versioning: plugins require version match with config

infer version 0.1.0 when config is missing an explicit "cniVersion" field

pkg/version/reconcile.go

@@ -0,0 +1,47 @@
+// Copyright 2016 CNI 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 version
+
+import "fmt"
+
+type ErrorIncompatible struct {
+	Config string
+	Plugin []string
+}
+
+func (e *ErrorIncompatible) Details() string {
+	return fmt.Sprintf("config is %q, plugin supports %q", e.Config, e.Plugin)
+}
+
+func (e *ErrorIncompatible) Error() string {
+	return fmt.Sprintf("incompatible CNI versions: %s", e.Details())
+}
+
+type Reconciler struct{}
+
+func (*Reconciler) Check(configVersion string, pluginInfo PluginInfo) *ErrorIncompatible {
+	pluginVersions := pluginInfo.SupportedVersions()
+
+	for _, pluginVersion := range pluginVersions {
+		if configVersion == pluginVersion {
+			return nil
+		}
+	}
+
+	return &ErrorIncompatible{
+		Config: configVersion,
+		Plugin: pluginVersions,
+	}
+}