This section was added in Shorewall 4.4.23. Rules in this section are applied, regardless of the connection tracking state of the packet and are applied before rules in the other sections.

Packets in the ESTABLISHED state are processed by rules in this section.

The only ACTIONs allowed in this section are ACCEPT, DROP, REJECT, LOG, NFLOG, NFQUEUE and QUEUE

There is an implicit ACCEPT rule inserted at the end of this section.

Packets in the RELATED state are processed by rules in this section.

The only ACTIONs allowed in this section are ACCEPT, DROP, REJECT, LOG, NFLOG, NFQUEUE and QUEUE

There is an implicit rule added at the end of this section that invokes the RELATED_DISPOSITION (shorewall.conf(5)).

Added in Shorewall 4.5.13. Packets in the INVALID state are processed by rules in this section.

The only Actions allowed in this section are ACCEPT, DROP, REJECT, LOG, NFLOG, NFQUEUE and QUEUE.

There is an implicit rule added at the end of this section that invokes the INVALID_DISPOSITION (shorewall.conf(5)).

Added in Shorewall 4.5.13. Packets in the UNTRACKED state are processed by rules in this section.

The only Actions allowed in this section are ACCEPT, DROP, REJECT, LOG, NFLOG, NFQUEUE and QUEUE.

There is an implicit rule added at the end of this section that invokes the UNTRACKED_DISPOSITION (shorewall.conf(5)).

Packets in the NEW state are processed by rules in this section. If the INVALID and/or UNTRACKED sections are empty or not included, then the packets in the corresponding state(s) are also processed in this section.

Specifies the action to be taken if the connection request matches the rule. target must be one of the following.

The target may optionally be followed by ":" and a syslog log level (e.g, REJECT:info or Web(ACCEPT):debug). This causes the packet to be logged at the specified level. Note that if the ACTION involves destination network address translation (DNAT, REDIRECT, etc.) then the packet is logged before the destination address is rewritten.

If the ACTION names an action declared in shorewall-actions(5) or in /usr/share/shorewall/actions.std then:

You may also specify ULOG (IPv4 only) or NFLOG (must be in upper case) as a log level.This will log to the ULOG or NFLOG target for routing to a separate log through use of ulogd (shorewall-logging(5)).

Actions specifying logging may be followed by a log tag (a string of alphanumeric characters) which is appended to the string generated by the LOGPREFIX (in shorewall.conf(5)).

Example: ACCEPT:info:ftp would include 'ftp ' at the end of the log prefix generated by the LOGPREFIX setting.

Source hosts to which the rule applies.

source-spec is one of the following:

Beginning with Shorewall 5.1.0, multiple source-specs may be listed, provided that extended forms of the source-spec are used:

Examples:

Destination hosts to which the rule applies.

dest-spec is one of the following:

If the DEST zone is a bport zone, then either:

Beginning with Shorewall 5.1.0, multiple dest-specs may be listed, provided that extended forms of the source-spec are used:

Multiple dest-specs are not permitted in DNAT[-] and REDIRECT[-] rules.

Examples:

Optional Protocol - ipp2p* requires ipp2p match support in your kernel and iptables. tcp:syn implies tcp plus the SYN flag must be set and the RST, ACK and FIN flags must be reset. Beginning with Shorewall 5.1.3, you may also specify tcp:!syn, which matches if SYN is not set or if RST, ACK or FIN is set.

Beginning with Shorewall 4.4.19, this column can contain a comma-separated list of protocol-numbers and/or protocol names.

Optional destination Ports. A comma-separated list of Port names (from services(5)), port numbers or port ranges; if the protocol is icmp, this column is interpreted as the destination icmp-type(s). ICMP types may be specified as a numeric type, a numeric type and code separated by a slash (e.g., 3/4), or a typename. See https://shorewall.org/configuration_file_basics.htm#ICMP. Note that prior to Shorewall 4.4.19, only a single ICMP type may be listed.

If the protocol is ipp2p, this column is interpreted as an ipp2p option without the leading "--" (example bit for bit-torrent). If no port is given, ipp2p is assumed.

A port range is expressed as lowport:highport.

This column is ignored if PROTO = all but must be entered if any of the following columns are supplied. In that case, it is suggested that this field contain a dash (-).

