可不是原創文章,沒辦法,找不到合適的標題項!

Generated by iptables-save v1.3.5 on Fri Mar 31 18:52:44 2006
man iptables |col -b >iptables.txt

得到的說明方法,呵呵,可以以TXT的格式看,沒有了亂碼,覺得不錯,相當不錯,貼出來共享下,好好學學啦!
感謝我同事,小沈對此獲取方法的提供!!
這年頭,要看英文的說明啦!!


IPTABLES(8)??????????IPTABLES(8)

NAME
?????? iptables - administration tool for IPv4 packet filtering and NAT
SYNOPSIS
?????? iptables [-t table] -[AD] chain rule-specification [options]
?????? iptables [-t table] -I chain [rulenum] rule-specification [options]
?????? iptables [-t table] -R chain rulenum rule-specification [options]
?????? iptables [-t table] -D chain rulenum [options]
?????? iptables [-t table] -[LFZ] [chain] [options]
?????? iptables [-t table] -N chain
?????? iptables [-t table] -X [chain]
?????? iptables [-t table] -P chain target [options]
?????? iptables [-t table] -E old-chain-name new-chain-name
DESCRIPTION
?????? 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??ta-
?????? ble.

TARGETS
?????? A??firewall rule specifies criteria for a packet, and a target. If the
?????? packet does not match, the next rule in the chain is the??examined;??if
?????? it does match, then the next rule is specified by the value of the tar-
?????? get, which can be the name of a user-defined chain or one of??the??spe-
?????? cial values ACCEPT, Drop, QUEUE, or RETURN.
?????? ACCEPT??means to let the packet through.??Drop means to drop the packet
?????? on the floor.??QUEUE means to pass the packet to userspace.?? (How??the
?????? packet can be received by a userspace process differs by the particular
?????? queue handler.??2.4.x and??2.6.x??kernels??up??to??2.6.13??include??the
?????? ip_queue??queue handler.??Kernels 2.6.14 and later additionally include
?????? the nfnetlink_queue queue handler.??Packets with a target of QUEUE will
?????? be??sent??to queue number '0' in this case. Please also see the NFQUEUE
?????? target as described??later??in??this??man??page.)?? RETURN??means??stop
?????? traversing??this??chain and??resume??at??the next rule in the previous
?????? (calling) chain.??If the end of a built-in chain is reached or??a??rule
?????? in a built-in chain with target RETURN is matched, the target specified
?????? by the chain policy determines the fate of the packet.
TABLES
?????? There are currently three independent tables (which tables are??present
?????? at??any time depends on the kernel configuration options and which mod-
?????? ules are present).
?????? -t, --table table
?????? This option specifies the packet matching table which??the??com-
?????? mand??should operate on. If the kernel is configured with auto-
?????? matic module loading, an attempt will be made to load the appro-
?????? priate 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).
?????? nat:
????This table is consulted when a packet??that??creates a??new
????connection??is encountered.??It consists of three built-ins:
????PREROUTING (for altering packets as soon as they??come??in),
????OUTPUT??(for altering locally-generated packets before rout-
????ing), and POSTROUTING (for??altering packets??as??they??are
????about to go out).
?????? mangle:
????This table is used for specialized packet alteration.??Until
????kernel 2.4.17 it had two built-in??chains:??PREROUTING??(for
????altering??incoming??packets??before routing) and OUTPUT (for
????altering locally-generated packets before??routing).??Since
????kernel??2.4.18,??three??other??built-in chains are also sup-
????ported: INPUT (for packets coming into the box itself), FOR-
????WARD (for??altering packets being routed through the box),
????and POSTROUTING (for altering packets as they are??about??to
????go out).
?????? raw:
????This table??is??used mainly for configuring exemptions from
????connection tracking in combination with the NOTRACK??target.
????It registers at the netfilter hooks with higher priority and
????is thus called before ip_conntrack, or any other IP??tables.
????It??provides the following built-in chains: PREROUTING (for
????packets arriving via any??network??interface)??OUTPUT??(for
????packets generated by local processes)
OPTIONS
?????? The options that are recognized by iptables 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 iptables can differentiate it
?????? from all other options.
?????? -A, --append chain rule-specification
?????? Append one or more rules to the end of the selected chain.??When
?????? the??source??and/or??destination names resolve to more than one
?????? address, a rule will be added for each possible address combina-
?????? tion.
?????? -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 des-
?????? tination names resolve to multiple addresses, the??command??will
?????? fail.??Rules are numbered starting at 1.
?????? -L, --list [chain]
?????? List??all rules in the selected chain.??If no chain is selected,
?????? all chains are listed.??As??every??other iptables??command,??it
?????? applies??to??the specified table (filter is the default), so NAT
?????? rules get listed by
????????iptables -t nat -n -L
?????? Please note that it is often used with the -n option,??in??order
?????? to??avoid??long reverse DNS lookups.??It is legal to specify the
?????? -Z (zero) option as well, in which case??the??chain(s)??will??be
?????? atomically??listed??and zeroed.??The exact output is affected by
?????? the other arguments given. The exact rules are suppressed??until
?????? you use
????????iptables -L -v
?????? -F, --flush [chain]
?????? Flush the selected chain (all the chains in the table if none is
?????? given).??This is equivalent to deleting all??the rules??one??by
?????? one.
?????? -Z, --zero [chain]
?????? Zero the packet and byte counters in all chains. It is legal to
?????? specify the -L, --list (list) option as well, to see??the??coun-
?????? ters immediately before they are cleared. (See above.)
?????? -N, --new-chain chain
?????? Create??a??new user-defined chain by the given name.??There must
?????? be no target of that name already.
?????? -X, --delete-chain [chain]
?????? Delete the optional user-defined chain specified.??There must be
?????? no??references??to??the chain.??If there are, you must delete or
?????? replace the referring rules before the??chain??can??be??deleted.
