--- /dev/null
+.TH IPTABLES 8 "Mar 09, 2002" "" ""
+.\"
+.\" Man page written by Herve Eychenne <rv@wallfire.org> (May 1999)
+.\" It is based on ipchains page.
+.\" TODO: add a word for protocol helpers (FTP, IRC, SNMP-ALG)
+.\"
+.\" ipchains page by Paul ``Rusty'' Russell March 1997
+.\" Based on the original ipfwadm man page by Jos Vos <jos@xos.nl>
+.\"
+.\" This program is free software; you can redistribute it and/or modify
+.\" it under the terms of the GNU General Public License as published by
+.\" the Free Software Foundation; either version 2 of the License, or
+.\" (at your option) any later version.
+.\"
+.\" This program is distributed in the hope that it will be useful,
+.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
+.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+.\" GNU General Public License for more details.
+.\"
+.\" You should have received a copy of the GNU General Public License
+.\" along with this program; if not, write to the Free Software
+.\" Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+.\"
+.\"
+.SH NAME
+iptables \- administration tool for IPv4 packet filtering and NAT
+.SH SYNOPSIS
+.BR "iptables [-t table] -[AD] " "chain rule-specification [options]"
+.br
+.BR "iptables [-t table] -I " "chain [rulenum] rule-specification [options]"
+.br
+.BR "iptables [-t table] -R " "chain rulenum rule-specification [options]"
+.br
+.BR "iptables [-t table] -D " "chain rulenum [options]"
+.br
+.BR "iptables [-t table] -[LFZ] " "[chain] [options]"
+.br
+.BR "iptables [-t table] -N " "chain"
+.br
+.BR "iptables [-t table] -X " "[chain]"
+.br
+.BR "iptables [-t table] -P " "chain target [options]"
+.br
+.BR "iptables [-t table] -E " "old-chain-name new-chain-name"
+.SH DESCRIPTION
+.B Iptables
+is used to set up, maintain, and inspect the tables of IP 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.
+
+.SH 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
+.IR ACCEPT ,
+.IR DROP ,
+.IR QUEUE ,
+or
+.IR RETURN .
+.PP
+.I ACCEPT
+means to let the packet through.
+.I DROP
+means to drop the packet on the floor.
+.I QUEUE
+means to pass the packet to userspace (if supported by the kernel).
+.I 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
+.I RETURN
+is matched, the target specified by the chain policy determines the
+fate of the packet.
+.SH 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).
+.TP
+.BI "-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:
+.RS
+.TP .4i
+.BR "filter" :
+This is the default table (if no -t option is passed). It contains
+the built-in chains
+.B INPUT
+(for packets destined to local sockets),
+.B FORWARD
+(for packets being routed through the box), and
+.B OUTPUT
+(for locally-generated packets).
+.TP
+.BR "nat" :
+This table is consulted when a packet that creates a new
+connection is encountered. It consists of three built-ins:
+.B PREROUTING
+(for altering packets as soon as they come in),
+.B OUTPUT
+(for altering locally-generated packets before routing), and
+.B POSTROUTING
+(for altering packets as they are about to go out).
+.TP
+.BR "mangle" :
+This table is used for specialized packet alteration. Until kernel
+2.4.17 it had two built-in chains:
+.B PREROUTING
+(for altering incoming packets before routing) and
+.B OUTPUT
+(for altering locally-generated packets before routing).
+Since kernel 2.4.18, three other built-in chains are also supported:
+.B INPUT
+(for packets coming into the box itself),
+.B FORWARD
+(for altering packets being routed through the box), and
+.B POSTROUTING
+(for altering packets as they are about to go out).
+.TP
+.BR "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:
+.B PREROUTING
+(for packets arriving via any network interface)
+.B OUTPUT
+(for packets generated by local processes)
+.RE
+.SH OPTIONS
+The options that are recognized by
+.B iptables
+can be divided into several different groups.
+.SS 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
+.B iptables
+can differentiate it from all other options.
+.TP
+.BI "-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.
+.TP
+.BI "-D, --delete " "chain rule-specification"
+.ns
+.TP
+.BI "-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.
+.TP
+.BR "-I, --insert " "\fIchain\fP [\fIrulenum\fP] \fIrule-specification\fP"
+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.
+.TP
+.BI "-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.
+.TP
+.BR "-L, --list " "[\fIchain\fP]"
+List all rules in the selected chain. If no chain is selected, all
+chains are listed. As every other iptables command, it applies to the
+specified table (filter is the default), so NAT rules get listed by
+.nf
+ iptables -t nat -n -L
+.fi
+Please note that it is often used with the
+.B -n
+option, in order to avoid long reverse DNS lookups.
+It is legal to specify the
+.B -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
+.nf
+ iptables -L -v
+.fi
+.TP
+.BR "-F, --flush " "[\fIchain\fP]"
+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.
+.TP
+.BR "-Z, --zero " "[\fIchain\fP]"
+Zero the packet and byte counters in all chains. It is legal to
+specify the
+.B "-L, --list"
+(list) option as well, to see the counters immediately before they are
+cleared. (See above.)
+.TP
+.BI "-N, --new-chain " "chain"
+Create a new user-defined chain by the given name. There must be no
+target of that name already.
+.TP
+.BR "-X, --delete-chain " "[\fIchain\fP]"
+Delete the optional user-defined chain specified. There must be no references
+to the chain. If there are, you must delete or replace the referring
+rules before the chain can be deleted. If no argument is given, it
+will attempt to delete every non-builtin chain in the table.
+.TP
+.BI "-P, --policy " "chain target"
+Set the policy for the chain to the given target. See the section
+.B 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.
+.TP
+.BI "-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.
+.TP
+.B -h
+Help.
+Give a (currently very brief) description of the command syntax.
+.SS PARAMETERS
+The following parameters make up a rule specification (as used in the
+add, delete, insert, replace and append commands).
+.TP
+.BR "-p, --protocol " "[!] \fIprotocol\fP"
+The protocol of the rule or of the packet to check.
+The specified protocol can be one of
+.IR tcp ,
+.IR udp ,
+.IR icmp ,
+or
+.IR 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.
+A "!" argument before the protocol inverts the
+test. The number zero is equivalent to
+.IR all .
+Protocol
+.I all
+will match with all protocols and is taken as default when this
+option is omitted.
+.TP
+.BR "-s, --source " "[!] \fIaddress\fP[/\fImask\fP]"
+Source specification.
+.I Address
+can be either a network name, a hostname (please note that specifying
+any name to be resolved with a remote query such as DNS is a really bad idea),
+a network IP address (with /mask), or a plain IP address.
+The
+.I mask
+can be either a network mask or a plain number,
+specifying the number of 1's at the left side of the network mask.
+Thus, a mask of
+.I 24
+is equivalent to
+.IR 255.255.255.0 .
+A "!" argument before the address specification inverts the sense of
+the address. The flag
+.B --src
+is an alias for this option.
+.TP
+.BR "-d, --destination " "[!] \fIaddress\fP[/\fImask\fP]"
+Destination specification.
+See the description of the
+.B -s
+(source) flag for a detailed description of the syntax. The flag
+.B --dst
+is an alias for this option.
+.TP
+.BI "-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
+.B EXTENSIONS
+below). If this
+option is omitted in a rule, then matching the rule will have no
+effect on the packet's fate, but the counters on the rule will be
+incremented.
+.TP
+.BR "-i, --in-interface " "[!] \fIname\fP"
+Name of an interface via which a packet was received (only for
+packets entering the
+.BR INPUT ,
+.B FORWARD
+and
+.B 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.
