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This commit adds a layer writer that can be used for extracting an image layer tar into a Block CIM format. Existing forked CIM layer writer was renamed to a common base type `cimLayerWriter`. Forked CIM layer writer & Block CIM layer writer both now extend this common base type to write layers in that specific format. Signed-off-by: Amit Barve <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,126 @@ | ||
| //go:build windows | ||
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| package cim | ||
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| import ( | ||
| "context" | ||
| "fmt" | ||
| "path/filepath" | ||
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| "github.com/Microsoft/go-winio" | ||
| "github.com/Microsoft/hcsshim/pkg/cimfs" | ||
| ) | ||
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| // A BlockCIMLayerWriter implements the CIMLayerWriter interface to allow writing | ||
| // container image layers in the blocked cim format. | ||
| type BlockCIMLayerWriter struct { | ||
| *cimLayerWriter | ||
| // the layer that we are writing | ||
| layer *cimfs.BlockCIM | ||
| // parent layers | ||
| parentLayers []*cimfs.BlockCIM | ||
| // added files maintains a map of all files that have been added to this layer | ||
| addedFiles map[string]struct{} | ||
| } | ||
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| var _ CIMLayerWriter = &BlockCIMLayerWriter{} | ||
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| // NewBlockCIMLayerWriter writes the layer files in the block CIM format. | ||
| func NewBlockCIMLayerWriter(ctx context.Context, layer *cimfs.BlockCIM, parentLayers []*cimfs.BlockCIM) (_ *BlockCIMLayerWriter, err error) { | ||
| if !cimfs.IsBlockCimSupported() { | ||
| return nil, fmt.Errorf("BlockCIM not supported on this build") | ||
| } else if layer.Type != cimfs.BlockCIMTypeSingleFile { | ||
| // we only support writing single file CIMs for now because in layer | ||
| // writing process we still need to write some files (registry hives) | ||
| // outside the CIM. We currently use the parent directory of the CIM (i.e | ||
| // the parent directory of block path in this case) for this. This can't | ||
| // be reliably done with the block device CIM since the block path | ||
| // provided will be a volume path. However, once we get rid of hive rollup | ||
| // step during layer import we should be able to support block device | ||
| // CIMs. | ||
| return nil, ErrBlockCIMWriterNotSupported | ||
| } | ||
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| parentLayerPaths := make([]string, 0, len(parentLayers)) | ||
| for _, pl := range parentLayers { | ||
| if pl.Type != layer.Type { | ||
| return nil, ErrBlockCIMParentTypeMismatch | ||
| } | ||
| parentLayerPaths = append(parentLayerPaths, filepath.Dir(pl.BlockPath)) | ||
| } | ||
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| cim, err := cimfs.CreateBlockCIM(layer.BlockPath, layer.CimName, layer.Type) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("error in creating a new cim: %w", err) | ||
| } | ||
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| // std file writer writes registry hives outside the CIM for 2 reasons. 1. We can | ||
| // merge the hives of this layer with the parent layer hives and then write the | ||
| // merged hives into the CIM. 2. When importing child layer of this layer, we | ||
| // have access to the merges hives of this layer. | ||
| sfw, err := newStdFileWriter(filepath.Dir(layer.BlockPath), parentLayerPaths) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("error in creating new standard file writer: %w", err) | ||
| } | ||
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| return &BlockCIMLayerWriter{ | ||
| layer: layer, | ||
| parentLayers: parentLayers, | ||
| addedFiles: make(map[string]struct{}), | ||
| cimLayerWriter: &cimLayerWriter{ | ||
| ctx: ctx, | ||
| cimWriter: cim, | ||
| stdFileWriter: sfw, | ||
| layerPath: filepath.Dir(layer.BlockPath), | ||
| parentLayerPaths: parentLayerPaths, | ||
| }, | ||
| }, nil | ||
| } | ||
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| // Add adds a file to the layer with given metadata. | ||
| func (cw *BlockCIMLayerWriter) Add(name string, fileInfo *winio.FileBasicInfo, fileSize int64, securityDescriptor []byte, extendedAttributes []byte, reparseData []byte) error { | ||
