Function supportsIDMap

core/mount/mount_linux_test.go:497–538

(path string)

}

func supportsIDMap(path string) bool {
	treeFD, err := unix.OpenTree(-1, path, uint(unix.OPEN_TREE_CLONE|unix.OPEN_TREE_CLOEXEC))
	if err != nil {
		return false
	}
	defer unix.Close(treeFD)

	// We want to test if idmap mounts are supported.
	// So we use just some random mapping, it doesn't really matter which one.
	// For the helper command, we just need something that is alive while we
	// test this, a sleep 5 will do it.
	cmd := exec.Command("sleep", "5")
	cmd.SysProcAttr = &syscall.SysProcAttr{
		Cloneflags:  syscall.CLONE_NEWUSER,
		UidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
		GidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
	}
	if err := cmd.Start(); err != nil {
		return false
	}
	defer func() {
		_ = cmd.Process.Kill()
		_ = cmd.Wait()
	}()

	usernsFD := fmt.Sprintf("/proc/%d/ns/user", cmd.Process.Pid)
	var usernsFile *os.File
	if usernsFile, err = os.Open(usernsFD); err != nil {
		return false
	}
	defer usernsFile.Close()

	attr := unix.MountAttr{
		Attr_set:  unix.MOUNT_ATTR_IDMAP,
		Userns_fd: uint64(usernsFile.Fd()),
	}
	if err := unix.MountSetattr(treeFD, "", unix.AT_EMPTY_PATH, &attr); err != nil {
		return false
	}

	return true
}

func TestBuildIDMappedPaths(t *testing.T) {
	testCases := []struct {