horten the unix socket path for shim

Use sha256 hash to shorten the unix socket path to satisfy the
length limitation of abstract socket path

This commit also backports the feature storing address path to
a file from v2 to keep compatibility

Fixes #3032

Signed-off-by: Eric Lin <linxiulei@gmail.com>

container_test.go

@@ -32,7 +32,9 @@ import (
 	// Register the typeurl
 	"github.com/containerd/containerd/cio"
 	"github.com/containerd/containerd/containers"
+	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/oci"
+	"github.com/containerd/containerd/platforms"
 	_ "github.com/containerd/containerd/runtime"
 	"github.com/containerd/typeurl"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
@@ -1528,3 +1530,59 @@ func TestContainerHook(t *testing.T) {
 	}
 	defer task.Delete(ctx, WithProcessKill)
 }
+
+func TestShimSockLength(t *testing.T) {
+	t.Parallel()
+
+	// Max length of namespace should be 76
+	namespace := strings.Repeat("n", 76)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	ctx = namespaces.WithNamespace(ctx, namespace)
+
+	client, err := newClient(t, address)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer client.Close()
+
+	image, err := client.Pull(ctx, testImage,
+		WithPlatformMatcher(platforms.Default()),
+		WithPullUnpack,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	id := strings.Repeat("c", 64)
+
+	// We don't have limitation with length of container name,
+	// but 64 bytes of sha256 is the common case
+	container, err := client.NewContainer(ctx, id,
+		WithNewSnapshot(id, image),
+		WithNewSpec(oci.WithImageConfig(image), withExitStatus(0)),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer container.Delete(ctx, WithSnapshotCleanup)
+
+	task, err := container.NewTask(ctx, empty())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer task.Delete(ctx)
+
+	statusC, err := task.Wait(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := task.Start(ctx); err != nil {
+		t.Fatal(err)
+	}
+
+	<-statusC
+}