Configuration Files Tips and HintsTomEastep2001-2010Thomas M. EastepPermission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation; with
no Invariant Sections, with no Front-Cover, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
GNU Free Documentation
License.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.If you copy or edit your configuration files on a system running
Microsoft Windows, you must run them through dos2unix
before you use them with Shorewall.IntroductionThis article offers hints about how to accomplish common tasks with
Shorewall. The Introduction to
Shorewall is required reading for being able to use this article
effectively. For information about setting up your first Shorewall-based
firewall, see the Quickstart
Guides.Files/etc/shorewall/shorewall.conf - used to
set global firewall parameters./etc/shorewall/params - use this file to
set shell variables that you will expand in other files./etc/shorewall/zones - partition the
firewall's view of the world into zones./etc/shorewall/policy - establishes
firewall high-level policy./etc/shorewall/interfaces - describes the
interfaces on the firewall system./etc/shorewall/hosts - allows defining
zones in terms of individual hosts and subnetworks./etc/shorewall/masq - directs the
firewall where to use many-to-one (dynamic) Network Address
Translation (a.k.a. Masquerading) and Source Network Address
Translation (SNAT)./etc/shorewall/rules - defines rules that
are exceptions to the overall policies established in
/etc/shorewall/policy./etc/shorewall/nat - defines one-to-one
NAT rules./etc/shorewall/proxyarp - defines use of
Proxy ARP./etc/shorewall/routestopped - defines
hosts accessible when Shorewall is stopped./etc/shorewall/tcrules - defines marking
of packets for later use by traffic control/shaping or policy
routing./etc/shorewall/tos - defines rules for
setting the TOS field in packet headers./etc/shorewall/tunnels - defines tunnels
(VPN) with end-points on the firewall system./etc/shorewall/blacklist - lists
blacklisted IP/subnet/MAC addresses./etc/shorewall/init - commands that you
wish to execute at the beginning of a shorewall start
or shorewall restart./etc/shorewall/start - commands that you
wish to execute at the completion of a shorewall
start or shorewall restart/etc/shorewall/stop - commands that you
wish to execute at the beginning of a shorewall
stop./etc/shorewall/stopped - commands that
you wish to execute at the completion of a shorewall
stop./etc/shorewall/ecn - disable Explicit
Congestion Notification (ECN - RFC 3168) to remote hosts or
networks./etc/shorewall/accounting - define IP
traffic accounting rules/etc/shorewall/actions and
/usr/share/shorewall/action.template allow
user-defined actions./etc/shorewall/providers - defines an
alternate routing table./etc/shorewall/route_rules - Defines
routing rules to be used in conjunction with the routing tables
defined in /etc/shorewall/providers./etc/shorewall/tcdevices,
/etc/shorewall/tcclasses,
/etc/shorewall/tcfilters - Define complex
traffic shaping./etc/shorewall/tcrules - Mark or classify
traffic for traffic shaping or multiple providers./etc/shorewall/tcinterfaces and
/etc/shorewall-tcpri - Define simple traffic
shaping./etc/shorewall/vardir - Determines the
directory where Shorewall maintains its state./usr/share/shorewall/actions.std -
Actions defined by Shorewall./usr/share/shorewall/action.* - Details
of actions defined by Shorewall./usr/share/shorewall/macro.* - Details of
macros defined by Shorewall./usr/share/shorewall/modules - directs
the firewall to load kernel modules./usr/share/modules — Specifies the kernel
modules to be loaded during shorewall start/restart./usr/share/helpers — Added in Shorewall
4.4.7. Specifies the kernel modules to be loaded during shorewall
start/restart when LOAD_HELPERS_ONLY=Yes in
shorewall.conf.If you need to change a file in
/usr/share/shorewall/, copy it to /etc/shorewall and
modify the copyMan PagesMan pages are provided in section 5 for each of the Shorewall
configuration files. The name of the page is formed by prefixing the file
name with "shorewall-".Example — To view the manual page for
/etc/shorewall/interfaces:man shorewall-interfacesThe /etc/shorewall/shorewall.conf file is an exception -- the man
page for that file is 'shorewall.conf':man shorewall.confCommentsYou may place comments in configuration files by making the first
non-whitespace character a pound sign (#). You may also
place comments at the end of any line, again by delimiting the comment
