Provided by: iptables_1.4.12-1ubuntu4_amd64 bug

NAME

       ip6tables — IPv6 packet filter administration

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 table.

TARGETS

       A  firewall  rule  specifies  criteria  for a packet and a target.  If the packet does not
       match, the next rule in the chain is the examined; if it does match, then the next rule is
       specified by the value of the target, which can be the name of a user-defined chain or one
       of the special values ACCEPT, DROP, QUEUE or RETURN.

       ACCEPT means to let the packet through.  DROP means to  drop  the  packet  on  the  floor.
       QUEUE  means  to  pass  the  packet  to  userspace.   (How the packet can be received by a
       userspace process differs by the particular queue handler.  2.4.x and 2.6.x kernels up  to
       2.6.13  include the ip_queue queue handler.  Kernels 2.6.14 and later additionally include
       the nfnetlink_queue queue handler.  Packets with a target of QUEUE will be sent  to  queue
       number '0' in this case. Please also see the NFQUEUE target as described later in this man
       page.)  RETURN means stop traversing this chain  and  resume  at  the  next  rule  in  the
       previous (calling) chain.  If the end of a built-in chain is reached or a rule in a built-
       in chain with target  RETURN  is  matched,  the  target  specified  by  the  chain  policy
       determines the fate of the packet.

TABLES

       There are currently three independent tables (which tables are present at any time depends
       on the kernel configuration options and which modules are present).

       -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  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 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 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) networking rules, such as
                  those enabled by the SECMARK and CONNSECMARK targets.  Mandatory Access Control
                  is  implemented  by Linux Security Modules such as SELinux.  The security 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 several different groups.

   COMMANDS
       These options specify the specific action to perform.  Only one of them can  be  specified
       on  the  command  line unless otherwise specified below.  For all the long versions of the
       command and option names, you need to use only enough letters to ensure that ip6tables can
       differentiate it from all other options.

       -A, --append chain rule-specification
              Append  one or more rules to the end of the selected chain.  When the source and/or
              destination names resolve to more than one address, a rule will be added  for  each
              possible address combination.

       -C, --check chain rule-specification
              Check  whether  a rule matching the specification does exist in the selected chain.
              This command uses the same logic as -D to find a matching entry, but does not alter
              the  existing  iptables configuration and uses its exit code to indicate success or
              failure.

       -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 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  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.  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 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.  The chain must be empty, i.e. not contain any rules.  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.

       -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.

       -h     Help.  Give a (currently very brief) description of the command syntax.

   PARAMETERS
       The following parameters make up a rule specification (as used in the add, delete, insert,
       replace and append commands).

       [!] -p, --protocol protocol
              The protocol of the rule or of the packet to check.  The specified protocol can  be
              one  of  tcp, udp, udplite, icmpv6, esp, mh or the special keyword "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. "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.  (Resolving  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  specification 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.

       -g, --goto chain
              This specifies that the processing should  continue  in  a  user  specified  chain.
              Unlike  the  --jump  option  return  will not continue processing in this chain but
              instead in the chain that called us via --jump.

       [!] -i, --in-interface name
              Name of an interface via which a packet was 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, 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
              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. -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 applicable).

       -x, --exact
              Expand  numbers.   Display the exact value of the packet and byte counters, instead
              of only the rounded number in K's (multiples of 1000) M's (multiples of  1000K)  or
              G's (multiples of 1000M).  This option is only relevant for the -L command.

       --line-numbers
              When  listing  rules, add line numbers to the beginning of each rule, corresponding
              to that rule's position in the chain.

       --modprobe=command
              When adding or inserting rules into a chain, use  command  to  load  any  necessary
              modules (targets, match extensions, etc).

MATCH EXTENSIONS

       ip6tables  can  use  extended  packet  matching  modules.   These  are loaded in two ways:
       implicitly, when -p or --protocol is  specified,  or  with  the  -m  or  --match  options,
       followed  by  the  matching  module  name; after these, various extra command line options
       become available, depending on the specific module.  You  can  specify  multiple  extended
       match  modules  in one line, and you can use the -h or --help options after the module has
       been specified to receive help specific to that module.

   ah
       This module matches the parameters in Authentication header of IPsec packets.

