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Full Discussion: Editing rules on iptables
Special Forums Cybersecurity Editing rules on iptables Post 302526019 by garric on Monday 30th of May 2011 05:11:12 AM
Old 05-30-2011
Editing rules on iptables

Hello,

I was playing around with iptables to setup an isolated system. On a SLES10 system, I ran the below to setup my first draft of rules. I noticed that the rules come into effect immediately and do not require any restart of iptables.

Code:
iptables -A INPUT -j ACCEPT
iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -j ACCEPT -p tcp --dport 80 -d xx.xx.xx.xx

iptables -A OUTPUT -o lo -j ACCEPT
iptables -P OUTPUT DROP

Now, I want to add a new rule in the middle (lets say, open outbound communication on port 500 for ip yy.yy.yy.yy). But since the rules are evaluated sequentially, it will become effective after my last rule (which is iptables -P OUTPUT DROP). Since all packets match this default rule for output, I cannot add a new rule without rebooting the machine.

I wanted to know if there is a way to introduce new rules without having to reboot a machine, ie introduce a rule above the 'iptables -P OUTPUT DROP'. Any help or leads into documentation will help.

Last edited by pludi; 05-30-2011 at 09:06 AM..
 

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IPTABLES-APPLY(8)						  iptables 1.6.1						 IPTABLES-APPLY(8)

NAME
iptables-apply - a safer way to update iptables remotely SYNOPSIS
iptables-apply [-hV] [-t timeout] [-w savefile] {[rulesfile]|-c [runcmd]} DESCRIPTION
iptables-apply will try to apply a new rulesfile (as output by iptables-save, read by iptables-restore) or run a command to configure iptables and then prompt the user whether the changes are okay. If the new iptables rules cut the existing connection, the user will not be able to answer affirmatively. In this case, the script rolls back to the previous working iptables rules after the timeout expires. Successfully applied rules can also be written to savefile and later used to roll back to this state. This can be used to implement a store last good configuration mechanism when experimenting with an iptables setup script: iptables-apply -w /etc/network/iptables.up.rules -c /etc/network/iptables.up.run When called as ip6tables-apply, the script will use ip6tables-save/-restore and IPv6 default values instead. Default value for rulesfile is '/etc/network/iptables.up.rules'. OPTIONS
-t seconds, --timeout seconds Sets the timeout in seconds after which the script will roll back to the previous ruleset (default: 10). -w savefile, --write savefile Specify the savefile where successfully applied rules will be written to (default if empty string is given: /etc/network/iptables.up.rules). -c runcmd, --command runcmd Run command runcmd to configure iptables instead of applying a rulesfile (default: /etc/network/iptables.up.run). -h, --help Display usage information. -V, --version Display version information. SEE ALSO
iptables-restore(8), iptables-save(8), iptables(8). LEGALESE
Original iptables-apply - Copyright 2006 Martin F. Krafft <madduck@madduck.net>. Version 1.1 - Copyright 2010 GW <gw.2010@tnode.com or http://gw.tnode.com/>. This manual page was written by Martin F. Krafft <madduck@madduck.net> and extended by GW <gw.2010@tnode.com or http://gw.tnode.com/>. Permission is granted to copy, distribute and/or modify this document under the terms of the Artistic License 2.0. iptables 1.6.1 IPTABLES-APPLY(8)
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