[net80211] don't add IBSS node table entries for neighbors from other SSIDs.

The adhoc probe/beacon input path was creating nodes for all SSIDs.
This wasn't a problem when the NICs were configured to only process
frames for the current BSSID, but that didn't allow IBSS merges.
Once avos and I flipped on "beacons from all BSSIDs" to allow for
correct IBSS merging, we found this interesting behaviour.

This adds a check against the current SSID.

* If there's no VAP SSID, allow anything
* If there's a VAP SSID, check if the incoming frame has a suitable
  SSID and if so, allow it.

This prevents nodes being created for other SSIDs in probe and beacon
frames - ie, beacons overlapping IBSSes with different SSIDs, and
probe requests from arbitrary devices.

Tested:

* AR9380, IBSS mode, both local and other IBSSes.

Reviewed by:	avos
Differential Revision:	https://reviews.freebsd.org/D7959

sys/net80211/ieee80211_adhoc.c

@@ -747,8 +747,20 @@ adhoc_recv_mgmt(struct ieee80211_node *ni, struct mbuf *m0,
 			if (!IEEE80211_ADDR_EQ(wh->i_addr2, ni->ni_macaddr)) {
 				/*
 				 * Create a new entry in the neighbor table.
+				 *
+				 * XXX TODO:
+				 *
+				 * Here we're not scanning; so if we have an
+				 * SSID then make sure it matches our SSID.
+				 * Otherwise this code will match on all IBSS
+				 * beacons/probe requests for all SSIDs,
+				 * filling the node table with nodes that
+				 * aren't ours.
 				 */
-				ni = ieee80211_add_neighbor(vap, wh, &scan);
+				if (ieee80211_ibss_node_check_new(ni, &scan))
+					ni = ieee80211_add_neighbor(vap, wh, &scan);
+				else
+					ni = NULL;
 			} else if (ni->ni_capinfo == 0) {
 				/*
 				 * Update faked node created on transmit.

sys/net80211/ieee80211_node.c

@@ -578,6 +578,62 @@ ieee80211_ibss_merge_check(struct ieee80211_node *ni)
 	return 1;
 }
 
+/*
+ * Check if the given node should populate the node table.
+ *
+ * We need to be in "see all beacons for all ssids" mode in order
+ * to do IBSS merges, however this means we will populate nodes for
+ * /all/ IBSS SSIDs, versus just the one we care about.
+ *
+ * So this check ensures the node can actually belong to our IBSS
+ * configuration.  For now it simply checks the SSID.
+ */
+int
+ieee80211_ibss_node_check_new(struct ieee80211_node *ni,
+    const struct ieee80211_scanparams *scan)
+{
+	struct ieee80211vap *vap = ni->ni_vap;
+	int i;
+
+	/*
+	 * If we have no SSID and no scan SSID, return OK.
+	 */
+	if (vap->iv_des_nssid == 0 && scan->ssid == NULL)
+		goto ok;
+
+	/*
+	 * If we have one of (SSID, scan SSID) then return error.
+	 */
+	if (!! (vap->iv_des_nssid == 0) != !! (scan->ssid == NULL))
+		goto mismatch;
+
+	/*
+	 * Double-check - we need scan SSID.
+	 */
+	if (scan->ssid == NULL)
+		goto mismatch;
+
+	/*
+	 * Check if the scan SSID matches the SSID list for the VAP.
+	 */
+	for (i = 0; i < vap->iv_des_nssid; i++) {
+
+		/* Sanity length check */
+		if (vap->iv_des_ssid[i].len != scan->ssid[1])
+			continue;
+
+		/* Note: SSID in the scan entry is the IE format */
+		if (memcmp(vap->iv_des_ssid[i].ssid, scan->ssid + 2,
+		    vap->iv_des_ssid[i].len) == 0)
+			goto ok;
+	}
+
+mismatch:
+	return (0);
+ok:
+	return (1);
+}
+
 /*
  * Handle 802.11 ad hoc network merge.  The
  * convention, set by the Wireless Ethernet Compatibility Alliance

sys/net80211/ieee80211_node.h

@@ -65,6 +65,7 @@
 struct ieee80211_node_table;
 struct ieee80211com;
 struct ieee80211vap;
+struct ieee80211_scanparams;
 
 /*
  * Information element ``blob''.  We use this structure
@@ -330,6 +331,8 @@ void	ieee80211_setupcurchan(struct ieee80211com *,
 void	ieee80211_setcurchan(struct ieee80211com *, struct ieee80211_channel *);
 void	ieee80211_update_chw(struct ieee80211com *);
 int	ieee80211_ibss_merge_check(struct ieee80211_node *);
+int	ieee80211_ibss_node_check_new(struct ieee80211_node *ni,
+	    const struct ieee80211_scanparams *);
 int	ieee80211_ibss_merge(struct ieee80211_node *);
 struct ieee80211_scan_entry;
 int	ieee80211_sta_join(struct ieee80211vap *, struct ieee80211_channel *,