Documentation

iptables - Modify the systems iptables

New in version 2.0.

Synopsis

  • Iptables is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel.
  • This module does not handle the saving and/or loading of rules, but rather only manipulates the current rules that are present in memory. This is the same as the behaviour of the iptables and ip6tables command which this module uses internally.

Parameters

Parameter Choices/Defaults Comments
action
(added in 2.2)
    Choices:
  • append ←
  • insert
Whether the rule should be appended at the bottom or inserted at the top.
If the rule already exists the chain won't be modified.
chain
Chain to operate on.
This option can either be the name of a user defined chain or any of the builtin chains: 'INPUT', 'FORWARD', 'OUTPUT', 'PREROUTING', 'POSTROUTING', 'SECMARK', 'CONNSECMARK'.
comment
This specifies a comment that will be added to the rule.
ctstate
    Choices:
  • DNAT
  • ESTABLISHED
  • INVALID
  • NEW
  • RELATED
  • SNAT
  • UNTRACKED
Default:
[]
ctstate is a list of the connection states to match in the conntrack module. Possible states are: 'INVALID', 'NEW', 'ESTABLISHED', 'RELATED', 'UNTRACKED', 'SNAT', 'DNAT'
destination
Destination specification.
Address can be either a network name, a hostname, a network IP address (with /mask), or a plain IP address.
Hostnames will be resolved once only, before the rule is submitted to the kernel. Please note that specifying any name to be resolved with a remote query such as DNS is a really bad idea.
The mask can be either a network mask or a plain number, specifying the number of 1's at the left side of the network mask. Thus, a mask of 24 is equivalent to 255.255.255.0. A "!" argument before the address specification inverts the sense of the address.
destination_port
Destination 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 first:last. If the first port is omitted, '0' is assumed; if the last is omitted, '65535' is assumed. If the first port is greater than the second one they will be swapped. This is only valid if the rule also specifies one of the following protocols: tcp, udp, dccp or sctp.
flush
(added in 2.2)
Flushes the specified table and chain of all rules.
If no chain is specified then the entire table is purged.
Ignores all other parameters.
fragment
This means that the rule only refers to second and further fragments of fragmented packets. Since there is no way to tell the source or destination ports of such a packet (or ICMP type), such a packet will not match any rules which specify them. When the "!" argument precedes fragment argument, the rule will only match head fragments, or unfragmented packets.
goto
This specifies that the processing should continue in a user specified chain. Unlike the jump argument return will not continue processing in this chain but instead in the chain that called us via jump.
icmp_type
(added in 2.2)
This allows specification of the ICMP type, which can be a numeric ICMP type, type/code pair, or one of the ICMP type names shown by the command 'iptables -p icmp -h'
in_interface
Name of an interface via which a packet was received (only for packets entering the INPUT, FORWARD and PREROUTING chains). When the "!" argument is used before the interface name, the sense is inverted. If the interface name ends in a "+", then any interface which begins with this name will match. If this option is omitted, any interface name will match.
ip_version
    Choices:
  • ipv4 ←
  • ipv6
Which version of the IP protocol this rule should apply to.
jump
This specifies the target of the rule; i.e., what to do if the packet matches it. The target can be a user-defined chain (other than the one this rule is in), one of the special builtin targets which decide the fate of the packet immediately, or an extension (see EXTENSIONS below). If this option is omitted in a rule (and the goto parameter 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.
limit
Specifies the maximum average number of matches to allow per second.
The number can specify units explicitly, using `/second', `/minute', `/hour' or `/day', or parts of them (so `5/second' is the same as `5/s').
limit_burst
(added in 2.1)
Specifies the maximum burst before the above limit kicks in.
log_prefix
(added in 2.5)
Specifies a log text for the rule. Only make sense with a LOG jump.
match Default:
[]
Specifies a match to use, that is, an extension module that tests for a specific property. The set of matches make up the condition under which a target is invoked. Matches are evaluated first to last if specified as an array and work in short-circuit fashion, i.e. if one extension yields false, evaluation will stop.
out_interface
Name of an interface via which a packet is going to be sent (for packets entering the FORWARD, OUTPUT and POSTROUTING chains). When the "!" argument is used before the interface name, the sense is inverted. If the interface name ends in a "+", then any interface which begins with this name will match. If this option is omitted, any interface name will match.
policy
(added in 2.2)
    Choices:
  • ACCEPT
  • DROP
  • QUEUE
  • RETURN
Set the policy for the chain to the given target.
Only built-in chains can have policies.
This parameter requires the chain parameter.
Ignores all other parameters.
protocol
The protocol of the rule or of the packet to check.
The specified protocol can be one of tcp, udp, udplite, icmp, esp, ah, sctp or the special keyword "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. "all" will match with all protocols and is taken as default when this option is omitted.
reject_with
(added in 2.1)
Specifies the error packet type to return while rejecting. It implies "jump: REJECT"
rule_num
(added in 2.5)
Insert the rule as the given rule number. This works only with action = 'insert'.
set_counters
This enables the administrator to initialize the packet and byte counters of a rule (during INSERT, APPEND, REPLACE operations).
set_dscp_mark
(added in 2.1)
This allows specifying a DSCP mark to be added to packets. It takes either an integer or hex value.
Mutually exclusive with set_dscp_mark_class.
set_dscp_mark_class
(added in 2.1)
This allows specifying a predefined DiffServ class which will be translated to the corresponding DSCP mark.
Mutually exclusive with set_dscp_mark.
source
Source specification.
Address can be either a network name, a hostname, a network IP address (with /mask), or a plain IP address.
Hostnames will be resolved once only, before the rule is submitted to the kernel. Please note that specifying any name to be resolved with a remote query such as DNS is a really bad idea.
The mask can be either a network mask or a plain number, specifying the number of 1's at the left side of the network mask. Thus, a mask of 24 is equivalent to 255.255.255.0. A "!" argument before the address specification inverts the sense of the address.
source_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 first:last. If the first port is omitted, '0' is assumed; if the last is omitted, '65535' is assumed. If the first port is greater than the second one they will be swapped.
state
    Choices:
  • absent
  • present ←
Whether the rule should be absent or present.
syn
(added in 2.5)
    Choices:
  • ignore ←
  • match
  • negate
This allows matching packets that have the SYN bit set and the ACK and RST bits unset.
When negated, this matches all packets with the RST or the ACK bits set.
table
    Choices:
  • filter ←
  • nat
  • mangle
  • raw
  • security
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.
tcp_flags
(added in 2.4)
Default:
{}
TCP flags specification.
tcp_flags expects a dict with the two keys flags and flags_set.
flags
List of flags you want to examine.
flags_set
Flags to be set.
to_destination
(added in 2.1)
This specifies a destination address to use with DNAT.
Without this, the destination address is never altered.
to_ports
This specifies a destination port or range of ports to use: without this, the destination port is never altered. This is only valid if the rule also specifies one of the following protocols: tcp, udp, dccp or sctp.
to_source
(added in 2.2)
This specifies a source address to use with SNAT.
Without this, the source address is never altered.
uid_owner
(added in 2.1)
Specifies the UID or username to use in match by owner rule. From Ansible 2.6 when the ! argument is prepended then the it inverts the rule to apply instead to all users except that one specified.

