# Accept the packets we actually want to forward
#
$IPTABLES -A FORWARD -i $LAN_IFACE -j ACCEPT
$IPTABLES -A FORWARD -m state –state ESTABLISHED,RELATED -j ACCEPT
#
# Log weird packets that don't match the above.
#
$IPTABLES -A FORWARD -m limit –limit 3/minute –limit-burst 3 -j LOG \
–log-level DEBUG –log-prefix "IPT FORWARD packet died: "
#
# 4.1.6 OUTPUT chain
#
#
# Bad TCP packets we don't want.
#
$IPTABLES -A OUTPUT -p tcp -j bad_tcp_packets
#
# Special OUTPUT rules to decide which IP's to allow.
#
$IPTABLES -A OUTPUT -p ALL -s $LO_IP -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -s $LAN_IP -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -o $INET_IFACE -j ACCEPT
#
# Log weird packets that don't match the above.
#
$IPTABLES -A OUTPUT -m limit –limit 3/minute –limit-burst 3 -j LOG \
–log-level DEBUG –log-prefix "IPT OUTPUT packet died: "
######
# 4.2 nat table
#
#
# 4.2.1 Set policies
#
#
# 4.2.2 Create user specified chains
#
#
# 4.2.3 Create content in user specified chains
#
#
# 4.2.4 PREROUTING chain
#
#
# 4.2.5 POSTROUTING chain
#
if [ $PPPOE_PMTU == «yes» ] ; then
$IPTABLES -t nat -A POSTROUTING -p tcp –tcp-flags SYN,RST SYN \
–j TCPMSS –clamp-mss-to-pmtu
fi
$IPTABLES -t nat -A POSTROUTING -o $INET_IFACE -j MASQUERADE
#
# 4.2.6 OUTPUT chain
#
######
# 4.3 mangle table
#
#
# 4.3.1 Set policies
#
#
# 4.3.2 Create user specified chains
#
#
# 4.3.3 Create content in user specified chains
#
#
# 4.3.4 PREROUTING chain
#
#
# 4.3.5 INPUT chain
#
#
# 4.3.6 FORWARD chain
#
#
# 4.3.7 OUTPUT chain
#
#
# 4.3.8 POSTROUTING chain
#
I.5. Пример rc.flush-iptables
#!/bin/sh
#
# rc.flush-iptables – Resets iptables to default values.
#
# Copyright (C) 2001 Oskar Andreasson
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program or from the site that you downloaded it
# from; if not, write to the Free Software Foundation, Inc., 59 Temple
# Place, Suite 330, Boston, MA 02111-1307 USA
#
# Configurations
#
IPTABLES="/usr/sbin/iptables"
#
# reset the default policies in the filter table.
#
$IPTABLES -P INPUT ACCEPT
$IPTABLES -P FORWARD ACCEPT
$IPTABLES -P OUTPUT ACCEPT
#
# reset the default policies in the nat table.
#
$IPTABLES -t nat -P PREROUTING ACCEPT
$IPTABLES -t nat -P POSTROUTING ACCEPT
$IPTABLES -t nat -P OUTPUT ACCEPT
#
# reset the default policies in the mangle table.
#
$IPTABLES -t mangle -P PREROUTING ACCEPT
$IPTABLES -t mangle -P OUTPUT ACCEPT
#
# flush all the rules in the filter and nat tables.
#
$IPTABLES -F
$IPTABLES -t nat -F
$IPTABLES -t mangle -F
#
# erase all chains that's not default in filter and nat table.
#
$IPTABLES -X
$IPTABLES -t nat -X
$IPTABLES -t mangle -X
I.6. Пример rc.test-iptables
#!/bin/bash
#
# rc.test-iptables – test script for iptables chains and tables.
#
# Copyright (C) 2001 Oskar Andreasson
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program or from the site that you downloaded it
# from; if not, write to the Free Software Foundation, Inc., 59 Temple
# Place, Suite 330, Boston, MA 02111-1307 USA
#
#
# Filter table, all chains
#
iptables -t filter -A INPUT -p icmp –icmp-type echo-request \
–j LOG –log-prefix="filter INPUT:"
iptables -t filter -A INPUT -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="filter INPUT:"
iptables -t filter -A OUTPUT -p icmp –icmp-type echo-request \
–j LOG –log-prefix="filter OUTPUT:"
iptables -t filter -A OUTPUT -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="filter OUTPUT:"
iptables -t filter -A FORWARD -p icmp –icmp-type echo-request \
–j LOG –log-prefix="filter FORWARD:"
iptables -t filter -A FORWARD -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="filter FORWARD:"
#
# NAT table, all chains except OUTPUT which don't work.
#
iptables -t nat -A PREROUTING -p icmp –icmp-type echo-request \
–j LOG –log-prefix="nat PREROUTING:"
iptables -t nat -A PREROUTING -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="nat PREROUTING:"
iptables -t nat -A POSTROUTING -p icmp –icmp-type echo-request \
–j LOG –log-prefix="nat POSTROUTING:"
iptables -t nat -A POSTROUTING -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="nat POSTROUTING:"
iptables -t nat -A OUTPUT -p icmp –icmp-type echo-request \
–j LOG –log-prefix="nat OUTPUT:"
iptables -t nat -A OUTPUT -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="nat OUTPUT:"
#
# Mangle table, all chains
#
iptables -t mangle -A PREROUTING -p icmp –icmp-type echo-request \
–j LOG –log-prefix="mangle PREROUTING:"
iptables -t mangle -A PREROUTING -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="mangle PREROUTING:"
iptables -t mangle -I FORWARD 1 -p icmp –icmp-type echo-request \
–j LOG –log-prefix="mangle FORWARD:"
iptables -t mangle -I FORWARD 1 -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="mangle FORWARD:"
iptables -t mangle -I INPUT 1 -p icmp –icmp-type echo-request \
–j LOG –log-prefix="mangle INPUT:"
iptables -t mangle -I INPUT 1 -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="mangle INPUT:"
iptables -t mangle -A OUTPUT -p icmp –icmp-type echo-request \
–j LOG –log-prefix="mangle OUTPUT:"
iptables -t mangle -A OUTPUT -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="mangle OUTPUT:"
iptables -t mangle -I POSTROUTING 1 -p icmp –icmp-type echo-request \
–j LOG –log-prefix="mangle POSTROUTING:"
iptables -t mangle -I POSTROUTING 1 -p icmp –icmp-type echo-reply \
–j LOG –log-prefix="mangle POSTROUTING:"