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A little maintenance of the FAQ

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git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@4517 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
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teastep 2006-09-04 16:55:31 +00:00
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docs/FAQ.xml
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@ -399,7 +399,9 @@ DNAT net fw:192.168.1.1:22 tcp 4104</programlisting>
192.168.1.0/24, then:<warning>
<para>All traffic redirected through use of this hack will look to
the server as if it came from the firewall (192.168.1.254) rather
than from the original client!</para>
than from the original client! So the server's access logs will be
useless for determining which local hosts are accessing the
server.</para>
</warning></para>
<itemizedlist>
@ -605,8 +607,8 @@ to debug/develop the newnat interface.</programlisting></para>
<section>
<title>Open Ports</title>
<section id="faq0">
<title>(FAQ 0) How do I Open Ports in Shorewall?</title>
<section id="faq51">
<title>(FAQ 51) How do I Open Ports in Shorewall?</title>
<para><emphasis role="bold">Answer:</emphasis> No one who has installed
Shorewall using one of the <ulink
@ -665,11 +667,11 @@ to debug/develop the newnat interface.</programlisting></para>
<filename>/usr/share/shorewall/action.Drop</filename> which in turn
invokes the <emphasis role="bold">Auth</emphasis> macro (defined in
<filename>/usr/share/shorewall/macro.Auth</filename>) specifying the
<emphasis role="bold">DROP</emphasis> action (i.e., <emphasis
role="bold">Auth/DROP</emphasis>). This is necessary to prevent outgoing
connection problems to services that use the <quote>Auth</quote>
mechanism for identifying requesting users. That is the only service
which the default setup rejects.</para>
<emphasis role="bold">REJECT</emphasis> action (i.e., <emphasis
role="bold">Auth/REJECT</emphasis>). This is necessary to prevent
outgoing connection problems to services that use the
<quote>Auth</quote> mechanism for identifying requesting users. That is
the only service which the default setup rejects.</para>
<para>If you are seeing closed TCP ports other than 113 (auth) then
either you have added rules to REJECT those ports or a router outside of
@ -712,26 +714,6 @@ to debug/develop the newnat interface.</programlisting></para>
PortSentry.</para>
</section>
</section>
<section id="faq51">
<title>(FAQ 51) How do I "Open a Port" with Shorewall</title>
<para><emphasis role="bold">Answer</emphasis>: It depends…</para>
<para>If the application serving the port is running on the same system
as Shorewall then add this rule:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT net $FW &lt;protocol&gt; &lt;port number&gt;</programlisting>
<para>Where &lt;protocol&gt; is either <emphasis>tcp</emphasis> or
<emphasis>udp</emphasis> and &lt;port number&gt; is the port that you
wish to "open".</para>
<para>If the application serving the port is running on one of the
systems in your local network then please see <link linkend="faq1">FAQ
1</link>.</para>
</section>
</section>
<section>
@ -1618,6 +1600,16 @@ iptables: Invalid argument
</listitem>
</orderedlist>
</section>
<section id="faq59">
<title>(FAQ 59) After I start Shorewall, there are lots of unused
Netfilter modules loaded. How do I avoid that?</title>
<para>Answer: Copy <filename>/usr/share/shorewall/modules</filename> (or
<filename>/usr/share/shorewall/xmodules</filename> if appropriate) to
<filename>/etc/shorewall/modules </filename>and modify the copy to
include only the modules that you need.</para>
</section>
</section>
<section>
@ -1664,7 +1656,7 @@ iptables: Invalid argument
<title>About Shorewall</title>
<section id="faq10">
<title>(FAQ 10) What Distributions does it work with?</title>
<title>(FAQ 10) What Distributions does Shorewall work with?</title>
