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shorewall_code/manpages/shorewall-interfaces.xml
Tom Eastep 9e922d6967 A couple of documentation updates 
Signed-off-by: Tom Eastep <teastep@shorewall.net>
2010-09-08 12:10:40 -07:00

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
<refentry>
<refmeta>
<refentrytitle>shorewall-interfaces</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>interfaces</refname>
<refpurpose>Shorewall interfaces file</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>/etc/shorewall/interfaces</command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>The interfaces file serves to define the firewall's network
interfaces to Shorewall. The order of entries in this file is not
significant in determining zone composition.</para>
<para>The columns in the file are as follows.</para>
<variablelist>
<varlistentry>
<term><emphasis role="bold">ZONE</emphasis> -
<emphasis>zone-name</emphasis></term>
<listitem>
<para>Zone for this interface. Must match the name of a zone
declared in /etc/shorewall/zones. You may not list the firewall zone
in this column.</para>
<para>If the interface serves multiple zones that will be defined in
the <ulink url="shorewall-hosts.html">shorewall-hosts</ulink>(5)
file, you should place "-" in this column.</para>
<para>If there are multiple interfaces to the same zone, you must
list them in separate entries.</para>
<para>Example:</para>
<blockquote>
<programlisting>#ZONE INTERFACE BROADCAST
loc eth1 -
loc eth2 -</programlisting>
</blockquote>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">INTERFACE</emphasis> -
<emphasis>interface</emphasis><emphasis
role="bold">[:</emphasis><emphasis>port</emphasis><emphasis
role="bold">]</emphasis></term>
<listitem>
<para>Logical name of interface. Each interface may be listed only
once in this file. You may NOT specify the name of a "virtual"
interface (e.g., eth0:0) here; see <ulink
url="http://www.shorewall.net/FAQ.htm#faq18">http://www.shorewall.net/FAQ.htm#faq18</ulink>.
If the <option>physical</option> option is not specified, then the
logical name is also the name of the actual interface.</para>
<para>You may use wildcards here by specifying a prefix followed by
the plus sign ("+"). For example, if you want to make an entry that
applies to all PPP interfaces, use 'ppp+'; that would match ppp0,
ppp1, ppp2, …</para>
<para>When using Shorewall versions before 4.1.4, care must be
exercised when using wildcards where there is another zone that uses
a matching specific interface. See <ulink
url="shorewall-nesting.html">shorewall-nesting</ulink>(5) for a
discussion of this problem.</para>
<para>Shorewall allows '+' as an interface name.</para>
<para>There is no need to define the loopback interface (lo) in this
file.</para>
<para>If a <replaceable>port</replaceable> is given, then the
<replaceable>interface</replaceable> must have been defined
previously with the <option>bridge</option> option. The OPTIONS
column may not contain the following options when a
<replaceable>port</replaceable> is given.</para>
<simplelist>
<member>arp_filter</member>
<member>arp_ignore</member>
<member>bridge</member>
<member>log_martians</member>
<member>mss</member>
<member>optional</member>
<member>proxyarp</member>
<member>required</member>
<member>routefilter</member>
<member>sourceroute</member>
<member>upnp</member>
<member>wait</member>
</simplelist>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">BROADCAST</emphasis> (Optional) -
{<emphasis role="bold">-</emphasis>|<emphasis
role="bold">detect</emphasis>|<emphasis>address</emphasis>[,<emphasis>address</emphasis>]...}</term>
<listitem>
<para>If you use the special value <emphasis
role="bold">detect</emphasis>, Shorewall will detect the broadcast
address(es) for you if your iptables and kernel include Address Type
Match support.</para>
<para>If your iptables and/or kernel lack Address Type Match support
then you may list the broadcast address(es) for the network(s) to
which the interface belongs. For P-T-P interfaces, this column is
left blank. If the interface has multiple addresses on multiple
subnets then list the broadcast addresses as a comma-separated
list.</para>
<para>If you don't want to give a value for this column but you want
to enter a value in the OPTIONS column, enter <emphasis
role="bold">-</emphasis> in this column.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">OPTIONS</emphasis> (Optional) -
[<emphasis>option</emphasis>[<emphasis
role="bold">,</emphasis><emphasis>option</emphasis>]...]</term>
<listitem>
<para>A comma-separated list of options from the following list. The
order in which you list the options is not significant but the list
should have no embedded white space.</para>
<variablelist>
<varlistentry>
<term><emphasis role="bold">arp_filter[={0|1}]</emphasis></term>
<listitem>
<para>If specified, this interface will only respond to ARP
who-has requests for IP addresses configured on the interface.
