ip6tables


SYNOPSIS
       ip6tables [-t table] {-A|-C|-D} 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] -S [chain [rulenum]]

       ip6tables [-t table] {-F|-L|-Z} [chain [rulenum]] [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  ta-
       ble.

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 tar-
       get, which can be the name of a user-defined chain or one of  the  spe-
       cial 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
              filter:
                  This  is  the  default table (if no -t option is passed). It
                  contains the built-in chains INPUT (for packets destined  to
                  local  sockets),  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  sup-
                  ported: INPUT (for packets coming into the box itself), FOR-
                  WARD (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 ip_conntrack, or any other IP tables.
                  It provides the following built-in chains:  PREROUTING  (for
                  packets  arriving  via  any  network  interface) OUTPUT (for
                  packets generated by local processes)

              security:
                  This table is used for Mandatory Access Control  (MAC)  net-
                  working  rules,  such  as  those  enabled by the SECMARK and
                  CONNSECMARK targets.  Mandatory  Access  Control  is  imple-
                  mented by Linux Security Modules such as SELinux.  The secu-
                  rity table is called after the filter  table,  allowing  any
                  Discretionary Access Control (DAC) rules in the filter table
                  to take effect before MAC rules.  This  table  provides  the
                  following  built-in  chains:  INPUT (for packets coming into
                  the box  itself),  OUTPUT  (for  altering  locally-generated
                  packets  before  routing), and FORWARD (for altering packets
                  being routed through the box).

OPTIONS
       The options that are recognized by ip6tables can be divided  into  sev-
       eral 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 combina-
              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 chain [rulenum] rule-specification
              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 des-
              tination  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. Like every other ip6tables command, it
              applies to the specified table (filter is the default).

              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

       -S, --list-rules [chain]
              Print all rules in the selected chain.  If no chain is selected,
              all chains are printed like  ip6tables-save.  Like  every  other
              ip6tables  command, it applies to the specified table (filter is
              the default).

       -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 [rulenum]]
              Zero the packet and byte counters in all  chains,  or  only  the
              given  chain,  or only the given rule in a chain. It is legal to
              specify the -L, --list (list) option as well, to see  the  coun-
              ters 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.
              The  chain  must  be  empty,  i.e. not contain any rules.  If no

       -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 combina-
              tion.

       -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  speci-
              fied  protocol  can be one of tcp, udp, udplite, icmpv6, esp, mh
              or the special keyword "all", or it can be a numeric value, rep-
              resenting  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. "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 be a hostname, a
              network IP address (with /mask), or a plain IP  address.   Names
              will  be resolved once only, before the rule is submitted to the
              kernel.  Please note that specifying any  name  to  be  resolved
              with  a remote query such as DNS is a really bad idea.  (Resolv-
              ing network names is not supported at this time.)  The mask is a
              plain  number,  specifying the number of 1's at the left side of
              the network mask.  A "!" argument before the address  specifica-
              tion  inverts  the  sense  of  the address. The flag --src is an
              alias for this option.  Multiple addresses can be specified, but
              this  will  expand  to  multiple rules (when adding with -A), or
              will cause multiple rules to be deleted (with -D).

       [!] -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 (and -g is not used), then matching the rule will have no
              effect on the packet's fate, but the counters on the  rule  will
              be incremented.
              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, OUTPUT  and  POSTROUTING  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 packets 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  multipli-
              ers  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. -v may
              be specified multiple times to possibly emit more detailed debug
              statements.

       -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 appli-
              cable).

       -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
              Total length of this header in octets.

       --ahres
              Matches if the reserved field is filled with zero.

   cluster
       Allows you to deploy gateway and back-end load-sharing clusters without
       the need of load-balancers.

       This  match requires that all the nodes see the same packets. Thus, the
       cluster match decides if this node has to handle  a  packet  given  the
       following options:

       --cluster-total-nodes num
              Set number of total nodes in cluster.

       [!] --cluster-local-node num
              Set the local node number ID.

       [!] --cluster-local-nodemask mask
              Set  the  local  node  number  ID  mask. You can use this option
              instead of --cluster-local-node.

       --cluster-hash-seed value
              Set seed value of the Jenkins hash.

       Example:

              iptables -A PREROUTING -t mangle  -i  eth1  -m  cluster  --clus-
              ter-total-nodes  2  --cluster-local-node  1  --cluster-hash-seed
              0xdeadbeef -j MARK --set-mark 0xffff

              iptables -A PREROUTING -t mangle  -i  eth2  -m  cluster  --clus-
              ter-total-nodes  2  --cluster-local-node  1  --cluster-hash-seed
              0xdeadbeef -j MARK --set-mark 0xffff

              iptables -A PREROUTING -t mangle -i eth1 -m mark ! --mark 0xffff
              -j DROP

              iptables -A PREROUTING -t mangle -i eth2 -m mark ! --mark 0xffff
              -j DROP

       And the following commands to make all nodes see the same packets:

              ip maddr add 01:00:5e:00:01:01 dev eth1

              ip maddr add 01:00:5e:00:01:02 dev eth2

              arptables -A OUTPUT -o eth1 --h-length 6 -j mangle --mangle-mac-
              s 01:00:5e:00:01:01

              arptables  -A  INPUT  -i  eth1  --h-length  6  --destination-mac
              01:00:5e:00:01:01 -j mangle --mangle-mac-d 00:zz:yy:xx:5a:27

       Allows you to add comments (up to 256 characters) to any rule.

       --comment comment

       Example:
              iptables -A INPUT -i eth1 -m comment --comment "my local LAN"

   connbytes
       Match  by  how  many  bytes  or packets a connection (or one of the two
       flows constituting the connection) has transferred so far, or by  aver-
       age bytes per packet.

       The counters are 64-bit and are thus not expected to overflow ;)

       The  primary  use is to detect long-lived downloads and mark them to be
       scheduled using a lower priority band in traffic control.

       The transferred bytes per connection can also be viewed  through  `con-
       ntrack -L` and accessed via ctnetlink.

