versioning: plugins require version match with config

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

pkg/version/plugin.go

@@ -59,7 +59,7 @@ func PluginSupports(supportedVersions ...string) PluginInfo {
 // PluginDecoder can decode the response returned by a plugin's VERSION command
 type PluginDecoder struct{}
 
-func (_ *PluginDecoder) Decode(jsonBytes []byte) (PluginInfo, error) {
+func (*PluginDecoder) Decode(jsonBytes []byte) (PluginInfo, error) {
 	var info pluginInfo
 	err := json.Unmarshal(jsonBytes, &info)
 	if err != nil {

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,
+	}
+}

pkg/version/reconcile_test.go

@@ -0,0 +1,51 @@
+// 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_test
+
+import (
+	"github.com/containernetworking/cni/pkg/version"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Reconcile versions of net config with versions supported by plugins", func() {
+	var (
+		reconciler *version.Reconciler
+		pluginInfo version.PluginInfo
+	)
+
+	BeforeEach(func() {
+		reconciler = &version.Reconciler{}
+		pluginInfo = version.PluginSupports("1.2.3", "4.3.2")
+	})
+
+	It("succeeds if the config version is supported by the plugin", func() {
+		err := reconciler.Check("4.3.2", pluginInfo)
+		Expect(err).NotTo(HaveOccurred())
+	})
+
+	Context("when the config version is not supported by the plugin", func() {
+		It("returns a helpful error", func() {
+			err := reconciler.Check("0.1.0", pluginInfo)
+
+			Expect(err).To(Equal(&version.ErrorIncompatible{
+				Config: "0.1.0",
+				Plugin: []string{"1.2.3", "4.3.2"},
+			}))
+
+			Expect(err.Error()).To(Equal(`incompatible CNI versions: config is "0.1.0", plugin supports ["1.2.3" "4.3.2"]`))
+		})
+	})
+})