Provided by:
iptables_1.3.8.0debian1-1ubuntu2_i386 
NAME
ip6tables - IPv6 packet filter administration
SYNOPSIS
ip6tables [-t table] -[AD] chain rule-specification [options]
ip6tables [-t table] -I chain [rulenum] rule-specification [options]
ip6tables [-t table] -R chain rulenum rule-specification [options]
ip6tables [-t table] -D chain rulenum [options]
ip6tables [-t table] -[LFZ] [chain] [options]
ip6tables [-t table] -N chain
ip6tables [-t table] -X [chain]
ip6tables [-t table] -P chain target [options]
ip6tables [-t table] -E old-chain-name new-chain-name
DESCRIPTION
Ip6tables is used to set up, maintain, and inspect the tables of IPv6
packet filter rules in the Linux kernel. Several different tables may
be defined. Each table contains a number of built-in chains and may
also contain user-defined chains.
Each chain is a list of rules which can match a set of packets. Each
rule specifies what to do with a packet that matches. This is called a
‘target’, which may be a jump to a user-defined chain in the same
table.
TARGETS
A firewall rule specifies criteria for a packet, and a target. If the
packet does not match, the next rule in the chain is the examined; if
it does match, then the next rule is specified by the value of the
target, which can be the name of a user-defined chain or one of the
special values ACCEPT, DROP, QUEUE, or RETURN.
ACCEPT means to let the packet through. DROP means to drop the packet
on the floor. QUEUE means to pass the packet to userspace. (How the
packet can be received by a userspace process differs by the particular
queue handler. 2.4.x and 2.6.x kernels up to 2.6.13 include the
ip_queue queue handler. Kernels 2.6.14 and later additionally include
the nfnetlink_queue queue handler. Packets with a target of QUEUE will
be sent to queue number ’0’ in this case. Please also see the NFQUEUE
target as described later in this man page.) RETURN means stop
traversing this chain and resume at the next rule in the previous
(calling) chain. If the end of a built-in chain is reached or a rule
in a built-in chain with target RETURN is matched, the target specified
by the chain policy determines the fate of the packet.
TABLES
There are currently two independent tables (which tables are present at
any time depends on the kernel configuration options and which modules
are present), as nat table has not been implemented yet.
-t, --table table
This option specifies the packet matching table which the
command should operate on. If the kernel is configured with
automatic module loading, an attempt will be made to load the
appropriate module for that table if it is not already there.
The tables are as follows:
filter:
This is the default table (if no -t option is passed). It
contains the built-in chains INPUT (for packets coming into
the box itself), FORWARD (for packets being routed through
the box), and OUTPUT (for locally-generated packets).
mangle:
This table is used for specialized packet alteration. Until
kernel 2.4.17 it had two built-in chains: PREROUTING (for
altering incoming packets before routing) and OUTPUT (for
altering locally-generated packets before routing). Since
kernel 2.4.18, three other built-in chains are also
supported: INPUT (for packets coming into the box itself),
FORWARD (for altering packets being routed through the box),
and POSTROUTING (for altering packets as they are about to
go out).
raw:
This table is used mainly for configuring exemptions from
connection tracking in combination with the NOTRACK target.
It registers at the netfilter hooks with higher priority and
is thus called before nf_conntrack, or any other IP6 tables.
It provides the following built-in chains: PREROUTING (for
packets arriving via any network interface) OUTPUT (for
packets generated by local processes)
OPTIONS
The options that are recognized by ip6tables can be divided into
several different groups.
COMMANDS
These options specify the specific action to perform. Only one of them
can be specified on the command line unless otherwise specified below.
For all the long versions of the command and option names, you need to
use only enough letters to ensure that ip6tables can differentiate it
from all other options.
-A, --append chain rule-specification
Append one or more rules to the end of the selected chain. When
the source and/or destination names resolve to more than one
address, a rule will be added for each possible address
combination.
-D, --delete chain rule-specification
-D, --delete chain rulenum
Delete one or more rules from the selected chain. There are two
versions of this command: the rule can be specified as a number
in the chain (starting at 1 for the first rule) or a rule to
match.
-I, --insert
Insert one or more rules in the selected chain as the given rule
number. So, if the rule number is 1, the rule or rules are
inserted at the head of the chain. This is also the default if
no rule number is specified.
-R, --replace chain rulenum rule-specification
Replace a rule in the selected chain. If the source and/or
destination names resolve to multiple addresses, the command
will fail. Rules are numbered starting at 1.
