Provided by: shorewall_4.5.21.6-1_all bug

NAME

       interfaces - Shorewall interfaces file

SYNOPSIS

       /etc/shorewall/interfaces

DESCRIPTION

       The interfaces file serves to define the firewall's network interfaces to Shorewall. The
       order of entries in this file is not significant in determining zone composition.

       Beginning with Shorewall 4.5.3, the interfaces file supports two different formats:

       FORMAT 1 (default - deprecated)
           There is a BROADCAST column which can be used to specify the broadcast address
           associated with the interface.

       FORMAT 2
           The BROADCAST column is omitted.

       The format is specified by a line as follows:

       [?]FORMAT {1|2}

       The optional '?' was introduced in Shorewall 4.5.11 and ?FORMAT is the preferred form; the
       form without the '?' is deprecated.

       The columns in the file are as follows.

       ZONE - zone-name
           Zone for this interface. Must match the name of a zone declared in
           /etc/shorewall/zones. You may not list the firewall zone in this column.

           If the interface serves multiple zones that will be defined in the
           shorewall-hosts[1](5) file, you should place "-" in this column.

           If there are multiple interfaces to the same zone, you must list them in separate
           entries.

           Example:

               #ZONE   INTERFACE       BROADCAST
               loc     eth1            -
               loc     eth2            -

       INTERFACE - interface[:port]
           Logical name of interface. Each interface may be listed only once in this file. You
           may NOT specify the name of a "virtual" interface (e.g., eth0:0) here; see
           http://www.shorewall.net/FAQ.htm#faq18. If the physical option is not specified, then
           the logical name is also the name of the actual interface.

           You may use wildcards here by specifying a prefix followed by the plus sign ("+"). For
           example, if you want to make an entry that applies to all PPP interfaces, use 'ppp+';
           that would match ppp0, ppp1, ppp2, ... Please note that the '+' means 'one or more
           additional characters' so 'ppp' does not match 'ppp+'.

           When using Shorewall versions before 4.1.4, care must be exercised when using
           wildcards where there is another zone that uses a matching specific interface. See
           shorewall-nesting[2](5) for a discussion of this problem.

           Shorewall allows '+' as an interface name.

           There is no need to define the loopback interface (lo) in this file.

           If a port is given, then the interface must have been defined previously with the
           bridge option. The OPTIONS column may not contain the following options when a port is
           given.
               arp_filter
               arp_ignore
               bridge
               log_martians
               mss
               optional
               proxyarp
               required
               routefilter
               sourceroute
               upnp
               wait
           Beginning with Shorewall 4.5.17, if you specify a zone for the 'lo' interface, then
           that zone must be defined as type local in shorewall6-zones[3](5).

       BROADCAST (Optional) - {-|detect|address[,address]...}
           Only available if FORMAT 1.

           If you use the special value detect, Shorewall will detect the broadcast address(es)
           for you if your iptables and kernel include Address Type Match support.

           If your iptables and/or kernel lack Address Type Match support then you may list the
           broadcast address(es) for the network(s) to which the interface belongs. For P-T-P
           interfaces, this column is left blank. If the interface has multiple addresses on
           multiple subnets then list the broadcast addresses as a comma-separated list.

           If you don't want to give a value for this column but you want to enter a value in the
           OPTIONS column, enter - in this column.

       OPTIONS (Optional) - [option[,option]...]
           A comma-separated list of options from the following list. The order in which you list
           the options is not significant but the list should have no embedded white-space.

           arp_filter[={0|1}]
               If specified, this interface will only respond to ARP who-has requests for IP
               addresses configured on the interface. If not specified, the interface can respond
               to ARP who-has requests for IP addresses on any of the firewall's interface. The
               interface must be up when Shorewall is started.

               Only those interfaces with the arp_filter option will have their setting changed;
               the value assigned to the setting will be the value specified (if any) or 1 if no
               value is given.

                   Note
                   This option does not work with a wild-card interface name (e.g., eth0.+) in
                   the INTERFACE column.

           arp_ignore[=number]
               If specified, this interface will respond to arp requests based on the value of
               number (defaults to 1).

               1 - reply only if the target IP address is local address configured on the
               incoming interface

               2 - reply only if the target IP address is local address configured on the
               incoming interface and the sender's IP address is part from same subnet on this
               interface's address

               3 - do not reply for local addresses configured with scope host, only resolutions
               for global and link

               4-7 - reserved

               8 - do not reply for all local addresses

                   Note
                   This option does not work with a wild-card interface name (e.g., eth0.+) in
                   the INTERFACE column.

