shorewall_code/STABLE/documentation/troubleshoot.htm
teastep f3790a541b Shorwall 1.4.0
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<h1 align="center"><font color="#ffffff">Shorewall Troubleshooting<img
src="images/obrasinf.gif" alt="Beating head on table" width="90"
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<h3 align="left">Check the Errata</h3>
<p align="left">Check the <a href="errata.htm">Shorewall Errata</a> to be
sure that there isn't an update that you are missing for your version
of the firewall.</p>
<h3 align="left">Check the FAQs</h3>
<p align="left">Check the <a href="FAQ.htm">FAQs</a> for solutions to common
problems.</p>
<h3 align="left">If the firewall fails to start</h3>
If you receive an error message when starting or restarting
the firewall and you can't determine the cause, then do the following:
<ul>
<li>Make a note of the error message that you see.<br>
</li>
<li>shorewall debug start 2&gt; /tmp/trace</li>
<li>Look at the /tmp/trace file and see if that helps you
determine what the problem is. Be sure you find the place in the log
where the error message you saw is generated -- in 99.9% of the cases, it
will not be near the end of the log because after startup errors, Shorewall
goes through a "shorewall stop" phase which will also be traced.</li>
<li>If you still can't determine what's wrong then see the
<a href="support.htm">support page</a>.</li>
</ul>
Here's an example. During startup, a user sees the following:<br>
<blockquote>
<pre>Adding Common Rules<br>iptables: No chain/target/match by that name<br>Terminated<br></pre>
</blockquote>
A search through the trace for "No chain/target/match by that name" turned
up the following:<3A>
<blockquote>
<pre>+ echo 'Adding Common Rules'<br>+ add_common_rules<br>+ run_iptables -A reject -p tcp -j REJECT --reject-with tcp-reset<br>++ echo -A reject -p tcp -j REJECT --reject-with tcp-reset<br>++ sed 's/!/! /g'<br>+ iptables -A reject -p tcp -j REJECT --reject-with tcp-reset<br>iptables: No chain/target/match by that name<br></pre>
</blockquote>
The command that failed was: "iptables -A reject -p tcp -j REJECT --reject-with
tcp-reset". In this case, the user had compiled his own kernel and had forgotten
to include REJECT target support (see <a href="kernel.htm">kernel.htm</a>)
<h3>Your network environment</h3>
<p>Many times when people have problems with Shorewall, the problem is
actually an ill-conceived network setup. Here are several popular snafus:
</p>
<ul>
<li>Port Forwarding where client and server are in
the same subnet. See <a href="FAQ.htm">FAQ 2.</a></li>
<li>Changing the IP address of a local system to be in the
external subnet, thinking that Shorewall will suddenly believe that
the system is in the 'net' zone.</li>
<li>Multiple interfaces connected to the same HUB or Switch.
Given the way that the Linux kernel respond to ARP "who-has" requests,
this type of setup does NOT work the way that you expect it to.</li>
</ul>
<h3 align="left">If you are having connection problems:</h3>
<p align="left">If the appropriate policy for the connection that you are
trying to make is ACCEPT, please DO NOT ADD ADDITIONAL ACCEPT RULES TRYING
TO MAKE IT WORK. Such additional rules will NEVER make it work, they
add clutter to your rule set and they represent a big security hole in
the event that you forget to remove them later.</p>
<p align="left">I also recommend against setting all of your policies to
ACCEPT in an effort to make something work. That robs you of one of
your best diagnostic tools - the "Shorewall" messages that Netfilter
will generate when you try to connect in a way that isn't permitted
by your rule set.</p>
<p align="left">Check your log ("/sbin/shorewall show log"). If you don't
see Shorewall messages, then your problem is probably NOT a Shorewall
problem. If you DO see packet messages, it may be an indication that you
are missing one or more rules -- see <a href="FAQ.htm#faq17">FAQ 17</a>.</p>
<p align="left">While you are troubleshooting, it is a good idea to clear
two variables in /etc/shorewall/shorewall.conf:</p>
<p align="left">LOGRATE=""<br>
LOGBURST=""</p>
<p align="left">This way, you will see all of the log messages being
generated (be sure to restart shorewall after clearing these variables).</p>
<p align="left">Example:</p>
<font face="Century Gothic, Arial, Helvetica">
<p align="left"><font face="Courier">Jun 27 15:37:56 gateway kernel:
Shorewall:all2all:REJECT:IN=eth2 OUT=eth1 SRC=192.168.2.2 DST=192.168.1.3
LEN=67 TOS=0x00 PREC=0x00 TTL=63 ID=5805 DF PROTO=UDP SPT=1803 DPT=53
