Merge pull request #37999 from Microsoft/jjh/tar2vhd

LCOW: ApplyDiff() use tar2ext4, not SVM

daemon/graphdriver/lcow/lcow.go

@@ -71,20 +71,33 @@ import (
 	"time"
 
 	"github.com/Microsoft/hcsshim"
+	"github.com/Microsoft/hcsshim/ext4/tar2ext4"
 	"github.com/Microsoft/opengcs/client"
 	"github.com/docker/docker/daemon/graphdriver"
 	"github.com/docker/docker/pkg/archive"
 	"github.com/docker/docker/pkg/containerfs"
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/pkg/ioutils"
+	"github.com/docker/docker/pkg/reexec"
 	"github.com/docker/docker/pkg/system"
 	"github.com/sirupsen/logrus"
 )
 
+// noreexec controls reexec functionality. Off by default, on for debugging purposes.
+var noreexec = false
+
 // init registers this driver to the register. It gets initialised by the
 // function passed in the second parameter, implemented in this file.
 func init() {
 	graphdriver.Register("lcow", InitDriver)
+	// DOCKER_LCOW_NOREEXEC allows for inline processing which makes
+	// debugging issues in the re-exec codepath significantly easier.
+	if os.Getenv("DOCKER_LCOW_NOREEXEC") != "" {
+		logrus.Warnf("LCOW Graphdriver is set to not re-exec. This is intended for debugging purposes only.")
+		noreexec = true
+	} else {
+		reexec.Register("docker-lcow-tar2ext4", tar2ext4Reexec)
+	}
 }
 
 const (
@@ -846,32 +859,72 @@ func (d *Driver) Diff(id, parent string) (io.ReadCloser, error) {
 func (d *Driver) ApplyDiff(id, parent string, diff io.Reader) (int64, error) {
 	logrus.Debugf("lcowdriver: applydiff: id %s", id)
 
-	svm, err := d.startServiceVMIfNotRunning(id, nil, fmt.Sprintf("applydiff %s", id))
+	// Log failures here as it's undiagnosable sometimes, due to a possible panic.
+	// See https://github.com/moby/moby/issues/37955 for more information.
+
+	dest := filepath.Join(d.dataRoot, id, layerFilename)
+	if !noreexec {
+		cmd := reexec.Command([]string{"docker-lcow-tar2ext4", dest}...)
+		stdout := bytes.NewBuffer(nil)
+		stderr := bytes.NewBuffer(nil)
+		cmd.Stdin = diff
+		cmd.Stdout = stdout
+		cmd.Stderr = stderr
+
+		if err := cmd.Start(); err != nil {
+			logrus.Warnf("lcowdriver: applydiff: id %s failed to start re-exec: %s", id, err)
+			return 0, err
+		}
+
+		if err := cmd.Wait(); err != nil {
+			logrus.Warnf("lcowdriver: applydiff: id %s failed %s", id, err)
+			return 0, fmt.Errorf("re-exec error: %v: stderr: %s", err, stderr)
+		}
+		return strconv.ParseInt(stdout.String(), 10, 64)
+	}
+	// The inline case
+	size, err := tar2ext4Actual(dest, diff)
+	if err != nil {
+		logrus.Warnf("lcowdriver: applydiff: id %s failed %s", id, err)
+	}
+	return size, err
+}
+
+// tar2ext4Reexec is the re-exec entry point for writing a layer from a tar file
+func tar2ext4Reexec() {
+	size, err := tar2ext4Actual(os.Args[1], os.Stdin)
+	if err != nil {
+		fmt.Fprint(os.Stderr, err)
+		os.Exit(1)
+	}
+	fmt.Fprint(os.Stdout, size)
+}
+
+// tar2ext4Actual is the implementation of tar2ext to write a layer from a tar file.
+// It can be called through re-exec (default), or inline for debugging.
+func tar2ext4Actual(dest string, diff io.Reader) (int64, error) {
+	// maxDiskSize is not relating to the sandbox size - this is the
+	// maximum possible size a layer VHD generated can be from an EXT4
+	// layout perspective.
+	const maxDiskSize = 128 * 1024 * 1024 * 1024 // 128GB
+	out, err := os.Create(dest)
 	if err != nil {
 		return 0, err
 	}
-	defer d.terminateServiceVM(id, fmt.Sprintf("applydiff %s", id), false)
-
-	logrus.Debugf("lcowdriver: applydiff: waiting for svm to finish booting")
-	err = svm.getStartError()
+	defer out.Close()
+	if err := tar2ext4.Convert(
+		diff,
+		out,
+		tar2ext4.AppendVhdFooter,
+		tar2ext4.ConvertWhiteout,
+		tar2ext4.MaximumDiskSize(maxDiskSize)); err != nil {
+		return 0, err
+	}
+	fi, err := os.Stat(dest)
 	if err != nil {
-		return 0, fmt.Errorf("lcowdriver: applydiff: svm failed to boot: %s", err)
-	}
-
-	// TODO @jhowardmsft - the retries are temporary to overcome platform reliability issues.
-	// Obviously this will be removed as platform bugs are fixed.
-	retries := 0
-	for {
-		retries++
-		size, err := svm.config.TarToVhd(filepath.Join(d.dataRoot, id, layerFilename), diff)
-		if err != nil {
-			if retries <= 10 {
-				continue
-			}
-			return 0, err
-		}
-		return size, err
+		return 0, err
 	}
+	return fi.Size(), nil
 }
 
