Fix: Removed the old “TCP by default” code.

Release: v0.5.6

VERSION

-0.5.5
+0.5.6

dns_utils.go

@@ -48,14 +48,11 @@ func NameserverHasChallenge(nameserver, fqdn, challenge string) bool {
 		nameserver = strings.Join([]string{nameserver, "53"}, ":")
 	}
 
-	client.Net = "tcp"
-
 	// build request
 	var msg dns.Msg
 	msg.SetQuestion(dns.CanonicalName(challengeName), dns.TypeTXT)
-	// Raise MTU limit from 512 to 1280 which should be safe on all modern networks
-	// (see https://en.wikipedia.org/wiki/Maximum_transmission_unit#MTUs_for_common_media)
-	msg.SetEdns0(1280, false)
+	// Raise MTU limit from 512 to 4096 which is the default used by dig.
+	msg.SetEdns0(4096, false)
 
 	// request all TXT records
 	TXTAnswer, _, err := client.Exchange(&msg, nameserver)