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ddns.go
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ddns.go
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// Copyright 2017-2019 mikan.
package main
import (
"encoding/json"
"errors"
"flag"
"fmt"
"io"
"io/ioutil"
"log"
"net"
"net/http"
"os"
"strings"
)
// ClassName defines supported class names.
type ClassName string
const (
ValueDomain = ClassName("valuedomain")
Cloudflare = ClassName("cloudflare")
)
// JSON "target" element
type Target struct {
Class ClassName `json:"class"`
Domain string `json:"domain"` // vd: domain name, cf: zone id
Password string `json:"password"` // vd: password, cf: api token
Host string `json:"host"` // vd: host name, cf: record name
Proxied bool `json:"proxied"` // vd: unused, cf: proxy enabled
}
// JSON "checker" element
type Checker struct {
Method string `json:"method"`
URL string `json:"url"`
Last string `json:"last"`
}
// JSON "log" element
type Log struct {
File string `json:"file"`
}
// JSON configuration file layout
type Config struct {
Targets []Target `json:"targets"`
Checker Checker `json:"checker"`
Log Log `json:"log"`
}
func main() {
configFile := flag.String("c", "ddns.json", "path to configuration file")
flag.Parse()
// Load config
config, err := loadConfig(*configFile)
if err != nil {
log.Fatalf("[Config] Failed to load %s: %v\n", *configFile, err)
}
setupLogFile(config.Log)
// Load last IP
last, err := loadLastIP(config.Checker.Last)
if err != nil {
log.Fatalf("[Last] Failed to load %s: %v\n", config.Checker.Last, err)
}
// Check IP
ip, err := checkIP(config.Checker)
if err != nil {
log.Fatalf("[Checker] Failed to check: %v\n", err)
}
// Detect change
if last == ip {
fmt.Printf("[Checker] IP not changed: %s\n", ip) // console write only
return
}
// Submit IP for each targets
success := make([]bool, len(config.Targets))
for i, target := range config.Targets {
switch target.Class {
case ValueDomain:
success[i] = handleValueDomain(target, ip)
case Cloudflare:
success[i] = handleCloudflare(target, ip)
}
}
// Don't save if failed result included
for _, entry := range success {
if !entry {
os.Exit(1)
}
}
// Save last successful IP
if err := writeLastIP(config.Checker.Last, ip); err != nil {
log.Fatalf("[Last] Failed to write %s: %v\n", config.Checker.Last, err)
}
}
func loadConfig(path string) (*Config, error) {
configData, err := ioutil.ReadFile(path)
if err != nil {
return nil, err
}
var config Config
err = json.Unmarshal(configData, &config)
if err != nil {
return nil, err
}
return &config, nil
}
func setupLogFile(logConfig Log) {
f, err := os.OpenFile(logConfig.File, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
if err != nil {
log.Fatal(err)
}
log.SetOutput(io.MultiWriter(os.Stdout, f))
}
func checkIP(checker Checker) (string, error) {
res, err := http.Get(checker.URL)
if err != nil {
return "", err
}
if res.StatusCode != 200 {
return "", errors.New(fmt.Sprintf("[Checker] HTTP %d: %s", res.StatusCode, res.Status))
}
rawBody, err := ioutil.ReadAll(res.Body)
if err != nil {
return "", err
}
ipStr := strings.TrimSuffix(string(rawBody), "\n")
if ip := net.ParseIP(ipStr); ip == nil {
return "", errors.New("[Checker] Illegal response: " + ipStr)
}
return ipStr, nil
}
func loadLastIP(lastFilePath string) (string, error) {
_, err := os.Stat(lastFilePath)
if err != nil {
return "", nil // empty string if file isn't exists
}
file, err := os.Open(lastFilePath)
if err != nil {
return "", err
}
defer func() {
if err := file.Close(); err != nil {
log.Printf("[Last] Failed to close %s: %v", lastFilePath, err)
}
}()
data, err := ioutil.ReadAll(file)
if err != nil {
return "", err
}
return string(data), nil
}
func writeLastIP(lastFilePath string, ip string) error {
_, err := os.Stat(lastFilePath)
if err == nil {
if err := os.Remove(lastFilePath); err != nil {
log.Printf("[Last] Failed to remove %s: %v", lastFilePath, err)
}
}
return ioutil.WriteFile(lastFilePath, []byte(ip), 0644)
}