only send Version Negotiation packets for packets larger than 1200 bytes

server.go

@@ -351,6 +351,13 @@ func (s *baseServer) handlePacketImpl(p *receivedPacket) bool /* is the buffer s
 	}
 	// send a Version Negotiation Packet if the client is speaking a different protocol version
 	if !protocol.IsSupportedVersion(s.config.Versions, hdr.Version) {
+		if p.Size() < protocol.MinUnknownVersionPacketSize {
+			s.logger.Debugf("Dropping a packet with an unknown version that is too small (%d bytes)", p.Size())
+			if s.config.Tracer != nil {
+				s.config.Tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeNotDetermined, p.Size(), logging.PacketDropUnexpectedPacket)
+			}
+			return false
+		}
 		go s.sendVersionNegotiationPacket(p, hdr)
 		return false
 	}