libvirt users - Oct 2018 - Re: KVM + libvirt + nftables without iptables?

On 10/18/2018 10:14 AM, Daniel P. Berrangé wrote:
> On Wed, Oct 17, 2018 at 05:57:11PM +0200, Roman Vesely wrote:
>> Hi everyone,
>>
>> I use Debian 9.5 Stretch and NFTABLES as a firewall.
>> Using NFTABLES  together with IPTABLES is not recommended,
>> but libvirt depends on IPTABLES.
>>
>> Is it safe to run libvirt + kvm + virsh without IPTABLES?
>>
>> By the doc https://libvirt.org/firewall.html,
>> IPTABLES are used for settingup filtering which I do not need.
> 
> Currently it is *NOT* ok.
Pardon me if I misread the question but I think Roman is actually asking
if he turns off iptables in libvirt. Well, that would work but all the
forwarding rules, rules that prevent one domain to see traffic of the
other, etc - you would have to do them yourself. Or trust your guests.

But Dan is right - if iptables are enabled in libvirt such setup will
break terribly.

Michal

Michal Privoznik <mprivozn@redhat.com> wrote:
> On 10/18/2018 10:14 AM, Daniel P. Berrangé wrote:
> > On Wed, Oct 17, 2018 at 05:57:11PM +0200, Roman Vesely wrote:  
> >> Hi everyone,
> >>
> >> I use Debian 9.5 Stretch and NFTABLES as a firewall.
> >> Using NFTABLES  together with IPTABLES is not recommended,
> >> but libvirt depends on IPTABLES.
> >>
> >> Is it safe to run libvirt + kvm + virsh without IPTABLES?
> >>
> >> By the doc https://libvirt.org/firewall.html,
> >> IPTABLES are used for settingup filtering which I do not need.  
> > 
> > Currently it is *NOT* ok.  
> 
> Pardon me if I misread the question but I think Roman is actually
> asking if he turns off iptables in libvirt.
Thank you Michal, you said it exactly.
I only use nftables.
I need to remove iptables and set libvirt to work without them.
> Well, that would work but
> all the forwarding rules, rules that prevent one domain to see
> traffic of the other, etc - you would have to do them yourself. Or
> trust your guests.
Yes, I understand and I will create rules manually with NFTABLES.
And I also manage all kvm guests.

I've found some tips on how to "turn off" iptables in libvirt:

 virsh net-destroy default
 virsh net-autostart --disable default

Is this the right and safe way to remove all dependency to iptables?

Thank you,

Roman

On 10/18/2018 11:09 PM, Roman Vesely wrote:
> Michal Privoznik <mprivozn@redhat.com> wrote:
> 
>> On 10/18/2018 10:14 AM, Daniel P. Berrangé wrote:
>>> On Wed, Oct 17, 2018 at 05:57:11PM +0200, Roman Vesely wrote:  
>>>> Hi everyone,
>>>>
>>>> I use Debian 9.5 Stretch and NFTABLES as a firewall.
>>>> Using NFTABLES  together with IPTABLES is not recommended,
>>>> but libvirt depends on IPTABLES.
>>>>
>>>> Is it safe to run libvirt + kvm + virsh without IPTABLES?
>>>>
>>>> By the doc https://libvirt.org/firewall.html,
>>>> IPTABLES are used for settingup filtering which I do not need.
>>>
>>> Currently it is *NOT* ok.  
>>
>> Pardon me if I misread the question but I think Roman is actually
>> asking if he turns off iptables in libvirt.
> 
> Thank you Michal, you said it exactly.
> I only use nftables.
> I need to remove iptables and set libvirt to work without them.
> 
>> Well, that would work but
>> all the forwarding rules, rules that prevent one domain to see
>> traffic of the other, etc - you would have to do them yourself. Or
>> trust your guests.
> 
> Yes, I understand and I will create rules manually with NFTABLES.
> And I also manage all kvm guests.
> 
> I've found some tips on how to "turn off" iptables in
libvirt:
> 
>  virsh net-destroy default
>  virsh net-autostart --disable default
> 
> Is this the right and safe way to remove all dependency to iptables?
You also have to make sure none of the domain interfaces will use
nwfilter. And I think that's all.

Also, the default network is NATed one, which won't fly with nftables.
If you still want libvirt to create TAP devices for your domain and plug
them into a bridge you can define network type='bridge' (or domain
interface of the corresponding type).

Michal