mac80211: skip mpath lookup also for control port tx

When using 802.1X over mesh networks, at first an ordinary
mesh peering is established, then the 802.1X EAPOL dialog
happens, afterwards an authenticated mesh peering exchange
(AMPE) happens, finally the peering is complete and we can
set the STA authorized flag.

As 802.1X is an intermediate step here and key material is
not yet exchanged for stations we have to skip mesh path lookup
for these EAPOL frames. Otherwise the already configure mesh
group encryption key would be used to send a mesh path request
which no one can decipher, because we didn't already establish
key material on both peers, like with SAE and directly using AMPE.
Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>
Link: https://lore.kernel.org/r/20200617082637.22670-2-markus.theil@tu-ilmenau.de
[remove pointless braces, remove unnecessary local variable,
 the list can only process one such frame (or its fragments)]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -3996,6 +3996,9 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 	skb_list_walk_safe(skb, skb, next) {
 		skb_mark_not_on_list(skb);
 
+		if (skb->protocol == sdata->control_port_protocol)
+			ctrl_flags |= IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP;
+
 		skb = ieee80211_build_hdr(sdata, skb, info_flags,
 					  sta, ctrl_flags, cookie);
 		if (IS_ERR(skb)) {
@@ -5371,7 +5374,8 @@ int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
 		return -EINVAL;
 
 	if (proto == sdata->control_port_protocol)
-		ctrl_flags |= IEEE80211_TX_CTRL_PORT_CTRL_PROTO;
+		ctrl_flags |= IEEE80211_TX_CTRL_PORT_CTRL_PROTO |
+			      IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP;
 
 	if (unencrypted)
 		flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;