[libvirt-users] Passing multiple addresses with masks to nwfilter

Brooks Swinnerton bswinnerton at gmail.com
Wed Jan 1 20:46:32 UTC 2020


Looking at
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/virtualization_deployment_and_administration_guide/sect-virtual_networking-applying_network_filtering#sect-Applying_network_filtering-Usage_of_variables_in_filters,
it sounds like the preferred approach is to use something like:

<filter name='no-ipv6-spoofing' chain='ipv6-ip' priority='-710'>
  <rule action='return' direction='out' priority='500'>
    <ipv6 srcipaddr='$IPV6[@1]' srcipmask='$IPV6_MASK[@1]'/>
  </rule>
  <rule action='drop' direction='out' priority='1000'/>
</filter>

The documentation reads:

Assign concrete values to SRCIPADDRESSES and DSTPORTS as shown:

SRCIPADDRESSES = [ 10.0.0.1, 11.1.2.3 ]
DSTPORTS = [ 80, 8080 ]


But I'm not sure how to pass through an array of <parameter>s in the
filterref. Is this possible?



On Wed, Jan 1, 2020 at 12:39 PM Brooks Swinnerton <bswinnerton at gmail.com>
wrote:

> Hello,
>
> I have a nwfilter that I'm using to ensure that libvirt domains can't
> spoof IPv6 traffic. It looks like this:
>
> <filter name='no-ipv6-spoofing' chain='ipv6-ip' priority='-710'>
>   <rule action='return' direction='out' priority='500'>
>     <ipv6 srcipaddr='$IPV6' srcipmask='$IPV6MASK'/>
>   </rule>
>   <rule action='drop' direction='out' priority='1000'/>
> </filter>
>
> The goal is to allow any traffic coming from the entire prefix (e.g.
> 2001:db8::/32). This theoretically would work fine when passing in the
> variables from the domain definition like so:
>
> <filterref filter='no-ipv6-spoofing'>
>   <parameter name='IPV6' value='2001:db8:1:6:dc:d2ff:fef2:2181'/>
>   <parameter name='IPV6_MASK' value='32'/>
> </filterref>
>
> But the problem comes when wanting to allow multiple prefixes (and thus
> multiple $IPV6 and $IPV6_MASK variables). If there is more than one
> definition of $IPV6, how could I associate it with a corresponding
> $IPV6_MASK?
>
> Ideally I would be able to pass an address in CIDR notation directly to
> srcipaddr, but I don't believe that's an option.
>
> Any guidance would be appreciated. The ultimate goal is to automate this
> process, so having something like $IPV6_1 and $IPV6_1 would be less than
> ideal.
>
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