       NOTE  that  for  connections  which have no accounting information, the
       match will always return false.  The  "net.netfilter.nf_conntrack_acct"
       sysctl  flag  controls  whether  new  connections  will  be byte/packet
       counted. Existing connection flows will  not  be  gaining/losing  a/the
       accounting structure when be sysctl flag is flipped.

       [!] --connbytes from[:to]
              match  packets  from  a  connection  whose packets/bytes/average
              packet size is more than FROM and less than TO bytes/packets. if
              TO  is  omitted  only  FROM  check is done. "!" is used to match
              packets not falling in the range.

       --connbytes-dir {original|reply|both}
              which packets to consider

       --connbytes-mode {packets|bytes|avgpkt}
              whether to check the amount of packets, number of  bytes  trans-
              ferred or the average size (in bytes) of all packets received so
              far. Note that when "both" is used together with  "avgpkt",  and
              data is going (mainly) only in one direction (for example HTTP),
              the average packet size will be about half of  the  actual  data
              packets.

       Example:
              iptables    ..    -m    connbytes    --connbytes    10000:100000
              --connbytes-dir both --connbytes-mode bytes ...

   connlimit
       Allows you to restrict the number of parallel connections to  a  server
       per client IP address (or client address block).

       --connlimit-upto n
              Match if the number of existing connections is below or equal n.

       --connlimit-daddr
              Apply the limit onto the destination group.

       Examples:

       # allow 2 telnet connections per client host
              iptables  -A  INPUT  -p  tcp  --syn  --dport  23  -m   connlimit
              --connlimit-above 2 -j REJECT

       # you can also match the other way around:
              iptables   -A  INPUT  -p  tcp  --syn  --dport  23  -m  connlimit
              --connlimit-upto 2 -j ACCEPT

       # limit the number of parallel HTTP requests to 16 per  class  C  sized
       source network (24 bit netmask)
              iptables  -p tcp --syn --dport 80 -m connlimit --connlimit-above
              16 --connlimit-mask 24 -j REJECT

       # limit the number of parallel HTTP requests to 16 for the  link  local
       network
              (ipv6)  ip6tables  -p  tcp  --syn  --dport  80  -s  fe80::/64 -m
              connlimit --connlimit-above 16 --connlimit-mask 64 -j REJECT

       # Limit the number of connections to a particular host:
              ip6tables -p tcp --syn --dport  49152:65535  -d  2001:db8::1  -m
              connlimit --connlimit-above 100 -j REJECT

   connmark
       This  module matches the netfilter mark field associated with a connec-
       tion (which can be set using the CONNMARK target below).

       [!] --mark value[/mask]
              Matches packets in connections with the given mark value  (if  a
              mask  is specified, this is logically ANDed with the mark before
              the comparison).

   conntrack
       This module, when combined with connection tracking, allows  access  to
       the connection tracking state for this packet/connection.

       [!] --ctstate statelist
              statelist  is a comma separated list of the connection states to
              match.  Possible states are listed below.

       [!] --ctproto l4proto
              Layer-4 protocol to match (by number or name)

       [!] --ctorigsrc address[/mask]

       [!] --ctorigdst address[/mask]

       [!] --ctreplsrc address[/mask]

       [!] --ctrepldst address[/mask]

       [!] --ctstatus statelist
              statuslist is a comma separated list of the connection  statuses
              to match.  Possible statuses are listed below.

       [!] --ctexpire time[:time]
              Match remaining lifetime in seconds against given value or range
              of values (inclusive)

       --ctdir {ORIGINAL|REPLY}
              Match packets that are flowing in the  specified  direction.  If
              this  flag  is  not  specified  at  all, matches packets in both
              directions.

       States for --ctstate:

       INVALID
              meaning that the packet is associated with no known connection

       NEW    meaning that the packet has started a new connection, or  other-
              wise  associated with a connection which has not seen packets in
              both directions, and

       ESTABLISHED
              meaning that the packet is associated with  a  connection  which
              has seen packets in both directions,

       RELATED
              meaning  that  the  packet  is starting a new connection, but is
              associated with an existing connection,  such  as  an  FTP  data
              transfer, or an ICMP error.

       UNTRACKED
              meaning  that the packet is not tracked at all, which happens if
              you use the NOTRACK target in raw table.

       SNAT   A virtual state, matching if the original source address differs
              from the reply destination.

       DNAT   A  virtual  state,  matching if the original destination differs
              from the reply source.

       Statuses for --ctstatus:

       NONE   None of the below.

       EXPECTED
              This is an expected connection (i.e. a conntrack helper  set  it
              up)

       SEEN_REPLY
              Conntrack has seen packets in both directions.

       ASSURED
       Example:

       iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 0 -j REDI-
       RECT --to-port 8080

       iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 1 -j REDI-
       RECT --to-port 8081

       Available since Linux 2.6.36.

   dccp
       [!] --source-port,--sport port[:port]

       [!] --destination-port,--dport port[:port]

       [!] --dccp-types mask
              Match when the DCCP packet type is one of 'mask'.  'mask'  is  a
              comma-separated list of packet types.  Packet types are: REQUEST
              RESPONSE DATA ACK DATAACK  CLOSEREQ  CLOSE  RESET  SYNC  SYNCACK
              INVALID.

       [!] --dccp-option number
              Match if DCP option set.

   dscp
       This module matches the 6 bit DSCP field within the TOS field in the IP
       header.  DSCP has superseded TOS within the IETF.

       [!] --dscp value
              Match against a numeric (decimal or hex) value [0-63].

       [!] --dscp-class class
              Match the DiffServ class. This value may be any of the  BE,  EF,
              AFxx or CSx classes.  It will then be converted into its accord-
              ing numeric value.

   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 autoconfigured IPv6
       address.  It compares the EUI-64 derived from the source MAC address in
              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.

   hashlimit
       hashlimit uses hash buckets to express a rate limiting match (like  the
       limit  match)  for a group of connections using a single iptables rule.
       Grouping can be done per-hostgroup (source and/or destination  address)
       and/or  per-port.  It  gives  you the ability to express "N packets per
       time quantum per group" (see below for some examples).

       A hash limit option (--hashlimit-upto, --hashlimit-above)  and  --hash-
       limit-name are required.

