Managing sysctl knobs with BPF

Posted Apr 10, 2019 3:00 UTC (Wed) by wahern (subscriber, #37304)
In reply to: Managing sysctl knobs with BPF by Cyberax
Parent article: Managing sysctl knobs with BPF

The BPF train left the station years ago, LSM is just another inevitable victim.

What I find interesting is that the traditional BSD sysctl interface uses integer constants. And while most distributions have disabled the sysctl syscall, AFAIU /proc/sys was and continues to be just another interface to the same underlying mechanism. Are newer knobs no longer exposed via the old syscall interface? I ask because the new BPF interface exposes string paths, which seems not just unwise but possibly unnecessary if there already exist fixed integer identifiers.

Managing sysctl knobs with BPF

Posted Apr 10, 2019 3:25 UTC (Wed) by ebiederm (subscriber, #35028) [Link]

New sysctl knobs are no longer exposed via the binary sysctl paths. Only the binary sysctl emulation layer even knows the old binary paths.

On Linux unlike BSD, the binary mechanism is an emulation layer of /proc/sys. While at one point the binary layer was almost equal, that is no longer the case.

The binary layer kept having conflicting paths added, was not used, was never tested, and had security holes the /proc/sys path did not. So a while ago I just reduced it to an emulation layer so we could forget about it.

Which is a long way of saying about the only thing the BSD and Linux sysctl implementations have in common is their name.