This is strikingly similar to previous incidents with the NTP protocol (https://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse https://en.wikipedia.org/wiki/

This is strikingly similar to previous incidents with the NTP protocol (https://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse https://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse). Several of these incidents also displayed the "retry immediately on failure" behavior. In this case, since it's TCP, there might have been an alternate solution: use the iptables hashlimit module (or a similar in his operating system) to drop the SYN packet if the client retries too fast. The sending TCP stack should make it wait for a reasonable timeout before trying again, assuming the application only retries after the previous connection attempt finished.