public void addTunnel(UserTunnel tunnel) {
        this.access();
        tunnels.put(tunnel.getUUID().toString(), tunnel);
    }
Associates the given tunnel with this session, such that it is taken
into account when determining session activity.

@param tunnel The tunnel to associate with this session.
guacamole/src/main/java/org/apache/guacamole/GuacamoleSession.java