<para>Shorewall works with any GNU/Linux distribution that includes the
<ulink url="shorewall_prerequisites.htm">proper
@ -1672,7 +1664,7 @@ iptables: Invalid argument
</section>
<section id="faq11">
<title>(FAQ 11) What Features does it have?</title>
<title>(FAQ 11) What Features does Shorewall have?</title>
<para><emphasis role="bold">Answer:</emphasis> See the <ulink
url="shorewall_features.htm">Shorewall Feature List</ulink>.</para>
@ -1681,8 +1673,9 @@ iptables: Invalid argument
<section id="faq12">
<title>(FAQ 12) Is there a GUI?</title>
<para><emphasis role="bold">Answer:</emphasis> Yes. Shorewall support is
included in Webmin 1.060 and later versions. See <ulink
<para><emphasis role="bold">Answer:</emphasis> Yes and No. Shorewall
support is included in Webmin 1.060 and later versions but the support
is woefully out of date. See <ulink
url="http://www.webmin.com">http://www.webmin.com</ulink></para>
</section>
@ -1707,7 +1700,7 @@ iptables: Invalid argument
</section>
<section id="faq25">
<title>(FAQ 25) How to I tell which version of Shorewall or Shorewall
<title>(FAQ 25) How do I tell which version of Shorewall or Shorewall
Lite I am running?</title>
<para>At the shell prompt, type:</para>
@ -1859,10 +1852,10 @@ iptables: Invalid argument
<programlisting>Mar 1 18:20:07 Mail kernel: Shorewall:OUTPUT:REJECT:IN= OUT=eth0 SRC=192.168.1.2 DST=192.168.1.1 LEN=60
TOS=0x00 PREC=0x00 TTL=64 ID=26774 DF PROTO=TCP SPT=32797 DPT=80 WINDOW=5840 RES=0x00 SYN URGP=0 </programlisting>
<para>Answer: The fact that the message is being logged from the
OUTPUT chain means that the destination IP address is not in any
defined zone (see <link linkend="faq17">FAQ 17</link>). You need
to:</para>
<para><emphasis role="bold">Answer</emphasis>: The fact that the
message is being logged from the OUTPUT chain means that the
destination IP address is not in any defined zone (see <link
linkend="faq17">FAQ 17</link>). You need to:</para>
<orderedlist>
<listitem>
@ -1907,7 +1900,7 @@ ACCEPT loc modem tcp 80</programlisting>
eth0 eth1 # eth1 = interface to local network</programlisting>
<para>For an example of this when the ADSL/Cable modem is bridged, see
<ulink url="myfiles.htm">my configuration</ulink>. In that case, I
<ulink url="XenMyWay.html">my configuration</ulink>. In that case, I
masquerade using the IP address of my local interface!</para>
</section>
</section>
@ -1962,7 +1955,7 @@ eth0 eth1 # eth1 = interface to local netwo
shorewall.net, the two laptop systems have the full Shorewall product
installed as does my personal Linux desktop system. All other Linux
systems that run a firewall use Shorewall Lite and have their
configuration directories on my desktop.</para>
configuration directories on my desktop system.</para>
</section>
</section>
@ -2095,13 +2088,13 @@ REJECT fw net:216.239.39.99 all</programlisting>Given that
name-based multiple hosting is a common practice (another example:
lists.shorewall.net and www1.shorewall.net are both hosted on the same
system with a single IP address), it is not possible to filter
connections to a particular name by examiniation of protocol headers
connections to a particular name by examination of protocol headers
alone. While some protocols such as <ulink url="FTP.html">FTP</ulink>
require the firewall to examine and possibly modify packet payload,
parsing the payload of individual packets doesn't always work because
the application-level data stream can be split across packets in
arbitrary ways. This is one of the weaknesses of the 'string match'
Netfilter extension available in Patch-O-Matic. The only sure way to
Netfilter extension available in Patch-O-Matic-ng. The only sure way to
filter on packet content is to proxy the connections in question -- in
the case of HTTP, this means running something like <ulink
url="Shorewall_Squid_Usage.html">Squid</ulink>. Proxying allows the