| cw.addedFiles[name] = struct{}{} | ||
| return cw.cimLayerWriter.Add(name, fileInfo, fileSize, securityDescriptor, extendedAttributes, reparseData) | ||
| } | ||
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| // Remove removes a file that was present in a parent layer from the layer. | ||
| func (cw *BlockCIMLayerWriter) Remove(name string) error { | ||
| // set active write to nil so that we panic if layer tar is incorrectly formatted. | ||
| cw.activeWriter = nil | ||
| err := cw.cimWriter.AddTombstone(name) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to remove file : %w", err) | ||
| } | ||
| return nil | ||
| } | ||
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| // AddLink adds a hard link to the layer. Note that the link added here is evaluated only | ||
| // at the CIM merge time. So an invalid link will not throw an error here. | ||
| func (cw *BlockCIMLayerWriter) AddLink(name string, target string) error { | ||
| // set active write to nil so that we panic if layer tar is incorrectly formatted. | ||
| cw.activeWriter = nil | ||
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| // when adding links to a block CIM, we need to know if the target file is present | ||
| // in this same block CIM or if it is coming from one of the parent layers. If the | ||
| // file is in the same CIM we add a standard hard link. If the file is not in the | ||
| // same CIM we add a special type of link called merged link. This merged link is | ||
| // resolved when all the individual block CIM layers are merged. In order to | ||
| // reliably know if the target is a part of the CIM or not, we wait until all | ||
| // files are added and then lookup the added entries in a map to make the | ||
| // decision. | ||
| pendingLinkOp := func(c *cimfs.CimFsWriter) error { | ||
| if _, ok := cw.addedFiles[target]; ok { | ||
| // target was added in this layer - add a normal link. Once a | ||
| // hardlink is added that hardlink also becomes a valid target for | ||
| // other links so include it in the map. | ||
| cw.addedFiles[name] = struct{}{} | ||
| return c.AddLink(target, name) | ||
| } else { | ||
| // target is from a parent layer - add a merged link | ||
| return c.AddMergedLink(target, name) | ||
| } | ||
| } | ||
| cw.pendingOps = append(cw.pendingOps, pendingCimOpFunc(pendingLinkOp)) | ||
| return nil | ||
|
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||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,47 @@ | ||
| //go:build windows | ||
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| package cim | ||
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| import ( | ||
| "context" | ||
| "errors" | ||
| "testing" | ||
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| "github.com/Microsoft/hcsshim/pkg/cimfs" | ||
| ) | ||
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| func TestSingleFileWriterTypeMismatch(t *testing.T) { | ||
| layer := &cimfs.BlockCIM{ | ||
| Type: cimfs.BlockCIMTypeSingleFile, | ||
| BlockPath: "", | ||
| CimName: "", | ||
| } | ||
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| parent := &cimfs.BlockCIM{ | ||
| Type: cimfs.BlockCIMTypeDevice, | ||
| BlockPath: "", | ||
| CimName: "", | ||
| } | ||
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| _, err := NewBlockCIMLayerWriter(context.TODO(), layer, []*cimfs.BlockCIM{parent}) | ||
| if !errors.Is(err, ErrBlockCIMParentTypeMismatch) { | ||
| t.Fatalf("expected error `%s`, got `%s`", ErrBlockCIMParentTypeMismatch, err) | ||
| } | ||
| } | ||
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| func TestSingleFileWriterInvalidBlockType(t *testing.T) { | ||
| layer := &cimfs.BlockCIM{ | ||
| BlockPath: "", | ||
| CimName: "", | ||
| } | ||
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| parent := &cimfs.BlockCIM{ | ||
| BlockPath: "", | ||
| CimName: "", | ||
| } | ||
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| _, err := NewBlockCIMLayerWriter(context.TODO(), layer, []*cimfs.BlockCIM{parent}) | ||
| if !errors.Is(err, ErrBlockCIMWriterNotSupported) { | ||
| t.Fatalf("expected error `%s`, got `%s`", ErrBlockCIMWriterNotSupported, err) | ||
| } | ||
| } |
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