1SHOREWALL-NESTING(5)            [FIXME: manual]           SHOREWALL-NESTING(5)
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NAME

6       nesting - Shorewall Nested Zones
7

SYNOPSIS

9       child-zone[:parent-zone[,parent-zone]...]
10

DESCRIPTION

12       In shorewall-zones[1](5), a zone may be declared to be a sub-zone of
13       one or more other zones using the above syntax. The child-zone may be
14       neither the firewall zone nor a vserver zone. The firewall zone may not
15       appear as a parent zone, although all vserver zones are handled as
16       sub-zones of the firewall zone.
17
18       Where zones are nested, the CONTINUE policy in shorewall-policy[2](5)
19       allows hosts that are within multiple zones to be managed under the
20       rules of all of these zones.
21

EXAMPLE

23       /etc/shorewall/zones:
24
25                   #ZONE    TYPE        OPTION
26                   fw       firewall
27                   net      ipv4
28                   sam:net  ipv4
29                   loc      ipv4
30
31       /etc/shorewall/interfaces:
32
33                   #ZONE     INTERFACE     BROADCAST     OPTIONS
34                   -         eth0          detect        dhcp,norfc1918
35                   loc       eth1          detect
36
37       /etc/shorewall/hosts:
38
39                   #ZONE     HOST(S)                     OPTIONS
40                   net       eth0:0.0.0.0/0
41                   sam       eth0:206.191.149.197
42
43       /etc/shorewall/policy:
44
45                   #SOURCE      DEST        POLICY       LOG LEVEL
46                   loc          net         ACCEPT
47                   sam          all         CONTINUE
48                   net          all         DROP         info
49                   all          all         REJECT       info
50
51       The second entry above says that when Sam is the client, connection
52       requests should first be processed under rules where the source zone is
53       sam and if there is no match then the connection request should be
54       treated under rules where the source zone is net. It is important that
55       this policy be listed BEFORE the next policy (net to all). You can have
56       this policy generated for you automatically by using the
57       IMPLICIT_CONTINUE option in shorewall.conf[3](5).
58
59       Partial /etc/shorewall/rules:
60
61                   #ACTION   SOURCE    DEST            PROTO    DEST PORT(S)
62                   ...
63                   DNAT      sam       loc:192.168.1.3 tcp      ssh
64                   DNAT      net       loc:192.168.1.5 tcp      www
65                   ...
66
67       Given these two rules, Sam can connect to the firewall's internet
68       interface with ssh and the connection request will be forwarded to
69       192.168.1.3. Like all hosts in the net zone, Sam can connect to the
70       firewall's internet interface on TCP port 80 and the connection request
71       will be forwarded to 192.168.1.5. The order of the rules is not
72       significant. Sometimes it is necessary to suppress port forwarding for
73       a sub-zone. For example, suppose that all hosts can SSH to the firewall
74       and be forwarded to 192.168.1.5 EXCEPT Sam. When Sam connects to the
75       firewall's external IP, he should be connected to the firewall itself.
76       Because of the way that Netfilter is constructed, this requires two
77       rules as follows:
78
79                   #ACTION   SOURCE    DEST            PROTO    DEST PORT(S)
80                   ...
81                   ACCEPT+   sam       $FW             tcp      ssh
82                   DNAT      net       loc:192.168.1.3 tcp      ssh
83                   ...
84
85       The first rule allows Sam SSH access to the firewall. The second rule
86       says that any clients from the net zone with the exception of those in
87       the “sam” zone should have their connection port forwarded to
88       192.168.1.3. If you need to exclude more than one zone, simply use
89       multiple ACCEPT+ rules. This technique also may be used when the ACTION
90       is REDIRECT.
91
92       Care must be taken when nesting occurs as a result of the use of
93       wildcard interfaces (interface names ends in '+').
94
95       Here's an example.  /etc/shorewall/zones:
96
97       /etc/shorewall/interfaces:
98
99                   #ZONE    INTERFACE      BROADCAST        OPTIONS
100                   net      ppp0
101                   loc      eth1
