in reply to Re^8: scandns.pl
in thread scandns.pl

Greetings again. :)

In answer to your question; yes. I did. But without success.

Frankly. I find this whole thing quite an enticing puzzle.
OH. Indeed. It really is a POS (excuse my language). But here we are, you insist that my logic is flawed, and you explain why. I attempt your solution, and find it doesn't work.
I examine the code, and come to a different solution, and explain why. I try it, and it works.

Don't you find this a bit of an intriguing puzzle?

Sure. The code seems hardly worth it. But just from a purely analytical perspective. I think it's interesting. I'd love to find a conclusive resolution.

Best wishes.

--Chris

#!/usr/bin/perl -Tw
use Perl::Always or die;
my $perl_version = (5.12.5);
print $perl_version;

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Re^10: scandns.pl
by jdporter (Paladin) on Nov 15, 2013 at 20:12 UTC

    I don't find it all that intriguing. I made exactly one change to the OP's code — s/my $x;/my $x=0;/ — and the warning went away.

    You say you got different results, but I have zero confidence that you haven't mucked with the code in other ways, so I'm not inclined to think that my fix doesn't and wouldn't work for you.

    Maybe you should post your version of the code so I can try it.

[reply]
[d/l]

      OK. Sounds good. Here ya go: 

      #!/usr/bin/perl -w
#
# File:           scandns.pl
# Summary:        dns cleanup tool
#
# Author:         Jon Schatz
# E-Mail:         jon@divisionbyzero.com
# Org:
#
# Orig-Date:      22-Mar-00 at 13:30:53
# Last-Mod:       19-Jun-00 at 16:24:42 by
#
#    This program is free software; you can redistribute it and/or mod
+ify it
#    under the terms of the GNU General Public License as published
#    by the Free Software Foundation; either version 1, or (at your op
+tion)
#    any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See either
#    the GNU General Public License or the Artistic License for more d
+etails.
#
#
# $Source: /home/jschatz/.cvs/el/file-hdr/hdr.perl,v $
# $Date: 1999/12/23 00:06:23 $
# $Revision: 1.1.1.1 $
# $Author: tkunze $
# $State: Exp $
# $Locker:  $
#
# -*- EOF -*-

use IO::Socket;
use Net::Netmask;
use strict;

my ($network)=@ARGV;

#separate the netmask from the network

my ($ip_address,$netmask) = split /[\/||:]/ , $network;
my $address;

&usage unless ($ip_address); #complain if @ARGV was incorrect
&badip unless (&validip($ip_address)); #copmlain if $ip_address is inv
+alid

#complain if $netmask is bad. unfortunately Net::Netmask only warns if
+ it's
#given an invalid netmask. I'm working on a patch so that the module w
+ill
#be smart enough to return something useful when it cant parse the net
+mask.

&badnet unless (&validnet($netmask));

#if the netmask is given as a netmask (ie, 255.255.255.0 as opposed to
+ CIDR
# notation (/24)), then ditch the "/" since Net::Netmask isn't smart e
+nough
# to do that either.

$network=~s/\//:/ if (validip($netmask));

#create the netmask object

(my $obj=Net::Netmask->new ($network)) or die "Invalid address / netma
+sk\n";

#return an array of all addresses in the given network

my (@addresses)=$obj->enumerate();


foreach $address (@addresses) {
  &checkdns($address);
}

#the good stuff

sub checkdns {
  my ($ip_address)=@_;
  my ($packed_ip_address)=&get_packed_ip($ip_address);
  my ($hostname)=gethostbyaddr($packed_ip_address, AF_INET);

  if (! $hostname) {
    &no_ptr("$ip_address");
    return;
  }

  my $reverse_packed_ip_address;
  $reverse_packed_ip_address=gethostbyname($hostname);

  if (length($reverse_packed_ip_address)!=4) {
    &no_a("$ip_address","$hostname");
    return;
  }

  my ($reverse_ip_address)=inet_ntoa($reverse_packed_ip_address);

  if ($reverse_ip_address ne $ip_address) {
    print("$ip_address => $hostname => $reverse_ip_address \n");
  }

  else {
    print("$ip_address => $hostname \n");
  }
}

sub no_ptr {
  my ($ip_address)=@_;
  print "$ip_address => no PTR record\n";

  return;
}

sub no_a {
  my ($ip_address, $hostname)=@_;
  print "$ip_address => $hostname => $hostname has no A record\n";
  return;
}

sub badip {
  print "$ip_address is an invalid address.\n";
  exit 1;
}

sub badnet {
  print "/$netmask is an invalid netmask.\n";
  exit 1;
}

sub usage {
  print "Usage: scandns.pl <address>[/netmask]\n";
  exit 1;
}

sub validnet {
  my ($netmask)=@_;
  return(1) if (validip($netmask)) ;
  return(1) if (($netmask>=0)&&($netmask<=32));
}

#this is an ip checker that seems simpler to me than the enormous rege
+x in
#the cookbook. since it's only executed twice, it's probably not gener
+ating
#that much overhead.

sub validip {
  my ($ip)=@_;
  my $x;
  foreach ($ip=~/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/){
    $x++ if(($_>=0)&&($_<=255));
  }
  return($x);
}

sub get_packed_ip {

  my ($ip)=@_;
  chomp $ip;
  my $a;
  my $b;
  my $c;
  my $d;
  ($a, $b, $c, $d)=split(/\./,$ip);
  my $packed_ip=pack "C4","$a","$b","$c","$d";
  return $packed_ip;
}

sub bin2dec {
  my $str= unpack("B8", pack("N", shift));
  $str=~s/^0+(?=\d)//;
  return $str;
}

sub dec2bin {
  return unpack("N",pack("B8", substr("0"x 8, -8)));
}

      [download]
      Please let me know your results.

      --Chris

      #!/usr/bin/perl -Tw
use Perl::Always or die;
my $perl_version = (5.12.5);
print $perl_version;
[reply]
[d/l]

        Well, I don't know what to tell you, man. I took your code and re-fixed it by doing both

        • s/ my $x; / my $x=0; /
        • s/ return($x); / return($x==4); /
        and now it works correctly, in that it reports both:
        • 209.197.123.153/29 is valid
        • 209.197.123.666/29 is invalid
        Same results as the code I was using before.

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