?????? The??chain??must be??empty,??i.e. not contain any rules.??If no
?????? 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 sec-
?????? tion TARGETS for the legal targets.?? Only??built-in??(non-user-
?????? defined) chains can??have??policies,??and neither built-in nor
?????? user-defined chains can be policy targets.
?????? -E, --rename-chain old-chain new-chain
?????? Rename the user specified chain to the user supplied name.??This
?????? is cosmetic, and has no effect on the structure of the table.
?????? -h???? Help.?? Give a (currently very brief) description of the command
?????? syntax.
?? PARAMETERS
?????? The following parameters make up a rule specification (as used??in??the
?????? add, delete, insert, replace and append commands).
?????? -p, --protocol [!] protocol
?????? The??protocol of the rule or of the packet to check.??The speci-
?????? fied protocol can be one of tcp, udp, icmp, or all, or it can be
?????? a??numeric??value, representing one of these protocols or a dif-
?????? ferent??one.?? A protocol??name from??/etc/protocols??is??also
?????? allowed.??A??"!" argument before the protocol inverts the test.
?????? The number zero is equivalent to all.??Protocol all??will??match
?????? with??all??protocols and is taken as default when this option is
?????? omitted.
?????? -s, --source [!] address[/mask]
?????? Source specification.??Address can be either a 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 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 24
?????? is equivalent to 255.255.255.0.??A??"!"??argument??before??the
?????? address specification inverts the sense of the address. The flag
?????? --src is an alias for this option.
?????? -d, --destination [!] address[/mask]
?????? Destination??specification.?? See??the??description??of??the??-s
?????? (source) flag??for??a??detailed description of the syntax.??The
?????? flag --dst is an alias for this option.
?????? -j, --jump target
?????? This specifies the target of the rule; i.e., what to do??if??the
?????? packet??matches??it.?? The??target??can??be a user-defined chain
?????? (other than the one this rule is in), one of the special builtin
?????? targets??which??decide the fate of the packet immediately, or an
?????? extension (see EXTENSIONS below).??If this option is omitted??in
?????? a rule (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??con-
?????? tinue??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.
?????? [!]??-f, --fragment
?????? This means that the rule only refers to second and further frag-
?????? ments??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.
?????? -c, --set-counters PKTS BYTES
?????? This enables the administrator to initialize the packet and byte
?????? counters of a rule (during Insert, APPEND, REPLACE??operations).
?? OTHER OPTIONS
?????? The following additional options can be specified:
?????? -v, --verbose
?????? Verbose??output.??This??option??makes the list command show the
?????? interface name, the rule options (if any), and??the??TOS masks.
?????? The??packet??and byte counters are also listed, with the suffix
?????? 'K', 'M' or 'G' for 1000, 1,000,000 and 1,000,000,000??multipli-
?????? ers??respectively??(but??see??the??-x flag to change this).??For
?????? appending, insertion,??deletion??and??replacement,??this causes
?????? detailed information on the rule or rules to be printed.
?????? -n, --numeric
?????? Numeric??output.??IP addresses and port numbers will be printed
?????? in numeric format.??By default, the program will try to??display
?????? them??as host names, network names, or services (whenever appli-
?????? cable).
?????? -x, --exact
?????? Expand numbers.??Display the exact value of the packet and??byte
?????? counters,??instead??of only the rounded number in K's (multiples
?????? of 1000) M's (multiples of 1000K) or G's (multiples??of??1000M).
?????? This option is only relevant for the -L command.
?????? --line-numbers
?????? When??listing??rules,??add line numbers to the beginning of each
?????? rule, corresponding to that rule's position in the chain.
?????? --modprobe=command
?????? When adding or inserting rules into a chain, use command to load
?????? any necessary modules (targets, match extensions, etc).
MATCH EXTENSIONS
?????? iptables 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 mod-
?????? ules in one line, and you can use the -h or --help??options??after??the
?????? module has been specified to receive help specific to that module.
?????? The??following??are included in the base package, and most of these can
?????? be preceded by a !??to invert the sense of the match.
?? account
?????? Account traffic for all hosts in defined network/netmask.
?????? Features:
?????? - long (one counter per protocol TCP/UDP/IMCP/Other) and short??statis-
?????? tics
?????? - one iptables rule for all hosts in network/netmask
?????? - loading/saving counters (by reading/writting to procfs entries)

?????? --aaddr network/netmask
?????? defines network/netmask for which make statistics.
?????? --aname name
?????? defines??name??of??list??where statistics will be kept. If no is
?????? specified DEFAULT will be used.
?????? --ashort
?????? table will colect only short??statistics (only??total??counters
?????? without splitting it into protocols.
?????? 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:
??[url]http://www.barbara.eu.org/~quaker/ipt_account/[/url]
?? addrtype
?????? This module matches packets based on their 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.
?????? The following address types are possible:
?????? UNSPEC an unspecified address (i.e. 0.0.0.0) UNICAST an unicast address
?????? LOCAL??a local address BROADCAST a broadcast address ANYCAST an
?????? anycast packet MULTICAST a multicast address BLACKHOLE a black-
?????? hole??address UNREACHABLE an unreachable address PROHIBIT a pro-
?????? hibited address THROW FIXME NAT FIXME XRESOLVE FIXME
?????? --src-type type
?????? Matches if the source address is of given type
?????? --dst-type type
?????? Matches if the destination address is of given type
?? ah
?????? This module matches the SPIs in Authentication header of IPsec packets.
?????? --ahspi [!] spi[:spi]
?? 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.
?????? --childlevel [!] level
?? comment
?????? Allows you to add comments (up to 256 characters) to any rule.
?????? --comment comment
?????? Example:
?????? iptables -A INPUT -s 192.168.0.0/16 -m comment --comment "A pri-
?????? vatized IP block"
?? condition
?????? This matches if a specific /proc filename is '0' or '1'.
