How to configure the Linux kernel/net/ipv4/netfilter

Howto configure the Linux kernel / net / ipv4 / netfilter


 * IP netfilter configuration
 * IP netfilter configuration

IP: Netfilter Configuration

 * depends on INET && NETFILTER


 * Option: NF_CONNTRACK_IPV4
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) IPv4 support for new connection tracking (EXPERIMENTAL)
 * depends on EXPERIMENTAL && NF_CONNTRACK
 * Connection tracking keeps a record of what packets have passed through your machine, in order to figure out how they are related into connections.
 * This is IPv4 support on Layer 3 independent connection tracking. Layer 3 independent connection tracking is experimental scheme which generalize ip_conntrack to support other layer 3 protocols.
 * To compile it as a module, choose M here. If unsure, say N.


 * connection tracking, helpers and protocols


 * Option: IP_NF_CONNTRACK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Connection tracking (required for masq/NAT)
 * Connection tracking keeps a record of what packets have passed through your machine, in order to figure out how they are related into connections.
 * This is required to do Masquerading or other kinds of Network Address Translation (except for Fast NAT). It can also be used to enhance packet filtering (see `Connection state match support' below).
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_CT_ACCT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) Connection tracking flow accounting
 * depends on IP_NF_CONNTRACK
 * If this option is enabled, the connection tracking code will keep per-flow packet and byte counters.
 * Those counters can be used for flow-based accounting or the `connbytes' match.
 * If unsure, say `N'.


 * Option: IP_NF_CONNTRACK_MARK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off)  'Connection mark tracking support'
 * depends on IP_NF_CONNTRACK
 * This option enables support for connection marks, used by the `CONNMARK' target and `connmark' match. Similar to the mark value of packets, but this mark value is kept in the conntrack session instead of the individual packets.


 * Option: IP_NF_CONNTRACK_EVENTS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) Connection tracking events (EXPERIMENTAL)
 * depends on EXPERIMENTAL && IP_NF_CONNTRACK
 * If this option is enabled, the connection tracking code will provide a notifier chain that can be used by other kernel code to get notified about changes in the connection tracking state. IF unsure, say `N'.


 * Option: IP_NF_CONNTRACK_NETLINK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) 'Connection tracking netlink interface (EXPERIMENTAL)'
 * depends on EXPERIMENTAL && IP_NF_CONNTRACK && NETFILTER_NETLINK
 * depends on IP_NF_CONNTRACK!=y || NETFILTER_NETLINK!=m
 * This option enables support for a netlink-based userspace interface


 * Option: IP_NF_CT_PROTO_SCTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'SCTP protocol connection tracking support (EXPERIMENTAL)'
 * depends on IP_NF_CONNTRACK && EXPERIMENTAL
 * With this option enabled, the connection tracking code will be able to do state tracking on SCTP connections.
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_FTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) FTP protocol support
 * depends on IP_NF_CONNTRACK
 * Tracking FTP connections is problematic: special helpers are required for tracking them, and doing masquerading and other forms of Network Address Translation on them.
 * To compile it as a module, choose M here. If unsure, say Y.


 * Option: IP_NF_IRC
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) IRC protocol support
 * depends on IP_NF_CONNTRACK
 * There is a commonly-used extension to IRC called Direct Client-to-Client Protocol (DCC). This enables users to send files to each other, and also chat to each other without the need of a server.  DCC Sending is used anywhere you send files over IRC, and DCC Chat is most commonly used by Eggdrop bots.  If you are using NAT, this extension will enable you to send files and initiate chats.  Note that you do NOT need this extension to get files or have others initiate chats, or everything else in IRC.
 * To compile it as a module, choose M here. If unsure, say Y.


