PREROUTING chain.

FORWARD chain.

POSTROUTING chain.

INPUT chain.

PREROUTING chain in the nat table.

INPUT chain in the nat table.

OUTPUT chain in the nat table.

POSTROUTING chain in the nat table.

Added in Shorewall 5.0.7. action must be an action declared with the mangle option in shorewall-actions(5). If the action accepts parameters, they are specified as a comma-separated list within parentheses following the action name.

Added in Shorewall 4.6.7. Causes addresses and/or port numbers to be added to the named ipset. The flags specify the address or tuple to be added to the set and must match the type of ipset involved. For example, for an iphash ipset, either the SOURCE or DESTINATION address can be added using flags src or dst respectively (see the -A command in ipset (8)).

ADD is non-terminating. Even if a packet matches the rule, it is passed on to the next rule.

Compute and fill in the checksum in a packet that lacks a checksum. This is particularly useful if you need to work around old applications, such as dhcp clients, that do not work well with checksum offloads, but you don't want to disable checksum offload in your device.

Requires 'Checksum Target' support in your kernel and iptables.

A classification Id (classid) is of the form major:minor where major and minor are integers. Corresponds to the 'class' specification in these traffic shaping modules:

       atm
       cbq
       dsmark
       pfifo_fast
       htb
       prio

Classification occurs in the POSTROUTING chain except when the SOURCE is $FW[:address] in which case classification occurs in the OUTPUT chain.

When using Shorewall's built-in traffic shaping tool, the major class is the device number (the first device in shorewall-tcdevices(5) is major class 1, the second device is major class 2, and so on) and the minor class is the class's MARK value in shorewall-tcclasses(5) preceded by the number 1 (MARK 1 corresponds to minor class 11, MARK 5 corresponds to minor class 15, MARK 22 corresponds to minor class 122, etc.).

The rest of the line will be attached as a comment to the Netfilter rule(s) generated by the following entries. The comment will appear delimited by "/* ... */" in the output of shorewall show mangle

To stop the comment from being attached to further rules, simply include ?COMMENT on a line by itself.

Identical to MARK with the exception that the mark is assigned to connection to which the packet belongs is marked rather than to the packet itself.

Don't process any more marking rules in the table.

Currently, CONTINUE may not be used with exclusion (see the SOURCE and DEST columns below); that restriction will be removed when iptables/Netfilter provides the necessary support.

Added in Shorewall 4.6.7. Causes an entry to be deleted from the named ipset. The flags specify the address or tuple to be deleted from the set and must match the type of ipset involved. For example, for an iphash ipset, either the SOURCE or DESTINATION address can be deleted using flags src or dst respectively (see the -D command in ipset (8)).

DEL is non-terminating. Even if a packet matches the rule, it is passed on to the next rule.

Two DIVERT rule should precede the TPROXY rule and should select DEST PORT tcp 80 and SOURCE PORT tcp 80 respectively (assuming that tcp port 80 is being proxied). DIVERT avoids sending packets to the TPROXY target once a socket connection to Squid3 has been established by TPROXY. DIVERT marks the packet with a unique mark and exempts it from any rules that follow.

Added in Shorewall 5.0.4. To setup the HAProxy configuration described at http://www.loadbalancer.org/blog/setting-up-haproxy-with-transparent-mode-on-centos-6-x, place this entry in shorewall-providers(5):

#NAME    NUMBER   MARK    DUPLICATE  INTERFACE GATEWAY         OPTIONS               COPY
TProxy   1        -       -          lo        -               tproxy

and use this DIVERTHA entry:

#ACTION         SOURCE          DEST            PROTO   DPORT   SPORT   USER    TEST    LENGTH  TOS   CONNBYTES         HELPER    PROBABILITY DSCP
DIVERTHA        -               -               tcp

Causes matching packets to be discarded.