from the rest of the line with a pound sign.Comments in a Configuration File# This is a comment
ACCEPT net $FW tcp www #This is an end-of-line commentAttach Comment to Netfilter RulesIf you kernel and iptables contain comment match support (see the
output of shorewall show capabilities), then you can
attach comments to Netfilter rules. This feature is available in the
following files:/etc/shorewall/accounting/etc/shorewall/masq/etc/shorewall/nat/etc/shorewall/notrack/etc/shorewall/rules/etc/shorewall/tcrules/etc/shorewall/tunnelsAction definition files
(/etc/shorewall/action.*)Macro definition files (/etc/shorewall/macro.*)To attach a comment to one or more rules, insert a record above the
rules that begins with the word COMMENT (must be in all caps). The
remainder of the line is treated as a comment -- that comment will appear
delimited by "/* ... */" in the output of the shorewall[-lite]
show and shorewall[-lite] dump commands. The
comment will be attached to each generated rule until another COMMENT line
appears. To stop attaching comments to rules, simply insert a line that
contains the single word COMMENT.Example (/etc/shorewall/rules):COMMENT Stop NETBIOS noise
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
COMMENT Stop my idiotic work laptop from sending to the net with an HP source/dest IP address
DROP loc:!192.168.0.0/22 net
COMMENTHere's the corresponding output from
/sbin/shorewall-lite:gateway:~ # shorewall-lite show loc2net
Shorewall Lite 4.3.3 Chains loc2net at gateway - Mon Oct 16 15:04:52 PDT 2008
Counters reset Mon Oct 16 14:52:17 PDT 2006
Chain loc2net (1 references)
pkts bytes target prot opt in out source destination
0 0 LOG tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25 LOG flags 0 level 6 prefix `FW:loc2net:REJECT:'
0 0 reject tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
0 0 LOG udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:1025:1031 LOG flags 0 level 6 prefix `FW:loc2net:REJECT:'
0 0 reject udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:1025:1031
0 0 reject tcp -- * * 0.0.0.0/0 0.0.0.0/0 multiport dports 137,445 /* Stop NETBIOS noise */
0 0 reject udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:137:139 /* Stop NETBIOS noise */
0 0 DROP all -- * * !192.168.0.0/22 0.0.0.0/0 /* Stop my idiotic work laptop from sending to the net with an HP source/dest IP address */
5 316 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
gateway:~ #
COMMENT lines in macro files work somewhat differently from other
files. COMMENT lines in macros are ignored if COMMENT support is not
available or if there was a COMMENT in use when the top-level macro was
invoked. This allows the following:/usr/share/shorewall/macro.SSH:#ACTION SOURCE DEST PROTO DEST SOURCE RATE USER/
# PORT(S) PORT(S) LIMIT GROUP
COMMENT SSH
PARAM - - tcp 22 /etc/shorewall/rules:COMMENT Allow SSH from home
SSH/ALLOW net:$MYIP $FW
COMMENTThe comment line in macro.SSH will not override the
COMMENT line in the rules file and the generated rule will show /* Allow SSH from home */ when displayed through
the Shorewall show and dump commands."Blank" ColumnsIf you don't want to supply a value in a column but want to supply a
value in a following column, simply enter '-' to make the column appear
empty.Example:#INTERFACE BROADCAST OPTIONS
br0 - routebackLine ContinuationYou may continue lines in the configuration files using the usual
backslash (\) followed immediately by a new line character
(Enter key).Line ContinuationACCEPT net $FW tcp \↵
smtp,www,pop3,imap #Services running on the firewallIn certain cases, leading white space is ignored in continuation
lines:The continued line ends with a colon (":")The continued line ends with a comma (",")Example (/etc/shorewall/rules):#ACTION SOURCE DEST PROTO DEST
# PORT(S)
ACCEPT net:\
206.124.146.177,\
206.124.146.178,\
206.124.146.180\
dmz tcp 873The leading white space on the first through third continuation
lines is ignored so the SOURCE column effectively contains
"net:206.124.146.177,206.124.147.178,206.124.146.180". Because the third
continuation line does not end with a comma or colon, the leading white
space in the last line is not ignored.Specifying SOURCE and DESTEntries in Shorewall configuration files often deal with the source
(SOURCE) and destination (DEST) of connections and Shorewall implements a
uniform way for specifying them.A SOURCE or DEST consists of one to three parts separated by colons
(":"):ZONE — The name of a zone declared in
/etc/shorewall/zones or
