.TH ARPTABLES 8  "March 2019"

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.SH NAME

arptables \- ARP table administration (nft-based)

.SH SYNOPSIS

.BR "arptables " [ "-t table" ] " -" [ AD ] " chain rule-specification " [ options ]

.br

.BR "arptables " [ "-t table" ] " -" [ RI ] " chain rulenum rule-specification " [ options ]

.br

.BR "arptables " [ "-t table" ] " -D chain rulenum " [ options ]

.br

.BR "arptables " [ "-t table" ] " -" [ "LFZ" ] " " [ chain ] " " [ options ]

.br

.BR "arptables " [ "-t table" ] " -" [ "NX" ] " chain"

.br

.BR "arptables " [ "-t table" ] " -E old-chain-name new-chain-name"

.br

.BR "arptables " [ "-t table" ] " -P chain target " [ options ]

.SH DESCRIPTION

.B arptables

is a user space tool, it is used to set up and maintain the

tables of ARP rules in the Linux kernel. These rules inspect

the ARP frames which they see.

.B arptables

is analogous to the

.B iptables

user space tool, but

.B arptables

is less complicated.

.SS CHAINS

The kernel table is used to divide functionality into

different sets of rules. Each set of rules is called a chain.

Each chain is an ordered list of rules that can match ARP frames. If a

rule matches an ARP frame, then a processing specification tells

what to do with that matching frame. The processing specification is

called a 'target'. However, if the frame does not match the current

rule in the chain, then the next rule in the chain is examined and so forth.

The user can create new (user-defined) chains which can be used as the 'target' of a rule.

.SS TARGETS

A firewall rule specifies criteria for an ARP frame and a frame

processing specification called a target.  When a frame matches a rule,

then the next action performed by the kernel is specified by the target.

The target can be one of these values:

.IR ACCEPT ,

.IR DROP ,

.IR CONTINUE ,

.IR RETURN ,

an 'extension' (see below) or a user-defined chain.

.PP

.I ACCEPT

means to let the frame through.

.I DROP

means the frame has to be dropped.

.I CONTINUE

means the next rule has to be checked. This can be handy to know how many

frames pass a certain point in the chain or to log those frames.

.I RETURN

means stop traversing this chain and resume at the next rule in the

previous (calling) chain.

For the extension targets please see the

.B "TARGET EXTENSIONS"

section of this man page.

.SS TABLES

There is only one ARP table in the Linux

kernel.  The table is

.BR filter.

You can drop the '-t filter' argument to the arptables command.

The -t argument must be the

first argument on the arptables command line, if used.

.TP

.B "-t, --table"

.br

.BR filter ,

is the only table and contains two built-in chains:

.B INPUT 

(for frames destined for the host) and

.B OUTPUT 

(for locally-generated frames).

.br

.br

.SH ARPTABLES COMMAND LINE ARGUMENTS

After the initial arptables command line argument, the remaining

arguments can be divided into several different groups.  These groups

are commands, miscellaneous commands, rule-specifications, match-extensions,

and watcher-extensions.

.SS COMMANDS

The arptables command arguments specify the actions to perform on the table

defined with the -t argument.  If you do not use the -t argument to name

a table, the commands apply to the default filter table.

With the exception of the

.B "-Z"

command, only one command may be used on the command line at a time.

.TP

.B "-A, --append"

Append a rule to the end of the selected chain.

.TP

.B "-D, --delete"

Delete the specified rule from the selected chain. There are two ways to

use this command. The first is by specifying an interval of rule numbers

to delete, syntax: start_nr[:end_nr]. Using negative numbers is allowed, for more

details about using negative numbers, see the -I command. The second usage is by

specifying the complete rule as it would have been specified when it was added.

.TP

.B "-I, --insert"

Insert the specified rule into the selected chain at the specified rule number.

If the current number of rules equals N, then the specified number can be

between -N and N+1. For a positive number i, it holds that i and i-N-1 specify the

same place in the chain where the rule should be inserted. The number 0 specifies

the place past the last rule in the chain and using this number is therefore

equivalent with using the -A command.

.TP

.B "-R, --replace"

Replaces the specified rule into the selected chain at the specified rule number.

If the current number of rules equals N, then the specified number can be

between 1 and N. i specifies the place in the chain where the rule should be replaced.

.TP

.B "-P, --policy"

Set the policy for the chain to the given target. The policy can be

.BR ACCEPT ", " DROP " or " RETURN .

.TP

.B "-F, --flush"

Flush the selected chain. If no chain is selected, then every chain will be

flushed. Flushing the chain does not change the policy of the

chain, however.

.TP

.B "-Z, --zero"

Set the counters of the selected chain to zero. If no chain is selected, all the counters

are set to zero. The

.B "-Z"

command can be used in conjunction with the 

.B "-L"

command.

When both the

.B "-Z"

and

.B "-L"

commands are used together in this way, the rule counters are printed on the screen

before they are set to zero.

.TP

.B "-L, --list"

List all rules in the selected chain. If no chain is selected, all chains

are listed.

.TP

.B "-N, --new-chain"

Create a new user-defined chain with the given name. The number of

user-defined chains is unlimited. A user-defined chain name has maximum

length of 31 characters.

.TP

.B "-X, --delete-chain"

Delete the specified user-defined chain. There must be no remaining references

to the specified chain, otherwise

.B arptables

will refuse to delete it. If no chain is specified, all user-defined

chains that aren't referenced will be removed.

