shorewall_code/docs/XenMyWay.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
<article>
  <!--$Id$-->

  <articleinfo>
    <title>Xen and the Art of Consolidation</title>

    <authorgroup>
      <author>
        <firstname>Tom</firstname>

        <surname>Eastep</surname>
      </author>
    </authorgroup>

    <pubdate><?dbtimestamp format="Y/m/d"?></pubdate>

    <copyright>
      <year>2006</year>

      <year>2007</year>

      <holder>Thomas M. Eastep</holder>
    </copyright>

    <legalnotice>
      <para>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, no Front-Cover Texts, and no Back-Cover
      Texts. A copy of the license is included in the section entitled
      <quote><ulink url="GnuCopyright.htm">GNU Free Documentation
      License</ulink></quote>.</para>
    </legalnotice>
  </articleinfo>

  <caution>
    <para>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.</para>
  </caution>

  <section>
    <title>Xen Network Environment</title>

    <para><ulink
    url="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/">Xen</ulink> is a
    <firstterm>paravirtualization</firstterm> 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
    <trademark>SUSE</trademark> distributions.</para>

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

    <para>Xen virtualizes a network interface named <filename
    class="devicefile">eth0</filename><footnote>
        <para>This assumes the default Xen configuration created by
        <command>xend </command>and assumes that the host system has a single
        Ethernet interface named <filename
        class="devicefile">eth0</filename>.</para>
      </footnote>in each domain. In Dom0, Xen also creates a bridge (<filename
    class="devicefile">xenbr0</filename>) and a number of virtual interfaces
    as shown in the following diagram.</para>

    <graphic align="center" fileref="images/Xen1.png"/>

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

    <para>The bridge has a number of ports:</para>

    <itemizedlist>
      <listitem>
        <para>peth0 — This is the port that connects to the physical network
        interface in your system.</para>
      </listitem>

      <listitem>
        <para>vif0.0 — This is the bridge port that is used by traffic to/from
        Domain 0.</para>
      </listitem>

      <listitem>
        <para>vifX.0 — This is the bridge port that is used by traffic to/from
        Domain X.</para>
      </listitem>
    </itemizedlist>
  </section>

  <section id="Before">
    <title>Before Xen</title>

    <para>Prior to adopting Xen, I had a home office crowded with 5 systems,
    three monitors a scanner and a printer. The systems were:</para>

    <orderedlist>
      <listitem>
        <para>Firewall</para>
      </listitem>

      <listitem>
        <para>Public Server in a DMZ (mail)</para>
      </listitem>

      <listitem>
        <para>Private Server (wookie)</para>
      </listitem>

      <listitem>
        <para>My personal Linux Desktop (ursa)</para>
      </listitem>

      <listitem>
        <para>My work system (docked laptop running Windows XP).</para>
      </listitem>
    </orderedlist>

    <para>The result was a very crowded and noisy room.</para>
  </section>

  <section id="After">
    <title>After Xen</title>

    <para>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.</para>

    <para>The systems now include:</para>

    <orderedlist>
      <listitem>
        <para>Combination Firewall/Public Server/Private Server/Wireless
        Gateway using Xen (created by building out my Linux desktop
        system).</para>
      </listitem>

      <listitem>
        <para>My work system.</para>
      </listitem>

      <listitem>
        <para>My Linux desktop (wookie, which is actually the old public
        server box)</para>
      </listitem>
    </orderedlist>

    <para>Most of the Linux systems run <trademark>SUSE </trademark>10.1; my
    personal Linux desktop system and our Linux Laptop run
    <trademark>Ubuntu</trademark> "Dapper Drake".</para>

    <para><emphasis role="bold">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
    <ulink url="XenMyWay-Routed.html">this article</ulink>. I am now using the
    routed configuration because it results in one fewer domains to
    administer.</emphasis></para>

    <para>Here is a high-level diagram of our network.</para>

    <graphic align="center" fileref="images/Xen5.png"/>

    <para>As shown in this diagram, the Xen system has three physical network
    interfaces. These are:</para>

