add AXFR request handling to support slaves

config.cfg

@@ -18,6 +18,12 @@ records = [
     # specify that auth.example.org will resolve any *.auth.example.org records
     "auth.example.org. NS auth.example.org.",
 ]
+# path to cache SOA serial
+serialpath = "soa-serial.save"
+# slaves to notify on update and allowed to request AXFR
+slaves = [
+    # "10.5.1.1"
+]
 # debug messages from CORS etc
 debug = false
 

pkg/acmedns/interfaces.go

@@ -10,6 +10,7 @@ type AcmednsDB interface {
 	Register(cidrslice Cidrslice) (ACMETxt, error)
 	GetByUsername(uuid.UUID) (ACMETxt, error)
 	GetTXTForDomain(string) ([]string, error)
+	GetTXTForAllDomains() ([]TXTRecord, error)
 	Update(ACMETxtPost) error
 	GetBackend() *sql.DB
 	SetBackend(*sql.DB)
@@ -21,4 +22,10 @@ type AcmednsNS interface {
 	SetOwnAuthKey(key string)
 	SetNotifyStartedFunc(func())
 	ParseRecords()
+	BumpSerial() error
+}
+
+type TXTRecord struct {
+	Subdomain string
+	Value     string
 }

pkg/acmedns/types.go

@@ -25,6 +25,8 @@ type general struct {
 	Nsadmin       string
 	Debug         bool
 	StaticRecords []string `toml:"records"`
+	Serialpath    string
+	SlaveHosts    []string `toml:"slaves"`
 }
 
 type dbsettings struct {

pkg/api/api.go

@@ -19,6 +19,7 @@ type AcmednsAPI struct {
 	DB         acmedns.AcmednsDB
 	Logger     *zap.SugaredLogger
 	errChan    chan error
+	dnsServers []acmedns.AcmednsNS
 }
 
 func Init(config *acmedns.AcmeDnsConfig, db acmedns.AcmednsDB, logger *zap.SugaredLogger, errChan chan error) AcmednsAPI {
@@ -27,6 +28,8 @@ func Init(config *acmedns.AcmeDnsConfig, db acmedns.AcmednsDB, logger *zap.Sugar
 }
 
 func (a *AcmednsAPI) Start(dnsservers []acmedns.AcmednsNS) {
+	//we need the dnsservers later to bump serial
+	a.dnsServers = dnsservers
 	var err error
 	//TODO: do we want to debug log the HTTP server?
 	stderrorlog, err := zap.NewStdLogAt(a.Logger.Desugar(), zap.ErrorLevel)

pkg/api/update.go

@@ -49,6 +49,10 @@ func (a *AcmednsAPI) webUpdatePost(w http.ResponseWriter, r *http.Request, _ htt
 			upd = []byte("{\"txt\": \"" + atxt.Value + "\"}")
 		}
 	}
+	for _, s := range a.dnsServers {
+		//bump SOA serial on update (and notify slaves if configured)
+		s.BumpSerial()
+	}
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(updStatus)
 	_, _ = w.Write(upd)

pkg/database/db.go

@@ -263,6 +263,50 @@ func (d *acmednsdb) GetByUsername(u uuid.UUID) (acmedns.ACMETxt, error) {
 	return acmedns.ACMETxt{}, fmt.Errorf("user not found: %s", u.String())
 }
 
+func (d *acmednsdb) GetTXTForAllDomains() ([]acmedns.TXTRecord, error) {
+	d.Mutex.Lock()
+	defer d.Mutex.Unlock()
+
+	var txts []acmedns.TXTRecord
+
+	getSQL := `
+        SELECT Subdomain, Value FROM txt
+    `
+	if d.Config.Database.Engine == "sqlite" {
+		getSQL = getSQLiteStmt(getSQL)
+	}
+
+	sm, err := d.DB.Prepare(getSQL)
+	if err != nil {
+		return txts, err
+	}
+	defer sm.Close()
+
+	rows, err := sm.Query()
+	if err != nil {
+		return txts, err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var subdomain string
+		var value string
+
+		err = rows.Scan(&subdomain, &value)
+		if err != nil {
+			return txts, err
+		}
+
+		d.Logger.Debugw("GetTXTForAllDomains() TXT Record:", subdomain, value)
+		txts = append(txts, acmedns.TXTRecord{
+			Subdomain: subdomain,
+			Value:     value,
+		})
+	}
+
+	return txts, nil
+}
+
 func (d *acmednsdb) GetTXTForDomain(domain string) ([]string, error) {
 	d.Mutex.Lock()
 	defer d.Mutex.Unlock()

pkg/nameserver/handler.go

@@ -2,12 +2,48 @@ package nameserver
 
 import (
 	"fmt"
+	"net"
 	"strings"
 