.TP

.B "-E, --rename-chain"

Rename the specified chain to a new name.  Besides renaming a user-defined

chain, you may rename a standard chain name to a name that suits your

taste. For example, if you like PREBRIDGING more than PREROUTING,

then you can use the -E command to rename the PREROUTING chain. If you do

rename one of the standard

.B arptables

chain names, please be sure to mention

this fact should you post a question on the

.B arptables

mailing lists.

It would be wise to use the standard name in your post. Renaming a standard

.B arptables

chain in this fashion has no effect on the structure or function

of the

.B arptables

kernel table.

.SS MISCELLANOUS COMMANDS

.TP

.B "-V, --version"

Show the version of the arptables userspace program.

.TP

.B "-h, --help"

Give a brief description of the command syntax.

.TP

.BR "-j, --jump " "\fItarget\fP"

The target of the rule. This is one of the following values:

.BR ACCEPT ,

.BR DROP ,

.BR CONTINUE ,

.BR RETURN ,

a target extension (see

.BR "TARGET EXTENSIONS" ")"

or a user-defined chain name.

.TP

.BI "-c, --set-counters " "PKTS BYTES"

This enables the administrator to initialize the packet and byte

counters of a rule (during

.B INSERT,

.B APPEND,

.B REPLACE

operations).

.SS RULE-SPECIFICATIONS

The following command line arguments make up a rule specification (as used 

in the add and delete commands). A "!" option before the specification 

inverts the test for that specification. Apart from these standard rule 

specifications there are some other command line arguments of interest.

.TP

.BR "-s, --source-ip " "[!] \fIaddress\fP[/\fImask]\fP"

The Source IP specification.

.TP 

.BR "-d, --destination-ip " "[!] \fIaddress\fP[/\fImask]\fP"

The Destination IP specification.

.TP 

.BR "--source-mac " "[!] \fIaddress\fP[/\fImask\fP]"

The source mac address. Both mask and address are written as 6 hexadecimal

numbers separated by colons.

.TP

.BR "--destination-mac " "[!] \fIaddress\fP[/\fImask\fP]"

The destination mac address. Both mask and address are written as 6 hexadecimal

numbers separated by colons.

.TP 

.BR "-i, --in-interface " "[!] \fIname\fP"

The interface via which a frame is received (for the

.B INPUT

chain). The flag

.B --in-if

is an alias for this option.

.TP

.BR "-o, --out-interface " "[!] \fIname\fP"

The interface via which a frame is going to be sent (for the

.B OUTPUT

chain). The flag

.B --out-if

is an alias for this option.

.TP

.BR "-l, --h-length " "\fIlength\fP[/\fImask\fP]"

The hardware length (nr of bytes)

.TP

.BR "--opcode " "\fIcode\fP[/\fImask\fP]

The operation code (2 bytes). Available values are:

.BR 1 = Request

.BR 2 = Reply

.BR 3 = Request_Reverse

.BR 4 = Reply_Reverse

.BR 5 = DRARP_Request

.BR 6 = DRARP_Reply

.BR 7 = DRARP_Error

.BR 8 = InARP_Request

.BR 9 = ARP_NAK .

.TP

.BR "--h-type " "\fItype\fP[/\fImask\fP]"

The hardware type (2 bytes, hexadecimal). Available values are:

.BR 1 = Ethernet .

.TP

.BR "--proto-type " "\fItype\fP[/\fImask\fP]"

The protocol type (2 bytes). Available values are:

.BR 0x800 = IPv4 .

.SS TARGET-EXTENSIONS

.B arptables

extensions are precompiled into the userspace tool. So there is no need

to explicitly load them with a -m option like in

.BR iptables .

However, these

extensions deal with functionality supported by supplemental kernel modules.

.SS mangle

.TP

.BR "--mangle-ip-s IP address"

Mangles Source IP Address to given value.

.TP

.BR "--mangle-ip-d IP address"

Mangles Destination IP Address to given value.

.TP

.BR "--mangle-mac-s MAC address"

Mangles Source MAC Address to given value.

.TP

.BR "--mangle-mac-d MAC address"

Mangles Destination MAC Address to given value.

.TP

.BR "--mangle-target target "

Target of ARP mangle operation

.BR "" ( DROP ", " CONTINUE " or " ACCEPT " -- default is " ACCEPT ).

.SS CLASSIFY

This  module  allows you to set the skb->priority value (and thus clas-

sify the packet into a specific CBQ class).

.TP

.BR "--set-class major:minor"

Set the major and minor  class  value.  The  values  are  always

interpreted as hexadecimal even if no 0x prefix is given.

.SS MARK

This  module  allows you to set the skb->mark value (and thus classify

the packet by the mark in u32)

.TP

.BR "--set-mark mark"

Set the mark value. The  values  are  always

interpreted as hexadecimal even if no 0x prefix is given

.TP

.BR "--and-mark mark"

Binary AND the mark with bits.

.TP

.BR "--or-mark mark"

Binary OR the mark with bits.

.SH NOTES

In this nft-based version of

.BR arptables ,

support for

.B FORWARD

chain has not been implemented. Since ARP packets are "forwarded" only by Linux

bridges, the same may be achieved using

.B FORWARD

chain in

.BR ebtables .

.SH MAILINGLISTS

.BR "" "See " http://netfilter.org/mailinglists.html

.SH SEE ALSO

.BR xtables-nft "(8), " iptables "(8), " ebtables "(8), " ip (8)

.PP

.BR "" "See " https://wiki.nftables.org