libpod: support for cgroup namespace

allow a container to run in a new cgroup namespace.

When running in a new cgroup namespace, the current cgroup appears to
be the root, so that there is no way for the container to access
cgroups outside of its own subtree.

By default it uses --cgroup=host to keep the previous behavior.

To create a new namespace, --cgroup=private must be provided.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/spec/createconfig.go

@@ -63,6 +63,7 @@ type CreateConfig struct {
 	CapDrop            []string // cap-drop
 	CidFile            string
 	ConmonPidFile      string
+	Cgroupns           string
 	CgroupParent       string // cgroup-parent
 	Command            []string
 	Detach             bool              // detach
@@ -101,6 +102,7 @@ type CreateConfig struct {
 	NetworkAlias       []string               //network-alias
 	PidMode            namespaces.PidMode     //pid
 	Pod                string                 //pod
+	CgroupMode         namespaces.CgroupMode  //cgroup
 	PortBindings       nat.PortMap
 	Privileged         bool     //privileged
 	Publish            []string //publish
@@ -268,6 +270,23 @@ func (c *CreateConfig) getContainerCreateOptions(runtime *libpod.Runtime, pod *l
 		options = append(options, libpod.WithNetNS(portBindings, postConfigureNetNS, string(c.NetMode), networks))
 	}
 
+	if c.CgroupMode.IsNS() {
+		ns := c.CgroupMode.NS()
+		if ns == "" {
+			return nil, errors.Errorf("invalid empty user-defined network namespace")
+		}
+		_, err := os.Stat(ns)
+		if err != nil {
+			return nil, err
+		}
+	} else if c.CgroupMode.IsContainer() {
+		connectedCtr, err := runtime.LookupContainer(c.CgroupMode.Container())
+		if err != nil {
+			return nil, errors.Wrapf(err, "container %q not found", c.CgroupMode.Container())
+		}
+		options = append(options, libpod.WithCgroupNSFrom(connectedCtr))
+	}
+
 	if c.PidMode.IsContainer() {
 		connectedCtr, err := runtime.LookupContainer(c.PidMode.Container())
 		if err != nil {