?????? --condition [!] filename
?????? Match??on??boolean value stored in /proc/net/ipt_condition/file-
?????? name file
?? 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 aver-
?????? age 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
?????? [!] --connbytes from:[to]
?????? match packets??from??a??connection??whose??packets/bytes/average
?????? packet size is more than FROM and less than TO bytes/packets. if
?????? TO is omitted only FROM check is done.??"!"??is??used??to??match
?????? packets not falling in the range.
?????? --connbytes-dir [original|reply|both]
?????? which packets to consider
?????? --connbytes-mode [packets|bytes|avgpkt]
?????? whether??to??check the amount of packets, number of bytes trans-
?????? ferred or the average size (in bytes) of all packets received so
?????? far.??Note??that when "both" is used together with "avgpkt", and
?????? data is going (mainly) only in one direction (for example HTTP),
?????? the??average??packet??size will be about half of the actual data
?????? packets.
?????? Example:
?????? iptables .. -m connbytes --connbytes??10000:100000??--connbytes-
?????? dir both --connbytes-mode bytes ...
?? connlimit
?????? Allows??you??to restrict??the??number of parallel TCP connections to a
?????? server per client IP address (or address block).
?????? [!] --connlimit-above n
?????? match if the number of existing tcp connections is (not) above n
?????? --connlimit-mask bits
?????? group hosts using mask
?????? Examples:
?????? # allow 2 telnet connections per client host
?????? iptables -p tcp --syn --dport 23 -m connlimit --connlimit-above
?????? 2 -j REJECT
?????? # you can also match the other way around:
?????? iptables -p tcp --syn --dport 23 -m??connlimit??!??--connlimit-
?????? above 2 -j ACCEPT
?????? #??limit??the nr of parallel http requests to 16 per class C sized net-
?????? work (24 bit netmask)
?????? iptables -p tcp --syn --dport 80 -m connlimit --connlimit-above
?????? 16 --connlimit-mask 24 -j REJECT
?? connmark
?????? This module matches the netfilter mark field associated with a??connec-
?????? tion (which can be set using the CONNMARK target below).
?????? --mark value[/mask]
?????? Matches??packets in connections with the given mark value (if a
?????? mask is specified, this is logically ANDed with the mark before
?????? the comparison).
?? connrate
?????? This module matches the current transfer rate in a connection.
?????? --connrate [!] [from]:[to]
?????? 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.
?? 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 support-
?????? ing this feature)
?????? --ctstate state
?????? Where state is a comma separated list of the??connection states
?????? to??match.?? Possible states are INVALID meaning that the packet
?????? is associated with no known connection, ESTABLISHED meaning that
?????? the??packet is associated with a connection which has seen pack-
?????? ets 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 mean-
?????? ing that the packet is starting a new connection, but is associ-
?????? ated with an existing connection, such as an FTP data??transfer,
?????? or??an ICMP error.??SNAT A virtual state, matching if the origi-
?????? nal source address differs from the reply destination.?? DNAT??A
?????? virtual state, matching if the original destination differs from
?????? the reply source.
?????? --ctproto proto
?????? Protocol to match (by number or name)
?????? --ctorigsrc [!] address[/mask]
?????? Match against original source address
?????? --ctorigdst [!] address[/mask]
?????? Match against original destination address
?????? --ctreplsrc [!] address[/mask]
?????? Match against reply source address
?????? --ctrepldst [!] address[/mask]
?????? Match against reply destination address
?????? --ctstatus [NONE|EXPECTED|SEEN_REPLY|ASSURED][,...]
?????? Match against internal conntrack states
?????? --ctexpire time[:time]
?????? Match remaining lifetime in seconds against given value or range
?????? of values (inclusive)
?? 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 [0-32].
?????? --dscp-class DiffServ Class
?????? 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.
?? 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.
?????? THIS MODULE IS DEPRECATED AND HAS BEEN REPLACED BY ''hashlimit''
?????? --dstlimit avg
?????? Maximum average match rate (packets per second??unless??followed
?????? by /sec /minute /hour /day postfixes).
?????? --dstlimit-mode mode
?????? The limiting hashmode.??Is the specified limit per dstip, dstip-
?????? dstport tuple,??srcip-dstip??tuple,??or??per??srcipdstip-dstport
?????? tuple.
?????? --dstlimit-name name
?????? Name for /proc/net/ipt_dstlimit/* file entry
?????? [--dstlimit-burst burst]
?????? Number of packets to match in a burst.??Default: 5
?????? [--dstlimit-htable-size size]
?????? Number of buckets in the hashtable
?????? [--dstlimit-htable-max max]
?????? Maximum number of entries in the hashtable
?????? [--dstlimit-htable-gcinterval interval]
?????? Interval between??garbage??collection runs of the hashtable (in
?????? miliseconds).??Default is 1000 (1 second).
?????? [--dstlimit-htable-expire time
?????? After which time are idle entries??expired??from hashtable??(in
?????? miliseconds)???Default is 10000 (10 seconds).
?? 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
?????? --ecn-tcp-cwr
?????? This matches if the TCP ECN CWR (Congestion Window Received) bit
?????? is set.
?????? --ecn-tcp-ece
?????? This matches if the TCP ECN ECE (ECN Echo) bit is set.
?????? --ecn-ip-ect num
?????? This matches a particular IPv4 ECT (ECN-Capable Transport).??You
?????? have to specify a number between '0' and '3'.
?? esp
?????? This module matches the SPIs in ESP header of IPsec packets.
?????? --espspi [!] spi[:spi]
?? fuzzy
?????? This??module??matches??a??rate??limit based on a fuzzy logic controller
?????? [FLC]
?????? --lower-limit number
?????? Specifies the lower limit (in packets per second).
?????? --upper-limit number
?????? Specifies the upper limit (in packets per second).
?? hashlimit
?????? This patch adds a new match called 'hashlimit'. The idea??is??to??have
?????? something??like 'limit',??but??either??per destination-ip or per (des-
?????? tip,destport) tuple.