 	"github.com/miekg/dns"
 )
 
 func (n *Nameserver) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
+
+	if len(r.Question) == 1 {
+		q := r.Question[0]
+		if q.Qtype == dns.TypeAXFR || q.Qtype == dns.TypeIXFR { // Get remote IP
+			remoteIP, _, err := net.SplitHostPort(w.RemoteAddr().String())
+			if err != nil {
+				n.Logger.Errorw("Failed to parse remote address", "err", err)
+				m := new(dns.Msg)
+				m.SetReply(r)
+				m.Rcode = dns.RcodeRefused
+				_ = w.WriteMsg(m)
+				return
+			}
+
+			// Check if remote IP is in slave list
+			allowed := false
+			for _, slave := range n.Config.General.SlaveHosts {
+				if remoteIP == slave {
+					allowed = true
+					break
+				}
+			}
+
+			if !allowed {
+				n.Logger.Warnw("AXFR/IXFR request denied", "remote", remoteIP)
+				m := new(dns.Msg)
+				m.SetReply(r)
+				m.Rcode = dns.RcodeRefused
+				_ = w.WriteMsg(m)
+				return
+			}
+			n.handleAXFR(w, r)
+			return
+		}
+	}
 	m := new(dns.Msg)
 	m.SetReply(r)
 	// handle edns0
@@ -71,6 +107,9 @@ func (n *Nameserver) answer(q dns.Question) ([]dns.RR, int, bool, error) {
 			r = append(r, txtRRs...)
 		}
 	}
+	if q.Qtype == dns.TypeSOA {
+		r = append(r, n.SOA)
+	}
 	if len(r) > 0 {
 		// Make sure that we return NOERROR if there were dynamic records for the domain
 		rcode = dns.RcodeSuccess
@@ -158,3 +197,77 @@ func (n *Nameserver) getRecord(name string, qtype uint16) ([]dns.RR, error) {
 	}
 	return rr, nil
 }
+
+func (n *Nameserver) handleAXFR(w dns.ResponseWriter, r *dns.Msg) {
+
+	if len(r.Question) == 0 {
+		return
+	}
+
+	zone := dns.Fqdn(r.Question[0].Name)
+
+	records, ok := n.Domains[zone]
+	if !ok {
+		m := new(dns.Msg)
+		m.SetRcode(r, dns.RcodeNameError)
+		_ = w.WriteMsg(m)
+		return
+	}
+
+	// AXFR muss über Transfer laufen
+	tr := new(dns.Transfer)
+
+	c := make(chan *dns.Envelope)
+
+	go func() {
+		defer close(c)
+
+		var rr []dns.RR
+
+		// Start SOA
+		rr = append(rr, n.SOA)
+
+		// NS
+		rr = append(rr, records.NS...)
+
+		// Andere Records
+		// rr = append(rr, filterSOA(records.Records)...)
+		rr = append(rr, records.Records...)
+
+		// TXT Records nur für diese Zone!
+		txtRecords, err := n.DB.GetTXTForAllDomains()
+		if err == nil {
+			for _, rec := range txtRecords {
+				if rec.Value == "" {
+					continue
+				}
+
+				fqdn := dns.Fqdn(rec.Subdomain + "." + zone)
+
+				txtRR := &dns.TXT{
+					Hdr: dns.RR_Header{
+						Name:   fqdn,
+						Rrtype: dns.TypeTXT,
+						Class:  dns.ClassINET,
+						Ttl:    1,
+					},
+					Txt: []string{rec.Value},
+				}
+
+				rr = append(rr, txtRR)
+
+				n.Logger.Debugw("handleAXFR TXT Record", "subdomain", rec.Subdomain, "value", rec.Value, "fqdn", fqdn)
+				rr = append(rr, txtRR)
+			}
+		} else {
+			n.Logger.Errorw("Failed to get TXT records for AXFR", "error", err)
+		}
+
+		// End SOA
+		rr = append(rr, n.SOA)
+
+		c <- &dns.Envelope{RR: rr}
+	}()
+
+	_ = tr.Out(w, r, c)
+}

pkg/nameserver/initialize.go

@@ -14,6 +14,7 @@ import (
 // Records is a slice of ResourceRecords
 type Records struct {
 	Records []dns.RR
+	NS      []dns.RR
 }
 
 type Nameserver struct {
@@ -23,7 +24,7 @@ type Nameserver struct {
 	Server            *dns.Server
 	OwnDomain         string
 	NotifyStartedFunc func()
-	SOA               dns.RR
+	SOA               *dns.SOA
 	mu                sync.RWMutex
 	personalAuthKey   string
 	Domains           map[string]Records

pkg/nameserver/parseconfig.go

@@ -2,12 +2,64 @@ package nameserver
 
 import (
 	"fmt"
+	"os"
+	"strconv"
 	"strings"
 	"time"
 
 	"github.com/miekg/dns"
 )
 
