Copyright © 2008, 2009, 2016, 2017 Thomas M. Eastep
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2020/02/16
Table of Contents
Caution
This article applies to Shorewall 4.3 and later. If you are running a version of Shorewall earlier than Shorewall 4.3.5 then please see the documentation for that release.
Beginning with Shorewall 4.2.4, support for firewalling IPv6 is included as part of Shorewall.
In order to use Shorewall with IPv6, your firewall must meet the following prerequisites:
Iptables 1.4.0 or later (1.4.1.1 is strongly recommended)
If you wish to include DNS names in your IPv6 configuration files, you must have Perl 5.10 and must install the Perl Socket6 library.
Shorewall IPv6 support introduced two new packages:
Shorewall6. This package provides
/sbin/shorewall6which is the IPv6 equivalent of/sbin/shorewall./sbin/shorewallonly handles IPv4 while/sbin/shorewall6handles only IPv6.. Shorewall6 depends on Shorewall. The Shorewall6 configuration is stored in/etc/shorewall6.Shorewall6 Lite. This package is to IPv6 what Shorewall Lite is to IPv4. The package stores its configuration in
/etc/shorewall6-lite. As with Shorewall Lite, Shorewall6 Lite usually requires no configuration changes on the firewall system.
IP connections are either IPv4 or IPv6; there is no such thing as a mixed IPv4/6 connecton. IPv4 connections are controlled by Shorewall (or Shorewall-lite); IPv6 connections are controlled by Shorewall6 (or Shorewall6-lite). Starting and stopping the firewall for one address family has no effect on the other address family.
As a consequence, there is very little interaction between Shorewall and Shorewall6.
An obvious area where the configuration of Shorewall affects
Shorewall6 is the DISABLE_IPV6 setting in
/etc/shorewall/shorewall.conf. When configuring
Shorewall6, you will want to set DISABLE_IPV6=No and restart Shorewall
or Shorewall-lite.
Another area where their configurations overlap is in traffic
shaping; the tcdevices and tcclasses files do
exactly the same thing in both Shorewall and Shorewall6. Consequently,
you will have TC_ENABLED=Internal in Shorewall or in Shorewall6 and
TC_ENABLED=No in the other product. Also, you will want CLEAR_TC=No in
the configuration with TC_ENABLED=No.
Regardless of which product has TC_ENABLED=Internal:
IPv4 packet marking is controlled by /etc/shorewall/mangle (Shorewall 4.6.0 and later) or by /etc/shorewall/tcrules
IPv6 packet marking is controlled by /etc/shorewall6/mangle (Shorewall 4.6.0 and later) or by /etc/shorewall6/tcrules
Multi-ISP users will need to be aware of this one. When there
are entries in the providers file, Shorewall normally installs a
modified /etc/iproute2/rt_tables during
shorewall start and shorewall
restart and restores a default file during
shorewall stop. Setting KEEP_RT_TABLES=Yes in
shorewall.conf(5)
stops Shorewall (Shorewall lite) from modifying
/etc/iproute2/rt_tables.
Shorewall6 is also capable of modifying
/etc/iproute2/rt_tables in a similar way.
Our recommendation to Multi-ISP users is to:
Select the same names for similar providers.
Set KEEP_RT_TABLES=No in shorewall.conf(5) and set KEEP_RT_TABLES=Yes in shorewall6.conf(5).
These setting allow Shorewall to control the contents of
/etc/iproute2/rt_tables.
Configuring and operating Shorewall6 is very similar to configuring Shorewall with some notable exceptions:
- Default Zone Type
The default zone type in Shorewall6 is ipv6. It is suggested that you specify ipv6 in the TYPE column of
/etc/shorewall6/zonesand a type of ipv4 in/etc/shorewall/zones; that way, if you run the wrong utility on a configuration, you will get an instant error.- Interface Options
The following interface options are available in
/etc/shorewall6/interfaces:- blacklist
Same as in Shorewall
- bridge
Same as in Shorewall
- dhcp
Interface is assigned by IPv6 DHCP or the firewall hosts an IPv6 DHCP server on the interface.
- maclist
Same as in Shorewall
- nosmurfs
Checks the source IP address of packets arriving on the interface and drops packets whose SOURCE address is:
An IPv6 multicast address
The subnet-router anycast address for any of the global unicast addresses assigned to the interface.
