[libvirt-users] netfilter+libvirt=(smth got broken?)
Eric Blake
eblake at redhat.com
Thu Mar 21 03:18:21 UTC 2013
On 03/20/2013 08:30 PM, Pablo Neira Ayuso wrote:
>>
>> So apparently, netfilter's behaviour was indeed reversed at some
>> point, therefore libvirt stopped working properly.
>
> --ctdir was broken and it was fixed in patch:
In other words, the kernel folks made a silent change in ABI. Eww.
How can we reliably tell which kernels have the old behavior, and which
have the new, so that libvirt knows which sense to use?
> By looking at the changes you made:
>
>> --A FI-vnet0 -p tcp -m tcp --sport 110 -m conntrack --ctstate
>> ESTABLISHED -m conntrack --ctdir ORIGINAL -j RETURN
>> +-A FI-vnet0 -p tcp -m tcp --sport 110 -m conntrack --ctstate
>> ESTABLISHED -m conntrack --ctdir REPLY -j RETURN
>
> The first rule looks wrong to me indeed, traffic coming in the
> original direction will initiate the connection to destination port
> TCP/110. Therefore, your change is correct.
Correct for the new kernel interpretation, but we also want to support
use of libvirt with older kernels, preferably with a runtime check so
that a binary compiled on an older kernel will still work after a kernel
upgrade.
>
> It's unfortunate nobody noticed this rule was incorrect so far (even
> if it was working).
It's also unfortunate that the kernel folks did a silent ABI change,
without offering any witness of which behavior is in operation.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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