Provided by: shorewall6_4.4.26.1-1_all bug


       shorewall6.conf - Shorewall6 global configuration file




       This file sets options that apply to Shorewall6 as a whole.

       The file consists of Shell comments (lines beginning with '#'), blank lines and assignment
       statements (variable=value). If the value contains shell metacharacters or white-space,
       then it must be enclosed in quotes. Example: LOG_LEVEL="NFLOG(1,0,1)".


       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 Shorewall6 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 Shorewall6 logging, a level of 6 (info) is appropriate. Shorewall6 log messages
       are generated by NetFilter and are logged using facility 'kern' and the level that you
       specifify. 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 NFLOG target support, you may also specify a log level
       of NFLOG (must be all caps). Rather than log its messages to syslogd, Shorewall6 will
       direct netfilter to log the messages via the 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). Ulogd is also available from and can be configured to log all
       Shorewall6 message to their own log file

       The following options may be set in shorewall6.conf.





           To allow for default rules to be applied when USE_ACTIONS=No, the DROP_DEFAULT,

           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
               b) The name of a macro
                           (Shorewall6-shell only)
               c) None or none
           The default values are:
           If USE_ACTIONS=Yes, then these values refer to action.Drop and action.Reject
           respectively. If USE_ACTIONS=No, then these values refer to macro.Drop and

           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 shorewall6-policy[1](5).

           Added in Shorewall 4.4.7. If set to Yes, Shorewall6 accounting is enabled (see
           shorewall6-accounting[2](5)). If not specified or set to the empty value,
           ACCOUNTING=Yes is assumed.

           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[3](5).

           The value of this variable affects Shorewall6's stopped state. When
           ADMINISABSENTMINDED=No, only traffic to/from those addresses listed in
           shorewall6-routestopped[4](5) is accepted when Shorewall6 is stopped. When
           ADMINISABSENTMINDED=Yes, in addition to traffic to/from addresses in
           shorewall6-routestopped[4](5), connections that were active when Shorewall6 stopped
           continue to work and all new connections from the firewall system itself are allowed.
           If this variable is not set or is given the empty value then ADMINISABSENTMINDED=No is

           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>". The AUTO_COMMENT
           option has a default value of 'Yes'.

           If set, the behavior of the start and restart commands is change; if no files in
           /etc/shorewall have been changed since the last successful start or restart command,
           then the compilation step is skipped and the compiled script that executed the last
           start or restart command is used. The default is AUTOMAKE=No.

           The setting of the AUTOMAKE option is ignored if the start or restart command includes
           a directory name (e.g., shorewall6 restart /etc/

           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. The
           BLACKLIST_DISPOSITION setting has no effect on entries in the BLACKLIST section of
           shorewall6-rules[5] (5). It determines the disposition of packets sent to the blacklog
           target of shorewall6-blrules[6](5).

           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_LOGLEVEL=debug). If you do not assign a value or if you assign an
           empty value then packets from blacklisted hosts are not logged. The BLACKLIST_LOGLEVEL
           setting has no effect on entries in the BLACKLIST section of shorewall6-rules[5] (5).
           It determines the log level of packets sent to the blacklog target of

           When set to Yes or yes, blacklists are only consulted for new connections. This
           includes entries in the shorewall-blrules[7] (5) file and in the BLACKLIST section of
           shorewall6-rules[5] (5).

           When set to No or no, blacklists are consulted for every packet (will slow down your
           firewall noticably if you have large blacklists). If the BLACKLISTNEWONLY option is
           not set or is set to the empty value then BLACKLISTNEWONLY=No is assumed.

               BLACKLISTNEWONLY=No is incompatible with FASTACCEPT=Yes.

           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.

           If this option is set to No then Shorewall6 won't clear the current traffic control
           rules during [re]start. This setting is intended for use by people that 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/shorewall6/tcstart file. That way, your traffic
           shaping rules can still use the “fwmark” classifier based on packet marking defined in
           shorewall6-tcrules[8](5). If not specified, CLEAR_TC=No is assumed.