If your kernel contains multi-port match support, then only a single Netfilter rule will be generated if in this list and the SPORT list below:

1. There are 15 or less ports listed.

2. No port ranges are included or your kernel and iptables contain extended multi-port match support.

Beginning with Shorewall 4.6.0, an ipset name can be specified in this column. This is intended to be used with bitmap:port ipsets.

This column was formerly labelled DEST PORT(S).

Optional port(s) used by the client. If omitted, any source port is acceptable. Specified as a comma- separated list of port names, port numbers or port ranges.

Beginning with Shorewall 4.5.15, you may place '=' in this column, provided that the DPORT column is non-empty. This causes the rule to match when either the source port or the destination port in a packet matches one of the ports specified in DEST PORTS(S). Use of '=' requires multi-port match in your iptables and kernel.

If you don't want to restrict client ports but need to specify an ORIGDEST in the next column, then place "-" in this column.

If your kernel contains multi-port match support, then only a single Netfilter rule will be generated if in this list and the DPORT list above:

1. There are 15 or less ports listed.

2. No port ranges are included or your kernel and iptables contain extended multi-port match support.

Beginning with Shorewall 4.6.0, an ipset name can be specified in this column. This is intended to be used with bitmap:port ipsets.

This column was formerly labelled SOURCE PORT(S).

Optional. If ACTION is DNAT[-] or REDIRECT[-] then if this column is included and is different from the IP address given in the DEST column, then connections destined for that address will be forwarded to the IP and port specified in the DEST column.

A comma-separated list of addresses may also be used. This is most useful with the REDIRECT target where you want to redirect traffic destined for particular set of hosts. Finally, if the list of addresses begins with "!" (exclusion) then the rule will be followed only if the original destination address in the connection request does not match any of the addresses listed.

Beginning with Shorewall 4.4.17, the primary IP address of a firewall interface can be specified by an ampersand ('&') followed by the logical name of the interface as found in the INTERFACE column of shorewall-interfaces (5).

For other actions, this column may be included and may contain one or more addresses (host or network) separated by commas. Address ranges are not allowed. When this column is supplied, rules are generated that require that the original destination address matches one of the listed addresses. This feature is most useful when you want to generate a filter rule that corresponds to a DNAT- or REDIRECT- rule. In this usage, the list of addresses should not begin with "!".

It is also possible to specify a set of addresses then exclude part of those addresses. For example, 192.168.1.0/24!192.168.1.16/28 specifies the addresses 192.168.1.0-182.168.1.15 and 192.168.1.32-192.168.1.255. See shorewall-exclusion(5).

See https://shorewall.org/PortKnocking.html for an example of using an entry in this column with a user-defined action rule.

This column was formerly labelled ORIGINAL DEST.

where limit is one of:

You may optionally rate-limit the rule by placing a value in this column:

rate* is the number of connections per interval (sec or min) and burst* is the largest burst permitted. If no burst is given, a value of 5 is assumed. There may be no no white-space embedded in the specification.

Example: 10/sec:20

When s: or d: is specified, the rate applies per source IP address or per destination IP address respectively. The names may be chosen by the user and specify a hash table to be used to count matching connections. If not given, the name shorewallN (where N is a unique integer) is assumed. Where more than one rule or POLICY specifies the same name, the connections counts for the rules are aggregated and the individual rates apply to the aggregated count. Beginning with Shorewall 5.2.1, the s or d may be followed by a slash ("/") and an integer vlsm. When a vlsm is specified, all source or destination addresses encountered will be grouped according to the given prefix length and the so-created subnet will be subject to the rate limit.

Example: s/24::10/sec

Beginning with Shorewall 4.6.5, two limits may be specified, separated by a comma. In this case, the first limit (name1, rate1, burst1) specifies the per-source IP limit and the second limit specifies the per-destination IP limit.

Example: client:10/sec:20,:60/sec:100

In this example, the 'client' hash table will be used to enforce the per-source limit and the compiler will pick a unique name for the hash table that tracks the per-destination limit.

Beginning with Shorewall 5.2.1, the table name, if any, may be followed by two integers separated by commas and enclosed in parentheses. The first integer (ht-buckets) specifies the number of buckets in the generated hash table. The second integer (ht-max) specifies the maximum number of entries in the hash table.

Example: s:netfw(1024,65536):10/sec

This column was formerly labelled RATE LIMIT.

This optional column may only be non-empty if the SOURCE is the firewall itself.