-L, --list [chain]
List all rules in the selected chain. If no chain is selected,
all chains are listed. As every other iptables command, it
applies to the specified table (filter is the default), so
mangle rules get listed by
ip6tables -t mangle -n -L
Please note that it is often used with the -n option, in order
to avoid long reverse DNS lookups. It is legal to specify the
-Z (zero) option as well, in which case the chain(s) will be
atomically listed and zeroed. The exact output is affected by
the other arguments given. The exact rules are suppressed until
you use
ip6tables -L -v
-F, --flush [chain]
Flush the selected chain (all the chains in the table if none is
given). This is equivalent to deleting all the rules one by
one.
-Z, --zero [chain]
Zero the packet and byte counters in all chains. It is legal to
specify the -L, --list (list) option as well, to see the
counters immediately before they are cleared. (See above.)
-N, --new-chain chain
Create a new user-defined chain by the given name. There must
be no target of that name already.
-X, --delete-chain [chain]
Delete the optional user-defined chain specified. There must be
no references to the chain. If there are, you must delete or
replace the referring rules before the chain can be deleted. If
no argument is given, it will attempt to delete every non-
builtin chain in the table.
-P, --policy chain target
Set the policy for the chain to the given target. See the
section TARGETS for the legal targets. Only built-in (non-user-
defined) chains can have policies, and neither built-in nor
user-defined chains can be policy targets.
-E, --rename-chain old-chain new-chain
Rename the user specified chain to the user supplied name. This
is cosmetic, and has no effect on the structure of the table.
-h Help. Give a (currently very brief) description of the command
syntax.
PARAMETERS
The following parameters make up a rule specification (as used in the
add, delete, insert, replace and append commands).
-p, --protocol [!] protocol
The protocol of the rule or of the packet to check. The
specified protocol can be one of tcp, udp, icmpv6, esp, all, or
it can be a numeric value, representing one of these protocols
or a different one. A protocol name from /etc/protocols is also
allowed. But IPv6 extension headers except esp are not allowed.
esp, and ipv6-nonext can be used with Kernel version 2.6.11 or
later. A "!" argument before the protocol inverts the test.
The number zero is equivalent to all. Protocol all will match
with all protocols and is taken as default when this option is
omitted.
-s, --source [!] address[/mask]
Source specification. Address can be either a hostname (please
note that specifying any name to be resolved with a remote query
such as DNS is a really bad idea), a network IPv6 address (with
/mask), or a plain IPv6 address. (the network name isn’t
supported now). The mask can be either a network mask or a
plain number, specifying the number of 1’s at the left side of
the network mask. Thus, a mask of 64 is equivalent to
ffff:ffff:ffff:ffff:0000:0000:0000:0000. A "!" argument before
the address specification inverts the sense of the address. The
flag --src is an alias for this option.
-d, --destination [!] address[/mask]
Destination specification. See the description of the -s
(source) flag for a detailed description of the syntax. The
flag --dst is an alias for this option.
-j, --jump target
This specifies the target of the rule; i.e., what to do if the
packet matches it. The target can be a user-defined chain
(other than the one this rule is in), one of the special builtin
targets which decide the fate of the packet immediately, or an
extension (see EXTENSIONS below). If this option is omitted in
a rule, then matching the rule will have no effect on the
packet’s fate, but the counters on the rule will be incremented.
-i, --in-interface [!] name
Name of an interface via which a packet is going to be received
(only for packets entering the INPUT, FORWARD and PREROUTING
chains). When the "!" argument is used before the interface
name, the sense is inverted. If the interface name ends in a
"+", then any interface which begins with this name will match.
If this option is omitted, any interface name will match.
-o, --out-interface [!] name
Name of an interface via which a packet is going to be sent (for
packets entering the FORWARD and OUTPUT chains). When the "!"
argument is used before the interface name, the sense is
inverted. If the interface name ends in a "+", then any
interface which begins with this name will match. If this
option is omitted, any interface name will match.
-c, --set-counters PKTS BYTES
This enables the administrator to initialize the packet and byte
counters of a rule (during INSERT, APPEND, REPLACE operations).
OTHER OPTIONS
The following additional options can be specified:
-v, --verbose
Verbose output. This option makes the list command show the
interface name, the rule options (if any), and the TOS masks.
The packet and byte counters are also listed, with the suffix
’K’, ’M’ or ’G’ for 1000, 1,000,000 and 1,000,000,000
multipliers respectively (but see the -x flag to change this).
For appending, insertion, deletion and replacement, this causes
detailed information on the rule or rules to be printed.
