Strong Firewall in a Routed Xen Dom0
Tom
Eastep
2006
Thomas M. Eastep
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation; with
no Invariant Sections, with no Front-Cover, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
GNU Free Documentation
License
.
This article applies to Shorewall 3.0 and later. If you are running
a version of Shorewall earlier than Shorewall 3.0.0 then please see the
documentation for that release.
Before Xen
Prior to adopting Xen, I had a home
office crowded with 5 systems, three monitors a scanner and a printer. The
systems were:
Firewall
Public Server in a DMZ (mail)
Private Server (wookie)
My personal Linux Desktop (ursa)
My work system (docked laptop running Windows XP).
The result was a very crowded and noisy room.
After Xen
Xen has allowed me to reduce the noise and clutter considerably. I
now have three systems with two monitors. I've also replaced the
individual printer and scanner with a Multifunction
FAX/Scanner/Printer.
The systems now include:
Combination Firewall/Public Server/Private Server/Wireless
Gateway using Xen (created by building out my Linux desktop
system).
My work system.
My Linux desktop (wookie, which is actually the old public
server box)
Most of the Linux systems run SuSE 10.1; my
personal Linux desktop system and our Linux Laptop run
Ubuntu "Dapper Drake".
Here is a high-level diagram of our network.
![]()
As shown in this diagram, the Xen system has three physical network
interfaces. These are:
eth0 -- connected to our
DSL "Modem".
eth1 -- connected to the
switch in my office. That switch is cabled to a second switch in my
wife's office where my wife has her desktop and networked printer (I
sure wish that there had been wireless back when I strung that CAT-5
cable halfway across the house).
eth2 -- connected to a
Wireless Access Point (WAP) that interfaces to our wireless
network.
There are Two Xen domains.
Dom0 (DNS name gateway.shorewall.net) is used as our main
firewall and wireless gateway as well as a local file server.
The DomU (Domain name lists,
DNS name lists.shorewall.net) is used
as a public Web/FTP/Mail/DNS server.
Shorewall runs in Dom0.
As the developer of Shorewall, I have enough experience to be very
comfortable with Linux networking and Shorewall/iptables. I arrived at
this configuration after a fair amount of trial and error
experimentation (see Xen and Shorewall and
Xen and the art of Consolidation). If
you are a Linux networking novice, I recommend that you do not attempt a
configuration like this one for your first Shorewall installation. You
are very likely to frustrate both yourself and the Shorewall support
team. Rather I suggest that you start with something simple like a
standalone installation in a DomU;
once you are comfortable with that then you will be ready to try
something more substantial.
As Paul Gear says: Shorewall might make iptables easy,
but it doesn't make understanding fundamental networking principles,
traffic shaping, or multi-ISP routing any easier.
The same goes for Xen networking.
Domain Configuration
Below are the relevant configuration files for the two domains. I
use a partition on my hard drives for the DomU storage device.
There is not much documentation about how to configure Xen for
routed operation. I've tried to mark the relevant parts with bold font.
/boot/grub/menu.lst — here is the entry
that boots Xen in Dom0.
title XEN
root (hd0,1)
kernel /boot/xen.gz Dom0_mem=458752 sched=bvt
module /boot/vmlinuz-xen root=/dev/hda2 vga=0x31a selinux=0 resume=/dev/hda1 splash=silent showopts
module /boot/initrd-xen
/etc/modprobe.conf.local (This may need to
go in /etc/modprobe.conf or
/etc/modprobe.d/options on your system)
options netloop nloopbacks=0 #Stop netloop from creating 8 useless vifs
/etc/xen/auto/01-lists — configuration file
for the lists domain. Placed in /etc/xen/auto/ so it is started
automatically by Xen's xendomains service.
# -*- mode: python; -*-
# configuration name:
name = "lists"
# usable ram:
memory = 512
# kernel and initrd:
kernel = "/xen2/vmlinuz-xen"
ramdisk = "/xen2/initrd-xen"
# boot device:
root = "/dev/hda3"
# boot to run level:
extra = "3"
# network interface:
vif = [ 'mac=aa:cc:00:00:00:01, ip=206.124.146.177, vifname=eth3' ]
# storage devices:
disk = [ 'phy:hda3,hda3,w' ]
Note that the vifname is set to 'eth3' for the virtual
interface to this DomU. This will cause the Dom0 interface to the
server to have a fixed name (eth3) which makes it a lot easier to
deal with in Shorewall and elsewhere.
