一个防火墙启动／停止脚本


#!/bin/bash
# An enhanced stateful firewall for a workstation, laptop or router that isn't
# running any network services like a web server, SMTP server, ftp server, etc.
#change this to the name of the interface that provides your "uplink"
#(connection to the Internet)
UPLINK="eth1"

#if you're a router (and thus should forward IP packets between interfaces),
#you want ROUTER="yes"; otherwise, ROUTER="no"
ROUTER="yes"
#change this next line to the static IP of your uplink interface for static SNAT, or
#"dynamic" if you have a dynamic IP. If you don't need any NAT, set NAT to "" to
#disable it.
NAT="1.2.3.4"
#change this next line so it lists all your network interfaces, including lo
INTERFACES="lo eth0 eth1"
if [ "$1" = "start" ]
then
echo "Starting firewall..."
iptables -P INPUT DROP
iptables -A INPUT -i ! ${UPLINK} -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p tcp -i ${UPLINK} -j REJECT --reject-with tcp-reset
iptables -A INPUT -p udp -i ${UPLINK} -j REJECT --reject-with icmp-port-unreachable
#explicitly disable ECN
if [ -e /proc/sys/net/ipv4/tcp_ecn ]
then
echo 0 > /proc/sys/net/ipv4/tcp_ecn
fi
#disable spoofing on all interfaces
for x in ${INTERFACES}
do
echo 1 > /proc/sys/net/ipv4/conf/${x}/rp_filter
done
if [ "$ROUTER" = "yes" ]
then
#we're a router of some kind, enable IP forwarding
echo 1 > /proc/sys/net/ipv4/ip_forward
if [ "$NAT" = "dynamic" ]
then
#dynamic IP address, use masquerading
echo "Enabling masquerading (dynamic ip)..."
iptables -t nat -A POSTROUTING -o ${UPLINK} -j MASQUERADE
elif [ "$NAT" != "" ]
then
#static IP, use SNAT
echo "Enabling SNAT (static ip)..."
iptables -t nat -A POSTROUTING -o ${UPLINK} -j SNAT --to ${UPIP}
fi
fi
elif [ "$1" = "stop" ]
then
echo "Stopping firewall..."
iptables -F INPUT
iptables -P INPUT ACCEPT
#turn off NAT/masquerading, if any
iptables -t nat -F POSTROUTING
fi