308 lines
7.7 KiB
Go
308 lines
7.7 KiB
Go
// Copyright 2014-2016 CNI authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package skel provides skeleton code for a CNI plugin.
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// In particular, it implements argument parsing and validation.
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package skel
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import (
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"bytes"
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"encoding/json"
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"fmt"
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"io"
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"io/ioutil"
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"log"
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"os"
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"strings"
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"github.com/containernetworking/cni/pkg/types"
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"github.com/containernetworking/cni/pkg/version"
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)
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// CmdArgs captures all the arguments passed in to the plugin
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// via both env vars and stdin
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type CmdArgs struct {
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ContainerID string
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Netns string
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IfName string
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Args string
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Path string
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StdinData []byte
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}
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type dispatcher struct {
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Getenv func(string) string
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Stdin io.Reader
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Stdout io.Writer
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Stderr io.Writer
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ConfVersionDecoder version.ConfigDecoder
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VersionReconciler version.Reconciler
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}
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type reqForCmdEntry map[string]bool
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// internal only error to indicate lack of required environment variables
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type missingEnvError struct {
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msg string
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}
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func (e missingEnvError) Error() string {
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return e.msg
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}
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func (t *dispatcher) getCmdArgsFromEnv() (string, *CmdArgs, error) {
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var cmd, contID, netns, ifName, args, path string
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vars := []struct {
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name string
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val *string
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reqForCmd reqForCmdEntry
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}{
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{
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"CNI_COMMAND",
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&cmd,
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reqForCmdEntry{
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"ADD": true,
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"CHECK": true,
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"DEL": true,
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},
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},
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{
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"CNI_CONTAINERID",
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&contID,
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reqForCmdEntry{
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"ADD": true,
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"CHECK": true,
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"DEL": true,
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},
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},
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{
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"CNI_NETNS",
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&netns,
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reqForCmdEntry{
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"ADD": true,
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"CHECK": true,
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"DEL": false,
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},
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},
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{
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"CNI_IFNAME",
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&ifName,
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reqForCmdEntry{
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"ADD": true,
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"CHECK": true,
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"DEL": true,
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},
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},
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{
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"CNI_ARGS",
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&args,
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reqForCmdEntry{
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"ADD": false,
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"CHECK": false,
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"DEL": false,
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},
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},
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{
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"CNI_PATH",
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&path,
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reqForCmdEntry{
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"ADD": true,
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"CHECK": true,
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"DEL": true,
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},
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},
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}
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argsMissing := make([]string, 0)
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for _, v := range vars {
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*v.val = t.Getenv(v.name)
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if *v.val == "" {
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if v.reqForCmd[cmd] || v.name == "CNI_COMMAND" {
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argsMissing = append(argsMissing, v.name)
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}
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}
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}
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if len(argsMissing) > 0 {
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joined := strings.Join(argsMissing, ",")
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return "", nil, missingEnvError{fmt.Sprintf("required env variables [%s] missing", joined)}
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}
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if cmd == "VERSION" {
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t.Stdin = bytes.NewReader(nil)
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}
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stdinData, err := ioutil.ReadAll(t.Stdin)
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if err != nil {
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return "", nil, fmt.Errorf("error reading from stdin: %v", err)
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}
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cmdArgs := &CmdArgs{
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ContainerID: contID,
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Netns: netns,
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IfName: ifName,
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Args: args,
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Path: path,
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StdinData: stdinData,
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}
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return cmd, cmdArgs, nil
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}
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func createTypedError(f string, args ...interface{}) *types.Error {
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return &types.Error{
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Code: 100,
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Msg: fmt.Sprintf(f, args...),
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}
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}
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func (t *dispatcher) checkVersionAndCall(cmdArgs *CmdArgs, pluginVersionInfo version.PluginInfo, toCall func(*CmdArgs) error) error {
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configVersion, err := t.ConfVersionDecoder.Decode(cmdArgs.StdinData)
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if err != nil {
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return err
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}
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verErr := t.VersionReconciler.Check(configVersion, pluginVersionInfo)
