cloudinit/config/config.go

/*
   Copyright 2014 CoreOS, Inc.

   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 config

import (
	"fmt"
	"reflect"
	"strings"

	"github.com/coreos/coreos-cloudinit/Godeps/_workspace/src/github.com/coreos/yaml"
)

// CloudConfig encapsulates the entire cloud-config configuration file and maps
// directly to YAML. Fields that cannot be set in the cloud-config (fields
// used for internal use) have the YAML tag '-' so that they aren't marshalled.
type CloudConfig struct {
	SSHAuthorizedKeys []string `yaml:"ssh_authorized_keys"`
	CoreOS            CoreOS   `yaml:"coreos"`
	WriteFiles        []File   `yaml:"write_files"`
	Hostname          string   `yaml:"hostname"`
	Users             []User   `yaml:"users"`
	ManageEtcHosts    EtcHosts `yaml:"manage_etc_hosts"`
	NetworkConfigPath string   `yaml:"-"`
	NetworkConfig     string   `yaml:"-"`
}

type CoreOS struct {
	Etcd      Etcd      `yaml:"etcd"`
	Flannel   Flannel   `yaml:"flannel"`
	Fleet     Fleet     `yaml:"fleet"`
	Locksmith Locksmith `yaml:"locksmith"`
	OEM       OEM       `yaml:"oem"`
	Update    Update    `yaml:"update"`
	Units     []Unit    `yaml:"units"`
}

func IsCloudConfig(userdata string) bool {
	header := strings.SplitN(userdata, "\n", 2)[0]

	// Explicitly trim the header so we can handle user-data from
	// non-unix operating systems. The rest of the file is parsed
	// by yaml, which correctly handles CRLF.
	header = strings.TrimSuffix(header, "\r")

	return (header == "#cloud-config")
}

// NewCloudConfig instantiates a new CloudConfig from the given contents (a
// string of YAML), returning any error encountered. It will ignore unknown
// fields but log encountering them.
func NewCloudConfig(contents string) (*CloudConfig, error) {
	yaml.UnmarshalMappingKeyTransform = func(nameIn string) (nameOut string) {
		return strings.Replace(nameIn, "-", "_", -1)
	}
	var cfg CloudConfig
	err := yaml.Unmarshal([]byte(contents), &cfg)
	return &cfg, err
}

func (cc CloudConfig) String() string {
	bytes, err := yaml.Marshal(cc)
	if err != nil {
		return ""
	}

	stringified := string(bytes)
	stringified = fmt.Sprintf("#cloud-config\n%s", stringified)

	return stringified
}

// IsZero returns whether or not the parameter is the zero value for its type.
// If the parameter is a struct, only the exported fields are considered.
func IsZero(c interface{}) bool {
	return isZero(reflect.ValueOf(c))
}

type ErrorValid struct {
	Value string
	Valid []string
	Field string
}

func (e ErrorValid) Error() string {
	return fmt.Sprintf("invalid value %q for option %q (valid options: %q)", e.Value, e.Field, e.Valid)
}

// AssertStructValid checks the fields in the structure and makes sure that
// they contain valid values as specified by the 'valid' flag. Empty fields are
// implicitly valid.
func AssertStructValid(c interface{}) error {
	ct := reflect.TypeOf(c)
	cv := reflect.ValueOf(c)
	for i := 0; i < ct.NumField(); i++ {
		ft := ct.Field(i)
		if !isFieldExported(ft) {
			continue
		}

		if err := AssertValid(cv.Field(i), ft.Tag.Get("valid")); err != nil {
			err.Field = ft.Name
			return err
		}
	}
	return nil
}

// AssertValid checks to make sure that the given value is in the list of
// valid values. Zero values are implicitly valid.
func AssertValid(value reflect.Value, valid string) *ErrorValid {
	if valid == "" || isZero(value) {
		return nil
	}
	vs := fmt.Sprintf("%v", value.Interface())
	valids := strings.Split(valid, ",")
	for _, valid := range valids {
		if vs == valid {
			return nil
		}
	}
	return &ErrorValid{
		Value: vs,
		Valid: valids,
	}
}

func isZero(v reflect.Value) bool {
	switch v.Kind() {
	case reflect.Struct:
		vt := v.Type()
		for i := 0; i < v.NumField(); i++ {
			if isFieldExported(vt.Field(i)) && !isZero(v.Field(i)) {
				return false
			}
		}
		return true
	default:
		return v.Interface() == reflect.Zero(v.Type()).Interface()
	}
}

func isFieldExported(f reflect.StructField) bool {
	return f.PkgPath == ""
}