用原始套接字监听局域网内的数据包，为什么只能得到ip头内的源IP地址而目的IP地址总是会等于源IP地址？？

[kxyes]

奇怪了为什么就是不能得到目的IP地址？？


#include "stdafx.h"
#include <stdio.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <Mstcpip.h>
#pragma comment(lib,"Ws2_32")
#define MAX_PACK_LEN 1024
typedef struct ip_hdr //定义IP首部
{
unsigned char h_lenver; //4位首部长度,4位IP版本号
unsigned char tos; //8位服务类型TOS
unsigned short total_len; //16位总长度（字节）
unsigned short ident; //16位标识
unsigned short th_flag; //3位标志位
unsigned char ttl; //8位生存时间 TTL
unsigned char iProtocol; //8位协议 (TCP, UDP 或其他)
unsigned short checksum; //16位IP首部校验和
unsigned int sourceIP; //32位源IP地址
unsigned int destIP; //32位目的IP地址
}IP_HEADER;

void DeCodeIP(char *buf,int iBufSize) //解析侦听到的IP数据包

{

IP_HEADER * pIPhdr;

pIPhdr=(IP_HEADER * )buf;

sockaddr_in dest,src;

dest.sin_family=AF_INET;
dest.sin_addr.S_un.S_addr=pIPhdr->destIP;
src.sin_family=AF_INET;
src.sin_addr.S_un.S_addr=pIPhdr->sourceIP;
char *lpdest=inet_ntoa(dest.sin_addr);
char *lpsrc=inet_ntoa(src.sin_addr);
printf("dest:%s,src:%s\n",lpdest,lpsrc);

}
int main(int argc, char* argv[])
{
int iErrorCode;

char RecvBuf[MAX_PACK_LEN];

WSADATA wsaData;

iErrorCode = WSAStartup(MAKEWORD(2,2),&wsaData);

SOCKET SockRaw = WSASocket(AF_INET, SOCK_RAW, IPPROTO_IP, NULL, 0, WSA_FLAG_OVERLAPPED);

SOCKADDR_IN sa;

sa.sin_family = AF_INET;

sa.sin_port = htons(6000);

sa.sin_addr.S_un.S_addr=inet_addr("192.168.0.1");



if(bind(SockRaw, (PSOCKADDR)&sa, sizeof(sa))!=0)
{
printf("bind error!");
WSACleanup();
}


DWORD dwBufferLen[10] ;

DWORD dwBufferInLen=1;

DWORD dwBytesReturned=0;

iErrorCode=WSAIoctl(SockRaw, SIO_RCVALL,&dwBufferInLen, sizeof(dwBufferInLen),

NULL, 0,&dwBytesReturned , NULL , NULL );
if(iErrorCode==SOCKET_ERROR)
{
printf("ioctl error!");
WSACleanup();
}


while(1)

{

memset(RecvBuf, 0, sizeof(RecvBuf));
iErrorCode = recv(SockRaw, RecvBuf, sizeof(RecvBuf),0);
if(iErrorCode!=SOCKET_ERROR&&iErrorCode>20)
DeCodeIP(RecvBuf, iErrorCode);

}

return 0;
}

[tide2355]

看到inet_ntoa（）函数没？
查查 msdn 。这个函数返回的是一个静态的数据缓冲，所以你这样用
char *lpdest=inet_ntoa(dest.sin_addr);
char *lpsrc=inet_ntoa(src.sin_addr);
printf("dest:%s,src:%s\n",lpdest,lpsrc);
是错误的。
必须自己申请2块char的缓冲，把inet_ntoa返回的缓冲里面的数据拷贝进去。
char *lpdest = new char[15];
strcpy(lpdest,inet_ntoa(dest.sin_addr));
char *lpsrc = new char[15];
strcpy(lpsrc,inet_ntoa(dest.sin_addr));
printf("dest:%s,src:%s\n",lpdest,lpsrc);

[tide2355]

ps
注意释放内存
delete lpsrc;
delete lpdest;

[kxyes]

这样还是一样不能得到目的IP地址啊？？
仍然和源IP地址一样~！！