               If you also run Shorewall and if you have TC_ENABLED=Internal in your
               shorewall-conf[9](5), then you will want CLEAR_TC=No in this file.

           Added in Shorewall6 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 Shorewall6 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.

           Specifies where configuration files other than shorewall6.conf may be found.
           CONFIG_PATH is specifies as a list of directory names separated by colons (":"). When
           looking for a configuration file other than shorewall6.conf:

           ·   If the command is "try" or a "<configuration directory>" was specified in the
               command (e.g., shorewall6 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/shorewall6/configpath are used. As released from, that file
           sets the CONFIG_PATH to /etc/shorewall6:/usr/share/shorewall6:/usr/share/shorewall but
           your particular distribution may set it differently. See the output of shorewall6 show
           config for the default on your system.

           Note that the setting in /usr/share/shorewall6/configpath is always used to locate

           If set to Yes (the default value), entries in the /etc/shorewall6/route_stopped 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.

           Causes Shorewall6 to not load the listed kernel modules.

           Added in Shorewall 4.4.7. When set to No or no, dynamic blacklisting using the
           shorewall6 drop, shorewall6 reject, shorewall6 logdrop and shorewall6 logreject is
           disabled. Default is Yes.

           Normally, when the SOURCE or DEST columns in shorewall-policy(5) contains 'all', a
           single policy chain is created and the 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 'net2all' 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.

           Added in Shorewall 4.4.17. When set to Yes when compiling for use by Shorewall6 Lite
           (shorewall6 load, shorewall6 reload or shorewall6 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/shorewall6 but will copy the found in another location on the

           When compiling for direct use by Shorewall6, 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.

           Deprecated beginning with Shorewall 4.4.17.

           Beginning with Shorewall 4.4.17, the variables set in the 'params' file at compile
           time are available at run time with EXPORTPARAMS=No. As a consequence, beginning with
           that version the recommended setting is EXPORTPARAMS=No.

           It is quite difficult to code a 'params' file that assigns other than constant values
           such that it works correctly with Shorewall6 Lite. The EXPORTPARAMS option works
           around this problem. When EXPORTPARAMS=No, the 'params' file is not copied to the
           compiler output.

           With EXPORTPARAMS=No, if you need to set environmental variables on the firewall
           system for use by your extension scripts, then do so in the init extension script.

           The default is EXPORTPARAMS=Yes which is the recommended setting unless you are
           running Shorewall6 Lite.

           Normally, Shorewall6 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
           'loc2net' chain.

           If you set FASTACCEPT=Yes, then ESTABLISHED/RELEATED 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 shorewall6-rules[5](5).

               FASTACCEPT=Yes is incompatible with BLACKLISTNEWONLY=No.

           Added in Shorewall 4.4.11 Beta 3. 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

           Deprecated in Shorewall 4.4.26 in favor of PROVIDER_OFFSET.

           You may set HIGH_ROUTE_MARKS=Yes in to effectively divide the packet mark and
           connection mark into two mark fields.

           The width of the fields are determined by the setting of the WIDE_TC_MARKS option.

           When WIDE_TC_MARKS=No (the default):

            1. The MARK field in the providers file must have a value that is less than 65536 and
               that is a multiple of 256 (using hex representation, the values are 0x0100-0xFF00
               with the low-order 8 bits being zero).

            2. You may only set those mark values in the PREROUTING chain.

            3. Marks used for traffic shaping must still be in the range of 1-255 and may still
               not be set in the PREROUTING chain.

           When WIDE_TC_MARKS=Yes:

            1. The MARK field in the providers file must have a value that is a multiple of 65536
               (using hex representation, the values are 0x010000-0xFF0000 with the low-order 16
               bits being zero).