If not specified, the interface can respond to ARP who-has
requests for IP addresses on any of the firewall's interface.
The interface must be up when Shorewall is started.</para>
<para>Only those interfaces with the
<option>arp_filter</option> option will have their setting
changed; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.</para>
<para></para>
<note>
<para>This option does not work with a wild-card
<replaceable>interface</replaceable> name (e.g., eth0.+) in
the INTERFACE column.</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">arp_ignore</emphasis>[=<emphasis>number</emphasis>]</term>
<listitem>
<para>If specified, this interface will respond to arp
requests based on the value of <emphasis>number</emphasis>
(defaults to 1).</para>
<para>1 - reply only if the target IP address is local address
configured on the incoming interface</para>
<para>2 - reply only if the target IP address is local address
configured on the incoming interface and the sender's IP
address is part from same subnet on this interface's
address</para>
<para>3 - do not reply for local addresses configured with
scope host, only resolutions for global and link</para>
<para>4-7 - reserved</para>
<para>8 - do not reply for all local addresses</para>
<para></para>
<note>
<para>This option does not work with a wild-card
<replaceable>interface</replaceable> name (e.g., eth0.+) in
the INTERFACE column.</para>
</note>
<para></para>
<warning>
<para>Do not specify <emphasis
role="bold">arp_ignore</emphasis> for any interface involved
in <ulink url="../ProxyARP.htm">Proxy ARP</ulink>.</para>
</warning>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">blacklist</emphasis></term>
<listitem>
<para>Check packets arriving on this interface against the
<ulink
url="shorewall-blacklist.html">shorewall-blacklist</ulink>(5)
file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">bridge</emphasis></term>
<listitem>
<para>Designates the interface as a bridge. Beginning with
Shorewall 4.4.7, setting this option also sets
<option>routeback</option>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">dhcp</emphasis></term>
<listitem>
<para>Specify this option when any of the following are
true:</para>
<orderedlist spacing="compact">
<listitem>
<para>the interface gets its IP address via DHCP</para>
</listitem>
<listitem>
<para>the interface is used by a DHCP server running on
the firewall</para>
</listitem>
<listitem>
<para>the interface has a static IP but is on a LAN
segment with lots of DHCP clients.</para>
</listitem>
<listitem>
<para>the interface is a <ulink
url="../SimpleBridge.html">simple bridge</ulink> with a
DHCP server on one port and DHCP clients on another
port.</para>
<note>
<para>If you use <ulink
url="../bridge-Shorewall-perl.html">Shorewall-perl for
firewall/bridging</ulink>, then you need to include
DHCP-specific rules in <ulink
url="shorewall-rules.html">shorewall-rules</ulink>(8).
DHCP uses UDP ports 67 and 68.</para>
</note>
</listitem>
</orderedlist>
<para>This option allows DHCP datagrams to enter and leave the
interface.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">logmartians[={0|1}]</emphasis></term>
<listitem>
<para>Turn on kernel martian logging (logging of packets with
impossible source addresses. It is strongly suggested that if
you set <emphasis role="bold">routefilter</emphasis> on an
interface that you also set <emphasis
role="bold">logmartians</emphasis>. Even if you do not specify
the <option>routefilter</option> option, it is a good idea to
specify <option>logmartians</option> because your distribution
may have enabled route filtering without you knowing
it.</para>
<para>Only those interfaces with the
<option>logmartians</option> option will have their setting
changed; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.</para>
<para>To find out if route filtering is set on a given
<replaceable>interface</replaceable>, check the contents of
<filename>/proc/sys/net/ipv4/conf/<replaceable>interface</replaceable>/rp_filter</filename>
- a non-zero value indicates that route filtering is
enabled.</para>
<para>Example:</para>
<programlisting> teastep@lists:~$ <command>cat /proc/sys/net/ipv4/conf/eth0/rp_filter </command>
1
teastep@lists:~$ </programlisting>
<para></para>
<note>
<para>This option does not work with a wild-card
<replaceable>interface</replaceable> name (e.g., eth0.+) in
the INTERFACE column.</para>
</note>
<blockquote>
<para>This option may also be enabled globally in the <ulink
url="shorewall.conf.html">shorewall.conf</ulink>(5)
file.</para>
</blockquote>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">maclist</emphasis></term>
<listitem>
<para>Connection requests from this interface are compared
against the contents of <ulink
url="shorewall-maclist.html">shorewall-maclist</ulink>(5). If
this option is specified, the interface must be an ethernet
NIC and must be up before Shorewall is started.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">mss</emphasis>=<emphasis>number</emphasis></term>
<listitem>
<para>Added in Shorewall 4.0.3. Causes forwarded TCP SYN
packets entering or leaving on this interface to have their
MSS field set to the specified
<replaceable>number</replaceable>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">nets=(<emphasis>net</emphasis>[,...])</emphasis></term>
<listitem>
<para>Limit the zone named in the ZONE column to only the
listed networks. The parentheses may be omitted if only a
single <replaceable>net</replaceable> is given (e.g.,
nets=192.168.1.0/24). Limited broadcast to the zone is
supported. Beginning with Shorewall 4.4.1, multicast traffic
to the zone is also supported.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">nets=dynamic</emphasis></term>
<listitem>
<para>Defines the zone as <firstterm>dynamic</firstterm>.