+.TP
+.BR "-o, --out-interface " "[!] \fIname\fP"
+Name of an interface via which a packet is going to be sent (for packets
+entering the
+.BR FORWARD ,
+.B OUTPUT
+and
+.B 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.
+.TP
+.B "[!] " "-f, --fragment"
+This means that the rule only refers to second and further fragments
+of fragmented packets. Since there is no way to tell the source or
+destination ports of such a packet (or ICMP type), such a packet will
+not match any rules which specify them. When the "!" argument
+precedes the "-f" flag, the rule will only match head fragments, or
+unfragmented packets.
+.TP
+.BI "-c, --set-counters " "PKTS BYTES"
+This enables the administrator to initialize the packet and byte
+counters of a rule (during
+.B INSERT,
+.B APPEND,
+.B REPLACE
+operations).
+.SS "OTHER OPTIONS"
+The following additional options can be specified:
+.TP
+.B "-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
+.B -x
+flag to change this).
+For appending, insertion, deletion and replacement, this causes
+detailed information on the rule or rules to be printed.
+.TP
+.B "-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).
+.TP
+.B "-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
+.B -L
+command.
+.TP
+.B "--line-numbers"
+When listing rules, add line numbers to the beginning of each rule,
+corresponding to that rule's position in the chain.
+.TP
+.B "--modprobe=command"
+When adding or inserting rules into a chain, use
+.B command
+to load any necessary modules (targets, match extensions, etc).
+.SH MATCH EXTENSIONS
+iptables can use extended packet matching modules. These are loaded
+in two ways: implicitly, when
+.B -p
+or
+.B --protocol
+is specified, or with the
+.B -m
+or
+.B --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
+.B -h
+or
+.B --help
+options after the module has been specified to receive help specific
+to that module.
+
+The following are included in the base package, and most of these can
+be preceded by a
+.B !
+to invert the sense of the match.
+.\" @MATCH@
+.SS account
+Account traffic for all hosts in defined network/netmask.
+
+Features:
+
+- long (one counter per protocol TCP/UDP/IMCP/Other) and short statistics
+
+- one iptables rule for all hosts in network/netmask
+
+- loading/saving counters (by reading/writting to procfs entries)
+
+.TP
+.BI "--aaddr " "network/netmask"
+defines network/netmask for which make statistics.
+.TP
+.BI "--aname " "name"
+defines name of list where statistics will be kept. If no is
+specified DEFAULT will be used.
+.TP
+.B "--ashort"
+table will colect only short statistics (only total counters
+without splitting it into protocols.
+.P
+Example usage:
+
+account traffic for/to 192.168.0.0/24 network into table mynetwork:
+
+# iptables -A FORWARD -m account --aname mynetwork --aaddr 192.168.0.0/24
+
+account traffic for/to WWW serwer for 192.168.0.0/24 network into table mywwwserver:
+
+# iptables -A INPUT -p tcp --dport 80
+ -m account --aname mywwwserver --aaddr 192.168.0.0/24 --ashort
+
+# iptables -A OUTPUT -p tcp --sport 80
+ -m account --aname mywwwserver --aaddr 192.168.0.0/24 --ashort
+
+read counters:
+
+# cat /proc/net/ipt_account/mynetwork
+# cat /proc/net/ipt_account/mywwwserver
+
+set counters:
+
+# echo "ip = 192.168.0.1 packets_src = 0" > /proc/net/ipt_account/mywwserver
+
+Webpage:
+ http://www.barbara.eu.org/~quaker/ipt_account/
+.SS addrtype
+This module matches packets based on their
+.B address type.
+Address types are used within the kernel networking stack and categorize
+addresses into various groups. The exact definition of that group depends on the specific layer three protocol.
+.TP
+The following address types are possible:
+.TP
+.BI "UNSPEC"
+an unspecified address (i.e. 0.0.0.0)
+.BI "UNICAST"
+an unicast address
+.BI "LOCAL"
+a local address
+.BI "BROADCAST"
+a broadcast address
+.BI "ANYCAST"
+an anycast packet
+.BI "MULTICAST"
+a multicast address
+.BI "BLACKHOLE"
+a blackhole address
+.BI "UNREACHABLE"
+an unreachable address
+.BI "PROHIBIT"
+a prohibited address
+.BI "THROW"
+FIXME
+.BI "NAT"
+FIXME
+.BI "XRESOLVE"
+FIXME
+.TP
+.BI "--src-type " "type"
+Matches if the source address is of given type
+.TP
+.BI "--dst-type " "type"
+Matches if the destination address is of given type
+.SS ah
+This module matches the SPIs in AH header of IPSec packets.
+.TP
+.BR "--ahspi " "[!] \fIspi\fP[:\fIspi\fP]"
+.SS childlevel
+This is an experimental module. It matches on whether the
+packet is part of a master connection or one of its children (or grandchildren,
+etc). For instance, most packets are level 0. FTP data transfer is level 1.
+.TP
+.BR "--childlevel " "[!] \fIlevel\fP"
+.SS comment
+Allows you to add comments (up to 256 characters) to any rule.
+.TP
+.BI "--comment " "comment"
+.TP
+Example:
+iptables -A INPUT -s 192.168.0.0/16 -m comment --comment "A privatized IP block"
+.SS condition
+This matches if a specific /proc filename is '0' or '1'.
+.TP
+.BI "--condition " "[!] filename"
+Match on boolean value stored in /proc/net/ipt_condition/filename file
+.SS connbytes
+Match by how many bytes or packets a connection (or one of the two
+flows constituting the connection) have tranferred so far, or by
+average bytes per packet.
+
+The counters are 64bit 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 transfered bytes per connection can also be viewed through
+/proc/net/ip_conntrack and accessed via ctnetlink
+.TP
+[\fB!\fR]\fB --connbytes \fIfrom\fB:\fR[\fIto\fR]
+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.
+.TP
+\fB--connbytes-dir\fR [\fBoriginal\fR|\fBreply\fR|\fBboth\fR]
+which packets to consider
+.TP
+\fB--connbytes-mode\fR [\fBpackets\fR|\fBbytes\fR|\fBavgpkt\fR]
+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.
+.TP
+Example:
+iptables .. -m connbytes --connbytes 10000:100000 --connbytes-dir both --connbytes-mode bytes ...
+.SS connlimit
+Allows you to restrict the number of parallel TCP connections to a
+server per client IP address (or address block).
+.TP
+[\fB!\fR] \fB--connlimit-above \fIn\fR
+match if the number of existing tcp connections is (not) above n
+.TP
+.BI "--connlimit-mask " "bits"
+group hosts using mask
+.P
+Examples:
+.TP
+# allow 2 telnet connections per client host
+iptables -p tcp --syn --dport 23 -m connlimit --connlimit-above 2 -j REJECT
+.TP
+# you can also match the other way around:
+iptables -p tcp --syn --dport 23 -m connlimit ! --connlimit-above 2 -j ACCEPT
+.TP
+# limit the nr of parallel http requests to 16 per class C sized \
+network (24 bit netmask)
+iptables -p tcp --syn --dport 80 -m connlimit --connlimit-above 16
+--connlimit-mask 24 -j REJECT
+.SS connmark
+This module matches the netfilter mark field associated with a connection
+(which can be set using the
+.B CONNMARK
+target below).
+.TP
+.BI "--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).
+.SS connrate
+This module matches the current transfer rate in a connection.
+.TP
+.BI "--connrate " "[!] [\fIfrom\fP]:[\fIto\fP]"
+Match against the current connection transfer rate being within 'from'
+and 'to' bytes per second. When the "!" argument is used before the
+range, the sense of the match is inverted.
