/*
 *   no time for sarcasm...  the kideez would take it seriously, anyway.
 * you don't need to supply a switch for an address type...  either the
 * full address or a netmask will work just fine.
 *
 * the only switches left are:
 *  x - address provided is in hexadecimal
 *  a - show hostname aliases also
 *  f - output to a file and background the process
 *
 *          max-q
 */

#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include "netdb.h"

#define S_HEX   "%x.%x.%x.%x"
#define S_DEC   "%d.%d.%d.%d"

void
bad_addr(addr)
  int   addr;
{
  fprintf(stderr, "Value %d is not valid.\n", addr);
  exit(-1);
}

void
check_addr(addr)
  int   addr[];
{
  register int  i;
  for(i=0;i<4;i++)
    if(addr[i]<0||addr[i]>255)
      bad_addr(addr[i]);
}

void
usage(name)
  int   *name;
{
  fprintf(stderr,
   "usage: %s [-x] [-a] [-f <outfile>] aaa.bbb.[ccc||0].[ddd||0]\n",
   name);
  exit(-1);
}


void
main(argc, argv)
  int   argc;
  char  *argv[];
{
  char                  addr[4], **ptr,
                        *progname = argv[0];
  register int          s;
  int                   a[4], arg, c, d,
                        classB, classC, single,
                        alias, hex, file;
  extern char           *optarg;
  struct hostent        *host,
                        *gethostbyaddr();
  FILE                  *outfd = stdout;

  classB = classC = single = alias = hex = file = 0;
  c = d = 0;

  while((arg = getopt(argc, argv, "xaf:")) != EOF) {
    switch(arg) {
    case 'x':
      hex++;
      break;
    case 'a':
      alias++;
      break;
    case 'f':
      file++;
      if((outfd=fopen(optarg, "a"))==NULL) {
        perror("open");
        exit(-1);
      }
      break;
    default:
      usage(progname);
    }
  }

  argv += ((file)?2:0)+((alias)?1:0)+((hex)?1:0);
  argc -= ((file)?2:0)+((alias)?1:0)+((hex)?1:0);

  if(argc!=2)
    usage(progname);

  sscanf(argv[1], (hex)?S_HEX:S_DEC, &a[0], &a[1], &a[2], &a[3]);

  check_addr(a);

  if(!a[3]) {
    if(!a[2])
      classB++;
    else
      classC++;
  } else
    single++;

  if(!classB && !classC && !single)
    usage(progname);

  if(file) {
    if((s=fork()) >0) {
      fprintf(stderr, "[%s - pid %d]\n", progname, s);
      exit(0);
    } else if(s<0) {
      perror("fork");
      exit(-1);
    }

    if((s=open("/dev/tty", O_RDWR)) >0) {
       ioctl(s, TIOCNOTTY, (char *) NULL);
       close(s);
    }
  }

  addr[0] = (unsigned char) a[0];
  addr[1] = (unsigned char) a[1];

  if(classC)
    goto jmpC;
  else if(single)
    goto jmpS;

  fprintf(((file)?outfd:stderr), "Scanning Class B network %d.%d...\n",
   a[0], a[1]);

  while(c<256) {
    a[2] = c++;
    d = 0;
jmpC:
    fprintf(((file)?outfd:stderr), "Scanning Class C network %d.%d.%d...\n",
     a[0], a[1], a[2]);

    while(d<256) {
      a[3] = d++;
jmpS:
      addr[2] = (unsigned char) a[2];
      addr[3] = (unsigned char) a[3];

      if((host = gethostbyaddr(addr, 4, AF_INET)) != NULL) {
        fprintf(outfd, "%d.%d.%d.%d => %s\n", a[0], a[1], a[2], a[3], host->h_name);

        ptr = host->h_aliases;
        if(alias)
          while(*ptr != NULL) {
            fprintf(outfd, "%d.%d.%d.%d => %s (alias)\n",
             a[0], a[1], a[2], a[3], *ptr);
            ptr++;
          }

        fflush(outfd);
        if(single) exit(0);
      } else if(single) {
        fprintf(stderr, "Cannot resolve %d.%d.%d.%d\n", a[0], a[1], a[2], a[3]);        exit(0);
      }
    }
    if(classC) exit(0);
  }
}