Re: CentO 8 and nftables default policy

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I had the same problem.

If you are not using virtual machines then

   # systemctl disable libvirtd

works and is easily reversible.

Alan

On 18/04/2020 23:03, Alessandro Baggi wrote:
Il 17/04/20 11:01, Alessandro Baggi ha scritto:
Hi list,

I'm studying nftables. I'm using CentOS 8.1 (Gnome) and I disabled firewalld. I noticed that a default policy is created with tables and chains probably for firewalld.

So I created a .nft script where I stored my rules with a flush for previous ruleset, then saved on /etc/sysconfig/nftables.conf and the enabled nftables service.

Running the script with nft -f script.nft all work as expected but when rebooting, running nft list ruleset I find my rules and the default policy (chains and tables) that I would not have in my configuration.

My nftables.conf contains only my ruleset.

For example, running nft list tables I found several default tables like:

table ip filter
table ip6 filter
table bridge filter
table ip nat
table ip mangle

So probably there is something that is applying its policy but I ignore what is.

Can someone point me in the right direction?

Thank you in advance.

Hi have not received any replies but I tried to investigate. After checking configuration files in my system I supposed that this could caused by a daemon, so I found that libvirtd push some rules.

running virsh nwfilter-list I get:

 UUID                                  Nome
------------------------------------------------------------------
 34fe8cba-af99-4438-8efc-b135143425e2  allow-arp
 dc110112-3824-4cf3-946f-ba6e15cd29c3  allow-dhcp
 fecc383a-bab5-465d-a5be-98834fb626ce  allow-dhcp-server
 761e7132-8738-47c2-8101-275d6fd6a347  allow-incoming-ipv4
 d37b017f-8f21-4ad0-9fa6-052a5cb1ed2e  allow-ipv4
 a8c740d5-328c-452e-bae7-9828c54f95b7  clean-traffic
 296bdfad-11d9-4aa0-9817-4656ef2be6e5  clean-traffic-gateway
 69215a61-bff5-482a-b913-589bb1ce18f2  no-arp-ip-spoofing
 70c61f0a-c005-407f-843d-d13c2495f05d  no-arp-mac-spoofing
 386cd2f4-7272-43e2-ba1f-80cb3518649c  no-arp-spoofing
 9117fa21-e3d6-4c32-9cdf-af97ebd6599e  no-ip-multicast
 7a964470-4f74-4eef-9fec-a0e9a79e168d  no-ip-spoofing
 8c9e45a3-5d44-4641-b23d-eded5c1f1632  no-mac-broadcast
 82dcd4f0-f55a-43ad-b520-d4c8d4bf37cd  no-mac-spoofing
 bdd0ba54-7ce0-4a2c-9c25-c24072d364ba  no-other-l2-traffic
 fc50783e-d32b-42ba-8380-7576c4388244  no-other-rarp-traffic
 edfc1bb3-b325-4f8d-8c5b-423e55da66eb  qemu-announce-self
 8556bd82-dc97-47b0-b573-5986ebbad3b2  qemu-announce-self-rarp

If I will remove these libvirt filters I will get errors?

Thank you in advance.

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