packetCapture.c

#include <stdio.h>
#include <net/if.h>
#include <net/ethernet.h>

void *mac_ntoa(u_char *d){
	static char str[18];
	sprintf(str, "%02x:%02x:%02x:%02x:%02x:%02x\n", d[0], d[1],d[2],d[3],d[4],d[5]);
	return str;
}

void analyzePacket(u_char *buf){
	analyzePacketHeader(buf);
}

void analyzePacketHeader(u_char *buf){
	struct ether_header *eth;
	static int packetCount=0;
	eth = (struct ether_header *)buf;
	if (ntohs(eth->ether_type)==0x0800){
		printf("IPv4 Packet:\n");	
		printf("\tDst MAC addr    : %17s\n", mac_ntoa(eth->ether_dhost));
		printf("\tSrc MAC addr    : %17s\n", mac_ntoa(eth->ether_shost));
		printf("\tEthernet Type   : 0x%04x\n", ntohs(eth->ether_type));
	}
}

int main(){
	int socketNumber;
	u_char buf[1<<16-1];
	socketNumber = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
	while(1){
		read(socketNumber, buf, sizeof(buf));
		analyzePacket(buf);
		printf("\n");
	}
	return 0;
}