libpcap抓包源码

*程序功能:对捕获的数据包只输出网络访问层报头为以太祯 网际层报头为ip4 传输层报头为tcp的 源目的主机的,mac地址,ip地址,端口号*/

 

*程序功能:对捕获的数据包只输出网络访问层报头为以太祯 网际层报头为ip4 传输层报头为tcp的 源目的主机的,mac地址,ip地址,端口号*/


#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <pcap.h>



#include <netinet/if_ether.h>


#define IP 2048
#define TCP 6

typedef unsigned char UINT1;

typedef unsigned short UINT2;

typedef unsigned int UINT4;



typedef struct ether
{

  UINT1 dest[6];

  UINT1 src[6];

  UINT2 proto;

  UINT1 data[0];

} tEther;



typedef struct ip
{

  UINT1 hlen;   /*首部长度+版本 */

  UINT1 tos;   /*服务 */

  UINT2 len;   /*总长度 */

  UINT2 ipid;   /*标示 */

  UINT2 flagoff;  /*标示加偏移 */

  UINT1 ttl;   /*生存时间 */

  UINT1 proto;   /*协议 */

  UINT2 cksum;   /*首部检验和 */

  UINT4 src;   /*源地址 */

  UINT4 dest;   /*目地地址 */

  UINT1 data[0];



} tIp;


typedef struct tcp
{

  UINT2 sport;

  UINT2 dport;

  UINT4 seq;

  UINT4 ack;

  UINT1 hlen;

  UINT1 code;

  UINT2 window;

  UINT2 chsum;

  UINT2 urg;

  char data[0];



} tTcp;





void proc_pkt (u_char * user, const struct pcap_pkthdr *hp,
        const u_char * packet);

void net_host (UINT4 ipaddr);

int
main ()
{

  char *dev = NULL;

  pcap_t *descr;

  struct pcap_pkthdr hdr;

  u_char *packet;

  char errbuf[PCAP_ERRBUF_SIZE];

  int promisc = 0, cnt = 5;

  int pcap_time_out = 100;

  struct tEther *pEpkt;

  UINT4 net, mask;

  dev = pcap_lookupdev (errbuf);

  pcap_lookupnet (dev, &net, &mask, errbuf);

  descr = pcap_open_live (dev, BUFSIZ, promisc, pcap_time_out, errbuf);
  printf ("网络号:");
  net_host (net);
  printf ("网络掩码:");
  net_host (mask);
  printf ("\n\n");
  pcap_loop (descr, -1, proc_pkt, NULL);





  printf ("%s\n", dev);


  return 0;
}



void
proc_pkt (u_char * user, const struct pcap_pkthdr *hp, const u_char * packet)
{
  tEther *pEther;
  tIp *pIp;
  int i;
  pEther = (tEther *) packet;


  if (ntohs (pEther->proto) == IP) /*网络层的报头为IP*/
    {


      pIp = (tIp *) pEther->data;

      if (pIp->proto == TCP) /*传输层的报头为为tcp */
 {


   tTcp *pTcp;

   pTcp = (tTcp *) pIp->data;


   printf ("目的MAC地址:");
   for (i = 0; i < 6; i++)
     {
       if ((pEther->dest[i]) < 16)
  printf ("0");
       printf ("%x ", pEther->dest[i]);
     }
   printf ("\n源MAC地址:");
   for (i = 0; i < 6; i++)
     {
       if (((pEther->src[i]) < 16))
  printf ("0");
       printf ("%x ", pEther->src[i]);

     }
   printf ("\n");
   printf ("源IP地址:");

   net_host (pIp->src);

   printf ("目的IP地址:");

   net_host (pIp->dest);


   printf ("源端口:");

   printf ("%hu\n", ntohs (pTcp->sport));

   printf ("目的端口:");

   printf ("%hu\n\n\n", ntohs (pTcp->dport));

 }

    }

  return;
}

void
net_host (UINT4 ip_mask) /*将网络字节序的ip地址以及网络掩码转换转化为人们常用的形式 */
{
  UINT4 one, two, three, four;

  one = ip_mask;


  one = one >> 24;

  two = ip_mask;
  two = two >> 16;

  two = two & 0xff;
  three = ip_mask;

  three = three >> 8;

  three = three & 0xff;

  four = ip_mask;


  four = four & 0xff;

  printf ("%u.%u.%u.%u\n", four, three, two, one);
}