    <itemizedlist>
      <listitem>
        <para><filename class="devicefile">eth0</filename> -- 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).</para>
      </listitem>

      <listitem>
        <para><filename class="devicefile">eth1</filename> -- connected to our
        DSL "Modem".</para>
      </listitem>

      <listitem>
        <para><filename class="devicefile">eth2</filename> -- connected to a
        Wireless Access Point (WAP) that interfaces to our wireless
        network.</para>
      </listitem>
    </itemizedlist>

    <para>There are three Xen domains.</para>

    <orderedlist>
      <listitem>
        <para>Dom0 (DNS name ursa.shorewall.net) is used as a local file
        server (NFS and Samba).</para>
      </listitem>

      <listitem>
        <para>The first DomU (Dom name <emphasis
        role="bold">firewall</emphasis>, DNS name gateway.shorewall.net) is
        used as our main firewall and wireless gateway.</para>
      </listitem>

      <listitem>
        <para>The second DomU (Dom name <emphasis
        role="bold">lists</emphasis>, DNS name lists.shorewall.net) is used as
        a public Web/FTP/Mail/DNS server.</para>
      </listitem>
    </orderedlist>

    <para>Shorewall runs in Dom0 and in the firewall domain.</para>

    <caution>
      <para>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 <ulink url="standalone.htm">standalone
      installation</ulink> in a domU; once you are comfortable with that then
      you will be ready to try something more substantial.</para>

      <para>As Paul Gear says: <emphasis>Shorewall might make iptables easy,
      but it doesn't make understanding fundamental networking principles,
      traffic shaping, or multi-ISP routing any easier</emphasis>.</para>

      <para>The same goes for Xen networking.</para>
    </caution>

    <section id="Domains">
      <title>Domain Configuration</title>

      <para>Below are the relevant configuration files for the three domains.
      I use partitions on my hard drives for DomU storage devices.</para>

      <blockquote>
        <para><filename>/boot/grub/menu.lst</filename> — here is the entry
        that boots Xen in Dom0.</para>

        <programlisting>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</programlisting>

        <para><filename>/etc/modprobe.conf.local</filename></para>

        <para><filename class="devicefile">eth1</filename> (PCI 00:09.0) and
        <filename class="devicefile">eth2</filename> (PCI 00:0a.0) are
        delegated to the firewall DomU where they become <filename
        class="devicefile">eth3</filename> and <filename
        class="devicefile">eth4</filename> 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
        <ulink
        url="http://wiki.xensource.com/xenwiki/Assign_hardware_to_DomU_with_PCIBack_as_module">http://wiki.xensource.com/xenwiki/Assign_hardware_to_DomU_with_PCIBack_as_module</ulink>).</para>

        <programlisting>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</programlisting>

        <para><filename>/etc/xen/auto/01-firewall</filename> — configuration
        file for the firewall domain</para>

        <programlisting>#  -*- 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' ]</programlisting>

        <para><filename>/etc/xen/auto/02-lists</filename> — configuration file
        for the lists domain</para>

        <programlisting>#  -*- 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' ]</programlisting>
      </blockquote>

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

      <graphic align="center" fileref="images/Xen4.png"/>

      <para>The zones correspond to the Shorewall zones in the firewall DomU
      configuration.</para>

      <note>
        <para>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
        <ulink url="two-interface.htm">normal Shorewall two-interface sample
        configuration</ulink> in the DomU.</para>
      </note>

      <caution>
        <para>Under some circumstances, UDP and/or TCP communication from a
        domU won't work for no obvious reason. That happened with the
        <emphasis role="bold">lists</emphasis> domain in my setup. Looking at
        the IP traffic with <command>tcpdump -nvvi eth1</command> in the
        <emphasis role="bold">firewall</emphasis> domU showed that UDP packets
        from the <emphasis role="bold">lists</emphasis> domU had incorrect
        checksums. That problem was corrected by arranging for the following
        command to be executed in the <emphasis role="bold">lists</emphasis>
        domain when its <filename class="devicefile">eth0</filename> device
        was brought up:</para>

