lowercase the names

defaults.go

@@ -3,6 +3,7 @@ package dns
 import (
 	"net"
 	"strconv"
+	"strings"
 )
 
 const hexDigit = "0123456789abcdef"
@@ -215,7 +216,7 @@ func IsDomainName(s string) (uint8, uint8, bool) { // copied from net package.
 // IsSubDomain checks if child is indeed a child of the parent.
 func IsSubDomain(parent, child string) bool {
 	// Entire child is contained in parent
-	return CompareLabels(parent, child) == LenLabels(parent)
+	return CompareLabels(strings.ToLower(parent), strings.ToLower(child)) == LenLabels(parent)
 }
 
 // IsFqdn checks if a domain name is fully qualified.

labels.go

@@ -34,7 +34,8 @@ func SplitLabels(s string) []string {
 
 // CompareLabels compares the strings s1 and s2 and
 // returns how many labels they have in common starting from the right.
-// The comparison stops at the first inequality.
+// The comparison stops at the first inequality. The labels are not downcased
+// before the comparison.
 //
 // www.miek.nl. and miek.nl. have two labels in common: miek and nl
 // www.miek.nl. and www.bla.nl. have one label in common: nl

zone.go

@@ -90,6 +90,10 @@ func toRadixName(d string) string {
 	}
 	s := ""
 	for _, l := range SplitLabels(d) {
+		if s == "" {
+			s = strings.ToLower(l) + s
+			continue
+		}
 		s = strings.ToLower(l) + "." + s
 	}
 	return s