                   Warning
                   Do not specify arp_ignore for any interface involved in Proxy ARP[4].

           blacklist
               Checks packets arriving on this interface against the shorewall-blacklist[5](5)
               file.

               Beginning with Shorewall 4.4.13:

               •   If a zone is given in the ZONES column, then the behavior is as if blacklist
                   had been specified in the IN_OPTIONS column of shorewall-zones[6](5).

               •   Otherwise, the option is ignored with a warning: WARNING: The 'blacklist'
                   option is ignored on multi-zone interfaces

           bridge
               Designates the interface as a bridge. Beginning with Shorewall 4.4.7, setting this
               option also sets routeback.

           destonly
               Added in Shorewall 4.5.17. Causes the compiler to omit rules to handle traffic
               from this interface.

           dhcp
               Specify this option when any of the following are true:

                1. the interface gets its IP address via DHCP

                2. the interface is used by a DHCP server running on the firewall

                3. the interface has a static IP but is on a LAN segment with lots of DHCP
                   clients.

                4. the interface is a simple bridge[7] with a DHCP server on one port and DHCP
                   clients on another port.

                       Note
                       If you use Shorewall-perl for firewall/bridging[8], then you need to
                       include DHCP-specific rules in shorewall-rules[9](8). DHCP uses UDP ports
                       67 and 68.

               This option allows DHCP datagrams to enter and leave the interface.

           ignore[=1]
               When specified, causes the generated script to ignore up/down events from
               Shorewall-init for this device. Additionally, the option exempts the interface
               from hairpin filtering. When '=1' is omitted, the ZONE column must contain '-' and
               ignore must be the only OPTION.

               Beginning with Shorewall 4.5.5, may be specified as 'ignore=1' which only causes
               the generated script to ignore up/down events from Shorewall-init; hairpin
               filtering is still applied. In this case, the above restrictions on the ZONE and
               OPTIONS columns are lifted.

           logmartians[={0|1}]
               Turn on kernel martian logging (logging of packets with impossible source
               addresses. It is strongly suggested that if you set routefilter on an interface
               that you also set logmartians. Even if you do not specify the routefilter option,
               it is a good idea to specify logmartians because your distribution may have
               enabled route filtering without you knowing it.

               Only those interfaces with the logmartians option will have their setting changed;
               the value assigned to the setting will be the value specified (if any) or 1 if no
               value is given.

               To find out if route filtering is set on a given interface, check the contents of
               /proc/sys/net/ipv4/conf/interface/rp_filter - a non-zero value indicates that
               route filtering is enabled.

               Example:

                           teastep@lists:~$ cat /proc/sys/net/ipv4/conf/eth0/rp_filter
                           1
                           teastep@lists:~$

                   Note
                   This option does not work with a wild-card interface name (e.g., eth0.+) in
                   the INTERFACE column.
               This option may also be enabled globally in the shorewall.conf[10](5) file.

           maclist
               Connection requests from this interface are compared against the contents of
               shorewall-maclist[11](5). If this option is specified, the interface must be an
               Ethernet NIC and must be up before Shorewall is started.

           mss=number
               Added in Shorewall 4.0.3. Causes forwarded TCP SYN packets entering or leaving on
               this interface to have their MSS field set to the specified number.

           nets=(net[,...])
               Limit the zone named in the ZONE column to only the listed networks. The
               parentheses may be omitted if only a single net is given (e.g.,
               nets=192.168.1.0/24). Limited broadcast to the zone is supported. Beginning with
               Shorewall 4.4.1, multicast traffic to the zone is also supported.

           nets=dynamic
               Defines the zone as dynamic. Requires ipset match support in your iptables and
               kernel. See http://www.shorewall.net/Dynamic.html for further information.

           nosmurfs
               Filter packets for smurfs (packets with a broadcast address as the source).

               Smurfs will be optionally logged based on the setting of SMURF_LOG_LEVEL in
               shorewall.conf[10](5). After logging, the packets are dropped.

           optional
               When optional is specified for an interface, Shorewall will be silent when:

               •   a /proc/sys/net/ipv4/conf/ entry for the interface cannot be modified
                   (including for proxy ARP).

               •   The first address of the interface cannot be obtained.

