Manual: ebtables-nft
EBTABLES(8) System Manager's Manual EBTABLES(8)
NAME
ebtables â Ethernet bridge frame table administration (nft-based)
SYNOPSIS
ebtables [-t table ] -[ACDI] chain rule specification [match extensions] [watcher extensions] target
ebtables [-t table ] -P chain ACCEPT | DROP | RETURN
ebtables [-t table ] -F [chain]
ebtables [-t table ] -Z [chain]
ebtables [-t table ] -L [-Z] [chain] [ [--Ln] | [--Lx] ] [--Lc] [--Lmac2]
ebtables [-t table ] -N chain [-P ACCEPT | DROP | RETURN]
ebtables [-t table ] -X [chain]
ebtables [-t table ] -E old-chain-name new-chain-name
ebtables [-t table ] --init-table
DESCRIPTION
ebtables is an application program used to set up and maintain the tables of rules (inside the Linux kernel) that inâ
spect Ethernet frames. It is analogous to the iptables application, but less complicated, due to the fact that the
Ethernet protocol is much simpler than the IP protocol.
CHAINS
There are three ebtables tables with built-in chains in the Linux kernel. These tables are used to divide functionalâ
ity into different sets of rules. Each set of rules is called a chain. Each chain is an ordered list of rules that
can match Ethernet frames. If a rule matches an Ethernet 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 curâ
rent rule in the chain, then the next rule in the chain is examined and so forth. The user can create new (user-deâ
fined) chains that can be used as the 'target' of a rule. User-defined chains are very useful to get better perforâ
mance over the linear traversal of the rules and are also essential for structuring the filtering rules into well-orâ
ganized and maintainable sets of rules.
TARGETS
A firewall rule specifies criteria for an Ethernet 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: ACCEPT, DROP, CONTINUE, RETURN, an 'extension' (see below) or a jump to a user-defined chain.
ACCEPT means to let the frame through. DROP means the frame has to be dropped. In the BROUTING chain however, the
ACCEPT and DROP target have different meanings (see the info provided for the -t option). CONTINUE means the next
rule has to be checked. This can be handy, f.e., to know how many frames pass a certain point in the chain, to log
those frames or to apply multiple targets on a frame. RETURN means stop traversing this chain and resume at the next
rule in the previous (calling) chain. For the extension targets please refer to the TARGET EXTENSIONS section of
this man page.
TABLES
As stated earlier, the table names are filter, nat and broute. Of these tables, the filter table is the default taâ
ble that the command operates on. If you are working with a table other than filter, you will need to provide the -t
argument. Moreover, the -t argument must be the first argument on the ebtables command line, if used.
-t, --table
filter is the default table and contains three built-in chains: INPUT (for frames destined for the bridge itâ
self, on the level of the MAC destination address), OUTPUT (for locally-generated or (b)routed frames) and
FORWARD (for frames being forwarded by the bridge).
nat is mostly used to change the mac addresses and contains three built-in chains: PREROUTING (for altering
frames as soon as they come in), OUTPUT (for altering locally generated or (b)routed frames before they are
bridged) and POSTROUTING (for altering frames as they are about to go out). A small note on the naming of
chains PREROUTING and POSTROUTING: it would be more accurate to call them PREFORWARDING and POSTFORWARDING,
but for all those who come from the iptables world to ebtables it is easier to have the same names. Note that
you can change the name (-E) if you don't like the default.
broute is used to make a brouter, it has one built-in chain: BROUTING. The targets DROP and ACCEPT have a
special meaning in the broute table (these names are used for compatibility reasons with ebtables-legacy).
DROP actually means the frame has to be routed, while ACCEPT means the frame has to be bridged. The BROUTING
chain is traversed very early. Normally those frames would be bridged, but you can decide otherwise here.
EBTABLES COMMAND LINE ARGUMENTS
After the initial ebtables '-t table' command line argument, the remaining arguments can be divided into several
groups. These groups are commands, miscellaneous commands, rule specifications, match extensions, watcher extensions
and target extensions.
COMMANDS
The ebtables 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. Only one command may be
used on the command line at a time, except when the commands -L and -Z are combined or the commands -N and -P are
combined.
-A, --append
Append a rule to the end of the selected chain.
