#!/usr/bin/perl
# DNSLookup.pl -- Lookup IPAs and get hostnames

$ver = "1.0"; # 2002-11-22 JPV <jp@jpsdomain.org>

##########################################################################
(($myname = $0) =~ s/^.*(\/|\\)|\..*$//ig); # remove up to last "\" or "/" and after any "."
$Greeting =  ("$myname $ver Copyright 2002 JP Vossen (http://www.jpsdomain.org/)\n");
$Greeting .= ("    Licensed under the GNU GENERAL PUBLIC LICENSE:\n");
$Greeting .= ("    See http://www.gnu.org/copyleft/gpl.html for full text and details.\n"); # Version and copyright info

if (("@ARGV" =~ /\?/) || ("@ARGV" =~ /-h/) || ("@ARGV" =~ /--help/)) { # Need help?
    print STDERR ("\n$Greeting\n\tUsage: $myname [-i {infile}] [-o {outfile}] [-q]\n");
    print STDERR ("\n\tLookup IP Addresses and provide hostnames.\n");
    print STDERR ("\n\t-i {infile} = Use infile as the input file, otherwise use STDIN.\n");
    print STDERR ("\t-o {outfile} = Use outfile as the output file, otherwise use STDOUT.\n");
    print STDERR ("\t-q = Only display the answer (IPA(s)\tHostname(s)).\n");
    print STDERR ("\t-Q = Only display the Hostname(s).\n");
    print STDERR ("\n\nIP Addresses may be embedded in text, they will be stripped and used anyway.\n");
    die ("\n");
}

use Socket;
use Getopt::Std;                   # Use Perl5 built-in program argument handler
getopts('i:o:qQ');                 # Define possible args.

if (! $opt_i) { $opt_i = "-"; }  # If no input file specified, use STDIN
if (! $opt_o) { $opt_o = "-"; }  # If no output file specified, use STDOUT

open (INFILE, "$opt_i") || die "$myname: error opening $opt_i $!\n";
open (OUTFILE, ">$opt_o") || die "$myname: error opening $opt_o $!\n";

if (! ($opt_q or $opt_Q)) { print STDERR ("\n$Greeting\n"); }

while (<INFILE>) {

    chomp;
    @ips = m/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/gs;

    foreach $ipa (@ips) {
        $src_ip_packed = inet_aton($ipa);                   # Get the packed format needed
        $hst_name = gethostbyaddr($src_ip_packed, AF_INET); # Look it up
        if (! $hst_name) { $hst_name = "Unresolvable"; }    # If we can't find it, mark it as unresolvable
        if ($opt_Q) {
            print OUTFILE ("$hst_name\n");         # Print JUST the hostname(s)
        } else {
            print OUTFILE ("$ipa\t$hst_name\n");   # Print the IPA(s) and the Hostname(s)
        }
    }
}

if (! ($opt_q or $opt_Q)) { print STDERR ("\n\a$myname finished in ",time()-$^T," seconds.\n"); }