Use IsFqdn and Fqdn helper functions more (#892)

defaults.go

@@ -176,9 +176,7 @@ func IsDomainName(s string) (labels int, ok bool) {
 		return 0, false
 	}
 
-	if !strings.HasSuffix(s, ".") {
-		s += "."
-	}
+	s = Fqdn(s)
 
 	// Each dot ends a segment of the name. Except for escaped dots (\.), which
 	// are normal dots.

labels.go

@@ -16,7 +16,7 @@ func SplitDomainName(s string) (labels []string) {
 	fqdnEnd := 0 // offset of the final '.' or the length of the name
 	idx := Split(s)
 	begin := 0
-	if s[len(s)-1] == '.' {
+	if IsFqdn(s) {
 		fqdnEnd = len(s) - 1
 	} else {
 		fqdnEnd = len(s)

msg.go

@@ -244,7 +244,7 @@ func packDomainName(s string, msg []byte, off int, compression compressionMap, c
 	}
 
 	// If not fully qualified, error out.
-	if s[ls-1] != '.' {
+	if !IsFqdn(s) {
 		return len(msg), ErrFqdn
 	}
 

scan.go

@@ -1262,7 +1262,7 @@ func toAbsoluteName(name, origin string) (absolute string, ok bool) {
 	}
 
 	// check if name is already absolute
-	if name[len(name)-1] == '.' {
+	if IsFqdn(name) {
 		return name, true
 	}