SHOREWALL-NESTING(5)						  [FIXME: manual]					      SHOREWALL-NESTING(5)

NAME

       nesting - Shorewall Nested Zones

SYNOPSIS

       child-zone[:parent-zone[,parent-zone]...]

DESCRIPTION

       In shorewall-zones[1](5), a zone may be declared to be a sub-zone of one or more other zones using the above syntax. The child-zone may be
       neither the firewall zone nor a vserver zone. The firewall zone may not appear as a parent zone, although all vserver zones are handled as
       sub-zones of the firewall zone.

       Where zones are nested, the CONTINUE policy in shorewall-policy[2](5) allows hosts that are within multiple zones to be managed under the
       rules of all of these zones.

EXAMPLE

       /etc/shorewall/zones:

		   #ZONE    TYPE	OPTION
		   fw	    firewall
		   net	    ipv4
		   sam:net  ipv4
		   loc	    ipv4

       /etc/shorewall/interfaces:

		   #ZONE     INTERFACE	   BROADCAST	 OPTIONS
		   -	     eth0	   detect	 dhcp,norfc1918
		   loc	     eth1	   detect

       /etc/shorewall/hosts:

		   #ZONE     HOST(S)			 OPTIONS
		   net	     eth0:0.0.0.0/0
		   sam	     eth0:206.191.149.197

       /etc/shorewall/policy:

		   #SOURCE	DEST	    POLICY	 LOG LEVEL
		   loc		net	    ACCEPT
		   sam		all	    CONTINUE
		   net		all	    DROP	 info
		   all		all	    REJECT	 info

       The second entry above says that when Sam is the client, connection requests should first be processed under rules where the source zone is
       sam and if there is no match then the connection request should be treated under rules where the source zone is net. It is important that
       this policy be listed BEFORE the next policy (net to all). You can have this policy generated for you automatically by using the
       IMPLICIT_CONTINUE option in shorewall.conf[3](5).

       Partial /etc/shorewall/rules:

		   #ACTION   SOURCE    DEST	       PROTO	DEST PORT(S)
		   ...
		   DNAT      sam       loc:192.168.1.3 tcp	ssh
		   DNAT      net       loc:192.168.1.5 tcp	www
		   ...

       Given these two rules, Sam can connect to the firewall's internet interface with ssh and the connection request will be forwarded to
       192.168.1.3. Like all hosts in the net zone, Sam can connect to the firewall's internet interface on TCP port 80 and the connection request
       will be forwarded to 192.168.1.5. The order of the rules is not significant. Sometimes it is necessary to suppress port forwarding for a
       sub-zone. For example, suppose that all hosts can SSH to the firewall and be forwarded to 192.168.1.5 EXCEPT Sam. When Sam connects to the
       firewall's external IP, he should be connected to the firewall itself. Because of the way that Netfilter is constructed, this requires two
       rules as follows:

		   #ACTION   SOURCE    DEST	       PROTO	DEST PORT(S)
		   ...
		   ACCEPT+   sam       $FW	       tcp	ssh
		   DNAT      net       loc:192.168.1.3 tcp	ssh
		   ...

       The first rule allows Sam SSH access to the firewall. The second rule says that any clients from the net zone with the exception of those
       in the "sam" zone should have their connection port forwarded to 192.168.1.3. If you need to exclude more than one zone, simply use
       multiple ACCEPT+ rules. This technique also may be used when the ACTION is REDIRECT.

       Care must be taken when nesting occurs as a result of the use of wildcard interfaces (interface names ends in '+').

       Here's an example.  /etc/shorewall/zones:

       /etc/shorewall/interfaces:

		   #ZONE    INTERFACE	   BROADCAST	    OPTIONS
		   net	    ppp0
		   loc	    eth1
		   loc	    ppp+
		   dmz	    eth2

       Because the net zone is declared before the loc zone, net is an implicit sub-zone of loc and in the absence of a net->... CONTINUE policy,
       traffic from the net zone will not be passed through loc->... rules. But DNAT and REDIRECT rules are an exception!

       o   DNAT and REDIRECT rules generate two Netfilter rules: a 'nat' table rule that rewrites the destination IP address and/or port number,
	   and a 'filter' table rule that ACCEPTs the rewritten connection.

       o   Policies only affect the 'filter' table.

       As a consequence, the following rules will have unexpected behavior:

		   #ACTION     SOURCE		    DEST      PROTO	   DEST
		   #							   PORT(S)
		   ACCEPT      net		    dmz       tcp	   80
		   REDIRECT    loc		    3128      tcp	   80

       The second rule is intended to redirect local web requests to a proxy running on the firewall and listening on TCP port 3128. But the 'nat'
       part of that rule will cause all connection requests for TCP port 80 arriving on interface ppp+ (including ppp0!) to have their destination
       port rewritten to 3128. Hence, the web server running in the DMZ will be inaccessible from the web.

       The above problem can be corrected in several ways.

       The preferred way is to use the ifname pppd option to change the 'net' interface to something other than ppp0. That way, it won't match
       ppp+.

       If you are running Shorewall version 4.1.4 or later, a second way is to simply make the nested zones explicit:

		   #ZONE    TYPE	OPTION
		   fw	    firewall
		   loc	    ipv4
		   net:loc  ipv4
		   dmz	    ipv4

       If you take this approach, be sure to set IMPLICIT_CONTINUE=No in shorewall.conf.

       When using other Shorewall versions, another way is to rewrite the DNAT rule (assume that the local zone is entirely within
       192.168.2.0/23):

		   #ACTION     SOURCE		      DEST	PROTO	   DEST
		   #							   PORT(S)
		   ACCEPT      net		      dmz	tcp	   80
		   REDIRECT    loc:192.168.2.0/23     3128	tcp	   80

       Another way is to restrict the definition of the loc zone:

       /etc/shorewall/interfaces:

		   #ZONE    INTERFACE	   BROADCAST	    OPTIONS
		   net	    ppp0
		   loc	    eth1
		   -	    ppp+
		   dmz	    eth2

       /etc/shorewall/hosts:

		   #ZONE    HOST(S)		OPTIONS
		   loc	    ppp+:192.168.2.0/23

FILES

       /etc/shorewall/zones

       /etc/shorewall/interfaces

       /etc/shorewall/hosts

       /etc/shorewall/policy

       /etc/shorewall/rules

SEE ALSO

       shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5), shorewall-hosts(5), shorewall_interfaces(5),
       shorewall-ipsets(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-rtrules(5), shorewall-routestopped(5), shorewall-rules(5),
       shorewall.conf(5), shorewall-secmarks(5), shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5), shorewall-tos(5),
       shorewall-tunnels(5), shorewall-zones(5)

NOTES

	1. shorewall-zones
	   http://www.shorewall.net/manpages/shorewall-zones.html

	2. shorewall-policy
	   http://www.shorewall.net/manpages/shorewall-policy.html

	3. shorewall.conf
	   http://www.shorewall.net/manpages/shorewall.conf.html

[FIXME: source] 						    06/28/2012						      SHOREWALL-NESTING(5)