+func loadSerial(path string) (uint32, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return 0, nil // first start
+		}
+		return 0, err
+	}
+
+	s := strings.TrimSpace(string(data))
+	val, err := strconv.ParseUint(s, 10, 32)
+	if err != nil {
+		return 0, err
+	}
+
+	return uint32(val), nil
+}
+
+func saveSerial(path string, serial uint32) error {
+	tmp := path + ".tmp"
+
+	data := []byte(fmt.Sprintf("%d\n", serial))
+
+	// write temp file
+	if err := os.WriteFile(tmp, data, 0644); err != nil {
+		return err
+	}
+
+	// atomic replace
+	return os.Rename(tmp, path)
+}
+
+func nextSerial(old uint32) uint32 {
+	today := time.Now().Format("20060102")
+
+	oldStr := fmt.Sprintf("%d", old)
+
+	if strings.HasPrefix(oldStr, today) {
+		return old + 1
+	}
+
+	newSerial, _ := strconv.Atoi(today + "00")
+
+	if uint32(newSerial) <= old {
+		return old + 1
+	}
+
+	return uint32(newSerial)
+}
+
 // ParseRecords parses a slice of DNS record string
 func (n *Nameserver) ParseRecords() {
 	for _, v := range n.Config.General.StaticRecords {
@@ -22,25 +74,72 @@ func (n *Nameserver) ParseRecords() {
 		n.appendRR(rr)
 	}
 	// Create serial
-	serial := time.Now().Format("2006010215")
-	// Add SOA
-	SOAstring := fmt.Sprintf("%s. SOA %s. %s. %s 28800 7200 604800 86400", strings.ToLower(n.Config.General.Domain), strings.ToLower(n.Config.General.Nsname), strings.ToLower(n.Config.General.Nsadmin), serial)
-	soarr, err := dns.NewRR(SOAstring)
+	serial, err := loadSerial(n.Config.General.Serialpath)
+
 	if err != nil {
-		n.Logger.Errorw("Error while adding SOA record",
-			"error", err.Error(),
-			"soa", SOAstring)
-	} else {
-		n.appendRR(soarr)
-		n.SOA = soarr
+		n.Logger.Errorw("Could not load temp serial",
+			"error", err.Error())
 	}
+	if serial == 0 {
+		serial = uint32(time.Now().Unix())
+	}
+	// Add SOA
+	//Refresh = 30s → Slaves fragen alle 30s nach Änderungen
+	//Retry = 10s → Wenn Master nicht erreichbar, probiert der Slave alle 10s erneut
+	//Expire = 604800s (1w) → Wie lange der Slave die Zone noch behält, falls Master ausfällt
+	//Minimum TTL = 20s → Resolver cachen die TXT-Einträge nur kurz
+	//SOAstring := fmt.Sprintf("%s. SOA %s. %s. %s 5 10 604800 20", strings.ToLower(n.Config.General.Domain), strings.ToLower(n.Config.General.Nsname), strings.ToLower(n.Config.General.Nsadmin), serial)
+	n.SOA = &dns.SOA{
+		Hdr: dns.RR_Header{
+			Name:   dns.Fqdn(n.Config.General.Domain),
+			Rrtype: dns.TypeSOA,
+			Class:  dns.ClassINET,
+			Ttl:    5,
+		},
+		Ns:      dns.Fqdn(n.Config.General.Nsname),
+		Mbox:    dns.Fqdn(n.Config.General.Nsadmin),
+		Serial:  serial,
+		Refresh: 5,
+		Retry:   10,
+		Expire:  604800,
+		Minttl:  1,
+	}
+}
+
+func sendNotify(zone string, slaveAddr string) error {
+	m := new(dns.Msg)
+	m.SetNotify(dns.Fqdn(zone)) // Set opcode to NOTIFY
+	m.Authoritative = true      // Must be authoritative
+
+	c := new(dns.Client)
+	_, _, err := c.Exchange(m, slaveAddr)
+	return err
+}
+
+func (n *Nameserver) BumpSerial() error {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	n.SOA.Serial = nextSerial(n.SOA.Serial)
+
+	for _, slave := range n.Config.General.SlaveHosts {
+		slave := slave + ":53"
+		if err := sendNotify(n.SOA.Hdr.Name, slave); err != nil {
+			n.Logger.Errorw("Failed to notify slave", "slave", slave, "err", err)
+		} else {
+			n.Logger.Debugw("Notify send to slave", "slave", slave)
+		}
+	}
+	return saveSerial(n.Config.General.Serialpath, n.SOA.Serial)
 }
 
 func (n *Nameserver) appendRR(rr dns.RR) {
 	addDomain := rr.Header().Name
 	_, ok := n.Domains[addDomain]
 	if !ok {
-		n.Domains[addDomain] = Records{[]dns.RR{rr}}
+		n.Domains[addDomain] = Records{
+			Records: []dns.RR{rr}, // initialisiere Records
+			NS:      []dns.RR{},   // leeres NS-Slice, sonst Fehler
+		}
 	} else {
 		drecs := n.Domains[addDomain]
 		drecs.Records = append(drecs.Records, rr)