[libvirt] [PATCH v2] nwfilter: probe for inverted ctdir

[Daniel P. Berrange]

On Fri, Mar 22, 2013 at 08:26:59AM -0400, Stefan Berger wrote:
> Linux netfilter at some point inverted the meaning of the '--ctdir reply'
> and newer netfilter implementations now expect '--ctdir original'
> instead and vice-versa.
> We probe for this netfilter change via a UDP message over loopback and 3
> filtering rules applied to INPUT. If the sent byte arrives, the newer
> netfilter implementation has been detected.

I think this is really very hackish. If this test capability goes
wrong for any reason, then we're going to silently setting up
incorrect rules, which would be a security flaw. I think we need
a more robust detection system for this.

Daniel
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