shim: Do not depend on pkg/oci

pkg/oci is a general utility package with dependency chains that are
uneccessary for the shim.
The shim only actually used it for a convenience function for reading
an oci spec file.
Instead of pulling in those deps just re-implement that internally in
the shim command.

Signed-off-by: Brian Goff <[email protected]>

Author: cpuguy83

cmd/containerd-shim-runc-v2/manager/manager_linux.go

@@ -40,7 +40,6 @@ import (
 	"github.com/containerd/containerd/v2/cmd/containerd-shim-runc-v2/runc"
 	"github.com/containerd/containerd/v2/core/mount"
 	"github.com/containerd/containerd/v2/pkg/namespaces"
-	"github.com/containerd/containerd/v2/pkg/oci"
 	"github.com/containerd/containerd/v2/pkg/schedcore"
 	"github.com/containerd/containerd/v2/pkg/shim"
 	"github.com/containerd/containerd/v2/version"
@@ -112,7 +111,8 @@ func newCommand(ctx context.Context, id, containerdAddress, containerdTTRPCAddre
 }
 
 func readSpec() (*spec, error) {
-	f, err := os.Open(oci.ConfigFilename)
+	const configFileName = "config.json"
+	f, err := os.Open(configFileName)
 	if err != nil {
 		return nil, err
 	}

cmd/containerd-shim-runc-v2/runc/util.go

@@ -20,17 +20,18 @@ package runc
 
 import (
 	"context"
+	"encoding/json"
+	"os"
 	"path/filepath"
 
-	"github.com/containerd/containerd/v2/pkg/oci"
 	"github.com/containerd/log"
 	"github.com/opencontainers/runtime-spec/specs-go"
 )
 
 // ShouldKillAllOnExit reads the bundle's OCI spec and returns true if
 // there is an error reading the spec or if the container has a private PID namespace
 func ShouldKillAllOnExit(ctx context.Context, bundlePath string) bool {
-	spec, err := oci.ReadSpec(filepath.Join(bundlePath, oci.ConfigFilename))
+	spec, err := readSpec(bundlePath)
 	if err != nil {
 		log.G(ctx).WithError(err).Error("shouldKillAllOnExit: failed to read config.json")
 		return true
@@ -45,3 +46,17 @@ func ShouldKillAllOnExit(ctx context.Context, bundlePath string) bool {
 	}
 	return true
 }
+
+func readSpec(p string) (*specs.Spec, error) {
+	const configFileName = "config.json"
+	f, err := os.Open(filepath.Join(p, configFileName))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	var s specs.Spec
+	if err := json.NewDecoder(f).Decode(&s); err != nil {
+		return nil, err
+	}
+	return &s, nil
+}