Xen and the Art of Consolidation

Tom 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.

2014/06/04


Caution

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.

Xen Network Environment

Xen is a paravirtualization tool that allows you to run multiple virtual machines on one physical machine. It is available on a wide number of platforms and is included in recent SUSE™ distributions.

Xen refers to the virtual machines as Domains. Domains are numbered with the first domain being domain 0, the second domain 1, and so on. Domain 0 (Dom0) is special because that is the domain created when the machine is booted. Additional domains (called DomU's) are created using the xm create command from within Domain 0. Additional domains can also be created automatically at boot time by using the xendomains service.

Xen virtualizes a network interface named eth0[1]in each domain. In Dom0, Xen also creates a bridge (xenbr0) and a number of virtual interfaces as shown in the following diagram.

I use the term Extended Dom0 to distinguish the bridge and virtual interfaces from Dom0 itself. That distinction is important when we try to apply Shorewall in this environment.

The bridge has a number of ports:

  • peth0 — This is the port that connects to the physical network interface in your system.

  • vif0.0 — This is the bridge port that is used by traffic to/from Domain 0.

  • vifX.0 — This is the bridge port that is used by traffic to/from Domain X.

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:

  1. Firewall

  2. Public Server in a DMZ (mail)

  3. Private Server (wookie)

  4. My personal Linux Desktop (ursa)

  5. 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:

  1. Combination Firewall/Public Server/Private Server/Wireless Gateway using Xen (created by building out my Linux desktop system).

  2. My work system.

  3. 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".

The configuration described below uses a bridged Xen Networking configuration; if you want to see how to accomplish a similar configuration using a Routed Xen configuration then please see this article. I am now using the routed configuration because it results in one fewer domains to administer.

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 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).

  • eth1 -- connected to our DSL "Modem".

  • eth2 -- connected to a Wireless Access Point (WAP) that interfaces to our wireless network.

There are three Xen domains.

  1. Dom0 (DNS name ursa.shorewall.net) is used as a local file server (NFS and Samba).

  2. The first DomU (Dom name firewall, DNS name gateway.shorewall.net) is used as our main firewall and wireless gateway.

  3. The second DomU (Dom name lists, DNS name lists.shorewall.net) is used as a public Web/FTP/Mail/DNS server.

Shorewall runs in Dom0 and in the firewall domain.

Caution

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. 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 three domains. I use partitions on my hard drives for DomU storage devices.

/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

eth1 (PCI 00:09.0) and eth2 (PCI 00:0a.0) are delegated to the firewall DomU where they become eth3 and eth4 respectively. The SUSE 10.1 Xen kernel compiles pciback as a module so the instructions for PCI delegation in the Xen Users Manual can't be followed directly (see http://wiki.xensource.com/xenwiki/Assign_hardware_to_DomU_with_PCIBack_as_module).

options pciback hide=(00:09.0)(00:0a.0)
install tulip /sbin/modprobe pciback ; /sbin/modprobe --first-time --ignore-install tulip
options netloop nloopbacks=1

/etc/xen/auto/01-firewall — configuration file for the firewall domain

#  -*- mode: python; -*-

# configuration name:
name     = "firewall"

# usable ram:
memory   = 384

# kernel and initrd:
kernel   = "/xen2/vmlinuz-xen"
ramdisk  = "/xen2/initrd-xen"

# boot device:
root     = "/dev/hdb2"

# boot to run level:
extra    = "3"

# network interface:
vif      = [ 'mac=aa:cc:00:00:00:02, bridge=xenbr0', 'mac=aa:cc:00:00:00:03, bridge=xenbr1' ]
# Interfaces delegated from Dom0
pci=[ '00:09.0' , '00:0a.0' ]

# storage devices:
disk     = [ 'phy:hdb2,hdb2,w' ]

/etc/xen/auto/02-lists — configuration file for the lists domain

#  -*- 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, bridge=xenbr1' ]
hostname = name

# storage devices:
disk     = [ 'phy:hda3,hda3,w' ]

With all three Xen domains up and running, the system looks as shown in the following diagram.

The zones correspond to the Shorewall zones in the firewall DomU configuration.

