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NAME

ip6tables - IPv6 packet filter administration
 

SYNOPSIS

DESCRIPTION

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

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

-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

COMMANDS

-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

-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

-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

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

--ahspi [!] spi[:spi]

Matches SPI.

--ahlen [!] length

Total length of this header in octets.

--ahres

Matches if the reserved field is filled with zero.

condition

--condition [!] filename

Match on boolean value stored in /proc/net/ip6t_condition/filename file

dst

--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

--espspi [!] spi[:spi]

eui64

frag

--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 fragement.

fuzzy

--lower-limit number

Specifies the lower limit (in packets per second).

--upper-limit number

Specifies the upper limit (in packets per second).

hbh

--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

--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.

icmpv6

--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

--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

--length [!] length[:length]

limit

--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

--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).

multiport

--source-ports [!] port[,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: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:port...]]

Match if the both the source and destination ports are equal to each other and to one of the given ports.

nth

--every value

Match every `value' packet

[--counter num]

Use internal counter number `num'. Default is `0'.

[--start num]

Initialize the counter at the number `num' insetad of `0'. Most between `0' and `value'-1.

[--packet num]

Match on `num' packet. Most be between `0' and `value'-1.

owner

--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.

--sid-owner sessionid

Matches if the packet was created by a process in the given session group.

NOTE: pid, sid and command matching are broken on SMP

physdev

--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

[!] --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

--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

random

--average percent

Matches the given percentage. If omitted, a probability of 50% is set.

rt

--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

--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

--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

HL

Don'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

--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

--set-mark mark

NFQUEUE

--queue-num value

This specifies the QUEUE number to use. Valud 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

--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.

ROUTE

--oif ifname

Route the packet through `ifname' network interface

--gw IPv6_address

Route the packet via this gateway

--continue

Behave like a non-terminating target and continue traversing the rules. Not valid in combination with `--tee'

--tee

Make a copy of the packet, and route that copy to the given destination. For the original, uncopied packet, behave like a non-terminating target and continue traversing the rules. Not valid in combination with `--continue'

TRACE

DIAGNOSTICS

BUGS

COMPATIBILITY WITH IPCHAINS

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

AUTHORS

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, aswell as TTL match+target and libipulog.

The Netfilter Core Team is: Marc Boucher, Martin Josefsson, Jozsef Kadlecsik, James Morris, 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>.

Index

NAME

SYNOPSIS

DESCRIPTION

TARGETS

TABLES

OPTIONS

COMMANDS

PARAMETERS

OTHER OPTIONS

MATCH EXTENSIONS

ah

condition

dst

esp

eui64

frag

fuzzy

hbh

hl

icmpv6

ipv6header

length

limit

mac

mark

multiport

nth

owner

physdev

policy

random

rt

tcp

udp

TARGET EXTENSIONS

HL

LOG

MARK

NFQUEUE

REJECT

ROUTE

TRACE

DIAGNOSTICS

BUGS

COMPATIBILITY WITH IPCHAINS

SEE ALSO

AUTHORS

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