initial commit

dns_update.go

@@ -0,0 +1,193 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"github.com/miekg/dns"
+	"net"
+	"time"
+)
+
+type DnsUpdate struct {
+	Timeout int
+	TSigKeyName string
+	TSigKey string
+	TSigAlgorithm string
+	DnsHost string
+	Zone string
+}
+
+
+func NewTestInstance() *DnsUpdate {
+	return &DnsUpdate{
+		DnsHost: "45.129.181.183:53",
+		Timeout: 300,
+		TSigKeyName: "ddns-key",
+		TSigAlgorithm: dns.HmacSHA512,
+		TSigKey: "rcDW6VdBFV8+LKH4JHXKRan0ZzoJBbbfeK6sL8VOSM60nt99Z/0jQbDp9PyF3q9TsmEBb0rTI2txySIH998Vfw==",
+		Zone: "hub.voglfrei.net",
+	}
+}
+
+
+func (d *DnsUpdate) createIp4Addr(host string, addr net.IP) *dns.A {
+
+	ip := addr.To4()
+	if ip == nil {
+		return nil
+	}
+
+	return &dns.A{
+		Hdr: dns.RR_Header{
+			Name:   dns.Fqdn(host+"."+d.Zone),
+			Rrtype: dns.TypeA,
+			Class:  dns.ClassINET,
+			Ttl:    uint32(d.Timeout),
+		},
+		A: ip,
+	}
+}
+
+func (d *DnsUpdate) createIp6Addr(host string, addr net.IP) *dns.AAAA {
+
+	ip := addr.To16()
+	if ip == nil {
+		return nil
+	}
+
+	return &dns.AAAA{
+		Hdr: dns.RR_Header{
+			Name:   dns.Fqdn(host+"."+d.Zone),
+			Rrtype: dns.TypeAAAA,
+			Class:  dns.ClassINET,
+			Ttl:    uint32(d.Timeout),
+		},
+		AAAA: ip,
+	}
+}
+
+func (d *DnsUpdate) createRemovals(host string) []dns.RR {
+	return []dns.RR{
+		&dns.RR_Header{Name: dns.Fqdn(host+"."+d.Zone)},
+	}
+}
+
+func (d *DnsUpdate) createInserts(host string, addr net.IP) []dns.RR {
+
+	var rr = make([]dns.RR,0)
+
+	if r := d.createIp4Addr(host, addr); r != nil {
+		rr = append(rr, r)
+	}
+
+	if r := d.createIp6Addr(host, addr); r != nil {
+		rr = append(rr, r)
+	}
+
+	return rr
+}
+func (d *DnsUpdate) exchange(msg *dns.Msg) (*dns.Msg, error) {
+	var client = new(dns.Client)
+
+	timeout := time.Duration(d.Timeout * int(time.Second))
+	client.DialTimeout = timeout
+	client.ReadTimeout = timeout
+	client.WriteTimeout = timeout
+	client.TsigSecret = map[string]string {dns.Fqdn(d.TSigKeyName): d.TSigKey  }
+
+	r, _, err := client.Exchange(msg, d.DnsHost)
+
+	if err != nil {
+		return nil, err
+	}
+
+	if r.Rcode == dns.RcodeSuccess {
+		return r, nil
+	} else {
+		return nil, errors.New(dns.RcodeToString[r.Rcode])
+	}
+}
+
+func (d *DnsUpdate) Remove(host string) error {
+	var msg = new(dns.Msg)
+	msg.SetUpdate(dns.Fqdn(d.Zone))
+	msg.RemoveName(d.createRemovals(host))
+	msg.SetTsig(dns.Fqdn(d.TSigKeyName), d.TSigAlgorithm, uint16(d.Timeout), time.Now().Unix())
+
+	_, err := d.exchange(msg)
+	return err
+
+}
+
+func (d *DnsUpdate) Resolve(host string) ([]string, error) {
+	var msg = new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(host + "." + d.Zone), dns.TypeA)
+
+	r, err := d.exchange(msg)
+	if err != nil {return nil, err}
+
+	hosts := make([]string, 0)
+	for _, v := range r.Answer {
+		if v.Header().Rrtype == dns.TypeA {
+			hosts = append(hosts, v.(*dns.A).A.To4().String())
+		} else if v.Header().Rrtype == dns.TypeAAAA {
+			hosts = append(hosts, v.(*dns.AAAA).AAAA.To16().String())
+		}
+	}
+
+	return hosts, nil
+}
+
+func (d *DnsUpdate) ExternalResolve(host string) ([]string, error ) {
+	r := &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+			d := net.Dialer{
+				Timeout: time.Millisecond * time.Duration(10000),
+			}
+			return d.DialContext(ctx, "udp", "8.8.8.8:53")
+		},
+	}
+	ip, err := r.LookupHost(context.Background(), host + "." + d.Zone)
+
+	if err != nil {
+		return nil, err
+	}
+	return ip, nil
+}
+
+
+
+func (d *DnsUpdate) Update(host string, addrs ...string) error {
+	var err error
+	err = d.Remove(host)
+	if err != nil {return err }
+
+	return d.AddMany(host, addrs...)
+}
+
+func (d *DnsUpdate) AddMany(host string, addrs ...string) error {
+	var err error
+
+	for _, v := range addrs {
+		err = d.Add(host, v)
+		if err != nil {return err }
+	}
+	return nil
+}
+
+func (d *DnsUpdate) Add(host string, addr string) error {
+	ip, err := net.ResolveIPAddr("ip", addr)
+	if err != nil {
+		return err
+	}
+
+	var msg = new(dns.Msg)
+	msg.SetUpdate(dns.Fqdn(d.Zone))
+	msg.Insert(d.createInserts(host, ip.IP))
+	msg.SetTsig(dns.Fqdn(d.TSigKeyName), d.TSigAlgorithm, uint16(d.Timeout), time.Now().Unix())
+
+	_, err = d.exchange(msg)
+	return err
+
+}