Sets the Differentiated Services Code Point field in the IP header. The dscp value may be given as an even number (hex or decimal) or as the name of a DSCP class. Valid class names and their associated hex numeric values are:

    CS0  => 0x00
    CS1  => 0x08
    CS2  => 0x10
    CS3  => 0x18
    CS4  => 0x20
    CS5  => 0x28
    CS6  => 0x30
    CS7  => 0x38
    BE   => 0x00
    AF11 => 0x0a
    AF12 => 0x0c
    AF13 => 0x0e
    AF21 => 0x12
    AF22 => 0x14
    AF23 => 0x16
    AF31 => 0x1a
    AF32 => 0x1c
    AF33 => 0x1e
    AF41 => 0x22
    AF42 => 0x24
    AF43 => 0x26
    EF   => 0x2e

To indicate more than one class, add their hex values together and specify the result. By default, DSCP rules are placed in the POSTROUTING chain.

Added in Shorewall 5.0.6 as an alternative to entries in shorewall-ecn(5). If a PROTO is specified, it must be 'tcp' (6). If no PROTO is supplied, TCP is assumed. This action causes all ECN bits in the TCP header to be cleared.

Specifies that the packet should be passed to the IMQ identified by number. Requires IMQ Target support in your kernel and iptables.

Allows you to place your own ip[6]tables matches at the end of the line following a semicolon (";") (deprecated) or two semicolons (";;") (preferred since Shoreall 5.0.0). If an action is specified, the compiler proceeds as if that action had been specified in this column. If no action is specified, then you may include your own jump ("-j target [option] ...") after any matches specified at the end of the rule. If the target is not one known to Shorewall, then it must be defined as a builtin action in shorewall-actions (5).

The following rules are equivalent:

2:P                   eth0              -         tcp 22
INLINE(MARK(2)):P     eth0              -         tcp 22
INLINE(MARK(2)):P     eth0              -                 ;; -p tcp
INLINE                eth0              -         tcp 22  ;; -j MARK --set-mark 2
INLINE                eth0              -                 ;; -p tcp -j MARK --set-mark 2

Assigns a mark to each matching packet based on the either the source or destination IP address. By default, it assigns a mark value equal to the low-order 8 bits of the source address. Default values are:

'src' and 'dst' specify whether the mark is to be based on the source or destination address respectively. The selected address is first shifted to the right by shift bits. The result is then LANDed with mask1 then LORed with mask2.

In a sense, the IPMARK target is more like an IPCLASSIFY target in that the mark value is later interpreted as a class ID. A packet mark is 32 bits wide; so is a class ID. The <major> class occupies the high-order 16 bits and the <minor> class occupies the low-order 16 bits. So the class ID 1:4ff (remember that class IDs are always in hex) is equivalent to a mark value of 0x104ff. Remember that Shorewall uses the interface number as the <major> number where the first interface in tcdevices has <major> number 1, the second has <major> number 2, and so on.

The IPMARK target assigns a mark to each matching packet based on the either the source or destination IP address. By default, it assigns a mark value equal to the low-order 8 bits of the source address. The syntax is as follows:

Default values are:

src and dst specify whether the mark is to be based on the source or destination address respectively. The selected address is first shifted right by shift, then LANDed with mask1 and then LORed with mask2. The shift argument is intended to be used primarily with IPv6 addresses.

Example:

It is important to realize that, while class IDs are composed of a major and a minor value, the set of values must be unique. That is, the same numeric value cannot be used as both a major and a minor number for the same interface unless class nesting occurs (which is not currently possible with Shorewall). You should keep this in mind when deciding how to map IP addresses to class IDs.

For example, suppose that your internal network is 192.168.1.0/29 (host IP addresses 192.168.1.1 - 192.168.1.6). Your first notion might be to use IPMARK(src,0xFF,0x10000) so as to produce class IDs 1:1 through 1:6. But 1:1 is an invalid class ID since the major and minor classes are equal. So you might choose instead to use IPMARK(src,0xFF,0x10100) as in the example above so that all of your minor classes will have a value > 256.

IPv6 only.

This action allows you to specify an iptables target with options (e.g., 'IP6TABLES(MARK --set-xmark 0x01/0xff)'. If the target is not one recognized by Shorewall, the following error message will be issued:

This error message may be eliminated by adding the target as a builtin action in shorewall-actions(5).

IPv4 only.

This action allows you to specify an iptables target with options (e.g., 'IPTABLES(MARK --set-xmark 0x01/0xff)'. If the target is not one recognized by Shorewall, the following error message will be issued:

This error message may be eliminated by adding the target as a builtin action in shorewall-actions(5).

where mark is a packet mark value.

