add support for pushing and pulling images

Signed-off-by: Avi Deitcher <avi@deitcher.net>

src/cmd/linuxkit/cache.go

@@ -26,5 +26,7 @@ func cacheCmd() *cobra.Command {
 	cmd.AddCommand(cacheLsCmd())
 	cmd.AddCommand(cacheExportCmd())
 	cmd.AddCommand(cacheImportCmd())
+	cmd.AddCommand(cachePullCmd())
+	cmd.AddCommand(cachePushCmd())
 	return cmd
 }

src/cmd/linuxkit/cache/pull.go

@@ -5,10 +5,18 @@ import (
 	"fmt"
 
 	"github.com/containerd/containerd/reference"
+	"github.com/google/go-containerregistry/pkg/authn"
+	namepkg "github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/layout"
+	"github.com/google/go-containerregistry/pkg/v1/match"
 	"github.com/google/go-containerregistry/pkg/v1/partial"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
 	"github.com/google/go-containerregistry/pkg/v1/validate"
 	lktspec "github.com/linuxkit/linuxkit/src/cmd/linuxkit/spec"
+	"github.com/linuxkit/linuxkit/src/cmd/linuxkit/util"
+	imagespec "github.com/opencontainers/image-spec/specs-go/v1"
+	log "github.com/sirupsen/logrus"
 )
 
 const (
@@ -118,3 +126,77 @@ func validateManifestContents(index v1.ImageIndex, digest v1.Hash) error {
 	}
 	return nil
 }
+
+// Pull pull a reference, whether it points to an arch-specific image or to an index.
+// If an index, optionally, try to pull its individual named references as well.
+func (p *Provider) Pull(name string, withArchReferences bool) error {
+	var (
+		err error
+	)
+	fullname := util.ReferenceExpand(name, util.ReferenceWithTag())
+	ref, err := namepkg.ParseReference(fullname)
+	if err != nil {
+		return err
+	}
+	v1ref, err := reference.Parse(ref.String())
+	if err != nil {
+		return err
+	}
+
+	// before we even try to push, let us see if it exists remotely
+	remoteOptions := []remote.Option{remote.WithAuthFromKeychain(authn.DefaultKeychain)}
+
+	desc, err := remote.Get(ref, remoteOptions...)
+	if err != nil {
+		return fmt.Errorf("error getting manifest for trusted image %s: %v", name, err)
+	}
+
+	// use the original image name in the annotation
+	annotations := map[string]string{
+		imagespec.AnnotationRefName: fullname,
+	}
+
+	// first attempt as an index
+	ii, err := desc.ImageIndex()
+	if err == nil {
+		log.Debugf("ImageWrite retrieved %s is index, saving", fullname)
+
+		if err := p.cache.WriteIndex(ii); err != nil {
+			return fmt.Errorf("unable to write index: %v", err)
+		}
+		if _, err := p.DescriptorWrite(&v1ref, desc.Descriptor); err != nil {
+			return fmt.Errorf("unable to write index descriptor to cache: %v", err)
+		}
+		if withArchReferences {
+			im, err := ii.IndexManifest()
+			if err != nil {
+				return fmt.Errorf("unable to get IndexManifest: %v", err)
+			}
+			for _, m := range im.Manifests {
+				if m.MediaType.IsImage() && m.Platform != nil && m.Platform.Architecture != unknown && m.Platform.OS != unknown {
+					archSpecific := fmt.Sprintf("%s-%s", ref.String(), m.Platform.Architecture)
+					archRef, err := reference.Parse(archSpecific)
+					if err != nil {
+						return fmt.Errorf("unable to parse arch-specific reference %s: %v", archSpecific, err)
+					}
+					if _, err := p.DescriptorWrite(&archRef, m); err != nil {
+						return fmt.Errorf("unable to write index descriptor to cache: %v", err)
+					}
+				}
+			}
+		}
+	} else {
+		var im v1.Image
+		// try an image
+		im, err = desc.Image()
+		if err != nil {
+			return fmt.Errorf("provided image is neither an image nor an index: %s", name)
+		}
+		log.Debugf("ImageWrite retrieved %s is image, saving", fullname)
+		if err = p.cache.ReplaceImage(im, match.Name(fullname), layout.WithAnnotations(annotations)); err != nil {
+			return fmt.Errorf("unable to save image to cache: %v", err)
+		}
+	}
+
+	return nil
+}

