Description

shorewall-interfaces 5 interfaces Shorewall interfaces file /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. 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(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] 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 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(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 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 routefilter sourceroute upnp BROADCAST (Optional) - {-|detect|address[,address]...} 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 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. 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 This option does not work with a wild-card interface name (e.g., eth0.+) in the INTERFACE column. Do not specify arp_ignore for any interface involved in Proxy ARP. blacklist Check packets arriving on this interface against the shorewall-blacklist(5) file. bridge Designates the interface as a bridge. dhcp Specify this option when any of the following are true: the interface gets its IP address via DHCP the interface is used by a DHCP server running on the firewall the interface has a static IP but is on a LAN segment with lots of DHCP clients. the interface is a simple bridge with a DHCP server on one port and DHCP clients on another port. If you use Shorewall-perl for firewall/bridging, then you need to include DHCP-specific rules in shorewall-rules(8). DHCP uses UDP ports 67 and 68. This option allows DHCP datagrams to enter and leave the interface. 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 option, it is a good idea to specify because your distribution may have enabled route filtering without you knowing it. Only those interfaces with the 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:~$ 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(5) file.

maclist Connection requests from this interface are compared against the contents of shorewall-maclist(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(5). After logging, the packets are dropped. optional When 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.

I specify on interfaces to Xen virtual machines that may or may not be running when Shorewall is [re]started. Use at your own risk. If you [re]start Shorewall when an 'optional' interface is not available and then do a shorewall save, subsequent shorewall restore and shorewall -f start operations will instantiate a ruleset that does not support that interface, even if it is available at the time of the restore/start.

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(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. Note: This option does not work with a wild-card interface name (e.g., eth0.+) in the INTERFACE column. Only those interfaces with the 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. routeback 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. routefilter[={0|1}] Turn on kernel route filtering for this interface (anti-spoofing measure). Only those interfaces with the 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. 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 in the shorewall.conf(5) file.

sourceroute[={0|1}] If this option is not specified for an interface, then source-routed packets will not be accepted from that interface (sets /proc/sys/net/ipv4/conf/interface/accept_source_route to 1). Only set this option if you know what you are doing. This might represent a security risk and is usually unneeded. Only those interfaces with the 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. 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. upnp Incoming requests from this interface may be remapped via UPNP (upnpd). See http://www.shorewall.net/UPnP.html. 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. 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 entries for this setup would look like: #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: #ZONE INTERFACE BROADCAST OPTIONS net eth0 detect dhcp loc eth1 detect dmz eth2 detect Example 3: You have a simple dial-in system with no ethernet connections. #ZONE INTERFACE BROADCAST OPTIONS net ppp0 - FILES /etc/shorewall/interfaces See ALSO shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5), shorewall-hosts(5), shorewall-ipsec(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-route_rules(5), shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5), shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5), shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)