/*th a FIN flag and pass it through a raw socket.
 * 
 * Thamer Al-Herbish shadows@whitefang.com
 */

#include <stdlib.h>
#include <stdio.h>

#include <sys/types.h>
#include <sys/socket.h>

#include <netinet/in.h>
#include <arpa/inet.h>

#include <netinet/in_systm.h>

#if defined(LINUX)
#include <linux/ip.h>
#include <linux/tcp.h>
#else
#include <netinet/ip.h>
#include <netinet/tcp.h>
#endif

#include <string.h>
#include <unistd.h>
#include <time.h>

#include <rawsock_utils.h>

int main(int argc,char *argv[])
{
  unsigned char packet[
#if !defined(LINUX)
  sizeof(struct ip) +
#else /* LINUX */
  sizeof(struct iphdr) +
#endif /* LINUX */
  sizeof(struct tcphdr)];
  struct sockaddr_in mysocket;
  unsigned short sport, dport;
  struct in_addr saddr, daddr;
  struct tcphdr *tcp;
  unsigned long seq, ack;
  int sockd, on = 1;
  
  if(argc < 5)  {
    fprintf(stderr,"usage: %s source_port source_address dest_port dest_address\n",
	    argv[0]);
    exit(1);
  }
  
  sport = (unsigned short)atoi(argv[1]);
  saddr.s_addr = inet_addr(argv[2]);
  
  dport = (unsigned short)atoi(argv[3]);
  daddr.s_addr = inet_addr(argv[4]);
  
  if((sockd = socket(AF_INET,SOCK_RAW,IPPROTO_RAW)) < 0)  {
    perror("socket");
    exit(1);
  }
  
  if(setsockopt(sockd,IPPROTO_IP,IP_HDRINCL,(char *)&on,sizeof(on)) < 0)  {
    perror("setsockopt");
    exit(1);
  }
  
  /* Very bad random sequence number generator */
  
  srand(getpid());
  
  seq = rand()%time(NULL);
  ack = rand()%time(NULL);
  
  ip_gen(packet,IPPROTO_TCP,saddr,daddr,sizeof(packet));
  
#if !defined(LINUX)

  tcp = (struct tcphdr *)(packet + sizeof(struct ip));

  tcp_gen((char *)tcp,sport,dport,seq,ack);

#if !defined(SOLARIS_CKSUM_BUG)
  tcp->th_sum = trans_check(IPPROTO_TCP,(char *)tcp,
			    sizeof(struct tcphdr),
			    saddr,
			    daddr);
  
#else /* SOLARIS_CKSUM_BUG */

  tcp->th_sum = sizeof(struct tcphdr);

#endif /* SOLARIS_CKSUM_BUG */

#else /* LINUX */
  
  tcp = (struct tcphdr *)(packet + sizeof(struct iphdr));

  tcp_gen((char *)tcp,sport,dport,seq,ack);
  
#if !defined(SOLARIS_CKSUM_BUG)
  tcp->check = trans_check(IPPROTO_TCP,(char *)tcp,
			   sizeof(struct tcphdr),
			   saddr,
			   daddr);
#else /* SOLARIS_CKSUM_BUG */

  tcp->check = sizeof(struct tcphdr);

#endif /* SOLARIS_CKSUM_BUG */

#endif /* LINUX */
  
  memset(&mysocket,'\0',sizeof(mysocket));
  
  mysocket.sin_family = AF_INET;
  mysocket.sin_port = htons(dport);
  mysocket.sin_addr = daddr;
  
  if(sendto(sockd,&packet,sizeof(packet),0x0,(struct sockaddr *)&mysocket,
	    sizeof(mysocket)) != sizeof(packet))  {
    perror("sendto");
    exit(1);
  }
  
  exit(0);
}