Make the udp msg size configurable

dns.go

@@ -69,6 +69,7 @@ import (
 const (
 	Year68         = 2 << (32 - 1) // For RFC1982 (Serial Arithmetic) calculations in 32 bits.
 	DefaultMsgSize = 4096          // A standard default for larger than 512 packets.
+        UDPMsgSize     = 1024          // A nice default for servers receiving UDP packets.
 	MaxMsgSize     = 65536         // Largest possible DNS packet.
 	DefaultTtl     = 3600          // Default TTL.
 )

server.go

@@ -81,9 +81,8 @@ func Refused(w ResponseWriter, r *Msg) {
 func RefusedHandler() Handler { return HandlerFunc(Refused) }
 
 // ...
-func ListenAndServe(addr string, network string, handler Handler) error {
-        //TODO(mg): make message size configurable....
-        server := &Server{Addr: addr, Net: network, Handler: handler, UDPSize: DefaultMsgSize}
+func ListenAndServe(addr string, network string, handler Handler, size int) error {
+	server := &Server{Addr: addr, Net: network, Handler: handler, UDPSize: size}
 	return server.ListenAndServe()
 }
 
@@ -142,13 +141,13 @@ type Server struct {
 	Addr         string            // address to listen on, ":dns" if empty
 	Net          string            // if "tcp" it will invoke a TCP listener, otherwise an UDP one
 	Handler      Handler           // handler to invoke, dns.DefaultServeMux if nil
-        UDPSize   int                // default buffer to use to read incoming UDP messages
+	UDPSize      int               // default buffer to use to read incoming UDP messages
 	ReadTimeout  int64             // the net.Conn.SetReadTimeout value for new connections
 	WriteTimeout int64             // the net.Conn.SetWriteTimeout value for new connections
 	TsigSecret   map[string]string // secret(s) for Tsig map[<zonename>]<base64 secret>
 }
 
-// ...
+// ListenAndServe starts a nameserver on the configured address.
 func (srv *Server) ListenAndServe() error {
 	addr := srv.Addr
 	if addr == "" {
@@ -235,6 +234,9 @@ func (srv *Server) ServeUDP(l *net.UDPConn) error {
 	if handler == nil {
 		handler = DefaultServeMux
 	}
+	if srv.UDPSize == 0 {
+		srv.UDPSize = UDPMsgSize
+	}
 	for {
 		m := make([]byte, srv.UDPSize)
 		n, a, e := l.ReadFromUDP(m)

server_test.go

@@ -18,7 +18,7 @@ func HelloServer(w ResponseWriter, req *Msg) {
 func TestServing(t *testing.T) {
 	HandleFunc("miek.nl.", HelloServer)
 	go func() {
-		err := ListenAndServe(":8053", "udp", nil)
+		err := ListenAndServe(":8053", "udp", nil, 0)
 		if err != nil {
 			t.Log("ListenAndServe: ", err.Error())
 			t.Fail()
@@ -32,7 +32,7 @@ func BenchmarkServing(b *testing.B) {
 	// Again start a server
 	HandleFunc("miek.nl.", HelloServer)
 	go func() {
-		ListenAndServe("127.0.0.1:8053", "udp", nil)
+		ListenAndServe("127.0.0.1:8053", "udp", nil, 0)
 	}()
 
 	c := NewClient()