            2. You may only set those mark values in the PREROUTING chain.

            3. Marks used for traffic shaping must be in the range of 1-16383 and may still not
               be set in the PREROUTING chain.

           Regardless of the setting of WIDE_TC_MARKS, when you SAVE or RESTORE in tcrules, only
           the TC mark value is saved or restored. Shorewall handles saving and restoring the
           routing (provider) marks.

           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
           shorewall6-zones[10](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 shorewall6-nesting[11](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).

           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.

           This rather useless parameter determines whether Shorewall6 enables or disables IPV6
           Packet Forwarding on all interfaces (/proc/sys/net/ipv6/config/all/forwarding).
           Possible values are:

           On or on
               packet forwarding will be enabled.

           Off or off
               packet forwarding will be disabled.

           Keep or keep
               Shorewall6 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.

           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.

           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.

           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, refresh, restore on
           restart command.

           The default is KEEP_RT_TABLES=No.

           Added in Shorewall6 4.4.20. If not specified, the default is Yes which preserves the
           legacy behavior of start -f (the modification times of the files in /etc/shorewall6
           are compare with that of /var/lib/shorewall6/restore). If set to No, then the times
           are compared with that of /var/lib/shorewall6/firewall, which is consistant with the
           way that restart -f works.

           Added in Shorewall 4.4.7. When set to Yes, restricts the set of modules loaded by
           shorewall to those listed in /var/lib/shorewall6/helpers and those that are actually
           used. When not set, or set to the empty value, LOAD_HELPERS_ONLY=No is assumed.

           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.

           This option is intended for use as a debugging aid. When set to a log level, this
           option causes Shorewall6 to generate a logging rule as the first rule in each builtin

           ·   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:


               To help insure that all packets in the NEW state are logged, rate limiting
               (LOGBURST and LOGRATE) 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.

               Do not use this option if the resulting log messages will be sent to another

           This parameter tells the /sbin/shorewall6 program where to look for Shorewall6
           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.

           The value of this variable generate the --log-prefix setting for Shorewall6 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
           “Shorewall6:%s:%s:” is assumed.

               The setting of LOGFORMAT has an effect of the permitted length of zone names. See
               shorewall6-zones[10] (5).

           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.

           Deprecated in Shorewall 4.4.12.

           As of Shorewall 4.4.12, these parameters are Deprecated.

           These parameters set the match rate and initial burst size for logged packets. Please
           see ip6tables(8) for a description of the behavior of these parameters (the ip6tables
           option --limit is set by LOGRATE and --limit-burst is set by LOGBURST). If both
           parameters are set empty, no rate-limiting will occur. If you supply one of these,
           then you should also supply the other.



           For 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, 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.

           Using the default LOGFORMAT, chain names may not exceed 11 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.

           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

           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 ip6tables.

           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="").

           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 with

           The performance of configurations with a large numbers of entries in
           shorewall-maclist[12](5) can be improved by setting the MACLIST_TTL variable in

           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[12](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).

           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.

           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 /sbin/shorewall6 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.

           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). 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,
           WIDE_TC_MARKS=No,      TC_BITS=8, PROVIDER_BITS=8,
           WIDE_TC_MARKS=Yes,     TC_BITS=14, PROVIDER_BITS=8,
           WIDE_TC_MARKS=Yes,     TC_BITS=14, PROVIDER_BITS=8,

       MODULE_SUFFIX=["extension ..."]
           The value of this option determines the possible file extensions of kernel modules.
           The default value is "ko ko.gz o o.gz gz".

           This parameter specifies the directory/directories where your kernel netfilter modules
           may be found. If you leave the variable empty, Shorewall6 will supply
           "/lib/modules/`uname -r`/kernel/net/ipv4/netfilter:/lib/modules/`uname

           The value of this variable determines the number of seconds that programs will wait
           for exclusive access to the Shorewall6 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 shorewall6 restart command.

           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.

