Move dynamic plugins to a subpackage

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

plugin/dynamic/dynamic.go

@@ -0,0 +1,37 @@
+/*
+   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 dynamic
+
+import "fmt"
+
+// Load loads all plugins at the provided path into containerd.
+//
+// Load is currently only implemented on non-static, non-gccgo builds for amd64
+// and arm64, and plugins must be built with the exact same version of Go as
+// containerd itself.
+func Load(path string) (err error) {
+	defer func() {
+		if v := recover(); v != nil {
+			rerr, ok := v.(error)
+			if !ok {
+				rerr = fmt.Errorf("%s", v)
+			}
+			err = rerr
+		}
+	}()
+	return loadPlugins(path)
+}

plugin/dynamic/dynamic_supported.go

@@ -0,0 +1,62 @@
+//go:build (amd64 || arm64) && !static_build && !gccgo
+
+/*
+   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 dynamic
+
+import (
+	"fmt"
+	"path/filepath"
+	"plugin"
+	"runtime"
+)
+
+// loadPlugins loads all plugins for the OS and Arch
+// that containerd is built for inside the provided path
+func loadPlugins(path string) error {
+	abs, err := filepath.Abs(path)
+	if err != nil {
+		return err
+	}
+	pattern := filepath.Join(abs, fmt.Sprintf(
+		"*-%s-%s.%s",
+		runtime.GOOS,
+		runtime.GOARCH,
+		getLibExt(),
+	))
+	libs, err := filepath.Glob(pattern)
+	if err != nil {
+		return err
+	}
+	for _, lib := range libs {
+		if _, err := plugin.Open(lib); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// getLibExt returns a platform specific lib extension for
+// the platform that containerd is running on
+func getLibExt() string {
+	switch runtime.GOOS {
+	case "windows":
+		return "dll"
+	default:
+		return "so"
+	}
+}

plugin/dynamic/dynamic_unsupported.go

@@ -0,0 +1,28 @@
+//go:build (!amd64 && !arm64) || static_build || gccgo
+
+/*
+   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 dynamic
+
+// loadPlugins is not supported;
+//
+// - with gccgo: gccgo has no plugin support golang/go#36403
+// - on static builds; https://github.com/containerd/containerd/commit/0d682e24a1ba8e93e5e54a73d64f7d256f87492f
+// - on architectures other than amd64 and arm64 (other architectures need to be tested)
+func loadPlugins(path string) error {
+	return nil
+}