+.SS conntrack
+This module, when combined with connection tracking, allows access to
+more connection tracking information than the "state" match.
+(this module is present only if iptables was compiled under a kernel
+supporting this feature)
+.TP
+.BI "--ctstate " "state"
+Where state is a comma separated list of the connection states to
+match. Possible states are
+.B INVALID
+meaning that the packet is associated with no known connection,
+.B ESTABLISHED
+meaning that the packet is associated with a connection which has seen
+packets in both directions,
+.B 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
+.B 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.
+.B SNAT
+A virtual state, matching if the original source address differs from
+the reply destination.
+.B DNAT
+A virtual state, matching if the original destination differs from the
+reply source.
+.TP
+.BI "--ctproto " "proto"
+Protocol to match (by number or name)
+.TP
+.BI "--ctorigsrc " "[!] \fIaddress\fP[/\fImask\fP]"
+Match against original source address
+.TP
+.BI "--ctorigdst " "[!] \fIaddress\fP[/\fImask\fP]"
+Match against original destination address
+.TP
+.BI "--ctreplsrc " "[!] \fIaddress\fP[/\fImask\fP]"
+Match against reply source address
+.TP
+.BI "--ctrepldst " "[!] \fIaddress\fB[/\fImask\fP]"
+Match against reply destination address
+.TP
+.BI "--ctstatus " "[\fINONE|EXPECTED|SEEN_REPLY|ASSURED\fP][,...]"
+Match against internal conntrack states
+.TP
+.BI "--ctexpire " "\fItime\fP[\fI:time\fP]"
+Match remaining lifetime in seconds against given value
+or range of values (inclusive)
+.SS dscp
+This module matches the 6 bit DSCP field within the TOS field in the
+IP header. DSCP has superseded TOS within the IETF.
+.TP
+.BI "--dscp " "value"
+Match against a numeric (decimal or hex) value [0-32].
+.TP
+.BI "--dscp-class " "\fIDiffServ Class\fP"
+Match the DiffServ class. This value may be any of the
+BE, EF, AFxx or CSx classes. It will then be converted
+into it's according numeric value.
+.SS dstlimit
+This module allows you to limit the packet per second (pps) rate on a per
+destination IP or per destination port base. As opposed to the `limit' match,
+every destination ip / destination port has it's own limit.
+.TP
+.BI "--dstlimit " "avg"
+Maximum average match rate (packets per second unless followed by /sec /minute /hour /day postfixes).
+.TP
+.BI "--dstlimit-mode " "mode"
+The limiting hashmode. Is the specified limit per
+.B dstip, dstip-dstport
+tuple,
+.B srcip-dstip
+tuple, or per
+.B srcipdstip-dstport
+tuple.
+.TP
+.BI "--dstlimit-name " "name"
+Name for /proc/net/ipt_dstlimit/* file entry
+.TP
+.BI "[" "--dstlimit-burst " "burst" "]"
+Number of packets to match in a burst. Default: 5
+.TP
+.BI "[" "--dstlimit-htable-size " "size" "]"
+Number of buckets in the hashtable
+.TP
+.BI "[" "--dstlimit-htable-max " "max" "]"
+Maximum number of entries in the hashtable
+.TP
+.BI "[" "--dstlimit-htable-gcinterval " "interval" "]"
+Interval between garbage collection runs of the hashtable (in miliseconds).
+Default is 1000 (1 second).
+.TP
+.BI "[" "--dstlimit-htable-expire " "time"
+After which time are idle entries expired from hashtable (in miliseconds)?
+Default is 10000 (10 seconds).
+.SS ecn
+This allows you to match the ECN bits of the IPv4 and TCP header. ECN is the Explicit Congestion Notification mechanism as specified in RFC3168
+.TP
+.BI "--ecn-tcp-cwr"
+This matches if the TCP ECN CWR (Congestion Window Received) bit is set.
+.TP
+.BI "--ecn-tcp-ece"
+This matches if the TCP ECN ECE (ECN Echo) bit is set.
+.TP
+.BI "--ecn-ip-ect " "num"
+This matches a particular IPv4 ECT (ECN-Capable Transport). You have to specify
+a number between `0' and `3'.
+.SS esp
+This module matches the SPIs in ESP header of IPSec packets.
+.TP
+.BR "--espspi " "[!] \fIspi\fP[:\fIspi\fP]"
+.SS fuzzy
+This module matches a rate limit based on a fuzzy logic controller [FLC]
+.TP
+.BI "--lower-limit "number"
+Specifies the lower limit (in packets per second).
+.TP
+.BI "--upper-limit " "number"
+Specifies the upper limit (in packets per second).
+.SS hashlimit
+This patch adds a new match called 'hashlimit'.
+The idea is to have something like 'limit', but either per
+destination-ip or per (destip,destport) tuple.
+
+It gives you the ability to express
+.IP
+ '1000 packets per second for every host in 192.168.0.0/16'
+.IP
+ '100 packets per second for every service of 192.168.1.1'
+.P
+with a single iptables rule.
+.TP
+.BI "--hashlimit " "rate"
+A rate just like the limit match
+.TP
+.BI "--hashlimit-burst " "num"
+Burst value, just like limit match
+.TP
+.BI "--hashlimit-mode " "destip | destip-destport"
+Limit per IP or per port
+.TP
+.BI "--hashlimit-name " "foo"
+The name for the /proc/net/ipt_hashlimit/foo entry
+.TP
+.BI "--hashlimit-htable-size " "num"
+The number of buckets of the hash table
+.TP
+.BI "--hashlimit-htable-max " "num"
+Maximum entries in the hash
+.TP
+.BI "--hashlimit-htable-expire " "num"
+After how many miliseconds do hash entries expire
+.TP
+.BI "--hashlimit-htable-gcinterval " "num"
+How many miliseconds between garbage collection intervals
+.SS helper
+This module matches packets related to a specific conntrack-helper.
+.TP
+.BI "--helper " "string"
+Matches packets related to the specified conntrack-helper.
+.RS
+.PP
+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".
+.PP
+Same rules apply for other conntrack-helpers.
+.RE
+.SS icmp
+This extension is loaded if `--protocol icmp' is specified. It
+provides the following option:
+.TP
+.BR "--icmp-type " "[!] \fItypename\fP"
+This allows specification of the ICMP type, which can be a numeric
+ICMP type, or one of the ICMP type names shown by the command
+.nf
+ iptables -p icmp -h
+.fi
+.SS iprange
+This matches on a given arbitrary range of IPv4 addresses
+.TP
+.BI "[!]" "--src-range " "ip-ip"
+Match source IP in the specified range.
+.TP
+.BI "[!]" "--dst-range " "ip-ip"
+Match destination IP in the specified range.
+.SS ipv4options
+Match on IPv4 header options like source routing, record route,
+timestamp and router-alert.
+.TP
+.B "--ssrr"
+To match packets with the flag strict source routing.
+.TP
+.B "--lsrr"
+To match packets with the flag loose source routing.
+.TP
+.B "--no-srr"
+To match packets with no flag for source routing.
+.TP
+.B "\fR[\fB!\fR]\fB --rr"
+To match packets with the RR flag.
+.TP
+.B "\fR[\fB!\fR]\fB --ts"
+To match packets with the TS flag.
+.TP
+.B "\fR[\fB!\fR]\fB --ra"
+To match packets with the router-alert option.