?????? It gives you the ability to express
????????'1000 packets per second for every host in 192.168.0.0/16'
????????'100 packets per second for every service of 192.168.1.1'
?????? with a single iptables rule.
?????? --hashlimit rate
?????? A rate just like the limit match
?????? --hashlimit-burst num
?????? Burst value, just like limit match
?????? --hashlimit-mode destip | destip-destport
?????? Limit per IP or per port
?????? --hashlimit-name foo
?????? The name for the /proc/net/ipt_hashlimit/foo entry
?????? --hashlimit-htable-size num
?????? The number of buckets of the hash table
?????? --hashlimit-htable-max num
?????? Maximum entries in the hash
?????? --hashlimit-htable-expire num
?????? After how many miliseconds do hash entries expire
?????? --hashlimit-htable-gcinterval num
?????? How many miliseconds between garbage collection intervals
?? 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.
?? icmp
?????? This extension is loaded if '--protocol icmp' is??specified.?? It??pro-
?????? vides the following option:
?????? --icmp-type [!] typename
?????? 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
????????iptables -p icmp -h
?? iprange
?????? This matches on a given arbitrary range of IPv4 addresses
?????? [!]--src-range ip-ip
?????? Match source IP in the specified range.
?????? [!]--dst-range ip-ip
?????? Match destination IP in the specified range.
?? ipv4options
?????? Match??on IPv4 header options like source routing, record route, times-
?????? tamp and router-alert.
?????? --***r To match packets with the flag strict source routing.
?????? --lsrr To match packets with the flag loose source routing.
?????? --no-srr
?????? To match packets with no flag for source routing.
?????? [!] --rr
?????? To match packets with the RR flag.
?????? [!] --ts
?????? To match packets with the TS flag.
?????? [!] --ra
?????? To match packets with the router-alert option.
?????? [!] --any-opt
?????? To match a packet with at least one IP option, or no??IP option
?????? at all if ! is chosen.
?????? Examples:
?????? $ iptables -A input -m ipv4options --rr -j Drop
?????? will drop packets with the record-route flag.
?????? $ iptables -A input -m ipv4options --ts -j Drop
?????? will drop packets with the timestamp flag.
?? length
?????? This??module matches the length 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
?????? (unless the '!' flag is used).??It can be used in combination with??the
?????? LOG target to give limited logging, for example.
?????? --limit rate
?????? Maximum??average matching??rate: specified as a number, with an
?????? optional '/second', '/minute', '/hour', or??'/day'??suffix;??the
?????? default is 3/hour.
?????? --limit-burst number
?????? Maximum??initial number of??packets to match: this number gets
?????? recharged by one every time the limit??specified above??is??not
?????? reached, up to this number; the default is 5.
?? mac
?????? --mac-source [!] address
?????? Match?? source?? MAC?? address.??It?? must?? be??of??the??form
?????? XX:XX:XX:XX:XX:XX.??Note that this only makes sense for??packets
?????? coming from an Ethernet device and entering the PREROUTING, FOR-
?????? WARD or INPUT chains.
?? mark
?????? This module matches the netfilter mark field associated with??a packet
?????? (which can be set using the MARK target below).
?????? --mark value[/mask]
?????? Matches packets with the given unsigned mark value (if a mask is
?????? specified, this is logically ANDed with the mask before the com-
?????? parison).
?? 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 -p tcp
?????? or -p udp.
?????? --source-ports port[,port[,port...]]
?????? Match??if??the??source port is one of the given ports.??The flag
?????? --sports is a convenient alias for this option.
?????? --destination-ports port[,port[,port...]]
?????? Match if the destination port is one of the??given??ports.?? The
?????? flag --dports is a convenient alias for this option.
?????? --ports port[,port[,port...]]
?????? Match??if the both the source and destination ports are equal to
?????? each other and to one of the given ports.
?? 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 [!] port[,port[,port:port...]]
?????? Match if the source port is one of the given??ports.?? The??flag
?????? --sports is a convenient alias for this option.
?????? --destination-ports [!] port[,port[,port:port...]]
?????? Match??if??the??destination port is one of the given ports.??The
?????? flag --dports is a convenient alias for this option.
?????? --ports [!] port[,port[,port:port...]]
?????? Match if either the source or destination ports are equal to one
?????? of the given ports.
?? nth
?????? This module matches every 'n'th packet
?????? --every value
?????? Match every 'value' packet
?????? [--counter num]
?????? Use internal counter number 'num'.??Default is '0'.
?????? [--start num]
?????? Initialize the counter at the number 'num' insetad of '0'.??Most
?????? between '0' and 'value'-1.
?????? [--packet num]
?????? Match on 'num' packet.??Most be between '0' and 'value'-1.
?? 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
?????? <[email]lcamtuf@coredump.cx[/email]>.
?????? 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.
?????? --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:
?????? ipt_osf: Windows??[2000:SP3:Windows??XP Pro??SP1,??2000??SP3]:
?????? 11.22.33.55:4024 -> 11.22.33.44:139
?????? ipt_osf:?????? Unknown:????????16384:106:1:48:020405B401010402
?????? 44.33.22.11:1239 -> 11.22.33.44:80
?????? --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.
?????? --netlink
?????? If??present,??OSF??will??log??all??events??also??through netlink
?????? NETLINK_NFLOG groupt 1.
?????? --genre [!] string
?????? Match a OS genre by passive fingerprinting
?????? 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:
?????? echo -en FLUSH > /proc/sys/net/ipv4/osf
?????? Only one fingerprint per open/write/close.
?????? Fingerprints??can??be?? downloaded?? from?? [url]http://www.openbsd.org/cgi-[/url]
?????? bin/cvsweb/src/etc/pf.os
?? owner
?????? This??module??attempts??to??match various characteristics of the packet
?????? creator, for locally-generated packets. It is only valid in the OUTPUT
?????? chain,??and??even??this some packets (such as ICMP ping responses) may
?????? have no owner, and hence never match.