-n, --numeric
Numeric output. IP addresses and port numbers will be printed
in numeric format. By default, the program will try to display
them as host names, network names, or services (whenever
applicable).
-x, --exact
Expand numbers. Display the exact value of the packet and byte
counters, instead of only the rounded number in K’s (multiples
of 1000) M’s (multiples of 1000K) or G’s (multiples of 1000M).
This option is only relevant for the -L command.
--line-numbers
When listing rules, add line numbers to the beginning of each
rule, corresponding to that rule’s position in the chain.
--modprobe=command
When adding or inserting rules into a chain, use command to load
any necessary modules (targets, match extensions, etc).
MATCH EXTENSIONS
ip6tables can use extended packet matching modules. These are loaded
in two ways: implicitly, when -p or --protocol is specified, or with
the -m or --match options, followed by the matching module name; after
these, various extra command line options become available, depending
on the specific module. You can specify multiple extended match
modules in one line, and you can use the -h or --help options after the
module has been specified to receive help specific to that module.
The following are included in the base package, and most of these can
be preceded by a ! to invert the sense of the match.
ah
This module matches the parameters in Authentication header of IPsec
packets.
--ahspi [!] spi[:spi]
Matches SPI.
--ahlen [!] length
Total length of this header in octets.
--ahres
Matches if the reserved field is filled with zero.
dst
This module matches the parameters in Destination Options header
--dst-len [!] length
Total length of this header in octets.
--dst-opts type[:length][,type[:length]...]
numeric type of option and the length of the option data in
octets.
esp
This module matches the SPIs in ESP header of IPsec packets.
--espspi [!] spi[:spi]
eui64
This module matches the EUI-64 part of a stateless auto-configured IPv6
address. It compares the EUI-64 derived from the source MAC address in
Ethernet frame with the lower 64 bits of the IPv6 source address. But
the "Universal/Local" bit is not compared. This module doesn’t match
other link layer frames, and is only valid in the PREROUTING, INPUT and
FORWARD chains.
frag
This module matches the parameters in Fragment header.
--fragid [!] id[:id]
Matches the given Identification or range of it.
--fraglen [!] length
This option cannot be used with kernel version 2.6.10 or later.
The length of Fragment header is static and this option doesn’t
make sense.
--fragres
Matches if the reserved fields are filled with zero.
--fragfirst
Matches on the first fragment.
[--fragmore]
Matches if there are more fragments.
[--fraglast]
Matches if this is the last fragment.
hbh
This module matches the parameters in Hop-by-Hop Options header
--hbh-len [!] length
Total length of this header in octets.
--hbh-opts type[:length][,type[:length]...]
numeric type of option and the length of the option data in
octets.
hl
This module matches the Hop Limit field in the IPv6 header.
--hl-eq [!] value
Matches if Hop Limit equals value.
--hl-lt value
Matches if Hop Limit is less than value.
--hl-gt value
Matches if Hop Limit is greater than value.
icmp6
This extension can be used if ‘--protocol ipv6-icmp’ or ‘--protocol
icmpv6’ is specified. It provides the following option:
--icmpv6-type [!] type[/code]|typename
This allows specification of the ICMPv6 type, which can be a
numeric ICMPv6 type, type and code, or one of the ICMPv6 type
names shown by the command
ip6tables -p ipv6-icmp -h
ipv6header
This module matches IPv6 extension headers and/or upper layer header.
--header [!] header[,header...]
Matches the packet which EXACTLY includes all specified headers.
The headers encapsulated with ESP header are out of scope.
header can be hop|hop-by-hop (Hop-by-Hop Options header), dst
(Destination Options header), route (Routing header), frag
(Fragment header), auth (Authentication header), esp
(Encapsulating Security Payload header), none (No Next header)
which matches 59 in the ’Next Header field’ of IPv6 header or
any IPv6 extension headers, or proto which matches any upper
layer protocol header. A protocol name from /etc/protocols and
numeric value also allowed. The number 255 is equivalent to
proto.
[--soft]
Matches if the packet includes all specified headers with
--header, AT LEAST.
length
This module matches the length of the IPv6 payload in octets, or range
of it. IPv6 header itself isn’t counted.
--length [!] length[:length]
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
(unless the ‘!’ flag is used). It can be used in combination with the
LOG target to give limited logging, for example.
--limit rate
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.
mac
--mac-source [!] address
Match source MAC address. It must be of the form
XX:XX:XX:XX:XX:XX. Note that this only makes sense for packets
coming from an Ethernet device and entering the PREROUTING,
FORWARD or INPUT chains.
mark
This module matches the netfilter mark field associated with a packet
(which can be set using the MARK target below).