/etc/shorewall6/zones. This part is only
available in the rules file (/etc/shorewall/rules
and /etc/shorewall6/rules).INTERFACE — The name of an interface that matches an entry in
/etc/shorewall/interfaces
(/etc/shorewall6/interfaces).ADDRESS LIST — A list of one or more addresses (host or network)
or address ranges, separated by commas. In an IPv6 configuration, this
list must be includes in angled brackets ("<...>"). The list may
have exclusion.Examples.All hosts in the net zone —
netSubnet 192.168.1.0/29 in the loc zone — loc:192.168.1.0/29All hosts in the net zone connecting through ppp0 — net:ppp0All hosts interfaced by eth3 — eth3Subnet 10.0.1.0/24 interfacing through eth2 — eth2:10.0.1.0/24Host 2002:ce7c:92b4:1:a00:27ff:feb1:46a9 in the loc zone — loc:<2002:ce7c:92b4:1:a00:27ff:feb1:46a9>INCLUDE DirectiveAny configuration file may contain INCLUDE directives. An INCLUDE
directive consists of the word INCLUDE followed by a path name and causes
the contents of the named file to be logically included into the file
containing the INCLUDE. Relative path names given in an INCLUDE directive
are resolved using the current CONFIG_PATH setting (see shorewall.conf(5)).INCLUDE's may be nested to a level of 3 -- further nested INCLUDE
directives are ignored with a warning message.If you are using Shorewall Lite , it is not
advisable to use INCLUDE in the params file in an
export directory. If you do that, you must ensure that the included file
is also present on the firewall system's /etc/shorewall-lite/ directory.If you only need the params file at compile
time, you can set EXPORTPARAMS=No in
shorewall.conf. That prevents the
params file from being copied into the compiled
script. With EXPORTPARAMS=No, it is perfectly okay to use INCLUDE in the
params file.Use of INCLUDE shorewall/params.mgmt:
MGMT_SERVERS=1.1.1.1,2.2.2.2,3.3.3.3
TIME_SERVERS=4.4.4.4
BACKUP_SERVERS=5.5.5.5
----- end params.mgmt -----
shorewall/params:
# Shorewall 1.3 /etc/shorewall/params
[..]
#######################################
INCLUDE params.mgmt
# params unique to this host here
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
----- end params -----
shorewall/rules.mgmt:
ACCEPT net:$MGMT_SERVERS $FW tcp 22
ACCEPT $FW net:$TIME_SERVERS udp 123
ACCEPT $FW net:$BACKUP_SERVERS tcp 22
----- end rules.mgmt -----
shorewall/rules:
# Shorewall version 1.3 - Rules File
[..]
#######################################
INCLUDE rules.mgmt
# rules unique to this host here
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
----- end rules -----You may include multiple files in one command using an embedded shell command.Example (include all of the files ending in ".rules" in a
directory:):gateway:/etc/shorewall # ls rules.d
ALL.rules DNAT.rules FW.rules NET.rules REDIRECT.rules VPN.rules
gateway:/etc/shorewall # /etc/shorewall/rules:SECTION NEW
SHELL cat /etc/shorewall/rules.d/*.rulesUsing Shell VariablesYou may use the /etc/shorewall/params file to
set shell variables that you can then use in the other configuration
files.It is suggested that variable names begin with an upper case letter
to distinguish them from variables used internally within the Shorewall
programsThe following variable names must be avoided. Those in bold font must be avoided in all Shorewall
versions; those in regular font must be avoided in versions prior to
4.4.8.Any option from shorewall.conf
(5)COMMANDCONFDIRDEBUGECHO_EECHO_NEXPORTFASTFILEMODEHOSTNAMEIPT_OPTIONSNOROUTESPREVIEWPRODUCTPROFILEPURGERECOVERINGRESTOREPATHRING_BELLSHAREDIRAny name beginning with SHOREWALL_ or
SW_STOPPINGTESTTIMESTAMPUSE_VERBOSITYVARDIRVERBOSEVERBOSE_OFFSETVERSIONExample:
/etc/shorewall/params
NET_IF=eth0
NET_BCAST=130.252.100.255
NET_OPTIONS=routefilter,routefilter
/etc/shorewall/interfaces record:
net $NET_IF $NET_BCAST $NET_OPTIONS
The result will be the same as if the record had been written
net eth0 130.252.100.255 routefilter,routefilter
Variables may be used anywhere in the other configuration
files.If you use "$FW" on the right side of assignments in the
/etc/shorewall/params file, you must also set the
FW variable in that file.Example:/etc/shorewall/zones:
#ZONE TYPE OPTIONS
fw firewall
/etc/shorewall/params:
FW=fw
BLARG=$FW:206.124.146.176Because the /etc/shorewall/params file is
simply sourced into the shell, you can place arbitrary shell code in the
file and it will be executed each time that the file is read. Any code
included should follow these guidelines:The code should not have side effects, especially on other
