Comment by tytso

There's an assumption which this article makes which is not true; namely, that the only utilities which do (or should) use ioctl's are system programs like ipconfig which are shipped with the kernel. There are other programs, like for example Kerberos, who want to know what network addresses are used by the network, and requiring them to screen scrape ipconfig is not especially reasonable. So if you randomly change ioctls, then you randomly break other programs that might not be shipped with the kernel that need to use those ioctls. Maintaining proper backwards compatibility for userspace applications, and not labelling some set of interfaces as "can randomly change, and if you use them and you're aren't part of the privileged set of programs shipped with the kernel, well, it just sucks to be you", is not, in my opinion a professional way to run an OS.