       [!] --ahspi spi[:spi]
              Matches SPI.

       [!] --ahlen length
              Total length of this header in octets.

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

   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 --cluster-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  --cluster-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

              arptables -A OUTPUT -o eth2 --h-length 6 -j mangle --mangle-mac-s 01:00:5e:00:01:02

              arptables -A INPUT -i eth2  --h-length  6  --destination-mac  01:00:5e:00:01:02  -j
              mangle --mangle-mac-d 00:zz:yy:xx:5a:27

       In  the  case  of TCP connections, pickup facility has to be disabled to avoid marking TCP
       ACK packets coming in the reply direction as valid.

              echo 0 > /proc/sys/net/netfilter/nf_conntrack_tcp_loose

   comment
       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 average 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  `conntrack  -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 transferred 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-above n
              Match if the number of existing connections is above n.

       --connlimit-mask prefix_length
              Group hosts using the prefix length. For  IPv4,  this  must  be  a  number  between
              (including)  0  and  32. For IPv6, between 0 and 128. If not specified, the maximum
              prefix length for the applicable protocol is used.

       --connlimit-saddr
              Apply the limit onto the source group.

       --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 connection (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]
              Match against original/reply source/destination address

       [!] --ctorigsrcport port[:port]

       [!] --ctorigdstport port[:port]

       [!] --ctreplsrcport port[:port]

       [!] --ctrepldstport port[:port]
              Match  against  original/reply  source/destination  port (TCP/UDP/etc.) or GRE key.
              Matching against port ranges is only supported in kernel versions above 2.6.38.

       [!] --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 otherwise 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
              Conntrack entry should never be early-expired.

       CONFIRMED
              Connection is confirmed: originating packet has left box.

   cpu
       [!] --cpu number
              Match  cpu  handling this packet. cpus are numbered from 0 to NR_CPUS-1 Can be used
              in combination with RPS (Remote Packet  Steering)  or  multiqueue  NICs  to  spread
              network traffic on different queues.

       Example:

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

       iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 1 -j REDIRECT --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 according 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 Ethernet frame with  the  lower
       64 bits of the IPv6 source address. But "Universal/Local" bit is not compared. This module
       doesn't match other link layer frame, and is only  valid  in  the  PREROUTING,  INPUT  and
       FORWARD chains.

   frag
       This module matches the parameters in Fragment header.

       [!] --fragid id[:id]
              Matches the given Identification or range of it.

       [!] --fraglen length
              This  option  cannot  be  used  with  kernel version 2.6.10 or later. The length of
              Fragment header is static and this option doesn't make sense.

       --fragres
              Matches if the reserved fields are filled with zero.

       --fragfirst
              Matches on the first fragment.

       --fragmore
              Matches if there are more fragments.

       --fraglast
              Matches if this is the last fragment.

   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  --hashlimit-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-srcmask 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-name foo
              The name for the /proc/net/ipt_hashlimit/foo entry.

       --hashlimit-htable-size buckets
              The number of buckets of the hash table

       --hashlimit-htable-max entries
              Maximum entries in the hash.

       --hashlimit-htable-expire msec
              After how many milliseconds do hash entries expire.

       --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
       This extension can be used if `--protocol ipv6-icmp' or `--protocol icmpv6' is  specified.
       It provides the following option:

       [!] --icmpv6-type type[/code]|typename
              This  allows  specification of the ICMPv6 type, which can be a numeric ICMPv6 type,
              type and code, or one of the ICMPv6 type names shown by the command
               ip6tables -p ipv6-icmp -h

   iprange
       This matches on a given arbitrary range of IP addresses.

