derp: add an unexported key.Public zero value variable to be less verbose

derp/derp_server.go

@@ -548,60 +548,63 @@ func (s *Server) sendServerInfo(bw *bufio.Writer, clientKey key.Public) error {
 func (s *Server) recvClientKey(br *bufio.Reader) (clientKey key.Public, info *clientInfo, err error) {
 	fl, err := readFrameTypeHeader(br, frameClientInfo)
 	if err != nil {
-		return key.Public{}, nil, err
+		return zpub, nil, err
 	}
 	const minLen = keyLen + nonceLen
 	if fl < minLen {
-		return key.Public{}, nil, errors.New("short client info")
+		return zpub, nil, errors.New("short client info")
 	}
 	// We don't trust the client at all yet, so limit its input size to limit
 	// things like JSON resource exhausting (http://github.com/golang/go/issues/31789).
 	if fl > 256<<10 {
-		return key.Public{}, nil, errors.New("long client info")
+		return zpub, nil, errors.New("long client info")
 	}
 	if _, err := io.ReadFull(br, clientKey[:]); err != nil {
-		return key.Public{}, nil, err
+		return zpub, nil, err
 	}
 	var nonce [24]byte
 	if _, err := io.ReadFull(br, nonce[:]); err != nil {
-		return key.Public{}, nil, fmt.Errorf("nonce: %v", err)
+		return zpub, nil, fmt.Errorf("nonce: %v", err)
 	}
 	msgLen := int(fl - minLen)
 	msgbox := make([]byte, msgLen)
 	if _, err := io.ReadFull(br, msgbox); err != nil {
-		return key.Public{}, nil, fmt.Errorf("msgbox: %v", err)
+		return zpub, nil, fmt.Errorf("msgbox: %v", err)
 	}
 	msg, ok := box.Open(nil, msgbox, &nonce, (*[32]byte)(&clientKey), s.privateKey.B32())
 	if !ok {
-		return key.Public{}, nil, fmt.Errorf("msgbox: cannot open len=%d with client key %x", msgLen, clientKey[:])
+		return zpub, nil, fmt.Errorf("msgbox: cannot open len=%d with client key %x", msgLen, clientKey[:])
 	}
 	info = new(clientInfo)
 	if err := json.Unmarshal(msg, info); err != nil {
-		return key.Public{}, nil, fmt.Errorf("msg: %v", err)
+		return zpub, nil, fmt.Errorf("msg: %v", err)
 	}
 	return clientKey, info, nil
 }
 
 func (s *Server) recvPacket(br *bufio.Reader, frameLen uint32) (dstKey key.Public, contents []byte, err error) {
 	if frameLen < keyLen {
-		return key.Public{}, nil, errors.New("short send packet frame")
+		return zpub, nil, errors.New("short send packet frame")
 	}
 	if _, err := io.ReadFull(br, dstKey[:]); err != nil {
-		return key.Public{}, nil, err
+		return zpub, nil, err
 	}
 	packetLen := frameLen - keyLen
 	if packetLen > MaxPacketSize {
-		return key.Public{}, nil, fmt.Errorf("data packet longer (%d) than max of %v", packetLen, MaxPacketSize)
+		return zpub, nil, fmt.Errorf("data packet longer (%d) than max of %v", packetLen, MaxPacketSize)
 	}
 	contents = make([]byte, packetLen)
 	if _, err := io.ReadFull(br, contents); err != nil {
-		return key.Public{}, nil, err
+		return zpub, nil, err
 	}
 	s.packetsRecv.Add(1)
 	s.bytesRecv.Add(int64(len(contents)))
 	return dstKey, contents, nil
 }
 
+// zpub is the key.Public zero value.
+var zpub key.Public
+
 // sclient is a client connection to the server.
 //
 // (The "s" prefix is to more explicitly distinguish it from Client in derp_client.go)