?????? --uid-owner userid
?????? Matches if the packet was created by a process??with??the??given
?????? effective user id.
?????? --gid-owner groupid
?????? Matches??if??the packet was created by a process with the given
?????? effective group id.
?????? --pid-owner processid
?????? Matches if the packet was created by a process??with??the??given
?????? process id.
?????? --sid-owner sessionid
?????? Matches if the packet was created by a process in the given ses-
?????? sion group.
?????? --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 com-
?????? piled under a kernel supporting this feature)
?????? NOTE: pid, sid and command matching are broken on SMP
?? physdev
?????? This module matches??on the??bridge??port??input??and??output??devices
?????? enslaved??to??a bridge device. This module is a part of the infrastruc-
?????? ture that enables a transparent bridging IP firewall and is only useful
?????? for kernel versions above version 2.5.44.
?????? --physdev-in [!] name
?????? Name??of a bridge port via which a packet is received (only for
?????? packets entering the INPUT, FORWARD and PREROUTING??chains).??If
?????? the??interface??name??ends??in??a??"+", then any interface which
?????? begins with this name will match. If the packet didn't arrive
?????? through??a??bridge??device, this packet won't match this option,
?????? unless '!' is used.
?????? --physdev-out [!] name
?????? Name of a bridge port via which a packet is??going??to??be??sent
?????? (for??packets??entering??the??FORWARD,??OUTPUT??and??POSTROUTING
?????? chains). If the interface name ends in a "+", then??any inter-
?????? face??which??begins??with this name will match. Note that in the
?????? nat and mangle OUTPUT chains one cannot match on the bridge out-
?????? put??port,??however??one can in the filter OUTPUT chain. If the
?????? packet won't leave by a bridge device or it is yet unknown??what
?????? the??output??device??will??be,??then the packet won't match this
?????? option, unless
?????? [!] --physdev-is-in
?????? Matches if the packet has entered through a bridge interface.
?????? [!] --physdev-is-out
?????? Matches if the packet will leave through a bridge interface.
?????? [!] --physdev-is-bridged
?????? Matches if the packet is being??bridged??and??therefore??is??not
?????? being??routed.??This is only useful in the FORWARD and POSTROUT-
?????? ING 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??decapsula-
?????? tion??or the policy that will be used for encapsulation.??in is
?????? valid in the PREROUTING, INPUT and FORWARD chains, out is??valid
?????? in the POSTROUTING, OUTPUT and FORWARD chains.
?????? --pol none|ipsec
?????? Matches if the packet is subject to IPsec processing.
?????? --strict
?????? Selects??whether to match the exact policy or match if any rule
?????? of the policy matches the given policy.
?????? --reqid id
?????? Matches the reqid of the policy rule. The reqid can be specified
?????? with setkey(8) using unique:id as level.
?????? --spi spi
?????? Matches the SPI of the SA.
?????? --proto ah|esp|ipcomp
?????? Matches the encapsulation protocol.
?????? --mode tunnel|transport
?????? Matches the encapsulation mode.
?????? --tunnel-src addr[/mask]
?????? Matches??the source end-point address of a tunnel mode SA.??Only
?????? valid with --mode tunnel.
?????? --tunnel-dst addr[/mask]
?????? Matches the destination end-point address of a tunnel??mode??SA.
?????? Only valid with --mode tunnel.
?????? --next Start??the next element in the policy specification. Can only be
?????? used with --strict
?? psd
?????? Attempt to detect TCP and UDP port scans. This match was??derived??from
?????? Solar Designer's scanlogd.
?????? --psd-weight-threshold threshold
?????? Total weight of the latest TCP/UDP packets with different desti-
?????? nation ports coming from the same host to??be??treated??as??port
?????? scan sequence.
?????? --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.
?????? --psd-lo-ports-weight weight
?????? Weight??of the packet with privileged (<=1024) destination port.
?????? --psd-hi-ports-weight weight
?????? Weight of the packet with non-priviliged destination port.
?? quota
?????? Implements network quotas by decrementing??a??byte??counter??with??each
?????? packet.
?????? --quota bytes
?????? The quota in bytes.
?????? KNOWN BUGS: this does not work on SMP systems.
?? random
?????? This module randomly matches a certain percentage of all packets.
?????? --average percent
?????? Matches??the given percentage.??If omitted, a probability of 50%
?????? is set.
?? realm
?????? This matches the routing realm. Routing realms are??used??in??complex
?????? routing setups involving dynamic routing protocols like BGP.
?????? --realm [!]value[/mask]
?????? Matches a given realm number (and optionally mask).
?? 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.
?????? --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).
?????? [!] --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.
?????? [!] --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.
?????? --rttl 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??the??TTL??of??the??current
?????? packet matches that of the packet which hit the --set rule. This
?????? may be useful if you have??problems??with??people??faking??their
?????? source??address in order to DoS you via this module by disallow-
?????? ing others access to your site by sending bogus packets to??you.
?????? Examples:
?????? # iptables -A FORWARD -m recent --name badguy --rcheck --seconds
?????? 60 -j Drop
?????? # iptables -A FORWARD -p tcp??-i eth0??--dport??139??-m recent
?????? --name badguy --set -j Drop
?????? Official??website??([url]http://snowman.net/projects/ipt_recent/[/url])??also??has
?????? some examples of usage.
?????? /proc/net/ipt_recent/* are the current lists of addresses and??informa-
?????? tion 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:
?????? echo xx.xx.xx.xx > /proc/net/ipt_recent/DEFAULT
?????? to Add to the DEFAULT list
?????? echo -xx.xx.xx.xx > /proc/net/ipt_recent/DEFAULT
?????? to Remove from the DEFAULT list
?????? echo clear > /proc/net/ipt_recent/DEFAULT
?????? to empty the DEFAULT list.
?????? 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/ipt_recent/* files
?????? debug=0
?????? Set to 1 to get lots of debugging info
?? 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
?????? chunk type???? available flags
?????? DATA??????U B E 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 modules macthes IP sets which can be defined by ipset(8).
