UnprivilegedMountFlags is from https://github.com/moby/moby/blob/v20.10.5/daemon/oci_linux.go#L420-L450 Get the set of mount flags that are set on the mount that contains the given path and are locked by CL_UNPRIVILEGED.

DefaultPropagationMode is the default propagation of mounts where user doesn't specify mount propagation explicitly.