       --hashlimit-upto amount[/second|/minute|/hour|/day]
              Match  if  the  rate  is below or equal to amount/quantum. It is
              specified as a number, with an optional time quantum suffix; the
              default is 3/hour.

       --hashlimit-above amount[/second|/minute|/hour|/day]
              Match if the rate is above amount/quantum.

       --hashlimit-burst amount
              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.

       --hashlimit-mode {srcip|srcport|dstip|dstport},...
              A comma-separated list of objects to take into consideration. If
              no --hashlimit-mode option is given, hashlimit acts like  limit,
              but at the expensive of doing the hash housekeeping.

       --hashlimit-srcmask prefix
              When  --hashlimit-mode  srcip  is  used,  all  source  addresses
              encountered will be grouped according to the given prefix length
              and  the  so-created subnet will be subject to hashlimit. prefix
              must be between (inclusive) 0 and 32. Note that --hashlimit-src-
              mask 0 is basically doing the same thing as not specifying srcip
              for --hashlimit-mode, but is technically more expensive.

       --hashlimit-dstmask prefix
              Like --hashlimit-srcmask, but for destination addresses.

       --hashlimit-htable-gcinterval msec
              How many milliseconds between garbage collection intervals.

       Examples:

       matching on source host
              "1000 packets per second for every host in 192.168.0.0/16" => -s
              192.168.0.0/16 --hashlimit-mode srcip --hashlimit-upto 1000/sec

       matching on source port
              "100  packets per second for every service of 192.168.1.1" => -s
              192.168.1.1 --hashlimit-mode srcport --hashlimit-upto 100/sec

       matching on subnet
              "10000 packets per minute for every  /28  subnet  (groups  of  8
              addresses)  in  10.0.0.0/8"  =>  -s 10.0.0.8 --hashlimit-mask 28
              --hashlimit-upto 10000/min

   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.

   helper
       This module matches packets related to a specific conntrack-helper.

       [!] --helper string
              Matches packets related to the specified conntrack-helper.

              string  can  be  "ftp"  for  packets related to a ftp-session on
              default port.  For other ports append -portnr to the value,  ie.
              "ftp-2121".

              Same rules apply for other conntrack-helpers.

   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
       [!] --src-range from[-to]
              Match source IP in the specified range.

       [!] --dst-range from[-to]
              Match destination IP in the specified range.

   ipv6header
       This module matches IPv6 extension headers and/or upper layer header.

       --soft Matches if the packet includes any of the headers specified with
              --header.

       [!] --header header[,header...]
              Matches the packet which EXACTLY includes all specified headers.
              The headers encapsulated with ESP header are out of scope.  Pos-
              sible header types 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

       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.

   ipvs
       Match IPVS connection properties.

       [!] --ipvs
              packet belongs to an IPVS connection

       Any of the following options implies --ipvs (even negated)

       [!] --vproto protocol
              VIP protocol to match; by number or name, e.g. "tcp"

       [!] --vaddr address[/mask]
              VIP address to match

       [!] --vport port
              VIP port to match; by number or name, e.g. "http"


       [!] --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.   It
       can be used in combination with the LOG target to give limited logging,
       for example.

       xt_limit has no negation support - you will have to use -m hashlimit  !
       --hashlimit rate in this case whilst omitting --hashlimit-mode.

       --limit rate[/second|/minute|/hour|/day]
              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, FOR-
              WARD 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 com-
              parison).

   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.  A port range (port:port) counts as two ports.
       It can only be used in conjunction with -p tcp or -p udp.

       [!] --source-ports,--sports port[,port|,port:port]...
              of the given ports.

   owner
       This module attempts to match various  characteristics  of  the  packet
       creator, for locally generated packets. This match is only valid in the
       OUTPUT and POSTROUTING chains. Forwarded packets do not have any socket
       associated with them. Packets from kernel threads do have a socket, but
       usually no owner.

       [!] --uid-owner username

       [!] --uid-owner userid[-userid]
              Matches if the packet socket's file structure (if it has one) is
              owned  by  the given user. You may also specify a numerical UID,
              or an UID range.

       [!] --gid-owner groupname

       [!] --gid-owner groupid[-groupid]
              Matches if the packet socket's file structure is  owned  by  the
              given  group.   You  may  also specify a numerical GID, or a GID
              range.

       [!] --socket-exists
              Matches if the packet is associated with a socket.

   physdev
       This module matches  on  the  bridge  port  input  and  output  devices
       enslaved  to  a bridge device. This module is a part of the infrastruc-
       ture 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  inter-
              face  which  begins  with this name will match. Note that in the
              nat and mangle OUTPUT chains one cannot match on the bridge out-
              put  port,  however  one  can in the filter OUTPUT chain. If the
              packet won't leave by a bridge device or if 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.


   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  decapsula-
              tion  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. --pol none
              cannot be combined with --strict.

       --strict
              Selects whether to match the exact policy or match if  any  rule
              of the policy matches the given policy.

       For  each  policy  element  that is to be described, one can use one or
       more of the following options. When --strict is in effect, at least one
       must be used per element.

       [!] --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.

   quota
       Implements  network  quotas  by  decrementing  a byte counter with each
       packet. The condition matches until  the  byte  counter  reaches  zero.
       Behavior  is  reversed with negation (i.e. the condition does not match
       until the byte counter reaches zero).

       [!] --quota bytes
              The quota in bytes.

       o   rateest operator rateest-pps

       o   (rateest minus rateest-bps1) operator rateest-bps2

       o   (rateest minus rateest-pps1) operator rateest-pps2

       o   rateest1 operator rateest2 rateest-bps(without rate!)

       o   rateest1 operator rateest2 rateest-pps(without rate!)

       o   (rateest1 minus rateest-bps1)  operator  (rateest2  minus  rateest-
           bps2)

       o   (rateest1  minus  rateest-pps1)  operator  (rateest2 minus rateest-
           pps2)

       --rateest-delta
           For each estimator (either absolute or  relative  mode),  calculate
           the  difference  between the estimator-determined flow rate and the
           static value chosen with the BPS/PPS options. If the flow  rate  is
           higher than the specified BPS/PPS, 0 will be used instead of a neg-
           ative value. In other words, "max(0, rateest#_rate - rateest#_bps)"
           is used.

