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Where are Iptables Rules Restored from and how to Reset Rule
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RAPHEAD
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Joined: 20 Jun 2003
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PostPosted: Wed Mar 25, 2015 8:05 am    Post subject: Where are Iptables Rules Restored from and how to Reset Rule Reply with quote

I cloned a server which was running shorewall previously.
I shut it down permanently but could not make connections to the system.
Then I figured out that there were these rules even after stopping shorewall:

Code:
    $ iptables --list-rules
    -P INPUT DROP
    -P FORWARD DROP
    -P OUTPUT DROP
    ...some more...


They persist even after reboots!
So I checked `/etc/init.d/iptables` but it's disabled.
And `/var/lib/iptables/` is empty.
So my question is, where are those rules stored and
what is restoring them after reboots?

I finally could successfully reset them with `iptables --flush` and then `iptables-save`
but I don't know why this worked.
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charles17
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PostPosted: Wed Mar 25, 2015 9:09 am    Post subject: Reply with quote

Did you check the directories listed by equery?
Code:
$ equery f iptables | grep /var

Also, https://wiki.gentoo.org/wiki/Iptables#General_Rules might help.
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RAPHEAD
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PostPosted: Wed Mar 25, 2015 9:28 am    Post subject: Reply with quote

cool way of checking the potential locations :)
Yes, I checked and they are empty (except for `.keep_net-firewall_iptables-0`).
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i92guboj
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PostPosted: Wed Mar 25, 2015 10:08 am    Post subject: Reply with quote

RAPHEAD wrote:
cool way of checking the potential locations :)
Yes, I checked and they are empty (except for `.keep_net-firewall_iptables-0`).


Then see what else lives in the directory where that file is ;)
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RAPHEAD
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PostPosted: Wed Mar 25, 2015 12:22 pm    Post subject: Reply with quote

Again, it is empty! Neither in the ipv4 nor in the ipv6 dir there is somehting.
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i92guboj
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PostPosted: Wed Mar 25, 2015 12:43 pm    Post subject: Reply with quote

Sorry. I don't know how I read that :lol:

iptables usually saves the files into /var/lib/iptables/, but there are many ways to run iptables.

It could be a bash script in /etc/local.d/, or some init script in /etc/init.d. Maybe even a cron script.

If it's under /var/lib/iptables, then they should stop to load if you rc-update del iptables, but, as said, there are many ways to run them.
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charles17
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PostPosted: Wed Mar 25, 2015 9:52 pm    Post subject: Re: Where are Iptables Rules Restored from and how to Reset Reply with quote

RAPHEAD wrote:
They persist even after reboots!
So I checked `/etc/init.d/iptables` but it's disabled.
"disbabled" - Does that mean you are not having iptables/ip6tables in a runlevel?
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RAPHEAD
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PostPosted: Wed Mar 25, 2015 9:53 pm    Post subject: Reply with quote

yes, `rc-update | grep iptables` returns no result.
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jonathan183
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PostPosted: Wed Mar 25, 2015 10:40 pm    Post subject: Re: Where are Iptables Rules Restored from and how to Reset Reply with quote

RAPHEAD wrote:
So my question is, where are those rules stored and
what is restoring them after reboots?


On my system there is /etc/conf.d/iptables which has an entry
Code:
IPTABLES_SAVE="/var/lib/iptables/rules-save"


I actually have never use the save feature and run iptables from a script /etc/local.d/001-firewall.start
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RAPHEAD
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PostPosted: Thu Mar 26, 2015 8:20 am    Post subject: Reply with quote

@i92guboj
Good hint with /etc/local.d/ I actually had a forgotten script there once ut not in this case :(


@jonathan183
On the system in question, I have an /etc/conf.d/iptables like:

Code:

# Location in which iptables initscript will save set rules on
# service shutdown
IPTABLES_SAVE="/var/lib/iptables/rules-save"

# Options to pass to iptables-save and iptables-restore
SAVE_RESTORE_OPTIONS="-c"

# Save state on stopping iptables
SAVE_ON_STOP="yes"

...commented stuff


But my understanding is that this would only be used, if /etc/init.d/iptables would run. And again `/var/lib/iptables/rules-save` is empty.
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pietinger
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PostPosted: Thu Mar 26, 2015 11:40 am    Post subject: Reply with quote

IF
- the skript iptables isnt in your runlevel
AND
- you have firewall rules activated
THEN something other must activate it.

I would temp. rename /sbin/iptables and look if a skript throws an error ....
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cboldt
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PostPosted: Thu May 21, 2015 10:37 pm    Post subject: Reply with quote

iptables-save, on its own, just writes to stdout, so unless you are redirecting the output to some persistent place, all you've done is get a view of the firewall as currently constituted.

When the firewall is completely flushed, it will have three policies (which is what you showed), one for each of three empty chains.

You can see this by running `iptables -F; iptables -X; iptables-save | less`. You will be looking at an empty firewall.

If it gets populated (you can check anytime with `iptables-save | less`), then something is running iptables commands, either a string of separate `iptables` commands, or `iptables-restore`. If I was running into the firewall being built, I'd look for the typical firewall builders (I don't know the names of all of them, but ipkunfu is one); and if none of those are present, then I'd run grep against /etc

grep -r iptables-restore /etc
grep -r iptables /etc

I'd run against iptables-restore first, because a match on that might get lost in a sea of matches on iptables
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RAPHEAD
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PostPosted: Fri May 22, 2015 4:52 am    Post subject: Reply with quote

Hi cboldt,

many thanks for your insights.
The tables were definitely not empty *just three entries)
but at some points they were and I can still not say
what solved it in the end -- see described procedure.
I know that the only firewall related script I had installed
was shorewall which I deactivated.
Maybe it was some forgotten own script that I cleaned up
on the go.
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cboldt
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PostPosted: Fri May 22, 2015 12:36 pm    Post subject: Reply with quote

One other point, that I forgot to mention - the policies are persistent, meaning that if you flush the firewall and remove all the rules, the policies, whatever they are, remain. If the INPUT policy is DROP, you are locked out.

If shorewall built a firewall, and set the policies to DROP, and you remove shorewall, the policies are "stuck" on DROP until somehow changed, even if you flush the firewall and remove all the other rule chains. An iptables command can change the policy (iptables -P INPUT ACCEPT), and the default on rebooting is to have the three primary chains (INPUT, FORWARD, and OUTPUT) on a policy of ACCEPT. I would guess that even this default can be modified by informing the kernel.

Glad to hear your situation was resolved. If you are a bit like me, the issue bugs me persistently until I figure out what the heck was going on! Sometimes the light comes on many months after the issue.
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