?????? --set setname flag[,flag...]
?????? where flags are src and/or dst and there can be no more than six
?????? of them. Hence the command
????????iptables -A FORWARD -m set --set test src,dst
?????? 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.
?? state
?????? This module, when combined with connection tracking, allows??access??to
?????? the connection tracking state for this packet.
?????? --state state
?????? Where??state??is a comma separated list of the connection states
?????? to match.??Possible states are INVALID meaning that??the packet
?????? could??not??be identified for some reason which includes running
?????? out of memory and ICMP errors??which??don't??correspond??to??any
?????? known connection, ESTABLISHED meaning that the packet is associ-
?????? ated with a connection which has seen??packets??in??both direc-
?????? tions, NEW meaning that the packet has started a new connection,
?????? or otherwise associated with a connection??which has??not??seen
?????? packets??in both directions, and RELATED meaning that the packet
?????? is starting a new connection, but is associated with an existing
?????? connection, such as an FTP data transfer, or an ICMP error.
?? 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 from which it starts looking for any matching. 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 are loaded if '--protocol tcp' is specified.??It??pro-
?????? vides the following options:
?????? --source-port [!] port[:port]
?????? Source??port??or port range specification. This can either be a
?????? service name or a port number. An inclusive range??can??also??be
?????? specified,??using??the??format??port:port.??If the first port is
?????? omitted, "0" is assumed; if the??last??is??omitted,??"65535"??is
?????? assumed. If the second port greater then the first they will be
?????? swapped. The flag??--sport??is??a??convenient??alias??for??this
?????? option.
?????? --destination-port [!] port[:port]
?????? Destination??port or port range specification.??The flag --dport
?????? is a convenient alias for this option.
?????? --tcp-flags [!] mask comp
?????? Match when the TCP flags are as specified.??The??first??argument
?????? is??the??flags which we should examine, written as a comma-sepa-
?????? rated list, and the second argument is a comma-separated list of
?????? flags which must be set. Flags are: SYN ACK FIN RST URG PSH ALL
?????? NONE.??Hence the command
????????iptables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST SYN
?????? will only match packets with the SYN flag set, and the ACK,??FIN
?????? and RST flags unset.
?????? [!] --syn
?????? Only??match TCP packets with the SYN bit set and the ACK,RST and
?????? FIN bits cleared.??Such packets are used to request TCP??connec-
?????? tion initiation; for example, blocking such packets coming in an
?????? 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.
?????? --mss value[:value]
?????? Match??TCP??SYN??or SYN/ACK packets with the specified MSS value
?????? (or range), which control the maximum packet size for that??con-
?????? nection.
?? 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 facultative.
--timestart value
?????? Match??only??if??it is after 'value' (Inclusive, format: HH:MM ;
?????? default 00:00).
?????? --timestop??value
?????? Match only if it is before 'value' (Inclusive, format:??HH:MM??;
?????? default 23:59).
?????? --days listofdays
?????? Match??only??if??today??is??one??of??the given??days.??(format:
?????? Mon,Tue,Wed,Thu,Fri,Sat,Sun ; default everyday)
?????? --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)
?????? --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)
?? tos
?????? This module matches the 8 bits of Type??of??Service??field??in??the??IP
?????? header (ie. including the precedence bits).
?????? --tos tos
?????? The argument is either a standard name, (use
????????iptables -m tos -h
?????? to see the list), or a numeric value to match.
?? ttl
?????? This module matches the time to live field in the IP header.
?????? --ttl-eq ttl
?????? Matches the given TTL value.
?????? --ttl-gt ttl
?????? Matches if TTL is greater than the given TTL value.
?????? --ttl-lt ttl
?????? Matches if TTL is less than the given TTL value.
?? 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 spec-
?????? ification 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.
?? udp
?????? These??extensions are loaded if '--protocol udp' is specified.??It pro-
?????? vides the following options:
?????? --source-port [!] port[:port]
?????? Source port or port range specification. See the description of
?????? the --source-port option of the TCP extension for details.
?????? --destination-port [!] port[:port]
?????? Destination??port or port range specification.??See the descrip-
?????? tion of the --destination-port option of the TCP extension??for
?????? details.
?? unclean
?????? This??module takes no options, but attempts to match packets which seem
?????? malformed or unusual.??This is regarded as experimental.
TARGET EXTENSIONS
?????? iptables can use extended target modules: the following are included in
?????? the standard distribution.
?? BALANCE
?????? This??allows??you to DNAT connections in a round-robin way over a given
?????? range of destination addresses.
?????? --to-destination ipaddr-ipaddr
?????? Address range to round-robin over.
?? CLASSIFY
?????? This module allows you to set the skb->priority value (and??thus??clas-
?????? sify the packet into a specific CBQ class).
?????? --set-class MAJOR:MINOR
?????? Set the major and minor class value.
?? 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.
?????? --new??Create a new ClusterIP.??You always have to??set??this??on??the
?????? first rule for a given ClusterIP.
?????? --hashmode mode
?????? Specify??the hashing mode.??Has to be one of sourceip, sourceip-
?????? sourceport, sourceip-sourceport-destport
?????? --clustermac mac
?????? Specify the ClusterIP MAC address.??Has to be a link-layer??mul-
?????? ticast address
?????? --total-nodes num
?????? Number of total nodes within this cluster.
?????? --local-node num
?????? Local node number within this cluster.
?????? --hash-init rnd
?????? Specify the random seed used for hash initialization.
?? CONNMARK
?????? This module sets the netfilter mark value associated with a connection
?????? --set-mark mark[/mask]
?????? Set connection mark. If a mask is specified then only those bits
?????? set in the mask is modified.
?????? --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.
?????? --restore-mark [--mask mask]
?????? Copy the connection mark value to the packet. If a mask is spec-
?????? ified then only those bits are copied. This is only valid in the
?????? mangle table.