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if verErr != nil {
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return &types.Error{
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Code: types.ErrIncompatibleCNIVersion,
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Msg: "incompatible CNI versions",
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Details: verErr.Details(),
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}
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}
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return toCall(cmdArgs)
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}
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func validateConfig(jsonBytes []byte) error {
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var conf struct {
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Name string `json:"name"`
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}
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if err := json.Unmarshal(jsonBytes, &conf); err != nil {
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return fmt.Errorf("error reading network config: %s", err)
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}
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if conf.Name == "" {
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return fmt.Errorf("missing network name")
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}
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return nil
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}
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func (t *dispatcher) pluginMain(cmdAdd, cmdCheck, cmdDel func(_ *CmdArgs) error, versionInfo version.PluginInfo, about string) *types.Error {
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cmd, cmdArgs, err := t.getCmdArgsFromEnv()
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if err != nil {
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// Print the about string to stderr when no command is set
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if _, ok := err.(missingEnvError); ok && t.Getenv("CNI_COMMAND") == "" && about != "" {
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fmt.Fprintln(t.Stderr, about)
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return nil
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}
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return createTypedError(err.Error())
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}
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if cmd != "VERSION" {
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err = validateConfig(cmdArgs.StdinData)
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if err != nil {
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return createTypedError(err.Error())
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}
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}
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switch cmd {
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case "ADD":
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err = t.checkVersionAndCall(cmdArgs, versionInfo, cmdAdd)
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case "CHECK":
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configVersion, err := t.ConfVersionDecoder.Decode(cmdArgs.StdinData)
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if err != nil {
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return createTypedError(err.Error())
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}
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if gtet, err := version.GreaterThanOrEqualTo(configVersion, "0.4.0"); err != nil {
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return createTypedError(err.Error())
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} else if !gtet {
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return &types.Error{
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Code: types.ErrIncompatibleCNIVersion,
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Msg: "config version does not allow CHECK",
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}
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}
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for _, pluginVersion := range versionInfo.SupportedVersions() {
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gtet, err := version.GreaterThanOrEqualTo(pluginVersion, configVersion)
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if err != nil {
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return createTypedError(err.Error())
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} else if gtet {
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if err := t.checkVersionAndCall(cmdArgs, versionInfo, cmdCheck); err != nil {
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return createTypedError(err.Error())
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}
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return nil
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}
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}
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return &types.Error{
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Code: types.ErrIncompatibleCNIVersion,
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Msg: "plugin version does not allow CHECK",
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}
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case "DEL":
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err = t.checkVersionAndCall(cmdArgs, versionInfo, cmdDel)
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case "VERSION":
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err = versionInfo.Encode(t.Stdout)
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default:
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return createTypedError("unknown CNI_COMMAND: %v", cmd)
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}
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if err != nil {
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if e, ok := err.(*types.Error); ok {
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// don't wrap Error in Error
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return e
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}
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return createTypedError(err.Error())
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}
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return nil
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}
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// PluginMainWithError is the core "main" for a plugin. It accepts
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// callback functions for add, check, and del CNI commands and returns an error.
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//
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// The caller must also specify what CNI spec versions the plugin supports.
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//
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// It is the responsibility of the caller to check for non-nil error return.
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//
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// For a plugin to comply with the CNI spec, it must print any error to stdout
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// as JSON and then exit with nonzero status code.
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//
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// To let this package automatically handle errors and call os.Exit(1) for you,
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// use PluginMain() instead.
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func PluginMainWithError(cmdAdd, cmdCheck, cmdDel func(_ *CmdArgs) error, versionInfo version.PluginInfo, about string) *types.Error {
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return (&dispatcher{
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Getenv: os.Getenv,
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Stdin: os.Stdin,
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Stdout: os.Stdout,
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Stderr: os.Stderr,
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}).pluginMain(cmdAdd, cmdCheck, cmdDel, versionInfo, about)
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}
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// PluginMain is the core "main" for a plugin which includes automatic error handling.
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//
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// The caller must also specify what CNI spec versions the plugin supports.
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//
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// The caller can specify an "about" string, which is printed on stderr
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// when no CNI_COMMAND is specified. The recommended output is "CNI plugin <foo> v<version>"
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//
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// When an error occurs in either cmdAdd, cmdCheck, or cmdDel, PluginMain will print the error
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// as JSON to stdout and call os.Exit(1).
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//
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// To have more control over error handling, use PluginMainWithError() instead.
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func PluginMain(cmdAdd, cmdCheck, cmdDel func(_ *CmdArgs) error, versionInfo version.PluginInfo, about string) {
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if e := PluginMainWithError(cmdAdd, cmdCheck, cmdDel, versionInfo, about); e != nil {
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if err := e.Print(); err != nil {
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log.Print("Error writing error JSON to stdout: ", err)
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}
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os.Exit(1)
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}
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}
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