A mark value which is an integer in the range 1-255.

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; neither may be used with connection marks (see below).

May optionally be followed by :P, :F,:T or :I where :P indicates that marking should occur in the PREROUTING chain, :F indicates that marking should occur in the FORWARD chain, :I indicates that marking should occur in the INPUT chain (added in Shorewall 4.4.13), and :T indicates that marking should occur in the POSTROUTING chain. If neither :P, :F nor :T follow the mark value then the chain is determined as follows:

- If the SOURCE is $FW[:address-or-range[,address-or-range]...], then the rule is inserted into the OUTPUT chain. When HIGH_ROUTE_MARKS=Yes, only high mark values may be assigned there. Packet marking rules for traffic shaping of packets originating on the firewall must be coded in the POSTROUTING chain (see below).

- Otherwise, the chain is determined by the setting of MARK_IN_FORWARD_CHAIN in shorewall.conf(5).

Please note that :I is included for completeness and affects neither traffic shaping nor policy routing.

If your kernel and iptables include CONNMARK support then you can also mark the connection rather than the packet.

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.

The mark and optional mask are then followed by one of:

A mark range which is a pair of integers separated by a dash ("-"). Added in Shorewall 4.5.9.

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)).

May optionally be followed by :P, :F,:T or :I where :P indicates that marking should occur in the PREROUTING chain, :F indicates that marking should occur in the FORWARD chain, :I indicates that marking should occur in the INPUT chain (added in Shorewall 4.4.13), and :T indicates that marking should occur in the POSTROUTING chain. If neither :P, :F nor :T follow the mark value then the chain is determined as follows:

- If the SOURCE is $FW[:address-or-range[,address-or-range]...], then the rule is inserted into the OUTPUT chain. When HIGH_ROUTE_MARKS=Yes, only high mark values may be assigned there. Packet marking rules for traffic shaping of packets originating on the firewall must be coded in the POSTROUTING chain (see below).

- Otherwise, the chain is determined by the setting of MARK_IN_FORWARD_CHAIN in shorewall.conf(5).

Please note that :I is included for completeness and affects neither traffic shaping nor policy routing.

If your kernel and iptables include CONNMARK support then you can also mark the connection rather than the packet.

The mark range and optional mask can then followed by one of:

A classification Id (classid) 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.).

Beginning with Shorewall 4.4.27, the classid may be optionally followed by ':' and a capital letter designating the chain where classification is to occur.

CHECKSUM

Added in Shorewall 4.5.9. 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.

[?]COMMENT -- 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.

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

As in 1) above, may be followed by :P or :F. 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.

DIVERT

Added in Shorewall 4.5.4 and only available when FORMAT is 2. 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.

DROP

Added in Shorewall 4.5.21.4. Causes matching packets to be discarded.

DSCP(dscp)

Added in Shorewall 4.5.1. 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.

May be optionally followed by ':' and a capital letter designating the chain where classification is to occur.

IMQ(number)

Added in Shorewall 4.5.1. Specifies that the packet should be passed to the IMQ identified by number. Requires IMQ Target support in your kernel and iptables.

INLINE[(action)]

Added in Shorewall 4.6.0. Allows you to place your own ip[6]tables matches at the end of the line following a semicolon (";"). If an action is specified, the compiler procedes 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(2):P     eth0              -         tcp 22
INLINE(2):P     eth0              -                 ; -p tcp
INLINE          eth0              -         tcp 22  ; -j MARK --set-mark 2
INLINE          eth0              -                 ; -p tcp -j MARK --set-mark 2

If INLINE_MATCHES=Yes in shorewall.conf(5) then the third rule above can be specified as follows:

2:P             eth0              -                 ; -p tcp

IPMARK ‒ 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.

RESTORE[/mask] -- restore the packet's mark from the connection's mark using the supplied mask if any. Your kernel and iptables must include CONNMARK support.

As in 1) above, may be followed by :P or :F

SAME 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      DEST
#                                                        PORT(S)
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      DEST
#                                                        PORT(S)
SAME              $FW            0.0.0.0/0    tcp        80,443

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 five minutes 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[/mask] -- save the packet's mark to the connection's mark using the supplied mask if any. Your kernel and iptables must include CONNMARK support.

As in 1) above, may be followed by :P or :F

TOS(tos[/mask])

Added in Shorewall 4.5.1. 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.

May be optionally followed by ':' and a capital letter designating the chain where classification is to occur.

TPROXY(mark[,[port][,[address]]]) -- FORMAT 1

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

There are three parameters to TPROXY - only the first (mark) is required:

TPROXY([port][,address]) -- FORMAT 2

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:

TTL([-|+]number)

Added in Shorewall 4.4.24.

Prior to Shorewall 4.5.7.2, may be optionally followed by :F but the resulting rule is always added to the FORWARD chain. Beginning with Shorewall 4.5.7.s, it may be optionally followed by :P, in which case the rule is added to the PREROUTING chain.

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.

An interface name - matches traffic entering the firewall on the specified interface. May not be used in classify rules or in rules using the :T chain qualifier.

A comma-separated list of host or network IP addresses or MAC addresses. 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.

Examples:

An interface name followed by a colon (":") followed by a comma-separated list of host or network IP addresses or MAC addresses. May not be used in classify rules or in rules using the :T chain qualifier.

$FW optionally followed by a colon (":") and a comma-separated list of host or network IP addresses. Matches packets originating on the firewall. May not be used with a chain qualifier (:P, :F, etc.) in the ACTION column.

An interface name. 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)). The interface name may be optionally followed by a colon (":") and an IP address list.

A comma-separated list of host or network IP addresses. The list may include ip address ranges if your kernel and iptables include iprange support.

Beginning with Shorewall 4.4.13, $FW may be specified by itself or qualified by an address list. This causes marking to occur in the INPUT chain.