);
-	else
-		freq = rx_status->freq;
-
-	channel = ieee80211_get_channel(local->hw.wiphy, freq);
-
-	if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
-		return;
-
 #ifdef CONFIG_MAC80211_MESH
 	if (elems->mesh_config)
 		bss = ieee80211_rx_mesh_bss_get(local, elems->mesh_id,
@@ -2723,6 +2721,8 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 
 	bss->band = band;
 
+	beacon_timestamp = le64_to_cpu(mgmt->u.beacon.timestamp);
+
 	bss->timestamp = beacon_timestamp;
 	bss->last_update = jiffies;
 	bss->signal = rx_status->signal;