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NAME | SYNOPSIS | DESCRIPTION | EBTABLES COMMAND LINE ARGUMENTS | FILES | ENVIRONMENT VARIABLES | MAILINGLISTS | BUGS | SEE ALSO | COLOPHON |
EBTABLES(8) System Manager's Manual EBTABLES(8)
ebtables - Ethernet bridge frame table administration (nft-based)
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
ebtables [-t table ] [--atomic-file file] --atomic-commit
ebtables [-t table ] [--atomic-file file] --atomic-init
ebtables [-t table ] [--atomic-file file] --atomic-save
ebtables is an application program used to set up and maintain the
tables of rules (inside the Linux kernel) that inspect 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 two ebtables tables with built-in chains in the Linux
kernel. These tables are 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 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 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 that can be
used as the 'target' of a rule. User-defined chains are very useful
to get better performance over the linear traversal of the rules and
are also essential for structuring the filtering rules into well-
organized 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. 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, there are two ebtables tables in the Linux kernel.
The table names are filter and nat. Of these two tables, the filter
table is the default table that the command operates on. If you are
working with the filter table, then you can drop the '-t filter'
argument to the ebtables command. However, you will need to provide
the -t argument for nat table. 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 itself, 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.
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, the commands -N and
-P are combined, or when --atomic-file is used.
-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 <pcnt> <bcnt>' 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
<pcnt> <bcnt>' 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
effect on the structure or functioning of the ebtables kernel
table.
--init-table
Replace the current table data by the initial table data.
--atomic-init
Copy the kernel's initial data of the table to the specified
file. This can be used as the first action, after which rules
are added to the file. The file can be specified using the
--atomic-file command or through the EBTABLES_ATOMIC_FILE
environment variable.
--atomic-save
Copy the kernel's current data of the table to the specified
file. This can be used as the first action, after which rules
are added to the file. The file can be specified using the
--atomic-file command or through the EBTABLES_ATOMIC_FILE
environment variable.
--atomic-commit
Replace the kernel table data with the data contained in the
specified file. This is a useful command that allows you to
load all your rules of a certain table into the kernel at
once, saving the kernel a lot of precious time and allowing
atomic updates of the tables. The file which contains the
table data is constructed by using either the --atomic-init or
the --atomic-save command to generate a starting file. After
that, using the --atomic-file command when constructing rules
or setting the EBTABLES_ATOMIC_FILE environment variable
allows you to extend the file and build the complete table
before committing it to the kernel. This command can be very
useful in boot scripts to populate the ebtables tables in a
fast way.
MISCELLANOUS COMMANDS
-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 extension (see TARGET
EXTENSIONS) or a user-defined chain name.
--atomic-file file
Let the command operate on the specified file. The data of
the table to operate on will be extracted from the file and
the result of the operation will be saved back into the file.
If specified, this option should come before the command
specification. An alternative that should be preferred, is
setting the EBTABLES_ATOMIC_FILE environment variable.
-M, --modprobe program
When talking to the kernel, use this program to try to
automatically load missing kernel modules.
--concurrent
Use a file lock to support concurrent scripts updating the
ebtables kernel tables.
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. 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 protocols.
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, PREROUTING 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, FORWARD 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. Alternatively 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,
Broadcast=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-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 --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-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 --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 option.
--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 option.
--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 separated 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 suffix; 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 address), 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 (0-255), 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 (0-255), 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 (0-65535) 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 (0-4294967295) range.
--stp-sender-prio [!] [prio][:prio]
The BPDU's sender priority (0-65535) 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 (0-65535) range.
--stp-msg-age [!] [age][:age]
The message age timer (0-65535) range.
--stp-max-age [!] [age][:age]
The max age timer (0-65535) range.
--stp-hello-time [!] [time][:time]
The hello time timer (0-65535) range.
--stp-forward-delay [!] [delay][:delay]
The forward delay timer (0-65535) 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 watchers 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 loggin 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 information
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 (1 - 2^32-1) 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 destination 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 ebtables 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 address."
--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 extensions 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.
/etc/ethertypes
EBTABLES_ATOMIC_FILE
See http://netfilter.org/mailinglists.html
The version of ebtables this man page ships with does not support the
broute table. Also there is no support for string match. And finally,
this list is probably not complete.
xtables-nft(8), iptables(8), ip(8)
See https://wiki.nftables.org
This page is part of the iptables (administer and maintain packet
filter rules) project. Information about the project can be found at
⟨http://www.netfilter.org/⟩. If you have a bug report for this man‐
ual page, see ⟨http://bugzilla.netfilter.org/⟩. This page was
obtained from the project's upstream Git repository
⟨git://git.netfilter.org/iptables⟩ on 2020-08-13. (At that time, the
date of the most recent commit that was found in the repository was
2020-07-31.) If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-to-
date source for the page, or you have corrections or improvements to
the information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
December 2011 EBTABLES(8)
Pages that refer to this page: arptables(8) , arptables-nft(8) , ip6tables-translate(8) , iptables-translate(8) , xtables-nft(8) , xtables-translate(8)