       [!] --rateest-lt
           Match if rate is less than given rate/estimator.

       [!] --rateest-gt
           Match if rate is greater than given rate/estimator.

       [!] --rateest-eq
           Match if rate is equal to given rate/estimator.

       In  the  so-called "absolute mode", only one rate estimator is used and
       compared against a static value, while in  "relative  mode",  two  rate
       estimators are compared against another.

       --rateest name
              Name of the one rate estimator for absolute mode.

       --rateest1 name

       --rateest2 name
              The names of the two rate estimators for relative mode.

       --rateest-bps [value]

       --rateest-pps [value]

       --rateest-bps1 [value]

       --rateest-bps2 [value]

       --rateest-pps1 [value]
       # Estimate outgoing rates

       iptables  -t  mangle  -A  POSTROUTING -o eth0 -j RATEEST --rateest-name
       eth0 --rateest-interval 250ms --rateest-ewma 0.5s

       iptables -t mangle -A POSTROUTING -o  ppp0  -j  RATEEST  --rateest-name
       ppp0 --rateest-interval 250ms --rateest-ewma 0.5s

       # Mark based on available bandwidth

       iptables  -t  mangle  -A  balance  -m conntrack --ctstate NEW -m helper
       --helper ftp -m rateest --rateest-delta --rateest1 eth0  --rateest-bps1
       2.5mbit  --rateest-gt  --rateest2 ppp0 --rateest-bps2 2mbit -j CONNMARK
       --set-mark 1

       iptables -t mangle -A balance -m  conntrack  --ctstate  NEW  -m  helper
       --helper  ftp -m rateest --rateest-delta --rateest1 ppp0 --rateest-bps1
       2mbit --rateest-gt --rateest2 eth0 --rateest-bps2 2.5mbit  -j  CONNMARK
       --set-mark 2

       iptables -t mangle -A balance -j CONNMARK --restore-mark

   recent
       Allows  you to dynamically create a list of IP addresses and then match
       against that list in a few different ways.

       For example, you can create a "badguy" list out of people attempting to
       connect  to  port 139 on your firewall and then DROP all future packets
       from them without considering them.

       --set, --rcheck, --update and --remove are mutually exclusive.

       --name name
              Specify the list to use for the commands. If no  name  is  given
              then DEFAULT will be used.

       [!] --set
              This  will  add the source address of the packet to the list. If
              the source address is already in the list, this will update  the
              existing entry. This will always return success (or failure if !
              is passed in).

       --rsource
              Match/save the source address of each packet in the recent  list
              table. This is the default.

       --rdest
              Match/save  the destination address of each packet in the recent
              list table.

       [!] --rcheck
              Check if the source address of the packet is  currently  in  the
              list.

              --update. When used, this will narrow the match to  only  happen
              when  the  address  is  in the list and was seen within the last
              given number of seconds.

       --reap reap
              This option can only be  used  in  conjunction  with  --seconds.
              When  used,  this  will cause entries older then 'seconds' to be
              purged.

       --hitcount hits
              This option must be used in conjunction with one of --rcheck  or
              --update.  When  used, this will narrow the match to only happen
              when the address is in the list and packets  had  been  received
              greater  than  or  equal  to the given value. This option may be
              used along with --seconds  to  create  an  even  narrower  match
              requiring a certain number of hits within a specific time frame.
              The maximum value for the hitcount parameter  is  given  by  the
              "ip_pkt_list_tot"  parameter  of  the  xt_recent  kernel module.
              Exceeding this value on the command line will cause the rule  to
              be rejected.

       --rttl This option may only be used in conjunction with one of --rcheck
              or --update. When used, this will narrow the match to only  hap-
              pen  when  the address is in the list and the TTL of the current
              packet matches that of the packet which hit the --set rule. This
              may  be  useful  if  you  have problems with people faking their
              source address in order to DoS you via this module by  disallow-
              ing others access to your site by sending bogus packets to you.

       Examples:

              iptables  -A  FORWARD -m recent --name badguy --rcheck --seconds
              60 -j DROP

              iptables -A FORWARD -p tcp -i eth0 --dport 139 -m recent  --name
              badguy --set -j DROP

       Steve's  ipt_recent  website  (http://snowman.net/projects/ipt_recent/)
       also has some examples of usage.

       /proc/net/xt_recent/* are the current lists of addresses  and  informa-
       tion about each entry of each list.

       Each  file  in /proc/net/xt_recent/ can be read from to see the current
       list or written two using the following commands to modify the list:

       echo +addr >/proc/net/xt_recent/DEFAULT
              to add addr to the DEFAULT list

       echo -addr >/proc/net/xt_recent/DEFAULT
              to remove addr from the DEFAULT list

       echo / >/proc/net/xt_recent/DEFAULT
              to flush the DEFAULT list (remove all entries).

       ip_list_perms=0644
              Permissions for /proc/net/xt_recent/* files.

       ip_list_uid=0
              Numerical UID for ownership of /proc/net/xt_recent/* files.

       ip_list_gid=0
              Numerical GID for ownership of /proc/net/xt_recent/* files.

   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.

   sctp
       [!] --source-port,--sport port[:port]

       [!] --destination-port,--dport port[:port]

       [!] --chunk-types {all|any|only} chunktype[:flags] [...]
              The  flag  letter  in  upper  case indicates that the flag is to
              match if set, in the lower case indicates to match if unset.

              Chunk types: DATA INIT  INIT_ACK  SACK  HEARTBEAT  HEARTBEAT_ACK
              ABORT   SHUTDOWN   SHUTDOWN_ACK   ERROR  COOKIE_ECHO  COOKIE_ACK
              ECN_ECNE ECN_CWR SHUTDOWN_COMPLETE ASCONF ASCONF_ACK FORWARD_TSN

              chunk type            available flags
              DATA                  I U B E i u b e
              ABORT                 T t
              SHUTDOWN_COMPLETE     T t

              (lowercase means flag should be "off", uppercase means "on")

       Examples:

       iptables -A INPUT -p sctp --dport 80 -j DROP

               iptables -A FORWARD -m set --match-set test src,dst

              will match packets, for which (if the set type is ipportmap) the
              source  address  and  destination  port pair can be found in the
              specified set. If the set type of the specified  set  is  single
              dimension (for example ipmap), then the command will match pack-
              ets for which the source address can be found in  the  specified
              set.