 * Option: IP_NF_NETBIOS_NS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) NetBIOS name service protocol support (EXPERIMENTAL)
 * depends on IP_NF_CONNTRACK && EXPERIMENTAL
 * NetBIOS name service requests are sent as broadcast messages from an unprivileged port and responded to with unicast messages to the same port. This make them hard to firewall properly because connection tracking doesn't deal with broadcasts. This helper tracks locally originating NetBIOS name service requests and the corresponding responses. It relies on correct IP address configuration, specifically netmask and broadcast address. When properly configured, the output of "ip address show" should look similar to this:
 * $ ip -4 address show eth0 4: eth0:  mtu 1500 qdisc pfifo_fast qlen 1000    inet 172.16.2.252/24 brd 172.16.2.255 scope global eth0  To compile it as a module, choose M here.  If unsure, say N.


 * Option: IP_NF_TFTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) TFTP protocol support
 * depends on IP_NF_CONNTRACK
 * TFTP connection tracking helper, this is required depending on how restrictive your ruleset is. If you are using a tftp client behind -j SNAT or -j MASQUERADING you will need this.
 * To compile it as a module, choose M here. If unsure, say Y.


 * Option: IP_NF_AMANDA
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Amanda backup protocol support
 * depends on IP_NF_CONNTRACK
 * If you are running the Amanda backup package  on this machine or machines that will be MASQUERADED through this machine, then you may want to enable this feature. This allows the connection tracking and natting code to allow the sub-channels that Amanda requires for communication of the backup data, messages and index.
 * To compile it as a module, choose M here. If unsure, say Y.


 * Option: IP_NF_PPTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'PPTP protocol support'
 * depends on IP_NF_CONNTRACK
 * This module adds support for PPTP (Point to Point Tunnelling Protocol, RFC2637) connection tracking and NAT.
 * If you are running PPTP sessions over a stateful firewall or NAT box, you may want to enable this feature.
 * Please note that not all PPTP modes of operation are supported yet. For more info, read top of the file net/ipv4/netfilter/ip_conntrack_pptp.c
 * If you want to compile it as a module, say M here and read Documentation/modules.txt. If unsure, say `N'.


 * Option: IP_NF_QUEUE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) IP Userspace queueing via NETLINK (OBSOLETE)
 * Netfilter has the ability to queue packets to user space: the netlink device can be used to access them using this driver.
 * This option enables the old IPv4-only "ip_queue" implementation which has been obsoleted by the new "nfnetlink_queue" code (see CONFIG_NETFILTER_NETLINK_QUEUE).
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_IPTABLES
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) IP tables support (required for filtering/masq/NAT)
 * iptables is a general, extensible packet identification framework. The packet filtering and full NAT (masquerading, port forwarding, etc.) subsystems now use this: say `Y' or `M' here if you want to use either of those.
 * To compile it as a module, choose M here. If unsure, say N.


 * The matches.