 // Changes produces a list of changes between the specified layer

vendor.conf

@@ -1,6 +1,6 @@
 # the following lines are in sorted order, FYI
 github.com/Azure/go-ansiterm d6e3b3328b783f23731bc4d058875b0371ff8109
-github.com/Microsoft/hcsshim v0.7.6
+github.com/Microsoft/hcsshim v0.7.9
 github.com/Microsoft/go-winio v0.4.11
 github.com/docker/libtrust 9cbd2a1374f46905c68a4eb3694a130610adc62a
 github.com/go-check/check 4ed411733c5785b40214c70bce814c3a3a689609 https://github.com/cpuguy83/check.git

vendor/github.com/Microsoft/hcsshim/ext4/internal/format/format.go

@@ -0,0 +1,411 @@
+package format
+
+type SuperBlock struct {
+	InodesCount          uint32
+	BlocksCountLow       uint32
+	RootBlocksCountLow   uint32
+	FreeBlocksCountLow   uint32
+	FreeInodesCount      uint32
+	FirstDataBlock       uint32
+	LogBlockSize         uint32
+	LogClusterSize       uint32
+	BlocksPerGroup       uint32
+	ClustersPerGroup     uint32
+	InodesPerGroup       uint32
+	Mtime                uint32
+	Wtime                uint32
+	MountCount           uint16
+	MaxMountCount        uint16
+	Magic                uint16
+	State                uint16
+	Errors               uint16
+	MinorRevisionLevel   uint16
+	LastCheck            uint32
+	CheckInterval        uint32
+	CreatorOS            uint32
+	RevisionLevel        uint32
+	DefaultReservedUid   uint16
+	DefaultReservedGid   uint16
+	FirstInode           uint32
+	InodeSize            uint16
+	BlockGroupNr         uint16
+	FeatureCompat        CompatFeature
+	FeatureIncompat      IncompatFeature
+	FeatureRoCompat      RoCompatFeature
+	UUID                 [16]uint8
+	VolumeName           [16]byte
+	LastMounted          [64]byte
+	AlgorithmUsageBitmap uint32
+	PreallocBlocks       uint8
+	PreallocDirBlocks    uint8
+	ReservedGdtBlocks    uint16
+	JournalUUID          [16]uint8
+	JournalInum          uint32
+	JournalDev           uint32
+	LastOrphan           uint32
+	HashSeed             [4]uint32
+	DefHashVersion       uint8
+	JournalBackupType    uint8
+	DescSize             uint16
+	DefaultMountOpts     uint32
+	FirstMetaBg          uint32
+	MkfsTime             uint32
+	JournalBlocks        [17]uint32
+	BlocksCountHigh      uint32
+	RBlocksCountHigh     uint32
+	FreeBlocksCountHigh  uint32
+	MinExtraIsize        uint16
+	WantExtraIsize       uint16
+	Flags                uint32
+	RaidStride           uint16
+	MmpInterval          uint16
+	MmpBlock             uint64
+	RaidStripeWidth      uint32
+	LogGroupsPerFlex     uint8
+	ChecksumType         uint8
+	ReservedPad          uint16
+	KbytesWritten        uint64
+	SnapshotInum         uint32
+	SnapshotID           uint32
+	SnapshotRBlocksCount uint64
+	SnapshotList         uint32
+	ErrorCount           uint32
+	FirstErrorTime       uint32
+	FirstErrorInode      uint32
+	FirstErrorBlock      uint64
+	FirstErrorFunc       [32]uint8
+	FirstErrorLine       uint32
+	LastErrorTime        uint32
