IPChains - Create and Manipulate ipchains via Perl
$fw = IPChains->new(-option => value, ... );
This module acts as an interface to the
utility by Paul ``Rusty'' Russell
(http://www.rustcorp.com/linux/ipchains/). It attempts to include all the
functionality of the original code with a simplified user interface via
Perl. In addition, plans for log parsing facilities, an integrated
interface to ipmasqadm, and possibly traffic shaping are slated for up and
attribute() methods support the
Specifies origination address of packet. Appending hostmask to this address
using a / is OK, as well as specifying it separately (see SourceMask).
Hostmask for origination address. Can either be in 24 or 255.255.255.0
Specific port or port range (use xxx:xxx to denote range), requires
specific protocol specification.
Specifies destination address of packet. Appending hostmask to this address
using a / is OK, as well as specifying it separately (see DestMask)
Destination address, (see SourceMask).
Destination Port, (see SourcePort).
Protocol. Can be tcp, udp, icmp, or all. Required for specifying specific
ICMP Name/Code (in place of port when ICMP is specified as protocol).
Here is a small table of some of the most common ICMP packets:
Number Name Required by
0 echo-reply ping
3 destination-unreachable Any TCP/UDP traffic.
5 redirect routing if not running
8 echo-request ping
11 time-exceeded traceroute
Target. Can be ACCEPT, DENY, REJECT, MASQ, REDIRECT, RETURN, or a
user-defined chain. Note: This is case sensitive.
Specify a specify interface as part of the criteria (ie, eth0, ppp0, etc.).
Rule only refers to second and further fragments of fragmented packets (1
Makes criteria effective in both directions (1 or 0).
Set verbose option for setting rules or
list() (1 or 0).
Show output from
list() in numeric format. No DNS lookups,
etc.. (1 or 0).
Enable kernel logging (via syslog, kern.info) of matched packets (1 or 0).
Copy matching packets to the userspace device (advanced).
Mark matching packets with specified number (advanced).
Used for modifying the TOS field in the IP header. Takes 2 args, AND and
XOR masks, (ie, (TOS => [``0x01'', ``0x10''])). This feature is highly
The first mask is ANDed with the packet's current TOS, and the second mask
is XORed with it. Use the following table for reference:
TOS Name Value Typical Uses
Minimum Delay 0x01 0x10 ftp, telnet
Maximum Throughput 0x01 0x08 ftp-data
Maximum Reliability 0x01 0x04 snmp
Minimum Cost 0x01 0x02 nntp
Display exact numbers in byte counters instead of numbers rounded in K's,
M's, or G's (1 or 0).
Only match TCP packets with the SYN bit set and the ACK and FIN bits
cleared (1 or 0).
The following methods are available to you:
$fw = IPChains->new(option => value, ...) create new fw
object with options
$fw->attribute(option, value) to set option to value, OR
$value = $obj->attribute(option) to get current value of
$fw->clopts() clears all option settings (do this before calling methods
that take only a few specific options).
$fw->append(chain) appends current rule to end of chain
$fw->insert(chain, rulenum) inserts rule at position rulenum in chain.
If rulenum is omitted 1 is assumed.
$fw->replace(chain, rulenum) replace rule at rulenum in chain with
$fw->delete(chain, rulenum) deletes rule rulenum from chain.
$fw->check(chain) check given packet against chain for testing.
$fw->flush(chain) deletes all rules from chain.
$fw->list(chain) lists all rules defined for chain.
$fw->zero(chain) zero's all packet counters for chain. Cannot zero
counters for chain policy.
$fw->masq() lists current masqueraded connections.
$fw->new_chain(chain) creates new user defined chain.
$fw->del_chain(chain) delete user defined chain.
$fw->set_policy(chain) set default policy for chain. Takes Rule option
Much of this is highly untested. Masquerading timeout setting isn't yet
implemented. Much of what's planned to be done hasn't been yet. This is to
be considered nothing more than an early beta to work out bugs in the basic
code, and get feedback on usefulness and improvements that could be made.
Jessica Quaintance (firstname.lastname@example.org). Please
feel free to email me with feedback, questions, or comments (or indeed
This package is free software; you can redistribute it and/or modify it
under the same terms as Perl itself, with the exception of the libipfwc.c,
ipchains.c, and the files in include/ which have separate terms derived
from those of the original ipchains sources. See COPYING for details of
this license. Please see README.ipchains for the README that was included
with the original source code for ipchains and contains copyrights and
credits for such.
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