focal (5) shorewall-interfaces.5.gz

Provided by: shorewall_5.2.3.4-1_all bug

NAME

       interfaces - Shorewall interfaces file

SYNOPSIS

       /etc/shorewall[6]/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 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[2].
           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, ...

           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[3](5) for a discussion
           of this problem.

           Shorewall allows '+' as an interface name, but that usage is deprecated. A better approach is to
           specify 'physical=+' in the OPTIONS column (see below).

           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[4](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.

           accept_ra[={0|1|2}]
               IPv6 only; added in Shorewall 4.5.16. Values are:

               0
                   Do not accept Router Advertisements.

               1
                   Accept Route Advertisements if forwarding is disabled.

               2
                   Overrule forwarding behavior. Accept Route Advertisements even if forwarding is enabled.

               If the option is specified without a value, then the value 1 is assumed.

                   Note
                   This option does not work with a wild-card physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.

           arp_filter[={0|1}]
               IPv4 only. 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 physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.

           arp_ignore[=number]
               IPv4 only. 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 physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.

                   Warning
                   Do not specify arp_ignore for any interface involved in Proxy ARP[5].

           blacklist
               Checks packets arriving on this interface against the shorewall-blacklist[6](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[7](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.

                   Note
                   If you have a bridge that you don't intend to define bport zones on, then it is best to omit
                   this option and simply specify routeback.

           dbl={none|src|dst|src-dst}
               Added in Shorewall 5.0.10. This option defined whether or not dynamic blacklisting is applied to
               packets entering the firewall through this interface and whether the source address and/or
               destination address is to be compared against the ipset-based dynamic blacklist
               (DYNAMIC_BLACKLIST=ipset... in shorewall.conf(5)[8]). The default is determine by the setting of
               DYNAMIC_BLACKLIST:

               DYNAMIC_BLACKLIST=No
                   Default is none (e.g., no dynamic blacklist checking).

               DYNAMIC_BLACKLIST=Yes
                   Default is src (e.g., the source IP address is checked).

               DYNAMIC_BLACKLIST=ipset[-only]
                   Default is src.

               DYNAMIC_BLACKLIST=ipset[-only],src-dst...
                   Default is src-dst (e.g., the source IP addresses in checked against the ipset on input and
                   the destination IP address is checked against the ipset on packets originating from the
                   firewall and leaving through this interface).

               The normal setting for this option will be dst or none for internal interfaces and src or src-dst
               for Internet-facing interfaces.

           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[9] with a DHCP server on one port and DHCP clients on
                   another port.

                       Note
                       If you use Shorewall-perl for firewall/bridging[10], then you need to include
                       DHCP-specific rules in shorewall-rules[11](5). DHCP uses UDP ports 67 and 68.

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

           forward[={0|1}]
               IPv6 only Sets the /proc/sys/net/ipv6/conf/interface/forwarding option to the specified value. If
               no value is supplied, then 1 is assumed.

                   Note
                   This option does not work with a wild-card physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.

           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.

           loopback
               Added in Shorewall 4.6.6. Designates the interface as the loopback interface. This option is
               assumed if the interface's physical name is 'lo'. Only one interface man have the loopback option
               specified.

           logmartians[={0|1}]
               IPv4 only. 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 physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.
               This option may also be enabled globally in the shorewall.conf[8](5) file.

           maclist
               Connection requests from this interface are compared against the contents of
               shorewall-maclist[12](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[13] for further information.

           nodbl
               Added in Shorewall 5.0.8. When specified, dynamic blacklisting is disabled on the interface.
               Beginning with Shorewall 5.0.10, nodbl is equivalent to dbl=none.

           nosmurfs
               IPv4 only. 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[8](5).
               After logging, the packets are dropped.

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

               •   a /proc/sys/net/ipv[46]/conf/ entry for the interface cannot be modified (including for proxy
                   ARP or proxy NDP).

               •   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[14].

