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<h1 align="center"><font color="#ffffff">Logging</font></h1>
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<br>
By default, Shorewall directs NetFilter to log using syslog (8). Syslog
classifies log messages by a <i>facility</i> and a <i>priority</i> (using
the notation <i>facility.priority</i>). <br>
<br>
The facilities defined by syslog are <i>auth, authpriv, cron, daemon,
kern, lpr, mail, mark, news, syslog, user, uucp</i> and <i>local0</i>
through <i>local7</i>.<br>
<br>
Throughout the Shorewall documentation, I will use the term <i>level</i>
rather than <i>priority</i> since <i>level</i> is the term used by NetFilter.
The syslog documentation uses the term <i>priority</i>.<br>
<h3>Syslog Levels<br>
</h3>
Syslog levels are a method of describing to syslog (8) the importance
of a message and a number of Shorewall parameters have a syslog level
as their value.<br>
<br>
Valid levels are:<br>
<br>
7
debug<br>
6
info<br>
5
notice<br>
4
warning<br>
3
err<br>
2
crit<br>
1
alert<br>
0
emerg<br>
<br>
For most Shorewall logging, a level of 6 (info) is appropriate.
Shorewall log messages are generated by NetFilter and are logged using
the <i>kern</i> facility and the level that you specify. If you are
unsure of the level to choose, 6 (info) is a safe bet. You may specify
levels by name or by number.<br>
<br>
Syslogd writes log messages to files (typically in /var/log/*)
based on their facility and level. The mapping of these facility/level
pairs to log files is done in /etc/syslog.conf (5). If you make changes
to this file, you must restart syslogd before the changes can take effect.<br>
<h3>Configuring a Separate Log for Shorewall Messages</h3>
There are a couple of limitations to syslogd-based logging:<br>
<ol>
<li>If you give, for example, kern.info it's own log destination then
that destination will also receive all kernel messages of levels 5 (notice)
through 0 (emerg).</li>
<li>All kernel.info messages will go to that destination and not just
those from NetFilter.<br>
</li>
</ol>
Beginning with Shorewall version 1.3.12, if your kernel has ULOG
target support (and most vendor-supplied kernels do), you may also specify
a log level of ULOG (must be all caps). When ULOG is used, Shorewall will
direct netfilter to log the related messages via the ULOG target which
will send them to a process called 'ulogd'. The ulogd program is available
from http://www.gnumonks.org/projects/ulogd and can be configured to log
all Shorewall message to their own log file.<br>
<br>
<b>Note: </b>The ULOG logging mechanism is <u>completely separate</u>
from syslog. Once you switch to ULOG, the settings in /etc/syslog.conf have
absolutely no effect on your Shorewall logging (except for Shorewall status
messages which still go to syslog).<br>
<br>
You will need to have the kernel source available to compile ulogd.<br>
<br>
Download the ulod tar file and:<br>
<ol>
<li>Be sure that /usr/src/linux is linked to your kernel source tree<br>
</li>
<li>cd /usr/local/src (or wherever you do your builds)</li>
<li>tar -zxf <i>source-tarball-that-you-downloaded</i></li>
<li>cd ulogd-<i>version</i><br>
</li>
<li>./configure</li>
<li>make</li>
<li>make install<br>
</li>
</ol>
If you are like me and don't have a development environment on your
firewall, you can do the first six steps on another system then either NFS
mount your /usr/local/src directory or tar up the /usr/local/src/ulogd-<i>version</i>
directory and move it to your firewall system.<br>
<br>
Now on the firewall system, edit /usr/local/etc/ulogd.conf and set:<br>
<ol>
<li>syslogfile <i><file that you wish to log to></i></li>
<li>syslogsync 1</li>
</ol>
Also on the firewall system:<br>
<blockquote>touch <<i>file that you wish to log to</i>><br>
</blockquote>
I also copied the file /usr/local/src/ulogd-<i>version</i>/ulogd.init
to /etc/init.d/ulogd. I had to edit the line that read "daemon /usr/local/sbin/ulogd"
to read daemon /usr/local/sbin/ulogd -d". On a RedHat system, a simple
"chkconfig --level 3 ulogd on" starts ulogd during boot up. Your init system
may need something else done to activate the script.<br>
<br>
You will need to change all instances of log levels (usually 'info') in
your configuration files to 'ULOG' - this includes entries in the policy,
rules and shorewall.conf files. Here's what I have:<br>
<pre> [root@gateway shorewall]# grep ULOG *<br> policy:loc fw REJECT ULOG<br> policy:net all DROP ULOG 10/sec:40<br> policy:all all REJECT ULOG<br> rules:REJECT:ULOG loc net tcp 6667<br> shorewall.conf:TCP_FLAGS_LOG_LEVEL=ULOG<br> shorewall.conf:RFC1918_LOG_LEVEL=ULOG<br> [root@gateway shorewall]#<br></pre>
Finally edit /etc/shorewall/shorewall.conf and set LOGFILE=<i><file
that you wish to log to></i>. This tells the /sbin/shorewall program
where to look for the log when processing its "show log", "logwatch" and
"monitor" commands.<br>
<p><font size="2"> Updated 7/25/2003 - <a href="support.htm">Tom Eastep</a>
</font></p>
<p><a href="copyright.htm"><font size="2">Copyright</font> ©
<font size="2">2001, 2002, 2003 Thomas M. Eastep</font></a><br>
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