When this column is non-empty, the rule applies only if the program generating the output is running under the effective user and/or group specified (or is NOT running under that id if "!" is given).

Beginning with Shorewall 4.5.8, multiple user or group names/ids separated by commas may be specified.

Examples:

This column was formerly labelled USER/GROUP.

Defines a test on the existing packet or connection mark. The rule will match only if the test returns true.

If you don't want to define a test but need to specify anything in the following columns, place a "-" in this field.

May be used to limit the number of simultaneous connections to/from each individual host or network to limit connections. Requires connlimit match in your kernel and iptables. While the limit is only checked on rules specifying CONNLIMIT, the number of current connections is calculated over all current connections from the SOURCE or DESTINATION host. By default, limiting is done by SOURCE host or net, but if the specification begins with d:, then limiting will be donw by destination host or net.

By default, the limit is applied to each host but can be made to apply to networks of hosts by specifying a mask. The mask specifies the width of a VLSM mask to be applied to the source address; the number of current connections is then taken over all hosts in the subnet source-address/mask. When ! is specified, the rule matches when the number of connection exceeds the limit.

May be used to limit the rule to a particular time period each day, to particular days of the week or month, or to a range defined by dates and times. Requires time match support in your kernel and iptables.

timeelement may be:

This column is only used in IPv6. In IPv4, supply "-" in this column if you with to place a value in one of the following columns.

The header-list consists of a comma-separated list of headers from the following list.

If any: is specified, the rule will match if any of the listed headers are present. If exactly: is specified, the will match packets that exactly include all specified headers. If neither is given, any: is assumed.

If ! is entered, the rule will match those packets which would not be matched when ! is omitted.

Added in Shorewall 4.4.24 and allows enabling and disabling the rule without requiring shorewall reload.

The rule is enabled if the value stored in /proc/net/nf_condition/switch-name is 1. The rule is disabled if that file contains 0 (the default). If '!' is supplied, the test is inverted such that the rule is enabled if the file contains 0.

Within the switch-name, '@0' and '@{0}' are replaced by the name of the chain to which the rule is a added. The switch-name (after '@...' expansion) must begin with a letter and be composed of letters, decimal digits, underscores or hyphens. Switch names must be 30 characters or less in length.

Switches are normally off. To turn a switch on:

To turn it off again:

Switch settings are retained over shorewall reload.

Beginning with Shorewall 4.5.10, when the switch-name is followed by =0 or =1, then the switch is initialized to off or on respectively by the start command. Other commands do not affect the switch setting.

Added in Shorewall 4.5.7.

In the NEW section, causes the named conntrack helper to be associated with this connection; the contents of this column are ignored unless ACTION is ACCEPT*, DNAT* or REDIRECT*.

In the RELATED section, will only match if the related connection has the named helper associated with it.

The helper may be one of:

If the HELPERS option is specified in shorewall.conf(5), then any module specified in this column must be listed in the HELPERS setting.

Accept SMTP requests from the DMZ to the internet

         #ACTION SOURCE  DEST      PROTO      DPORT   SPORT   ORIGDEST
         ACCEPT  dmz     net       tcp        smtp

Forward all ssh and http connection requests from the internet to local system 192.168.1.3

        #ACTION SOURCE  DEST            PROTO   DPORT   SPORT   ORIGDEST
        DNAT    net     loc:192.168.1.3 tcp     ssh,http

Forward all http connection requests from the internet to local system 192.168.1.3 with a limit of 3 per second and a maximum burst of 10

        #ACTION SOURCE DEST             PROTO  DPORT SPORT   ORIGDEST RATE
        DNAT    net    loc:192.168.1.3  tcp    http  -       -        3/sec:10

Redirect all locally-originating www connection requests to port 3128 on the firewall (Squid running on the firewall system) except when the destination address is 192.168.2.2

        #ACTION  SOURCE DEST      PROTO DPORT   SPORT   ORIGDEST
        REDIRECT loc    3128      tcp   www      -      !192.168.2.2

All http requests from the internet to address 130.252.100.69 are to be forwarded to 192.168.1.3

        #ACTION  SOURCE DEST            PROTO   DPORT   SPORT   ORIGDEST
        DNAT      net   loc:192.168.1.3 tcp     80      -       130.252.100.69

You want to accept SSH connections to your firewall only from internet IP addresses 130.252.100.69 and 130.252.100.70

        #ACTION  SOURCE DEST            PROTO   DPORT   SPORT   ORIGDEST
        ACCEPT   net:130.252.100.69,130.252.100.70 \
                        $FW             tcp     22

You wish to accept connections from the internet to your firewall on port 2222 and you want to forward them to local system 192.168.1.3, port 22

        #ACTION  SOURCE DEST                PROTO   DPORT   SPORT   ORIGDEST
        DNAT     net    loc:192.168.1.3:22  tcp     2222

You want to redirect connection requests to port 80 randomly to the port range 81-90.