LEN=47</font></p>
</font>
<p align="left">Let's look at the important parts of this message:</p>
<ul>
<li>all2all:REJECT - This packet was REJECTed out of the all2all
chain -- the packet was rejected under the "all"-&gt;"all" REJECT
policy (see <a href="FAQ.htm#faq17">FAQ 17).</a></li>
<li>IN=eth2 - the packet entered the firewall via eth2</li>
<li>OUT=eth1 - if accepted, the packet would be sent on eth1</li>
<li>SRC=192.168.2.2 - the packet was sent by 192.168.2.2</li>
<li>DST=192.168.1.3 - the packet is destined for 192.168.1.3</li>
<li>PROTO=UDP - UDP Protocol</li>
<li>DPT=53 - DNS</li>
</ul>
<p align="left">In this case, 192.168.2.2 was in the "dmz" zone and 192.168.1.3
is in the "loc" zone. I was missing the rule:</p>
<p align="left">ACCEPT<EFBFBD><EFBFBD><EFBFBD> dmz<6D><7A><EFBFBD> loc<6F><63><EFBFBD> udp<64><70><EFBFBD> 53<br>
</p>
<p align="left">See <a href="FAQ.htm#faq17">FAQ 17</a> for additional information
about how to interpret the chain name appearing in a Shorewall log message.<br>
</p>
<h3 align="left">'Ping' Problems?</h3>
Either can't ping when you think you should be able to or are able to ping
when you think that you shouldn't be allowed? Shorewall's 'Ping' Management<a
href="ping.html"> is described here</a>.<br>
<h3 align="left">Other Gotchas</h3>
<ul>
<li>Seeing rejected/dropped packets logged out of the INPUT
or FORWARD chains? This means that:
<ol>
<li>your zone definitions are screwed up and the host that
is sending the packets or the destination host isn't in any zone
(using an <a href="Documentation.htm#Hosts">/etc/shorewall/hosts</a>
file are you?); or</li>
<li>the source and destination hosts are both connected to
the same interface and you don't have a policy or rule for the
source zone to or from the destination zone.</li>
</ol>
</li>
<li>Remember that Shorewall doesn't automatically allow ICMP
type 8 ("ping") requests to be sent between zones. If you want
pings to be allowed between zones, you need a rule of the form:<br>
<br>
<20><><EFBFBD> ACCEPT<50><54><EFBFBD> &lt;source zone&gt;<EFBFBD><EFBFBD><EFBFBD> &lt;destination zone&gt;<EFBFBD><EFBFBD><EFBFBD>
icmp<6D><70><EFBFBD> echo-request<br>
<br>
The ramifications of this can be subtle. For example, if you
have the following in /etc/shorewall/nat:<br>
<br>
<20><><EFBFBD> 10.1.1.2<EFBFBD><EFBFBD><EFBFBD> eth0<68><30><EFBFBD> 130.252.100.18<br>
<br>
and you ping 130.252.100.18, unless you have allowed icmp
type 8 between the zone containing the system you are pinging from
and the zone containing 10.1.1.2, the ping requests will be dropped.<2E></li>
<li>If you specify "routefilter" for an interface, that
interface must be up prior to starting the firewall.</li>
<li>Is your routing correct? For example, internal systems
usually need to be configured with their default gateway set to
the IP address of their nearest firewall interface. One often overlooked
aspect of routing is that in order for two hosts to communicate, the
routing between them must be set up <u>in both directions.</u> So
when setting up routing between <b>A</b> and<b> B</b>, be sure to
verify that the route from <b>B</b> back to <b>A</b> is defined.</li>
<li>Some versions of LRP (EigerStein2Beta for example) have
a shell with broken variable expansion. <a
href="ftp://ftp.shorewall.net/pub/shorewall/ash.gz"> You can get a corrected
shell from the Shorewall Errata download site.</a> </li>
<li>Do you have your kernel properly configured? <a
href="kernel.htm">Click here to see my kernel configuration.</a> </li>
<li>Shorewall requires the "ip" program. That program is
generally included in the "iproute" package which should be included
with your distribution (though many distributions don't install iproute
by default). You may also download the latest source tarball from <a
href="ftp://ftp.inr.ac.ru/ip-routing" target="_blank"> ftp://ftp.inr.ac.ru/ip-routing</a>
.</li>
<li>Problems with NAT? Be sure that you let Shorewall
add all external addresses to be use with NAT unless you have set <a
href="Documentation.htm#Aliases"> ADD_IP_ALIASES</a> =No in /etc/shorewall/shorewall.conf.</li>
</ul>
<h3>Still Having Problems?</h3>
<p>See the<a href="support.htm"> support page.<br>
</a></p>
<font face="Century Gothic, Arial, Helvetica">
<blockquote> </blockquote>
</font>
<p><font size="2">Last updated 2/21/2003 - Tom Eastep</font> </p>
<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font>
<20> <font size="2">2001, 2002 Thomas M. Eastep.</font></a></font><br>
</p>
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