               May not be specified with required.

           physical=name
               Added in Shorewall 4.4.4. When specified, the interface or port name in the
               INTERFACE column is a logical name that refers to the name given in this option.
               It is useful when you want to specify the same wildcard port name on two or more
               bridges. See http://www.shorewall.net/bridge-Shorewall-perl.html#Multiple.

               If the interface name is a wildcard name (ends with '+'), then the physical name
               must also end in '+'.

               If physical is not specified, then it's value defaults to the interface name.

           proxyarp[={0|1}]
               Sets /proc/sys/net/ipv4/conf/interface/proxy_arp. Do NOT use this option if you
               are employing Proxy ARP through entries in shorewall-proxyarp[12](5). This option
               is intended solely for use with Proxy ARP sub-networking as described at:
               http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html.[13]

               Note: This option does not work with a wild-card interface name (e.g., eth0.+) in
               the INTERFACE column.

               Only those interfaces with the proxyarp option will have their setting changed;
               the value assigned to the setting will be the value specified (if any) or 1 if no
               value is given.

           required
               Added in Shorewall 4.4.10. If this option is set, the firewall will fail to start
               if the interface is not usable. May not be specified together with optional.

           routeback[={0|1}]
               If specified, indicates that Shorewall should include rules that allow traffic
               arriving on this interface to be routed back out that same interface. This option
               is also required when you have used a wildcard in the INTERFACE column if you want
               to allow traffic between the interfaces that match the wildcard.

               Beginning with Shorewall 4.4.20, if you specify this option, then you should also
               specify either sfilter (see below) or routefilter on all interfaces (see below).

               Beginning with Shorewall 4.5.18, you may specify this option to explicitly reset
               (e.g., routeback=0). This can be used to override Shorewall's default setting for
               bridge devices which is routeback=1.

           routefilter[={0|1|2}]
               Turn on kernel route filtering for this interface (anti-spoofing measure).

               Only those interfaces with the routefilter option will have their setting changes;
               the value assigned to the setting will be the value specified (if any) or 1 if no
               value is given.

               The value 2 is only available with Shorewall 4.4.5.1 and later when the kernel
               version is 2.6.31 or later. It specifies a loose form of reverse path filtering.

                   Note
                   This option does not work with a wild-card interface name (e.g., eth0.+) in
                   the INTERFACE column.
               This option can also be enabled globally via the ROUTE_FILTER option in the
               shorewall.conf[10](5) file.

                   Important
                   If ROUTE_FILTER=Yes in shorewall.conf[10](5), or if your distribution sets
                   net.ipv4.conf.all.rp_filter=1 in /etc/sysctl.conf, then setting routefilter=0
                   in an interface entry will not disable route filtering on that interface! The
                   effective setting for an interface is the maximum of the contents of
                   /proc/sys/net/ipv4/conf/all/rp_filter and the routefilter setting specified in
                   this file (/proc/sys/net/ipv4/conf/interface/rp_filter).

                   Note
                   There are certain cases where routefilter cannot be used on an interface:

                   •   If USE_DEFAULT_RT=Yes in shorewall.conf[10](5) and the interface is listed
                       in shorewall-providers[14](5).

                   •   If there is an entry for the interface in shorewall-providers[14](5) that
                       doesn't specify the balance option.

                   •   If IPSEC is used to allow a road-warrior to have a local address, then any
                       interface through which the road-warrior might connect cannot specify
                       routefilter.

           rpfilter
               Added in Shorewall 4.5.7. This is an anti-spoofing measure that requires the
               'RPFilter Match' capability in your iptables and kernel. It provides a more
               efficient alternative to the sfilter option below. It performs a function similar
               to routefilter (see above) but works with Multi-ISP configurations that do now use
               balanced routes.

           sfilter=(net[,...])
               Added in Shorewall 4.4.20. This option provides an anti-spoofing alternative to
               routefilter on interfaces where that option cannot be used, but where the
               routeback option is required (on a bridge, for example). On these interfaces,
               sfilter should list those local networks that are connected to the firewall
               through other interfaces.

           sourceroute[={0|1}]
               If this option is not specified for an interface, then source-routed packets will
               not be accepted from that interface unless it has been explicitly enabled via
               sysconf. Only set this option to 1 (enable source routing) if you know what you
               are doing. This might represent a security risk and is usually unneeded.

