Move diff/lcow to plugins/diff/lcow

Signed-off-by: Derek McGowan <derek@mcg.dev>

plugins/diff/lcow/lcow.go

@@ -0,0 +1,218 @@
+//go:build windows
+// +build windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package lcow
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"runtime"
+	"time"
+
+	"github.com/Microsoft/go-winio/pkg/security"
+	"github.com/Microsoft/hcsshim/ext4/tar2ext4"
+	"github.com/containerd/containerd/v2/core/content"
+	"github.com/containerd/containerd/v2/diff"
+	"github.com/containerd/containerd/v2/errdefs"
+	"github.com/containerd/containerd/v2/metadata"
+	"github.com/containerd/containerd/v2/mount"
+	"github.com/containerd/containerd/v2/plugins"
+	"github.com/containerd/log"
+	"github.com/containerd/plugin"
+	"github.com/containerd/plugin/registry"
+	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+const (
+	// maxLcowVhdSizeGB is the max size in GB of any layer
+	maxLcowVhdSizeGB = 128 * 1024 * 1024 * 1024
+)
+
+func init() {
+	registry.Register(&plugin.Registration{
+		Type: plugins.DiffPlugin,
+		ID:   "windows-lcow",
+		Requires: []plugin.Type{
+			plugins.MetadataPlugin,
+		},
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			md, err := ic.GetSingle(plugins.MetadataPlugin)
+			if err != nil {
+				return nil, err
+			}
+
+			ic.Meta.Platforms = append(ic.Meta.Platforms, ocispec.Platform{
+				OS:           "linux",
+				Architecture: runtime.GOARCH,
+			})
+			return NewWindowsLcowDiff(md.(*metadata.DB).ContentStore())
+		},
+	})
+}
+
+// CompareApplier handles both comparison and
+// application of layer diffs.
+type CompareApplier interface {
+	diff.Applier
+	diff.Comparer
+}
+
+// windowsLcowDiff does filesystem comparison and application
+// for Windows specific Linux layer diffs.
+type windowsLcowDiff struct {
+	store content.Store
+}
+
+var emptyDesc = ocispec.Descriptor{}
+
+// NewWindowsLcowDiff is the Windows LCOW container layer implementation
+// for comparing and applying Linux filesystem layers on Windows
+func NewWindowsLcowDiff(store content.Store) (CompareApplier, error) {
+	return windowsLcowDiff{
+		store: store,
+	}, nil
+}
+
+// Apply applies the content associated with the provided digests onto the
+// provided mounts. Archive content will be extracted and decompressed if
+// necessary.
+func (s windowsLcowDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []mount.Mount, opts ...diff.ApplyOpt) (d ocispec.Descriptor, err error) {
+	t1 := time.Now()
+	defer func() {
+		if err == nil {
+			log.G(ctx).WithFields(log.Fields{
+				"d":      time.Since(t1),
+				"digest": desc.Digest,
+				"size":   desc.Size,
+				"media":  desc.MediaType,
+			}).Debugf("diff applied")
+		}
+	}()
+
+	var config diff.ApplyConfig
+	for _, o := range opts {
+		if err := o(ctx, desc, &config); err != nil {
+			return emptyDesc, fmt.Errorf("failed to apply config opt: %w", err)
+		}
+	}
+
+	layer, _, err := mountsToLayerAndParents(mounts)
+	if err != nil {
+		return emptyDesc, err
+	}
+
+	ra, err := s.store.ReaderAt(ctx, desc)
+	if err != nil {
+		return emptyDesc, fmt.Errorf("failed to get reader from content store: %w", err)
+	}
+	defer ra.Close()
+
+	processor := diff.NewProcessorChain(desc.MediaType, content.NewReader(ra))
+	for {
+		if processor, err = diff.GetProcessor(ctx, processor, config.ProcessorPayloads); err != nil {
+			return emptyDesc, fmt.Errorf("failed to get stream processor for %s: %w", desc.MediaType, err)
+		}
+		if processor.MediaType() == ocispec.MediaTypeImageLayer {
+			break
+		}
+	}
+	defer processor.Close()
+
+	// Calculate the Digest as we go
+	digester := digest.Canonical.Digester()
+	rc := &readCounter{
+		r: io.TeeReader(processor, digester.Hash()),
+	}
+
+	layerPath := path.Join(layer, "layer.vhd")
+	outFile, err := os.Create(layerPath)
+	if err != nil {
+		return emptyDesc, err
+	}
+	defer func() {
+		if err != nil {
+			outFile.Close()
+			os.Remove(layerPath)
+		}
+	}()
+
+	err = tar2ext4.Convert(rc, outFile, tar2ext4.ConvertWhiteout, tar2ext4.AppendVhdFooter, tar2ext4.MaximumDiskSize(maxLcowVhdSizeGB))
+	if err != nil {
+		return emptyDesc, fmt.Errorf("failed to convert tar2ext4 vhd: %w", err)
+	}
+	err = outFile.Sync()
+	if err != nil {
+		return emptyDesc, fmt.Errorf("failed to sync tar2ext4 vhd to disk: %w", err)
+	}
+	outFile.Close()
+
+	// Read any trailing data
+	if _, err := io.Copy(io.Discard, rc); err != nil {
+		return emptyDesc, err
+	}
+
+	err = security.GrantVmGroupAccess(layerPath)
+	if err != nil {
+		return emptyDesc, fmt.Errorf("failed GrantVmGroupAccess on layer vhd: %v: %w", layerPath, err)
+	}
+
+	return ocispec.Descriptor{
+		MediaType: ocispec.MediaTypeImageLayer,
+		Size:      rc.c,
+		Digest:    digester.Digest(),
+	}, nil
+}
+
+// Compare creates a diff between the given mounts and uploads the result
+// to the content store.
+func (s windowsLcowDiff) Compare(ctx context.Context, lower, upper []mount.Mount, opts ...diff.Opt) (d ocispec.Descriptor, err error) {
+	return emptyDesc, fmt.Errorf("windowsLcowDiff does not implement Compare method: %w", errdefs.ErrNotImplemented)
+}
+
+type readCounter struct {
+	r io.Reader
+	c int64
+}
+
+func (rc *readCounter) Read(p []byte) (n int, err error) {
+	n, err = rc.r.Read(p)
+	rc.c += int64(n)
+	return
+}
+
+func mountsToLayerAndParents(mounts []mount.Mount) (string, []string, error) {
+	if len(mounts) != 1 {
+		return "", nil, fmt.Errorf("number of mounts should always be 1 for Windows lcow-layers: %w", errdefs.ErrInvalidArgument)
+	}
+	mnt := mounts[0]
+	if mnt.Type != "lcow-layer" {
+		return "", nil, fmt.Errorf("mount layer type must be lcow-layer: %w", errdefs.ErrNotImplemented)
+	}
+
+	parentLayerPaths, err := mnt.GetParentPaths()
+	if err != nil {
+		return "", nil, err
+	}
+
+	return mnt.Source, parentLayerPaths, nil
+}