+	LastErrorInode       uint32
+	LastErrorLine        uint32
+	LastErrorBlock       uint64
+	LastErrorFunc        [32]uint8
+	MountOpts            [64]uint8
+	UserQuotaInum        uint32
+	GroupQuotaInum       uint32
+	OverheadBlocks       uint32
+	BackupBgs            [2]uint32
+	EncryptAlgos         [4]uint8
+	EncryptPwSalt        [16]uint8
+	LpfInode             uint32
+	ProjectQuotaInum     uint32
+	ChecksumSeed         uint32
+	WtimeHigh            uint8
+	MtimeHigh            uint8
+	MkfsTimeHigh         uint8
+	LastcheckHigh        uint8
+	FirstErrorTimeHigh   uint8
+	LastErrorTimeHigh    uint8
+	Pad                  [2]uint8
+	Reserved             [96]uint32
+	Checksum             uint32
+}
+
+const SuperBlockMagic uint16 = 0xef53
+
+type CompatFeature uint32
+type IncompatFeature uint32
+type RoCompatFeature uint32
+
+const (
+	CompatDirPrealloc   CompatFeature = 0x1
+	CompatImagicInodes  CompatFeature = 0x2
+	CompatHasJournal    CompatFeature = 0x4
+	CompatExtAttr       CompatFeature = 0x8
+	CompatResizeInode   CompatFeature = 0x10
+	CompatDirIndex      CompatFeature = 0x20
+	CompatLazyBg        CompatFeature = 0x40
+	CompatExcludeInode  CompatFeature = 0x80
+	CompatExcludeBitmap CompatFeature = 0x100
+	CompatSparseSuper2  CompatFeature = 0x200
+
+	IncompatCompression IncompatFeature = 0x1
+	IncompatFiletype    IncompatFeature = 0x2
+	IncompatRecover     IncompatFeature = 0x4
+	IncompatJournalDev  IncompatFeature = 0x8
+	IncompatMetaBg      IncompatFeature = 0x10
+	IncompatExtents     IncompatFeature = 0x40
+	Incompat_64Bit      IncompatFeature = 0x80
+	IncompatMmp         IncompatFeature = 0x100
+	IncompatFlexBg      IncompatFeature = 0x200
+	IncompatEaInode     IncompatFeature = 0x400
+	IncompatDirdata     IncompatFeature = 0x1000
+	IncompatCsumSeed    IncompatFeature = 0x2000
+	IncompatLargedir    IncompatFeature = 0x4000
+	IncompatInlineData  IncompatFeature = 0x8000
+	IncompatEncrypt     IncompatFeature = 0x10000
+
+	RoCompatSparseSuper  RoCompatFeature = 0x1
+	RoCompatLargeFile    RoCompatFeature = 0x2
+	RoCompatBtreeDir     RoCompatFeature = 0x4
+	RoCompatHugeFile     RoCompatFeature = 0x8
+	RoCompatGdtCsum      RoCompatFeature = 0x10
+	RoCompatDirNlink     RoCompatFeature = 0x20
+	RoCompatExtraIsize   RoCompatFeature = 0x40
+	RoCompatHasSnapshot  RoCompatFeature = 0x80
+	RoCompatQuota        RoCompatFeature = 0x100
+	RoCompatBigalloc     RoCompatFeature = 0x200
+	RoCompatMetadataCsum RoCompatFeature = 0x400
+	RoCompatReplica      RoCompatFeature = 0x800
+	RoCompatReadonly     RoCompatFeature = 0x1000
+	RoCompatProject      RoCompatFeature = 0x2000
+)
+
+type BlockGroupFlag uint16
+
+const (
+	BlockGroupInodeUninit BlockGroupFlag = 0x1
+	BlockGroupBlockUninit BlockGroupFlag = 0x2
+	BlockGroupInodeZeroed BlockGroupFlag = 0x4
+)
+
+type GroupDescriptor struct {
+	BlockBitmapLow     uint32
+	InodeBitmapLow     uint32
+	InodeTableLow      uint32
+	FreeBlocksCountLow uint16