 * Option: IP_NF_MATCH_LIMIT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) limit match support
 * depends on IP_NF_IPTABLES
 * limit matching allows you to control the rate at which a rule can be matched: mainly useful in combination with the LOG target ("LOG target support", below) and to avoid some Denial of Service attacks.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_IPRANGE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) IP range match support
 * depends on IP_NF_IPTABLES
 * This option makes possible to match IP addresses against IP address ranges.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_MAC
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) MAC address match support
 * depends on IP_NF_IPTABLES
 * MAC matching allows you to match packets based on the source Ethernet address of the packet.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_PKTTYPE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Packet type match support
 * depends on IP_NF_IPTABLES
 * Packet type matching allows you to match a packet by its "class", e.g. BROADCAST, MULTICAST, ...
 * Typical usage: iptables -A INPUT -m pkttype—pkt-type broadcast -j LOG
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_MARK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) netfilter MARK match support
 * depends on IP_NF_IPTABLES
 * Netfilter mark matching allows you to match packets based on the `nfmark' value in the packet. This can be set by the MARK target (see below).
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_MULTIPORT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Multiple port match support
 * depends on IP_NF_IPTABLES
 * Multiport matching allows you to match TCP or UDP packets based on a series of source or destination ports: normally a rule can only match a single range of ports.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_TOS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) TOS match support
 * depends on IP_NF_IPTABLES
 * TOS matching allows you to match packets based on the Type Of Service fields of the IP packet.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_RECENT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) recent match support
 * depends on IP_NF_IPTABLES
 * This match is used for creating one or many lists of recently used addresses and then matching against that/those list(s).
 * Short options are available by using 'iptables -m recent -h' Official Website: 
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_ECN
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) ECN match support
 * depends on IP_NF_IPTABLES
 * This option adds a `ECN' match, which allows you to match against the IPv4 and TCP header ECN fields.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_DSCP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) DSCP match support
 * depends on IP_NF_IPTABLES
 * This option adds a `DSCP' match, which allows you to match against the IPv4 header DSCP field (DSCP codepoint).
 * The DSCP codepoint can have any value between 0x0 and 0x4f.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_AH_ESP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) AH/ESP match support
 * depends on IP_NF_IPTABLES
 * These two match extensions (`ah' and `esp') allow you to match a range of SPIs inside AH or ESP headers of IPSec packets.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_LENGTH
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) LENGTH match support
 * depends on IP_NF_IPTABLES
 * This option allows you to match the length of a packet against a specific value or range of values.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_TTL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) TTL match support
 * depends on IP_NF_IPTABLES
 * This adds CONFIG_IP_NF_MATCH_TTL option, which enabled the user to match packets by their TTL value.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_TCPMSS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) tcpmss match support
 * depends on IP_NF_IPTABLES
 * This option adds a `tcpmss' match, which allows you to examine the MSS value of TCP SYN packets, which control the maximum packet size for that connection.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_HELPER
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Helper match support
 * depends on IP_NF_IPTABLES
 * depends on IP_NF_CONNTRACK || NF_CONNTRACK_IPV4
 * Helper matching allows you to match packets in dynamic connections tracked by a conntrack-helper, i.e. ip_conntrack_ftp
 * To compile it as a module, choose M here. If unsure, say Y.


 * Option: IP_NF_MATCH_STATE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Connection state match support
 * depends on IP_NF_IPTABLES
 * depends on IP_NF_CONNTRACK || NF_CONNTRACK_IPV4
 * Connection state matching allows you to match packets based on their relationship to a tracked connection (i.e. previous packets). This is a powerful tool for packet classification.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_CONNTRACK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Connection tracking match support
 * depends on IP_NF_IPTABLES
 * depends on IP_NF_CONNTRACK || NF_CONNTRACK_IPV4
 * This is a general conntrack match module, a superset of the state match.
 * It allows matching on additional conntrack information, which is useful in complex configurations, such as NAT gateways with multiple internet links or tunnels.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_OWNER
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Owner match support
 * depends on IP_NF_IPTABLES
 * Packet owner matching allows you to match locally-generated packets based on who created them: the user, group, process or session.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_PHYSDEV
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Physdev match support
 * depends on IP_NF_IPTABLES && BRIDGE_NETFILTER
 * Physdev packet matching matches against the physical bridge ports the IP packet arrived on or will leave by.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_MATCH_ADDRTYPE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'address type match support'
 * depends on IP_NF_IPTABLES
 * This option allows you to match what routing thinks of an address, e.g. UNICAST, LOCAL, BROADCAST, ...
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_MATCH_REALM
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'realm match support'
 * depends on IP_NF_IPTABLES
 * select NET_CLS_ROUTE
 * This option adds a `realm' match, which allows you to use the realm key from the routing subsystem inside iptables.
 * This match pretty much resembles the CONFIG_NET_CLS_ROUTE4 option in tc world.
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_MATCH_SCTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'SCTP protocol match support'
 * depends on IP_NF_IPTABLES
 * With this option enabled, you will be able to use the iptables `sctp' match in order to match on SCTP source/destination ports and SCTP chunk types.
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_MATCH_DCCP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'DCCP protocol match support'
 * depends on IP_NF_IPTABLES
 * With this option enabled, you will be able to use the iptables `dccp' match in order to match on DCCP source/destination ports and DCCP flags.
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_MATCH_COMMENT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'comment match support'
 * depends on IP_NF_IPTABLES
 * This option adds a `comment' dummy-match, which allows you to put comments in your iptables ruleset.
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_MATCH_CONNMARK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'Connection mark match support'
 * depends on IP_NF_IPTABLES
 * depends on (IP_NF_CONNTRACK && IP_NF_CONNTRACK_MARK) || (NF_CONNTRACK_MARK && NF_CONNTRACK_IPV4)
 * This option adds a `connmark' match, which allows you to match the connection mark value previously set for the session by `CONNMARK'.
 * If you want to compile it as a module, say M here and read . The module will be called ipt_connmark.o.  If unsure, say `N'.


