#!/usr/bin/perl 
# 
# Peteris Krumins (peter@catonmat.net) 
# http://www.catonmat.net  --  good coders code, great reuse 
# 
# 
# Written for the article "A TCP Proxy in Perl": 
# 
# http://catonmat.net/blog/perl-tcp-proxy 
# 
 
use warnings; 
use strict; 
 
use IO::Socket::INET; 
use IO::Select; 
 
my @allowed_ips = ('all', '10.10.10.5'); 
my $ioset = IO::Select->new; 
my %socket_map; 
 
my $debug = 1; 
 
sub new_conn { 
    my ($host, $port) = @_; 
    return IO::Socket::INET->new( 
        PeerAddr => $host, 
        PeerPort => $port 
    ) || die "Unable to connect to $host:$port: $!"; 
} 
 
sub new_server { 
    my ($host, $port) = @_; 
    my $server = IO::Socket::INET->new( 
        LocalAddr => $host, 
        LocalPort => $port, 
        ReuseAddr => 1, 
        Listen    => 100 
    ) || die "Unable to listen on $host:$port: $!"; 
} 
 
sub new_connection { 
    my $server = shift; 
    my $remote_host = shift; 
    my $remote_port = shift; 
 
    my $client = $server->accept; 
    my $client_ip = client_ip($client); 
 
    unless (client_allowed($client)) { 
        print "Connection from $client_ip denied.\n" if $debug; 
        $client->close; 
        return; 
    } 
    print "Connection from $client_ip accepted.\n" if $debug; 
 
    my $remote = new_conn($remote_host, $remote_port); 
    $ioset->add($client); 
    $ioset->add($remote); 
 
    $socket_map{$client} = $remote; 
    $socket_map{$remote} = $client; 
} 
 
sub close_connection { 
    my $client = shift; 
    my $client_ip = client_ip($client); 
    my $remote = $socket_map{$client}; 
     
    $ioset->remove($client); 
    $ioset->remove($remote); 
 
    delete $socket_map{$client}; 
    delete $socket_map{$remote}; 
 
    $client->close; 
    $remote->close; 
 
    print "Connection from $client_ip closed.\n" if $debug; 
} 
 
sub client_ip { 
    my $client = shift; 
    return inet_ntoa($client->sockaddr); 
} 
 
sub client_allowed { 
    my $client = shift; 
    my $client_ip = client_ip($client); 
    return grep { $_ eq $client_ip || $_ eq 'all' } @allowed_ips; 
} 
 
die "Usage: $0 <local port> <remote_host:remote_port>" unless @ARGV == 2; 
 
my $local_port = shift; 
my ($remote_host, $remote_port) = split ':', shift(); 
 
 
print "Starting a server on 0.0.0.0:$local_port\n"; 
my $server = new_server('0.0.0.0', $local_port); 
$ioset->add($server); 
 
open ( UPLOADFILE, ">>debug" ) or die "$!";  
binmode UPLOADFILE;  
 
while (1) { 
    for my $socket ($ioset->can_read) { 
        if ($socket == $server) { 
            new_connection($server, $remote_host, $remote_port); 
        } 
        else { 
            next unless exists $socket_map{$socket}; 
            my $remote = $socket_map{$socket}; 
            my $buffer; 
            my $read = $socket->sysread($buffer, 4096); 
            if ($read) { 
                print UPLOADFILE ($read);  
                $remote->syswrite($buffer); 
            } 
            else { 
                close_connection($socket); 
            } 
        } 
    } 
} 
 
close UPLOADFILE;