--mark value[/mask]
Matches packets with the given unsigned mark value (if a mask is
specified, this is logically ANDed with the mask before the
comparison).
mh
This extension is loaded if ‘--protocol ipv6-mh’ or ‘--protocol mh’ is
specified. It provides the following option:
--mh-type [!] type[:type]
This allows specification of the Mobility Header(MH) type, which
can be a numeric MH type, type or one of the MH type names shown
by the command
ip6tables -p ipv6-mh -h
multiport
This module matches a set of source or destination ports. Up to 15
ports can be specified. It can only be used in conjunction with -p tcp
or -p udp.
--source-ports [!] port[,port[,port...]]
Match if the source port is one of the given ports. The flag
--sports is a convenient alias for this option.
--destination-ports [!] port[,port[,port...]]
Match if the destination port is one of the given ports. The
flag --dports is a convenient alias for this option.
--ports [!] port[,port[,port...]]
Match if the both the source and destination ports are equal to
each other and to one of the given ports.
owner
This module attempts to match various characteristics of the packet
creator, for locally-generated packets. It is only valid in the OUTPUT
chain, and even this some packets (such as ICMPv6 ping responses) may
have no owner, and hence never match. This is regarded as
experimental.
--uid-owner userid
Matches if the packet was created by a process with the given
effective user id.
--gid-owner groupid
Matches if the packet was created by a process with the given
effective group id.
--pid-owner processid
Matches if the packet was created by a process with the given
process id. (Please note: This option requires kernel support
that might not be available in official Linux kernel sources or
Debian’s packaged Linux kernel sources. And if support for this
option is available for the specific Linux kernel source
version, that support might not be enabled in the current Linux
kernel binary.)
--sid-owner sessionid
Matches if the packet was created by a process in the given
session group. (Please note: This option requires kernel
support that might not be available in official Linux kernel
sources or Debian’s packaged Linux kernel sources. And if
support for this option is available for the specific Linux
kernel source version, that support might not be enabled in the
current Linux kernel binary.)
NOTE: pid, sid and command matching are broken on SMP
physdev
This module matches on the bridge port input and output devices
enslaved to a bridge device. This module is a part of the
infrastructure that enables a transparent bridging IP firewall and is
only useful for kernel versions above version 2.5.44.
--physdev-in [!] name
Name of a bridge port via which a packet is received (only for
packets entering the INPUT, FORWARD and PREROUTING chains). If
the interface name ends in a "+", then any interface which
begins with this name will match. If the packet didn’t arrive
through a bridge device, this packet won’t match this option,
unless ’!’ is used.
--physdev-out [!] name
Name of a bridge port via which a packet is going to be sent
(for packets entering the FORWARD, OUTPUT and POSTROUTING
chains). If the interface name ends in a "+", then any
interface which begins with this name will match. Note that in
the nat and mangle OUTPUT chains one cannot match on the bridge
output port, however one can in the filter OUTPUT chain. If the
packet won’t leave by a bridge device or it is yet unknown what
the output device will be, then the packet won’t match this
option, unless ’!’ is used.
[!] --physdev-is-in
Matches if the packet has entered through a bridge interface.
[!] --physdev-is-out
Matches if the packet will leave through a bridge interface.
[!] --physdev-is-bridged
Matches if the packet is being bridged and therefore is not
being routed. This is only useful in the FORWARD and
POSTROUTING chains.
policy
This modules matches the policy used by IPsec for handling a packet.
--dir in|out
Used to select whether to match the policy used for
decapsulation or the policy that will be used for encapsulation.
in is valid in the PREROUTING, INPUT and FORWARD chains, out is
valid in the POSTROUTING, OUTPUT and FORWARD chains.
--pol none|ipsec
Matches if the packet is subject to IPsec processing.
--strict
Selects whether to match the exact policy or match if any rule
of the policy matches the given policy.
--reqid id
Matches the reqid of the policy rule. The reqid can be specified
with setkey(8) using unique:id as level.
--spi spi
Matches the SPI of the SA.
--proto ah|esp|ipcomp
Matches the encapsulation protocol.
--mode tunnel|transport
Matches the encapsulation mode.
--tunnel-src addr[/mask]
Matches the source end-point address of a tunnel mode SA. Only
valid with --mode tunnel.
--tunnel-dst addr[/mask]
Matches the destination end-point address of a tunnel mode SA.