       The  option --match-set can be replaced by --set if that does not clash
       with an option of other extensions.

       Use of -m set requires that ipset kernel support is provided. As  stan-
       dard  kernels  do  not ship this currently, the ipset or Xtables-addons
       package needs to be installed.

   socket
       This matches if an open socket can be found by doing a socket lookup on
       the packet.

       --transparent
              Ignore non-transparent sockets.

   state
       This  module,  when combined with connection tracking, allows access to
       the connection tracking state for this packet.

       [!] --state state
              Where state is a comma separated list of the  connection  states
              to  match.   Possible states are INVALID meaning that the packet
              could not be identified for some reason which  includes  running
              out  of  memory  and  ICMP  errors which don't correspond to any
              known connection, ESTABLISHED meaning that the packet is associ-
              ated  with  a  connection  which has seen packets in both direc-
              tions, NEW meaning that the packet has started a new connection,
              or  otherwise  associated  with  a connection which has not seen
              packets in both directions, and RELATED meaning that the  packet
              is starting a new connection, but is associated with an existing
              connection, such as an FTP data  transfer,  or  an  ICMP  error.
              UNTRACKED  meaning  that the packet is not tracked at all, which
              happens if you use the NOTRACK target in raw table.

   statistic
       This module matches packets based on some statistic condition.  It sup-
       ports two distinct modes settable with the --mode option.

       Supported options:

       --mode mode
              Set  the matching mode of the matching rule, supported modes are
              random and nth.

       [!] --probability p

   string
       This modules matches a given string  by  using  some  pattern  matching
       strategy. It requires a linux kernel >= 2.6.14.

       --algo {bm|kmp}
              Select  the  pattern matching strategy. (bm = Boyer-Moore, kmp =
              Knuth-Pratt-Morris)

       --from offset
              Set the offset from which it starts looking for any matching. If
              not passed, default is 0.

       --to offset
              Set the offset up to which should be scanned. That is, byte off-
              set-1 (counting from 0) is the last one that is scanned.  If not
              passed, default is the packet size.

       [!] --string pattern
              Matches the given pattern.

       [!] --hex-string pattern
              Matches the given pattern in hex notation.

   tcp
       These  extensions can be used if `--protocol tcp' is specified. It pro-
       vides the following options:

       [!] --source-port,--sport 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 first:last.  If the  first  port  is
              omitted,  "0"  is  assumed;  if  the last is omitted, "65535" is
              assumed.  If the first port is greater than the second one  they
              will  be  swapped.   The  flag --sport is a convenient alias for
              this option.

       [!] --destination-port,--dport 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
              mask is the flags which we should examine, written as  a  comma-
              separated  list,  and  the second argument comp is a comma-sepa-
              rated list of flags which must be set.  Flags are: SYN  ACK  FIN
              RST URG PSH ALL NONE.  Hence the command
               iptables -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,RST  and
              FIN  bits cleared.  Such packets are used to request TCP connec-
              tion initiation; for example, blocking such packets coming in an

       time.

       [!] --mss value[:value]
              Match a given TCP MSS value or range.

   time
       This  matches  if the packet arrival time/date is within a given range.
       All options are optional, but are ANDed when specified. All  times  are
       interpreted as UTC by default.

       --datestart YYYY[-MM[-DD[Thh[:mm[:ss]]]]]

       --datestop YYYY[-MM[-DD[Thh[:mm[:ss]]]]]
              Only  match during the given time, which must be in ISO 8601 "T"
              notation.  The possible time  range  is  1970-01-01T00:00:00  to
              2038-01-19T04:17:07.

              If  --datestart or --datestop are not specified, it will default
              to 1970-01-01 and 2038-01-19, respectively.

       --timestart hh:mm[:ss]

       --timestop hh:mm[:ss]
              Only match during the given daytime. The possible time range  is
              00:00:00  to 23:59:59. Leading zeroes are allowed (e.g. "06:03")
              and correctly interpreted as base-10.

       [!] --monthdays day[,day...]
              Only match on the given days of the month. Possible values are 1
              to  31.  Note  that  specifying  31  will of course not match on
              months which do not have a 31st day; the same goes  for  28-  or
              29-day February.

       [!] --weekdays day[,day...]
              Only  match on the given weekdays. Possible values are Mon, Tue,
              Wed, Thu, Fri, Sat, Sun, or values from 1  to  7,  respectively.
              You may also use two-character variants (Mo, Tu, etc.).

       --kerneltz
              Use  the  kernel  timezone instead of UTC to determine whether a
              packet meets the time regulations.

       About kernel timezones: Linux keeps the system time in UTC, and  always
       does  so.   On boot, system time is initialized from a referential time
       source. Where this time source has no timezone information, such as the
       x86 CMOS RTC, UTC will be assumed. If the time source is however not in
       UTC, userspace should provide the correct system time and  timezone  to
       the kernel once it has the information.

       Local  time  is  a  feature on top of the (timezone independent) system
       time. Each process has its own idea of local time, specified via the TZ
       environment variable. The kernel also has its own timezone offset vari-
       able. The TZ userspace environment variable specifies how the UTC-based
       system time is displayed, e.g. when you run date(1), or what you see on
       so running it will not resolve the issue. As such, one may encounter  a
       timezone that is always +0000, or one that is wrong half of the time of
       the year. As such, using --kerneltz is highly discouraged.

