SHOREWALL-INTERFACE(5)SHOREWALL-INTERFACE(5)NAMEinterfaces - 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.
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, ...
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
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 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[3].
blacklist
Check packets arriving on this interface against the
shorewall-blacklist[4](5) file.
bridge
Designates the interface as a bridge. Beginning with Shorewall
4.4.7, setting this option also sets routeback.
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[5] with a DHCP server on
one port and DHCP clients on another port.
Note
If you use Shorewall-perl for firewall/bridging[6], then
you need to include DHCP-specific rules in
shorewall-rules[7](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 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[8](5) file.
maclist
Connection requests from this interface are compared against
the contents of shorewall-maclist[9](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[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/ipv4/conf/ entry for the interface cannot
be modified (including for proxy ARP).
· The first address of the interface cannot be obtained.
I specify optional on interfaces to Xen virtual machines
that may or may not be running when Shorewall is
[re]started.
Caution
Use optional 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.
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[10](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. [11]
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.
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|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 in the
shorewall.conf[8](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 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.
upnp
Incoming requests from this interface may be remapped via UPNP
(upnpd). See http://www.shorewall.net/UPnP.html[12].
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 -
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.
#ZONE INTERFACE BROADCAST OPTIONS
- br0 - routeback
FILES
/etc/shorewall/interfaces
SEE ALSOshorewall(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)NOTES
1. shorewall-hosts
shorewall-hosts.html
2. shorewall-nesting
shorewall-nesting.html
3. Proxy ARP
../ProxyARP.htm
4. shorewall-blacklist
shorewall-blacklist.html
5. simple bridge
../SimpleBridge.html
6. Shorewall-perl for firewall/bridging
../bridge-Shorewall-perl.html
7. shorewall-rules
shorewall-rules.html
8. shorewall.conf
shorewall.conf.html
9. shorewall-maclist
shorewall-maclist.html
10. shorewall-proxyarp
shorewall-proxyarp.html
11. http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html.
http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html
12. http://www.shorewall.net/UPnP.html
../UPnP.html
05/07/2010 SHOREWALL-INTERFACE(5)
