r2dr2 is a UDP amplification attack tool for committing DRDoS denial of service attacks.
You can download it from the following link: https://packetstormsecurity.com/files/download/127193/r2dr2-udp-drdos-tool-master.zip
Source: https://packetstormsecurity.com/files/127193/r2dr2-UDP-DrDoS-Amplification-Tool.html