       [!] --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.  Possible 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"

       --vdir {ORIGINAL|REPLY}
              flow direction of packet

       [!] --vmethod {GATE|IPIP|MASQ}
              IPVS forwarding method used

       [!] --vportctl port
              VIP port of the controlling connection to match, e.g. 21 for FTP

   length
       This  module  matches  the length of the layer-3 payload (e.g. layer-4 packet) of a packet
       against a specific value or range of values.

       [!] --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, FORWARD or INPUT chains.

   mark
       This  module  matches  the netfilter mark field associated with a packet (which can be set
       using the MARK target below).

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

   mh
       This  extension  is  loaded  if  `--protocol  ipv6-mh' or `--protocol mh' is specified. It
       provides the following option:

       [!] --mh-type type[:type]
              This allows specification of the Mobility Header(MH) type, which can be  a  numeric
              MH type, type or one of the MH type names shown by the command
               ip6tables -p ipv6-mh -h

   multiport
       This  module  matches  a  set  of  source  or  destination  ports.   Up to 15 ports can be
       specified.  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]...
              Match  if  the  source  port  is  one  of  the given ports.  The flag --sports is a
              convenient alias for this option. Multiple ports or port ranges are separated using
              a  comma,  and  a  port  range  is  specified  using  a colon.  53,1024:65535 would
              therefore match ports 53 and all from 1024 through 65535.

       [!] --destination-ports,--dports 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  either  the  source  or  destination ports are equal to one 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 infrastructure that enables a transparent bridging IP
       firewall and is only useful for kernel versions above version 2.5.44.

       [!] --physdev-in name
              Name of a bridge port via which a packet is received (only for packets entering the
              INPUT, FORWARD and PREROUTING chains). If the interface name ends in  a  "+",  then
              any  interface  which begins with this name will match. If the packet didn't arrive
              through a bridge device, this packet won't match this option, unless '!' is used.

       [!] --physdev-out name
              Name of a bridge port via which a packet is going to be sent (for packets  entering
              the  FORWARD, OUTPUT and POSTROUTING chains).  If the interface name ends in a "+",
              then any interface which begins with this name will match. Note that in the nat and
              mangle OUTPUT chains one cannot match on the bridge output port, however one can in
              the filter OUTPUT chain. If the packet won't leave by a bridge device or 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.

       [!] --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.

   pkttype
       This module matches the link-layer packet type.

       [!] --pkt-type {unicast|broadcast|multicast}

   policy
       This modules matches the policy used by IPsec for handling a packet.

       --dir {in|out}
              Used  to  select  whether  to match the policy used for decapsulation or the policy
              that will be used for encapsulation.  in is valid  in  the  PREROUTING,  INPUT  and
              FORWARD chains, out is valid in the POSTROUTING, OUTPUT and FORWARD chains.

       --pol {none|ipsec}
              Matches if the packet is subject to IPsec processing. --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.

   rateest
       The  rate  estimator  can  match on estimated rates as collected by the RATEEST target. It
       supports matching on absolute bps/pps values, comparing two rate estimators  and  matching
       on the difference between two rate estimators.

       For a better understanding of the available options, these are all possible combinations:

       ·   rateest operator rateest-bps

       ·   rateest operator rateest-pps

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

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

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

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

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

       ·   (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 negative 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]

       --rateest-pps2 [value]
              Compare the estimator(s) by bytes or packets per second, and  compare  against  the
              chosen  value.  See  the  above bullet list for which option is to be used in which
              case. A unit suffix may be used - available ones are: bit,  [kmgt]bit,  [KMGT]ibit,
              Bps, [KMGT]Bps, [KMGT]iBps.

       Example:  This  is  what can be used to route outgoing data connections from an FTP server
       over two lines based on the available bandwidth  at  the  time  the  data  connection  was
       started:

       # 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
              Like --rcheck, except it will update the "last seen" timestamp if it matches.

       [!] --remove
              Check  if  the source address of the packet is currently in the list and if so that
              address will be removed from the list and the rule will return true. If the address
              is not found, false is returned.

       --seconds seconds
              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
              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 happen 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 disallowing 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 information 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).

