How can i modify NS/NA message of ipv6 in java?

Question

if I want to edit ns/na messages of ipv6 (that are an exchange between server and client) in Java, what should I do?

when the client sends ns message to the server, another client runs a dos attack on 'Duplicate address Detection' protocol. is there any code/resource available for this? I need to run that with server-client in java.

Did you search before asking? Please share the code that you try! — Nasser Ali Karimi
IPv6 doesn't use a client/server model. IPv6 is a connectionless peering model. The client/server model is an application model. Also, you should check what protection from LAN attacks are available on your switches. For example, DHCP snooping, RA guard, Dynamic ARP inspection, etc. — Ron Maupin