               If the interface name is a wildcard name (ends with '+'), then the physical name must also end in
               '+'. The physical name may end in '+' (or be exactly '+') when the interface name is not a
               wildcard name.

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

           proxyarp[={0|1}]
               IPv4 only. 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[15](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.[16]

                   Note
                   This option does not work with a wild-card physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.
               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.

           proxyndp[={0|1}]
               IPv6 only. Sets /proc/sys/net/ipv6/conf/interface/proxy_ndp.

                   Note
                   This option does not work with a wild-card physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.
               Only those interfaces with the proxyndp 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}]
               IPv4 only. 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 physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.
               This option can also be enabled globally via the ROUTE_FILTER option in the shorewall.conf[8](5)
               file.

                   Important
                   If ROUTE_FILTER=Yes in shorewall.conf[8](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[8](5) and the interface is listed in
                       shorewall-providers[17](5).

                   •   If there is an entry for the interface in shorewall-providers[17](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.
               Beginning with Shorewall 5.1.1, when routefilter is set to a non-zero value, the logmartians
               option is also implicitly set. If you actually want route filtering without logging, then you
               must also specify logmartians=0 after 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 not 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 physical name (e.g., eth0.+). Beginning with
                   Shorewall 5.1.10, If this option is specified, a warning is issued and the option is ignored.

           tcpflags[={0|1}]
               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.

               Beginning with Shorewall 4.6.0, tcpflags=1 is the default. To disable this option, specify
               tcpflags=0.

           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
                       proxyarp
                       proxyudp
                       sourceroute

           upnp
               Incoming requests from this interface may be remapped via UPNP (upnpd). See
               http://www.shorewall.net/UPnP.html[18]. Supported in IPv4 and in IPv6 in Shorewall 5.1.4 and
               later.

           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.
               Supported in IPv4 and in IPv6 in Shorewall 5.1.4 and later.

           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

       IPv4 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       bridge

FILES

       /etc/shorewall/interfaces

       /etc/shorewall6/interfaces

SEE ALSO

       http://www.shorewall.net/configuration_file_basics.htm#Pairs[19]

       shorewall(8)

NOTES

        1. shorewall-hosts
           http://www.shorewall.org/manpages/shorewall-hosts.html

        2. http://www.shorewall.net/FAQ.htm#faq18
           http://www.shorewall.org/FAQ.htm#faq18

        3. shorewall-nesting
           http://www.shorewall.org/manpages/shorewall-nesting.html

        4. shorewall6-zones
           http://www.shorewall.org/manpages6/shorewall6-zones.html

        5. Proxy ARP
           http://www.shorewall.org/ProxyARP.htm

        6. shorewall-blacklist
           http://www.shorewall.org/manpages/shorewall-blacklist.html

        7. shorewall-zones
           http://www.shorewall.org/manpages/shorewall-zones.html

        8. shorewall.conf(5)
           http://www.shorewall.org/manpages/shorewall.conf.html

        9. simple bridge
           http://www.shorewall.org/SimpleBridge.html

       10. Shorewall-perl for firewall/bridging
           http://www.shorewall.org/bridge-Shorewall-perl.html

       11. shorewall-rules
           http://www.shorewall.org/manpages/shorewall-rules.html

       12. shorewall-maclist
           http://www.shorewall.org/manpages/shorewall-maclist.html

       13. http://www.shorewall.net/Dynamic.html
           http://www.shorewall.org/Dynamic.html

       14. http://www.shorewall.net/bridge-Shorewall-perl.html#Multiple
           http://www.shorewall.org/bridge-Shorewall-perl.html#Multiple

       15. shorewall-proxyarp
           http://www.shorewall.org/manpages/shorewall-proxyarp.html

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

       17. shorewall-providers
           http://www.shorewall.org/manpages/shorewall-providers.html

       18. http://www.shorewall.net/UPnP.html
           http://www.shorewall.org/UPnP.html

       19. http://www.shorewall.net/configuration_file_basics.htm#Pairs
           http://www.shorewall.org/configuration_file_basics.htm#Pairs