shorewall configuration files.The code should be safe to execute multiple times without
producing different results.Should not depend on where the code is called from (the params
file is sourced by both /sbin/shorewall and
/usr/lib/shorewall/firewall).Should not assume anything about the state of Shorewall.The names of any functions or variables declared should begin
with an upper case letter.The /etc/shorewall/params file is processed
by the compiler at compile-time and by the compiled script at
run-time. If you have set EXPORTPARAMS=No in
shorewall.conf, then the
params file is only
processed by the compiler; it is not run by the compiled
script.If you are using Shorewall Lite and if the
params script needs to set shell variables based
on the configuration of the firewall system, you can use this
trick:EXT_IP=$(ssh root@firewall "/sbin/shorewall-lite call find_first_interface_address eth0")The shorewall-lite call command allows you to
to call interactively any Shorewall function that you can call in an
extension script.Within your configuration files, only the $VAR and ${VAR} forms of
variable expansion are supported. You may not use the more exotic forms
supported by the shell (${VAR:=val}, ${VAR:-val}, ...)Embedded Shell and PerlEarlier versions of Shorewall offered extension scripts to allow
users to extend Shorewall's functionality. Extension scripts were designed
to work under the limitations of the Bourne Shell. With the current
Perl-based compiler, Embedded scripts offer a
richer and more flexible extension capability.While inline scripts may be written in either Shell or Perl, those
written in Perl have a lot more power.Embedded scripts can be either single-line or multi-line. Single
line scripts take one of the following forms:PERL <perl
script>SHELL <shell
script>Shell scripts run in a child shell process and their output is piped
back to the compiler which processes that output as if it were embedded at
the point of the script.Example: The following entries in
/etc/shorewall/rules are equivalent:SHELL for z in net loc dmz; do echo "ACCEPT $z fw tcp 22"; doneACCEPT net fw tcp 22
ACCEPT loc fw tcp 22
ACCEPT dmz fw tcp 22Perl scripts run in the context of of the compiler process using
Perl's eval() function. Perl scripts are implicitly prefixed by the
following:package Shorewall::User;
use Shorewall::Config qw/shorewall/;To produce output that will be processed by the compiler as if it
were embedded in the file at the point of the script, pass that output to
the Shorewall::Config::shorewall() function. The Perl equivalent of the
above SHELL script would be:PERL for ( qw/net loc dmz/ ) { shorewall "ACCEPT $_ fw tcp 22"; }A
couple of more points should be mentioned:Compile-time extension scripts are also implicitly prefixed by
"package Shorewall::User;".A compile extension script is
supported. That script is run early in the compilation process and
allows users to load additional modules and to define data and
functions for use in subsequent embedded scripts and extension
scripts.Manual Chains may be
added in the compile extension
script..Multi-line scripts use one of the following forms:BEGIN SHELL
<shell script>
END [ SHELL ]BEGIN PERL [;]
<perl script>
END [ PERL ] [;]Note: The '[' and ']' above are
meta-characters which indicate that what they enclose is optional and may
be omitted. So you may follow PERL with a semicolon ( ';') or you may omit
the semicolon.Using DNS NamesI personally recommend strongly against using DNS names in
Shorewall configuration files. If you use DNS names and you are called
out of bed at 2:00AM because Shorewall won't start as a result of DNS
problems then don't say that you were not forewarned.Host addresses in Shorewall configuration files may be specified as
either IP addresses or DNS Names.DNS names in iptables rules aren't nearly as useful as they first
appear. When a DNS name appears in a rule, the iptables utility resolves
the name to one or more IP addresses and inserts those addresses into the
rule. So changes in the DNS->IP address relationship that occur after
the firewall has started have absolutely no effect on the firewall's rule
set.For some sites, using DNS names is very risky. Here's an
example:teastep@ursa:~$ dig pop.gmail.com
; <<>> DiG 9.4.2-P1 <<>> pop.gmail.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1774
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 7, ADDITIONAL: 0
;; QUESTION SECTION:
;pop.gmail.com. IN A
;; ANSWER SECTION:
pop.gmail.com. 300 IN CNAME gmail-pop.l.google.com.