-D, --delete
Delete the specified rule or rules from the selected chain. There are two ways to use this command. The first
is by specifying an interval of rule numbers to delete (directly after -D). Syntax: start_nr[:end_nr] (use -L
--Ln to list the rules with their rule number). When end_nr is omitted, all rules starting from start_nr are
deleted. 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. Only
the first encountered rule that is the same as this specified rule, in other words the matching rule with the
lowest (positive) rule number, is deleted.
-C, --change-counters
Change the counters of the specified rule or rules from the selected chain. There are two ways to use this
command. The first is by specifying an interval of rule numbers to do the changes on (directly after -C).
Syntax: start_nr[:end_nr] (use -L --Ln to list the rules with their rule number). The details are the same as
for the -D command. The second usage is by specifying the complete rule as it would have been specified when
it was added. Only the counters of the first encountered rule that is the same as this specified rule, in
other words the matching rule with the lowest (positive) rule number, are changed. In the first usage, the
counters are specified directly after the interval specification, in the second usage directly after -C.
First the packet counter is specified, then the byte counter. If the specified counters start with a '+', the
counter values are added to the respective current counter values. If the specified counters start with a
'-', the counter values are decreased from the respective current counter values. No bounds checking is done.
If the counters don't start with '+' or '-', the current counters are changed to the specified counters.
-I, --insert
Insert the specified rule into the selected chain at the specified rule number. If the rule number is not
specified, the rule is added at the head of the chain. 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 rule number 0 specifies the place past the last
rule in the chain and using this number is therefore equivalent to using the -A command. Rule numbers
structly smaller than 0 can be useful when more than one rule needs to be inserted in a chain.
-P, --policy
Set the policy for the chain to the given target. The policy can be ACCEPT, DROP or RETURN.
-F, --flush
Flush the selected chain. If no chain is selected, then every chain will be flushed. Flushing a chain does not
change the policy of the chain, however.
-Z, --zero
Set the counters of the selected chain to zero. If no chain is selected, all the counters are set to zero. The
-Z command can be used in conjunction with the -L command. When both the -Z and -L commands are used together
in this way, the rule counters are printed on the screen before they are set to zero.
-L, --list
List all rules in the selected chain. If no chain is selected, all chains are listed.
The following options change the output of the -L command.
--Ln
Places the rule number in front of every rule. This option is incompatible with the --Lx option.
--Lc
Shows the counters at the end of each rule displayed by the -L command. Both a frame counter (pcnt) and a byte
counter (bcnt) are displayed. The frame counter shows how many frames have matched the specific rule, the
byte counter shows the sum of the frame sizes of these matching frames. Using this option in combination with
the --Lx option causes the counters to be written out in the '-c ' option format.
--Lx
Changes the output so that it produces a set of ebtables commands that construct the contents of the chain,
when specified. If no chain is specified, ebtables commands to construct the contents of the table are given,
including commands for creating the user-defined chains (if any). You can use this set of commands in an
ebtables boot or reload script. For example the output could be used at system startup. The --Lx option is
incompatible with the --Ln listing option. Using the --Lx option together with the --Lc option will cause the
counters to be written out in the '-c ' option format.
--Lmac2
Shows all MAC addresses with the same length, adding leading zeroes if necessary. The default representation
omits leading zeroes in the addresses.
-N, --new-chain
Create a new user-defined chain with the given name. The number of user-defined chains is limited only by the
number of possible chain names. A user-defined chain name has a maximum length of 31 characters. The standard
policy of the user-defined chain is ACCEPT. The policy of the new chain can be initialized to a different
standard target by using the -P command together with the -N command. In this case, the chain name does not
have to be specified for the -P command.
-X, --delete-chain
Delete the specified user-defined chain. There must be no remaining references (jumps) to the specified chain,
otherwise ebtables will refuse to delete it. If no chain is specified, all user-defined chains that aren't
referenced will be removed.
-E, --rename-chain
Rename the specified chain to a new name. Besides renaming a user-defined chain, you can rename a standard
chain to a name that suits your taste. For example, if you like PREFORWARDING more than PREROUTING, then you
can use the -E command to rename the PREROUTING chain. If you do rename one of the standard ebtables chain
names, please be sure to mention this fact should you post a question on the ebtables mailing lists. It would
be wise to use the standard name in your post. Renaming a standard ebtables chain in this fashion has no efâ
fect on the structure or functioning of the ebtables kernel table.
