利用libpcap打印ip包

 #include <stdio.h>
 #include <pcap.h>
 #include <time.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <errno.h>
 #include <string.h>
 #include <iostream>

 using namespace std;

 //IP层数据包格式
 typedef struct
 {
     int header_len:;
     int version:;
     u_char tos:;
     int total_len:;
     int ident:;
     int flags:;
     u_char ttl:;
     u_char proto:;
     int checksum:;
     u_char sourceIP[];
     u_char destIP[];
 }IPHEADER;

 void callback(u_char* user,const struct pcap_pkthdr* header,const u_char* pkt_data);

 int main(int argc, char **argv)
 {
     char *device = NULL;
     char errbuf[];
     pcap_t *pcap;
     int link_data;

     if((device = pcap_lookupdev(errbuf)) == NULL)
     {
         perror(errbuf);
         return ;
     }

     pcap = pcap_open_live(device, , , , errbuf);
     if(pcap == NULL)
     {
         perror(errbuf);
         return ;
     }

     if((link_data = pcap_datalink(pcap)) == -)
     {
         fprintf(stderr,"pcap_link_data: %s\n",pcap_geterr(pcap));
         return ;
     }

     cout<<"开始抓包"<<endl;
     pcap_loop(pcap, -, callback, NULL);

     return ;
 }

 void callback(u_char* user,const struct pcap_pkthdr* header,const u_char* pkt_data)
 {
     cout<<"\t\t抓到一个包"<<endl;
     cout<<"-------------------------------------------------"<<endl;
     //解析数据包IP头部
     if(header->len>=){
         IPHEADER *ip_header=(IPHEADER*)(pkt_data+);
         //解析协议类型
         cout<<"|版本 "<<ip_header->version<<"|首部长度"<<ip_header->header_len*<<"字节|\t\t|"
             "总长度"<<ip_header->total_len<<"字节|"<<endl;
         cout<<"-------------------------------------------------"<<endl;
         cout<<"|\t\t\t|\t|\t\t|"<<endl;
         cout<<"-------------------------------------------------"<<endl;
         cout<<"|ttl "<<int(ip_header->ttl)<<"\t|协议 ";
         switch(ip_header->proto)
         {
           case :
             cout<<"ICMP";
             break;
           case :
             cout<<"IGMP";
             break;
           case :
             cout<<"TCP ";
             break;
           case :
             cout<<"UDP ";
             break;
           case :
             cout<<"IPv6";
             break;
           default:
             cout<<"IPv4";
         }
         cout<<"\t|首部校验和 "<<ip_header->checksum<<"\t|"<<endl;
         cout<<"-------------------------------------------------"<<endl;
         printf("|\t\t源地址 : %d.%d.%d.%d\t\t|\n",\
           ip_header->sourceIP[],ip_header->sourceIP[],ip_header->sourceIP[],ip_header->sourceIP[]);
         cout<<"-------------------------------------------------"<<endl;
         printf("|\t\t目的地址 : %d.%d.%d.%d\t\t|\n",\
           ip_header->destIP[],ip_header->destIP[],ip_header->destIP[],ip_header->destIP[]);
         cout<<"-------------------------------------------------"<<endl;
         cout<<endl;
     }
 }