Merge pull request grandcat#48 from neilalexander/master

Fix appendAddrs behavior for proxy services

server.go

@@ -600,13 +600,15 @@ func (s *Server) unregister() error {
 }
 
 func (s *Server) appendAddrs(list []dns.RR, ttl uint32, ifIndex int, flushCache bool) []dns.RR {
-	var v4, v6 []net.IP
-	iface, _ := net.InterfaceByIndex(ifIndex)
-	if iface != nil {
-		v4, v6 = addrsForInterface(iface)
-	} else {
-		v4 = s.service.AddrIPv4
-		v6 = s.service.AddrIPv6
+	v4 := s.service.AddrIPv4
+	v6 := s.service.AddrIPv6
+	if len(v4) == 0 && len(v6) == 0 {
+		iface, _ := net.InterfaceByIndex(ifIndex)
+		if iface != nil {
+			a4, a6 := addrsForInterface(iface)
+			v4 = append(v4, a4...)
+			v6 = append(v6, a6...)
+		}
 	}
 	if ttl > 0 {
 		// RFC6762 Section 10 says A/AAAA records SHOULD