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// Copyright 2014-2016 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 skel provides skeleton code for a CNI plugin.
// In particular, it implements argument parsing and validation.
package skel
import (
"bytes"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"log"
"os"
"strings"
"github.com/containernetworking/cni/pkg/types"
"github.com/containernetworking/cni/pkg/version"
)
// CmdArgs captures all the arguments passed in to the plugin
// via both env vars and stdin
type CmdArgs struct {
ContainerID string
Netns string
IfName string
Args string
Path string
StdinData []byte
}
type dispatcher struct {
Getenv func(string) string
Stdin io.Reader
Stdout io.Writer
Stderr io.Writer
ConfVersionDecoder version.ConfigDecoder
VersionReconciler version.Reconciler
}
type reqForCmdEntry map[string]bool
// internal only error to indicate lack of required environment variables
type missingEnvError struct {
msg string
}
func (e missingEnvError) Error() string {
return e.msg
}
func (t *dispatcher) getCmdArgsFromEnv() (string, *CmdArgs, error) {
var cmd, contID, netns, ifName, args, path string
vars := []struct {
name string
val *string
reqForCmd reqForCmdEntry
}{
{
"CNI_COMMAND",
&cmd,
reqForCmdEntry{
"ADD": true,
"GET": true,
"DEL": true,
},
},
{
"CNI_CONTAINERID",
&contID,
reqForCmdEntry{
"ADD": true,
"GET": true,
"DEL": true,
},
},
{
"CNI_NETNS",
&netns,
reqForCmdEntry{
"ADD": true,
"GET": true,
"DEL": false,
},
},
{
"CNI_IFNAME",
&ifName,
reqForCmdEntry{
"ADD": true,
"GET": true,
"DEL": true,
},
},
{
"CNI_ARGS",
&args,
reqForCmdEntry{
"ADD": false,
"GET": false,
"DEL": false,
},
},
{
"CNI_PATH",
&path,
reqForCmdEntry{
"ADD": true,
"GET": true,
"DEL": true,
},
},
}
argsMissing := make([]string, 0)
for _, v := range vars {
*v.val = t.Getenv(v.name)
if *v.val == "" {
if v.reqForCmd[cmd] || v.name == "CNI_COMMAND" {
argsMissing = append(argsMissing, v.name)
}
}
}
if len(argsMissing) > 0 {
joined := strings.Join(argsMissing, ",")
return "", nil, missingEnvError{fmt.Sprintf("required env variables [%s] missing", joined)}
}
if cmd == "VERSION" {
t.Stdin = bytes.NewReader(nil)
}
stdinData, err := ioutil.ReadAll(t.Stdin)
if err != nil {
return "", nil, fmt.Errorf("error reading from stdin: %v", err)
}
cmdArgs := &CmdArgs{
ContainerID: contID,
Netns: netns,
IfName: ifName,
Args: args,
Path: path,
StdinData: stdinData,
}
return cmd, cmdArgs, nil
}
func createTypedError(f string, args ...interface{}) *types.Error {
return &types.Error{
Code: 100,
Msg: fmt.Sprintf(f, args...),
}
}
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
}
verErr := t.VersionReconciler.Check(configVersion, pluginVersionInfo)
if verErr != nil {
return &types.Error{
Code: types.ErrIncompatibleCNIVersion,
Msg: "incompatible CNI versions",
Details: verErr.Details(),
}
}
return toCall(cmdArgs)
}
func validateConfig(jsonBytes []byte) error {
var conf struct {
Name string `json:"name"`
}
if err := json.Unmarshal(jsonBytes, &conf); err != nil {
return fmt.Errorf("error reading network config: %s", err)
}
if conf.Name == "" {
return fmt.Errorf("missing network name")
}
return nil
}
func (t *dispatcher) pluginMain(cmdAdd, cmdGet, cmdDel func(_ *CmdArgs) error, versionInfo version.PluginInfo, about string) *types.Error {
cmd, cmdArgs, err := t.getCmdArgsFromEnv()
if err != nil {
// Print the about string to stderr when no command is set
if _, ok := err.(missingEnvError); ok && t.Getenv("CNI_COMMAND") == "" && about != "" {
fmt.Fprintln(t.Stderr, about)
return nil
}
return createTypedError(err.Error())
}
if cmd != "VERSION" {
err = validateConfig(cmdArgs.StdinData)
if err != nil {
return createTypedError(err.Error())
}
}
switch cmd {
case "ADD":
err = t.checkVersionAndCall(cmdArgs, versionInfo, cmdAdd)
case "GET":
configVersion, err := t.ConfVersionDecoder.Decode(cmdArgs.StdinData)
if err != nil {
return createTypedError(err.Error())
}
if gtet, err := version.GreaterThanOrEqualTo(configVersion, "0.4.0"); err != nil {
return createTypedError(err.Error())
} else if !gtet {
return &types.Error{
Code: types.ErrIncompatibleCNIVersion,
Msg: "config version does not allow GET",
}
}
for _, pluginVersion := range versionInfo.SupportedVersions() {
gtet, err := version.GreaterThanOrEqualTo(pluginVersion, configVersion)
if err != nil {
return createTypedError(err.Error())
} else if gtet {
if err := t.checkVersionAndCall(cmdArgs, versionInfo, cmdGet); err != nil {
return createTypedError(err.Error())
}
return nil
}
}
return &types.Error{
Code: types.ErrIncompatibleCNIVersion,
Msg: "plugin version does not allow GET",
}
case "DEL":
err = t.checkVersionAndCall(cmdArgs, versionInfo, cmdDel)
case "VERSION":
err = versionInfo.Encode(t.Stdout)
default:
return createTypedError("unknown CNI_COMMAND: %v", cmd)
}
if err != nil {
if e, ok := err.(*types.Error); ok {
// don't wrap Error in Error
return e
}
return createTypedError(err.Error())
}
return nil
}
// PluginMainWithError is the core "main" for a plugin. It accepts
// callback functions for add, get, and del CNI commands and returns an error.
//
// The caller must also specify what CNI spec versions the plugin supports.
//
// It is the responsibility of the caller to check for non-nil error return.
//
// For a plugin to comply with the CNI spec, it must print any error to stdout
// as JSON and then exit with nonzero status code.
//
// To let this package automatically handle errors and call os.Exit(1) for you,
// use PluginMain() instead.
func PluginMainWithError(cmdAdd, cmdGet, cmdDel func(_ *CmdArgs) error, versionInfo version.PluginInfo, about string) *types.Error {
return (&dispatcher{
Getenv: os.Getenv,
Stdin: os.Stdin,
Stdout: os.Stdout,
Stderr: os.Stderr,
}).pluginMain(cmdAdd, cmdGet, cmdDel, versionInfo, about)
}
// PluginMain is the core "main" for a plugin which includes automatic error handling.
//
// The caller must also specify what CNI spec versions the plugin supports.
//
// The caller can specify an "about" string, which is printed on stderr
// when no CNI_COMMAND is specified. The reccomended output is "CNI plugin <foo> v<version>"
//
// When an error occurs in either cmdAdd, cmdGet, or cmdDel, PluginMain will print the error
// as JSON to stdout and call os.Exit(1).
//
// To have more control over error handling, use PluginMainWithError() instead.
func PluginMain(cmdAdd, cmdGet, cmdDel func(_ *CmdArgs) error, versionInfo version.PluginInfo, about string) {
if e := PluginMainWithError(cmdAdd, cmdGet, cmdDel, versionInfo, about); e != nil {
if err := e.Print(); err != nil {
log.Print("Error writing error JSON to stdout: ", err)
}
os.Exit(1)
}
}