versioning: plugins require version match with config

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

pkg/skel/skel.go

@@ -17,7 +17,6 @@
 package skel
 
 import (
-	"encoding/json"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -44,6 +43,9 @@ type dispatcher struct {
 	Stdin  io.Reader
 	Stdout io.Writer
 	Stderr io.Writer
+
+	ConfVersionDecoder version.ConfigDecoder
+	VersionReconciler  version.Reconciler
 }
 
 type reqForCmdEntry map[string]bool
@@ -144,16 +146,20 @@ func createTypedError(f string, args ...interface{}) *types.Error {
 	}
 }
 
-func (t *dispatcher) validateVersion(stdinData []byte) error {
-	var netconf types.NetConf
-	if err := json.Unmarshal(stdinData, &netconf); err != nil {
+func (t *dispatcher) checkVersionAndCall(cmdArgs *CmdArgs, pluginVersionInfo version.PluginInfo, toCall func(*CmdArgs) error) error {
+	configVersion, err := t.ConfVersionDecoder.Decode(cmdArgs.StdinData)
+	if err != nil {
 		return err
 	}
-	if netconf.CNIVersion == "" {
-		return fmt.Errorf("missing required config cniVersion")
+	verErr := t.VersionReconciler.Check(configVersion, pluginVersionInfo)
+	if verErr != nil {
+		return &types.Error{
+			Code:    types.ErrIncompatibleCNIVersion,
+			Msg:     "incompatible CNI versions",
+			Details: verErr.Details(),
+		}
 	}
-
-	return nil
+	return toCall(cmdArgs)
 }
 
 func (t *dispatcher) pluginMain(cmdAdd, cmdDel func(_ *CmdArgs) error, versionInfo version.PluginInfo) *types.Error {
@@ -162,20 +168,13 @@ func (t *dispatcher) pluginMain(cmdAdd, cmdDel func(_ *CmdArgs) error, versionIn
 		return createTypedError(err.Error())
 	}
 
-	if err = t.validateVersion(cmdArgs.StdinData); err != nil {
-		return createTypedError(err.Error())
-	}
-
 	switch cmd {
 	case "ADD":
-		err = cmdAdd(cmdArgs)
-
+		err = t.checkVersionAndCall(cmdArgs, versionInfo, cmdAdd)
 	case "DEL":
-		err = cmdDel(cmdArgs)
-
+		err = t.checkVersionAndCall(cmdArgs, versionInfo, cmdDel)
 	case "VERSION":
 		err = versionInfo.Encode(t.Stdout)
-
 	default:
 		return createTypedError("unknown CNI_COMMAND: %v", cmd)
 	}

pkg/skel/skel_test.go

@@ -150,14 +150,38 @@ var _ = Describe("dispatching to the correct callback", func() {
 				dispatch.Stdin = strings.NewReader(`{ "some": "config" }`)
 			})
 
-			It("immediately returns a useful error", func() {
-				err := dispatch.pluginMain(cmdAdd.Func, cmdDel.Func, versionInfo)
-				Expect(err).To(MatchError("missing required config cniVersion"))
+			Context("when the plugin supports version 0.1.0", func() {
+				BeforeEach(func() {
+					versionInfo = version.PluginSupports("0.1.0")
+					expectedCmdArgs.StdinData = []byte(`{ "some": "config" }`)
+				})
+
+				It("infers the config is 0.1.0 and calls the cmdAdd callback", func() {
+					err := dispatch.pluginMain(cmdAdd.Func, cmdDel.Func, versionInfo)
+					Expect(err).NotTo(HaveOccurred())
+
+					Expect(cmdAdd.CallCount).To(Equal(1))
+					Expect(cmdAdd.Received.CmdArgs).To(Equal(expectedCmdArgs))
+				})
 			})
 
-			It("does not call either callback", func() {
-				Expect(cmdAdd.CallCount).To(Equal(0))
-				Expect(cmdDel.CallCount).To(Equal(0))
+			Context("when the plugin does not support 0.1.0", func() {
+				BeforeEach(func() {
+					versionInfo = version.PluginSupports("4.3.2")
+				})
+
+				It("immediately returns a useful error", func() {
+					err := dispatch.pluginMain(cmdAdd.Func, cmdDel.Func, versionInfo)
+					Expect(err.Code).To(Equal(uint(1))) // see https://github.com/containernetworking/cni/blob/master/SPEC.md#well-known-error-codes
+					Expect(err.Msg).To(Equal("incompatible CNI versions"))
+					Expect(err.Details).To(Equal(`config is "0.1.0", plugin supports ["4.3.2"]`))
+				})
+
+				It("does not call either callback", func() {
+					dispatch.pluginMain(cmdAdd.Func, cmdDel.Func, versionInfo)
+					Expect(cmdAdd.CallCount).To(Equal(0))
+					Expect(cmdDel.CallCount).To(Equal(0))
+				})
 			})
 		})
 	})
@@ -223,6 +247,22 @@ var _ = Describe("dispatching to the correct callback", func() {
 			Entry("args", "CNI_ARGS", false),
 			Entry("path", "CNI_PATH", false),
 		)
+
+		Context("when the stdin is empty", func() {
+			BeforeEach(func() {
+				dispatch.Stdin = strings.NewReader("")
+			})
+
+			It("succeeds without error", func() {
+				err := dispatch.pluginMain(cmdAdd.Func, cmdDel.Func, versionInfo)
+
+				Expect(err).NotTo(HaveOccurred())
+				Expect(stdout).To(MatchJSON(`{
+					"cniVersion": "0.2.0",
+					"supportedVersions": ["9.8.7"]
+			}`))
+			})
+		})
 	})
 
 	Context("when the CNI_COMMAND is unrecognized", func() {

pkg/types/types.go

@@ -112,6 +112,14 @@ type Route struct {
 	GW  net.IP
 }
 
+// Well known error codes
+// see https://github.com/containernetworking/cni/blob/master/SPEC.md#well-known-error-codes
+const (
+	ErrUnknown                uint = iota // 0
+	ErrIncompatibleCNIVersion             // 1
+	ErrUnsupportedField                   // 2
+)
+
 type Error struct {
 	Code    uint   `json:"code"`
 	Msg     string `json:"msg"`

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"]`))
+		})
+	})
+})