test.c

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <linux/if_ether.h>
//#include <linux/in.h>
#include <netinet/in.h>

#define BUFFER_MAX 2048
int main(int argc,char* argv[]){
    int sock_fd;
    int proto;
    int n_read;
    char buffer[BUFFER_MAX];
    char *eth_head;
    char *ip_head;
    char *tcp_head;
    char *udp_head;
    char *icmp_head;
    unsigned char *p;
    if((sock_fd=socket(PF_PACKET,SOCK_RAW,htons(ETH_P_IP)))<0){
        printf("error create raw socket\n");
        return -1;
    }
    while(1){
        n_read = recvfrom(sock_fd,buffer,2048,0,NULL,NULL);
        if(n_read < 42)
        {
            printf("error when recv msg \n");
            return -1;
        }
        eth_head = buffer;
        p = eth_head;
        printf("MAC address: %.2x:%02x:%02x:%02x:%02x:%02x ==> %.2x:%02x:%02x:%02x:%02x:%02x\n",
        p[6],p[7],p[8],p[9],p[10],p[11],p[0],p[1],p[2],p[3],p[4],p[5]);
        ip_head = eth_head+14;
        p = ip_head+12;
        printf("IP:%d.%d.%d.%d==> %d.%d.%d.%d\n",p[0],p[1],p[2],p[3],p[4],p[5],p[6],p[7]);
        proto = (ip_head + 9)[0];
        p = ip_head +12;
        printf("Protocol:");
        switch(proto){
            case IPPROTO_ICMP:printf("icmp\n");break;
            case IPPROTO_IGMP:printf("igmp\n");break;
            case IPPROTO_IPIP:printf("ipip\n");break;
            case IPPROTO_TCP:printf("tcp\n");break;
            case IPPROTO_UDP:printf("udp\n");break;
            default:printf("Pls query yourself\n");
        }
    }
    return -1;
}