gmail-pop.l.google.com. 300 IN A 209.85.201.109
gmail-pop.l.google.com. 300 IN A 209.85.201.111Note that the TTL is 300 -- 300 seconds is only 5 minutes. So five
minutes later, the answer may change!So this rule may work for five minutes then suddently stop
working:#ACTION SOURCE DEST PROTO DEST
# PORT(S)
POP(ACCEPT) loc net:pop.gmail.comIf your firewall rules include DNS names then:If your /etc/resolv.conf is wrong then your
firewall won't start.If your /etc/nsswitch.conf is wrong then
your firewall won't start.If your Name Server(s) is(are) down then your firewall won't
start.If your startup scripts try to start your firewall before
starting your DNS server then your firewall won't start.Factors totally outside your control (your ISP's router is down
for example), can prevent your firewall from starting.You must bring up your network interfaces prior to starting your
firewall.Each DNS name must be fully qualified and include a minimum of two
periods (although one may be trailing). This restriction is imposed by
Shorewall to insure backward compatibility with existing configuration
files.Valid DNS Namesmail.shorewall.netshorewall.net. (note the trailing period).Invalid DNS Namesmail (not fully qualified)shorewall.net (only one period)DNS names may not be used as:The server address in a DNAT rule (/etc/shorewall/rules
file)In the ADDRESS column of an entry in /etc/shorewall/masq.In the /etc/shorewall/nat file.These restrictions are imposed by Netfilter and not by
Shorewall.Comma-separated ListsComma-separated lists are allowed in a number of contexts within the
configuration files. A comma separated list:Must not have any embedded white space. Valid: routefilter,dhcp,arpfilter
Invalid: routefilter, dhcp, arpfilterIf you use line continuation to break a comma-separated list,
the comma must be the last thing on the continued line before '\'
unless the continuation line has no leading white space.Entries in a comma-separated list may appear in any
order.Complementing an Address or SubnetWhere specifying an IP address, a subnet or an interface, you can
precede the item with ! to specify the complement of the
item. For example, !192.168.1.4 means any host but
192.168.1.4. There must be no white space following the
!.Exclusion ListsWhere a comma-separated list of addresses is accepted, an
exclusion list may also be included. An exclusion
list is a comma-separated list of addresses that begins with "!".Example:!192.168.1.3,192.168.1.12,192.168.1.32/27The above list refers to "All addresses except 192.168.1.3,
192.168.1.12 and 192.168.1.32-192.168.1.63.Exclusion lists can also be added after a network address.Example:192.168.1.0/24!192.168.1.3,192.168.1.12,192.168.1.32/27The above list refers to "All addresses in 192.168.1.0-192.168.1.255
except 192.168.1.3, 192.168.1.12 and 192.168.1.32-192.168.1.63.IP Address RangesIf you kernel and iptables have iprange match support, you may use
IP address ranges in Shorewall configuration file entries; IP address
ranges have the syntax <low IP
address>-<high IP address>.
Example: 192.168.1.5-192.168.1.12.To see if your kernel and iptables have the required support, use
the shorewall show capabilities command:>~ shorewall show capabilities
...
