/* Generate a TCP packet * with 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);}