mac80211: accept public action frames with mismatched BSSID

Arik's patch "mac80211: allow action frames with unknown
BSSID in GO mode" allowed any action frames in P2P mode
to go through, but only to cooked monitor interfaces as
the IEEE80211_RX_RA_MATCH was still cleared. As a result
my no-monitor patches broke invitation responses.

Instead of allowing any action frames in P2P GO mode to
go through with a wrong BSSID like that patch did, allow
all public action frames. They will never be processed
by mac80211, but can be reported via nl80211 then.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/ieee80211.h

@@ -1694,6 +1694,23 @@ static inline bool ieee80211_is_robust_mgmt_frame(struct ieee80211_hdr *hdr)
 	return false;
 }
 
+/**
+ * ieee80211_is_public_action - check if frame is a public action frame
+ * @hdr: the frame
+ * @len: length of the frame
+ */
+static inline bool ieee80211_is_public_action(struct ieee80211_hdr *hdr,
+					      size_t len)
+{
+	struct ieee80211_mgmt *mgmt = (void *)hdr;
+
+	if (len < IEEE80211_MIN_ACTION_SIZE)
+		return false;
+	if (!ieee80211_is_action(hdr->frame_control))
+		return false;
+	return mgmt->u.action.category == WLAN_CATEGORY_PUBLIC;
+}
+
 /**
  * ieee80211_fhss_chan_to_freq - get channel frequency
  * @channel: the FHSS channel

net/mac80211/rx.c

@@ -2797,10 +2797,17 @@ static int prepare_for_handlers(struct ieee80211_rx_data *rx,
 				return 0;
 		} else if (!ieee80211_bssid_match(bssid,
 					sdata->vif.addr)) {
+			/*
+			 * Accept public action frames even when the
+			 * BSSID doesn't match, this is used for P2P
+			 * and location updates. Note that mac80211
+			 * itself never looks at these frames.
+			 */
+			if (!(status->rx_flags & IEEE80211_RX_IN_SCAN) &&
+			    ieee80211_is_public_action(hdr, skb->len))
+				return 1;
 			if (!(status->rx_flags & IEEE80211_RX_IN_SCAN) &&
-			    !ieee80211_is_beacon(hdr->frame_control) &&
-			    !(ieee80211_is_action(hdr->frame_control) &&
-			      sdata->vif.p2p))
+			    !ieee80211_is_beacon(hdr->frame_control))
 				return 0;
 			status->rx_flags &= ~IEEE80211_RX_RA_MATCH;
 		}