        <para><command>ethtool -K eth0 tx off</command></para>

        <para>Under SUSE 10.1, I placed the following in
        <filename>/etc/sysconfig/network/if-up.d/resettx</filename> (that file
        is executable):</para>

        <programlisting>#!/bin/sh

if [ $2 = eth0 ]; then
    ethtool -K eth0 tx off
    echo "TX Checksum reset on eth0"
fi</programlisting>

        <para>Under other distributions, the technique will vary. For example,
        under <trademark>Debian</trademark> or <trademark>Ubuntu</trademark>,
        you can just add a 'post-up' entry to
        <filename>/etc/network/interfaces</filename> as shown here:</para>

        <programlisting> iface eth0 inet static
         address 206.124.146.177
         netmask 255.255.255.0
         post-up ethtool -K eth0 tx off</programlisting>
      </caution>

      <caution>
        <para>Update. Under SUSE 10.2, communication from a domU works okay
        without running ethtool <emphasis role="bold">but traffic shaping in
        dom0 doesn't work!</emphasis> So it's a good idea to run it just to be
        safe.</para>
      </caution>

      <para>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.</para>

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

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

    <section id="Dom0">
      <title>Dom0 Configuration</title>

      <para>The goals for the Shorewall configuration in Dom0 are as
      follows:</para>

      <itemizedlist>
        <listitem>
          <para>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.</para>
        </listitem>

        <listitem>
          <para>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).</para>
        </listitem>
      </itemizedlist>

      <para>The configuration is a simple one:</para>

      <blockquote>
        <para><filename>/etc/shorewall/zones</filename>:</para>

        <programlisting>#ZONE   TYPE            OPTIONS         IN_OPTIONS              OUT_OPTIONS
fw      firewall
loc     ipv4
dmz     ipv4</programlisting>

        <para><filename>/etc/shorewall/policy</filename> (Note the unusual use
        of an ACCEPT all-&gt;all policy):</para>

        <programlisting>#SOURCE         DEST            POLICY          LOGLEVEL             LIMIT
dmz             all             REJECT          info
all             dmz             REJECT          info
all             all             ACCEPT</programlisting>

        <para><filename>/etc/shorewall/interfaces</filename>:</para>

        <programlisting>#ZONE   INTERFACE       BROADCAST       OPTIONS
loc     xenbr0          192.168.1.255   dhcp,routeback
dmz     xenbr1          -               routeback</programlisting>
      </blockquote>
    </section>

    <section id="Firewall">
      <title>Firewall DomU Configuration</title>

      <para>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 <ulink url="shorewall_setup_guide.htm">Shorewall Setup
      Guide</ulink> with the exception that I've added a fourth interface for
      our wireless network. The firewall runs a routed <ulink
      url="OPENVPN.html">OpenVPN server</ulink> 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:</para>

      <graphic align="center" fileref="images/network4.png"/>

      <para>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.</para>

      <para>The Shorewall configuration files are shown below. All routing and
      secondary IP addresses are handled in the SUSE network
      configuration.</para>

      <blockquote>
        <para>/etc/shorewall/shorewall.conf:</para>

        <programlisting>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</programlisting>

        <para><filename>/etc/shorewall/zones</filename>:</para>

        <programlisting>#ZONE   TYPE            OPTIONS         IN_OPTIONS              OUT_OPTIONS
fw      firewall
net     ipv4            #Internet
loc     ipv4            #Local wired Zone
dmz     ipv4            #DMZ
vpn     ipv4            #Open VPN clients
wifi    ipv4            #Local Wireless Zone</programlisting>

        <para><filename>/etc/shorewall/policy</filename>:</para>

        <programlisting>#SOURCE         DEST            POLICY          LOGLEVEL        LIMIT
$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</programlisting>