+.TP
+.B "\fR[\fB!\fR]\fB --any-opt"
+To match a packet with at least one IP option, or no IP option
+at all if ! is chosen.
+.TP
+Examples:
+.TP
+$ iptables -A input -m ipv4options --rr -j DROP
+will drop packets with the record-route flag.
+.TP
+$ iptables -A input -m ipv4options --ts -j DROP
+will drop packets with the timestamp flag.
+.SS length
+This module matches the length of a packet against a specific value
+or range of values.
+.TP
+.BR "--length " "\fIlength\fP[:\fIlength\fP]"
+.SS limit
+This module matches at a limited rate using a token bucket filter.
+A rule using this extension will match until this limit is reached
+(unless the `!' flag is used). It can be used in combination with the
+.B LOG
+target to give limited logging, for example.
+.TP
+.BI "--limit " "rate"
+Maximum average matching rate: specified as a number, with an optional
+`/second', `/minute', `/hour', or `/day' suffix; the default is
+3/hour.
+.TP
+.BI "--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.
+.SS mac
+.TP
+.BR "--mac-source " "[!] \fIaddress\fP"
+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
+.BR PREROUTING ,
+.B FORWARD
+or
+.B INPUT
+chains.
+.SS mark
+This module matches the netfilter mark field associated with a packet
+(which can be set using the
+.B MARK
+target below).
+.TP
+.BR "--mark " "\fIvalue\fP[/\fImask\fP]"
+Matches packets with the given unsigned mark value (if a mask is
+specified, this is logically ANDed with the mask before the
+comparison).
+.SS mport
+This module matches a set of source or destination ports. Up to 15
+ports can be specified. It can only be used in conjunction with
+.B "-p tcp"
+or
+.BR "-p udp" .
+.TP
+.BR "--source-ports " "\fIport\fP[,\fIport\fP[,\fIport\fP...]]"
+Match if the source port is one of the given ports. The flag
+.B --sports
+is a convenient alias for this option.
+.TP
+.BR "--destination-ports " "\fIport\fP[,\fIport\fP[,\fIport\fP...]]"
+Match if the destination port is one of the given ports. The flag
+.B --dports
+is a convenient alias for this option.
+.TP
+.BR "--ports " "\fIport\fP[,\fIport\fP[,\fIport\fP...]]"
+Match if the both the source and destination ports are equal to each
+other and to one of the given ports.
+.SS 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
+.B "-p tcp"
+or
+.BR "-p udp" .
+.TP
+.BR "--source-ports " "\fI[!] port\fP[,\fIport\fP[,\fIport:port\fP...]]"
+Match if the source port is one of the given ports. The flag
+.B --sports
+is a convenient alias for this option.
+.TP
+.BR "--destination-ports " "\fI[!] port\fP[,\fIport\fP[,\fIport:port\fP...]]"
+Match if the destination port is one of the given ports. The flag
+.B --dports
+is a convenient alias for this option.
+.TP
+.BR "--ports " "\fI[!] port\fP[,\fIport\fP[,\fIport:port\fP...]]"
+Match if either the source or destination ports are equal to one of
+the given ports.
+.SS nth
+This module matches every `n'th packet
+.TP
+.BI "--every " "value"
+Match every `value' packet
+.TP
+.BI "[" "--counter " "num" "]"
+Use internal counter number `num'. Default is `0'.
+.TP
+.BI "[" "--start " "num" "]"
+Initialize the counter at the number `num' insetad of `0'. Most between `0'
+and `value'-1.
+.TP
+.BI "[" "--packet " "num" "]"
+Match on `num' packet. Most be between `0' and `value'-1.
+.SS osf
+The idea of passive OS fingerprint matching exists for quite a long time,
+but was created as extension fo OpenBSD pf only some weeks ago.
+Original idea was lurked in some OpenBSD mailing list (thanks
+grange@open...) and than adopted for Linux netfilter in form of this code.
+
+Original fingerprint table was created by Michal Zalewski <lcamtuf@coredump.cx>.
+
+This module compares some data(WS, MSS, options and it's order, ttl,
+df and others) from first SYN packet (actually from packets with SYN
+bit set) with dynamically loaded OS fingerprints.
+.TP
+.B "--log 1/0"
+If present, OSF will log determined genres even if they don't match
+desired one.
+0 - log all determined entries,
+1 - only first one.
+
+In syslog you find something like this:
+.IP
+ipt_osf: Windows [2000:SP3:Windows XP Pro SP1, 2000 SP3]: 11.22.33.55:4024 -> 11.22.33.44:139
+.IP
+ipt_osf: Unknown: 16384:106:1:48:020405B401010402 44.33.22.11:1239 -> 11.22.33.44:80
+.TP
+.B "--smart"
+if present, OSF will use some smartness to determine remote OS.
+OSF will use initial TTL only if source of connection is in our local network.
+.TP
+.B "--netlink"
+If present, OSF will log all events also through netlink NETLINK_NFLOG groupt 1.
+.TP
+.BI "--genre " "[!] string"
+Match a OS genre by passive fingerprinting
+.P
+Example:
+
+#iptables -I INPUT -j ACCEPT -p tcp -m osf --genre Linux --log 1 --smart
+
+NOTE: -p tcp is obviously required as it is a TCP match.
+
+Fingerprints can be loaded and read through /proc/sys/net/ipv4/osf file.
+One can flush all fingerprints with following command:
+.IP
+echo -en FLUSH > /proc/sys/net/ipv4/osf
+.P
+Only one fingerprint per open/write/close.
+
+Fingerprints can be downloaded from http://www.openbsd.org/cgi-bin/cvsweb/src/etc/pf.os
+.SS owner
+This module attempts to match various characteristics of the packet
+creator, for locally-generated packets. It is only valid in the
+.B OUTPUT
+chain, and even this some packets (such as ICMP ping responses) may
+have no owner, and hence never match.
+.TP
+.BI "--uid-owner " "userid"
+Matches if the packet was created by a process with the given
+effective user id.
+.TP
+.BI "--gid-owner " "groupid"
+Matches if the packet was created by a process with the given
+effective group id.
+.TP
+.BI "--pid-owner " "processid"
+Matches if the packet was created by a process with the given
+process id.
+.TP
+.BI "--sid-owner " "sessionid"
+Matches if the packet was created by a process in the given session
+group.
+.TP
+.BI "--cmd-owner " "name"
+Matches if the packet was created by a process with the given command name.
+(this option is present only if iptables was compiled under a kernel
+supporting this feature)
+.TP
+.B NOTE: pid, sid and command matching are broken on SMP
+.SS 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.
+.TP
+.B --physdev-in name
+Name of a bridge port via which a packet is received (only for
+packets entering the
+.BR INPUT ,
+.B FORWARD
+and
+.B 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.
+.TP
+.B --physdev-out name
+Name of a bridge port via which a packet is going to be sent (for packets
+entering the
+.BR FORWARD ,
+.B OUTPUT
+and
+.B POSTROUTING
+chains). If the interface name ends in a "+", then any
+interface which begins with this name will match. Note that in the
+.BR nat " and " mangle
+.B OUTPUT
+chains one cannot match on the bridge output port, however one can in the
+.B "filter OUTPUT"
+chain. If the packet won't leave by a bridge device or it is yet unknown what
+the output device will be, then the packet won't match this option, unless
+'!' is used.
+.TP
+.B --physdev-is-in
+Matches if the packet has entered through a bridge interface.
+.TP
+.B --physdev-is-out
+Matches if the packet will leave through a bridge interface.
+.TP
+.B --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.
+.SS pkttype
+This module matches the link-layer packet type.
