That could possibly work, but only if you dup() the same original FD. If you just try dup()ing any random FD the internal file description pointer won't match,

That could possibly work, but only if you dup() the same original FD. If you just try dup()ing any random FD the internal file description pointer won't match, so epoll won't reconize it. But of course, if you have any threads then it's a big race condition.