--init-table
Replace the current table data by the initial table data.
MISCELLANEOUS COMMANDS
-v, --verbose
Verbose mode. For appending, insertion, deletion and replacement, this causes detailed information on the
rule or rules to be printed. -v may be specified multiple times to possibly emit more detailed debug stateâ
ments.
-V, --version
Show the version of the ebtables userspace program.
-h, --help [list of module names]
Give a brief description of the command syntax. Here you can also specify names of extensions and ebtables
will try to write help about those extensions. E.g. ebtables -h snat log ip arp. Specify list_extensions to
list all extensions supported by the userspace utility.
-j, --jump target
The target of the rule. This is one of the following values: ACCEPT, DROP, CONTINUE, RETURN, a target extenâ
sion (see TARGET EXTENSIONS) or a user-defined chain name.
-M, --modprobe program
When talking to the kernel, use this program to try to automatically load missing kernel modules.
--concurrent
This would use a file lock to support concurrent scripts updating the ebtables kernel tables. It is not needed
with ebtables-nft though and thus ignored.
RULE SPECIFICATIONS
The following command line arguments make up a rule specification (as used in the add and delete commands). A "!" opâ
tion before the specification inverts the test for that specification. Apart from these standard rule specifications
there are some other command line arguments of interest. See both the MATCH EXTENSIONS and the WATCHER EXTENSIONS
below.
[!] -p, --protocol protocol
The protocol that was responsible for creating the frame. This can be a hexadecimal number, above 0x0600, a
name (e.g. ARP ) or LENGTH. The protocol field of the Ethernet frame can be used to denote the length of the
header (802.2/802.3 networks). When the value of that field is below or equals 0x0600, the value equals the
size of the header and shouldn't be used as a protocol number. Instead, all frames where the protocol field is
used as the length field are assumed to be of the same 'protocol'. The protocol name used in ebtables for
these frames is LENGTH.
The file /etc/ethertypes can be used to show readable characters instead of hexadecimal numbers for the protoâ
cols. For example, 0x0800 will be represented by IPV4. The use of this file is not case sensitive. See that
file for more information. The flag --proto is an alias for this option.
[!] -i, --in-interface name
The interface (bridge port) via which a frame is received (this option is useful in the INPUT, FORWARD, PREâ
ROUTING and BROUTING chains). If the interface name ends with '+', then any interface name that begins with
this name (disregarding '+') will match. The flag --in-if is an alias for this option.
[!] --logical-in name
The (logical) bridge interface via which a frame is received (this option is useful in the INPUT, FORWARD,
PREROUTING and BROUTING chains). If the interface name ends with '+', then any interface name that begins
with this name (disregarding '+') will match.
[!] -o, --out-interface name
The interface (bridge port) via which a frame is going to be sent (this option is useful in the OUTPUT, FORâ
WARD and POSTROUTING chains). If the interface name ends with '+', then any interface name that begins with
this name (disregarding '+') will match. The flag --out-if is an alias for this option.
[!] --logical-out name
The (logical) bridge interface via which a frame is going to be sent (this option is useful in the OUTPUT,
FORWARD and POSTROUTING chains). If the interface name ends with '+', then any interface name that begins
with this name (disregarding '+') will match.
[!] -s, --source address[/mask]
The source MAC address. Both mask and address are written as 6 hexadecimal numbers separated by colons. Alterâ
natively one can specify Unicast, Multicast, Broadcast or BGA (Bridge Group Address):
Unicast=00:00:00:00:00:00/01:00:00:00:00:00, Multicast=01:00:00:00:00:00/01:00:00:00:00:00, Broadâ
cast=ff:ff:ff:ff:ff:ff/ff:ff:ff:ff:ff:ff or BGA=01:80:c2:00:00:00/ff:ff:ff:ff:ff:ff. Note that a broadcast
address will also match the multicast specification. The flag --src is an alias for this option.
[!] -d, --destination address[/mask]
The destination MAC address. See -s (above) for more details on MAC addresses. The flag --dst is an alias for
this option.
-c, --set-counter pcnt bcnt
If used with -A or -I, then the packet and byte counters of the new rule will be set to pcnt, resp. bcnt. If
used with the -C or -D commands, only rules with a packet and byte count equal to pcnt, resp. bcnt will match.
