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

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

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

Packets in the NEW and INVALID states are processed by rules in this section.

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

Source hosts to which the rule applies. May be a zone declared in /etc/shorewall/zones, $FW to indicate the firewall itself, all, all+, all-, all+- or none.

When none is used either in the SOURCE or DEST column, the rule is ignored.

all means "All Zones", including the firewall itself. all- means "All Zones, except the firewall itself". When all[-] is used either in the SOURCE or DEST column intra-zone traffic is not affected. When all+[-] is "used, intra-zone traffic is affected.

Except when all[+][-] is specified, clients may be further restricted to a list of networks and/or hosts by appending ":" and a comma-separated list of network and/or host addresses. Hosts may be specified by IP or MAC address; mac addresses must begin with "~" and must use "-" as a separator.

Hosts may also be specified as an IP address range using the syntax lowaddress-highaddress. This requires that your kernel and iptables contain iprange match support. If your kernel and iptables have ipset match support then you may give the name of an ipset prefaced by "+". The ipset name may be optionally followed by a number from 1 to 6 enclosed in square brackets ([]) to indicate the number of levels of source bindings to be matched.

You may exclude certain hosts from the set already defined through use of an exclusion (see shorewall-exclusion(5)).

Examples:

Examples:

Location of Server. May be a zone declared in shorewall-zones(5), $FW to indicate the firewall itself, all. all+ or none.

When none is used either in the SOURCE or DEST column, the rule is ignored.

When all is used either in the SOURCE or DEST column intra-zone traffic is not affected. When all+ is used, intra-zone traffic is affected.

Beginning with Shorewall 4.1.4, the zone should be omitted in DNAT-, REDIRECT- and NONAT rules.

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

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.

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).

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 CLIENT PORT(S) list below:

1. There are 15 or less ports listed.

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

Otherwise, unless you are using Shorewall-perl, a separate rule will be generated for each port. Shorewall-perl does not automatically break up lists into individual rules.

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.

If ACTION is DNAT[-] or REDIRECT[-] then if this column is included and is different from the IP address given in the SERVER 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.

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

You may 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 whitespace embedded in the specification.

Example: 10/sec:20

This 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).

Examples:

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.

Added in Shorewall-perl 4.2.1. May be used to limit the number of simultaneous connections from each individual host 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 host. 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.

Added in Shorewall-perl 4.2.1. 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:

Accept SMTP requests from the DMZ to the internet

         #ACTION SOURCE  DEST PROTO      DEST    SOURCE  ORIGINAL
         #                               PORT    PORT(S) DEST
         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   DEST    SOURCE  ORIGINAL
        #                                       PORT    PORT(S) DEST
        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  DEST  SOURCE  ORIGINAL RATE
        #                                     PORT  PORT(S) DEST     LIMIT
        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 DEST    SOURCE  ORIGINAL
        #                               PORT    PORT(S) DEST
        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   DEST    SOURCE  ORIGINAL
        #                                       PORT    PORT(S) DEST
        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   DEST    SOURCE  ORIGINAL
        #                                       PORT    PORT(S) DEST
        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   DEST    SOURCE  ORIGINAL
        #                                           PORT    PORT(S) DEST
        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 DEST    SOURCE  ORIGINAL
        #                                   PORT  PORT(S) DEST
        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(8):

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

shorewall-interfaces(8):

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

shorewall-host(8):

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

rules:

        #ACTION     SOURCE          DEST       PROTO       DEST
        #                                                  PORT(S)
        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.