mac80211: mesh: avoid pointless station lookup

In ieee80211_build_hdr(), the station is looked up to build the
header correctly (QoS field) and to check for authorization. For
mesh, authorization isn't checked here, and QoS capability is
mandatory, so the station lookup can be avoided.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -2052,12 +2052,14 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
 	}
 
 	/*
-	 * There's no need to try to look up the destination
-	 * if it is a multicast address (which can only happen
-	 * in AP mode)
+	 * There's no need to try to look up the destination station
+	 * if it is a multicast address. In mesh, there's no need to
+	 * look up the station at all as it always must be QoS capable
+	 * and mesh mode checks authorization later.
 	 */
 	multicast = is_multicast_ether_addr(hdr.addr1);
-	if (!multicast && !have_station) {
+	if (!multicast && !have_station &&
+	    !ieee80211_vif_is_mesh(&sdata->vif)) {
 		sta = sta_info_get(sdata, hdr.addr1);
 		if (sta) {
 			authorized = test_sta_flag(sta, WLAN_STA_AUTHORIZED);