Specifying an IP address (ip=206.124.146.177) causes the
vif-route script to create a host route to that IP address on
eth3.
gateway:~ # ip route ls dev eth3
206.124.146.177 scope link src 206.124.146.176
gateway:~ #
Note that the source for the route is 206.124.146.176. That is
the primary IP address of Dom0's eth0. Xen configures eth3 to have that same IP
address.
Excerpt from
/etc/xen/xend-config.sxp:
…
# It is possible to use the network-bridge script in more complicated
# scenarios, such as having two outgoing interfaces, with two bridges, and
# two fake interfaces per guest domain. To do things like this, write
# yourself a wrapper script, and call network-bridge from it, as appropriate.
#
#(network-script network-bridge)
…
# If you are using only one bridge, the vif-bridge script will discover that,
# so there is no need to specify it explicitly.
#
#(vif-script vif-bridge)
## Use the following if network traffic is routed, as an alternative to the
# settings for bridged networking given above.
(network-script network-route)
(vif-script vif-route)
With both Xen domains up and running, the system looks as shown in
the following diagram.
![]()
The zones correspond to the Shorewall zones in the Dom0
configuration.
Under some circumstances, UDP and/or TCP communication from a
DomU won't work for no obvious reason. That happened with the
lists domain in my setup. Looking at
the IP traffic with tcpdump -nvvi eth1 in Dom0
showed that UDP packets from the lists DomU had incorrect checksums. That
problem was corrected by arranging for the following command to be
executed in the lists domain when its
eth0 device was brought
up:
ethtool -K eth0 tx off
Under SuSE 10.1, I placed the following
in /etc/sysconfig/network/if-up.d/resettx (that
file is executable):
#!/bin/sh
if [ $2 = eth0 ]; then
ethtool -K eth0 tx off
echo "TX Checksum reset on eth0"
fi
Under other distributions, the technique will vary. For example,
under Debian or Ubuntu,
you can just add a 'post-up' entry to
/etc/network/interfaces as shown here:
iface eth0 inet static
address 206.124.146.177
netmask 255.255.255.0
post-up ethtool -K eth0 tx off
Dom0 Shorewall Configuration
In Dom0, I run a conventional three-interface firewall with Proxy
ARP DMZ -- it is very similar to the firewall described in the Shorewall Setup Guide with the
exception that I've added a fourth interface for our wireless network.
The firewall runs a routed OpenVPN
server to provide roadwarrior access for our two laptops and a
bridged OpenVPN server for the wireless network in our home. Here is the
firewall's view of the network:
![]()
The two laptops can be directly attached to the LAN as shown above
or they can be attached wirelessly -- their IP addresses are the same in
either case; when they are directly attached, the IP address is assigned
by the DHCP server running in Dom0 and when they are attached
wirelessly, the IP address is assigned by OpenVPN.
The Shorewall configuration files are shown below. All routing and
secondary IP addresses are handled in the SuSE network
configuration.