       EXAMPLES. To match on weekends, use:

              -m time --weekdays Sa,Su

       Or, to match (once) on a national holiday block:

              -m time --datestart 2007-12-24 --datestop 2007-12-27

       Since the stop time is actually inclusive, you would need the following
       stop time to not match the first second of the new day:

              -m      time     --datestart     2007-01-01T17:00     --datestop
              2007-01-01T23:59:59

       During lunch hour:

              -m time --timestart 12:30 --timestop 13:30

       The fourth Friday in the month:

              -m time --weekdays Fr --monthdays 22,23,24,25,26,27,28

       (Note that this exploits a certain mathematical  property.  It  is  not
       possible  to  say "fourth Thursday OR fourth Friday" in one rule. It is
       possible with multiple rules, though.)

   tos
       This module matches the 8-bit Type of Service field in the IPv4  header
       (i.e.   including  the  "Precedence" bits) or the (also 8-bit) Priority
       field in the IPv6 header.

       [!] --tos value[/mask]
              Matches packets with the given TOS mark  value.  If  a  mask  is
              specified,  it  is  logically ANDed with the TOS mark before the
              comparison.

       [!] --tos symbol
              You can specify a symbolic name when using  the  tos  match  for
              IPv4.  The list of recognized TOS names can be obtained by call-
              ing iptables with -m tos -h.  Note that this implies a  mask  of
              0x3F, i.e. all but the ECN bits.

   u32
       U32  tests  whether quantities of up to 4 bytes extracted from a packet
       have specified values. The specification of what to extract is  general
       enough to find data at given offsets from tcp headers or payloads.

       [!] --u32 tests
              The  argument amounts to a program in a small language described
              below.

           operator := "&" | "<<" | ">>" | "@"

       The  operators &, <<, >> and && mean the same as in C.  The = is really
       a set membership operator and the value syntax describes a set.  The  @
       operator is what allows moving to the next header and is described fur-
       ther below.

       There are currently some artificial implementation limits on  the  size
       of the tests:

           *  no more than 10 of "=" (and 9 "&&"s) in the u32 argument

           *  no more than 10 ranges (and 9 commas) per value

           *  no more than 10 numbers (and 9 operators) per location

       To describe the meaning of location, imagine the following machine that
       interprets it. There are three registers:

              A is of type char *, initially the address of the IP header

              B and C are unsigned 32 bit integers, initially zero

       The instructions are:

              number B = number;

              C = (*(A+B)<<24) + (*(A+B+1)<<16) + (*(A+B+2)<<8) + *(A+B+3)

              &number C = C & number

              << number C = C << number

              >> number C = C >> number

              @number A = A + C; then do the instruction number

       Any access of memory outside [skb->data,skb->end] causes the  match  to
       fail.  Otherwise the result of the computation is the final value of C.

       Whitespace is allowed but not required in the tests. However, the char-
       acters that do occur there are likely to require shell quoting,  so  it
       is a good idea to enclose the arguments in quotes.

       Example:

              match IP packets with total length >= 256

              The IP header contains a total length field in bytes 2-3.

              --u32 "0 & 0xFFFF = 0x100:0xFFFF"

              read bytes 0-3

              read  bytes  6-9,  use & to throw away bytes 6-8 and compare the
              result to 1. Next test that it is not a  fragment.  (If  so,  it
              might be part of such a packet but we cannot always tell.) N.B.:
              This test is generally needed if  you  want  to  match  anything
              beyond  the IP header. The last 6 bits of byte 6 and all of byte
              7 are 0 iff this is a complete packet (not a fragment). Alterna-
              tively, you can allow first fragments by only testing the last 5
              bits of byte 6.

               ... 4 & 0x3FFF = 0 && ...

              Last test: the first byte past the IP header (the  type)  is  0.
              This  is  where we have to use the @syntax. The length of the IP
              header (IHL) in 32 bit words is stored in the right half of byte
              0 of the IP header itself.

               ... 0 >> 22 & 0x3C @ 0 >> 24 = 0"

              The  first 0 means read bytes 0-3, >>22 means shift that 22 bits
              to the right. Shifting 24 bits would give  the  first  byte,  so
              only  22  bits is four times that plus a few more bits. &3C then
              eliminates the two extra bits on the right and  the  first  four
              bits  of  the  first  byte.  For instance, if IHL=5, then the IP
              header is 20 (4 x 5) bytes long. In this case, bytes 0-1 are (in
              binary)   xxxx0101   yyzzzzzz,  >>22  gives  the  10  bit  value
              xxxx0101yy and &3C gives 010100. @ means to use this number as a
              new  offset  into  the packet, and read four bytes starting from
              there. This is the first 4 bytes of the ICMP payload,  of  which
              byte 0 is the ICMP type. Therefore, we simply shift the value 24
              to the right to throw out all but the first byte and compare the
              result with 0.

       Example:

              TCP payload bytes 8-12 is any of 1, 2, 5 or 8

              First we test that the packet is a tcp packet (similar to ICMP).

              --u32 "6 & 0xFF = 6 && ...

              Next, test that it is not a fragment (same as above).

               ... 0 >> 22 & 0x3C @ 12 >> 26 & 0x3C @ 8 = 1,2,5,8"

              0>>22&3C as above computes the number of bytes in the IP header.
              @ makes this the new offset into the packet, which is the  start
              of the TCP header. The length of the TCP header (again in 32 bit
              words) is the left half of  byte  12  of  the  TCP  header.  The
              12>>26&3C  computes  this  length  in  bytes  (similar to the IP
              header before). "@" makes this the  new  offset,  which  is  the
              start  of  the  TCP  payload. Finally, 8 reads bytes 8-12 of the
              payload and = checks whether the result is any of 1, 2, 5 or 8.

   udp

TARGET EXTENSIONS
       ip6tables can use extended target modules: the following  are  included
       in the standard distribution.

   AUDIT
       This target allows to create audit records for packets hitting the tar-
       get.  It can be used to record accepted, dropped, and rejected packets.
       See auditd(8) for additional details.

       --type {accept|drop|reject}
              Set type of audit record.

       Example:

              iptables -N AUDIT_DROP

              iptables -A AUDIT_DROP -j AUDIT --type drop

              iptables -A AUDIT_DROP -j DROP

   CHECKSUM
       This  target allows to selectively work around broken/old applications.
       It can only be used in the mangle table.

       --checksum-fill
              Compute and fill in the checksum in a packet that lacks a check-
              sum.   This  is  particularly useful, if you need to work around
              old applications such as dhcp clients, that  do  not  work  well
              with  checksum offloads, but don't want to disable checksum off-
              load in your device.

