Creating a Reverse Proxy using Jpcap
- by Ramon Marco Navarro
I need to create a program that receives HTTP request and forwards those requests to the web servers.
I have successfully made this using only Java Sockets but the client needed the program to be implemented in Jpcap. I'd like to know if this is possible and what literature I should be reading for this project.
This is what I have now by stitching together pieces from the Jpcap tutorial:
import java.net.InetAddress;
import java.io.*;
import jpcap.*;
import jpcap.packet.*;
public class Router {
public static void main(String args[]) {
//Obtain the list of network interfaces
NetworkInterface[] devices = JpcapCaptor.getDeviceList();
//for each network interface
for (int i = 0; i < devices.length; i++) {
//print out its name and description
System.out.println(i+": "+devices[i].name + "(" + devices[i].description+")");
//print out its datalink name and description
System.out.println(" datalink: "+devices[i].datalink_name + "(" + devices[i].datalink_description+")");
//print out its MAC address
System.out.print(" MAC address:");
for (byte b : devices[i].mac_address)
System.out.print(Integer.toHexString(b&0xff) + ":");
System.out.println();
//print out its IP address, subnet mask and broadcast address
for (NetworkInterfaceAddress a : devices[i].addresses)
System.out.println(" address:"+a.address + " " + a.subnet + " "+ a.broadcast);
}
int index = 1; // set index of the interface that you want to open.
//Open an interface with openDevice(NetworkInterface intrface, int snaplen, boolean promics, int to_ms)
JpcapCaptor captor = null;
try {
captor = JpcapCaptor.openDevice(devices[index], 65535, false, 20);
captor.setFilter("port 80 and host 192.168.56.1", true);
} catch(java.io.IOException e) {
System.err.println(e);
}
//call processPacket() to let Jpcap call PacketPrinter.receivePacket() for every packet capture.
captor.loopPacket(-1,new PacketPrinter());
captor.close();
}
}
class PacketPrinter implements PacketReceiver {
//this method is called every time Jpcap captures a packet
public void receivePacket(Packet p) {
JpcapSender sender = null;
try {
NetworkInterface[] devices = JpcapCaptor.getDeviceList();
sender = JpcapSender.openDevice(devices[1]);
} catch(IOException e) {
System.err.println(e);
}
IPPacket packet = (IPPacket)p;
try {
// IP Address of machine sending HTTP requests (the client)
// It's still on the same LAN as the servers for testing purposes.
packet.dst_ip = InetAddress.getByName("192.168.56.2");
} catch(java.net.UnknownHostException e) {
System.err.println(e);
}
//create an Ethernet packet (frame)
EthernetPacket ether=new EthernetPacket();
//set frame type as IP
ether.frametype=EthernetPacket.ETHERTYPE_IP;
//set source and destination MAC addresses
// MAC Address of machine running reverse proxy server
ether.src_mac = new MacAddress("08:00:27:00:9C:80").getAddress();
// MAC Address of machine running web server
ether.dst_mac = new MacAddress("08:00:27:C7:D2:4C").getAddress();
//set the datalink frame of the packet as ether
packet.datalink=ether;
//send the packet
sender.sendPacket(packet);
sender.close();
//just print out a captured packet
System.out.println(packet);
}
}
Any help would be greatly appreciated. Thank you.
