this.subnetMask = new IPv4Address(skbuf, 8);
this.subnetMask = subnetMask;
	public ICMPAddressMaskHeader(SocketBuffer skbuf) {		super(skbuf);		final int type = getType();		if ((type != ICMP_ADDRESS) && (type != ICMP_ADDRESSREPLY)) {			throw new IllegalArgumentException("Invalid type " + type);		}		this.subnetMask = new IPv4Address(skbuf, 8);	}