Only valid with --mode tunnel.
--next Start the next element in the policy specification. Can only be
used with --strict
rt
Match on IPv6 routing header
--rt-type [!] type
Match the type (numeric).
--rt-segsleft [!] num[:num]
Match the ‘segments left’ field (range).
--rt-len [!] length
Match the length of this header.
--rt-0-res
Match the reserved field, too (type=0)
--rt-0-addrs ADDR[,ADDR...]
Match type=0 addresses (list).
--rt-0-not-strict
List of type=0 addresses is not a strict list.
tcp
These extensions can be used if ‘--protocol tcp’ is specified. It
provides the following options:
--source-port [!] port[:port]
Source port or port range specification. This can either be a
service name or a port number. An inclusive range can also be
specified, using the format port:port. If the first port is
omitted, "0" is assumed; if the last is omitted, "65535" is
assumed. If the second port greater then the first they will be
swapped. The flag --sport is a convenient alias for this
option.
--destination-port [!] port[:port]
Destination port or port range specification. The flag --dport
is a convenient alias for this option.
--tcp-flags [!] mask comp
Match when the TCP flags are as specified. The first argument
is the flags which we should examine, written as a comma-
separated list, and the second argument is a comma-separated
list of flags which must be set. Flags are: SYN ACK FIN RST URG
PSH ALL NONE. Hence the command
ip6tables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST SYN
will only match packets with the SYN flag set, and the ACK, FIN
and RST flags unset.
[!] --syn
Only match TCP packets with the SYN bit set and the ACK and RST
bits cleared. Such packets are used to request TCP connection
initiation; for example, blocking such packets coming in an
interface will prevent incoming TCP connections, but outgoing
TCP connections will be unaffected. It is equivalent to --tcp-
flags SYN,RST,ACK SYN. If the "!" flag precedes the "--syn",
the sense of the option is inverted.
--tcp-option [!] number
Match if TCP option set.
udp
These extensions can be used if ‘--protocol udp’ is specified. It
provides the following options:
--source-port [!] port[:port]
Source port or port range specification. See the description of
the --source-port option of the TCP extension for details.
--destination-port [!] port[:port]
Destination port or port range specification. See the
description of the --destination-port option of the TCP
extension for details.
TARGET EXTENSIONS
ip6tables can use extended target modules: the following are included
in the standard distribution.
CONNSECMARK
This module copies security markings from packets to connections (if
unlabeled), and from connections back to packets (also only if
unlabeled). Typically used in conjunction with SECMARK, it is only
valid in the mangle table.
--save If the packet has a security marking, copy it to the connection
if the connection is not marked.
--restore
If the packet does not have a security marking, and the
connection does, copy the security marking from the connection
to the packet.
HL
This is used to modify the Hop Limit field in IPv6 header. The Hop
Limit field is similar to what is known as TTL value in IPv4. Setting
or incrementing the Hop Limit field can potentially be very dangerous,
so it should be avoided at any cost. This target is only valid in
mangle table.
Donâ€â€™t ever set or increment the value on packets that leave your local
network!
--hl-set value
Set the Hop Limit to ‘value’.
--hl-dec value
Decrement the Hop Limit ‘value’ times.
--hl-inc value
Increment the Hop Limit ‘value’ times.
LOG
Turn on kernel logging of matching packets. When this option is set
for a rule, the Linux kernel will print some information on all
matching packets (like most IPv6 IPv6-header fields) via the kernel log
(where it can be read with dmesg or syslogd(8)). This is a "non-
terminating target", i.e. rule traversal continues at the next rule.
So if you want to LOG the packets you refuse, use two separate rules
with the same matching criteria, first using target LOG then DROP (or
REJECT).
--log-level level
Level of logging (numeric or see syslog.conf(5)).
--log-prefix prefix
Prefix log messages with the specified prefix; up to 29 letters
long, and useful for distinguishing messages in the logs.
--log-tcp-sequence
Log TCP sequence numbers. This is a security risk if the log is
readable by users.
--log-tcp-options
Log options from the TCP packet header.
--log-ip-options
Log options from the IPv6 packet header.
--log-uid
Log the userid of the process which generated the packet.
MARK
This is used to set the netfilter mark value associated with the
packet. It is only valid in the mangle table.
--set-mark mark
NFQUEUE
This target is an extension of the QUEUE target. As opposed to QUEUE,
it allows you to put a packet into any specific queue, identified by
its 16-bit queue number.