Shorewall has detected the following iptables/netfilter capabilities:
NAT: Available
Packet Mangling: Available
Multi-port Match: Available
Connection Tracking Match: Available
Packet Type Match: Not available
Policy Match: Available
Physdev Match: Available
IP range Match: Available <--------------Protocol Number/Names and Port Numbers/Service NamesUnless otherwise specified, when giving a protocol number you can
use either an integer or a protocol name from
/etc/protocols. Similarly, when giving a port number
you can use either an integer or a service name from
/etc/services.The rules compiler translates protocol names to protocol numbers
and service names to port numbers itself.Also, unless otherwise documented, a protocol number/name can be
preceded by '!' to specify "All protocols except this one" (e.g.,
"!tcp").ICMP and ICMP6 Types and CodesWhen dealing with ICMP, the DEST PORT specifies the type or type and
code. You may specify the numeric type, the numeric type and code
separated by a slash (e.g., 3/4) or you may use a type name.Type names for IPv4 and their corresponding type or type/code
are:echo-reply' => 0
destination-unreachable => 3
network-unreachable => 3/0
host-unreachable => 3/1
protocol-unreachable => 3/2
port-unreachable => 3/3
fragmentation-needed => 3/4
source-route-failed => 3/5
network-unknown => 3/6
host-unknown => 3/7
network-prohibited => 3/9
host-prohibited => 3/10
TOS-network-unreachable => 3/11
TOS-host-unreachable => 3/12
communication-prohibited => 3/13
host-precedence-violation => 3/14
precedence-cutoff => 3/15
source-quench => 4
redirect => 5
network-redirect => 5/0
host-redirect => 5/1
TOS-network-redirect => 5/2
TOS-host-redirect => 5/3
echo-request => 8
router-advertisement => 9
router-solicitation => 10
time-exceeded => 11
ttl-zero-during-transit => 11/0
ttl-zero-during-reassembly=> 11/1
parameter-problem => 12
ip-header-bad => 12/0
required-option-missing => 12/1
timestamp-request => 13
timestamp-reply => 14
address-mask-request => 17
address-mask-reply => 18Type names for IPv6 and their corresponding type or type/code
are:destination-unreachable => 1
no-route' => 1/0
communication-prohibited => 1/1
address-unreachable' => 1/2
port-unreachable' => 1/3
packet-too-big => 2
time-exceeded' => 3
ttl-exceeded' => 3
ttl-zero-during-transit => 3/0
ttl-zero-during-reassembly => 3/1
parameter-problem => 4
bad-header => 4/0
unknown-header-type => 4/1
unknown-option => 4/2
echo-request => 128
echo-reply => 129
router-solicitation => 133
router-advertisement => 134
neighbour-solicitation => 135
neighbour-advertisement => 136
redirect => 137Port RangesIf you need to specify a range of ports, the proper syntax is
<low port number>:<high port number>. For example, if you want
to forward the range of tcp ports 4000 through 4100 to local host
192.168.1.3, the entry in /etc/shorewall/rules is:#ACTION SOURCE DESTINATION PROTO DEST PORTS(S)
DNAT net loc:192.168.1.3 tcp 4000:4100If you omit the low port number, a value of zero is assumed; if you
omit the high port number, a value of 65535 is assumed.Also, unless otherwise documented, a port range can be preceded by
'!' to specify "All ports except those in this range" (e.g.,
"!4000:4100").Port ListsIn most cases where a port or port range may appear, a
comma-separated list of ports or port ranges may also be entered.
Shorewall requires the Netfilter multiport match capability if ports lists are used
(see the output of "shorewall show
capabilities").Also, unless otherwise documented, a port list can be preceded by
'!' to specify "All ports except these" (e.g., "!80,443").Prior to Shorewall 4.4.4, port lists appearing in the shorewall-routestopped
(5) file may specify no more than 15 ports; port ranges appearing in a
list count as two ports each.Using MAC AddressesMedia Access Control (MAC) addresses can be used to specify packet
source in several of the configuration files. In order to control traffic
to/from a host by its MAC address, the host must be on the same network as
the firewall.To use this feature, your kernel must have MAC Address Match support
(CONFIG_IP_NF_MATCH_MAC) included.MAC addresses are 48 bits wide and each Ethernet Controller has a
unique MAC address.In GNU/Linux, MAC addresses are usually written as a series of 6 hex
numbers separated by colons.MAC Address of an Ethernet Controller gateway:~ # ip link ls dev eth0
4: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc htb qlen 1000
link/ether 02:00:08:E3:FA:55 brd ff:ff:ff:ff:ff:ff
gateway:~ #Because Shorewall uses colons as a separator for address fields,
Shorewall requires MAC addresses to be written in another way. In
Shorewall, MAC addresses begin with a tilde (~) and consist
of 6 hex numbers separated by hyphens. In Shorewall, the MAC address in
the example above would be written ~02-00-08-E3-FA-55.It is not necessary to use the special Shorewall notation in the