+.TP
+.BI "--pkt-type " "[\fIunicast\fP|\fIbroadcast\fP|\fImulticast\fP]"
+.SS psd
+Attempt to detect TCP and UDP port scans. This match was derived from
+Solar Designer's scanlogd.
+.TP
+.BI "--psd-weight-threshold " "threshold"
+Total weight of the latest TCP/UDP packets with different
+destination ports coming from the same host to be treated as port
+scan sequence.
+.TP
+.BI "--psd-delay-threshold " "delay"
+Delay (in hundredths of second) for the packets with different
+destination ports coming from the same host to be treated as
+possible port scan subsequence.
+.TP
+.BI "--psd-lo-ports-weight " "weight"
+Weight of the packet with privileged (<=1024) destination port.
+.TP
+.BI "--psd-hi-ports-weight " "weight"
+Weight of the packet with non-priviliged destination port.
+.SS quota
+Implements network quotas by decrementing a byte counter with each
+packet.
+.TP
+.BI "--quota " "bytes"
+The quota in bytes.
+.P
+KNOWN BUGS: this does not work on SMP systems.
+.SS random
+This module randomly matches a certain percentage of all packets.
+.TP
+.BI "--average " "percent"
+Matches the given percentage. If omitted, a probability of 50% is set.
+.SS realm
+This matches the routing realm. Routing realms are used in complex routing
+setups involving dynamic routing protocols like BGP.
+.TP
+.BI "--realm " "[!]" "value[/mask]"
+Matches a given realm number (and optionally mask).
+.SS 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.
+.TP
+.BI "--name " "name"
+Specify the list to use for the commands. If no name is given then 'DEFAULT'
+will be used.
+.TP
+[\fB!\fR] \fB--set\fR
+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).
+.TP
+[\fB!\fR] \fB--rcheck\fR
+Check if the source address of the packet is currently in
+the list.
+.TP
+[\fB!\fR] \fB--update\fR
+Like \fB--rcheck\fR, except it will update the "last seen" timestamp if it
+matches.
+.TP
+[\fB!\fR] \fB--remove\fR
+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.
+.TP
+[\fB!\fR] \fB--seconds \fIseconds\fR
+This option must be used in conjunction with one of \fB--rcheck\fR or
+\fB--update\fR. 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.
+.TP
+[\fB!\fR] \fB--hitcount \fIhits\fR
+This option must be used in conjunction with one of \fB--rcheck\fR or
+\fB--update\fR. 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
+\fB--seconds\fR to create an even narrower match requiring a certain
+number of hits within a specific time frame.
+.TP
+\fB--rttl\fR
+This option must be used in conjunction with one of \fB--rcheck\fR or
+\fB--update\fR. 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 \fB--set\fR 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.
+.P
+Examples:
+.IP
+# 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
+.P
+Official website (http://snowman.net/projects/ipt_recent/) also has
+some examples of usage.
+
+/proc/net/ipt_recent/* are the current lists of addresses and information
+about each entry of each list.
+
+Each file in /proc/net/ipt_recent/ can be read from to see the current list
+or written two using the following commands to modify the list:
+.TP
+echo xx.xx.xx.xx > /proc/net/ipt_recent/DEFAULT
+to Add to the DEFAULT list
+.TP
+echo -xx.xx.xx.xx > /proc/net/ipt_recent/DEFAULT
+to Remove from the DEFAULT list
+.TP
+echo clear > /proc/net/ipt_recent/DEFAULT
+to empty the DEFAULT list.
+.P
+The module itself accepts parameters, defaults shown:
+.TP
+.BI "ip_list_tot=" "100"
+Number of addresses remembered per table
+.TP
+.BI "ip_pkt_list_tot=" "20"
+Number of packets per address remembered
+.TP
+.BI "ip_list_hash_size=" "0"
+Hash table size. 0 means to calculate it based on ip_list_tot, default: 512
+.TP
+.BI "ip_list_perms=" "0644"
+Permissions for /proc/net/ipt_recent/* files
+.TP
+.BI "debug=" "0"
+Set to 1 to get lots of debugging info
+.SS sctp
+.TP
+\fB--source-port\fR,\fB--sport \fR[\fB!\fR] \fIport\fR[\fB:\fIport\fR]
+.TP
+\fB--destination-port\fR,\fB--dport \fR[\fB!\fR] \fIport\fR[\fB:\fIport\fR]
+.TP
+\fB--chunk-types\fR [\fB!\fR] \fBall\fR|\fBany\fR|\fBonly \fIchunktype\fR[\fB:\fIflags\fR] [...]
+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
+
+chunk type available flags
+.br
+DATA U B E u b e
+.br
+ABORT T t
+.br
+SHUTDOWN_COMPLETE T t
+
+(lowercase means flag should be "off", uppercase means "on")
+.P
+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
+.SS set
+This modules macthes IP sets which can be defined by ipset(8).
+.TP
+.BR "--set " "setname flag[,flag...]"
+where flags are
+.BR "src"
+and/or
+.BR "dst"
+and there can be no more than six of them. Hence the command
+.nf
+ iptables -A FORWARD -m set --set test src,dst
+.fi
+will match packets, for which (depending on the type of the set) the source
+address or port number of the packet can be found in the specified set. If
+there is a binding belonging to the mached set element or there is a default
+binding for the given set, then the rule will match the packet only if
+additionally (depending on the type of the set) the destination address or
+port number of the packet can be found in the set according to the binding.
+.SS state
+This module, when combined with connection tracking, allows access to
+the connection tracking state for this packet.
+.TP
+.BI "--state " "state"
+Where state is a comma separated list of the connection states to
+match. Possible states are
+.B 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,
+.B ESTABLISHED
+meaning that the packet is associated with a connection which has seen
+packets in both directions,
+.B 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
+.B 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.
+.SS tcp
+These extensions are loaded if `--protocol tcp' is specified. It
+provides the following options:
+.TP
+.BR "--source-port " "[!] \fIport\fP[:\fIport\fP]"
+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
+.IR port : port .
+If the first port is omitted, "0" is assumed; if the last is omitted,
+"65535" is assumed.
+If the second port greater then the first they will be swapped.
+The flag
+.B --sport
+is a convenient alias for this option.
+.TP
+.BR "--destination-port " "[!] \fIport\fP[:\fIport\fP]"
+Destination port or port range specification. The flag
+.B --dport
+is a convenient alias for this option.
+.TP
+.BR "--tcp-flags " "[!] \fImask\fP \fIcomp\fP"
+Match when the TCP flags are as specified. The first argument is the
+flags which we should examine, written as a comma-separated list, and
+the second argument is a comma-separated list of flags which must be
+set. Flags are:
+.BR "SYN ACK FIN RST URG PSH ALL NONE" .
+Hence the command
+.nf
+ iptables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST SYN
+.fi
+will only match packets with the SYN flag set, and the ACK, FIN and
+RST flags unset.
+.TP
+.B "[!] --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 \fB--tcp-flags SYN,RST,ACK,FIN SYN\fP.
+If the "!" flag precedes the "--syn", the sense of the
+option is inverted.
+.TP
+.BR "--tcp-option " "[!] \fInumber\fP"
+Match if TCP option set.
+.TP
+.BR "--mss " "\fIvalue\fP[:\fIvalue\fP]"
+Match TCP SYN or SYN/ACK packets with the specified MSS value (or range),
+which control the maximum packet size for that connection.
+.SS 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.
+.TP
+.BI "[!] "--mss " "value[:value]"
+Match a given TCP MSS value or range.
