[libvirt] Proposed: always allow packets internal to an interface

Eric Blake eblake at redhat.com
Mon Nov 5 16:34:49 UTC 2012

On 11/04/2012 10:18 AM, Gene Czarcinski wrote:
> On 11/02/2012 07:46 AM, Gene Czarcinski wrote:
>> Currently, when an interface (virtual network) is started, if no ip
>> address is defined, then no rule is added to bemit "internal" network
>> traffic.  However, virtual guests can use such a network to
>> communicate if a rule is added to the iptables/ip6tables rule set.
>> This will work even if no ip address is defined on an interface (which
>> is valid).
>> I propose that rules of the following forms be added when an interface
>> is started and removed when it is destroyed:
>> iptables -I FORWARD 1 -i  virbr18 -o  virbr18  -j  ACCEPT
>> ip6tables -I FORWARD 1 -i  virbr18 -o  virbr18  -j  ACCEPT

I'm not as familiar with this as others, so I'll defer on whether this
makes sense.

>> If a user wants a "very private network", the user has to run the
>> above commands.  The proposal simply does this automatically.
> It appears that this patch is not necessary since I can do this now
> using nwfilters.
> Question:  I see little discussed or anything about nwfilters.  Is
> nwfilters an active concept or is it still included because of legacy? 
> Will this still work with firewalld?

But this I can answer.  Yes, nwfilters is still an actively maintained
concept, and yes, it is supposed to work with firewalld.

Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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