Note

If you want to run a simple NAT gateway in a Xen DomU, just omit the second bridge (xenbr1), the second delegated interface, and the second DomU from the above configuration. You can then install the normal Shorewall two-interface sample configuration in the DomU.

Caution

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 the firewall domU 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

Caution

Update. Under SUSE 10.2, communication from a domU works okay without running ethtool but traffic shaping in dom0 doesn't work! So it's a good idea to run it just to be safe.

SUSE 10.1 includes Xen 3.0.2 which supports PCI delegation. The network interfaces that connect to the net and wifi zones are delegated to the firewall DomU.

When Shorewall starts during bootup of Dom0, it creates the two bridges using this /etc/shorewall/init extension script:

for bridge in xenbr0 xenbr1; do
    if [ -z "$(/sbin/brctl show 2> /dev/null | fgrep $bridge)" ]; then
         /sbin/brctl addbr $bridge
         /sbin/ip link set dev $bridge up
   fi
done

Dom0 Configuration

The goals for the Shorewall configuration in Dom0 are as follows:

  • Allow traffic to flow unrestricted through the two bridges. This is done by configuring the hosts connected to each bridge as a separate zone and relying on Shorewall's implicit intra-zone ACCEPT policy to permit traffic through the bridge.

  • Ensure that there is no stray traffic between the zones. This is a "belt+suspenders" measure since there should be no routing between the bridges (because they don't have IP addresses).

The configuration is a simple one:

/etc/shorewall/zones:

#ZONE   TYPE            OPTIONS         IN                      OUT
#                                       OPTIONS                 OPTIONS
fw      firewall
loc     ipv4
dmz     ipv4
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE

/etc/shorewall/policy (Note the unusual use of an ACCEPT all->all policy):

#SOURCE         DEST            POLICY          LOG             LIMIT:BURST
#                                               LEVEL
dmz             all             REJECT          info
all             dmz             REJECT          info
all             all             ACCEPT
#LAST LINE -- DO NOT REMOVE

/etc/shorewall/interfaces:

#ZONE   INTERFACE       OPTIONS
loc     xenbr0          dhcp,routeback
dmz     xenbr1          routeback
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE

/etc/shorewall/rules:

#ACTION         SOURCE                          DEST            PROTO   DEST    SOURCE          ORIGINAL        RATE            USER/
#                                                                       PORT    PORT(S)         DEST            LIMIT           GROUP
#SECTION ESTABLISHED
#SECTION RELATED
SECTION NEW
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE

Firewall DomU Configuration

In the firewall DomU, 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 road warrior 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="Shorewall:%s:%s:"
LOGTAGONLY=No
LOGRATE=
LOGBURST=
LOGALLNEW=
BLACKLIST_LOGLEVEL=
MACLIST_LOG_LEVEL=$LOG
TCP_FLAGS_LOG_LEVEL=$LOG
SMURF_LOG_LEVEL=$LOG
LOG_MARTIANS=No
IPTABLES=/usr/sbin/iptables
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin
SHOREWALL_SHELL=/bin/bash
SUBSYSLOCK=
MODULESDIR=
CONFIG_PATH=/etc/shorewall:/usr/share/shorewall
RESTOREFILE=standard
IPSECFILE=zones
IP_FORWARDING=On
ADD_IP_ALIASES=No
ADD_SNAT_ALIASES=No
RETAIN_ALIASES=No
TC_ENABLED=Internal
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=No
MODULE_SUFFIX=
DISABLE_IPV6=Yes
BRIDGING=No
DYNAMIC_ZONES=No
PKTTYPE=No
MACLIST_TTL=60
SAVE_IPSETS=No
MAPOLDACTIONS=No
FASTACCEPT=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
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
wifi            all             REJECT          $LOG
loc             $FW             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

/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=eth0
DMZ_IF=eth1
EXT_IF=eth3
WIFI_IF=eth4