/etc/shorewall/shorewall.conf
STARTUP_ENABLED=Yes
VERBOSITY=0
LOGFILE=/var/log/firewall
LOGFORMAT="FW:%s:%s:"
LOGTAGONLY=No
LOGRATE=
LOGBURST=
LOGALLNEW=
BLACKLIST_LOGLEVEL=
MACLIST_LOG_LEVEL=$LOG
TCP_FLAGS_LOG_LEVEL=$LOG
RFC1918_LOG_LEVEL=$LOG
SMURF_LOG_LEVEL=$LOG
LOG_MARTIANS=No
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin
SHOREWALL_SHELL=/bin/ash
SUBSYSLOCK=/var/lock/subsys/shorewall-lite
MODULESDIR=
CONFIG_PATH=/usr/share/shorewall-lite:/usr/share/shorewall/configfiles:/usr/share/shorewall
RESTOREFILE=restore
IPSECFILE=zones
IP_FORWARDING=On
ADD_IP_ALIASES=No
ADD_SNAT_ALIASES=No
RETAIN_ALIASES=No
TC_ENABLED=Internal
TC_EXPERT=No
CLEAR_TC=Yes
MARK_IN_FORWARD_CHAIN=Yes
CLAMPMSS=Yes
ROUTE_FILTER=No
DETECT_DNAT_IPADDRS=Yes
MUTEX_TIMEOUT=60
ADMINISABSENTMINDED=Yes
BLACKLISTNEWONLY=Yes
DELAYBLACKLISTLOAD=Yes
MODULE_SUFFIX=
DISABLE_IPV6=Yes
BRIDGING=No
DYNAMIC_ZONES=No
PKTTYPE=No
RFC1918_STRICT=Yes
MACLIST_TTL=60
SAVE_IPSETS=No
MAPOLDACTIONS=No
FASTACCEPT=Yes
HIGH_ROUTE_MARKS=Yes
BLACKLIST_DISPOSITION=DROP
MACLIST_TABLE=mangle
MACLIST_DISPOSITION=DROP
TCP_FLAGS_DISPOSITION=DROP
/etc/shorewall/zones:
#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall #The firewall itself.
net ipv4 #Internet
loc ipv4 #Local wired Zone
dmz ipv4 #DMZ
vpn ipv4 #Open VPN clients
wifi ipv4 #Local Wireless Zone
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
/etc/shorewall/policy:
#SOURCE DEST POLICY LOG LIMIT:BURST
# LEVEL
$FW $FW ACCEPT
$FW net ACCEPT
loc net ACCEPT
$FW vpn ACCEPT
vpn net ACCEPT
vpn loc ACCEPT
loc vpn ACCEPT
$FW loc ACCEPT
loc $FW ACCEPT
wifi all REJECT $LOG
net $FW DROP $LOG 1/sec:2
net loc DROP $LOG 2/sec:4
net dmz DROP $LOG 8/sec:30
net vpn DROP $LOG
all all REJECT $LOG
#LAST LINE -- DO NOT REMOVE
Note that the firewall<->local network interface
is wide open so from a security point of view, the firewall system is
part of the local zone.
/etc/shorewall/params (edited):
MIRRORS=<comma-separated list of Shorewall mirrors>
NTPSERVERS=<comma-separated list of NTP servers I sync with>
POPSERVERS=<comma-separated list of server IP addresses>
LOG=info
INT_IF=br0
DMZ_IF=eth3
EXT_IF=eth0
WIFI_IF=eth2
OMAK=<IP address at our second home>
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
/etc/shorewall/init:
echo 1 > /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_be_liberal
/etc/shorewall/interfaces:
#ZONE INTERFACE BROADCAST OPTIONS
net $EXT_IF 206.124.146.255 dhcp,norfc1918,logmartians,blacklist,tcpflags,nosmurfs
dmz $DMZ_IF 192.168.0.255 logmartians
loc $INT_IF 192.168.1.255 dhcp,routeback,logmartians
wifi $WIFI_IF 192.168.3.255 dhcp,maclist
vpn tun+ -
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/nat:
#EXTERNAL INTERFACE INTERNAL ALL LOCAL
# INTERFACES
206.124.146.178 $EXT_IF 192.168.1.3 No No #Wookie
206.124.146.180 $EXT_IF 192.168.1.6 No No #Work LapTop
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
/etc/shorewall/masq (Note the cute trick here and in
the following proxyarp file that allows me to
access the DSL "Modem" using it's default IP address
(192.168.1.1)). The leading "+" is required to place the
rule before the SNAT rules generated by entries in
/etc/shorewall/nat above.
