4 files changed, 155 insertions, 20 deletions

diff --git a/pkg/bindings/images/build.go b/pkg/bindings/images/build.go
index f5e7c0c98..b56afbceb 100644
--- a/pkg/bindings/images/build.go
+++ b/pkg/bindings/images/build.go
@@ -28,6 +28,11 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+type devino struct {
+	Dev uint64
+	Ino uint64
+}
+
 var (
 	iidRegex = regexp.MustCompile(`^[0-9a-f]{12}`)
 )
@@ -402,7 +407,7 @@ func nTar(excludes []string, sources ...string) (io.ReadCloser, error) {
 		defer pw.Close()
 		defer gw.Close()
 		defer tw.Close()
-
+		seen := make(map[devino]string)
 		for _, src := range sources {
 			s, err := filepath.Abs(src)
 			if err != nil {
@@ -431,25 +436,40 @@ func nTar(excludes []string, sources ...string) (io.ReadCloser, error) {
 				}
 
 				if info.Mode().IsRegular() { // add file item
-					f, lerr := os.Open(path)
-					if lerr != nil {
-						return lerr
+					di, isHardLink := checkHardLink(info)
+					if err != nil {
+						return err
 					}
 
-					hdr, lerr := tar.FileInfoHeader(info, name)
-					if lerr != nil {
-						f.Close()
-						return lerr
+					hdr, err := tar.FileInfoHeader(info, "")
+					if err != nil {
+						return err
+					}
+					orig, ok := seen[di]
+					if ok {
+						hdr.Typeflag = tar.TypeLink
+						hdr.Linkname = orig
+						hdr.Size = 0
+
+						return tw.WriteHeader(hdr)
+					}
+					f, err := os.Open(path)
+					if err != nil {
+						return err
 					}
+
 					hdr.Name = name
-					if lerr := tw.WriteHeader(hdr); lerr != nil {
+					if err := tw.WriteHeader(hdr); err != nil {
 						f.Close()
-						return lerr
+						return err
 					}
 
-					_, cerr := io.Copy(tw, f)
+					_, err = io.Copy(tw, f)
 					f.Close()
-					return cerr
+					if err == nil && isHardLink {
+						seen[di] = name
+					}
+					return err
 				} else if info.Mode().IsDir() { // add folders
 					hdr, lerr := tar.FileInfoHeader(info, name)
 					if lerr != nil {
diff --git a/pkg/bindings/images/build_unix.go b/pkg/bindings/images/build_unix.go
new file mode 100644
index 000000000..0afb1deb6
--- /dev/null
+++ b/pkg/bindings/images/build_unix.go
@@ -0,0 +1,16 @@
+// +build !windows
+
+package images
+
+import (
+	"os"
+	"syscall"
+)
+
+func checkHardLink(fi os.FileInfo) (devino, bool) {
+	st := fi.Sys().(*syscall.Stat_t)
+	return devino{
+		Dev: uint64(st.Dev),
+		Ino: uint64(st.Ino),
+	}, st.Nlink > 1
+}
diff --git a/pkg/bindings/images/build_windows.go b/pkg/bindings/images/build_windows.go
new file mode 100644
index 000000000..bd71d1bf0
--- /dev/null
+++ b/pkg/bindings/images/build_windows.go
@@ -0,0 +1,9 @@
+package images
+
+import (
+	"os"
+)
+
+func checkHardLink(fi os.FileInfo) (devino, bool) {
+	return devino{}, false
+}
diff --git a/pkg/cgroups/cgroups.go b/pkg/cgroups/cgroups.go
index aefb5183b..911edeb5b 100644
--- a/pkg/cgroups/cgroups.go
+++ b/pkg/cgroups/cgroups.go
@@ -128,28 +128,118 @@ func init() {
 // getAvailableControllers get the available controllers
 func getAvailableControllers(exclude map[string]controllerHandler, cgroup2 bool) ([]controller, error) {
 	if cgroup2 {
-		return nil, fmt.Errorf("getAvailableControllers not implemented yet for cgroup v2")
+		controllers := []controller{}
+		subtreeControl := cgroupRoot + "/cgroup.subtree_control"
+		// rootless cgroupv2: check available controllers for current user ,systemd or servicescope will inherit
+		if rootless.IsRootless() {
+			userSlice, err := getCgroupPathForCurrentProcess()
+			if err != nil {
+				return controllers, err
+			}
+			//userSlice already contains '/' so not adding here
+			basePath := cgroupRoot + userSlice
+			subtreeControl = fmt.Sprintf("%s/cgroup.subtree_control", basePath)
+		}
+		subtreeControlBytes, err := ioutil.ReadFile(subtreeControl)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed while reading controllers for cgroup v2 from %q", subtreeControl)
+		}
+		for _, controllerName := range strings.Fields(string(subtreeControlBytes)) {
+			c := controller{
+				name:    controllerName,
+				symlink: false,
+			}
+			controllers = append(controllers, c)
+		}
+		return controllers, nil
 	}
 
-	infos, err := ioutil.ReadDir(cgroupRoot)
-	if err != nil {
-		return nil, err
-	}
+	subsystems, _ := cgroupV1GetAllSubsystems()
 	controllers := []controller{}
-	for _, i := range infos {
-		name := i.Name()
+	// cgroupv1 and rootless: No subsystem is available: delegation is unsafe.
+	if rootless.IsRootless() {
+		return controllers, nil
+	}
+
+	for _, name := range subsystems {
 		if _, found := exclude[name]; found {
 			continue
 		}
+		isSymLink := false
+		fileInfo, err := os.Stat(cgroupRoot + "/" + name)
+		if err != nil {
+			isSymLink = !fileInfo.IsDir()
+		}
 		c := controller{
 			name:    name,
-			symlink: !i.IsDir(),
+			symlink: isSymLink,
 		}
 		controllers = append(controllers, c)
 	}
+
 	return controllers, nil
 }
 
+// GetAvailableControllers get string:bool map of all the available controllers
+func GetAvailableControllers(exclude map[string]controllerHandler, cgroup2 bool) ([]string, error) {
+	availableControllers, err := getAvailableControllers(exclude, cgroup2)
+	if err != nil {
+		return nil, err
+	}
+	controllerList := []string{}
+	for _, controller := range availableControllers {
+		controllerList = append(controllerList, controller.name)
+	}
+
+	return controllerList, nil
+}
+
+func cgroupV1GetAllSubsystems() ([]string, error) {
+	f, err := os.Open("/proc/cgroups")
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	subsystems := []string{}
+
+	s := bufio.NewScanner(f)
+	for s.Scan() {
+		text := s.Text()
+		if text[0] != '#' {
+			parts := strings.Fields(text)
+			if len(parts) >= 4 && parts[3] != "0" {
+				subsystems = append(subsystems, parts[0])
+			}
+		}
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+	return subsystems, nil
+}
+
+func getCgroupPathForCurrentProcess() (string, error) {
+	path := fmt.Sprintf("/proc/%d/cgroup", os.Getpid())
+	f, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	cgroupPath := ""
+	s := bufio.NewScanner(f)
+	for s.Scan() {
+		text := s.Text()
+		procEntries := strings.SplitN(text, "::", 2)
+		cgroupPath = procEntries[1]
+	}
+	if err := s.Err(); err != nil {
+		return cgroupPath, err
+	}
+	return cgroupPath, nil
+}
+
 // getCgroupv1Path is a helper function to get the cgroup v1 path
 func (c *CgroupControl) getCgroupv1Path(name string) string {
 	return filepath.Join(cgroupRoot, name, c.path)