?? DNAT
?????? This??target is only valid in the nat table, in the PREROUTING and OUT-
?????? PUT 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:
?????? --to-destination ipaddr[-ipaddr][:port-port]
?????? which can specify a single new destination IP address, an inclu-
?????? sive??range of IP addresses, and optionally, a port range (which
?????? is only valid if the rule also specifies -p tcp or -p udp).?? If
?????? no port range is specified, then the destination port will never
?????? be modified.
?????? In Kernels up to 2.6.10 you??can add??several??--to-destination
?????? options. For those kernels, if you specify more than one desti-
?????? nation 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??addresses.
?????? Later??Kernels??(>= 2.6.11-rc1) don't have the ability to NAT to
?????? multiple ranges anymore.

?? 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.
?? ECN
?????? This target allows to selectively work around known ECN blackholes.??It
?????? can only be used in the mangle table.
?????? --ecn-tcp-remove
?????? Remove all ECN bits from the TCP header. Of course, it can only
?????? be used in conjunction with -p tcp.
?? 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.
?????? --addr src/dst
?????? Use source or destination IP address.
?????? --and-mask mask
?????? Perform bitwise 'and' on the IP address and this mask.
?????? --or-mask mask
?????? Perform bitwise 'or' on the IP address and this mask.
?????? 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 per-
?????? formed, 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:
?????? tc filter add dev eth3 parent 1:0 protocol ip fw
?????? Earlier we had many rules just like below:
?????? iptables -t mangle -A POSTROUTING -o eth3 -d 192.168.5.2 -j MARK
?????? --set-mark 0x10502
?????? iptables -t mangle -A POSTROUTING -o eth3 -d 192.168.5.3 -j MARK
?????? --set-mark 0x10503
?????? Using??IPMARK target we can replace all the mangle/mark rules with only
?????? one:
?????? iptables -t mangle -A POSTROUTING -o eth3 -j??IPMARK??--addr=dst
?????? --and-mask=0xffff --or-mask=0x10000
?????? On??the routers with hundreds of users there should be significant load
?????? decrease (e.g. twice).
?? 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
?? 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 match-
?????? ing??packets??(like most IP header fields) via the kernel log (where it
?????? can be read with dmesg or syslogd(8)).??This is a "non-terminating tar-
?????? get",??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 IP packet header.
?????? --log-uid
?????? Log the userid of the process which generated the packet.
?? MARK
?????? This??is??used??to??set the??netfilter mark value associated with the
?????? packet. It is only valid in the mangle table.??It can for??example??be
?????? used in conjunction with iproute2.
?????? --set-mark mark
?? MASQUERADE
?????? This??target??is only valid in the nat table, in the POSTROUTING chain.
?????? It should only be used with dynamically assigned??IP??(dialup)??connec-
?????? tions: 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 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??any-
?????? way).??It takes one option:
?????? --to-ports port[-port]
?????? This??specifies??a??range of source ports to use, overriding the
?????? default SNAT source port-selection heuristics (see above).??This
?????? is only valid if the rule also specifies -p tcp or -p udp.
?? 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 INPUT, FORWARD and PREROUTING chains, and user-
?????? defined chains which are only called from those chains. Note that??the
?????? outgoing??packets??are NOT seen by any packet filtering chains, connec-
?????? tion tracking or NAT, to avoid loops and other problems.
?? 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 nat table.
?????? --to address[/mask]
?????? Network address to map to.??The resulting address will??be??con-
?????? structed 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.
?? NFQUEUE
?????? This??target??is an extension of the QUEUE target. As opposed to QUEUE,
?????? it allows you to put a packet into any specific queue, identified??by
?????? its 16-bit queue number.
?????? --queue-num value
?????? This??specifies the QUEUE number to use. Valud queue numbers are
?????? 0 to 65535. The default value is 0.
?????? It can only be used with Kernel versions??2.6.14??or??later,??since??it
?????? requires
?????? the nfnetlink_queue kernel support.
?? NOTRACK
?????? This target disables connection tracking for all packets matching??that
?????? rule.
?????? It can only be used in the
?????? raw table.
?? REDIRECT
?????? This??target is only valid in the nat table, in the PREROUTING and OUT-
?????? PUT 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:
?????? --to-ports port[-port]
?????? 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 -p tcp or -p udp.
?? 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 TAR-
?????? GET, ending rule traversal.??This target is only valid??in??the INPUT,
?????? FORWARD and??OUTPUT??chains,??and??user-defined??chains which are only
?????? called from those chains.??The following option controls the nature??of
?????? the error packet returned:
?????? --reject-with type
?????? The type given can be
????????icmp-net-unreachable
????????icmp-host-unreachable
????????icmp-port-unreachable
????????icmp-proto-unreachable
????????icmp-net-prohibited
????????icmp-host-prohibited or
????????icmp-admin-prohibited (*)
?????? which??return??the appropriate ICMP error message (port-unreach-
?????? able is the default).??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).
?????? (*) Using icmp-admin-prohibited with kernels that??do??not??support??it
?????? will result in a plain Drop instead of REJECT
?? ROUTE
?????? This is used to explicitly override the core??network??stack's??routing
?????? decision.??mangle table.
?????? --oif ifname
?????? Route the packet through 'ifname' network interface
?????? --iif ifname
?????? Change the packet's incoming interface to 'ifname'
?????? --gw IP_address
?????? Route the packet via this gateway
?????? --continue
?????? Behave like a non-terminating target and continue traversing the
?????? rules.??Not valid in combination with '--iif' or '--tee'
?????? --tee??Make a copy of the packet, and route that copy to the given des-
?????? tination.??For the original, uncopied packet, behave like a non-
?????? terminating target and continue traversing the rules.??Not valid
?????? in combination with '--iif' or '--continue'
?? 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-/destina-
?????? tion-address for each connection.
?????? --to <ipaddr>-<ipaddr>
?????? Addresses??to map source to. May be specified more than once for
?????? multiple ranges.