102                   loc      ppp+
103                   dmz      eth2
104
105       Because the net zone is declared before the loc zone, net is an
106       implicit sub-zone of loc and in the absence of a net->... CONTINUE
107       policy, traffic from the net zone will not be passed through loc->...
108       rules. But DNAT and REDIRECT rules are an exception!
109
110       ·   DNAT and REDIRECT rules generate two Netfilter rules: a 'nat' table
111           rule that rewrites the destination IP address and/or port number,
112           and a 'filter' table rule that ACCEPTs the rewritten connection.
113
114       ·   Policies only affect the 'filter' table.
115
116       As a consequence, the following rules will have unexpected behavior:
117
118                   #ACTION     SOURCE               DEST      PROTO        DEST
119                   #                                                       PORT(S)
120                   ACCEPT      net                  dmz       tcp          80
121                   REDIRECT    loc                  3128      tcp          80
122
123       The second rule is intended to redirect local web requests to a proxy
124       running on the firewall and listening on TCP port 3128. But the 'nat'
125       part of that rule will cause all connection requests for TCP port 80
126       arriving on interface ppp+ (including ppp0!) to have their destination
127       port rewritten to 3128. Hence, the web server running in the DMZ will
128       be inaccessible from the web.
129
130       The above problem can be corrected in several ways.
131
132       The preferred way is to use the ifname pppd option to change the 'net'
133       interface to something other than ppp0. That way, it won't match ppp+.
134
135       If you are running Shorewall version 4.1.4 or later, a second way is to
136       simply make the nested zones explicit:
137
138                   #ZONE    TYPE        OPTION
139                   fw       firewall
140                   loc      ipv4
141                   net:loc  ipv4
142                   dmz      ipv4
143
144       If you take this approach, be sure to set IMPLICIT_CONTINUE=No in
145       shorewall.conf.
146
147       When using other Shorewall versions, another way is to rewrite the DNAT
148       rule (assume that the local zone is entirely within 192.168.2.0/23):
149
150                   #ACTION     SOURCE                 DEST      PROTO      DEST
151                   #                                                       PORT(S)
152                   ACCEPT      net                    dmz       tcp        80
153                   REDIRECT    loc:192.168.2.0/23     3128      tcp        80
154
155       Another way is to restrict the definition of the loc zone:
156
157       /etc/shorewall/interfaces:
158
159                   #ZONE    INTERFACE      BROADCAST        OPTIONS
160                   net      ppp0
161                   loc      eth1
162                   -        ppp+
163                   dmz      eth2
164
165       /etc/shorewall/hosts:
166
167                   #ZONE    HOST(S)             OPTIONS
168                   loc      ppp+:192.168.2.0/23
169

FILES

171       /etc/shorewall/zones
172
173       /etc/shorewall/interfaces
174
175       /etc/shorewall/hosts
176
177       /etc/shorewall/policy
178
179       /etc/shorewall/rules
180

SEE ALSO

182       shorewall(8), shorewall-accounting(5), shorewall-actions(5),
183       shorewall-blacklist(5), shorewall-hosts(5), shorewall_interfaces(5),
184       shorewall-ipsets(5), shorewall-maclist(5), shorewall-masq(5),
185       shorewall-nat(5), shorewall-netmap(5), shorewall-params(5),
186       shorewall-policy(5), shorewall-providers(5), shorewall-proxyarp(5),
187       shorewall-route_rules(5), shorewall-routestopped(5),
188       shorewall-rules(5), shorewall.conf(5), shorewall-secmarks(5),
189       shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5),
190       shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)
191

NOTES

193        1. shorewall-zones
194           http://www.shorewall.net/manpages/shorewall-zones.html
195
196        2. shorewall-policy
197           http://www.shorewall.net/manpages/shorewall-policy.html
198
199        3. shorewall.conf
200           http://www.shorewall.net/manpages/shorewall.conf.html
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204[FIXME: source]                   09/16/2011              SHOREWALL-NESTING(5)
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