MATCH EXTENSIONS
Ebtables extensions are dynamically loaded into the userspace tool, there is therefore no need to explicitly load
them with a -m option like is done in iptables. These extensions deal with functionality supported by kernel modules
supplemental to the core ebtables code.
802_3
Specify 802.3 DSAP/SSAP fields or SNAP type. The protocol must be specified as LENGTH (see the option -p above).
[!] --802_3-sap sap
DSAP and SSAP are two one byte 802.3 fields. The bytes are always equal, so only one byte (hexadecimal) is
needed as an argument.
[!] --802_3-type type
If the 802.3 DSAP and SSAP values are 0xaa then the SNAP type field must be consulted to determine the payload
protocol. This is a two byte (hexadecimal) argument. Only 802.3 frames with DSAP/SSAP 0xaa are checked for
type.
among
Match a MAC address or MAC/IP address pair versus a list of MAC addresses and MAC/IP address pairs. A list entry has
the following format: xx:xx:xx:xx:xx:xx[=ip.ip.ip.ip][,]. Multiple list entries are separated by a comma, specifying
an IP address corresponding to the MAC address is optional. Multiple MAC/IP address pairs with the same MAC address
but different IP address (and vice versa) can be specified. If the MAC address doesn't match any entry from the list,
the frame doesn't match the rule (unless "!" was used).
[!] --among-dst list
Compare the MAC destination to the given list. If the Ethernet frame has type IPv4 or ARP, then comparison
with MAC/IP destination address pairs from the list is possible.
[!] --among-src list
Compare the MAC source to the given list. If the Ethernet frame has type IPv4 or ARP, then comparison with
MAC/IP source address pairs from the list is possible.
[!] --among-dst-file file
Same as --among-dst but the list is read in from the specified file.
[!] --among-src-file file
Same as --among-src but the list is read in from the specified file.
arp
Specify (R)ARP fields. The protocol must be specified as ARP or RARP.
[!] --arp-opcode opcode
The (R)ARP opcode (decimal or a string, for more details see ebtables -h arp).
[!] --arp-htype hardware-type
The hardware type, this can be a decimal or the string Ethernet (which sets type to 1). Most (R)ARP packets
have Eternet as hardware type.
[!] --arp-ptype protocol-type
The protocol type for which the (r)arp is used (hexadecimal or the string IPv4, denoting 0x0800). Most (R)ARP
packets have protocol type IPv4.
[!] --arp-ip-src address[/mask]
The (R)ARP IP source address specification.
[!] --arp-ip-dst address[/mask]
The (R)ARP IP destination address specification.
[!] --arp-mac-src address[/mask]
The (R)ARP MAC source address specification.
[!] --arp-mac-dst address[/mask]
The (R)ARP MAC destination address specification.
[!] --arp-gratuitous
Checks for ARP gratuitous packets: checks equality of IPv4 source address and IPv4 destination address inside
the ARP header.
ip
Specify IPv4 fields. The protocol must be specified as IPv4.
[!] --ip-source address[/mask]
The source IP address. The flag --ip-src is an alias for this option.
[!] --ip-destination address[/mask]
The destination IP address. The flag --ip-dst is an alias for this option.
[!] --ip-tos tos
The IP type of service, in hexadecimal numbers. IPv4.
[!] --ip-protocol protocol
The IP protocol. The flag --ip-proto is an alias for this option.
[!] --ip-source-port port1[:port2]
The source port or port range for the IP protocols 6 (TCP), 17 (UDP), 33 (DCCP) or 132 (SCTP). The --ip-protoâ
col option must be specified as TCP, UDP, DCCP or SCTP. If port1 is omitted, 0:port2 is used; if port2 is
omitted but a colon is specified, port1:65535 is used. The flag --ip-sport is an alias for this option.
[!] --ip-destination-port port1[:port2]
The destination port or port range for ip protocols 6 (TCP), 17 (UDP), 33 (DCCP) or 132 (SCTP). The --ip-proâ
tocol option must be specified as TCP, UDP, DCCP or SCTP. If port1 is omitted, 0:port2 is used; if port2 is
omitted but a colon is specified, port1:65535 is used. The flag --ip-dport is an alias for this option.
ip6
Specify IPv6 fields. The protocol must be specified as IPv6.
[!] --ip6-source address[/mask]
The source IPv6 address. The flag --ip6-src is an alias for this option.
