Use strings.ToLower in server (#3304)

Automatically submitted.

core/dnsserver/server.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"net"
 	"runtime"
+	"strings"
 	"sync"
 	"time"
 
@@ -217,27 +218,18 @@ func (s *Server) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 		return
 	}
 
-	q := r.Question[0].Name
-	b := make([]byte, len(q))
-	var off int
-	var end bool
-
-	var dshandler *Config
-
 	// Wrap the response writer in a ScrubWriter so we automatically make the reply fit in the client's buffer.
 	w = request.NewScrubWriter(r, w)
 
-	for {
-		l := len(q[off:])
-		for i := 0; i < l; i++ {
-			b[i] = q[off+i]
-			// normalize the name for the lookup
-			if b[i] >= 'A' && b[i] <= 'Z' {
-				b[i] |= ('a' - 'A')
-			}
-		}
+	q := strings.ToLower(r.Question[0].Name)
+	var (
+		off       int
+		end       bool
+		dshandler *Config
+	)
 
-		if h, ok := s.zones[string(b[:l])]; ok {
+	for {
+		if h, ok := s.zones[q[off:]]; ok {
 			if r.Question[0].Qtype != dns.TypeDS {
 				if h.FilterFunc == nil {
 					rcode, _ := h.pluginChain.ServeDNS(ctx, w, r)