Requires ipset match support in your iptables and kernel. See
<ulink
url="http://www.shorewall.net/Dynamic.html">http://www.shorewall.net/Dynamic.html</ulink>
for further information.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>nosmurfs</term>
<listitem>
<para>Filter packets for smurfs (packets with a broadcast
address as the source).</para>
<para>Smurfs will be optionally logged based on the setting of
SMURF_LOG_LEVEL in <ulink
url="shorewall.conf.html">shorewall.conf</ulink>(5). After
logging, the packets are dropped.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">optional</emphasis></term>
<listitem>
<para>When <option>optional</option> is specified for an
interface, Shorewall will be silent when:</para>
<itemizedlist>
<listitem>
<para>a <filename
class="directory">/proc/sys/net/ipv4/conf/</filename>
entry for the interface cannot be modified (including for
proxy ARP).</para>
</listitem>
<listitem>
<para>The first address of the interface cannot be
obtained.</para>
</listitem>
</itemizedlist>
<para>May not be specified with <emphasis
role="bold">required</emphasis>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">physical</emphasis>=<emphasis
role="bold"><emphasis>name</emphasis></emphasis></term>
<listitem>
<para>Added in Shorewall 4.4.4. When specified, the interface
or port name in the INTERFACE column is a logical name that
refers to the name given in this option. It is useful when you
want to specify the same wildcard port name on two or more
bridges. See <ulink
url="http://www.shorewall.net/bridge-Shorewall-perl.html#Multiple">http://www.shorewall.net/bridge-Shorewall-perl.html#Multiple</ulink>.</para>
<para>If the <emphasis>interface</emphasis> name is a wildcard
name (ends with '+'), then the physical
<emphasis>name</emphasis> must also end in '+'.</para>
<para>If <option>physical</option> is not specified, then it's
value defaults to the <emphasis>interface</emphasis>
name.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">proxyarp[={0|1}]</emphasis></term>
<listitem>
<para>Sets
/proc/sys/net/ipv4/conf/<emphasis>interface</emphasis>/proxy_arp.
Do NOT use this option if you are employing Proxy ARP through
entries in <ulink
url="shorewall-proxyarp.html">shorewall-proxyarp</ulink>(5).
This option is intended solely for use with Proxy ARP
sub-networking as described at: <ulink
url="http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html">http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html.
</ulink></para>
<para><emphasis role="bold">Note</emphasis>: This option does
not work with a wild-card <replaceable>interface</replaceable>
name (e.g., eth0.+) in the INTERFACE column.</para>
<para>Only those interfaces with the <option>proxyarp</option>
option will have their setting changed; the value assigned to
the setting will be the value specified (if any) or 1 if no
value is given.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">required</emphasis></term>
<listitem>
<para>Added in Shorewall 4.4.10. If this option is set, the
firewall will fail to start if the interface is not usable.