/etc/shorewall/maclist
file.Rate Limiting (Rate and Burst)Shorewall supports rate limiting in a number of ways. When
specifying a rate limit, both a rate and a
burst value are given.Example from shorewall.conf (5):LOGRATE=10/minuteLOGBURST=5For each logging rule, the first time the rule is reached, the
packet will be logged; in fact, since the burst is 5, the first five
packets will be logged. After this, it will be 6 seconds (1 minute divided
by the rate of 10) before a message will be logged from the rule,
regardless of how many packets reach it. Also, every 6 seconds which
passes, one of the bursts will be regained; if no packets hit the rule for
30 seconds, the burst will be fully recharged; back where we
started.Logical Interface NamesWhen dealing with a complex configuration, it is often awkward to
use physical interface names in the Shorewall configuration.You need to remember which interface is which.If you move the configuration to another firewall, the interface
names might not be the same.Beginning with Shorewall 4.4.4, you can use logical interface names
which are mapped to the actual interface using the
option in shorewall-interfraces
(5).Here is an example:#ZONE INTERFACE BROADCAST OPTIONS
net COM_IF detect dhcp,blacklist,tcpflags,optional,upnp,routefilter=0,nosmurfs,logmartians=0,physical=eth0
net EXT_IF detect dhcp,blacklist,tcpflags,optional,routefilter=0,nosmurfs,logmartians=0,proxyarp=1,physical=eth2
loc INT_IF detect dhcp,logmartians=1,routefilter=1,tcpflags,nets=172.20.1.0/24,physical=eth1
dmz VPS_IF detect logmartians=1,routefilter=0,routeback,physical=venet0
loc TUN_IF detect physical=tun+In this example, COM_IF is a logical interface name that refers to
Ethernet interface eth0, EXT_IF is
a logical interface name that refers to Ethernet interface eth2, and so on.Here are a couple of more files from the same configuration:shorewall-masq
(5):#INTERFACE SOURCE ADDRESS
COMMENT Masquerade Local Network
COM_IF 0.0.0.0/0
EXT_IF !206.124.146.0/24 206.124.146.179:persistentshorewall-providers
(5)#NAME NUMBER MARK DUPLICATE INTERFACE GATEWAY OPTIONS COPY
Avvanta 1 0x10000 main EXT_IF 206.124.146.254 loose,fallback INT_IF,VPS_IF,TUN_IF
Comcast 2 0x20000 main COM_IF detect balance INT_IF,VPS_IF,TUN_IFNote in particular that Shorewall translates TUN_IF to tun* in the COPY column.Shorewall ConfigurationsShorewall allows you to have configuration directories other than
/etc/shorewall. The shorewall
check, start and restart commands allow you to specify an alternate
configuration directory and Shorewall will use the files in the alternate
directory rather than the corresponding files in /etc/shorewall. The
alternate directory need not contain a complete configuration; those files
not in the alternate directory will be read from /etc/shorewall.Shorewall requires that the file
/etc/shorewall/shorewall.conf to always exist.
Certain global settings are always obtained from that file. If you
create alternative configuration directories, do not remove
/etc/shorewall/shorewall.conf.This facility permits you to easily create a test or temporary
configuration bycopying the files that need modification from /etc/shorewall to
a separate directory;modify those files in the separate directory; andspecifying the separate directory in a shorewall
start or shorewall restart command (e.g.,
shorewall restart /etc/testconfig )Saved ConfigurationsShorewall allows you to save the
currently-running configuration in a form that permits it to be
re-installed quickly. When you save the configuration using the
shorewall save command, the running configuration is
saved in a file in the /var/lib/shorewall directory. The default
name of that file is /var/lib/shorewall/restore but
you can specify a different name as part of the command. For example, the
command shorewall save standard will save the running
configuration in /var/lib/shorewall/standard. A saved
configuration is re-installed using the shorewall
restore command. Again, that command normally will restore the
configuration saved in /var/lib/shorewall/restore but
as with the save command, you can specify a different
file name in the command. For example, shorewall restore
standard will re-install the configuration saved in
/var/lib/shorewall/standard. By permitting you to
save different configurations under different names, Shorewall provides a
means for quickly switching between these different saved
configurations.As mentioned above, the default configuration is called 'restore'
but like most things in Shorewall, that default can be changed. The
default name is specified using the RESTOREFILE option in
/etc/shorewall/shorewall.conf.The default saved configuration is used by Shorewall in a number
of ways besides in the restore command; to avoid
surprises, I recommend that you read the Shorewall Operations
documentation section about saved configurations before creating
one.