epoll/ip_snif.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <errno.h>
   4 #include <unistd.h>
   5 #include <sys/types.h>
   6 #include <sys/socket.h>
   7 #include <netinet/in.h>
   8 #include <netinet/ip.h>
   9 #include <netinet/if_ether.h>
  10
  11 int main(int argc, char **argv) {
  12         int sock, n;
  13         char buffer[2048];
  14         struct ethhdr *eth;
  15         struct iphdr *iph;
  16
  17         if (0>(sock=socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP)))) {
  18                 perror("socket");
  19                 exit(1);
  20         }
  21         //混杂模式
  22         struct ifreq ethreq;
  23         strncpy(ethreq.ifr_name,"eth0",IFNAMSIZ);
  24         if(-1 == ioctl(sock,SIOCGIFFLAGS,&ethreq)){
  25                 perror("ioctl");
  26                 close(sock);
  27                 exit(1);
  28         }
  29         ethreq.ifr_flags |=IFF_PROMISC;
  30         if(-1 == ioctl(sock,SIOCGIFFLAGS,&ethreq)){
  31                 perror("ioctl");
  32                 close(sock);
  33                 exit(1);
  34         }
  35
  36         while (1) {
  37                 printf("=====================================\n");
  38                 //注意：在这之前我没有调用bind函数，原因是什么呢？
  39                 n = recvfrom(sock,buffer,2048,0,NULL,NULL);
  40                 printf("%d bytes read\n",n);
  41
  42                 //接收到的数据帧头6字节是目的MAC地址，紧接着6字节是源MAC地址。
  43                 eth=(struct ethhdr*)buffer;
  44                 printf("Dest MAC addr:%02x:%02x:%02x:%02x:%02x:%02x\n",eth->h_dest[0],eth->h_dest[1],eth->h_dest[2],eth->h_dest[3],eth->h_dest[4],eth->h_dest[5]);
  45                 printf("Source MAC addr:%02x:%02x:%02x:%02x:%02x:%02x\n",eth->h_source[0],eth->h_source[1],eth->h_source[2],eth->h_source[3],eth->h_source[4],eth->h_source[5]);
  46
  47                 iph=(struct iphdr*)(buffer+sizeof(struct ethhdr));
  48                 //我们只对IPV4且没有选项字段的IPv4报文感兴趣
  49                 if(iph->version ==4 && iph->ihl == 5){
  50                         printf("Source host:%s\n",inet_ntoa(iph->saddr));
  51                         printf("Dest host:%s\n",inet_ntoa(iph->daddr));
  52                 }
  53         }
  54 }