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"
	"log"
	"reflect"
	"strings"

	"github.com/coreos/coreos-cloudinit/Godeps/_workspace/src/gopkg.in/yaml.v1"
)

// 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            struct {
		Etcd   Etcd   `yaml:"etcd"`
		Fleet  Fleet  `yaml:"fleet"`
		OEM    OEM    `yaml:"oem"`
		Update Update `yaml:"update"`
		Units  []Unit `yaml:"units"`
	} `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:"-"`
}

// 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) {
	var cfg CloudConfig
	err := yaml.Unmarshal([]byte(contents), &cfg)
	if err != nil {
		return &cfg, err
	}
	warnOnUnrecognizedKeys(contents, log.Printf)
	return &cfg, nil
}

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))
}

// AssertValid 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 AssertValid(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
		}

		valid := ft.Tag.Get("valid")
		val := cv.Field(i)
		if !isValid(val, valid) {
			return fmt.Errorf("invalid value \"%v\" for option %q (valid options: %q)", val.Interface(), ft.Name, valid)
		}
	}
	return nil
}

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 == ""
}

func isValid(v reflect.Value, valid string) bool {
	if valid == "" || isZero(v) {
		return true
	}
	vs := fmt.Sprintf("%v", v.Interface())
	for _, valid := range strings.Split(valid, ",") {
		if vs == valid {
			return true
		}
	}
	return false
}

type warner func(format string, v ...interface{})

// warnOnUnrecognizedKeys parses the contents of a cloud-config file and calls
// warn(msg, key) for every unrecognized key (i.e. those not present in CloudConfig)
func warnOnUnrecognizedKeys(contents string, warn warner) {
	// Generate a map of all understood cloud config options
	var cc map[string]interface{}
	b, _ := yaml.Marshal(&CloudConfig{})
	yaml.Unmarshal(b, &cc)

	// Now unmarshal the entire provided contents
	var c map[string]interface{}
	yaml.Unmarshal([]byte(contents), &c)

	// Check that every key in the contents exists in the cloud config
	for k, _ := range c {
		if _, ok := cc[k]; !ok {
			warn("Warning: unrecognized key %q in provided cloud config - ignoring section", k)
		}
	}

	// Check for unrecognized coreos options, if any are set
	if coreos, ok := c["coreos"]; ok {
		if set, ok := coreos.(map[interface{}]interface{}); ok {
			known := cc["coreos"].(map[interface{}]interface{})
			for k, _ := range set {
				if key, ok := k.(string); ok {
					if _, ok := known[key]; !ok {
						warn("Warning: unrecognized key %q in coreos section of provided cloud config - ignoring", key)
					}
				} else {
					warn("Warning: unrecognized key %q in coreos section of provided cloud config - ignoring", k)
				}
			}
		}
	}

	// Check for any badly-specified users, if any are set
	if users, ok := c["users"]; ok {
		var known map[string]interface{}
		b, _ := yaml.Marshal(&User{})
		yaml.Unmarshal(b, &known)

		if set, ok := users.([]interface{}); ok {
			for _, u := range set {
				if user, ok := u.(map[interface{}]interface{}); ok {
					for k, _ := range user {
						if key, ok := k.(string); ok {
							if _, ok := known[key]; !ok {
								warn("Warning: unrecognized key %q in user section of cloud config - ignoring", key)
							}
						} else {
							warn("Warning: unrecognized key %q in user section of cloud config - ignoring", k)
						}
					}
				}
			}
		}
	}

	// Check for any badly-specified files, if any are set
	if files, ok := c["write_files"]; ok {
		var known map[string]interface{}
		b, _ := yaml.Marshal(&File{})
		yaml.Unmarshal(b, &known)

		if set, ok := files.([]interface{}); ok {
			for _, f := range set {
				if file, ok := f.(map[interface{}]interface{}); ok {
					for k, _ := range file {
						if key, ok := k.(string); ok {
							if _, ok := known[key]; !ok {
								warn("Warning: unrecognized key %q in file section of cloud config - ignoring", key)
							}
						} else {
							warn("Warning: unrecognized key %q in file section of cloud config - ignoring", k)
						}
					}
				}
			}
		}
	}
}