           ·   Optimization category 1 - Traditionally, Shorewall has created rules for the
               complete matrix of host groups defined by the zones, interfaces and hosts
               files[14]. 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.

           ·   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 preceed 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


               ·   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.

           ·   Optimization category 8 - Added in Shorewall 4.4.9. When set, causes chains with
               identical rules to be collapsed into a single chain.

           ·   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 combatible rules is often generated when macros are invoked in

               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 concatinated comment
                   reaches 255 characters.

               When either of these limits would be exceeded, the current combined rule is
               emitted and the compiler attemts 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'.

               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 reult in the combined
                   comment "Others and FOO, BAR". Note: Optimize level 16 requires "Extended
                   Multi-port Match" in your iptables and kernel.

           The default value is zero which disables all optimizations.

           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.

           Determines the order in which Shorewall6 searches directories for executable files.

           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 Shorewall6 falls back to /usr/bin/perl/

           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.

           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.


           Eariler generations of Shorewall6 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 shorewall6.conf:.RS 4 RSH_COMMAND
       The default values for these are as follows:.RS 4 RSH_COMMAND: ssh ${root}@${system}
           RCP_COMMAND: scp ${files}
       Shell variables that will be set when the commands are envoked are as follows:.RS 4 root -
       root user. Normally
                     root but may be overridden using the '-r'
           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

           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[15].

           Specifies the simple name of a file in /var/lib/shorewall6 to be used as the default
           restore script in the shorewall6 save, shorewall6 restore, shorewall6 forget and
           shorewall6 -f start commands.

           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.

           Added in Shorewall 4.4.20. The default setting is DROP which causes smurf packets (see
           the nosmurfs option in shorewall-interfaces[16](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 ip6tables.

           Specifies the logging level for smurf packets (see the nosmurfs option in
           shorewall6-interfaces[17](5)). If set to the empty value ( SMURF_LOG_LEVEL="" ) then
           smurfs are not logged.

           Added in Shorewall 4.4.20. Determines the disposition of packets matching the filter
           option (see shorewall6-interfaces[17](5)) and of hairpin packets on interfaces without
           the routeback option.[18] interfaces without the routeback option.

           Added on Shorewall 4.4.20. Determines the logging of packets matching the filter
           option (see shorewall6-interfaces[17](5)) and of hairpin packets on interfaces without
           the routeback option.[19] interfaces without the routeback option. The default is
           info. If you don't wish for these packets to be logged, use SFILTER_LOG_LEVEL=none.

           Determines if Shorewall6 is allowed to start. As released from, this
           option is set to No. When set to Yes or yes, Shorewall6 may be started. Used as a
           guard against Shorewall6 being accidentally started before it has been configured.

           If specified, determines where Shorewall6 will log the details of each start, restart
           and refresh command. Logging verbosity is determined by the setting of LOG_VERBOSITY

           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 Shorewall6 to work with your distribution's initscripts. For RedHat, this
           should be set to /var/lock/subsys/shorewall6. For Debian, the value is
           /var/lock/shorewall6 and in LEAF it is /var/run/shorwall.

           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.

           Added in Shorewall 4.4.26. 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

           If you say Yes or yes here, Shorewall6 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=Internal or internal or leave the option empty then Shorewall6
           will use its builtin traffic shaper (tc4shorewall6 written by Arne Bernin.

           Beginning with Shorewall 4.4.15, if you set TC_ENABLED=Shared or shared, then you
           should create symbolic links from your Shorewall6 configuration directory (normally
           /etc/shorewall6/) to your Shorewall tcdevices and tcclasses files. This allows the
           compiler to have access to your Shorewall traffic shaping configuration so that it can
           validate CLASSIFY rules in shorewall6-tcrules[20] (5).

               If you also run Shorewall and if you have TC_ENABLED=Internal in your
               shorewall-conf[9](5), then you will want TC_ENABLED=No or TC_ENABLED=Shared in
               this file.

