mac80211: mesh: advertise gates in mesh formation

The Connected to Mesh Gate subfield (802.11-2016 9.4.2.98.7) in the Mesh
Formation Info field is currently unset.  This field may be useful in
determining which MBSSes to join or which mesh STAs to peer with.

If this mesh STA is a gate, by having turned on mesh gate announcements,
or if we have a path to one (e.g. by having received RANNs) then set this
bit to 1.
Signed-off-by: Bob Copeland <bobcopeland@fb.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mesh.c

@@ -254,6 +254,8 @@ int mesh_add_meshconf_ie(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 	u8 *pos, neighbors;
 	u8 meshconf_len = sizeof(struct ieee80211_meshconf_ie);
+	bool is_connected_to_gate = ifmsh->num_gates > 0 ||
+		ifmsh->mshcfg.dot11MeshGateAnnouncementProtocol;
 
 	if (skb_tailroom(skb) < 2 + meshconf_len)
 		return -ENOMEM;
@@ -278,7 +280,7 @@ int mesh_add_meshconf_ie(struct ieee80211_sub_if_data *sdata,
 	/* Mesh Formation Info - number of neighbors */
 	neighbors = atomic_read(&ifmsh->estab_plinks);
 	neighbors = min_t(int, neighbors, IEEE80211_MAX_MESH_PEERINGS);
-	*pos++ = neighbors << 1;
+	*pos++ = (neighbors << 1) | is_connected_to_gate;
 	/* Mesh capability */
 	*pos = 0x00;
 	*pos |= ifmsh->mshcfg.dot11MeshForwarding ?