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[libvirt] Fwd: Re: [PATCH] nwfilter: add XML attribute to control match target



 On 06/11/2010 10:53 AM, Daniel P. Berrange wrote:
On Fri, Jun 11, 2010 at 10:41:50AM -0400, Stefan Berger wrote:
This patch adds an optional XML attribute to a nwfilter rule to give the
user control over whether the rule is supposed to be using the match
target or not. A rule may now look like as follows with the nomatch
attribute either having value '1' or 'true' (case-insensitive).

[...]
<rule action='accept' direction='in' nomatch='true'>
Having inverted boolean flags is a little wierd. Can't this
be written as match=false instead ?
Ok, I'll invert the logic.

<tcp srcmacaddr='1:2:3:4:5:6'
            srcipaddr='10.1.2.3' srcipmask='32'
            dscp='33'
            srcportstart='20' srcportend='21'
            dstportstart='100' dstportend='1111'/>
</rule>
[...]

I am also extending the nwfilter schema and add this attribute to a test
case.
I'm not sure I really understand what this is doing. Can you give a
quick example of what the iptables command looks like, with and
without the nomatch attribute set

Background: I can specify rules so that the ssh port 22 (tcp) is reachable on my system and no other traffic is possible. If I don't use the --match target on this tcp port 22 rule, I could initiate traffic inside the VM from TCP port 22 (client port) towards an allowed target. If the --match NEW, ESTABLISHED target is added on incoming traffic, I get control over directionality due to the NEW. The outgoing direction will then have --match ESTABLISHED. Since the NEW will be missing on outgoing traffic, I won't be able to initiate that traffic.

In essence it's

iptables -p tcp --dport 22 -j ACCEPT

versus

iptables -p tcp --dport 22 -m state --state NEW, ESTABLISHED



Regards,
Daniel


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