+.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.