使用Sshuttle时如何在Java套接字中获取正确的客户端IP？

Question

I am using the utility sshuttle to access internet on my computer.

sudo sshuttle --dns -vr user@172.16.30.30 0/0

I have a simple java client server program

Client (My computer running sshuttle)

// client ip is 172.16.23.6
class client {
   public static void main(String args[]) {
     Socket s = new Socket("172.16.30.20",port); // different server
   }
}

The server program, running on 172.16.30.20

class server {
   public static void main(String args[]) {
      ServerSocket s = new ServerSocket(port);
      Socket cl = s.accept();
      System.out.println(cl);
   }
}

When I run the the server and connect the client, the IP address which the socket cl holds is 172.16.30.30 (IP of server to which I did sshuttle) instead of its own IP which is 172.16.23.6

When I stop sshuttle, the program works fine and the correct IP address is displayed.

I have to run both the programs simultaneously but am unable to do so.

Answer 1

You are out of the luck. sshuttle is like a proxy. The sshuttle server creates completely independent TCP connection from 172.16.30.30 to 172.16.30.20 and it copies incoming data from client connection to this connection. Your server 172.16.30.20 cannot get the information about the real client address because it is present neither in IP nor in TCP header. Your java server is able read sender address from the IP header but it is IP address of host that established the connection and it is 172.16.30.30 (sshuttle server).

Application protocols like HTTP have mechanism how to indicate the real client IP address. HTTP proxy may add HTTP header X-Forwarded-For and server then may learn the client IP from it. But it is possible only if application proxy adds this information to the forwarded data. sshuttle is application protocol independent so it cannot add such information.