           Normally, Shorewall6 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 shorewall6-providers[21](5).

           If you know what you are doing, you can set TC_EXPERT=Yes and Shorewall6 will not
           include these cautionary checks.

           Added in Shorewall 4.4.6. Determines the mapping of a packet's TOS field to priority
           bands. See shorewall6-tcpri[22](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".

           Determines the disposition of TCP packets that fail the checks enabled by the tcpflags
           interface option (see shorewall6-interfaces[17](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.

           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="").

           Added in Shorewall 4.4.3. When set to Yes, causes the track option to be assumed on
           all providers defined in shorewall6-providers[21](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 shorewall6-tcrules[8](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
           shorewall6-route_rules[23](5) 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.

           Added in Shorewall6 4.4.25. When set to 'Yes', this option causes the Shorewall6
           multi-ISP feature to create a different 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 Shorewall6-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 shorewall6-providers[21](5) file must
               remain empty (or contain "-").

            2. The default route is added to the the 'default' table rather than to the main

            3. balance is assumed unless loose is specified.

            4. Packets are sent through the main routing table by a rule with priority 999. In
               shorewall6-routing_rules[24](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.

            6. You should disable all default route management outside of Shorewall6. 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).

           If USE_DEFAULT_RT is not set or if it is set to the empty string then
           USE_DEFAULT_RT=No is assumed.

           Shorewall6 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
               1 - Major progress messages displayed
               2 - All progress messages displayed (pre Shorewall6-3.2.0
           If not specified, then 2 is assumed.

           Deprecated in Shorewall 4.4.26 in favor of TC_BITS and MASK_BITS.

           When set to No (the default), traffic shaping marks are 8 bytes wide (possible values
           are 1-255). When WIDE_TC_MARKS=Yes, traffic shaping marks are 14 bytes wide (values
           1-16383). The setting of WIDE_TC_MARKS also has an effect on the HIGH_ROUTE_MARKS
           option (see above).

           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.

           Added in Shorewall 4.4.4. This option determines how Shorewall constructs chain names
           involving zone names and/or 'all'. The default is '2' (e.g., fw2net).




       shorewall6(8), shorewall6-accounting(5), shorewall6-actions(5), shorewall6-blacklist(5),
       shorewall6-hosts(5), shorewall6-interfaces(5), shorewall6-ipsec(5), shorewall6-maclist(5),
       shorewall6-masq(5), shorewall6-nat(5), shorewall6-netmap(5),
       shoewall6-netmap(5),shorewall6-params(5), shorewall6-policy(5), shorewall6-providers(5),
       shorewall6-proxyarp(5), shorewall6-route_rules(5), shorewall6-routestopped(5),
       shorewall6-rules(5), shorewall6-tcclasses(5), shorewall6-tcdevices(5),
       shorewall6-tcrules(5), shorewall6-tos(5), shorewall6-tunnels(5), shorewall6-zones(5)


        1. shorewall6-policy

        2. shorewall6-accounting

        3. shorewall-accounting

        4. shorewall6-routestopped

        5. shorewall6-rules

        6. shorewall6-blrules

        7. shorewall-blrules

        8. shorewall6-tcrules

        9. shorewall-conf

       10. shorewall6-zones

       11. shorewall6-nesting

       12. shorewall-maclist

       13. shorewall.conf

       14. the complete matrix of host groups defined by the zones, interfaces and hosts files

       15. Shorewall Init Package

       16. shorewall-interfaces

       17. shorewall6-interfaces

       18. Hairpin packets are packets that are routed out of the same interface that they
           arrived on.

       19. Hairpin packets are packets that are routed out of the same interface that they
           arrived on.

       20. shorewall6-tcrules

       21. shorewall6-providers

       22. shorewall6-tcpri

       23. shorewall6-route_rules

       24. shorewall6-routing_rules

[FIXME: source]                             12/13/2011                         SHOREWALL6.CONF(5)