[!] --ip6-destination address[/mask]
The destination IPv6 address. The flag --ip6-dst is an alias for this option.
[!] --ip6-tclass tclass
The IPv6 traffic class, in hexadecimal numbers.
[!] --ip6-protocol protocol
The IP protocol. The flag --ip6-proto is an alias for this option.
[!] --ip6-source-port port1[:port2]
The source port or port range for the IPv6 protocols 6 (TCP), 17 (UDP), 33 (DCCP) or 132 (SCTP). The
--ip6-protocol option must be specified as TCP, UDP, DCCP or SCTP. If port1 is omitted, 0:port2 is used; if
port2 is omitted but a colon is specified, port1:65535 is used. The flag --ip6-sport is an alias for this opâ
tion.
[!] --ip6-destination-port port1[:port2]
The destination port or port range for IPv6 protocols 6 (TCP), 17 (UDP), 33 (DCCP) or 132 (SCTP). The
--ip6-protocol option must be specified as TCP, UDP, DCCP or SCTP. If port1 is omitted, 0:port2 is used; if
port2 is omitted but a colon is specified, port1:65535 is used. The flag --ip6-dport is an alias for this opâ
tion.
[!] --ip6-icmp-type {type[:type]/code[:code]|typename}
Specify ipv6-icmp type and code to match. Ranges for both type and code are supported. Type and code are sepâ
arated by a slash. Valid numbers for type and range are 0 to 255. To match a single type including all valid
codes, symbolic names can be used instead of numbers. The list of known type names is shown by the command
ebtables --help ip6
This option is only valid for --ip6-prococol ipv6-icmp.
limit
This module matches at a limited rate using a token bucket filter. A rule using this extension will match until this
limit is reached. It can be used with the --log watcher to give limited logging, for example. Its use is the same as
the limit match of iptables.
--limit [value]
Maximum average matching rate: specified as a number, with an optional /second, /minute, /hour, or /day sufâ
fix; the default is 3/hour.
--limit-burst [number]
Maximum initial number of packets to match: this number gets recharged by one every time the limit specified
above is not reached, up to this number; the default is 5.
mark_m
[!] --mark [value][/mask]
Matches frames with the given unsigned mark value. If a value and mask are specified, the logical AND of the
mark value of the frame and the user-specified mask is taken before comparing it with the user-specified mark
value. When only a mark value is specified, the packet only matches when the mark value of the frame equals
the user-specified mark value. If only a mask is specified, the logical AND of the mark value of the frame
and the user-specified mask is taken and the frame matches when the result of this logical AND is non-zero.
Only specifying a mask is useful to match multiple mark values.
pkttype
[!] --pkttype-type type
Matches on the Ethernet "class" of the frame, which is determined by the generic networking code. Possible
values: broadcast (MAC destination is the broadcast address), multicast (MAC destination is a multicast adâ
dress), host (MAC destination is the receiving network device), or otherhost (none of the above).
stp
Specify stp BPDU (bridge protocol data unit) fields. The destination address (-d) must be specified as the bridge
group address (BGA). For all options for which a range of values can be specified, it holds that if the lower bound
is omitted (but the colon is not), then the lowest possible lower bound for that option is used, while if the upper
bound is omitted (but the colon again is not), the highest possible upper bound for that option is used.
[!] --stp-type type
The BPDU type (0â255), recognized non-numerical types are config, denoting a configuration BPDU (=0), and tcn,
denothing a topology change notification BPDU (=128).
[!] --stp-flags flag
The BPDU flag (0â255), recognized non-numerical flags are topology-change, denoting the topology change flag
(=1), and topology-change-ack, denoting the topology change acknowledgement flag (=128).
[!] --stp-root-prio [prio][:prio]
The root priority (0â65535) range.
[!] --stp-root-addr [address][/mask]
The root mac address, see the option -s for more details.
[!] --stp-root-cost [cost][:cost]
The root path cost (0â4294967295) range.
[!] --stp-sender-prio [prio][:prio]
The BPDU's sender priority (0â65535) range.
[!] --stp-sender-addr [address][/mask]
The BPDU's sender mac address, see the option -s for more details.
[!] --stp-port [port][:port]
The port identifier (0â65535) range.
[!] --stp-msg-age [age][:age]
The message age timer (0â65535) range.