        <para><filename>/etc/shorewall/params (edited)</filename>:</para>

        <programlisting>MIRRORS=&lt;comma-separated list of Shorewall mirrors&gt;

NTPSERVERS=&lt;comma-separated list of NTP servers I sync with&gt;

POPSERVERS=&lt;comma-separated list of server IP addresses&gt;

LOG=info

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

OMAK=&lt;IP address at our second home&gt;</programlisting>

        <para><filename>/etc/shorewall/init</filename>:</para>

        <programlisting>echo 1 &gt; /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_be_liberal</programlisting>

        <para><filename>/etc/shorewall/interfaces</filename>:</para>

        <programlisting>#ZONE   INTERFACE       BROADCAST               OPTIONS
net     $EXT_IF         206.124.146.255         dhcp,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+            -
</programlisting>

        <para><filename>/etc/shorewall/nat</filename>:</para>

        <programlisting>#EXTERNAL               INTERFACE       INTERNAL        ALLINTS         LOCAL
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
</programlisting>

        <para><filename>/etc/shorewall/masq (Note the cute trick here and in
        the <filename>following proxyarp</filename> file that allows me to
        access the DSL "Modem" using its default IP address
        (192.168.1.1))</filename>. The leading "+" is required to place the
        rule before the SNAT rules generated by entries in
        <filename>/etc/shorewall/nat</filename> above.</para>

        <programlisting>#INTERFACE              SUBNET          ADDRESS         PROTO   DPORT 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</programlisting>

        <para><filename>/etc/shorewall/proxyarp</filename>:</para>

        <programlisting>#ADDRESS        INTERFACE       EXTERNAL        HAVEROUTE       PERSISTENT
192.168.1.1     $EXT_IF         $INT_IF         yes
206.124.146.177 $DMZ_IF         $EXT_IF         yes</programlisting>

        <para><filename>/etc/shorewall/tunnels</filename>:</para>

        <programlisting>#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
</programlisting>

        <para><filename>/etc/shorewall/actions</filename>:</para>

        <programlisting>#ACTION
Mirrors             # Accept traffic from Shorewall Mirrors
</programlisting>

        <para><filename>/etc/shorewall/action.Mirrors</filename>:</para>

        <programlisting>#TARGET SOURCE          DEST            PROTO   PORT    SPORT      ORIGDEST     RATE
ACCEPT  $MIRRORS</programlisting>

        <para><filename>/etc/shorewall/rules</filename>:</para>

        <programlisting>?SECTION NEW
###############################################################################################################################################################################
#ACTION         SOURCE                          DEST                    PROTO   DPORT                                   SPORT           ORIGDEST        RATE    USER
###############################################################################################################################################################################
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 &amp; 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
</programlisting>

        <para><filename>/etc/shorewall/tcdevices</filename></para>

        <programlisting>#INTERFACE      IN_BANDWITH     OUT_BANDWIDTH
$EXT_IF         1300kbit        384kbit</programlisting>

        <para><filename>/etc/shorewall/tcclasses</filename><programlisting>#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</programlisting></para>

        <para><filename>/etc/shorewall/mangle</filename><programlisting>#ACTION           SOURCE          DEST            PROTO   DPORT   SPORT   USER    TEST
CLASSIFY(1:110)   192.168.0.0/22  $EXT_IF                                         #Our internal nets get priority
                                                                                  #over the server
CLASSIFY(1:130)   206.124.146.177 $EXT_IF         tcp     -       873             #Throttle rsync traffic to the
                                                                                  #Shorewall Mirrors.
</programlisting></para>
      </blockquote>

      <para>The tap0 device used by the bridged OpenVPN server is bridged to
      eth0 using a SUSE-specific SysV init script:</para>

      <blockquote>
        <programlisting>#!/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 https://shorewall.org
#
#       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
</programlisting>
      </blockquote>
    </section>
  </section>
</article>