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       OPTIONS
net     $EXT_IF         dhcp,logmartians,blacklist,tcpflags,nosmurfs
dmz     $DMZ_IF         logmartians
loc     $INT_IF         dhcp,routeback,logmartians
wifi    $WIFI_IF        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 its 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
#
DROP            loc:!192.168.0.0/22             fw                      # Silently drop traffic with an HP source IP from my XP box
ACCEPT          loc                             fw                      tcp     22
ACCEPT          loc                             fw                      tcp     time,631,8080
ACCEPT          loc                             fw                      udp     161,ntp,631
ACCEPT          loc:192.168.1.5                 fw                      udp     111
DROP            loc                             fw                      tcp     3185          #SUSE Meta pppd
Ping(ACCEPT)    loc                             fw
REDIRECT        loc                             3128                    tcp     80                                      -               !206.124.146.177
###############################################################################################################################################################################
# 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
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:$LOG:SSHA,3,60\
                net                             dmz                     tcp     22
Trcrt(ACCEPT)   net                             dmz
##############################################################################################################################################################################
#
# Net to Local
#
# When I'm "on the road", the following two rules allow me VPN access back home using PPTP.
#
DNAT            net                             loc:192.168.1.4         tcp     1729
DNAT            net                             loc:192.168.1.4         gre
#
# Roadwarrior access to Wookie
#
ACCEPT          net:$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
#
# 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          dmz                             fw                      tcp     161,ssh
ACCEPT          dmz                             fw                      udp     161
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
###############################################################################################################################################################################
# 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 internal 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 bridged to eth0 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/licenses/old-licenses/gpl-2.0.txt]
#
#     (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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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="eth0"

#
# 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
    mac=$1
    local first
    local second
    local rest
    local 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
    interfaces=
    local 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


[1] This assumes the default Xen configuration created by xend and assumes that the host system has a single Ethernet interface named eth0.

Documentation


Frequently Used Articles

- FAQs - IPv4 Manpages - IPv6 Manpages - Configuration File Basics - Beginner Documentation - Troubleshooting

Shorewall 4.0/4.2 Documentation


Current HOWTOs and Other Articles

- 6to4 and 6in4 Tunnels - Accounting - Actions - Aliased (virtual) Interfaces (e.g., eth0:0) - Anatomy of Shorewall - Anti-Spoofing Measures - AUDIT Target support - Bandwidth Control - Blacklisting/Whitelisting - Bridge/Firewall - Building Shorewall from GIT - Commands - Compiled Programs - Configuration File Basics - DHCP - DNAT - Dynamic Zones - ECN Disabling by host or subnet - Events - Extension Scripts - Fallback/Uninstall - FAQs - Features - Fool's Firewall - Forwarding Traffic on the Same Interface - FTP and Shorewall - Helpers/Helper Modules - Installation/Upgrade - IPP2P - IPSEC - Ipsets - IPv6 Support - ISO 3661 Country Codes - Kazaa Filtering - Kernel Configuration - KVM (Kernel-mode Virtual Machine) - Limiting Connection Rates - Linux Containers (LXC) - Linux-vserver - Logging - Macros - MAC Verification - Manpages (IPv4) (IPv6) - Manual Chains - Masquerading - Multiple Internet Connections from a Single Firewall - Multiple Zones Through One Interface - My Shorewall Configuration - Netfilter Overview - Network Mapping - No firewalling of traffic between bridge port - One-to-one NAT - Operating Shorewall - OpenVPN - OpenVZ - Packet Marking - Packet Processing in a Shorewall-based Firewall - 'Ping' Management - Port Forwarding - Port Information - Port Knocking (deprecated) - Port Knocking, Auto Blacklisting and Other Uses of the 'Recent Match' - PPTP - Proxy ARP - QuickStart Guides - Release Model - Requirements - Routing and Shorewall - Routing on One Interface - Samba - Shorewall Events - Shorewall Init - Shorewall Lite - Shorewall on a Laptop - Shorewall Perl - Shorewall Setup Guide - SMB - SNAT - Split DNS the Easy Way - Squid with Shorewall - Starting/stopping the Firewall - Static (one-to-one) NAT - Support - Tips and Hints - Traffic Shaping/QOS - Simple - Traffic Shaping/QOS - Complex - Transparent Proxy - UPnP - Upgrade Issues - Upgrading to Shorewall 4.4 (Upgrading Debian Lenny to Squeeze) - VPN - VPN Passthrough - White List Creation - Xen - Shorewall in a Bridged Xen DomU - Xen - Shorewall in Routed Xen Dom0

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