[!] --stp-max-age [age][:age]
The max age timer (0â65535) range.
[!] --stp-hello-time [time][:time]
The hello time timer (0â65535) range.
[!] --stp-forward-delay [delay][:delay]
The forward delay timer (0â65535) range.
vlan
Specify 802.1Q Tag Control Information fields. The protocol must be specified as 802_1Q (0x8100).
[!] --vlan-id id
The VLAN identifier field (VID). Decimal number from 0 to 4095.
[!] --vlan-prio prio
The user priority field, a decimal number from 0 to 7. The VID should be set to 0 ("null VID") or unspecified
(in the latter case the VID is deliberately set to 0).
[!] --vlan-encap type
The encapsulated Ethernet frame type/length. Specified as a hexadecimal number from 0x0000 to 0xFFFF or as a
symbolic name from /etc/ethertypes.
WATCHER EXTENSIONS
Watchers only look at frames passing by, they don't modify them nor decide to accept the frames or not. These watchâ
ers only see the frame if the frame matches the rule, and they see it before the target is executed.
log
The log watcher writes descriptive data about a frame to the syslog.
--log
Log with the default logging options: log-level= info, log-prefix="", no ip logging, no arp logging.
--log-level level
Defines the logging level. For the possible values, see ebtables -h log. The default level is info.
--log-prefix text
Defines the prefix text to be printed at the beginning of the line with the logging information.
--log-ip
Will log the ip information when a frame made by the ip protocol matches the rule. The default is no ip inforâ
mation logging.
--log-ip6
Will log the ipv6 information when a frame made by the ipv6 protocol matches the rule. The default is no ipv6
information logging.
--log-arp
Will log the (r)arp information when a frame made by the (r)arp protocols matches the rule. The default is no
(r)arp information logging.
nflog
The nflog watcher passes the packet to the loaded logging backend in order to log the packet. This is usually used in
combination with nfnetlink_log as logging backend, which will multicast the packet through a netlink socket to the
specified multicast group. One or more userspace processes may subscribe to the group to receive the packets.
--nflog
Log with the default logging options
--nflog-group nlgroup
The netlink group (1â2^32-1) to which packets are (only applicable for nfnetlink_log). The default value is 1.
--nflog-prefix prefix
A prefix string to include in the log message, up to 30 characters long, useful for distinguishing messages in
the logs.
--nflog-range size
The number of bytes to be copied to userspace (only applicable for nfnetlink_log). nfnetlink_log instances may
specify their own range, this option overrides it.
--nflog-threshold size
Number of packets to queue inside the kernel before sending them to userspace (only applicable for
nfnetlink_log). Higher values result in less overhead per packet, but increase delay until the packets reach
userspace. The default value is 1.
ulog
The ulog watcher passes the packet to a userspace logging daemon using netlink multicast sockets. This differs from
the log watcher in the sense that the complete packet is sent to userspace instead of a descriptive text and that
netlink multicast sockets are used instead of the syslog. This watcher enables parsing of packets with userspace
programs, the physical bridge in and out ports are also included in the netlink messages. The ulog watcher module
accepts 2 parameters when the module is loaded into the kernel (e.g. with modprobe): nlbufsiz specifies how big the
buffer for each netlink multicast group is. If you say nlbufsiz=8192, for example, up to eight kB of packets will get
accumulated in the kernel until they are sent to userspace. It is not possible to allocate more than 128kB. Please
also keep in mind that this buffer size is allocated for each nlgroup you are using, so the total kernel memory usage
increases by that factor. The default is 4096. flushtimeout specifies after how many hundredths of a second the
queue should be flushed, even if it is not full yet. The default is 10 (one tenth of a second).
--ulog
Use the default settings: ulog-prefix="", ulog-nlgroup=1, ulog-cprange=4096, ulog-qthreshold=1.
--ulog-prefix text
Defines the prefix included with the packets sent to userspace.
--ulog-nlgroup group
Defines which netlink group number to use (a number from 1 to 32). Make sure the netlink group numbers used
for the iptables ULOG target differ from those used for the ebtables ulog watcher. The default group number
is 1.
--ulog-cprange range
Defines the maximum copy range to userspace, for packets matching the rule. The default range is 0, which
means the maximum copy range is given by nlbufsiz. A maximum copy range larger than 128*1024 is meaningless
as the packets sent to userspace have an upper size limit of 128*1024.
