handle SRV queries

wgsd.go

@@ -51,6 +51,14 @@ func (p *WGSD) ServeDNS(ctx context.Context, w dns.ResponseWriter,
 	name := strings.TrimSuffix(state.Name(), p.zone)
 	qtype := state.QType()
 
+	device, err := p.client.Device(p.device)
+	if err != nil {
+		return dns.RcodeServerFailure, nil
+	}
+	if len(device.Peers) == 0 {
+		return nxdomain(p.zone, w, r)
+	}
+
 	// setup our reply message
 	m := new(dns.Msg)
 	m.SetReply(r)
@@ -58,17 +66,10 @@ func (p *WGSD) ServeDNS(ctx context.Context, w dns.ResponseWriter,
 
 	switch {
 	case name == spPrefix && qtype == dns.TypePTR:
-		device, err := p.client.Device(p.device)
-		if err != nil {
-			return dns.RcodeServerFailure, nil
-		}
-		if len(device.Peers) == 0 {
-			return nxdomain(p.zone, w, r)
-		}
 		for _, peer := range device.Peers {
 			m.Answer = append(m.Answer, &dns.PTR{
 				Hdr: dns.RR_Header{
-					Name:   fmt.Sprintf("%s%s", spPrefix, p.zone),
+					Name:   state.Name(),
 					Rrtype: dns.TypePTR,
 					Class:  dns.ClassINET,
 					Ttl:    0,
@@ -81,7 +82,55 @@ func (p *WGSD) ServeDNS(ctx context.Context, w dns.ResponseWriter,
 		w.WriteMsg(m) // nolint: errcheck
 		return dns.RcodeSuccess, nil
 	case len(name) == serviceInstanceLen && qtype == dns.TypeSRV:
-		// TODO: return SRV + A/AAAA of peer
+		pubKey := name[:44]
+		for _, peer := range device.Peers {
+			if base64.StdEncoding.EncodeToString(peer.PublicKey[:]) == pubKey {
+				endpoint := peer.Endpoint
+				if endpoint.IP == nil {
+					return nxdomain(p.zone, w, r)
+				}
+				srvTarget := fmt.Sprintf("%s.%s", pubKey, p.zone)
+				m.Answer = append(m.Answer, &dns.SRV{
+					Hdr: dns.RR_Header{
+						Name:   state.Name(),
+						Rrtype: dns.TypeSRV,
+						Class:  dns.ClassINET,
+						Ttl:    0,
+					},
+					Priority: 0,
+					Weight:   0,
+					Port:     uint16(endpoint.Port),
+					Target:   srvTarget,
+				})
+				switch {
+				case endpoint.IP.To4() != nil:
+					m.Extra = append(m.Extra, &dns.A{
+						Hdr: dns.RR_Header{
+							Name:   srvTarget,
+							Rrtype: dns.TypeA,
+							Class:  dns.ClassINET,
+							Ttl:    0,
+						},
+						A: endpoint.IP,
+					})
+				case endpoint.IP.To16() != nil:
+					m.Extra = append(m.Extra, &dns.AAAA{
+						Hdr: dns.RR_Header{
+							Name:   srvTarget,
+							Rrtype: dns.TypeAAAA,
+							Class:  dns.ClassINET,
+							Ttl:    0,
+						},
+						AAAA: endpoint.IP,
+					})
+				default:
+					// TODO: this shouldn't happen
+				}
+				w.WriteMsg(m) // nolint: errcheck
+				return dns.RcodeSuccess, nil
+			}
+		}
+		return nxdomain(p.zone, w, r)
 	case len(name) == keyLen+len(".") && (qtype == dns.TypeA ||
 		qtype == dns.TypeAAAA):
 		// TODO: return A/AAAA for of peer