I made a Terrible decision of a project at Netflix. The idea was that you could swap out an IPv4 (AF_INET/SOCK_STREAM) socket with an AF_INET6 one.

Turns out actually doing this with the Linux kernel is exceptionally difficult. You can swap out the underlying sk, but doing it safely is damn near impossible because the two data structures aren’t really built like that.

One day, I’d love if someone added the ability to swap Unix sockets for TCP sockets at runtime to the kernel — for other reasons.