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IPTable: Issue with owner module?

+2 votes
105 views

I have some issue with module (owner) in iptables v1.4.14

Current rule fails:
iptables -t nat -A OUTPUT -o eth0 -p tcp -s x.x.x.x -m owner --gid-owner usergroup -j DNAT --to-destination x.x.x.x:80;
I tried to use numeric gid, it failed too..

But this rule works fine:
iptables -t nat -A OUTPUT -o eth0 -p tcp -s x.x.x.x -m owner --uid-owner user -j DNAT --to-destination x.x.x.x:80;

Is it a BUG or I am missing something?

posted Dec 15, 2013 by Anderson

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1. What is the kernel version?
2. Fails how? Please provide more details.

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I wanted to make a white list using the settings below.

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I am trying to queue the packets of a process so I can use libnetfilter_queue to modify them.

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Consider the following example: you have a router between two networks, and you want to cut off the
router from the outside world using some iptables rules. However, all traffic that is forwarded by the router between the two networks basically is to be ignored by iptables (i.e., the router does not play firewall for any of the two networks).

Currently, if conntrack is loaded on the router, then conntrack -L on the router lists all the connections, not only those to and from the router, but also all connections between the two. Certainly, it takes some CPU cycles for the router to keep track of all the connections. Also, the number of connections that conntrack can take of is limited.

So is there a way to let Linux "bypass" conntrack and maybe other netfilter stuff when it comes to forwarded packets?

+1 vote

Is there a way to find out if there any iptables rules set on a machine ?

There are some indirect ways which will not always work; for example, I know that on most hosts, iptables -S will return the following output (when no iptable rules are set)
-P INPUT ACCEPT
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So you can check whether or not the number of output lines is greater than 3 (as an indication of whether or not iptables rules are set). But there are hosts on which there are more chains then these 3; these chains are set by application/services, even without any iptable rules which are set. And after running iptables -F on these machines, iptables -S will still show more than 3 chains, even that there are no iptables rules set in these chains.

So the question is - is there a way to know whether or not netfilter rules are set on a host, regardless of the number of chains ?

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