+.SS time
+This matches if the packet arrival time/date is within a given range. All options are facultative.
+.TP
+.BI " --timestart " "value"
+Match only if it is after `value' (Inclusive, format: HH:MM ; default 00:00).
+.TP
+.BI "--timestop " "value"
+Match only if it is before `value' (Inclusive, format: HH:MM ; default 23:59).
+.TP
+.BI "--days " "listofdays"
+Match only if today is one of the given days. (format: Mon,Tue,Wed,Thu,Fri,Sat,Sun ; default everyday)
+.TP
+.BI "--datestart " "date"
+Match only if it is after `date' (Inclusive, format: YYYY[:MM[:DD[:hh[:mm[:ss]]]]] ; h,m,s start from 0 ; default to 1970)
+.TP
+.BI "--datestop " "date"
+Match only if it is before `date' (Inclusive, format: YYYY[:MM[:DD[:hh[:mm[:ss]]]]] ; h,m,s start from 0 ; default to 2037)
+.SS tos
+This module matches the 8 bits of Type of Service field in the IP
+header (ie. including the precedence bits).
+.TP
+.BI "--tos " "tos"
+The argument is either a standard name, (use
+.br
+ iptables -m tos -h
+.br
+to see the list), or a numeric value to match.
+.SS ttl
+This module matches the time to live field in the IP header.
+.TP
+.BI "--ttl-eq " "ttl"
+Matches the given TTL value.
+.TP
+.BI "--ttl-gt " "ttl"
+Matches if TTL is greater than the given TTL value.
+.TP
+.BI "--ttl-lt " "ttl"
+Matches if TTL is less than the given TTL value.
+.SS u32
+U32 allows you to extract quantities of up to 4 bytes from a packet,
+AND them with specified masks, shift them by specified amounts and
+test whether the results are in any of a set of specified ranges.
+The specification of what to extract is general enough to skip over
+headers with lengths stored in the packet, as in IP or TCP header
+lengths.
+
+Details and examples are in the kernel module source.
+.SS udp
+These extensions are loaded if `--protocol udp' is specified. It
+provides the following options:
+.TP
+.BR "--source-port " "[!] \fIport\fP[:\fIport\fP]"
+Source port or port range specification.
+See the description of the
+.B --source-port
+option of the TCP extension for details.
+.TP
+.BR "--destination-port " "[!] \fIport\fP[:\fIport\fP]"
+Destination port or port range specification.
+See the description of the
+.B --destination-port
+option of the TCP extension for details.
+.SS unclean
+This module takes no options, but attempts to match packets which seem
+malformed or unusual. This is regarded as experimental.
+.SH TARGET EXTENSIONS
+iptables can use extended target modules: the following are included
+in the standard distribution.
+.\" @TARGET@
+.SS BALANCE
+This allows you to DNAT connections in a round-robin way over a given range of destination addresses.
+.TP
+.BI "--to-destination " "ipaddr-ipaddr"
+Address range to round-robin over.
+.SS CLASSIFY
+This module allows you to set the skb->priority value (and thus classify the packet into a specific CBQ class).
+.TP
+.BI "--set-class " "MAJOR:MINOR"
+Set the major and minor class value.
+.SS CLUSTERIP
+This module allows you to configure a simple cluster of nodes that share
+a certain IP and MAC address without an explicit load balancer in front of
+them. Connections are statically distributed between the nodes in this
+cluster.
+.TP
+.BI "--new "
+Create a new ClusterIP. You always have to set this on the first rule
+for a given ClusterIP.
+.TP
+.BI "--hashmode " "mode"
+Specify the hashing mode. Has to be one of
+.B sourceip, sourceip-sourceport, sourceip-sourceport-destport
+.TP
+.BI "--clustermac " "mac"
+Specify the ClusterIP MAC address. Has to be a link-layer multicast address
+.TP
+.BI "--total-nodes " "num"
+Number of total nodes within this cluster.
+.TP
+.BI "--local-node " "num"
+Local node number within this cluster.
+.TP
+.BI "--hash-init " "rnd"
+Specify the random seed used for hash initialization.
+.SS CONNMARK
+This module sets the netfilter mark value associated with a connection
+.TP
+.B --set-mark mark[/mask]
+Set connection mark. If a mask is specified then only those bits set in the
+mask is modified.
+.TP
+.B --save-mark [--mask mask]
+Copy the netfilter packet mark value to the connection mark. If a mask
+is specified then only those bits are copied.
+.TP
+.B --restore-mark [--mask mask]
+Copy the connection mark value to the packet. If a mask is specified
+then only those bits are copied. This is only valid in the
+.B mangle
+table.
+.SS DNAT
+This target is only valid in the
+.B nat
+table, in the
+.B PREROUTING
+and
+.B OUTPUT
+chains, and user-defined chains which are only called from those
+chains. It specifies that the destination address of the packet
+should be modified (and all future packets in this connection will
+also be mangled), and rules should cease being examined. It takes one
+type of option:
+.TP
+.BR "--to-destination " "\fIipaddr\fP[-\fIipaddr\fP][:\fIport\fP-\fIport\fP]"
+which can specify a single new destination IP address, an inclusive
+range of IP addresses, and optionally, a port range (which is only
+valid if the rule also specifies
+.B "-p tcp"
+or
+.BR "-p udp" ).
+If no port range is specified, then the destination port will never be
+modified.
+.RS
+.PP
+You can add several --to-destination options. If you specify more
+than one destination address, either via an address range or multiple
+--to-destination options, a simple round-robin (one after another in
+cycle) load balancing takes place between these adresses.
+.SS 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.
+.TP
+.BI "--set-dscp " "value"
+Set the DSCP field to a numerical value (can be decimal or hex)
+.TP
+.BI "--set-dscp-class " "class"
+Set the DSCP field to a DiffServ class.
+.SS ECN
+This target allows to selectively work around known ECN blackholes.
+It can only be used in the mangle table.
+.TP
+.BI "--ecn-tcp-remove"
+Remove all ECN bits from the TCP header. Of course, it can only be used
+in conjunction with
+.BR "-p tcp" .
+.SS IPMARK
+Allows you to mark a received packet basing on its IP address. This
+can replace many mangle/mark entries with only one, if you use
+firewall based classifier.
+
+This target is to be used inside the mangle table, in the PREROUTING,
+POSTROUTING or FORWARD hooks.
+.TP
+.BI "--addr " "src/dst"
+Use source or destination IP address.
+.TP
+.BI "--and-mask " "mask"
+Perform bitwise `and' on the IP address and this mask.
+.TP
+.BI "--or-mask " "mask"
+Perform bitwise `or' on the IP address and this mask.
+.P
+The order of IP address bytes is reversed to meet "human order of bytes":
+192.168.0.1 is 0xc0a80001. At first the `and' operation is performed, then
+`or'.
+
+Examples:
+
+We create a queue for each user, the queue number is adequate
+to the IP address of the user, e.g.: all packets going to/from 192.168.5.2
+are directed to 1:0502 queue, 192.168.5.12 -> 1:050c etc.
+
+We have one classifier rule:
+.IP
+tc filter add dev eth3 parent 1:0 protocol ip fw
+.P
+Earlier we had many rules just like below:
+.IP
+iptables -t mangle -A POSTROUTING -o eth3 -d 192.168.5.2 -j MARK
+--set-mark 0x10502
+.IP
+iptables -t mangle -A POSTROUTING -o eth3 -d 192.168.5.3 -j MARK
+--set-mark 0x10503
+.P
+Using IPMARK target we can replace all the mangle/mark rules with only one:
+.IP
+iptables -t mangle -A POSTROUTING -o eth3 -j IPMARK --addr=dst
+--and-mask=0xffff --or-mask=0x10000
+.P
+On the routers with hundreds of users there should be significant load
+decrease (e.g. twice).