   CLASSIFY
       This module allows you to set the skb->priority value (and  thus  clas-
       sify the packet into a specific CBQ class).

       --set-class major:minor
              Set  the  major  and  minor  class  value. The values are always
              interpreted as hexadecimal even if no 0x prefix is given.

   CONNMARK
       This module sets the netfilter mark value associated with a connection.
       The mark is 32 bits wide.

       --set-xmark value[/mask]
              Zero out the bits given by mask and XOR value into the ctmark.

       --save-mark [--nfmask nfmask] [--ctmask ctmask]
              Copy  the  packet  mark (nfmark) to the connection mark (ctmark)
              using the given masks. The new nfmark  value  is  determined  as
              follows:

              ctmark = (ctmark & ~ctmask) ^ (nfmark & nfmask)

              i.e.  ctmask  defines what bits to clear and nfmask what bits of
              0xFFFFFFFF.

              --restore-mark is only valid in the mangle table.

       The following mnemonics are available for --set-xmark:

       --and-mark bits
              Binary  AND  the  ctmark  with  bits.  (Mnemonic for --set-xmark
              0/invbits, where invbits is the binary negation of bits.)

       --or-mark bits
              Binary OR  the  ctmark  with  bits.  (Mnemonic  for  --set-xmark
              bits/bits.)

       --xor-mark bits
              Binary  XOR  the  ctmark  with  bits.  (Mnemonic for --set-xmark
              bits/0.)

       --set-mark value[/mask]
              Set the connection mark. If a mask is specified then only  those
              bits set in the mask are modified.

       --save-mark [--mask mask]
              Copy  the  nfmark  to  the  ctmark. If a mask is specified, only
              those bits are copied.

       --restore-mark [--mask mask]
              Copy the ctmark to the nfmark. If  a  mask  is  specified,  only
              those bits are copied. This is only valid in the mangle table.

   CONNSECMARK
       This  module  copies  security markings from packets to connections (if
       unlabeled), and from connections back to packets (also  only  if  unla-
       beled).  Typically used in conjunction with SECMARK, it is valid in the
       security table (for backwards compatibility with older kernels,  it  is
       also 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  connec-
              tion  does, copy the security marking from the connection to the
              packet.


   CT
       The CT target allows to set parameters for a packet or  its  associated
       connection.  The target attaches a "template" connection tracking entry
       to the packet, which is then used by the conntrack core when initializ-
       ing a new ct entry. This target is thus only valid in the "raw" table.

       --notrack
              Disables connection tracking for this packet.

       --expevents event[,...]
              Only generate the specified expectation events for this  connec-
              tion.  Possible event types are: new.

       --zone id
              Assign this packet to zone id and only have lookups done in that
              zone.  By default, packets have zone 0.

   DSCP
       This target allows to alter the value of the DSCP bits within  the  TOS
       header  of  the IPv4 packet.  As this manipulates a packet, it can only
       be used in the mangle table.

       --set-dscp value
              Set the DSCP field to a numerical value (can be decimal or hex)

       --set-dscp-class class
              Set the DSCP field to a DiffServ class.

   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 man-
       gle table.

       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.

   IDLETIMER
       This  target can be used to identify when interfaces have been idle for
       a certain period of time.  Timers are identified by labels and are cre-
       ated  when a rule is set with a new label.  The rules also take a time-
       out value (in seconds) as an option.  If more than one  rule  uses  the
       same timer label, the timer will be restarted whenever any of the rules
       get a hit.  One entry  for  each  timer  is  created  in  sysfs.   This
       attribute  contains  the  timer remaining for the timer to expire.  The
       attributes are located under the xt_idletimer class:

       /sys/class/xt_idletimer/timers/<label>

       When the timer expires, the target module sends a sysfs notification to
       the userspace, which can then decide what to do (eg. disconnect to save
       power).

       nating  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 target is used to set the Netfilter mark value associated with the
       packet.  It can, for example, be used in conjunction with routing based
       on fwmark (needs iproute2). If you plan on doing so, note that the mark
       needs to be set in the PREROUTING chain of the mangle table  to  affect
       routing.  The mark field is 32 bits wide.

       --set-xmark value[/mask]
              Zeroes out the bits given by mask and XORs value into the packet
              mark ("nfmark"). If mask is omitted, 0xFFFFFFFF is assumed.

       --set-mark value[/mask]
              Zeroes out the bits given by mask and ORs value into the  packet
              mark. If mask is omitted, 0xFFFFFFFF is assumed.

       The following mnemonics are available:

       --and-mark bits
              Binary  AND  the  nfmark  with  bits.  (Mnemonic for --set-xmark
              0/invbits, where invbits is the binary negation of bits.)

       --or-mark bits
              Binary OR  the  nfmark  with  bits.  (Mnemonic  for  --set-xmark
              bits/bits.)

       --xor-mark bits
              Binary  XOR  the  nfmark  with  bits.  (Mnemonic for --set-xmark
              bits/0.)

   NFLOG

       --nflog-prefix prefix
              A prefix string to include in the log message, up to 64  charac-
              ters 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.

   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.  It can only  be  used  with  Kernel  versions
       2.6.14  or later, since it requires the nfnetlink_queue kernel support.
       The queue-balance option was added in  Linux  2.6.31,  queue-bypass  in
       2.6.39.

       --queue-num value
              This  specifies the QUEUE number to use. Valid queue numbers are
              0 to 65535. The default value is 0.

       --queue-balance value:value
              This specifies a range of queues to use. Packets are  then  bal-
              anced  across  the  given  queues.  This is useful for multicore
              systems: start multiple instances of the  userspace  program  on
              queues  x, x+1, .. x+n and use "--queue-balance x:x+n".  Packets
              belonging to the same connection are put into the same nfqueue.

       --queue-bypass
              By default, if no userspace program is listening on an  NFQUEUE,
              then  all  packets that are to be queued are dropped.  When this
              option is used, the NFQUEUE rule is silently  bypassed  instead.
              The packet will move on to the next rule.

   NOTRACK
       This  target disables connection tracking for all packets matching that
       rule.