       The module itself accepts parameters, defaults shown:

       ip_list_tot=100
              Number of addresses remembered per table.

       ip_pkt_list_tot=20
              Number of packets per address remembered.

       ip_list_hash_size=0
              Hash table size. 0 means to calculate it based on ip_list_tot, default: 512.

       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 INPUT -p sctp --chunk-types any DATA,INIT -j DROP

       iptables -A INPUT -p sctp --chunk-types any DATA:Be -j ACCEPT

   set
       This module matches IP sets which can be defined by ipset(8).

       [!] --match-set setname flag[,flag]...
              where flags are the comma separated list of src and/or dst specifications and there
              can be no more than six of them. Hence the command

               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
              packets 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 standard 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  associated  with a
              connection which has seen packets in both directions, 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 supports 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
              Set the probability for a packet to be randomly matched. It  only  works  with  the
              random  mode.  p  must  be  within  0.0  and  1.0.  The supported granularity is in
              1/2147483648th increments.

       [!] --every n
              Match one packet every nth packet. It works only with the nth mode  (see  also  the
              --packet option).

       --packet p
              Set the initial counter value (0 <= p <= n-1, default 0) for the nth mode.

   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 offset-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 provides  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-separated 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 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,FIN SYN.  If the "!" flag precedes the "--syn", the sense of the option
              is inverted.

       [!] --tcp-option number
              Match if TCP option set.

   tcpmss
       This matches the TCP MSS (maximum segment size) field of the TCP header.  You can only use
       this on TCP SYN or SYN/ACK packets, since the  MSS  is  only  negotiated  during  the  TCP
       handshake at connection startup 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 variable. 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  your
       desktop  clock.   The TZ string may resolve to different offsets at different dates, which
       is what enables the automatic time-jumping in userspace. when DST  changes.  The  kernel's
       timezone  offset  variable is used when it has to convert between non-UTC sources, such as
       FAT filesystems, to UTC (since the latter is what the rest of the system uses).

       The caveat with the kernel timezone is that Linux distributions  may  ignore  to  set  the
       kernel  timezone,  and instead only set the system time. Even if a particular distribution
       does set the timezone at boot, it is usually does not keep the kernel  timezone  offset  -
       which  is  what  changes on DST - up to date.  ntpd will not touch the kernel timezone, 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 calling 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.

              tests := location "=" value | tests "&&" location "=" value

              value := range | value "," range

              range := number | number ":" number

       a  single  number,  n,  is interpreted the same as n:n. n:m is interpreted as the range of
       numbers >=n and <=m.

           location := number | location operator number

           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 further 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 characters 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

              AND that with 0xFFFF (giving bytes 2-3), and test whether  that  is  in  the  range
              [0x100:0xFFFF]

       Example: (more realistic, hence more complicated)

              match ICMP packets with icmp type 0

              First test that it is an ICMP packet, true iff byte 9 (protocol) = 1

              --u32 "6 & 0xFF = 1 && ...

              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). Alternatively, 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
       These extensions can be used if `--protocol udp' is specified. It provides  the  following
       options:

       [!] --source-port,--sport port[:port]
              Source  port or port range specification.  See the description of the --source-port
              option of the TCP extension for details.

       [!] --destination-port,--dport port[:port]
              Destination  port  or  port  range  specification.   See  the  description  of  the
              --destination-port option of the TCP extension for details.

TARGET EXTENSIONS

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

   AUDIT
       This target allows to create audit records for packets hitting the target.  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  checksum.   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 offload in your device.

   CLASSIFY
       This module allows you to set the skb->priority value (and thus classify 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 the nfmark to XOR
              into the ctmark. ctmask and nfmask default to 0xFFFFFFFF.

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

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

              i.e.  nfmask  defines  what bits to clear and ctmask what bits of the ctmark to XOR
              into the nfmark. ctmask and nfmask default to 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 unlabeled).  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 connection 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 initializing a new ct entry. This target is thus only valid  in
       the "raw" table.

       --notrack
              Disables connection tracking for this packet.