 * Option: IP_NF_MATCH_CONNBYTES
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'Connection byte/packet counter match support'
 * depends on IP_NF_IPTABLES
 * depends on (IP_NF_CONNTRACK && IP_NF_CT_ACCT) || (NF_CT_ACCT && NF_CONNTRACK_IPV4)
 * This option adds a `connbytes' match, which allows you to match the number of bytes and/or packets for each direction within a connection.
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_MATCH_HASHLIMIT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'hashlimit match support'
 * depends on IP_NF_IPTABLES
 * This option adds a new iptables `hashlimit' match.
 * As opposed to `limit', this match dynamically crates a hash table of limit buckets, based on your selection of source/destination ip addresses and/or ports.
 * It enables you to express policies like `10kpps for any given destination IP' or `500pps from any given source IP' with a single IPtables rule.


 * Option: IP_NF_MATCH_STRING
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'string match support'
 * depends on IP_NF_IPTABLES
 * select TEXTSEARCH
 * select TEXTSEARCH_KMP
 * select TEXTSEARCH_BM
 * select TEXTSEARCH_FSM
 * This option adds a `string' match, which allows you to look for pattern matchings in packets.
 * To compile it as a module, choose M here. If unsure, say N.


 * `filter', generic and specific targets


 * Option: IP_NF_FILTER
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Packet filtering
 * depends on IP_NF_IPTABLES
 * Packet filtering defines a table `filter', which has a series of rules for simple packet filtering at local input, forwarding and local output. See the man page for iptables(8).
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_REJECT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) REJECT target support
 * depends on IP_NF_FILTER
 * The REJECT target allows a filtering rule to specify that an ICMP error should be issued in response to an incoming packet, rather than silently being dropped.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_LOG
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) LOG target support
 * depends on IP_NF_IPTABLES
 * This option adds a `LOG' target, which allows you to create rules in any iptables table which records the packet header to the syslog.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_ULOG
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) ULOG target support (OBSOLETE)
 * depends on IP_NF_IPTABLES
 * This option enables the old IPv4-only "ipt_ULOG" implementation which has been obsoleted by the new "nfnetlink_log" code (see CONFIG_NETFILTER_NETLINK_LOG).
 * This option adds a `ULOG' target, which allows you to create rules in any iptables table. The packet is passed to a userspace logging daemon using netlink multicast sockets; unlike the LOG target which can only be viewed through syslog.
 * The appropriate userspace logging daemon (ulogd) may be obtained from 
 * To compile it as a module, choose M here. If unsure, say N.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_TCPMSS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) TCPMSS target support
 * depends on IP_NF_IPTABLES
 * This option adds a `TCPMSS' target, which allows you 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).
 * This 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 configuration like:
 * iptables -A FORWARD -p tcp—tcp-flags SYN,RST SYN \ -j TCPMSS—clamp-mss-to-pmtu
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_NFQUEUE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) NFQUEUE Target Support
 * depends on IP_NF_IPTABLES
 * This Target replaced the old obsolete QUEUE target.
 * As opposed to QUEUE, it supports 65535 different queues, not just one.
 * To compile it as a module, choose M here. If unsure, say N.