+	FreeInodesCountLow uint16
+	UsedDirsCountLow   uint16
+	Flags              BlockGroupFlag
+	ExcludeBitmapLow   uint32
+	BlockBitmapCsumLow uint16
+	InodeBitmapCsumLow uint16
+	ItableUnusedLow    uint16
+	Checksum           uint16
+}
+
+type GroupDescriptor64 struct {
+	GroupDescriptor
+	BlockBitmapHigh     uint32
+	InodeBitmapHigh     uint32
+	InodeTableHigh      uint32
+	FreeBlocksCountHigh uint16
+	FreeInodesCountHigh uint16
+	UsedDirsCountHigh   uint16
+	ItableUnusedHigh    uint16
+	ExcludeBitmapHigh   uint32
+	BlockBitmapCsumHigh uint16
+	InodeBitmapCsumHigh uint16
+	Reserved            uint32
+}
+
+const (
+	S_IXOTH  = 0x1
+	S_IWOTH  = 0x2
+	S_IROTH  = 0x4
+	S_IXGRP  = 0x8
+	S_IWGRP  = 0x10
+	S_IRGRP  = 0x20
+	S_IXUSR  = 0x40
+	S_IWUSR  = 0x80
+	S_IRUSR  = 0x100
+	S_ISVTX  = 0x200
+	S_ISGID  = 0x400
+	S_ISUID  = 0x800
+	S_IFIFO  = 0x1000
+	S_IFCHR  = 0x2000
+	S_IFDIR  = 0x4000
+	S_IFBLK  = 0x6000
+	S_IFREG  = 0x8000
+	S_IFLNK  = 0xA000
+	S_IFSOCK = 0xC000
+
+	TypeMask uint16 = 0xF000
+)
+
+type InodeNumber uint32
+
+const (
+	InodeRoot = 2
+)
+
+type Inode struct {
+	Mode                 uint16
+	Uid                  uint16
+	SizeLow              uint32
+	Atime                uint32
+	Ctime                uint32
+	Mtime                uint32
+	Dtime                uint32
+	Gid                  uint16
+	LinksCount           uint16
+	BlocksLow            uint32
+	Flags                InodeFlag
+	Version              uint32
+	Block                [60]byte
+	Generation           uint32
+	XattrBlockLow        uint32
+	SizeHigh             uint32
+	ObsoleteFragmentAddr uint32
+	BlocksHigh           uint16
+	XattrBlockHigh       uint16
+	UidHigh              uint16
+	GidHigh              uint16
+	ChecksumLow          uint16
+	Reserved             uint16
+	ExtraIsize           uint16
+	ChecksumHigh         uint16
+	CtimeExtra           uint32
+	MtimeExtra           uint32
+	AtimeExtra           uint32
+	Crtime               uint32
+	CrtimeExtra          uint32
+	VersionHigh          uint32
+	Projid               uint32
+}
+
+type InodeFlag uint32
+
+const (
+	InodeFlagSecRm              InodeFlag = 0x1
+	InodeFlagUnRm               InodeFlag = 0x2
+	InodeFlagCompressed         InodeFlag = 0x4
+	InodeFlagSync               InodeFlag = 0x8
+	InodeFlagImmutable          InodeFlag = 0x10
+	InodeFlagAppend             InodeFlag = 0x20
+	InodeFlagNoDump             InodeFlag = 0x40
+	InodeFlagNoAtime            InodeFlag = 0x80
+	InodeFlagDirtyCompressed    InodeFlag = 0x100
+	InodeFlagCompressedClusters InodeFlag = 0x200
+	InodeFlagNoCompress         InodeFlag = 0x400
+	InodeFlagEncrypted          InodeFlag = 0x800
+	InodeFlagHashedIndex        InodeFlag = 0x1000
+	InodeFlagMagic              InodeFlag = 0x2000
+	InodeFlagJournalData        InodeFlag = 0x4000
+	InodeFlagNoTail             InodeFlag = 0x8000
+	InodeFlagDirSync            InodeFlag = 0x10000
