Add validation for CGroup parents. Pass CGroups path into runc

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

Closes: #507
Approved by: baude

libpod/container.go

@@ -39,8 +39,12 @@ const (
 	ContainerStatePaused ContainerStatus = iota
 )
 
-// DefaultCgroupParent is the default prefix to a cgroup path in libpod
-var DefaultCgroupParent = "/libpod_parent"
+// CgroupfsDefaultCgroupParent is the cgroup parent for CGroupFS in libpod
+const CgroupfsDefaultCgroupParent = "/libpod_parent"
+
+// SystemdDefaultCgroupParent is the cgroup parent for the systemd cgroup
+// manager in libpod
+const SystemdDefaultCgroupParent = "system.slice"
 
 // LinuxNS represents a Linux namespace
 type LinuxNS int
@@ -851,7 +855,8 @@ func (c *Container) NamespacePath(ns LinuxNS) (string, error) {
 
 // CGroupPath returns a cgroups "path" for a given container.
 func (c *Container) CGroupPath() cgroups.Path {
-	return cgroups.StaticPath(filepath.Join(c.config.CgroupParent, fmt.Sprintf("libpod-conmon-%s/%s", c.ID(), c.ID())))
+	// TODO add support for systemd cgroup paths
+	return cgroups.StaticPath(filepath.Join(c.config.CgroupParent, fmt.Sprintf("libpod-conmon-%s", c.ID())))
 }
 
 // RootFsSize returns the root FS size of the container

libpod/container_internal.go

@@ -160,7 +160,6 @@ func newContainer(rspec *spec.Spec, lockDir string) (*Container, error) {
 	ctr.config.CreatedTime = time.Now()
 
 	ctr.config.ShmSize = DefaultShmSize
-	ctr.config.CgroupParent = DefaultCgroupParent
 
 	ctr.state.BindMounts = make(map[string]string)
 
@@ -1129,6 +1128,13 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) {
 		g.AddProcessEnv("container", "libpod")
 	}
 
+	cgroupPath, err := c.CGroupPath()("")
+	if err != nil {
+		return nil, errors.Wrapf(err, "error retrieving CGroup path for container %s", c.ID())
+	}
+	logrus.Debugf("Setting CGroup path for container %s to %s", c.ID(), cgroupPath)
+	g.SetLinuxCgroupsPath(cgroupPath)
+
 	return g.Spec(), nil
 }
 

libpod/runtime_ctr.go

@@ -3,6 +3,7 @@ package libpod
 import (
 	"context"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 	"time"
@@ -60,6 +61,24 @@ func (r *Runtime) NewContainer(ctx context.Context, rSpec *spec.Spec, options ..
 		ctr.config.Name = name
 	}
 
+	// Check CGroup parent sanity, and set it if it was not set
+	switch r.config.CgroupManager {
+	case CgroupfsCgroupsManager:
+		if ctr.config.CgroupParent == "" {
+			ctr.config.CgroupParent = CgroupfsDefaultCgroupParent
+		} else if strings.HasSuffix(path.Base(ctr.config.CgroupParent), ".slice") {
+			return nil, errors.Wrapf(ErrInvalidArg, "systemd slice received as cgroup parent when using cgroupfs")
+		}
+	case SystemdCgroupsManager:
+		if ctr.config.CgroupParent == "" {
+			ctr.config.CgroupParent = SystemdDefaultCgroupParent
+		} else if len(ctr.config.CgroupParent) < 6 || !strings.HasSuffix(path.Base(ctr.config.CgroupParent), ".slice") {
+			return nil, errors.Wrapf(ErrInvalidArg, "did not receive systemd slice as cgroup parent when using systemd to manage cgroups")
+		}
+	default:
+		return nil, errors.Wrapf(ErrInvalidArg, "unsupported CGroup manager: %s - cannot validate cgroup parent", r.config.CgroupManager)
+	}
+
 	// Set up storage for the container
 	if err := ctr.setupStorage(ctx); err != nil {
 		return nil, err