virtcontainers: honor OCI cgroupsPath

Create cgroup path relative the cgroups mount point if it's absolute,
or create it relative to a runtime-determined location if the path
is relative.

fixes #1365
fixes #1357

Signed-off-by: Julio Montes <julio.montes@intel.com>

virtcontainers/api_test.go

@@ -23,6 +23,7 @@ import (
 	vcTypes "github.com/kata-containers/runtime/virtcontainers/pkg/types"
 	"github.com/kata-containers/runtime/virtcontainers/store"
 	"github.com/kata-containers/runtime/virtcontainers/types"
+	"github.com/kata-containers/runtime/virtcontainers/utils"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/stretchr/testify/assert"
 )
@@ -888,6 +889,7 @@ func TestStatusSandboxSuccessfulStateReady(t *testing.T) {
 				ID: containerID,
 				State: types.State{
 					State:      types.StateReady,
+					CgroupPath: utils.DefaultCgroupPath,
 				},
 				PID:         0,
 				RootFs:      filepath.Join(testDir, testBundle),
@@ -946,6 +948,7 @@ func TestStatusSandboxSuccessfulStateRunning(t *testing.T) {
 				ID: containerID,
 				State: types.State{
 					State:      types.StateRunning,
+					CgroupPath: utils.DefaultCgroupPath,
 				},
 				PID:         0,
 				RootFs:      filepath.Join(testDir, testBundle),
@@ -1769,6 +1772,7 @@ func TestStatusContainerStateReady(t *testing.T) {
 		ID: contID,
 		State: types.State{
 			State:      types.StateReady,
+			CgroupPath: utils.DefaultCgroupPath,
 		},
 		PID:         0,
 		RootFs:      filepath.Join(testDir, testBundle),
@@ -1844,6 +1848,7 @@ func TestStatusContainerStateRunning(t *testing.T) {
 		ID: contID,
 		State: types.State{
 			State:      types.StateRunning,
+			CgroupPath: utils.DefaultCgroupPath,
 		},
 		PID:         0,
 		RootFs:      filepath.Join(testDir, testBundle),

virtcontainers/container.go

@@ -1288,14 +1288,14 @@ func (c *Container) newCgroups() error {
 		resources.CPU = validCPUResources(spec.Linux.Resources.CPU)
 	}
 
+	c.state.CgroupPath = utils.ValidCgroupPath(spec.Linux.CgroupsPath)
 	cgroup, err := cgroupsNewFunc(cgroups.V1,
-		cgroups.StaticPath(spec.Linux.CgroupsPath), &resources)
+		cgroups.StaticPath(c.state.CgroupPath), &resources)
 	if err != nil {
-		return fmt.Errorf("Could not create cgroup for %v: %v", spec.Linux.CgroupsPath, err)
+		return fmt.Errorf("Could not create cgroup for %v: %v", c.state.CgroupPath, err)
 	}
 
 	c.state.Resources = resources
-	c.state.CgroupPath = spec.Linux.CgroupsPath
 
 	// Add shim into cgroup
 	if c.process.Pid > 0 {

virtcontainers/utils/utils.go

@@ -14,6 +14,9 @@ import (
 	"path/filepath"
 )
 
+// DefaultCgroupPath runtime-determined location in the cgroups hierarchy.
+const DefaultCgroupPath = "/vc"
+
 const cpBinaryName = "cp"
 
 const fileMode0755 = os.FileMode(0755)
@@ -241,3 +244,18 @@ func SupportsVsocks() bool {
 
 	return true
 }
+
+// ValidCgroupPath returns a valid cgroup path.
+// see https://github.com/opencontainers/runtime-spec/blob/master/config-linux.md#cgroups-path
+func ValidCgroupPath(path string) string {
+	// In the case of an absolute path (starting with /), the runtime MUST
+	// take the path to be relative to the cgroups mount point.
+	if filepath.IsAbs(path) {
+		return filepath.Clean(path)
+	}
+
+	// In the case of a relative path (not starting with /), the runtime MAY
+	// interpret the path relative to a runtime-determined location in the cgroups hierarchy.
+	// clean up path and return a new path relative to defaultCgroupPath
+	return filepath.Join(DefaultCgroupPath, filepath.Clean("/"+path))
+}

virtcontainers/utils/utils_test.go

@@ -325,3 +325,18 @@ func TestSupportsVsocks(t *testing.T) {
 
 	assert.True(SupportsVsocks())
 }
+
+func TestValidCgroupPath(t *testing.T) {
+	assert := assert.New(t)
+
+	assert.Equal(DefaultCgroupPath, ValidCgroupPath("../../../"))
+	assert.Equal(filepath.Join(DefaultCgroupPath, "foo"), ValidCgroupPath("../../../foo"))
+	assert.Equal("/hi", ValidCgroupPath("/../hi"))
+	assert.Equal("/hi/foo", ValidCgroupPath("/../hi/foo"))
+	assert.Equal(DefaultCgroupPath, ValidCgroupPath(""))
+	assert.Equal(DefaultCgroupPath, ValidCgroupPath(""))
+	assert.Equal(DefaultCgroupPath, ValidCgroupPath("../"))
+	assert.Equal(DefaultCgroupPath, ValidCgroupPath("."))
+	assert.Equal(DefaultCgroupPath, ValidCgroupPath("./../"))
+	assert.Equal(filepath.Join(DefaultCgroupPath, "o / g"), ValidCgroupPath("o / m /../ g"))
+}