oci: do not use specified cgroup dir path

get cgroup directory path from mountinfo instead of
using /sys/fs/cgroup/, since maybe not all os use that path.

Fixes #719.

Signed-off-by: Ace Tang <[email protected]>

oci.go

@@ -15,11 +15,13 @@
 package main
 
 import (
+	"bufio"
 	"errors"
 	"fmt"
 	"net"
 	"os"
 	"path/filepath"
+	"strings"
 	"syscall"
 
 	vc "github.com/containers/virtcontainers"
@@ -44,7 +46,9 @@ const (
 
 var errNeedLinuxResource = errors.New("Linux resource cannot be empty")
 
-var cgroupsDirPath = "/sys/fs/cgroup"
+var cgroupsDirPath string
+
+var procMountInfo = "/proc/self/mountinfo"
 
 // getContainerInfo returns the container status and its pod ID.
 // It internally expands the container ID from the prefix provided.
@@ -191,6 +195,12 @@ func processCgroupsPathForResource(ociSpec oci.CompatOCISpec, resource string, i
 		return "", errNeedLinuxResource
 	}
 
+	var err error
+	cgroupsDirPath, err = getCgroupsDirPath(procMountInfo)
+	if err != nil {
+		return "", fmt.Errorf("get CgroupsDirPath error: %s", err)
+	}
+
 	// Relative cgroups path provided.
 	if filepath.IsAbs(ociSpec.Linux.CgroupsPath) == false {
 		return filepath.Join(cgroupsDirPath, resource, ociSpec.Linux.CgroupsPath), nil
@@ -302,3 +312,41 @@ func noNeedForOutput(detach bool, tty bool) bool {
 
 	return true
 }
+
+func getCgroupsDirPath(mountInfoFile string) (string, error) {
+	if cgroupsDirPath != "" {
+		return cgroupsDirPath, nil
+	}
+
+	f, err := os.Open(mountInfoFile)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	var cgroupRootPath string
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		text := scanner.Text()
+		index := strings.Index(text, " - ")
+		if index < 0 {
+			continue
+		}
+		fields := strings.Split(text, " ")
+		postSeparatorFields := strings.Fields(text[index+3:])
+		numPostFields := len(postSeparatorFields)
+
+		if len(fields) < 5 || postSeparatorFields[0] != "cgroup" || numPostFields < 3 {
+			continue
+		}
+
+		cgroupRootPath = filepath.Dir(fields[4])
+		break
+	}
+
+	if _, err = os.Stat(cgroupRootPath); err != nil {
+		return "", err
+	}
+
+	return cgroupRootPath, nil
+}

oci_test.go

@@ -530,7 +530,12 @@ func TestIsCgroupMounted(t *testing.T) {
 
 	assert.False(isCgroupMounted(os.TempDir()), "%s is not a cgroup", os.TempDir())
 
-	memoryCgroupPath := "/sys/fs/cgroup/memory"
+	cgroupsDirPath = ""
+	cgroupRootPath, err := getCgroupsDirPath(procMountInfo)
+	if err != nil {
+		assert.NoError(err)
+	}
+	memoryCgroupPath := filepath.Join(cgroupRootPath, "memory")
 	if _, err := os.Stat(memoryCgroupPath); os.IsNotExist(err) {
 		t.Skipf("memory cgroup does not exist: %s", memoryCgroupPath)
 	}
@@ -562,3 +567,56 @@ func TestProcessCgroupsPathForResource(t *testing.T) {
 		assert.False(vcMock.IsMockError(err))
 	}
 }
+
+func TestGetCgroupsDirPath(t *testing.T) {
+	assert := assert.New(t)
+
+	type testData struct {
+		contents       string
+		expectedResult string
+		expectError    bool
+	}
+
+	dir, err := ioutil.TempDir("", "")
+	if err != nil {
+		assert.NoError(err)
+	}
+	defer os.RemoveAll(dir)
+
+	// make sure tested cgroupsDirPath is existed
+	testedCgroupDir := filepath.Join(dir, "weirdCgroup")
+	err = os.Mkdir(testedCgroupDir, testDirMode)
+	assert.NoError(err)
+
+	weirdCgroupPath := filepath.Join(testedCgroupDir, "memory")
+
+	data := []testData{
+		{fmt.Sprintf("num1 num2 num3 / %s num6 num7 - cgroup cgroup rw,memory", weirdCgroupPath), testedCgroupDir, false},
+		// cgroup mount is not properly formated, if fields post - less than 3
+		{fmt.Sprintf("num1 num2 num3 / %s num6 num7 - cgroup cgroup ", weirdCgroupPath), "", true},
+		{"a a a a a a a - b c d", "", true},
+		{"a \na b \na b c\na b c d", "", true},
+		{"", "", true},
+	}
+
+	file := filepath.Join(dir, "mountinfo")
+
+	//file does not exist, should error here
+	_, err = getCgroupsDirPath(file)
+	assert.Error(err)
+
+	for _, d := range data {
+		err := ioutil.WriteFile(file, []byte(d.contents), testFileMode)
+		assert.NoError(err)
+
+		cgroupsDirPath = ""
+		path, err := getCgroupsDirPath(file)
+		if d.expectError {
+			assert.Error(err, fmt.Sprintf("got %q, test data: %+v", path, d))
+		} else {
+			assert.NoError(err, fmt.Sprintf("got %q, test data: %+v", path, d))
+		}
+
+		assert.Equal(d.expectedResult, path)
+	}
+}