#INTERFACE SUBNET ADDRESS PROTO PORT(S) IPSEC
+$EXT_IF:192.168.1.1 0.0.0.0/0 192.168.1.254
$EXT_IF 192.168.0.0/22 206.124.146.179
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
/etc/shorewall/proxyarp:
#ADDRESS INTERFACE EXTERNAL HAVEROUTE PERSISTENT
192.168.1.1 $EXT_IF $INT_IF yes
206.124.146.177 $DMZ_IF $EXT_IF yes
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tunnels:
#TYPE ZONE GATEWAY GATEWAY
# ZONE
openvpnserver:udp net 0.0.0.0/0 #Routed server for RoadWarrior access
openvpnserver:udp wifi 192.168.3.0/24 #Home wireless network server
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/actions:
#ACTION
Mirrors # Accept traffic from Shorewall Mirrors
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
/etc/shorewall/action.Mirrors:
#TARGET SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE
# PORT PORT(S) DEST LIMIT
ACCEPT $MIRRORS
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/rules:
SECTION NEW
###############################################################################################################################################################################
#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/
# PORT PORT(S) DEST LIMIT GROUP
###############################################################################################################################################################################
REJECT:$LOG loc net tcp 25
REJECT:$LOG loc net udp 1025:1031
#
# Stop NETBIOS crap
#
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
#
# Stop my idiotic work laptop from sending to the net with an HP source/dest IP address
#
DROP loc:!192.168.0.0/22 net
###############################################################################################################################################################################
# Local Network to Firewall
#
REDIRECT- loc 3128 tcp 80 - !192.168.1.1,192.168.0.7,206.124.146.177,155.98.64.80
###############################################################################################################################################################################
# Road Warriors to Firewall
#
ACCEPT vpn fw tcp ssh,time,631,8080
ACCEPT vpn fw udp 161,ntp,631
Ping/ACCEPT vpn fw
###############################################################################################################################################################################
# Road Warriors to DMZ
#
ACCEPT vpn dmz udp domain
ACCEPT vpn dmz tcp www,smtp,smtps,domain,ssh,imap,https,imaps,ftp,10023,pop3 -
Ping/ACCEPT vpn dmz
###############################################################################################################################################################################
# Local network to DMZ
#
ACCEPT loc dmz udp domain
ACCEPT loc dmz tcp ssh,smtps,www,ftp,imaps,domain,https -
ACCEPT loc dmz tcp smtp
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# Internet to ALL -- drop NewNotSyn packets
#
dropNotSyn net fw tcp
#dropNotSyn net loc tcp
dropNotSyn net dmz tcp
###############################################################################################################################################################################
# Internet to DMZ
#
ACCEPT net dmz udp domain
LOG:$LOG net:64.126.128.0/18 dmz tcp smtp
ACCEPT net dmz tcp smtps,www,ftp,imaps,domain,https -
ACCEPT net dmz tcp smtp - 206.124.146.177,206.124.146.178
ACCEPT net dmz udp 33434:33454
Mirrors net dmz tcp rsync
Limit:$LOG:SSHA,3,60\
net dmz tcp 22
Trcrt/ACCEPT net dmz
##############################################################################################################################################################################