+	InodeFlagTopDir             InodeFlag = 0x20000
+	InodeFlagHugeFile           InodeFlag = 0x40000
+	InodeFlagExtents            InodeFlag = 0x80000
+	InodeFlagEaInode            InodeFlag = 0x200000
+	InodeFlagEOFBlocks          InodeFlag = 0x400000
+	InodeFlagSnapfile           InodeFlag = 0x01000000
+	InodeFlagSnapfileDeleted    InodeFlag = 0x04000000
+	InodeFlagSnapfileShrunk     InodeFlag = 0x08000000
+	InodeFlagInlineData         InodeFlag = 0x10000000
+	InodeFlagProjectIDInherit   InodeFlag = 0x20000000
+	InodeFlagReserved           InodeFlag = 0x80000000
+)
+
+const (
+	MaxLinks = 65000
+)
+
+type ExtentHeader struct {
+	Magic      uint16
+	Entries    uint16
+	Max        uint16
+	Depth      uint16
+	Generation uint32
+}
+
+const ExtentHeaderMagic uint16 = 0xf30a
+
+type ExtentIndexNode struct {
+	Block    uint32
+	LeafLow  uint32
+	LeafHigh uint16
+	Unused   uint16
+}
+
+type ExtentLeafNode struct {
+	Block     uint32
+	Length    uint16
+	StartHigh uint16
+	StartLow  uint32
+}
+
+type ExtentTail struct {
+	Checksum uint32
+}
+
+type DirectoryEntry struct {
+	Inode        InodeNumber
+	RecordLength uint16
+	NameLength   uint8
+	FileType     FileType
+	//Name         []byte
+}
+
+type FileType uint8
+
+const (
+	FileTypeUnknown      FileType = 0x0
+	FileTypeRegular      FileType = 0x1
+	FileTypeDirectory    FileType = 0x2
+	FileTypeCharacter    FileType = 0x3
+	FileTypeBlock        FileType = 0x4
+	FileTypeFIFO         FileType = 0x5
+	FileTypeSocket       FileType = 0x6
+	FileTypeSymbolicLink FileType = 0x7
+)
+
+type DirectoryEntryTail struct {
+	ReservedZero1 uint32
+	RecordLength  uint16
+	ReservedZero2 uint8
+	FileType      uint8
+	Checksum      uint32
+}
+
+type DirectoryTreeRoot struct {
+	Dot            DirectoryEntry
+	DotName        [4]byte
+	DotDot         DirectoryEntry
+	DotDotName     [4]byte
+	ReservedZero   uint32
+	HashVersion    uint8
+	InfoLength     uint8
+	IndirectLevels uint8
+	UnusedFlags    uint8
+	Limit          uint16
+	Count          uint16
+	Block          uint32
+	//Entries        []DirectoryTreeEntry
+}
+
+type DirectoryTreeNode struct {
+	FakeInode        uint32
+	FakeRecordLength uint16
+	NameLength       uint8
+	FileType         uint8
+	Limit            uint16
+	Count            uint16
+	Block            uint32
+	//Entries          []DirectoryTreeEntry
+}
+
+type DirectoryTreeEntry struct {
+	Hash  uint32
+	Block uint32
+}
+
+type DirectoryTreeTail struct {
+	Reserved uint32
+	Checksum uint32
+}
+
+type XAttrInodeBodyHeader struct {
+	Magic uint32
+}
+
+type XAttrHeader struct {
+	Magic          uint32
+	ReferenceCount uint32
+	Blocks         uint32
+	Hash           uint32
+	Checksum       uint32
+	Reserved       [3]uint32
+}
+
+const XAttrHeaderMagic uint32 = 0xea020000
+
+type XAttrEntry struct {
+	NameLength  uint8
+	NameIndex   uint8
+	ValueOffset uint16
+	ValueInum   uint32
+	ValueSize   uint32
+	Hash        uint32
+	//Name        []byte
+}

