If you’re ok with programming you could write a program that fabricates packet(s) with a fake source IP. There are probably libraries for generating raw packets out there. GIYF.

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Here is a tutorial for implementing raw sockets in c++:
[https://www.binarytides.com/raw-sockets-using-winsock/](https://www.binarytides.com/raw-sockets-using-winsock/)