class VirtualNetworkFilter implements IFloodlightModule, IVirtualNetworkService, IOFMessageListener {

    @Override
    public void deleteHost(MACAddress mac, String port) {
        if (log.isDebugEnabled()) {
            log.debug("Removing host {} from port {}", mac, port);
        }
        if (mac == null && port == null) return;
        if (port != null) {
            MACAddress host = portToMac.remove(port);
            if(host !=null && vNetsByGuid.get(macToGuid.get(host)) != null)
                vNetsByGuid.get(macToGuid.get(host)).removeHost(host);
			if(host !=null)
	            macToGuid.remove(host);
        } else if (mac != null) {
            if (!portToMac.isEmpty()) {
                for (Entry<String, MACAddress> entry : portToMac.entrySet()) {
                    if (entry.getValue().equals(mac)) {
                        if(vNetsByGuid.get(macToGuid.get(entry.getValue())) != null)
                            vNetsByGuid.get(macToGuid.get(entry.getValue())).removeHost(entry.getValue());
                        portToMac.remove(entry.getKey());
                        macToGuid.remove(entry.getValue());
                        return;
                    }
                }
            }
        }
    }

}