Add one more line murmur to README

Author: lxd

README.md

@@ -4,6 +4,12 @@ This code serves as a VPN server for [NE PacketTunnel Illustration](), everythin
 
 Inspired by [simpletun](http://backreference.org/2010/03/26/tuntap-interface-tutorial/), [mptun](https://github.com/cloudwu/mptun) and [ShadowVPN](https://github.com/clowwindy/ShadowVPN).
 
+
+Usage & Configuration
+=====================
+Just compile and run, all configurations are at the beginning of source code `vpn.c` as C `#define` macros.
+
+
 License
 =======
 The MIT License (MIT)

vpn.c

@@ -13,13 +13,19 @@
 #include <linux/if.h>
 #include <linux/if_tun.h>
 
+/*
+ * The following lines serve as configurations
+ * Uncomment first 2 lines to run as vpn client
+ */
+
 // #define AS_CLIENT YES
 // #define SERVER_HOST ""
 
 #define PORT 54345
 #define MTU 1400
 #define BIND_HOST "0.0.0.0"
 
+
 static int max(int a, int b) {
   return a > b ? a : b;
 }