vendor/github.com/Microsoft/hcsshim/ext4/tar2ext4/tar2ext4.go

@@ -0,0 +1,174 @@
+package tar2ext4
+
+import (
+	"archive/tar"
+	"bufio"
+	"encoding/binary"
+	"io"
+	"path"
+	"strings"
+
+	"github.com/Microsoft/hcsshim/ext4/internal/compactext4"
+)
+
+type params struct {
+	convertWhiteout bool
+	appendVhdFooter bool
+	ext4opts        []compactext4.Option
+}
+
+// Option is the type for optional parameters to Convert.
+type Option func(*params)
+
+// ConvertWhiteout instructs the converter to convert OCI-style whiteouts
+// (beginning with .wh.) to overlay-style whiteouts.
+func ConvertWhiteout(p *params) {
+	p.convertWhiteout = true
+}
+
+// AppendVhdFooter instructs the converter to add a fixed VHD footer to the
+// file.
+func AppendVhdFooter(p *params) {
+	p.appendVhdFooter = true
+}
+
+// InlineData instructs the converter to write small files into the inode
+// structures directly. This creates smaller images but currently is not
+// compatible with DAX.
+func InlineData(p *params) {
+	p.ext4opts = append(p.ext4opts, compactext4.InlineData)
+}
+
+// MaximumDiskSize instructs the writer to limit the disk size to the specified
+// value. This also reserves enough metadata space for the specified disk size.
+// If not provided, then 16GB is the default.
+func MaximumDiskSize(size int64) Option {
+	return func(p *params) {
+		p.ext4opts = append(p.ext4opts, compactext4.MaximumDiskSize(size))
+	}
+}
+
+const (
+	whiteoutPrefix = ".wh."
+	opaqueWhiteout = ".wh..wh..opq"
+)
+
+// Convert writes a compact ext4 file system image that contains the files in the
+// input tar stream.
+func Convert(r io.Reader, w io.ReadWriteSeeker, options ...Option) error {
+	var p params
+	for _, opt := range options {
+		opt(&p)
+	}
+	t := tar.NewReader(bufio.NewReader(r))
+	fs := compactext4.NewWriter(w, p.ext4opts...)
+	for {
+		hdr, err := t.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return err
+		}
+
+		if p.convertWhiteout {
+			dir, name := path.Split(hdr.Name)
+			if strings.HasPrefix(name, whiteoutPrefix) {
+				if name == opaqueWhiteout {
+					// Update the directory with the appropriate xattr.
+					f, err := fs.Stat(dir)
+					if err != nil {
+						return err
+					}
+					f.Xattrs["trusted.overlay.opaque"] = []byte("y")
+					err = fs.Create(dir, f)
+					if err != nil {
+						return err
+					}
+				} else {
+					// Create an overlay-style whiteout.
+					f := &compactext4.File{
+						Mode:     compactext4.S_IFCHR,
+						Devmajor: 0,
+						Devminor: 0,
+					}
+					err = fs.Create(path.Join(dir, name[len(whiteoutPrefix):]), f)
+					if err != nil {
+						return err
+					}
+				}
+
+				continue
+			}
+		}
+
+		if hdr.Typeflag == tar.TypeLink {
+			err = fs.Link(hdr.Linkname, hdr.Name)
+			if err != nil {
+				return err
+			}
+		} else {
+			f := &compactext4.File{
+				Mode:     uint16(hdr.Mode),
+				Atime:    hdr.AccessTime,
+				Mtime:    hdr.ModTime,
+				Ctime:    hdr.ChangeTime,
+				Crtime:   hdr.ModTime,
+				Size:     hdr.Size,
+				Uid:      uint32(hdr.Uid),
+				Gid:      uint32(hdr.Gid),
+				Linkname: hdr.Linkname,
+				Devmajor: uint32(hdr.Devmajor),
+				Devminor: uint32(hdr.Devminor),
+				Xattrs:   make(map[string][]byte),
+			}
+			for key, value := range hdr.PAXRecords {
+				const xattrPrefix = "SCHILY.xattr."
+				if strings.HasPrefix(key, xattrPrefix) {
+					f.Xattrs[key[len(xattrPrefix):]] = []byte(value)
+				}
+			}
+
+			var typ uint16
+			switch hdr.Typeflag {
+			case tar.TypeReg, tar.TypeRegA:
+				typ = compactext4.S_IFREG
+			case tar.TypeSymlink:
+				typ = compactext4.S_IFLNK
+			case tar.TypeChar:
+				typ = compactext4.S_IFCHR
+			case tar.TypeBlock:
+				typ = compactext4.S_IFBLK
+			case tar.TypeDir:
+				typ = compactext4.S_IFDIR
+			case tar.TypeFifo:
+				typ = compactext4.S_IFIFO
+			}
+			f.Mode &= ^compactext4.TypeMask
+			f.Mode |= typ
+			err = fs.Create(hdr.Name, f)
+			if err != nil {
+				return err
+			}
+			_, err = io.Copy(fs, t)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	err := fs.Close()
+	if err != nil {
+		return err
+	}
+	if p.appendVhdFooter {
+		size, err := w.Seek(0, io.SeekEnd)
+		if err != nil {
+			return err
+		}
+		err = binary.Write(w, binary.BigEndian, makeFixedVHDFooter(size))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