#
# Net to Local
#
# When I'm "on the road", the following two rules allow me VPN access back home using PPTP.
#
DNAT net loc:192.168.1.4 tcp 1729
DNAT net loc:192.168.1.4 gre
#
# Roadwarrior access to Ursa
#
ACCEPT net:$OMAK loc tcp 22
Limit:$LOG:SSHA,3,60\
net loc tcp 22
#
# ICQ
#
ACCEPT net loc:192.168.1.3 tcp 113,4000:4100
#
# Bittorrent
#
ACCEPT net loc:192.168.1.3 tcp 6881:6889,6969
ACCEPT net loc:192.168.1.3 udp 6881:6889,6969
#
# Real Audio
#
ACCEPT net loc:192.168.1.3 udp 6970:7170
#
# Overnet
#
#ACCEPT net loc:192.168.1.3 tcp 4662
#ACCEPT net loc:192.168.1.3 udp 12112
#
# OpenVPN
#
ACCEPT net loc:192.168.1.3 udp 1194
ACCEPT net loc:192.168.1.6 udp 1194
# Skype
#
ACCEPT net loc:192.168.1.6 tcp 1194
#
# Traceroute
#
Trcrt/ACCEPT net loc:192.168.1.3
#
# Silently Handle common probes
#
REJECT net loc tcp www,ftp,https
DROP net loc icmp 8
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net udp domain,ntp
ACCEPT dmz net tcp echo,ftp,ssh,smtp,whois,domain,www,81,https,cvspserver,2702,2703,8080
ACCEPT dmz net:$POPSERVERS tcp pop3
Ping/ACCEPT dmz net
#
# Some FTP clients seem prone to sending the PORT command split over two packets. This prevents the FTP connection tracking
# code from processing the command and setting up the proper expectation. The following rule allows active FTP to work in these cases
# but logs the connection so I can keep an eye on this potential security hole.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# Local to DMZ
#
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,rsync,https,imaps,ftp,10023,pop3,3128
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# DMZ to Local
#
ACCEPT dmz loc:192.168.1.5 udp 123
ACCEPT dmz loc:192.168.1.5 tcp 21
Ping/ACCEPT dmz loc
###############################################################################################################################################################################
# DMZ to Firewall -- ntp & snmp, Silently reject Auth
#
#ACCEPT net loc:192.168.1.3 udp 12112
#
# OpenVPN
#
ACCEPT net loc:192.168.1.3 udp 1194
ACCEPT net loc:192.168.1.6 udp 1194
# Skype
#
ACCEPT net loc:192.168.1.6 tcp 1194
#
# Traceroute
#
Trcrt/ACCEPT net loc:192.168.1.3
#
# Silently Handle common probes
#
REJECT net loc tcp www,ftp,https
DROP net loc icmp 8
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net udp domain,ntp
ACCEPT dmz net tcp echo,ftp,ssh,smtp,whois,domain,www,81,https,cvspserver,2702,2703,8080
ACCEPT dmz net:$POPSERVERS tcp pop3
Ping/ACCEPT dmz net
#
# Some FTP clients seem prone to sending the PORT command split over two packets. This prevents the FTP connection tracking
# code from processing the command and setting up the proper expectation. The following rule allows active FTP to work in these cases
# but logs the connection so I can keep an eye on this potential security hole.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# Local to DMZ
#
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,rsync,https,imaps,ftp,10023,pop3,3128
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# DMZ to Local
#
ACCEPT dmz loc:192.168.1.5 udp 123
ACCEPT dmz loc:192.168.1.5 tcp 21
Ping/ACCEPT dmz loc
###############################################################################################################################################################################
# DMZ to Firewall -- ntp & snmp, Silently reject Auth
#
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,rsync,https,imaps,ftp,10023,pop3,3128
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# DMZ to Local
#
ACCEPT dmz loc:192.168.1.5 udp 123
ACCEPT dmz loc:192.168.1.5 tcp 21
Ping/ACCEPT dmz loc
###############################################################################################################################################################################
# DMZ to Firewall -- ntp & snmp, Silently reject Auth
#
ACCEPT dmz fw tcp 161,ssh
ACCEPT dmz fw udp 161,ntp
REJECT dmz fw tcp auth
Ping/ACCEPT dmz fw
###############################################################################################################################################################################
# Internet to Firewall
#
REJECT net fw tcp www,ftp,https
DROP net fw icmp 8
ACCEPT net fw udp 33434:33454
ACCEPT net:$OMAK fw udp ntp
ACCEPT net fw tcp auth
ACCEPT net:$OMAK fw tcp 22
Limit:$LOG:SSHA,3,60\
net fw tcp 22
Trcrt/ACCEPT net fw
#
# Bittorrent
#
ACCEPT net fw tcp 6881:6889,6969
ACCEPT net fw udp 6881:6889,6969
###############################################################################################################################################################################
# Firewall to DMZ
#
ACCEPT fw dmz tcp domain,www,ftp,ssh,smtp,https,993,465
ACCEPT fw dmz udp domain
REJECT fw dmz udp 137:139
Ping/ACCEPT fw dmz
##############################################################################################################################################################################
# Avoid logging Freenode.net probes
#
DROP net:82.96.96.3 all
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tcdevices
#INTERFACE IN-BANDWITH OUT-BANDWIDTH
$EXT_IF 1300kbit 384kbit
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tcclasses#INTERFACE MARK RATE CEIL PRIORITY OPTIONS
$EXT_IF 10 5*full/10 full 1 tcp-ack,tos-minimize-delay
$EXT_IF 20 3*full/10 9*full/10 2 default
$EXT_IF 30 2*full/10 6*full/10 3
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tcrules#MARK SOURCE DEST PROTO PORT(S) CLIENT USER TEST
# PORT(S)
1:110 192.168.0.0/22 $EXT_IF #Our internel nets get priority
#over the server
1:130 206.124.146.177 $EXT_IF tcp - 873 #Throttle rsync traffic to the
#Shorewall Mirrors.
