.I DROP
means to drop the packet on the floor.
.I QUEUE
-means to pass the packet to userspace (if supported by the kernel).
+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
+.B
+ip_queue
+queue handler. Kernels 2.6.14 and later additionally include the
+.B
+nfnetlink_queue
+queue handler. Packets with a target of QUEUE will be sent to queue number '0'
+in this case. Please also see the
+.B
+NFQUEUE
+target as described later in this man page.)
.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
This is the default table (if no -t option is passed). It contains
the built-in chains
.B INPUT
-(for packets coming into the box itself),
+(for packets destined to local sockets),
.B FORWARD
(for packets being routed through the box), and
.B OUTPUT
(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
.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.
+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.
.TP
.BI "-P, --policy " "chain target"
Set the policy for the chain to the given target. See the section
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
+option is omitted in a rule (and
+.B -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.
.TP
+.BI "-g, --goto " "chain"
+This specifies that the processing should continue in a user
+specified chain. Unlike the --jump option return will not continue
+processing in this chain but instead in the chain that called us via
+--jump.
+.TP
.BR "-i, --in-interface " "[!] \fIname\fP"
-Name of an interface via which a packet is going to be received (only for
+Name of an interface via which a packet was received (only for
packets entering the
.BR INPUT ,
.B FORWARD
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.
+This module matches the SPIs in Authentication 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 " "[!] \fIfilename\fP"
+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.
.BI "--ctexpire " "\fItime\fP[\fI:time\fP]"
Match remaining lifetime in seconds against given value
or range of values (inclusive)
+.SS dccp
+.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--dccp-types\fR [\fB!\fR] \fImask\fP
+Match when the DCCP packet type is one of 'mask'. 'mask' is a comma-separated
+list of packet types. Packet types are:
+.BR "REQUEST RESPONSE DATA ACK DATAACK CLOSEREQ CLOSE RESET SYNC SYNCACK INVALID" .
+.TP
+\fB--dccp-option\fR [\fB!\fR\] \fInumber\fP
+Match if DCP option set.
.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.
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
+THIS MODULE IS DEPRECATED AND HAS BEEN REPLACED BY ``hashlimit''
+.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.
+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
.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]"
+.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
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
+Matches packets with the given unsigned mark value (if a \fImask\fP is
+specified, this is logically ANDed with the \fImask\fP before the
comparison).
-.SS multiport
+.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"
.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
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
+.BR --physdev-in " [!] \fIname\fP"
Name of a bridge port via which a packet is received (only for
packets entering the
.BR INPUT ,
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
+.BR --physdev-out " [!] \fIname\fP"
Name of a bridge port via which a packet is going to be sent (for packets
entering the
.BR FORWARD ,
the output device will be, then the packet won't match this option, unless
'!' is used.
.TP
-.B --physdev-is-in
+.RB "[!] " --physdev-is-in
Matches if the packet has entered through a bridge interface.
.TP
-.B --physdev-is-out
+.RB "[!] " --physdev-is-out
Matches if the packet will leave through a bridge interface.
.TP
-.B --physdev-is-bridged
+.RB "[!] " --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 policy
+This modules matches the policy used by IPsec for handling a packet.
+.TP
+.BI "--dir " "in|out"
+Used to select whether to match the policy used for decapsulation or the
+policy that will be used for encapsulation.
+.B in
+is valid in the
+.B PREROUTING, INPUT and FORWARD
+chains,
+.B out
+is valid in the
+.B POSTROUTING, OUTPUT and FORWARD
+chains.
+.TP
+.BI "--pol " "none|ipsec"
+Matches if the packet is subject to IPsec processing.
+.TP
+.BI "--strict"
+Selects whether to match the exact policy or match if any rule of
+the policy matches the given policy.
+.TP
+.BI "--reqid " "id"
+Matches the reqid of the policy rule. The reqid can be specified with
+.B setkey(8)
+using
+.B unique:id
+as level.
+.TP
+.BI "--spi " "spi"
+Matches the SPI of the SA.
+.TP
+.BI "--proto " "ah|esp|ipcomp"
+Matches the encapsulation protocol.
+.TP
+.BI "--mode " "tunnel|transport"
+Matches the encapsulation mode.
+.TP
+.BI "--tunnel-src " "addr[/mask]"
+Matches the source end-point address of a tunnel mode SA.
