#include "stdio.h"
#include "alt_types.h"


void Revert_Ping(void)  //回復Ping數據包
{
   UINT i,Data_Len,Data_SUM,Len;
   //開始拼接Ping的回復數據包開始
   HEAD_Ethernet();        //以太網頭
   HEAD_IP();   //IP首部
   Len=Start_ICMP;
   //ICMP首部
   Data_Len=Receive_Buffer[14+2]*256+Receive_Buffer[14+2+1]-20;  //ICMP包的長度
   Send_Buffer[Len++]=0;  //回顯應答（Ping應答）
   Send_Buffer[Len++]=0;
   Send_Buffer[Len++]=0;  //校驗和
   Send_Buffer[Len++]=0;
   for (i=0;i<4;i++)
      Send_Buffer[Len++]=Receive_Buffer[Len];  //表示符和序號
   for (i=0;i<Data_Len-8;i++)
      Send_Buffer[Len++]=Receive_Buffer[Len];  //選項數據

   //計算校驗和
   Data_SUM=CHECK_SUM(Send_Buffer,14+20,Data_Len); //ICMP首部校驗和
   Send_Buffer[14+20+2]=Data_SUM/0x100;
   Send_Buffer[14+20+3]=Data_SUM&0xff;

   //拼接數據包結束

   NET_Send_Packet(Send_Buffer,Len);  //發送數據包
}