       --helper name
              Use  the  helper  identified by name for the connection. This is more flexible than
              loading the conntrack helper modules with preset ports.

       --ctevents event[,...]
              Only generate the specified conntrack events for this  connection.  Possible  event
              types  are:  new,  related,  destroy, reply, assured, protoinfo, helper, mark (this
              refers to the ctmark, not nfmark), natseqinfo, secmark (ctsecmark).

       --expevents event[,...]
              Only generate the specified expectation events for this connection.  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 mangle 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 created when a rule is set with a new
       label.  The rules also take a timeout 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).

       --timeout amount
              This is the time in seconds that will trigger the notification.

       --label string
              This is a unique identifier for the timer.  The maximum length for the label string
              is 27 characters.

   LOG
       Turn on kernel logging of matching packets.  When this option is set for a rule, the Linux
       kernel  will  print  some  information on all matching packets (like most IPv6 IPv6-header
       fields) via the kernel log (where it can be read with dmesg or  syslogd(8)).   This  is  a
       "non-terminating  target", i.e. rule traversal continues at the next rule.  So if you want
       to LOG the packets you refuse, use two separate rules with  the  same  matching  criteria,
       first using target LOG then DROP (or REJECT).

       --log-level level
              Level of logging (numeric or see syslog.conf(5)).

       --log-prefix prefix
              Prefix  log  messages  with the specified prefix; up to 29 letters long, and useful
              for distinguishing messages in the logs.

       --log-tcp-sequence
              Log TCP sequence numbers. This is a security risk if the log is readable by users.

       --log-tcp-options
              Log options from the TCP packet header.

       --log-ip-options
              Log options from the IPv6 packet header.

       --log-uid
              Log the userid of the process which generated the packet.

   MARK
       This 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
       This target provides logging of matching packets. When this target is set for a rule,  the
       Linux kernel will pass the packet to the loaded logging backend to log the packet. This is
       usually used in combination with nfnetlink_log as logging backend,  which  will  multicast
       the  packet  through  a  netlink  socket  to  the  specified  multicast group. One or more
       userspace processes may subscribe to the group to receive the packets. Like LOG, this is a
       non-terminating target, i.e. rule traversal continues at the next rule.

       --nflog-group nlgroup
              The  netlink  group  (0  -  2^16-1)  to  which  packets  are  (only  applicable for
              nfnetlink_log). The default value is 0.

       --nflog-prefix prefix
              A prefix string to include in the log message, up to 64 characters long, useful for
              distinguishing messages in the logs.

       --nflog-range size
              The  number of bytes to be copied to userspace (only applicable for nfnetlink_log).
              nfnetlink_log instances may specify their own range, this option overrides it.

       --nflog-threshold size
              Number of packets to queue inside the kernel before sending them to userspace (only
              applicable  for  nfnetlink_log).  Higher values result in less overhead per packet,
              but increase delay until the packets reach userspace. The default value is 1.

   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 balanced 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 calculation 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 is freely choosable.

       --rateest-interval amount{s|ms|us}
              Rate measurement interval, in seconds, milliseconds or microseconds.

       --rateest-ewmalog value
              Rate measurement averaging time constant.

   REJECT
       This is used to send back an error packet in response to the matched packet: otherwise  it
       is  equivalent  to DROP so it is a terminating TARGET, ending rule traversal.  This target
       is only valid in the INPUT, FORWARD and OUTPUT chains, and user-defined chains  which  are
       only  called  from  those  chains.   The following option controls the nature of the error
       packet returned:

       --reject-with type
              The   type   given   can   be   icmp6-no-route,   no-route,   icmp6-adm-prohibited,
              adm-prohibited,  icmp6-addr-unreachable,  addr-unreach,  icmp6-port-unreachable  or
              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 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 standard 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 control the maximum  size
       for  that  connection  (usually  limiting it to your outgoing interface's MTU minus 40 for
       IPv4 or 60 for IPv6, respectively).  Of course, it can only be used in conjunction with -p
       tcp.