An RFC 2526 anycast address for any of the global unicast addresses assigned to the interface.
- optional
Same as in Shorewall
- routeback
Same as in Shorewall
- sourceroute[={0|1}]
Same as in Shorewall
- tcpflags
Same as in Shorewall
- mss=
mss Same as in Shorewall
- forward[={0|1}]
Override the setting of IP_FORWARDING in shorewall6.conf with respect to how the system behaves on this interface. If 1, behave as a router; if 0, behave as a host.
- Host Options
The following host options are available in
/etc/shorewall6/hosts:- blacklist
Same as in Shorewall
- maclist
Same as in Shorewall
- routeback
Same as in Shorewall
- tcpflags
Same as in Shorewall
- Specifying Addresses
Shorewall follows the usual convention of distinguishing IPv6 address by enclosing them in square brackets ("[" and "]").
Anywhere that an address or address list follows a colon (":"), the address or list may be enclosed in square brackets to improve readability.
Example (
/etc/shorewall6/rules):#ACTION SOURCE DEST PROTO DPORT ?SECTION NEW ACCEPT net $FW:[2002:ce7c:92b4::3] tcp 22
When the colon is preceeded by an interface name, the angle brackets are required. This is true even when the address is a MAC address in Shorewall format.
Example (
/etc/shorewall6/rules):#ACTION SOURCE DEST PROTO DPORT ?SECTION NEW ACCEPT net:wlan0:[2002:ce7c:92b4::3] $FW tcp 22
Prior to Shorewall 4.5.4, angled brackets ("<" and ">") were used. While these are still accepted, their use is deprecated in favor of square brackets.
Example (
/etc/shorewall6/rules):#ACTION SOURCE DEST PROTO DPORT SECTION NEW ACCEPT net:wlan0:<2002:ce7c:92b4::3> $FW tcp 22
Prior to Shorewall 4.5.9, network addresses were required to be enclosed in either angle brackets or square brackets (e.g. [2001:470:b:787::/64]). Beginning with Shorewall 4.5.9, the more common representation that places the VLSM outside the brackets is accepted and preferred (e.g., [2001:470:b:787::]/64).
Beginning with Shorewall 4.5.14, the rules compiler translates "<" and ">" to "[" and "]" respectively before parsing. So square brackets may appear in error messages even when angled brackets were used.
- Stopped State
When Shorewall6 or Shorewall6 Lite is in the stopped state, the following traffic is still allowed.
Traffic with a multicast destination IP address (ff00::/8).
Traffic with a link local source address (ff800::/8)
Traffic with a link local destination address.
- Multi-ISP
The Linux IPv6 stack does not support balancing (multi-hop) routes. Thehe
balanceandfallbackoptions in shorewall6-providers(5) and USE_DEFAULT_RT=Yes in shorewall6.conf(5) are supported, but at most one provider can have thebalanceoption and at most one provider can have thefallbackoption.- /sbin/shorewall6 and /sbin/shorewall6-lite Commands
Several commands supported by
/sbin/shorewalland/sbin/shorewall-liteare not supported by/sbin/shorewall6and/sbin/shorewall6-lite:hits
ipcalc
iprange
- Macros
The Shorewall6 package depends on Shorewall for application macros. Only certain address-family specific macros such as macro.AllowICMPs are included in Shorewall6. As a consequence, /usr/share/shorewall/ is included in the default Shorewall6 CONFIG_PATH.
You will need at least the following packages:
Shorewall 4.3.5 or later.
Shorewall6 4.3.5 or later.
You may also with to install Shorewall6-lite 4.3.5 or later on your remote firewalls to allow for central IPv6 firewall administration.
Normally, the configuration files for Shorewall are kept in /etc/shorewall/ and those for Shorewall6 are kept in /etc/shorewall6/. It is possible, however, to share almost all of those files as shown in this article.
I strongly suggest that you read the Linux IPv6 HOWTO. The 6to4 Tunnels page also includes instructions for setting up your first IPv6 environment.
In addition to the Linux IPv6 HOWTO, I have found the following two books to be useful:
IPv6 Essentials, Silvia Hagen, 2002, O'Reilly Media, Inc, ISBN 0-596-00125-8.
O'Reilly published a second edition of this book in 2006.
IPV6 Theory, Protocol, and Practice, Second Edition, Pete Loshin, 2004, Morgan-Kaufmann Publishers, IBSN 1-55860-820-9
