#! /usr/bin/perl -Tw

use strict;
use vars qw/ $opt_b $opt_n $opt_q $opt_r $opt_s $opt_t /;
use constant TIMEOUT => 1;

use Getopt::Std;
use Socket;
use Net::Ping;

getopts( 'bnrqst:' );

$opt_r   = 1 if $opt_n or $opt_s;
$opt_q   = 1 if $opt_b;
$opt_t ||= TIMEOUT;

die "This script must be installed setuid root.\n" unless $> == 0;

my $first_taint = shift or die "No first IP address given (e.g. 172.17
+.1.1)\n";
my $last_taint  = shift or die "No last IP address given (e.g. 127)\n"
+;

my ($net,$first) = ($first_taint   =~ /^(\d{1,3}\.\d{1,3}\.\d{1,3})\.(
+\d{1,3})$/ );
die "Couldn't determine the network part in $first_taint.\n" unless $n
+et;
die "Couldn't determine the host part in $first_taint.\n" unless $firs
+t;

my ($last) = ($last_taint =~ /^(\d{1,3})$/ );
die "Couldn't determine the host part in $last_taint.\n" unless $last;

($last, $first) = ($first, $last) if $last < $first;

my $p = Net::Ping->new( 'icmp' );
foreach my $host ( $first..$last )
{
    my $ip = "$net.$host";
    my $hostname = do {
        if( $opt_r and my $resolve = gethostbyaddr( inet_aton($ip), AF
+_INET )) {
            $resolve =~ s/\..*$// if $opt_s;
            $resolve .= " ($ip)" if $opt_n;
            $resolve;
        }
        else {
            $ip;
        }
    };

    if( $p->ping($ip, $opt_t) ) {
        print $hostname;
        print ' is reachable.' unless $opt_b;
        print "\n";
    }
    elsif( ! $opt_q ) {
        print "$hostname is NOT reachable.\n";
    }
}
$p->close();

=head1 NAME

pinger - ping a range of hosts

=head1 SYNOPSIS

B<pinger> [B<-bnqrs>] [B<-t> timeout] host last

=head1 DESCRIPTION

Ping a range of hosts using ICMP.

=head1 OPTIONS

=over 5

=item B<-b>

Brief. Do not print the "is reachable/is NOT reachable" text.
Probably needs B<-q> as well to be of any use to a program downstream.

=item B<-n>

Numeric. Print the numeric IP address as well as the resolved host nam
+e. (Sets B<-r>).

=item B<-q>

Quiet. Only report hosts that are pinged successfully.

=item B<-r>

Resolve. Resolve the numeric address to a FQDN host (implies -q unless
+ -n).

=item B<-s>

Short. Like B<-r>, but resolves the numeric address to a simple host n
+ame (stopping at the first dot).

=item B<-t timeout>

Timeout. Set the time out to t seconds (defaults to 1). A low timeout 
+value is used as this
script is destined to be used on internal networks where it is normal 
+to have sub-second
response times. The value may be easily edited in the source to a high
+er value if required.

=back

=head1 EXAMPLES

C<pinger 192.168.0.1 10>

Pings the machines from 192.168.0.1 to 192.168.0.10. Sample output loo
+ks like:

    192.168.0.1 is reachable.
    192.168.0.2 is NOT reachable.
    192.168.0.3 is reachable.
    192.168.0.4 is reachable.
    192.168.0.5 is NOT reachable.
    192.168.0.6 is reachable.
    192.168.0.7 is NOT reachable.
    192.168.0.8 is reachable.
    192.168.0.9 is reachable.
    192.168.0.10 is reachable.

C<pinger -r 192.168.0.1 6>

Pings the machines from 192.168.0.1 to 192.168.0.6 and resolves the ho
+stnames. In the following
example no A record for 192.168.0.3 exists, so the numeric IP address 
+is used instead.

    profane.example.com is reachable.
    slothrop.example.com is NOT reachable.
    192.168.0.3 is reachable.
    godolphin.example.com is reachable.
    stencil.example.com is NOT reachable.
    porpentine.example.com is reachable.

C<pinger -n 192.168.0.1 6>

Like the above, but also includes the numeric IP address alongside the
+ resolved host name.

    profane.example.com (192.168.0.1) is reachable.
    slothrop.example.com (192.168.0.2) is NOT reachable.
    192.168.0.3 is reachable.
    godolphin.example.com (192.168.0.4) is reachable.
    stencil.example.com (192.168.0.5) is NOT reachable.
    porpentine.example.com (192.168.0.6) is reachable.

C<pinger -sq 192.168.0.1 6>

This time, only display the local hostnames without the domain, and on
+ly report hosts that are pinged
successfully.

    profane is reachable.
    192.168.0.3 is reachable.
    godolphin is reachable.
    porpentine is reachable.

C<pinger -bq 192.168.0.1 6>

Report the IP addresses of all hosts that are pinged successfully.

    192.168.0.1
    192.168.0.3
    192.168.0.4
    192.168.0.6

=head1 BUGS

Due to the way Net::Ping works, and TCP/IP in general, this script
must be installed setuid root. In light of this constraint, the
script runs in tainted mode. To install the script, run the following
command:

C<chmod 4555 pinger>

The way the behaviour is controlled by the command-line switches is
unnecessarily obfuscated and should be cleaned up. This is a by-produc
+t
of the script's evolution. By and large, however, they tend to do
The Right Thing.

=head1 SEE ALSO

L<Net::Ping>

=head1 COPYRIGHT

Copyright 1999-2001 David Landgren.

This script is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

=head1 AUTHOR

     David "grinder" Landgren
     eval {join chr(64) => qw[landgren bpinet.com]}

=cut
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