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
The tap0 device used by
the bridged OpenVPN server is created and bridged to eth1 using a SuSE-specific SysV init
script:
#!/bin/sh
#
# The Shoreline Firewall (Shorewall) Packet Filtering Firewall - V3.0
#
# This program is under GPL [http://www.gnu.org/copyleft/gpl.htm]
#
# (c) 1999,2000,2001,2002,2003,2004,2005 - Tom Eastep (teastep@shorewall.net)
#
# On most distributions, this file should be called /etc/init.d/shorewall.
#
# Complete documentation is available at http://shorewall.net
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of Version 2 of the GNU General Public License
# as published by the Free Software Foundation.
#
# 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; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA
#
# If an error occurs while starting or restarting the firewall, the
# firewall is automatically stopped.
#
# Commands are:
#
# bridge start Starts the bridge
# bridge restart Restarts the bridge
# bridge reload Restarts the bridge
# bridge stop Stops the bridge
# bridge status Displays bridge status
#
# chkconfig: 2345 4 99
# description: Packet filtering firewall
### BEGIN INIT INFO
# Provides: bridge
# Required-Start: boot.udev
# Required-Stop:
# Default-Start: 2 3 5
# Default-Stop: 0 1 6
# Description: starts and stops the bridge
### END INIT INFO
################################################################################
# Interfaces to be bridged -- may be listed by device name or by MAC
#
INTERFACES="eth1"
#
# Tap Devices
#
TAPS="tap0"
################################################################################
# Give Usage Information #
################################################################################
usage() {
echo "Usage: $0 start|stop|reload|restart|status"
exit 1
}
#################################################################################
# Find the interface with the passed MAC address
#################################################################################
find_interface_by_mac() {
local mac=$1 first second rest dev
/sbin/ip link ls | while read first second rest; do
case $first in
*:)
dev=$second
;;
*)
if [ "$second" = $mac ]; then
echo ${dev%:}
return
fi
esac
done
}
################################################################################
# Convert MAC addresses to interface names
################################################################################
get_interfaces() {
local interfaces= interface
for interface in $INTERFACES; do
case $interface in
*:*:*)
interface=$(find_interface_by_mac $interface)
[ -n "$interface" ] || echo "WARNING: Can't find an interface with MAC address $mac"
;;
esac
interfaces="$interfaces $interface"
done
INTERFACES="$interfaces"
}
################################################################################
# Start the Bridge
################################################################################
do_start()
{
local interface
get_interfaces
for interface in $TAPS; do
/usr/sbin/openvpn --mktun --dev $interface
done
/sbin/brctl addbr br0
for interface in $INTERFACES $TAPS; do
/sbin/ip link set $interface up
/sbin/brctl addif br0 $interface
done
}
################################################################################
# Stop the Bridge
################################################################################
do_stop()
{
local interface
get_interfaces
for interface in $INTERFACES $TAPS; do
/sbin/brctl delif br0 $interface
/sbin/ip link set $interface down
done
/sbin/ip link set br0 down
/sbin/brctl delbr br0
for interface in $TAPS; do
/usr/sbin/openvpn --rmtun --dev $interface
done
}
################################################################################
# E X E C U T I O N B E G I N S H E R E #
################################################################################
command="$1"
case "$command" in
start)
do_start
;;
stop)
do_stop
;;
restart|reload)
do_stop
do_start
;;
status)
/sbin/brctl show
;;
*)
usage
;;
esac