        #ACTION  SOURCE DEST                PROTO DPORT   SPORT   ORIGDEST
        REDIRECT net    $FW::81-90:random   tcp   www

Shorewall does not impose as much structure on the Netfilter rules in the 'nat' table as it does on those in the filter table. As a consequence, when using Shorewall versions before 4.1.4, care must be exercised when using DNAT and REDIRECT rules with zones defined with wildcard interfaces (those ending with '+'. Here is an example:

shorewall-zones(5):

        #ZONE       TYPE    OPTIONS
        fw          firewall
        net         ipv4
        dmz         ipv4
        loc         ipv4

shorewall-interfaces(5):

        #ZONE       INTERFACE       BROADCAST      OPTIONS
        net         ppp0
        loc         eth1            detect
        dmz         eth2            detect
        -           ppp+                           # Addresses are assigned from 192.168.3.0/24

shorewall-host(5):

        #ZONE       HOST(S)              OPTIONS
        loc         ppp+:192.168.3.0/24

rules:

        #ACTION     SOURCE          DEST       PROTO       DPORT
        REDIRECT    loc             3128       tcp         80                                                   

Note that it would have been tempting to simply define the loc zone entirely in shorewall-interfaces(8):

        #******************* INCORRECT *****************
        #ZONE       INTERFACE       BROADCAST      OPTIONS
        net         ppp0
        loc         eth1            detect
        loc         ppp+
        dmz         eth2

This would have made it impossible to run a internet-accessible web server in the DMZ because all traffic entering ppp+ interfaces would have been redirected to port 3128 on the firewall and there would have been no net->fw ACCEPT rule for that traffic.

Add the tuple (source IP, dest port, dest IP) of an incoming SSH connection to the ipset S:

        #ACTION                       SOURCE           DEST           PROTO       DPORT
        ADD(+S:dst,src,dst)           net              fw             tcp         22

You wish to limit SSH connections from remote systems to 1/min with a burst of three (to allow for limited retry):

        #ACTION     SOURCE          DEST       PROTO       DPORT        SPORT     ORIGDEST         RATE
        SSH(ACCEPT) net             all        -           -            -         -                s:1/min:3

Forward port 80 to dmz host $BACKUP if switch 'primary_down' is on.

        #ACTION     SOURCE          DEST        PROTO       DPORT        SPORT     ORIGDEST   RATE      USER      MARK    CONNLIMIT     TIME     HEADERS    SWITCH
        DNAT        net             dmz:$BACKUP tcp         80           -         -          -         -         -       -             -        -          primary_down

Drop all email from the Anonymous Proxy and Satellite Provider address ranges:

        #ACTION                       SOURCE           DEST           PROTO       DPORT
        DROP                          net:^A1,A2       fw             tcp         25

You want to generate your own rule involving iptables targets and matches not supported by Shorewall.

        #ACTION                       SOURCE           DEST           PROTO       DPORT
        INLINE                        $FW              net ; -p 6 -m mickey-mouse --name test -m set --match-set set1 src -m mickey-mouse --name test2 -j SECCTX --name test3

The above will generate the following iptables-restore input:

        -A fw2net -p 6 -m mickey-mouse --name test -m set --match-set set1 src -m mickey-mouse --name test2 -j SECCTX --name test3

Note that SECCTX must be defined as a builtin action in shorewall-actions(5):

        #ACTION            OPTIONS
        SECCTX             builtin

You want to accept SSH connections to your firewall only from internet IP addresses 2002:ce7c::92b4:1::2 and 2002:ce7c::92b4:1::22

        #ACTION  SOURCE DEST            PROTO   DPORT   SPORT   ORIGDEST
        ACCEPT   net:<2002:ce7c::92b4:1::2,2002:ce7c::92b4:1::22> \
                        $FW              tcp     22