Normally will set the mark value. If preceded by a vertical bar ("|"), the mark value will be logically ORed with the current mark value to produce a new mark value. If preceded by an ampersand ("&"), will be logically ANDed with the current mark value to produce a new mark value.

Both "|" and "&" require Extended MARK Target support in your kernel and iptables.

The mark value may be optionally followed by "/" and a mask value (used to determine those bits of the connection mark to actually be set). When a mask is specified, the result of logically ANDing the mark value with the mask must be the same as the mark value.

A mark range is a pair of integers separated by a dash ("-").

May be optionally followed by a slash ("/") and a mask and requires the Statistics Match capability in iptables and kernel. Marks in the specified range are assigned to packets on a round-robin fashion.

When a mask is specified, the result of logically ANDing each mark value with the mask must be the same as the mark value. The least significant bit in the mask is used as an increment. For example, if '0x200-0x400/0xff00' is specified, then the assigned mark values are 0x200, 0x300 and 0x400 in equal proportions. If no mask is specified, then ( 2 ** MASK_BITS ) - 1 is assumed (MASK_BITS is set in shorewall.conf(5)).

Added in Shorewall 5.0.9. Logs matching packets using NFLOG. The nflog-parameters are a comma-separated list of up to 3 numbers:

Restore the packet's mark from the connection's mark using the supplied mask if any. Your kernel and iptables must include CONNMARK support.

Some websites run applications that require multiple connections from a client browser. Where multiple 'balanced' providers are configured, this can lead to problems when some of the connections are routed through one provider and some through another. The SAME target allows you to work around that problem. SAME may be used in the PREROUTING and OUTPUT chains. When used in PREROUTING, it causes matching connections from an individual local system to all use the same provider. For example:

#ACTION           SOURCE         DEST         PROTO      DPORT
SAME:P            192.168.1.0/24 0.0.0.0/0    tcp        80,443

If a host in 192.168.1.0/24 attempts a connection on TCP port 80 or 443 and it has sent a packet on either of those ports in the last five minutes then the new connection will use the same provider as the connection over which that last packet was sent.

When used in the OUTPUT chain, it causes all matching connections to an individual remote system to all use the same provider. For example:

#ACTION           SOURCE         DEST         PROTO      DPORT
SAME              $FW            0.0.0.0/0    tcp        80,443

The optional timeout parameter was added in Shorewall 4.6.7 and specifies a number of seconds . When not specified, a value of 300 seconds (5 minutes) is assumed. If the firewall attempts a connection on TCP port 80 or 443 and it has sent a packet on either of those ports in the last timeout seconds to the same remote system then the new connection will use the same provider as the connection over which that last packet was sent.

Save the packet's mark to the connection's mark using the supplied mask if any. Your kernel and iptables must include CONNMARK support.

Added in Shorewall 5.1.9. This target only applies to TCP traffic and alters the MSS value in SYN packets. It may be used in the FORWARD and POSTROUTING chains; the default is FORWARD.

The mss parameter may be either pmtu or an integer in the range 500:65533. The value pmtu automatically clamps the MSS value to (path_MTU - 40 for IPv4; -60 for IPv6). This may not function as desired where asymmetric routes with differing path MTU exist — the kernel uses the path MTU which it would use to send packets from itself to the source and destination IP addresses. Prior to Linux 2.6.25, only the path MTU to the destination IP address was considered by this option; subsequent kernels also consider the path MTU to the source IP address. If an integer is given, the MSS option is set to the specified value. If the MSS of the packet is already lower than mss, it will not be increased (from Linux 2.6.25 onwards) to avoid more problems with hosts relying on a proper MSS. If mss is omitted, pmtu is assumed.

The ipsec parameter determines whether the rule applies to IPSEC traffic (ipsec is passed), non-IPSEC traffic (none is passed) or both (all is passed). If omitted, all is assumed.

Sets the Type of Service field in the IP header. The tos value may be given as an number (hex or decimal) or as the name of a TOS type. Valid type names and their associated hex numeric values are:

Minimize-Delay       => 0x10,
Maximize-Throughput  => 0x08,
Maximize-Reliability => 0x04,
Minimize-Cost        => 0x02,
Normal-Service       => 0x00

To indicate more than one class, add their hex values together and specify the result.

