I was considering enabling libvirt's built-in filtering chains, which would prevent spoofing activities between VMs, if integration with Nix is possible

• no-arp-spoofing
• no-ip-spoofing
• no-ipv6-spoofing
• clean-traffic
  Reference: https://libvirt.org/formatnwfilter.html#filtering-chains

What do you think about it?

I was considering enabling libvirt's built-in filtering chains, which would prevent spoofing activities between VMs, if integration with Nix is possible

* no-arp-spoofing

* no-ip-spoofing

* no-ipv6-spoofing

* clean-traffic
  Reference: https://libvirt.org/formatnwfilter.html#filtering-chains

What do you think about it?

Would be great to use a generic mechanism, but that would imply running libvirtd?

I haven't done thorough research yet. However, it may require libvrtd to be running on the host. We could merge this PR and investigate libvirtd later.

Tested on Lenovo-X1

• instructed arp spoofing test:
  succeeds with ghaf mainline / fails with arp-protect branch

• ci-test-automation ipspoofing test:
  succeeds with ghaf mainline / fails with arp-protect branch
  With this PR image connection to stealer vm (chrome-vm) is completely lost during the ipspoofing test. Had to modify the test to save the outputs to /home/appuser/Unsafe share/stolen.txt to be able to check them manually after the test.

• Checked that all vms have internet connection

• Run ci-test-automation network test (iperf) few times, didn't notice clear change compared to mainline

• Desktop and apps seem normal

Tested arp spoofing on Orin AGX as below

Set up WiFi connection on net-vm
sudo nmcli dev wifi con "SSID" --ask

ssh ghaf@ghaf-host
sudo su
nix-shell -p bettercap
arp -s 192.168.100.1 02:ad:00:00:00:01
iptables -P FORWARD ACCEPT

bettercap
> net.probe on
> set arp.spoof.targets 192.168.100.103
> arp.spoof on
> net.sniff on

Then connected to admin-vm via ssh and sent some http requests, for example:
curl -X GET http:/www.google.com

--> bettercap reported:

HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
Accept-Ranges: none
Date: Mon, 25 Aug 2025 10:48:18 GMT
Expires: -1
Cache-Control: private, max-age=0
Content-Type: text/html; charset=ISO-8859-1
Server: gws
Set-Cookie: AEC=AVh_V2iJ_tSinWfcMV40v-RXxneOg3PW8hJ8P0G-4yKodwbEzUqkOd6XIA; expires=Sat, 21-Feb-2026 10:48:18 GMT; path=/; domain=.google.com; Secure; HttpOnly; SameSite=lax
Vary: Accept-Encoding
Content-Security-Policy-Report-Only: object-src 'none';base-uri 'self';script-src 'nonce-KW2FkHwRQ4paTH9ajPIagg' 'strict-dynamic' 'report-sample' 'unsafe-eval' 'unsafe-inline' https: http:;report-uri https://csp.withgoogle.com/csp/gws/other-hp
X-Xss-Protection: 0

arp spoofing succeeded both with ghaf mainline image and with image built from this PR

Tested arp spoofing on Orin AGX as below
...

The host network runs on the bridge, so it can by default see all the traffic - no need for arp spoofing. If you run net.probe on and net.sniff on you will see the traffic between the VMs (like your curl) already without spoofing.

What you could do to test the setup on orin:

1. Watch the arp entries in admin-vm:

watch -n 1 arp

2. Spoof from ghaf-host:

(sudo su)
nix-shell -p bettercap
arp -s 192.168.100.1 02:ad:00:00:00:01
iptables -P FORWARD ACCEPT
bettercap
# set the target as the admin-vm, and start spoofing
> set arp.spoof.targets 192.168.100.3 
> arp.spoof on

In main, you should see in the admin-vm arp table that the net-vm MAC changes to the ghaf-host MAC, with the patch nothing should happen. You can also toggle arp.spoof on and arp.spoof off on the fly to see the difference.

If you want to dig more into it, you can include the tcpdump package in the build (on-the-fly install will probably not work in admin-vm) and monitor arp traffic on ethint0 (target VM) and virbr0 (host bridge). Also, you could try to spoof the host from admin-vm, but again need to include the bettercap package in the build.

Tested arp spoofing on Orin AGX as below
...

The host network runs on the bridge, so it can by default see all the traffic - no need for arp spoofing. If you run net.probe on and net.sniff on you will see the traffic between the VMs (like your curl) already without spoofing.

What you could do to test the setup on orin:

1. Watch the arp entries in admin-vm:

watch -n 1 arp

2. Spoof from ghaf-host:

(sudo su)
nix-shell -p bettercap
arp -s 192.168.100.1 02:ad:00:00:00:01
iptables -P FORWARD ACCEPT
bettercap
# set the target as the admin-vm, and start spoofing
> set arp.spoof.targets 192.168.100.3 
> arp.spoof on

In main, you should see in the admin-vm arp table that the net-vm MAC changes to the ghaf-host MAC, with the patch nothing should happen. You can also toggle arp.spoof on and arp.spoof off on the fly to see the difference.

If you want to dig more into it, you can include the tcpdump package in the build (on-the-fly install will probably not work in admin-vm) and monitor arp traffic on ethint0 (target VM) and virbr0 (host bridge). Also, you could try to spoof the host from admin-vm, but again need to include the bettercap package in the build.

I tested again on Orin AGX.

Toggling net-vm MAC address shown on ghaf-host works in main but nothing happens with your branch as you explained.

For some reason I was not able to see any http request traffic to ghaf-host with (modified) main image when running bettercap on admin-vm. Maybe if I had set up another vm for running http request it would have worked.

Anyways, the arp protection works as you described both on x86 and ARM device.

Changes:

• rebased with latest firewall changes
• removed additional kernel modules; changed the logic to filter arp traffic on tap-* interfaces. This works on all targets without additional changes.

useful command on the host to verify the effectiveness: ebtables -L --Lc showing the package counter for the rules, can be triggered via arping or actual spoofing. tcpdump shows traffic only on originating interface, both internal bridge and other VM interfaces do not show traffic (tcpdump -i (ethint0/virbr0/tap-<vm>) -n 'arp')

Tested on Lenovo-X1 again after the latest changes

• arp spoofing does not succeed (ebtables -L --Lc shows the effect of spoofing at firewall)
• Updating system time form internet works in ghaf-host and in every VM (NTP service)
• systemctl status does not reveal any services failing in VMs

Test again also on Orin AGX after the latest changes

• arp spoofing does not succeed (ran bettercap in admin-vm)
• Running ebtables -L --Lc in ghaf-host shows the effect of spoofing at firewall
• Updating system time form internet works in ghaf-host and in VMs (NTP service)
• systemctl status does not reveal any services failing in VMs