使用Jpcap创建反向代理

Question

我需要创建一个接收HTTP请求的程序，并将这些请求转发到web服务器。

Diagram http://img269.imageshack.us/img269/1862/h98trsly.jpg

我只使用Java Sockets就成功地实现了这一点，但是客户端需要用Jpcap实现该程序。我想知道这是否可能，以及我应该为这个项目阅读哪些文献。

这是我现在通过将Jpcap教程中的片段缝合在一起得到的：

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);
    }
}

任何帮助都将不胜感激。谢谢。

Answer 1

为什么？他的理由是什么？他真的想为你已经做过的同样的事情付出十倍的代价吗？

您不需要Jpcap来实现HTTP代理。它可以完全在java.net或java.nio中完成。

Answer 2

我不认为你能做到这一点，至少在Windows机器上是这样。Jpcap只是Winpcap的一个包装器，这个底层机制不能丢弃观察到的数据包：

http://www.mirrorservice.org/sites/ftp.wiretapped.net/pub/security/packet-capture/winpcap/misc/faq.htm#Q-17

因此，我不明白如何“在网络上”构建反向代理。您不需要执行以下操作：

1. 通过实时拼接数据包并使其不被目标主机接收来观察传入的HTTP请求。
2. 根据您正在使用的任何代理规则发出备用HTTP请求，并从请求中发出响应，并在线路上推出数据包，从而伪造来自原始主机的响应-

既然您不能丢弃入站数据包，那么目标主机不会尝试处理请求并将自己的数据包抛到线路上作为响应吗？可能还有更多我不知道的东西，因为我不是网络专家。这个问题只是让我好奇，使用这样的“垫片”是可能的。