src/cmd/linuxkit/cache_pull.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	cachepkg "github.com/linuxkit/linuxkit/src/cmd/linuxkit/cache"
+	"github.com/linuxkit/linuxkit/src/cmd/linuxkit/util"
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+func cachePullCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "pull",
+		Short: "pull images to the linuxkit cache from registry",
+		Long: `Pull named images from their registry to the linuxkit cache. Can provide short name, like linuxkit/kernel:6.6.13
+		or nginx, or canonical name, like docker.io/library/nginx:latest. Will be saved into cache as canonical.
+		Will replace in cache if found. Blobs with the same content are not replaced.`,
+		Args: cobra.MinimumNArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			names := args
+			for _, name := range names {
+				fullname := util.ReferenceExpand(name, util.ReferenceWithTag())
+
+				p, err := cachepkg.NewProvider(cacheDir)
+				if err != nil {
+					log.Fatalf("unable to read a local cache: %v", err)
+				}
+
+				if err := p.Pull(fullname, true); err != nil {
+					log.Fatalf("unable to push image named %s: %v", name, err)
+				}
+			}
+			return nil
+		},
+	}
+
+	return cmd
+}

src/cmd/linuxkit/cache_push.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	cachepkg "github.com/linuxkit/linuxkit/src/cmd/linuxkit/cache"
+	"github.com/linuxkit/linuxkit/src/cmd/linuxkit/util"
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+func cachePushCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "push",
+		Short: "push images from the linuxkit cache",
+		Long: `Push named images from the linuxkit cache to registry. Can provide short name, like linuxkit/kernel:6.6.13
+		or nginx, or canonical name, like docker.io/library/nginx:latest.
+		It is efficient, as blobs with the same content are not replaced.`,
+		Args: cobra.MinimumNArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			names := args
+			for _, name := range names {
+				fullname := util.ReferenceExpand(name)
+
+				p, err := cachepkg.NewProvider(cacheDir)
+				if err != nil {
+					log.Fatalf("unable to read a local cache: %v", err)
+				}
+
+				if err := p.Push(fullname, true); err != nil {
+					log.Fatalf("unable to push image named %s: %v", name, err)
+				}
+			}
+			return nil
+		},
+	}
+
+	return cmd
+}

src/cmd/linuxkit/util/reference.go

@@ -2,15 +2,37 @@ package util
 
 import "strings"
 
+type refOpts struct {
+	withTag bool
+}
+type ReferenceOption func(r *refOpts)
+
+// ReferenceWithTag returns a ReferenceOption that ensures a tag is filled. If the tag is not provided,
+// the default is added
+func ReferenceWithTag() ReferenceOption {
+	return func(r *refOpts) {
+		r.withTag = true
+	}
+}
+
 // ReferenceExpand expands "redis" to "docker.io/library/redis" so all images have a full domain
-func ReferenceExpand(ref string) string {
+func ReferenceExpand(ref string, options ...ReferenceOption) string {
+	var opts refOpts
+	for _, opt := range options {
+		opt(&opts)
+	}
+	var ret string
 	parts := strings.Split(ref, "/")
 	switch len(parts) {
 	case 1:
-		return "docker.io/library/" + ref
+		ret = "docker.io/library/" + ref
 	case 2:
-		return "docker.io/" + ref
+		ret = "docker.io/" + ref
 	default:
-		return ref
+		ret = ref
 	}
+	if opts.withTag && !strings.Contains(ret, ":") {
+		ret += ":latest"
+	}
+	return ret
 }