Many of the fields in LinuxResources struct are pointers to scalars for
some reason, presumably to differentiate between set-to-zero and unset
when unmarshaling from JSON, despite zero being outside the acceptable
range for the corresponding kernel tunables. When creating the OCI spec
for a container, the daemon sets the container's OCI spec CPUShares and
BlkioWeight parameters to zero when the corresponding Docker container
configuration values are zero, signifying unset, despite the minimum
acceptable value for CPUShares being two, and BlkioWeight ten. This has
gone unnoticed as runC does not distingiush set-to-zero from unset as it
also uses zero internally to represent unset for those fields. However,
kata-containers v3.2.0-alpha.3 tries to apply the explicit-zero resource
parameters to the container, exactly as instructed, and fails loudly.
The OCI runtime-spec is silent on how the runtime should handle the case
when those parameters are explicitly set to out-of-range values and
kata's behaviour is not unreasonable, so the daemon must therefore be in
the wrong.
Translate unset values in the Docker container's resources HostConfig to
omit the corresponding fields in the container's OCI spec when starting
and updating a container in order to maximize compatibility with
runtimes.
Signed-off-by: Cory Snider <csnider@mirantis.com>
dea870f4ea