When tos is given as a number, it may be optionally followed by '/' and a mask. When no mask is given, the value 0xff is assumed. When tos is given as a type name, the mask 0x3f is assumed.

The action performed is to zero out the bits specified by the mask, then set the bits specified by tos.

Transparently redirects a packet without altering the IP header. Requires a tproxy provider to be defined in shorewall-providers(5).

There are three parameters to TPROXY - neither is required:

If + is included, packets matching the rule will have their TTL incremented by number. Similarly, if - is included, matching packets have their TTL decremented by number. If neither + nor - is given, the TTL of matching packets is set to number. The valid range of values for number is 1-255.

where interface is the logical name of an interface defined in shorewall-interfaces(5). Matches packets entering the firewall from the named interface. May not be used in CLASSIFY rules or in rules using the :T chain qualifier.

Beginning with Shorweall 5.2.1, the interface may be preceded with '!' which matches all interfaces except the one specified.

where address is:

Matches traffic whose source IP address matches one of the listed addresses and that does not match an address listed in the exclusion (see shorewall-exclusion(5)).

This form will not match traffic that originates on the firewall itself unless either <major><minor> or the :T chain qualifier is used in the ACTION column.

This form combines the preceding two forms and matches when both the incoming interface and source IP address match.

Beginning with Shorweall 5.2.1, the interface may be preceded with '!' which matches all interfaces except the one specified.

This form matches packets arriving through the named interface and whose source IP address does not match any of the addresses in the exclusion.

Beginning with Shorweall 5.2.1, the interface may be preceded with '!' which matches all interfaces except the one specified.

Matches packets originating on the firewall system. May not be used with a chain qualifier (:P, :F, etc.) in the ACTION column.

where address is as above (MAC addresses are not permitted). Matches packets originating on the firewall and whose source IP address matches one of the listed addresses and does not match any address listed in the exclusion. May not be used with a chain qualifier (:P, :F, etc.) in the ACTION column.

Matches traffic originating on the firewall, provided that the source IP address does not match any address listed in the exclusion.

where interface is the logical name of an interface defined in shorewall-interfaces(5). Matches packets leaving the firewall through the named interface. May not be used in the PREROUTING chain (:P in the mark column or no chain qualifier and MARK_IN_FORWARD_CHAIN=No in shorewall.conf (5)).

where address is:

Matches traffic whose destination IP address matches one of the listed addresses and that does not match an address listed in the exclusion (see shorewall-exclusion(5)).

This form combines the preceding two forms and matches when both the outgoing interface and destination IP address match. May not be used in the PREROUTING chain (:P in the mark column or no chain qualifier and MARK_IN_FORWARD_CHAIN=No in shorewall.conf (5)).

This form matches packets leaving through the named interface and whose destination IP address does not match any of the addresses in the exclusion. May not be used in the PREROUTING chain (:P in the mark column or no chain qualifier and MARK_IN_FORWARD_CHAIN=No in shorewall.conf (5)).

Matches packets originating on the firewall system. May not be used with a chain qualifier (:P, :F, etc.) in the ACTION column.

where address is as above (MAC addresses are not permitted). Matches packets destined for the firewall and whose destination IP address matches one of the listed addresses and does not match any address listed in the exclusion. May not be used with a chain qualifier (:P, :F, etc.) in the ACTION column.

Matches traffic destined for the firewall, provided that the destination IP address does not match any address listed in the exclusion.

program must be run by joe

program must be run by a member of the 'kids' group

program must not be run by a member of the 'kids' group

#program named upnpd

Inverts the test (not equal)

Value of the packet or connection mark.

A mask to be applied to the mark before testing.

Designates a connection mark. If omitted, the packet mark's value is tested.

Defines the starting time of day.

Defines the ending time of day.

Added in Shoreawll 5.0.12. When timestop is smaller than timestart value, match this as a single time period instead of distinct intervals.

Times are expressed in Greenwich Mean Time.

Deprecated by the Netfilter team in favor of kerneltz. Times are expressed in Local Civil Time (default).

Added in Shorewall 4.5.2. Times are expressed in Local Kernel Time (requires iptables 1.4.12 or later).

where ddd is one of Mon, Tue, Wed, Thu, Fri, Sat or Sun

where dd is an ordinal day of the month

Defines the starting date and time.

Defines the ending date and time.