mac80211: tx: do not drop management frames to non-MFP STA.

When drop_unencrypted is enabled and MFP is disabled, non-robust management frames for not-yet associated STA are dropped. This isn't visible as many management frames sent from the kernel have TX_INTFL_DONT_ENCRYPT set and management frames injected from a monitor vif have TX_CTL_INJECTED so aren't dropped. But management frames sent from userspace via NL80211_CMD_FRAME do not have this flag set, so are dropped.

This patch make it drop non-management frames as usual, but only MFP STA are subject to drops when drop_unencrypted is set to 1.

This shouldn't break anything, as drop_unencrypted is only enabled in IBSS mode when PRIVACY is requested.

---

Found this while trying to handle auth frames in userspace
on a IBSS RSN network.
I'm a bit surprised that drop_unencrypted is disabled both
in AP and managed mode, but only enabled in IBSS RSN, which does not support MFP yet, so the MFP handling is somewhat useless for now.

index af25c4e..9f61e64 100644
@@ -558,9 +558,10 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
 	else if (tx->sdata->drop_unencrypted &&
 		 (tx->skb->protocol != tx->sdata->control_port_protocol) &&
 		 !(info->flags & IEEE80211_TX_CTL_INJECTED) &&
-		 (!ieee80211_is_robust_mgmt_frame(hdr) ||
-		  (ieee80211_is_action(hdr->frame_control) &&
-		   tx->sta && test_sta_flag(tx->sta, WLAN_STA_MFP)))) {
+		 (!ieee80211_is_mgmt(hdr->frame_control) ||
+		  (!ieee80211_is_robust_mgmt_frame(hdr) ||
+		   ieee80211_is_action(hdr->frame_control)) &&
+		   tx->sta && test_sta_flag(tx->sta, WLAN_STA_MFP))) {
 		I802_DEBUG_INC(tx->local->tx_handlers_drop_unencrypted);
 		return TX_DROP;
 	} else

-- 1.7.10.4