 * NAT + specific targets


 * Option: IP_NF_NAT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Full NAT
 * depends on IP_NF_IPTABLES && IP_NF_CONNTRACK
 * The Full NAT option allows masquerading, port forwarding and other forms of full Network Address Port Translation. It is controlled by the `nat' table in iptables: see the man page for iptables(8).
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_NAT_NEEDED
 * Kernel Versions: 2.6.15.6 ...
 * (on/off)
 * depends on IP_NF_NAT != n
 * default y


 * Option: IP_NF_TARGET_MASQUERADE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) MASQUERADE target support
 * depends on IP_NF_NAT
 * Masquerading is a special case of NAT: all outgoing connections are changed to seem to come from a particular interface's address, and if the interface goes down, those connections are lost. This is only useful for dialup accounts with dynamic IP address (i.e. your IP address will be different on next dialup).
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_REDIRECT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) REDIRECT target support
 * depends on IP_NF_NAT
 * REDIRECT is a special case of NAT: all incoming connections are mapped onto the incoming interface's address, causing the packets to come to the local machine instead of passing through. This is useful for transparent proxies.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_NETMAP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) NETMAP target support
 * depends on IP_NF_NAT
 * NETMAP is an implementation of static 1:1 NAT mapping of network addresses. It maps the network address part, while keeping the host address part intact. It is similar to Fast NAT, except that Netfilter's connection tracking doesn't work well with Fast NAT.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_SAME
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) SAME target support
 * depends on IP_NF_NAT
 * This option adds a `SAME' target, which works like the standard SNAT target, but attempts to give clients the same IP for all connections.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_NAT_SNMP_BASIC
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Basic SNMP-ALG support (EXPERIMENTAL)
 * depends on EXPERIMENTAL && IP_NF_NAT
 * This module implements an Application Layer Gateway (ALG) for SNMP payloads. In conjunction with NAT, it allows a network management system to access multiple private networks with conflicting addresses.  It works by modifying IP addresses inside SNMP payloads to match IP-layer NAT mapping.
 * This is the "basic" form of SNMP-ALG, as described in RFC 2962
 * To compile it as a module, choose M here. If unsure, say N.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_NAT_IRC
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)
 * depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
 * default IP_NF_NAT if IP_NF_IRC=y
 * default m if IP_NF_IRC=m


 * If they want FTP, set to $CONFIG_IP_NF_NAT (m or y),
 * or $CONFIG_IP_NF_FTP (m or y), whichever is weaker. Argh.


 * Option: IP_NF_NAT_FTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)
 * depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
 * default IP_NF_NAT if IP_NF_FTP=y
 * default m if IP_NF_FTP=m


 * Option: IP_NF_NAT_TFTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)
 * depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
 * default IP_NF_NAT if IP_NF_TFTP=y
 * default m if IP_NF_TFTP=m


 * Option: IP_NF_NAT_AMANDA
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)
 * depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
 * default IP_NF_NAT if IP_NF_AMANDA=y
 * default m if IP_NF_AMANDA=m


 * Option: IP_NF_NAT_PPTP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)
 * depends on IP_NF_NAT!=n && IP_NF_PPTP!=n
 * default IP_NF_NAT if IP_NF_PPTP=y
 * default m if IP_NF_PPTP=m