       It can only be used in the raw table.

   RATEEST
       The RATEEST target collects statistics, performs rate estimation calcu-
       lation  and  saves  the  results for later evaluation using the rateest
       match.

       --rateest-name name
              Count matched packets into the pool referred to by  name,  which

       GET, 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-pro-
              hibited, adm-prohibited,  icmp6-addr-unreachable,  addr-unreach,
              icmp6-port-unreachable  or  port-unreach which return the appro-
              priate 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 later.

   SECMARK
       This is used to set the security mark value associated with the  packet
       for  use  by  security  subsystems such as SELinux.  It is valid in the
       security table (for backwards compatibility with older kernels,  it  is
       also valid in the mangle table). The mark is 32 bits wide.

       --selctx security_context

   SET
       This  modules  adds  and/or  deletes  entries from IP sets which can be
       defined by ipset(8).

       --add-set setname flag[,flag...]
              add the address(es)/port(s) of the packet to the sets

       --del-set setname flag[,flag...]
              delete the address(es)/port(s) of the packet from the sets

              where flags are src and/or dst specifications and there  can  be
              no more than six of them.

       --timeout value
              when  adding  entry,  the  timeout  value  to use instead of the
              default one from the set definition

       --exist
              when adding entry if it already exists, reset the timeout  value
              to the specified one or to the default from the set definition

       Use  of -j SET requires that ipset kernel support is provided. As stan-
       dard kernels do not ship this currently, the  ipset  or  Xtables-addons
       package needs to be installed.

   TCPMSS
       This  target  allows to alter the MSS value of TCP SYN packets, to con-
       trol the maximum size for that connection (usually limiting it to  your
       outgoing  interface's  MTU  minus  40  for IPv4 or 60 for IPv6, respec-
       3.  ssh works fine, but scp hangs after initial handshaking.

       Workaround: activate this option and add a rule to your  firewall  con-
       figuration like:

               iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN
                           -j TCPMSS --clamp-mss-to-pmtu

       --set-mss value
              Explicitly sets MSS option to specified value. If the MSS of the
              packet is already lower than value, it  will  not  be  increased
              (from  Linux  2.6.25  onwards) to avoid more problems with hosts
              relying on a proper MSS.

       --clamp-mss-to-pmtu
              Automatically clamp MSS value to (path_MTU - 40  for  IPv4;  -60
              for  IPv6).   This  may not function as desired where asymmetric
              routes with differing path MTU exist -- the kernel uses the path
              MTU which it would use to send packets from itself to the source
              and destination IP addresses. Prior to Linux  2.6.25,  only  the
              path  MTU  to  the destination IP address was considered by this
              option; subsequent kernels also consider the  path  MTU  to  the
              source IP address.

       These options are mutually exclusive.

   TCPOPTSTRIP
       This  target will strip TCP options off a TCP packet. (It will actually
       replace them by NO-OPs.) As such, you will  need  to  add  the  -p  tcp
       parameters.

       --strip-options option[,option...]
              Strip  the  given option(s). The options may be specified by TCP
              option number or  by  symbolic  name.  The  list  of  recognized
              options  can be obtained by calling iptables with -j TCPOPTSTRIP
              -h.

   TEE
       The TEE target will clone a packet and redirect this clone  to  another
       machine  on the local network segment. In other words, the nexthop must
       be the target, or you will have to configure the nexthop to forward  it
       further if so desired.

       --gateway ipaddr
              Send  the  cloned  packet  to the host reachable at the given IP
              address.  Use of 0.0.0.0 (for IPv4  packets)  or  ::  (IPv6)  is
              invalid.

       To  forward  all  incoming  traffic on eth0 to an Network Layer logging
       box:

       -t mangle -A PREROUTING -i eth0 -j TEE --gateway 2001:db8::1

   TOS
              IPv4. It implies a mask of 0xFF (see NOTE below).  The  list  of
              recognized TOS names can be obtained by calling iptables with -j
              TOS -h.

       The following mnemonics are available:

       --and-tos bits
              Binary AND the TOS value  with  bits.  (Mnemonic  for  --set-tos
              0/invbits,  where  invbits  is the binary negation of bits.  See
              NOTE below.)

       --or-tos bits
              Binary OR the TOS  value  with  bits.  (Mnemonic  for  --set-tos
              bits/bits. See NOTE below.)

       --xor-tos bits
              Binary  XOR  the  TOS  value  with bits. (Mnemonic for --set-tos
              bits/0. See NOTE below.)

       NOTE: In Linux kernels up to and including 2.6.38, with  the  exception
       of  longterm  releases  2.6.32.42  (or later) and 2.6.33.15 (or later),
       there is a bug whereby IPv6 TOS mangling does not behave as  documented
       and  differs from the IPv4 version. The TOS mask indicates the bits one
       wants to zero out, so it needs to be inverted before applying it to the
       original TOS field. However, the aformentioned kernels forgo the inver-
       sion which breaks --set-tos and its mnemonics.

   TPROXY
       This target is only valid in the mangle table, in the PREROUTING  chain
       and user-defined chains which are only called from this chain. It redi-
       rects the packet to a local socket without changing the  packet  header
       in any way. It can also change the mark value which can then be used in
       advanced routing rules.  It takes three options:

       --on-port port
              This specifies a destination port  to  use.  It  is  a  required
              option,  0  means  the  new  destination port is the same as the
              original. This is only valid if the rule also specifies  -p  tcp
              or -p udp.

       --on-ip address
              This  specifies  a  destination  address  to use. By default the
              address is the IP address of the  incoming  interface.  This  is
              only valid if the rule also specifies -p tcp or -p udp.

       --tproxy-mark value[/mask]
              Marks  packets  with  the given value/mask. The fwmark value set
              here can be used by advanced routing. (Required for  transparent
              proxying  to  work:  otherwise these packets will get forwarded,
              which is probably not what you want.)

   TRACE
       This target marks packes so that the kernel will log every  rule  which
       match the packets as those traverse the tables, chains, rules.
       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  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 Neul-
       ing.

       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 every-
       where.

       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>.

VERSION
       This manual page applies to ip6tables @PACKAGE_VERSION@.
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