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#!/bin/sh
#
# firewall-masq This script sets up firewall rules for a machine
# acting as a masquerading gateway
#
# Copyright (C) 2000 Roaring Penguin Software Inc. This software may
# be distributed under the terms of the GNU General Public License, version
# 2 or any later version.
# Interface to Internet
EXTIF=ppp+
ANY=0.0.0.0/0
ipchains -P input ACCEPT
ipchains -P output ACCEPT
ipchains -P forward DENY
ipchains -F forward
ipchains -F input
ipchains -F output
# Deny TCP and UDP packets to privileged ports
ipchains -A input -l -i $EXTIF -d $ANY 0:1023 -p udp -j DENY
ipchains -A input -l -i $EXTIF -d $ANY 0:1023 -p tcp -j DENY
# Deny TCP connection attempts
ipchains -A input -l -i $EXTIF -p tcp -y -j DENY
# Deny ICMP echo-requests
ipchains -A input -l -i $EXTIF -s $ANY echo-request -p icmp -j DENY
# Do masquerading
ipchains -A forward -j MASQ
echo 1 > /proc/sys/net/ipv4/ip_forward
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