Ah, found the explanation: The problem with that idea is that the kernel cannot count on those types being consistently defined for all configurations, and can

Ah, found the explanation: The problem with that idea is that the kernel cannot count on those types being consistently defined for all configurations, and cannot create its own definitions for the standard types. So the kernel/user interface must continue to be defined using kernel-specific types (__u16 and such). From: https://lwn.net/Articles/113349/ https://lwn.net/Articles/113349/ And as close to Word Of God as I can get: http://yarchive.net/comp/linux/int_types.html http://yarchive.net/comp/linux/int_types.html