Pearlwall

use strict;

package Pearlwall;
use base 'Exporter';
our @EXPORT = qw(iface port net mode oneof from to filter mangle nat raw flush with by user group marked list forwarding chain record on off);

my $_table = '';
my $_dry_run = 0;

BEGIN {

    no strict 'refs';

    sub apply($)
    {
        my $command = "iptables -t $Pearlwall::_table $_[0]";
        if ($Pearlwall::_dry_run)
        {
            print "$command\\n";
        }
        else
        {
            system $command;
        }
    }

    sub list
    {
        print "Table $Pearlwall::_table:\\n";
        apply "-v -L " . ($_[0]||'');
        print "\\n";
    }

    sub parse_opts
    {
        my ($opts, $pfx) = @_;
        $pfx ||= '';
        return join(" ", map { my ($a, $b) = ($pfx.$_, $opts->{$_}); $a =~ s/_/-/g; "--$a " . ($b == 1? '': $b) } keys %{$opts});
    }

    my %bare_actions = qw(deny DROP allow ACCEPT mask MASQUERADE);
    my %opts_actions = qw(forbid REJECT mark MARK throw REDIRECT pass SNAT);
    while (my ($name, $action) = each(%bare_actions))
    {
        *{"main::$name"} = sub { apply "$_[0] $action"; return $_[0]; };
    }
    while (my ($name, $action) = each(%opts_actions))
    {
        *{"main::$name"} = sub { my $a = pop; apply "$a $action " . parse_opts({@_}) ; return $a; };
    }
    sub record
    {
        my $filter = pop;
        my $opts = parse_opts({@_}, 'log-');
        apply "$filter LOG $opts";
        return $filter;
    }

    my %chain_names = qw(input INPUT output OUTPUT forward FORWARD before_route PREROUTING after_route POSTROUTING);
    while (my ($name, $chain) = each(%chain_names))
    {
        *{"main::$name"} = sub { return @_? " -A $chain ".join(" ", @_)." -j ": " -P $chain "; };
    }
    sub chain($;$)
    {
        my $chainname = shift;
        if (@_) {
            if ($_[0]) {
                apply "-E $chainname $_[0]";
            } else {
                apply "-X $chainname";
            }
        } else {
            apply "-N $chainname";
            bless sub { return @_? " -A $chainname ".join(" ", @_)." -j ": " -P $chainname "; }, $chainname;
        }
    }

    foreach my $proto (qw(tcp udp udplite icmp esp ah sctp all))
    {
        *{"main::$proto"} = sub { return Pearlwall::Inversible->new(" -p $proto "), @_; };
    }

    sub by($)
    {
        return " --reject-with $_[0] ";
    }
    sub with($)
    {
        return Pearlwall::MarkMask->new($_[0]);
    }

    sub flush(;$)
    {
        apply " -F " . ($_[0]||'');
    }

    sub iface($)
    {
        return Pearlwall::Iface->new($_[0]);
    }
    sub mode($)
    {
        my $mode = uc(shift);
        return Pearlwall::Inversible->new(" --state $mode ", " -m state ");
    }
    sub port($)
    {
        return Pearlwall::Port->new($_[0]);
    }
    sub net($)
    {
        return Pearlwall::Network->new($_[0]);
    }
    sub user($)
    {
        return Pearlwall::Inversible->new(" --uid-owner $_[0] ", " -m owner ");
    }
    sub group($)
    {
        return Pearlwall::Inversible->new(" --gid-owner $_[0] ", " -m owner ");
    }
    sub marked($)
    {
        return Pearlwall::Inversible->new(" --mark $_[0] ", " -m mark ");
    }

    sub oneof(@)
    {
        return join(',', @_);
    }

    sub from(@)
    {
        return join " ", map { UNIVERSAL::isa($_, 'Pearlwall::Object')? $_->from(): $_ } @_;
    }
    sub to(@)
    {
        return join " ", map { UNIVERSAL::isa($_, 'Pearlwall::Object')? $_->to(): $_ } @_;
    }

    sub filter(&)
    {
        local $Pearlwall::_table = 'filter';
        $_[0]->();
    }
    sub mangle(&)
    {
        local $Pearlwall::_table = 'mangle';
        $_[0]->();
    }
    sub nat(&)
    {
        local $Pearlwall::_table = 'nat';
        $_[0]->();
    }
    sub raw(&)
    {
        local $Pearlwall::_table = 'raw';
        $_[0]->();
    }

    sub forwarding($)
    {
        open my $fh, ">", "/proc/sys/net/ipv4/ip_forward";
        print $fh 0+(!!$_[0]);
        close $fh;
    }

    sub on()
    {
        return 1;
    }
    sub off()
    {
        return 0;
    }
}

1;

package Pearlwall::Inversible;

use overload
    '!' => sub {
        $_[0]->[1] = !$_[0]->[1];
        return $_[0];
    },
    '""' => sub {
        return $_[0]->[2] . ($_[0]->[1]? '!': '') . $_[0]->[0];
    };

sub new
{
    my $class = shift;
    my $self = [ shift, 0, shift||'' ];
    bless $self, $class;
}

1;

package Pearlwall::Object;
use base 'Pearlwall::Inversible';

sub from
{
    return $_[0]->[2] . ($_[0]->[1]? '!': '') . $_[0]->_from();
}

sub to
{
    return $_[0]->[2] . ($_[0]->[1]? '!': '') . $_[0]->_to();
}

1;

package Pearlwall::Iface;
use base 'Pearlwall::Object';

sub _from
{
    return " -i $_[0]->[0] ";
}

sub _to
{
    return " -o $_[0]->[0] ";
}

1;

package Pearlwall::Port;
use base 'Pearlwall::Object';

sub _from
{
    return " --sport $_[0]->[0] ";
}

sub _to
{
    return " --dport $_[0]->[0] ";
}

1;

package Pearlwall::Network;
use base 'Pearlwall::Object';

sub _from
{
    return " -s $_[0]->[0] ";
}

sub _to
{
    return " -d  $_[0]->[0] ";
}

1;

package Pearlwall::MarkMask;

use overload '""' => sub {
        return "$_[0]->[1] $_[0]->[0]$_[0]->[2]";
    },
    '/' => sub {
        $_[0]->[2] = "/$_[1]";
        return $_[0];
    },
    '|' => sub {
        $_[0]->[1] = 'set-mark';
        $_[0]->[2] = "/$_[1]";
        return $_[0];
    },
    '^' => sub {
        $_[0]->[1] = 'set-xmark';
        $_[0]->[2] = "/$_[1]";
        return $_[0];
    },
    '~' => sub {
        $_[0]->[1] = 'set-xmark';
        $_[0]->[2] = "";
        return $_[0];
    },
    '&' => sub {
        $_[0]->[0] = $_[1];
        $_[0]->[1] = 'and-mark';
        $_[0]->[2] = "";
        return $_[0];
    };

sub new
{
    my $class = shift;
    my $self = [ shift, 'set-mark', '' ];
    bless $self, $class;
}

1;