InetAddress src = InetAddress.getByName("192.168.1.1");
Ip4 ip = packet.getHeader(new Ip4());
Tcp tcp = packet.getHeader(new Tcp());
ip.destination(dst.getAddress());
ip.source(src.getAddress());
ip.checksum(ip.calculateChecksum());
tcp.checksum(tcp.calculateChecksum());
packet.scan(Ethernet.ID);