Starting/Stopping and Monitoring the Firewall

If you have a permanent internet connection such as DSL or Cable, I recommend that you start the firewall automatically at boot. Once you have installed "firewall" in your init.d directory, simply type "chkconfig --add firewall". This will start the firewall in run levels 2-5 and stop it in run levels 1 and 6. If you want to configure your firewall differently from this default, you can use the "--level" option in chkconfig (see "man chkconfig") or using your favorite graphical run-level editor.

Important Notes:

Shorewall startup is disabled by default. Once you have configured your firewall, you can enable startup by removing the file /etc/shorewall/startup_disabled. Note: Users of the .deb package must edit /etc/default/shorewall and set 'startup=1'.
If you use dialup, you may want to start the firewall in your /etc/ppp/ip-up.local script. I recommend just placing "shorewall restart" in that script.

You can manually start and stop Shoreline Firewall using the "shorewall" shell program:

shorewall start - starts the firewall
shorewall stop - stops the firewall
shorewall restart - stops the firewall (if it's running) and then starts it again
shorewall reset - reset the packet and byte counters in the firewall
shorewall clear - remove all rules and chains installed by Shoreline Firewall
shorewall refresh - refresh the rules involving the broadcast addresses of firewall interfaces and the black and white lists.

If you include the keyword debug as the first argument, then a shell trace of the command is produced as in:

	shorewall debug start 2> /tmp/trace

The above command would trace the 'start' command and place the trace information in the file /tmp/trace

The Shorewall State Diagram is shown at the bottom of this page.

The "shorewall" program may also be used to monitor the firewall.

shorewall status - produce a verbose report about the firewall (iptables -L -n -v)
shorewall show chain - produce a verbose report about chain (iptables -L chain -n -v)
shorewall show nat - produce a verbose report about the nat table (iptables -t nat -L -n -v)
shorewall show tos - produce a verbose report about the mangle table (iptables -t mangle -L -n -v)
shorewall show log - display the last 20 packet log entries.
shorewall show connections - displays the IP connections currently being tracked by the firewall.
shorewall show tc - displays information about the traffic control/shaping configuration.
shorewall monitor [ delay ] - Continuously display the firewall status, last 20 log entries and nat. When the log entry display changes, an audible alarm is sounded.
shorewall hits - Produces several reports about the Shorewall packet log messages in the current /var/log/messages file.
shorewall version - Displays the installed version number.
shorewall check - Performs a cursory validation of the zones, interfaces, hosts, rules and policy files. The "check" command does not parse and validate the generated iptables commands so even though the "check" command completes successfully, the configuration may fail to start. See the recommended way to make configuration changes described below.
shorewall try configuration-directory [ timeout ] - Restart shorewall using the specified configuration and if an error occurs or if the timeout option is given and the new configuration has been up for that many seconds then shorewall is restarted using the standard configuration.
shorewall deny, shorewall reject, shorewall accept and shorewall save implement dynamic blacklisting.
shorewall logwatch (added in version 1.3.2) - Monitors the LOGFILE and produces an audible alarm when new Shorewall messages are logged.

Finally, the "shorewall" program may be used to dynamically alter the contents of a zone.

shorewall add interface[:host] zone - Adds the specified interface (and host if included) to the specified zone.
shorewall delete interface[:host] zone - Deletes the specified interface (and host if included) from the specified zone.

Examples:

shorewall add ipsec0:192.0.2.24 vpn1 -- adds the address 192.0.2.24 from interface ipsec0 to the zone vpn1
shorewall delete ipsec0:192.0.2.24 vpn1 -- deletes the address 192.0.2.24 from interface ipsec0 from zone vpn1

The shorewall start, shorewall restart, shorewall check and shorewall try commands allow you to specify which Shorewall configuration to use:

shorewall [ -c configuration-directory ] {start|restart|check}
shorewall try configuration-directory

If a configuration-directory is specified, each time that Shorewall is going to use a file in /etc/shorewall it will first look in the configuration-directory . If the file is present in the configuration-directory, that file will be used; otherwise, the file in /etc/shorewall will be used.

When changing the configuration of a production firewall, I recommend the following:

mkdir /etc/test
cd /etc/test
<copy any files that you need to change from /etc/shorewall to . and change them here>
shorewall -c . check
<correct any errors found by check and check again>
/sbin/shorewall try .

If the configuration starts but doesn't work, just "shorewall restart" to restore the old configuration. If the new configuration fails to start, the "try" command will automatically start the old one for you.

When the new configuration works then just

cp * /etc/shorewall
cd
rm -rf /etc/test

The Shorewall State Diargram is depicted below.

You will note that the commands that result in state transitions use the word "firewall" rather than "shorewall". That is because the actual transitions are done by /usr/lib/shorewall/firewall (/usr/share/shorewall/firewall on Debian); /sbin/shorewall runs 'firewall" according to the following table:

shorewall start	firewall start
shorewall stop	firewall stop
shorewall restart	firewall restart
shorewall add	firewall add
shorewall delete	firewall delete
shorewall refresh	firewall refresh
shorewall try	firewall -c <new configuration> restart If unsuccessful then firewall start (standard configuration) If timeout then firewall restart (standard configuration)

Updated 2/10/2003 - Tom Eastep