               Only those interfaces with the sourceroute option will have their setting changed;
               the value assigned to the setting will be the value specified (if any) or 1 if no
               value is given.

                   Note
                   This option does not work with a wild-card interface name (e.g., eth0.+) in
                   the INTERFACE column.

           tcpflags
               Packets arriving on this interface are checked for certain illegal combinations of
               TCP flags. Packets found to have such a combination of flags are handled according
               to the setting of TCP_FLAGS_DISPOSITION after having been logged according to the
               setting of TCP_FLAGS_LOG_LEVEL.

           unmanaged
               Added in Shorewall 4.5.18. Causes all traffic between the firewall and hosts on
               the interface to be accepted. When this option is given:

               •   The ZONE column must contain '-'.

               •   Only the following other options are allowed with unmanaged:
                       arp_filter
                       arp_ignore
                       ignore
                       routefilter
                       optional
                       physical
                       routefilter
                       sourceroute
                       proxyndp

           upnp
               Incoming requests from this interface may be remapped via UPNP (upnpd). See
               http://www.shorewall.net/UPnP.html[15].

           upnpclient
               This option is intended for laptop users who always run Shorewall on their system
               yet need to run UPnP-enabled client apps such as Transmission (BitTorrent client).
               The option causes Shorewall to detect the default gateway through the interface
               and to accept UDP packets from that gateway. Note that, like all aspects of UPnP,
               this is a security hole so use this option at your own risk.

           wait=seconds
               Added in Shorewall 4.4.10. Causes the generated script to wait up to seconds
               seconds for the interface to become usable before applying the required or
               optional options.

EXAMPLE

       Example 1:
           Suppose you have eth0 connected to a DSL modem and eth1 connected to your local
           network and that your local subnet is 192.168.1.0/24. The interface gets its IP
           address via DHCP from subnet 206.191.149.192/27. You have a DMZ with subnet
           192.168.2.0/24 using eth2. Your iptables and/or kernel do not support "Address Type
           Match" and you prefer to specify broadcast addresses explicitly rather than having
           Shorewall detect them.

           Your entries for this setup would look like:

               FORMAT 1
               #ZONE   INTERFACE BROADCAST        OPTIONS
               net     eth0      206.191.149.223  dhcp
               loc     eth1      192.168.1.255
               dmz     eth2      192.168.2.255

       Example 2:
           The same configuration without specifying broadcast addresses is:

               FORMAT 2
               #ZONE   INTERFACE OPTIONS
               net     eth0      dhcp
               loc     eth1
               dmz     eth2

       Example 3:
           You have a simple dial-in system with no Ethernet connections.

               FORMAT 2
               #ZONE   INTERFACE OPTIONS
               net     ppp0      -

       Example 4 (Shorewall 4.4.9 and later):
           You have a bridge with no IP address and you want to allow traffic through the bridge.

               FORMAT 2
               #ZONE   INTERFACE OPTIONS
               -       br0       routeback

FILES

       /etc/shorewall/interfaces

SEE ALSO

       http://shorewall.net/configuration_file_basics.htm#Pairs

       shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5),
       shorewall-hosts(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-hosts
           http://www.shorewall.netshorewall-hosts.html

        2. shorewall-nesting
           http://www.shorewall.netshorewall-nesting.html

        3. shorewall6-zones
           http://www.shorewall.netshorewall6-zones.html

        4. Proxy ARP
           http://www.shorewall.net../ProxyARP.htm

        5. shorewall-blacklist
           http://www.shorewall.netshorewall-blacklist.html

        6. shorewall-zones
           http://www.shorewall.netshorewall-zones.html

        7. simple bridge
           http://www.shorewall.net../SimpleBridge.html

        8. Shorewall-perl for firewall/bridging
           http://www.shorewall.net../bridge-Shorewall-perl.html

        9. shorewall-rules
           http://www.shorewall.netshorewall-rules.html

       10. shorewall.conf
           http://www.shorewall.netshorewall.conf.html

       11. shorewall-maclist
           http://www.shorewall.netshorewall-maclist.html

       12. shorewall-proxyarp
           http://www.shorewall.netshorewall-proxyarp.html

       13. http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html.
           http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html

       14. shorewall-providers
           http://www.shorewall.netshorewall-providers.html

       15. http://www.shorewall.net/UPnP.html
           http://www.shorewall.net../UPnP.html

[FIXME: source]                             01/30/2014                     SHOREWALL-INTERFACE(5)