+.SS IPV4OPTSSTRIP
+Strip all the IP options from a packet.
+
+The target doesn't take any option, and therefore is extremly easy to use :
+
+# iptables -t mangle -A PREROUTING -j IPV4OPTSSTRIP
+.SS 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 IP header fields) via the kernel log
+(where it can be read with
+.I dmesg
+or
+.IR 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).
+.TP
+.BI "--log-level " "level"
+Level of logging (numeric or see \fIsyslog.conf\fP(5)).
+.TP
+.BI "--log-prefix " "prefix"
+Prefix log messages with the specified prefix; up to 29 letters long,
+and useful for distinguishing messages in the logs.
+.TP
+.B --log-tcp-sequence
+Log TCP sequence numbers. This is a security risk if the log is
+readable by users.
+.TP
+.B --log-tcp-options
+Log options from the TCP packet header.
+.TP
+.B --log-ip-options
+Log options from the IP packet header.
+.TP
+.B --log-uid
+Log the userid of the process which generated the packet.
+.SS MARK
+This is used to set the netfilter mark value associated with the
+packet. It is only valid in the
+.B mangle
+table. It can for example be used in conjunction with iproute2.
+.TP
+.BI "--set-mark " "mark"
+.SS MASQUERADE
+This target is only valid in the
+.B nat
+table, in the
+.B POSTROUTING
+chain. It should only be used with dynamically assigned IP (dialup)
+connections: if you have a static IP address, you should use the SNAT
+target. Masquerading is equivalent to specifying a mapping to the IP
+address of the interface the packet is going out, but also has the
+effect that connections are
+.I forgotten
+when the interface goes down. This is the correct behavior when the
+next dialup is unlikely to have the same interface address (and hence
+any established connections are lost anyway). It takes one option:
+.TP
+.BR "--to-ports " "\fIport\fP[-\fIport\fP]"
+This specifies a range of source ports to use, overriding the default
+.B SNAT
+source port-selection heuristics (see above). This is only valid
+if the rule also specifies
+.B "-p tcp"
+or
+.BR "-p udp" .
+.SS MIRROR
+This is an experimental demonstration target which inverts the source
+and destination fields in the IP header and retransmits the packet.
+It is only valid in the
+.BR INPUT ,
+.B FORWARD
+and
+.B PREROUTING
+chains, and user-defined chains which are only called from those
+chains. Note that the outgoing packets are
+.B NOT
+seen by any packet filtering chains, connection tracking or NAT, to
+avoid loops and other problems.
+.SS NETMAP
+This target allows you to statically map a whole network of addresses onto
+another network of addresses. It can only be used from rules in the
+.B nat
+table.
+.TP
+.BI "--to " "address[/mask]"
+Network address to map to. The resulting address will be constructed in the
+following way: All 'one' bits in the mask are filled in from the new `address'.
+All bits that are zero in the mask are filled in from the original address.
+.SS NOTRACK
+This target disables connection tracking for all packets matching that rule.
+.TP
+It can only be used in the
+.B raw
+table.
+.SS REDIRECT
+This target is only valid in the
+.B nat
+table, in the
+.B PREROUTING
+and
+.B OUTPUT
+chains, and user-defined chains which are only called from those
+chains. It redirects the packet to the machine itself by changing the
+destination IP to the primary address of the incoming interface
+(locally-generated packets are mapped to the 127.0.0.1 address). It
+takes one option:
+.TP
+.BR "--to-ports " "\fIport\fP[-\fIport\fP]"
+This specifies a destination port or range of ports to use: without
+this, the destination port is never altered. This is only valid
+if the rule also specifies
+.B "-p tcp"
+or
+.BR "-p udp" .
+.SS REJECT
+This is used to send back an error packet in response to the matched
+packet: otherwise it is equivalent to
+.B DROP
+so it is a terminating TARGET, ending rule traversal.
+This target is only valid in the
+.BR INPUT ,
+.B FORWARD
+and
+.B OUTPUT
+chains, and user-defined chains which are only called from those
+chains. The following option controls the nature of the error packet
+returned:
+.TP
+.BI "--reject-with " "type"
+The type given can be
+.nf
+.B " icmp-net-unreachable"
+.B " icmp-host-unreachable"
+.B " icmp-port-unreachable"
+.B " icmp-proto-unreachable"
+.B " icmp-net-prohibited"
+.B " icmp-host-prohibited or"
+.B " icmp-admin-prohibited (*)"
+.fi
+which return the appropriate ICMP error message (\fBport-unreachable\fP is
+the default). The option
+.B 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
+.I ident
+(113/tcp) probes which frequently occur when sending mail to broken mail
+hosts (which won't accept your mail otherwise).
+.TP
+(*) Using icmp-admin-prohibited with kernels that do not support it will result in a plain DROP instead of REJECT
+.SS ROUTE
+This is used to explicitly override the core network stack's routing decision.
+.B mangle
+table.
+.TP
+.BI "--oif " "ifname"
+Route the packet through `ifname' network interface
+.TP
+.BI "--iif " "ifname"
+Change the packet's incoming interface to `ifname'
+.TP
+.BI "--gw " "IP_address"
+Route the packet via this gateway
+.TP
+.BI "--continue "
+Behave like a non-terminating target and continue traversing the rules. Not valid in combination with `--iif' or `--tee'
+.TP
+.BI "--tee "
+Make a copy of the packet, and route that copy to the given destination. For the original, uncopied packet, behave like a non-terminating target and continue traversing the rules. Not valid in combination with `--iif' or `--continue'
+.SS SAME
+Similar to SNAT/DNAT depending on chain: it takes a range of addresses
+(`--to 1.2.3.4-1.2.3.7') and gives a client the same
+source-/destination-address for each connection.
+.TP
+.BI "--to " "<ipaddr>-<ipaddr>"
+Addresses to map source to. May be specified more than once for
+multiple ranges.
+.TP
+.B "--nodst"
+Don't use the destination-ip in the calculations when selecting the
+new source-ip
+.SS SET
+This modules adds and/or deletes entries from IP sets which can be defined
+by ipset(8).
+.TP
+.BR "--add-set " "setname flag[,flag...]"
+add the address(es)/port(s) of the packet to the sets
+.TP
+.BR "--del-set " "setname flag[,flag...]"
+delete the address(es)/port(s) of the packet from the sets,
+where flags are
+.BR "src"
+and/or
+.BR "dst"
+and there can be no more than six of them.
+.TP
+The bindings to follow must previously be defined in order to use
+multilevel adding/deleting by the SET target.
+.SS SNAT
+This target is only valid in the
+.B nat
+table, in the
+.B POSTROUTING
+chain. It specifies that the source address of the packet should be
+modified (and all future packets in this connection will also be
+mangled), and rules should cease being examined. It takes one type
+of option:
+.TP
+.BR "--to-source " "\fIipaddr\fP[-\fIipaddr\fP][:\fIport\fP-\fIport\fP]"
+which can specify a single new source IP address, an inclusive range
+of IP addresses, and optionally, a port range (which is only valid if
+the rule also specifies
+.B "-p tcp"
+or
+.BR "-p udp" ).
+If no port range is specified, then source ports below 512 will be
+mapped to other ports below 512: those between 512 and 1023 inclusive
+will be mapped to ports below 1024, and other ports will be mapped to
+1024 or above. Where possible, no port alteration will occur.
