/* 
MassResolve (C) 2000 John Anderson (john@ev6.net)
This program performs reverse dns lookups for network blocks
or an input file and supports multi threading.

*/

#include <stdio.h>
#include <fcntl.h>
#include <netdb.h>
#include <signal.h>
#include <sys/time.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <setjmp.h>

char *
rlookup (u_long ip)
{
  static char hostname[256];
  struct hostent *host;
  struct sockaddr_in addr;

  addr.sin_addr.s_addr = ip;

  host =
    gethostbyaddr ((char *) &addr.sin_addr, sizeof (addr.sin_addr), AF_INET);

  if (host == NULL)
    {
      printf ("%s does not resolve.\n", inet_ntoa (ip));
      fflush (stdout);
    }
  else
    {
      printf ("%s resolves to %s\n", inet_ntoa (ip), host->h_name);
      fflush (stdout);
    }
}

int maxforq = 0;

int
main (int argc, char **argv)
{
  int pid, k, j, frk, i, mforks;
  char *pt;
  char mehost[200], sv[3];
  FILE *inp;

  mforks = 64;			/* default */
  if (argv[1] == NULL)
    {
      printf ("Usage: %s <subnet or filename to resolve> <forks>\n", argv[0]);
      exit (0);
    }
  if (!argv[2] == NULL)
    {
      mforks = atoi (argv[2]);
    }
/*  printf ("Resolving all hosts in %s with %d threads\n", argv[1], mforks); */
  if((inp=fopen(argv[1],"r"))!=NULL)
  {
      while(fgets(mehost,sizeof(mehost),inp))
      {
          sscanf(mehost,"%s\n",mehost);
                  frk = fork ();
                  if (frk == 0)
                    {
                      fflush (stdout);
                      rlookup (inet_addr (mehost));
                      exit (0);
                    }
                  else
                    {           /* frk = 0 */
                      maxforq++;
                      if (maxforq > mforks)
                        {
                          wait (NULL);  // waiting until the child died
                          maxforq--;
                        }

                    }

      }
      fclose(inp);
      exit(0);
  }

  pt = strchr (argv[1], '.');
  if (pt == NULL)
    {				/* ANET */
      for (k = 0; k <= 255; k++)
	{
	  for (j = 0; j <= 255; j++)
	    {
	      for (i = 1; i <= 255; i++)
		{

		  frk = fork ();
		  if (frk == 0)
		    {
		      snprintf (mehost, sizeof (mehost), "%s.%u.%u.%u",
				argv[1], k, j, i);
		      fflush (stdout);
		      rlookup (inet_addr (mehost));
		      exit (0);
		    }
		  else
		    {		/* frk = 0 */
		      maxforq++;
		      if (maxforq > mforks)
			{
			  wait (NULL);	// waiting until the child died
			  maxforq--;
			}

		    }
		}
	    }
	}
      fprintf (stderr, "%u ", j);
    }
  else
    {
      pt++;
      pt = strchr (pt, '.');
      if (pt == NULL)
	{			/* BNET */
	  for (j = 0; j <= 255; j++)
	    {
	      for (i = 1; i <= 255; i++)
		{

		  frk = fork ();
		  if (frk == 0)
		    {
		      snprintf (mehost, sizeof (mehost), "%s.%u.%u",
				argv[1], j, i);
		      fflush (stdout);
		      rlookup (inet_addr (mehost));
		      exit (0);
		    }
		  else
		    {
		      maxforq++;
		      if (maxforq > mforks)
			{
			  wait (NULL);	// waiting until the child died
			  maxforq--;
			}

		    }
		}
	    }
	  fprintf (stderr, "%u ", j);
	}
      else
	{			/* CNET */
	  pt++;
	  pt = strchr (pt, '.');
	  if (pt != NULL)	/* Single host? */
	    {
	      rlookup (inet_addr (argv[1]));
	    }
	  else
	    {
	      for (i = 1; i <= 255; i++)
		{
		  frk = fork ();
		  if (frk == 0)
		    {
		      snprintf (mehost, sizeof (mehost), "%s.%u", argv[1], i);
		      fflush (stdout);
		      rlookup (inet_addr (mehost));
		      exit (0);
		    }
		  else
		    {
		      maxforq++;
		      if (maxforq > mforks)
			{
			  wait (NULL);	// waiting until the child died
			  maxforq--;
			}

		    }
		}
	      fprintf (stderr, "!! %u !!", k);
	    }
	}
    }
}