--ulog-qthreshold threshold
Queue at most threshold number of packets before sending them to userspace with a netlink socket. Note that
packets can be sent to userspace before the queue is full, this happens when the ulog kernel timer goes off
(the frequency of this timer depends on flushtimeout).
TARGET EXTENSIONS
arpreply
The arpreply target can be used in the PREROUTING chain of the nat table. If this target sees an ARP request it will
automatically reply with an ARP reply. The used MAC address for the reply can be specified. The protocol must be
specified as ARP. When the ARP message is not an ARP request or when the ARP request isn't for an IP address on an
Ethernet network, it is ignored by this target (CONTINUE). When the ARP request is malformed, it is dropped (DROP).
--arpreply-mac address
Specifies the MAC address to reply with: the Ethernet source MAC and the ARP payload source MAC will be filled
in with this address.
--arpreply-target target
Specifies the standard target. After sending the ARP reply, the rule still has to give a standard target so
ebtables knows what to do with the ARP request. The default target is DROP.
dnat
The dnat target can only be used in the PREROUTING and OUTPUT chains of the nat table. It specifies that the destiâ
nation MAC address has to be changed.
--to-destination address
Change the destination MAC address to the specified address. The flag --to-dst is an alias for this option.
--dnat-target target
Specifies the standard target. After doing the dnat, the rule still has to give a standard target so ebtables
knows what to do with the dnated frame. The default target is ACCEPT. Making it CONTINUE could let you use
multiple target extensions on the same frame. Making it DROP only makes sense in the BROUTING chain but using
the redirect target is more logical there. RETURN is also allowed. Note that using RETURN in a base chain is
not allowed (for obvious reasons).
mark
The mark target can be used in every chain of every table. It is possible to use the marking of a frame/packet in
both ebtables and iptables, if the bridge-nf code is compiled into the kernel. Both put the marking at the same
place. This allows for a form of communication between ebtables and iptables.
--mark-set value
Mark the frame with the specified non-negative value.
--mark-or value
Or the frame with the specified non-negative value.
--mark-and value
And the frame with the specified non-negative value.
--mark-xor value
Xor the frame with the specified non-negative value.
--mark-target target
Specifies the standard target. After marking the frame, the rule still has to give a standard target so ebtaâ
bles knows what to do. The default target is ACCEPT. Making it CONTINUE can let you do other things with the
frame in subsequent rules of the chain.
redirect
The redirect target will change the MAC target address to that of the bridge device the frame arrived on. This target
can only be used in the PREROUTING chain of the nat table. The MAC address of the bridge is used as destination adâ
dress."
--redirect-target target
Specifies the standard target. After doing the MAC redirect, the rule still has to give a standard target so
ebtables knows what to do. The default target is ACCEPT. Making it CONTINUE could let you use multiple target
extensions on the same frame. Making it DROP in the BROUTING chain will let the frames be routed. RETURN is
also allowed. Note that using RETURN in a base chain is not allowed.
snat
The snat target can only be used in the POSTROUTING chain of the nat table. It specifies that the source MAC address
has to be changed.
--to-source address
Changes the source MAC address to the specified address. The flag --to-src is an alias for this option.
--snat-target target
Specifies the standard target. After doing the snat, the rule still has to give a standard target so ebtables
knows what to do. The default target is ACCEPT. Making it CONTINUE could let you use multiple target extenâ
sions on the same frame. Making it DROP doesn't make sense, but you could do that too. RETURN is also allowed.
Note that using RETURN in a base chain is not allowed.
--snat-arp
Also change the hardware source address inside the arp header if the packet is an arp message and the hardware
address length in the arp header is 6 bytes.
FILES
/etc/ethertypes
MAILINGLISTS
See http://netfilter.org/mailinglists.html
BUGS
The version of ebtables this man page ships with does not support the string match. Further, support for atomic-opâ
tions (--atomic-file, --atomic-init, --atomic-save, --atomic-commit) has not been implemented, although ebtables-save
and ebtables-restore might replace them entirely given the inherent atomicity of nftables. Finally, this list is
probably not complete.
SEE ALSO
xtables-nft(8), iptables(8), ip(8)
See https://wiki.nftables.org
December 2011 EBTABLES(8)