+Only valid with --mode tunnel.
+.TP
+.BI "--tunnel-dst " "addr[/mask]"
+Matches the destination end-point address of a tunnel mode SA.
+Only valid with --mode tunnel.
+.TP
+.BI "--next"
+Start the next element in the policy specification. Can only be used with
+--strict
+.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.
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 string
+This modules matches a given string by using some pattern matching strategy. It requires a linux kernel >= 2.6.14.
+.TP
+.BI "--algo " "bm|kmp"
+Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morris)
+.TP
+.BI "--from " "offset"
+Set the offset from which it starts looking for any matching. If not passed, default is 0.
+.TP
+.BI "--to " "offset"
+Set the offset from which it starts looking for any matching. If not passed, default is the packet size.
+.TP
+.BI "--string " "pattern"
+Matches the given pattern.
+.BI "--hex-string " "pattern"
+Matches the given pattern in hex notation.
.SS tcp
These extensions are loaded if `--protocol tcp' is specified. It
provides the following options:
RST flags unset.
.TP
.B "[!] --syn"
-Only match TCP packets with the SYN bit set and the ACK and RST bits
+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 SYN\fP.
+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 "--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).
.SS ttl
This module matches the time to live field in the IP header.
.TP
-.BI "--ttl " "ttl"
+.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:
.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
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.
+In Kernels up to 2.6.10 you can add several --to-destination options. For
+those kernels, 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 addresses.
+Later Kernels (>= 2.6.11-rc1) don't have the ability to NAT to multiple ranges
+anymore.
+
.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
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
.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 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 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.
+.TP
+.BR "--queue-num " "\fIvalue"
+This specifies the QUEUE number to use. Valud queue numbers are 0 to 65535. The default value is 0.
+.TP
+It can only be used with Kernel versions 2.6.14 or later, since it requires
+the
+.B
+nfnetlink_queue
+kernel support.
+.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
and
.B OUTPUT
chains, and user-defined chains which are only called from those
-chains. It alters the destination IP address to send the packet to
-the machine itself (locally-generated packets are mapped to the
-127.0.0.1 address). It takes one option:
+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
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
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.
+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.
+.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" .
+It is only valid in the
+.BR mangle
+table.
.br
This target is used to overcome criminally braindead ISPs or servers
which block ICMP Fragmentation Needed packets. The symptoms of this
Workaround: activate this option and add a rule to your firewall
configuration like:
.nf
- iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN \\
+ iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN \\
-j TCPMSS --clamp-mss-to-pmtu
.fi
.TP
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
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
other errors cause an exit code of 1.
.SH BUGS
Bugs? What's this? ;-)
-Well... the counters are not reliable on sparc64.
+Well, you might want to have a look at http://bugzilla.netfilter.org/
.SH COMPATIBILITY WITH IPCHAINS
This
.B iptables
.BR iptables-restore (8),
.BR ip6tables (8),
.BR ip6tables-save (8),
-.BR ip6tables-restore (8).
+.BR ip6tables-restore (8),
+.BR libipq (3).
.P
The packet-filtering-HOWTO details iptables usage for
packet filtering, the NAT-HOWTO details NAT,
See
.BR "http://www.netfilter.org/" .
.SH AUTHORS
-Rusty Russell wrote iptables, in early consultation with Michael
+Rusty Russell originally wrote iptables, in early consultation with Michael
Neuling.
.PP
Marc Boucher made Rusty abandon ipnatctl by lobbying for a generic packet
.PP
Jozsef Kadlecsik wrote the REJECT target.
.PP
-Harald Welte wrote the ULOG target, TTL, DSCP, ECN matches and targets.
+Harald Welte wrote the ULOG and NFQUEUE target, the new libiptc, as well as the TTL, DSCP, ECN matches and targets.
.PP
The Netfilter Core Team is: Marc Boucher, Martin Josefsson, Jozsef Kadlecsik,
-James Morris, Harald Welte and Rusty Russell.
+Patrick McHardy, James Morris, Harald Welte and Rusty Russell.
.PP
-Man page written by Herve Eychenne <rv@wallfire.org>.
+Man page originally written by Herve Eychenne <rv@wallfire.org>.
.\" .. and did I mention that we are incredibly cool people?
.\" .. sexy, too ..
.\" .. witty, charming, powerful ..
git://git.onelab.eu / iptables.git / blobdiff