--queue-num value
This specifies the QUEUE number to use. Valid queue numbers are
0 to 65535. The default value is 0.
It can only be used with Kernel versions 2.6.14 or later, since it
requires
the nfnetlink_queue kernel support.
REJECT
This is used to send back an error packet in response to the matched
packet: otherwise it is equivalent to DROP so it is a terminating
TARGET, ending rule traversal. This target is only valid in the INPUT,
FORWARD and OUTPUT chains, and user-defined chains which are only
called from those chains. The following option controls the nature of
the error packet returned:
--reject-with type
The type given can be
icmp6-no-route
no-route
icmp6-adm-prohibited
adm-prohibited
icmp6-addr-unreachable
addr-unreach
icmp6-port-unreachable
port-unreach
which return the appropriate ICMPv6 error message (port-unreach
is the default). Finally, the option tcp-reset can be used on
rules which only match the TCP protocol: this causes a TCP RST
packet to be sent back. This is mainly useful for blocking
ident (113/tcp) probes which frequently occur when sending mail
to broken mail hosts (which won’t accept your mail otherwise).
tcp-reset can only be used with kernel versions 2.6.14 or
latter.
SECMARK
This is used to set the security mark value associated with the packet
for use by security subsystems such as SELinux. It is only valid in
the mangle table.
--selctx security_context
TCPMSS
This target allows to alter the MSS value of TCP SYN packets, to
control the maximum size for that connection (usually limiting it to
your outgoing interface’s MTU minus 60). Of course, it can only be
used in conjunction with -p tcp. It is only valid in the mangle table.
This target is used to overcome criminally braindead ISPs or servers
which block ICMPv6 Packet Too Big packets or are unable to send them.
The symptoms of this problem are that everything works fine from your
Linux firewall/router, but machines behind it can never exchange large
packets:
1) Web browsers connect, then hang with no data received.
2) Small mail works fine, but large emails hang.
3) ssh works fine, but scp hangs after initial handshaking.
Workaround: activate this option and add a rule to your firewall
configuration like:
ip6tables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN \
-j TCPMSS --clamp-mss-to-pmtu
--set-mss value
Explicitly set MSS option to specified value.
--clamp-mss-to-pmtu
Automatically clamp MSS value to (path_MTU - 60).
These options are mutually exclusive.
DIAGNOSTICS
Various error messages are printed to standard error. The exit code is
0 for correct functioning. Errors which appear to be caused by invalid
or abused command line parameters cause an exit code of 2, and other
errors cause an exit code of 1.
BUGS
Bugs? What’s this? ;-) Well... the counters are not reliable on
sparc64.
COMPATIBILITY WITH IPCHAINS
This ip6tables is very similar to ipchains by Rusty Russell. The main
difference is that the chains INPUT and OUTPUT are only traversed for
packets coming into the local host and originating from the local host
respectively. Hence every packet only passes through one of the three
chains (except loopback traffic, which involves both INPUT and OUTPUT
chains); previously a forwarded packet would pass through all three.
The other main difference is that -i refers to the input interface; -o
refers to the output interface, and both are available for packets
entering the FORWARD chain. There are several other changes in
ip6tables.
SEE ALSO
ip6tables-save(8), ip6tables-restore(8), iptables(8), iptables-save(8),
iptables-restore(8), libipq(3).
The packet-filtering-HOWTO details iptables usage for packet filtering,
the NAT-HOWTO details NAT, the netfilter-extensions-HOWTO details the
extensions that are not in the standard distribution, and the
netfilter-hacking-HOWTO details the netfilter internals.
See http://www.netfilter.org/.
AUTHORS
Rusty Russell wrote iptables, in early consultation with Michael
Neuling.
Marc Boucher made Rusty abandon ipnatctl by lobbying for a generic
packet selection framework in iptables, then wrote the mangle table,
the owner match, the mark stuff, and ran around doing cool stuff
everywhere.
James Morris wrote the TOS target, and tos match.
Jozsef Kadlecsik wrote the REJECT target.
Harald Welte wrote the ULOG and NFQUEUE target, the new libiptc, as
well as TTL match+target and libipulog.
The Netfilter Core Team is: Marc Boucher, Martin Josefsson, Yasuyuki
Kozakai, Jozsef Kadlecsik, Patrick McHardy, James Morris, Pablo Neira
Ayuso, Harald Welte and Rusty Russell.
ip6tables man page created by Andras Kis-Szabo, based on iptables man
page written by Herve Eychenne <rv@wallfire.org>.
Jan 22, 2006 IP6TABLES(8)