使用 Jpcap 创建反向代理

Question

我需要创建一个程序来接收 HTTP 请求并将这些请求转发到 Web 服务器。

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

我仅使用 Java Sockets 成功完成了此任务，但客户端需要在 Jpcap 中实现该程序。我想知道这是否可行以及我应该为这个项目阅读哪些文献。

这就是我现在通过将 Jpcap 教程中的片段拼接在一起得到的：

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);
    }
}

任何帮助将不胜感激。谢谢。

Answer 1

为什么？他的理由是什么？他真的愿意为你已经做过的同样的事情支付十倍的费用吗？

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

我认为你不可能做到这一点，至少在 Windows 机器上是这样。 Jpcap 只是 Winpcap 的包装器，这种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

所以，我不明白如何“在线”构建反向代理。您是否必须执行以下操作：

1. 通过实时拼凑数据包并阻止目标主机接收它们来观察传入的 HTTP 请求。

2. 根据您正在实施的任何代理规则发出备用 HTTP 请求。

3. 从您的请求中获取响应，并在网络上推送数据包，从而伪造来自原始主机的响应？

   从

由于您无法丢弃入站数据包，因此目标主机不会尝试处理请求并将其自己的数据包扔到线路上作为响应吗？由于我不是网络专家，可能还有更多我不知道的事情。这个问题让我很好奇使用这样的“垫片”会发生什么。