Notes

Note

  • This module just deals with individual rules. If you need advanced chaining of rules the recommended way is to template the iptables restore file.

Examples

# Block specific IP
- iptables:
    chain: INPUT
    source: 8.8.8.8
    jump: DROP
  become: yes

# Forward port 80 to 8600
- iptables:
    table: nat
    chain: PREROUTING
    in_interface: eth0
    protocol: tcp
    match: tcp
    destination_port: 80
    jump: REDIRECT
    to_ports: 8600
    comment: Redirect web traffic to port 8600
  become: yes

# Allow related and established connections
- iptables:
    chain: INPUT
    ctstate: ESTABLISHED,RELATED
    jump: ACCEPT
  become: yes

# Allow new incoming SYN packets on TCP port 22 (SSH).
- iptables:
    chain: INPUT
    protocol: tcp
    destination_port: 22
    ctstate: NEW
    syn: match
    jump: ACCEPT
    comment: Accept new SSH connections.

# Tag all outbound tcp packets with DSCP mark 8
- iptables:
    chain: OUTPUT
    jump: DSCP
    table: mangle
    set_dscp_mark: 8
    protocol: tcp

# Tag all outbound tcp packets with DSCP DiffServ class CS1
- iptables:
    chain: OUTPUT
    jump: DSCP
    table: mangle
    set_dscp_mark_class: CS1
    protocol: tcp

# Insert a rule on line 5
- iptables:
    chain: INPUT
    protocol: tcp
    destination_port: 8080
    jump: ACCEPT
    rule_num: 5

# Set the policy for the INPUT chain to DROP
- iptables:
    chain: INPUT
    policy: DROP

# Reject tcp with tcp-reset
- iptables:
    chain: INPUT
    protocol: tcp
    reject_with: tcp-reset
    ip_version: ipv4

# Set tcp flags
- iptables:
    chain: OUTPUT
    jump: DROP
    protocol: tcp
    tcp_flags:
      flags: ALL
      flags_set:
        - ACK
        - RST
        - SYN
        - FIN

Status

This module is flagged as preview which means that it is not guaranteed to have a backwards compatible interface.

Maintenance

This module is flagged as core which means that it is maintained by the Ansible Core Team. See Module Maintenance & Support for more info.

For a list of other modules that are also maintained by the Ansible Core Team, see here.

Support

For more information about Red Hat’s support of this module, please refer to this Knowledge Base article

Author

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