May not be specified together with <emphasis
role="bold">optional</emphasis>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">routeback</emphasis></term>
<listitem>
<para>If specified, indicates that Shorewall should include
rules that allow traffic arriving on this interface to be
routed back out that same interface. This option is also
required when you have used a wildcard in the INTERFACE column
if you want to allow traffic between the interfaces that match
the wildcard.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">routefilter[={0|1|2}]</emphasis></term>
<listitem>
<para>Turn on kernel route filtering for this interface
(anti-spoofing measure).</para>
<para>Only those interfaces with the
<option>routefilter</option> option will have their setting
changes; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.</para>
<para>The value 2 is only available with Shorewall 4.4.5.1 and
later when the kernel version is 2.6.31 or later. It specifies
a <firstterm>loose</firstterm> form of reverse path
filtering.</para>
<note>
<para>This option does not work with a wild-card
<replaceable>interface</replaceable> name (e.g., eth0.+) in
the INTERFACE column.</para>
</note>
<para>This option can also be enabled globally in the <ulink
url="shorewall.conf.html">shorewall.conf</ulink>(5)
file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">sourceroute[={0|1}]</emphasis></term>
<listitem>
<para>If this option is not specified for an interface, then
source-routed packets will not be accepted from that interface
(sets
/proc/sys/net/ipv4/conf/<emphasis>interface</emphasis>/accept_source_route
to 1). Only set this option if you know what you are doing.
This might represent a security risk and is usually
unneeded.</para>
<para>Only those interfaces with the
<option>sourceroute</option> option will have their setting
changed; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.</para>
<para></para>
<note>
<para>This option does not work with a wild-card
<replaceable>interface</replaceable> name (e.g., eth0.+) in
the INTERFACE column.</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">tcpflags</emphasis></term>
<listitem>
<para>Packets arriving on this interface are checked for
certain illegal combinations of TCP flags. Packets found to
have such a combination of flags are handled according to the
setting of TCP_FLAGS_DISPOSITION after having been logged
according to the setting of TCP_FLAGS_LOG_LEVEL.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">upnp</emphasis></term>
<listitem>
<para>Incoming requests from this interface may be remapped
via UPNP (upnpd). See <ulink
url="../UPnP.html">http://www.shorewall.net/UPnP.html</ulink>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">upnpclient</emphasis></term>
<listitem>
<para>This option is intended for laptop users who always run
Shorewall on their system yet need to run UPnP-enabled client
apps such as Transmission (BitTorrent client). The option
causes Shorewall to detect the default gateway through the
interface and to accept UDP packets from that gateway. Note
that, like all aspects of UPnP, this is a security hole so use
this option at your own risk.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">wait</emphasis>=<emphasis>seconds</emphasis></term>
<listitem>
<para>Added in Shorewall 4.4.10. Causes the generated script
to wait up to <emphasis>seconds</emphasis> seconds for the
interface to become usable before applying the <emphasis
role="bold">required</emphasis> or <emphasis
role="bold">optional</emphasis> options.</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Example</title>
<variablelist>
<varlistentry>
<term>Example 1:</term>
<listitem>
<para>Suppose you have eth0 connected to a DSL modem and eth1
connected to your local network and that your local subnet is
192.168.1.0/24. The interface gets its IP address via DHCP from
subnet 206.191.149.192/27. You have a DMZ with subnet 192.168.2.0/24
using eth2.</para>
<para>Your entries for this setup would look like:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net eth0 206.191.149.223 dhcp
loc eth1 192.168.1.255
dmz eth2 192.168.2.255</programlisting>
</listitem>
</varlistentry>
<varlistentry>
<term>Example 2:</term>
<listitem>
<para>The same configuration without specifying broadcast addresses
is:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net eth0 detect dhcp
loc eth1 detect
dmz eth2 detect</programlisting>
</listitem>
</varlistentry>
<varlistentry>
<term>Example 3:</term>
<listitem>
<para>You have a simple dial-in system with no ethernet
connections.</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net ppp0 -</programlisting>
</listitem>
</varlistentry>
<varlistentry>
<term>Example 4 (Shorewall 4.4.9 and later):</term>
<listitem>
<para>You have a bridge with no IP address and you want to allow
traffic through the bridge.</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
- br0 - routeback</programlisting>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>FILES</title>
<para>/etc/shorewall/interfaces</para>
</refsect1>
<refsect1>
<title>See ALSO</title>
<para>shorewall(8), shorewall-accounting(5), shorewall-actions(5),
shorewall-blacklist(5), shorewall-hosts(5), shorewall-ipsec(5),
shorewall-maclist(5), shorewall-masq(5), shorewall-nat(5),
shorewall-netmap(5), shorewall-params(5), shorewall-policy(5),
shorewall-providers(5), shorewall-proxyarp(5), shorewall-route_rules(5),
shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5),
shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5),
shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)</para>
</refsect1>
</refentry>
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