       This  target  is  used  to overcome criminally braindead ISPs or servers which block "ICMP
       Fragmentation Needed" or "ICMPv6 Packet Too Big" packets.  The symptoms  of  this  problem
       are that everything works fine from your Linux firewall/router, but machines behind it can
       never exchange large packets:

       1.  Web browsers connect, then hang with no data received.

       2.  Small mail works fine, but large emails hang.

       3.  ssh works fine, but scp hangs after initial handshaking.

       Workaround: activate this option and add a rule to your firewall configuration like:

               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
       This  module sets the Type of Service field in the IPv4 header (including the "precedence"
       bits) or the Priority field in the IPv6 header. Note that TOS shares the same bits as DSCP
       and ECN. The TOS target is only valid in the mangle table.

       --set-tos value[/mask]
              Zeroes  out  the  bits  given  by  mask  (see  NOTE  below) and XORs value into the
              TOS/Priority field. If mask is omitted, 0xFF is assumed.

       --set-tos symbol
              You can specify a symbolic name when using the TOS target for 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 inversion 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 redirects 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.

       A logging backend, such as ip(6)t_LOG or nfnetlink_log, must be  loaded  for  this  to  be
       visible.     The    packets    are    logged    with    the    string    prefix:   "TRACE:
       tablename:chainname:type:rulenum " where type can be "rule" for plain rule,  "return"  for
       implicit  rule at the end of a user defined chain and "policy" for the policy of the built
       in chains.
       It can only be used in the raw table.

DIAGNOSTICS

       Various error messages are printed to standard error.  The exit  code  is  0  for  correct
       functioning.   Errors  which  appear  to  be  caused  by  invalid  or  abused command line
       parameters cause an exit code of 2, and other errors cause an exit code of 1.

BUGS

       Bugs?  What's this? ;-) Well... the counters are not reliable on sparc64.

COMPATIBILITY WITH IPCHAINS

       This ip6tables is very similar to ipchains by Rusty Russell.  The main difference is  that
       the  chains INPUT and OUTPUT are only traversed for packets coming into the local host and
       originating from the local host respectively.  Hence every packet only passes through  one
       of  the  three  chains  (except  loopback  traffic,  which  involves both INPUT and OUTPUT
       chains); previously a forwarded packet would pass through all three.

       The other main difference is that -i refers to the  input  interface;  -o  refers  to  the
       output  interface,  and  both are available for packets entering the FORWARD chain.  There
       are several other changes in ip6tables.

SEE ALSO

       ip6tables-save(8),       ip6tables-restore(8),       iptables(8),        iptables-save(8),
       iptables-restore(8), libipq(3).

       The  packet-filtering-HOWTO  details  iptables  usage for packet filtering, the netfilter-
       extensions-HOWTO details the extensions that are not in the standard distribution, and the
       netfilter-hacking-HOWTO details the netfilter internals.
       See http://www.netfilter.org/.

AUTHORS

       Rusty Russell wrote iptables, in early consultation with Michael Neuling.

       Marc  Boucher  made  Rusty  abandon  ipnatctl  by  lobbying for a generic packet selection
       framework in iptables, then wrote the mangle table, the owner match, the mark  stuff,  and
       ran around doing cool stuff everywhere.

       James Morris wrote the TOS target, and tos match.

       Jozsef Kadlecsik wrote the REJECT target.

       Harald  Welte  wrote  the  ULOG  and  NFQUEUE  target,  the  new  libiptc,  as well as TTL
       match+target and libipulog.

       The Netfilter Core Team is: Marc  Boucher,  Martin  Josefsson,  Yasuyuki  Kozakai,  Jozsef
       Kadlecsik,  Patrick  McHardy,  James  Morris,  Pablo  Neira  Ayuso, Harald Welte and Rusty
       Russell.

       ip6tables man page created by Andras Kis-Szabo, based on  iptables  man  page  written  by
       Herve Eychenne <rv@wallfire.org>.

VERSION

       This manual page applies to ip6tables @PACKAGE_VERSION@.