Under certain, unclear scenarios (this has come up two-three times, but I've never managed to pin it down, no matter what), when doing 'ifdown <ipv6-device>' you get like: error: 'net.ipv6.conf.sit0.forwarding' is an unknown key error: 'net.ipv6.conf.sit0.accept_ra' is an unknown key error: 'net.ipv6.conf.sit0.accept_redirects' is an unknown key , because the interface has already been deleted. A good (open) question is, why this only happens rather rarely. These should probably be hidden. It can be done with the attached patch.
Created attachment 31215 [details] only try to set sysctl values if the corresponding device still exists
This has to be fixed by now. In any case, 6.63-1 will add '-e' to all the invocations.