?????? --nodst
?????? Don't use the destination-ip in the calculations when??selecting
?????? the new source-ip
?? 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 and there can be no more than six
?????? of them.
?????? The bindings to follow must previously be defined in order to use
?????? multilevel adding/deleting by the SET target.
?? SNAT
?????? This target is only valid in the nat table, in the??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:
?????? --to-source??ipaddr[-ipaddr][:port-port]
?????? 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 -p tcp or -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 alter-
?????? ation will occur.
?????? In Kernels??up??to??2.6.10,??you can??add??several??--to-source
?????? options. For those kernels, 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 addresses.??Later??Kernels??(>=??2.6.11-rc1)
?????? don't have the ability to NAT to multiple ranges anymore.
?? TARPIT
?????? Captures??and holds incoming TCP connections using no local per-connec-
?????? tion resources. Connections are accepted, but immediately??switched??to
?????? the persist state (0 byte window), in which the remote side stops send-
?????? ing 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?? <[url]http://www.hack-[/url]
?????? busters.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:
?????? iptables -A INPUT -p tcp -m tcp --dport 80 -j TARPIT
?????? 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:
?????? iptables -A FORWARD -p tcp -j TARPIT
?????? iptables -A FORWARD -j Drop
?????? NOTE:??If you use the conntrack module while you are using TARPIT,??you
?????? should??also use the NOTRACK target, or the kernel will unneces-
?????? sarily allocate resources??for??each??TARPITted??connection.??To
?????? TARPIT incoming connections to the standard IRC port while using
?????? conntrack, you could:
?????? iptables -t raw -A PREROUTING -p tcp --dport 6667 -j NOTRACK
?????? iptables -A INPUT -p tcp --dport 6667 -j TARPIT
?? TCPMSS
?????? This target allows to alter the MSS value of TCP SYN packets,??to??con-
?????? trol??the maximum size for that connection (usually limiting it to your
?????? outgoing interface's MTU minus 40).??Of course, it can only be used??in
?????? conjunction with -p tcp.??It is only valid in the mangle table.
?????? This??target??is??used to overcome criminally braindead ISPs or servers
?????? which block 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:
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??con-
?????? figuration like:
iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN \
??????-j TCPMSS --clamp-mss-to-pmtu
?????? --set-mss value
?????? Explicitly set MSS option to specified value.
?????? --clamp-mss-to-pmtu
?????? Automatically clamp MSS value to (path_MTU - 40).
?????? These options are mutually exclusive.
?? TOS
?????? This??is??used to set the 8-bit Type of Service field in the IP header.
?????? It is only valid in the mangle table.
?????? --set-tos tos
?????? You can use a numeric TOS values, or use
????????iptables -j TOS -h
?????? to see the list of valid TOS names.
?? TRACE
?????? This target has no options.??It just turns on packet??tracing??for??all
?????? packets that match this rule.
?? TTL
?????? This is used to modify the IPv4 TTL header field.??The TTL field deter-
?????? mines how many hops (routers) a packet can traverse until it's time??to
?????? live is exceeded.
?????? Setting or??incrementing the TTL field can potentially be very danger-
?????? ous,
?????? so it should be avoided at any cost.
?????? Don't??ever set or increment the value on packets that leave your local
?????? network!
?????? mangle table.
?????? --ttl-set value
?????? Set the TTL value to 'value'.
?????? --ttl-dec value
?????? Decrement the TTL value 'value' times.
?????? --ttl-inc value
?????? Increment the TTL value 'value' times.
?? 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 netlink socket. One or more userspace processes may then sub-
?????? scribe 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.
?????? --ulog-nlgroup nlgroup
?????? This specifies the netlink group (1-32) to which the??packet??is
?????? sent.??Default value is 1.
?????? --ulog-prefix prefix
?????? Prefix??log messages with the specified prefix; up to 32 charac-
?????? ters long, and useful for distinguishing messages in the logs.
?????? --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.
?????? --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).
?? XOR
?????? Encrypt TCP and UDP traffic using a simple XOR encryption
?????? --key string
?????? Set key to "string"
?????? --block-size
?????? Set block size
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,??you??might??want??to??have??a??look??at
?????? [url]http://bugzilla.netfilter.org/[/url]
COMPATIBILITY WITH IPCHAINS
?????? This??iptables??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.
?????? iptables is a pure packet filter when using the default 'filter' table,
?????? with optional extension modules.??This should simplify much of the pre-
?????? vious confusion over the combination of IP masquerading and packet fil-
?????? tering??seen??previously.??So the following options are handled differ-
?????? ently:
-j MASQ
-M -S
-M -L
?????? There are several other changes in iptables.
SEE ALSO
?????? iptables-save(8), iptables-restore(8), ip6tables(8), ip6tables-save(8),
?????? ip6tables-restore(8), libipq(3).
?????? The packet-filtering-HOWTO details iptables usage for packet filtering,
?????? the NAT-HOWTO details NAT, the netfilter-extensions-HOWTO??details??the
?????? extensions??that??are not in the standard distribution, and the netfil-
?????? ter-hacking-HOWTO details the netfilter internals.
?????? See [url]http://www.netfilter.org/.[/url]
AUTHORS
?????? Rusty Russell originally 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 every-
?????? where.
?????? James Morris wrote the TOS target, and tos match.
?????? Jozsef Kadlecsik wrote the REJECT target.
?????? Harald Welte wrote the ULOG and NFQUEUE target, the??new??libiptc,??as
?????? well as the TTL, DSCP, ECN matches and targets.
?????? The??Netfilter??Core??Team??is: Marc Boucher, Martin Josefsson, Jozsef
?????? Kadlecsik, Patrick McHardy, James Morris, Harald Welte and??Rusty??Rus-
?????? sell.
?????? Man page originally written by Herve Eychenne <[email]rv@wallfire.org[/email]>.

???? Mar 09, 2002??????IPTABLES(8)

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