 * mangle + specific targets


 * Option: IP_NF_MANGLE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) Packet mangling
 * depends on IP_NF_IPTABLES
 * This option adds a `mangle' table to iptables: see the man page for iptables(8). This table is used for various packet alterations which can effect how the packet is routed.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_TOS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) TOS target support
 * depends on IP_NF_MANGLE
 * This option adds a `TOS' target, which allows you to create rules in the `mangle' table which alter the Type Of Service field of an IP packet prior to routing.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_ECN
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) ECN target support
 * depends on IP_NF_MANGLE
 * This option adds a `ECN' target, which can be used in the iptables mangle table.
 * You can use this target to remove the ECN bits from the IPv4 header of an IP packet. This is particularly useful, if you need to work around existing ECN blackholes on the internet, but don't want to disable ECN support in general.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_DSCP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) DSCP target support
 * depends on IP_NF_MANGLE
 * This option adds a `DSCP' match, which allows you to match against the IPv4 header DSCP field (DSCP codepoint).
 * The DSCP codepoint can have any value between 0x0 and 0x4f.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_MARK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) MARK target support
 * depends on IP_NF_MANGLE
 * This option adds a `MARK' target, which allows you to create rules in the `mangle' table which alter the netfilter mark (nfmark) field associated with the packet prior to routing. This can change the routing method (see `Use netfilter MARK value as routing key') and can also be used by other subsystems to change their behavior.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_CLASSIFY
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) CLASSIFY target support
 * depends on IP_NF_MANGLE
 * This option adds a `CLASSIFY' target, which enables the user to set the priority of a packet. Some qdiscs can use this value for classification, among these are:
 * atm, cbq, dsmark, pfifo_fast, htb, prio
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_TTL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'TTL target support'
 * depends on IP_NF_MANGLE
 * This option adds a `TTL' target, which enables the user to modify the TTL value of the IP header.
 * While it is safe to decrement/lower the TTL, this target also enables functionality to increment and set the TTL value of the IP header to arbitrary values. This is EXTREMELY DANGEROUS since you can easily create immortal packets that loop forever on the network.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_TARGET_CONNMARK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'CONNMARK target support'
 * depends on IP_NF_MANGLE
 * depends on (IP_NF_CONNTRACK && IP_NF_CONNTRACK_MARK) || (NF_CONNTRACK_MARK && NF_CONNTRACK_IPV4)
 * This option adds a `CONNMARK' target, which allows one to manipulate the connection mark value. Similar to the MARK target, but affects the connection mark value rather than the packet mark value.
 * If you want to compile it as a module, say M here and read . The module will be called ipt_CONNMARK.o.  If unsure, say `N'.


 * Option: IP_NF_TARGET_CLUSTERIP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) CLUSTERIP target support (EXPERIMENTAL)
 * depends on IP_NF_MANGLE && EXPERIMENTAL
 * depends on (IP_NF_CONNTRACK && IP_NF_CONNTRACK_MARK) || (NF_CONNTRACK_MARK && NF_CONNTRACK_IPV4)
 * The CLUSTERIP target allows you to build load-balancing clusters of network servers without having a dedicated load-balancing router/server/switch.
 * To compile it as a module, choose M here. If unsure, say N.


 * raw + specific targets


 * Option: IP_NF_RAW
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'raw table support (required for NOTRACK/TRACE)'
 * depends on IP_NF_IPTABLES
 * This option adds a `raw' table to iptables. This table is the very first in the netfilter framework and hooks in at the PREROUTING and OUTPUT chains.
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * Option: IP_NF_TARGET_NOTRACK
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module)  'NOTRACK target support'
 * depends on IP_NF_RAW
 * depends on IP_NF_CONNTRACK || NF_CONNTRACK_IPV4
 * The NOTRACK target allows a select rule to specify which packets *not* to enter the conntrack/NAT subsystem with all the consequences (no ICMP error tracking, no protocol helpers for the selected packets).
 * If you want to compile it as a module, say M here and read . If unsure, say `N'.


 * ARP tables


 * Option: IP_NF_ARPTABLES
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) ARP tables support
 * arptables is a general, extensible packet identification framework. The ARP packet filtering and mangling (manipulation)subsystems use this: say Y or M here if you want to use either of those.
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_ARPFILTER
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) ARP packet filtering
 * depends on IP_NF_ARPTABLES
 * ARP packet filtering defines a table `filter', which has a series of rules for simple ARP packet filtering at local input and local output. On a bridge, you can also specify filtering rules for forwarded ARP packets. See the man page for arptables(8).
 * To compile it as a module, choose M here. If unsure, say N.


 * Option: IP_NF_ARP_MANGLE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off/module) ARP payload mangling
 * depends on IP_NF_ARPTABLES
 * Allows altering the ARP packet payload: source and destination hardware and network addresses.

Linux Kernel Configuration