Merge ee1e4d33f8f01f8a53be3a726f922ad5eb6195aa into e42f0e573221c5e0146c02fd5d71f32aa93c7221

cppcheck reports:
network.cpp:1717:22: error: Null pointer dereference: payload [ctunullpointer]
    memcpy(tcp_data, payload, payloadlen);
                     ^
client.cpp:193:22: note: Calling function send_raw0, 2nd argument is null
            send_raw0(raw_info, 0, 0);
                     ^
network.cpp:2534:20: note: Calling function send_raw_tcp, 2nd argument is null
            return send_raw_tcp(raw_info, payload, payloadlen);
                   ^
network.cpp:1717:22: note: Dereferencing argument payload that is null
    memcpy(tcp_data, payload, payloadlen);
                     ^

README.md

@@ -81,7 +81,7 @@ Assume your UDP is blocked or being QOS-ed or just poorly supported. Assume your
 Now,an encrypted raw tunnel has been established between client and server through TCP port 4096. Connecting to UDP port 3333 at the client side is equivalent to connecting to port 7777 at the server side. No UDP traffic will be exposed.
 
 ### Note
-To run on Android, check [Android_Guide](/doc/android_guide.md)
+To run on Android, check [Android_Guide](https://github.com/wangyu-/udp2raw/wiki/Android-Guide)
 
 `-a` option automatically adds an iptables rule (or a few iptables rules) for you, udp2raw relies on this iptables rule to work stably. Be aware you dont forget `-a` (its a common mistake). If you dont want udp2raw to add iptables rule automatically, you can add it manually(take a look at `-g` option) and omit `-a`.
 

network.cpp

@@ -1714,7 +1714,8 @@ int send_raw_tcp(raw_info_t &raw_info, const char *payload, int payloadlen) {  /
 
     char *tcp_data = send_raw_tcp_buf + +tcph->doff * 4;
 
-    memcpy(tcp_data, payload, payloadlen);
+    if (payload)
+        memcpy(tcp_data, payload, payloadlen);
     int tcp_totlen = tcph->doff * 4 + payloadlen;
 
     if (raw_ip_version == AF_INET) {