vendor/github.com/Microsoft/hcsshim/ext4/tar2ext4/vhdfooter.go

@@ -0,0 +1,76 @@
+package tar2ext4
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/binary"
+)
+
+// Constants for the VHD footer
+const (
+	cookieMagic            = "conectix"
+	featureMask            = 0x2
+	fileFormatVersionMagic = 0x00010000
+	fixedDataOffset        = -1
+	creatorVersionMagic    = 0x000a0000
+	diskTypeFixed          = 2
+)
+
+type vhdFooter struct {
+	Cookie             [8]byte
+	Features           uint32
+	FileFormatVersion  uint32
+	DataOffset         int64
+	TimeStamp          uint32
+	CreatorApplication [4]byte
+	CreatorVersion     uint32
+	CreatorHostOS      [4]byte
+	OriginalSize       int64
+	CurrentSize        int64
+	DiskGeometry       uint32
+	DiskType           uint32
+	Checksum           uint32
+	UniqueID           [16]uint8
+	SavedState         uint8
+	Reserved           [427]uint8
+}
+
+func makeFixedVHDFooter(size int64) *vhdFooter {
+	footer := &vhdFooter{
+		Features:          featureMask,
+		FileFormatVersion: fileFormatVersionMagic,
+		DataOffset:        fixedDataOffset,
+		CreatorVersion:    creatorVersionMagic,
+		OriginalSize:      size,
+		CurrentSize:       size,
+		DiskType:          diskTypeFixed,
+		UniqueID:          generateUUID(),
+	}
+	copy(footer.Cookie[:], cookieMagic)
+	footer.Checksum = calculateCheckSum(footer)
+	return footer
+}
+
+func calculateCheckSum(footer *vhdFooter) uint32 {
+	oldchk := footer.Checksum
+	footer.Checksum = 0
+
+	buf := &bytes.Buffer{}
+	binary.Write(buf, binary.BigEndian, footer)
+
+	var chk uint32
+	bufBytes := buf.Bytes()
+	for i := 0; i < len(bufBytes); i++ {
+		chk += uint32(bufBytes[i])
+	}
+	footer.Checksum = oldchk
+	return uint32(^chk)
+}
+
+func generateUUID() [16]byte {
+	res := [16]byte{}
+	if _, err := rand.Read(res[:]); err != nil {
+		panic(err)
+	}
+	return res
+}

vendor/github.com/Microsoft/hcsshim/version.go

@@ -1,6 +0,0 @@
-package hcsshim
-
-// IsTP4 returns whether the currently running Windows build is at least TP4.
-func IsTP4() bool {
-	return false
-}