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package devices
import (
"bytes"
"errors"
"reflect"
"github.com/moby/sys/userns"
"github.com/opencontainers/cgroups"
devices "github.com/opencontainers/cgroups/devices/config"
)
var testingSkipFinalCheck bool
func setV1(path string, r *cgroups.Resources) error {
if userns.RunningInUserNS() || r.SkipDevices {
return nil
}
// Generate two emulators, one for the current state of the cgroup and one
// for the requested state by the user.
current, err := loadEmulator(path)
if err != nil {
return err
}
target, err := buildEmulator(r.Devices)
if err != nil {
return err
}
// Compute the minimal set of transition rules needed to achieve the
// requested state.
transitionRules, err := current.Transition(target)
if err != nil {
return err
}
for _, rule := range transitionRules {
file := "devices.deny"
if rule.Allow {
file = "devices.allow"
}
if err := cgroups.WriteFile(path, file, rule.CgroupString()); err != nil {
return err
}
}
// Final safety check -- ensure that the resulting state is what was
// requested. This is only really correct for white-lists, but for
// black-lists we can at least check that the cgroup is in the right mode.
//
// This safety-check is skipped for the unit tests because we cannot
// currently mock devices.list correctly.
if !testingSkipFinalCheck {
currentAfter, err := loadEmulator(path)
if err != nil {
return err
}
if !target.IsBlacklist() && !reflect.DeepEqual(currentAfter, target) {
return errors.New("resulting devices cgroup doesn't precisely match target")
} else if target.IsBlacklist() != currentAfter.IsBlacklist() {
return errors.New("resulting devices cgroup doesn't match target mode")
}
}
return nil
}
func loadEmulator(path string) (*emulator, error) {
list, err := cgroups.ReadFile(path, "devices.list")
if err != nil {
return nil, err
}
return emulatorFromList(bytes.NewBufferString(list))
}
func buildEmulator(rules []*devices.Rule) (*emulator, error) {
// This defaults to a white-list -- which is what we want!
emu := &emulator{}
for _, rule := range rules {
if err := emu.Apply(*rule); err != nil {
return nil, err
}
}
return emu, nil
}
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