Make ddns behave more standard conform, like SOA records

README.md

@@ -50,11 +50,11 @@ host.
     $ sudo vim /etc/powerdns/pdns.d/pipe.conf
 
 `pipe.conf` should have the following content. Please adjust the path of `ddns`
-and the supplied domain name `--domain=sub.example.com`:
+and the values supplied to `--domain` and `--soa_fqdn`:
 
     launch=pipe
     pipebackend-abi-version=1
-    pipe-command=/home/user/gocode/bin/ddns --domain=sub.example.com backend
+    pipe-command=/home/user/gocode/bin/ddns --soa_fqdn=dns.example.com --domain=sub.example.com backend
 
 Then restart `pdns`:
 

backend.go

@@ -5,60 +5,95 @@ import (
 	"fmt"
 	"os"
 	"strings"
+	"time"
 )
 
+type responder func()
+
+func respondWithFAIL() {
+	fmt.Printf("FAIL\n")
+}
+
+func respondWithEND() {
+	fmt.Printf("END\n")
+}
+
 // This function implements the PowerDNS-Pipe-Backend protocol and generates
 // the response data it possible
 func RunBackend(conn *RedisConnection) {
+	bio := bufio.NewReader(os.Stdin)
 
 	// handshake with PowerDNS
+	_, _, _ = bio.ReadLine()
 	fmt.Printf("OK\tDDNS Go Backend\n")
 
-	bio := bufio.NewReader(os.Stdin)
-
 	for {
 		line, _, err := bio.ReadLine()
+		if err != nil {
+			respondWithFAIL()
+			continue
+		}
 
-		HandleErr(err)
+		HandleRequest(string(line), conn)()
-		HandleRequest(string(line), conn)
 	}
 }
 
-func HandleRequest(line string, conn *RedisConnection) {
+func HandleRequest(line string, conn *RedisConnection) responder {
-	defer fmt.Printf("END\n")
-
 	if Verbose {
 		fmt.Printf("LOG\t'%s'\n", line)
 	}
 
 	parts := strings.Split(line, "\t")
 	if len(parts) != 6 {
-		return
+		return respondWithFAIL
 	}
 
 	query_name := parts[1]
 	query_class := parts[2]
-	// query_type  := parts[3] // TODO Handle SOA Requests
+	query_type := parts[3]
 	query_id := parts[4]
 
-	// get the host part of the fqdn
+	var response, record string
-	// pi.d.example.org -> pi
+	record = query_type
+
+	switch query_type {
+	case "SOA":
+		response = fmt.Sprintf("%s. hostmaster.example.com. %d 1800 3600 7200 5",
+			DdnsSoaFqdn, getSoaSerial())
+
+	case "NS":
+		response = DdnsSoaFqdn
+
+	case "A":
+	case "ANY":
+		// get the host part of the fqdn: pi.d.example.org -> pi
 		hostname := ""
 		if strings.HasSuffix(query_name, DdnsDomain) {
 			hostname = query_name[:len(query_name)-len(DdnsDomain)]
 		}
 
 		if hostname == "" || !conn.HostExist(hostname) {
-		return
+			return respondWithFAIL
 		}
 
 		host := conn.GetHost(hostname)
+		response = host.Ip
 
-	record := "A"
+		record = "A"
 		if !host.IsIPv4() {
 			record = "AAAA"
 		}
 
-	fmt.Printf("DATA\t%s\t%s\t%s\t10\t%s\t%s\n",
+	default:
-		query_name, query_class, record, query_id, host.Ip)
+		return respondWithFAIL
+	}
+
+	fmt.Printf("DATA\t%s\t%s\t%s\t10\t%s\t%s\n",
+		query_name, query_class, record, query_id, response)
+	return respondWithEND
+}
+
+func getSoaSerial() int64 {
+	// return current time in milliseconds
+	return time.Now().UnixNano()
 }

ddns.go

@@ -12,10 +12,16 @@ func HandleErr(err error) {
 	}
 }
 
+const (
+	CmdBackend string = "backend"
+	CmdWeb     string = "web"
+)
+
 var (
 	DdnsDomain          string
 	DdnsWebListenSocket string
 	DdnsRedisHost       string
+	DdnsSoaFqdn         string
 	Verbose             bool
 )
 
@@ -29,28 +35,37 @@ func init() {
 	flag.StringVar(&DdnsRedisHost, "redis", ":6379",
 		"The Redis socket that should be used")
 
+	flag.StringVar(&DdnsSoaFqdn, "soa_fqdn", "",
+		"The FQDN of the DNS server which is returned as a SOA record")
+
 	flag.BoolVar(&Verbose, "verbose", false,
 		"Be more verbose")
 }
 
-func ValidateCommandArgs() {
+func ValidateCommandArgs(cmd string) {
 	if DdnsDomain == "" {
 		log.Fatal("You have to supply the domain via --domain=DOMAIN")
 	} else if !strings.HasPrefix(DdnsDomain, ".") {
 		// get the domain in the right format
 		DdnsDomain = "." + DdnsDomain
 	}
+
+	if cmd == CmdBackend {
+		if DdnsSoaFqdn == "" {
+			log.Fatal("You have to supply the server FQDN via --soa_fqdn=FQDN")
+		}
+	}
 }
 
 func PrepareForExecution() string {
 	flag.Parse()
-	ValidateCommandArgs()
 
 	if len(flag.Args()) != 1 {
 		usage()
 	}
 	cmd := flag.Args()[0]
 
+	ValidateCommandArgs(cmd)
 	return cmd
 }
 
@@ -61,10 +76,10 @@ func main() {
 	defer conn.Close()
 
 	switch cmd {
-	case "backend":
+	case CmdBackend:
 		log.Printf("Starting PDNS Backend\n")
 		RunBackend(conn)
-	case "web":
+	case CmdWeb:
 		log.Printf("Starting Web Service\n")
 		RunWebService(conn)
 	default: