Provided by: shorewall_5.2.8-2_all 
NAME
shorewall.conf - Shorewall global configuration file
SYNOPSIS
/etc/shorewall/shorewall.conf
/etc/shorewall6/shorewall6.conf
DESCRIPTION
The IPv4 and IPv6 environments each have their own configuration. The IPv4 configuration
resides in /etc/shorewall/ while the IPv6 configuration resides in /etc/shorewall6/.
The .conf files set options that apply to Shorewall and Shorewall6 as a whole.
The .conf files consist of Shell comments (lines beginning with '#'), blank lines and
assignment statements (variable=value). If the value contains shell meta characters or
white-space, then it must be enclosed in quotes. Example:
MACLIST_LOG_LEVEL="NFLOG(1,0,1)".
OPTIONS
Many options have as their value a log-level. Log levels are a method of describing to
syslog (8) the importance of a message and a number of parameters in this file have log
levels as their value.
These levels are defined by syslog and are used to determine the destination of the
messages through entries in /etc/syslog.conf (5). The syslog documentation refers to these
as "priorities"; Netfilter calls them "levels" and Shorewall also uses that term.
Valid levels are:
7 debug
6 info
5 notice
4 warning
3 err
2 crit
1 alert
0 emerg
For most Shorewall logging, a level of 6 (info) is appropriate. Shorewall log messages are
generated by NetFilter and are logged using facility 'kern' and the level that you
specify. If you are unsure of the level to choose, 6 (info) is a safe bet. You may specify
levels by name or by number.
If you have built your kernel with ULOG (IPv4 only) and/or NFLOG target support, you may
also specify a log level of ULOG and/or NFLOG (must be all caps). Rather than log its
messages to syslogd, Shorewall will direct netfilter to log the messages via the ULOG or
NFLOG target which will send them to a process called 'ulogd'. ulogd is available with
most Linux distributions (although it probably isn't installed by default).
Note
If you want to specify parameters to ULOG or NFLOG (e.g., NFLOG(1,0,1)), then you must
quote the setting.
Example:
LOG_LEVEL="NFLOG(1,0,1)"
Beginning with Shorewall 5.0.0, the log level may be followed by a colon (":") and a log
tag. The log tag normally follows the packet disposition in Shorewall-generated Netfilter
log messages, separated from the disposition by a colon (e.g, "DROP:mytag"). See
LOGTAGONLY below for additional information.
Beginning with Shorewall 4.4.22, LOGMARK is also a valid level which logs the packet's
mark value along with the other usual information. The syntax is:
LOGMARK[(priority)]
where priority is one of the levels listed in the list above. If omitted, the default is
info (6).
The following options may be set in shorewall.conf.
ACCEPT_DEFAULT={action[(parameters)][:level][,...]|none}
BLACKLIST_DEFAULT={action[(parameters)][:level][,...]|none}
DROP_DEFAULT={action[(parameters)][:level][,...]|none}
NFQUEUE_DEFAULT={action[(parameters)][:level][,...]|none}
QUEUE_DEFAULT={action[(parameters)][:level][,...]|none}
REJECT_DEFAULT={action[(parameters)][:level][,...]|none}
In earlier Shorewall versions, a "default action" for DROP and REJECT policies was
specified in the file /usr/share/shorewall/actions.std.
In Shorewall 4.4.0, the DROP_DEFAULT, REJECT_DEFAULT, ACCEPT_DEFAULT, QUEUE_DEFAULT
and NFQUEUE_DEFAULT options were added.
DROP_DEFAULT describes the rules to be applied before a connection request is dropped
by a DROP policy; REJECT_DEFAULT describes the rules to be applied if a connection
request is rejected by a REJECT policy. The other three are similar for ACCEPT, QUEUE
and NFQUEUE policies.
The value applied to these may be:
a) The name of an action. The
name may optionally be followed by a comma-separated list of
parameters enclosed in parentheses if the specified action accepts
parameters (e.g., 'Drop(audit)').
c) None or none
Prior to Shorewall 5.1.2, the default values are:
DROP_DEFAULT="Drop"
REJECT_DEFAULT="Reject"
BLACKLIST_DEFAULT="Drop" (added in Shorewall
5.1.1)
ACCEPT_DEFAULT="none"
QUEUE_DEFAULT="none"
NFQUEUE_DEFAULT="none"
Beginning with Shorewall 5.1.2, the default value is 'none' for all of these. Note
that the sample configuration files do, however, provide settings for DROP_DEFAULT,
BLACKLIST_DEFAULT and REJECT_DEFAULT.
If you set the value of either option to "None" then no default action will be used
and the default action or macro must be specified in shorewall-policy[1](5).
You can pass parameters to the specified action (e.g., myaction(audit,DROP)).
Beginning with Shorewall 4.5.10, the action name can be followed optionally by a colon
and a log level. The level will be applied to each rule in the action or body that
does not already have a log level.
Beginning with Shorewall 5.1.2, multiple action[(parameters)][:level] specifications
may be listed, separated by commas.
ACCOUNTING=[Yes|No]
Added in Shorewall 4.4.7. If set to Yes, Shorewall accounting is enabled (see
shorewall-accounting[2](5)). If not specified or set to the empty value,
ACCOUNTING=Yes is assumed.
ACCOUNTING_TABLE=[filter|mangle]
Added in Shorewall 4.4.20. This setting determines which Netfilter table the
accounting rules are added in. By default, ACCOUNTING_TABLE=filter is assumed. See
also shorewall-accounting[2](5).
ADD_IP_ALIASES=[Yes|No]
This parameter determines whether Shorewall automatically adds the external
address(es) in shorewall-nat[3](5), and is only available in IPv4 configurations. If
the variable is set to Yes or yes then Shorewall automatically adds these aliases. If
it is set to No or no, you must add these aliases yourself using your distribution's
network configuration tools.
If this variable is not set or is given an empty value (ADD_IP_ALIASES="") then
ADD_IP_ALIASES=Yes is assumed.
Warning
Addresses added by ADD_IP_ALIASES=Yes are deleted and re-added during shorewall
reload and shorewall restart. As a consequence, connections using those addresses
may be severed.
ADD_SNAT_ALIASES=[Yes|No]
This parameter determines whether Shorewall automatically adds the SNAT ADDRESS in
shorewall-masq[4](5), and is only available in IPv4 configurations. If the variable is
set to Yes or yes then Shorewall automatically adds these addresses. If it is set to
No or no, you must add these addresses yourself using your distribution's network
configuration tools.
If this variable is not set or is given an empty value (ADD_SNAT_ALIASES="") then
ADD_SNAT_ALIASES=No is assumed.
Warning
Addresses added by ADD_SNAT_ALIASES=Yes are deleted and re-added during shorewall
reload and shorewall restart. As a consequence, connections using those addresses
may be severed.
ADMINISABSENTMINDED=[Yes|No]
The value of this variable affects Shorewall's stopped state. The behavior differs
depending on whether shorewall-routestopped[5](5) or shorewall-stoppedrules[6](5) is
used:
routestopped
When ADMINISABSENTMINDED=No, only traffic to/from those addresses listed in
routestopped is accepted when Shorewall is stopped. When ADMINISABSENTMINDED=Yes,
in addition to traffic to/from addresses in routestopped, connections that were
active when Shorewall stopped continue to work and all new connections from the
firewall system itself are allowed.
Note that the routestopped file is not supported in Shorewall 5.0 and later
versions.
stoppedrules
All existing connections continue to work. To sever all existing connections when
the firewall is stopped, install the conntrack utility and place the command
conntrack -F in the stopped user exit (/etc/shorewall/stopped).
If ADMINISABSENTMINDED=No, only new connections matching entries in stoppedrules
are accepted when Shorewall is stopped. Response packets and related connections
are automatically accepted.
If ADMINISABSENTMINDED=Yes, in addition to connections matching entries in
stoppedrules, all new connections from the firewall system itself are allowed when
the firewall is stopped. Response packets and related connections are
automatically accepted.
If this variable is not set or is given the empty value then ADMINISABSENTMINDED=No is
assumed.
ARPTABLES=[pathname]
Added in Shorewall 4.5.12 and available in IPv4 only. This parameter names the
arptables executable to be used by Shorewall. If not specified or if specified as a
null value, then the arptables executable located using the PATH option is used.
Regardless of how the arptables utility is located (specified via arptables= or
located via PATH), Shorewall uses the arptables-restore and arptables-save utilities
from that same directory.
AUTOCOMMENT=[Yes|No]
Formerly named AUTO_COMMENT. If set, if there is not a current comment when a macro is
invoked, the behavior is as if the first line of the macro file was "COMMENT <macro
name>". If not specified, the AUTO_COMMENT option has a default value of 'Yes'.
AUTOHELPERS=[Yes|No]
Added in Shorewall 4.5.7. When set to Yes (the default), the generated ruleset will
automatically associate helpers with applications that require them (FTP, IRC, etc.).
When configuring your firewall on systems running kernel 3.5 or later, it is
recommended that you:
1. Set AUTOHELPERS=No.
2. Modify the HELPERS setting (see below) to list the helpers that you need.
3. Either:
1. Modify shorewall-conntrack[7] (5) to only apply helpers where they are
required; or
2. Specify the appropriate helper in the HELPER column in shorewall-rules[8] (5).
Note
The macros for those applications requiring a helper automatically specify
the appropriate HELPER where required.
AUTOMAKE=[Yes|No|recursive|depth]
If set, the behavior of the start, reload and restart commands are changed; if no
files in CONFIG_PATH (see below) have been changed since the last successful start,
reload or restart command, then the compilation step is skipped and the compiled
script that executed the last start, reload or restart command is used. If not
specified, the default is AUTOMAKE=No.
The setting of the AUTOMAKE option is ignored if the start, reload or restart command
includes a directory name (e.g., shorewall restart /etc/shorewall.new).
When AUTOMAKE=Yes, each directory in the CONFIG_PATH was originally searched
recursively for files newer than the compiled script. That was changed in Shorewall
5.1.10.2 such that only the listed directories themselves were searched. That broke
some configurations that played tricks with embedded SHELL such as "SHELL cat
/etc/shorewall/rules.d/loc/*.rules". Prior to 5.1.10.2, a change to a file in or
adding a file to /etc/shorewall/rules.d/loc/ would trigger recompilation. Beginning
with 5.1.10.2, such changes would not trigger recompilation. Beginning with Shorewall
5.2.0, the pre-5.1.10.2 behavior can be obtained by setting AUTOMAKE=recursive.
Also beginning with Shorewall 5.2.0, AUTOMAKE may be set to a numeric depth which
specifies how deeply each listed directory is to be searched. AUTOMAKE=1 only searches
each directory itself and is equivalent to AUTOMAKE=Yes. AUTOMAKE=2 will search each
directory and its immediate sub-directories; AUTOMAKE=3 will search each directory,
each of its immediate sub-directories, and each of their immediate sub-directories,
etc.
BALANCE_PROVIDERS=[Yes|No]
Added in Shorewall 5.1.1. When USE_DEFAULT_RT=Yes, this option determines whether the
balance provider option (see shorewall-providers(5)[9]) is the default. When
BALANCE_PROVIDERS=Yes, then the balance option is assumed unless the fallback, loose,
load or tproxy option is specified. If this option is not set or is set to the empty
value, then the default value is the value of USE_DEFAULT_RT.
BASIC_FILTERS=[Yes|No]
Added in Shorewall-4.6.0. When set to Yes, causes entries in
shorewall-tcfilters(5)[10] to generate a basic filter rather than a u32 filter. This
setting requires the Basic Ematch capability in your kernel and iptables.
Note
One of the advantages of basic filters is that ipset matches are supported in
newer iproute2 and kernel versions. Because Shorewall cannot reliably detect this
capability, use of basic filters is controlled by this option.
The default value is No which causes u32 filters to be generated.
BLACKLIST=[{ALL|state[,...]}]
where state is one of NEW, ESTABLISHED, RELATED, INVALID,or UNTRACKED.
Added in Shorewall 4.5.13 to replace the BLACKLISTNEWONLY option. Specifies the
connection tracking states that are to be subject to blacklist screening. If BLACKLIST
is not specified then the states subject to blacklisting are
NEW,ESTABLISHED,INVALID,UNTRACKED.
ALL sends all packets through the blacklist chains.
Note: The ESTABLISHED state may not be specified if FASTACCEPT=Yes is specified.
BLACKLIST_DISPOSITION=[DROP|A_DROP|REJECT|A_REJECT]
This parameter determines the disposition of packets from blacklisted hosts. It may
have the value DROP if the packets are to be dropped or REJECT if the packets are to
be replied with an ICMP port unreachable reply or a TCP RST (tcp only). If you do not
assign a value or if you assign an empty value then DROP is assumed.
A_DROP and A_REJECT are audited versions of DROP and REJECT respectively and were
added in Shorewall 4.4.20. They require AUDIT_TARGET in the kernel and iptables.
The BLACKLIST_DISPOSITION setting determines the disposition of packets sent to the
blacklog target of shorewall-blrules[11](5), but otherwise does not affect entries in
that file.
BLACKLIST_LOG_LEVEL=[log-level[:log-tag]]
Formerly named BLACKLIST_LOGLEVEL. This parameter determines if packets from
blacklisted hosts are logged and it determines the syslog level that they are to be
logged at. Its value is a syslog level (Example: BLACKLIST_LOG_LEVEL=debug). If you do
not assign a value or if you assign an empty value then packets from blacklisted hosts
are not logged. The setting determines the log level of packets sent to the blacklog
target of shorewall-blrules[11](5).
CLAMPMSS=[Yes|No|value]
This parameter enables the TCP Clamp MSS to PMTU feature of Netfilter and is usually
required when your internet connection is through PPPoE or PPTP. If set to Yes or yes,
the feature is enabled. If left blank or set to No or no, the feature is not enabled.
Important: This option requires CONFIG_IP_NF_TARGET_TCPMSS in your kernel.
You may also set CLAMPMSS to a numeric value (e.g., CLAMPMSS=1400). This will set the
MSS field in TCP SYN packets going through the firewall to the value that you specify.
CLEAR_TC=[Yes|No]
If this option is set to No then Shorewall won't clear the current traffic control
rules during [re]start or reload. This setting is intended for use by people who
prefer to configure traffic shaping when the network interfaces come up rather than
when the firewall is started. If that is what you want to do, set TC_ENABLED=Yes and
CLEAR_TC=No and do not supply an /etc/shorewall/tcstart file. That way, your traffic
shaping rules can still use the “fwmark” classifier based on packet marking defined in
shorewall-tcrules[12](5). If not specified, CLEAR_TC=Yes is assumed.
Warning
When you specify TC_ENABLED=shared (see below), then you should also specify
CLEAR_TC=No.
COMPLETE=[Yes|No]
Added in Shorewall 4.4.12. When you set this option to Yes, you are asserting that the
configuration is complete so that your set of zones encompasses any hosts that can
send or receive traffic to/from/through the firewall. This causes Shorewall to omit
the rules that catch packets in which the source or destination IP address is outside
of any of your zones. Default is No. It is recommended that this option only be set to
Yes if:
• You have defined an interface whose effective physical setting is '+'.
• That interface is assigned to a zone.
• You have no CONTINUE policies or rules.
CONFIG_PATH=[[:]directory[:directory]...]
Specifies where configuration files other than shorewall[6].conf may be found.
CONFIG_PATH is specifies as a list of directory names separated by colons (":"). When
looking for a configuration file:
• If the command is "try" or a "<configuration directory>" was specified in the
command (e.g., shorewall [-6] check ./gateway) then the directory given in the
command is searched first.
• Next, each directory in the CONFIG_PATH setting is searched in sequence.
If CONFIG_PATH is not given or if it is set to the empty value then the contents of
/usr/share/shorewall/configpath are used. As released from shorewall.net, that file
sets the CONFIG_PATH to /etc/shorewall:/usr/share/shorewall but your particular
distribution may set it differently. See the output of shorewall show config for the
default on your system.
Beginning with Shorewall 5.1.10, the CONFIG_PATH setting may begin with a colon (":"),
to signal that the first directory listed will be skipped if the user performing a
compilation is not root or if the configuration is being compiled for export (-e
option specified or if running one of the remote-* commands) . This prevents the
compiler from looking in /etc/shorewall[6]/ when compilation is being done by a
non-root user or if the generated script is to be sent to a remote firewall system.
DEFER_DNS_RESOLUTION=[Yes|No]
Added in Shorewall 4.5.12. When set to 'Yes' (the default), DNS names are validated in
the compiler and then passed on to the generated script where they are resolved by
ip[6]tables-restore. This is an advantage if you use AUTOMAKE=Yes and the IP address
associated with the DNS name is subject to change. When DEFER_DNS_RESOLUTION=No, DNS
names are converted into IP addresses by the compiler. This has the advantage that
when AUTOMAKE=Yes, the start, reload and restart commands will succeed even if no DNS
server is reachable (assuming that the configuration hasn't changed since the compiled
script was last generated).
Important
When DEFER_DNS_RESOLUTION=No and AUTOMAKE=Yes and a DNS change makes it necessary
to recompile an existing firewall script, the -c option must be used with the
reload or restart command to force recompilation.
DELETE_THEN_ADD={Yes|No}
If set to Yes (the default value), entries in the /etc/shorewall[6]/rtrules files
cause an 'ip rule del' command to be generated in addition to an 'ip rule add'
command. Setting this option to No, causes the 'ip rule del' command to be omitted.
DETECT_DNAT_IPADDRS=[Yes|No]
IPv4 only.
If set to Yes or yes, Shorewall will detect the first IP address of the interface to
the source zone and will include this address in DNAT rules as the original
destination IP address. If set to No or no, Shorewall will not detect this address and
any destination IP address will match the DNAT rule. If not specified or empty,
“DETECT_DNAT_IPADDRS=Yes” is assumed.
DISABLE_IPV6=[Yes|No]
IPv4 only.
If set to Yes or yes, IPv6 traffic to, from and through the firewall system is
disabled. If set to No or no, Shorewall will take no action with respect to allowing
or disallowing IPv6 traffic. If not specified or empty, “DISABLE_IPV6=No” is assumed.
It is important to note that changing DISABLE_IPV6=Yes to DISABLE_IPV6=No does not
enable IPV6. The recommended approach for enabling IPv6 on your system is:
• Install, configure and start Shorewall6[13].
• Change DISABLE_IPV6=Yes to DISABLE_IPV6=No in /etc/shorewall/shorewall.conf.
• Reload Shorewall
DOCKER=[Yes|No]
Added in Shorewall 5.0.6; IPv4 only. When set to Yes, the generated script will save
Docker-generated rules before and restore them after executing the start, stop, reload
and restart commands. If set to No (the default), the generated script will delete any
Docker-generated rules when executing those commands.
Seehttps://shorewall.org/Docker.html[14] for additional information.
DOCKER_BRIDGE=[bridgename]
Added in Shorewall 5.2.4; IPv4 only. Specifies the name of the default Docker bridge.
If not specified, the value 'docker0' is assumed.
DONT_LOAD=[module[,module]...]
Causes Shorewall to not load the listed kernel modules.
DYNAMIC_BLACKLIST={Yes|No||ipset[-only][,option[,...]][:[setname][:log_level|:log_tag]]]}
Added in Shorewall 4.4.7. When set to No or no, chain-based dynamic blacklisting using
shorewall [-6] [-l] drop, shorewall [-6] [-l] reject, shorewall logdrop and shorewall
[-6] [-l] logreject is disabled. Default is Yes. Beginning with Shorewall 5.0.8,
ipset-based dynamic blacklisting using the shorewall blacklist command is also
supported. The name of the set (setname) and the level (log_level), if any, at which
blacklisted traffic is to be logged may also be specified. The default IPv4 set name
is SW_DBL4 and the default IPv6 set name is SW_DBL6. The default log level is none (no
logging). If ipset-only is given, then chain-based dynamic blacklisting is disabled
just as if DYNAMIC_BLACKLISTING=No had been specified.
Possible options are:
src-dst
Normally, only packets whose source address matches an entry in the ipset are
dropped. If src-dst is included, then packets whose destination address matches an
entry in the ipset are also dropped.
disconnect
The disconnect option was added in Shorewall 5.0.13 and requires that the
conntrack utility be installed on the firewall system. When an address is
blacklisted using the blacklist command, all connections originating from that
address are disconnected. if the src-dst option was also specified, then all
connections to that address are also disconnected.
timeout=seconds
Added in Shorewall 5.0.13. Normally, Shorewall creates the dynamic blacklisting
ipset with timeout 0 which means that entries are permanent. If you want entries
in the set that are not accessed for a period of time to be deleted from the set,
you may specify that period using this option. Note that the blacklist command can
override the ipset's timeout setting.
Important
Once the dynamic blacklisting ipset has been created, changing this option
setting requires a complete restart of the firewall; shorewall [-6] restart if
RESTART=restart, otherwise shorewall [-6] [-l] stop && shorewall [-6] [-l]
start
log
Added in Shorewall 5.2.5. When specified, successful 'blacklist' and 'allow'
commands will log a message to the system log.
noupdate
Added in Shorewall 5.2.5. Normally, once an address has been blacklisted, each
time that a packet is received from the packet, the ipset's entry for the address
is updated to reset the timeout to the value specifyed in the timeout option
above. Setting the noupdate option, inhibits this resetting of the entry's
timeout. This option is ignored when the timeout option is not specified.
When ipset-based dynamic blacklisting is enabled, the contents of the blacklist will
be preserved over stop/reboot/start sequences.
EXPAND_POLICIES={Yes|No}
Normally, when the SOURCE or DEST columns in shorewall-policy(5) contains 'all', a
single policy chain is created and thes policy is enforced in that chain. For example,
if the policy entry is
#SOURCE DEST POLICY LOG
# LEVEL
net all DROP info
then the chain name is 'net-all' ('net2all if ZONE2ZONE=2) which is also the chain
named in Shorewall log messages generated as a result of the policy. If
EXPAND_POLICIES=Yes, then Shorewall will create a separate chain for each pair of
zones covered by the policy. This makes the resulting log messages easier to interpret
since the chain in the messages will have a name of the form 'a2b' where 'a' is the
SOURCE zone and 'b' is the DEST zone.
EXPORTMODULES=[Yes|No]
Added in Shorewall 4.4.17. When set to Yes when compiling for use by Shorewall Lite
(shorewall [-6] remote-start, shorewall [-6] remote-reload, shorewall [-6]
remote-restart or shorewall [-6] export commands), the compiler will copy the modules
or helpers file from the administrative system into the script. When set to No or not
specified, the compiler will not copy the modules or helpers file from
/usr/share/shorewall[6] but will copy those found in another location on the
CONFIG_PATH.
When compiling for direct use by Shorewall, causes the contents of the local module or
helpers file to be copied into the compiled script. When set to No or not set, the
compiled script reads the file itself.
FASTACCEPT={Yes|No}
Normally, Shorewall defers accepting ESTABLISHED/RELATED packets until these packets
reach the chain in which the original connection was accepted. So for packets going
from the 'loc' zone to the 'net' zone, ESTABLISHED/RELATED packets are ACCEPTED in the
'loc-net' or 'loc2net' chain, depending on the setting of ZONE2ZONE (see below).
If you set FASTACCEPT=Yes, then ESTABLISHED/RELATED packets are accepted early in the
INPUT, FORWARD and OUTPUT chains. If you set FASTACCEPT=Yes then you may not include
rules in the ESTABLISHED or RELATED sections of shorewall-rules[8](5).
FIREWALL=[dnsname-or-ip-address]
This option was added in Shorewall 5.0.13 and may be used on an administrative system
in directories containing the configurations of remote firewalls. The contents of the
variable are the default value for the system parameter to the remote-start,
remote-reload and remote-restart commands.
FORWARD_CLEAR_MARK={Yes|No}
Added in Shorewall 4.4.11. Traditionally, Shorewall has cleared the packet mark in the
first rule in the mangle FORWARD chain. This behavior is maintained with the default
setting of this option (FORWARD_CLEAR_MARK=Yes). If FORWARD_CLEAR_MARK is set to 'No',
packet marks set in the mangle PREROUTING chain are retained in the FORWARD chains.
GEOIPDIR=[pathname]
Added in Shorewall 4.5.4. Specifies the pathname of the directory containing the GeoIP
Match database. See https://shorewall.org/ISO-3661.html[15]. If not specified, the
default value is /usr/share/xt_geoip/LE which is the default location of the
little-endian database.
HELPERS=[helper[,helper...]]
Added in Shorewall 4.5.7. This option specifies a comma-separated list naming the
Netfilter application helpers that are to be enabled. If not specified, the default is
to enable all helpers.
Possible values for helper are:
• amanda
• ftp
• h323
• irc
• netbios-ns
• none - This special value was added in Shorewall 4.5.16 and indicates that no
helpers are to be enabled. It also prevents the compiler for probing for helper
support; such probing generates messages on the system log of the form "xt_CT: No
such helper XXX" where XXX is the helper name. When used, none must be the only
helper specified.
• pptp
• sane
• sip
• snmp
• tftp
When HELPERS is specified on a system running Kernel 3.5.0 or later, automatic
association of helpers to connections is disabled.
IGNOREUNKNOWNVARIABLES=[Yes|No]
Added in Shorewall 4.5.11. Normally, if an unknown shell variable is encountered in a
configuration file (except in ?IF and ?ELSIF directives), the compiler raises a fatal
error. If IGNOREUNKNOWNVARIABLES is set to Yes, then such variables simply expand to
an empty string. Default is No.
IMPLICIT_CONTINUE={Yes|No}
When this option is set to Yes, it causes subzones to be treated differently with
respect to policies.
Subzones are defined by following their name with ":" and a list of parent zones (in
shorewall-zones[16](5)). Normally, you want to have a set of special rules for the
subzone and if a connection doesn't match any of those subzone-specific rules then you
want the parent zone rules and policies to be applied; see shorewall-nesting[17](5).
With IMPLICIT_CONTINUE=Yes, that happens automatically.
If IMPLICIT_CONTINUE=No or if IMPLICIT_CONTINUE is not set, then subzones are not
subject to this special treatment. With IMPLICIT_CONTINUE=Yes, an implicit CONTINUE
policy may be overridden by including an explicit policy (one that does not specify
"all" in either the SOURCE or the DEST columns).
INVALID_DISPOSITION=[A_DROP|A_REJECT|DROP|REJECT|CONTINUE]
Added in Shorewall 4.5.13. Shorewall has traditionally passed INVALID packets through
the NEW section of shorewall-rules[8] (5). When a packet in INVALID state fails to
match any rule in the INVALID section, the packet is disposed of based on this
setting. The default value is CONTINUE for compatibility with earlier versions.
INVALID_LOG_LEVEL=log-level[:log-tag]
Added in Shorewall 4.5.13. Packets in the INVALID state that do not match any rule in
the INVALID section of shorewall-rules[8] (5) are logged at this level. The default
value is empty which means no logging is performed.
IP=[pathname]
If specified, gives the pathname of the 'ip' executable. If not specified, 'ip' is
assumed and the utility will be located using the current PATH setting.
IP_FORWARDING=[On|Off|Keep]
This IPv4 parameter determines whether Shorewall enables or disables IPv4 Packet
Forwarding (/proc/sys/net/ipv4/ip_forward). In an IPv6 configuration, this parameter
determines the setting of /proc/sys/net/ipv6/config/all/ip_forwarding.
Possible values are:
On or on
packet forwarding will be enabled.
Off or off
packet forwarding will be disabled.
Keep or keep
Shorewall will neither enable nor disable packet forwarding.
If this variable is not set or is given an empty value (IP_FORWARD="") then
IP_FORWARD=On is assumed.
IPSET=[pathname]
If specified, gives the pathname of the 'ipset' executable. If not specified, 'ipset'
is assumed and the utility will be located using the current PATH setting.
IPSET_WARNINGS={Yes|No}
Added in Shorewall 4.5.2. Default is Yes. When set, causes the rules compiler to issue
a warning when:
• The compiler is being run by root and an ipset specified in the configuration does
not exists. Only one warning is issued for each missing ipset.
• When [src] is specified in a destination column and when [dst] is specified in a
source column.
IPTABLES=[pathname]
IPv4 only.
This parameter names the iptables executable to be used by Shorewall. If not specified
or if specified as a null value, then the iptables executable located using the PATH
option is used.
Regardless of how the iptables utility is located (specified via IPTABLES= or located
via PATH), Shorewall uses the iptables-restore and iptables-save utilities from that
same directory.
IP6TABLES=[pathname]
IPv6 only.
This parameter names the ip6tables executable to be used by Shorewall6. If not
specified or if specified as a null value, then the ip6tables executable located using
the PATH option is used.
Regardless of how the ip6tables utility is located (specified via IP6TABLES= or
located via PATH), Shorewall6 uses the ip6tables-restore and ip6tables-save utilities
from that same directory.
KEEP_RT_TABLES={Yes|No}
IPv4: When set to Yes, this option prevents generated scripts from altering the
/etc/iproute2/rt_tables database when there are entries in /etc/shorewall/providers.
If you set this option to Yes while Shorewall (Shorewall-lite) is running, you should
remove the file /var/lib/shorewall/rt_tables (/var/lib/shorewall-lite/rt_tables)
before your next stop, restore, reload or restart command. IPv6: When set to Yes,
this option prevents scripts generated by Shorewall6 from altering the
/etc/iproute2/rt_tables database when there are entries in /etc/shorewall6/providers.
If you set this option to Yes while Shorewall6 (Shorewall6-lite) is running, you
should remove the file /var/lib/shorewall6/rt_tables
(/var/lib/shorewall6-lite/rt_tables) before your next stop, restore, reload or restart
command.
Important
When both IPv4 and IPv6 Shorewall configurations are present, KEEP_RT_TABLES=No
should be specified in only one of the two configurations unless the two provider
configurations are identical with respect to interface and provider names and
numbers.
The default is KEEP_RT_TABLES=No.
LOAD_HELPERS_ONLY={Yes|No}
Added in Shorewall 4.4.7. When set to Yes, restricts the set of modules loaded by
shorewall to those listed in /var/lib/shorewall[6]/helpers and those that are actually
used. When not set, or set to the empty value, LOAD_HELPERS_ONLY=No is assumed in
Shorewall versions 5.2.2 and earlier. Beginning with Shorewall 5.2.3, the
LOAD_HELPERS_ONLY option is removed, and the behavior is as if LOAD_HELPERS_ONLY=Yes
had been specified.
LOCKFILE=[pathname]
Specifies the name of the Shorewall[6] lock file, used to prevent simultaneous
state-changing commands. If not specified, ${VARDIR}/shorewall[6]/lock is assumed
(${VARDIR} is normally /var/lib but can be changed when Shorewall-core is installed --
see the output of shorewall show vardir).
LOG_BACKEND=[backend]
Added in Shorewall 4.6.4. LOG_BACKEND determines the logging backend to be used for
the iptrace command (see shorewall(8)[18]).
backend is one of:
LOG
Use standard kernel logging.
ULOG
IPv4 only.
Use ULOG logging to ulogd.
netlink
Use netlink logging to ulogd version 2 or later.
LOG_ZONE=[src|dst|both]
Added in Shorewall 5.2.0. When a log message is issued from a chain that relates to a
pair of zones (e.g, 'fw-net'), the chain name normally appears in the log message
(unless LOGTAGONLY=Yes and a log tag is specified). This can prevent OPTIMIZE category
8 from combining chains which are identical except for the names of the zones
involved. LOG_ZONE allows for only the source or destination zone to appear in the
messages by setting LOG_ZONE to src or dest respectively. If LOG_ZONE=both (the
default), then the full chain name is included in log messages.
LOG_LEVEL=log-level[:log-tag]
Added in Shorewall 5.1.2. Beginning with that release, the sample configurations use
this as the default log level and changing it will change all packet logging done by
the configuration. In any configuration file (except shorewall-params(5)[19]),
$LOG_LEVEL will expand to this value.
LOG_MARTIANS=[Yes|No|Keep]
IPv4 only.
If set to Yes or yes, sets /proc/sys/net/ipv4/conf/*/log_martians to 1 with the
exception of /proc/sys/net/ipv4/conf/all/log_martians which is set to 0. The default
value is Yes which sets both of the above to one. If you do not enable martian logging
for all interfaces, you may still enable it for individual interfaces using the
logmartians interface option in shorewall-interfaces[20](5).
The value Keep causes Shorewall to ignore the option. If the option is set to Yes,
then martians are logged on all interfaces. If the option is set to No, then martian
logging is disabled on all interfaces except those specified in
shorewall-interfaces[20](5).
LOG_VERBOSITY=[number]
This option controls the amount of information logged to the file specified in the
STARTUP_LOG option.
Values are:
-1 - Logging is disabled
0 - Silent. Only error messages are logged.
1 - Major progress messages logged.
2 - All progress messages logged
If not specified, then -1 is assumed.
LOGALLNEW=[log-level]
This option is intended for use as a debugging aid. When set to a log level, this
option causes Shorewall to generate a logging rule as the first rule in each builtin
chain.
• The table name is used as the chain name in the log prefix.
• The chain name is used as the target in the log prefix.
For example, using the default LOGFORMAT, the log prefix for logging from the nat
table's PREROUTING chain is as follows in versions prior to 5.1.0:
Shorewall:nat:PREROUTING
In Shorewall 5.1.0 and later releases, the log prefix is:
nat:PREROUTING
Important
To help insure that all packets in the NEW state are logged, rate limiting
(LOGLIMIT) should be disabled when using LOGALLNEW. Use LOGALLNEW at your own
risk; it may cause high CPU and disk utilization and you may not be able to
control your firewall after you enable this option.
Caution
Do not use this option if the resulting log messages will be sent to another
system.
LOGFILE=[pathname|systemd]
This parameter tells the /sbin/shorewall program where to look for Shorewall messages
when processing the dump, logwatch, show log, and hits commands. If not assigned or if
assigned an empty value, /var/log/messages is assumed. For further information, see
shorewall-logging(8)[21]. Beginning with Shorewall 5.0.10.1, you may specify systemd
to use journelctl -r to read the log.
LOGFORMAT=["formattemplate"]
The value of this variable generate the --log-prefix setting for Shorewall logging
rules. It contains a “printf” formatting template which accepts three arguments (the
chain name, logging rule number (optional) and the disposition). To use LOGFORMAT with
fireparse, set it as:
LOGFORMAT="fp=%s:%d a=%s "
If the LOGFORMAT value contains the substring “%d” then the logging rule number is
calculated and formatted in that position; if that substring is not included then the
rule number is not included. If not supplied or supplied as empty (LOGFORMAT="") then
“Shorewall:%s:%s:” is assumed.
Note
The setting of LOGFORMAT has an effect of the permitted length of zone names. See
shorewall-zones[16] (5).
Caution
Beginning with Shorewall 5.1.0, the default and sample shorewall[6].conf files set
LOGFORMAT="%s %s ".
Regardless of the LOGFORMAT setting, Shorewall IPv4 log messages that use this
LOGFORMAT can be uniquely identified using the following regular expression:
'IN=.* OUT=.* SRC=.*\..* DST='
and Shorewall IPv6 log messages can be uniquely identified using the following
regular expression:
'IN=.* OUT=.* SRC=.*:.* DST='
To match all Netfilter log messages (Both IPv4 and IPv6 and regardless of the
LOGFORMAT setting), use:
'IN=.* OUT=.* SRC=.* DST='
LOGLIMIT=[[{s|d}:]rate/{sec|second|min|minute|hour|day}[:burst]]
Added in Shorewall 4.4.12. Limits the logging rate, either overall, or by source or
destination IP address.
If the value starts with 's:' then logging is limited per source IP. If the value
starts with 'd:', then logging is limited per destination IP. Otherwise, the overall
logging rate is limited.
If burst is not specified, then a value of 5 is assumed.
The keywords second and minute are accepted beginning with Shorewall 4.6.13.
LOGTAGONLY=[Yes|No]
Using LOGFORMAT=“Shorewall:%s:%s:”, chain names may not exceed 5 characters or
truncation of the log prefix may occur. Longer chain names may be used with log tags
if you set LOGTAGONLY=Yes. With LOGTAGONLY=Yes, if a log tag is specified then the tag
is included in the log prefix in place of the chain name.
Beginning with Shorewall 4.5.12, when LOGTAGONLY=Yes, you have more control over the
generated log prefix. Beginning with that release, the tag is interpreted as a chain
name and a disposition separated by a comma. So this rule:
#ACTION SOURCE DEST
LOG:info:foo,bar net fw
would generate the following log prefix when using LOGFORMAT=“Shorewall:%s:%s:”:
Shorewall:foo:bar:
Similarly,
#ACTION SOURCE DEST
LOG:info:,bar net fw
would generate
Shorewall:net2fw:bar:
MACLIST_DISPOSITION=[ACCEPT|DROP|REJECT|A_DROP|A_REJECT]
Determines the disposition of connections requests that fail MAC Verification and must
have the value ACCEPT (accept the connection request anyway), REJECT (reject the
connection request) or DROP (ignore the connection request). If not set or if set to
the empty value (e.g., MACLIST_DISPOSITION="") then MACLIST_DISPOSITION=REJECT is
assumed.
A_DROP and A_REJECT are audited versions of DROP and REJECT respectively and were
added in Shorewall 4.4.20. They require AUDIT_TARGET in the kernel and ip[6]tables.
MACLIST_LOG_LEVEL=[log-level[:log-tag]]
Determines the syslog level for logging connection requests that fail MAC
Verification. The value must be a valid syslogd log level. If you don't want to log
these connection requests, set to the empty value (e.g., MACLIST_LOG_LEVEL="").
MACLIST_TABLE=[filter|mangle]
Normally, MAC verification occurs in the filter table (INPUT and FORWARD) chains. When
forwarding a packet from an interface with MAC verification to a bridge interface,
that doesn't work.
This problem can be worked around by setting MACLIST_TABLE=mangle which will cause Mac
verification to occur out of the PREROUTING chain. Because REJECT isn't available in
that environment, you may not specify MACLIST_DISPOSITION=REJECT or
MACLIST_DISPOSITION=A_REJECT with MACLIST_TABLE=mangle.
MACLIST_TTL=[number]
The performance of configurations with a large numbers of entries in
shorewall-maclist[22](5) can be improved by setting the MACLIST_TTL variable in
shorewall[6].conf[23](5).
If your iptables and kernel support the "Recent Match" (see the output of "shorewall
check" near the top), you can cache the results of a 'maclist' file lookup and thus
reduce the overhead associated with MAC Verification.
When a new connection arrives from a 'maclist' interface, the packet passes through
then list of entries for that interface in shorewall-maclist[22](5). If there is a
match then the source IP address is added to the 'Recent' set for that interface.
Subsequent connection attempts from that IP address occurring within $MACLIST_TTL
seconds will be accepted without having to scan all of the entries. After $MACLIST_TTL
from the first accepted connection request from an IP address, the next connection
request from that IP address will be checked against the entire list.
If MACLIST_TTL is not specified or is specified as empty (e.g, MACLIST_TTL="" or is
specified as zero then 'maclist' lookups will not be cached).
MANGLE_ENABLED=[Yes|No]
Determines whether Shorewall will generate rules in the Netfilter mangle table.
Setting MANGLE_ENABLED=No disables all Shorewall features that require the mangle
table. The default is MANGLE_ENABLED=Yes.
MINIUPNPD=[Yes|No]
Added in Shorewall 5.0.8. If set to Yes, Shorewall will create a chain in the nat
table named MINIUPNPD-POSTROUTING and will add jumps from POSTROUTING to that chain
for each interface with the upnpd option specified. Default is No.
MARK_IN_FORWARD_CHAIN=[Yes|No]
If your kernel has a FORWARD chain in the mangle table, you may set
MARK_IN_FORWARD_CHAIN=Yes to cause the marking specified in the tcrules file to occur
in that chain rather than in the PREROUTING chain. This permits you to mark inbound
traffic based on its destination address when DNAT is in use. To determine if your
kernel has a FORWARD chain in the mangle table, use the shorewall [-6] show mangle
command; if a FORWARD chain is displayed then your kernel will support this option. If
this option is not specified or if it is given the empty value (e.g.,
MARK_IN_FORWARD_CHAIN="") then MARK_IN_FORWARD_CHAIN=No is assumed.
MASK_BITS=[number]
Added in Shorewall 4.4.26. Number of bits on the right of the 32-bit packet mark to be
masked when clearing the traffic shaping mark. Must be >= TC_BITS and <=
PROVIDER_OFFSET (if PROVIDER_OFFSET > 0). Prior to Shorewall 5.0.0, default value and
the default values of the other mark layout options is determined as follows:
Table 1. Default Packet Mark Layout
WIDE_TC_MARKS=No, TC_BITS=8, PROVIDER_BITS=8,
HIGH_ROUTE_MARKS=No PROVIDER_OFFSET=0,
MASK_BITS=8
WIDE_TC_MARKS=No, TC_BITS=8, PROVIDER_BITS=8,
HIGH_ROUTE_MARKS=Yes PROVIDER_OFFSET=8,
MASK_BITS=8
WIDE_TC_MARKS=Yes, TC_BITS=14, PROVIDER_BITS=8,
HIGH_ROUTE_MARKS=No PROVIDER_OFFSET=0,
MASK_BITS=16
WIDE_TC_MARKS=Yes, TC_BITS=14, PROVIDER_BITS=8,
HIGH_ROUTE_MARKS=Yes PROVIDER_OFFSET=16,
MASK_BITS=16
From 5.0.0 onward, the default value of MASK_BITS is 8, the default value of
PROVIDER_BITS, TC_BITS, MASK_BITS and PROVIDER_OFFSET is 8.
MODULESDIR=[[+]pathname[:pathname]...]
This parameter specifies the directory/directories where your kernel netfilter modules
may be found. If you leave the variable empty, Shorewall will supply the value
"/lib/modules/$uname/kernel/net/ipv${g_family}/netfilter:/lib/modules/$uname/kernel/net/netfilter:/lib/modules/$uname/kernel/net/sched:/lib/modules/$uname/extra:/lib/modules/$uname/extra/ipset"
where uname holds the output of 'uname -r' and g_family holds '4' in IPv4
configurations and '6' in IPv6 configurations.
The option plus sign ('+') was added in Shorewall 5.0.3 and causes the listed
pathnames to be appended to the default list above.
MULTICAST=[Yes|No]
IPv4 only.
This option will normally be set to 'No' (the default). It should be set to 'Yes'
under the following circumstances:
1. You have an interface that has parallel zones defined via /etc/shorewall/hosts.
2. You want to forward multicast packets to two or more of those parallel zones.
In such cases, you will configure a destonly network on each zone receiving
multicasts.
MUTEX_TIMEOUT=[seconds]
The value of this variable determines the number of seconds that programs will wait
for exclusive access to the Shorewall[6] lock file. After the number of seconds
corresponding to the value of this variable, programs will assume that the last
program to hold the lock died without releasing the lock.
If not set or set to the empty value, a value of 60 (60 seconds) is assumed.
An appropriate value for this parameter would be twice the length of time that it
takes your firewall system to process a shorewall [-6] restart command.
NFACCT=[pathname]
Added in Shorewall 4.5.7. Specifies the pathname of the nfacct utility. If not
specified, Shorewall will use the PATH setting to find the program.
NULL_ROUTE_RFC1918=[Yes|No|blackhole|unreachable|prohibit]
IPv4 only.
When set to Yes, causes Shorewall to null-route the IPv4 address ranges reserved by
RFC1918. The default value is 'No'.
When combined with route filtering (ROUTE_FILTER=Yes or routefilter in
shorewall-interfaces[20](5)), this option ensures that packets with an RFC1918 source
address are only accepted from interfaces having known routes to networks using such
addresses.
Beginning with Shorewall 4.5.15, you may specify blackhole, unreachable or prohibit to
set the type of route to be created. See
https://shorewall.org/MultiISP.html#null_routing[24].
OPTIMIZE=[value]
The specified value enables certain optimizations. Each optimization category is
associated with a power of two. To enable multiple optimization categories, simply add
their corresponding numbers together.
Beginning with Shorewall 4.5.20, you may specify OPTIMIZE=All to enable all
optimization categories, and you may also specify OPTIMIZE=None to disable
optimization.
• Optimization category 1 - Traditionally, Shorewall has created rules for the
complete matrix of host groups defined by the zones, interfaces and hosts files.
Any traffic that didn't correspond to an element of that matrix was rejected in
one of the built-in chains. When the matrix is sparse, this results in lots of
largely useless rules.
These extra rules can be eliminated by setting the 1 bit in OPTIMIZE.
The 1 bit setting also controls the suppression of redundant wildcard rules (those
specifying "all" in the SOURCE or DEST column). A wildcard rule is considered to
be redundant when it has the same ACTION and Log Level as the applicable policy.
Note
Optimization level 1 is ignored when optimization level 4 is also selected,
since level 4 performs similar optimizations in a more robust way.
• Optimization category 2 - Added in Shorewall 4.4.7. When set, suppresses
superfluous ACCEPT rules in a policy chain that implements an ACCEPT policy. Any
ACCEPT rules that immediately precede the final blanket ACCEPT rule in the chain
are now omitted.
• Optimization category 4 - Added in Shorewall 4.4.7. When set, causes short chains
(those with less than 2 rules) to be optimized away. The following chains are
excluded from optimization:
• accounting chains (unless OPTIMIZE_ACCOUNTING=Yes)
• action chains (user-defined)
• 'blacklst' chain
• dynamic
• forwardUPnP
• UPnP (nat table)
Additionally:
• If a built-in chain has a single rule that branches to a second chain, then
the rules from the second chain are moved to the built-in chain and the target
chain is omitted.
• Chains with no references are deleted.
• Accounting chains are subject to optimization if the OPTIMIZE_ACCOUNTING
option is set to 'Yes'.
• If a chain ends with an unconditional branch to a second chain (other than to
'reject'), then the branch is deleted from the first chain and the rules from
the second chain are appended to it.
An additional optimization was added in Shorewall 4.5.4. If the last rule in a
chain is an unqualified jump to a simple target, then all immediately preceding
rules with the same simple target are omitted.
For example, consider this chain:
-A fw-net -p udp --dport 67:68 -j ACCEPT
-A fw-net -p udp --sport 1194 -j ACCEPT
-A fw-net -p 41 -j ACCEPT
-A fw-net -j ACCEPT
Since all of the rules are jumps to the simple target ACCEPT, this chain is
totally optimized away and jumps to the chain are replace with jumps to ACCEPT.
• Optimization category 8 - Added in Shorewall 4.4.9. When set, causes chains with
identical rules to be collapsed into a single chain.
Warning
While Optimization category 8 can significantly reduce the size of the
generated iptables ruleset, it can also take significant system resources
during compilation. If you find that compilation takes an unreasonably long
time, try disabling this category by setting OPTIMIZE=23.
• Optimization category 16 - Added in Shorewall 4.4.26. When set, causes sequences
of compatible rules to be combined into a single rule. Rules are considered
compatible if they differ only in their destination ports and comments.
A sequence of compatible rules is often generated when macros are invoked in
sequence.
The ability to combine adjacent rules is limited by two factors:
• Destination port lists may only be combined up to a maximum of 15 ports, where
a port-pair counts as two ports.
• Rules may only be combined until the length of their concatenated comment
reaches 255 characters.
When either of these limits would be exceeded, the current combined rule is
emitted and the compiler attempts to combine rules beginning with the one that
would have exceeded the limit. Adjacent combined comments are separated by ', '.
Empty comments at the front of a group of combined comments are replaced by
'Others and'. Empty comments at the end of a group of combined comments are
replaced by 'and others'.
Beginning in Shorewall 4.5.10, this option also suppresses duplicate adjacent
rules and duplicate non-adjacent rules that don't include mark, connmark, dscp,
ecn, set, tos or u32 matches.
Example 1:
Rules with comments "FOO", <empty> and "BAR" would result in the combined
comment "FOO and others, BAR".
Example 2:
Rules with comments <empty>, "FOO" and "BAR" would result in the combined
comment "Others and FOO, BAR". Note: Optimize level 16 requires "Extended
Multi-port Match" in your iptables and kernel.
In versions prior to 5.1.0, the default value is zero which disables all
optimizations. Beginning with Shorewall 5.1.0, the default value is All which enables
all optimizations.
OPTIMIZE_ACCOUNTING=[Yes|No]
Added in Shorewall 4.4.7. If set to Yes, Shorewall accounting changes are subject to
optimization (OPTIMIZE=4,5,6 or 7). If not specified or set to the empty value,
OPTIMIZE_ACCOUNTING=No is assumed.
PAGER=pathname
Added in Shorewall 5.0.6. Specifies a path name of a pager program like less or more.
When PAGER is given, the output of verbose status commands and the dump command are
piped through the named program when the output file is a terminal.
Beginning with Shorewall 5.0.12, the default value of this option is the DEFAULT_PAGER
setting in shorewallrc.
PATH=pathname[:pathname]...
Determines the order in which Shorewall searches directories for executable files.
PERL=pathname
Added in Shorewall 4.4.11 RC1. Specifies the path name of the Perl executable. Default
is /usr/bin/perl. If the pathname specified by this option does not exist or the named
file is not executable, then Shorewall falls back to /usr/bin/perl
PERL_HASH_SEED=seed|random
Added in Shorewall 5.1.4. Sets the Perl hash seed (an integer in the range 0-99999)
when running the Shorewall rules compiler. If not specified, the value 0 is assumed.
If random is specified, a random seed will be chosed by Perl. See perlsec(1) for
additional information.
PROVIDER_BITS=[number]
Added in Shorewall 4.4.26. The number of bits in the 32-bit packet mark to be used for
provider numbers. May be zero. See MASK_BITS above for default value.
PROVIDER_OFFSET=[number]If
Added in Shorewall 4.4.26. The offset from the right (low-order end) of the provider
number field in the 32-bit packet mark. If non-zero, must be >= TC_BITS (Shorewall
automatically adjusts PROVIDER_OFFSET's value). PROVIDER_OFFSET + PROVIDER_BITS +
ZONE_BITS must be < 32. See MASK_BITS above for default value.
RCP_COMMAND="command"
RSH_COMMAND="command"
Earlier generations of Shorewall Lite required that remote root login via ssh be
enabled in order to use the load and reload commands. Beginning with release 3.9.5,
you may define an alternative means for accessing the remote firewall system. In that
release, two new options were added to shorewall.conf:
RSH_COMMAND
RCP_COMMAND
The default values for these are as follows:
RSH_COMMAND: ssh ${root}@${system} ${command}
RCP_COMMAND: scp ${files} ${root}@${system}:${destination}
Shell variables that will be set when the commands are invoked are as follows:
root - root user. Normally root but may be overridden using the '-r' option.
system - The name/IP address of the remote firewall system.
command - For RSH_COMMAND, the command to be executed on the firewall system.
files - For RCP_COMMAND, a space-separated list of files to be copied to the remote firewall system.
destination - The directory on the remote system that the files are to be copied into.
RELATED_DISPOSITION=[ACCEPT|A_ACCEPT|A_DROP|A_REJECT|DROP|REJECT|CONTINUE]
Added in Shorewall 4.4.27. Shorewall has traditionally ACCEPTed RELATED packets that
don't match any rule in the RELATED section of shorewall-rules[8] (5). Concern about
the safety of this practice resulted in the addition of this option. When a packet in
RELATED state fails to match any rule in the RELATED section, the packet is disposed
of based on this setting. The default value is ACCEPT for compatibility with earlier
versions.
RELATED_LOG_LEVEL=log-level[:log-tag]
Added in Shorewall 4.4.27. Packets in the related state that do not match any rule in
the RELATED section of shorewall-rules[8] (5) are logged at this level. The default
value is empty which means no logging is performed.
REJECT_ACTION=action
Added in Shorewall 4.5.21. When a REJECT target is specified, Shorewall normally
handles the response as follows:
• If the destination address of the packet is a broadcast or multicast address, the
packet is dropped.
• if the protocol is ICMP (2) then the packet is dropped.
• if the protocol is TCP (6) then the packet is rejected with an RST.
• if the protocol is UDP (17) then the packet is rejected with an 'port-unreachable'
ICMP.
• if the protocol is ICMP (1) then the packet is rejected with a 'host-unreachable'
ICMP.
• if the protocol is ICMP6 (1) then the packet is rejected with a
'icmp6-addr-unreachable' ICMP6.
• otherwise, the packet is rejected with a 'host-prohibited' ICMP.
You can modify this behavior by implementing your own action that handles REJECT and
specifying it's name in this option. The nolog and noinline options will automatically
be assumed for the specified action.
The following action implements the default reject action:
?format 2
#TARGET SOURCE DEST PROTO
Broadcast(DROP) - - -
DROP - - 2
INLINE - - 6 ;; -j REJECT --reject-with tcp-reset
?if __ENHANCED_REJECT
INLINE - - 17 ;; -j REJECT
?if __IPV4
INLINE - - 1 ;; -j REJECT --reject-with icmp-host-unreachable
INLINE - - - ;; -j REJECT --reject-with icmp-host-prohibited
?else
INLINE - - 58 ;; -j REJECT --reject-with icmp6-addr-unreachable
INLINE - - - ;; -j REJECT --reject-with icmp6-adm-prohibited
?endif
?else
INLINE - - - ;; -j REJECT
?endif
RENAME_COMBINED=[Yes|No]
Added in Shorewall 5.2.0. Traditionally, when OPTIMIZE category 8 is enabled,
identical chains are combined under a name beginning with '~comb' or '~blacklist'.
This behavior is maintained under the default setting RENAME_COMBINED=Yes. If
RENAMED_COMBINED=No, the chains are combined under the original name of one of the
chains.
REQUIRE_INTERFACE=[Yes|No]
Added in Shorewall 4.4.10. The default is No. If set to Yes, at least one optional
interface must be up in order for the firewall to be in the started state. Intended to
be used with the Shorewall Init Package[25].
RESTART=[restart|reload]
Added in Shorewall 5.0.1 to replace LEGACY_RESTART which was added in Shorewall 5.0.0.
In that release, the reload command was redefined to do what restart had done in
earlier releases and restart became a true restart (equivalent to stop followed by
start). When RESTART=reload, the restart command performs the same operation as the
reload command making it compatible with earlier releases. If not specified,
RESTART=reload is assumed.
RESTORE_DEFAULT_ROUTE=[Yes|No]
This option determines whether to restore the default route saved when here are
'balance' providers defined but all of them are down.
The default is RESTORE_DEFAULT_ROUTE=Yes which preserves the pre-4.2.6 behavior.
RESTORE_DEFAULT_ROUTE=No is appropriate when you don't want a default route in the
main table (USE_DEFAULT_RT=No) or in the default table (USE_DEFAULT_RT=Yes) when there
are no balance providers available. In that case, RESTORE_DEFAULT_ROUTE=No will cause
any default route in the relevant table to be deleted.
RESTORE_ROUTEMARKS=[Yes|No]
Added in Shorewall 4.5.9. When set to Yes (the default), provider marks are restored
unconditionally at the top of the mangle OUTPUT and PREROUTING chains, even if the
saved mark is zero. When this option is set to No, the mark is restored only if it is
non-zero. If you have problems with IPSEC ESP packets not being routed correctly on
output, try setting this option to No.
RESTOREFILE=filename
Specifies the simple name of a file in /var/lib/shorewall to be used as the default
restore script in the shorewall [-6] save, shorewall [-6] restore, shorewall [-6]
forget and shorewall [6] -f start commands.
RETAIN_ALIASES={Yes|No}
IPv4 only.
During shorewall start, IP addresses to be added as a consequence of
ADD_IP_ALIASES=Yes and ADD_SNAT_ALIASES=Yes are quietly deleted when
shorewall-nat[3](5) and shorewall-masq[4](5) are processed then are re-added later.
This is done to help ensure that the addresses can be added with the specified labels
but can have the undesirable side effect of causing routes to be quietly deleted. When
RETAIN_ALIASES is set to Yes, existing addresses will not be deleted. Regardless of
the setting of RETAIN_ALIASES, addresses added during shorewall start are still
deleted at a subsequent shorewall [stop, shorewall reload or shorewall restart.
ROUTE_FILTER=[Yes|No|Keep]
If this parameter is given the value Yes or yes then route filtering (anti-spoofing)
is enabled on all network interfaces which are brought up while Shorewall is in the
started state. The default value is no.
The value Keep causes Shorewall to ignore the option. If the option is set to Yes,
then route filtering occurs on all interfaces. If the option is set to No, then route
filtering is disabled on all interfaces except those specified in
shorewall-interfaces[20](5).
Important
If you need to disable route filtering on any interface, then you must set
ROUTE_FILTER=No then set routefilter=1 or routefilter=2 on those interfaces where
you want route filtering. See shorewall-interfaces[20](5) for additional details.
RPFILTER_DISPOSITION=[DROP|REJECT|A_DROP|A_REJECT]
Added in Shorewall 4.5.7. Determines the disposition of packets entering from
interfaces the rpfilter option (see shorewall-interfaces[20](5)). Packets disposed of
by this option are those whose response packets would not be sent through the same
interface receiving the packet.
RPFILTER_LOG_LEVEL=log-level[:log-tag]
Added in shorewall 4.5.7. Determines the logging of packets disposed via the
RPFILTER_DISPOSITION. The default value is info.
SAVE_ARPTABLES={Yes|No}
Added in Shorewall 4.5.12. If SAVE_ARPTABLES=Yes, then the current arptables contents
will be saved by shorewall save command and restored by shorewall restore command.
Default value is No.
SAVE_IPSETS={Yes|No|ipv4|setlist}
Re-enabled in Shorewall 4.4.6. If SAVE_IPSETS=Yes, then the current contents of your
ipsets will be saved by the shorewall stop and shorewall save commands and restored by
the shorewall start and shorewall restore commands.
Beginning with Shorewall 4.6.4, you can restrict the set of ipsets saved by specifying
a setlist (a comma-separated list of ipv4 ipset names). You may also restrict the
saved sets to just the ipv4 ones by specifying ipv4.
SFILTER_DISPOSITION=[DROP|REJECT|A_DROP|A_REJECT]
Added in Shorewall 4.4.20. Determines the disposition of packets matching the sfilter
option (see shorewall-interfaces[20](5)) and of hairpin packets on interfaces without
the routeback option.[26]
SFILTER_LOG_LEVEL=log-level[:log-tag]
Added on Shorewall 4.4.20. Determines the logging of packets matching the sfilter
option (see shorewall-interfaces[20](5)) and of hairpin packets on interfaces without
the routeback option.[27] The default is info. If you don't wish for these packets to
be logged, use SFILTER_LOG_LEVEL=none.
SHOREWALL_SHELL=[pathname]
This option is used to specify the shell program to be used to interpret the compiled
script. If not specified or specified as a null value, /bin/sh is assumed. Using a
light-weight shell such as ash or dash can significantly improve performance.
SMURF_DISPOSITION=[DROP|A_DROP]
Added in Shorewall 4.4.20. The default setting is DROP which causes smurf packets (see
the nosmurfs option in shorewall-interfaces[20](5)) to be dropped. A_DROP causes the
packets to be audited prior to being dropped and requires AUDIT_TARGET support in the
kernel and iptables.
SMURF_LOG_LEVEL=[log-level[:log-tag]]
Specifies the logging level for smurf packets (see the nosmurfs option in
shorewall-interfaces[20](5)). If set to the empty value ( SMURF_LOG_LEVEL="" ) then
smurfs are not logged.
STARTUP_ENABLED={Yes|No}
Determines if Shorewall is allowed to start. As released from shorewall.net, this
option is set to No. When set to Yes or yes, Shorewall may be started. Used as a guard
against Shorewall being accidentally started before it has been configured.
STARTUP_LOG=[pathname]
If specified, determines where Shorewall will log the details of each start, reload,
restart, try, and safe-* command. Logging verbosity is determined by the setting of
LOG_VERBOSITY above.
SUBSYSLOCK=[pathname]
This parameter should be set to the name of a file that the firewall should create if
it starts successfully and remove when it stops. Creating and removing this file
allows Shorewall to work with your distribution's initscripts. For OpenSuSE, this
should be set to /var/lock/subsys/shorewall (var/lock/subsys/shorewall-lite if
building for export). For Gentoo, it should be set to /run/lock/shorewall
(/run/lock/shorewall-lite). For Redhat and derivatives as well as Debian and
derivatives, the pathname should be omitted.
Important
Beginning with Shorewall 5.1.0, this setting is ignored when SERVICEDIR is
non-empty in ${SHAREDIR}/shorewall/shorewallrc (usually
/usr/share/shorewall/shorewallrc).
TC=[pathname]
If specified, gives the pathname of the 'tc' executable. If not specified, 'tc' is
assumed and the utility will be located using the current PATH setting.
TC_BITS=[number]
The number of bits at the low end of the 32-bit packet mark to be used for traffic
shaping marking. May be zero. See MASK_BITS above for default value.
TC_ENABLED=[Yes|No|Internal|Simple|Shared]
If you say Yes or yes here, Shorewall will use a script that you supply to configure
traffic shaping. The script must be named 'tcstart' and must be placed in a directory
on your CONFIG_PATH.
If you say No or no then traffic shaping is not enabled.
If you set TC_ENABLED=Simple (Shorewall 4.4.6 and later), simple traffic shaping using
shorewall-tcinterfaces[28](5) and shorewall-tcpri[29](5) is enabled.
If you set TC_ENABLED=Internal or internal or leave the option empty then Shorewall
will use its builtin traffic shaper (tc4shorewall written by Arne Bernin.
Beginning with Shorewall 4.4.15, you can set TC_ENABLED=Shared. This allows you to
configure the tcdevices and tcclasses in your Shorewall6 configuration yet make them
available to the compiler when compiling your Shorewall configuration. In addition to
setting TC_ENABLED=Shared, you need to create symbolic links from your Shorewall
configuration directory (normally /etc/shorewall/) to the tcdevices and tcclasses
files in your Shorewall6 configuration directory (normally /etc/shorewall6/).
TC_EXPERT={Yes|No}
Normally, Shorewall tries to protect users from themselves by preventing PREROUTING
and OUTPUT tcrules from being applied to packets that have been marked by the 'track'
option in shorewall-providers[9](5).
If you know what you are doing, you can set TC_EXPERT=Yes and Shorewall will not
include these cautionary checks.
TC_PRIOMAP=map
Added in Shorewall 4.4.6. Determines the mapping of a packet's TOS field to priority
bands. See shorewall-tcpri[29](5). The map consists of 16 space-separated digits with
values 1, 2 or 3. A value of 1 corresponds to Linux priority 0, 2 to Linux priority 1,
and 3 to Linux Priority 2. The first entry gives the priority of TOS value 0, the
second of TOS value 1, and so on. See tc-prio(8) for additional information.
The default setting is TC_PRIOMAP="2 3 3 3 2 3 1 1 2 2 2 2 2 2 2 2".
TCP_FLAGS_DISPOSITION=[ACCEPT|DROP|REJECT|A_DROP|A_REJECT]
Determines the disposition of TCP packets that fail the checks enabled by the tcpflags
interface option (see shorewall-interfaces[20](5)) and must have a value of ACCEPT
(accept the packet), REJECT (send an RST response) or DROP (ignore the packet). If not
set or if set to the empty value (e.g., TCP_FLAGS_DISPOSITION="") then
TCP_FLAGS_DISPOSITION=DROP is assumed.
A_DROP and A_REJECT are audited versions of DROP and REJECT respectively and were
added in Shorewall 4.4.20. They require AUDIT_TARGET in the kernel and iptables.
TCP_FLAGS_LOG_LEVEL=[log-level[:log-tag]]
Determines the syslog level for logging packets that fail the checks enabled by the
tcpflags interface option. The value must be a valid syslogd log level. If you don't
want to log these packets, set to the empty value (e.g., TCP_FLAGS_LOG_LEVEL="").
TRACK_PROVIDERS={Yes|No}
Added in Shorewall 4.4.3. When set to Yes, causes the track option to be assumed on
all providers defined in shorewall-providers[9](5). May be overridden on an individual
provider through use of the notrack option. The default value is 'No'.
Beginning in Shorewall 4.4.6, setting this option to 'Yes' also simplifies PREROUTING
rules in shorewall-tcrules[12](5). Previously, when TC_EXPERT=No, packets arriving
through 'tracked' provider interfaces were unconditionally passed to the PREROUTING
tcrules. This was done so that tcrules could reset the packet mark to zero, thus
allowing the packet to be routed using the 'main' routing table. Using the main table
allowed dynamic routes (such as those added for VPNs) to be effective. The rtrules
file was created to provide a better alternative to clearing the packet mark. As a
consequence, passing these packets to PREROUTING complicates things without providing
any real benefit. Beginning with Shorewall 4.4.6, when TRACK_PROVIDERS=Yes and
TC_EXPERT=No, packets arriving through 'tracked' interfaces will not be passed to the
PREROUTING rules. Since TRACK_PROVIDERS was just introduced in 4.4.3, this change
should be transparent to most, if not all, users.
TRACK_RULES={Yes|No|File}
Added in Shorewall 4.5.20. If set to Yes, causes the compiler to add a comment to
iptables rules to indicate the file name and line number of the configuration entry
that generated the rule. If set to No (the default), then no such comments are added.
Setting this option to Yes requires the Comments capability in iptables and kernel.
Beginning with Shorewall 5.0.5, the option may also be set to File. That setting
causes similar comments to be added to the .iptables-restore-input file, which is
normally created in /var/lib/shorewall.
