ip6tables Linux Service

ip6tables service:

Ip6tables is used to set up, maintain, and inspect the tables of IPv6 packet filter rules in the Linux kernel.
Now lets see the manual of ip6tables service.
Manual ip6tables:
NAME
ip6tables - IPv6 packet filter administration
SYNOPSIS
ip6tables [-t table] -[AD] chain rule-specification [options]
ip6tables [-t table] -I chain [rulenum] rule-specification [options]
ip6tables [-t table] -R chain rulenum rule-specification [options]
ip6tables [-t table] -D chain rulenum [options]
ip6tables [-t table] -[LFZ] [chain] [options]
ip6tables [-t table] -N chain
ip6tables [-t table] -X [chain]
ip6tables [-t table] -P chain target [options]
ip6tables [-t table] -E old-chain-name new-chain-name
DESCRIPTION
Ip6tables is used to set up, maintain, and inspect the tables of IPv6 packet filter rules in the Linux kernel. Several different tables may be defined. Each table contains a number of built-in chains and may also contain user-defined chains.
Each chain is a list of rules which can match a set of packets. Each rule specifies what to do with a packet that matches. This is called a 'target', which may be a jump to a user-defined chain in the same table.
TARGETS
A firewall rule specifies criteria for a packet, and a target. If the packet does not match, the next rule in the chain is the examined; if it does match, then the next rule is specified by the value of the target, which can be the name of a user-defined chain or one of the special values 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 (if supported by the kernel). 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 two independent tables (which tables are present at any time depends on the kernel configuration options and which modules are present), as nat table has not been implemented yet.
-t, --table table
This option specifies the packet matching table which the command should operate on. If the kernel is configured with automatic module loading, an attempt will be made to load the appropriate module for that table if it is not already there.
The tables are as follows:
filter:
This is the default table (if no -t option is passed). It contains the built-in chains INPUT (for packets coming into the box itself), FORWARD (for packets being routed through the box), and OUTPUT (for locally-generated packets).
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 supported: INPUT (for packets coming into the box itself), FORWARD (for altering packets being routed through the box), and POSTROUTING (for altering packets as they are about to go out).
OPTIONS
The options that are recognized by ip6tables 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 ip6tables 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 combination.
-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
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 destination 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 mangle rules get listed by ip6tables -t mangle -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
ip6tables -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 counters 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. 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 section 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 specified protocol can be one of tcp, udp, ipv6-icmp|icmpv6, or all, or it can be a numeric value, representing one of these protocols or a different one. A protocol name from /etc/protocols is also allowed. A "!" argument before the protocol inverts the test. The number zero is equivalent to 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 hostname (please note that specifying any name to be resolved with a remote query such as DNS is a really bad idea), a network IPv6 address (with /mask), or a plain IPv6 address. (the network name isn't supported now). 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 64 is equivalent to ffff:ffff:ffff:ffff:0000:0000:0000:0000. 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 userdefined 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, then matching the rule will have no effect on the packet's fate, but the counters on the rule will be incremented.
-i, --in-interface [!] name
Name of an interface via which a packet is going to be 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 and OUTPUT 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.
-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 multipliers 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 applicable).
-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
ip6tables 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 modules 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.
ah
This module matches the SPIs in AH header of IPSec packets.
--ahspi [!] spi[:spi]
condition
This matches if a specific /proc filename is '0' or '1'.
--condition [!] filename
Match on boolean value stored in /proc/net/ip6t_condition/filename file
dst
This module matches the IPv6 destination header options
--dst-len[!]length
Total length of this header
--dst-opts TYPE[:LEN],[,TYPE[:LEN]...]
Options and it's length (List).
esp
This module matches the SPIs in ESP header of IPSec packets.
--espspi [!] spi[:spi]
eui64
This module matches the EUI64 part of a stateless autoconfigured IPv6 address. It compares the source MAC address with the lower 64 bits of the IPv6 address.
frag
This module matches the time IPv6 fragmentathion header
--fragid [!]id[:id]
Matches the given fragmentation ID (range).
--fraglen [!]length
Matches the total length of this header.
--fragres
Matches the reserved field, too.
--fragfirst
Matches on the first fragment.
[--fragmore]
Matches if there are more fragments.
[--fraglast]
Matches if this is the last fragement.
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).
hbh
This module matches the IPv6 hop-by-hop header options
--hbh-len[!]length
Total length of this header
--hbh-opts TYPE[:LEN],[,TYPE[:LEN]...]
Options and it's length (List).
hl
This module matches the HOPLIMIT field in the IPv6 header.
--hl-eq value
Matches if HOPLIMIT equals the given value.
--hl-lt ttl
Matches if HOPLIMIT is less than the given value.
--hl-gt ttl
Matches if HOPLIMIT is greater than the given value.
icmpv6
This extension is loaded if '--protocol ipv6-icmp' or '--protocol icmpv6' is specified. It provides the following option:
--icmpv6-type [!] typename
This allows specification of the ICMP type, which can be a numeric IPv6-ICMP type, or one of the IPv6-ICMP type names shown by the command
ip6tables -p ipv6-icmp -h
ipv6header
This module matches on IPv6 option headers
--header [!]headers
Matches the given type of headers. Names: hop,dst,route,frag,auth,esp,none,proto Long Names: hop-by- hop,ipv6-opts,ipv6-route,ipv6-frag,ah,esp,ipv6-nonxt,protocol Numbers: 0,60,43,44,51,50,59
--soft The header CONTAINS the specified extensions.
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, FORWARD 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 comparison).
multiport
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.
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.
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. This is regarded as experimental.
--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 session group.
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.
rt
Match on IPv6 routing header
--rt-type [!]type
Match the type (numeric).
--rt-segsleft[!]num[:num]
Match the 'segments left' field (range).
--rt-len[!]length
Match the length of this header
--rt-0-res
Match the reserved field, too (type=0)
--rt-0-addrs ADDR[,ADDR...]
Match type=0 addresses (list).
--rt-0-not-strict
List of type=0 addresses is not a strict list.
tcp
These extensions are loaded if '--protocol tcp' is specified. It provides 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-separated 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
ip6tables -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 and RST 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 --tcp-flags SYN,RST,ACK SYN. If the "!" flag precedes the "--syn", the sense of the option is inverted.
--tcp-option [!] number
Match if TCP option set.
udp
These extensions are loaded if '--protocol udp' is specified. It provides 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 description of the --destination-port option of the TCP extension for details.
TARGET EXTENSIONS
ip6tables can use extended target modules: the following are included in the standard distribution.
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... the counters are not reliable on sparc64.
COMPATIBILITY WITH IPCHAINS
This ip6tables 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. There are several other changes in ip6tables.
SEE ALSO
ip6tables-save(8), ip6tables-restore(8), iptables(8), iptables-save(8), iptables-restore(8).
The packet-filtering-HOWTO details iptables usage for packet filtering, the NAT-HOWTO details NAT, the netfilter- extensions-HOWTO details the extensions that are not in the standard distribution, and the netfilter-hacking-HOWTO details the netfilter internals.
See http://www.netfilter.org/.
AUTHORS
Rusty Russell 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 everywhere.
James Morris wrote the TOS target, and tos match.
Jozsef Kadlecsik wrote the REJECT target.
Harald Welte wrote the ULOG target, TTL match+target and libipulog.
The Netfilter Core Team is: Marc Boucher, Martin Josefsson, Jozsef Kadlecsik, James Morris, Harald Welte and Rusty Russell.
ip6tables man page created by Andras Kis-Szabo, based on iptables man page written by Herve Eychenne <rv@wallfire.org>.