+.RS
+.PP
+You can add several --to-source options. If you specify more
+than one source address, either via an address range or multiple
+--to-source options, a simple round-robin (one after another in
+cycle) takes place between these adresses.
+.SS TARPIT
+Captures and holds incoming TCP connections using no local
+per-connection resources. Connections are accepted, but immediately
+switched to the persist state (0 byte window), in which the remote
+side stops sending data and asks to continue every 60-240 seconds.
+Attempts to close the connection are ignored, forcing the remote side
+to time out the connection in 12-24 minutes.
+
+This offers similar functionality to LaBrea
+<http://www.hackbusters.net/LaBrea/> but doesn't require dedicated
+hardware or IPs. Any TCP port that you would normally DROP or REJECT
+can instead become a tarpit.
+
+To tarpit connections to TCP port 80 destined for the current machine:
+.IP
+iptables -A INPUT -p tcp -m tcp --dport 80 -j TARPIT
+.P
+To significantly slow down Code Red/Nimda-style scans of unused address
+space, forward unused ip addresses to a Linux box not acting as a router
+(e.g. "ip route 10.0.0.0 255.0.0.0 ip.of.linux.box" on a Cisco), enable IP
+forwarding on the Linux box, and add:
+.IP
+iptables -A FORWARD -p tcp -j TARPIT
+.IP
+iptables -A FORWARD -j DROP
+.TP
+NOTE:
+If you use the conntrack module while you are using TARPIT, you should
+also use the NOTRACK target, or the kernel will unnecessarily allocate
+resources for each TARPITted connection. To TARPIT incoming
+connections to the standard IRC port while using conntrack, you could:
+.IP
+iptables -t raw -A PREROUTING -p tcp --dport 6667 -j NOTRACK
+.IP
+iptables -A INPUT -p tcp --dport 6667 -j TARPIT
+.SS 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). Of course, it can only be used
+in conjunction with
+.BR "-p tcp" .
+.br
+This target is used to overcome criminally braindead ISPs or servers
+which block ICMP Fragmentation Needed 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:
+.PD 0
+.RS 0.1i
+.TP 0.3i
+1)
+Web browsers connect, then hang with no data received.
+.TP
+2)
+Small mail works fine, but large emails hang.
+.TP
+3)
+ssh works fine, but scp hangs after initial handshaking.
+.RE
+.PD
+Workaround: activate this option and add a rule to your firewall
+configuration like:
+.nf
+ iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN \\
+ -j TCPMSS --clamp-mss-to-pmtu
+.fi
+.TP
+.BI "--set-mss " "value"
+Explicitly set MSS option to specified value.
+.TP
+.B "--clamp-mss-to-pmtu"
+Automatically clamp MSS value to (path_MTU - 40).
+.TP
+These options are mutually exclusive.
+.SS TOS
+This is used to set the 8-bit Type of Service field in the IP header.
+It is only valid in the
+.B mangle
+table.
+.TP
+.BI "--set-tos " "tos"
+You can use a numeric TOS values, or use
+.nf
+ iptables -j TOS -h
+.fi
+to see the list of valid TOS names.
+.SS TRACE
+This target has no options. It just turns on
+.B packet tracing
+for all packets that match this rule.
+.SS TTL
+This is used to modify the IPv4 TTL header field. The TTL field determines
+how many hops (routers) a packet can traverse until it's time to live is
+exceeded.
+.TP
+Setting or incrementing the TTL field can potentially be very dangerous,
+so it should be avoided at any cost.
+.TP
+.B Don't ever set or increment the value on packets that leave your local network!
+.B mangle
+table.
+.TP
+.BI "--ttl-set " "value"
+Set the TTL value to `value'.
+.TP
+.BI "--ttl-dec " "value"
+Decrement the TTL value `value' times.
+.TP
+.BI "--ttl-inc " "value"
+Increment the TTL value `value' times.
+.SS ULOG
+This target provides userspace logging of matching packets. When this
+target is set for a rule, the Linux kernel will multicast this packet
+through a
+.IR netlink
+socket. One or more userspace processes may then subscribe to various
+multicast groups and receive the packets.
+Like LOG, this is a "non-terminating target", i.e. rule traversal
+continues at the next rule.
+.TP
+.BI "--ulog-nlgroup " "nlgroup"
+This specifies the netlink group (1-32) to which the packet is sent.
+Default value is 1.
+.TP
+.BI "--ulog-prefix " "prefix"
+Prefix log messages with the specified prefix; up to 32 characters
+long, and useful for distinguishing messages in the logs.
+.TP
+.BI "--ulog-cprange " "size"
+Number of bytes to be copied to userspace. A value of 0 always copies
+the entire packet, regardless of its size. Default is 0.
+.TP
+.BI "--ulog-qthreshold " "size"
+Number of packet to queue inside kernel. Setting this value to, e.g. 10
+accumulates ten packets inside the kernel and transmits them as one
+netlink multipart message to userspace. Default is 1 (for backwards
+compatibility).
+.br
+.SS XOR
+Encrypt TCP and UDP traffic using a simple XOR encryption
+.TP
+.BI "--key " "string"
+Set key to "string"
+.TP
+.BI "--block-size"
+Set block size
+.SH 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.
+.SH BUGS
+Bugs? What's this? ;-)
+Well, you might want to have a look at http://bugzilla.netfilter.org/
+.SH COMPATIBILITY WITH IPCHAINS
+This
+.B iptables
+is very similar to ipchains by Rusty Russell. The main difference is
+that the chains
+.B INPUT
+and
+.B 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.
+.PP
+The other main difference is that
+.B -i
+refers to the input interface;
+.B -o
+refers to the output interface, and both are available for packets
+entering the
+.B FORWARD
+chain.
+.PP The various forms of NAT have been separated out;
+.B iptables
+is a pure packet filter when using the default `filter' table, with
+optional extension modules. This should simplify much of the previous
+confusion over the combination of IP masquerading and packet filtering
+seen previously. So the following options are handled differently:
+.nf
+ -j MASQ
+ -M -S
+ -M -L
+.fi
+There are several other changes in iptables.
+.SH SEE ALSO
+.BR iptables-save (8),
+.BR iptables-restore (8),
+.BR ip6tables (8),
+.BR ip6tables-save (8),
+.BR ip6tables-restore (8).
+.P
+The packet-filtering-HOWTO details iptables usage for
+packet filtering, the NAT-HOWTO details NAT,
+the netfilter-extensions-HOWTO details the extensions that are
+not in the standard distribution,
+and the netfilter-hacking-HOWTO details the netfilter internals.
+.br
+See
+.BR "http://www.netfilter.org/" .
+.SH AUTHORS
+Rusty Russell wrote iptables, in early consultation with Michael
+Neuling.
+.PP
+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.
+.PP
+James Morris wrote the TOS target, and tos match.
+.PP
+Jozsef Kadlecsik wrote the REJECT target.
+.PP
+Harald Welte wrote the ULOG target, TTL, DSCP, ECN matches and targets.
+.PP
+The Netfilter Core Team is: Marc Boucher, Martin Josefsson, Jozsef Kadlecsik,
+Patrick McHardy, James Morris, Harald Welte and Rusty Russell.
+.PP
+Man page written by Herve Eychenne <rv@wallfire.org>.
+.\" .. and did I mention that we are incredibly cool people?
+.\" .. sexy, too ..
+.\" .. witty, charming, powerful ..
+.\" .. and most of all, modest ..
git://git.onelab.eu / iptables.git / blobdiff