UNTRACKED_DISPOSITION=[ACCEPT|A_ACCEPT|A_DROP|A_REJECT|DROP|REJECT|CONTINUE]
Added in Shorewall 4.5.13. Shorewall has traditionally passed UNTRACKED packets
through the NEW section of shorewall-rules[8] (5). When a packet in UNTRACKED state
fails to match any rule in the UNTRACKED section, the packet is disposed of based on
this setting. The default value is CONTINUE for compatibility with earlier versions.
UNTRACKED_LOG_LEVEL=log-level[:log-tag]
Added in Shorewall 4.5.13. Packets in the UNTRACKED state that do not match any rule
in the UNTRACKED section of shorewall-rules[8] (5) are logged at this level. The
default value is empty which means no logging is performed.
USE_DEFAULT_RT=[Yes|No]
When set to 'Yes', this option causes the Shorewall multi-ISP feature to create a set
of routing rules which are resilient to changes in the main routing table. Such
changes can occur for a number of reasons, VPNs going up and down being an example.
The idea is to send packets through the main table prior to applying any of the
Shorewall-generated routing rules. So changes to the main table will affect the
routing of packets by default.
When USE_DEFAULT_RT=Yes:
1. Both the DUPLICATE and the COPY columns in providers[9](5) file must remain empty
(or contain "-").
2. The default route is added to the the 'default' table rather than to the main
table.
3. If running Shorewall 5.1.0 or earlier or if BALANCE_PROVIDERS=Yes (Shorewall 5.1.1
or later), then the balance provider option is assumed unless the fallback, loose,
load or tproxy option is specified.
4. Packets are sent through the main routing table by a rule with priority 999. In
shorewall-rtrules[30](5), the range 1-998 may be used for inserting rules that
bypass the main table.
5. All provider gateways must be specified explicitly in the GATEWAY column. detect
may not be specified..if n .sp
Note
detect may be specified for interfaces whose configuration is managed by
dhcpcd. Shorewall will use dhcpcd's database to find the interface's gateway.
6. You should disable all default route management outside of Shorewall. If a default
route is added to the main table while Shorewall is started, then all policy
routing will stop working (except for those routing rules in the priority range
1-998).
Prior to Shorewall 4.6.0, if USE_DEFAULT_RT was not set or if it was set to the empty
string then USE_DEFAULT_RT=No was assumed. Beginning with Shorewall 4.6.0, the default
is USE_DEFAULT_RT=Yes and use of USE_DEFAULT_RT=No is deprecated.
Warning
The enable, disable and reenable commands do not work correctly when
USE_DEFAULT_RT=No.
USE_NFLOG_SIZE=[Yes|No]
Added in Shorewall 5.1.5. The second parameter to the NFLOG target specifies how many
bytes of the packet to copy to the log; if omitted or if supplied as zero, the entire
packet is copied. This feature has traditionally been implemented using the
--nflog-range option to the NFLOG iptables target. Unfortuntely, the --nflog-range
option never worked (the entire packet was always copied). To deal with this issue,
the Netfilter team:
• Added a warning message when --nflog-range is used
• Added --nflog-size which works like --nflog-range was intended to work.
When USE_NFLOG_SIZE=Yes, Shorewall will attempt to use the new --nflog-size feature.
If that feature is not available in the running kernel and ip[6]tables, an error is
raised.
When USE_NFLOG_SIZE is not supplied, USE_NFLOG_SIZE=No is assumed. When USE_NFLOG_SIZE
is added by shorewall update, it is added with setting No.
USE_PHYSICAL_NAMES=[Yes|No]
Added in Shorewall 4.4.27. Normally, when Shorewall creates a Netfilter chain that
relates to an interface, it uses the interface's logical name as the base of the chain
name. For example, if the logical name for an interface is OAKLAND, then the input
chain for traffic arriving on that interface would be 'OAKLAND_in'. If this option is
set to Yes, then the physical name of the interface will be used the base of the chain
name.
USE_RT_NAMES=[Yes|No]
Added in Shorewall 4.5.15. When set to 'Yes', Shorewall will use routing table
(provider) names in the generated script rather than table numbers. When set to 'No'
(the default), routing table numbers will be used.
Caution
If you set USE_RT_NAMES=Yes and KEEP_RT_TABLES=Yes, then you must insure that all
of your providers have entries in /etc/iproute2/rt_tables as well as the following
entries:
255 local
254 main
253 default
250 balance
0 unspec
Without these entries, the firewall will fail to start.
VERBOSE_MESSAGES=[Yes|No]
Added in Shorewall 5.0.9. When Yes (the default), messages produced by the ?INFO and
?WARNING directives include the filename and linenumber of the directive. When set to
No, that additional information is omitted. The setting may be overridden on a
directive by directive basis by following ?INFO or ?WARNING with '!' (no intervening
white space).
VERBOSITY=[number]
Shorewall has traditionally been very noisy (produced lots of output). You may set the
default level of verbosity using the VERBOSITY OPTION.
Values are:
0 - Silent. You may make it more verbose using the -v
option
1 - Major progress messages displayed
2 - All progress messages displayed (pre Shorewall-3.2.0
behavior)
If not specified, then 2 is assumed.
WARNOLDCAPVERSION=[Yes|No]
Added in Shorewall 4.5.12. When set to Yes (the default), the compiler issues a
warning when it finds a capabilities file that doesn't specify all of the capabilities
supported by the compiler. When WARNOLDCAPVERSION is set to No, no warning is issued.
WORKAROUNDS=[Yes|No]
Added in Shorewall 4.6.11. Over time, there have been a number of changes in Shorewall
that work around defects in other products such as iptables and ipset. When
WORKAROUNDS=Yes, these workarounds are enabled; when WORKAROUNDS=No, they are
disabled. If not specified or if specified as empty, WORKAROUNDS=Yes is assumed.
Warning
Do not set WORKAROUNDS=Yes if you need to be able to use Shorewall-generated
scripts (such as created by the save command) built by Shorewall 4.4.7 or older.
ZERO_MARKS=[Yes|No]
Added in Shorewall 5.0.12, this is a workaround for an issue where packet marks are
not zeroed by the kernel. It should be set to No (the default) unless you find that
incoming packets are being mis-routed for no apparent reasons.
Caution
Do not set this option to Yes if you have IPSEC software running on the firewall
system.
ZONE_BITS=[number]
Added in Shorewall 4.4.26. When non-zero, enables automatic packet marking by source
zone and determines the number of bits in the 32-bit packet mark to be used for the
zone mark. Default value is 0.
ZONE2ZONE=[2|-]
Added in Shorewall 4.4.4. This option determines how Shorewall constructs chain names
involving zone names and/or 'all'. Beginning with Shorewall 4.6.0, the default is '-'
(e.g., fw-net); prior to that release, the default was '2' (e.g., fw2net).
FILES
/etc/shorewall/shorewall.conf
/etc/shorewall6/shorewall6.conf
SEE ALSO
shorewall(8)
NOTES
1. shorewall-policy
https://shorewall.org/manpages/shorewall-policy.html
2. shorewall-accounting
https://shorewall.org/manpages/shorewall-accounting.html
3. shorewall-nat
https://shorewall.org/manpages/shorewall-nat.html
4. shorewall-masq
https://shorewall.org/manpages/shorewall-masq.html
5. shorewall-routestopped
https://shorewall.org/manpages/shorewall-routestopped.html
6. shorewall-stoppedrules
https://shorewall.org/manpages/shorewall-stoppedrules.html
7. shorewall-conntrack
https://shorewall.org/manpages/shorewall-conntrack.html
8. shorewall-rules
https://shorewall.org/manpages/shorewall-rules.html
9. shorewall-providers(5)
https://shorewall.org/manpages/shorewall-providers.html
10. shorewall-tcfilters(5)
https://shorewall.org/manpages/shorewall-tcfilters.html
11. shorewall-blrules
https://shorewall.org/manpages/shorewall-blrules.html
12. shorewall-tcrules
https://shorewall.org/manpages/shorewall-tcrules.html
13. Shorewall6
https://shorewall.org/IPv6Support.html
14. https://shorewall.org/Docker.html
https://shorewall.org/Docker.html
15. https://shorewall.org/ISO-3661.html
https://shorewall.org/ISO-3661.html
16. shorewall-zones
https://shorewall.org/manpages/shorewall-zones.html
17. shorewall-nesting
https://shorewall.org/manpages/shorewall-nesting.html
18. shorewall(8)
https://shorewall.org/manpages/shorewall.html
19. shorewall-params(5)
https://shorewall.org/manpages/shorewall-params.html
20. shorewall-interfaces
https://shorewall.org/manpages/shorewall-interfaces.html
21. shorewall-logging(8)
https://shorewall.org/manpages/shorewall-logging.html
22. shorewall-maclist
https://shorewall.org/manpages/shorewall-maclist.html
23. shorewall[6].conf
https://shorewall.org/manpages/shorewall.conf.html
24. https://shorewall.org/MultiISP.html#null_routing
https://shorewall.org/MultiISP.html#null_routing
25. Shorewall Init Package
https://shorewall.org/manpages/shorewall-init.html
26. Hairpin packets are packets that are routed out of the same interface that they
arrived on.
27. Hairpin packets are packets that are routed out of the same interface that they
arrived on.
28. shorewall-tcinterfaces
https://shorewall.org/manpages/shorewall-tcinterfaces.html
29. shorewall-tcpri
https://shorewall.org/manpages/shorewall-tcpri.html
30. shorewall-rtrules
https://shorewall.org/manpages/shorewall-rtrules.html