/*
 ============================================================================
 Name        : PacketFilterWrite.c
 Author      : lasko
 Version     :
 Copyright   : Your copyright notice
 Description : Hello World in C, Ansi-style
 ============================================================================
 *
 */

#include <sys/types.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/udp.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <net/bpf.h>
#include <net/if.h>
#include <stdlib.h>
#include <stdio.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <err.h>

char bpf_dev[] = "/dev/bpf0";	/* the BPF device to use */
char inter[] = "en0";		/* the ethernet device we'll attach to */
char src[] = "10.20.3.131";	/* our address */
char dest[] = "10.20.3.130";	/* the target system's address */
int sport = 255;		/* the source port for the UDP datagram */
int dport = 9;			/* the decoy destination port */
int real_dport = 7;		/* the real destination port */
int s;				/* the socket im use */
union {
	unsigned long l[3];
	unsigned short s[6];
	unsigned char c[12];
}     pseudo;


int blen;
u_char *bbuff;
struct ifreq req;
struct bpf_hdr *bhdr;

struct udphdr *udph;
struct ip *iph;
struct sockaddr_in daddr;
struct timeval to = {0, 500000};

unsigned char dgram[276];
//Datagram frame to send over ethernet.
//

#define USEBPF
#define ioctl ioctl_socket

void
dump_hex(u_char * buffer, int size)
{
	int i, off = 0;
	while (off < size) {
		printf("%.4x:", off);
		for (i = 0; i < 16 && i + off < size; i++)
			printf(" %.2x", buffer[i + off]);
		printf("\n");
		off += i;
	}
}

int
main(int argc, char *argv[])
{
	int bpf;
	int i, true = 1;

	printf("Starting program\n");


	if ((s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
		err(1, "socket");
	
	if (setsockopt(s, IPPROTO_IP, IP_HDRINCL, &true, sizeof(true)) < 0)
		err(1, "setsockopt");
	if ((bpf = open(bpf_dev, O_RDWR)) < 0)
		err(1, "open");
	if (ioctl(bpf, BIOCGBLEN, &blen) < 0)
		err(1, "ioctl(BIOCGBLEN)");
	if ((bbuff = malloc(blen)) == NULL)
		err(1, "malloc");
	strcpy(req.ifr_name, inter);
	if (ioctl(bpf, BIOCSETIF, &req) < 0)
		err(1, "ioctl(BIOSETIF)");
	if (ioctl(bpf, BIOCSRTIMEOUT, &to) < 0)
		err(1, "ioctl(BIOCSRTIMEOUT)");

	daddr.sin_len = sizeof(daddr);
	daddr.sin_family = AF_INET;
	daddr.sin_port = dport;
	daddr.sin_addr.s_addr = inet_addr(dest);

	for (i = 0; i < sizeof(dgram); dgram[i++] = 27);
	for (i = 0; i < 3; pseudo.l[i++] = 0);

	iph = (struct ip *) & dgram[0];
	udph = (struct udphdr *) & dgram[20];
	printf("Print ip vers");
	iph->ip_v = IPVERSION;
	iph->ip_hl = 5;

	iph->ip_len = 276;

	iph->ip_id = 1;
	iph->ip_ttl = 255;
	iph->ip_p = pseudo.c[9] = IPPROTO_UDP;
	iph->ip_src.s_addr = pseudo.l[0] = inet_addr(src);
	iph->ip_dst.s_addr = pseudo.l[1] = inet_addr(dest);

	iph->ip_off = 0x2000;

	//iph->ip_sum = ~calc_sum(0, (u_short *) iph, 10);

	udph->uh_sport = ntohs(sport);
	udph->uh_dport = ntohs(dport);
	udph->uh_ulen = pseudo.s[5] = ntohs(256);
	//udph->uh_sum = ~calc_sum(calc_sum(0, pseudo.s, 6), (u_short *) udph, 128);

	/* send the first half of the decoy */

#ifndef USEBPF
	if (sendto(s, &dgram, 276, 0, (struct sockaddr *) & daddr,
	    sizeof(daddr)) < 0) {
		err(1, "sendto");
	}
#else
	if (write(bpf, &dgram, 276) == -1)
		err(1, "write");
#endif
	iph->ip_off = 32;
	iph->ip_sum = 0;
	//iph->ip_sum = calc_sum(0, (u_short *) iph, 10);
	for (i = 20; i < 276; dgram[i++] = 66);

	/* send the second half of the decoy */

#ifndef USEBPF
	if (sendto(s, &dgram, 276, 0, (struct sockaddr *) & daddr,
	    sizeof(daddr)) < 0) {
		err(1, "sendto");

	}
#else
	if (write(bpf, &dgram, 276) == -1)
		err(1, "write");
#endif
	iph->ip_id++;
	iph->ip_sum = 0;
	//iph->ip_sum = ~calc_sum(0, (u_short *) iph, 10);

	udph->uh_sport = ntohs(sport);
	udph->uh_dport = ntohs(real_dport);
	udph->uh_ulen = pseudo.s[5] = ntohs(256);
	//udph->uh_sum = ~calc_sum(calc_sum(0, pseudo.s, 6), (u_short *) udph, 128);

	/*
	   send the first half of the real datagram
	   we have kept the offset settings from above
	   offset = 256, length = 256, MF = 0
	   -> total length is set to 512 by this fragment
	*/

#ifndef USEBPF
	if (sendto(s, &dgram, 276, 0, (struct sockaddr *) & daddr,
	    sizeof(daddr)) < 0) {
		err(1, "sendto");
	}
#else
	if (write(bpf, &dgram, 276) == -1)
		err(1, "write");
#endif
	iph->ip_off = 0x2040;

	iph->ip_sum = 0;
	//iph->ip_sum = calc_sum(0, (u_short *) iph, 10);
	for (i = 20; i < 276; dgram[i++] = 0);

	/*
	 * send the second half of the real
	 * datagram
	 */

#ifndef USEBPF
	if (sendto(s, &dgram, 276, 0, (struct sockaddr *) & daddr,
	    sizeof(daddr)) < 0) {
		err(1, "sendto");
	}
#else
	if (write(bpf, &dgram, 276) == -1)
		err(1, "write");
#endif
	printf("Packet sendt\n");


	free(bbuff);
	close(bpf);
	close(s);
	printf("--- Packet data ----\n");
	dump_hex(dgram, sizeof(dgram));

	return EXIT_SUCCESS;
}