mac80211: drop multicast fragments

These are not permitted by the spec, just drop them.

Link: https://lore.kernel.org/r/20210609161305.23def022b750.Ibd6dd3cdce573dae262fcdc47f8ac52b883a9c50@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rx.c

@@ -2240,17 +2240,15 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 	sc = le16_to_cpu(hdr->seq_ctrl);
 	frag = sc & IEEE80211_SCTL_FRAG;
 
-	if (is_multicast_ether_addr(hdr->addr1)) {
-		I802_DEBUG_INC(rx->local->dot11MulticastReceivedFrameCount);
-		goto out_no_led;
-	}
-
 	if (rx->sta)
 		cache = &rx->sta->frags;
 
 	if (likely(!ieee80211_has_morefrags(fc) && frag == 0))
 		goto out;
 
+	if (is_multicast_ether_addr(hdr->addr1))
+		return RX_DROP_MONITOR;
+
 	I802_DEBUG_INC(rx->local->rx_handlers_fragments);
 
 	if (skb_linearize(rx->skb))
@@ -2376,7 +2374,6 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 
  out:
 	ieee80211_led_rx(rx->local);
- out_no_led:
 	if (rx->sta)
 		rx->sta->rx_stats.packets++;
 	return RX_CONTINUE;