resolver/dns: support ipv6 addrs

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

resolver/dns/dns.go

@@ -42,23 +42,29 @@ func (r *Resolver) Resolve(name string) ([]*resolver.Record, error) {
 		return records, nil
 	}
 
+	for _, q := range []uint16{dns.TypeA, dns.TypeAAAA} {
 		m := new(dns.Msg)
-	m.SetQuestion(dns.Fqdn(host), dns.TypeA)
+		m.SetQuestion(dns.Fqdn(host), q)
 		rec, err := dns.ExchangeContext(context.Background(), m, r.Address)
 		if err != nil {
 			return nil, err
 		}
 
+		var addr string
 		for _, answer := range rec.Answer {
 			h := answer.Header()
 			// check record type matches
-		if h.Rrtype != dns.TypeA {
+			switch h.Rrtype {
+			case dns.TypeA:
+				arec, _ := answer.(*dns.A)
+				addr = arec.A.String()
+			case dns.TypeAAAA:
+				arec, _ := answer.(*dns.AAAA)
+				addr = arec.AAAA.String()
+			default:
 				continue
 			}
 
-		arec, _ := answer.(*dns.A)
-		addr := arec.A.String()
-
 			// join resolved record with port
 			address := net.JoinHostPort(addr, port)
 			// append to record set
@@ -66,6 +72,7 @@ func (r *Resolver) Resolve(name string) ([]*resolver.Record, error) {
 				Address: address,
 			})
 		}
+	}
 
 	// no records returned so just best effort it
 	if len(records) == 0 {