/* 
	An example packet sniffer for Linux 2.4 
	Version 2.0

	By j00n1x (c) 2003

	This packet sniffer allows a bind to a specific network 
	device before sniffing. Also sets promiscuous mode to sniff all 
	traffic reaching that network device. 

	This program requires superuser (root).

	Note:
	It uses pf_packet/sock_dgram. 
*/

#define DEVICE "eth0"

// standard C include files
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// unix header files
#include <unistd.h> // for write(), close()

// BSD socket header files
#include <sys/socket.h>
#include <sys/types.h>

// resolver header files
#include <netdb.h>
#include <netinet/in.h>

// hostname to ip address conversion functions
#include <arpa/inet.h>

// raw packet files - IP
#include <netinet/ip.h>

// pf_packet files
#include <asm/types.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>

// netdevice(7) 
#include <sys/ioctl.h>
#include <linux/if.h>

int main(int argc, char **argv)
{
	int fd; 
	char buf[1024*64];
	struct iphdr *iph;
	struct sockaddr_in to;
	char source[1024], dest[1024]; // source/dest ip address
	char *p;
	struct protoent *pent;
	char protocol[1024];
	struct sockaddr_ll eth;
	struct ifreq ifr;
	struct packet_mreq pmreq;

	fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
	if (fd < 0) { 
		perror("socket");
		exit(1);
	}

	// find DEVICE's ifindex -- man 7 netdevice
	strcpy(ifr.ifr_name, DEVICE);
	if (ioctl(fd, SIOCGIFINDEX, &ifr) < 0) {
		perror("ioctl");
		exit(1);
	}

	printf("ifindex: %d\n", ifr.ifr_ifindex);

	// bind to DEVICE, using bind() - man 7 packet
	memset(&eth, 0, sizeof(eth));

	eth.sll_family = AF_PACKET;
	eth.sll_protocol = htons(ETH_P_IP);
	eth.sll_ifindex = ifr.ifr_ifindex;
	eth.sll_hatype = ARPHRD_VOID;
	eth.sll_pkttype = PACKET_HOST;
//	eth.sll_pkttype = PACKET_OUTGOING; // doesn't seem to work
	eth.sll_halen = 0;
	
	if (bind(fd, (struct sockaddr *) &eth, sizeof(eth)) < 0) {
		perror("bind");
		exit(1);
	}

	// set promiscuous mode - man 7 packet

	pmreq.mr_ifindex = ifr.ifr_ifindex;
	pmreq.mr_type = PACKET_MR_PROMISC;
	pmreq.mr_alen = 0;

	if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &pmreq, sizeof(pmreq)) < 0) {
		perror("setsockopt");
		exit(1);
	}

	// setup pointers to point inside buffer
	iph = (void *) buf;

	// main loop

	while (1) {
		if (recvfrom(fd, buf, sizeof(buf), 0, NULL, NULL) < 0) {
			perror("recvfrom");
		}

		// convert our data into strings, so we can
		// print them out 'nicely'

		to.sin_addr.s_addr = iph->saddr;
		p = inet_ntoa(to.sin_addr);
		strcpy(source, p);

		to.sin_addr.s_addr = iph->daddr;
		p = inet_ntoa(to.sin_addr);
		strcpy(dest, p);

		pent = getprotobynumber(iph->protocol);
		if (!pent) {
			perror("getprotobynumber");
			strcpy(protocol, "");
		}
		else {
			strcpy(protocol, pent->p_name);
		}

		// print out details

		printf("%s -> %s\n", source, dest);
		printf("version: %d\t", iph->version);
		printf("ihl: %d\t", iph->ihl);
		printf("tos: %d\t", iph->tos);
		printf("tot_len: %d\t", ntohs(iph->tot_len));
		printf("id: %d\t", ntohs(iph->id));
		printf("frag_off: %d\n", ntohs(iph->frag_off));
		printf("ttl: %d\t", iph->ttl);
		if (pent)
			printf("protocol: %d (%s)\t", iph->protocol, protocol);
		else 
			printf("protocol: %d\t", iph->protocol);
		printf("check: %d\t", ntohs(iph->check));

		printf("\n\n");
	}

	close(fd);

	return 0;
}