/* RAW socket utility routine: *  * Write out a TCP header. * shadows@whitefang.com * Thamer Al-Herbish */#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/tcp.h>#else#include <netinet/tcp.h>#endif#include <unistd.h>#include <string.h>#if defined(X2_OFF)         /* SCO */#define TH_OFFSET 0x50         /* TCP header offset */#else#define TH_OFFSET 5#endif#define TCP_WINDOW_SIZE 512 /* Just have it hardcoded. */void tcp_gen(char *packet,unsigned short sport,	     unsigned short dport,unsigned long seq,	     unsigned long ack){  struct tcphdr *tcp;    tcp = (struct tcphdr *)packet;  memset((char *)tcp,'\0',sizeof(struct tcphdr));#if !defined(LINUX)  tcp->th_sport = htons(sport);  tcp->th_dport = htons(dport);    tcp->th_seq = htonl(seq);  tcp->th_ack = htonl(ack);  #ifdef X2_OFF  tcp->th_x2_off = TH_OFFSET;#else /* X2_OFF */  tcp->th_off = TH_OFFSET;  tcp->th_x2 = 0;#endif /* X2_OFF */  tcp->th_win = htons(TCP_WINDOW_SIZE);  tcp->th_flags = TH_FIN;  #else /* LINUX */  tcp->source = htons(sport);  tcp->dest = htons(dport);    tcp->seq = htonl(seq);  tcp->ack_seq = htonl(ack);    tcp->res1 = 0;  tcp->doff = TH_OFFSET;  tcp->window = htons(TCP_WINDOW_SIZE);  tcp->fin = 1;#endif /* LINUX */  return;}